import of libc++ 6.0.0

114 files changed, 17235 insertions, 8386 deletions

diff --git a/lib/libcxx/include/CMakeLists.txt b/lib/libcxx/include/CMakeLists.txt
index 219d1b73083..b98e09260ca 100644
--- a/lib/libcxx/include/CMakeLists.txt
+++ b/lib/libcxx/include/CMakeLists.txt
@@ -10,31 +10,31 @@ set(LIBCXX_HEADER_PATTERN
   ${LIBCXX_SUPPORT_HEADER_PATTERN}
   )
 
-file(COPY .
-  DESTINATION "${CMAKE_BINARY_DIR}/include/c++/v1"
-  FILES_MATCHING
-  ${LIBCXX_HEADER_PATTERN}
-  )
+if(NOT LIBCXX_USING_INSTALLED_LLVM AND LLVM_BINARY_DIR)
+  file(COPY .
+    DESTINATION "${LLVM_BINARY_DIR}/include/c++/v1"
+    FILES_MATCHING
+    ${LIBCXX_HEADER_PATTERN}
+    )
+endif()
 
 if (LIBCXX_INSTALL_HEADERS)
   install(DIRECTORY .
-    DESTINATION include/c++/v1
-    COMPONENT libcxx-headers
+    DESTINATION ${LIBCXX_INSTALL_PREFIX}include/c++/v1
+    COMPONENT cxx-headers
     FILES_MATCHING
     ${LIBCXX_HEADER_PATTERN}
     PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
   )
 
   if (LIBCXX_NEEDS_SITE_CONFIG)
-    set(UNIX_CAT cat)
-    if (WIN32)
-      set(UNIX_CAT type)
-    endif()
     # Generate and install a custom __config header. The new header is created
     # by  prepending __config_site to the current __config header.
     add_custom_command(OUTPUT ${LIBCXX_BINARY_DIR}/__generated_config
-      COMMAND ${CMAKE_COMMAND} -E copy ${LIBCXX_BINARY_DIR}/__config_site ${LIBCXX_BINARY_DIR}/__generated_config
-      COMMAND ${UNIX_CAT} ${LIBCXX_SOURCE_DIR}/include/__config >> ${LIBCXX_BINARY_DIR}/__generated_config
+      COMMAND ${PYTHON_EXECUTABLE} ${LIBCXX_SOURCE_DIR}/utils/cat_files.py
+        ${LIBCXX_BINARY_DIR}/__config_site
+        ${LIBCXX_SOURCE_DIR}/include/__config
+        -o ${LIBCXX_BINARY_DIR}/__generated_config
       DEPENDS ${LIBCXX_SOURCE_DIR}/include/__config
               ${LIBCXX_BINARY_DIR}/__config_site
     )
@@ -44,20 +44,26 @@ if (LIBCXX_INSTALL_HEADERS)
     set(generated_config_deps generate_config_header)
     # Install the generated header as __config.
     install(FILES ${LIBCXX_BINARY_DIR}/__generated_config
-      DESTINATION include/c++/v1
+      DESTINATION ${LIBCXX_INSTALL_PREFIX}include/c++/v1
       PERMISSIONS OWNER_READ OWNER_WRITE GROUP_READ WORLD_READ
       RENAME __config
-      COMPONENT libcxx-headers)
+      COMPONENT cxx-headers)
   endif()
 
   if (NOT CMAKE_CONFIGURATION_TYPES)
     # this target is just needed as a placeholder for the distribution target
-    add_custom_target(libcxx-headers)
-    add_custom_target(install-libcxx-headers
-                      DEPENDS libcxx-headers ${generated_config_deps}
+    add_custom_target(cxx-headers)
+    add_custom_target(install-cxx-headers
+                      DEPENDS cxx-headers ${generated_config_deps}
                       COMMAND "${CMAKE_COMMAND}"
-                              -DCMAKE_INSTALL_COMPONENT=libcxx-headers
+                              -DCMAKE_INSTALL_COMPONENT=cxx-headers
                               -P "${CMAKE_BINARY_DIR}/cmake_install.cmake")
+    # Stripping is a no-op for headers
+    add_custom_target(install-cxx-headers-stripped DEPENDS install-cxx-headers)
+
+    add_custom_target(libcxx-headers)
+    add_custom_target(install-libcxx-headers DEPENDS install-cxx-headers)
+    add_custom_target(install-libcxx-headers-stripped DEPENDS install-cxx-headers-stripped)
   endif()
 
 endif()
diff --git a/lib/libcxx/include/__bit_reference b/lib/libcxx/include/__bit_reference
index 5659ed06824..3e4a21d261f 100644
--- a/lib/libcxx/include/__bit_reference
+++ b/lib/libcxx/include/__bit_reference
@@ -14,12 +14,14 @@
 #include <__config>
 #include <algorithm>
 
-#include <__undef_min_max>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Cp, bool _IsConst, typename _Cp::__storage_type = 0> class __bit_iterator;
@@ -40,11 +42,8 @@ class __bit_reference
     __storage_pointer __seg_;
     __storage_type    __mask_;
 
-#if defined(__clang__) || defined(__IBMCPP__) || defined(_LIBCPP_MSVC)
     friend typename _Cp::__self;
-#else
-    friend class _Cp::__self;
-#endif
+
     friend class __bit_const_reference<_Cp>;
     friend class __bit_iterator<_Cp, false>;
 public:
@@ -130,11 +129,7 @@ class __bit_const_reference
     __storage_pointer        __seg_;
     __storage_type __mask_;
 
-#if defined(__clang__) || defined(__IBMCPP__) || defined(_LIBCPP_MSVC)
     friend typename _Cp::__self;
-#else
-    friend class _Cp::__self;
-#endif
     friend class __bit_iterator<_Cp, true>;
 public:
     _LIBCPP_INLINE_VISIBILITY
@@ -163,7 +158,7 @@ __find_bool_true(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type
 {
     typedef __bit_iterator<_Cp, _IsConst> _It;
     typedef typename _It::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    static const int __bits_per_word = _It::__bits_per_word;
     // do first partial word
     if (__first.__ctz_ != 0)
     {
@@ -199,7 +194,7 @@ __find_bool_false(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type
 {
     typedef __bit_iterator<_Cp, _IsConst> _It;
     typedef typename _It::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    const int __bits_per_word = _It::__bits_per_word;
     // do first partial word
     if (__first.__ctz_ != 0)
     {
@@ -251,7 +246,7 @@ __count_bool_true(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_type
     typedef __bit_iterator<_Cp, _IsConst> _It;
     typedef typename _It::__storage_type __storage_type;
     typedef typename _It::difference_type difference_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    const int __bits_per_word = _It::__bits_per_word;
     difference_type __r = 0;
     // do first partial word
     if (__first.__ctz_ != 0)
@@ -282,7 +277,7 @@ __count_bool_false(__bit_iterator<_Cp, _IsConst> __first, typename _Cp::size_typ
     typedef __bit_iterator<_Cp, _IsConst> _It;
     typedef typename _It::__storage_type __storage_type;
     typedef typename _It::difference_type difference_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    const int __bits_per_word = _It::__bits_per_word;
     difference_type __r = 0;
     // do first partial word
     if (__first.__ctz_ != 0)
@@ -324,7 +319,7 @@ __fill_n_false(__bit_iterator<_Cp, false> __first, typename _Cp::size_type __n)
 {
     typedef __bit_iterator<_Cp, false> _It;
     typedef typename _It::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    const int __bits_per_word = _It::__bits_per_word;
     // do first partial word
     if (__first.__ctz_ != 0)
     {
@@ -354,7 +349,7 @@ __fill_n_true(__bit_iterator<_Cp, false> __first, typename _Cp::size_type __n)
 {
     typedef __bit_iterator<_Cp, false> _It;
     typedef typename _It::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    const int __bits_per_word = _It::__bits_per_word;
     // do first partial word
     if (__first.__ctz_ != 0)
     {
@@ -412,7 +407,7 @@ __copy_aligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsCon
     typedef __bit_iterator<_Cp, _IsConst> _In;
     typedef  typename _In::difference_type difference_type;
     typedef typename _In::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _In::__bits_per_word;
+    const int __bits_per_word = _In::__bits_per_word;
     difference_type __n = __last - __first;
     if (__n > 0)
     {
@@ -461,7 +456,7 @@ __copy_unaligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsC
     typedef __bit_iterator<_Cp, _IsConst> _In;
     typedef  typename _In::difference_type difference_type;
     typedef typename _In::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _In::__bits_per_word;
+    static const int __bits_per_word = _In::__bits_per_word;
     difference_type __n = __last - __first;
     if (__n > 0)
     {
@@ -551,7 +546,7 @@ __copy_backward_aligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_C
     typedef __bit_iterator<_Cp, _IsConst> _In;
     typedef  typename _In::difference_type difference_type;
     typedef typename _In::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _In::__bits_per_word;
+    const int __bits_per_word = _In::__bits_per_word;
     difference_type __n = __last - __first;
     if (__n > 0)
     {
@@ -600,7 +595,7 @@ __copy_backward_unaligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<
     typedef __bit_iterator<_Cp, _IsConst> _In;
     typedef  typename _In::difference_type difference_type;
     typedef typename _In::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _In::__bits_per_word;
+    const int __bits_per_word = _In::__bits_per_word;
     difference_type __n = __last - __first;
     if (__n > 0)
     {
@@ -718,7 +713,7 @@ __swap_ranges_aligned(__bit_iterator<__C1, false> __first, __bit_iterator<__C1,
     typedef __bit_iterator<__C1, false> _I1;
     typedef  typename _I1::difference_type difference_type;
     typedef typename _I1::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _I1::__bits_per_word;
+    const int __bits_per_word = _I1::__bits_per_word;
     difference_type __n = __last - __first;
     if (__n > 0)
     {
@@ -768,7 +763,7 @@ __swap_ranges_unaligned(__bit_iterator<__C1, false> __first, __bit_iterator<__C1
     typedef __bit_iterator<__C1, false> _I1;
     typedef  typename _I1::difference_type difference_type;
     typedef typename _I1::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _I1::__bits_per_word;
+    const int __bits_per_word = _I1::__bits_per_word;
     difference_type __n = __last - __first;
     if (__n > 0)
     {
@@ -959,7 +954,7 @@ __equal_unaligned(__bit_iterator<_Cp, _IC1> __first1, __bit_iterator<_Cp, _IC1>
     typedef __bit_iterator<_Cp, _IC1> _It;
     typedef  typename _It::difference_type difference_type;
     typedef typename _It::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    static const int __bits_per_word = _It::__bits_per_word;
     difference_type __n = __last1 - __first1;
     if (__n > 0)
     {
@@ -1041,7 +1036,7 @@ __equal_aligned(__bit_iterator<_Cp, _IC1> __first1, __bit_iterator<_Cp, _IC1> __
     typedef __bit_iterator<_Cp, _IC1> _It;
     typedef  typename _It::difference_type difference_type;
     typedef typename _It::__storage_type __storage_type;
-    static const unsigned __bits_per_word = _It::__bits_per_word;
+    static const int __bits_per_word = _It::__bits_per_word;
     difference_type __n = __last1 - __first1;
     if (__n > 0)
     {
@@ -1221,11 +1216,8 @@ private:
     __bit_iterator(__storage_pointer __s, unsigned __ctz) _NOEXCEPT
         : __seg_(__s), __ctz_(__ctz) {}
 
-#if defined(__clang__) || defined(__IBMCPP__) || defined(_LIBCPP_MSVC)
     friend typename _Cp::__self;
-#else
-    friend class _Cp::__self;
-#endif
+
     friend class __bit_reference<_Cp>;
     friend class __bit_const_reference<_Cp>;
     friend class __bit_iterator<_Cp, true>;
@@ -1283,4 +1275,6 @@ private:
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP___BIT_REFERENCE
diff --git a/lib/libcxx/include/__bsd_locale_defaults.h b/lib/libcxx/include/__bsd_locale_defaults.h
index f315ca2949e..cbc407d1030 100644
--- a/lib/libcxx/include/__bsd_locale_defaults.h
+++ b/lib/libcxx/include/__bsd_locale_defaults.h
@@ -15,6 +15,10 @@
 #ifndef _LIBCPP_BSD_LOCALE_DEFAULTS_H
 #define _LIBCPP_BSD_LOCALE_DEFAULTS_H
 
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
 #define __libcpp_mb_cur_max_l(loc)                          MB_CUR_MAX_L(loc)
 #define __libcpp_btowc_l(ch, loc)                           btowc_l(ch, loc)
 #define __libcpp_wctob_l(wch, loc)                          wctob_l(wch, loc)
diff --git a/lib/libcxx/include/__bsd_locale_fallbacks.h b/lib/libcxx/include/__bsd_locale_fallbacks.h
index cbc8ad226fd..5e9e0948307 100644
--- a/lib/libcxx/include/__bsd_locale_fallbacks.h
+++ b/lib/libcxx/include/__bsd_locale_fallbacks.h
@@ -15,31 +15,33 @@
 #define _LIBCPP_BSD_LOCALE_FALLBACKS_DEFAULTS_H
 
 #include <stdlib.h>
+#include <stdarg.h>
 #include <memory>
 
-_LIBCPP_BEGIN_NAMESPACE_STD
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
 
-typedef _VSTD::remove_pointer<locale_t>::type __use_locale_struct;
-typedef _VSTD::unique_ptr<__use_locale_struct, decltype(&uselocale)> __locale_raii;
+_LIBCPP_BEGIN_NAMESPACE_STD
 
 inline _LIBCPP_ALWAYS_INLINE
 decltype(MB_CUR_MAX) __libcpp_mb_cur_max_l(locale_t __l)
 {
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     return MB_CUR_MAX;
 }
 
 inline _LIBCPP_ALWAYS_INLINE
 wint_t __libcpp_btowc_l(int __c, locale_t __l)
 {
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     return btowc(__c);
 }
 
 inline _LIBCPP_ALWAYS_INLINE
 int __libcpp_wctob_l(wint_t __c, locale_t __l)
 {
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     return wctob(__c);
 }
 
@@ -47,14 +49,14 @@ inline _LIBCPP_ALWAYS_INLINE
 size_t __libcpp_wcsnrtombs_l(char *__dest, const wchar_t **__src, size_t __nwc,
                          size_t __len, mbstate_t *__ps, locale_t __l)
 {
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     return wcsnrtombs(__dest, __src, __nwc, __len, __ps);
 }
 
 inline _LIBCPP_ALWAYS_INLINE
 size_t __libcpp_wcrtomb_l(char *__s, wchar_t __wc, mbstate_t *__ps, locale_t __l)
 {
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     return wcrtomb(__s, __wc, __ps);
 }
 
@@ -62,7 +64,7 @@ inline _LIBCPP_ALWAYS_INLINE
 size_t __libcpp_mbsnrtowcs_l(wchar_t * __dest, const char **__src, size_t __nms,
                       size_t __len, mbstate_t *__ps, locale_t __l)
 {
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     return mbsnrtowcs(__dest, __src, __nms, __len, __ps);
 }
 
@@ -70,28 +72,28 @@ inline _LIBCPP_ALWAYS_INLINE
 size_t __libcpp_mbrtowc_l(wchar_t *__pwc, const char *__s, size_t __n,
                    mbstate_t *__ps, locale_t __l)
 {
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     return mbrtowc(__pwc, __s, __n, __ps);
 }
 
 inline _LIBCPP_ALWAYS_INLINE
 int __libcpp_mbtowc_l(wchar_t *__pwc, const char *__pmb, size_t __max, locale_t __l)
 {
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     return mbtowc(__pwc, __pmb, __max);
 }
 
 inline _LIBCPP_ALWAYS_INLINE
 size_t __libcpp_mbrlen_l(const char *__s, size_t __n, mbstate_t *__ps, locale_t __l)
 {
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     return mbrlen(__s, __n, __ps);
 }
 
 inline _LIBCPP_ALWAYS_INLINE
 lconv *__libcpp_localeconv_l(locale_t __l)
 {
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     return localeconv();
 }
 
@@ -99,7 +101,7 @@ inline _LIBCPP_ALWAYS_INLINE
 size_t __libcpp_mbsrtowcs_l(wchar_t *__dest, const char **__src, size_t __len,
                      mbstate_t *__ps, locale_t __l)
 {
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     return mbsrtowcs(__dest, __src, __len, __ps);
 }
 
@@ -107,7 +109,7 @@ inline
 int __libcpp_snprintf_l(char *__s, size_t __n, locale_t __l, const char *__format, ...) {
     va_list __va;
     va_start(__va, __format);
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     int __res = vsnprintf(__s, __n, __format, __va);
     va_end(__va);
     return __res;
@@ -117,7 +119,7 @@ inline
 int __libcpp_asprintf_l(char **__s, locale_t __l, const char *__format, ...) {
     va_list __va;
     va_start(__va, __format);
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     int __res = vasprintf(__s, __format, __va);
     va_end(__va);
     return __res;
@@ -127,7 +129,7 @@ inline
 int __libcpp_sscanf_l(const char *__s, locale_t __l, const char *__format, ...) {
     va_list __va;
     va_start(__va, __format);
-    __locale_raii __current( uselocale(__l), uselocale );
+    __libcpp_locale_guard __current(__l);
     int __res = vsscanf(__s, __format, __va);
     va_end(__va);
     return __res;
diff --git a/lib/libcxx/include/__config_site.in b/lib/libcxx/include/__config_site.in
index 6c2b7bb446d..86418a3e17b 100644
--- a/lib/libcxx/include/__config_site.in
+++ b/lib/libcxx/include/__config_site.in
@@ -12,6 +12,8 @@
 
 #cmakedefine _LIBCPP_ABI_VERSION @_LIBCPP_ABI_VERSION@
 #cmakedefine _LIBCPP_ABI_UNSTABLE
+#cmakedefine _LIBCPP_ABI_FORCE_ITANIUM
+#cmakedefine _LIBCPP_ABI_FORCE_MICROSOFT
 #cmakedefine _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
 #cmakedefine _LIBCPP_HAS_NO_STDIN
 #cmakedefine _LIBCPP_HAS_NO_STDOUT
@@ -20,5 +22,11 @@
 #cmakedefine _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
 #cmakedefine _LIBCPP_HAS_MUSL_LIBC
 #cmakedefine _LIBCPP_HAS_THREAD_API_PTHREAD
+#cmakedefine _LIBCPP_HAS_THREAD_API_EXTERNAL
+#cmakedefine _LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL
+#cmakedefine _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS
+#cmakedefine _LIBCPP_NO_VCRUNTIME
+
+@_LIBCPP_ABI_DEFINES@
 
 #endif // _LIBCPP_CONFIG_SITE
diff --git a/lib/libcxx/include/__debug b/lib/libcxx/include/__debug
index a21f9a89884..d01bacdf7ed 100644
--- a/lib/libcxx/include/__debug
+++ b/lib/libcxx/include/__debug
@@ -17,23 +17,103 @@
 #pragma GCC system_header
 #endif
 
-#if _LIBCPP_DEBUG_LEVEL >= 1
+#if defined(_LIBCPP_HAS_NO_NULLPTR)
+# include <cstddef>
+#endif
+
+#if _LIBCPP_DEBUG_LEVEL >= 1 || defined(_LIBCPP_BUILDING_LIBRARY)
 #   include <cstdlib>
 #   include <cstdio>
 #   include <cstddef>
-#   ifndef _LIBCPP_ASSERT
-#      define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : (_VSTD::fprintf(stderr, "%s\n", m), _VSTD::abort()))
-#   endif
+#   include <exception>
+#endif
+
+#if _LIBCPP_DEBUG_LEVEL >= 1 && !defined(_LIBCPP_ASSERT)
+# define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : \
+  _VSTD::__libcpp_debug_function(_VSTD::__libcpp_debug_info(__FILE__, __LINE__, #x, m)))
+#endif
+
+#if _LIBCPP_DEBUG_LEVEL >= 2
+#ifndef _LIBCPP_DEBUG_ASSERT
+#define _LIBCPP_DEBUG_ASSERT(x, m) _LIBCPP_ASSERT(x, m)
+#endif
+#define _LIBCPP_DEBUG_MODE(...) __VA_ARGS__
 #endif
 
 #ifndef _LIBCPP_ASSERT
 #   define _LIBCPP_ASSERT(x, m) ((void)0)
 #endif
+#ifndef _LIBCPP_DEBUG_ASSERT
+#   define _LIBCPP_DEBUG_ASSERT(x, m) ((void)0)
+#endif
+#ifndef _LIBCPP_DEBUG_MODE
+#define _LIBCPP_DEBUG_MODE(...) ((void)0)
+#endif
 
-#if _LIBCPP_DEBUG_LEVEL >= 2
+#if _LIBCPP_DEBUG_LEVEL < 1
+class _LIBCPP_EXCEPTION_ABI __libcpp_debug_exception;
+#endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+struct _LIBCPP_TEMPLATE_VIS __libcpp_debug_info {
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+  __libcpp_debug_info()
+      : __file_(nullptr), __line_(-1), __pred_(nullptr), __msg_(nullptr) {}
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+  __libcpp_debug_info(const char* __f, int __l, const char* __p, const char* __m)
+    : __file_(__f), __line_(__l), __pred_(__p), __msg_(__m) {}
+  const char* __file_;
+  int __line_;
+  const char* __pred_;
+  const char* __msg_;
+};
+
+/// __libcpp_debug_function_type - The type of the assertion failure handler.
+typedef void(*__libcpp_debug_function_type)(__libcpp_debug_info const&);
+
+/// __libcpp_debug_function - The handler function called when a _LIBCPP_ASSERT
+///    fails.
+extern _LIBCPP_EXTERN_VIS __libcpp_debug_function_type __libcpp_debug_function;
+
+/// __libcpp_abort_debug_function - A debug handler that aborts when called.
+_LIBCPP_NORETURN _LIBCPP_FUNC_VIS
+void __libcpp_abort_debug_function(__libcpp_debug_info const&);
+
+/// __libcpp_throw_debug_function - A debug handler that throws
+///   an instance of __libcpp_debug_exception when called.
+ _LIBCPP_NORETURN _LIBCPP_FUNC_VIS
+void __libcpp_throw_debug_function(__libcpp_debug_info const&);
+
+/// __libcpp_set_debug_function - Set the debug handler to the specified
+///    function.
+_LIBCPP_FUNC_VIS
+bool __libcpp_set_debug_function(__libcpp_debug_function_type __func);
+
+// Setup the throwing debug handler during dynamic initialization.
+#if _LIBCPP_DEBUG_LEVEL >= 1 && defined(_LIBCPP_DEBUG_USE_EXCEPTIONS)
+# if defined(_LIBCPP_NO_EXCEPTIONS)
+#   error _LIBCPP_DEBUG_USE_EXCEPTIONS cannot be used when exceptions are disabled.
+# endif
+static bool __init_dummy = __libcpp_set_debug_function(__libcpp_throw_debug_function);
+#endif
+
+#if _LIBCPP_DEBUG_LEVEL >= 1 || defined(_LIBCPP_BUILDING_LIBRARY)
+class _LIBCPP_EXCEPTION_ABI __libcpp_debug_exception : public exception {
+public:
+  __libcpp_debug_exception() _NOEXCEPT;
+  explicit __libcpp_debug_exception(__libcpp_debug_info const& __i);
+  __libcpp_debug_exception(__libcpp_debug_exception const&);
+  ~__libcpp_debug_exception() _NOEXCEPT;
+  const char* what() const _NOEXCEPT;
+private:
+  struct __libcpp_debug_exception_imp;
+  __libcpp_debug_exception_imp *__imp_;
+};
+#endif
+
+#if _LIBCPP_DEBUG_LEVEL >= 2 || defined(_LIBCPP_BUILDING_LIBRARY)
+
 struct _LIBCPP_TYPE_VIS __c_node;
 
 struct _LIBCPP_TYPE_VIS __i_node
@@ -42,7 +122,7 @@ struct _LIBCPP_TYPE_VIS __i_node
     __i_node* __next_;
     __c_node* __c_;
 
-#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+#ifndef _LIBCPP_CXX03_LANG
     __i_node(const __i_node&) = delete;
     __i_node& operator=(const __i_node&) = delete;
 #else
@@ -65,7 +145,7 @@ struct _LIBCPP_TYPE_VIS __c_node
     __i_node** end_;
     __i_node** cap_;
 
-#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+#ifndef _LIBCPP_CXX03_LANG
     __c_node(const __c_node&) = delete;
     __c_node& operator=(const __c_node&) = delete;
 #else
@@ -102,7 +182,7 @@ struct _C_node
 };
 
 template <class _Cont>
-bool
+inline bool
 _C_node<_Cont>::__dereferenceable(const void* __i) const
 {
     typedef typename _Cont::const_iterator iterator;
@@ -112,7 +192,7 @@ _C_node<_Cont>::__dereferenceable(const void* __i) const
 }
 
 template <class _Cont>
-bool
+inline bool
 _C_node<_Cont>::__decrementable(const void* __i) const
 {
     typedef typename _Cont::const_iterator iterator;
@@ -122,7 +202,7 @@ _C_node<_Cont>::__decrementable(const void* __i) const
 }
 
 template <class _Cont>
-bool
+inline bool
 _C_node<_Cont>::__addable(const void* __i, ptrdiff_t __n) const
 {
     typedef typename _Cont::const_iterator iterator;
@@ -132,7 +212,7 @@ _C_node<_Cont>::__addable(const void* __i, ptrdiff_t __n) const
 }
 
 template <class _Cont>
-bool
+inline bool
 _C_node<_Cont>::__subscriptable(const void* __i, ptrdiff_t __n) const
 {
     typedef typename _Cont::const_iterator iterator;
@@ -152,7 +232,7 @@ class _LIBCPP_TYPE_VIS __libcpp_db
 
     __libcpp_db();
 public:
-#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+#ifndef _LIBCPP_CXX03_LANG
     __libcpp_db(const __libcpp_db&) = delete;
     __libcpp_db& operator=(const __libcpp_db&) = delete;
 #else
@@ -214,9 +294,9 @@ _LIBCPP_FUNC_VIS __libcpp_db* __get_db();
 _LIBCPP_FUNC_VIS const __libcpp_db* __get_const_db();
 
 
-_LIBCPP_END_NAMESPACE_STD
+#endif // _LIBCPP_DEBUG_LEVEL >= 2 || defined(_LIBCPP_BUILDING_LIBRARY)
 
-#endif
+_LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_DEBUG_H
 
diff --git a/lib/libcxx/include/__functional_03 b/lib/libcxx/include/__functional_03
index 4edbb0996ca..13d8a3d9600 100644
--- a/lib/libcxx/include/__functional_03
+++ b/lib/libcxx/include/__functional_03
@@ -445,7 +445,7 @@ __func<_Fp, _Alloc, _Rp(_A0, _A1, _A2)>::target_type() const
 }  // __function
 
 template<class _Rp>
-class _LIBCPP_TYPE_VIS_ONLY function<_Rp()>
+class _LIBCPP_TEMPLATE_VIS function<_Rp()>
 {
     typedef __function::__base<_Rp()> __base;
     aligned_storage<3*sizeof(void*)>::type __buf_;
@@ -642,6 +642,8 @@ template<class _Rp>
 void
 function<_Rp()>::swap(function& __f)
 {
+    if (_VSTD::addressof(__f) == this)
+      return;
     if (__f_ == (__base*)&__buf_ && __f.__f_ == (__base*)&__f.__buf_)
     {
         typename aligned_storage<sizeof(__buf_)>::type __tempbuf;
@@ -679,10 +681,8 @@ template<class _Rp>
 _Rp
 function<_Rp()>::operator()() const
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__f_ == 0)
-        throw bad_function_call();
-#endif  // _LIBCPP_NO_EXCEPTIONS
+        __throw_bad_function_call();
     return (*__f_)();
 }
 
@@ -704,7 +704,7 @@ function<_Rp()>::target()
 {
     if (__f_ == 0)
         return (_Tp*)0;
-    return (_Tp*)__f_->target(typeid(_Tp));
+    return (_Tp*) const_cast<void *>(__f_->target(typeid(_Tp)));
 }
 
 template<class _Rp>
@@ -720,7 +720,7 @@ function<_Rp()>::target() const
 #endif  // _LIBCPP_NO_RTTI
 
 template<class _Rp, class _A0>
-class _LIBCPP_TYPE_VIS_ONLY function<_Rp(_A0)>
+class _LIBCPP_TEMPLATE_VIS function<_Rp(_A0)>
     : public unary_function<_A0, _Rp>
 {
     typedef __function::__base<_Rp(_A0)> __base;
@@ -918,6 +918,8 @@ template<class _Rp, class _A0>
 void
 function<_Rp(_A0)>::swap(function& __f)
 {
+    if (_VSTD::addressof(__f) == this)
+      return;
     if (__f_ == (__base*)&__buf_ && __f.__f_ == (__base*)&__f.__buf_)
     {
         typename aligned_storage<sizeof(__buf_)>::type __tempbuf;
@@ -955,10 +957,8 @@ template<class _Rp, class _A0>
 _Rp
 function<_Rp(_A0)>::operator()(_A0 __a0) const
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__f_ == 0)
-        throw bad_function_call();
-#endif  // _LIBCPP_NO_EXCEPTIONS
+        __throw_bad_function_call();
     return (*__f_)(__a0);
 }
 
@@ -980,7 +980,7 @@ function<_Rp(_A0)>::target()
 {
     if (__f_ == 0)
         return (_Tp*)0;
-    return (_Tp*)__f_->target(typeid(_Tp));
+    return (_Tp*) const_cast<void *>(__f_->target(typeid(_Tp)));
 }
 
 template<class _Rp, class _A0>
@@ -996,7 +996,7 @@ function<_Rp(_A0)>::target() const
 #endif  // _LIBCPP_NO_RTTI
 
 template<class _Rp, class _A0, class _A1>
-class _LIBCPP_TYPE_VIS_ONLY function<_Rp(_A0, _A1)>
+class _LIBCPP_TEMPLATE_VIS function<_Rp(_A0, _A1)>
     : public binary_function<_A0, _A1, _Rp>
 {
     typedef __function::__base<_Rp(_A0, _A1)> __base;
@@ -1194,6 +1194,8 @@ template<class _Rp, class _A0, class _A1>
 void
 function<_Rp(_A0, _A1)>::swap(function& __f)
 {
+    if (_VSTD::addressof(__f) == this)
+      return;
     if (__f_ == (__base*)&__buf_ && __f.__f_ == (__base*)&__f.__buf_)
     {
         typename aligned_storage<sizeof(__buf_)>::type __tempbuf;
@@ -1231,10 +1233,8 @@ template<class _Rp, class _A0, class _A1>
 _Rp
 function<_Rp(_A0, _A1)>::operator()(_A0 __a0, _A1 __a1) const
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__f_ == 0)
-        throw bad_function_call();
-#endif  // _LIBCPP_NO_EXCEPTIONS
+        __throw_bad_function_call();
     return (*__f_)(__a0, __a1);
 }
 
@@ -1256,7 +1256,7 @@ function<_Rp(_A0, _A1)>::target()
 {
     if (__f_ == 0)
         return (_Tp*)0;
-    return (_Tp*)__f_->target(typeid(_Tp));
+    return (_Tp*) const_cast<void *>(__f_->target(typeid(_Tp)));
 }
 
 template<class _Rp, class _A0, class _A1>
@@ -1272,7 +1272,7 @@ function<_Rp(_A0, _A1)>::target() const
 #endif  // _LIBCPP_NO_RTTI
 
 template<class _Rp, class _A0, class _A1, class _A2>
-class _LIBCPP_TYPE_VIS_ONLY function<_Rp(_A0, _A1, _A2)>
+class _LIBCPP_TEMPLATE_VIS function<_Rp(_A0, _A1, _A2)>
 {
     typedef __function::__base<_Rp(_A0, _A1, _A2)> __base;
     aligned_storage<3*sizeof(void*)>::type __buf_;
@@ -1470,6 +1470,8 @@ template<class _Rp, class _A0, class _A1, class _A2>
 void
 function<_Rp(_A0, _A1, _A2)>::swap(function& __f)
 {
+    if (_VSTD::addressof(__f) == this)
+      return;
     if (__f_ == (__base*)&__buf_ && __f.__f_ == (__base*)&__f.__buf_)
     {
         typename aligned_storage<sizeof(__buf_)>::type __tempbuf;
@@ -1507,10 +1509,8 @@ template<class _Rp, class _A0, class _A1, class _A2>
 _Rp
 function<_Rp(_A0, _A1, _A2)>::operator()(_A0 __a0, _A1 __a1, _A2 __a2) const
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__f_ == 0)
-        throw bad_function_call();
-#endif  // _LIBCPP_NO_EXCEPTIONS
+        __throw_bad_function_call();
     return (*__f_)(__a0, __a1, __a2);
 }
 
@@ -1532,7 +1532,7 @@ function<_Rp(_A0, _A1, _A2)>::target()
 {
     if (__f_ == 0)
         return (_Tp*)0;
-    return (_Tp*)__f_->target(typeid(_Tp));
+    return (_Tp*) const_cast<void *>(__f_->target(typeid(_Tp)));
 }
 
 template<class _Rp, class _A0, class _A1, class _A2>
diff --git a/lib/libcxx/include/__functional_base b/lib/libcxx/include/__functional_base
index 1a08ea29dee..12af4dc9675 100644
--- a/lib/libcxx/include/__functional_base
+++ b/lib/libcxx/include/__functional_base
@@ -16,6 +16,7 @@
 #include <typeinfo>
 #include <exception>
 #include <new>
+#include <utility>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
@@ -23,15 +24,8 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Arg, class _Result>
-struct _LIBCPP_TYPE_VIS_ONLY unary_function
-{
-    typedef _Arg    argument_type;
-    typedef _Result result_type;
-};
-
 template <class _Arg1, class _Arg2, class _Result>
-struct _LIBCPP_TYPE_VIS_ONLY binary_function
+struct _LIBCPP_TEMPLATE_VIS binary_function
 {
     typedef _Arg1   first_argument_type;
     typedef _Arg2   second_argument_type;
@@ -54,7 +48,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY less : binary_function<_Tp, _Tp, bool>
+struct _LIBCPP_TEMPLATE_VIS less : binary_function<_Tp, _Tp, bool>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY 
     bool operator()(const _Tp& __x, const _Tp& __y) const
@@ -63,7 +57,7 @@ struct _LIBCPP_TYPE_VIS_ONLY less : binary_function<_Tp, _Tp, bool>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY less<void>
+struct _LIBCPP_TEMPLATE_VIS less<void>
 {
     template <class _T1, class _T2> 
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -257,7 +251,7 @@ struct __weak_result_type<_Rp (_Cp::*)(_A1) const volatile>
 };
 
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 // 3 or more arguments
 
 template <class _Rp, class _A1, class _A2, class _A3, class ..._A4>
@@ -302,10 +296,6 @@ struct __weak_result_type<_Rp (_Cp::*)(_A1, _A2, _A3...) const volatile>
     typedef _Rp result_type;
 };
 
-#endif // _LIBCPP_HAS_NO_VARIADICS
-
-#ifndef _LIBCPP_CXX03_LANG
-
 template <class _Tp, class ..._Args>
 struct __invoke_return
 {
@@ -322,7 +312,7 @@ struct __invoke_return
 template <class _Ret>
 struct __invoke_void_return_wrapper
 {
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
     template <class ..._Args>
     static _Ret __call(_Args&&... __args) {
         return __invoke(_VSTD::forward<_Args>(__args)...);
@@ -353,7 +343,7 @@ struct __invoke_void_return_wrapper
 template <>
 struct __invoke_void_return_wrapper<void>
 {
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
     template <class ..._Args>
     static void __call(_Args&&... __args) {
         __invoke(_VSTD::forward<_Args>(__args)...);
@@ -382,7 +372,7 @@ struct __invoke_void_return_wrapper<void>
 };
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY reference_wrapper
+class _LIBCPP_TEMPLATE_VIS reference_wrapper
     : public __weak_result_type<_Tp>
 {
 public:
@@ -395,7 +385,7 @@ public:
     // construct/copy/destroy
     _LIBCPP_INLINE_VISIBILITY reference_wrapper(type& __f) _NOEXCEPT
         : __f_(_VSTD::addressof(__f)) {}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     private: reference_wrapper(type&&); public: // = delete; // do not bind to temps
 #endif
 
@@ -403,7 +393,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY operator type&    () const _NOEXCEPT {return *__f_;}
     _LIBCPP_INLINE_VISIBILITY          type& get() const _NOEXCEPT {return *__f_;}
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
     // invoke
     template <class... _ArgTypes>
     _LIBCPP_INLINE_VISIBILITY
@@ -516,7 +506,7 @@ public:
     operator() (_A0 const& __a0, _A1 const& __a1, _A2 const& __a2) const {
         return __invoke(get(), __a0, __a1, __a2);
     }
-#endif // _LIBCPP_HAS_NO_VARIADICS
+#endif // _LIBCPP_CXX03_LANG
 };
 
 
@@ -552,45 +542,29 @@ cref(reference_wrapper<_Tp> __t) _NOEXCEPT
     return cref(__t.get());
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
-
+#ifndef _LIBCPP_CXX03_LANG
 template <class _Tp> void ref(const _Tp&&) = delete;
 template <class _Tp> void cref(const _Tp&&) = delete;
-
-#else  // _LIBCPP_HAS_NO_DELETED_FUNCTIONS
-
-template <class _Tp> void ref(const _Tp&&);// = delete;
-template <class _Tp> void cref(const _Tp&&);// = delete;
-
-#endif  // _LIBCPP_HAS_NO_DELETED_FUNCTIONS
-
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+#endif
 
 #if _LIBCPP_STD_VER > 11
-template <class _Tp1, class _Tp2 = void>
-struct __is_transparent
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::is_transparent* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp1>(0)) == 1;
-};
+template <class _Tp, class, class = void>
+struct __is_transparent : false_type {};
+
+template <class _Tp, class _Up>
+struct __is_transparent<_Tp, _Up,  
+                        typename __void_t<typename _Tp::is_transparent>::type>
+   : true_type {};
 #endif
 
 // allocator_arg_t
 
-struct _LIBCPP_TYPE_VIS_ONLY allocator_arg_t { };
+struct _LIBCPP_TEMPLATE_VIS allocator_arg_t { };
 
-#if defined(_LIBCPP_HAS_NO_CONSTEXPR) || defined(_LIBCPP_BUILDING_MEMORY)
+#if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_MEMORY)
 extern const allocator_arg_t allocator_arg;
 #else
-constexpr allocator_arg_t allocator_arg = allocator_arg_t();
+/* _LIBCPP_INLINE_VAR */ constexpr allocator_arg_t allocator_arg = allocator_arg_t();
 #endif
 
 // uses_allocator
@@ -620,19 +594,25 @@ struct __uses_allocator<_Tp, _Alloc, false>
 };
 
 template <class _Tp, class _Alloc>
-struct _LIBCPP_TYPE_VIS_ONLY uses_allocator
+struct _LIBCPP_TEMPLATE_VIS uses_allocator
     : public __uses_allocator<_Tp, _Alloc>
 {
 };
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#if _LIBCPP_STD_VER > 14
+template <class _Tp, class _Alloc>
+_LIBCPP_INLINE_VAR constexpr size_t uses_allocator_v = uses_allocator<_Tp, _Alloc>::value;
+#endif
+
+#ifndef _LIBCPP_CXX03_LANG
 
 // allocator construction
 
 template <class _Tp, class _Alloc, class ..._Args>
 struct __uses_alloc_ctor_imp
 {
-    static const bool __ua = uses_allocator<_Tp, _Alloc>::value;
+    typedef typename __uncvref<_Alloc>::type _RawAlloc;
+    static const bool __ua = uses_allocator<_Tp, _RawAlloc>::value;
     static const bool __ic =
         is_constructible<_Tp, allocator_arg_t, _Alloc, _Args...>::value;
     static const int value = __ua ? 2 - __ic : 0;
@@ -650,6 +630,7 @@ void __user_alloc_construct_impl (integral_constant<int, 0>, _Tp *__storage, con
     new (__storage) _Tp (_VSTD::forward<_Args>(__args)...);
 }
 
+// FIXME: This should have a version which takes a non-const alloc.
 template <class _Tp, class _Allocator, class... _Args>
 inline _LIBCPP_INLINE_VISIBILITY
 void __user_alloc_construct_impl (integral_constant<int, 1>, _Tp *__storage, const _Allocator &__a, _Args &&... __args )
@@ -657,6 +638,7 @@ void __user_alloc_construct_impl (integral_constant<int, 1>, _Tp *__storage, con
     new (__storage) _Tp (allocator_arg, __a, _VSTD::forward<_Args>(__args)...);
 }
 
+// FIXME: This should have a version which takes a non-const alloc.
 template <class _Tp, class _Allocator, class... _Args>
 inline _LIBCPP_INLINE_VISIBILITY
 void __user_alloc_construct_impl (integral_constant<int, 2>, _Tp *__storage, const _Allocator &__a, _Args &&... __args )
@@ -664,6 +646,7 @@ void __user_alloc_construct_impl (integral_constant<int, 2>, _Tp *__storage, con
     new (__storage) _Tp (_VSTD::forward<_Args>(__args)..., __a);
 }
 
+// FIXME: Theis should have a version which takes a non-const alloc.
 template <class _Tp, class _Allocator, class... _Args>
 inline _LIBCPP_INLINE_VISIBILITY
 void __user_alloc_construct (_Tp *__storage, const _Allocator &__a, _Args &&... __args)
@@ -673,7 +656,7 @@ void __user_alloc_construct (_Tp *__storage, const _Allocator &__a, _Args &&...
              __storage, __a, _VSTD::forward<_Args>(__args)...
         );
 }
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+#endif  // _LIBCPP_CXX03_LANG
 
 _LIBCPP_END_NAMESPACE_STD
 
diff --git a/lib/libcxx/include/__hash_table b/lib/libcxx/include/__hash_table
index 08bc519ae17..3f430af1283 100644
--- a/lib/libcxx/include/__hash_table
+++ b/lib/libcxx/include/__hash_table
@@ -18,9 +18,7 @@
 #include <algorithm>
 #include <cmath>
 #include <utility>
-
-#include <__undef_min_max>
-#include <__undef___deallocate>
+#include <type_traits>
 
 #include <__debug>
 
@@ -28,9 +26,12 @@
 #pragma GCC system_header
 #endif
 
-_LIBCPP_BEGIN_NAMESPACE_STD
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
 
 
+_LIBCPP_BEGIN_NAMESPACE_STD
+
 #ifndef _LIBCPP_CXX03_LANG
 template <class _Key, class _Tp>
 union __hash_value_type;
@@ -39,6 +40,15 @@ template <class _Key, class _Tp>
 struct __hash_value_type;
 #endif
 
+template <class _Key, class _Cp, class _Hash,
+          bool =  is_empty<_Hash>::value && !__libcpp_is_final<_Hash>::value>
+class __unordered_map_hasher;
+
+template <class _Key, class _Cp, class _Pred,
+          bool = is_empty<_Pred>::value && !__libcpp_is_final<_Pred>::value
+         >
+class __unordered_map_equal;
+
 #ifndef _LIBCPP_CXX03_LANG
 template <class _Tp>
 struct __is_hash_value_type_imp : false_type {};
@@ -59,9 +69,38 @@ size_t __next_prime(size_t __n);
 template <class _NodePtr>
 struct __hash_node_base
 {
+    typedef typename pointer_traits<_NodePtr>::element_type __node_type;
     typedef __hash_node_base __first_node;
+    typedef typename __rebind_pointer<_NodePtr, __first_node>::type __node_base_pointer;
+    typedef _NodePtr __node_pointer;
+
+#if defined(_LIBCPP_ABI_FIX_UNORDERED_NODE_POINTER_UB)
+  typedef __node_base_pointer __next_pointer;
+#else
+  typedef typename conditional<
+      is_pointer<__node_pointer>::value,
+      __node_base_pointer,
+      __node_pointer>::type   __next_pointer;
+#endif
+
+    __next_pointer    __next_;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __next_pointer __ptr() _NOEXCEPT {
+        return static_cast<__next_pointer>(
+            pointer_traits<__node_base_pointer>::pointer_to(*this));
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __node_pointer __upcast() _NOEXCEPT {
+        return static_cast<__node_pointer>(
+            pointer_traits<__node_base_pointer>::pointer_to(*this));
+    }
 
-    _NodePtr    __next_;
+    _LIBCPP_INLINE_VISIBILITY
+    size_t __hash() const _NOEXCEPT {
+        return static_cast<__node_type const&>(*this).__hash_;
+    }
 
     _LIBCPP_INLINE_VISIBILITY __hash_node_base() _NOEXCEPT : __next_(nullptr) {}
 };
@@ -75,7 +114,7 @@ struct __hash_node
 {
     typedef _Tp __node_value_type;
 
-    size_t     __hash_;
+    size_t            __hash_;
     __node_value_type __value_;
 };
 
@@ -98,18 +137,18 @@ inline _LIBCPP_INLINE_VISIBILITY
 size_t
 __next_hash_pow2(size_t __n)
 {
-    return size_t(1) << (std::numeric_limits<size_t>::digits - __clz(__n-1));
+    return __n < 2 ? __n : (size_t(1) << (std::numeric_limits<size_t>::digits - __clz(__n-1)));
 }
 
 
 template <class _Tp, class _Hash, class _Equal, class _Alloc> class __hash_table;
 
-template <class _NodePtr>      class _LIBCPP_TYPE_VIS_ONLY __hash_iterator;
-template <class _ConstNodePtr> class _LIBCPP_TYPE_VIS_ONLY __hash_const_iterator;
-template <class _NodePtr>      class _LIBCPP_TYPE_VIS_ONLY __hash_local_iterator;
-template <class _ConstNodePtr> class _LIBCPP_TYPE_VIS_ONLY __hash_const_local_iterator;
-template <class _HashIterator> class _LIBCPP_TYPE_VIS_ONLY __hash_map_iterator;
-template <class _HashIterator> class _LIBCPP_TYPE_VIS_ONLY __hash_map_const_iterator;
+template <class _NodePtr>      class _LIBCPP_TEMPLATE_VIS __hash_iterator;
+template <class _ConstNodePtr> class _LIBCPP_TEMPLATE_VIS __hash_const_iterator;
+template <class _NodePtr>      class _LIBCPP_TEMPLATE_VIS __hash_local_iterator;
+template <class _ConstNodePtr> class _LIBCPP_TEMPLATE_VIS __hash_const_local_iterator;
+template <class _HashIterator> class _LIBCPP_TEMPLATE_VIS __hash_map_iterator;
+template <class _HashIterator> class _LIBCPP_TEMPLATE_VIS __hash_map_const_iterator;
 
 template <class _Tp>
 struct __hash_key_value_types {
@@ -219,11 +258,14 @@ public:
   typedef typename __rebind_pointer<_NodePtr, __node_base_type>::type
                                                              __node_base_pointer;
 
+  typedef typename __node_base_type::__next_pointer          __next_pointer;
+
   typedef _Tp                                                 __node_value_type;
   typedef typename __rebind_pointer<_VoidPtr, __node_value_type>::type
                                                       __node_value_type_pointer;
   typedef typename __rebind_pointer<_VoidPtr, const __node_value_type>::type
                                                 __const_node_value_type_pointer;
+
 private:
     static_assert(!is_const<__node_type>::value,
                 "_NodePtr should never be a pointer to const");
@@ -233,8 +275,6 @@ private:
                           _NodePtr>::value), "_VoidPtr does not rebind to _NodePtr.");
 };
 
-
-
 template <class _HashIterator>
 struct __hash_node_types_from_iterator;
 template <class _NodePtr>
@@ -255,12 +295,13 @@ struct __make_hash_node_types {
 };
 
 template <class _NodePtr>
-class _LIBCPP_TYPE_VIS_ONLY __hash_iterator
+class _LIBCPP_TEMPLATE_VIS __hash_iterator
 {
     typedef __hash_node_types<_NodePtr> _NodeTypes;
-    typedef _NodePtr                    __node_pointer;
+    typedef _NodePtr                            __node_pointer;
+    typedef typename _NodeTypes::__next_pointer __next_pointer;
 
-    __node_pointer            __node_;
+    __next_pointer            __node_;
 
 public:
     typedef forward_iterator_tag                           iterator_category;
@@ -269,18 +310,11 @@ public:
     typedef value_type&                                    reference;
     typedef typename _NodeTypes::__node_value_type_pointer pointer;
 
-    _LIBCPP_INLINE_VISIBILITY __hash_iterator() _NOEXCEPT
-#if _LIBCPP_STD_VER > 11
-    : __node_(nullptr)
-#endif
-    {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-        __get_db()->__insert_i(this);
-#endif
+    _LIBCPP_INLINE_VISIBILITY __hash_iterator() _NOEXCEPT : __node_(nullptr) {
+        _LIBCPP_DEBUG_MODE(__get_db()->__insert_i(this));
     }
 
 #if _LIBCPP_DEBUG_LEVEL >= 2
-
     _LIBCPP_INLINE_VISIBILITY
     __hash_iterator(const __hash_iterator& __i)
         : __node_(__i.__node_)
@@ -304,35 +338,26 @@ public:
         }
         return *this;
     }
-
 #endif  // _LIBCPP_DEBUG_LEVEL >= 2
 
     _LIBCPP_INLINE_VISIBILITY
-        reference operator*() const
-        {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-            _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
-                           "Attempted to dereference a non-dereferenceable unordered container iterator");
-#endif
-            return __node_->__value_;
-        }
+    reference operator*() const {
+        _LIBCPP_DEBUG_ASSERT(__get_const_db()->__dereferenceable(this),
+                             "Attempted to dereference a non-dereferenceable unordered container iterator");
+        return __node_->__upcast()->__value_;
+    }
+
     _LIBCPP_INLINE_VISIBILITY
-        pointer operator->() const
-        {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-            _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
+    pointer operator->() const {
+        _LIBCPP_DEBUG_ASSERT(__get_const_db()->__dereferenceable(this),
                            "Attempted to dereference a non-dereferenceable unordered container iterator");
-#endif
-            return pointer_traits<pointer>::pointer_to(__node_->__value_);
-        }
+        return pointer_traits<pointer>::pointer_to(__node_->__upcast()->__value_);
+    }
 
     _LIBCPP_INLINE_VISIBILITY
-    __hash_iterator& operator++()
-    {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-        _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
+    __hash_iterator& operator++() {
+        _LIBCPP_DEBUG_ASSERT(__get_const_db()->__dereferenceable(this),
                        "Attempted to increment non-incrementable unordered container iterator");
-#endif
         __node_ = __node_->__next_;
         return *this;
     }
@@ -357,33 +382,33 @@ public:
 private:
 #if _LIBCPP_DEBUG_LEVEL >= 2
     _LIBCPP_INLINE_VISIBILITY
-    __hash_iterator(__node_pointer __node, const void* __c) _NOEXCEPT
+    __hash_iterator(__next_pointer __node, const void* __c) _NOEXCEPT
         : __node_(__node)
         {
             __get_db()->__insert_ic(this, __c);
         }
 #else
     _LIBCPP_INLINE_VISIBILITY
-    __hash_iterator(__node_pointer __node) _NOEXCEPT
+    __hash_iterator(__next_pointer __node) _NOEXCEPT
         : __node_(__node)
         {}
 #endif
-
     template <class, class, class, class> friend class __hash_table;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_const_iterator;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_map_iterator;
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY unordered_map;
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY unordered_multimap;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_const_iterator;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_map_iterator;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS unordered_map;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS unordered_multimap;
 };
 
 template <class _NodePtr>
-class _LIBCPP_TYPE_VIS_ONLY __hash_const_iterator
+class _LIBCPP_TEMPLATE_VIS __hash_const_iterator
 {
     static_assert(!is_const<typename pointer_traits<_NodePtr>::element_type>::value, "");
     typedef __hash_node_types<_NodePtr> _NodeTypes;
-    typedef _NodePtr __node_pointer;
+    typedef _NodePtr                            __node_pointer;
+    typedef typename _NodeTypes::__next_pointer __next_pointer;
 
-    __node_pointer __node_;
+    __next_pointer __node_;
 
 public:
     typedef __hash_iterator<_NodePtr> __non_const_iterator;
@@ -395,26 +420,18 @@ public:
     typedef typename _NodeTypes::__const_node_value_type_pointer pointer;
 
 
-    _LIBCPP_INLINE_VISIBILITY __hash_const_iterator() _NOEXCEPT
-#if _LIBCPP_STD_VER > 11
-    : __node_(nullptr)
-#endif
-    {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-        __get_db()->__insert_i(this);
-#endif
+    _LIBCPP_INLINE_VISIBILITY __hash_const_iterator() _NOEXCEPT : __node_(nullptr) {
+        _LIBCPP_DEBUG_MODE(__get_db()->__insert_i(this));
     }
+
     _LIBCPP_INLINE_VISIBILITY 
     __hash_const_iterator(const __non_const_iterator& __x) _NOEXCEPT
         : __node_(__x.__node_)
     {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-        __get_db()->__iterator_copy(this, &__x);
-#endif
+        _LIBCPP_DEBUG_MODE(__get_db()->__iterator_copy(this, &__x));
     }
 
 #if _LIBCPP_DEBUG_LEVEL >= 2
-
     _LIBCPP_INLINE_VISIBILITY
     __hash_const_iterator(const __hash_const_iterator& __i)
         : __node_(__i.__node_)
@@ -438,35 +455,25 @@ public:
         }
         return *this;
     }
-
 #endif  // _LIBCPP_DEBUG_LEVEL >= 2
 
     _LIBCPP_INLINE_VISIBILITY
-        reference operator*() const
-        {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-            _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
+    reference operator*() const {
+        _LIBCPP_DEBUG_ASSERT(__get_const_db()->__dereferenceable(this),
                            "Attempted to dereference a non-dereferenceable unordered container const_iterator");
-#endif
-            return __node_->__value_;
-        }
+        return __node_->__upcast()->__value_;
+    }
     _LIBCPP_INLINE_VISIBILITY
-        pointer operator->() const
-        {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-            _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
+    pointer operator->() const {
+        _LIBCPP_DEBUG_ASSERT(__get_const_db()->__dereferenceable(this),
                            "Attempted to dereference a non-dereferenceable unordered container const_iterator");
-#endif
-            return pointer_traits<pointer>::pointer_to(__node_->__value_);
-        }
+        return pointer_traits<pointer>::pointer_to(__node_->__upcast()->__value_);
+    }
 
     _LIBCPP_INLINE_VISIBILITY
-    __hash_const_iterator& operator++()
-    {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-        _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
-                       "Attempted to increment non-incrementable unordered container const_iterator");
-#endif
+    __hash_const_iterator& operator++() {
+        _LIBCPP_DEBUG_ASSERT(__get_const_db()->__dereferenceable(this),
+                             "Attempted to increment non-incrementable unordered container const_iterator");
         __node_ = __node_->__next_;
         return *this;
     }
@@ -491,31 +498,31 @@ public:
 private:
 #if _LIBCPP_DEBUG_LEVEL >= 2
     _LIBCPP_INLINE_VISIBILITY
-    __hash_const_iterator(__node_pointer __node, const void* __c) _NOEXCEPT
+    __hash_const_iterator(__next_pointer __node, const void* __c) _NOEXCEPT
         : __node_(__node)
         {
             __get_db()->__insert_ic(this, __c);
         }
 #else
     _LIBCPP_INLINE_VISIBILITY
-    __hash_const_iterator(__node_pointer __node) _NOEXCEPT
+    __hash_const_iterator(__next_pointer __node) _NOEXCEPT
         : __node_(__node)
         {}
 #endif
-
     template <class, class, class, class> friend class __hash_table;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_map_const_iterator;
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY unordered_map;
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY unordered_multimap;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_map_const_iterator;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS unordered_map;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS unordered_multimap;
 };
 
 template <class _NodePtr>
-class _LIBCPP_TYPE_VIS_ONLY __hash_local_iterator
+class _LIBCPP_TEMPLATE_VIS __hash_local_iterator
 {
     typedef __hash_node_types<_NodePtr> _NodeTypes;
-    typedef _NodePtr                    __node_pointer;
+    typedef _NodePtr                            __node_pointer;
+    typedef typename _NodeTypes::__next_pointer __next_pointer;
 
-    __node_pointer         __node_;
+    __next_pointer         __node_;
     size_t                 __bucket_;
     size_t                 __bucket_count_;
 
@@ -526,15 +533,11 @@ public:
     typedef value_type&                                         reference;
     typedef typename _NodeTypes::__node_value_type_pointer      pointer;
 
-    _LIBCPP_INLINE_VISIBILITY __hash_local_iterator() _NOEXCEPT
-    {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-        __get_db()->__insert_i(this);
-#endif
+    _LIBCPP_INLINE_VISIBILITY __hash_local_iterator() _NOEXCEPT : __node_(nullptr) {
+        _LIBCPP_DEBUG_MODE(__get_db()->__insert_i(this));
     }
 
 #if _LIBCPP_DEBUG_LEVEL >= 2
-
     _LIBCPP_INLINE_VISIBILITY
     __hash_local_iterator(const __hash_local_iterator& __i)
         : __node_(__i.__node_),
@@ -562,37 +565,28 @@ public:
         }
         return *this;
     }
-
 #endif  // _LIBCPP_DEBUG_LEVEL >= 2
 
     _LIBCPP_INLINE_VISIBILITY
-        reference operator*() const
-        {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-            _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
+    reference operator*() const {
+        _LIBCPP_DEBUG_ASSERT(__get_const_db()->__dereferenceable(this),
                            "Attempted to dereference a non-dereferenceable unordered container local_iterator");
-#endif
-            return __node_->__value_;
-        }
+        return __node_->__upcast()->__value_;
+    }
+
     _LIBCPP_INLINE_VISIBILITY
-        pointer operator->() const
-        {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-            _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
-                           "Attempted to dereference a non-dereferenceable unordered container local_iterator");
-#endif
-            return pointer_traits<pointer>::pointer_to(__node_->__value_);
-        }
+    pointer operator->() const {
+        _LIBCPP_DEBUG_ASSERT(__get_const_db()->__dereferenceable(this),
+                             "Attempted to dereference a non-dereferenceable unordered container local_iterator");
+        return pointer_traits<pointer>::pointer_to(__node_->__upcast()->__value_);
+    }
 
     _LIBCPP_INLINE_VISIBILITY
-    __hash_local_iterator& operator++()
-    {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-        _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
+    __hash_local_iterator& operator++() {
+        _LIBCPP_DEBUG_ASSERT(__get_const_db()->__dereferenceable(this),
                        "Attempted to increment non-incrementable unordered container local_iterator");
-#endif
         __node_ = __node_->__next_;
-        if (__node_ != nullptr && __constrain_hash(__node_->__hash_, __bucket_count_) != __bucket_)
+        if (__node_ != nullptr && __constrain_hash(__node_->__hash(), __bucket_count_) != __bucket_)
             __node_ = nullptr;
         return *this;
     }
@@ -617,7 +611,7 @@ public:
 private:
 #if _LIBCPP_DEBUG_LEVEL >= 2
     _LIBCPP_INLINE_VISIBILITY
-    __hash_local_iterator(__node_pointer __node, size_t __bucket,
+    __hash_local_iterator(__next_pointer __node, size_t __bucket,
                           size_t __bucket_count, const void* __c) _NOEXCEPT
         : __node_(__node),
           __bucket_(__bucket),
@@ -629,7 +623,7 @@ private:
         }
 #else
     _LIBCPP_INLINE_VISIBILITY
-    __hash_local_iterator(__node_pointer __node, size_t __bucket,
+    __hash_local_iterator(__next_pointer __node, size_t __bucket,
                           size_t __bucket_count) _NOEXCEPT
         : __node_(__node),
           __bucket_(__bucket),
@@ -640,17 +634,18 @@ private:
         }
 #endif
     template <class, class, class, class> friend class __hash_table;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_const_local_iterator;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_map_iterator;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_const_local_iterator;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_map_iterator;
 };
 
 template <class _ConstNodePtr>
-class _LIBCPP_TYPE_VIS_ONLY __hash_const_local_iterator
+class _LIBCPP_TEMPLATE_VIS __hash_const_local_iterator
 {
     typedef __hash_node_types<_ConstNodePtr> _NodeTypes;
-    typedef _ConstNodePtr                    __node_pointer;
+    typedef _ConstNodePtr                       __node_pointer;
+    typedef typename _NodeTypes::__next_pointer __next_pointer;
 
-    __node_pointer         __node_;
+    __next_pointer         __node_;
     size_t                 __bucket_;
     size_t                 __bucket_count_;
 
@@ -670,11 +665,8 @@ public:
     typedef typename _NodeTypes::__const_node_value_type_pointer pointer;
 
 
-    _LIBCPP_INLINE_VISIBILITY __hash_const_local_iterator() _NOEXCEPT
-    {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-        __get_db()->__insert_i(this);
-#endif
+    _LIBCPP_INLINE_VISIBILITY __hash_const_local_iterator() _NOEXCEPT : __node_(nullptr) {
+        _LIBCPP_DEBUG_MODE(__get_db()->__insert_i(this));
     }
 
     _LIBCPP_INLINE_VISIBILITY
@@ -683,13 +675,10 @@ public:
           __bucket_(__x.__bucket_),
           __bucket_count_(__x.__bucket_count_)
     {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-        __get_db()->__iterator_copy(this, &__x);
-#endif
+        _LIBCPP_DEBUG_MODE(__get_db()->__iterator_copy(this, &__x));
     }
 
 #if _LIBCPP_DEBUG_LEVEL >= 2
-
     _LIBCPP_INLINE_VISIBILITY
     __hash_const_local_iterator(const __hash_const_local_iterator& __i)
         : __node_(__i.__node_),
@@ -717,37 +706,28 @@ public:
         }
         return *this;
     }
-
 #endif  // _LIBCPP_DEBUG_LEVEL >= 2
 
     _LIBCPP_INLINE_VISIBILITY
-        reference operator*() const
-        {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-            _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
+    reference operator*() const {
+        _LIBCPP_DEBUG_ASSERT(__get_const_db()->__dereferenceable(this),
                            "Attempted to dereference a non-dereferenceable unordered container const_local_iterator");
-#endif
-            return __node_->__value_;
-        }
+        return __node_->__upcast()->__value_;
+    }
+
     _LIBCPP_INLINE_VISIBILITY
-        pointer operator->() const
-        {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-            _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
+    pointer operator->() const {
+        _LIBCPP_DEBUG_ASSERT(__get_const_db()->__dereferenceable(this),
                            "Attempted to dereference a non-dereferenceable unordered container const_local_iterator");
-#endif
-            return pointer_traits<pointer>::pointer_to(__node_->__value_);
-        }
+        return pointer_traits<pointer>::pointer_to(__node_->__upcast()->__value_);
+    }
 
     _LIBCPP_INLINE_VISIBILITY
-    __hash_const_local_iterator& operator++()
-    {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-        _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
+    __hash_const_local_iterator& operator++() {
+        _LIBCPP_DEBUG_ASSERT(__get_const_db()->__dereferenceable(this),
                        "Attempted to increment non-incrementable unordered container const_local_iterator");
-#endif
         __node_ = __node_->__next_;
-        if (__node_ != nullptr && __constrain_hash(__node_->__hash_, __bucket_count_) != __bucket_)
+        if (__node_ != nullptr && __constrain_hash(__node_->__hash(), __bucket_count_) != __bucket_)
             __node_ = nullptr;
         return *this;
     }
@@ -772,7 +752,7 @@ public:
 private:
 #if _LIBCPP_DEBUG_LEVEL >= 2
     _LIBCPP_INLINE_VISIBILITY
-    __hash_const_local_iterator(__node_pointer __node, size_t __bucket,
+    __hash_const_local_iterator(__next_pointer __node, size_t __bucket,
                                 size_t __bucket_count, const void* __c) _NOEXCEPT
         : __node_(__node),
           __bucket_(__bucket),
@@ -784,7 +764,7 @@ private:
         }
 #else
     _LIBCPP_INLINE_VISIBILITY
-    __hash_const_local_iterator(__node_pointer __node, size_t __bucket,
+    __hash_const_local_iterator(__next_pointer __node, size_t __bucket,
                                 size_t __bucket_count) _NOEXCEPT
         : __node_(__node),
           __bucket_(__bucket),
@@ -795,7 +775,7 @@ private:
         }
 #endif
     template <class, class, class, class> friend class __hash_table;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_map_const_iterator;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_map_const_iterator;
 };
 
 template <class _Alloc>
@@ -819,8 +799,7 @@ public:
         _NOEXCEPT_(is_nothrow_copy_constructible<allocator_type>::value)
         : __data_(__size, __a) {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     __bucket_list_deallocator(__bucket_list_deallocator&& __x)
         _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value)
@@ -828,8 +807,7 @@ public:
     {
         __x.size() = 0;
     }
-
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif
 
     _LIBCPP_INLINE_VISIBILITY
     size_type& size() _NOEXCEPT {return __data_.first();}
@@ -887,6 +865,37 @@ public:
     template <class> friend class __hash_map_node_destructor;
 };
 
+
+#ifndef _LIBCPP_CXX03_LANG
+template <class _Key, class _Hash, class _Equal, class _Alloc>
+struct __diagnose_hash_table_helper {
+  static constexpr bool __trigger_diagnostics()
+    _LIBCPP_DIAGNOSE_WARNING(__check_hash_requirements<_Key, _Hash>::value
+                         && !__invokable<_Hash const&, _Key const&>::value,
+      "the specified hash functor does not provide a const call operator")
+    _LIBCPP_DIAGNOSE_WARNING(is_copy_constructible<_Equal>::value
+                          && !__invokable<_Equal const&, _Key const&, _Key const&>::value,
+      "the specified comparator type does not provide a const call operator")
+  {
+    static_assert(__check_hash_requirements<_Key, _Hash>::value,
+      "the specified hash does not meet the Hash requirements");
+    static_assert(is_copy_constructible<_Equal>::value,
+      "the specified comparator is required to be copy constructible");
+    return true;
+  }
+};
+
+template <class _Key, class _Value, class _Hash, class _Equal, class _Alloc>
+struct __diagnose_hash_table_helper<
+  __hash_value_type<_Key, _Value>,
+  __unordered_map_hasher<_Key, __hash_value_type<_Key, _Value>, _Hash>,
+  __unordered_map_equal<_Key, __hash_value_type<_Key, _Value>, _Equal>,
+  _Alloc>
+: __diagnose_hash_table_helper<_Key, _Hash, _Equal, _Alloc>
+{
+};
+#endif // _LIBCPP_CXX03_LANG
+
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
 class __hash_table
 {
@@ -927,6 +936,7 @@ public:
     typedef typename _NodeTypes::__node_pointer      __node_const_pointer;
     typedef typename _NodeTypes::__node_base_type    __first_node;
     typedef typename _NodeTypes::__node_base_pointer __node_base_pointer;
+    typedef typename _NodeTypes::__next_pointer      __next_pointer;
 
 private:
     // check for sane allocator pointer rebinding semantics. Rebinding the
@@ -942,11 +952,15 @@ private:
 
 private:
 
-    typedef typename __rebind_alloc_helper<__node_traits, __node_pointer>::type __pointer_allocator;
+    typedef typename __rebind_alloc_helper<__node_traits, __next_pointer>::type __pointer_allocator;
     typedef __bucket_list_deallocator<__pointer_allocator> __bucket_list_deleter;
-    typedef unique_ptr<__node_pointer[], __bucket_list_deleter> __bucket_list;
+    typedef unique_ptr<__next_pointer[], __bucket_list_deleter> __bucket_list;
     typedef allocator_traits<__pointer_allocator>          __pointer_alloc_traits;
-    typedef typename __bucket_list_deleter::pointer __node_pointer_pointer;
+    typedef typename __bucket_list_deleter::pointer       __node_pointer_pointer;
+
+#ifndef _LIBCPP_CXX03_LANG
+    static_assert(__diagnose_hash_table_helper<_Tp, _Hash, _Equal, _Alloc>::__trigger_diagnostics(), "");
+#endif
 
     // --- Member data begin ---
     __bucket_list                                         __bucket_list_;
@@ -1033,8 +1047,10 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     size_type max_size() const _NOEXCEPT
     {
-        return allocator_traits<__pointer_allocator>::max_size(
-            __bucket_list_.get_deleter().__alloc());
+        return std::min<size_type>(
+            __node_traits::max_size(__node_alloc()),
+            numeric_limits<difference_type >::max()
+        );
     }
 
     pair<iterator, bool> __node_insert_unique(__node_pointer __nd);
@@ -1129,6 +1145,7 @@ public:
 
 #else  // !defined(_LIBCPP_CXX03_LANG)
     template <class _Key, class _Args>
+    _LIBCPP_INLINE_VISIBILITY
     pair<iterator, bool> __emplace_unique_key_args(_Key const&, _Args& __args);
 
     iterator __insert_multi(const __container_value_type& __x);
@@ -1207,7 +1224,7 @@ public:
 
     void swap(__hash_table& __u)
 #if _LIBCPP_STD_VER <= 11
-        _NOEXCEPT_(
+        _NOEXCEPT_DEBUG_(
             __is_nothrow_swappable<hasher>::value && __is_nothrow_swappable<key_equal>::value
             && (!allocator_traits<__pointer_allocator>::propagate_on_container_swap::value
                   || __is_nothrow_swappable<__pointer_allocator>::value)
@@ -1215,12 +1232,12 @@ public:
                   || __is_nothrow_swappable<__node_allocator>::value)
             );
 #else
-     _NOEXCEPT_(__is_nothrow_swappable<hasher>::value && __is_nothrow_swappable<key_equal>::value);
+     _NOEXCEPT_DEBUG_(__is_nothrow_swappable<hasher>::value && __is_nothrow_swappable<key_equal>::value);
 #endif
 
     _LIBCPP_INLINE_VISIBILITY
     size_type max_bucket_count() const _NOEXCEPT
-        {return __pointer_alloc_traits::max_size(__bucket_list_.get_deleter().__alloc());}
+        {return max_size(); }
     size_type bucket_size(size_type __n) const;
     _LIBCPP_INLINE_VISIBILITY float load_factor() const _NOEXCEPT
     {
@@ -1347,11 +1364,11 @@ private:
         void __move_assign_alloc(__hash_table&, false_type) _NOEXCEPT {}
 #endif // _LIBCPP_CXX03_LANG
 
-    void __deallocate(__node_pointer __np) _NOEXCEPT;
-    __node_pointer __detach() _NOEXCEPT;
+    void __deallocate_node(__next_pointer __np) _NOEXCEPT;
+    __next_pointer __detach() _NOEXCEPT;
 
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY unordered_map;
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY unordered_multimap;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS unordered_map;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS unordered_multimap;
 };
 
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
@@ -1384,7 +1401,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(const hasher& __hf,
                                                        const key_equal& __eql,
                                                        const allocator_type& __a)
     : __bucket_list_(nullptr, __bucket_list_deleter(__pointer_allocator(__a), 0)),
-      __p1_(__node_allocator(__a)),
+      __p1_(__second_tag(), __node_allocator(__a)),
       __p2_(0, __hf),
       __p3_(1.0f, __eql)
 {
@@ -1393,7 +1410,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(const hasher& __hf,
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(const allocator_type& __a)
     : __bucket_list_(nullptr, __bucket_list_deleter(__pointer_allocator(__a), 0)),
-      __p1_(__node_allocator(__a)),
+      __p1_(__second_tag(), __node_allocator(__a)),
       __p2_(0),
       __p3_(1.0f)
 {
@@ -1405,7 +1422,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(const __hash_table& __u)
           __bucket_list_deleter(allocator_traits<__pointer_allocator>::
               select_on_container_copy_construction(
                   __u.__bucket_list_.get_deleter().__alloc()), 0)),
-      __p1_(allocator_traits<__node_allocator>::
+      __p1_(__second_tag(), allocator_traits<__node_allocator>::
           select_on_container_copy_construction(__u.__node_alloc())),
       __p2_(0, __u.hash_function()),
       __p3_(__u.__p3_)
@@ -1416,7 +1433,7 @@ template <class _Tp, class _Hash, class _Equal, class _Alloc>
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(const __hash_table& __u,
                                                        const allocator_type& __a)
     : __bucket_list_(nullptr, __bucket_list_deleter(__pointer_allocator(__a), 0)),
-      __p1_(__node_allocator(__a)),
+      __p1_(__second_tag(), __node_allocator(__a)),
       __p2_(0, __u.hash_function()),
       __p3_(__u.__p3_)
 {
@@ -1439,8 +1456,8 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(__hash_table&& __u)
 {
     if (size() > 0)
     {
-        __bucket_list_[__constrain_hash(__p1_.first().__next_->__hash_, bucket_count())] =
-            static_cast<__node_pointer>(pointer_traits<__node_base_pointer>::pointer_to(__p1_.first()));
+        __bucket_list_[__constrain_hash(__p1_.first().__next_->__hash(), bucket_count())] =
+            __p1_.first().__ptr();
         __u.__p1_.first().__next_ = nullptr;
         __u.size() = 0;
     }
@@ -1450,7 +1467,7 @@ template <class _Tp, class _Hash, class _Equal, class _Alloc>
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(__hash_table&& __u,
                                                        const allocator_type& __a)
     : __bucket_list_(nullptr, __bucket_list_deleter(__pointer_allocator(__a), 0)),
-      __p1_(__node_allocator(__a)),
+      __p1_(__second_tag(), __node_allocator(__a)),
       __p2_(0, _VSTD::move(__u.hash_function())),
       __p3_(_VSTD::move(__u.__p3_))
 {
@@ -1463,8 +1480,8 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(__hash_table&& __u,
         {
             __p1_.first().__next_ = __u.__p1_.first().__next_;
             __u.__p1_.first().__next_ = nullptr;
-            __bucket_list_[__constrain_hash(__p1_.first().__next_->__hash_, bucket_count())] =
-                static_cast<__node_pointer>(pointer_traits<__node_base_pointer>::pointer_to(__p1_.first()));
+            __bucket_list_[__constrain_hash(__p1_.first().__next_->__hash(), bucket_count())] =
+                __p1_.first().__ptr();
             size() = __u.size();
             __u.size() = 0;
         }
@@ -1476,11 +1493,14 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(__hash_table&& __u,
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::~__hash_table()
 {
+#if defined(_LIBCPP_CXX03_LANG)
     static_assert((is_copy_constructible<key_equal>::value),
                  "Predicate must be copy-constructible.");
     static_assert((is_copy_constructible<hasher>::value),
                  "Hasher must be copy-constructible.");
-    __deallocate(__p1_.first().__next_);
+#endif
+
+    __deallocate_node(__p1_.first().__next_);
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __get_db()->__erase_c(this);
 #endif
@@ -1518,13 +1538,13 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::operator=(const __hash_table& __u)
 
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
 void
-__hash_table<_Tp, _Hash, _Equal, _Alloc>::__deallocate(__node_pointer __np)
+__hash_table<_Tp, _Hash, _Equal, _Alloc>::__deallocate_node(__next_pointer __np)
     _NOEXCEPT
 {
     __node_allocator& __na = __node_alloc();
     while (__np != nullptr)
     {
-        __node_pointer __next = __np->__next_;
+        __next_pointer __next = __np->__next_;
 #if _LIBCPP_DEBUG_LEVEL >= 2
         __c_node* __c = __get_db()->__find_c_and_lock(this);
         for (__i_node** __p = __c->end_; __p != __c->beg_; )
@@ -1540,21 +1560,22 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__deallocate(__node_pointer __np)
         }
         __get_db()->unlock();
 #endif
-        __node_traits::destroy(__na, _NodeTypes::__get_ptr(__np->__value_));
-        __node_traits::deallocate(__na, __np, 1);
+        __node_pointer __real_np = __np->__upcast();
+        __node_traits::destroy(__na, _NodeTypes::__get_ptr(__real_np->__value_));
+        __node_traits::deallocate(__na, __real_np, 1);
         __np = __next;
     }
 }
 
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
-typename __hash_table<_Tp, _Hash, _Equal, _Alloc>::__node_pointer
+typename __hash_table<_Tp, _Hash, _Equal, _Alloc>::__next_pointer
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::__detach() _NOEXCEPT
 {
     size_type __bc = bucket_count();
     for (size_type __i = 0; __i < __bc; ++__i)
         __bucket_list_[__i] = nullptr;
     size() = 0;
-    __node_pointer __cache = __p1_.first().__next_;
+    __next_pointer __cache = __p1_.first().__next_;
     __p1_.first().__next_ = nullptr;
     return __cache;
 }
@@ -1582,8 +1603,8 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__move_assign(
     __p1_.first().__next_ = __u.__p1_.first().__next_;
     if (size() > 0)
     {
-        __bucket_list_[__constrain_hash(__p1_.first().__next_->__hash_, bucket_count())] =
-            static_cast<__node_pointer>(pointer_traits<__node_base_pointer>::pointer_to(__p1_.first()));
+        __bucket_list_[__constrain_hash(__p1_.first().__next_->__hash(), bucket_count())] =
+            __p1_.first().__ptr();
         __u.__p1_.first().__next_ = nullptr;
         __u.size() = 0;
     }
@@ -1606,7 +1627,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__move_assign(
         max_load_factor() = __u.max_load_factor();
         if (bucket_count() != 0)
         {
-            __node_pointer __cache = __detach();
+            __next_pointer __cache = __detach();
 #ifndef _LIBCPP_NO_EXCEPTIONS
             try
             {
@@ -1614,20 +1635,21 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__move_assign(
                 const_iterator __i = __u.begin();
                 while (__cache != nullptr && __u.size() != 0)
                 {
-                    __cache->__value_ = _VSTD::move(__u.remove(__i++)->__value_);
-                    __node_pointer __next = __cache->__next_;
-                    __node_insert_multi(__cache);
+                    __cache->__upcast()->__value_ =
+                        _VSTD::move(__u.remove(__i++)->__value_);
+                    __next_pointer __next = __cache->__next_;
+                    __node_insert_multi(__cache->__upcast());
                     __cache = __next;
                 }
 #ifndef _LIBCPP_NO_EXCEPTIONS
             }
             catch (...)
             {
-                __deallocate(__cache);
+                __deallocate_node(__cache);
                 throw;
             }
 #endif  // _LIBCPP_NO_EXCEPTIONS
-            __deallocate(__cache);
+            __deallocate_node(__cache);
         }
         const_iterator __i = __u.begin();
         while (__u.size() != 0)
@@ -1669,27 +1691,27 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__assign_unique(_InputIterator __first
 
     if (bucket_count() != 0)
     {
-        __node_pointer __cache = __detach();
+        __next_pointer __cache = __detach();
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
 #endif  // _LIBCPP_NO_EXCEPTIONS
             for (; __cache != nullptr && __first != __last; ++__first)
             {
-                __cache->__value_ = *__first;
-                __node_pointer __next = __cache->__next_;
-                __node_insert_unique(__cache);
+                __cache->__upcast()->__value_ = *__first;
+                __next_pointer __next = __cache->__next_;
+                __node_insert_unique(__cache->__upcast());
                 __cache = __next;
             }
 #ifndef _LIBCPP_NO_EXCEPTIONS
         }
         catch (...)
         {
-            __deallocate(__cache);
+            __deallocate_node(__cache);
             throw;
         }
 #endif  // _LIBCPP_NO_EXCEPTIONS
-        __deallocate(__cache);
+        __deallocate_node(__cache);
     }
     for (; __first != __last; ++__first)
         __insert_unique(*__first);
@@ -1709,27 +1731,27 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__assign_multi(_InputIterator __first,
                   " or the nodes value type");
     if (bucket_count() != 0)
     {
-        __node_pointer __cache = __detach();
+        __next_pointer __cache = __detach();
 #ifndef _LIBCPP_NO_EXCEPTIONS
         try
         {
 #endif  // _LIBCPP_NO_EXCEPTIONS
             for (; __cache != nullptr && __first != __last; ++__first)
             {
-                __cache->__value_ = *__first;
-                __node_pointer __next = __cache->__next_;
-                __node_insert_multi(__cache);
+                __cache->__upcast()->__value_ = *__first;
+                __next_pointer __next = __cache->__next_;
+                __node_insert_multi(__cache->__upcast());
                 __cache = __next;
             }
 #ifndef _LIBCPP_NO_EXCEPTIONS
         }
         catch (...)
         {
-            __deallocate(__cache);
+            __deallocate_node(__cache);
             throw;
         }
 #endif  // _LIBCPP_NO_EXCEPTIONS
-        __deallocate(__cache);
+        __deallocate_node(__cache);
     }
     for (; __first != __last; ++__first)
         __insert_multi(_NodeTypes::__get_value(*__first));
@@ -1789,7 +1811,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::clear() _NOEXCEPT
 {
     if (size() > 0)
     {
-        __deallocate(__p1_.first().__next_);
+        __deallocate_node(__p1_.first().__next_);
         __p1_.first().__next_ = nullptr;
         size_type __bc = bucket_count();
         for (size_type __i = 0; __i < __bc; ++__i)
@@ -1805,7 +1827,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__node_insert_unique(__node_pointer __
     __nd->__hash_ = hash_function()(__nd->__value_);
     size_type __bc = bucket_count();
     bool __inserted = false;
-    __node_pointer __ndptr;
+    __next_pointer __ndptr;
     size_t __chash;
     if (__bc != 0)
     {
@@ -1814,10 +1836,10 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__node_insert_unique(__node_pointer __
         if (__ndptr != nullptr)
         {
             for (__ndptr = __ndptr->__next_; __ndptr != nullptr &&
-                                             __constrain_hash(__ndptr->__hash_, __bc) == __chash;
+                                             __constrain_hash(__ndptr->__hash(), __bc) == __chash;
                                                      __ndptr = __ndptr->__next_)
             {
-                if (key_eq()(__ndptr->__value_, __nd->__value_))
+                if (key_eq()(__ndptr->__upcast()->__value_, __nd->__value_))
                     goto __done;
             }
         }
@@ -1831,23 +1853,23 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__node_insert_unique(__node_pointer __
             __chash = __constrain_hash(__nd->__hash_, __bc);
         }
         // insert_after __bucket_list_[__chash], or __first_node if bucket is null
-        __node_pointer __pn = __bucket_list_[__chash];
+        __next_pointer __pn = __bucket_list_[__chash];
         if (__pn == nullptr)
         {
-            __pn = static_cast<__node_pointer>(pointer_traits<__node_base_pointer>::pointer_to(__p1_.first()));
+            __pn =__p1_.first().__ptr();
             __nd->__next_ = __pn->__next_;
-            __pn->__next_ = __nd;
+            __pn->__next_ = __nd->__ptr();
             // fix up __bucket_list_
             __bucket_list_[__chash] = __pn;
             if (__nd->__next_ != nullptr)
-                __bucket_list_[__constrain_hash(__nd->__next_->__hash_, __bc)] = __nd;
+                __bucket_list_[__constrain_hash(__nd->__next_->__hash(), __bc)] = __nd->__ptr();
         }
         else
         {
             __nd->__next_ = __pn->__next_;
-            __pn->__next_ = __nd;
+            __pn->__next_ = __nd->__ptr();
         }
-        __ndptr = __nd;
+        __ndptr = __nd->__ptr();
         // increment size
         ++size();
         __inserted = true;
@@ -1873,21 +1895,22 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__node_insert_multi(__node_pointer __c
         __bc = bucket_count();
     }
     size_t __chash = __constrain_hash(__cp->__hash_, __bc);
-    __node_pointer __pn = __bucket_list_[__chash];
+    __next_pointer __pn = __bucket_list_[__chash];
     if (__pn == nullptr)
     {
-        __pn = static_cast<__node_pointer>(pointer_traits<__node_base_pointer>::pointer_to(__p1_.first()));
+        __pn =__p1_.first().__ptr();
         __cp->__next_ = __pn->__next_;
-        __pn->__next_ = __cp;
+        __pn->__next_ = __cp->__ptr();
         // fix up __bucket_list_
         __bucket_list_[__chash] = __pn;
         if (__cp->__next_ != nullptr)
-            __bucket_list_[__constrain_hash(__cp->__next_->__hash_, __bc)] = __cp;
+            __bucket_list_[__constrain_hash(__cp->__next_->__hash(), __bc)]
+                = __cp->__ptr();
     }
     else
     {
         for (bool __found = false; __pn->__next_ != nullptr &&
-                                   __constrain_hash(__pn->__next_->__hash_, __bc) == __chash;
+                                   __constrain_hash(__pn->__next_->__hash(), __bc) == __chash;
                                                            __pn = __pn->__next_)
         {
             //      __found    key_eq()     action
@@ -1895,8 +1918,8 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__node_insert_multi(__node_pointer __c
             //      true        true        loop
             //      false       true        set __found to true
             //      true        false       break
-            if (__found != (__pn->__next_->__hash_ == __cp->__hash_ &&
-                            key_eq()(__pn->__next_->__value_, __cp->__value_)))
+            if (__found != (__pn->__next_->__hash() == __cp->__hash_ &&
+                            key_eq()(__pn->__next_->__upcast()->__value_, __cp->__value_)))
             {
                 if (!__found)
                     __found = true;
@@ -1905,19 +1928,19 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__node_insert_multi(__node_pointer __c
             }
         }
         __cp->__next_ = __pn->__next_;
-        __pn->__next_ = __cp;
+        __pn->__next_ = __cp->__ptr();
         if (__cp->__next_ != nullptr)
         {
-            size_t __nhash = __constrain_hash(__cp->__next_->__hash_, __bc);
+            size_t __nhash = __constrain_hash(__cp->__next_->__hash(), __bc);
             if (__nhash != __chash)
-                __bucket_list_[__nhash] = __cp;
+                __bucket_list_[__nhash] = __cp->__ptr();
         }
     }
     ++size();
 #if _LIBCPP_DEBUG_LEVEL >= 2
-    return iterator(__cp, this);
+    return iterator(__cp->__ptr(), this);
 #else
-    return iterator(__cp);
+    return iterator(__cp->__ptr());
 #endif
 }
 
@@ -1933,8 +1956,8 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__node_insert_multi(
 #endif
     if (__p != end() && key_eq()(*__p, __cp->__value_))
     {
-        __node_pointer __np = __p.__node_;
-        __cp->__hash_ = __np->__hash_;
+        __next_pointer __np = __p.__node_;
+        __cp->__hash_ = __np->__hash();
         size_type __bc = bucket_count();
         if (size()+1 > __bc * max_load_factor() || __bc == 0)
         {
@@ -1943,16 +1966,16 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__node_insert_multi(
             __bc = bucket_count();
         }
         size_t __chash = __constrain_hash(__cp->__hash_, __bc);
-        __node_pointer __pp = __bucket_list_[__chash];
+        __next_pointer __pp = __bucket_list_[__chash];
         while (__pp->__next_ != __np)
             __pp = __pp->__next_;
         __cp->__next_ = __np;
-        __pp->__next_ = __cp;
+        __pp->__next_ = static_cast<__next_pointer>(__cp);
         ++size();
 #if _LIBCPP_DEBUG_LEVEL >= 2
-        return iterator(__cp, this);
+        return iterator(static_cast<__next_pointer>(__cp), this);
 #else
-        return iterator(__cp);
+        return iterator(static_cast<__next_pointer>(__cp));
 #endif
     }
     return __node_insert_multi(__cp);
@@ -1963,13 +1986,11 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__node_insert_multi(
 #ifndef _LIBCPP_CXX03_LANG
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
 template <class _Key, class ..._Args>
-_LIBCPP_INLINE_VISIBILITY
 pair<typename __hash_table<_Tp, _Hash, _Equal, _Alloc>::iterator, bool>
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::__emplace_unique_key_args(_Key const& __k, _Args&&... __args)
 #else
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
 template <class _Key, class _Args>
-_LIBCPP_INLINE_VISIBILITY
 pair<typename __hash_table<_Tp, _Hash, _Equal, _Alloc>::iterator, bool>
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::__emplace_unique_key_args(_Key const& __k, _Args& __args)
 #endif
@@ -1978,7 +1999,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__emplace_unique_key_args(_Key const&
     size_t __hash = hash_function()(__k);
     size_type __bc = bucket_count();
     bool __inserted = false;
-    __node_pointer __nd;
+    __next_pointer __nd;
     size_t __chash;
     if (__bc != 0)
     {
@@ -1987,10 +2008,10 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__emplace_unique_key_args(_Key const&
         if (__nd != nullptr)
         {
             for (__nd = __nd->__next_; __nd != nullptr &&
-                                       __constrain_hash(__nd->__hash_, __bc) == __chash;
+                (__nd->__hash() == __hash || __constrain_hash(__nd->__hash(), __bc) == __chash);
                                                            __nd = __nd->__next_)
             {
-                if (key_eq()(__nd->__value_, __k))
+                if (key_eq()(__nd->__upcast()->__value_, __k))
                     goto __done;
             }
         }
@@ -2009,23 +2030,24 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__emplace_unique_key_args(_Key const&
             __chash = __constrain_hash(__hash, __bc);
         }
         // insert_after __bucket_list_[__chash], or __first_node if bucket is null
-        __node_pointer __pn = __bucket_list_[__chash];
+        __next_pointer __pn = __bucket_list_[__chash];
         if (__pn == nullptr)
         {
-            __pn = static_cast<__node_pointer>(static_cast<__void_pointer>(pointer_traits<__node_base_pointer>::pointer_to(__p1_.first())));
+            __pn = __p1_.first().__ptr();
             __h->__next_ = __pn->__next_;
-            __pn->__next_ = __h.get();
+            __pn->__next_ = __h.get()->__ptr();
             // fix up __bucket_list_
             __bucket_list_[__chash] = __pn;
             if (__h->__next_ != nullptr)
-                __bucket_list_[__constrain_hash(__h->__next_->__hash_, __bc)] = __h.get();
+                __bucket_list_[__constrain_hash(__h->__next_->__hash(), __bc)]
+                    = __h.get()->__ptr();
         }
         else
         {
             __h->__next_ = __pn->__next_;
-            __pn->__next_ = __h.get();
+            __pn->__next_ = static_cast<__next_pointer>(__h.get());
         }
-        __nd = __h.release();
+        __nd = static_cast<__next_pointer>(__h.release());
         // increment size
         ++size();
         __inserted = true;
@@ -2149,17 +2171,17 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__rehash(size_type __nbc)
     {
         for (size_type __i = 0; __i < __nbc; ++__i)
             __bucket_list_[__i] = nullptr;
-        __node_pointer __pp(static_cast<__node_pointer>(pointer_traits<__node_base_pointer>::pointer_to(__p1_.first())));
-        __node_pointer __cp = __pp->__next_;
+        __next_pointer __pp = __p1_.first().__ptr();
+        __next_pointer __cp = __pp->__next_;
         if (__cp != nullptr)
         {
-            size_type __chash = __constrain_hash(__cp->__hash_, __nbc);
+            size_type __chash = __constrain_hash(__cp->__hash(), __nbc);
             __bucket_list_[__chash] = __pp;
             size_type __phash = __chash;
             for (__pp = __cp, __cp = __cp->__next_; __cp != nullptr;
                                                            __cp = __pp->__next_)
             {
-                __chash = __constrain_hash(__cp->__hash_, __nbc);
+                __chash = __constrain_hash(__cp->__hash(), __nbc);
                 if (__chash == __phash)
                     __pp = __cp;
                 else
@@ -2172,9 +2194,10 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__rehash(size_type __nbc)
                     }
                     else
                     {
-                        __node_pointer __np = __cp;
+                        __next_pointer __np = __cp;
                         for (; __np->__next_ != nullptr &&
-                               key_eq()(__cp->__value_, __np->__next_->__value_);
+                               key_eq()(__cp->__upcast()->__value_,
+                                        __np->__next_->__upcast()->__value_);
                                                            __np = __np->__next_)
                             ;
                         __pp->__next_ = __np->__next_;
@@ -2198,15 +2221,16 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::find(const _Key& __k)
     if (__bc != 0)
     {
         size_t __chash = __constrain_hash(__hash, __bc);
-        __node_pointer __nd = __bucket_list_[__chash];
+        __next_pointer __nd = __bucket_list_[__chash];
         if (__nd != nullptr)
         {
             for (__nd = __nd->__next_; __nd != nullptr &&
-                (__nd->__hash_ == __hash
-                  || __constrain_hash(__nd->__hash_, __bc) == __chash);
+                (__nd->__hash() == __hash
+                  || __constrain_hash(__nd->__hash(), __bc) == __chash);
                                                            __nd = __nd->__next_)
             {
-                if ((__nd->__hash_ == __hash) && key_eq()(__nd->__value_, __k))
+                if ((__nd->__hash() == __hash)
+                    && key_eq()(__nd->__upcast()->__value_, __k))
 #if _LIBCPP_DEBUG_LEVEL >= 2
                     return iterator(__nd, this);
 #else
@@ -2228,14 +2252,16 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::find(const _Key& __k) const
     if (__bc != 0)
     {
         size_t __chash = __constrain_hash(__hash, __bc);
-        __node_const_pointer __nd = __bucket_list_[__chash];
+        __next_pointer __nd = __bucket_list_[__chash];
         if (__nd != nullptr)
         {
             for (__nd = __nd->__next_; __nd != nullptr &&
-                (__hash == __nd->__hash_ || __constrain_hash(__nd->__hash_, __bc) == __chash);
+                (__hash == __nd->__hash()
+                    || __constrain_hash(__nd->__hash(), __bc) == __chash);
                                                            __nd = __nd->__next_)
             {
-                if ((__nd->__hash_ == __hash) && key_eq()(__nd->__value_, __k))
+                if ((__nd->__hash() == __hash)
+                    && key_eq()(__nd->__upcast()->__value_, __k))
 #if _LIBCPP_DEBUG_LEVEL >= 2
                     return const_iterator(__nd, this);
 #else
@@ -2320,7 +2346,7 @@ template <class _Tp, class _Hash, class _Equal, class _Alloc>
 typename __hash_table<_Tp, _Hash, _Equal, _Alloc>::iterator
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::erase(const_iterator __p)
 {
-    __node_pointer __np = __p.__node_;
+    __next_pointer __np = __p.__node_;
 #if _LIBCPP_DEBUG_LEVEL >= 2
     _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__p) == this,
         "unordered container erase(iterator) called with an iterator not"
@@ -2354,7 +2380,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::erase(const_iterator __first,
         ++__first;
         erase(__p);
     }
-    __node_pointer __np = __last.__node_;
+    __next_pointer __np = __last.__node_;
 #if _LIBCPP_DEBUG_LEVEL >= 2
     return iterator (__np, this);
 #else
@@ -2398,26 +2424,27 @@ typename __hash_table<_Tp, _Hash, _Equal, _Alloc>::__node_holder
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::remove(const_iterator __p) _NOEXCEPT
 {
     // current node
-    __node_pointer __cn = __p.__node_;
+    __next_pointer __cn = __p.__node_;
     size_type __bc = bucket_count();
-    size_t __chash = __constrain_hash(__cn->__hash_, __bc);
+    size_t __chash = __constrain_hash(__cn->__hash(), __bc);
     // find previous node
-    __node_pointer __pn = __bucket_list_[__chash];
+    __next_pointer __pn = __bucket_list_[__chash];
     for (; __pn->__next_ != __cn; __pn = __pn->__next_)
         ;
     // Fix up __bucket_list_
         // if __pn is not in same bucket (before begin is not in same bucket) &&
         //    if __cn->__next_ is not in same bucket (nullptr is not in same bucket)
-    if (__pn == static_cast<__node_pointer>(pointer_traits<__node_base_pointer>::pointer_to(__p1_.first()))
-                            || __constrain_hash(__pn->__hash_, __bc) != __chash)
+    if (__pn == __p1_.first().__ptr()
+            || __constrain_hash(__pn->__hash(), __bc) != __chash)
     {
-        if (__cn->__next_ == nullptr || __constrain_hash(__cn->__next_->__hash_, __bc) != __chash)
+        if (__cn->__next_ == nullptr
+            || __constrain_hash(__cn->__next_->__hash(), __bc) != __chash)
             __bucket_list_[__chash] = nullptr;
     }
         // if __cn->__next_ is not in same bucket (nullptr is in same bucket)
     if (__cn->__next_ != nullptr)
     {
-        size_t __nhash = __constrain_hash(__cn->__next_->__hash_, __bc);
+        size_t __nhash = __constrain_hash(__cn->__next_->__hash(), __bc);
         if (__nhash != __chash)
             __bucket_list_[__nhash] = __pn;
     }
@@ -2427,20 +2454,20 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::remove(const_iterator __p) _NOEXCEPT
     --size();
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __c_node* __c = __get_db()->__find_c_and_lock(this);
-    for (__i_node** __p = __c->end_; __p != __c->beg_; )
+    for (__i_node** __dp = __c->end_; __dp != __c->beg_; )
     {
-        --__p;
-        iterator* __i = static_cast<iterator*>((*__p)->__i_);
+        --__dp;
+        iterator* __i = static_cast<iterator*>((*__dp)->__i_);
         if (__i->__node_ == __cn)
         {
-            (*__p)->__c_ = nullptr;
-            if (--__c->end_ != __p)
-                memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
+            (*__dp)->__c_ = nullptr;
+            if (--__c->end_ != __dp)
+                memmove(__dp, __dp+1, (__c->end_ - __dp)*sizeof(__i_node*));
         }
     }
     __get_db()->unlock();
 #endif
-    return __node_holder(__cn, _Dp(__node_alloc(), true));
+    return __node_holder(__cn->__upcast(), _Dp(__node_alloc(), true));
 }
 
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
@@ -2543,7 +2570,7 @@ template <class _Tp, class _Hash, class _Equal, class _Alloc>
 void
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::swap(__hash_table& __u)
 #if _LIBCPP_STD_VER <= 11
-    _NOEXCEPT_(
+    _NOEXCEPT_DEBUG_(
         __is_nothrow_swappable<hasher>::value && __is_nothrow_swappable<key_equal>::value
         && (!allocator_traits<__pointer_allocator>::propagate_on_container_swap::value
               || __is_nothrow_swappable<__pointer_allocator>::value)
@@ -2551,9 +2578,13 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::swap(__hash_table& __u)
               || __is_nothrow_swappable<__node_allocator>::value)
             )
 #else
-  _NOEXCEPT_(__is_nothrow_swappable<hasher>::value && __is_nothrow_swappable<key_equal>::value)
+  _NOEXCEPT_DEBUG_(__is_nothrow_swappable<hasher>::value && __is_nothrow_swappable<key_equal>::value)
 #endif
 {
+    _LIBCPP_ASSERT(__node_traits::propagate_on_container_swap::value ||
+                   this->__node_alloc() == __u.__node_alloc(),
+                   "list::swap: Either propagate_on_container_swap must be true"
+                   " or the allocators must compare equal");
     {
     __node_pointer_pointer __npp = __bucket_list_.release();
     __bucket_list_.reset(__u.__bucket_list_.release());
@@ -2567,11 +2598,11 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::swap(__hash_table& __u)
     __p2_.swap(__u.__p2_);
     __p3_.swap(__u.__p3_);
     if (size() > 0)
-        __bucket_list_[__constrain_hash(__p1_.first().__next_->__hash_, bucket_count())] =
-            static_cast<__node_pointer>(pointer_traits<__node_base_pointer>::pointer_to(__p1_.first()));
+        __bucket_list_[__constrain_hash(__p1_.first().__next_->__hash(), bucket_count())] =
+            __p1_.first().__ptr();
     if (__u.size() > 0)
-        __u.__bucket_list_[__constrain_hash(__u.__p1_.first().__next_->__hash_, __u.bucket_count())] =
-            static_cast<__node_pointer>(pointer_traits<__node_base_pointer>::pointer_to(__u.__p1_.first()));
+        __u.__bucket_list_[__constrain_hash(__u.__p1_.first().__next_->__hash(), __u.bucket_count())] =
+            __u.__p1_.first().__ptr();
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __get_db()->swap(this, &__u);
 #endif
@@ -2583,13 +2614,13 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::bucket_size(size_type __n) const
 {
     _LIBCPP_ASSERT(__n < bucket_count(),
         "unordered container::bucket_size(n) called with n >= bucket_count()");
-    __node_const_pointer __np = __bucket_list_[__n];
+    __next_pointer __np = __bucket_list_[__n];
     size_type __bc = bucket_count();
     size_type __r = 0;
     if (__np != nullptr)
     {
         for (__np = __np->__next_; __np != nullptr &&
-                                   __constrain_hash(__np->__hash_, __bc) == __n;
+                                   __constrain_hash(__np->__hash(), __bc) == __n;
                                                     __np = __np->__next_, ++__r)
             ;
     }
@@ -2637,6 +2668,9 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__subscriptable(const const_iterator*,
 }
 
 #endif  // _LIBCPP_DEBUG_LEVEL >= 2
+
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP__HASH_TABLE
diff --git a/lib/libcxx/include/__libcpp_version b/lib/libcxx/include/__libcpp_version
new file mode 100644
index 00000000000..a77fd92cf17
--- /dev/null
+++ b/lib/libcxx/include/__libcpp_version
@@ -0,0 +1 @@
+6000
diff --git a/lib/libcxx/include/__mutex_base b/lib/libcxx/include/__mutex_base
index 38a76ac6f2e..402a52d945e 100644
--- a/lib/libcxx/include/__mutex_base
+++ b/lib/libcxx/include/__mutex_base
@@ -16,10 +16,15 @@
 #include <system_error>
 #include <__threading_support>
 
+
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #ifndef _LIBCPP_HAS_NO_THREADS
@@ -34,7 +39,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 class _LIBCPP_TYPE_VIS _LIBCPP_THREAD_SAFETY_ANNOTATION(capability("mutex")) mutex
 {
-#ifndef _LIBCPP_HAS_NO_CONSTEXPR
+#ifndef _LIBCPP_CXX03_LANG
     __libcpp_mutex_t __m_ = _LIBCPP_MUTEX_INITIALIZER;
 #else
     __libcpp_mutex_t __m_;
@@ -42,8 +47,8 @@ class _LIBCPP_TYPE_VIS _LIBCPP_THREAD_SAFETY_ANNOTATION(capability("mutex")) mut
 
 public:
     _LIBCPP_INLINE_VISIBILITY
-#ifndef _LIBCPP_HAS_NO_CONSTEXPR
-    constexpr mutex() _NOEXCEPT _LIBCPP_DEFAULT
+#ifndef _LIBCPP_CXX03_LANG
+    constexpr mutex() = default;
 #else
     mutex() _NOEXCEPT {__m_ = (__libcpp_mutex_t)_LIBCPP_MUTEX_INITIALIZER;}
 #endif
@@ -62,11 +67,14 @@ public:
     _LIBCPP_INLINE_VISIBILITY native_handle_type native_handle() {return &__m_;}
 };
 
+static_assert(is_nothrow_default_constructible<mutex>::value,
+              "the default constructor for std::mutex must be nothrow");
+
 struct _LIBCPP_TYPE_VIS defer_lock_t {};
 struct _LIBCPP_TYPE_VIS try_to_lock_t {};
 struct _LIBCPP_TYPE_VIS adopt_lock_t {};
 
-#if defined(_LIBCPP_HAS_NO_CONSTEXPR) || defined(_LIBCPP_BUILDING_MUTEX)
+#if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_MUTEX)
 
 extern const defer_lock_t  defer_lock;
 extern const try_to_lock_t try_to_lock;
@@ -74,27 +82,15 @@ extern const adopt_lock_t  adopt_lock;
 
 #else
 
-constexpr defer_lock_t  defer_lock  = defer_lock_t();
-constexpr try_to_lock_t try_to_lock = try_to_lock_t();
-constexpr adopt_lock_t  adopt_lock  = adopt_lock_t();
-
-#endif
-
+/* _LIBCPP_INLINE_VAR */ constexpr defer_lock_t  defer_lock  = defer_lock_t();
+/* _LIBCPP_INLINE_VAR */ constexpr try_to_lock_t try_to_lock = try_to_lock_t();
+/* _LIBCPP_INLINE_VAR */ constexpr adopt_lock_t  adopt_lock  = adopt_lock_t();
 
-// Forward declare lock_guard as a variadic template even in C++03 to keep
-// the mangling consistent between dialects.
-#if defined(_LIBCPP_ABI_VARIADIC_LOCK_GUARD)
-template <class ..._Mutexes>
-class _LIBCPP_TYPE_VIS_ONLY lock_guard;
 #endif
 
 template <class _Mutex>
-class _LIBCPP_TYPE_VIS_ONLY _LIBCPP_THREAD_SAFETY_ANNOTATION(scoped_lockable)
-#if !defined(_LIBCPP_ABI_VARIADIC_LOCK_GUARD)
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_THREAD_SAFETY_ANNOTATION(scoped_lockable)
 lock_guard
-#else
-lock_guard<_Mutex>
-#endif
 {
 public:
     typedef _Mutex mutex_type;
@@ -118,7 +114,7 @@ private:
 };
 
 template <class _Mutex>
-class _LIBCPP_TYPE_VIS_ONLY unique_lock
+class _LIBCPP_TEMPLATE_VIS unique_lock
 {
 public:
     typedef _Mutex mutex_type;
@@ -162,7 +158,7 @@ private:
     unique_lock& operator=(unique_lock const&); // = delete;
 
 public:
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     unique_lock(unique_lock&& __u) _NOEXCEPT
         : __m_(__u.__m_), __owns_(__u.__owns_)
@@ -179,7 +175,7 @@ public:
             return *this;
         }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     void lock();
     bool try_lock();
@@ -291,7 +287,7 @@ _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(cv_status)
 
 class _LIBCPP_TYPE_VIS condition_variable
 {
-#ifndef _LIBCPP_HAS_NO_CONSTEXPR
+#ifndef _LIBCPP_CXX03_LANG
     __libcpp_condvar_t __cv_ = _LIBCPP_CONDVAR_INITIALIZER;
 #else
     __libcpp_condvar_t __cv_;
@@ -299,8 +295,8 @@ class _LIBCPP_TYPE_VIS condition_variable
 
 public:
     _LIBCPP_INLINE_VISIBILITY
-#ifndef _LIBCPP_HAS_NO_CONSTEXPR
-    constexpr condition_variable() _NOEXCEPT _LIBCPP_DEFAULT
+#ifndef _LIBCPP_CXX03_LANG
+    constexpr condition_variable() _NOEXCEPT = default;
 #else
     condition_variable() _NOEXCEPT {__cv_ = (__libcpp_condvar_t)_LIBCPP_CONDVAR_INITIALIZER;}
 #endif
@@ -316,20 +312,24 @@ public:
 
     void wait(unique_lock<mutex>& __lk) _NOEXCEPT;
     template <class _Predicate>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         void wait(unique_lock<mutex>& __lk, _Predicate __pred);
 
     template <class _Clock, class _Duration>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         cv_status
         wait_until(unique_lock<mutex>& __lk,
                    const chrono::time_point<_Clock, _Duration>& __t);
 
     template <class _Clock, class _Duration, class _Predicate>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         bool
         wait_until(unique_lock<mutex>& __lk,
                    const chrono::time_point<_Clock, _Duration>& __t,
                    _Predicate __pred);
 
     template <class _Rep, class _Period>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         cv_status
         wait_for(unique_lock<mutex>& __lk,
                  const chrono::duration<_Rep, _Period>& __d);
@@ -410,8 +410,8 @@ condition_variable::wait_for(unique_lock<mutex>& __lk,
     typedef time_point<system_clock, duration<long double, nano> > __sys_tpf;
     typedef time_point<system_clock, nanoseconds> __sys_tpi;
     __sys_tpf _Max = __sys_tpi::max();
-    system_clock::time_point __s_now = system_clock::now();
     steady_clock::time_point __c_now = steady_clock::now();
+    system_clock::time_point __s_now = system_clock::now();
     if (_Max - __d > __s_now)
         __do_timed_wait(__lk, __s_now + __ceil<nanoseconds>(__d));
     else
@@ -435,4 +435,6 @@ condition_variable::wait_for(unique_lock<mutex>& __lk,
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP___MUTEX_BASE
diff --git a/lib/libcxx/include/__nullptr b/lib/libcxx/include/__nullptr
index 95415a6325a..a341234f5d1 100644
--- a/lib/libcxx/include/__nullptr
+++ b/lib/libcxx/include/__nullptr
@@ -21,7 +21,7 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-struct _LIBCPP_TYPE_VIS_ONLY nullptr_t
+struct _LIBCPP_TEMPLATE_VIS nullptr_t
 {
     void* __lx;
 
@@ -42,10 +42,6 @@ struct _LIBCPP_TYPE_VIS_ONLY nullptr_t
 
     friend _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR bool operator==(nullptr_t, nullptr_t) {return true;}
     friend _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR bool operator!=(nullptr_t, nullptr_t) {return false;}
-    friend _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR bool operator<(nullptr_t, nullptr_t) {return false;}
-    friend _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR bool operator<=(nullptr_t, nullptr_t) {return true;}
-    friend _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR bool operator>(nullptr_t, nullptr_t) {return false;}
-    friend _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR bool operator>=(nullptr_t, nullptr_t) {return true;}
 };
 
 inline _LIBCPP_ALWAYS_INLINE _LIBCPP_CONSTEXPR nullptr_t __get_nullptr_t() {return nullptr_t(0);}
diff --git a/lib/libcxx/include/__split_buffer b/lib/libcxx/include/__split_buffer
index 79d1aa1d7c4..1daa4e5ada3 100644
--- a/lib/libcxx/include/__split_buffer
+++ b/lib/libcxx/include/__split_buffer
@@ -6,12 +6,14 @@
 #include <type_traits>
 #include <algorithm>
 
-#include <__undef_min_max>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <bool>
@@ -66,7 +68,7 @@ public:
     __split_buffer(size_type __cap, size_type __start, __alloc_rr& __a);
     ~__split_buffer();
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     __split_buffer(__split_buffer&& __c)
         _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value);
     __split_buffer(__split_buffer&& __c, const __alloc_rr& __a);
@@ -74,7 +76,7 @@ public:
         _NOEXCEPT_((__alloc_traits::propagate_on_container_move_assignment::value &&
                 is_nothrow_move_assignable<allocator_type>::value) ||
                !__alloc_traits::propagate_on_container_move_assignment::value);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY       iterator begin() _NOEXCEPT       {return __begin_;}
     _LIBCPP_INLINE_VISIBILITY const_iterator begin() const _NOEXCEPT {return __begin_;}
@@ -99,14 +101,12 @@ public:
     void shrink_to_fit() _NOEXCEPT;
     void push_front(const_reference __x);
     _LIBCPP_INLINE_VISIBILITY void push_back(const_reference __x);
-#if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+#ifndef _LIBCPP_CXX03_LANG
     void push_front(value_type&& __x);
     void push_back(value_type&& __x);
-#if !defined(_LIBCPP_HAS_NO_VARIADICS)
     template <class... _Args>
         void emplace_back(_Args&&... __args);
-#endif  // !defined(_LIBCPP_HAS_NO_VARIADICS)
-#endif  // !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+#endif  // !defined(_LIBCPP_CXX03_LANG)
 
     _LIBCPP_INLINE_VISIBILITY void pop_front() {__destruct_at_begin(__begin_+1);}
     _LIBCPP_INLINE_VISIBILITY void pop_back() {__destruct_at_end(__end_-1);}
@@ -343,7 +343,7 @@ __split_buffer<_Tp, _Allocator>::~__split_buffer()
         __alloc_traits::deallocate(__alloc(), __first_, capacity());
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 __split_buffer<_Tp, _Allocator>::__split_buffer(__split_buffer&& __c)
@@ -361,7 +361,7 @@ __split_buffer<_Tp, _Allocator>::__split_buffer(__split_buffer&& __c)
 
 template <class _Tp, class _Allocator>
 __split_buffer<_Tp, _Allocator>::__split_buffer(__split_buffer&& __c, const __alloc_rr& __a)
-    : __end_cap_(__a)
+    : __end_cap_(__second_tag(), __a)
 {
     if (__a == __c.__alloc())
     {
@@ -405,7 +405,7 @@ __split_buffer<_Tp, _Allocator>::operator=(__split_buffer&& __c)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 void
@@ -492,7 +492,7 @@ __split_buffer<_Tp, _Allocator>::push_front(const_reference __x)
     --__begin_;
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 void
@@ -524,7 +524,7 @@ __split_buffer<_Tp, _Allocator>::push_front(value_type&& __x)
     --__begin_;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -556,7 +556,7 @@ __split_buffer<_Tp, _Allocator>::push_back(const_reference __x)
     ++__end_;
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 void
@@ -588,8 +588,6 @@ __split_buffer<_Tp, _Allocator>::push_back(value_type&& __x)
     ++__end_;
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
 template <class _Tp, class _Allocator>
 template <class... _Args>
 void
@@ -621,9 +619,7 @@ __split_buffer<_Tp, _Allocator>::emplace_back(_Args&&... __args)
     ++__end_;
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -634,7 +630,8 @@ swap(__split_buffer<_Tp, _Allocator>& __x, __split_buffer<_Tp, _Allocator>& __y)
     __x.swap(__y);
 }
 
-
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_SPLIT_BUFFER
diff --git a/lib/libcxx/include/__sso_allocator b/lib/libcxx/include/__sso_allocator
index ca3b937c013..8147e75ec2c 100644
--- a/lib/libcxx/include/__sso_allocator
+++ b/lib/libcxx/include/__sso_allocator
@@ -15,8 +15,6 @@
 #include <type_traits>
 #include <new>
 
-#include <__undef___deallocate>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
@@ -64,7 +62,7 @@ public:
         if (__p == (pointer)&buf_)
             __allocated_ = false;
         else
-            _VSTD::__deallocate(__p);
+            _VSTD::__libcpp_deallocate(__p);
     }
     _LIBCPP_INLINE_VISIBILITY size_type max_size() const throw() {return size_type(~0) / sizeof(_Tp);}
 
diff --git a/lib/libcxx/include/__std_stream b/lib/libcxx/include/__std_stream
index f867cd23bdd..db90795f66f 100644
--- a/lib/libcxx/include/__std_stream
+++ b/lib/libcxx/include/__std_stream
@@ -17,12 +17,14 @@
 #include <__locale>
 #include <cstdio>
 
-#include <__undef_min_max>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 static const int __limit = 8;
@@ -297,7 +299,7 @@ __stdoutbuf<_CharT>::overflow(int_type __c)
                         return traits_type::eof();
                     if (__r == codecvt_base::partial)
                     {
-                        pbase = (char_type*)__e;
+                        pbase = const_cast<char_type*>(__e);
                     }
                 }
                 else
@@ -355,4 +357,6 @@ __stdoutbuf<_CharT>::imbue(const locale& __loc)
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP___STD_STREAM
diff --git a/lib/libcxx/include/__string b/lib/libcxx/include/__string
new file mode 100644
index 00000000000..d30c7fddc8d
--- /dev/null
+++ b/lib/libcxx/include/__string
@@ -0,0 +1,877 @@
+// -*- C++ -*-
+//===-------------------------- __string ----------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___STRING
+#define _LIBCPP___STRING
+
+/*
+    string synopsis
+
+namespace std
+{
+
+template <class charT>
+struct char_traits
+{
+    typedef charT     char_type;
+    typedef ...       int_type;
+    typedef streamoff off_type;
+    typedef streampos pos_type;
+    typedef mbstate_t state_type;
+
+    static constexpr void assign(char_type& c1, const char_type& c2) noexcept;
+    static constexpr bool eq(char_type c1, char_type c2) noexcept;
+    static constexpr bool lt(char_type c1, char_type c2) noexcept;
+
+    static constexpr int    compare(const char_type* s1, const char_type* s2, size_t n);
+    static constexpr size_t length(const char_type* s);
+    static constexpr const char_type* 
+                            find(const char_type* s, size_t n, const char_type& a);
+    static char_type*       move(char_type* s1, const char_type* s2, size_t n);
+    static char_type*       copy(char_type* s1, const char_type* s2, size_t n);
+    static char_type*       assign(char_type* s, size_t n, char_type a);
+
+    static constexpr int_type  not_eof(int_type c) noexcept;
+    static constexpr char_type to_char_type(int_type c) noexcept;
+    static constexpr int_type  to_int_type(char_type c) noexcept;
+    static constexpr bool      eq_int_type(int_type c1, int_type c2) noexcept;
+    static constexpr int_type  eof() noexcept;
+};
+
+template <> struct char_traits<char>;
+template <> struct char_traits<wchar_t>;
+
+}  // std
+
+*/
+
+#include <__config>
+#include <algorithm>  // for search and min
+#include <cstdio>     // For EOF.
+#include <memory>     // for __murmur2_or_cityhash
+
+#include <__debug>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// char_traits
+
+template <class _CharT>
+struct _LIBCPP_TEMPLATE_VIS char_traits
+{
+    typedef _CharT    char_type;
+    typedef int       int_type;
+    typedef streamoff off_type;
+    typedef streampos pos_type;
+    typedef mbstate_t state_type;
+
+    static inline void _LIBCPP_CONSTEXPR_AFTER_CXX14
+        assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
+    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
+        {return __c1 == __c2;}
+    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
+        {return __c1 < __c2;}
+
+    static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    int compare(const char_type* __s1, const char_type* __s2, size_t __n);
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    size_t length(const char_type* __s);
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    const char_type* find(const char_type* __s, size_t __n, const char_type& __a);
+    static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n);
+    _LIBCPP_INLINE_VISIBILITY
+    static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n);
+    _LIBCPP_INLINE_VISIBILITY
+    static char_type*       assign(char_type* __s, size_t __n, char_type __a);
+
+    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
+        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
+    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
+        {return char_type(__c);}
+    static inline _LIBCPP_CONSTEXPR int_type  to_int_type(char_type __c) _NOEXCEPT
+        {return int_type(__c);}
+    static inline _LIBCPP_CONSTEXPR bool      eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
+        {return __c1 == __c2;}
+    static inline _LIBCPP_CONSTEXPR int_type  eof() _NOEXCEPT
+        {return int_type(EOF);}
+};
+
+template <class _CharT>
+_LIBCPP_CONSTEXPR_AFTER_CXX14 int
+char_traits<_CharT>::compare(const char_type* __s1, const char_type* __s2, size_t __n)
+{
+    for (; __n; --__n, ++__s1, ++__s2)
+    {
+        if (lt(*__s1, *__s2))
+            return -1;
+        if (lt(*__s2, *__s1))
+            return 1;
+    }
+    return 0;
+}
+
+template <class _CharT>
+inline
+_LIBCPP_CONSTEXPR_AFTER_CXX14 size_t
+char_traits<_CharT>::length(const char_type* __s)
+{
+    size_t __len = 0;
+    for (; !eq(*__s, char_type(0)); ++__s)
+        ++__len;
+    return __len;
+}
+
+template <class _CharT>
+inline
+_LIBCPP_CONSTEXPR_AFTER_CXX14 const _CharT*
+char_traits<_CharT>::find(const char_type* __s, size_t __n, const char_type& __a)
+{
+    for (; __n; --__n)
+    {
+        if (eq(*__s, __a))
+            return __s;
+        ++__s;
+    }
+    return 0;
+}
+
+template <class _CharT>
+_CharT*
+char_traits<_CharT>::move(char_type* __s1, const char_type* __s2, size_t __n)
+{
+    char_type* __r = __s1;
+    if (__s1 < __s2)
+    {
+        for (; __n; --__n, ++__s1, ++__s2)
+            assign(*__s1, *__s2);
+    }
+    else if (__s2 < __s1)
+    {
+        __s1 += __n;
+        __s2 += __n;
+        for (; __n; --__n)
+            assign(*--__s1, *--__s2);
+    }
+    return __r;
+}
+
+template <class _CharT>
+inline
+_CharT*
+char_traits<_CharT>::copy(char_type* __s1, const char_type* __s2, size_t __n)
+{
+    _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
+    char_type* __r = __s1;
+    for (; __n; --__n, ++__s1, ++__s2)
+        assign(*__s1, *__s2);
+    return __r;
+}
+
+template <class _CharT>
+inline
+_CharT*
+char_traits<_CharT>::assign(char_type* __s, size_t __n, char_type __a)
+{
+    char_type* __r = __s;
+    for (; __n; --__n, ++__s)
+        assign(*__s, __a);
+    return __r;
+}
+
+// char_traits<char>
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS char_traits<char>
+{
+    typedef char      char_type;
+    typedef int       int_type;
+    typedef streamoff off_type;
+    typedef streampos pos_type;
+    typedef mbstate_t state_type;
+
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+    void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
+    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
+            {return __c1 == __c2;}
+    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
+        {return (unsigned char)__c1 < (unsigned char)__c2;}
+
+    static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    int compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+    static inline size_t _LIBCPP_CONSTEXPR_AFTER_CXX14
+    length(const char_type* __s)  _NOEXCEPT {return __builtin_strlen(__s);}
+    static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;
+    static inline char_type* move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+        {return __n == 0 ? __s1 : (char_type*) memmove(__s1, __s2, __n);}
+    static inline char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+        {
+            _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
+            return __n == 0 ? __s1 : (char_type*)memcpy(__s1, __s2, __n);
+        }
+    static inline char_type* assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
+        {return __n == 0 ? __s : (char_type*)memset(__s, to_int_type(__a), __n);}
+
+    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
+        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
+    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
+        {return char_type(__c);}
+    static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
+        {return int_type((unsigned char)__c);}
+    static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
+        {return __c1 == __c2;}
+    static inline _LIBCPP_CONSTEXPR int_type  eof() _NOEXCEPT
+        {return int_type(EOF);}
+};
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+int
+char_traits<char>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+{
+    if (__n == 0)
+        return 0;
+#if __has_feature(cxx_constexpr_string_builtins)
+    return __builtin_memcmp(__s1, __s2, __n);
+#elif _LIBCPP_STD_VER <= 14
+    return memcmp(__s1, __s2, __n);
+#else
+    for (; __n; --__n, ++__s1, ++__s2)
+    {
+        if (lt(*__s1, *__s2))
+            return -1;
+        if (lt(*__s2, *__s1))
+            return 1;
+    }
+    return 0;
+#endif
+}
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+const char*
+char_traits<char>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
+{
+    if (__n == 0)
+        return NULL;
+#if __has_feature(cxx_constexpr_string_builtins)
+    return __builtin_char_memchr(__s, to_int_type(__a), __n);
+#elif _LIBCPP_STD_VER <= 14
+    return (const char_type*) memchr(__s, to_int_type(__a), __n);
+#else
+    for (; __n; --__n)
+    {
+        if (eq(*__s, __a))
+            return __s;
+        ++__s;
+    }
+    return NULL;
+#endif
+}
+
+
+// char_traits<wchar_t>
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS char_traits<wchar_t>
+{
+    typedef wchar_t   char_type;
+    typedef wint_t    int_type;
+    typedef streamoff off_type;
+    typedef streampos pos_type;
+    typedef mbstate_t state_type;
+
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+    void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
+    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
+        {return __c1 == __c2;}
+    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
+        {return __c1 < __c2;}
+
+    static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    int compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+    static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    size_t length(const char_type* __s) _NOEXCEPT;
+    static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;
+    static inline char_type* move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+        {return __n == 0 ? __s1 : (char_type*)wmemmove(__s1, __s2, __n);}
+    static inline char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+        {
+            _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
+            return __n == 0 ? __s1 : (char_type*)wmemcpy(__s1, __s2, __n);
+        }
+    static inline char_type* assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
+        {return __n == 0 ? __s : (char_type*)wmemset(__s, __a, __n);}
+
+    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
+        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
+    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
+        {return char_type(__c);}
+    static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
+        {return int_type(__c);}
+    static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
+        {return __c1 == __c2;}
+    static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
+        {return int_type(WEOF);}
+};
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+int
+char_traits<wchar_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+{
+    if (__n == 0)
+        return 0;
+#if __has_feature(cxx_constexpr_string_builtins)
+    return __builtin_wmemcmp(__s1, __s2, __n);
+#elif _LIBCPP_STD_VER <= 14
+    return wmemcmp(__s1, __s2, __n);
+#else
+    for (; __n; --__n, ++__s1, ++__s2)
+    {
+        if (lt(*__s1, *__s2))
+            return -1;
+        if (lt(*__s2, *__s1))
+            return 1;
+    }
+    return 0;
+#endif
+}
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+size_t
+char_traits<wchar_t>::length(const char_type* __s) _NOEXCEPT
+{
+#if __has_feature(cxx_constexpr_string_builtins)
+    return __builtin_wcslen(__s);
+#elif _LIBCPP_STD_VER <= 14
+    return wcslen(__s);
+#else
+    size_t __len = 0;
+    for (; !eq(*__s, char_type(0)); ++__s)
+        ++__len;
+    return __len;
+#endif
+}
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+const wchar_t*
+char_traits<wchar_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
+{
+    if (__n == 0)
+        return NULL;
+#if __has_feature(cxx_constexpr_string_builtins)
+        return __builtin_wmemchr(__s, __a, __n);
+#elif _LIBCPP_STD_VER <= 14
+    return wmemchr(__s, __a, __n);
+#else
+    for (; __n; --__n)
+    {
+        if (eq(*__s, __a))
+            return __s;
+        ++__s;
+    }
+    return NULL;
+#endif
+}
+
+
+#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS char_traits<char16_t>
+{
+    typedef char16_t       char_type;
+    typedef uint_least16_t int_type;
+    typedef streamoff      off_type;
+    typedef u16streampos   pos_type;
+    typedef mbstate_t      state_type;
+
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+    void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
+    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
+        {return __c1 == __c2;}
+    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
+        {return __c1 < __c2;}
+
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    int              compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    size_t           length(const char_type* __s) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    static char_type*       assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT;
+
+    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
+        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
+    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
+        {return char_type(__c);}
+    static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
+        {return int_type(__c);}
+    static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
+        {return __c1 == __c2;}
+    static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
+        {return int_type(0xFFFF);}
+};
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+int
+char_traits<char16_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+{
+    for (; __n; --__n, ++__s1, ++__s2)
+    {
+        if (lt(*__s1, *__s2))
+            return -1;
+        if (lt(*__s2, *__s1))
+            return 1;
+    }
+    return 0;
+}
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+size_t
+char_traits<char16_t>::length(const char_type* __s) _NOEXCEPT
+{
+    size_t __len = 0;
+    for (; !eq(*__s, char_type(0)); ++__s)
+        ++__len;
+    return __len;
+}
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+const char16_t*
+char_traits<char16_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
+{
+    for (; __n; --__n)
+    {
+        if (eq(*__s, __a))
+            return __s;
+        ++__s;
+    }
+    return 0;
+}
+
+inline
+char16_t*
+char_traits<char16_t>::move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+{
+    char_type* __r = __s1;
+    if (__s1 < __s2)
+    {
+        for (; __n; --__n, ++__s1, ++__s2)
+            assign(*__s1, *__s2);
+    }
+    else if (__s2 < __s1)
+    {
+        __s1 += __n;
+        __s2 += __n;
+        for (; __n; --__n)
+            assign(*--__s1, *--__s2);
+    }
+    return __r;
+}
+
+inline
+char16_t*
+char_traits<char16_t>::copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+{
+    _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
+    char_type* __r = __s1;
+    for (; __n; --__n, ++__s1, ++__s2)
+        assign(*__s1, *__s2);
+    return __r;
+}
+
+inline
+char16_t*
+char_traits<char16_t>::assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
+{
+    char_type* __r = __s;
+    for (; __n; --__n, ++__s)
+        assign(*__s, __a);
+    return __r;
+}
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS char_traits<char32_t>
+{
+    typedef char32_t       char_type;
+    typedef uint_least32_t int_type;
+    typedef streamoff      off_type;
+    typedef u32streampos   pos_type;
+    typedef mbstate_t      state_type;
+
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+    void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
+    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
+        {return __c1 == __c2;}
+    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
+        {return __c1 < __c2;}
+
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    int              compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    size_t           length(const char_type* __s) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    static char_type*       assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT;
+
+    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
+        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
+    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
+        {return char_type(__c);}
+    static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
+        {return int_type(__c);}
+    static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
+        {return __c1 == __c2;}
+    static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
+        {return int_type(0xFFFFFFFF);}
+};
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+int
+char_traits<char32_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+{
+    for (; __n; --__n, ++__s1, ++__s2)
+    {
+        if (lt(*__s1, *__s2))
+            return -1;
+        if (lt(*__s2, *__s1))
+            return 1;
+    }
+    return 0;
+}
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+size_t
+char_traits<char32_t>::length(const char_type* __s) _NOEXCEPT
+{
+    size_t __len = 0;
+    for (; !eq(*__s, char_type(0)); ++__s)
+        ++__len;
+    return __len;
+}
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+const char32_t*
+char_traits<char32_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
+{
+    for (; __n; --__n)
+    {
+        if (eq(*__s, __a))
+            return __s;
+        ++__s;
+    }
+    return 0;
+}
+
+inline
+char32_t*
+char_traits<char32_t>::move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+{
+    char_type* __r = __s1;
+    if (__s1 < __s2)
+    {
+        for (; __n; --__n, ++__s1, ++__s2)
+            assign(*__s1, *__s2);
+    }
+    else if (__s2 < __s1)
+    {
+        __s1 += __n;
+        __s2 += __n;
+        for (; __n; --__n)
+            assign(*--__s1, *--__s2);
+    }
+    return __r;
+}
+
+inline
+char32_t*
+char_traits<char32_t>::copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+{
+    _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
+    char_type* __r = __s1;
+    for (; __n; --__n, ++__s1, ++__s2)
+        assign(*__s1, *__s2);
+    return __r;
+}
+
+inline
+char32_t*
+char_traits<char32_t>::assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
+{
+    char_type* __r = __s;
+    for (; __n; --__n, ++__s)
+        assign(*__s, __a);
+    return __r;
+}
+
+#endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
+
+// helper fns for basic_string and string_view
+
+// __str_find
+template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
+inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+__str_find(const _CharT *__p, _SizeT __sz, 
+             _CharT __c, _SizeT __pos) _NOEXCEPT
+{
+    if (__pos >= __sz)
+        return __npos;
+    const _CharT* __r = _Traits::find(__p + __pos, __sz - __pos, __c);
+    if (__r == 0)
+        return __npos;
+    return static_cast<_SizeT>(__r - __p);
+}
+
+template <class _CharT, class _Traits>
+inline _LIBCPP_CONSTEXPR_AFTER_CXX11 const _CharT *
+__search_substring(const _CharT *__first1, const _CharT *__last1,
+                   const _CharT *__first2, const _CharT *__last2) {
+  // Take advantage of knowing source and pattern lengths.
+  // Stop short when source is smaller than pattern.
+  const ptrdiff_t __len2 = __last2 - __first2;
+  if (__len2 == 0)
+    return __first1;
+
+  ptrdiff_t __len1 = __last1 - __first1;
+  if (__len1 < __len2)
+    return __last1;
+
+  // First element of __first2 is loop invariant.
+  _CharT __f2 = *__first2;
+  while (true) {
+    __len1 = __last1 - __first1;
+    // Check whether __first1 still has at least __len2 bytes.
+    if (__len1 < __len2)
+      return __last1;
+
+    // Find __f2 the first byte matching in __first1.
+    __first1 = _Traits::find(__first1, __len1 - __len2 + 1, __f2);
+    if (__first1 == 0)
+      return __last1;
+
+    // It is faster to compare from the first byte of __first1 even if we
+    // already know that it matches the first byte of __first2: this is because
+    // __first2 is most likely aligned, as it is user's "pattern" string, and
+    // __first1 + 1 is most likely not aligned, as the match is in the middle of
+    // the string.
+    if (_Traits::compare(__first1, __first2, __len2) == 0)
+      return __first1;
+
+    ++__first1;
+  }
+}
+
+template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
+inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+__str_find(const _CharT *__p, _SizeT __sz, 
+       const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
+{
+    if (__pos > __sz)
+        return __npos;
+
+    if (__n == 0) // There is nothing to search, just return __pos.
+        return __pos;
+
+    const _CharT *__r = __search_substring<_CharT, _Traits>(
+        __p + __pos, __p + __sz, __s, __s + __n);
+
+    if (__r == __p + __sz)
+        return __npos;
+    return static_cast<_SizeT>(__r - __p);
+}
+
+
+// __str_rfind
+
+template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
+inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+__str_rfind(const _CharT *__p, _SizeT __sz, 
+              _CharT __c, _SizeT __pos) _NOEXCEPT
+{
+    if (__sz < 1)
+        return __npos;
+    if (__pos < __sz)
+        ++__pos;
+    else
+        __pos = __sz;
+    for (const _CharT* __ps = __p + __pos; __ps != __p;)
+    {
+        if (_Traits::eq(*--__ps, __c))
+            return static_cast<_SizeT>(__ps - __p);
+    }
+    return __npos;
+}
+
+template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
+inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+__str_rfind(const _CharT *__p, _SizeT __sz, 
+        const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
+{
+    __pos = _VSTD::min(__pos, __sz);
+    if (__n < __sz - __pos)
+        __pos += __n;
+    else
+        __pos = __sz;
+    const _CharT* __r = _VSTD::__find_end(
+                  __p, __p + __pos, __s, __s + __n, _Traits::eq, 
+                        random_access_iterator_tag(), random_access_iterator_tag());
+    if (__n > 0 && __r == __p + __pos)
+        return __npos;
+    return static_cast<_SizeT>(__r - __p);
+}
+
+// __str_find_first_of
+template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
+inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+__str_find_first_of(const _CharT *__p, _SizeT __sz,
+                const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
+{
+    if (__pos >= __sz || __n == 0)
+        return __npos;
+    const _CharT* __r = _VSTD::__find_first_of_ce
+        (__p + __pos, __p + __sz, __s, __s + __n, _Traits::eq );
+    if (__r == __p + __sz)
+        return __npos;
+    return static_cast<_SizeT>(__r - __p);
+}
+
+
+// __str_find_last_of
+template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
+inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+__str_find_last_of(const _CharT *__p, _SizeT __sz,
+               const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
+    {
+    if (__n != 0)
+    {
+        if (__pos < __sz)
+            ++__pos;
+        else
+            __pos = __sz;
+        for (const _CharT* __ps = __p + __pos; __ps != __p;)
+        {
+            const _CharT* __r = _Traits::find(__s, __n, *--__ps);
+            if (__r)
+                return static_cast<_SizeT>(__ps - __p);
+        }
+    }
+    return __npos;
+}
+
+
+// __str_find_first_not_of
+template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
+inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+__str_find_first_not_of(const _CharT *__p, _SizeT __sz,
+                    const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
+{
+    if (__pos < __sz)
+    {
+        const _CharT* __pe = __p + __sz;
+        for (const _CharT* __ps = __p + __pos; __ps != __pe; ++__ps)
+            if (_Traits::find(__s, __n, *__ps) == 0)
+                return static_cast<_SizeT>(__ps - __p);
+    }
+    return __npos;
+}
+
+
+template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
+inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+__str_find_first_not_of(const _CharT *__p, _SizeT __sz,
+                          _CharT __c, _SizeT __pos) _NOEXCEPT
+{
+    if (__pos < __sz)
+    {
+        const _CharT* __pe = __p + __sz;
+        for (const _CharT* __ps = __p + __pos; __ps != __pe; ++__ps)
+            if (!_Traits::eq(*__ps, __c))
+                return static_cast<_SizeT>(__ps - __p);
+    }
+    return __npos;
+}
+
+
+// __str_find_last_not_of
+template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
+inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+__str_find_last_not_of(const _CharT *__p, _SizeT __sz,
+                   const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
+{
+    if (__pos < __sz)
+        ++__pos;
+    else
+        __pos = __sz;
+    for (const _CharT* __ps = __p + __pos; __ps != __p;)
+        if (_Traits::find(__s, __n, *--__ps) == 0)
+            return static_cast<_SizeT>(__ps - __p);
+    return __npos;
+}
+
+
+template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
+inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+__str_find_last_not_of(const _CharT *__p, _SizeT __sz,
+                         _CharT __c, _SizeT __pos) _NOEXCEPT
+{
+    if (__pos < __sz)
+        ++__pos;
+    else
+        __pos = __sz;
+    for (const _CharT* __ps = __p + __pos; __ps != __p;)
+        if (!_Traits::eq(*--__ps, __c))
+            return static_cast<_SizeT>(__ps - __p);
+    return __npos;
+}
+
+template<class _Ptr>
+inline _LIBCPP_INLINE_VISIBILITY
+size_t __do_string_hash(_Ptr __p, _Ptr __e)
+{
+    typedef typename iterator_traits<_Ptr>::value_type value_type;
+    return __murmur2_or_cityhash<size_t>()(__p, (__e-__p)*sizeof(value_type));
+}
+
+template <class _CharT, class _Iter, class _Traits=char_traits<_CharT> >
+struct __quoted_output_proxy
+{
+    _Iter  __first;
+    _Iter  __last;
+    _CharT  __delim;
+    _CharT  __escape;
+
+    __quoted_output_proxy(_Iter __f, _Iter __l, _CharT __d, _CharT __e)
+    : __first(__f), __last(__l), __delim(__d), __escape(__e) {}
+    //  This would be a nice place for a string_ref 
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif  // _LIBCPP___STRING
diff --git a/lib/libcxx/include/__threading_support b/lib/libcxx/include/__threading_support
index c9a4ea9d094..5d4c907966e 100644
--- a/lib/libcxx/include/__threading_support
+++ b/lib/libcxx/include/__threading_support
@@ -12,194 +12,628 @@
 #define _LIBCPP_THREADING_SUPPORT
 
 #include <__config>
+#include <chrono>
+#include <errno.h>
 
 #ifndef _LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER
 #pragma GCC system_header
 #endif
 
-#ifndef _LIBCPP_HAS_NO_THREADS
+#if defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
+# include <__external_threading>
+#elif !defined(_LIBCPP_HAS_NO_THREADS)
 
 #if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
-#include <pthread.h>
-#include <sched.h>
+# include <pthread.h>
+# include <sched.h>
+#elif defined(_LIBCPP_HAS_THREAD_API_WIN32)
+#include <windows.h>
+#include <process.h>
+#include <fibersapi.h>
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
+#if defined(_LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL) || \
+    defined(_LIBCPP_BUILDING_THREAD_LIBRARY_EXTERNAL)
+#define _LIBCPP_THREAD_ABI_VISIBILITY _LIBCPP_FUNC_VIS
+#else
+#define _LIBCPP_THREAD_ABI_VISIBILITY inline _LIBCPP_INLINE_VISIBILITY
+#endif
+
+#if defined(__FreeBSD__) && defined(__clang__) && __has_attribute(no_thread_safety_analysis)
+#define _LIBCPP_NO_THREAD_SAFETY_ANALYSIS __attribute__((no_thread_safety_analysis))
+#else
+#define _LIBCPP_NO_THREAD_SAFETY_ANALYSIS
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
-
 // Mutex
-#define _LIBCPP_MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
 typedef pthread_mutex_t __libcpp_mutex_t;
+#define _LIBCPP_MUTEX_INITIALIZER PTHREAD_MUTEX_INITIALIZER
+
+typedef pthread_mutex_t __libcpp_recursive_mutex_t;
+
+// Condition Variable
+typedef pthread_cond_t __libcpp_condvar_t;
+#define _LIBCPP_CONDVAR_INITIALIZER PTHREAD_COND_INITIALIZER
+
+// Execute once
+typedef pthread_once_t __libcpp_exec_once_flag;
+#define _LIBCPP_EXEC_ONCE_INITIALIZER PTHREAD_ONCE_INIT
+
+// Thread id
+typedef pthread_t __libcpp_thread_id;
+
+// Thread
+#define _LIBCPP_NULL_THREAD 0U
+
+typedef pthread_t __libcpp_thread_t;
+
+// Thrad Local Storage
+typedef pthread_key_t __libcpp_tls_key;
+
+#define _LIBCPP_TLS_DESTRUCTOR_CC
+#else
+// Mutex
+typedef SRWLOCK __libcpp_mutex_t;
+#define _LIBCPP_MUTEX_INITIALIZER SRWLOCK_INIT
+
+typedef CRITICAL_SECTION __libcpp_recursive_mutex_t;
+
+// Condition Variable
+typedef CONDITION_VARIABLE __libcpp_condvar_t;
+#define _LIBCPP_CONDVAR_INITIALIZER CONDITION_VARIABLE_INIT
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_recursive_mutex_init(__libcpp_mutex_t* __m)
+// Execute Once
+typedef INIT_ONCE __libcpp_exec_once_flag;
+#define _LIBCPP_EXEC_ONCE_INITIALIZER INIT_ONCE_STATIC_INIT
+
+// Thread ID
+typedef DWORD __libcpp_thread_id;
+
+// Thread
+#define _LIBCPP_NULL_THREAD 0U
+
+typedef HANDLE __libcpp_thread_t;
+
+// Thread Local Storage
+typedef DWORD __libcpp_tls_key;
+
+#define _LIBCPP_TLS_DESTRUCTOR_CC WINAPI
+#endif
+
+// Mutex
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_recursive_mutex_init(__libcpp_recursive_mutex_t *__m);
+
+_LIBCPP_THREAD_ABI_VISIBILITY _LIBCPP_NO_THREAD_SAFETY_ANALYSIS
+int __libcpp_recursive_mutex_lock(__libcpp_recursive_mutex_t *__m);
+
+_LIBCPP_THREAD_ABI_VISIBILITY _LIBCPP_NO_THREAD_SAFETY_ANALYSIS
+bool __libcpp_recursive_mutex_trylock(__libcpp_recursive_mutex_t *__m);
+
+_LIBCPP_THREAD_ABI_VISIBILITY _LIBCPP_NO_THREAD_SAFETY_ANALYSIS
+int __libcpp_recursive_mutex_unlock(__libcpp_recursive_mutex_t *__m);
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_recursive_mutex_destroy(__libcpp_recursive_mutex_t *__m);
+
+_LIBCPP_THREAD_ABI_VISIBILITY _LIBCPP_NO_THREAD_SAFETY_ANALYSIS
+int __libcpp_mutex_lock(__libcpp_mutex_t *__m);
+
+_LIBCPP_THREAD_ABI_VISIBILITY _LIBCPP_NO_THREAD_SAFETY_ANALYSIS
+bool __libcpp_mutex_trylock(__libcpp_mutex_t *__m);
+
+_LIBCPP_THREAD_ABI_VISIBILITY _LIBCPP_NO_THREAD_SAFETY_ANALYSIS
+int __libcpp_mutex_unlock(__libcpp_mutex_t *__m);
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_mutex_destroy(__libcpp_mutex_t *__m);
+
+// Condition variable
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_signal(__libcpp_condvar_t* __cv);
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_broadcast(__libcpp_condvar_t* __cv);
+
+_LIBCPP_THREAD_ABI_VISIBILITY _LIBCPP_NO_THREAD_SAFETY_ANALYSIS
+int __libcpp_condvar_wait(__libcpp_condvar_t* __cv, __libcpp_mutex_t* __m);
+
+_LIBCPP_THREAD_ABI_VISIBILITY _LIBCPP_NO_THREAD_SAFETY_ANALYSIS
+int __libcpp_condvar_timedwait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m,
+                               timespec *__ts);
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_condvar_destroy(__libcpp_condvar_t* __cv);
+
+// Execute once
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_execute_once(__libcpp_exec_once_flag *flag,
+                          void (*init_routine)(void));
+
+// Thread id
+_LIBCPP_THREAD_ABI_VISIBILITY
+bool __libcpp_thread_id_equal(__libcpp_thread_id t1, __libcpp_thread_id t2);
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+bool __libcpp_thread_id_less(__libcpp_thread_id t1, __libcpp_thread_id t2);
+
+// Thread
+_LIBCPP_THREAD_ABI_VISIBILITY
+bool __libcpp_thread_isnull(const __libcpp_thread_t *__t);
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_thread_create(__libcpp_thread_t *__t, void *(*__func)(void *),
+                           void *__arg);
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+__libcpp_thread_id __libcpp_thread_get_current_id();
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+__libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t *__t);
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_thread_join(__libcpp_thread_t *__t);
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_thread_detach(__libcpp_thread_t *__t);
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+void __libcpp_thread_yield();
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+void __libcpp_thread_sleep_for(const chrono::nanoseconds& __ns);
+
+// Thread local storage
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_tls_create(__libcpp_tls_key* __key,
+                        void(_LIBCPP_TLS_DESTRUCTOR_CC* __at_exit)(void*));
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+void *__libcpp_tls_get(__libcpp_tls_key __key);
+
+_LIBCPP_THREAD_ABI_VISIBILITY
+int __libcpp_tls_set(__libcpp_tls_key __key, void *__p);
+
+#if !defined(_LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL) || \
+    defined(_LIBCPP_BUILDING_THREAD_LIBRARY_EXTERNAL)
+
+#if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
+
+int __libcpp_recursive_mutex_init(__libcpp_recursive_mutex_t *__m)
 {
-    pthread_mutexattr_t attr;
-    int __ec = pthread_mutexattr_init(&attr);
-    if (__ec) return __ec;
-    __ec = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
-    if (__ec)
-    {
-        pthread_mutexattr_destroy(&attr);
-        return __ec;
-    }
-    __ec = pthread_mutex_init(__m, &attr);
-    if (__ec)
-    {
-        pthread_mutexattr_destroy(&attr);
-        return __ec;
-    }
-    __ec = pthread_mutexattr_destroy(&attr);
-    if (__ec)
-    {
-        pthread_mutex_destroy(__m);
-        return __ec;
-    }
-    return 0;
+  pthread_mutexattr_t attr;
+  int __ec = pthread_mutexattr_init(&attr);
+  if (__ec)
+    return __ec;
+  __ec = pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
+  if (__ec) {
+    pthread_mutexattr_destroy(&attr);
+    return __ec;
+  }
+  __ec = pthread_mutex_init(__m, &attr);
+  if (__ec) {
+    pthread_mutexattr_destroy(&attr);
+    return __ec;
+  }
+  __ec = pthread_mutexattr_destroy(&attr);
+  if (__ec) {
+    pthread_mutex_destroy(__m);
+    return __ec;
+  }
+  return 0;
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_mutex_lock(__libcpp_mutex_t* __m)
+int __libcpp_recursive_mutex_lock(__libcpp_recursive_mutex_t *__m)
 {
-    return pthread_mutex_lock(__m);
+  return pthread_mutex_lock(__m);
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_mutex_trylock(__libcpp_mutex_t* __m)
+bool __libcpp_recursive_mutex_trylock(__libcpp_recursive_mutex_t *__m)
 {
-    return pthread_mutex_trylock(__m);
+  return pthread_mutex_trylock(__m) == 0;
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_mutex_unlock(__libcpp_mutex_t* __m)
+int __libcpp_recursive_mutex_unlock(__libcpp_mutex_t *__m)
 {
-    return pthread_mutex_unlock(__m);
+  return pthread_mutex_unlock(__m);
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_mutex_destroy(__libcpp_mutex_t* __m)
+int __libcpp_recursive_mutex_destroy(__libcpp_recursive_mutex_t *__m)
 {
-    return pthread_mutex_destroy(__m);
+  return pthread_mutex_destroy(__m);
 }
 
-// Condition variable
-#define _LIBCPP_CONDVAR_INITIALIZER PTHREAD_COND_INITIALIZER
-typedef pthread_cond_t __libcpp_condvar_t;
+int __libcpp_mutex_lock(__libcpp_mutex_t *__m)
+{
+  return pthread_mutex_lock(__m);
+}
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_condvar_signal(__libcpp_condvar_t* __cv)
+bool __libcpp_mutex_trylock(__libcpp_mutex_t *__m)
 {
-    return pthread_cond_signal(__cv);
+  return pthread_mutex_trylock(__m) == 0;
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_condvar_broadcast(__libcpp_condvar_t* __cv)
+int __libcpp_mutex_unlock(__libcpp_mutex_t *__m)
 {
-    return pthread_cond_broadcast(__cv);
+  return pthread_mutex_unlock(__m);
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_condvar_wait(__libcpp_condvar_t* __cv, __libcpp_mutex_t* __m)
+int __libcpp_mutex_destroy(__libcpp_mutex_t *__m)
 {
-    return pthread_cond_wait(__cv, __m);
+  return pthread_mutex_destroy(__m);
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_condvar_timedwait(__libcpp_condvar_t* __cv, __libcpp_mutex_t* __m, timespec* __ts)
+// Condition Variable
+int __libcpp_condvar_signal(__libcpp_condvar_t *__cv)
 {
-    return pthread_cond_timedwait(__cv, __m, __ts);
+  return pthread_cond_signal(__cv);
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_condvar_destroy(__libcpp_condvar_t* __cv)
+int __libcpp_condvar_broadcast(__libcpp_condvar_t *__cv)
 {
-    return pthread_cond_destroy(__cv);
+  return pthread_cond_broadcast(__cv);
 }
 
-// Thread id
-typedef pthread_t __libcpp_thread_id;
+int __libcpp_condvar_wait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m)
+{
+  return pthread_cond_wait(__cv, __m);
+}
+
+int __libcpp_condvar_timedwait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m,
+                               timespec *__ts)
+{
+  return pthread_cond_timedwait(__cv, __m, __ts);
+}
 
+int __libcpp_condvar_destroy(__libcpp_condvar_t *__cv)
+{
+  return pthread_cond_destroy(__cv);
+}
+
+// Execute once
+int __libcpp_execute_once(__libcpp_exec_once_flag *flag,
+                          void (*init_routine)(void)) {
+  return pthread_once(flag, init_routine);
+}
+
+// Thread id
 // Returns non-zero if the thread ids are equal, otherwise 0
-inline _LIBCPP_ALWAYS_INLINE
 bool __libcpp_thread_id_equal(__libcpp_thread_id t1, __libcpp_thread_id t2)
 {
-    return pthread_equal(t1, t2) != 0;
+  return pthread_equal(t1, t2) != 0;
 }
 
 // Returns non-zero if t1 < t2, otherwise 0
-inline _LIBCPP_ALWAYS_INLINE
 bool __libcpp_thread_id_less(__libcpp_thread_id t1, __libcpp_thread_id t2)
 {
-    return t1 < t2;
+  return t1 < t2;
 }
 
 // Thread
-typedef pthread_t __libcpp_thread_t;
+bool __libcpp_thread_isnull(const __libcpp_thread_t *__t) {
+  return *__t == 0;
+}
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_thread_create(__libcpp_thread_t* __t, void* (*__func)(void*), void* __arg)
+int __libcpp_thread_create(__libcpp_thread_t *__t, void *(*__func)(void *),
+                           void *__arg)
 {
-    return pthread_create(__t, 0, __func, __arg);
+  return pthread_create(__t, 0, __func, __arg);
 }
 
-inline _LIBCPP_ALWAYS_INLINE
 __libcpp_thread_id __libcpp_thread_get_current_id()
 {
-    return pthread_self();
+  return pthread_self();
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-__libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t* __t)
+__libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t *__t)
 {
-    return *__t;
+  return *__t;
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_thread_join(__libcpp_thread_t* __t)
+int __libcpp_thread_join(__libcpp_thread_t *__t)
 {
-    return pthread_join(*__t, 0);
+  return pthread_join(*__t, 0);
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_thread_detach(__libcpp_thread_t* __t)
+int __libcpp_thread_detach(__libcpp_thread_t *__t)
 {
-    return pthread_detach(*__t);
+  return pthread_detach(*__t);
 }
 
-inline _LIBCPP_ALWAYS_INLINE
 void __libcpp_thread_yield()
 {
-    sched_yield();
+  sched_yield();
+}
+
+void __libcpp_thread_sleep_for(const chrono::nanoseconds& __ns)
+{
+   using namespace chrono;
+   seconds __s = duration_cast<seconds>(__ns);
+   timespec __ts;
+   typedef decltype(__ts.tv_sec) ts_sec;
+   _LIBCPP_CONSTEXPR ts_sec __ts_sec_max = numeric_limits<ts_sec>::max();
+
+   if (__s.count() < __ts_sec_max)
+   {
+     __ts.tv_sec = static_cast<ts_sec>(__s.count());
+     __ts.tv_nsec = static_cast<decltype(__ts.tv_nsec)>((__ns - __s).count());
+   }
+   else
+   {
+     __ts.tv_sec = __ts_sec_max;
+     __ts.tv_nsec = 999999999; // (10^9 - 1)
+   }
+
+   while (nanosleep(&__ts, &__ts) == -1 && errno == EINTR);
 }
 
 // Thread local storage
-typedef pthread_key_t __libcpp_tl_key;
+int __libcpp_tls_create(__libcpp_tls_key *__key, void (*__at_exit)(void *))
+{
+  return pthread_key_create(__key, __at_exit);
+}
+
+void *__libcpp_tls_get(__libcpp_tls_key __key)
+{
+  return pthread_getspecific(__key);
+}
 
-inline _LIBCPP_ALWAYS_INLINE
-int __libcpp_tl_create(__libcpp_tl_key* __key, void (*__at_exit)(void*))
+int __libcpp_tls_set(__libcpp_tls_key __key, void *__p)
 {
-    return pthread_key_create(__key, __at_exit);
+    return pthread_setspecific(__key, __p);
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-void* __libcpp_tl_get(__libcpp_tl_key __key)
+#elif defined(_LIBCPP_HAS_THREAD_API_WIN32)
+
+// Mutex
+int __libcpp_recursive_mutex_init(__libcpp_recursive_mutex_t *__m)
 {
-    return pthread_getspecific(__key);
+  InitializeCriticalSection(__m);
+  return 0;
 }
 
-inline _LIBCPP_ALWAYS_INLINE
-void __libcpp_tl_set(__libcpp_tl_key __key, void* __p)
+int __libcpp_recursive_mutex_lock(__libcpp_recursive_mutex_t *__m)
 {
-    pthread_setspecific(__key, __p);
+  EnterCriticalSection(__m);
+  return 0;
 }
 
-#else // !_LIBCPP_HAS_THREAD_API_PTHREAD
-  #error "No thread API selected."
-#endif
+bool __libcpp_recursive_mutex_trylock(__libcpp_recursive_mutex_t *__m)
+{
+  return TryEnterCriticalSection(__m) != 0;
+}
+
+int __libcpp_recursive_mutex_unlock(__libcpp_recursive_mutex_t *__m)
+{
+  LeaveCriticalSection(__m);
+  return 0;
+}
+
+int __libcpp_recursive_mutex_destroy(__libcpp_recursive_mutex_t *__m)
+{
+  DeleteCriticalSection(__m);
+  return 0;
+}
+
+int __libcpp_mutex_lock(__libcpp_mutex_t *__m)
+{
+  AcquireSRWLockExclusive(__m);
+  return 0;
+}
+
+bool __libcpp_mutex_trylock(__libcpp_mutex_t *__m)
+{
+  return TryAcquireSRWLockExclusive(__m) != 0;
+}
+
+int __libcpp_mutex_unlock(__libcpp_mutex_t *__m)
+{
+  ReleaseSRWLockExclusive(__m);
+  return 0;
+}
+
+int __libcpp_mutex_destroy(__libcpp_mutex_t *__m)
+{
+  static_cast<void>(__m);
+  return 0;
+}
+
+// Condition Variable
+int __libcpp_condvar_signal(__libcpp_condvar_t *__cv)
+{
+  WakeConditionVariable(__cv);
+  return 0;
+}
+
+int __libcpp_condvar_broadcast(__libcpp_condvar_t *__cv)
+{
+  WakeAllConditionVariable(__cv);
+  return 0;
+}
+
+int __libcpp_condvar_wait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m)
+{
+  SleepConditionVariableSRW(__cv, __m, INFINITE, 0);
+  return 0;
+}
+
+int __libcpp_condvar_timedwait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m,
+                               timespec *__ts)
+{
+  using namespace _VSTD::chrono;
+
+  auto duration = seconds(__ts->tv_sec) + nanoseconds(__ts->tv_nsec);
+  auto abstime =
+      system_clock::time_point(duration_cast<system_clock::duration>(duration));
+  auto timeout_ms = duration_cast<milliseconds>(abstime - system_clock::now());
+
+  if (!SleepConditionVariableSRW(__cv, __m,
+                                 timeout_ms.count() > 0 ? timeout_ms.count()
+                                                        : 0,
+                                 0))
+    {
+      auto __ec = GetLastError();
+      return __ec == ERROR_TIMEOUT ? ETIMEDOUT : __ec;
+    }
+  return 0;
+}
+
+int __libcpp_condvar_destroy(__libcpp_condvar_t *__cv)
+{
+  static_cast<void>(__cv);
+  return 0;
+}
+
+// Execute Once
+static inline _LIBCPP_ALWAYS_INLINE BOOL CALLBACK
+__libcpp_init_once_execute_once_thunk(PINIT_ONCE __init_once, PVOID __parameter,
+                                      PVOID *__context)
+{
+  static_cast<void>(__init_once);
+  static_cast<void>(__context);
+
+  void (*init_routine)(void) = reinterpret_cast<void (*)(void)>(__parameter);
+  init_routine();
+  return TRUE;
+}
+
+int __libcpp_execute_once(__libcpp_exec_once_flag *__flag,
+                          void (*__init_routine)(void))
+{
+  if (!InitOnceExecuteOnce(__flag, __libcpp_init_once_execute_once_thunk,
+                           reinterpret_cast<void *>(__init_routine), NULL))
+    return GetLastError();
+  return 0;
+}
+
+// Thread ID
+bool __libcpp_thread_id_equal(__libcpp_thread_id __lhs,
+                              __libcpp_thread_id __rhs)
+{
+  return __lhs == __rhs;
+}
+
+bool __libcpp_thread_id_less(__libcpp_thread_id __lhs, __libcpp_thread_id __rhs)
+{
+  return __lhs < __rhs;
+}
+
+// Thread
+struct __libcpp_beginthreadex_thunk_data
+{
+  void *(*__func)(void *);
+  void *__arg;
+};
+
+static inline _LIBCPP_ALWAYS_INLINE unsigned WINAPI
+__libcpp_beginthreadex_thunk(void *__raw_data)
+{
+  auto *__data =
+      static_cast<__libcpp_beginthreadex_thunk_data *>(__raw_data);
+  auto *__func = __data->__func;
+  void *__arg = __data->__arg;
+  delete __data;
+  return static_cast<unsigned>(reinterpret_cast<uintptr_t>(__func(__arg)));
+}
+
+bool __libcpp_thread_isnull(const __libcpp_thread_t *__t) {
+  return *__t == 0;
+}
+
+int __libcpp_thread_create(__libcpp_thread_t *__t, void *(*__func)(void *),
+                           void *__arg)
+{
+  auto *__data = new __libcpp_beginthreadex_thunk_data;
+  __data->__func = __func;
+  __data->__arg = __arg;
+
+  *__t = reinterpret_cast<HANDLE>(_beginthreadex(nullptr, 0,
+                                                 __libcpp_beginthreadex_thunk,
+                                                 __data, 0, nullptr));
+
+  if (*__t)
+    return 0;
+  return GetLastError();
+}
+
+__libcpp_thread_id __libcpp_thread_get_current_id()
+{
+  return GetCurrentThreadId();
+}
+
+__libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t *__t)
+{
+  return GetThreadId(*__t);
+}
+
+int __libcpp_thread_join(__libcpp_thread_t *__t)
+{
+  if (WaitForSingleObjectEx(*__t, INFINITE, FALSE) == WAIT_FAILED)
+    return GetLastError();
+  if (!CloseHandle(*__t))
+    return GetLastError();
+  return 0;
+}
+
+int __libcpp_thread_detach(__libcpp_thread_t *__t)
+{
+  if (!CloseHandle(*__t))
+    return GetLastError();
+  return 0;
+}
+
+void __libcpp_thread_yield()
+{
+  SwitchToThread();
+}
+
+void __libcpp_thread_sleep_for(const chrono::nanoseconds& __ns)
+{
+  using namespace chrono;
+  // round-up to the nearest milisecond
+  milliseconds __ms =
+      duration_cast<milliseconds>(__ns + chrono::nanoseconds(999999));
+  // FIXME(compnerd) this should be an alertable sleep (WFSO or SleepEx)
+  Sleep(__ms.count());
+}
+
+// Thread Local Storage
+int __libcpp_tls_create(__libcpp_tls_key* __key,
+                        void(_LIBCPP_TLS_DESTRUCTOR_CC* __at_exit)(void*))
+{
+  *__key = FlsAlloc(__at_exit);
+  if (*__key == FLS_OUT_OF_INDEXES)
+    return GetLastError();
+  return 0;
+}
+
+void *__libcpp_tls_get(__libcpp_tls_key __key)
+{
+  return FlsGetValue(__key);
+}
+
+int __libcpp_tls_set(__libcpp_tls_key __key, void *__p)
+{
+  if (!FlsSetValue(__key, __p))
+    return GetLastError();
+  return 0;
+}
+
+#endif // _LIBCPP_HAS_THREAD_API_PTHREAD
+
+#endif // !_LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL || _LIBCPP_BUILDING_THREAD_LIBRARY_EXTERNAL
 
 _LIBCPP_END_NAMESPACE_STD
 
-#endif // _LIBCPP_HAS_NO_THREADS
+_LIBCPP_POP_MACROS
+
+#endif // !_LIBCPP_HAS_NO_THREADS
 
 #endif // _LIBCPP_THREADING_SUPPORT
diff --git a/lib/libcxx/include/__tree b/lib/libcxx/include/__tree
index b560bf071e8..3ccfcb70031 100644
--- a/lib/libcxx/include/__tree
+++ b/lib/libcxx/include/__tree
@@ -21,13 +21,17 @@
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Tp, class _Compare, class _Allocator> class __tree;
 template <class _Tp, class _NodePtr, class _DiffType>
-    class _LIBCPP_TYPE_VIS_ONLY __tree_iterator;
+    class _LIBCPP_TEMPLATE_VIS __tree_iterator;
 template <class _Tp, class _ConstNodePtr, class _DiffType>
-    class _LIBCPP_TYPE_VIS_ONLY __tree_const_iterator;
+    class _LIBCPP_TEMPLATE_VIS __tree_const_iterator;
 
 template <class _Pointer> class __tree_end_node;
 template <class _VoidPtr> class __tree_node_base;
@@ -41,9 +45,13 @@ template <class _Key, class _Value>
 struct __value_type;
 #endif
 
+template <class _Key, class _CP, class _Compare,
+    bool = is_empty<_Compare>::value && !__libcpp_is_final<_Compare>::value>
+class __map_value_compare;
+
 template <class _Allocator> class __map_node_destructor;
-template <class _TreeIterator> class _LIBCPP_TYPE_VIS_ONLY __map_iterator;
-template <class _TreeIterator> class _LIBCPP_TYPE_VIS_ONLY __map_const_iterator;
+template <class _TreeIterator> class _LIBCPP_TEMPLATE_VIS __map_iterator;
+template <class _TreeIterator> class _LIBCPP_TEMPLATE_VIS __map_const_iterator;
 
 /*
 
@@ -76,7 +84,7 @@ __tree_is_left_child(_NodePtr __x) _NOEXCEPT
     return __x == __x->__parent_->__left_;
 }
 
-// Determintes if the subtree rooted at __x is a proper red black subtree.  If
+// Determines if the subtree rooted at __x is a proper red black subtree.  If
 //    __x is a proper subtree, returns the black height (null counts as 1).  If
 //    __x is an improper subtree, returns 0.
 template <class _NodePtr>
@@ -111,7 +119,7 @@ __tree_sub_invariant(_NodePtr __x)
     return __h + __x->__is_black_;  // return black height of this node
 }
 
-// Determintes if the red black tree rooted at __root is a proper red black tree.
+// Determines if the red black tree rooted at __root is a proper red black tree.
 //    __root == nullptr is a proper tree.  Returns true is __root is a proper
 //    red black tree, else returns false.
 template <class _NodePtr>
@@ -797,7 +805,7 @@ public:
 
 
 template <class _Tp, class _NodePtr, class _DiffType>
-class _LIBCPP_TYPE_VIS_ONLY __tree_iterator
+class _LIBCPP_TEMPLATE_VIS __tree_iterator
 {
     typedef __tree_node_types<_NodePtr>                     _NodeTypes;
     typedef _NodePtr                                        __node_pointer;
@@ -861,16 +869,16 @@ private:
     _LIBCPP_INLINE_VISIBILITY
     __node_pointer __get_np() const { return static_cast<__node_pointer>(__ptr_); }
     template <class, class, class> friend class __tree;
-    template <class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY __tree_const_iterator;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __map_iterator;
-    template <class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY map;
-    template <class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY multimap;
-    template <class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY set;
-    template <class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY multiset;
+    template <class, class, class> friend class _LIBCPP_TEMPLATE_VIS __tree_const_iterator;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __map_iterator;
+    template <class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS map;
+    template <class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS multimap;
+    template <class, class, class> friend class _LIBCPP_TEMPLATE_VIS set;
+    template <class, class, class> friend class _LIBCPP_TEMPLATE_VIS multiset;
 };
 
 template <class _Tp, class _NodePtr, class _DiffType>
-class _LIBCPP_TYPE_VIS_ONLY __tree_const_iterator
+class _LIBCPP_TEMPLATE_VIS __tree_const_iterator
 {
     typedef __tree_node_types<_NodePtr>                     _NodeTypes;
     typedef typename _NodeTypes::__node_pointer             __node_pointer;
@@ -947,13 +955,32 @@ private:
     __node_pointer __get_np() const { return static_cast<__node_pointer>(__ptr_); }
 
     template <class, class, class> friend class __tree;
-    template <class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY map;
-    template <class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY multimap;
-    template <class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY set;
-    template <class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY multiset;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __map_const_iterator;
+    template <class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS map;
+    template <class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS multimap;
+    template <class, class, class> friend class _LIBCPP_TEMPLATE_VIS set;
+    template <class, class, class> friend class _LIBCPP_TEMPLATE_VIS multiset;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __map_const_iterator;
+
+};
+
+#ifndef _LIBCPP_CXX03_LANG
+template <class _Tp, class _Compare, class _Allocator>
+struct __diagnose_tree_helper {
+  static constexpr bool __trigger_diagnostics()
+      _LIBCPP_DIAGNOSE_WARNING(!__invokable<_Compare const&, _Tp const&, _Tp const&>::value,
+            "the specified comparator type does not provide a const call operator")
+  { return true; }
+};
 
+template <class _Key, class _Value, class _KeyComp, class _Alloc>
+struct __diagnose_tree_helper<
+    __value_type<_Key, _Value>,
+    __map_value_compare<_Key, __value_type<_Key, _Value>, _KeyComp>,
+    _Alloc
+> : __diagnose_tree_helper<_Key, _KeyComp, _Alloc>
+{
 };
+#endif // !_LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Compare, class _Allocator>
 class __tree
@@ -1080,7 +1107,7 @@ public:
         void __assign_unique(_InputIterator __first, _InputIterator __last);
     template <class _InputIterator>
         void __assign_multi(_InputIterator __first, _InputIterator __last);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     __tree(__tree&& __t)
         _NOEXCEPT_(
             is_nothrow_move_constructible<__node_allocator>::value &&
@@ -1091,7 +1118,7 @@ public:
             __node_traits::propagate_on_container_move_assignment::value &&
             is_nothrow_move_assignable<value_compare>::value &&
             is_nothrow_move_assignable<__node_allocator>::value);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif // _LIBCPP_CXX03_LANG
 
     ~__tree();
 
@@ -1106,19 +1133,22 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     size_type max_size() const _NOEXCEPT
-        {return __node_traits::max_size(__node_alloc());}
+        {return std::min<size_type>(
+                __node_traits::max_size(__node_alloc()),
+                numeric_limits<difference_type >::max());}
 
     void clear() _NOEXCEPT;
 
     void swap(__tree& __t)
+#if _LIBCPP_STD_VER <= 11
         _NOEXCEPT_(
             __is_nothrow_swappable<value_compare>::value
-#if _LIBCPP_STD_VER <= 11
             && (!__node_traits::propagate_on_container_swap::value ||
                  __is_nothrow_swappable<__node_allocator>::value)
-#endif
             );
-
+#else
+        _NOEXCEPT_(__is_nothrow_swappable<value_compare>::value);
+#endif
 
 #ifndef _LIBCPP_CXX03_LANG
     template <class _Key, class ..._Args>
@@ -1394,10 +1424,17 @@ private:
     __node_base_pointer&
         __find_leaf(const_iterator __hint,
                     __parent_pointer& __parent, const key_type& __v);
+    // FIXME: Make this function const qualified. Unfortunetly doing so
+    // breaks existing code which uses non-const callable comparators.
     template <class _Key>
     __node_base_pointer&
         __find_equal(__parent_pointer& __parent, const _Key& __v);
     template <class _Key>
+    _LIBCPP_INLINE_VISIBILITY __node_base_pointer&
+    __find_equal(__parent_pointer& __parent, const _Key& __v) const {
+      return const_cast<__tree*>(this)->__find_equal(__parent, __v);
+    }
+    template <class _Key>
     __node_base_pointer&
         __find_equal(const_iterator __hint, __parent_pointer& __parent,
                      __node_base_pointer& __dummy,
@@ -1425,7 +1462,7 @@ private:
         __node_alloc() = __t.__node_alloc();
         }
     _LIBCPP_INLINE_VISIBILITY
-    void __copy_assign_alloc(const __tree& __t, false_type) {}
+    void __copy_assign_alloc(const __tree&, false_type) {}
 
     void __move_assign(__tree& __t, false_type);
     void __move_assign(__tree& __t, true_type)
@@ -1445,13 +1482,13 @@ private:
         _NOEXCEPT_(is_nothrow_move_assignable<__node_allocator>::value)
         {__node_alloc() = _VSTD::move(__t.__node_alloc());}
     _LIBCPP_INLINE_VISIBILITY
-    void __move_assign_alloc(__tree& __t, false_type) _NOEXCEPT {}
+    void __move_assign_alloc(__tree&, false_type) _NOEXCEPT {}
 
     __node_pointer __detach();
     static __node_pointer __detach(__node_pointer);
 
-    template <class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY map;
-    template <class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY multimap;
+    template <class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS map;
+    template <class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS multimap;
 };
 
 template <class _Tp, class _Compare, class _Allocator>
@@ -1467,7 +1504,7 @@ __tree<_Tp, _Compare, _Allocator>::__tree(const value_compare& __comp)
 template <class _Tp, class _Compare, class _Allocator>
 __tree<_Tp, _Compare, _Allocator>::__tree(const allocator_type& __a)
     : __begin_node_(__iter_pointer()),
-      __pair1_(__node_allocator(__a)),
+      __pair1_(__second_tag(), __node_allocator(__a)),
       __pair3_(0)
 {
     __begin_node() = __end_node();
@@ -1477,7 +1514,7 @@ template <class _Tp, class _Compare, class _Allocator>
 __tree<_Tp, _Compare, _Allocator>::__tree(const value_compare& __comp,
                                            const allocator_type& __a)
     : __begin_node_(__iter_pointer()),
-      __pair1_(__node_allocator(__a)),
+      __pair1_(__second_tag(), __node_allocator(__a)),
       __pair3_(0, __comp)
 {
     __begin_node() = __end_node();
@@ -1634,13 +1671,13 @@ __tree<_Tp, _Compare, _Allocator>::__assign_multi(_InputIterator __first, _Input
 template <class _Tp, class _Compare, class _Allocator>
 __tree<_Tp, _Compare, _Allocator>::__tree(const __tree& __t)
     : __begin_node_(__iter_pointer()),
-      __pair1_(__node_traits::select_on_container_copy_construction(__t.__node_alloc())),
+      __pair1_(__second_tag(), __node_traits::select_on_container_copy_construction(__t.__node_alloc())),
       __pair3_(0, __t.value_comp())
 {
     __begin_node() = __end_node();
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Compare, class _Allocator>
 __tree<_Tp, _Compare, _Allocator>::__tree(__tree&& __t)
@@ -1664,7 +1701,7 @@ __tree<_Tp, _Compare, _Allocator>::__tree(__tree&& __t)
 
 template <class _Tp, class _Compare, class _Allocator>
 __tree<_Tp, _Compare, _Allocator>::__tree(__tree&& __t, const allocator_type& __a)
-    : __pair1_(__node_allocator(__a)),
+    : __pair1_(__second_tag(), __node_allocator(__a)),
       __pair3_(0, _VSTD::move(__t.value_comp()))
 {
     if (__a == __t.__alloc())
@@ -1770,14 +1807,18 @@ __tree<_Tp, _Compare, _Allocator>::operator=(__tree&& __t)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Compare, class _Allocator>
 __tree<_Tp, _Compare, _Allocator>::~__tree()
 {
     static_assert((is_copy_constructible<value_compare>::value),
                  "Comparator must be copy-constructible.");
-    destroy(__root());
+#ifndef _LIBCPP_CXX03_LANG
+    static_assert((__diagnose_tree_helper<_Tp, _Compare, _Allocator>::
+                     __trigger_diagnostics()), "");
+#endif
+  destroy(__root());
 }
 
 template <class _Tp, class _Compare, class _Allocator>
@@ -1797,13 +1838,15 @@ __tree<_Tp, _Compare, _Allocator>::destroy(__node_pointer __nd) _NOEXCEPT
 template <class _Tp, class _Compare, class _Allocator>
 void
 __tree<_Tp, _Compare, _Allocator>::swap(__tree& __t)
+#if _LIBCPP_STD_VER <= 11
         _NOEXCEPT_(
             __is_nothrow_swappable<value_compare>::value
-#if _LIBCPP_STD_VER <= 11
             && (!__node_traits::propagate_on_container_swap::value ||
                  __is_nothrow_swappable<__node_allocator>::value)
-#endif
             )
+#else
+        _NOEXCEPT_(__is_nothrow_swappable<value_compare>::value)
+#endif
 {
     using _VSTD::swap;
     swap(__begin_node_, __t.__begin_node_);
@@ -2644,4 +2687,6 @@ swap(__tree<_Tp, _Compare, _Allocator>& __x,
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP___TREE
diff --git a/lib/libcxx/include/__tuple b/lib/libcxx/include/__tuple
index cc9fbbebc09..69d6ee96111 100644
--- a/lib/libcxx/include/__tuple
+++ b/lib/libcxx/include/__tuple
@@ -22,38 +22,56 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Tp> class _LIBCPP_TYPE_VIS_ONLY tuple_size;
+template <class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_size;
+
+#if !defined(_LIBCPP_CXX03_LANG)
+template <class _Tp, class...>
+using __enable_if_tuple_size_imp = _Tp;
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY tuple_size<const _Tp>
-    : public tuple_size<_Tp> {};
+class _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
+    const _Tp,
+    typename enable_if<!is_volatile<_Tp>::value>::type,
+    integral_constant<size_t, sizeof(tuple_size<_Tp>)>>>
+    : public integral_constant<size_t, tuple_size<_Tp>::value> {};
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY tuple_size<volatile _Tp>
-    : public tuple_size<_Tp> {};
+class _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
+    volatile _Tp,
+    typename enable_if<!is_const<_Tp>::value>::type,
+    integral_constant<size_t, sizeof(tuple_size<_Tp>)>>>
+    : public integral_constant<size_t, tuple_size<_Tp>::value> {};
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY tuple_size<const volatile _Tp>
-    : public tuple_size<_Tp> {};
+class _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
+    const volatile _Tp,
+    integral_constant<size_t, sizeof(tuple_size<_Tp>)>>>
+    : public integral_constant<size_t, tuple_size<_Tp>::value> {};
 
-template <size_t _Ip, class _Tp> class _LIBCPP_TYPE_VIS_ONLY tuple_element;
+#else
+template <class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_size<const _Tp> : public tuple_size<_Tp> {};
+template <class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_size<volatile _Tp> : public tuple_size<_Tp> {};
+template <class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_size<const volatile _Tp> : public tuple_size<_Tp> {};
+#endif
+
+template <size_t _Ip, class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_element;
 
 template <size_t _Ip, class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY tuple_element<_Ip, const _Tp>
+class _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, const _Tp>
 {
 public:
     typedef typename add_const<typename tuple_element<_Ip, _Tp>::type>::type type;
 };
 
 template <size_t _Ip, class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY tuple_element<_Ip, volatile _Tp>
+class _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, volatile _Tp>
 {
 public:
     typedef typename add_volatile<typename tuple_element<_Ip, _Tp>::type>::type type;
 };
 
 template <size_t _Ip, class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY tuple_element<_Ip, const volatile _Tp>
+class _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, const volatile _Tp>
 {
 public:
     typedef typename add_cv<typename tuple_element<_Ip, _Tp>::type>::type type;
@@ -67,7 +85,7 @@ template <class _Tp> struct __tuple_like<const volatile _Tp> : public __tuple_li
 
 // tuple specializations
 
-#if !defined(_LIBCPP_HAS_NO_VARIADICS)
+#ifndef _LIBCPP_CXX03_LANG
 
 template <size_t...> struct __tuple_indices {};
 
@@ -142,10 +160,16 @@ struct __make_tuple_indices
 };
 
 
-template <class ..._Tp> class _LIBCPP_TYPE_VIS_ONLY tuple;
+template <class ..._Tp> class _LIBCPP_TEMPLATE_VIS tuple;
 
 template <class... _Tp> struct __tuple_like<tuple<_Tp...> > : true_type {};
 
+template <class ..._Tp>
+class _LIBCPP_TEMPLATE_VIS tuple_size<tuple<_Tp...> >
+    : public integral_constant<size_t, sizeof...(_Tp)>
+{
+};
+
 template <size_t _Ip, class ..._Tp>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename tuple_element<_Ip, tuple<_Tp...> >::type&
@@ -165,7 +189,8 @@ template <size_t _Ip, class ..._Tp>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 const typename tuple_element<_Ip, tuple<_Tp...> >::type&&
 get(const tuple<_Tp...>&&) _NOEXCEPT;
-#endif
+
+#endif // !defined(_LIBCPP_CXX03_LANG)
 
 // pair specializations
 
@@ -181,7 +206,7 @@ _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 const typename tuple_element<_Ip, pair<_T1, _T2> >::type&
 get(const pair<_T1, _T2>&) _NOEXCEPT;
 
-#if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+#ifndef _LIBCPP_CXX03_LANG
 template <size_t _Ip, class _T1, class _T2>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename tuple_element<_Ip, pair<_T1, _T2> >::type&&
@@ -195,7 +220,7 @@ get(const pair<_T1, _T2>&&) _NOEXCEPT;
 
 // array specializations
 
-template <class _Tp, size_t _Size> struct _LIBCPP_TYPE_VIS_ONLY array;
+template <class _Tp, size_t _Size> struct _LIBCPP_TEMPLATE_VIS array;
 
 template <class _Tp, size_t _Size> struct __tuple_like<array<_Tp, _Size> > : true_type {};
 
@@ -209,7 +234,7 @@ _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 const _Tp&
 get(const array<_Tp, _Size>&) _NOEXCEPT;
 
-#if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+#ifndef _LIBCPP_CXX03_LANG
 template <size_t _Ip, class _Tp, size_t _Size>
 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 _Tp&&
@@ -221,8 +246,7 @@ const _Tp&&
 get(const array<_Tp, _Size>&&) _NOEXCEPT;
 #endif
 
-#if !defined(_LIBCPP_HAS_NO_VARIADICS)
-
+#ifndef _LIBCPP_CXX03_LANG
 
 // __tuple_types
 
@@ -258,7 +282,7 @@ using __type_pack_element = typename decltype(
 #endif
 
 template <size_t _Ip, class ..._Types>
-class _LIBCPP_TYPE_VIS_ONLY tuple_element<_Ip, __tuple_types<_Types...>>
+class _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, __tuple_types<_Types...>>
 {
 public:
     static_assert(_Ip < sizeof...(_Types), "tuple_element index out of range");
@@ -267,7 +291,7 @@ public:
 
 
 template <class ..._Tp>
-class _LIBCPP_TYPE_VIS_ONLY tuple_size<__tuple_types<_Tp...> >
+class _LIBCPP_TEMPLATE_VIS tuple_size<__tuple_types<_Tp...> >
     : public integral_constant<size_t, sizeof...(_Tp)>
 {
 };
@@ -368,7 +392,7 @@ template <bool ..._Preds>
 struct __all_dummy;
 
 template <bool ..._Pred>
-using __all = is_same<__all_dummy<_Pred...>, __all_dummy<(_Pred, true)...>>;
+using __all = is_same<__all_dummy<_Pred...>, __all_dummy<((void)_Pred, true)...>>;
 
 struct __tuple_sfinae_base {
   template <template <class, class...> class _Trait,
@@ -431,7 +455,101 @@ struct __tuple_assignable<_Tp, _Up, true, true>
     >
 {};
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+
+template <size_t _Ip, class ..._Tp>
+class _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, tuple<_Tp...> >
+{
+public:
+    typedef typename tuple_element<_Ip, __tuple_types<_Tp...> >::type type;
+};
+
+#if _LIBCPP_STD_VER > 11
+template <size_t _Ip, class ..._Tp>
+using tuple_element_t = typename tuple_element <_Ip, _Tp...>::type;
+#endif
+
+template <bool _IsTuple, class _SizeTrait, size_t _Expected>
+struct __tuple_like_with_size_imp : false_type {};
+
+template <class _SizeTrait, size_t _Expected>
+struct __tuple_like_with_size_imp<true, _SizeTrait, _Expected>
+    : integral_constant<bool, _SizeTrait::value == _Expected> {};
+
+template <class _Tuple, size_t _ExpectedSize,
+          class _RawTuple = typename __uncvref<_Tuple>::type>
+using __tuple_like_with_size = __tuple_like_with_size_imp<
+                                   __tuple_like<_RawTuple>::value,
+                                   tuple_size<_RawTuple>, _ExpectedSize
+                              >;
+
+struct _LIBCPP_TYPE_VIS __check_tuple_constructor_fail {
+    template <class ...>
+    static constexpr bool __enable_default() { return false; }
+    template <class ...>
+    static constexpr bool __enable_explicit() { return false; }
+    template <class ...>
+    static constexpr bool __enable_implicit() { return false; }
+    template <class ...>
+    static constexpr bool __enable_assign() { return false; }
+};
+#endif // !defined(_LIBCPP_CXX03_LANG)
+
+#if _LIBCPP_STD_VER > 14
+
+template <bool _CanCopy, bool _CanMove>
+struct __sfinae_ctor_base {};
+template <>
+struct __sfinae_ctor_base<false, false> {
+  __sfinae_ctor_base() = default;
+  __sfinae_ctor_base(__sfinae_ctor_base const&) = delete;
+  __sfinae_ctor_base(__sfinae_ctor_base &&) = delete;
+  __sfinae_ctor_base& operator=(__sfinae_ctor_base const&) = default;
+  __sfinae_ctor_base& operator=(__sfinae_ctor_base&&) = default;
+};
+template <>
+struct __sfinae_ctor_base<true, false> {
+  __sfinae_ctor_base() = default;
+  __sfinae_ctor_base(__sfinae_ctor_base const&) = default;
+  __sfinae_ctor_base(__sfinae_ctor_base &&) = delete;
+  __sfinae_ctor_base& operator=(__sfinae_ctor_base const&) = default;
+  __sfinae_ctor_base& operator=(__sfinae_ctor_base&&) = default;
+};
+template <>
+struct __sfinae_ctor_base<false, true> {
+  __sfinae_ctor_base() = default;
+  __sfinae_ctor_base(__sfinae_ctor_base const&) = delete;
+  __sfinae_ctor_base(__sfinae_ctor_base &&) = default;
+  __sfinae_ctor_base& operator=(__sfinae_ctor_base const&) = default;
+  __sfinae_ctor_base& operator=(__sfinae_ctor_base&&) = default;
+};
+
+template <bool _CanCopy, bool _CanMove>
+struct __sfinae_assign_base {};
+template <>
+struct __sfinae_assign_base<false, false> {
+  __sfinae_assign_base() = default;
+  __sfinae_assign_base(__sfinae_assign_base const&) = default;
+  __sfinae_assign_base(__sfinae_assign_base &&) = default;
+  __sfinae_assign_base& operator=(__sfinae_assign_base const&) = delete;
+  __sfinae_assign_base& operator=(__sfinae_assign_base&&) = delete;
+};
+template <>
+struct __sfinae_assign_base<true, false> {
+  __sfinae_assign_base() = default;
+  __sfinae_assign_base(__sfinae_assign_base const&) = default;
+  __sfinae_assign_base(__sfinae_assign_base &&) = default;
+  __sfinae_assign_base& operator=(__sfinae_assign_base const&) = default;
+  __sfinae_assign_base& operator=(__sfinae_assign_base&&) = delete;
+};
+template <>
+struct __sfinae_assign_base<false, true> {
+  __sfinae_assign_base() = default;
+  __sfinae_assign_base(__sfinae_assign_base const&) = default;
+  __sfinae_assign_base(__sfinae_assign_base &&) = default;
+  __sfinae_assign_base& operator=(__sfinae_assign_base const&) = delete;
+  __sfinae_assign_base& operator=(__sfinae_assign_base&&) = default;
+};
+#endif // _LIBCPP_STD_VER > 14
 
 _LIBCPP_END_NAMESPACE_STD
 
diff --git a/lib/libcxx/include/__undef_macros b/lib/libcxx/include/__undef_macros
new file mode 100644
index 00000000000..60ab1dbfb5f
--- /dev/null
+++ b/lib/libcxx/include/__undef_macros
@@ -0,0 +1,34 @@
+// -*- C++ -*-
+//===------------------------ __undef_macros ------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+
+#ifdef min
+#if !defined(_LIBCPP_DISABLE_MACRO_CONFLICT_WARNINGS)
+#if defined(_LIBCPP_WARNING)
+_LIBCPP_WARNING("macro min is incompatible with C++.  Try #define NOMINMAX "
+                "before any Windows header. #undefing min")
+#else
+#warning: macro min is incompatible with C++.  #undefing min
+#endif
+#endif
+#undef min
+#endif
+
+#ifdef max
+#if !defined(_LIBCPP_DISABLE_MACRO_CONFLICT_WARNINGS)
+#if defined(_LIBCPP_WARNING)
+_LIBCPP_WARNING("macro max is incompatible with C++.  Try #define NOMINMAX "
+                "before any Windows header. #undefing max")
+#else
+#warning: macro max is incompatible with C++.  #undefing max
+#endif
+#endif
+#undef max
+#endif
diff --git a/lib/libcxx/include/algorithm b/lib/libcxx/include/algorithm
index 7a6db7abd26..35c6129ea50 100644
--- a/lib/libcxx/include/algorithm
+++ b/lib/libcxx/include/algorithm
@@ -35,6 +35,9 @@ template <class InputIterator, class Function>
     Function
     for_each(InputIterator first, InputIterator last, Function f);
 
+template<class InputIterator, class Size, class Function>
+    InputIterator for_each_n(InputIterator first, Size n, Function f); // C++17
+
 template <class InputIterator, class T>
     InputIterator
     find(InputIterator first, InputIterator last, const T& value);
@@ -89,7 +92,7 @@ template <class InputIterator1, class InputIterator2>
 
 template <class InputIterator1, class InputIterator2>
     pair<InputIterator1, InputIterator2>
-    mismatch(InputIterator1 first1, InputIterator1 last1, 
+    mismatch(InputIterator1 first1, InputIterator1 last1,
              InputIterator2 first2, InputIterator2 last2); // **C++14**
 
 template <class InputIterator1, class InputIterator2, class BinaryPredicate>
@@ -109,7 +112,7 @@ template <class InputIterator1, class InputIterator2>
 
 template <class InputIterator1, class InputIterator2>
     bool
-    equal(InputIterator1 first1, InputIterator1 last1, 
+    equal(InputIterator1 first1, InputIterator1 last1,
           InputIterator2 first2, InputIterator2 last2); // **C++14**
 
 template <class InputIterator1, class InputIterator2, class BinaryPredicate>
@@ -281,12 +284,18 @@ template <class ForwardIterator, class OutputIterator>
 
 template <class RandomAccessIterator>
     void
-    random_shuffle(RandomAccessIterator first, RandomAccessIterator last); // deprecated in C++14
+    random_shuffle(RandomAccessIterator first, RandomAccessIterator last); // deprecated in C++14, removed in C++17
 
 template <class RandomAccessIterator, class RandomNumberGenerator>
     void
     random_shuffle(RandomAccessIterator first, RandomAccessIterator last,
-                   RandomNumberGenerator& rand);  // deprecated in C++14
+                   RandomNumberGenerator& rand);  // deprecated in C++14, removed in C++17
+
+template<class PopulationIterator, class SampleIterator,
+         class Distance, class UniformRandomBitGenerator>
+    SampleIterator sample(PopulationIterator first, PopulationIterator last,
+                          SampleIterator out, Distance n,
+                          UniformRandomBitGenerator&& g); // C++17
 
 template<class RandomAccessIterator, class UniformRandomNumberGenerator>
     void shuffle(RandomAccessIterator first, RandomAccessIterator last,
@@ -638,18 +647,20 @@ template <class BidirectionalIterator, class Compare>
 #if defined(__IBMCPP__)
 #include "support/ibm/support.h"
 #endif
-#if defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
-#include "support/win32/support.h"
+#if defined(_LIBCPP_COMPILER_MSVC)
+#include <intrin.h>
 #endif
 
-#include <__undef_min_max>
-
 #include <__debug>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 // I'd like to replace these with _VSTD::equal_to<void>, but can't because:
@@ -688,7 +699,7 @@ struct __equal_to<_T1, const _T1>
 template <class _T1, class _T2 = _T1>
 struct __less
 {
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     bool operator()(const _T1& __x, const _T1& __y) const {return __x < __y;}
 
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
@@ -723,15 +734,15 @@ struct __less<_T1, const _T1>
 };
 
 template <class _Predicate>
-class __negate
+class __invert // invert the sense of a comparison
 {
 private:
     _Predicate __p_;
 public:
-    _LIBCPP_INLINE_VISIBILITY __negate() {}
+    _LIBCPP_INLINE_VISIBILITY __invert() {}
 
     _LIBCPP_INLINE_VISIBILITY
-    explicit __negate(_Predicate __p) : __p_(__p) {}
+    explicit __invert(_Predicate __p) : __p_(__p) {}
 
     template <class _T1>
     _LIBCPP_INLINE_VISIBILITY
@@ -739,7 +750,7 @@ public:
 
     template <class _T1, class _T2>
     _LIBCPP_INLINE_VISIBILITY
-    bool operator()(const _T1& __x, const _T2& __y) {return !__p_(__x, __y);}
+    bool operator()(const _T1& __x, const _T2& __y) {return __p_(__y, __x);}
 };
 
 #ifdef _LIBCPP_DEBUG
@@ -749,65 +760,160 @@ struct __debug_less
 {
     _Compare __comp_;
     __debug_less(_Compare& __c) : __comp_(__c) {}
+
     template <class _Tp, class _Up>
     bool operator()(const _Tp& __x, const _Up& __y)
     {
         bool __r = __comp_(__x, __y);
         if (__r)
-            _LIBCPP_ASSERT(!__comp_(__y, __x), "Comparator does not induce a strict weak ordering");
+            __do_compare_assert(0, __y, __x);
         return __r;
     }
+
+    template <class _LHS, class _RHS>
+    inline _LIBCPP_INLINE_VISIBILITY
+    decltype((void)_VSTD::declval<_Compare&>()(
+        _VSTD::declval<_LHS const&>(), _VSTD::declval<_RHS const&>()))
+    __do_compare_assert(int, _LHS const& __l, _RHS const& __r) {
+        _LIBCPP_ASSERT(!__comp_(__l, __r),
+            "Comparator does not induce a strict weak ordering");
+    }
+
+    template <class _LHS, class _RHS>
+    inline _LIBCPP_INLINE_VISIBILITY
+    void __do_compare_assert(long, _LHS const&, _RHS const&) {}
 };
 
 #endif  // _LIBCPP_DEBUG
 
 // Precondition:  __x != 0
 inline _LIBCPP_INLINE_VISIBILITY
-unsigned
-__ctz(unsigned __x)
-{
+unsigned __ctz(unsigned __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
     return static_cast<unsigned>(__builtin_ctz(__x));
+#else
+  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
+  static_assert(sizeof(unsigned long) == 4, "");
+  unsigned long where;
+  // Search from LSB to MSB for first set bit.
+  // Returns zero if no set bit is found.
+  if (_BitScanForward(&where, __x))
+    return where;
+  return 32;
+#endif
 }
 
 inline _LIBCPP_INLINE_VISIBILITY
-unsigned long
-__ctz(unsigned long __x)
-{
+unsigned long __ctz(unsigned long __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
     return static_cast<unsigned long>(__builtin_ctzl(__x));
+#else
+    static_assert(sizeof(unsigned long) == sizeof(unsigned), "");
+    return __ctz(static_cast<unsigned>(__x));
+#endif
 }
 
 inline _LIBCPP_INLINE_VISIBILITY
-unsigned long long
-__ctz(unsigned long long __x)
-{
+unsigned long long __ctz(unsigned long long __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
     return static_cast<unsigned long long>(__builtin_ctzll(__x));
+#else
+    unsigned long where;
+// Search from LSB to MSB for first set bit.
+// Returns zero if no set bit is found.
+#if defined(_LIBCPP_HAS_BITSCAN64)
+    (defined(_M_AMD64) || defined(__x86_64__))
+  if (_BitScanForward64(&where, __x))
+    return static_cast<int>(where);
+#else
+  // Win32 doesn't have _BitScanForward64 so emulate it with two 32 bit calls.
+  // Scan the Low Word.
+  if (_BitScanForward(&where, static_cast<unsigned long>(__x)))
+    return where;
+  // Scan the High Word.
+  if (_BitScanForward(&where, static_cast<unsigned long>(__x >> 32)))
+    return where + 32; // Create a bit offset from the LSB.
+#endif
+  return 64;
+#endif // _LIBCPP_COMPILER_MSVC
 }
 
 // Precondition:  __x != 0
 inline _LIBCPP_INLINE_VISIBILITY
-unsigned
-__clz(unsigned __x)
-{
+unsigned __clz(unsigned __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
     return static_cast<unsigned>(__builtin_clz(__x));
+#else
+  static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
+  static_assert(sizeof(unsigned long) == 4, "");
+  unsigned long where;
+  // Search from LSB to MSB for first set bit.
+  // Returns zero if no set bit is found.
+  if (_BitScanReverse(&where, __x))
+    return 31 - where;
+  return 32; // Undefined Behavior.
+#endif
 }
 
 inline _LIBCPP_INLINE_VISIBILITY
-unsigned long
-__clz(unsigned long __x)
-{
+unsigned long __clz(unsigned long __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
     return static_cast<unsigned long>(__builtin_clzl (__x));
+#else
+    static_assert(sizeof(unsigned) == sizeof(unsigned long), "");
+    return __clz(static_cast<unsigned>(__x));
+#endif
 }
 
 inline _LIBCPP_INLINE_VISIBILITY
-unsigned long long
-__clz(unsigned long long __x)
-{
+unsigned long long __clz(unsigned long long __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
     return static_cast<unsigned long long>(__builtin_clzll(__x));
+#else
+  unsigned long where;
+// BitScanReverse scans from MSB to LSB for first set bit.
+// Returns 0 if no set bit is found.
+#if defined(_LIBCPP_HAS_BITSCAN64)
+  if (_BitScanReverse64(&where, __x))
+    return static_cast<int>(63 - where);
+#else
+  // Scan the high 32 bits.
+  if (_BitScanReverse(&where, static_cast<unsigned long>(__x >> 32)))
+    return 63 - (where + 32); // Create a bit offset from the MSB.
+  // Scan the low 32 bits.
+  if (_BitScanReverse(&where, static_cast<unsigned long>(__x)))
+    return 63 - where;
+#endif
+  return 64; // Undefined Behavior.
+#endif // _LIBCPP_COMPILER_MSVC
+}
+
+inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
+  return __builtin_popcount  (__x);
+#else
+  static_assert(sizeof(unsigned) == 4, "");
+  return __popcnt(__x);
+#endif
 }
 
-inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned           __x) {return __builtin_popcount  (__x);}
-inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned      long __x) {return __builtin_popcountl (__x);}
-inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned long long __x) {return __builtin_popcountll(__x);}
+inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned long __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
+  return __builtin_popcountl (__x);
+#else
+  static_assert(sizeof(unsigned long) == 4, "");
+  return __popcnt(__x);
+#endif
+}
+
+inline _LIBCPP_INLINE_VISIBILITY int __pop_count(unsigned long long __x) {
+#ifndef _LIBCPP_COMPILER_MSVC
+  return __builtin_popcountll(__x);
+#else
+  static_assert(sizeof(unsigned long long) == 8, "");
+  return __popcnt64(__x);
+#endif
+}
 
 // all_of
 
@@ -857,9 +963,29 @@ for_each(_InputIterator __first, _InputIterator __last, _Function __f)
 {
     for (; __first != __last; ++__first)
         __f(*__first);
-    return _LIBCPP_EXPLICIT_MOVE(__f);  // explicitly moved for (emulated) C++03
+    return __f;
 }
 
+#if _LIBCPP_STD_VER > 14
+// for_each_n
+
+template <class _InputIterator, class _Size, class _Function>
+inline _LIBCPP_INLINE_VISIBILITY
+_InputIterator
+for_each_n(_InputIterator __first, _Size __orig_n, _Function __f)
+{
+    typedef decltype(__convert_to_integral(__orig_n)) _IntegralSize;
+    _IntegralSize __n = __orig_n;
+    while (__n > 0)
+    {
+         __f(*__first);
+         ++__first;
+         --__n;
+    }
+    return __first;
+}
+#endif
+
 // find
 
 template <class _InputIterator, class _Tp>
@@ -1215,7 +1341,7 @@ equal(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2 __first
 template <class _BinaryPredicate, class _InputIterator1, class _InputIterator2>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-__equal(_InputIterator1 __first1, _InputIterator1 __last1, 
+__equal(_InputIterator1 __first1, _InputIterator1 __last1,
         _InputIterator2 __first2, _InputIterator2 __last2, _BinaryPredicate __pred,
         input_iterator_tag, input_iterator_tag )
 {
@@ -1228,8 +1354,8 @@ __equal(_InputIterator1 __first1, _InputIterator1 __last1,
 template <class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-__equal(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1, 
-        _RandomAccessIterator2 __first2, _RandomAccessIterator2 __last2, _BinaryPredicate __pred, 
+__equal(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1,
+        _RandomAccessIterator2 __first2, _RandomAccessIterator2 __last2, _BinaryPredicate __pred,
       random_access_iterator_tag, random_access_iterator_tag )
 {
     if ( _VSTD::distance(__first1, __last1) != _VSTD::distance(__first2, __last2))
@@ -1242,11 +1368,11 @@ __equal(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1,
 template <class _InputIterator1, class _InputIterator2, class _BinaryPredicate>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-equal(_InputIterator1 __first1, _InputIterator1 __last1, 
+equal(_InputIterator1 __first1, _InputIterator1 __last1,
       _InputIterator2 __first2, _InputIterator2 __last2, _BinaryPredicate __pred )
 {
     return _VSTD::__equal<typename add_lvalue_reference<_BinaryPredicate>::type>
-       (__first1, __last1, __first2, __last2, __pred, 
+       (__first1, __last1, __first2, __last2, __pred,
         typename iterator_traits<_InputIterator1>::iterator_category(),
         typename iterator_traits<_InputIterator2>::iterator_category());
 }
@@ -1254,7 +1380,7 @@ equal(_InputIterator1 __first1, _InputIterator1 __last1,
 template <class _InputIterator1, class _InputIterator2>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-equal(_InputIterator1 __first1, _InputIterator1 __last1, 
+equal(_InputIterator1 __first1, _InputIterator1 __last1,
       _InputIterator2 __first2, _InputIterator2 __last2)
 {
     typedef typename iterator_traits<_InputIterator1>::value_type __v1;
@@ -1328,7 +1454,7 @@ is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
 template<class _BinaryPredicate, class _ForwardIterator1, class _ForwardIterator2>
 bool
 __is_permutation(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
-                 _ForwardIterator2 __first2, _ForwardIterator2 __last2, 
+                 _ForwardIterator2 __first2, _ForwardIterator2 __last2,
                  _BinaryPredicate __pred,
                  forward_iterator_tag, forward_iterator_tag )
 {
@@ -1379,7 +1505,7 @@ __next_iter:;
 template<class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
 bool
 __is_permutation(_RandomAccessIterator1 __first1, _RandomAccessIterator2 __last1,
-               _RandomAccessIterator1 __first2, _RandomAccessIterator2 __last2, 
+               _RandomAccessIterator1 __first2, _RandomAccessIterator2 __last2,
                _BinaryPredicate __pred,
                random_access_iterator_tag, random_access_iterator_tag )
 {
@@ -1458,7 +1584,7 @@ __search(_ForwardIterator1 __first1, _ForwardIterator1 __last1,
 }
 
 template <class _BinaryPredicate, class _RandomAccessIterator1, class _RandomAccessIterator2>
-_LIBCPP_CONSTEXPR_AFTER_CXX11 
+_LIBCPP_CONSTEXPR_AFTER_CXX11
 pair<_RandomAccessIterator1, _RandomAccessIterator1>
 __search(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1,
          _RandomAccessIterator2 __first2, _RandomAccessIterator2 __last2, _BinaryPredicate __pred,
@@ -1474,9 +1600,9 @@ __search(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1,
     if (__len1 < __len2)
         return make_pair(__last1, __last1);
     const _RandomAccessIterator1 __s = __last1 - (__len2 - 1);  // Start of pattern match can't go beyond here
+
     while (true)
     {
-#if !_LIBCPP_UNROLL_LOOPS
         while (true)
         {
             if (__first1 == __s)
@@ -1485,40 +1611,9 @@ __search(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1,
                 break;
             ++__first1;
         }
-#else  // !_LIBCPP_UNROLL_LOOPS
-        for (_D1 __loop_unroll = (__s - __first1) / 4; __loop_unroll > 0; --__loop_unroll)
-        {
-            if (__pred(*__first1, *__first2))
-                goto __phase2;
-            if (__pred(*++__first1, *__first2))
-                goto __phase2;
-            if (__pred(*++__first1, *__first2))
-                goto __phase2;
-            if (__pred(*++__first1, *__first2))
-                goto __phase2;
-            ++__first1;
-        }
-        switch (__s - __first1)
-        {
-        case 3:
-            if (__pred(*__first1, *__first2))
-                break;
-            ++__first1;
-        case 2:
-            if (__pred(*__first1, *__first2))
-                break;
-            ++__first1;
-        case 1:
-            if (__pred(*__first1, *__first2))
-                break;
-        case 0:
-            return make_pair(__last1, __last1);
-        }
-    __phase2:
-#endif  // !_LIBCPP_UNROLL_LOOPS
+
         _RandomAccessIterator1 __m1 = __first1;
         _RandomAccessIterator2 __m2 = __first2;
-#if !_LIBCPP_UNROLL_LOOPS
          while (true)
          {
              if (++__m2 == __last2)
@@ -1530,43 +1625,6 @@ __search(_RandomAccessIterator1 __first1, _RandomAccessIterator1 __last1,
                  break;
              }
          }
-#else  // !_LIBCPP_UNROLL_LOOPS
-        ++__m2;
-        ++__m1;
-        for (_D2 __loop_unroll = (__last2 - __m2) / 4; __loop_unroll > 0; --__loop_unroll)
-        {
-            if (!__pred(*__m1, *__m2))
-                goto __continue;
-            if (!__pred(*++__m1, *++__m2))
-                goto __continue;
-            if (!__pred(*++__m1, *++__m2))
-                goto __continue;
-            if (!__pred(*++__m1, *++__m2))
-                goto __continue;
-            ++__m1;
-            ++__m2;
-        }
-        switch (__last2 - __m2)
-        {
-        case 3:
-            if (!__pred(*__m1, *__m2))
-                break;
-            ++__m1;
-            ++__m2;
-        case 2:
-            if (!__pred(*__m1, *__m2))
-                break;
-            ++__m1;
-            ++__m2;
-        case 1:
-            if (!__pred(*__m1, *__m2))
-                break;
-        case 0:
-            return make_pair(__first1, __first1 + __len2);
-        }
-    __continue:
-        ++__first1;
-#endif  // !_LIBCPP_UNROLL_LOOPS
     }
 }
 
@@ -1729,6 +1787,20 @@ __unwrap_iter(__wrap_iter<_Tp*> __i)
     return __i.base();
 }
 
+#else
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+typename enable_if
+<
+    is_trivially_copy_assignable<_Tp>::value,
+    __wrap_iter<_Tp*>
+>::type
+__unwrap_iter(__wrap_iter<_Tp*> __i)
+{
+    return __i;
+}
+
 #endif  // _LIBCPP_DEBUG_LEVEL < 2
 
 template <class _InputIterator, class _OutputIterator>
@@ -1802,7 +1874,9 @@ _BidirectionalIterator2
 copy_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
               _BidirectionalIterator2 __result)
 {
-    return _VSTD::__copy_backward(__unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
+    return _VSTD::__copy_backward(__unwrap_iter(__first),
+                                  __unwrap_iter(__last),
+                                  __unwrap_iter(__result));
 }
 
 // copy_if
@@ -2417,7 +2491,7 @@ __rotate_forward(_ForwardIterator __first, _ForwardIterator __middle, _ForwardIt
 template<typename _Integral>
 inline _LIBCPP_INLINE_VISIBILITY
 _Integral
-__gcd(_Integral __x, _Integral __y)
+__algo_gcd(_Integral __x, _Integral __y)
 {
     do
     {
@@ -2442,7 +2516,7 @@ __rotate_gcd(_RandomAccessIterator __first, _RandomAccessIterator __middle, _Ran
         _VSTD::swap_ranges(__first, __middle, __middle);
         return __middle;
     }
-    const difference_type __g = _VSTD::__gcd(__m1, __m2);
+    const difference_type __g = _VSTD::__algo_gcd(__m1, __m2);
     for (_RandomAccessIterator __p = __first + __g; __p != __first;)
     {
         value_type __t(_VSTD::move(*--__p));
@@ -2580,7 +2654,7 @@ min(const _Tp& __a, const _Tp& __b)
     return _VSTD::min(__a, __b, __less<_Tp>());
 }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
 
 template<class _Tp, class _Compare>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
@@ -2598,7 +2672,7 @@ min(initializer_list<_Tp> __t)
     return *_VSTD::min_element(__t.begin(), __t.end(), __less<_Tp>());
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 // max_element
 
@@ -2645,7 +2719,7 @@ max(const _Tp& __a, const _Tp& __b)
     return _VSTD::max(__a, __b, __less<_Tp>());
 }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
 
 template<class _Tp, class _Compare>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
@@ -2663,7 +2737,7 @@ max(initializer_list<_Tp> __t)
     return *_VSTD::max_element(__t.begin(), __t.end(), __less<_Tp>());
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 #if _LIBCPP_STD_VER > 14
 // clamp
@@ -2764,7 +2838,7 @@ minmax(const _Tp& __a, const _Tp& __b)
     return _VSTD::minmax(__a, __b, __less<_Tp>());
 }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
 
 template<class _Tp, class _Compare>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
@@ -2785,7 +2859,7 @@ minmax(initializer_list<_Tp> __t, _Compare __comp)
             __result.second = *__first;
         ++__first;
     }
-    
+
     while (__first != __last)
     {
         _Tp __prev = *__first++;
@@ -2797,7 +2871,7 @@ minmax(initializer_list<_Tp> __t, _Compare __comp)
             if ( __comp(__prev, __result.first))    __result.first  = __prev;
             if (!__comp(*__first, __result.second)) __result.second = *__first;
             }
-                
+
         __first++;
     }
     return __result;
@@ -2811,7 +2885,7 @@ minmax(initializer_list<_Tp> __t)
     return _VSTD::minmax(__t, __less<_Tp>());
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 // random_shuffle
 
@@ -2836,11 +2910,11 @@ struct __log2_imp<0, _Rp>
     static const size_t value = _Rp + 1;
 };
 
-template <class _UI, _UI _Xp>
+template <class _UIntType, _UIntType _Xp>
 struct __log2
 {
     static const size_t value = __log2_imp<_Xp,
-                                         sizeof(_UI) * __CHAR_BIT__ - 1>::value;
+                                         sizeof(_UIntType) * __CHAR_BIT__ - 1>::value;
 };
 
 template<class _Engine, class _UIntType>
@@ -2869,7 +2943,7 @@ private:
     _Engine_result_type __mask0_;
     _Engine_result_type __mask1_;
 
-#ifdef _LIBCPP_HAS_NO_CONSTEXPR
+#ifdef _LIBCPP_CXX03_LANG
     static const _Working_result_type _Rp = _Engine::_Max - _Engine::_Min
                                           + _Working_result_type(1);
 #else
@@ -2939,6 +3013,7 @@ template<class _Engine, class _UIntType>
 _UIntType
 __independent_bits_engine<_Engine, _UIntType>::__eval(true_type)
 {
+    const size_t _WRt = numeric_limits<result_type>::digits;
     result_type _Sp = 0;
     for (size_t __k = 0; __k < __n0_; ++__k)
     {
@@ -2947,7 +3022,7 @@ __independent_bits_engine<_Engine, _UIntType>::__eval(true_type)
         {
             __u = __e_() - _Engine::min();
         } while (__u >= __y0_);
-        if (__w0_ < _WDt)
+        if (__w0_ < _WRt)
             _Sp <<= __w0_;
         else
             _Sp = 0;
@@ -2960,7 +3035,7 @@ __independent_bits_engine<_Engine, _UIntType>::__eval(true_type)
         {
             __u = __e_() - _Engine::min();
         } while (__u >= __y1_);
-        if (__w0_ < _WDt - 1)
+        if (__w0_ < _WRt - 1)
             _Sp <<= __w0_ + 1;
         else
             _Sp = 0;
@@ -3058,6 +3133,8 @@ uniform_int_distribution<_IntType>::operator()(_URNG& __g, const param_type& __p
     return static_cast<result_type>(__u + __p.a());
 }
 
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_RANDOM_SHUFFLE) \
+  || defined(_LIBCPP_BUILDING_LIBRARY)
 class _LIBCPP_TYPE_VIS __rs_default;
 
 _LIBCPP_FUNC_VIS __rs_default __rs_get();
@@ -3110,7 +3187,7 @@ random_shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last)
 template <class _RandomAccessIterator, class _RandomNumberGenerator>
 void
 random_shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last,
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
                _RandomNumberGenerator&& __rand)
 #else
                _RandomNumberGenerator& __rand)
@@ -3127,10 +3204,83 @@ random_shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last,
         }
     }
 }
+#endif
+
+template <class _PopulationIterator, class _SampleIterator, class _Distance,
+          class _UniformRandomNumberGenerator>
+_LIBCPP_INLINE_VISIBILITY
+_SampleIterator __sample(_PopulationIterator __first,
+                         _PopulationIterator __last, _SampleIterator __output_iter,
+                         _Distance __n,
+                         _UniformRandomNumberGenerator & __g,
+                         input_iterator_tag) {
+
+  _Distance __k = 0;
+  for (; __first != __last && __k < __n; ++__first, (void)++__k)
+    __output_iter[__k] = *__first;
+  _Distance __sz = __k;
+  for (; __first != __last; ++__first, (void)++__k) {
+    _Distance __r = _VSTD::uniform_int_distribution<_Distance>(0, __k)(__g);
+    if (__r < __sz)
+      __output_iter[__r] = *__first;
+  }
+  return __output_iter + _VSTD::min(__n, __k);
+}
+
+template <class _PopulationIterator, class _SampleIterator, class _Distance,
+          class _UniformRandomNumberGenerator>
+_LIBCPP_INLINE_VISIBILITY
+_SampleIterator __sample(_PopulationIterator __first,
+                         _PopulationIterator __last, _SampleIterator __output_iter,
+                         _Distance __n,
+                         _UniformRandomNumberGenerator& __g,
+                         forward_iterator_tag) {
+  _Distance __unsampled_sz = _VSTD::distance(__first, __last);
+  for (__n = _VSTD::min(__n, __unsampled_sz); __n != 0; ++__first) {
+    _Distance __r =
+        _VSTD::uniform_int_distribution<_Distance>(0, --__unsampled_sz)(__g);
+    if (__r < __n) {
+      *__output_iter++ = *__first;
+      --__n;
+    }
+  }
+  return __output_iter;
+}
+
+template <class _PopulationIterator, class _SampleIterator, class _Distance,
+          class _UniformRandomNumberGenerator>
+_LIBCPP_INLINE_VISIBILITY
+_SampleIterator __sample(_PopulationIterator __first,
+                         _PopulationIterator __last, _SampleIterator __output_iter,
+                         _Distance __n, _UniformRandomNumberGenerator& __g) {
+  typedef typename iterator_traits<_PopulationIterator>::iterator_category
+        _PopCategory;
+  typedef typename iterator_traits<_PopulationIterator>::difference_type
+        _Difference;
+  static_assert(__is_forward_iterator<_PopulationIterator>::value ||
+                __is_random_access_iterator<_SampleIterator>::value,
+                "SampleIterator must meet the requirements of RandomAccessIterator");
+  typedef typename common_type<_Distance, _Difference>::type _CommonType;
+  _LIBCPP_ASSERT(__n >= 0, "N must be a positive number.");
+  return _VSTD::__sample(
+      __first, __last, __output_iter, _CommonType(__n),
+      __g, _PopCategory());
+}
+
+#if _LIBCPP_STD_VER > 14
+template <class _PopulationIterator, class _SampleIterator, class _Distance,
+          class _UniformRandomNumberGenerator>
+inline _LIBCPP_INLINE_VISIBILITY
+_SampleIterator sample(_PopulationIterator __first,
+                       _PopulationIterator __last, _SampleIterator __output_iter,
+                       _Distance __n, _UniformRandomNumberGenerator&& __g) {
+    return _VSTD::__sample(__first, __last, __output_iter, __n, __g);
+}
+#endif // _LIBCPP_STD_VER > 14
 
 template<class _RandomAccessIterator, class _UniformRandomNumberGenerator>
     void shuffle(_RandomAccessIterator __first, _RandomAccessIterator __last,
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
                  _UniformRandomNumberGenerator&& __g)
 #else
                  _UniformRandomNumberGenerator& __g)
@@ -4085,10 +4235,6 @@ sort(__wrap_iter<_Tp*> __first, __wrap_iter<_Tp*> __last, _Compare __comp)
     _VSTD::sort<_Tp*, _Comp_ref>(__first.base(), __last.base(), __comp);
 }
 
-#ifdef _LIBCPP_MSVC
-#pragma warning( push )
-#pragma warning( disable: 4231)
-#endif // _LIBCPP_MSVC
 _LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<char>&, char*>(char*, char*, __less<char>&))
 _LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<wchar_t>&, wchar_t*>(wchar_t*, wchar_t*, __less<wchar_t>&))
 _LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS void __sort<__less<signed char>&, signed char*>(signed char*, signed char*, __less<signed char>&))
@@ -4122,9 +4268,6 @@ _LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less
 _LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS bool __insertion_sort_incomplete<__less<long double>&, long double*>(long double*, long double*, __less<long double>&))
 
 _LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS unsigned __sort5<__less<long double>&, long double*>(long double*, long double*, long double*, long double*, long double*, __less<long double>&))
-#ifdef _LIBCPP_MSVC
-#pragma warning( pop )
-#endif  // _LIBCPP_MSVC
 
 // lower_bound
 
@@ -4423,9 +4566,9 @@ __buffered_inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator
             ::new(__p) value_type(_VSTD::move(*__i));
         typedef reverse_iterator<_BidirectionalIterator> _RBi;
         typedef reverse_iterator<value_type*> _Rv;
-        __half_inplace_merge(_Rv(__p), _Rv(__buff), 
+        __half_inplace_merge(_Rv(__p), _Rv(__buff),
                              _RBi(__middle), _RBi(__first),
-                             _RBi(__last), __negate<_Compare>(__comp));
+                             _RBi(__last), __invert<_Compare>(__comp));
     }
 }
 
@@ -4871,7 +5014,8 @@ push_heap(_RandomAccessIterator __first, _RandomAccessIterator __last)
 
 template <class _Compare, class _RandomAccessIterator>
 void
-__sift_down(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp,
+__sift_down(_RandomAccessIterator __first, _RandomAccessIterator /*__last*/,
+            _Compare __comp,
             typename iterator_traits<_RandomAccessIterator>::difference_type __len,
             _RandomAccessIterator __start)
 {
@@ -5403,9 +5547,9 @@ __set_union(_InputIterator1 __first1, _InputIterator1 __last1,
         }
         else
         {
-            *__result = *__first1;
             if (!__comp(*__first1, *__first2))
                 ++__first2;
+            *__result = *__first1;
             ++__first1;
         }
     }
@@ -5756,4 +5900,6 @@ prev_permutation(_BidirectionalIterator __first, _BidirectionalIterator __last)
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_ALGORITHM
diff --git a/lib/libcxx/include/any b/lib/libcxx/include/any
new file mode 100644
index 00000000000..d7161b0d6f4
--- /dev/null
+++ b/lib/libcxx/include/any
@@ -0,0 +1,667 @@
+// -*- C++ -*-
+//===------------------------------ any -----------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_ANY
+#define _LIBCPP_ANY
+
+/*
+   any synopsis
+
+namespace std {
+
+  class bad_any_cast : public bad_cast
+  {
+  public:
+    virtual const char* what() const noexcept;
+  };
+
+  class any
+  {
+  public:
+
+    // 6.3.1 any construct/destruct
+    any() noexcept;
+
+    any(const any& other);
+    any(any&& other) noexcept;
+
+    template <class ValueType>
+      any(ValueType&& value);
+
+    ~any();
+
+    // 6.3.2 any assignments
+    any& operator=(const any& rhs);
+    any& operator=(any&& rhs) noexcept;
+
+    template <class ValueType>
+      any& operator=(ValueType&& rhs);
+
+    // 6.3.3 any modifiers
+    template <class ValueType, class... Args>
+      decay_t<ValueType>& emplace(Args&&... args);
+    template <class ValueType, class U, class... Args>
+      decay_t<ValueType>& emplace(initializer_list<U>, Args&&...);
+    void reset() noexcept;
+    void swap(any& rhs) noexcept;
+
+    // 6.3.4 any observers
+    bool has_value() const noexcept;
+    const type_info& type() const noexcept;
+  };
+
+   // 6.4 Non-member functions
+  void swap(any& x, any& y) noexcept;
+
+  template <class T, class ...Args>
+    any make_any(Args&& ...args);
+  template <class T, class U, class ...Args>
+    any make_any(initializer_list<U>, Args&& ...args);
+
+  template<class ValueType>
+    ValueType any_cast(const any& operand);
+  template<class ValueType>
+    ValueType any_cast(any& operand);
+  template<class ValueType>
+    ValueType any_cast(any&& operand);
+
+  template<class ValueType>
+    const ValueType* any_cast(const any* operand) noexcept;
+  template<class ValueType>
+    ValueType* any_cast(any* operand) noexcept;
+
+} // namespace std
+
+*/
+
+#include <experimental/__config>
+#include <memory>
+#include <new>
+#include <typeinfo>
+#include <type_traits>
+#include <cstdlib>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+namespace std {
+class _LIBCPP_EXCEPTION_ABI bad_any_cast : public bad_cast
+{
+public:
+    virtual const char* what() const _NOEXCEPT;
+};
+} // namespace std
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 14
+
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+void __throw_bad_any_cast()
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw bad_any_cast();
+#else
+	_VSTD::abort();
+#endif
+}
+
+// Forward declarations
+class _LIBCPP_TEMPLATE_VIS any;
+
+template <class _ValueType>
+_LIBCPP_INLINE_VISIBILITY
+add_pointer_t<add_const_t<_ValueType>>
+any_cast(any const *) _NOEXCEPT;
+
+template <class _ValueType>
+_LIBCPP_INLINE_VISIBILITY
+add_pointer_t<_ValueType> any_cast(any *) _NOEXCEPT;
+
+namespace __any_imp
+{
+  using _Buffer = aligned_storage_t<3*sizeof(void*), alignment_of<void*>::value>;
+
+  template <class _Tp>
+  using _IsSmallObject = integral_constant<bool
+        , sizeof(_Tp) <= sizeof(_Buffer)
+          && alignment_of<_Buffer>::value
+             % alignment_of<_Tp>::value == 0
+          && is_nothrow_move_constructible<_Tp>::value
+        >;
+
+  enum class _Action {
+    _Destroy,
+    _Copy,
+    _Move,
+    _Get,
+    _TypeInfo
+  };
+
+  template <class _Tp> struct _SmallHandler;
+  template <class _Tp> struct _LargeHandler;
+
+  template <class _Tp>
+  struct  _LIBCPP_TEMPLATE_VIS __unique_typeinfo { static constexpr int __id = 0; };
+  template <class _Tp> constexpr int __unique_typeinfo<_Tp>::__id;
+
+  template <class _Tp>
+  inline _LIBCPP_INLINE_VISIBILITY
+  constexpr const void* __get_fallback_typeid() {
+      return &__unique_typeinfo<decay_t<_Tp>>::__id;
+  }
+
+  template <class _Tp>
+  inline _LIBCPP_INLINE_VISIBILITY
+  bool __compare_typeid(type_info const* __id, const void* __fallback_id)
+  {
+#if !defined(_LIBCPP_NO_RTTI)
+      if (__id && *__id == typeid(_Tp))
+          return true;
+#endif
+      if (!__id && __fallback_id == __any_imp::__get_fallback_typeid<_Tp>())
+          return true;
+      return false;
+  }
+
+  template <class _Tp>
+  using _Handler = conditional_t<
+    _IsSmallObject<_Tp>::value, _SmallHandler<_Tp>, _LargeHandler<_Tp>>;
+
+} // namespace __any_imp
+
+class _LIBCPP_TEMPLATE_VIS any
+{
+public:
+  // construct/destruct
+  _LIBCPP_INLINE_VISIBILITY
+  constexpr any() _NOEXCEPT : __h(nullptr) {}
+
+  _LIBCPP_INLINE_VISIBILITY
+  any(any const & __other) : __h(nullptr)
+  {
+    if (__other.__h) __other.__call(_Action::_Copy, this);
+  }
+
+  _LIBCPP_INLINE_VISIBILITY
+  any(any && __other) _NOEXCEPT : __h(nullptr)
+  {
+    if (__other.__h) __other.__call(_Action::_Move, this);
+  }
+
+  template <
+      class _ValueType
+    , class _Tp = decay_t<_ValueType>
+    , class = enable_if_t<
+        !is_same<_Tp, any>::value &&
+        !__is_inplace_type<_ValueType>::value &&
+        is_copy_constructible<_Tp>::value>
+    >
+  _LIBCPP_INLINE_VISIBILITY
+  any(_ValueType && __value);
+
+  template <class _ValueType, class ..._Args,
+    class _Tp = decay_t<_ValueType>,
+    class = enable_if_t<
+        is_constructible<_Tp, _Args...>::value &&
+        is_copy_constructible<_Tp>::value
+    >
+  >
+  _LIBCPP_INLINE_VISIBILITY
+  explicit any(in_place_type_t<_ValueType>, _Args&&... __args);
+
+  template <class _ValueType, class _Up, class ..._Args,
+    class _Tp = decay_t<_ValueType>,
+    class = enable_if_t<
+        is_constructible<_Tp, initializer_list<_Up>&, _Args...>::value &&
+        is_copy_constructible<_Tp>::value>
+  >
+  _LIBCPP_INLINE_VISIBILITY
+  explicit any(in_place_type_t<_ValueType>, initializer_list<_Up>, _Args&&... __args);
+
+  _LIBCPP_INLINE_VISIBILITY
+  ~any() { this->reset(); }
+
+  // assignments
+  _LIBCPP_INLINE_VISIBILITY
+  any & operator=(any const & __rhs) {
+    any(__rhs).swap(*this);
+    return *this;
+  }
+
+  _LIBCPP_INLINE_VISIBILITY
+  any & operator=(any && __rhs) _NOEXCEPT {
+    any(_VSTD::move(__rhs)).swap(*this);
+    return *this;
+  }
+
+  template <
+      class _ValueType
+    , class _Tp = decay_t<_ValueType>
+    , class = enable_if_t<
+          !is_same<_Tp, any>::value
+          && is_copy_constructible<_Tp>::value>
+    >
+  _LIBCPP_INLINE_VISIBILITY
+  any & operator=(_ValueType && __rhs);
+
+  template <class _ValueType, class ..._Args,
+    class _Tp = decay_t<_ValueType>,
+    class = enable_if_t<
+        is_constructible<_Tp, _Args...>::value &&
+        is_copy_constructible<_Tp>::value>
+    >
+  _LIBCPP_INLINE_VISIBILITY
+  _Tp& emplace(_Args&&... args);
+
+  template <class _ValueType, class _Up, class ..._Args,
+    class _Tp = decay_t<_ValueType>,
+    class = enable_if_t<
+        is_constructible<_Tp, initializer_list<_Up>&, _Args...>::value &&
+        is_copy_constructible<_Tp>::value>
+  >
+  _LIBCPP_INLINE_VISIBILITY
+  _Tp& emplace(initializer_list<_Up>, _Args&&...);
+
+  // 6.3.3 any modifiers
+  _LIBCPP_INLINE_VISIBILITY
+  void reset() _NOEXCEPT { if (__h) this->__call(_Action::_Destroy); }
+
+  _LIBCPP_INLINE_VISIBILITY
+  void swap(any & __rhs) _NOEXCEPT;
+
+  // 6.3.4 any observers
+  _LIBCPP_INLINE_VISIBILITY
+  bool has_value() const _NOEXCEPT { return __h != nullptr; }
+
+#if !defined(_LIBCPP_NO_RTTI)
+  _LIBCPP_INLINE_VISIBILITY
+  const type_info & type() const _NOEXCEPT {
+    if (__h) {
+        return *static_cast<type_info const *>(this->__call(_Action::_TypeInfo));
+    } else {
+        return typeid(void);
+    }
+  }
+#endif
+
+private:
+    typedef __any_imp::_Action _Action;
+    using _HandleFuncPtr =  void* (*)(_Action, any const *, any *, const type_info *,
+      const void* __fallback_info);
+
+    union _Storage {
+        constexpr _Storage() : __ptr(nullptr) {}
+        void *  __ptr;
+        __any_imp::_Buffer __buf;
+    };
+
+    _LIBCPP_ALWAYS_INLINE
+    void * __call(_Action __a, any * __other = nullptr,
+                  type_info const * __info = nullptr,
+                   const void* __fallback_info = nullptr) const
+    {
+        return __h(__a, this, __other, __info, __fallback_info);
+    }
+
+    _LIBCPP_ALWAYS_INLINE
+    void * __call(_Action __a, any * __other = nullptr,
+                  type_info const * __info = nullptr,
+                  const void* __fallback_info = nullptr)
+    {
+        return __h(__a, this, __other, __info, __fallback_info);
+    }
+
+    template <class>
+    friend struct __any_imp::_SmallHandler;
+    template <class>
+    friend struct __any_imp::_LargeHandler;
+
+    template <class _ValueType>
+    friend add_pointer_t<add_const_t<_ValueType>>
+    any_cast(any const *) _NOEXCEPT;
+
+    template <class _ValueType>
+    friend add_pointer_t<_ValueType>
+    any_cast(any *) _NOEXCEPT;
+
+    _HandleFuncPtr __h = nullptr;
+    _Storage __s;
+};
+
+namespace __any_imp
+{
+  template <class _Tp>
+  struct _LIBCPP_TEMPLATE_VIS _SmallHandler
+  {
+     _LIBCPP_INLINE_VISIBILITY
+     static void* __handle(_Action __act, any const * __this, any * __other,
+                           type_info const * __info, const void* __fallback_info)
+     {
+        switch (__act)
+        {
+        case _Action::_Destroy:
+          __destroy(const_cast<any &>(*__this));
+          return nullptr;
+        case _Action::_Copy:
+            __copy(*__this, *__other);
+            return nullptr;
+        case _Action::_Move:
+          __move(const_cast<any &>(*__this), *__other);
+          return nullptr;
+        case _Action::_Get:
+            return __get(const_cast<any &>(*__this), __info, __fallback_info);
+        case _Action::_TypeInfo:
+          return __type_info();
+        }
+    }
+
+    template <class ..._Args>
+    _LIBCPP_INLINE_VISIBILITY
+    static _Tp& __create(any & __dest, _Args&&... __args) {
+        _Tp* __ret = ::new (static_cast<void*>(&__dest.__s.__buf)) _Tp(_VSTD::forward<_Args>(__args)...);
+        __dest.__h = &_SmallHandler::__handle;
+        return *__ret;
+    }
+
+  private:
+    _LIBCPP_INLINE_VISIBILITY
+    static void __destroy(any & __this) {
+        _Tp & __value = *static_cast<_Tp *>(static_cast<void*>(&__this.__s.__buf));
+        __value.~_Tp();
+        __this.__h = nullptr;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    static void __copy(any const & __this, any & __dest) {
+        _SmallHandler::__create(__dest, *static_cast<_Tp const *>(
+            static_cast<void const *>(&__this.__s.__buf)));
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    static void __move(any & __this, any & __dest) {
+        _SmallHandler::__create(__dest, _VSTD::move(
+            *static_cast<_Tp*>(static_cast<void*>(&__this.__s.__buf))));
+        __destroy(__this);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    static void* __get(any & __this,
+                       type_info const * __info,
+                       const void* __fallback_id)
+    {
+        if (__any_imp::__compare_typeid<_Tp>(__info, __fallback_id))
+            return static_cast<void*>(&__this.__s.__buf);
+        return nullptr;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    static void* __type_info()
+    {
+#if !defined(_LIBCPP_NO_RTTI)
+        return const_cast<void*>(static_cast<void const *>(&typeid(_Tp)));
+#else
+        return nullptr;
+#endif
+    }
+  };
+
+  template <class _Tp>
+  struct _LIBCPP_TEMPLATE_VIS _LargeHandler
+  {
+    _LIBCPP_INLINE_VISIBILITY
+    static void* __handle(_Action __act, any const * __this,
+                          any * __other, type_info const * __info,
+                          void const* __fallback_info)
+    {
+        switch (__act)
+        {
+        case _Action::_Destroy:
+          __destroy(const_cast<any &>(*__this));
+          return nullptr;
+        case _Action::_Copy:
+          __copy(*__this, *__other);
+          return nullptr;
+        case _Action::_Move:
+          __move(const_cast<any &>(*__this), *__other);
+          return nullptr;
+        case _Action::_Get:
+            return __get(const_cast<any &>(*__this), __info, __fallback_info);
+        case _Action::_TypeInfo:
+          return __type_info();
+        }
+    }
+
+    template <class ..._Args>
+    _LIBCPP_INLINE_VISIBILITY
+    static _Tp& __create(any & __dest, _Args&&... __args) {
+        typedef allocator<_Tp> _Alloc;
+        typedef __allocator_destructor<_Alloc> _Dp;
+        _Alloc __a;
+        unique_ptr<_Tp, _Dp> __hold(__a.allocate(1), _Dp(__a, 1));
+        _Tp* __ret = ::new ((void*)__hold.get()) _Tp(_VSTD::forward<_Args>(__args)...);
+        __dest.__s.__ptr = __hold.release();
+        __dest.__h = &_LargeHandler::__handle;
+        return *__ret;
+    }
+
+  private:
+
+    _LIBCPP_INLINE_VISIBILITY
+    static void __destroy(any & __this){
+        delete static_cast<_Tp*>(__this.__s.__ptr);
+        __this.__h = nullptr;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    static void __copy(any const & __this, any & __dest) {
+        _LargeHandler::__create(__dest, *static_cast<_Tp const *>(__this.__s.__ptr));
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    static void __move(any & __this, any & __dest) {
+      __dest.__s.__ptr = __this.__s.__ptr;
+      __dest.__h = &_LargeHandler::__handle;
+      __this.__h = nullptr;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    static void* __get(any & __this, type_info const * __info,
+                       void const* __fallback_info)
+    {
+        if (__any_imp::__compare_typeid<_Tp>(__info, __fallback_info))
+            return static_cast<void*>(__this.__s.__ptr);
+        return nullptr;
+
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    static void* __type_info()
+    {
+#if !defined(_LIBCPP_NO_RTTI)
+        return const_cast<void*>(static_cast<void const *>(&typeid(_Tp)));
+#else
+        return nullptr;
+#endif
+    }
+  };
+
+} // namespace __any_imp
+
+
+template <class _ValueType, class _Tp, class>
+any::any(_ValueType && __v) : __h(nullptr)
+{
+  __any_imp::_Handler<_Tp>::__create(*this, _VSTD::forward<_ValueType>(__v));
+}
+
+template <class _ValueType, class ..._Args, class _Tp, class>
+any::any(in_place_type_t<_ValueType>, _Args&&... __args) {
+  __any_imp::_Handler<_Tp>::__create(*this, _VSTD::forward<_Args>(__args)...);
+};
+
+template <class _ValueType, class _Up, class ..._Args, class _Tp, class>
+any::any(in_place_type_t<_ValueType>, initializer_list<_Up> __il, _Args&&... __args) {
+  __any_imp::_Handler<_Tp>::__create(*this, __il, _VSTD::forward<_Args>(__args)...);
+}
+
+template <class _ValueType, class, class>
+inline _LIBCPP_INLINE_VISIBILITY
+any & any::operator=(_ValueType && __v)
+{
+  any(_VSTD::forward<_ValueType>(__v)).swap(*this);
+  return *this;
+}
+
+template <class _ValueType, class ..._Args, class _Tp, class>
+inline _LIBCPP_INLINE_VISIBILITY
+_Tp& any::emplace(_Args&&... __args) {
+  reset();
+  return __any_imp::_Handler<_Tp>::__create(*this, _VSTD::forward<_Args>(__args)...);
+}
+
+template <class _ValueType, class _Up, class ..._Args, class _Tp, class>
+inline _LIBCPP_INLINE_VISIBILITY
+_Tp& any::emplace(initializer_list<_Up> __il, _Args&&... __args) {
+  reset();
+  return __any_imp::_Handler<_Tp>::__create(*this, __il, _VSTD::forward<_Args>(__args)...);
+}
+
+inline _LIBCPP_INLINE_VISIBILITY
+void any::swap(any & __rhs) _NOEXCEPT
+{
+    if (this == &__rhs)
+      return;
+    if (__h && __rhs.__h) {
+        any __tmp;
+        __rhs.__call(_Action::_Move, &__tmp);
+        this->__call(_Action::_Move, &__rhs);
+        __tmp.__call(_Action::_Move, this);
+    }
+    else if (__h) {
+        this->__call(_Action::_Move, &__rhs);
+    }
+    else if (__rhs.__h) {
+        __rhs.__call(_Action::_Move, this);
+    }
+}
+
+// 6.4 Non-member functions
+
+inline _LIBCPP_INLINE_VISIBILITY
+void swap(any & __lhs, any & __rhs) _NOEXCEPT
+{
+    __lhs.swap(__rhs);
+}
+
+template <class _Tp, class ..._Args>
+inline _LIBCPP_INLINE_VISIBILITY
+any make_any(_Args&&... __args) {
+    return any(in_place_type<_Tp>, _VSTD::forward<_Args>(__args)...);
+}
+
+template <class _Tp, class _Up, class ..._Args>
+inline _LIBCPP_INLINE_VISIBILITY
+any make_any(initializer_list<_Up> __il, _Args&&... __args) {
+    return any(in_place_type<_Tp>, __il, _VSTD::forward<_Args>(__args)...);
+}
+
+template <class _ValueType>
+inline _LIBCPP_INLINE_VISIBILITY
+_ValueType any_cast(any const & __v)
+{
+    using _RawValueType = __uncvref_t<_ValueType>;
+    static_assert(is_constructible<_ValueType, _RawValueType const &>::value,
+                  "ValueType is required to be a const lvalue reference "
+                  "or a CopyConstructible type");
+    auto __tmp = _VSTD::any_cast<add_const_t<_RawValueType>>(&__v);
+    if (__tmp == nullptr)
+        __throw_bad_any_cast();
+    return static_cast<_ValueType>(*__tmp);
+}
+
+template <class _ValueType>
+inline _LIBCPP_INLINE_VISIBILITY
+_ValueType any_cast(any & __v)
+{
+    using _RawValueType = __uncvref_t<_ValueType>;
+    static_assert(is_constructible<_ValueType, _RawValueType &>::value,
+                  "ValueType is required to be an lvalue reference "
+                  "or a CopyConstructible type");
+    auto __tmp = _VSTD::any_cast<_RawValueType>(&__v);
+    if (__tmp == nullptr)
+        __throw_bad_any_cast();
+    return static_cast<_ValueType>(*__tmp);
+}
+
+template <class _ValueType>
+inline _LIBCPP_INLINE_VISIBILITY
+_ValueType any_cast(any && __v)
+{
+    using _RawValueType = __uncvref_t<_ValueType>;
+    static_assert(is_constructible<_ValueType, _RawValueType>::value,
+                  "ValueType is required to be an rvalue reference "
+                  "or a CopyConstructible type");
+    auto __tmp = _VSTD::any_cast<_RawValueType>(&__v);
+    if (__tmp == nullptr)
+        __throw_bad_any_cast();
+    return static_cast<_ValueType>(_VSTD::move(*__tmp));
+}
+
+template <class _ValueType>
+inline _LIBCPP_INLINE_VISIBILITY
+add_pointer_t<add_const_t<_ValueType>>
+any_cast(any const * __any) _NOEXCEPT
+{
+    static_assert(!is_reference<_ValueType>::value,
+                  "_ValueType may not be a reference.");
+    return _VSTD::any_cast<_ValueType>(const_cast<any *>(__any));
+}
+
+template <class _RetType>
+inline _LIBCPP_INLINE_VISIBILITY
+_RetType __pointer_or_func_cast(void* __p, /*IsFunction*/false_type) noexcept {
+  return static_cast<_RetType>(__p);
+}
+
+template <class _RetType>
+inline _LIBCPP_INLINE_VISIBILITY
+_RetType __pointer_or_func_cast(void*, /*IsFunction*/true_type) noexcept {
+  return nullptr;
+}
+
+template <class _ValueType>
+add_pointer_t<_ValueType>
+any_cast(any * __any) _NOEXCEPT
+{
+    using __any_imp::_Action;
+    static_assert(!is_reference<_ValueType>::value,
+                  "_ValueType may not be a reference.");
+    typedef typename add_pointer<_ValueType>::type _ReturnType;
+    if (__any && __any->__h) {
+      void *__p = __any->__call(_Action::_Get, nullptr,
+#if !defined(_LIBCPP_NO_RTTI)
+                          &typeid(_ValueType),
+#else
+                          nullptr,
+#endif
+                          __any_imp::__get_fallback_typeid<_ValueType>());
+        return _VSTD::__pointer_or_func_cast<_ReturnType>(
+            __p, is_function<_ValueType>{});
+    }
+    return nullptr;
+}
+
+#endif // _LIBCPP_STD_VER > 14
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_ANY
diff --git a/lib/libcxx/include/array b/lib/libcxx/include/array
index 719286d52ea..4eb2fe6fc62 100644
--- a/lib/libcxx/include/array
+++ b/lib/libcxx/include/array
@@ -108,18 +108,17 @@ template <size_t I, class T, size_t N> const T&& get(const array<T, N>&&) noexce
 #include <iterator>
 #include <algorithm>
 #include <stdexcept>
-#if defined(_LIBCPP_NO_EXCEPTIONS)
-    #include <cassert>
-#endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Tp, size_t _Size>
-struct _LIBCPP_TYPE_VIS_ONLY array
+struct _LIBCPP_TEMPLATE_VIS array
 {
     // types:
     typedef array __self;
@@ -152,31 +151,31 @@ struct _LIBCPP_TYPE_VIS_ONLY array
         { _VSTD::swap_ranges(__elems_, __elems_ + _Size, __a.__elems_);}
 
     // iterators:
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     iterator begin() _NOEXCEPT {return iterator(__elems_);}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     const_iterator begin() const _NOEXCEPT {return const_iterator(__elems_);}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     iterator end() _NOEXCEPT {return iterator(__elems_ + _Size);}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     const_iterator end() const _NOEXCEPT {return const_iterator(__elems_ + _Size);}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     reverse_iterator rbegin() _NOEXCEPT {return reverse_iterator(end());}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     const_reverse_iterator rbegin() const _NOEXCEPT {return const_reverse_iterator(end());}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     reverse_iterator rend() _NOEXCEPT {return reverse_iterator(begin());}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     const_reverse_iterator rend() const _NOEXCEPT {return const_reverse_iterator(begin());}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     const_iterator cbegin() const _NOEXCEPT {return begin();}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     const_iterator cend() const _NOEXCEPT {return end();}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     const_reverse_iterator crbegin() const _NOEXCEPT {return rbegin();}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     const_reverse_iterator crend() const _NOEXCEPT {return rend();}
 
     // capacity:
@@ -184,36 +183,37 @@ struct _LIBCPP_TYPE_VIS_ONLY array
     _LIBCPP_CONSTEXPR size_type size() const _NOEXCEPT {return _Size;}
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR size_type max_size() const _NOEXCEPT {return _Size;}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR bool empty() const _NOEXCEPT {return _Size == 0;}
 
     // element access:
-    _LIBCPP_INLINE_VISIBILITY reference operator[](size_type __n)             {return __elems_[__n];}
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const_reference operator[](size_type __n) const {return __elems_[__n];}
-    reference at(size_type __n);
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reference operator[](size_type __n)             {return __elems_[__n];}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    const_reference operator[](size_type __n) const {return __elems_[__n];}
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX14       reference at(size_type __n);
     _LIBCPP_CONSTEXPR_AFTER_CXX11 const_reference at(size_type __n) const;
 
-    _LIBCPP_INLINE_VISIBILITY reference front()             {return __elems_[0];}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 reference front()             {return __elems_[0];}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const_reference front() const {return __elems_[0];}
-    _LIBCPP_INLINE_VISIBILITY reference back()              {return __elems_[_Size > 0 ? _Size-1 : 0];}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 reference back()              {return __elems_[_Size > 0 ? _Size-1 : 0];}
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const_reference back() const  {return __elems_[_Size > 0 ? _Size-1 : 0];}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     value_type* data() _NOEXCEPT {return __elems_;}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
     const value_type* data() const _NOEXCEPT {return __elems_;}
 };
 
 template <class _Tp, size_t _Size>
+_LIBCPP_CONSTEXPR_AFTER_CXX14
 typename array<_Tp, _Size>::reference
 array<_Tp, _Size>::at(size_type __n)
 {
     if (__n >= _Size)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw out_of_range("array::at");
-#else
-        assert(!"array::at out_of_range");
-#endif
+        __throw_out_of_range("array::at");
+
     return __elems_[__n];
 }
 
@@ -223,11 +223,7 @@ typename array<_Tp, _Size>::const_reference
 array<_Tp, _Size>::at(size_type __n) const
 {
     if (__n >= _Size)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw out_of_range("array::at");
-#else
-        assert(!"array::at out_of_range");
-#endif
+        __throw_out_of_range("array::at");
     return __elems_[__n];
 }
 
@@ -294,12 +290,13 @@ swap(array<_Tp, _Size>& __x, array<_Tp, _Size>& __y)
 }
 
 template <class _Tp, size_t _Size>
-class _LIBCPP_TYPE_VIS_ONLY tuple_size<array<_Tp, _Size> >
+class _LIBCPP_TEMPLATE_VIS tuple_size<array<_Tp, _Size> >
     : public integral_constant<size_t, _Size> {};
 
 template <size_t _Ip, class _Tp, size_t _Size>
-class _LIBCPP_TYPE_VIS_ONLY tuple_element<_Ip, array<_Tp, _Size> >
+class _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, array<_Tp, _Size> >
 {
+    static_assert(_Ip < _Size, "Index out of bounds in std::tuple_element<> (std::array)");
 public:
     typedef _Tp type;
 };
@@ -322,7 +319,7 @@ get(const array<_Tp, _Size>& __a) _NOEXCEPT
     return __a.__elems_[_Ip];
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <size_t _Ip, class _Tp, size_t _Size>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
@@ -342,7 +339,7 @@ get(const array<_Tp, _Size>&& __a) _NOEXCEPT
     return _VSTD::move(__a.__elems_[_Ip]);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // !_LIBCPP_CXX03_LANG
 
 _LIBCPP_END_NAMESPACE_STD
 
diff --git a/lib/libcxx/include/atomic b/lib/libcxx/include/atomic
index 11f2152e5bc..f55e28ff5e9 100644
--- a/lib/libcxx/include/atomic
+++ b/lib/libcxx/include/atomic
@@ -557,10 +557,25 @@ void atomic_signal_fence(memory_order m) noexcept;
 #endif
 
 #if _LIBCPP_STD_VER > 14
-// FIXME: use the right feature test macro value as chose by SG10.
 # define __cpp_lib_atomic_is_always_lock_free 201603L
 #endif
 
+#define _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m) \
+  _LIBCPP_DIAGNOSE_WARNING(__m == memory_order_consume || \
+                           __m == memory_order_acquire || \
+                           __m == memory_order_acq_rel,   \
+                        "memory order argument to atomic operation is invalid")
+
+#define _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m) \
+  _LIBCPP_DIAGNOSE_WARNING(__m == memory_order_release || \
+                           __m == memory_order_acq_rel,   \
+                        "memory order argument to atomic operation is invalid")
+
+#define _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__m, __f) \
+  _LIBCPP_DIAGNOSE_WARNING(__f == memory_order_release || \
+                           __f == memory_order_acq_rel,   \
+                        "memory order argument to atomic operation is invalid")
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 typedef enum memory_order
@@ -580,11 +595,11 @@ struct __gcc_atomic_t {
 #endif
 
   _LIBCPP_INLINE_VISIBILITY
-#ifndef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
+#ifndef _LIBCPP_CXX03_LANG
     __gcc_atomic_t() _NOEXCEPT = default;
 #else
     __gcc_atomic_t() _NOEXCEPT : __a_value() {}
-#endif // _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
+#endif // _LIBCPP_CXX03_LANG
   _LIBCPP_CONSTEXPR explicit __gcc_atomic_t(_Tp value) _NOEXCEPT
     : __a_value(value) {}
   _Tp __a_value;
@@ -846,16 +861,29 @@ kill_dependency(_Tp __y) _NOEXCEPT
     return __y;
 }
 
-#define ATOMIC_BOOL_LOCK_FREE      __GCC_ATOMIC_BOOL_LOCK_FREE
-#define ATOMIC_CHAR_LOCK_FREE      __GCC_ATOMIC_CHAR_LOCK_FREE
-#define ATOMIC_CHAR16_T_LOCK_FREE  __GCC_ATOMIC_CHAR16_T_LOCK_FREE
-#define ATOMIC_CHAR32_T_LOCK_FREE  __GCC_ATOMIC_CHAR32_T_LOCK_FREE
-#define ATOMIC_WCHAR_T_LOCK_FREE   __GCC_ATOMIC_WCHAR_T_LOCK_FREE
-#define ATOMIC_SHORT_LOCK_FREE     __GCC_ATOMIC_SHORT_LOCK_FREE
-#define ATOMIC_INT_LOCK_FREE       __GCC_ATOMIC_INT_LOCK_FREE
-#define ATOMIC_LONG_LOCK_FREE      __GCC_ATOMIC_LONG_LOCK_FREE
-#define ATOMIC_LLONG_LOCK_FREE     __GCC_ATOMIC_LLONG_LOCK_FREE
-#define ATOMIC_POINTER_LOCK_FREE   __GCC_ATOMIC_POINTER_LOCK_FREE
+#if defined(__CLANG_ATOMIC_BOOL_LOCK_FREE)
+# define ATOMIC_BOOL_LOCK_FREE      __CLANG_ATOMIC_BOOL_LOCK_FREE
+# define ATOMIC_CHAR_LOCK_FREE      __CLANG_ATOMIC_CHAR_LOCK_FREE
+# define ATOMIC_CHAR16_T_LOCK_FREE  __CLANG_ATOMIC_CHAR16_T_LOCK_FREE
+# define ATOMIC_CHAR32_T_LOCK_FREE  __CLANG_ATOMIC_CHAR32_T_LOCK_FREE
+# define ATOMIC_WCHAR_T_LOCK_FREE   __CLANG_ATOMIC_WCHAR_T_LOCK_FREE
+# define ATOMIC_SHORT_LOCK_FREE     __CLANG_ATOMIC_SHORT_LOCK_FREE
+# define ATOMIC_INT_LOCK_FREE       __CLANG_ATOMIC_INT_LOCK_FREE
+# define ATOMIC_LONG_LOCK_FREE      __CLANG_ATOMIC_LONG_LOCK_FREE
+# define ATOMIC_LLONG_LOCK_FREE     __CLANG_ATOMIC_LLONG_LOCK_FREE
+# define ATOMIC_POINTER_LOCK_FREE   __CLANG_ATOMIC_POINTER_LOCK_FREE
+#else
+# define ATOMIC_BOOL_LOCK_FREE      __GCC_ATOMIC_BOOL_LOCK_FREE
+# define ATOMIC_CHAR_LOCK_FREE      __GCC_ATOMIC_CHAR_LOCK_FREE
+# define ATOMIC_CHAR16_T_LOCK_FREE  __GCC_ATOMIC_CHAR16_T_LOCK_FREE
+# define ATOMIC_CHAR32_T_LOCK_FREE  __GCC_ATOMIC_CHAR32_T_LOCK_FREE
+# define ATOMIC_WCHAR_T_LOCK_FREE   __GCC_ATOMIC_WCHAR_T_LOCK_FREE
+# define ATOMIC_SHORT_LOCK_FREE     __GCC_ATOMIC_SHORT_LOCK_FREE
+# define ATOMIC_INT_LOCK_FREE       __GCC_ATOMIC_INT_LOCK_FREE
+# define ATOMIC_LONG_LOCK_FREE      __GCC_ATOMIC_LONG_LOCK_FREE
+# define ATOMIC_LLONG_LOCK_FREE     __GCC_ATOMIC_LLONG_LOCK_FREE
+# define ATOMIC_POINTER_LOCK_FREE   __GCC_ATOMIC_POINTER_LOCK_FREE
+#endif
 
 // general atomic<T>
 
@@ -882,15 +910,19 @@ struct __atomic_base  // false
         {return static_cast<__atomic_base const volatile*>(this)->is_lock_free();}
     _LIBCPP_INLINE_VISIBILITY
     void store(_Tp __d, memory_order __m = memory_order_seq_cst) volatile _NOEXCEPT
+      _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m)
         {__c11_atomic_store(&__a_, __d, __m);}
     _LIBCPP_INLINE_VISIBILITY
     void store(_Tp __d, memory_order __m = memory_order_seq_cst) _NOEXCEPT
+      _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m)
         {__c11_atomic_store(&__a_, __d, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp load(memory_order __m = memory_order_seq_cst) const volatile _NOEXCEPT
+      _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
         {return __c11_atomic_load(&__a_, __m);}
     _LIBCPP_INLINE_VISIBILITY
     _Tp load(memory_order __m = memory_order_seq_cst) const _NOEXCEPT
+      _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
         {return __c11_atomic_load(&__a_, __m);}
     _LIBCPP_INLINE_VISIBILITY
     operator _Tp() const volatile _NOEXCEPT {return load();}
@@ -905,18 +937,22 @@ struct __atomic_base  // false
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_weak(_Tp& __e, _Tp __d,
                                memory_order __s, memory_order __f) volatile _NOEXCEPT
+      _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
         {return __c11_atomic_compare_exchange_weak(&__a_, &__e, __d, __s, __f);}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_weak(_Tp& __e, _Tp __d,
                                memory_order __s, memory_order __f) _NOEXCEPT
+      _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
         {return __c11_atomic_compare_exchange_weak(&__a_, &__e, __d, __s, __f);}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_strong(_Tp& __e, _Tp __d,
                                  memory_order __s, memory_order __f) volatile _NOEXCEPT
+      _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
         {return __c11_atomic_compare_exchange_strong(&__a_, &__e, __d, __s, __f);}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_strong(_Tp& __e, _Tp __d,
                                  memory_order __s, memory_order __f) _NOEXCEPT
+      _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
         {return __c11_atomic_compare_exchange_strong(&__a_, &__e, __d, __s, __f);}
     _LIBCPP_INLINE_VISIBILITY
     bool compare_exchange_weak(_Tp& __e, _Tp __d,
@@ -936,24 +972,24 @@ struct __atomic_base  // false
         {return __c11_atomic_compare_exchange_strong(&__a_, &__e, __d, __m, __m);}
 
     _LIBCPP_INLINE_VISIBILITY
-#ifndef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
+#ifndef _LIBCPP_CXX03_LANG
     __atomic_base() _NOEXCEPT = default;
 #else
     __atomic_base() _NOEXCEPT : __a_() {}
-#endif // _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
+#endif // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR __atomic_base(_Tp __d) _NOEXCEPT : __a_(__d) {}
-#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+#ifndef _LIBCPP_CXX03_LANG
     __atomic_base(const __atomic_base&) = delete;
     __atomic_base& operator=(const __atomic_base&) = delete;
     __atomic_base& operator=(const __atomic_base&) volatile = delete;
-#else  // _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+#else
 private:
     __atomic_base(const __atomic_base&);
     __atomic_base& operator=(const __atomic_base&);
     __atomic_base& operator=(const __atomic_base&) volatile;
-#endif  // _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+#endif
 };
 
 #if defined(__cpp_lib_atomic_is_always_lock_free)
@@ -1182,6 +1218,7 @@ template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 void
 atomic_store_explicit(volatile atomic<_Tp>* __o, _Tp __d, memory_order __m) _NOEXCEPT
+  _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m)
 {
     __o->store(__d, __m);
 }
@@ -1190,6 +1227,7 @@ template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 void
 atomic_store_explicit(atomic<_Tp>* __o, _Tp __d, memory_order __m) _NOEXCEPT
+  _LIBCPP_CHECK_STORE_MEMORY_ORDER(__m)
 {
     __o->store(__d, __m);
 }
@@ -1218,6 +1256,7 @@ template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 _Tp
 atomic_load_explicit(const volatile atomic<_Tp>* __o, memory_order __m) _NOEXCEPT
+  _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
 {
     return __o->load(__m);
 }
@@ -1226,6 +1265,7 @@ template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 _Tp
 atomic_load_explicit(const atomic<_Tp>* __o, memory_order __m) _NOEXCEPT
+  _LIBCPP_CHECK_LOAD_MEMORY_ORDER(__m)
 {
     return __o->load(__m);
 }
@@ -1310,6 +1350,7 @@ bool
 atomic_compare_exchange_weak_explicit(volatile atomic<_Tp>* __o, _Tp* __e,
                                       _Tp __d,
                                       memory_order __s, memory_order __f) _NOEXCEPT
+  _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
 {
     return __o->compare_exchange_weak(*__e, __d, __s, __f);
 }
@@ -1319,6 +1360,7 @@ inline _LIBCPP_INLINE_VISIBILITY
 bool
 atomic_compare_exchange_weak_explicit(atomic<_Tp>* __o, _Tp* __e, _Tp __d,
                                       memory_order __s, memory_order __f) _NOEXCEPT
+  _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
 {
     return __o->compare_exchange_weak(*__e, __d, __s, __f);
 }
@@ -1331,6 +1373,7 @@ bool
 atomic_compare_exchange_strong_explicit(volatile atomic<_Tp>* __o,
                                         _Tp* __e, _Tp __d,
                                         memory_order __s, memory_order __f) _NOEXCEPT
+  _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
 {
     return __o->compare_exchange_strong(*__e, __d, __s, __f);
 }
@@ -1341,6 +1384,7 @@ bool
 atomic_compare_exchange_strong_explicit(atomic<_Tp>* __o, _Tp* __e,
                                         _Tp __d,
                                         memory_order __s, memory_order __f) _NOEXCEPT
+  _LIBCPP_CHECK_EXCHANGE_MEMORY_ORDER(__s, __f)
 {
     return __o->compare_exchange_strong(*__e, __d, __s, __f);
 }
@@ -1691,25 +1735,25 @@ typedef struct atomic_flag
         {__c11_atomic_store(&__a_, false, __m);}
 
     _LIBCPP_INLINE_VISIBILITY
-#ifndef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
+#ifndef _LIBCPP_CXX03_LANG
     atomic_flag() _NOEXCEPT = default;
 #else
     atomic_flag() _NOEXCEPT : __a_() {}
-#endif // _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
+#endif // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     atomic_flag(bool __b) _NOEXCEPT : __a_(__b) {} // EXTENSION
 
-#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+#ifndef _LIBCPP_CXX03_LANG
     atomic_flag(const atomic_flag&) = delete;
     atomic_flag& operator=(const atomic_flag&) = delete;
     atomic_flag& operator=(const atomic_flag&) volatile = delete;
-#else  // _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+#else
 private:
     atomic_flag(const atomic_flag&);
     atomic_flag& operator=(const atomic_flag&);
     atomic_flag& operator=(const atomic_flag&) volatile;
-#endif  // _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+#endif
 } atomic_flag;
 
 inline _LIBCPP_INLINE_VISIBILITY
diff --git a/lib/libcxx/include/bitset b/lib/libcxx/include/bitset
index 3f9b964e45a..cd6c289b4c4 100644
--- a/lib/libcxx/include/bitset
+++ b/lib/libcxx/include/bitset
@@ -113,10 +113,6 @@ template <size_t N> struct hash<std::bitset<N>>;
 
 */
 
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
-#endif
-
 #include <__config>
 #include <__bit_reference>
 #include <cstddef>
@@ -125,11 +121,14 @@ template <size_t N> struct hash<std::bitset<N>>;
 #include <stdexcept>
 #include <iosfwd>
 #include <__functional_base>
-#if defined(_LIBCPP_NO_EXCEPTIONS)
-    #include <cassert>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
 #endif
 
-#include <__undef_min_max>
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
@@ -200,11 +199,11 @@ protected:
     _LIBCPP_INLINE_VISIBILITY
     size_t __hash_code() const _NOEXCEPT;
 private:
-#ifdef _LIBCPP_HAS_NO_CONSTEXPR
+#ifdef _LIBCPP_CXX03_LANG
     void __init(unsigned long long __v, false_type) _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     void __init(unsigned long long __v, true_type) _NOEXCEPT;
-#endif  // _LIBCPP_HAS_NO_CONSTEXPR
+#endif  // _LIBCPP_CXX03_LANG
     unsigned long to_ulong(false_type) const;
     _LIBCPP_INLINE_VISIBILITY
     unsigned long to_ulong(true_type) const;
@@ -220,24 +219,29 @@ template <size_t _N_words, size_t _Size>
 inline
 _LIBCPP_CONSTEXPR
 __bitset<_N_words, _Size>::__bitset() _NOEXCEPT
-#ifndef _LIBCPP_HAS_NO_CONSTEXPR
+#ifndef _LIBCPP_CXX03_LANG
     : __first_{0}
 #endif
 {
-#ifdef _LIBCPP_HAS_NO_CONSTEXPR
+#ifdef _LIBCPP_CXX03_LANG
     _VSTD::fill_n(__first_, _N_words, __storage_type(0));
 #endif
 }
 
-#ifdef _LIBCPP_HAS_NO_CONSTEXPR
+#ifdef _LIBCPP_CXX03_LANG
 
 template <size_t _N_words, size_t _Size>
 void
 __bitset<_N_words, _Size>::__init(unsigned long long __v, false_type) _NOEXCEPT
 {
     __storage_type __t[sizeof(unsigned long long) / sizeof(__storage_type)];
-    for (size_t __i = 0; __i < sizeof(__t)/sizeof(__t[0]); ++__i, __v >>= __bits_per_word)
-        __t[__i] = static_cast<__storage_type>(__v);
+    size_t __sz = _Size;
+    for (size_t __i = 0; __i < sizeof(__t)/sizeof(__t[0]); ++__i, __v >>= __bits_per_word, __sz -= __bits_per_word )
+        if ( __sz < __bits_per_word)
+        	__t[__i] = static_cast<__storage_type>(__v) & ( 1ULL << __sz ) - 1;
+        else
+        	__t[__i] = static_cast<__storage_type>(__v);
+
     _VSTD::copy(__t, __t + sizeof(__t)/sizeof(__t[0]), __first_);
     _VSTD::fill(__first_ + sizeof(__t)/sizeof(__t[0]), __first_ + sizeof(__first_)/sizeof(__first_[0]),
                __storage_type(0));
@@ -249,26 +253,31 @@ void
 __bitset<_N_words, _Size>::__init(unsigned long long __v, true_type) _NOEXCEPT
 {
     __first_[0] = __v;
+    if (_Size < __bits_per_word)
+    	__first_[0] &= ( 1ULL << _Size ) - 1;
+
     _VSTD::fill(__first_ + 1, __first_ + sizeof(__first_)/sizeof(__first_[0]), __storage_type(0));
 }
 
-#endif  // _LIBCPP_HAS_NO_CONSTEXPR
+#endif  // _LIBCPP_CXX03_LANG
 
 template <size_t _N_words, size_t _Size>
 inline
 _LIBCPP_CONSTEXPR
 __bitset<_N_words, _Size>::__bitset(unsigned long long __v) _NOEXCEPT
-#ifndef _LIBCPP_HAS_NO_CONSTEXPR
+#ifndef _LIBCPP_CXX03_LANG
 #if __SIZEOF_SIZE_T__ == 8
     : __first_{__v}
 #elif __SIZEOF_SIZE_T__ == 4
-    : __first_{__v, __v >> __bits_per_word}
+    : __first_{static_cast<__storage_type>(__v), 
+    			_Size >= 2 * __bits_per_word ? static_cast<__storage_type>(__v >> __bits_per_word)
+    			: static_cast<__storage_type>((__v >> __bits_per_word) & (__storage_type(1) << (_Size - __bits_per_word)) - 1)}
 #else
 #error This constructor has not been ported to this platform
 #endif
 #endif
 {
-#ifdef _LIBCPP_HAS_NO_CONSTEXPR
+#ifdef _LIBCPP_CXX03_LANG
     __init(__v, integral_constant<bool, sizeof(unsigned long long) == sizeof(__storage_type)>());
 #endif
 }
@@ -326,11 +335,8 @@ __bitset<_N_words, _Size>::to_ulong(false_type) const
     const_iterator __e = __make_iter(_Size);
     const_iterator __i = _VSTD::find(__make_iter(sizeof(unsigned long) * CHAR_BIT), __e, true);
     if (__i != __e)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw overflow_error("bitset to_ulong overflow error");
-#else
-        assert(!"bitset to_ulong overflow error");
-#endif
+        __throw_overflow_error("bitset to_ulong overflow error");
+
     return __first_[0];
 }
 
@@ -349,11 +355,8 @@ __bitset<_N_words, _Size>::to_ullong(false_type) const
     const_iterator __e = __make_iter(_Size);
     const_iterator __i = _VSTD::find(__make_iter(sizeof(unsigned long long) * CHAR_BIT), __e, true);
     if (__i != __e)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw overflow_error("bitset to_ullong overflow error");
-#else
-        assert(!"bitset to_ullong overflow error");
-#endif
+        __throw_overflow_error("bitset to_ullong overflow error");
+
     return to_ullong(true_type());
 }
 
@@ -510,7 +513,10 @@ template <size_t _Size>
 inline
 _LIBCPP_CONSTEXPR
 __bitset<1, _Size>::__bitset(unsigned long long __v) _NOEXCEPT
-    : __first_(static_cast<__storage_type>(__v))
+    : __first_(
+        _Size == __bits_per_word ? static_cast<__storage_type>(__v)
+                                 : static_cast<__storage_type>(__v) & ((__storage_type(1) << _Size) - 1)
+    )
 {
 }
 
@@ -655,11 +661,11 @@ __bitset<0, 0>::__bitset(unsigned long long) _NOEXCEPT
 {
 }
 
-template <size_t _Size> class _LIBCPP_TYPE_VIS_ONLY bitset;
+template <size_t _Size> class _LIBCPP_TEMPLATE_VIS bitset;
 template <size_t _Size> struct hash<bitset<_Size> >;
 
 template <size_t _Size>
-class _LIBCPP_TYPE_VIS_ONLY bitset
+class _LIBCPP_TEMPLATE_VIS bitset
     : private __bitset<_Size == 0 ? 0 : (_Size - 1) / (sizeof(size_t) * CHAR_BIT) + 1, _Size>
 {
 public:
@@ -763,11 +769,8 @@ bitset<_Size>::bitset(const _CharT* __str,
     size_t __rlen = _VSTD::min(__n, char_traits<_CharT>::length(__str));
     for (size_t __i = 0; __i < __rlen; ++__i)
         if (__str[__i] != __zero && __str[__i] != __one)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-            throw invalid_argument("bitset string ctor has invalid argument");
-#else
-            assert(!"bitset string ctor has invalid argument");
-#endif
+            __throw_invalid_argument("bitset string ctor has invalid argument");
+
     size_t _Mp = _VSTD::min(__rlen, _Size);
     size_t __i = 0;
     for (; __i < _Mp; ++__i)
@@ -789,19 +792,13 @@ bitset<_Size>::bitset(const basic_string<_CharT,_Traits,_Allocator>& __str,
        _CharT __zero, _CharT __one)
 {
     if (__pos > __str.size())
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw out_of_range("bitset string pos out of range");
-#else
-        assert(!"bitset string pos out of range");
-#endif
+        __throw_out_of_range("bitset string pos out of range");
+
     size_t __rlen = _VSTD::min(__n, __str.size() - __pos);
     for (size_t __i = __pos; __i < __pos + __rlen; ++__i)
         if (!_Traits::eq(__str[__i], __zero) && !_Traits::eq(__str[__i], __one))
-#ifndef _LIBCPP_NO_EXCEPTIONS
-            throw invalid_argument("bitset string ctor has invalid argument");
-#else
-            assert(!"bitset string ctor has invalid argument");
-#endif
+            __throw_invalid_argument("bitset string ctor has invalid argument");
+
     size_t _Mp = _VSTD::min(__rlen, _Size);
     size_t __i = 0;
     for (; __i < _Mp; ++__i)
@@ -876,11 +873,8 @@ bitset<_Size>&
 bitset<_Size>::set(size_t __pos, bool __val)
 {
     if (__pos >= _Size)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw out_of_range("bitset set argument out of range");
-#else
-        assert(!"bitset set argument out of range");
-#endif
+        __throw_out_of_range("bitset set argument out of range");
+
     (*this)[__pos] = __val;
     return *this;
 }
@@ -899,11 +893,8 @@ bitset<_Size>&
 bitset<_Size>::reset(size_t __pos)
 {
     if (__pos >= _Size)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw out_of_range("bitset reset argument out of range");
-#else
-        assert(!"bitset reset argument out of range");
-#endif
+        __throw_out_of_range("bitset reset argument out of range");
+
     (*this)[__pos] = false;
     return *this;
 }
@@ -932,11 +923,8 @@ bitset<_Size>&
 bitset<_Size>::flip(size_t __pos)
 {
     if (__pos >= _Size)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw out_of_range("bitset flip argument out of range");
-#else
-        assert(!"bitset flip argument out of range");
-#endif
+        __throw_out_of_range("bitset flip argument out of range");
+
     reference r = base::__make_ref(__pos);
     r = ~r;
     return *this;
@@ -1027,11 +1015,8 @@ bool
 bitset<_Size>::test(size_t __pos) const
 {
     if (__pos >= _Size)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw out_of_range("bitset test argument out of range");
-#else
-        assert(!"bitset test argument out of range");
-#endif
+        __throw_out_of_range("bitset test argument out of range");
+
     return (*this)[__pos];
 }
 
@@ -1102,7 +1087,7 @@ operator^(const bitset<_Size>& __x, const bitset<_Size>& __y) _NOEXCEPT
 }
 
 template <size_t _Size>
-struct _LIBCPP_TYPE_VIS_ONLY hash<bitset<_Size> >
+struct _LIBCPP_TEMPLATE_VIS hash<bitset<_Size> >
     : public unary_function<bitset<_Size>, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -1120,4 +1105,6 @@ operator<<(basic_ostream<_CharT, _Traits>& __os, const bitset<_Size>& __x);
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_BITSET
diff --git a/lib/libcxx/include/chrono b/lib/libcxx/include/chrono
index 68484e98243..809f773b6c6 100644
--- a/lib/libcxx/include/chrono
+++ b/lib/libcxx/include/chrono
@@ -26,7 +26,7 @@ duration_cast(const duration<Rep, Period>& fd);
 
 template <class Rep> struct treat_as_floating_point : is_floating_point<Rep> {};
 
-template <class Rep> constexpr bool treat_as_floating_point_v
+template <class Rep> inline constexpr bool treat_as_floating_point_v
     = treat_as_floating_point<Rep>::value;                       // C++17
 
 template <class Rep>
@@ -48,7 +48,7 @@ class duration
     static_assert(Period::num > 0, "duration period must be positive");
 public:
     typedef Rep rep;
-    typedef Period period;
+    typedef typename _Period::type period;
 
     constexpr duration() = default;
     template <class Rep2>
@@ -75,15 +75,15 @@ public:
 
     // arithmetic
 
-    constexpr duration  operator+() const;
-    constexpr duration  operator-() const;
-    duration& operator++();
-    duration  operator++(int);
-    duration& operator--();
-    duration  operator--(int);
+    constexpr common_type<duration>::type  operator+() const;
+    constexpr common_type<duration>::type  operator-() const;
+    constexpr duration& operator++();
+    constexpr duration  operator++(int);
+    constexpr duration& operator--();
+    constexpr duration  operator--(int);
 
-    duration& operator+=(const duration& d);
-    duration& operator-=(const duration& d);
+    constexpr duration& operator+=(const duration& d);
+    constexpr duration& operator-=(const duration& d);
 
     duration& operator*=(const rep& rhs);
     duration& operator/=(const rep& rhs);
@@ -283,18 +283,18 @@ typedef steady_clock high_resolution_clock;
 
 }  // chrono
 
-constexpr chrono::hours                                 operator "" h(unsigned long long); // C++14
-constexpr chrono::duration<unspecified , ratio<3600,1>> operator "" h(long double); // C++14
-constexpr chrono::minutes                               operator "" min(unsigned long long); // C++14
-constexpr chrono::duration<unspecified , ratio<60,1>>   operator "" min(long double); // C++14
-constexpr chrono::seconds                               operator "" s(unsigned long long); // C++14
-constexpr chrono::duration<unspecified >                operator "" s(long double); // C++14
-constexpr chrono::milliseconds                          operator "" ms(unsigned long long); // C++14
-constexpr chrono::duration<unspecified , milli>         operator "" ms(long double); // C++14
-constexpr chrono::microseconds                          operator "" us(unsigned long long); // C++14
-constexpr chrono::duration<unspecified , micro>         operator "" us(long double); // C++14
-constexpr chrono::nanoseconds                           operator "" ns(unsigned long long); // C++14
-constexpr chrono::duration<unspecified , nano>          operator "" ns(long double); // C++14
+constexpr chrono::hours                                 operator ""h(unsigned long long); // C++14
+constexpr chrono::duration<unspecified , ratio<3600,1>> operator ""h(long double); // C++14
+constexpr chrono::minutes                               operator ""min(unsigned long long); // C++14
+constexpr chrono::duration<unspecified , ratio<60,1>>   operator ""min(long double); // C++14
+constexpr chrono::seconds                               operator ""s(unsigned long long); // C++14
+constexpr chrono::duration<unspecified >                operator ""s(long double); // C++14
+constexpr chrono::milliseconds                          operator ""ms(unsigned long long); // C++14
+constexpr chrono::duration<unspecified , milli>         operator ""ms(long double); // C++14
+constexpr chrono::microseconds                          operator ""us(unsigned long long); // C++14
+constexpr chrono::duration<unspecified , micro>         operator ""us(long double); // C++14
+constexpr chrono::nanoseconds                           operator ""ns(unsigned long long); // C++14
+constexpr chrono::duration<unspecified , nano>          operator ""ns(long double); // C++14
 
 }  // std
 */
@@ -305,18 +305,20 @@ constexpr chrono::duration<unspecified , nano>          operator "" ns(long doub
 #include <ratio>
 #include <limits>
 
-#include <__undef_min_max>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace chrono
 {
 
-template <class _Rep, class _Period = ratio<1> > class _LIBCPP_TYPE_VIS_ONLY duration;
+template <class _Rep, class _Period = ratio<1> > class _LIBCPP_TEMPLATE_VIS duration;
 
 template <class _Tp>
 struct __is_duration : false_type {};
@@ -336,7 +338,7 @@ struct __is_duration<const volatile duration<_Rep, _Period> > : true_type  {};
 } // chrono
 
 template <class _Rep1, class _Period1, class _Rep2, class _Period2>
-struct _LIBCPP_TYPE_VIS_ONLY common_type<chrono::duration<_Rep1, _Period1>,
+struct _LIBCPP_TEMPLATE_VIS common_type<chrono::duration<_Rep1, _Period1>,
                                          chrono::duration<_Rep2, _Period2> >
 {
     typedef chrono::duration<typename common_type<_Rep1, _Rep2>::type,
@@ -414,15 +416,16 @@ duration_cast(const duration<_Rep, _Period>& __fd)
 }
 
 template <class _Rep>
-struct _LIBCPP_TYPE_VIS_ONLY treat_as_floating_point : is_floating_point<_Rep> {};
+struct _LIBCPP_TEMPLATE_VIS treat_as_floating_point : is_floating_point<_Rep> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Rep> _LIBCPP_CONSTEXPR bool treat_as_floating_point_v
+template <class _Rep>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool treat_as_floating_point_v
     = treat_as_floating_point<_Rep>::value;
 #endif
 
 template <class _Rep>
-struct _LIBCPP_TYPE_VIS_ONLY duration_values
+struct _LIBCPP_TEMPLATE_VIS duration_values
 {
 public:
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR _Rep zero() {return _Rep(0);}
@@ -485,7 +488,7 @@ round(const duration<_Rep, _Period>& __d)
 // duration
 
 template <class _Rep, class _Period>
-class _LIBCPP_TYPE_VIS_ONLY duration
+class _LIBCPP_TEMPLATE_VIS duration
 {
     static_assert(!__is_duration<_Rep>::value, "A duration representation can not be a duration");
     static_assert(__is_ratio<_Period>::value, "Second template parameter of duration must be a std::ratio");
@@ -523,13 +526,13 @@ class _LIBCPP_TYPE_VIS_ONLY duration
     
 public:
     typedef _Rep rep;
-    typedef _Period period;
+    typedef typename _Period::type period;
 private:
     rep __rep_;
 public:
 
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-#ifndef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
+#ifndef _LIBCPP_CXX03_LANG
         duration() = default;
 #else
         duration() {}
@@ -565,20 +568,20 @@ public:
 
     // arithmetic
 
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR duration  operator+() const {return *this;}
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR duration  operator-() const {return duration(-__rep_);}
-    _LIBCPP_INLINE_VISIBILITY duration& operator++()      {++__rep_; return *this;}
-    _LIBCPP_INLINE_VISIBILITY duration  operator++(int)   {return duration(__rep_++);}
-    _LIBCPP_INLINE_VISIBILITY duration& operator--()      {--__rep_; return *this;}
-    _LIBCPP_INLINE_VISIBILITY duration  operator--(int)   {return duration(__rep_--);}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR typename common_type<duration>::type operator+() const {return typename common_type<duration>::type(*this);}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR typename common_type<duration>::type operator-() const {return typename common_type<duration>::type(-__rep_);}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator++()      {++__rep_; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration  operator++(int)   {return duration(__rep_++);}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator--()      {--__rep_; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration  operator--(int)   {return duration(__rep_--);}
 
-    _LIBCPP_INLINE_VISIBILITY duration& operator+=(const duration& __d) {__rep_ += __d.count(); return *this;}
-    _LIBCPP_INLINE_VISIBILITY duration& operator-=(const duration& __d) {__rep_ -= __d.count(); return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator+=(const duration& __d) {__rep_ += __d.count(); return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator-=(const duration& __d) {__rep_ -= __d.count(); return *this;}
 
-    _LIBCPP_INLINE_VISIBILITY duration& operator*=(const rep& rhs) {__rep_ *= rhs; return *this;}
-    _LIBCPP_INLINE_VISIBILITY duration& operator/=(const rep& rhs) {__rep_ /= rhs; return *this;}
-    _LIBCPP_INLINE_VISIBILITY duration& operator%=(const rep& rhs) {__rep_ %= rhs; return *this;}
-    _LIBCPP_INLINE_VISIBILITY duration& operator%=(const duration& rhs) {__rep_ %= rhs.count(); return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator*=(const rep& rhs) {__rep_ *= rhs; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator/=(const rep& rhs) {__rep_ /= rhs; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator%=(const rep& rhs) {__rep_ %= rhs; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 duration& operator%=(const duration& rhs) {__rep_ %= rhs.count(); return *this;}
 
     // special values
 
@@ -828,7 +831,7 @@ operator%(const duration<_Rep1, _Period1>& __lhs, const duration<_Rep2, _Period2
 //////////////////////////////////////////////////////////
 
 template <class _Clock, class _Duration = typename _Clock::duration>
-class _LIBCPP_TYPE_VIS_ONLY time_point
+class _LIBCPP_TEMPLATE_VIS time_point
 {
     static_assert(__is_duration<_Duration>::value,
                   "Second template parameter of time_point must be a std::chrono::duration");
@@ -872,7 +875,7 @@ public:
 } // chrono
 
 template <class _Clock, class _Duration1, class _Duration2>
-struct _LIBCPP_TYPE_VIS_ONLY common_type<chrono::time_point<_Clock, _Duration1>,
+struct _LIBCPP_TEMPLATE_VIS common_type<chrono::time_point<_Clock, _Duration1>,
                                          chrono::time_point<_Clock, _Duration2> >
 {
     typedef chrono::time_point<_Clock, typename common_type<_Duration1, _Duration2>::type> type;
@@ -1026,7 +1029,8 @@ inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 time_point<_Clock, typename common_type<_Duration1, duration<_Rep2, _Period2> >::type>
 operator-(const time_point<_Clock, _Duration1>& __lhs, const duration<_Rep2, _Period2>& __rhs)
 {
-    return __lhs + (-__rhs);
+    typedef time_point<_Clock, typename common_type<_Duration1, duration<_Rep2, _Period2> >::type> _Ret;
+    return _Ret(__lhs.time_since_epoch() -__rhs);
 }
 
 // duration operator-(time_point x, time_point y);
@@ -1084,67 +1088,67 @@ inline namespace literals
   inline namespace chrono_literals
   {
 
-    constexpr chrono::hours operator"" h(unsigned long long __h)
+    constexpr chrono::hours operator""h(unsigned long long __h)
     {
         return chrono::hours(static_cast<chrono::hours::rep>(__h));
     }
 
-    constexpr chrono::duration<long double, ratio<3600,1>> operator"" h(long double __h)
+    constexpr chrono::duration<long double, ratio<3600,1>> operator""h(long double __h)
     {
         return chrono::duration<long double, ratio<3600,1>>(__h);
     }
 
 
-    constexpr chrono::minutes operator"" min(unsigned long long __m)
+    constexpr chrono::minutes operator""min(unsigned long long __m)
     {
         return chrono::minutes(static_cast<chrono::minutes::rep>(__m));
     }
 
-    constexpr chrono::duration<long double, ratio<60,1>> operator"" min(long double __m)
+    constexpr chrono::duration<long double, ratio<60,1>> operator""min(long double __m)
     {
         return chrono::duration<long double, ratio<60,1>> (__m);
     }
 
 
-    constexpr chrono::seconds operator"" s(unsigned long long __s)
+    constexpr chrono::seconds operator""s(unsigned long long __s)
     {
         return chrono::seconds(static_cast<chrono::seconds::rep>(__s));
     }
 
-    constexpr chrono::duration<long double> operator"" s(long double __s)
+    constexpr chrono::duration<long double> operator""s(long double __s)
     {
         return chrono::duration<long double> (__s);
     }
 
 
-    constexpr chrono::milliseconds operator"" ms(unsigned long long __ms)
+    constexpr chrono::milliseconds operator""ms(unsigned long long __ms)
     {
         return chrono::milliseconds(static_cast<chrono::milliseconds::rep>(__ms));
     }
 
-    constexpr chrono::duration<long double, milli> operator"" ms(long double __ms)
+    constexpr chrono::duration<long double, milli> operator""ms(long double __ms)
     {
         return chrono::duration<long double, milli>(__ms);
     }
 
 
-    constexpr chrono::microseconds operator"" us(unsigned long long __us)
+    constexpr chrono::microseconds operator""us(unsigned long long __us)
     {
         return chrono::microseconds(static_cast<chrono::microseconds::rep>(__us));
     }
 
-    constexpr chrono::duration<long double, micro> operator"" us(long double __us)
+    constexpr chrono::duration<long double, micro> operator""us(long double __us)
     {
         return chrono::duration<long double, micro> (__us);
     }
     
 
-    constexpr chrono::nanoseconds operator"" ns(unsigned long long __ns)
+    constexpr chrono::nanoseconds operator""ns(unsigned long long __ns)
     {
         return chrono::nanoseconds(static_cast<chrono::nanoseconds::rep>(__ns));
     }
 
-    constexpr chrono::duration<long double, nano> operator"" ns(long double __ns)
+    constexpr chrono::duration<long double, nano> operator""ns(long double __ns)
     {
         return chrono::duration<long double, nano> (__ns);
     }
@@ -1159,4 +1163,6 @@ namespace chrono { // hoist the literals into namespace std::chrono
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_CHRONO
diff --git a/lib/libcxx/include/cmath b/lib/libcxx/include/cmath
index b3e959405e9..917928a1f42 100644
--- a/lib/libcxx/include/cmath
+++ b/lib/libcxx/include/cmath
@@ -331,7 +331,6 @@ using ::double_t;
 using ::abs;
 #endif
 
-#ifndef __sun__
 using ::acos;
 using ::acosf;
 using ::asin;
@@ -346,58 +345,47 @@ using ::cos;
 using ::cosf;
 using ::cosh;
 using ::coshf;
-#endif // __sun__
 
 using ::exp;
 using ::expf;
 
-#ifndef __sun__
 using ::fabs;
 using ::fabsf;
 using ::floor;
 using ::floorf;
-#endif //__sun__
 
 using ::fmod;
 using ::fmodf;
 
-#ifndef __sun__
 using ::frexp;
 using ::frexpf;
 using ::ldexp;
 using ::ldexpf;
-#endif // __sun__
 
 using ::log;
 using ::logf;
 
-#ifndef __sun__
 using ::log10;
 using ::log10f;
 using ::modf;
 using ::modff;
-#endif // __sun__ 
 
 using ::pow;
 using ::powf;
 
-#ifndef __sun__
 using ::sin;
 using ::sinf;
 using ::sinh;
 using ::sinhf;
-#endif // __sun__
 
 using ::sqrt;
 using ::sqrtf;
 using ::tan;
 using ::tanf;
 
-#ifndef __sun__
 using ::tanh;
 using ::tanhf;
 
-#ifndef _LIBCPP_MSVCRT
 using ::acosh;
 using ::acoshf;
 using ::asinh;
@@ -406,12 +394,10 @@ using ::atanh;
 using ::atanhf;
 using ::cbrt;
 using ::cbrtf;
-#endif
 
 using ::copysign;
 using ::copysignf;
 
-#ifndef _LIBCPP_MSVCRT
 using ::erf;
 using ::erff;
 using ::erfc;
@@ -448,16 +434,10 @@ using ::lrint;
 using ::lrintf;
 using ::lround;
 using ::lroundf;
-#endif // _LIBCPP_MSVCRT
-#endif // __sun__
 
-#ifndef _LIBCPP_MSVCRT
 using ::nan;
 using ::nanf;
-#endif // _LIBCPP_MSVCRT
 
-#ifndef __sun__
-#ifndef _LIBCPP_MSVCRT
 using ::nearbyint;
 using ::nearbyintf;
 using ::nextafter;
@@ -480,7 +460,6 @@ using ::tgamma;
 using ::tgammaf;
 using ::trunc;
 using ::truncf;
-#endif // !_LIBCPP_MSVCRT
 
 using ::acosl;
 using ::asinl;
@@ -504,17 +483,14 @@ using ::sinhl;
 using ::sqrtl;
 using ::tanl;
 
-#ifndef _LIBCPP_MSVCRT
 using ::tanhl;
 using ::acoshl;
 using ::asinhl;
 using ::atanhl;
 using ::cbrtl;
-#endif  // !_LIBCPP_MSVCRT
 
 using ::copysignl;
 
-#ifndef _LIBCPP_MSVCRT
 using ::erfl;
 using ::erfcl;
 using ::exp2l;
@@ -545,12 +521,6 @@ using ::scalblnl;
 using ::scalbnl;
 using ::tgammal;
 using ::truncl;
-#endif // !_LIBCPP_MSVCRT
-
-#else 
-using ::lgamma;
-using ::lgammaf;
-#endif // __sun__
 
 #if _LIBCPP_STD_VER > 14
 inline _LIBCPP_INLINE_VISIBILITY float       hypot(       float x,       float y,       float z ) { return sqrt(x*x + y*y + z*z); }
@@ -559,23 +529,83 @@ inline _LIBCPP_INLINE_VISIBILITY long double hypot( long double x, long double y
 
 template <class _A1, class _A2, class _A3>
 inline _LIBCPP_INLINE_VISIBILITY
-typename std::__lazy_enable_if
+typename __lazy_enable_if
 <
-    std::is_arithmetic<_A1>::value &&
-    std::is_arithmetic<_A2>::value &&
-    std::is_arithmetic<_A3>::value,
-    std::__promote<_A1, _A2, _A3>
+    is_arithmetic<_A1>::value &&
+    is_arithmetic<_A2>::value &&
+    is_arithmetic<_A3>::value,
+    __promote<_A1, _A2, _A3>
 >::type
 hypot(_A1 __lcpp_x, _A2 __lcpp_y, _A3 __lcpp_z) _NOEXCEPT
 {
-    typedef typename std::__promote<_A1, _A2, _A3>::type __result_type;
-    static_assert((!(std::is_same<_A1, __result_type>::value &&
-                     std::is_same<_A2, __result_type>::value &&
-                     std::is_same<_A3, __result_type>::value)), "");
+    typedef typename __promote<_A1, _A2, _A3>::type __result_type;
+    static_assert((!(is_same<_A1, __result_type>::value &&
+                     is_same<_A2, __result_type>::value &&
+                     is_same<_A3, __result_type>::value)), "");
     return hypot((__result_type)__lcpp_x, (__result_type)__lcpp_y, (__result_type)__lcpp_z);
 }
 #endif
 
+template <class _A1>
+_LIBCPP_ALWAYS_INLINE
+_LIBCPP_CONSTEXPR typename enable_if<is_floating_point<_A1>::value, bool>::type
+__libcpp_isnan_or_builtin(_A1 __lcpp_x) _NOEXCEPT
+{
+#if __has_builtin(__builtin_isnan)
+    return __builtin_isnan(__lcpp_x);
+#else
+    return isnan(__lcpp_x);
+#endif
+}
+
+template <class _A1>
+_LIBCPP_ALWAYS_INLINE
+_LIBCPP_CONSTEXPR typename enable_if<!is_floating_point<_A1>::value, bool>::type
+__libcpp_isnan_or_builtin(_A1 __lcpp_x) _NOEXCEPT
+{
+    return isnan(__lcpp_x);
+}
+
+template <class _A1>
+_LIBCPP_ALWAYS_INLINE
+_LIBCPP_CONSTEXPR typename enable_if<is_floating_point<_A1>::value, bool>::type
+__libcpp_isinf_or_builtin(_A1 __lcpp_x) _NOEXCEPT
+{
+#if __has_builtin(__builtin_isinf)
+    return __builtin_isinf(__lcpp_x);
+#else
+    return isinf(__lcpp_x);
+#endif
+}
+
+template <class _A1>
+_LIBCPP_ALWAYS_INLINE
+_LIBCPP_CONSTEXPR typename enable_if<!is_floating_point<_A1>::value, bool>::type
+__libcpp_isinf_or_builtin(_A1 __lcpp_x) _NOEXCEPT
+{
+    return isinf(__lcpp_x);
+}
+
+template <class _A1>
+_LIBCPP_ALWAYS_INLINE
+_LIBCPP_CONSTEXPR typename enable_if<is_floating_point<_A1>::value, bool>::type
+__libcpp_isfinite_or_builtin(_A1 __lcpp_x) _NOEXCEPT
+{
+#if __has_builtin(__builtin_isfinite)
+    return __builtin_isfinite(__lcpp_x);
+#else
+    return isfinite(__lcpp_x);
+#endif
+}
+
+template <class _A1>
+_LIBCPP_ALWAYS_INLINE
+_LIBCPP_CONSTEXPR typename enable_if<!is_floating_point<_A1>::value, bool>::type
+__libcpp_isfinite_or_builtin(_A1 __lcpp_x) _NOEXCEPT
+{
+    return isfinite(__lcpp_x);
+}
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_CMATH
diff --git a/lib/libcxx/include/codecvt b/lib/libcxx/include/codecvt
index 6eff107cd1c..46f56acff71 100644
--- a/lib/libcxx/include/codecvt
+++ b/lib/libcxx/include/codecvt
@@ -182,7 +182,7 @@ protected:
 
 template <class _Elem, unsigned long _Maxcode = 0x10ffff,
           codecvt_mode _Mode = (codecvt_mode)0>
-class _LIBCPP_TYPE_VIS_ONLY codecvt_utf8
+class _LIBCPP_TEMPLATE_VIS codecvt_utf8
     : public __codecvt_utf8<_Elem>
 {
 public:
@@ -410,7 +410,7 @@ protected:
 
 template <class _Elem, unsigned long _Maxcode = 0x10ffff,
           codecvt_mode _Mode = (codecvt_mode)0>
-class _LIBCPP_TYPE_VIS_ONLY codecvt_utf16
+class _LIBCPP_TEMPLATE_VIS codecvt_utf16
     : public __codecvt_utf16<_Elem, _Mode & little_endian>
 {
 public:
@@ -533,7 +533,7 @@ protected:
 
 template <class _Elem, unsigned long _Maxcode = 0x10ffff,
           codecvt_mode _Mode = (codecvt_mode)0>
-class _LIBCPP_TYPE_VIS_ONLY codecvt_utf8_utf16
+class _LIBCPP_TEMPLATE_VIS codecvt_utf8_utf16
     : public __codecvt_utf8_utf16<_Elem>
 {
 public:
diff --git a/lib/libcxx/include/complex b/lib/libcxx/include/complex
index f56138fa2d1..41a47cfba47 100644
--- a/lib/libcxx/include/complex
+++ b/lib/libcxx/include/complex
@@ -245,9 +245,6 @@ template<class T, class charT, class traits>
 #include <stdexcept>
 #include <cmath>
 #include <sstream>
-#if defined(_LIBCPP_NO_EXCEPTIONS)
-    #include <cassert>
-#endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
@@ -255,13 +252,13 @@ template<class T, class charT, class traits>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template<class _Tp> class _LIBCPP_TYPE_VIS_ONLY complex;
+template<class _Tp> class _LIBCPP_TEMPLATE_VIS complex;
 
 template<class _Tp> complex<_Tp> operator*(const complex<_Tp>& __z, const complex<_Tp>& __w);
 template<class _Tp> complex<_Tp> operator/(const complex<_Tp>& __x, const complex<_Tp>& __y);
 
 template<class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY complex
+class _LIBCPP_TEMPLATE_VIS complex
 {
 public:
     typedef _Tp value_type;
@@ -319,11 +316,11 @@ public:
         }
 };
 
-template<> class _LIBCPP_TYPE_VIS_ONLY complex<double>;
-template<> class _LIBCPP_TYPE_VIS_ONLY complex<long double>;
+template<> class _LIBCPP_TEMPLATE_VIS complex<double>;
+template<> class _LIBCPP_TEMPLATE_VIS complex<long double>;
 
 template<>
-class _LIBCPP_TYPE_VIS_ONLY complex<float>
+class _LIBCPP_TEMPLATE_VIS complex<float>
 {
     float __re_;
     float __im_;
@@ -381,7 +378,7 @@ public:
 };
 
 template<>
-class _LIBCPP_TYPE_VIS_ONLY complex<double>
+class _LIBCPP_TEMPLATE_VIS complex<double>
 {
     double __re_;
     double __im_;
@@ -439,7 +436,7 @@ public:
 };
 
 template<>
-class _LIBCPP_TYPE_VIS_ONLY complex<long double>
+class _LIBCPP_TEMPLATE_VIS complex<long double>
 {
     long double __re_;
     long double __im_;
@@ -602,39 +599,39 @@ operator*(const complex<_Tp>& __z, const complex<_Tp>& __w)
     _Tp __bc = __b * __c;
     _Tp __x = __ac - __bd;
     _Tp __y = __ad + __bc;
-    if (isnan(__x) && isnan(__y))
+    if (__libcpp_isnan_or_builtin(__x) && __libcpp_isnan_or_builtin(__y))
     {
         bool __recalc = false;
-        if (isinf(__a) || isinf(__b))
+        if (__libcpp_isinf_or_builtin(__a) || __libcpp_isinf_or_builtin(__b))
         {
-            __a = copysign(isinf(__a) ? _Tp(1) : _Tp(0), __a);
-            __b = copysign(isinf(__b) ? _Tp(1) : _Tp(0), __b);
-            if (isnan(__c))
+            __a = copysign(__libcpp_isinf_or_builtin(__a) ? _Tp(1) : _Tp(0), __a);
+            __b = copysign(__libcpp_isinf_or_builtin(__b) ? _Tp(1) : _Tp(0), __b);
+            if (__libcpp_isnan_or_builtin(__c))
                 __c = copysign(_Tp(0), __c);
-            if (isnan(__d))
+            if (__libcpp_isnan_or_builtin(__d))
                 __d = copysign(_Tp(0), __d);
             __recalc = true;
         }
-        if (isinf(__c) || isinf(__d))
+        if (__libcpp_isinf_or_builtin(__c) || __libcpp_isinf_or_builtin(__d))
         {
-            __c = copysign(isinf(__c) ? _Tp(1) : _Tp(0), __c);
-            __d = copysign(isinf(__d) ? _Tp(1) : _Tp(0), __d);
-            if (isnan(__a))
+            __c = copysign(__libcpp_isinf_or_builtin(__c) ? _Tp(1) : _Tp(0), __c);
+            __d = copysign(__libcpp_isinf_or_builtin(__d) ? _Tp(1) : _Tp(0), __d);
+            if (__libcpp_isnan_or_builtin(__a))
                 __a = copysign(_Tp(0), __a);
-            if (isnan(__b))
+            if (__libcpp_isnan_or_builtin(__b))
                 __b = copysign(_Tp(0), __b);
             __recalc = true;
         }
-        if (!__recalc && (isinf(__ac) || isinf(__bd) ||
-                          isinf(__ad) || isinf(__bc)))
+        if (!__recalc && (__libcpp_isinf_or_builtin(__ac) || __libcpp_isinf_or_builtin(__bd) ||
+                          __libcpp_isinf_or_builtin(__ad) || __libcpp_isinf_or_builtin(__bc)))
         {
-            if (isnan(__a))
+            if (__libcpp_isnan_or_builtin(__a))
                 __a = copysign(_Tp(0), __a);
-            if (isnan(__b))
+            if (__libcpp_isnan_or_builtin(__b))
                 __b = copysign(_Tp(0), __b);
-            if (isnan(__c))
+            if (__libcpp_isnan_or_builtin(__c))
                 __c = copysign(_Tp(0), __c);
-            if (isnan(__d))
+            if (__libcpp_isnan_or_builtin(__d))
                 __d = copysign(_Tp(0), __d);
             __recalc = true;
         }
@@ -677,7 +674,7 @@ operator/(const complex<_Tp>& __z, const complex<_Tp>& __w)
     _Tp __c = __w.real();
     _Tp __d = __w.imag();
     _Tp __logbw = logb(fmax(fabs(__c), fabs(__d)));
-    if (isfinite(__logbw))
+    if (__libcpp_isfinite_or_builtin(__logbw))
     {
         __ilogbw = static_cast<int>(__logbw);
         __c = scalbn(__c, -__ilogbw);
@@ -686,24 +683,24 @@ operator/(const complex<_Tp>& __z, const complex<_Tp>& __w)
     _Tp __denom = __c * __c + __d * __d;
     _Tp __x = scalbn((__a * __c + __b * __d) / __denom, -__ilogbw);
     _Tp __y = scalbn((__b * __c - __a * __d) / __denom, -__ilogbw);
-    if (isnan(__x) && isnan(__y))
+    if (__libcpp_isnan_or_builtin(__x) && __libcpp_isnan_or_builtin(__y))
     {
-        if ((__denom == _Tp(0)) && (!isnan(__a) || !isnan(__b)))
+        if ((__denom == _Tp(0)) && (!__libcpp_isnan_or_builtin(__a) || !__libcpp_isnan_or_builtin(__b)))
         {
             __x = copysign(_Tp(INFINITY), __c) * __a;
             __y = copysign(_Tp(INFINITY), __c) * __b;
         }
-        else if ((isinf(__a) || isinf(__b)) && isfinite(__c) && isfinite(__d))
+        else if ((__libcpp_isinf_or_builtin(__a) || __libcpp_isinf_or_builtin(__b)) && __libcpp_isfinite_or_builtin(__c) && __libcpp_isfinite_or_builtin(__d))
         {
-            __a = copysign(isinf(__a) ? _Tp(1) : _Tp(0), __a);
-            __b = copysign(isinf(__b) ? _Tp(1) : _Tp(0), __b);
+            __a = copysign(__libcpp_isinf_or_builtin(__a) ? _Tp(1) : _Tp(0), __a);
+            __b = copysign(__libcpp_isinf_or_builtin(__b) ? _Tp(1) : _Tp(0), __b);
             __x = _Tp(INFINITY) * (__a * __c + __b * __d);
             __y = _Tp(INFINITY) * (__b * __c - __a * __d);
         }
-        else if (isinf(__logbw) && __logbw > _Tp(0) && isfinite(__a) && isfinite(__b))
+        else if (__libcpp_isinf_or_builtin(__logbw) && __logbw > _Tp(0) && __libcpp_isfinite_or_builtin(__a) && __libcpp_isfinite_or_builtin(__b))
         {
-            __c = copysign(isinf(__c) ? _Tp(1) : _Tp(0), __c);
-            __d = copysign(isinf(__d) ? _Tp(1) : _Tp(0), __d);
+            __c = copysign(__libcpp_isinf_or_builtin(__c) ? _Tp(1) : _Tp(0), __c);
+            __d = copysign(__libcpp_isinf_or_builtin(__d) ? _Tp(1) : _Tp(0), __d);
             __x = _Tp(0) * (__a * __c + __b * __d);
             __y = _Tp(0) * (__b * __c - __a * __d);
         }
@@ -795,45 +792,41 @@ operator!=(const _Tp& __x, const complex<_Tp>& __y)
 
 // 26.3.7 values:
 
-// real
+template <class _Tp, bool = is_integral<_Tp>::value,
+                     bool = is_floating_point<_Tp>::value
+                     >
+struct __libcpp_complex_overload_traits {};
 
-template<class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-_Tp
-real(const complex<_Tp>& __c)
+// Integral Types
+template <class _Tp>
+struct __libcpp_complex_overload_traits<_Tp, true, false>
 {
-    return __c.real();
-}
+    typedef double _ValueType;
+    typedef complex<double> _ComplexType;
+};
 
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-long double
-real(long double __re)
+// Floating point types
+template <class _Tp>
+struct __libcpp_complex_overload_traits<_Tp, false, true>
 {
-    return __re;
-}
+    typedef _Tp _ValueType;
+    typedef complex<_Tp> _ComplexType;
+};
 
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-double
-real(double __re)
-{
-    return __re;
-}
+// real
 
 template<class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-typename enable_if
-<
-    is_integral<_Tp>::value,
-    double
->::type
-real(_Tp  __re)
+_Tp
+real(const complex<_Tp>& __c)
 {
-    return __re;
+    return __c.real();
 }
 
+template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-float
-real(float  __re)
+typename __libcpp_complex_overload_traits<_Tp>::_ValueType
+real(_Tp __re)
 {
     return __re;
 }
@@ -848,35 +841,10 @@ imag(const complex<_Tp>& __c)
     return __c.imag();
 }
 
+template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-long double
-imag(long double __re)
-{
-    return 0;
-}
-
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-double
-imag(double __re)
-{
-    return 0;
-}
-
-template<class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-typename enable_if
-<
-    is_integral<_Tp>::value,
-    double
->::type
-imag(_Tp  __re)
-{
-    return 0;
-}
-
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-float
-imag(float  __re)
+typename __libcpp_complex_overload_traits<_Tp>::_ValueType
+imag(_Tp)
 {
     return 0;
 }
@@ -901,25 +869,22 @@ arg(const complex<_Tp>& __c)
     return atan2(__c.imag(), __c.real());
 }
 
+template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
-long double
-arg(long double __re)
+typename enable_if<
+    is_same<_Tp, long double>::value,
+    long double
+>::type
+arg(_Tp __re)
 {
     return atan2l(0.L, __re);
 }
 
-inline _LIBCPP_INLINE_VISIBILITY
-double
-arg(double __re)
-{
-    return atan2(0., __re);
-}
-
 template<class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
 <
-    is_integral<_Tp>::value,
+    is_integral<_Tp>::value || is_same<_Tp, double>::value,
     double
 >::type
 arg(_Tp __re)
@@ -927,9 +892,13 @@ arg(_Tp __re)
     return atan2(0., __re);
 }
 
+template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
-float
-arg(float __re)
+typename enable_if<
+    is_same<_Tp, float>::value,
+    float
+>::type
+arg(_Tp __re)
 {
     return atan2f(0.F, __re);
 }
@@ -941,44 +910,20 @@ inline _LIBCPP_INLINE_VISIBILITY
 _Tp
 norm(const complex<_Tp>& __c)
 {
-    if (isinf(__c.real()))
+    if (__libcpp_isinf_or_builtin(__c.real()))
         return abs(__c.real());
-    if (isinf(__c.imag()))
+    if (__libcpp_isinf_or_builtin(__c.imag()))
         return abs(__c.imag());
     return __c.real() * __c.real() + __c.imag() * __c.imag();
 }
 
+template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
-long double
-norm(long double __re)
-{
-    return __re * __re;
-}
-
-inline _LIBCPP_INLINE_VISIBILITY
-double
-norm(double __re)
-{
-    return __re * __re;
-}
-
-template<class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
-typename enable_if
-<
-    is_integral<_Tp>::value,
-    double
->::type
+typename __libcpp_complex_overload_traits<_Tp>::_ValueType
 norm(_Tp __re)
 {
-    return (double)__re * __re;
-}
-
-inline _LIBCPP_INLINE_VISIBILITY
-float
-norm(float __re)
-{
-    return __re * __re;
+    typedef typename __libcpp_complex_overload_traits<_Tp>::_ValueType _ValueType;
+    return static_cast<_ValueType>(__re) * __re;
 }
 
 // conj
@@ -991,38 +936,16 @@ conj(const complex<_Tp>& __c)
     return complex<_Tp>(__c.real(), -__c.imag());
 }
 
+template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
-complex<long double>
-conj(long double __re)
-{
-    return complex<long double>(__re);
-}
-
-inline _LIBCPP_INLINE_VISIBILITY
-complex<double>
-conj(double __re)
-{
-    return complex<double>(__re);
-}
-
-template<class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
-typename enable_if
-<
-    is_integral<_Tp>::value,
-    complex<double>
->::type
+typename __libcpp_complex_overload_traits<_Tp>::_ComplexType
 conj(_Tp __re)
 {
-    return complex<double>(__re);
+    typedef typename __libcpp_complex_overload_traits<_Tp>::_ComplexType _ComplexType;
+    return _ComplexType(__re);
 }
 
-inline _LIBCPP_INLINE_VISIBILITY
-complex<float>
-conj(float __re)
-{
-    return complex<float>(__re);
-}
+
 
 // proj
 
@@ -1032,48 +955,36 @@ complex<_Tp>
 proj(const complex<_Tp>& __c)
 {
     std::complex<_Tp> __r = __c;
-    if (isinf(__c.real()) || isinf(__c.imag()))
+    if (__libcpp_isinf_or_builtin(__c.real()) || __libcpp_isinf_or_builtin(__c.imag()))
         __r = complex<_Tp>(INFINITY, copysign(_Tp(0), __c.imag()));
     return __r;
 }
 
+template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
-complex<long double>
-proj(long double __re)
-{
-    if (isinf(__re))
-        __re = abs(__re);
-    return complex<long double>(__re);
-}
-
-inline _LIBCPP_INLINE_VISIBILITY
-complex<double>
-proj(double __re)
+typename enable_if
+<
+    is_floating_point<_Tp>::value,
+    typename __libcpp_complex_overload_traits<_Tp>::_ComplexType
+>::type
+proj(_Tp __re)
 {
-    if (isinf(__re))
+    if (__libcpp_isinf_or_builtin(__re))
         __re = abs(__re);
-    return complex<double>(__re);
+    return complex<_Tp>(__re);
 }
 
-template<class _Tp>
+template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
 <
     is_integral<_Tp>::value,
-    complex<double>
+    typename __libcpp_complex_overload_traits<_Tp>::_ComplexType
 >::type
 proj(_Tp __re)
 {
-    return complex<double>(__re);
-}
-
-inline _LIBCPP_INLINE_VISIBILITY
-complex<float>
-proj(float __re)
-{
-    if (isinf(__re))
-        __re = abs(__re);
-    return complex<float>(__re);
+    typedef typename __libcpp_complex_overload_traits<_Tp>::_ComplexType _ComplexType;
+    return _ComplexType(__re);
 }
 
 // polar
@@ -1082,25 +993,25 @@ template<class _Tp>
 complex<_Tp>
 polar(const _Tp& __rho, const _Tp& __theta = _Tp(0))
 {
-    if (isnan(__rho) || signbit(__rho))
+    if (__libcpp_isnan_or_builtin(__rho) || signbit(__rho))
         return complex<_Tp>(_Tp(NAN), _Tp(NAN));
-    if (isnan(__theta))
+    if (__libcpp_isnan_or_builtin(__theta))
     {
-        if (isinf(__rho))
+        if (__libcpp_isinf_or_builtin(__rho))
             return complex<_Tp>(__rho, __theta);
         return complex<_Tp>(__theta, __theta);
     }
-    if (isinf(__theta))
+    if (__libcpp_isinf_or_builtin(__theta))
     {
-        if (isinf(__rho))
+        if (__libcpp_isinf_or_builtin(__rho))
             return complex<_Tp>(__rho, _Tp(NAN));
         return complex<_Tp>(_Tp(NAN), _Tp(NAN));
     }
     _Tp __x = __rho * cos(__theta);
-    if (isnan(__x))
+    if (__libcpp_isnan_or_builtin(__x))
         __x = 0;
     _Tp __y = __rho * sin(__theta);
-    if (isnan(__y))
+    if (__libcpp_isnan_or_builtin(__y))
         __y = 0;
     return complex<_Tp>(__x, __y);
 }
@@ -1131,13 +1042,13 @@ template<class _Tp>
 complex<_Tp>
 sqrt(const complex<_Tp>& __x)
 {
-    if (isinf(__x.imag()))
+    if (__libcpp_isinf_or_builtin(__x.imag()))
         return complex<_Tp>(_Tp(INFINITY), __x.imag());
-    if (isinf(__x.real()))
+    if (__libcpp_isinf_or_builtin(__x.real()))
     {
         if (__x.real() > _Tp(0))
-            return complex<_Tp>(__x.real(), isnan(__x.imag()) ? __x.imag() : copysign(_Tp(0), __x.imag()));
-        return complex<_Tp>(isnan(__x.imag()) ? __x.imag() : _Tp(0), copysign(__x.real(), __x.imag()));
+            return complex<_Tp>(__x.real(), __libcpp_isnan_or_builtin(__x.imag()) ? __x.imag() : copysign(_Tp(0), __x.imag()));
+        return complex<_Tp>(__libcpp_isnan_or_builtin(__x.imag()) ? __x.imag() : _Tp(0), copysign(__x.real(), __x.imag()));
     }
     return polar(sqrt(abs(__x)), arg(__x) / _Tp(2));
 }
@@ -1149,21 +1060,21 @@ complex<_Tp>
 exp(const complex<_Tp>& __x)
 {
     _Tp __i = __x.imag();
-    if (isinf(__x.real()))
+    if (__libcpp_isinf_or_builtin(__x.real()))
     {
         if (__x.real() < _Tp(0))
         {
-            if (!isfinite(__i))
+            if (!__libcpp_isfinite_or_builtin(__i))
                 __i = _Tp(1);
         }
-        else if (__i == 0 || !isfinite(__i))
+        else if (__i == 0 || !__libcpp_isfinite_or_builtin(__i))
         {
-            if (isinf(__i))
+            if (__libcpp_isinf_or_builtin(__i))
                 __i = _Tp(NAN);
             return complex<_Tp>(__x.real(), __i);
         }
     }
-    else if (isnan(__x.real()) && __x.imag() == 0)
+    else if (__libcpp_isnan_or_builtin(__x.real()) && __x.imag() == 0)
         return __x;
     _Tp __e = exp(__x.real());
     return complex<_Tp>(__e * cos(__i), __e * sin(__i));
@@ -1221,23 +1132,23 @@ complex<_Tp>
 asinh(const complex<_Tp>& __x)
 {
     const _Tp __pi(atan2(+0., -0.));
-    if (isinf(__x.real()))
+    if (__libcpp_isinf_or_builtin(__x.real()))
     {
-        if (isnan(__x.imag()))
+        if (__libcpp_isnan_or_builtin(__x.imag()))
             return __x;
-        if (isinf(__x.imag()))
+        if (__libcpp_isinf_or_builtin(__x.imag()))
             return complex<_Tp>(__x.real(), copysign(__pi * _Tp(0.25), __x.imag()));
         return complex<_Tp>(__x.real(), copysign(_Tp(0), __x.imag()));
     }
-    if (isnan(__x.real()))
+    if (__libcpp_isnan_or_builtin(__x.real()))
     {
-        if (isinf(__x.imag()))
+        if (__libcpp_isinf_or_builtin(__x.imag()))
             return complex<_Tp>(__x.imag(), __x.real());
         if (__x.imag() == 0)
             return __x;
         return complex<_Tp>(__x.real(), __x.real());
     }
-    if (isinf(__x.imag()))
+    if (__libcpp_isinf_or_builtin(__x.imag()))
         return complex<_Tp>(copysign(__x.imag(), __x.real()), copysign(__pi/_Tp(2), __x.imag()));
     complex<_Tp> __z = log(__x + sqrt(pow(__x, _Tp(2)) + _Tp(1)));
     return complex<_Tp>(copysign(__z.real(), __x.real()), copysign(__z.imag(), __x.imag()));
@@ -1250,11 +1161,11 @@ complex<_Tp>
 acosh(const complex<_Tp>& __x)
 {
     const _Tp __pi(atan2(+0., -0.));
-    if (isinf(__x.real()))
+    if (__libcpp_isinf_or_builtin(__x.real()))
     {
-        if (isnan(__x.imag()))
+        if (__libcpp_isnan_or_builtin(__x.imag()))
             return complex<_Tp>(abs(__x.real()), __x.imag());
-        if (isinf(__x.imag()))
+        if (__libcpp_isinf_or_builtin(__x.imag()))
         {
             if (__x.real() > 0)
                 return complex<_Tp>(__x.real(), copysign(__pi * _Tp(0.25), __x.imag()));
@@ -1265,13 +1176,13 @@ acosh(const complex<_Tp>& __x)
             return complex<_Tp>(-__x.real(), copysign(__pi, __x.imag()));
         return complex<_Tp>(__x.real(), copysign(_Tp(0), __x.imag()));
     }
-    if (isnan(__x.real()))
+    if (__libcpp_isnan_or_builtin(__x.real()))
     {
-        if (isinf(__x.imag()))
+        if (__libcpp_isinf_or_builtin(__x.imag()))
             return complex<_Tp>(abs(__x.imag()), __x.real());
         return complex<_Tp>(__x.real(), __x.real());
     }
-    if (isinf(__x.imag()))
+    if (__libcpp_isinf_or_builtin(__x.imag()))
         return complex<_Tp>(abs(__x.imag()), copysign(__pi/_Tp(2), __x.imag()));
     complex<_Tp> __z = log(__x + sqrt(pow(__x, _Tp(2)) - _Tp(1)));
     return complex<_Tp>(copysign(__z.real(), _Tp(0)), copysign(__z.imag(), __x.imag()));
@@ -1284,21 +1195,21 @@ complex<_Tp>
 atanh(const complex<_Tp>& __x)
 {
     const _Tp __pi(atan2(+0., -0.));
-    if (isinf(__x.imag()))
+    if (__libcpp_isinf_or_builtin(__x.imag()))
     {
         return complex<_Tp>(copysign(_Tp(0), __x.real()), copysign(__pi/_Tp(2), __x.imag()));
     }
-    if (isnan(__x.imag()))
+    if (__libcpp_isnan_or_builtin(__x.imag()))
     {
-        if (isinf(__x.real()) || __x.real() == 0)
+        if (__libcpp_isinf_or_builtin(__x.real()) || __x.real() == 0)
             return complex<_Tp>(copysign(_Tp(0), __x.real()), __x.imag());
         return complex<_Tp>(__x.imag(), __x.imag());
     }
-    if (isnan(__x.real()))
+    if (__libcpp_isnan_or_builtin(__x.real()))
     {
         return complex<_Tp>(__x.real(), __x.real());
     }
-    if (isinf(__x.real()))
+    if (__libcpp_isinf_or_builtin(__x.real()))
     {
         return complex<_Tp>(copysign(_Tp(0), __x.real()), copysign(__pi/_Tp(2), __x.imag()));
     }
@@ -1316,11 +1227,11 @@ template<class _Tp>
 complex<_Tp>
 sinh(const complex<_Tp>& __x)
 {
-    if (isinf(__x.real()) && !isfinite(__x.imag()))
+    if (__libcpp_isinf_or_builtin(__x.real()) && !__libcpp_isfinite_or_builtin(__x.imag()))
         return complex<_Tp>(__x.real(), _Tp(NAN));
-    if (__x.real() == 0 && !isfinite(__x.imag()))
+    if (__x.real() == 0 && !__libcpp_isfinite_or_builtin(__x.imag()))
         return complex<_Tp>(__x.real(), _Tp(NAN));
-    if (__x.imag() == 0 && !isfinite(__x.real()))
+    if (__x.imag() == 0 && !__libcpp_isfinite_or_builtin(__x.real()))
         return __x;
     return complex<_Tp>(sinh(__x.real()) * cos(__x.imag()), cosh(__x.real()) * sin(__x.imag()));
 }
@@ -1331,13 +1242,13 @@ template<class _Tp>
 complex<_Tp>
 cosh(const complex<_Tp>& __x)
 {
-    if (isinf(__x.real()) && !isfinite(__x.imag()))
+    if (__libcpp_isinf_or_builtin(__x.real()) && !__libcpp_isfinite_or_builtin(__x.imag()))
         return complex<_Tp>(abs(__x.real()), _Tp(NAN));
-    if (__x.real() == 0 && !isfinite(__x.imag()))
+    if (__x.real() == 0 && !__libcpp_isfinite_or_builtin(__x.imag()))
         return complex<_Tp>(_Tp(NAN), __x.real());
     if (__x.real() == 0 && __x.imag() == 0)
         return complex<_Tp>(_Tp(1), __x.imag());
-    if (__x.imag() == 0 && !isfinite(__x.real()))
+    if (__x.imag() == 0 && !__libcpp_isfinite_or_builtin(__x.real()))
         return complex<_Tp>(abs(__x.real()), __x.imag());
     return complex<_Tp>(cosh(__x.real()) * cos(__x.imag()), sinh(__x.real()) * sin(__x.imag()));
 }
@@ -1348,19 +1259,19 @@ template<class _Tp>
 complex<_Tp>
 tanh(const complex<_Tp>& __x)
 {
-    if (isinf(__x.real()))
+    if (__libcpp_isinf_or_builtin(__x.real()))
     {
-        if (!isfinite(__x.imag()))
+        if (!__libcpp_isfinite_or_builtin(__x.imag()))
             return complex<_Tp>(_Tp(1), _Tp(0));
         return complex<_Tp>(_Tp(1), copysign(_Tp(0), sin(_Tp(2) * __x.imag())));
     }
-    if (isnan(__x.real()) && __x.imag() == 0)
+    if (__libcpp_isnan_or_builtin(__x.real()) && __x.imag() == 0)
         return __x;
     _Tp __2r(_Tp(2) * __x.real());
     _Tp __2i(_Tp(2) * __x.imag());
     _Tp __d(cosh(__2r) + cos(__2i));
     _Tp __2rsh(sinh(__2r));
-    if (isinf(__2rsh) && isinf(__d))
+    if (__libcpp_isinf_or_builtin(__2rsh) && __libcpp_isinf_or_builtin(__d))
         return complex<_Tp>(__2rsh > _Tp(0) ? _Tp(1) : _Tp(-1),
                             __2i > _Tp(0) ? _Tp(0) : _Tp(-0.));
     return  complex<_Tp>(__2rsh/__d, sin(__2i)/__d);
@@ -1383,11 +1294,11 @@ complex<_Tp>
 acos(const complex<_Tp>& __x)
 {
     const _Tp __pi(atan2(+0., -0.));
-    if (isinf(__x.real()))
+    if (__libcpp_isinf_or_builtin(__x.real()))
     {
-        if (isnan(__x.imag()))
+        if (__libcpp_isnan_or_builtin(__x.imag()))
             return complex<_Tp>(__x.imag(), __x.real());
-        if (isinf(__x.imag()))
+        if (__libcpp_isinf_or_builtin(__x.imag()))
         {
             if (__x.real() < _Tp(0))
                 return complex<_Tp>(_Tp(0.75) * __pi, -__x.imag());
@@ -1397,13 +1308,13 @@ acos(const complex<_Tp>& __x)
             return complex<_Tp>(__pi, signbit(__x.imag()) ? -__x.real() : __x.real());
         return complex<_Tp>(_Tp(0), signbit(__x.imag()) ? __x.real() : -__x.real());
     }
-    if (isnan(__x.real()))
+    if (__libcpp_isnan_or_builtin(__x.real()))
     {
-        if (isinf(__x.imag()))
+        if (__libcpp_isinf_or_builtin(__x.imag()))
             return complex<_Tp>(__x.real(), -__x.imag());
         return complex<_Tp>(__x.real(), __x.real());
     }
-    if (isinf(__x.imag()))
+    if (__libcpp_isinf_or_builtin(__x.imag()))
         return complex<_Tp>(__pi/_Tp(2), -__x.imag());
     if (__x.real() == 0 && (__x.imag() == 0 || isnan(__x.imag())))
         return complex<_Tp>(__pi/_Tp(2), -__x.imag());
diff --git a/lib/libcxx/include/condition_variable b/lib/libcxx/include/condition_variable
index 10e00770167..c45a326d898 100644
--- a/lib/libcxx/include/condition_variable
+++ b/lib/libcxx/include/condition_variable
@@ -133,12 +133,14 @@ public:
     void notify_all() _NOEXCEPT;
 
     template <class _Lock>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         void wait(_Lock& __lock);
     template <class _Lock, class _Predicate>
         _LIBCPP_INLINE_VISIBILITY
         void wait(_Lock& __lock, _Predicate __pred);
 
     template <class _Lock, class _Clock, class _Duration>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         cv_status
         wait_until(_Lock& __lock,
                    const chrono::time_point<_Clock, _Duration>& __t);
diff --git a/lib/libcxx/include/cstddef b/lib/libcxx/include/cstddef
index edd106c001b..adeefdac9be 100644
--- a/lib/libcxx/include/cstddef
+++ b/lib/libcxx/include/cstddef
@@ -28,6 +28,7 @@ Types:
     size_t
     max_align_t
     nullptr_t
+    byte // C++17
 
 }  // std
 
@@ -48,7 +49,8 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 using ::ptrdiff_t;
 using ::size_t;
 
-#if defined(__CLANG_MAX_ALIGN_T_DEFINED) || defined(_GCC_MAX_ALIGN_T)
+#if defined(__CLANG_MAX_ALIGN_T_DEFINED) || defined(_GCC_MAX_ALIGN_T) || \
+    defined(__DEFINED_max_align_t)
 // Re-use the compiler's <stddef.h> max_align_t where possible.
 using ::max_align_t;
 #else
@@ -57,4 +59,55 @@ typedef long double max_align_t;
 
 _LIBCPP_END_NAMESPACE_STD
 
+#if _LIBCPP_STD_VER > 14
+namespace std  // purposefully not versioned
+{
+enum class byte : unsigned char {};
+
+constexpr byte  operator| (byte  __lhs, byte __rhs) noexcept
+{
+	return static_cast<byte>(
+	  static_cast<unsigned char>(
+	     static_cast<unsigned int>(__lhs) | static_cast<unsigned int>(__rhs)
+	));
+}
+
+constexpr byte& operator|=(byte& __lhs, byte __rhs) noexcept
+{ return __lhs = __lhs | __rhs; }
+
+constexpr byte  operator& (byte  __lhs, byte __rhs) noexcept
+{
+	return static_cast<byte>(
+	  static_cast<unsigned char>(
+	     static_cast<unsigned int>(__lhs) & static_cast<unsigned int>(__rhs)
+	));
+}
+
+constexpr byte& operator&=(byte& __lhs, byte __rhs) noexcept
+{ return __lhs = __lhs & __rhs; }
+
+constexpr byte  operator^ (byte  __lhs, byte __rhs) noexcept
+{
+	return static_cast<byte>(
+	  static_cast<unsigned char>(
+	     static_cast<unsigned int>(__lhs) ^ static_cast<unsigned int>(__rhs)
+	));
+}
+
+constexpr byte& operator^=(byte& __lhs, byte __rhs) noexcept 
+{ return __lhs = __lhs ^ __rhs; }
+
+constexpr byte  operator~ (byte __b) noexcept
+{
+    return static_cast<byte>(
+      static_cast<unsigned char>(
+        ~static_cast<unsigned int>(__b)
+    ));
+}
+
+}
+
+#include <type_traits>  // rest of byte
+#endif
+
 #endif  // _LIBCPP_CSTDDEF
diff --git a/lib/libcxx/include/cstdlib b/lib/libcxx/include/cstdlib
index 10ed231078d..78c428403c3 100644
--- a/lib/libcxx/include/cstdlib
+++ b/lib/libcxx/include/cstdlib
@@ -89,6 +89,12 @@ void *aligned_alloc(size_t alignment, size_t size);                       // C11
 #pragma GCC system_header
 #endif
 
+#ifdef __GNUC__
+#define _LIBCPP_UNREACHABLE() __builtin_unreachable()
+#else
+#define _LIBCPP_UNREACHABLE() _VSTD::abort()
+#endif
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 using ::size_t;
@@ -124,8 +130,10 @@ using ::abort;
 using ::atexit;
 using ::exit;
 using ::_Exit;
+#ifndef _LIBCPP_WINDOWS_STORE_APP
 using ::getenv;
 using ::system;
+#endif
 using ::bsearch;
 using ::qsort;
 using ::abs;
@@ -138,11 +146,9 @@ using ::ldiv;
 #ifndef _LIBCPP_HAS_NO_LONG_LONG
 using ::lldiv;
 #endif // _LIBCPP_HAS_NO_LONG_LONG
-#ifndef _LIBCPP_HAS_NO_THREAD_UNSAFE_C_FUNCTIONS
 using ::mblen;
 using ::mbtowc;
 using ::wctomb;
-#endif
 using ::mbstowcs;
 using ::wcstombs;
 #ifdef _LIBCPP_HAS_QUICK_EXIT
diff --git a/lib/libcxx/include/ctype.h b/lib/libcxx/include/ctype.h
index 22d6c49be9e..e97ff3c4887 100644
--- a/lib/libcxx/include/ctype.h
+++ b/lib/libcxx/include/ctype.h
@@ -40,15 +40,6 @@ int toupper(int c);
 
 #ifdef __cplusplus
 
-#if defined(_LIBCPP_MSVCRT)
-// We support including .h headers inside 'extern "C"' contexts, so switch
-// back to C++ linkage before including these C++ headers.
-extern "C++" {
-  #include "support/win32/support.h"
-  #include "support/win32/locale_win32.h"
-}
-#endif // _LIBCPP_MSVCRT
-
 #undef isalnum
 #undef isalpha
 #undef isblank
diff --git a/lib/libcxx/include/cwchar b/lib/libcxx/include/cwchar
index 52dde9e1802..d268e8bbd39 100644
--- a/lib/libcxx/include/cwchar
+++ b/lib/libcxx/include/cwchar
@@ -123,11 +123,9 @@ using ::fwscanf;
 using ::swprintf;
 using ::vfwprintf;
 using ::vswprintf;
-#ifndef _LIBCPP_MSVCRT
 using ::swscanf;
 using ::vfwscanf;
 using ::vswscanf;
-#endif // _LIBCPP_MSVCRT
 using ::fgetwc;
 using ::fgetws;
 using ::fputwc;
@@ -137,10 +135,8 @@ using ::getwc;
 using ::putwc;
 using ::ungetwc;
 using ::wcstod;
-#ifndef _LIBCPP_MSVCRT
 using ::wcstof;
 using ::wcstold;
-#endif // _LIBCPP_MSVCRT
 using ::wcstol;
 #ifndef _LIBCPP_HAS_NO_LONG_LONG
 using ::wcstoll;
@@ -182,9 +178,7 @@ using ::wcsrtombs;
 
 #ifndef _LIBCPP_HAS_NO_STDIN
 using ::getwchar;
-#ifndef _LIBCPP_MSVCRT
 using ::vwscanf;
-#endif // _LIBCPP_MSVCRT
 using ::wscanf;
 #endif
 
diff --git a/lib/libcxx/include/deque b/lib/libcxx/include/deque
index 57650427645..08cb295408b 100644
--- a/lib/libcxx/include/deque
+++ b/lib/libcxx/include/deque
@@ -110,8 +110,8 @@ public:
     void push_front(value_type&& v);
     void push_back(const value_type& v);
     void push_back(value_type&& v);
-    template <class... Args> void emplace_front(Args&&... args);
-    template <class... Args> void emplace_back(Args&&... args);
+    template <class... Args> reference emplace_front(Args&&... args);  // reference in C++17
+    template <class... Args> reference emplace_back(Args&&... args);   // reference in C++17
     template <class... Args> iterator emplace(const_iterator p, Args&&... args);
     iterator insert(const_iterator p, const value_type& v);
     iterator insert(const_iterator p, value_type&& v);
@@ -150,10 +150,6 @@ template <class T, class Allocator>
 
 */
 
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
-#endif
-
 #include <__config>
 #include <__split_buffer>
 #include <type_traits>
@@ -162,16 +158,22 @@ template <class T, class Allocator>
 #include <algorithm>
 #include <stdexcept>
 
-#include <__undef_min_max>
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Tp, class _Allocator> class __deque_base;
-template <class _Tp, class _Allocator = allocator<_Tp> > class _LIBCPP_TYPE_VIS_ONLY deque;
+template <class _Tp, class _Allocator = allocator<_Tp> > class _LIBCPP_TEMPLATE_VIS deque;
 
 template <class _ValueType, class _Pointer, class _Reference, class _MapPointer,
           class _DiffType, _DiffType _BlockSize>
-class _LIBCPP_TYPE_VIS_ONLY __deque_iterator;
+class _LIBCPP_TEMPLATE_VIS __deque_iterator;
 
 template <class _RAIter,
           class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
@@ -276,7 +278,7 @@ template <class _ValueType, class _Pointer, class _Reference, class _MapPointer,
                                __deque_block_size<_ValueType, _DiffType>::value
 #endif
           >
-class _LIBCPP_TYPE_VIS_ONLY __deque_iterator
+class _LIBCPP_TEMPLATE_VIS __deque_iterator
 {
     typedef _MapPointer __map_iterator;
 public:
@@ -428,9 +430,9 @@ private:
         : __m_iter_(__m), __ptr_(__p) {}
 
     template <class _Tp, class _Ap> friend class __deque_base;
-    template <class _Tp, class _Ap> friend class _LIBCPP_TYPE_VIS_ONLY deque;
+    template <class _Tp, class _Ap> friend class _LIBCPP_TEMPLATE_VIS deque;
     template <class _Vp, class _Pp, class _Rp, class _MP, class _Dp, _Dp>
-        friend class _LIBCPP_TYPE_VIS_ONLY __deque_iterator;
+        friend class _LIBCPP_TEMPLATE_VIS __deque_iterator;
 
     template <class _RAIter,
               class _V2, class _P2, class _R2, class _M2, class _D2, _D2 _B2>
@@ -895,26 +897,22 @@ template <bool>
 class __deque_base_common
 {
 protected:
-    void __throw_length_error() const;
-    void __throw_out_of_range() const;
+    _LIBCPP_NORETURN void __throw_length_error() const;
+    _LIBCPP_NORETURN void __throw_out_of_range() const;
 };
 
 template <bool __b>
 void
 __deque_base_common<__b>::__throw_length_error() const
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    throw length_error("deque");
-#endif
+    _VSTD::__throw_length_error("deque");
 }
 
 template <bool __b>
 void
 __deque_base_common<__b>::__throw_out_of_range() const
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    throw out_of_range("deque");
-#endif
+    _VSTD::__throw_out_of_range("deque");
 }
 
 template <class _Tp, class _Allocator>
@@ -972,13 +970,12 @@ protected:
 public:
     ~__deque_base();
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
+#ifndef _LIBCPP_CXX03_LANG
     __deque_base(__deque_base&& __c)
         _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value);
     __deque_base(__deque_base&& __c, const allocator_type& __a);
+#endif  // _LIBCPP_CXX03_LANG
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     void swap(__deque_base& __c)
 #if _LIBCPP_STD_VER >= 14
         _NOEXCEPT;
@@ -1112,7 +1109,7 @@ __deque_base<_Tp, _Allocator>::~__deque_base()
         __alloc_traits::deallocate(__alloc(), *__i, __block_size);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 __deque_base<_Tp, _Allocator>::__deque_base(__deque_base&& __c)
@@ -1144,7 +1141,7 @@ __deque_base<_Tp, _Allocator>::__deque_base(__deque_base&& __c, const allocator_
     }
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 void
@@ -1187,7 +1184,7 @@ __deque_base<_Tp, _Allocator>::clear() _NOEXCEPT
 }
 
 template <class _Tp, class _Allocator /*= allocator<_Tp>*/>
-class _LIBCPP_TYPE_VIS_ONLY deque
+class _LIBCPP_TEMPLATE_VIS deque
     : private __deque_base<_Tp, _Allocator>
 {
 public:
@@ -1234,18 +1231,16 @@ public:
               typename enable_if<__is_input_iterator<_InputIter>::value>::type* = 0);
     deque(const deque& __c);
     deque(const deque& __c, const allocator_type& __a);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
+    deque& operator=(const deque& __c);
+
+#ifndef _LIBCPP_CXX03_LANG
     deque(initializer_list<value_type> __il);
     deque(initializer_list<value_type> __il, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
-    deque& operator=(const deque& __c);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     _LIBCPP_INLINE_VISIBILITY
     deque& operator=(initializer_list<value_type> __il) {assign(__il); return *this;}
-#endif   // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     deque(deque&& __c) _NOEXCEPT_(is_nothrow_move_constructible<__base>::value);
     _LIBCPP_INLINE_VISIBILITY
@@ -1254,7 +1249,10 @@ public:
     deque& operator=(deque&& __c)
         _NOEXCEPT_(__alloc_traits::propagate_on_container_move_assignment::value &&
                    is_nothrow_move_assignable<allocator_type>::value);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
+    _LIBCPP_INLINE_VISIBILITY
+    void assign(initializer_list<value_type> __il) {assign(__il.begin(), __il.end());}
+#endif  // _LIBCPP_CXX03_LANG
 
     template <class _InputIter>
         void assign(_InputIter __f, _InputIter __l,
@@ -1264,10 +1262,6 @@ public:
         void assign(_RAIter __f, _RAIter __l,
                     typename enable_if<__is_random_access_iterator<_RAIter>::value>::type* = 0);
     void assign(size_type __n, const value_type& __v);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-    _LIBCPP_INLINE_VISIBILITY
-    void assign(initializer_list<value_type> __il) {assign(__il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
     _LIBCPP_INLINE_VISIBILITY
     allocator_type get_allocator() const _NOEXCEPT;
@@ -1314,11 +1308,13 @@ public:
     size_type size() const _NOEXCEPT {return __base::size();}
     _LIBCPP_INLINE_VISIBILITY
     size_type max_size() const _NOEXCEPT
-        {return __alloc_traits::max_size(__base::__alloc());}
+        {return std::min<size_type>(
+            __alloc_traits::max_size(__base::__alloc()),
+            numeric_limits<difference_type>::max());}
     void resize(size_type __n);
     void resize(size_type __n, const value_type& __v);
     void shrink_to_fit() _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool empty() const _NOEXCEPT {return __base::size() == 0;}
 
     // element access:
@@ -1342,16 +1338,24 @@ public:
     // 23.2.2.3 modifiers:
     void push_front(const value_type& __v);
     void push_back(const value_type& __v);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-    template <class... _Args> void emplace_front(_Args&&... __args);
-    template <class... _Args> void emplace_back(_Args&&... __args);
+#ifndef _LIBCPP_CXX03_LANG
+#if _LIBCPP_STD_VER > 14
+    template <class... _Args> reference emplace_front(_Args&&... __args);
+    template <class... _Args> reference emplace_back (_Args&&... __args);
+#else
+    template <class... _Args> void      emplace_front(_Args&&... __args);
+    template <class... _Args> void      emplace_back (_Args&&... __args);
+#endif
     template <class... _Args> iterator emplace(const_iterator __p, _Args&&... __args);
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+
     void push_front(value_type&& __v);
     void push_back(value_type&& __v);
     iterator insert(const_iterator __p, value_type&& __v);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
+    _LIBCPP_INLINE_VISIBILITY
+    iterator insert(const_iterator __p, initializer_list<value_type> __il)
+        {return insert(__p, __il.begin(), __il.end());}
+#endif  // _LIBCPP_CXX03_LANG
     iterator insert(const_iterator __p, const value_type& __v);
     iterator insert(const_iterator __p, size_type __n, const value_type& __v);
     template <class _InputIter>
@@ -1365,11 +1369,7 @@ public:
     template <class _BiIter>
         iterator insert(const_iterator __p, _BiIter __f, _BiIter __l,
                          typename enable_if<__is_bidirectional_iterator<_BiIter>::value>::type* = 0);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-    _LIBCPP_INLINE_VISIBILITY
-    iterator insert(const_iterator __p, initializer_list<value_type> __il)
-        {return insert(__p, __il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
     void pop_front();
     void pop_back();
     iterator erase(const_iterator __p);
@@ -1524,7 +1524,19 @@ deque<_Tp, _Allocator>::deque(const deque& __c, const allocator_type& __a)
     __append(__c.begin(), __c.end());
 }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+template <class _Tp, class _Allocator>
+deque<_Tp, _Allocator>&
+deque<_Tp, _Allocator>::operator=(const deque& __c)
+{
+    if (this != &__c)
+    {
+        __copy_assign_alloc(__c);
+        assign(__c.begin(), __c.end());
+    }
+    return *this;
+}
+
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 deque<_Tp, _Allocator>::deque(initializer_list<value_type> __il)
@@ -1539,22 +1551,6 @@ deque<_Tp, _Allocator>::deque(initializer_list<value_type> __il, const allocator
     __append(__il.begin(), __il.end());
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
-template <class _Tp, class _Allocator>
-deque<_Tp, _Allocator>&
-deque<_Tp, _Allocator>::operator=(const deque& __c)
-{
-    if (this != &__c)
-    {
-        __copy_assign_alloc(__c);
-        assign(__c.begin(), __c.end());
-    }
-    return *this;
-}
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
 template <class _Tp, class _Allocator>
 inline
 deque<_Tp, _Allocator>::deque(deque&& __c)
@@ -1610,7 +1606,7 @@ deque<_Tp, _Allocator>::__move_assign(deque& __c, true_type)
     __base::__move_assign(__c);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 template <class _InputIter>
@@ -1806,8 +1802,20 @@ deque<_Tp, _Allocator>::push_back(const value_type& __v)
     ++__base::size();
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+template <class _Tp, class _Allocator>
+void
+deque<_Tp, _Allocator>::push_front(const value_type& __v)
+{
+    allocator_type& __a = __base::__alloc();
+    if (__front_spare() == 0)
+        __add_front_capacity();
+    // __front_spare() >= 1
+    __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), __v);
+    --__base::__start_;
+    ++__base::size();
+}
 
+#ifndef _LIBCPP_CXX03_LANG
 template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::push_back(value_type&& __v)
@@ -1820,39 +1828,27 @@ deque<_Tp, _Allocator>::push_back(value_type&& __v)
     ++__base::size();
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
 template <class _Tp, class _Allocator>
 template <class... _Args>
+#if _LIBCPP_STD_VER > 14
+typename deque<_Tp, _Allocator>::reference
+#else
 void
+#endif
 deque<_Tp, _Allocator>::emplace_back(_Args&&... __args)
 {
     allocator_type& __a = __base::__alloc();
     if (__back_spare() == 0)
         __add_back_capacity();
     // __back_spare() >= 1
-    __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), _VSTD::forward<_Args>(__args)...);
-    ++__base::size();
-}
-
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-template <class _Tp, class _Allocator>
-void
-deque<_Tp, _Allocator>::push_front(const value_type& __v)
-{
-    allocator_type& __a = __base::__alloc();
-    if (__front_spare() == 0)
-        __add_front_capacity();
-    // __front_spare() >= 1
-    __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), __v);
-    --__base::__start_;
+    __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()),
+                              _VSTD::forward<_Args>(__args)...);
     ++__base::size();
+#if _LIBCPP_STD_VER > 14
+    return *--__base::end();
+#endif
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
 template <class _Tp, class _Allocator>
 void
 deque<_Tp, _Allocator>::push_front(value_type&& __v)
@@ -1866,11 +1862,14 @@ deque<_Tp, _Allocator>::push_front(value_type&& __v)
     ++__base::size();
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
 
 template <class _Tp, class _Allocator>
 template <class... _Args>
+#if _LIBCPP_STD_VER > 14
+typename deque<_Tp, _Allocator>::reference
+#else
 void
+#endif
 deque<_Tp, _Allocator>::emplace_front(_Args&&... __args)
 {
     allocator_type& __a = __base::__alloc();
@@ -1880,14 +1879,14 @@ deque<_Tp, _Allocator>::emplace_front(_Args&&... __args)
     __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::forward<_Args>(__args)...);
     --__base::__start_;
     ++__base::size();
+#if _LIBCPP_STD_VER > 14
+    return *__base::begin();
+#endif
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
 template <class _Tp, class _Allocator>
 typename deque<_Tp, _Allocator>::iterator
-deque<_Tp, _Allocator>::insert(const_iterator __p, const value_type& __v)
+deque<_Tp, _Allocator>::insert(const_iterator __p, value_type&& __v)
 {
     size_type __pos = __p - __base::begin();
     size_type __to_end = __base::size() - __pos;
@@ -1899,23 +1898,20 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, const value_type& __v)
         // __front_spare() >= 1
         if (__pos == 0)
         {
-            __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), __v);
+            __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::move(__v));
             --__base::__start_;
             ++__base::size();
         }
         else
         {
-            const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
             iterator __b = __base::begin();
             iterator __bm1 = _VSTD::prev(__b);
-            if (__vt == pointer_traits<const_pointer>::pointer_to(*__b))
-                __vt = pointer_traits<const_pointer>::pointer_to(*__bm1);
             __alloc_traits::construct(__a, _VSTD::addressof(*__bm1), _VSTD::move(*__b));
             --__base::__start_;
             ++__base::size();
             if (__pos > 1)
-                __b = __move_and_check(_VSTD::next(__b), __b + __pos, __b, __vt);
-            *__b = *__vt;
+                __b = _VSTD::move(_VSTD::next(__b), __b + __pos, __b);
+            *__b = _VSTD::move(__v);
         }
     }
     else
@@ -1926,31 +1922,27 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, const value_type& __v)
         size_type __de = __base::size() - __pos;
         if (__de == 0)
         {
-            __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), __v);
+            __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), _VSTD::move(__v));
             ++__base::size();
         }
         else
         {
-            const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
             iterator __e = __base::end();
             iterator __em1 = _VSTD::prev(__e);
-            if (__vt == pointer_traits<const_pointer>::pointer_to(*__em1))
-                __vt = pointer_traits<const_pointer>::pointer_to(*__e);
             __alloc_traits::construct(__a, _VSTD::addressof(*__e), _VSTD::move(*__em1));
             ++__base::size();
             if (__de > 1)
-                __e = __move_backward_and_check(__e - __de, __em1, __e, __vt);
-            *--__e = *__vt;
+                __e = _VSTD::move_backward(__e - __de, __em1, __e);
+            *--__e = _VSTD::move(__v);
         }
     }
     return __base::begin() + __pos;
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
 template <class _Tp, class _Allocator>
+template <class... _Args>
 typename deque<_Tp, _Allocator>::iterator
-deque<_Tp, _Allocator>::insert(const_iterator __p, value_type&& __v)
+deque<_Tp, _Allocator>::emplace(const_iterator __p, _Args&&... __args)
 {
     size_type __pos = __p - __base::begin();
     size_type __to_end = __base::size() - __pos;
@@ -1962,12 +1954,13 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, value_type&& __v)
         // __front_spare() >= 1
         if (__pos == 0)
         {
-            __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::move(__v));
+            __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::forward<_Args>(__args)...);
             --__base::__start_;
             ++__base::size();
         }
         else
         {
+            __temp_value<value_type, _Allocator> __tmp(this->__alloc(), _VSTD::forward<_Args>(__args)...);
             iterator __b = __base::begin();
             iterator __bm1 = _VSTD::prev(__b);
             __alloc_traits::construct(__a, _VSTD::addressof(*__bm1), _VSTD::move(*__b));
@@ -1975,7 +1968,7 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, value_type&& __v)
             ++__base::size();
             if (__pos > 1)
                 __b = _VSTD::move(_VSTD::next(__b), __b + __pos, __b);
-            *__b = _VSTD::move(__v);
+            *__b = _VSTD::move(__tmp.get());
         }
     }
     else
@@ -1986,29 +1979,30 @@ deque<_Tp, _Allocator>::insert(const_iterator __p, value_type&& __v)
         size_type __de = __base::size() - __pos;
         if (__de == 0)
         {
-            __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), _VSTD::move(__v));
+            __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), _VSTD::forward<_Args>(__args)...);
             ++__base::size();
         }
         else
         {
+            __temp_value<value_type, _Allocator> __tmp(this->__alloc(), _VSTD::forward<_Args>(__args)...);
             iterator __e = __base::end();
             iterator __em1 = _VSTD::prev(__e);
             __alloc_traits::construct(__a, _VSTD::addressof(*__e), _VSTD::move(*__em1));
             ++__base::size();
             if (__de > 1)
                 __e = _VSTD::move_backward(__e - __de, __em1, __e);
-            *--__e = _VSTD::move(__v);
+            *--__e = _VSTD::move(__tmp.get());
         }
     }
     return __base::begin() + __pos;
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#endif  // _LIBCPP_CXX03_LANG
+
 
 template <class _Tp, class _Allocator>
-template <class... _Args>
 typename deque<_Tp, _Allocator>::iterator
-deque<_Tp, _Allocator>::emplace(const_iterator __p, _Args&&... __args)
+deque<_Tp, _Allocator>::insert(const_iterator __p, const value_type& __v)
 {
     size_type __pos = __p - __base::begin();
     size_type __to_end = __base::size() - __pos;
@@ -2020,21 +2014,23 @@ deque<_Tp, _Allocator>::emplace(const_iterator __p, _Args&&... __args)
         // __front_spare() >= 1
         if (__pos == 0)
         {
-            __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), _VSTD::forward<_Args>(__args)...);
+            __alloc_traits::construct(__a, _VSTD::addressof(*--__base::begin()), __v);
             --__base::__start_;
             ++__base::size();
         }
         else
         {
-            __temp_value<value_type, _Allocator> __tmp(this->__alloc(), _VSTD::forward<_Args>(__args)...);
+            const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
             iterator __b = __base::begin();
             iterator __bm1 = _VSTD::prev(__b);
+            if (__vt == pointer_traits<const_pointer>::pointer_to(*__b))
+                __vt = pointer_traits<const_pointer>::pointer_to(*__bm1);
             __alloc_traits::construct(__a, _VSTD::addressof(*__bm1), _VSTD::move(*__b));
             --__base::__start_;
             ++__base::size();
             if (__pos > 1)
-                __b = _VSTD::move(_VSTD::next(__b), __b + __pos, __b);
-            *__b = _VSTD::move(__tmp.get());
+                __b = __move_and_check(_VSTD::next(__b), __b + __pos, __b, __vt);
+            *__b = *__vt;
         }
     }
     else
@@ -2045,27 +2041,26 @@ deque<_Tp, _Allocator>::emplace(const_iterator __p, _Args&&... __args)
         size_type __de = __base::size() - __pos;
         if (__de == 0)
         {
-            __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), _VSTD::forward<_Args>(__args)...);
+            __alloc_traits::construct(__a, _VSTD::addressof(*__base::end()), __v);
             ++__base::size();
         }
         else
         {
-            __temp_value<value_type, _Allocator> __tmp(this->__alloc(), _VSTD::forward<_Args>(__args)...);
+            const_pointer __vt = pointer_traits<const_pointer>::pointer_to(__v);
             iterator __e = __base::end();
             iterator __em1 = _VSTD::prev(__e);
+            if (__vt == pointer_traits<const_pointer>::pointer_to(*__em1))
+                __vt = pointer_traits<const_pointer>::pointer_to(*__e);
             __alloc_traits::construct(__a, _VSTD::addressof(*__e), _VSTD::move(*__em1));
             ++__base::size();
             if (__de > 1)
-                __e = _VSTD::move_backward(__e - __de, __em1, __e);
-            *--__e = _VSTD::move(__tmp.get());
+                __e = __move_backward_and_check(__e - __de, __em1, __e, __vt);
+            *--__e = *__vt;
         }
     }
     return __base::begin() + __pos;
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
 template <class _Tp, class _Allocator>
 typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::insert(const_iterator __p, size_type __n, const value_type& __v)
@@ -2228,7 +2223,11 @@ deque<_Tp, _Allocator>::__append(_InpIter __f, _InpIter __l,
                                                    !__is_forward_iterator<_InpIter>::value>::type*)
 {
     for (; __f != __l; ++__f)
+#ifdef _LIBCPP_CXX03_LANG
         push_back(*__f);
+#else
+        emplace_back(*__f);
+#endif
 }
 
 template <class _Tp, class _Allocator>
@@ -2734,7 +2733,7 @@ deque<_Tp, _Allocator>::erase(const_iterator __f)
     difference_type __pos = __f - __b;
     iterator __p = __b + __pos;
     allocator_type& __a = __base::__alloc();
-    if (__pos <= (__base::size() - 1) / 2)
+    if (static_cast<size_t>(__pos) <= (__base::size() - 1) / 2)
     {   // erase from front
         _VSTD::move_backward(__b, __p, _VSTD::next(__p));
         __alloc_traits::destroy(__a, _VSTD::addressof(*__b));
@@ -2772,7 +2771,7 @@ deque<_Tp, _Allocator>::erase(const_iterator __f, const_iterator __l)
     if (__n > 0)
     {
         allocator_type& __a = __base::__alloc();
-        if (__pos <= (__base::size() - __n) / 2)
+        if (static_cast<size_t>(__pos) <= (__base::size() - __n) / 2)
         {   // erase from front
             iterator __i = _VSTD::move_backward(__b, __p, __p + __n);
             for (; __b != __i; ++__b)
@@ -2906,4 +2905,6 @@ swap(deque<_Tp, _Allocator>& __x, deque<_Tp, _Allocator>& __y)
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_DEQUE
diff --git a/lib/libcxx/include/exception b/lib/libcxx/include/exception
index 186d379f08f..79bd6ac2ae3 100644
--- a/lib/libcxx/include/exception
+++ b/lib/libcxx/include/exception
@@ -79,10 +79,11 @@ template <class E> void rethrow_if_nested(const E& e);
 
 #include <__config>
 #include <cstddef>
-#include <type_traits>
-#if defined(_LIBCPP_NO_EXCEPTIONS)
-#include <cstdio>
 #include <cstdlib>
+#include <type_traits>
+
+#if defined(_LIBCPP_ABI_MICROSOFT) && !defined(_LIBCPP_NO_VCRUNTIME)
+#include <vcruntime_exception.h>
 #endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -92,6 +93,7 @@ template <class E> void rethrow_if_nested(const E& e);
 namespace std  // purposefully not using versioning namespace
 {
 
+#if !defined(_LIBCPP_ABI_MICROSOFT) || defined(_LIBCPP_NO_VCRUNTIME)
 class _LIBCPP_EXCEPTION_ABI exception
 {
 public:
@@ -108,11 +110,16 @@ public:
     virtual ~bad_exception() _NOEXCEPT;
     virtual const char* what() const _NOEXCEPT;
 };
+#endif // !_LIBCPP_ABI_MICROSOFT || _LIBCPP_NO_VCRUNTIME
 
+#if _LIBCPP_STD_VER <= 14 \
+    || defined(_LIBCPP_ENABLE_CXX17_REMOVED_UNEXPECTED_FUNCTIONS) \
+    || defined(_LIBCPP_BUILDING_LIBRARY)
 typedef void (*unexpected_handler)();
 _LIBCPP_FUNC_VIS unexpected_handler set_unexpected(unexpected_handler) _NOEXCEPT;
 _LIBCPP_FUNC_VIS unexpected_handler get_unexpected() _NOEXCEPT;
 _LIBCPP_NORETURN _LIBCPP_FUNC_VIS void unexpected();
+#endif
 
 typedef void (*terminate_handler)();
 _LIBCPP_FUNC_VIS terminate_handler set_terminate(terminate_handler) _NOEXCEPT;
@@ -120,30 +127,33 @@ _LIBCPP_FUNC_VIS terminate_handler get_terminate() _NOEXCEPT;
 _LIBCPP_NORETURN _LIBCPP_FUNC_VIS void terminate() _NOEXCEPT;
 
 _LIBCPP_FUNC_VIS bool uncaught_exception() _NOEXCEPT;
-_LIBCPP_FUNC_VIS int uncaught_exceptions() _NOEXCEPT;
+_LIBCPP_FUNC_VIS _LIBCPP_AVAILABILITY_UNCAUGHT_EXCEPTIONS int uncaught_exceptions() _NOEXCEPT;
 
 class _LIBCPP_TYPE_VIS exception_ptr;
 
 _LIBCPP_FUNC_VIS exception_ptr current_exception() _NOEXCEPT;
 _LIBCPP_NORETURN _LIBCPP_FUNC_VIS void rethrow_exception(exception_ptr);
 
+#ifndef _LIBCPP_ABI_MICROSOFT
+
 class _LIBCPP_TYPE_VIS exception_ptr
 {
     void* __ptr_;
 public:
     _LIBCPP_INLINE_VISIBILITY exception_ptr() _NOEXCEPT : __ptr_() {}
     _LIBCPP_INLINE_VISIBILITY exception_ptr(nullptr_t) _NOEXCEPT : __ptr_() {}
+
     exception_ptr(const exception_ptr&) _NOEXCEPT;
     exception_ptr& operator=(const exception_ptr&) _NOEXCEPT;
     ~exception_ptr() _NOEXCEPT;
 
-    _LIBCPP_INLINE_VISIBILITY
-    _LIBCPP_EXPLICIT
-        operator bool() const _NOEXCEPT {return __ptr_ != nullptr;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_EXPLICIT operator bool() const _NOEXCEPT
+    {return __ptr_ != nullptr;}
 
     friend _LIBCPP_INLINE_VISIBILITY
     bool operator==(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT
         {return __x.__ptr_ == __y.__ptr_;}
+
     friend _LIBCPP_INLINE_VISIBILITY
     bool operator!=(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT
         {return !(__x == __y);}
@@ -165,9 +175,60 @@ make_exception_ptr(_Ep __e) _NOEXCEPT
     {
         return current_exception();
     }
-#endif  // _LIBCPP_NO_EXCEPTIONS
+#else
+    ((void)__e);
+    _VSTD::abort();
+#endif
 }
 
+#else // _LIBCPP_ABI_MICROSOFT
+
+class _LIBCPP_TYPE_VIS exception_ptr
+{
+#if defined(__clang__)
+#pragma clang diagnostic push
+#pragma clang diagnostic ignored "-Wunused-private-field"
+#endif
+    void* __ptr1_;
+    void* __ptr2_;
+#if defined(__clang__)
+#pragma clang diagnostic pop
+#endif
+public:
+    exception_ptr() _NOEXCEPT;
+    exception_ptr(nullptr_t) _NOEXCEPT;
+    exception_ptr(const exception_ptr& __other) _NOEXCEPT;
+    exception_ptr& operator=(const exception_ptr& __other) _NOEXCEPT;
+    exception_ptr& operator=(nullptr_t) _NOEXCEPT;
+    ~exception_ptr() _NOEXCEPT;
+    _LIBCPP_EXPLICIT operator bool() const _NOEXCEPT;
+};
+
+_LIBCPP_FUNC_VIS
+bool operator==(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT;
+
+inline _LIBCPP_INLINE_VISIBILITY
+bool operator!=(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT
+    {return !(__x == __y);}
+
+_LIBCPP_FUNC_VIS void swap(exception_ptr&, exception_ptr&) _NOEXCEPT;
+
+_LIBCPP_FUNC_VIS exception_ptr __copy_exception_ptr(void *__except, const void* __ptr);
+_LIBCPP_FUNC_VIS exception_ptr current_exception() _NOEXCEPT;
+_LIBCPP_NORETURN _LIBCPP_FUNC_VIS void rethrow_exception(exception_ptr p);
+
+// This is a built-in template function which automagically extracts the required
+// information.
+template <class _E> void *__GetExceptionInfo(_E);
+
+template<class _Ep>
+exception_ptr
+make_exception_ptr(_Ep __e) _NOEXCEPT
+{
+  return __copy_exception_ptr(_VSTD::addressof(__e), __GetExceptionInfo(__e));
+}
+
+#endif // _LIBCPP_ABI_MICROSOFT
 // nested_exception
 
 class _LIBCPP_EXCEPTION_ABI nested_exception
@@ -192,52 +253,71 @@ struct __nested
     _LIBCPP_INLINE_VISIBILITY explicit __nested(const _Tp& __t) : _Tp(__t) {}
 };
 
-template <class _Tp>
-_LIBCPP_NORETURN
-void
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-throw_with_nested(_Tp&& __t, typename enable_if<
-                  is_class<typename remove_reference<_Tp>::type>::value &&
-                  !is_base_of<nested_exception, typename remove_reference<_Tp>::type>::value
-                  && !__libcpp_is_final<typename remove_reference<_Tp>::type>::value
-                                    >::type* = 0)
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-throw_with_nested (_Tp& __t, typename enable_if<
-                  is_class<_Tp>::value && !is_base_of<nested_exception, _Tp>::value
-                                    >::type* = 0)
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-{
 #ifndef _LIBCPP_NO_EXCEPTIONS
-    throw __nested<typename remove_reference<_Tp>::type>(_VSTD::forward<_Tp>(__t));
+template <class _Tp, class _Up, bool>
+struct __throw_with_nested;
+
+template <class _Tp, class _Up>
+struct __throw_with_nested<_Tp, _Up, true> {
+    _LIBCPP_NORETURN static inline _LIBCPP_ALWAYS_INLINE void
+#ifndef _LIBCPP_CXX03_LANG
+    __do_throw(_Tp&& __t)
+#else
+    __do_throw (_Tp& __t)
+#endif  // _LIBCPP_CXX03_LANG
+    {
+        throw __nested<_Up>(_VSTD::forward<_Tp>(__t));
+    }
+};
+
+template <class _Tp, class _Up>
+struct __throw_with_nested<_Tp, _Up, false> {
+    _LIBCPP_NORETURN static inline _LIBCPP_ALWAYS_INLINE void
+#ifndef _LIBCPP_CXX03_LANG
+    __do_throw(_Tp&& __t)
+#else
+    __do_throw (_Tp& __t)
+#endif  // _LIBCPP_CXX03_LANG
+    {
+        throw _VSTD::forward<_Tp>(__t);
+    }
+};
 #endif
-}
 
 template <class _Tp>
 _LIBCPP_NORETURN
 void
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-throw_with_nested(_Tp&& __t, typename enable_if<
-                  !is_class<typename remove_reference<_Tp>::type>::value ||
-                  is_base_of<nested_exception, typename remove_reference<_Tp>::type>::value
-                  || __libcpp_is_final<typename remove_reference<_Tp>::type>::value
-                                    >::type* = 0)
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-throw_with_nested (_Tp& __t, typename enable_if<
-                  !is_class<_Tp>::value || is_base_of<nested_exception, _Tp>::value
-                                    >::type* = 0)
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
+throw_with_nested(_Tp&& __t)
+#else
+throw_with_nested (_Tp& __t)
+#endif // _LIBCPP_CXX03_LANG
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS
-    throw _VSTD::forward<_Tp>(__t);
+    typedef typename decay<_Tp>::type _Up;
+    static_assert( is_copy_constructible<_Up>::value, "type thrown must be CopyConstructible");
+    __throw_with_nested<_Tp, _Up,
+        is_class<_Up>::value &&
+        !is_base_of<nested_exception, _Up>::value &&
+        !__libcpp_is_final<_Up>::value>::
+            __do_throw(_VSTD::forward<_Tp>(__t));
+#else
+    ((void)__t);
+    // FIXME: Make this abort
 #endif
 }
 
+template <class _From, class _To>
+struct __can_dynamic_cast : public _LIBCPP_BOOL_CONSTANT(
+              is_polymorphic<_From>::value &&
+                 (!is_base_of<_To, _From>::value ||
+                   is_convertible<const _From*, const _To*>::value)) {};
+
 template <class _Ep>
 inline _LIBCPP_INLINE_VISIBILITY
 void
-rethrow_if_nested(const _Ep& __e, typename enable_if<
-                                   is_polymorphic<_Ep>::value
-                                                   >::type* = 0)
+rethrow_if_nested(const _Ep& __e,
+                  typename enable_if< __can_dynamic_cast<_Ep, nested_exception>::value>::type* = 0)
 {
     const nested_exception* __nep = dynamic_cast<const nested_exception*>(_VSTD::addressof(__e));
     if (__nep)
@@ -247,27 +327,11 @@ rethrow_if_nested(const _Ep& __e, typename enable_if<
 template <class _Ep>
 inline _LIBCPP_INLINE_VISIBILITY
 void
-rethrow_if_nested(const _Ep&, typename enable_if<
-                                   !is_polymorphic<_Ep>::value
-                                                   >::type* = 0)
+rethrow_if_nested(const _Ep&,
+                  typename enable_if<!__can_dynamic_cast<_Ep, nested_exception>::value>::type* = 0)
 {
 }
 
 }  // std
 
-_LIBCPP_BEGIN_NAMESPACE_STD
-
-template <class _Exception>
-_LIBCPP_INLINE_VISIBILITY
-inline void __libcpp_throw(_Exception const& __e) {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    throw __e;
-#else
-    _VSTD::fprintf(stderr, "%s\n", __e.what());
-    _VSTD::abort();
-#endif
-}
-
-_LIBCPP_END_NAMESPACE_STD
-
 #endif  // _LIBCPP_EXCEPTION
diff --git a/lib/libcxx/include/experimental/__config b/lib/libcxx/include/experimental/__config
index 9a7bbe85d8d..37f88c166dd 100644
--- a/lib/libcxx/include/experimental/__config
+++ b/lib/libcxx/include/experimental/__config
@@ -44,6 +44,13 @@
 #define _LIBCPP_END_NAMESPACE_EXPERIMENTAL_FILESYSTEM \
     } } _LIBCPP_END_NAMESPACE_EXPERIMENTAL
 
+#define _LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL_COROUTINES \
+  _LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL inline namespace coroutines_v1 {
+
+#define _LIBCPP_END_NAMESPACE_EXPERIMENTAL_COROUTINES \
+  } _LIBCPP_END_NAMESPACE_EXPERIMENTAL
+
+#define _VSTD_CORO _VSTD_EXPERIMENTAL::coroutines_v1
 
 #define _VSTD_FS ::std::experimental::filesystem::v1
 
diff --git a/lib/libcxx/include/experimental/algorithm b/lib/libcxx/include/experimental/algorithm
index 3902111c54e..a6a28f07181 100644
--- a/lib/libcxx/include/experimental/algorithm
+++ b/lib/libcxx/include/experimental/algorithm
@@ -39,17 +39,18 @@ SampleIterator sample(PopulationIterator first, PopulationIterator last,
 #include <algorithm>
 #include <type_traits>
 
-#include <__undef_min_max>
-
 #include <__debug>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
-_LIBCPP_BEGIN_NAMESPACE_LFTS
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
 
 
+_LIBCPP_BEGIN_NAMESPACE_LFTS
+
 template <class _ForwardIterator, class _Searcher>
 _LIBCPP_INLINE_VISIBILITY
 _ForwardIterator search(_ForwardIterator __f, _ForwardIterator __l, const _Searcher &__s)
@@ -58,63 +59,15 @@ _ForwardIterator search(_ForwardIterator __f, _ForwardIterator __l, const _Searc
 
 template <class _PopulationIterator, class _SampleIterator, class _Distance,
           class _UniformRandomNumberGenerator>
-_LIBCPP_INLINE_VISIBILITY
-_SampleIterator __sample(_PopulationIterator __first,
-                         _PopulationIterator __last, _SampleIterator __out,
-                         _Distance __n,
-                         _UniformRandomNumberGenerator &&__g,
-                         input_iterator_tag) {
-
-  _Distance __k = 0;
-  for (; __first != __last && __k < __n; ++__first, (void)++__k)
-    __out[__k] = *__first;
-  _Distance __sz = __k;
-  for (; __first != __last; ++__first, (void)++__k) {
-    _Distance __r = _VSTD::uniform_int_distribution<_Distance>(0, __k)(__g);
-    if (__r < __sz)
-      __out[__r] = *__first;
-  }
-  return __out + _VSTD::min(__n, __k);
-}
-
-template <class _PopulationIterator, class _SampleIterator, class _Distance,
-          class _UniformRandomNumberGenerator>
-_LIBCPP_INLINE_VISIBILITY
-_SampleIterator __sample(_PopulationIterator __first,
-                         _PopulationIterator __last, _SampleIterator __out,
-                         _Distance __n,
-                         _UniformRandomNumberGenerator &&__g,
-                         forward_iterator_tag) {
-  _Distance __unsampled_sz = _VSTD::distance(__first, __last);
-  for (__n = _VSTD::min(__n, __unsampled_sz); __n != 0; ++__first) {
-    _Distance __r =
-        _VSTD::uniform_int_distribution<_Distance>(0, --__unsampled_sz)(__g);
-    if (__r < __n) {
-      *__out++ = *__first;
-      --__n;
-    }
-  }
-  return __out;
-}
-
-template <class _PopulationIterator, class _SampleIterator, class _Distance,
-          class _UniformRandomNumberGenerator>
-_LIBCPP_INLINE_VISIBILITY
-_SampleIterator sample(_PopulationIterator __first,
-                         _PopulationIterator __last, _SampleIterator __out,
-                         _Distance __n, _UniformRandomNumberGenerator &&__g) {
-  typedef typename iterator_traits<_PopulationIterator>::iterator_category
-        _PopCategory;
-  typedef typename iterator_traits<_PopulationIterator>::difference_type
-        _Difference;
-  typedef typename common_type<_Distance, _Difference>::type _CommonType;
-  _LIBCPP_ASSERT(__n >= 0, "N must be a positive number.");
-  return _VSTD_LFTS::__sample(
-      __first, __last, __out, _CommonType(__n),
-      _VSTD::forward<_UniformRandomNumberGenerator>(__g),
-      _PopCategory());
+inline _LIBCPP_INLINE_VISIBILITY
+_SampleIterator sample(_PopulationIterator __first, _PopulationIterator __last,
+                       _SampleIterator __output_iter, _Distance __n,
+                       _UniformRandomNumberGenerator &&__g) {
+  return _VSTD::__sample(__first, __last, __output_iter, __n, __g);
 }
 
 _LIBCPP_END_NAMESPACE_LFTS
 
+_LIBCPP_POP_MACROS
+
 #endif /* _LIBCPP_EXPERIMENTAL_ALGORITHM */
diff --git a/lib/libcxx/include/experimental/any b/lib/libcxx/include/experimental/any
index 4c732496c52..083a2909033 100644
--- a/lib/libcxx/include/experimental/any
+++ b/lib/libcxx/include/experimental/any
@@ -82,7 +82,6 @@ inline namespace fundamentals_v1 {
 #include <typeinfo>
 #include <type_traits>
 #include <cstdlib>
-#include <cassert>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
@@ -90,7 +89,7 @@ inline namespace fundamentals_v1 {
 
 _LIBCPP_BEGIN_NAMESPACE_LFTS
 
-class _LIBCPP_EXCEPTION_ABI bad_any_cast : public bad_cast
+class _LIBCPP_EXCEPTION_ABI _LIBCPP_AVAILABILITY_BAD_ANY_CAST bad_any_cast : public bad_cast
 {
 public:
     virtual const char* what() const _NOEXCEPT;
@@ -98,13 +97,14 @@ public:
 
 #if _LIBCPP_STD_VER > 11                                            // C++ > 11
 
-_LIBCPP_NORETURN _LIBCPP_INLINE_VISIBILITY
-inline void __throw_bad_any_cast()
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+_LIBCPP_AVAILABILITY_THROW_BAD_ANY_CAST
+void __throw_bad_any_cast()
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS
     throw bad_any_cast();
 #else
-    assert(!"bad_any_cast");
+    _VSTD::abort();
 #endif
 }
 
@@ -293,7 +293,7 @@ namespace __any_imp
 {
 
   template <class _Tp>
-  struct _LIBCPP_TYPE_VIS_ONLY _SmallHandler
+  struct _LIBCPP_TEMPLATE_VIS _SmallHandler
   {
      _LIBCPP_INLINE_VISIBILITY
      static void* __handle(_Action __act, any const * __this, any * __other,
@@ -374,7 +374,7 @@ namespace __any_imp
   };
 
   template <class _Tp>
-  struct _LIBCPP_TYPE_VIS_ONLY _LargeHandler
+  struct _LIBCPP_TEMPLATE_VIS _LargeHandler
   {
     _LIBCPP_INLINE_VISIBILITY
     static void* __handle(_Action __act, any const * __this, any * __other,
@@ -507,7 +507,7 @@ void swap(any & __lhs, any & __rhs) _NOEXCEPT
 }
 
 template <class _ValueType>
-_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_THROW_BAD_ANY_CAST
 _ValueType any_cast(any const & __v)
 {
     static_assert(
@@ -523,7 +523,7 @@ _ValueType any_cast(any const & __v)
 }
 
 template <class _ValueType>
-_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_THROW_BAD_ANY_CAST
 _ValueType any_cast(any & __v)
 {
     static_assert(
@@ -538,7 +538,7 @@ _ValueType any_cast(any & __v)
 }
 
 template <class _ValueType>
-_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_THROW_BAD_ANY_CAST
 _ValueType any_cast(any && __v)
 {
     static_assert(
diff --git a/lib/libcxx/include/experimental/coroutine b/lib/libcxx/include/experimental/coroutine
new file mode 100644
index 00000000000..ce795ad452c
--- /dev/null
+++ b/lib/libcxx/include/experimental/coroutine
@@ -0,0 +1,296 @@
+// -*- C++ -*-
+//===----------------------------- coroutine -----------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXPERIMENTAL_COROUTINE
+#define _LIBCPP_EXPERIMENTAL_COROUTINE
+
+/**
+    experimental/coroutine synopsis
+
+// C++next
+
+namespace std {
+namespace experimental {
+inline namespace coroutines_v1 {
+
+  // 18.11.1 coroutine traits
+template <typename R, typename... ArgTypes>
+class coroutine_traits;
+// 18.11.2 coroutine handle
+template <typename Promise = void>
+class coroutine_handle;
+// 18.11.2.7 comparison operators:
+bool operator==(coroutine_handle<> x, coroutine_handle<> y) _NOEXCEPT;
+bool operator!=(coroutine_handle<> x, coroutine_handle<> y) _NOEXCEPT;
+bool operator<(coroutine_handle<> x, coroutine_handle<> y) _NOEXCEPT;
+bool operator<=(coroutine_handle<> x, coroutine_handle<> y) _NOEXCEPT;
+bool operator>=(coroutine_handle<> x, coroutine_handle<> y) _NOEXCEPT;
+bool operator>(coroutine_handle<> x, coroutine_handle<> y) _NOEXCEPT;
+// 18.11.3 trivial awaitables
+struct suspend_never;
+struct suspend_always;
+// 18.11.2.8 hash support:
+template <class T> struct hash;
+template <class P> struct hash<coroutine_handle<P>>;
+
+} // namespace coroutines_v1
+} // namespace experimental
+} // namespace std
+
+ */
+
+#include <experimental/__config>
+#include <new>
+#include <type_traits>
+#include <functional>
+#include <memory> // for hash<T*>
+#include <cstddef>
+#include <cassert>
+#include <__debug>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+#ifdef _LIBCPP_HAS_NO_COROUTINES
+# if defined(_LIBCPP_WARNING)
+    _LIBCPP_WARNING("<experimental/coroutine> cannot be used with this compiler")
+# else
+#   warning <experimental/coroutine> cannot be used with this compiler
+# endif
+#endif
+
+#ifndef _LIBCPP_HAS_NO_COROUTINES
+
+_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL_COROUTINES
+
+template <class _Tp, class = void>
+struct __coroutine_traits_sfinae {};
+
+template <class _Tp>
+struct __coroutine_traits_sfinae<
+    _Tp, typename __void_t<typename _Tp::promise_type>::type>
+{
+  using promise_type = typename _Tp::promise_type;
+};
+
+template <typename _Ret, typename... _Args>
+struct _LIBCPP_TEMPLATE_VIS coroutine_traits
+    : public __coroutine_traits_sfinae<_Ret>
+{
+};
+
+template <typename _Promise = void>
+class _LIBCPP_TEMPLATE_VIS coroutine_handle;
+
+template <>
+class _LIBCPP_TEMPLATE_VIS coroutine_handle<void> {
+public:
+    _LIBCPP_ALWAYS_INLINE
+    _LIBCPP_CONSTEXPR coroutine_handle() _NOEXCEPT : __handle_(nullptr) {}
+
+    _LIBCPP_ALWAYS_INLINE
+    _LIBCPP_CONSTEXPR coroutine_handle(nullptr_t) _NOEXCEPT : __handle_(nullptr) {}
+
+    _LIBCPP_ALWAYS_INLINE
+    coroutine_handle& operator=(nullptr_t) _NOEXCEPT {
+        __handle_ = nullptr;
+        return *this;
+    }
+
+    _LIBCPP_ALWAYS_INLINE
+    _LIBCPP_CONSTEXPR void* address() const _NOEXCEPT { return __handle_; }
+
+    _LIBCPP_ALWAYS_INLINE
+    _LIBCPP_CONSTEXPR explicit operator bool() const _NOEXCEPT { return __handle_; }
+
+    _LIBCPP_ALWAYS_INLINE
+    void operator()() { resume(); }
+
+    _LIBCPP_ALWAYS_INLINE
+    void resume() {
+      _LIBCPP_ASSERT(__is_suspended(),
+                     "resume() can only be called on suspended coroutines");
+      _LIBCPP_ASSERT(!done(),
+                "resume() has undefined behavior when the coroutine is done");
+      __builtin_coro_resume(__handle_);
+    }
+
+    _LIBCPP_ALWAYS_INLINE
+    void destroy() {
+      _LIBCPP_ASSERT(__is_suspended(),
+                     "destroy() can only be called on suspended coroutines");
+      __builtin_coro_destroy(__handle_);
+    }
+
+    _LIBCPP_ALWAYS_INLINE
+    bool done() const {
+      _LIBCPP_ASSERT(__is_suspended(),
+                     "done() can only be called on suspended coroutines");
+      return __builtin_coro_done(__handle_);
+    }
+
+public:
+    _LIBCPP_ALWAYS_INLINE
+    static coroutine_handle from_address(void* __addr) _NOEXCEPT {
+        coroutine_handle __tmp;
+        __tmp.__handle_ = __addr;
+        return __tmp;
+    }
+
+    // FIXME: Should from_address(nullptr) be allowed?
+    _LIBCPP_ALWAYS_INLINE
+    static coroutine_handle from_address(nullptr_t) _NOEXCEPT {
+      return coroutine_handle(nullptr);
+    }
+
+    template <class _Tp, bool _CallIsValid = false>
+    static coroutine_handle from_address(_Tp*) {
+      static_assert(_CallIsValid,
+       "coroutine_handle<void>::from_address cannot be called with "
+        "non-void pointers");
+    }
+
+private:
+  bool __is_suspended() const _NOEXCEPT  {
+    // FIXME actually implement a check for if the coro is suspended.
+    return __handle_;
+  }
+
+  template <class _PromiseT> friend class coroutine_handle;
+  void* __handle_;
+};
+
+// 18.11.2.7 comparison operators:
+inline _LIBCPP_ALWAYS_INLINE
+bool operator==(coroutine_handle<> __x, coroutine_handle<> __y) _NOEXCEPT {
+    return __x.address() == __y.address();
+}
+inline _LIBCPP_ALWAYS_INLINE
+bool operator!=(coroutine_handle<> __x, coroutine_handle<> __y) _NOEXCEPT {
+    return !(__x == __y);
+}
+inline _LIBCPP_ALWAYS_INLINE
+bool operator<(coroutine_handle<> __x, coroutine_handle<> __y) _NOEXCEPT {
+    return less<void*>()(__x.address(), __y.address());
+}
+inline _LIBCPP_ALWAYS_INLINE
+bool operator>(coroutine_handle<> __x, coroutine_handle<> __y) _NOEXCEPT {
+    return __y < __x;
+}
+inline _LIBCPP_ALWAYS_INLINE
+bool operator<=(coroutine_handle<> __x, coroutine_handle<> __y) _NOEXCEPT {
+    return !(__x > __y);
+}
+inline _LIBCPP_ALWAYS_INLINE
+bool operator>=(coroutine_handle<> __x, coroutine_handle<> __y) _NOEXCEPT {
+    return !(__x < __y);
+}
+
+template <typename _Promise>
+class _LIBCPP_TEMPLATE_VIS coroutine_handle : public coroutine_handle<> {
+    using _Base = coroutine_handle<>;
+public:
+#ifndef _LIBCPP_CXX03_LANG
+    // 18.11.2.1 construct/reset
+    using coroutine_handle<>::coroutine_handle;
+#else
+    _LIBCPP_ALWAYS_INLINE coroutine_handle() _NOEXCEPT : _Base() {}
+    _LIBCPP_ALWAYS_INLINE coroutine_handle(nullptr_t) _NOEXCEPT : _Base(nullptr) {}
+#endif
+    _LIBCPP_INLINE_VISIBILITY
+    coroutine_handle& operator=(nullptr_t) _NOEXCEPT {
+        _Base::operator=(nullptr);
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    _Promise& promise() const {
+        return *reinterpret_cast<_Promise*>(
+            __builtin_coro_promise(this->__handle_, __alignof(_Promise), false));
+    }
+
+public:
+    _LIBCPP_ALWAYS_INLINE
+    static coroutine_handle from_address(void* __addr) _NOEXCEPT {
+        coroutine_handle __tmp;
+        __tmp.__handle_ = __addr;
+        return __tmp;
+    }
+
+    // NOTE: this overload isn't required by the standard but is needed so
+    // the deleted _Promise* overload doesn't make from_address(nullptr)
+    // ambiguous.
+    // FIXME: should from_address work with nullptr?
+    _LIBCPP_ALWAYS_INLINE
+    static coroutine_handle from_address(nullptr_t) _NOEXCEPT {
+      return coroutine_handle(nullptr);
+    }
+
+    template <class _Tp, bool _CallIsValid = false>
+    static coroutine_handle from_address(_Tp*) {
+      static_assert(_CallIsValid,
+       "coroutine_handle<promise_type>::from_address cannot be called with "
+        "non-void pointers");
+    }
+
+    template <bool _CallIsValid = false>
+    static coroutine_handle from_address(_Promise*) {
+      static_assert(_CallIsValid,
+       "coroutine_handle<promise_type>::from_address cannot be used with "
+        "pointers to the coroutine's promise type; use 'from_promise' instead");
+    }
+
+    _LIBCPP_ALWAYS_INLINE
+    static coroutine_handle from_promise(_Promise& __promise) _NOEXCEPT {
+        typedef typename remove_cv<_Promise>::type _RawPromise;
+        coroutine_handle __tmp;
+        __tmp.__handle_ = __builtin_coro_promise(
+            _VSTD::addressof(const_cast<_RawPromise&>(__promise)),
+             __alignof(_Promise), true);
+        return __tmp;
+    }
+};
+
+struct _LIBCPP_TYPE_VIS suspend_never {
+  _LIBCPP_ALWAYS_INLINE
+  bool await_ready() const _NOEXCEPT { return true; }
+  _LIBCPP_ALWAYS_INLINE
+  void await_suspend(coroutine_handle<>) const _NOEXCEPT {}
+  _LIBCPP_ALWAYS_INLINE
+  void await_resume() const _NOEXCEPT {}
+};
+
+struct _LIBCPP_TYPE_VIS suspend_always {
+  _LIBCPP_ALWAYS_INLINE
+  bool await_ready() const _NOEXCEPT { return false; }
+  _LIBCPP_ALWAYS_INLINE
+  void await_suspend(coroutine_handle<>) const _NOEXCEPT {}
+  _LIBCPP_ALWAYS_INLINE
+  void await_resume() const _NOEXCEPT {}
+};
+
+_LIBCPP_END_NAMESPACE_EXPERIMENTAL_COROUTINES
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template <class _Tp>
+struct hash<_VSTD_CORO::coroutine_handle<_Tp> > {
+    using __arg_type = _VSTD_CORO::coroutine_handle<_Tp>;
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(__arg_type const& __v) const _NOEXCEPT
+    {return hash<void*>()(__v.address());}
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // !defined(_LIBCPP_HAS_NO_COROUTINES)
+
+#endif /* _LIBCPP_EXPERIMENTAL_COROUTINE */
diff --git a/lib/libcxx/include/experimental/dynarray b/lib/libcxx/include/experimental/dynarray
index 4a06908e11b..16193317ad2 100644
--- a/lib/libcxx/include/experimental/dynarray
+++ b/lib/libcxx/include/experimental/dynarray
@@ -11,9 +11,6 @@
 #ifndef _LIBCPP_DYNARRAY
 #define _LIBCPP_DYNARRAY
 
-#include <__config>
-#if _LIBCPP_STD_VER > 11
-
 /*
     dynarray synopsis
 
@@ -96,6 +93,8 @@ public:
 }}  // std::experimental
 
 */
+#include <__config>
+#if _LIBCPP_STD_VER > 11
 
 #include <__functional_base>
 #include <iterator>
@@ -104,20 +103,17 @@ public:
 #include <new>
 #include <algorithm>
 
-#include <__undef___deallocate>
-
-#if defined(_LIBCPP_NO_EXCEPTIONS)
-    #include <cassert>
-#endif
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 namespace std { namespace experimental { inline namespace __array_extensions_v1 {
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY dynarray
+struct _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_DYNARRAY dynarray
 {
 public:
     // types:
@@ -142,19 +138,14 @@ private:
     static inline _LIBCPP_INLINE_VISIBILITY value_type* __allocate ( size_t count )
     {
         if ( numeric_limits<size_t>::max() / sizeof (value_type) <= count )
-        {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-            throw bad_array_length();
-#else
-            assert(!"dynarray::allocation");
-#endif
-        }
+            __throw_bad_array_length();
+
         return static_cast<value_type *> (_VSTD::__allocate (sizeof(value_type) * count));
     }
 
-    static inline _LIBCPP_INLINE_VISIBILITY void __deallocate ( value_type* __ptr ) noexcept
+    static inline _LIBCPP_INLINE_VISIBILITY void __deallocate_value( value_type* __ptr ) noexcept
     {
-        _VSTD::__deallocate (static_cast<void *> (__ptr));
+        _VSTD::__libcpp_deallocate (static_cast<void *> (__ptr));
     }
 
 public:
@@ -274,7 +265,7 @@ dynarray<_Tp>::~dynarray()
     value_type *__data = data () + __size_;
     for ( size_t i = 0; i < __size_; ++i )
         (--__data)->value_type::~value_type();
-    __deallocate ( __base_ );
+    __deallocate_value( __base_ );
 }
 
 template <class _Tp>
@@ -283,13 +274,8 @@ typename dynarray<_Tp>::reference
 dynarray<_Tp>::at(size_type __n)
 {
     if (__n >= __size_)
-    {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw out_of_range("dynarray::at");
-#else
-        assert(!"dynarray::at out_of_range");
-#endif
-    }
+        __throw_out_of_range("dynarray::at");
+
     return data()[__n];
 }
 
@@ -299,13 +285,8 @@ typename dynarray<_Tp>::const_reference
 dynarray<_Tp>::at(size_type __n) const
 {
     if (__n >= __size_)
-    {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw out_of_range("dynarray::at");
-#else
-        assert(!"dynarray::at out_of_range");
-#endif
-    }
+        __throw_out_of_range("dynarray::at");
+
     return data()[__n];
 }
 
@@ -314,8 +295,10 @@ dynarray<_Tp>::at(size_type __n) const
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 template <class _Tp, class _Alloc>
-struct _LIBCPP_TYPE_VIS_ONLY uses_allocator<std::experimental::dynarray<_Tp>, _Alloc> : true_type {};
+struct _LIBCPP_TEMPLATE_VIS uses_allocator<std::experimental::dynarray<_Tp>, _Alloc> : true_type {};
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // if _LIBCPP_STD_VER > 11 
 #endif  // _LIBCPP_DYNARRAY
diff --git a/lib/libcxx/include/experimental/filesystem b/lib/libcxx/include/experimental/filesystem
index 7de93fdf8f1..674490f6038 100644
--- a/lib/libcxx/include/experimental/filesystem
+++ b/lib/libcxx/include/experimental/filesystem
@@ -81,10 +81,10 @@
     path canonical(const path& p, const path& base, error_code& ec);
 
     void copy(const path& from, const path& to);
-    void copy(const path& from, const path& to, error_code& ec) _NOEXCEPT;
+    void copy(const path& from, const path& to, error_code& ec);
     void copy(const path& from, const path& to, copy_options options);
     void copy(const path& from, const path& to, copy_options options,
-                   error_code& ec) _NOEXCEPT;
+                   error_code& ec);
 
     bool copy_file(const path& from, const path& to);
     bool copy_file(const path& from, const path& to, error_code& ec) _NOEXCEPT;
@@ -228,7 +228,7 @@
 #include <system_error>
 #include <utility>
 #include <iomanip> // for quoted
-#include <experimental/string_view>
+#include <string_view>
 
 #include <__debug>
 
@@ -249,7 +249,7 @@ struct _LIBCPP_TYPE_VIS space_info
   uintmax_t available;
 };
 
-enum class _LIBCPP_TYPE_VIS file_type : signed char
+enum class _LIBCPP_ENUM_VIS file_type : signed char
 {
     none       = 0,
     not_found  = -1,
@@ -263,7 +263,7 @@ enum class _LIBCPP_TYPE_VIS file_type : signed char
     unknown    = 8
 };
 
-enum class _LIBCPP_TYPE_VIS perms : unsigned
+enum class _LIBCPP_ENUM_VIS perms : unsigned
 {
     none         = 0,
 
@@ -323,7 +323,7 @@ _LIBCPP_INLINE_VISIBILITY
 inline perms& operator^=(perms& _LHS, perms _RHS)
 { return _LHS = _LHS ^ _RHS; }
 
-enum class _LIBCPP_TYPE_VIS copy_options : unsigned short
+enum class _LIBCPP_ENUM_VIS copy_options : unsigned short
 {
     none               = 0,
     skip_existing      = 1,
@@ -367,7 +367,7 @@ inline copy_options& operator^=(copy_options& _LHS, copy_options _RHS)
 { return _LHS = _LHS ^ _RHS; }
 
 
-enum class directory_options : unsigned char
+enum class _LIBCPP_ENUM_VIS directory_options : unsigned char
 {
     none                     = 0,
     follow_directory_symlink = 1,
@@ -408,8 +408,10 @@ class _LIBCPP_TYPE_VIS file_status
 public:
     // constructors
     _LIBCPP_INLINE_VISIBILITY
-    explicit file_status(file_type __ft = file_type::none,
-                         perms __prms   = perms::unknown) _NOEXCEPT
+    file_status() _NOEXCEPT : file_status(file_type::none) {}
+    _LIBCPP_INLINE_VISIBILITY
+    explicit file_status(file_type __ft,
+                         perms __prms = perms::unknown) _NOEXCEPT
       : __ft_(__ft), __prms_(__prms)
     {}
 
@@ -453,6 +455,9 @@ class _LIBCPP_TYPE_VIS directory_entry;
 template <class _Tp> struct __can_convert_char {
   static const bool value = false;
 };
+template <class _Tp> struct __can_convert_char<const _Tp>
+    : public __can_convert_char<_Tp> {
+};
 template <> struct __can_convert_char<char> {
     static const bool value = true;
     using __char_type = char;
@@ -498,6 +503,21 @@ struct __is_pathable_string<basic_string<_ECharT, _Traits, _Alloc>,
     }
 };
 
+
+template <class _ECharT, class _Traits>
+struct __is_pathable_string<basic_string_view<_ECharT, _Traits>,
+                            _Void<typename __can_convert_char<_ECharT>::__char_type>>
+: public __can_convert_char<_ECharT>
+{
+    using _Str = basic_string_view<_ECharT, _Traits>;
+    using _Base = __can_convert_char<_ECharT>;
+    static _ECharT const* __range_begin(_Str const& __s) { return __s.data(); }
+    static _ECharT const* __range_end(_Str const& __s) { return __s.data() + __s.length(); }
+    static _ECharT __first_or_null(_Str const& __s) {
+        return __s.empty() ? _ECharT{} : __s[0];
+    }
+};
+
 template <class _Source,
           class _DS = typename decay<_Source>::type,
           class _UnqualPtrType = typename remove_const<
@@ -605,13 +625,23 @@ struct _PathCVT {
 
 template <>
 struct _PathCVT<char> {
+
     template <class _Iter>
-    static void __append_range(string& __dest, _Iter __b, _Iter __e) {
+    static typename enable_if<
+        __is_exactly_input_iterator<_Iter>::value
+    >::type __append_range(string& __dest, _Iter __b, _Iter __e) {
         for (; __b != __e; ++__b)
             __dest.push_back(*__b);
     }
 
     template <class _Iter>
+    static typename enable_if<
+        __is_forward_iterator<_Iter>::value
+    >::type __append_range(string& __dest, _Iter __b, _Iter __e) {
+        __dest.__append_forward_unsafe(__b, __e);
+    }
+
+    template <class _Iter>
     static void __append_range(string& __dest, _Iter __b, _NullSentinal) {
         const char __sentinal = char{};
         for (; *__b != __sentinal; ++__b)
@@ -622,7 +652,8 @@ struct _PathCVT<char> {
     static void __append_source(string& __dest, _Source const& __s)
     {
         using _Traits = __is_pathable<_Source>;
-        __append_range(__dest, _Traits::__range_begin(__s), _Traits::__range_end(__s));
+        __append_range(__dest, _Traits::__range_begin(__s),
+                               _Traits::__range_end(__s));
     }
 };
 
@@ -642,6 +673,7 @@ class _LIBCPP_TYPE_VIS path
 public:
     typedef char value_type;
     typedef basic_string<value_type> string_type;
+    typedef _VSTD::string_view __string_view;
     static _LIBCPP_CONSTEXPR value_type preferred_separator = '/';
 
     // constructors and destructor
@@ -690,6 +722,7 @@ public:
         return *this;
     }
 
+    template <class = void>
     _LIBCPP_INLINE_VISIBILITY
     path& operator=(string_type&& __s) _NOEXCEPT {
         __pn_ = _VSTD::move(__s);
@@ -740,6 +773,8 @@ private:
 public:
     // appends
     path& operator/=(const path& __p) {
+        _LIBCPP_ASSERT(!__p.has_root_name(),
+                      "cannot append to a path with a root name");
         __append_sep_if_needed(__p.empty() ? char{} : __p.__pn_[0]);
         __pn_ += __p.native();
         return *this;
@@ -788,6 +823,12 @@ public:
     }
 
     _LIBCPP_INLINE_VISIBILITY
+    path& operator+=(__string_view __x) {
+        __pn_ += __x;
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
     path& operator+=(const value_type* __x) {
         __pn_ += __x;
         return *this;
@@ -799,7 +840,6 @@ public:
         return *this;
     }
 
-
     template <class _ECharT>
     typename enable_if<__can_convert_char<_ECharT>::value, path&>::type
     operator+=(_ECharT __x)
@@ -837,7 +877,15 @@ public:
     }
 
     path& make_preferred() { return *this; }
-    path& remove_filename() { return *this = parent_path(); }
+
+    _LIBCPP_INLINE_VISIBILITY
+    path& remove_filename() {
+      if (__pn_.size() == __root_path_raw().size())
+        clear();
+      else
+        __pn_ = __parent_path();
+      return *this;
+    }
 
     path& replace_filename(const path& __replacement) {
         remove_filename();
@@ -896,37 +944,40 @@ public:
     std::u32string generic_u32string() const { return string<char32_t>(); }
 
 private:
-    _LIBCPP_FUNC_VIS int __compare(const value_type*) const;
-    _LIBCPP_FUNC_VIS string_view __root_name() const;
-    _LIBCPP_FUNC_VIS string_view __root_directory() const;
-    _LIBCPP_FUNC_VIS string_view __relative_path() const;
-    _LIBCPP_FUNC_VIS string_view __parent_path() const;
-    _LIBCPP_FUNC_VIS string_view __filename() const;
-    _LIBCPP_FUNC_VIS string_view __stem() const;
-    _LIBCPP_FUNC_VIS string_view __extension() const;
+    int __compare(__string_view) const;
+    __string_view __root_name() const;
+    __string_view __root_directory() const;
+    __string_view __root_path_raw() const;
+    __string_view __relative_path() const;
+    __string_view __parent_path() const;
+    __string_view __filename() const;
+    __string_view __stem() const;
+    __string_view __extension() const;
 
 public:
     // compare
-    _LIBCPP_INLINE_VISIBILITY int compare(const path& __p) const _NOEXCEPT { return __compare(__p.c_str());}
-    _LIBCPP_INLINE_VISIBILITY int compare(const string_type& __s) const { return __compare(__s.c_str()); }
+    _LIBCPP_INLINE_VISIBILITY int compare(const path& __p) const _NOEXCEPT { return __compare(__p.__pn_);}
+    _LIBCPP_INLINE_VISIBILITY int compare(const string_type& __s) const { return __compare(__s); }
+    _LIBCPP_INLINE_VISIBILITY int compare(__string_view __s) const { return __compare(__s); }
     _LIBCPP_INLINE_VISIBILITY int compare(const value_type* __s) const  { return __compare(__s); }
 
     // decomposition
-    _LIBCPP_INLINE_VISIBILITY path root_name()      const { return  __root_name().to_string(); }
-    _LIBCPP_INLINE_VISIBILITY path root_directory() const { return  __root_directory().to_string(); }
-    _LIBCPP_INLINE_VISIBILITY path root_path()      const { return root_name().append(__root_directory().to_string()); }
-    _LIBCPP_INLINE_VISIBILITY path relative_path()  const { return __relative_path().to_string(); }
-    _LIBCPP_INLINE_VISIBILITY path parent_path()    const { return __parent_path().to_string(); }
-    _LIBCPP_INLINE_VISIBILITY path filename()       const { return __filename().to_string(); }
-    _LIBCPP_INLINE_VISIBILITY path stem()           const { return __stem().to_string();}
-    _LIBCPP_INLINE_VISIBILITY path extension()      const { return __extension().to_string(); }
+    _LIBCPP_INLINE_VISIBILITY path root_name()      const { return  string_type(__root_name()); }
+    _LIBCPP_INLINE_VISIBILITY path root_directory() const { return  string_type(__root_directory()); }
+    _LIBCPP_INLINE_VISIBILITY path root_path()      const { return root_name().append(string_type(__root_directory())); }
+    _LIBCPP_INLINE_VISIBILITY path relative_path()  const { return string_type(__relative_path()); }
+    _LIBCPP_INLINE_VISIBILITY path parent_path()    const { return string_type(__parent_path()); }
+    _LIBCPP_INLINE_VISIBILITY path filename()       const { return string_type(__filename()); }
+    _LIBCPP_INLINE_VISIBILITY path stem()           const { return string_type(__stem());}
+    _LIBCPP_INLINE_VISIBILITY path extension()      const { return string_type(__extension()); }
 
     // query
-    _LIBCPP_INLINE_VISIBILITY bool empty() const _NOEXCEPT { return __pn_.empty(); }
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY 
+    bool empty() const _NOEXCEPT { return __pn_.empty(); }
 
     _LIBCPP_INLINE_VISIBILITY bool has_root_name()      const { return !__root_name().empty(); }
     _LIBCPP_INLINE_VISIBILITY bool has_root_directory() const { return !__root_directory().empty(); }
-    _LIBCPP_INLINE_VISIBILITY bool has_root_path()      const { return !(__root_name().empty() && __root_directory().empty()); }
+    _LIBCPP_INLINE_VISIBILITY bool has_root_path()      const { return !__root_path_raw().empty(); }
     _LIBCPP_INLINE_VISIBILITY bool has_relative_path()  const { return !__relative_path().empty(); }
     _LIBCPP_INLINE_VISIBILITY bool has_parent_path()    const { return !__parent_path().empty(); }
     _LIBCPP_INLINE_VISIBILITY bool has_filename()       const { return !__filename().empty(); }
@@ -940,12 +991,12 @@ public:
     class _LIBCPP_TYPE_VIS iterator;
     typedef iterator const_iterator;
 
-    _LIBCPP_FUNC_VIS iterator begin() const;
-    _LIBCPP_FUNC_VIS iterator end() const;
+    iterator begin() const;
+    iterator end() const;
 
 private:
     inline _LIBCPP_INLINE_VISIBILITY
-    path& __assign_view(string_view const& __s) noexcept { __pn_ = __s.to_string(); return *this; }
+    path& __assign_view(__string_view const& __s) noexcept { __pn_ = string_type(__s); return *this; }
     string_type __pn_;
 };
 
@@ -1041,13 +1092,17 @@ class _LIBCPP_TYPE_VIS path::iterator
 {
 public:
     typedef bidirectional_iterator_tag iterator_category;
+
     typedef path                       value_type;
     typedef std::ptrdiff_t             difference_type;
     typedef const path*                pointer;
     typedef const path&                reference;
+
+    typedef void __stashing_iterator_tag; // See reverse_iterator and __is_stashing_iterator
 public:
     _LIBCPP_INLINE_VISIBILITY
-    iterator() : __elem_(), __path_ptr_(nullptr), __pos_(0) {}
+    iterator() : __stashed_elem_(), __path_ptr_(nullptr),
+                 __entry_(), __state_(__singular) {}
 
     iterator(const iterator&) = default;
     ~iterator() = default;
@@ -1056,16 +1111,20 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     reference operator*() const {
-        return __elem_;
+        return __stashed_elem_;
     }
 
     _LIBCPP_INLINE_VISIBILITY
     pointer operator->() const {
-        return &__elem_;
+        return &__stashed_elem_;
     }
 
     _LIBCPP_INLINE_VISIBILITY
     iterator& operator++() {
+        _LIBCPP_ASSERT(__state_ != __singular,
+                       "attempting to increment a singular iterator");
+        _LIBCPP_ASSERT(__state_ != __at_end,
+                      "attempting to increment the end iterator");
         return __increment();
     }
 
@@ -1078,6 +1137,10 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     iterator& operator--() {
+        _LIBCPP_ASSERT(__state_ != __singular,
+                       "attempting to decrement a singular iterator");
+        _LIBCPP_ASSERT(__entry_.data() != __path_ptr_->native().data(),
+                       "attempting to decrement the begin iterator");
         return __decrement();
     }
 
@@ -1090,20 +1153,26 @@ public:
 
 private:
     friend class path;
+
+    static constexpr unsigned char __singular = 0;
+    static constexpr unsigned char __at_end = 6;
+
+    inline _LIBCPP_INLINE_VISIBILITY
     friend bool operator==(const iterator&, const iterator&);
 
-    _LIBCPP_FUNC_VIS iterator& __increment();
-    _LIBCPP_FUNC_VIS iterator& __decrement();
+    iterator& __increment();
+    iterator& __decrement();
 
-    path __elem_;
+    path __stashed_elem_;
     const path* __path_ptr_;
-    size_t __pos_;
+    path::__string_view __entry_;
+    unsigned char __state_;
 };
 
 inline _LIBCPP_INLINE_VISIBILITY
 bool operator==(const path::iterator& __lhs, const path::iterator& __rhs) {
     return __lhs.__path_ptr_ == __rhs.__path_ptr_ &&
-           __lhs.__pos_      == __rhs.__pos_;
+           __lhs.__entry_.data() == __rhs.__entry_.data();
 }
 
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1143,7 +1212,6 @@ public:
         return __paths_->second;
     }
 
-    _LIBCPP_FUNC_VIS
     ~filesystem_error() override; // key function
 
     // TODO(ericwf): Create a custom error message.
@@ -1154,6 +1222,21 @@ private:
     shared_ptr<_Storage> __paths_;
 };
 
+template <class... _Args>
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+#ifndef _LIBCPP_NO_EXCEPTIONS
+void __throw_filesystem_error(_Args && ...__args)
+{
+    throw filesystem_error(std::forward<_Args>(__args)...);
+}
+#else
+void __throw_filesystem_error(_Args&&...)
+{
+    _VSTD::abort();
+}
+#endif
+
+
 // operational functions
 
 _LIBCPP_FUNC_VIS
@@ -1269,7 +1352,7 @@ void copy(const path& __from, const path& __to) {
 }
 
 inline _LIBCPP_INLINE_VISIBILITY
-void copy(const path& __from, const path& __to, error_code& __ec) _NOEXCEPT {
+void copy(const path& __from, const path& __to, error_code& __ec) {
     __copy(__from, __to, copy_options::none, &__ec);
 }
 
@@ -1280,7 +1363,7 @@ void copy(const path& __from, const path& __to, copy_options __opt) {
 
 inline _LIBCPP_INLINE_VISIBILITY
 void copy(const path& __from, const path& __to,
-          copy_options __opt, error_code& __ec) _NOEXCEPT {
+          copy_options __opt, error_code& __ec) {
     __copy(__from, __to, __opt, &__ec);
 }
 
@@ -1479,7 +1562,7 @@ bool is_empty(const path& __p) {
 }
 
 inline _LIBCPP_INLINE_VISIBILITY
-bool is_empty(const path& __p, error_code& __ec) _NOEXCEPT {
+bool is_empty(const path& __p, error_code& __ec) {
     return __fs_is_empty(__p, &__ec);
 }
 
@@ -1821,12 +1904,12 @@ public:
         : directory_iterator(__p, nullptr, __opts)
     { }
 
-    directory_iterator(const path& __p, error_code& __ec) _NOEXCEPT
+    directory_iterator(const path& __p, error_code& __ec)
         : directory_iterator(__p, &__ec)
     { }
 
     directory_iterator(const path& __p, directory_options __opts,
-                       error_code& __ec) _NOEXCEPT
+                       error_code& __ec)
         : directory_iterator(__p, &__ec, __opts)
     { }
 
@@ -1846,7 +1929,7 @@ public:
 
     const directory_entry& operator*() const {
         _LIBCPP_ASSERT(__imp_, "The end iterator cannot be dereferenced");
-        return __deref();
+        return __dereference();
     }
 
     const directory_entry* operator->() const
@@ -1861,20 +1944,24 @@ public:
         return __p;
     }
 
-    directory_iterator& increment(error_code& __ec) _NOEXCEPT
+    directory_iterator& increment(error_code& __ec)
     { return __increment(&__ec); }
 
 private:
+    inline _LIBCPP_INLINE_VISIBILITY
     friend bool operator==(const directory_iterator& __lhs,
                            const directory_iterator& __rhs) _NOEXCEPT;
 
     // construct the dir_stream
     _LIBCPP_FUNC_VIS
-    directory_iterator(const path&, error_code *, directory_options = directory_options::none);
+    directory_iterator(const path&, error_code *,
+                       directory_options = directory_options::none);
+
     _LIBCPP_FUNC_VIS
     directory_iterator& __increment(error_code * __ec = nullptr);
+
     _LIBCPP_FUNC_VIS
-    const directory_entry& __deref() const;
+    const directory_entry& __dereference() const;
 
 private:
     shared_ptr<__dir_stream> __imp_;
@@ -1927,12 +2014,12 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     recursive_directory_iterator(const path& __p,
-        directory_options __xoptions, error_code& __ec) _NOEXCEPT
+        directory_options __xoptions, error_code& __ec)
         : recursive_directory_iterator(__p, __xoptions, &__ec)
     { }
 
     _LIBCPP_INLINE_VISIBILITY
-    recursive_directory_iterator(const path& __p, error_code& __ec) _NOEXCEPT
+    recursive_directory_iterator(const path& __p, error_code& __ec)
         : recursive_directory_iterator(__p, directory_options::none,  &__ec)
     { }
 
@@ -1957,11 +2044,11 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     const directory_entry& operator*() const
-    { return __deref(); }
+    { return __dereference(); }
 
     _LIBCPP_INLINE_VISIBILITY
     const directory_entry* operator->() const
-    { return &__deref(); }
+    { return &__dereference(); }
 
     recursive_directory_iterator& operator++()
     { return __increment(); }
@@ -1974,7 +2061,7 @@ public:
     }
 
     _LIBCPP_INLINE_VISIBILITY
-    recursive_directory_iterator& increment(error_code& __ec) _NOEXCEPT
+    recursive_directory_iterator& increment(error_code& __ec)
     { return __increment(&__ec); }
 
     _LIBCPP_FUNC_VIS directory_options options() const;
@@ -2000,7 +2087,7 @@ private:
                                  error_code *__ec);
 
     _LIBCPP_FUNC_VIS
-    const directory_entry& __deref() const;
+    const directory_entry& __dereference() const;
 
     _LIBCPP_FUNC_VIS
     bool __try_recursion(error_code* __ec);
@@ -2014,6 +2101,7 @@ private:
     _LIBCPP_FUNC_VIS
     void __pop(error_code* __ec=nullptr);
 
+    inline _LIBCPP_INLINE_VISIBILITY
     friend bool operator==(const recursive_directory_iterator&,
                            const recursive_directory_iterator&) _NOEXCEPT;
 
@@ -2023,9 +2111,9 @@ private:
 };                                     // class recursive_directory_iterator
 
 
-_LIBCPP_INLINE_VISIBILITY
-inline bool operator==(const recursive_directory_iterator& __lhs,
-                        const recursive_directory_iterator& __rhs) _NOEXCEPT
+inline _LIBCPP_INLINE_VISIBILITY
+bool operator==(const recursive_directory_iterator& __lhs,
+                const recursive_directory_iterator& __rhs) _NOEXCEPT
 {
     return __lhs.__imp_ == __rhs.__imp_;
 }
diff --git a/lib/libcxx/include/experimental/functional b/lib/libcxx/include/experimental/functional
index 75fc8e99f35..a136cbb57c8 100644
--- a/lib/libcxx/include/experimental/functional
+++ b/lib/libcxx/include/experimental/functional
@@ -89,21 +89,22 @@ inline namespace fundamentals_v1 {
 
 #include <experimental/__config>
 #include <functional>
-
 #include <algorithm>
 #include <type_traits>
 #include <vector>
 #include <array>
 #include <unordered_map>
 
-#include <__undef_min_max>
-
 #include <__debug>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_LFTS
 
 #if _LIBCPP_STD_VER > 11
@@ -456,4 +457,6 @@ make_boyer_moore_horspool_searcher( _RandomAccessIterator __f, _RandomAccessIter
 
 _LIBCPP_END_NAMESPACE_LFTS
 
+_LIBCPP_POP_MACROS
+
 #endif /* _LIBCPP_EXPERIMENTAL_FUNCTIONAL */
diff --git a/lib/libcxx/include/experimental/iterator b/lib/libcxx/include/experimental/iterator
index da593febe2b..ea672e96631 100644
--- a/lib/libcxx/include/experimental/iterator
+++ b/lib/libcxx/include/experimental/iterator
@@ -75,19 +75,19 @@ public:
     typedef void                                 reference;
 
     ostream_joiner(ostream_type& __os, _Delim&& __d)
-        : __out(_VSTD::addressof(__os)), __delim(_VSTD::move(__d)), __first(true) {}
+        : __output_iter(_VSTD::addressof(__os)), __delim(_VSTD::move(__d)), __first(true) {}
         
     ostream_joiner(ostream_type& __os, const _Delim& __d)
-        : __out(_VSTD::addressof(__os)), __delim(__d), __first(true) {}
+        : __output_iter(_VSTD::addressof(__os)), __delim(__d), __first(true) {}
     
 
     template<typename _Tp>
     ostream_joiner& operator=(const _Tp& __v)
     {
         if (!__first)
-            *__out << __delim;
+            *__output_iter << __delim;
         __first = false;
-        *__out << __v;
+        *__output_iter << __v;
         return *this;
     }
 
@@ -96,7 +96,7 @@ public:
     ostream_joiner& operator++(int) _NOEXCEPT { return *this; }
 
 private:
-    ostream_type*   __out;
+    ostream_type*   __output_iter;
     _Delim          __delim;
     bool            __first;
 };
diff --git a/lib/libcxx/include/experimental/memory_resource b/lib/libcxx/include/experimental/memory_resource
index 9b345210ee5..d101f3e0811 100644
--- a/lib/libcxx/include/experimental/memory_resource
+++ b/lib/libcxx/include/experimental/memory_resource
@@ -82,6 +82,9 @@ namespace pmr {
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 _LIBCPP_BEGIN_NAMESPACE_LFTS_PMR
 
 // Round __s up to next multiple of __a.
@@ -93,7 +96,7 @@ size_t __aligned_allocation_size(size_t __s, size_t __a) _NOEXCEPT
 }
 
 // 8.5, memory.resource
-class _LIBCPP_TYPE_VIS_ONLY memory_resource
+class _LIBCPP_TEMPLATE_VIS memory_resource
 {
     static const size_t __max_align = alignof(max_align_t);
 
@@ -151,7 +154,7 @@ memory_resource * set_default_resource(memory_resource * __new_res) _NOEXCEPT;
 
 // 8.6.1, memory.polymorphic.allocator.overview
 template <class _ValueType>
-class _LIBCPP_TYPE_VIS_ONLY polymorphic_allocator
+class _LIBCPP_TEMPLATE_VIS polymorphic_allocator
 {
 public:
     typedef _ValueType value_type;
@@ -181,10 +184,10 @@ public:
     // 8.6.3, memory.polymorphic.allocator.mem
     _LIBCPP_INLINE_VISIBILITY
     _ValueType* allocate(size_t __n) {
-        if (__n > max_size()) {
-            __libcpp_throw(length_error(
+        if (__n > __max_size()) {
+            __throw_length_error(
                 "std::experimental::pmr::polymorphic_allocator<T>::allocate(size_t n)"
-                " 'n' exceeds maximum supported size"));
+                " 'n' exceeds maximum supported size");
         }
         return static_cast<_ValueType*>(
             __res_->allocate(__n * sizeof(_ValueType), alignof(_ValueType))
@@ -193,7 +196,7 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     void deallocate(_ValueType * __p, size_t __n) _NOEXCEPT {
-        _LIBCPP_ASSERT(__n <= max_size(),
+        _LIBCPP_ASSERT(__n <= __max_size(),
                        "deallocate called for size which exceeds max_size()");
         __res_->deallocate(__p, __n * sizeof(_ValueType), alignof(_ValueType));
     }
@@ -266,10 +269,6 @@ public:
         { __p->~_Tp(); }
 
     _LIBCPP_INLINE_VISIBILITY
-    size_t max_size() const _NOEXCEPT
-        { return numeric_limits<size_t>::max() / sizeof(value_type); }
-
-    _LIBCPP_INLINE_VISIBILITY
     polymorphic_allocator
     select_on_container_copy_construction() const _NOEXCEPT
         { return polymorphic_allocator(); }
@@ -309,6 +308,10 @@ private:
         return _Tup(_VSTD::get<_Idx>(_VSTD::move(__t))..., resource());
     }
 
+    _LIBCPP_INLINE_VISIBILITY
+    size_t __max_size() const _NOEXCEPT
+        { return numeric_limits<size_t>::max() / sizeof(value_type); }
+
     memory_resource * __res_;
 };
 
@@ -334,7 +337,7 @@ bool operator!=(polymorphic_allocator<_Tp> const & __lhs,
 
 // 8.7.1, memory.resource.adaptor.overview
 template <class _CharAlloc>
-class _LIBCPP_TYPE_VIS_ONLY __resource_adaptor_imp
+class _LIBCPP_TEMPLATE_VIS __resource_adaptor_imp
   : public memory_resource
 {
     using _CTraits = allocator_traits<_CharAlloc>;
@@ -383,9 +386,9 @@ protected:
     virtual void * do_allocate(size_t __bytes, size_t)
     {
         if (__bytes > __max_size()) {
-            __libcpp_throw(length_error(
+            __throw_length_error(
                 "std::experimental::pmr::resource_adaptor<T>::do_allocate(size_t bytes, size_t align)"
-                " 'bytes' exceeds maximum supported size"));
+                " 'bytes' exceeds maximum supported size");
         }
         size_t __s = __aligned_allocation_size(__bytes, _MaxAlign) / _MaxAlign;
         return __alloc_.allocate(__s);
@@ -419,4 +422,6 @@ using resource_adaptor = __resource_adaptor_imp<
 
 _LIBCPP_END_NAMESPACE_LFTS_PMR
 
+_LIBCPP_POP_MACROS
+
 #endif /* _LIBCPP_EXPERIMENTAL_MEMORY_RESOURCE */
diff --git a/lib/libcxx/include/experimental/numeric b/lib/libcxx/include/experimental/numeric
new file mode 100644
index 00000000000..d784c08f0fe
--- /dev/null
+++ b/lib/libcxx/include/experimental/numeric
@@ -0,0 +1,119 @@
+// -*- C++ -*-
+//===--------------------------- numeric ----------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXPERIMENTAL_NUMERIC
+#define _LIBCPP_EXPERIMENTAL_NUMERIC
+/*
+    experimental/numeric synopsis
+
+// C++1z
+namespace std {
+namespace experimental {
+inline namespace fundamentals_v2 {
+
+  // 13.1.2, Greatest common divisor
+  template<class M, class N>
+  constexpr common_type_t<M,N> gcd(M m, N n);
+
+  // 13.1.3, Least common multiple
+  template<class M, class N>
+  constexpr common_type_t<M,N> lcm(M m, N n);
+
+} // namespace fundamentals_v2
+} // namespace experimental
+} // namespace std
+
+ */
+
+#include <experimental/__config>
+#include <numeric>
+#include <type_traits>              // is_integral
+#include <limits>                   // numeric_limits
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+#if _LIBCPP_STD_VER > 11
+
+_LIBCPP_BEGIN_NAMESPACE_LFTS_V2
+
+template <typename _Result, typename _Source, bool _IsSigned = is_signed<_Source>::value> struct __abs;
+
+template <typename _Result, typename _Source>
+struct __abs<_Result, _Source, true> {
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    _Result operator()(_Source __t) const noexcept
+    {
+    if (__t >= 0) return __t;
+    if (__t == numeric_limits<_Source>::min()) return -static_cast<_Result>(__t);
+    return -__t;
+    }
+};
+
+template <typename _Result, typename _Source>
+struct __abs<_Result, _Source, false> {
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    _Result operator()(_Source __t) const noexcept { return __t; }
+};
+
+
+template<class _Tp>
+_LIBCPP_CONSTEXPR _LIBCPP_HIDDEN
+inline _Tp __gcd(_Tp __m, _Tp __n)
+{
+    static_assert((!is_signed<_Tp>::value), "" );
+    return __n == 0 ? __m : _VSTD_LFTS_V2::__gcd<_Tp>(__n, __m % __n);
+}
+
+
+template<class _Tp, class _Up>
+_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+common_type_t<_Tp,_Up>
+gcd(_Tp __m, _Up __n)
+{
+    static_assert((is_integral<_Tp>::value && is_integral<_Up>::value), "Arguments to gcd must be integer types");
+    static_assert((!is_same<typename remove_cv<_Tp>::type, bool>::value), "First argument to gcd cannot be bool" );
+    static_assert((!is_same<typename remove_cv<_Up>::type, bool>::value), "Second argument to gcd cannot be bool" );
+    using _Rp = common_type_t<_Tp,_Up>;
+    using _Wp = make_unsigned_t<_Rp>;
+    return static_cast<_Rp>(_VSTD_LFTS_V2::__gcd(
+      static_cast<_Wp>(__abs<_Rp, _Tp>()(__m)),
+      static_cast<_Wp>(__abs<_Rp, _Up>()(__n))));
+}
+
+template<class _Tp, class _Up>
+_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+common_type_t<_Tp,_Up>
+lcm(_Tp __m, _Up __n)
+{
+    static_assert((is_integral<_Tp>::value && is_integral<_Up>::value), "Arguments to lcm must be integer types");
+    static_assert((!is_same<typename remove_cv<_Tp>::type, bool>::value), "First argument to lcm cannot be bool" );
+    static_assert((!is_same<typename remove_cv<_Up>::type, bool>::value), "Second argument to lcm cannot be bool" );
+    if (__m == 0 || __n == 0)
+        return 0;
+
+    using _Rp = common_type_t<_Tp,_Up>;
+    _Rp __val1 = __abs<_Rp, _Tp>()(__m) / _VSTD_LFTS_V2::gcd(__m, __n);
+    _Rp __val2 = __abs<_Rp, _Up>()(__n);
+    _LIBCPP_ASSERT((numeric_limits<_Rp>::max() / __val1 > __val2), "Overflow in lcm");
+    return __val1 * __val2;
+}
+
+_LIBCPP_END_NAMESPACE_LFTS_V2
+
+#endif /* _LIBCPP_STD_VER > 11 */
+
+_LIBCPP_POP_MACROS
+
+#endif /* _LIBCPP_EXPERIMENTAL_NUMERIC */
diff --git a/lib/libcxx/include/experimental/optional b/lib/libcxx/include/experimental/optional
index 3912438ec10..b251748fbf3 100644
--- a/lib/libcxx/include/experimental/optional
+++ b/lib/libcxx/include/experimental/optional
@@ -8,8 +8,8 @@
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef _LIBCPP_OPTIONAL
-#define _LIBCPP_OPTIONAL
+#ifndef _LIBCPP_EXPERIMENTAL_OPTIONAL
+#define _LIBCPP_EXPERIMENTAL_OPTIONAL
 
 /*
     optional synopsis
@@ -143,9 +143,24 @@ namespace std { namespace experimental { inline namespace fundamentals_v1 {
 #include <experimental/__config>
 #include <functional>
 #include <stdexcept>
+#if _LIBCPP_STD_VER > 11
+#include <initializer_list>
+#include <type_traits>
+#include <new>
+#include <__functional_base>
+#include <__debug>
+#endif
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 
 _LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
-class _LIBCPP_EXCEPTION_ABI bad_optional_access
+class _LIBCPP_EXCEPTION_ABI _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS bad_optional_access
     : public std::logic_error
 {
 public:
@@ -160,17 +175,6 @@ _LIBCPP_END_NAMESPACE_EXPERIMENTAL
 
 #if _LIBCPP_STD_VER > 11
 
-#include <initializer_list>
-#include <type_traits>
-#include <new>
-#include <__functional_base>
-#include <__undef_min_max>
-#include <__debug>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
-#endif
-
 _LIBCPP_BEGIN_NAMESPACE_LFTS
 
 struct in_place_t {};
@@ -211,7 +215,7 @@ protected:
         :  __engaged_(__x.__engaged_)
         {
             if (__engaged_)
-                ::new(_VSTD::addressof(__val_)) value_type(__x.__val_);
+                ::new((void*)_VSTD::addressof(__val_)) value_type(__x.__val_);
         }
 
     _LIBCPP_INLINE_VISIBILITY
@@ -220,7 +224,7 @@ protected:
         :  __engaged_(__x.__engaged_)
         {
             if (__engaged_)
-                ::new(_VSTD::addressof(__val_)) value_type(_VSTD::move(__x.__val_));
+                ::new((void*)_VSTD::addressof(__val_)) value_type(_VSTD::move(__x.__val_));
         }
 
     _LIBCPP_INLINE_VISIBILITY
@@ -262,7 +266,7 @@ protected:
         :  __engaged_(__x.__engaged_)
         {
             if (__engaged_)
-                ::new(_VSTD::addressof(__val_)) value_type(__x.__val_);
+                ::new((void*)_VSTD::addressof(__val_)) value_type(__x.__val_);
         }
 
     _LIBCPP_INLINE_VISIBILITY
@@ -271,7 +275,7 @@ protected:
         :  __engaged_(__x.__engaged_)
         {
             if (__engaged_)
-                ::new(_VSTD::addressof(__val_)) value_type(_VSTD::move(__x.__val_));
+                ::new((void*)_VSTD::addressof(__val_)) value_type(_VSTD::move(__x.__val_));
         }
 
     _LIBCPP_INLINE_VISIBILITY
@@ -368,7 +372,7 @@ public:
             if (this->__engaged_)
                 this->__val_.~value_type();
             else
-                ::new(_VSTD::addressof(this->__val_)) value_type(__opt.__val_);
+                ::new((void*)_VSTD::addressof(this->__val_)) value_type(__opt.__val_);
             this->__engaged_ = __opt.__engaged_;
         }
         return *this;
@@ -390,7 +394,8 @@ public:
             if (this->__engaged_)
                 this->__val_.~value_type();
             else
-                ::new(_VSTD::addressof(this->__val_)) value_type(_VSTD::move(__opt.__val_));
+                ::new((void*)_VSTD::addressof(this->__val_))
+                    value_type(_VSTD::move(__opt.__val_));
             this->__engaged_ = __opt.__engaged_;
         }
         return *this;
@@ -412,7 +417,7 @@ public:
             this->__val_ = _VSTD::forward<_Up>(__v);
         else
         {
-            ::new(_VSTD::addressof(this->__val_)) value_type(_VSTD::forward<_Up>(__v));
+            ::new((void*)_VSTD::addressof(this->__val_)) value_type(_VSTD::forward<_Up>(__v));
             this->__engaged_ = true;
         }
         return *this;
@@ -429,7 +434,8 @@ public:
     emplace(_Args&&... __args)
     {
         *this = nullopt;
-        ::new(_VSTD::addressof(this->__val_)) value_type(_VSTD::forward<_Args>(__args)...);
+        ::new((void*)_VSTD::addressof(this->__val_))
+            value_type(_VSTD::forward<_Args>(__args)...);
         this->__engaged_ = true;
     }
 
@@ -444,7 +450,8 @@ public:
     emplace(initializer_list<_Up> __il, _Args&&... __args)
     {
         *this = nullopt;
-        ::new(_VSTD::addressof(this->__val_)) value_type(__il, _VSTD::forward<_Args>(__args)...);
+        ::new((void*)_VSTD::addressof(this->__val_))
+            value_type(__il, _VSTD::forward<_Args>(__args)...);
         this->__engaged_ = true;
     }
 
@@ -464,12 +471,14 @@ public:
         {
             if (this->__engaged_)
             {
-                ::new(_VSTD::addressof(__opt.__val_)) value_type(_VSTD::move(this->__val_));
+                ::new((void*)_VSTD::addressof(__opt.__val_))
+                    value_type(_VSTD::move(this->__val_));
                 this->__val_.~value_type();
             }
             else
             {
-                ::new(_VSTD::addressof(this->__val_)) value_type(_VSTD::move(__opt.__val_));
+                ::new((void*)_VSTD::addressof(this->__val_))
+                    value_type(_VSTD::move(__opt.__val_));
                 __opt.__val_.~value_type();
             }
             swap(this->__engaged_, __opt.__engaged_);
@@ -482,7 +491,11 @@ public:
     operator->() const
     {
         _LIBCPP_ASSERT(this->__engaged_, "optional operator-> called for disengaged value");
+#ifndef _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
+        return __builtin_addressof(this->__val_);
+#else
         return __operator_arrow(__has_operator_addressof<value_type>{});
+#endif
     }
 
     _LIBCPP_INLINE_VISIBILITY
@@ -513,27 +526,32 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     constexpr explicit operator bool() const noexcept {return this->__engaged_;}
 
-    _LIBCPP_INLINE_VISIBILITY
-    constexpr value_type const& value() const
-    {
-        if (!this->__engaged_)
+	_LIBCPP_NORETURN _LIBCPP_INLINE_VISIBILITY 
+#ifndef _LIBCPP_NO_EXCEPTIONS
+_LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS
+#endif
+	constexpr void __throw_bad_optional_access() const
+	{
 #ifndef _LIBCPP_NO_EXCEPTIONS
-            throw bad_optional_access();
+        throw bad_optional_access();
 #else
-            assert(!"bad optional access");
+        _VSTD::abort();
 #endif
+	}
+	
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS
+    constexpr value_type const& value() const
+    {
+        if (!this->__engaged_)
+            __throw_bad_optional_access();
         return this->__val_;
     }
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_AVAILABILITY_BAD_OPTIONAL_ACCESS
     value_type& value()
     {
         if (!this->__engaged_)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-            throw bad_optional_access();
-#else
-            assert(!"bad optional access");
-#endif
+            __throw_bad_optional_access();
         return this->__val_;
     }
 
@@ -710,7 +728,7 @@ template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 constexpr
 bool
-operator<=(nullopt_t, const optional<_Tp>& __x) noexcept
+operator<=(nullopt_t, const optional<_Tp>&) noexcept
 {
     return true;
 }
@@ -728,7 +746,7 @@ template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 constexpr
 bool
-operator>(nullopt_t, const optional<_Tp>& __x) noexcept
+operator>(nullopt_t, const optional<_Tp>&) noexcept
 {
     return false;
 }
@@ -883,7 +901,7 @@ _LIBCPP_END_NAMESPACE_LFTS
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY hash<std::experimental::optional<_Tp> >
+struct _LIBCPP_TEMPLATE_VIS hash<std::experimental::optional<_Tp> >
 {
     typedef std::experimental::optional<_Tp> argument_type;
     typedef size_t        result_type;
@@ -899,4 +917,6 @@ _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_STD_VER > 11
 
-#endif  // _LIBCPP_OPTIONAL
+_LIBCPP_POP_MACROS
+
+#endif  // _LIBCPP_EXPERIMENTAL_OPTIONAL
diff --git a/lib/libcxx/include/experimental/propagate_const b/lib/libcxx/include/experimental/propagate_const
index f267ba275c2..e7f7e9fc683 100644
--- a/lib/libcxx/include/experimental/propagate_const
+++ b/lib/libcxx/include/experimental/propagate_const
@@ -123,8 +123,14 @@ _LIBCPP_BEGIN_NAMESPACE_LFTS_V2
 
 template <class _Tp>
 class propagate_const;
-template <class _Up> _LIBCPP_CONSTEXPR const _Up& get_underlying(const propagate_const<_Up>& __pu) _NOEXCEPT;
-template <class _Up> _LIBCPP_CONSTEXPR _Up& get_underlying(propagate_const<_Up>& __pu) _NOEXCEPT;
+
+template <class _Up>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+const _Up& get_underlying(const propagate_const<_Up>& __pu) _NOEXCEPT;
+
+template <class _Up>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+_Up& get_underlying(propagate_const<_Up>& __pu) _NOEXCEPT;
 
 template <class _Tp>
 class propagate_const
@@ -462,14 +468,12 @@ _LIBCPP_CONSTEXPR void swap(propagate_const<_Tp>& __pc1, propagate_const<_Tp>& _
 }
 
 template <class _Tp>
-_LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR const _Tp& get_underlying(const propagate_const<_Tp>& __pt) _NOEXCEPT
 {
   return __pt.__t_;
 }
 
 template <class _Tp>
-_LIBCPP_INLINE_VISIBILITY
 _LIBCPP_CONSTEXPR _Tp& get_underlying(propagate_const<_Tp>& __pt) _NOEXCEPT
 {
   return __pt.__t_;
diff --git a/lib/libcxx/include/experimental/string_view b/lib/libcxx/include/experimental/string_view
index 0a7239b4c0b..da104f9a121 100644
--- a/lib/libcxx/include/experimental/string_view
+++ b/lib/libcxx/include/experimental/string_view
@@ -189,10 +189,13 @@ namespace std {
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 _LIBCPP_BEGIN_NAMESPACE_LFTS
 
     template<class _CharT, class _Traits = _VSTD::char_traits<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_string_view {
+    class _LIBCPP_TEMPLATE_VIS basic_string_view {
     public:
         // types
         typedef _Traits                                    traits_type;
@@ -281,7 +284,7 @@ _LIBCPP_BEGIN_NAMESPACE_LFTS
         const_reference at(size_type __pos) const
         {
             return __pos >= size()
-                ? (__libcpp_throw(out_of_range("string_view::at")), __data[0])
+                ? (__throw_out_of_range("string_view::at"), __data[0])
                 : __data[__pos];
         }
 
@@ -352,7 +355,7 @@ _LIBCPP_BEGIN_NAMESPACE_LFTS
         size_type copy(_CharT* __s, size_type __n, size_type __pos = 0) const
         {
             if ( __pos > size())
-                __libcpp_throw(out_of_range("string_view::copy"));
+                __throw_out_of_range("string_view::copy");
             size_type __rlen = _VSTD::min( __n, size() - __pos );
             _VSTD::copy_n(begin() + __pos, __rlen, __s );
             return __rlen;
@@ -362,11 +365,11 @@ _LIBCPP_BEGIN_NAMESPACE_LFTS
         basic_string_view substr(size_type __pos = 0, size_type __n = npos) const
         {
 //             if (__pos > size())
-//                 throw out_of_range("string_view::substr");
+//                 __throw_out_of_range("string_view::substr");
 //             size_type __rlen = _VSTD::min( __n, size() - __pos );
 //             return basic_string_view(data() + __pos, __rlen);
             return __pos > size()
-                ? (__libcpp_throw((out_of_range("string_view::substr"))), basic_string_view())
+                ? (__throw_out_of_range("string_view::substr"), basic_string_view())
                 : basic_string_view(data() + __pos, _VSTD::min(__n, size() - __pos));
         }
 
@@ -783,7 +786,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 // [string.view.hash]
 // Shamelessly stolen from <string>
 template<class _CharT, class _Traits>
-struct _LIBCPP_TYPE_VIS_ONLY hash<std::experimental::basic_string_view<_CharT, _Traits> >
+struct _LIBCPP_TEMPLATE_VIS hash<std::experimental::basic_string_view<_CharT, _Traits> >
     : public unary_function<std::experimental::basic_string_view<_CharT, _Traits>, size_t>
 {
     size_t operator()(const std::experimental::basic_string_view<_CharT, _Traits>& __val) const _NOEXCEPT;
@@ -810,4 +813,6 @@ quoted ( std::experimental::basic_string_view <_CharT, _Traits> __sv,
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif // _LIBCPP_LFTS_STRING_VIEW
diff --git a/lib/libcxx/include/experimental/type_traits b/lib/libcxx/include/experimental/type_traits
index ae49fc176c0..3a7593620a7 100644
--- a/lib/libcxx/include/experimental/type_traits
+++ b/lib/libcxx/include/experimental/type_traits
@@ -172,6 +172,45 @@ inline namespace fundamentals_v1 {
   template <class T>
     using raw_invocation_type_t = typename raw_invocation_type<T>::type;
 
+  // 3.3.3, Logical operator traits
+  template<class... B> struct conjunction;
+  template<class... B> constexpr bool conjunction_v = conjunction<B...>::value;
+  template<class... B> struct disjunction;
+  template<class... B> constexpr bool disjunction_v = disjunction<B...>::value;
+  template<class B> struct negation;
+  template<class B> constexpr bool negation_v = negation<B>::value;
+
+  // 3.3.4, Detection idiom
+  template <class...> using void_t = void;
+
+  struct nonesuch {
+    nonesuch() = delete;
+    ~nonesuch() = delete;
+    nonesuch(nonesuch const&) = delete;
+    void operator=(nonesuch const&) = delete;
+  };
+
+  template <template<class...> class Op, class... Args>
+    using is_detected = see below;
+  template <template<class...> class Op, class... Args>
+    constexpr bool is_detected_v = is_detected<Op, Args...>::value;
+  template <template<class...> class Op, class... Args>
+    using detected_t = see below;
+  template <class Default, template<class...> class Op, class... Args>
+    using detected_or = see below;
+  template <class Default, template<class...> class Op, class... Args>
+    using detected_or_t = typename detected_or<Default, Op, Args...>::type;
+  template <class Expected, template<class...> class Op, class... Args>
+    using is_detected_exact = is_same<Expected, detected_t<Op, Args...>>;
+  template <class Expected, template<class...> class Op, class... Args>
+    constexpr bool is_detected_exact_v
+      = is_detected_exact<Expected, Op, Args...>::value;
+  template <class To, template<class...> class Op, class... Args>
+     using is_detected_convertible = is_convertible<detected_t<Op, Args...>, To>;
+  template <class To, template<class...> class Op, class... Args>
+     constexpr bool is_detected_convertible_v
+       = is_detected_convertible<To, Op, Args...>::value;  
+
 } // namespace fundamentals_v1
 } // namespace experimental
 } // namespace std
@@ -402,16 +441,16 @@ template <class _Tp, class _Up> _LIBCPP_CONSTEXPR bool is_convertible_v
 // 3.3.2, Other type transformations
 /*
 template <class>
-class _LIBCPP_TYPE_VIS_ONLY raw_invocation_type;
+class _LIBCPP_TEMPLATE_VIS raw_invocation_type;
 
 template <class _Fn, class ..._Args>
-class _LIBCPP_TYPE_VIS_ONLY raw_invocation_type<_Fn(_Args...)>;
+class _LIBCPP_TEMPLATE_VIS raw_invocation_type<_Fn(_Args...)>;
 
 template <class>
-class _LIBCPP_TYPE_VIS_ONLY invokation_type;
+class _LIBCPP_TEMPLATE_VIS invokation_type;
 
 template <class _Fn, class ..._Args>
-class _LIBCPP_TYPE_VIS_ONLY invokation_type<_Fn(_Args...)>;
+class _LIBCPP_TEMPLATE_VIS invokation_type<_Fn(_Args...)>;
 
 template <class _Tp>
 using invokation_type_t = typename invokation_type<_Tp>::type;
@@ -420,6 +459,70 @@ template <class _Tp>
 using raw_invocation_type_t = typename raw_invocation_type<_Tp>::type;
 */
 
+// 3.3.3, Logical operator traits
+template <class...> using void_t = void;
+
+template <class... _Args>
+struct conjunction : _VSTD::__and_<_Args...> {};
+template <class... _Args>
+_LIBCPP_CONSTEXPR bool conjunction_v = conjunction<_Args...>::value;
+
+template <class... _Args>
+struct disjunction : _VSTD::__or_<_Args...> {};
+template <class... _Args>
+_LIBCPP_CONSTEXPR bool disjunction_v = disjunction<_Args...>::value;
+
+template <class _Tp>
+struct negation : _VSTD::__not_<_Tp> {};
+template<class _Tp>
+_LIBCPP_CONSTEXPR bool negation_v = negation<_Tp>::value;
+
+// 3.3.4, Detection idiom
+template <class...> using void_t = void;
+
+struct nonesuch {
+    nonesuch()  = delete;
+    ~nonesuch() = delete;
+    nonesuch      (nonesuch const&) = delete;
+    void operator=(nonesuch const&) = delete;
+  };
+
+template <class _Default, class _AlwaysVoid, template <class...> class _Op, class... _Args>
+struct _DETECTOR {
+   using value_t = false_type;
+   using type = _Default;
+   };
+
+template <class _Default, template <class...> class _Op, class... _Args>
+struct _DETECTOR<_Default, void_t<_Op<_Args...>>, _Op, _Args...> {
+   using value_t = true_type;
+   using type = _Op<_Args...>;
+   };
+     
+
+template <template<class...> class _Op, class... _Args>
+  using is_detected = typename _DETECTOR<nonesuch, void, _Op, _Args...>::value_t;
+template <template<class...> class _Op, class... _Args>
+  using detected_t = typename _DETECTOR<nonesuch, void, _Op, _Args...>::type;
+template <template<class...> class _Op, class... _Args>
+  _LIBCPP_CONSTEXPR bool is_detected_v = is_detected<_Op, _Args...>::value;
+
+template <class Default, template<class...> class _Op, class... _Args>
+  using detected_or = _DETECTOR<Default, void, _Op, _Args...>;
+template <class Default, template<class...> class _Op, class... _Args>
+  using detected_or_t = typename detected_or<Default, _Op, _Args...>::type;
+
+template <class Expected, template<class...> class _Op, class... _Args>
+  using is_detected_exact = is_same<Expected, detected_t<_Op, _Args...>>;
+template <class Expected, template<class...> class _Op, class... _Args>
+  _LIBCPP_CONSTEXPR bool is_detected_exact_v = is_detected_exact<Expected, _Op, _Args...>::value;
+
+template <class To, template<class...> class _Op, class... _Args>
+  using is_detected_convertible = is_convertible<detected_t<_Op, _Args...>, To>;
+template <class To, template<class...> class _Op, class... _Args>
+  _LIBCPP_CONSTEXPR bool is_detected_convertible_v = is_detected_convertible<To, _Op, _Args...>::value;  
+
+
 _LIBCPP_END_NAMESPACE_LFTS
 
 #endif /* _LIBCPP_STD_VER > 11 */
diff --git a/lib/libcxx/include/experimental/utility b/lib/libcxx/include/experimental/utility
index b5fca6c775b..8effa71c131 100644
--- a/lib/libcxx/include/experimental/utility
+++ b/lib/libcxx/include/experimental/utility
@@ -40,7 +40,7 @@ inline namespace fundamentals_v1 {
 
 _LIBCPP_BEGIN_NAMESPACE_LFTS
 
-  struct _LIBCPP_TYPE_VIS_ONLY erased_type { };
+  struct _LIBCPP_TEMPLATE_VIS erased_type { };
 
 _LIBCPP_END_NAMESPACE_LFTS
 
diff --git a/lib/libcxx/include/ext/__hash b/lib/libcxx/include/ext/__hash
index 5675d54055e..318cb1f97b0 100644
--- a/lib/libcxx/include/ext/__hash
+++ b/lib/libcxx/include/ext/__hash
@@ -19,9 +19,9 @@
 namespace __gnu_cxx {
 using namespace std;
 
-template <typename _Tp> struct _LIBCPP_TYPE_VIS_ONLY hash { };
+template <typename _Tp> struct _LIBCPP_TEMPLATE_VIS hash { };
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY hash<const char*>
+template <> struct _LIBCPP_TEMPLATE_VIS hash<const char*>
     : public unary_function<const char*, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -31,7 +31,7 @@ template <> struct _LIBCPP_TYPE_VIS_ONLY hash<const char*>
     }
 };
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY hash<char *>
+template <> struct _LIBCPP_TEMPLATE_VIS hash<char *>
     : public unary_function<char*, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -41,7 +41,7 @@ template <> struct _LIBCPP_TYPE_VIS_ONLY hash<char *>
     }
 };
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY hash<char>
+template <> struct _LIBCPP_TEMPLATE_VIS hash<char>
     : public unary_function<char, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -51,7 +51,7 @@ template <> struct _LIBCPP_TYPE_VIS_ONLY hash<char>
     }
 };
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY hash<signed char>
+template <> struct _LIBCPP_TEMPLATE_VIS hash<signed char>
     : public unary_function<signed char, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -61,7 +61,7 @@ template <> struct _LIBCPP_TYPE_VIS_ONLY hash<signed char>
     }
 };
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned char>
+template <> struct _LIBCPP_TEMPLATE_VIS hash<unsigned char>
     : public unary_function<unsigned char, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -71,7 +71,7 @@ template <> struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned char>
     }
 };
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY hash<short>
+template <> struct _LIBCPP_TEMPLATE_VIS hash<short>
     : public unary_function<short, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -81,7 +81,7 @@ template <> struct _LIBCPP_TYPE_VIS_ONLY hash<short>
     }
 };
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned short>
+template <> struct _LIBCPP_TEMPLATE_VIS hash<unsigned short>
     : public unary_function<unsigned short, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -91,7 +91,7 @@ template <> struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned short>
     }
 };
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY hash<int>
+template <> struct _LIBCPP_TEMPLATE_VIS hash<int>
     : public unary_function<int, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -101,7 +101,7 @@ template <> struct _LIBCPP_TYPE_VIS_ONLY hash<int>
     }
 };
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned int>
+template <> struct _LIBCPP_TEMPLATE_VIS hash<unsigned int>
     : public unary_function<unsigned int, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -111,7 +111,7 @@ template <> struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned int>
     }
 };
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY hash<long>
+template <> struct _LIBCPP_TEMPLATE_VIS hash<long>
     : public unary_function<long, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -121,7 +121,7 @@ template <> struct _LIBCPP_TYPE_VIS_ONLY hash<long>
     }
 };
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned long>
+template <> struct _LIBCPP_TEMPLATE_VIS hash<unsigned long>
     : public unary_function<unsigned long, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
diff --git a/lib/libcxx/include/ext/hash_map b/lib/libcxx/include/ext/hash_map
index 5e1e9f542b1..998e8f65994 100644
--- a/lib/libcxx/include/ext/hash_map
+++ b/lib/libcxx/include/ext/hash_map
@@ -207,7 +207,7 @@ template <class Key, class T, class Hash, class Pred, class Alloc>
 #include <ext/__hash>
 
 #if __DEPRECATED
-#if defined(_MSC_VER) && ! defined(__clang__)
+#if defined(_LIBCPP_WARNING)
     _LIBCPP_WARNING("Use of the header <ext/hash_map> is deprecated.  Migrate to <unordered_map>")
 #else
 #   warning Use of the header <ext/hash_map> is deprecated.  Migrate to <unordered_map>
@@ -331,7 +331,7 @@ public:
           __second_constructed(false)
         {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     __hash_map_node_destructor(__hash_node_destructor<allocator_type>&& __x)
         : __na_(__x.__na_),
@@ -340,7 +340,7 @@ public:
         {
             __x.__value_constructed = false;
         }
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#else  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     __hash_map_node_destructor(const __hash_node_destructor<allocator_type>& __x)
         : __na_(__x.__na_),
@@ -349,7 +349,7 @@ public:
         {
             const_cast<bool&>(__x.__value_constructed) = false;
         }
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     void operator()(pointer __p)
@@ -364,7 +364,7 @@ public:
 };
 
 template <class _HashIterator>
-class _LIBCPP_TYPE_VIS_ONLY __hash_map_iterator
+class _LIBCPP_TEMPLATE_VIS __hash_map_iterator
 {
     _HashIterator __i_;
 
@@ -401,15 +401,15 @@ public:
     bool operator!=(const __hash_map_iterator& __x, const __hash_map_iterator& __y)
         {return __x.__i_ != __y.__i_;}
 
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY hash_map;
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY hash_multimap;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_const_iterator;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_const_local_iterator;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_map_const_iterator;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS hash_map;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS hash_multimap;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_const_iterator;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_const_local_iterator;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_map_const_iterator;
 };
 
 template <class _HashIterator>
-class _LIBCPP_TYPE_VIS_ONLY __hash_map_const_iterator
+class _LIBCPP_TEMPLATE_VIS __hash_map_const_iterator
 {
     _HashIterator __i_;
 
@@ -454,15 +454,15 @@ public:
     bool operator!=(const __hash_map_const_iterator& __x, const __hash_map_const_iterator& __y)
         {return __x.__i_ != __y.__i_;}
 
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY hash_map;
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY hash_multimap;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_const_iterator;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_const_local_iterator;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS hash_map;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS hash_multimap;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_const_iterator;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_const_local_iterator;
 };
 
 template <class _Key, class _Tp, class _Hash = hash<_Key>, class _Pred = equal_to<_Key>,
           class _Alloc = allocator<pair<const _Key, _Tp> > >
-class _LIBCPP_TYPE_VIS_ONLY hash_map
+class _LIBCPP_TEMPLATE_VIS hash_map
 {
 public:
     // types
@@ -736,7 +736,7 @@ operator!=(const hash_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
 
 template <class _Key, class _Tp, class _Hash = hash<_Key>, class _Pred = equal_to<_Key>,
           class _Alloc = allocator<pair<const _Key, _Tp> > >
-class _LIBCPP_TYPE_VIS_ONLY hash_multimap
+class _LIBCPP_TEMPLATE_VIS hash_multimap
 {
 public:
     // types
diff --git a/lib/libcxx/include/ext/hash_set b/lib/libcxx/include/ext/hash_set
index 91850b566d5..38f81ed3b5c 100644
--- a/lib/libcxx/include/ext/hash_set
+++ b/lib/libcxx/include/ext/hash_set
@@ -199,7 +199,7 @@ template <class Value, class Hash, class Pred, class Alloc>
 #include <ext/__hash>
 
 #if __DEPRECATED
-#if defined(_MSC_VER) && ! defined(__clang__)
+#if defined(_LIBCPP_WARNING)
     _LIBCPP_WARNING("Use of the header <ext/hash_set> is deprecated.  Migrate to <unordered_set>")
 #else
 #   warning Use of the header <ext/hash_set> is deprecated.  Migrate to <unordered_set>
@@ -212,7 +212,7 @@ using namespace std;
 
 template <class _Value, class _Hash = hash<_Value>, class _Pred = equal_to<_Value>,
           class _Alloc = allocator<_Value> >
-class _LIBCPP_TYPE_VIS_ONLY hash_set
+class _LIBCPP_TEMPLATE_VIS hash_set
 {
 public:
     // types
@@ -434,7 +434,7 @@ operator!=(const hash_set<_Value, _Hash, _Pred, _Alloc>& __x,
 
 template <class _Value, class _Hash = hash<_Value>, class _Pred = equal_to<_Value>,
           class _Alloc = allocator<_Value> >
-class _LIBCPP_TYPE_VIS_ONLY hash_multiset
+class _LIBCPP_TEMPLATE_VIS hash_multiset
 {
 public:
     // types
diff --git a/lib/libcxx/include/forward_list b/lib/libcxx/include/forward_list
index 18b300d8470..7b820413720 100644
--- a/lib/libcxx/include/forward_list
+++ b/lib/libcxx/include/forward_list
@@ -87,7 +87,7 @@ public:
     reference       front();
     const_reference front() const;
 
-    template <class... Args> void emplace_front(Args&&... args);
+    template <class... Args> reference emplace_front(Args&&... args);  // reference in C++17
     void push_front(const value_type& v);
     void push_front(value_type&& v);
 
@@ -167,19 +167,20 @@ template <class T, class Allocator>
 */
 
 #include <__config>
-
 #include <initializer_list>
 #include <memory>
 #include <limits>
 #include <iterator>
 #include <algorithm>
 
-#include <__undef_min_max>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Tp, class _VoidPtr> struct __forward_list_node;
@@ -266,11 +267,11 @@ struct __forward_list_node
 };
 
 
-template <class _Tp, class _Alloc = allocator<_Tp> > class _LIBCPP_TYPE_VIS_ONLY forward_list;
-template<class _NodeConstPtr> class _LIBCPP_TYPE_VIS_ONLY __forward_list_const_iterator;
+template <class _Tp, class _Alloc = allocator<_Tp> > class _LIBCPP_TEMPLATE_VIS forward_list;
+template<class _NodeConstPtr> class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator;
 
 template <class _NodePtr>
-class _LIBCPP_TYPE_VIS_ONLY __forward_list_iterator
+class _LIBCPP_TEMPLATE_VIS __forward_list_iterator
 {
     typedef __forward_node_traits<_NodePtr>         __traits;
     typedef typename __traits::__node_pointer       __node_pointer;
@@ -302,8 +303,8 @@ class _LIBCPP_TYPE_VIS_ONLY __forward_list_iterator
     explicit __forward_list_iterator(__node_pointer __p) _NOEXCEPT
         : __ptr_(__traits::__as_iter_node(__p)) {}
 
-    template<class, class> friend class _LIBCPP_TYPE_VIS_ONLY forward_list;
-    template<class> friend class _LIBCPP_TYPE_VIS_ONLY __forward_list_const_iterator;
+    template<class, class> friend class _LIBCPP_TEMPLATE_VIS forward_list;
+    template<class> friend class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator;
 
 public:
     typedef forward_iterator_tag                              iterator_category;
@@ -348,7 +349,7 @@ public:
 };
 
 template <class _NodeConstPtr>
-class _LIBCPP_TYPE_VIS_ONLY __forward_list_const_iterator
+class _LIBCPP_TEMPLATE_VIS __forward_list_const_iterator
 {
     static_assert((!is_const<typename pointer_traits<_NodeConstPtr>::element_type>::value), "");
     typedef _NodeConstPtr _NodePtr;
@@ -478,14 +479,14 @@ protected:
     __forward_list_base(const allocator_type& __a)
         : __before_begin_(__begin_node(), __node_allocator(__a)) {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 public:
     _LIBCPP_INLINE_VISIBILITY
     __forward_list_base(__forward_list_base&& __x)
         _NOEXCEPT_(is_nothrow_move_constructible<__node_allocator>::value);
     _LIBCPP_INLINE_VISIBILITY
     __forward_list_base(__forward_list_base&& __x, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 private:
     __forward_list_base(const __forward_list_base&);
@@ -531,7 +532,7 @@ private:
     }
 
     _LIBCPP_INLINE_VISIBILITY
-    void __move_assign_alloc(__forward_list_base& __x, false_type) _NOEXCEPT
+    void __move_assign_alloc(__forward_list_base&, false_type) _NOEXCEPT
         {}
     _LIBCPP_INLINE_VISIBILITY
     void __move_assign_alloc(__forward_list_base& __x, true_type)
@@ -539,7 +540,7 @@ private:
         {__alloc() = _VSTD::move(__x.__alloc());}
 };
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Alloc>
 inline
@@ -563,7 +564,7 @@ __forward_list_base<_Tp, _Alloc>::__forward_list_base(__forward_list_base&& __x,
     }
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Alloc>
 __forward_list_base<_Tp, _Alloc>::~__forward_list_base()
@@ -604,7 +605,7 @@ __forward_list_base<_Tp, _Alloc>::clear() _NOEXCEPT
 }
 
 template <class _Tp, class _Alloc /*= allocator<_Tp>*/>
-class _LIBCPP_TYPE_VIS_ONLY forward_list
+class _LIBCPP_TEMPLATE_VIS forward_list
     : private __forward_list_base<_Tp, _Alloc>
 {
     typedef __forward_list_base<_Tp, _Alloc> base;
@@ -656,32 +657,33 @@ public:
                      >::type* = nullptr);
     forward_list(const forward_list& __x);
     forward_list(const forward_list& __x, const allocator_type& __a);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
+    forward_list& operator=(const forward_list& __x);
+
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     forward_list(forward_list&& __x)
         _NOEXCEPT_(is_nothrow_move_constructible<base>::value)
         : base(_VSTD::move(__x)) {}
     forward_list(forward_list&& __x, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
     forward_list(initializer_list<value_type> __il);
     forward_list(initializer_list<value_type> __il, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
-    // ~forward_list() = default;
-
-    forward_list& operator=(const forward_list& __x);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     forward_list& operator=(forward_list&& __x)
         _NOEXCEPT_(
              __node_traits::propagate_on_container_move_assignment::value &&
              is_nothrow_move_assignable<allocator_type>::value);
-#endif
-#ifndef  _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
     _LIBCPP_INLINE_VISIBILITY
     forward_list& operator=(initializer_list<value_type> __il);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
+    _LIBCPP_INLINE_VISIBILITY
+    void assign(initializer_list<value_type> __il);
+#endif  // _LIBCPP_CXX03_LANG
+
+    // ~forward_list() = default;
 
     template <class _InputIterator>
         typename enable_if
@@ -691,10 +693,6 @@ public:
         >::type
         assign(_InputIterator __f, _InputIterator __l);
     void assign(size_type __n, const value_type& __v);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-    _LIBCPP_INLINE_VISIBILITY
-    void assign(initializer_list<value_type> __il);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
     _LIBCPP_INLINE_VISIBILITY
     allocator_type get_allocator() const _NOEXCEPT
@@ -730,35 +728,41 @@ public:
     const_iterator cbefore_begin() const _NOEXCEPT
         {return const_iterator(base::__before_begin());}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool empty() const _NOEXCEPT
         {return base::__before_begin()->__next_ == nullptr;}
     _LIBCPP_INLINE_VISIBILITY
-    size_type max_size() const _NOEXCEPT
-        {return numeric_limits<size_type>::max();}
+    size_type max_size() const _NOEXCEPT {
+        return std::min<size_type>(
+            __node_traits::max_size(base::__alloc()),
+            numeric_limits<difference_type>::max());
+    }
 
     _LIBCPP_INLINE_VISIBILITY
     reference       front()       {return base::__before_begin()->__next_->__value_;}
     _LIBCPP_INLINE_VISIBILITY
     const_reference front() const {return base::__before_begin()->__next_->__value_;}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-    template <class... _Args> void emplace_front(_Args&&... __args);
+#ifndef _LIBCPP_CXX03_LANG
+#if _LIBCPP_STD_VER > 14
+    template <class... _Args> reference emplace_front(_Args&&... __args);
+#else
+    template <class... _Args> void      emplace_front(_Args&&... __args);
 #endif
     void push_front(value_type&& __v);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     void push_front(const value_type& __v);
 
     void pop_front();
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
     template <class... _Args>
         iterator emplace_after(const_iterator __p, _Args&&... __args);
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+
     iterator insert_after(const_iterator __p, value_type&& __v);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+    iterator insert_after(const_iterator __p, initializer_list<value_type> __il)
+        {return insert_after(__p, __il.begin(), __il.end());}
+#endif  // _LIBCPP_CXX03_LANG
     iterator insert_after(const_iterator __p, const value_type& __v);
     iterator insert_after(const_iterator __p, size_type __n, const value_type& __v);
     template <class _InputIterator>
@@ -769,10 +773,6 @@ public:
             iterator
         >::type
         insert_after(const_iterator __p, _InputIterator __f, _InputIterator __l);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-    iterator insert_after(const_iterator __p, initializer_list<value_type> __il)
-        {return insert_after(__p, __il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
     iterator erase_after(const_iterator __p);
     iterator erase_after(const_iterator __f, const_iterator __l);
@@ -792,7 +792,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     void clear() _NOEXCEPT {base::clear();}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void splice_after(const_iterator __p, forward_list&& __x);
     _LIBCPP_INLINE_VISIBILITY
@@ -800,7 +800,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     void splice_after(const_iterator __p, forward_list&& __x,
                       const_iterator __f, const_iterator __l);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     void splice_after(const_iterator __p, forward_list& __x);
     void splice_after(const_iterator __p, forward_list& __x, const_iterator __i);
     void splice_after(const_iterator __p, forward_list& __x,
@@ -810,14 +810,14 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     void unique() {unique(__equal_to<value_type>());}
     template <class _BinaryPredicate> void unique(_BinaryPredicate __binary_pred);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void merge(forward_list&& __x) {merge(__x, __less<value_type>());}
     template <class _Compare>
         _LIBCPP_INLINE_VISIBILITY
         void merge(forward_list&& __x, _Compare __comp)
         {merge(__x, _VSTD::move(__comp));}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void merge(forward_list& __x) {merge(__x, __less<value_type>());}
     template <class _Compare> void merge(forward_list& __x, _Compare __comp);
@@ -828,11 +828,11 @@ public:
 
 private:
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     void __move_assign(forward_list& __x, true_type)
         _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value);
     void __move_assign(forward_list& __x, false_type);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     template <class _Compare>
         static
@@ -873,8 +873,9 @@ forward_list<_Tp, _Alloc>::forward_list(size_type __n)
 
 #if _LIBCPP_STD_VER > 11
 template <class _Tp, class _Alloc>
-forward_list<_Tp, _Alloc>::forward_list(size_type __n, const allocator_type& __a)
-    : base ( __a )
+forward_list<_Tp, _Alloc>::forward_list(size_type __n,
+                                        const allocator_type& __base_alloc)
+    : base ( __base_alloc )
 {
     if (__n > 0)
     {
@@ -947,8 +948,19 @@ forward_list<_Tp, _Alloc>::forward_list(const forward_list& __x,
     insert_after(cbefore_begin(), __x.begin(), __x.end());
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+template <class _Tp, class _Alloc>
+forward_list<_Tp, _Alloc>&
+forward_list<_Tp, _Alloc>::operator=(const forward_list& __x)
+{
+    if (this != &__x)
+    {
+        base::__copy_assign_alloc(__x);
+        assign(__x.begin(), __x.end());
+    }
+    return *this;
+}
 
+#ifndef _LIBCPP_CXX03_LANG
 template <class _Tp, class _Alloc>
 forward_list<_Tp, _Alloc>::forward_list(forward_list&& __x,
                                         const allocator_type& __a)
@@ -961,10 +973,6 @@ forward_list<_Tp, _Alloc>::forward_list(forward_list&& __x,
     }
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Tp, class _Alloc>
 forward_list<_Tp, _Alloc>::forward_list(initializer_list<value_type> __il)
 {
@@ -979,22 +987,6 @@ forward_list<_Tp, _Alloc>::forward_list(initializer_list<value_type> __il,
     insert_after(cbefore_begin(), __il.begin(), __il.end());
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
-template <class _Tp, class _Alloc>
-forward_list<_Tp, _Alloc>&
-forward_list<_Tp, _Alloc>::operator=(const forward_list& __x)
-{
-    if (this != &__x)
-    {
-        base::__copy_assign_alloc(__x);
-        assign(__x.begin(), __x.end());
-    }
-    return *this;
-}
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
 template <class _Tp, class _Alloc>
 void
 forward_list<_Tp, _Alloc>::__move_assign(forward_list& __x, true_type)
@@ -1032,10 +1024,6 @@ forward_list<_Tp, _Alloc>::operator=(forward_list&& __x)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Tp, class _Alloc>
 inline
 forward_list<_Tp, _Alloc>&
@@ -1045,7 +1033,7 @@ forward_list<_Tp, _Alloc>::operator=(initializer_list<value_type> __il)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Alloc>
 template <class _InputIterator>
@@ -1082,7 +1070,7 @@ forward_list<_Tp, _Alloc>::assign(size_type __n, const value_type& __v)
         erase_after(__i, __e);
 }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Alloc>
 inline
@@ -1092,14 +1080,13 @@ forward_list<_Tp, _Alloc>::assign(initializer_list<value_type> __il)
     assign(__il.begin(), __il.end());
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
 template <class _Tp, class _Alloc>
 template <class... _Args>
+#if _LIBCPP_STD_VER > 14
+typename forward_list<_Tp, _Alloc>::reference
+#else
 void
+#endif
 forward_list<_Tp, _Alloc>::emplace_front(_Args&&... __args)
 {
     __node_allocator& __a = base::__alloc();
@@ -1109,10 +1096,11 @@ forward_list<_Tp, _Alloc>::emplace_front(_Args&&... __args)
                                   _VSTD::forward<_Args>(__args)...);
     __h->__next_ = base::__before_begin()->__next_;
     base::__before_begin()->__next_ = __h.release();
+#if _LIBCPP_STD_VER > 14
+    return base::__before_begin()->__next_->__value_;
+#endif
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-
 template <class _Tp, class _Alloc>
 void
 forward_list<_Tp, _Alloc>::push_front(value_type&& __v)
@@ -1125,7 +1113,7 @@ forward_list<_Tp, _Alloc>::push_front(value_type&& __v)
     base::__before_begin()->__next_ = __h.release();
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Alloc>
 void
@@ -1150,8 +1138,7 @@ forward_list<_Tp, _Alloc>::pop_front()
     __node_traits::deallocate(__a, __p, 1);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Alloc>
 template <class... _Args>
@@ -1169,8 +1156,6 @@ forward_list<_Tp, _Alloc>::emplace_after(const_iterator __p, _Args&&... __args)
     return iterator(__r->__next_);
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-
 template <class _Tp, class _Alloc>
 typename forward_list<_Tp, _Alloc>::iterator
 forward_list<_Tp, _Alloc>::insert_after(const_iterator __p, value_type&& __v)
@@ -1185,7 +1170,7 @@ forward_list<_Tp, _Alloc>::insert_after(const_iterator __p, value_type&& __v)
     return iterator(__r->__next_);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Alloc>
 typename forward_list<_Tp, _Alloc>::iterator
@@ -1421,7 +1406,7 @@ forward_list<_Tp, _Alloc>::splice_after(const_iterator __p,
 template <class _Tp, class _Alloc>
 void
 forward_list<_Tp, _Alloc>::splice_after(const_iterator __p,
-                                        forward_list& __x,
+                                        forward_list& /*__other*/,
                                         const_iterator __i)
 {
     const_iterator __lm1 = _VSTD::next(__i);
@@ -1436,7 +1421,7 @@ forward_list<_Tp, _Alloc>::splice_after(const_iterator __p,
 template <class _Tp, class _Alloc>
 void
 forward_list<_Tp, _Alloc>::splice_after(const_iterator __p,
-                                        forward_list& __x,
+                                        forward_list& /*__other*/,
                                         const_iterator __f, const_iterator __l)
 {
     if (__f != __l && __p != __f)
@@ -1453,7 +1438,7 @@ forward_list<_Tp, _Alloc>::splice_after(const_iterator __p,
     }
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Alloc>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1484,7 +1469,7 @@ forward_list<_Tp, _Alloc>::splice_after(const_iterator __p,
     splice_after(__p, __x, __f, __l);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Alloc>
 void
@@ -1735,4 +1720,6 @@ swap(forward_list<_Tp, _Alloc>& __x, forward_list<_Tp, _Alloc>& __y)
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_FORWARD_LIST
diff --git a/lib/libcxx/include/fstream b/lib/libcxx/include/fstream
index 3cb3b13bd10..f57908c8dfa 100644
--- a/lib/libcxx/include/fstream
+++ b/lib/libcxx/include/fstream
@@ -171,16 +171,18 @@ typedef basic_fstream<wchar_t> wfstream;
 #include <__locale>
 #include <cstdio>
 
-#include <__undef_min_max>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY basic_filebuf
+class _LIBCPP_TEMPLATE_VIS basic_filebuf
     : public basic_streambuf<_CharT, _Traits>
 {
 public:
@@ -193,13 +195,13 @@ public:
 
     // 27.9.1.2 Constructors/destructor:
     basic_filebuf();
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     basic_filebuf(basic_filebuf&& __rhs);
 #endif
     virtual ~basic_filebuf();
 
     // 27.9.1.3 Assign/swap:
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_filebuf& operator=(basic_filebuf&& __rhs);
 #endif
@@ -276,7 +278,7 @@ basic_filebuf<_CharT, _Traits>::basic_filebuf()
     setbuf(0, 4096);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 basic_filebuf<_CharT, _Traits>::basic_filebuf(basic_filebuf&& __rhs)
@@ -313,7 +315,7 @@ basic_filebuf<_CharT, _Traits>::basic_filebuf(basic_filebuf&& __rhs)
         else
             this->setp((char_type*)__extbuf_,
                        (char_type*)__extbuf_ + (__rhs. epptr() - __rhs.pbase()));
-        this->pbump(__rhs. pptr() - __rhs.pbase());
+        this->__pbump(__rhs. pptr() - __rhs.pbase());
     }
     else if (__rhs.eback())
     {
@@ -352,7 +354,7 @@ basic_filebuf<_CharT, _Traits>::operator=(basic_filebuf&& __rhs)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 basic_filebuf<_CharT, _Traits>::~basic_filebuf()
@@ -432,7 +434,7 @@ basic_filebuf<_CharT, _Traits>::swap(basic_filebuf& __rhs)
         ptrdiff_t __e = this->epptr() - this->pbase();
         this->setp((char_type*)__extbuf_min_,
                    (char_type*)__extbuf_min_ + __e);
-        this->pbump(__n);
+        this->__pbump(__n);
     }
     if (__rhs.eback() == (char_type*)__extbuf_min_)
     {
@@ -448,7 +450,7 @@ basic_filebuf<_CharT, _Traits>::swap(basic_filebuf& __rhs)
         ptrdiff_t __e = __rhs.epptr() - __rhs.pbase();
         __rhs.setp((char_type*)__rhs.__extbuf_min_,
                    (char_type*)__rhs.__extbuf_min_ + __e);
-        __rhs.pbump(__n);
+        __rhs.__pbump(__n);
     }
 }
 
@@ -615,13 +617,12 @@ basic_filebuf<_CharT, _Traits>::underflow()
                                  static_cast<size_t>(__extbufend_ - __extbufnext_));
             codecvt_base::result __r;
             __st_last_ = __st_;
-            size_t __nr = fread((void*)__extbufnext_, 1, __nmemb, __file_);
+            size_t __nr = fread((void*) const_cast<char *>(__extbufnext_), 1, __nmemb, __file_);
             if (__nr != 0)
             {
-#ifndef _LIBCPP_NO_EXCEPTIONS
                 if (!__cv_)
-                    throw bad_cast();
-#endif
+                    __throw_bad_cast();
+
                 __extbufend_ = __extbufnext_ + __nr;
                 char_type*  __inext;
                 __r = __cv_->in(__st_, __extbuf_, __extbufend_, __extbufnext_,
@@ -629,7 +630,8 @@ basic_filebuf<_CharT, _Traits>::underflow()
                                        this->eback() + __ibs_, __inext);
                 if (__r == codecvt_base::noconv)
                 {
-                    this->setg((char_type*)__extbuf_, (char_type*)__extbuf_, (char_type*)__extbufend_);
+                    this->setg((char_type*)__extbuf_, (char_type*)__extbuf_, 
+                                          (char_type*)const_cast<char *>(__extbufend_));
                     __c = traits_type::to_int_type(*this->gptr());
                 }
                 else if (__inext != this->eback() + __unget_sz)
@@ -700,10 +702,9 @@ basic_filebuf<_CharT, _Traits>::overflow(int_type __c)
             codecvt_base::result __r;
             do
             {
-#ifndef _LIBCPP_NO_EXCEPTIONS
                 if (!__cv_)
-                    throw bad_cast();
-#endif
+                    __throw_bad_cast();
+
                 const char_type* __e;
                 __r = __cv_->out(__st_, this->pbase(), this->pptr(), __e,
                                         __extbuf_, __extbuf_ + __ebs_, __extbe);
@@ -722,8 +723,8 @@ basic_filebuf<_CharT, _Traits>::overflow(int_type __c)
                         return traits_type::eof();
                     if (__r == codecvt_base::partial)
                     {
-                        this->setp((char_type*)__e, this->pptr());
-                        this->pbump(this->epptr() - this->pbase());
+                        this->setp(const_cast<char_type*>(__e), this->pptr());
+                        this->__pbump(this->epptr() - this->pbase());
                     }
                 }
                 else
@@ -793,10 +794,9 @@ typename basic_filebuf<_CharT, _Traits>::pos_type
 basic_filebuf<_CharT, _Traits>::seekoff(off_type __off, ios_base::seekdir __way,
                                         ios_base::openmode)
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (!__cv_)
-        throw bad_cast();
-#endif
+        __throw_bad_cast();
+
     int __width = __cv_->encoding();
     if (__file_ == 0 || (__width <= 0 && __off != 0) || sync())
         return pos_type(off_type(-1));
@@ -816,7 +816,7 @@ basic_filebuf<_CharT, _Traits>::seekoff(off_type __off, ios_base::seekdir __way,
     default:
         return pos_type(off_type(-1));
     }
-#if defined(_WIN32) || defined(_NEWLIB_VERSION)
+#if defined(_LIBCPP_HAS_NO_OFF_T_FUNCTIONS)
     if (fseek(__file_, __width > 0 ? __width * __off : 0, __whence))
         return pos_type(off_type(-1));
     pos_type __r = ftell(__file_);
@@ -835,7 +835,7 @@ basic_filebuf<_CharT, _Traits>::seekpos(pos_type __sp, ios_base::openmode)
 {
     if (__file_ == 0 || sync())
         return pos_type(off_type(-1));
-#if defined(_WIN32) || defined(_NEWLIB_VERSION)
+#if defined(_LIBCPP_HAS_NO_OFF_T_FUNCTIONS)
     if (fseek(__file_, __sp, SEEK_SET))
         return pos_type(off_type(-1));
 #else
@@ -852,10 +852,9 @@ basic_filebuf<_CharT, _Traits>::sync()
 {
     if (__file_ == 0)
         return 0;
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (!__cv_)
-        throw bad_cast();
-#endif
+        __throw_bad_cast();
+
     if (__cm_ & ios_base::out)
     {
         if (this->pptr() != this->pbase())
@@ -900,7 +899,7 @@ basic_filebuf<_CharT, _Traits>::sync()
                 }
             }
         }
-#if defined(_WIN32) || defined(_NEWLIB_VERSION)
+#if defined(_LIBCPP_HAS_NO_OFF_T_FUNCTIONS)
         if (fseek(__file_, -__c, SEEK_CUR))
             return -1;
 #else
@@ -1003,7 +1002,7 @@ basic_filebuf<_CharT, _Traits>::__write_mode()
 // basic_ifstream
 
 template <class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY basic_ifstream
+class _LIBCPP_TEMPLATE_VIS basic_ifstream
     : public basic_istream<_CharT, _Traits>
 {
 public:
@@ -1021,12 +1020,10 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     explicit basic_ifstream(const string& __s, ios_base::openmode __mode = ios_base::in);
 #endif
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_ifstream(basic_ifstream&& __rhs);
-#endif
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     basic_ifstream& operator=(basic_ifstream&& __rhs);
 #endif
@@ -1075,7 +1072,7 @@ basic_ifstream<_CharT, _Traits>::basic_ifstream(const string& __s, ios_base::ope
 }
 #endif
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 inline
@@ -1096,7 +1093,7 @@ basic_ifstream<_CharT, _Traits>::operator=(basic_ifstream&& __rhs)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 inline
@@ -1165,7 +1162,7 @@ basic_ifstream<_CharT, _Traits>::close()
 // basic_ofstream
 
 template <class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY basic_ofstream
+class _LIBCPP_TEMPLATE_VIS basic_ofstream
     : public basic_ostream<_CharT, _Traits>
 {
 public:
@@ -1181,12 +1178,10 @@ public:
     explicit basic_ofstream(const char* __s, ios_base::openmode __mode = ios_base::out);
     _LIBCPP_INLINE_VISIBILITY
     explicit basic_ofstream(const string& __s, ios_base::openmode __mode = ios_base::out);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_ofstream(basic_ofstream&& __rhs);
-#endif
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     basic_ofstream& operator=(basic_ofstream&& __rhs);
 #endif
@@ -1235,7 +1230,7 @@ basic_ofstream<_CharT, _Traits>::basic_ofstream(const string& __s, ios_base::ope
 }
 #endif
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 inline
@@ -1256,7 +1251,7 @@ basic_ofstream<_CharT, _Traits>::operator=(basic_ofstream&& __rhs)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 inline
@@ -1325,7 +1320,7 @@ basic_ofstream<_CharT, _Traits>::close()
 // basic_fstream
 
 template <class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY basic_fstream
+class _LIBCPP_TEMPLATE_VIS basic_fstream
     : public basic_iostream<_CharT, _Traits>
 {
 public:
@@ -1343,12 +1338,10 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     explicit basic_fstream(const string& __s, ios_base::openmode __mode = ios_base::in | ios_base::out);
 #endif
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_fstream(basic_fstream&& __rhs);
-#endif
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     basic_fstream& operator=(basic_fstream&& __rhs);
 #endif
@@ -1397,7 +1390,7 @@ basic_fstream<_CharT, _Traits>::basic_fstream(const string& __s, ios_base::openm
 }
 #endif
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 inline
@@ -1418,7 +1411,7 @@ basic_fstream<_CharT, _Traits>::operator=(basic_fstream&& __rhs)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 inline
@@ -1486,4 +1479,6 @@ basic_fstream<_CharT, _Traits>::close()
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_FSTREAM
diff --git a/lib/libcxx/include/functional b/lib/libcxx/include/functional
index 581f965b2b8..3e5215b137b 100644
--- a/lib/libcxx/include/functional
+++ b/lib/libcxx/include/functional
@@ -212,6 +212,13 @@ template <class F> unspecified not_fn(F&& f); // C++17
 template<class T> struct is_bind_expression;
 template<class T> struct is_placeholder;
 
+    // See C++14 20.9.9, Function object binders
+template <class T> inline constexpr bool is_bind_expression_v
+  = is_bind_expression<T>::value; // C++17
+template <class T> inline constexpr int is_placeholder_v
+  = is_placeholder<T>::value; // C++17
+
+
 template<class Fn, class... BoundArgs>
   unspecified bind(Fn&&, BoundArgs&&...);
 template<class R, class Fn, class... BoundArgs>
@@ -228,7 +235,7 @@ namespace placeholders {
 }
 
 template <class Operation>
-class binder1st
+class binder1st     // deprecated in C++11, removed in C++17
     : public unary_function<typename Operation::second_argument_type,
                             typename Operation::result_type>
 {
@@ -242,10 +249,10 @@ public:
 };
 
 template <class Operation, class T>
-binder1st<Operation> bind1st(const Operation& op, const T& x);
+binder1st<Operation> bind1st(const Operation& op, const T& x);  // deprecated in C++11, removed in C++17
 
 template <class Operation>
-class binder2nd
+class binder2nd     // deprecated in C++11, removed in C++17
     : public unary_function<typename Operation::first_argument_type,
                             typename Operation::result_type>
 {
@@ -259,9 +266,9 @@ public:
 };
 
 template <class Operation, class T>
-binder2nd<Operation> bind2nd(const Operation& op, const T& x);
+binder2nd<Operation> bind2nd(const Operation& op, const T& x);  // deprecated in C++11, removed in C++17
 
-template <class Arg, class Result>
+template <class Arg, class Result>      // deprecated in C++11, removed in C++17
 class pointer_to_unary_function : public unary_function<Arg, Result>
 {
 public:
@@ -270,9 +277,9 @@ public:
 };
 
 template <class Arg, class Result>
-pointer_to_unary_function<Arg,Result> ptr_fun(Result (*f)(Arg));
+pointer_to_unary_function<Arg,Result> ptr_fun(Result (*f)(Arg));      // deprecated in C++11, removed in C++17
 
-template <class Arg1, class Arg2, class Result>
+template <class Arg1, class Arg2, class Result>      // deprecated in C++11, removed in C++17
 class pointer_to_binary_function : public binary_function<Arg1, Arg2, Result>
 {
 public:
@@ -281,9 +288,9 @@ public:
 };
 
 template <class Arg1, class Arg2, class Result>
-pointer_to_binary_function<Arg1,Arg2,Result> ptr_fun(Result (*f)(Arg1,Arg2));
+pointer_to_binary_function<Arg1,Arg2,Result> ptr_fun(Result (*f)(Arg1,Arg2));      // deprecated in C++11, removed in C++17
 
-template<class S, class T>
+template<class S, class T>      // deprecated in C++11, removed in C++17
 class mem_fun_t : public unary_function<T*, S>
 {
 public:
@@ -292,18 +299,18 @@ public:
 };
 
 template<class S, class T, class A>
-class mem_fun1_t : public binary_function<T*, A, S>
+class mem_fun1_t : public binary_function<T*, A, S>      // deprecated in C++11, removed in C++17
 {
 public:
     explicit mem_fun1_t(S (T::*p)(A));
     S operator()(T* p, A x) const;
 };
 
-template<class S, class T>          mem_fun_t<S,T>    mem_fun(S (T::*f)());
-template<class S, class T, class A> mem_fun1_t<S,T,A> mem_fun(S (T::*f)(A));
+template<class S, class T>          mem_fun_t<S,T>    mem_fun(S (T::*f)());      // deprecated in C++11, removed in C++17
+template<class S, class T, class A> mem_fun1_t<S,T,A> mem_fun(S (T::*f)(A));     // deprecated in C++11, removed in C++17
 
 template<class S, class T>
-class mem_fun_ref_t : public unary_function<T, S>
+class mem_fun_ref_t : public unary_function<T, S>      // deprecated in C++11, removed in C++17
 {
 public:
     explicit mem_fun_ref_t(S (T::*p)());
@@ -311,18 +318,18 @@ public:
 };
 
 template<class S, class T, class A>
-class mem_fun1_ref_t : public binary_function<T, A, S>
+class mem_fun1_ref_t : public binary_function<T, A, S>      // deprecated in C++11, removed in C++17
 {
 public:
     explicit mem_fun1_ref_t(S (T::*p)(A));
     S operator()(T& p, A x) const;
 };
 
-template<class S, class T>          mem_fun_ref_t<S,T>    mem_fun_ref(S (T::*f)());
-template<class S, class T, class A> mem_fun1_ref_t<S,T,A> mem_fun_ref(S (T::*f)(A));
+template<class S, class T>          mem_fun_ref_t<S,T>    mem_fun_ref(S (T::*f)());      // deprecated in C++11, removed in C++17
+template<class S, class T, class A> mem_fun1_ref_t<S,T,A> mem_fun_ref(S (T::*f)(A));     // deprecated in C++11, removed in C++17
 
 template <class S, class T>
-class const_mem_fun_t : public unary_function<const T*, S>
+class const_mem_fun_t : public unary_function<const T*, S>      // deprecated in C++11, removed in C++17
 {
 public:
     explicit const_mem_fun_t(S (T::*p)() const);
@@ -330,18 +337,18 @@ public:
 };
 
 template <class S, class T, class A>
-class const_mem_fun1_t : public binary_function<const T*, A, S>
+class const_mem_fun1_t : public binary_function<const T*, A, S>      // deprecated in C++11, removed in C++17
 {
 public:
     explicit const_mem_fun1_t(S (T::*p)(A) const);
     S operator()(const T* p, A x) const;
 };
 
-template <class S, class T>          const_mem_fun_t<S,T>    mem_fun(S (T::*f)() const);
-template <class S, class T, class A> const_mem_fun1_t<S,T,A> mem_fun(S (T::*f)(A) const);
+template <class S, class T>          const_mem_fun_t<S,T>    mem_fun(S (T::*f)() const);      // deprecated in C++11, removed in C++17
+template <class S, class T, class A> const_mem_fun1_t<S,T,A> mem_fun(S (T::*f)(A) const);     // deprecated in C++11, removed in C++17
 
 template <class S, class T>
-class const_mem_fun_ref_t : public unary_function<T, S>
+class const_mem_fun_ref_t : public unary_function<T, S>      // deprecated in C++11, removed in C++17
 {
 public:
     explicit const_mem_fun_ref_t(S (T::*p)() const);
@@ -349,15 +356,15 @@ public:
 };
 
 template <class S, class T, class A>
-class const_mem_fun1_ref_t : public binary_function<T, A, S>
+class const_mem_fun1_ref_t : public binary_function<T, A, S>      // deprecated in C++11, removed in C++17
 {
 public:
     explicit const_mem_fun1_ref_t(S (T::*p)(A) const);
     S operator()(const T& p, A x) const;
 };
 
-template <class S, class T>          const_mem_fun_ref_t<S,T>    mem_fun_ref(S (T::*f)() const);
-template <class S, class T, class A> const_mem_fun1_ref_t<S,T,A> mem_fun_ref(S (T::*f)(A) const);
+template <class S, class T>          const_mem_fun_ref_t<S,T>    mem_fun_ref(S (T::*f)() const);   // deprecated in C++11, removed in C++17
+template <class S, class T, class A> const_mem_fun1_ref_t<S,T,A> mem_fun_ref(S (T::*f)(A) const);  // deprecated in C++11, removed in C++17
 
 template<class R, class T> unspecified mem_fn(R T::*);
 
@@ -386,15 +393,15 @@ public:
     template<class F>
       function(F);
     template<Allocator Alloc>
-      function(allocator_arg_t, const Alloc&) noexcept;
+      function(allocator_arg_t, const Alloc&) noexcept;            // removed in C++17
     template<Allocator Alloc>
-      function(allocator_arg_t, const Alloc&, nullptr_t) noexcept;
+      function(allocator_arg_t, const Alloc&, nullptr_t) noexcept; // removed in C++17
     template<Allocator Alloc>
-      function(allocator_arg_t, const Alloc&, const function&);
+      function(allocator_arg_t, const Alloc&, const function&);    // removed in C++17
     template<Allocator Alloc>
-      function(allocator_arg_t, const Alloc&, function&&);
+      function(allocator_arg_t, const Alloc&, function&&);         // removed in C++17
     template<class F, Allocator Alloc>
-      function(allocator_arg_t, const Alloc&, F);
+      function(allocator_arg_t, const Alloc&, F);                  // removed in C++17
 
     function& operator=(const function&);
     function& operator=(function&&) noexcept;
@@ -463,6 +470,7 @@ template <> struct hash<double>;
 template <> struct hash<long double>;
 
 template<class T> struct hash<T*>;
+template <> struct hash<nullptr_t>;  // C++17
 
 }  // std
 
@@ -478,6 +486,7 @@ POLICY:  For non-variadic implementations, the number of arguments is limited
 #include <exception>
 #include <memory>
 #include <tuple>
+#include <utility>
 
 #include <__functional_base>
 
@@ -492,7 +501,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY plus : binary_function<_Tp, _Tp, _Tp>
+struct _LIBCPP_TEMPLATE_VIS plus : binary_function<_Tp, _Tp, _Tp>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     _Tp operator()(const _Tp& __x, const _Tp& __y) const
@@ -501,7 +510,7 @@ struct _LIBCPP_TYPE_VIS_ONLY plus : binary_function<_Tp, _Tp, _Tp>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY plus<void>
+struct _LIBCPP_TEMPLATE_VIS plus<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -519,7 +528,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY minus : binary_function<_Tp, _Tp, _Tp>
+struct _LIBCPP_TEMPLATE_VIS minus : binary_function<_Tp, _Tp, _Tp>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     _Tp operator()(const _Tp& __x, const _Tp& __y) const
@@ -528,7 +537,7 @@ struct _LIBCPP_TYPE_VIS_ONLY minus : binary_function<_Tp, _Tp, _Tp>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY minus<void>
+struct _LIBCPP_TEMPLATE_VIS minus<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -546,7 +555,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY multiplies : binary_function<_Tp, _Tp, _Tp>
+struct _LIBCPP_TEMPLATE_VIS multiplies : binary_function<_Tp, _Tp, _Tp>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     _Tp operator()(const _Tp& __x, const _Tp& __y) const
@@ -555,7 +564,7 @@ struct _LIBCPP_TYPE_VIS_ONLY multiplies : binary_function<_Tp, _Tp, _Tp>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY multiplies<void>
+struct _LIBCPP_TEMPLATE_VIS multiplies<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -573,7 +582,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY divides : binary_function<_Tp, _Tp, _Tp>
+struct _LIBCPP_TEMPLATE_VIS divides : binary_function<_Tp, _Tp, _Tp>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     _Tp operator()(const _Tp& __x, const _Tp& __y) const
@@ -582,7 +591,7 @@ struct _LIBCPP_TYPE_VIS_ONLY divides : binary_function<_Tp, _Tp, _Tp>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY divides<void>
+struct _LIBCPP_TEMPLATE_VIS divides<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -600,7 +609,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY modulus : binary_function<_Tp, _Tp, _Tp>
+struct _LIBCPP_TEMPLATE_VIS modulus : binary_function<_Tp, _Tp, _Tp>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     _Tp operator()(const _Tp& __x, const _Tp& __y) const
@@ -609,7 +618,7 @@ struct _LIBCPP_TYPE_VIS_ONLY modulus : binary_function<_Tp, _Tp, _Tp>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY modulus<void>
+struct _LIBCPP_TEMPLATE_VIS modulus<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -627,7 +636,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY negate : unary_function<_Tp, _Tp>
+struct _LIBCPP_TEMPLATE_VIS negate : unary_function<_Tp, _Tp>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     _Tp operator()(const _Tp& __x) const
@@ -636,7 +645,7 @@ struct _LIBCPP_TYPE_VIS_ONLY negate : unary_function<_Tp, _Tp>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY negate<void>
+struct _LIBCPP_TEMPLATE_VIS negate<void>
 {
     template <class _Tp>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -654,7 +663,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY equal_to : binary_function<_Tp, _Tp, bool>
+struct _LIBCPP_TEMPLATE_VIS equal_to : binary_function<_Tp, _Tp, bool>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     bool operator()(const _Tp& __x, const _Tp& __y) const
@@ -663,7 +672,7 @@ struct _LIBCPP_TYPE_VIS_ONLY equal_to : binary_function<_Tp, _Tp, bool>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY equal_to<void>
+struct _LIBCPP_TEMPLATE_VIS equal_to<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -681,7 +690,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY not_equal_to : binary_function<_Tp, _Tp, bool>
+struct _LIBCPP_TEMPLATE_VIS not_equal_to : binary_function<_Tp, _Tp, bool>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     bool operator()(const _Tp& __x, const _Tp& __y) const
@@ -690,7 +699,7 @@ struct _LIBCPP_TYPE_VIS_ONLY not_equal_to : binary_function<_Tp, _Tp, bool>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY not_equal_to<void>
+struct _LIBCPP_TEMPLATE_VIS not_equal_to<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -708,7 +717,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY greater : binary_function<_Tp, _Tp, bool>
+struct _LIBCPP_TEMPLATE_VIS greater : binary_function<_Tp, _Tp, bool>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     bool operator()(const _Tp& __x, const _Tp& __y) const
@@ -717,7 +726,7 @@ struct _LIBCPP_TYPE_VIS_ONLY greater : binary_function<_Tp, _Tp, bool>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY greater<void>
+struct _LIBCPP_TEMPLATE_VIS greater<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -737,7 +746,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY greater_equal : binary_function<_Tp, _Tp, bool>
+struct _LIBCPP_TEMPLATE_VIS greater_equal : binary_function<_Tp, _Tp, bool>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     bool operator()(const _Tp& __x, const _Tp& __y) const
@@ -746,7 +755,7 @@ struct _LIBCPP_TYPE_VIS_ONLY greater_equal : binary_function<_Tp, _Tp, bool>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY greater_equal<void>
+struct _LIBCPP_TEMPLATE_VIS greater_equal<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -764,7 +773,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY less_equal : binary_function<_Tp, _Tp, bool>
+struct _LIBCPP_TEMPLATE_VIS less_equal : binary_function<_Tp, _Tp, bool>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     bool operator()(const _Tp& __x, const _Tp& __y) const
@@ -773,7 +782,7 @@ struct _LIBCPP_TYPE_VIS_ONLY less_equal : binary_function<_Tp, _Tp, bool>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY less_equal<void>
+struct _LIBCPP_TEMPLATE_VIS less_equal<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -791,7 +800,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY logical_and : binary_function<_Tp, _Tp, bool>
+struct _LIBCPP_TEMPLATE_VIS logical_and : binary_function<_Tp, _Tp, bool>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     bool operator()(const _Tp& __x, const _Tp& __y) const
@@ -800,7 +809,7 @@ struct _LIBCPP_TYPE_VIS_ONLY logical_and : binary_function<_Tp, _Tp, bool>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY logical_and<void>
+struct _LIBCPP_TEMPLATE_VIS logical_and<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -818,7 +827,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY logical_or : binary_function<_Tp, _Tp, bool>
+struct _LIBCPP_TEMPLATE_VIS logical_or : binary_function<_Tp, _Tp, bool>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     bool operator()(const _Tp& __x, const _Tp& __y) const
@@ -827,7 +836,7 @@ struct _LIBCPP_TYPE_VIS_ONLY logical_or : binary_function<_Tp, _Tp, bool>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY logical_or<void>
+struct _LIBCPP_TEMPLATE_VIS logical_or<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -845,7 +854,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY logical_not : unary_function<_Tp, bool>
+struct _LIBCPP_TEMPLATE_VIS logical_not : unary_function<_Tp, bool>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     bool operator()(const _Tp& __x) const
@@ -854,7 +863,7 @@ struct _LIBCPP_TYPE_VIS_ONLY logical_not : unary_function<_Tp, bool>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY logical_not<void>
+struct _LIBCPP_TEMPLATE_VIS logical_not<void>
 {
     template <class _Tp>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -872,7 +881,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY bit_and : binary_function<_Tp, _Tp, _Tp>
+struct _LIBCPP_TEMPLATE_VIS bit_and : binary_function<_Tp, _Tp, _Tp>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     _Tp operator()(const _Tp& __x, const _Tp& __y) const
@@ -881,7 +890,7 @@ struct _LIBCPP_TYPE_VIS_ONLY bit_and : binary_function<_Tp, _Tp, _Tp>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY bit_and<void>
+struct _LIBCPP_TEMPLATE_VIS bit_and<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -899,7 +908,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY bit_or : binary_function<_Tp, _Tp, _Tp>
+struct _LIBCPP_TEMPLATE_VIS bit_or : binary_function<_Tp, _Tp, _Tp>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     _Tp operator()(const _Tp& __x, const _Tp& __y) const
@@ -908,7 +917,7 @@ struct _LIBCPP_TYPE_VIS_ONLY bit_or : binary_function<_Tp, _Tp, _Tp>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY bit_or<void>
+struct _LIBCPP_TEMPLATE_VIS bit_or<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -926,7 +935,7 @@ template <class _Tp = void>
 #else
 template <class _Tp>
 #endif
-struct _LIBCPP_TYPE_VIS_ONLY bit_xor : binary_function<_Tp, _Tp, _Tp>
+struct _LIBCPP_TEMPLATE_VIS bit_xor : binary_function<_Tp, _Tp, _Tp>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     _Tp operator()(const _Tp& __x, const _Tp& __y) const
@@ -935,7 +944,7 @@ struct _LIBCPP_TYPE_VIS_ONLY bit_xor : binary_function<_Tp, _Tp, _Tp>
 
 #if _LIBCPP_STD_VER > 11
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY bit_xor<void>
+struct _LIBCPP_TEMPLATE_VIS bit_xor<void>
 {
     template <class _T1, class _T2>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -950,7 +959,7 @@ struct _LIBCPP_TYPE_VIS_ONLY bit_xor<void>
 
 #if _LIBCPP_STD_VER > 11
 template <class _Tp = void>
-struct _LIBCPP_TYPE_VIS_ONLY bit_not : unary_function<_Tp, _Tp>
+struct _LIBCPP_TEMPLATE_VIS bit_not : unary_function<_Tp, _Tp>
 {
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
     _Tp operator()(const _Tp& __x) const
@@ -958,7 +967,7 @@ struct _LIBCPP_TYPE_VIS_ONLY bit_not : unary_function<_Tp, _Tp>
 };
 
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY bit_not<void>
+struct _LIBCPP_TEMPLATE_VIS bit_not<void>
 {
     template <class _Tp>
     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
@@ -971,7 +980,7 @@ struct _LIBCPP_TYPE_VIS_ONLY bit_not<void>
 #endif
 
 template <class _Predicate>
-class _LIBCPP_TYPE_VIS_ONLY unary_negate
+class _LIBCPP_TEMPLATE_VIS unary_negate
     : public unary_function<typename _Predicate::argument_type, bool>
 {
     _Predicate __pred_;
@@ -990,7 +999,7 @@ unary_negate<_Predicate>
 not1(const _Predicate& __pred) {return unary_negate<_Predicate>(__pred);}
 
 template <class _Predicate>
-class _LIBCPP_TYPE_VIS_ONLY binary_negate
+class _LIBCPP_TEMPLATE_VIS binary_negate
     : public binary_function<typename _Predicate::first_argument_type,
                              typename _Predicate::second_argument_type,
                              bool>
@@ -1011,8 +1020,9 @@ inline _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
 binary_negate<_Predicate>
 not2(const _Predicate& __pred) {return binary_negate<_Predicate>(__pred);}
 
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_BINDERS)
 template <class __Operation>
-class _LIBCPP_TYPE_VIS_ONLY binder1st
+class _LIBCPP_TEMPLATE_VIS binder1st
     : public unary_function<typename __Operation::second_argument_type,
                             typename __Operation::result_type>
 {
@@ -1038,7 +1048,7 @@ bind1st(const __Operation& __op, const _Tp& __x)
     {return binder1st<__Operation>(__op, __x);}
 
 template <class __Operation>
-class _LIBCPP_TYPE_VIS_ONLY binder2nd
+class _LIBCPP_TEMPLATE_VIS binder2nd
     : public unary_function<typename __Operation::first_argument_type,
                             typename __Operation::result_type>
 {
@@ -1064,7 +1074,7 @@ bind2nd(const __Operation& __op, const _Tp& __x)
     {return binder2nd<__Operation>(__op, __x);}
 
 template <class _Arg, class _Result>
-class _LIBCPP_TYPE_VIS_ONLY pointer_to_unary_function
+class _LIBCPP_TEMPLATE_VIS pointer_to_unary_function
     : public unary_function<_Arg, _Result>
 {
     _Result (*__f_)(_Arg);
@@ -1082,7 +1092,7 @@ ptr_fun(_Result (*__f)(_Arg))
     {return pointer_to_unary_function<_Arg,_Result>(__f);}
 
 template <class _Arg1, class _Arg2, class _Result>
-class _LIBCPP_TYPE_VIS_ONLY pointer_to_binary_function
+class _LIBCPP_TEMPLATE_VIS pointer_to_binary_function
     : public binary_function<_Arg1, _Arg2, _Result>
 {
     _Result (*__f_)(_Arg1, _Arg2);
@@ -1100,7 +1110,7 @@ ptr_fun(_Result (*__f)(_Arg1,_Arg2))
     {return pointer_to_binary_function<_Arg1,_Arg2,_Result>(__f);}
 
 template<class _Sp, class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY mem_fun_t : public unary_function<_Tp*, _Sp>
+class _LIBCPP_TEMPLATE_VIS mem_fun_t : public unary_function<_Tp*, _Sp>
 {
     _Sp (_Tp::*__p_)();
 public:
@@ -1111,7 +1121,7 @@ public:
 };
 
 template<class _Sp, class _Tp, class _Ap>
-class _LIBCPP_TYPE_VIS_ONLY mem_fun1_t : public binary_function<_Tp*, _Ap, _Sp>
+class _LIBCPP_TEMPLATE_VIS mem_fun1_t : public binary_function<_Tp*, _Ap, _Sp>
 {
     _Sp (_Tp::*__p_)(_Ap);
 public:
@@ -1134,7 +1144,7 @@ mem_fun(_Sp (_Tp::*__f)(_Ap))
     {return mem_fun1_t<_Sp,_Tp,_Ap>(__f);}
 
 template<class _Sp, class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY mem_fun_ref_t : public unary_function<_Tp, _Sp>
+class _LIBCPP_TEMPLATE_VIS mem_fun_ref_t : public unary_function<_Tp, _Sp>
 {
     _Sp (_Tp::*__p_)();
 public:
@@ -1145,7 +1155,7 @@ public:
 };
 
 template<class _Sp, class _Tp, class _Ap>
-class _LIBCPP_TYPE_VIS_ONLY mem_fun1_ref_t : public binary_function<_Tp, _Ap, _Sp>
+class _LIBCPP_TEMPLATE_VIS mem_fun1_ref_t : public binary_function<_Tp, _Ap, _Sp>
 {
     _Sp (_Tp::*__p_)(_Ap);
 public:
@@ -1168,7 +1178,7 @@ mem_fun_ref(_Sp (_Tp::*__f)(_Ap))
     {return mem_fun1_ref_t<_Sp,_Tp,_Ap>(__f);}
 
 template <class _Sp, class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY const_mem_fun_t : public unary_function<const _Tp*, _Sp>
+class _LIBCPP_TEMPLATE_VIS const_mem_fun_t : public unary_function<const _Tp*, _Sp>
 {
     _Sp (_Tp::*__p_)() const;
 public:
@@ -1179,7 +1189,7 @@ public:
 };
 
 template <class _Sp, class _Tp, class _Ap>
-class _LIBCPP_TYPE_VIS_ONLY const_mem_fun1_t : public binary_function<const _Tp*, _Ap, _Sp>
+class _LIBCPP_TEMPLATE_VIS const_mem_fun1_t : public binary_function<const _Tp*, _Ap, _Sp>
 {
     _Sp (_Tp::*__p_)(_Ap) const;
 public:
@@ -1202,7 +1212,7 @@ mem_fun(_Sp (_Tp::*__f)(_Ap) const)
     {return const_mem_fun1_t<_Sp,_Tp,_Ap>(__f);}
 
 template <class _Sp, class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY const_mem_fun_ref_t : public unary_function<_Tp, _Sp>
+class _LIBCPP_TEMPLATE_VIS const_mem_fun_ref_t : public unary_function<_Tp, _Sp>
 {
     _Sp (_Tp::*__p_)() const;
 public:
@@ -1213,7 +1223,7 @@ public:
 };
 
 template <class _Sp, class _Tp, class _Ap>
-class _LIBCPP_TYPE_VIS_ONLY const_mem_fun1_ref_t
+class _LIBCPP_TEMPLATE_VIS const_mem_fun1_ref_t
     : public binary_function<_Tp, _Ap, _Sp>
 {
     _Sp (_Tp::*__p_)(_Ap) const;
@@ -1235,6 +1245,7 @@ inline _LIBCPP_INLINE_VISIBILITY
 const_mem_fun1_ref_t<_Sp,_Tp,_Ap>
 mem_fun_ref(_Sp (_Tp::*__f)(_Ap) const)
     {return const_mem_fun1_ref_t<_Sp,_Tp,_Ap>(__f);}
+#endif
 
 ////////////////////////////////////////////////////////////////////////////////
 //                                MEMFUN
@@ -1253,7 +1264,7 @@ private:
 public:
     _LIBCPP_INLINE_VISIBILITY __mem_fn(type __f) _NOEXCEPT : __f_(__f) {}
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
     // invoke
     template <class... _ArgTypes>
     _LIBCPP_INLINE_VISIBILITY
@@ -1380,9 +1391,25 @@ mem_fn(_Rp _Tp::* __pm) _NOEXCEPT
 class _LIBCPP_EXCEPTION_ABI bad_function_call
     : public exception
 {
+#ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
+public:
+    virtual ~bad_function_call() _NOEXCEPT;
+
+    virtual const char* what() const _NOEXCEPT;
+#endif
 };
 
-template<class _Fp> class _LIBCPP_TYPE_VIS_ONLY function; // undefined
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+void __throw_bad_function_call()
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw bad_function_call();
+#else
+	_VSTD::abort();
+#endif
+}
+
+template<class _Fp> class _LIBCPP_TEMPLATE_VIS function; // undefined
 
 namespace __function
 {
@@ -1427,7 +1454,7 @@ bool __not_null(function<_Fp> const& __f) { return !!__f; }
 
 } // namespace __function
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 
 namespace __function {
 
@@ -1558,7 +1585,7 @@ __func<_Fp, _Alloc, _Rp(_ArgTypes...)>::target_type() const _NOEXCEPT
 }  // __function
 
 template<class _Rp, class ..._ArgTypes>
-class _LIBCPP_TYPE_VIS_ONLY function<_Rp(_ArgTypes...)>
+class _LIBCPP_TEMPLATE_VIS function<_Rp(_ArgTypes...)>
     : public __function::__maybe_derive_from_unary_function<_Rp(_ArgTypes...)>,
       public __function::__maybe_derive_from_binary_function<_Rp(_ArgTypes...)>
 {
@@ -1570,9 +1597,11 @@ class _LIBCPP_TYPE_VIS_ONLY function<_Rp(_ArgTypes...)>
       return reinterpret_cast<__base*>(p);
     }
 
-    template <class _Fp, bool = !is_same<_Fp, function>::value &&
-                                __invokable<_Fp&, _ArgTypes...>::value>
-        struct __callable;
+    template <class _Fp, bool = __lazy_and<
+        integral_constant<bool, !is_same<__uncvref_t<_Fp>, function>::value>,
+        __invokable<_Fp&, _ArgTypes...>
+    >::value>
+    struct __callable;
     template <class _Fp>
         struct __callable<_Fp, true>
         {
@@ -1585,6 +1614,9 @@ class _LIBCPP_TYPE_VIS_ONLY function<_Rp(_ArgTypes...)>
         {
             static const bool value = false;
         };
+
+  template <class _Fp>
+  using _EnableIfCallable = typename enable_if<__callable<_Fp>::value>::type;
 public:
     typedef _Rp result_type;
 
@@ -1595,13 +1627,10 @@ public:
     function(nullptr_t) _NOEXCEPT : __f_(0) {}
     function(const function&);
     function(function&&) _NOEXCEPT;
-    template<class _Fp>
-      function(_Fp, typename enable_if
-                                     <
-                                        __callable<_Fp>::value &&
-                                        !is_same<_Fp, function>::value
-                                      >::type* = 0);
+    template<class _Fp, class = _EnableIfCallable<_Fp>>
+    function(_Fp);
 
+#if _LIBCPP_STD_VER <= 14
     template<class _Alloc>
       _LIBCPP_INLINE_VISIBILITY
       function(allocator_arg_t, const _Alloc&) _NOEXCEPT : __f_(0) {}
@@ -1612,21 +1641,15 @@ public:
       function(allocator_arg_t, const _Alloc&, const function&);
     template<class _Alloc>
       function(allocator_arg_t, const _Alloc&, function&&);
-    template<class _Fp, class _Alloc>
-      function(allocator_arg_t, const _Alloc& __a, _Fp __f,
-               typename enable_if<__callable<_Fp>::value>::type* = 0);
+    template<class _Fp, class _Alloc, class = _EnableIfCallable<_Fp>>
+      function(allocator_arg_t, const _Alloc& __a, _Fp __f);
+#endif
 
     function& operator=(const function&);
     function& operator=(function&&) _NOEXCEPT;
     function& operator=(nullptr_t) _NOEXCEPT;
-    template<class _Fp>
-      typename enable_if
-      <
-        __callable<typename decay<_Fp>::type>::value &&
-        !is_same<typename remove_reference<_Fp>::type, function>::value,
-        function&
-      >::type
-      operator=(_Fp&&);
+    template<class _Fp, class = _EnableIfCallable<_Fp>>
+    function& operator=(_Fp&&);
 
     ~function();
 
@@ -1675,6 +1698,7 @@ function<_Rp(_ArgTypes...)>::function(const function& __f)
         __f_ = __f.__f_->__clone();
 }
 
+#if _LIBCPP_STD_VER <= 14
 template<class _Rp, class ..._ArgTypes>
 template <class _Alloc>
 function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc&,
@@ -1690,6 +1714,7 @@ function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc&,
     else
         __f_ = __f.__f_->__clone();
 }
+#endif
 
 template<class _Rp, class ..._ArgTypes>
 function<_Rp(_ArgTypes...)>::function(function&& __f) _NOEXCEPT
@@ -1708,6 +1733,7 @@ function<_Rp(_ArgTypes...)>::function(function&& __f) _NOEXCEPT
     }
 }
 
+#if _LIBCPP_STD_VER <= 14
 template<class _Rp, class ..._ArgTypes>
 template <class _Alloc>
 function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc&,
@@ -1726,15 +1752,11 @@ function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc&,
         __f.__f_ = 0;
     }
 }
+#endif
 
 template<class _Rp, class ..._ArgTypes>
-template <class _Fp>
-function<_Rp(_ArgTypes...)>::function(_Fp __f,
-                                     typename enable_if
-                                     <
-                                        __callable<_Fp>::value &&
-                                        !is_same<_Fp, function>::value
-                                     >::type*)
+template <class _Fp, class>
+function<_Rp(_ArgTypes...)>::function(_Fp __f)
     : __f_(0)
 {
     if (__function::__not_null(__f))
@@ -1756,10 +1778,10 @@ function<_Rp(_ArgTypes...)>::function(_Fp __f,
     }
 }
 
+#if _LIBCPP_STD_VER <= 14
 template<class _Rp, class ..._ArgTypes>
-template <class _Fp, class _Alloc>
-function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc& __a0, _Fp __f,
-                                     typename enable_if<__callable<_Fp>::value>::type*)
+template <class _Fp, class _Alloc, class>
+function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc& __a0, _Fp __f)
     : __f_(0)
 {
     typedef allocator_traits<_Alloc> __alloc_traits;
@@ -1782,6 +1804,7 @@ function<_Rp(_ArgTypes...)>::function(allocator_arg_t, const _Alloc& __a0, _Fp _
         }
     }
 }
+#endif
 
 template<class _Rp, class ..._ArgTypes>
 function<_Rp(_ArgTypes...)>&
@@ -1828,13 +1851,8 @@ function<_Rp(_ArgTypes...)>::operator=(nullptr_t) _NOEXCEPT
 }
 
 template<class _Rp, class ..._ArgTypes>
-template <class _Fp>
-typename enable_if
-<
-    function<_Rp(_ArgTypes...)>::template __callable<typename decay<_Fp>::type>::value &&
-    !is_same<typename remove_reference<_Fp>::type, function<_Rp(_ArgTypes...)>>::value,
-    function<_Rp(_ArgTypes...)>&
->::type
+template <class _Fp, class>
+function<_Rp(_ArgTypes...)>&
 function<_Rp(_ArgTypes...)>::operator=(_Fp&& __f)
 {
     function(_VSTD::forward<_Fp>(__f)).swap(*this);
@@ -1854,6 +1872,8 @@ template<class _Rp, class ..._ArgTypes>
 void
 function<_Rp(_ArgTypes...)>::swap(function& __f) _NOEXCEPT
 {
+    if (_VSTD::addressof(__f) == this)
+      return;
     if ((void *)__f_ == &__buf_ && (void *)__f.__f_ == &__f.__buf_)
     {
         typename aligned_storage<sizeof(__buf_)>::type __tempbuf;
@@ -1891,10 +1911,8 @@ template<class _Rp, class ..._ArgTypes>
 _Rp
 function<_Rp(_ArgTypes...)>::operator()(_ArgTypes... __arg) const
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__f_ == 0)
-        throw bad_function_call();
-#endif  // _LIBCPP_NO_EXCEPTIONS
+        __throw_bad_function_call();
     return (*__f_)(_VSTD::forward<_ArgTypes>(__arg)...);
 }
 
@@ -1915,8 +1933,8 @@ _Tp*
 function<_Rp(_ArgTypes...)>::target() _NOEXCEPT
 {
     if (__f_ == 0)
-        return (_Tp*)0;
-    return (_Tp*)__f_->target(typeid(_Tp));
+        return nullptr;
+    return (_Tp*) const_cast<void *>(__f_->target(typeid(_Tp)));
 }
 
 template<class _Rp, class ..._ArgTypes>
@@ -1925,7 +1943,7 @@ const _Tp*
 function<_Rp(_ArgTypes...)>::target() const _NOEXCEPT
 {
     if (__f_ == 0)
-        return (const _Tp*)0;
+        return nullptr;
     return (const _Tp*)__f_->target(typeid(_Tp));
 }
 
@@ -1957,7 +1975,7 @@ void
 swap(function<_Rp(_ArgTypes...)>& __x, function<_Rp(_ArgTypes...)>& __y) _NOEXCEPT
 {return __x.swap(__y);}
 
-#else // _LIBCPP_HAS_NO_VARIADICS
+#else // _LIBCPP_CXX03_LANG
 
 #include <__functional_03>
 
@@ -1968,13 +1986,23 @@ swap(function<_Rp(_ArgTypes...)>& __x, function<_Rp(_ArgTypes...)>& __y) _NOEXCE
 //==============================================================================
 
 template<class _Tp> struct __is_bind_expression : public false_type {};
-template<class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_bind_expression
+template<class _Tp> struct _LIBCPP_TEMPLATE_VIS is_bind_expression
     : public __is_bind_expression<typename remove_cv<_Tp>::type> {};
 
+#if _LIBCPP_STD_VER > 14
+template <class _Tp>
+_LIBCPP_INLINE_VAR constexpr size_t is_bind_expression_v = is_bind_expression<_Tp>::value;
+#endif
+
 template<class _Tp> struct __is_placeholder : public integral_constant<int, 0> {};
-template<class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_placeholder
+template<class _Tp> struct _LIBCPP_TEMPLATE_VIS is_placeholder
     : public __is_placeholder<typename remove_cv<_Tp>::type> {};
 
+#if _LIBCPP_STD_VER > 14
+template <class _Tp>
+_LIBCPP_INLINE_VAR constexpr size_t is_placeholder_v = is_placeholder<_Tp>::value;
+#endif
+
 namespace placeholders
 {
 
@@ -1992,16 +2020,16 @@ _LIBCPP_FUNC_VIS extern const __ph<8>   _8;
 _LIBCPP_FUNC_VIS extern const __ph<9>   _9;
 _LIBCPP_FUNC_VIS extern const __ph<10> _10;
 #else
-constexpr __ph<1>   _1{};
-constexpr __ph<2>   _2{};
-constexpr __ph<3>   _3{};
-constexpr __ph<4>   _4{};
-constexpr __ph<5>   _5{};
-constexpr __ph<6>   _6{};
-constexpr __ph<7>   _7{};
-constexpr __ph<8>   _8{};
-constexpr __ph<9>   _9{};
-constexpr __ph<10> _10{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<1>   _1{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<2>   _2{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<3>   _3{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<4>   _4{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<5>   _5{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<6>   _6{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<7>   _7{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<8>   _8{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<9>   _9{};
+/* _LIBCPP_INLINE_VAR */ constexpr __ph<10> _10{};
 #endif // defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_BIND)
 
 }  // placeholders
@@ -2011,7 +2039,7 @@ struct __is_placeholder<placeholders::__ph<_Np> >
     : public integral_constant<int, _Np> {};
 
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Uj>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -2188,7 +2216,7 @@ typename __bind_return<_Fp, _BoundArgs, _Args>::type
 __apply_functor(_Fp& __f, _BoundArgs& __bound_args, __tuple_indices<_Indx...>,
                 _Args&& __args)
 {
-    return __invoke(__f, __mu(_VSTD::get<_Indx>(__bound_args), __args)...);
+    return _VSTD::__invoke(__f, _VSTD::__mu(_VSTD::get<_Indx>(__bound_args), __args)...);
 }
 
 template<class _Fp, class ..._BoundArgs>
@@ -2204,36 +2232,6 @@ private:
 
     typedef typename __make_tuple_indices<sizeof...(_BoundArgs)>::type __indices;
 public:
-#ifdef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
-
-    _LIBCPP_INLINE_VISIBILITY
-    __bind(const __bind& __b)
-        : __f_(__b.__f_),
-          __bound_args_(__b.__bound_args_) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    __bind& operator=(const __bind& __b)
-    {
-        __f_ = __b.__f_;
-        __bound_args_ = __b.__bound_args_;
-        return *this;
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    __bind(__bind&& __b)
-        : __f_(_VSTD::move(__b.__f_)),
-          __bound_args_(_VSTD::move(__b.__bound_args_)) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    __bind& operator=(__bind&& __b)
-    {
-        __f_ = _VSTD::move(__b.__f_);
-        __bound_args_ = _VSTD::move(__b.__bound_args_);
-        return *this;
-    }
-
-#endif  // _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
-
     template <class _Gp, class ..._BA,
               class = typename enable_if
                                <
@@ -2251,7 +2249,7 @@ public:
         typename __bind_return<_Fd, _Td, tuple<_Args&&...> >::type
         operator()(_Args&& ...__args)
         {
-            return __apply_functor(__f_, __bound_args_, __indices(),
+            return _VSTD::__apply_functor(__f_, __bound_args_, __indices(),
                                   tuple<_Args&&...>(_VSTD::forward<_Args>(__args)...));
         }
 
@@ -2260,7 +2258,7 @@ public:
         typename __bind_return<const _Fd, const _Td, tuple<_Args&&...> >::type
         operator()(_Args&& ...__args) const
         {
-            return __apply_functor(__f_, __bound_args_, __indices(),
+            return _VSTD::__apply_functor(__f_, __bound_args_, __indices(),
                                    tuple<_Args&&...>(_VSTD::forward<_Args>(__args)...));
         }
 };
@@ -2278,31 +2276,6 @@ class __bind_r
 public:
     typedef _Rp result_type;
 
-#ifdef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
-
-    _LIBCPP_INLINE_VISIBILITY
-    __bind_r(const __bind_r& __b)
-        : base(_VSTD::forward<const base&>(__b)) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    __bind_r& operator=(const __bind_r& __b)
-    {
-        base::operator=(_VSTD::forward<const base&>(__b));
-        return *this;
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    __bind_r(__bind_r&& __b)
-        : base(_VSTD::forward<base>(__b)) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    __bind_r& operator=(__bind_r&& __b)
-    {
-        base::operator=(_VSTD::forward<base>(__b));
-        return *this;
-    }
-
-#endif  // _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
 
     template <class _Gp, class ..._BA,
               class = typename enable_if
@@ -2366,241 +2339,12 @@ bind(_Fp&& __f, _BoundArgs&&... __bound_args)
     return type(_VSTD::forward<_Fp>(__f), _VSTD::forward<_BoundArgs>(__bound_args)...);
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<bool>
-    : public unary_function<bool, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(bool __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<char>
-    : public unary_function<char, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(char __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<signed char>
-    : public unary_function<signed char, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(signed char __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned char>
-    : public unary_function<unsigned char, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(unsigned char __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<char16_t>
-    : public unary_function<char16_t, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(char16_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<char32_t>
-    : public unary_function<char32_t, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(char32_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-#endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<wchar_t>
-    : public unary_function<wchar_t, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(wchar_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<short>
-    : public unary_function<short, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(short __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned short>
-    : public unary_function<unsigned short, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(unsigned short __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<int>
-    : public unary_function<int, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(int __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned int>
-    : public unary_function<unsigned int, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(unsigned int __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<long>
-    : public unary_function<long, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(long __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned long>
-    : public unary_function<unsigned long, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(unsigned long __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<long long>
-    : public __scalar_hash<long long>
-{
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<unsigned long long>
-    : public __scalar_hash<unsigned long long>
-{
-};
-
-#ifndef _LIBCPP_HAS_NO_INT128
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<__int128_t>
-    : public __scalar_hash<__int128_t>
-{
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<__uint128_t>
-    : public __scalar_hash<__uint128_t>
-{
-};
-
-#endif
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<float>
-    : public __scalar_hash<float>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(float __v) const _NOEXCEPT
-    {
-        // -0.0 and 0.0 should return same hash
-       if (__v == 0)
-           return 0;
-        return __scalar_hash<float>::operator()(__v);
-    }
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<double>
-    : public __scalar_hash<double>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(double __v) const _NOEXCEPT
-    {
-        // -0.0 and 0.0 should return same hash
-       if (__v == 0)
-           return 0;
-        return __scalar_hash<double>::operator()(__v);
-    }
-};
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<long double>
-    : public __scalar_hash<long double>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(long double __v) const _NOEXCEPT
-    {
-        // -0.0 and 0.0 should return same hash
-        if (__v == 0)
-            return 0;
-#if defined(__i386__)
-        // Zero out padding bits
-        union
-        {
-            long double __t;
-            struct
-            {
-                size_t __a;
-                size_t __b;
-                size_t __c;
-                size_t __d;
-            } __s;
-        } __u;
-        __u.__s.__a = 0;
-        __u.__s.__b = 0;
-        __u.__s.__c = 0;
-        __u.__s.__d = 0;
-        __u.__t = __v;
-        return __u.__s.__a ^ __u.__s.__b ^ __u.__s.__c ^ __u.__s.__d;
-#elif defined(__x86_64__)
-        // Zero out padding bits
-        union
-        {
-            long double __t;
-            struct
-            {
-                size_t __a;
-                size_t __b;
-            } __s;
-        } __u;
-        __u.__s.__a = 0;
-        __u.__s.__b = 0;
-        __u.__t = __v;
-        return __u.__s.__a ^ __u.__s.__b;
-#else
-        return __scalar_hash<long double>::operator()(__v);
-#endif
-    }
-};
-
-#if _LIBCPP_STD_VER > 11
-template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY hash
-    : public unary_function<_Tp, size_t>
-{
-    static_assert(is_enum<_Tp>::value, "This hash only works for enumeration types");
-
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(_Tp __v) const _NOEXCEPT
-    {
-        typedef typename underlying_type<_Tp>::type type;
-        return hash<type>{}(static_cast<type>(__v));
-    }
-};
-#endif
-
+#endif  // _LIBCPP_CXX03_LANG
 
 #if _LIBCPP_STD_VER > 14
 
+#define __cpp_lib_invoke 201411
+
 template <class _Fn, class ..._Args>
 result_of_t<_Fn&&(_Args&&...)>
 invoke(_Fn&& __f, _Args&&... __args)
@@ -2610,7 +2354,7 @@ invoke(_Fn&& __f, _Args&&... __args)
 }
 
 template <class _DecayFunc>
-class _LIBCPP_TYPE_VIS_ONLY __not_fn_imp {
+class _LIBCPP_TEMPLATE_VIS __not_fn_imp {
   _DecayFunc __fd;
 
 public:
@@ -2620,30 +2364,30 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     auto operator()(_Args&& ...__args) &
             noexcept(noexcept(!_VSTD::invoke(__fd, _VSTD::forward<_Args>(__args)...)))
-        -> decltype(!_VSTD::invoke(__fd, _VSTD::forward<_Args>(__args)...))
-        { return !_VSTD::invoke(__fd, _VSTD::forward<_Args>(__args)...); }
+        -> decltype(          !_VSTD::invoke(__fd, _VSTD::forward<_Args>(__args)...))
+        { return              !_VSTD::invoke(__fd, _VSTD::forward<_Args>(__args)...); }
 
     template <class ..._Args>
     _LIBCPP_INLINE_VISIBILITY
     auto operator()(_Args&& ...__args) &&
             noexcept(noexcept(!_VSTD::invoke(_VSTD::move(__fd), _VSTD::forward<_Args>(__args)...)))
-        -> decltype(!_VSTD::invoke(_VSTD::move(__fd), _VSTD::forward<_Args>(__args)...))
-        { return !_VSTD::invoke(_VSTD::move(__fd), _VSTD::forward<_Args>(__args)...); }
+        -> decltype(          !_VSTD::invoke(_VSTD::move(__fd), _VSTD::forward<_Args>(__args)...))
+        { return              !_VSTD::invoke(_VSTD::move(__fd), _VSTD::forward<_Args>(__args)...); }
 
     template <class ..._Args>
     _LIBCPP_INLINE_VISIBILITY
     auto operator()(_Args&& ...__args) const&
             noexcept(noexcept(!_VSTD::invoke(__fd, _VSTD::forward<_Args>(__args)...)))
-        -> decltype(!_VSTD::invoke(__fd, _VSTD::forward<_Args>(__args)...))
-        { return !_VSTD::invoke(__fd, _VSTD::forward<_Args>(__args)...); }
+        -> decltype(          !_VSTD::invoke(__fd, _VSTD::forward<_Args>(__args)...))
+        { return              !_VSTD::invoke(__fd, _VSTD::forward<_Args>(__args)...); }
 
 
     template <class ..._Args>
     _LIBCPP_INLINE_VISIBILITY
     auto operator()(_Args&& ...__args) const&&
             noexcept(noexcept(!_VSTD::invoke(_VSTD::move(__fd), _VSTD::forward<_Args>(__args)...)))
-        -> decltype(!_VSTD::invoke(_VSTD::move(__fd), _VSTD::forward<_Args>(__args)...))
-        { return !_VSTD::invoke(_VSTD::move(__fd), _VSTD::forward<_Args>(__args)...); }
+        -> decltype(          !_VSTD::invoke(_VSTD::move(__fd), _VSTD::forward<_Args>(__args)...))
+        { return              !_VSTD::invoke(_VSTD::move(__fd), _VSTD::forward<_Args>(__args)...); }
 
 private:
     template <class _RawFunc,
diff --git a/lib/libcxx/include/future b/lib/libcxx/include/future
index 936060e173b..a7c28a4746c 100644
--- a/lib/libcxx/include/future
+++ b/lib/libcxx/include/future
@@ -50,7 +50,7 @@ class future_error
 {
 public:
     future_error(error_code ec);  // exposition only
-
+    explicit future_error(future_errc); // C++17
     const error_code& code() const noexcept;
     const char*       what() const noexcept;
 };
@@ -156,7 +156,7 @@ public:
     ~future();
     future& operator=(const future& rhs) = delete;
     future& operator=(future&&) noexcept;
-    shared_future<R> share();
+    shared_future<R> share() noexcept;
 
     // retrieving the value
     R get();
@@ -183,7 +183,7 @@ public:
     ~future();
     future& operator=(const future& rhs) = delete;
     future& operator=(future&&) noexcept;
-    shared_future<R&> share();
+    shared_future<R&> share() noexcept;
 
     // retrieving the value
     R& get();
@@ -210,7 +210,7 @@ public:
     ~future();
     future& operator=(const future& rhs) = delete;
     future& operator=(future&&) noexcept;
-    shared_future<void> share();
+    shared_future<void> share() noexcept;
 
     // retrieving the value
     void get();
@@ -391,11 +391,11 @@ _LIBCPP_DECLARE_STRONG_ENUM(future_errc)
 _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(future_errc)
 
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY is_error_code_enum<future_errc> : public true_type {};
+struct _LIBCPP_TEMPLATE_VIS is_error_code_enum<future_errc> : public true_type {};
 
 #ifdef _LIBCPP_HAS_NO_STRONG_ENUMS
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY is_error_code_enum<future_errc::__lx> : public true_type { };
+struct _LIBCPP_TEMPLATE_VIS is_error_code_enum<future_errc::__lx> : public true_type { };
 #endif
 
 //enum class launch
@@ -499,30 +499,36 @@ make_error_condition(future_errc __e) _NOEXCEPT
     return error_condition(static_cast<int>(__e), future_category());
 }
 
-class _LIBCPP_EXCEPTION_ABI future_error
+class _LIBCPP_EXCEPTION_ABI _LIBCPP_AVAILABILITY_FUTURE_ERROR future_error
     : public logic_error
 {
     error_code __ec_;
 public:
     future_error(error_code __ec);
-
+#if _LIBCPP_STD_VERS > 14
+    explicit future_error(future_errc _Ev) : logic_error(), __ec_(make_error_code(_Ev)) {}
+#endif
     _LIBCPP_INLINE_VISIBILITY
     const error_code& code() const _NOEXCEPT {return __ec_;}
 
     virtual ~future_error() _NOEXCEPT;
 };
 
-inline _LIBCPP_ALWAYS_INLINE
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+#ifndef _LIBCPP_NO_EXCEPTIONS
+_LIBCPP_AVAILABILITY_FUTURE_ERROR
+#endif
 void __throw_future_error(future_errc _Ev)
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS
     throw future_error(make_error_code(_Ev));
 #else
-    assert(!"future_error");
+    ((void)_Ev);
+    _VSTD::abort();
 #endif
 }
 
-class _LIBCPP_TYPE_VIS __assoc_sub_state
+class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_FUTURE __assoc_sub_state
     : public __shared_count
 {
 protected:
@@ -579,6 +585,7 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         wait_for(const chrono::duration<_Rep, _Period>& __rel_time) const;
     template <class _Clock, class _Duration>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         future_status
         wait_until(const chrono::time_point<_Clock, _Duration>& __abs_time) const;
 
@@ -608,7 +615,7 @@ __assoc_sub_state::wait_for(const chrono::duration<_Rep, _Period>& __rel_time) c
 }
 
 template <class _Rp>
-class __assoc_state
+class _LIBCPP_AVAILABILITY_FUTURE __assoc_state
     : public __assoc_sub_state
 {
     typedef __assoc_sub_state base;
@@ -648,6 +655,7 @@ __assoc_state<_Rp>::__on_zero_shared() _NOEXCEPT
 
 template <class _Rp>
 template <class _Arg>
+_LIBCPP_AVAILABILITY_FUTURE
 void
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 __assoc_state<_Rp>::set_value(_Arg&& __arg)
@@ -703,7 +711,7 @@ __assoc_state<_Rp>::copy()
 }
 
 template <class _Rp>
-class __assoc_state<_Rp&>
+class _LIBCPP_AVAILABILITY_FUTURE __assoc_state<_Rp&>
     : public __assoc_sub_state
 {
     typedef __assoc_sub_state base;
@@ -763,7 +771,7 @@ __assoc_state<_Rp&>::copy()
 }
 
 template <class _Rp, class _Alloc>
-class __assoc_state_alloc
+class _LIBCPP_AVAILABILITY_FUTURE __assoc_state_alloc
     : public __assoc_state<_Rp>
 {
     typedef __assoc_state<_Rp> base;
@@ -791,7 +799,7 @@ __assoc_state_alloc<_Rp, _Alloc>::__on_zero_shared() _NOEXCEPT
 }
 
 template <class _Rp, class _Alloc>
-class __assoc_state_alloc<_Rp&, _Alloc>
+class _LIBCPP_AVAILABILITY_FUTURE __assoc_state_alloc<_Rp&, _Alloc>
     : public __assoc_state<_Rp&>
 {
     typedef __assoc_state<_Rp&> base;
@@ -817,7 +825,7 @@ __assoc_state_alloc<_Rp&, _Alloc>::__on_zero_shared() _NOEXCEPT
 }
 
 template <class _Alloc>
-class __assoc_sub_state_alloc
+class _LIBCPP_AVAILABILITY_FUTURE __assoc_sub_state_alloc
     : public __assoc_sub_state
 {
     typedef __assoc_sub_state base;
@@ -843,7 +851,7 @@ __assoc_sub_state_alloc<_Alloc>::__on_zero_shared() _NOEXCEPT
 }
 
 template <class _Rp, class _Fp>
-class __deferred_assoc_state
+class _LIBCPP_AVAILABILITY_FUTURE __deferred_assoc_state
     : public __assoc_state<_Rp>
 {
     typedef __assoc_state<_Rp> base;
@@ -890,7 +898,7 @@ __deferred_assoc_state<_Rp, _Fp>::__execute()
 }
 
 template <class _Fp>
-class __deferred_assoc_state<void, _Fp>
+class _LIBCPP_AVAILABILITY_FUTURE __deferred_assoc_state<void, _Fp>
     : public __assoc_sub_state
 {
     typedef __assoc_sub_state base;
@@ -938,7 +946,7 @@ __deferred_assoc_state<void, _Fp>::__execute()
 }
 
 template <class _Rp, class _Fp>
-class __async_assoc_state
+class _LIBCPP_AVAILABILITY_FUTURE __async_assoc_state
     : public __assoc_state<_Rp>
 {
     typedef __assoc_state<_Rp> base;
@@ -993,7 +1001,7 @@ __async_assoc_state<_Rp, _Fp>::__on_zero_shared() _NOEXCEPT
 }
 
 template <class _Fp>
-class __async_assoc_state<void, _Fp>
+class _LIBCPP_AVAILABILITY_FUTURE __async_assoc_state<void, _Fp>
     : public __assoc_sub_state
 {
     typedef __assoc_sub_state base;
@@ -1048,12 +1056,12 @@ __async_assoc_state<void, _Fp>::__on_zero_shared() _NOEXCEPT
     base::__on_zero_shared();
 }
 
-template <class _Rp> class _LIBCPP_TYPE_VIS_ONLY promise;
-template <class _Rp> class _LIBCPP_TYPE_VIS_ONLY shared_future;
+template <class _Rp> class _LIBCPP_TEMPLATE_VIS promise;
+template <class _Rp> class _LIBCPP_TEMPLATE_VIS shared_future;
 
 // future
 
-template <class _Rp> class _LIBCPP_TYPE_VIS_ONLY future;
+template <class _Rp> class _LIBCPP_TEMPLATE_VIS future;
 
 template <class _Rp, class _Fp>
 future<_Rp>
@@ -1072,7 +1080,7 @@ __make_async_assoc_state(_Fp __f);
 #endif
 
 template <class _Rp>
-class _LIBCPP_TYPE_VIS_ONLY future
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FUTURE future
 {
     __assoc_state<_Rp>* __state_;
 
@@ -1116,7 +1124,7 @@ public:
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     ~future();
     _LIBCPP_INLINE_VISIBILITY
-    shared_future<_Rp> share();
+    shared_future<_Rp> share() _NOEXCEPT;
 
     // retrieving the value
     _Rp get();
@@ -1175,7 +1183,7 @@ future<_Rp>::get()
 }
 
 template <class _Rp>
-class _LIBCPP_TYPE_VIS_ONLY future<_Rp&>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FUTURE future<_Rp&>
 {
     __assoc_state<_Rp&>* __state_;
 
@@ -1219,7 +1227,7 @@ public:
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     ~future();
     _LIBCPP_INLINE_VISIBILITY
-    shared_future<_Rp&> share();
+    shared_future<_Rp&> share() _NOEXCEPT;
 
     // retrieving the value
     _Rp& get();
@@ -1273,7 +1281,7 @@ future<_Rp&>::get()
 }
 
 template <>
-class _LIBCPP_TYPE_VIS future<void>
+class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_FUTURE future<void>
 {
     __assoc_sub_state* __state_;
 
@@ -1317,7 +1325,7 @@ public:
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     ~future();
     _LIBCPP_INLINE_VISIBILITY
-    shared_future<void> share();
+    shared_future<void> share() _NOEXCEPT;
 
     // retrieving the value
     void get();
@@ -1356,7 +1364,7 @@ swap(future<_Rp>& __x, future<_Rp>& __y) _NOEXCEPT
 template <class _Callable> class packaged_task;
 
 template <class _Rp>
-class _LIBCPP_TYPE_VIS_ONLY promise
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FUTURE promise
 {
     __assoc_state<_Rp>* __state_;
 
@@ -1523,7 +1531,7 @@ promise<_Rp>::set_exception_at_thread_exit(exception_ptr __p)
 // promise<R&>
 
 template <class _Rp>
-class _LIBCPP_TYPE_VIS_ONLY promise<_Rp&>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FUTURE promise<_Rp&>
 {
     __assoc_state<_Rp&>* __state_;
 
@@ -1659,7 +1667,7 @@ promise<_Rp&>::set_exception_at_thread_exit(exception_ptr __p)
 // promise<void>
 
 template <>
-class _LIBCPP_TYPE_VIS promise<void>
+class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_FUTURE promise<void>
 {
     __assoc_sub_state* __state_;
 
@@ -1671,6 +1679,7 @@ class _LIBCPP_TYPE_VIS promise<void>
 public:
     promise();
     template <class _Allocator>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         promise(allocator_arg_t, const _Allocator& __a);
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
@@ -1734,7 +1743,7 @@ swap(promise<_Rp>& __x, promise<_Rp>& __y) _NOEXCEPT
 }
 
 template <class _Rp, class _Alloc>
-    struct _LIBCPP_TYPE_VIS_ONLY uses_allocator<promise<_Rp>, _Alloc>
+    struct _LIBCPP_TEMPLATE_VIS uses_allocator<promise<_Rp>, _Alloc>
         : public true_type {};
 
 #ifndef _LIBCPP_HAS_NO_VARIADICS
@@ -1744,7 +1753,7 @@ template <class _Rp, class _Alloc>
 template<class _Fp> class __packaged_task_base;
 
 template<class _Rp, class ..._ArgTypes>
-class __packaged_task_base<_Rp(_ArgTypes...)>
+class _LIBCPP_AVAILABILITY_FUTURE __packaged_task_base<_Rp(_ArgTypes...)>
 {
     __packaged_task_base(const __packaged_task_base&);
     __packaged_task_base& operator=(const __packaged_task_base&);
@@ -1762,7 +1771,7 @@ public:
 template<class _FD, class _Alloc, class _FB> class __packaged_task_func;
 
 template<class _Fp, class _Alloc, class _Rp, class ..._ArgTypes>
-class __packaged_task_func<_Fp, _Alloc, _Rp(_ArgTypes...)>
+class _LIBCPP_AVAILABILITY_FUTURE __packaged_task_func<_Fp, _Alloc, _Rp(_ArgTypes...)>
     : public  __packaged_task_base<_Rp(_ArgTypes...)>
 {
     __compressed_pair<_Fp, _Alloc> __f_;
@@ -1820,7 +1829,7 @@ __packaged_task_func<_Fp, _Alloc, _Rp(_ArgTypes...)>::operator()(_ArgTypes&& ...
 template <class _Callable> class __packaged_task_function;
 
 template<class _Rp, class ..._ArgTypes>
-class __packaged_task_function<_Rp(_ArgTypes...)>
+class _LIBCPP_AVAILABILITY_FUTURE __packaged_task_function<_Rp(_ArgTypes...)>
 {
     typedef __packaged_task_base<_Rp(_ArgTypes...)> __base;
     typename aligned_storage<3*sizeof(void*)>::type __buf_;
@@ -1995,7 +2004,7 @@ __packaged_task_function<_Rp(_ArgTypes...)>::operator()(_ArgTypes... __arg) cons
 }
 
 template<class _Rp, class ..._ArgTypes>
-class _LIBCPP_TYPE_VIS_ONLY packaged_task<_Rp(_ArgTypes...)>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FUTURE packaged_task<_Rp(_ArgTypes...)>
 {
 public:
     typedef _Rp result_type; // extension
@@ -2124,7 +2133,7 @@ packaged_task<_Rp(_ArgTypes...)>::reset()
 }
 
 template<class ..._ArgTypes>
-class _LIBCPP_TYPE_VIS_ONLY packaged_task<void(_ArgTypes...)>
+class _LIBCPP_TEMPLATE_VIS _LIBCPP_AVAILABILITY_FUTURE packaged_task<void(_ArgTypes...)>
 {
 public:
     typedef void result_type; // extension
@@ -2263,7 +2272,7 @@ swap(packaged_task<_Callable>& __x, packaged_task<_Callable>& __y) _NOEXCEPT
 }
 
 template <class _Callable, class _Alloc>
-struct _LIBCPP_TYPE_VIS_ONLY uses_allocator<packaged_task<_Callable>, _Alloc>
+struct _LIBCPP_TEMPLATE_VIS uses_allocator<packaged_task<_Callable>, _Alloc>
     : public true_type {};
 
 template <class _Rp, class _Fp>
@@ -2326,6 +2335,7 @@ inline _LIBCPP_INLINE_VISIBILITY bool __does_policy_contain(launch __policy, lau
 { return (int(__policy) & int(__value)) != 0; }
 
 template <class _Fp, class... _Args>
+_LIBCPP_NODISCARD_AFTER_CXX17
 future<typename __invoke_of<typename decay<_Fp>::type, typename decay<_Args>::type...>::type>
 async(launch __policy, _Fp&& __f, _Args&&... __args)
 {
@@ -2351,7 +2361,7 @@ async(launch __policy, _Fp&& __f, _Args&&... __args)
 }
 
 template <class _Fp, class... _Args>
-inline _LIBCPP_INLINE_VISIBILITY
+_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY
 future<typename __invoke_of<typename decay<_Fp>::type, typename decay<_Args>::type...>::type>
 async(_Fp&& __f, _Args&&... __args)
 {
@@ -2364,7 +2374,7 @@ async(_Fp&& __f, _Args&&... __args)
 // shared_future
 
 template <class _Rp>
-class _LIBCPP_TYPE_VIS_ONLY shared_future
+class _LIBCPP_TEMPLATE_VIS shared_future
 {
     __assoc_state<_Rp>* __state_;
 
@@ -2372,7 +2382,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     shared_future() _NOEXCEPT : __state_(nullptr) {}
     _LIBCPP_INLINE_VISIBILITY
-    shared_future(const shared_future& __rhs) : __state_(__rhs.__state_)
+    shared_future(const shared_future& __rhs)  _NOEXCEPT : __state_(__rhs.__state_)
         {if (__state_) __state_->__add_shared();}
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
@@ -2383,7 +2393,7 @@ public:
         {__rhs.__state_ = nullptr;}
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     ~shared_future();
-    shared_future& operator=(const shared_future& __rhs);
+    shared_future& operator=(const shared_future& __rhs) _NOEXCEPT;
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     shared_future& operator=(shared_future&& __rhs) _NOEXCEPT
@@ -2427,7 +2437,7 @@ shared_future<_Rp>::~shared_future()
 
 template <class _Rp>
 shared_future<_Rp>&
-shared_future<_Rp>::operator=(const shared_future& __rhs)
+shared_future<_Rp>::operator=(const shared_future& __rhs) _NOEXCEPT
 {
     if (__rhs.__state_)
         __rhs.__state_->__add_shared();
@@ -2438,7 +2448,7 @@ shared_future<_Rp>::operator=(const shared_future& __rhs)
 }
 
 template <class _Rp>
-class _LIBCPP_TYPE_VIS_ONLY shared_future<_Rp&>
+class _LIBCPP_TEMPLATE_VIS shared_future<_Rp&>
 {
     __assoc_state<_Rp&>* __state_;
 
@@ -2512,7 +2522,7 @@ shared_future<_Rp&>::operator=(const shared_future& __rhs)
 }
 
 template <>
-class _LIBCPP_TYPE_VIS shared_future<void>
+class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_FUTURE shared_future<void>
 {
     __assoc_sub_state* __state_;
 
@@ -2577,7 +2587,7 @@ swap(shared_future<_Rp>& __x, shared_future<_Rp>& __y) _NOEXCEPT
 template <class _Rp>
 inline
 shared_future<_Rp>
-future<_Rp>::share()
+future<_Rp>::share() _NOEXCEPT
 {
     return shared_future<_Rp>(_VSTD::move(*this));
 }
@@ -2585,7 +2595,7 @@ future<_Rp>::share()
 template <class _Rp>
 inline
 shared_future<_Rp&>
-future<_Rp&>::share()
+future<_Rp&>::share() _NOEXCEPT
 {
     return shared_future<_Rp&>(_VSTD::move(*this));
 }
@@ -2594,7 +2604,7 @@ future<_Rp&>::share()
 
 inline
 shared_future<void>
-future<void>::share()
+future<void>::share() _NOEXCEPT
 {
     return shared_future<void>(_VSTD::move(*this));
 }
diff --git a/lib/libcxx/include/initializer_list b/lib/libcxx/include/initializer_list
index 663e49b6ee4..8c234aaaab2 100644
--- a/lib/libcxx/include/initializer_list
+++ b/lib/libcxx/include/initializer_list
@@ -53,10 +53,10 @@ template<class E> const E* end(initializer_list<E> il) noexcept; // constexpr in
 namespace std  // purposefully not versioned
 {
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
 
 template<class _Ep>
-class _LIBCPP_TYPE_VIS_ONLY initializer_list
+class _LIBCPP_TEMPLATE_VIS initializer_list
 {
     const _Ep* __begin_;
     size_t    __size_;
@@ -111,7 +111,7 @@ end(initializer_list<_Ep> __il) _NOEXCEPT
     return __il.end();
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // !defined(_LIBCPP_CXX03_LANG)
 
 }  // std
 
diff --git a/lib/libcxx/include/inttypes.h b/lib/libcxx/include/inttypes.h
index 5c5618bef88..058f54b5161 100644
--- a/lib/libcxx/include/inttypes.h
+++ b/lib/libcxx/include/inttypes.h
@@ -237,6 +237,13 @@ uintmax_t wcstoumax(const wchar_t* restrict nptr, wchar_t** restrict endptr, int
 #pragma GCC system_header
 #endif
 
+/* C99 stdlib (e.g. glibc < 2.18) does not provide format macros needed
+   for C++11 unless __STDC_FORMAT_MACROS is defined
+*/
+#if defined(__cplusplus) && !defined(__STDC_FORMAT_MACROS)
+#   define __STDC_FORMAT_MACROS
+#endif
+
 #include_next <inttypes.h>
 
 #ifdef __cplusplus
diff --git a/lib/libcxx/include/iomanip b/lib/libcxx/include/iomanip
index 9efcbe03d1a..a6bee736f45 100644
--- a/lib/libcxx/include/iomanip
+++ b/lib/libcxx/include/iomanip
@@ -44,6 +44,7 @@ template <class charT, class traits, class Allocator>
 */
 
 #include <__config>
+#include <__string>
 #include <istream>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -567,19 +568,6 @@ __quoted_input ( basic_istream<_CharT, _Traits> &__is, _String & __string, _Char
 }
 
 
-template <class _CharT, class _Iter, class _Traits=char_traits<_CharT> >
-struct __quoted_output_proxy
-{
-    _Iter  __first;
-    _Iter  __last;
-    _CharT  __delim;
-    _CharT  __escape;
-
-    __quoted_output_proxy(_Iter __f, _Iter __l, _CharT __d, _CharT __e)
-    : __first(__f), __last(__l), __delim(__d), __escape(__e) {}
-    //  This would be a nice place for a string_ref 
-};
-
 template <class _CharT, class _Traits, class _Iter>
 basic_ostream<_CharT, _Traits>& operator<<(
          basic_ostream<_CharT, _Traits>& __os, 
@@ -666,6 +654,15 @@ quoted ( basic_string <_CharT, _Traits, _Allocator> &__s, _CharT __delim = _Char
 {
     return __quoted(__s, __delim, __escape);
 }
+
+template <class _CharT, class _Traits>
+__quoted_output_proxy<_CharT, const _CharT *, _Traits>
+quoted (basic_string_view <_CharT, _Traits> __sv,
+             _CharT __delim = _CharT('"'), _CharT __escape=_CharT('\\'))
+{
+    return __quoted_output_proxy<_CharT, const _CharT *, _Traits> 
+         ( __sv.data(), __sv.data() + __sv.size(), __delim, __escape );
+}
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/lib/libcxx/include/ios b/lib/libcxx/include/ios
index cbea478a74a..61d00b90ee0 100644
--- a/lib/libcxx/include/ios
+++ b/lib/libcxx/include/ios
@@ -393,11 +393,11 @@ _LIBCPP_DECLARE_STRONG_ENUM(io_errc)
 _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(io_errc)
 
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY is_error_code_enum<io_errc> : public true_type { };
+struct _LIBCPP_TEMPLATE_VIS is_error_code_enum<io_errc> : public true_type { };
 
 #ifdef _LIBCPP_HAS_NO_STRONG_ENUMS
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY is_error_code_enum<io_errc::__lx> : public true_type { };
+struct _LIBCPP_TEMPLATE_VIS is_error_code_enum<io_errc::__lx> : public true_type { };
 #endif
 
 _LIBCPP_FUNC_VIS
@@ -572,8 +572,15 @@ ios_base::exceptions(iostate __iostate)
     clear(__rdstate_);
 }
 
+#if defined(_LIBCPP_CXX03_LANG)
+struct _LIBCPP_TYPE_VIS __cxx03_bool {
+  typedef void (__cxx03_bool::*__bool_type)();
+  void __true_value() {}
+};
+#endif
+
 template <class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY basic_ios
+class _LIBCPP_TEMPLATE_VIS basic_ios
     : public ios_base
 {
 public:
@@ -585,9 +592,19 @@ public:
     typedef typename traits_type::pos_type pos_type;
     typedef typename traits_type::off_type off_type;
 
+  // __true_value will generate undefined references when linking unless
+  // we give it internal linkage.
+
+#if defined(_LIBCPP_CXX03_LANG)
     _LIBCPP_ALWAYS_INLINE
-        _LIBCPP_EXPLICIT
-        operator bool() const {return !fail();}
+    operator __cxx03_bool::__bool_type() const {
+        return !fail() ? &__cxx03_bool::__true_value : nullptr;
+    }
+#else
+    _LIBCPP_ALWAYS_INLINE
+    _LIBCPP_EXPLICIT operator bool() const {return !fail();}
+#endif
+
     _LIBCPP_ALWAYS_INLINE bool operator!() const    {return  fail();}
     _LIBCPP_ALWAYS_INLINE iostate rdstate() const   {return ios_base::rdstate();}
     _LIBCPP_ALWAYS_INLINE void clear(iostate __state = goodbit) {ios_base::clear(__state);}
@@ -640,7 +657,7 @@ protected:
 
     _LIBCPP_INLINE_VISIBILITY 
     void move(basic_ios& __rhs);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_ALWAYS_INLINE
     void move(basic_ios&& __rhs) {move(__rhs);}
 #endif
diff --git a/lib/libcxx/include/iosfwd b/lib/libcxx/include/iosfwd
index e4149ef2237..d4384859e41 100644
--- a/lib/libcxx/include/iosfwd
+++ b/lib/libcxx/include/iosfwd
@@ -97,47 +97,47 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 class _LIBCPP_TYPE_VIS ios_base;
 
-template<class _CharT>  struct _LIBCPP_TYPE_VIS_ONLY char_traits;
-template<class _Tp>     class _LIBCPP_TYPE_VIS_ONLY allocator;
+template<class _CharT>  struct _LIBCPP_TEMPLATE_VIS char_traits;
+template<class _Tp>     class _LIBCPP_TEMPLATE_VIS allocator;
 
 template <class _CharT, class _Traits = char_traits<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_ios;
+    class _LIBCPP_TEMPLATE_VIS basic_ios;
 
 template <class _CharT, class _Traits = char_traits<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_streambuf;
+    class _LIBCPP_TEMPLATE_VIS basic_streambuf;
 template <class _CharT, class _Traits = char_traits<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_istream;
+    class _LIBCPP_TEMPLATE_VIS basic_istream;
 template <class _CharT, class _Traits = char_traits<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_ostream;
+    class _LIBCPP_TEMPLATE_VIS basic_ostream;
 template <class _CharT, class _Traits = char_traits<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_iostream;
+    class _LIBCPP_TEMPLATE_VIS basic_iostream;
 
 template <class _CharT, class _Traits = char_traits<_CharT>,
           class _Allocator = allocator<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_stringbuf;
+    class _LIBCPP_TEMPLATE_VIS basic_stringbuf;
 template <class _CharT, class _Traits = char_traits<_CharT>,
           class _Allocator = allocator<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_istringstream;
+    class _LIBCPP_TEMPLATE_VIS basic_istringstream;
 template <class _CharT, class _Traits = char_traits<_CharT>,
           class _Allocator = allocator<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_ostringstream;
+    class _LIBCPP_TEMPLATE_VIS basic_ostringstream;
 template <class _CharT, class _Traits = char_traits<_CharT>,
           class _Allocator = allocator<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_stringstream;
+    class _LIBCPP_TEMPLATE_VIS basic_stringstream;
 
 template <class _CharT, class _Traits = char_traits<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_filebuf;
+    class _LIBCPP_TEMPLATE_VIS basic_filebuf;
 template <class _CharT, class _Traits = char_traits<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_ifstream;
+    class _LIBCPP_TEMPLATE_VIS basic_ifstream;
 template <class _CharT, class _Traits = char_traits<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_ofstream;
+    class _LIBCPP_TEMPLATE_VIS basic_ofstream;
 template <class _CharT, class _Traits = char_traits<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_fstream;
+    class _LIBCPP_TEMPLATE_VIS basic_fstream;
 
 template <class _CharT, class _Traits = char_traits<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY istreambuf_iterator;
+    class _LIBCPP_TEMPLATE_VIS istreambuf_iterator;
 template <class _CharT, class _Traits = char_traits<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY ostreambuf_iterator;
+    class _LIBCPP_TEMPLATE_VIS ostreambuf_iterator;
 
 typedef basic_ios<char>              ios;
 typedef basic_ios<wchar_t>           wios;
@@ -172,7 +172,7 @@ typedef basic_ifstream<wchar_t>      wifstream;
 typedef basic_ofstream<wchar_t>      wofstream;
 typedef basic_fstream<wchar_t>       wfstream;
 
-template <class _State>             class _LIBCPP_TYPE_VIS_ONLY fpos;
+template <class _State>             class _LIBCPP_TEMPLATE_VIS fpos;
 typedef fpos<mbstate_t>    streampos;
 typedef fpos<mbstate_t>    wstreampos;
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
@@ -190,14 +190,14 @@ typedef long long streamoff;        // for char_traits in <string>
 template <class _CharT,             // for <stdexcept>
           class _Traits = char_traits<_CharT>,
           class _Allocator = allocator<_CharT> >
-    class _LIBCPP_TYPE_VIS_ONLY basic_string;
+    class _LIBCPP_TEMPLATE_VIS basic_string;
 typedef basic_string<char, char_traits<char>, allocator<char> > string;
 typedef basic_string<wchar_t, char_traits<wchar_t>, allocator<wchar_t> > wstring;
 
 
 // Include other forward declarations here
 template <class _Tp, class _Alloc = allocator<_Tp> >
-class _LIBCPP_TYPE_VIS_ONLY vector;
+class _LIBCPP_TEMPLATE_VIS vector;
 
 _LIBCPP_END_NAMESPACE_STD
 
diff --git a/lib/libcxx/include/istream b/lib/libcxx/include/istream
index ee694003a3d..5c73df38f65 100644
--- a/lib/libcxx/include/istream
+++ b/lib/libcxx/include/istream
@@ -162,16 +162,18 @@ template <class charT, class traits, class T>
 #include <__config>
 #include <ostream>
 
-#include <__undef_min_max>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY basic_istream
+class _LIBCPP_TEMPLATE_VIS basic_istream
     : virtual public basic_ios<_CharT, _Traits>
 {
     streamsize __gc_;
@@ -184,39 +186,49 @@ public:
     typedef typename traits_type::off_type off_type;
 
     // 27.7.1.1.1 Constructor/destructor:
-    explicit basic_istream(basic_streambuf<char_type, traits_type>* __sb);
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    explicit basic_istream(basic_streambuf<char_type, traits_type>* __sb) : __gc_(0)
+    { this->init(__sb); }
     virtual ~basic_istream();
 protected:
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
+#ifndef _LIBCPP_CXX03_LANG
+    inline _LIBCPP_INLINE_VISIBILITY
     basic_istream(basic_istream&& __rhs);
-#endif
+
     // 27.7.1.1.2 Assign/swap:
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
+    inline _LIBCPP_INLINE_VISIBILITY
     basic_istream& operator=(basic_istream&& __rhs);
 #endif
-    void swap(basic_istream& __rhs);
 
-#if _LIBCPP_STD_VER > 11
-#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    void swap(basic_istream& __rhs) {
+      _VSTD::swap(__gc_, __rhs.__gc_);
+      basic_ios<char_type, traits_type>::swap(__rhs);
+    }
+
+#ifndef _LIBCPP_CXX03_LANG
     basic_istream           (const basic_istream& __rhs) = delete;
     basic_istream& operator=(const basic_istream& __rhs) = delete;
-#else
-    basic_istream           (const basic_istream& __rhs); // not defined
-    basic_istream& operator=(const basic_istream& __rhs); // not defined
-#endif
 #endif
 public:
 
     // 27.7.1.1.3 Prefix/suffix:
-    class _LIBCPP_TYPE_VIS_ONLY sentry;
+    class _LIBCPP_TEMPLATE_VIS sentry;
 
     // 27.7.1.2 Formatted input:
-    basic_istream& operator>>(basic_istream& (*__pf)(basic_istream&));
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    basic_istream& operator>>(basic_istream& (*__pf)(basic_istream&))
+    { return __pf(*this); }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
     basic_istream& operator>>(basic_ios<char_type, traits_type>&
-                              (*__pf)(basic_ios<char_type, traits_type>&));
-    basic_istream& operator>>(ios_base& (*__pf)(ios_base&));
+                              (*__pf)(basic_ios<char_type, traits_type>&))
+    { __pf(*this); return *this; }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    basic_istream& operator>>(ios_base& (*__pf)(ios_base&))
+    { __pf(*this); return *this; }
+
     basic_istream& operator>>(basic_streambuf<char_type, traits_type>* __sb);
     basic_istream& operator>>(bool& __n);
     basic_istream& operator>>(short& __n);
@@ -236,13 +248,31 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     streamsize gcount() const {return __gc_;}
     int_type get();
-    basic_istream& get(char_type& __c);
-    basic_istream& get(char_type* __s, streamsize __n);
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    basic_istream& get(char_type& __c) {
+      int_type __ch = get();
+      if (__ch != traits_type::eof())
+        __c = traits_type::to_char_type(__ch);
+      return *this;
+    }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    basic_istream& get(char_type* __s, streamsize __n)
+    { return get(__s, __n, this->widen('\n')); }
+
     basic_istream& get(char_type* __s, streamsize __n, char_type __dlm);
-    basic_istream& get(basic_streambuf<char_type, traits_type>& __sb);
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    basic_istream& get(basic_streambuf<char_type, traits_type>& __sb)
+    { return get(__sb, this->widen('\n')); }
+
     basic_istream& get(basic_streambuf<char_type, traits_type>& __sb, char_type __dlm);
 
-    basic_istream& getline(char_type* __s, streamsize __n);
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    basic_istream& getline(char_type* __s, streamsize __n)
+    { return getline(__s, __n, this->widen('\n')); }
+
     basic_istream& getline(char_type* __s, streamsize __n, char_type __dlm);
 
     basic_istream& ignore(streamsize __n = 1, int_type __dlm = traits_type::eof());
@@ -260,7 +290,7 @@ public:
 };
 
 template <class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY basic_istream<_CharT, _Traits>::sentry
+class _LIBCPP_TEMPLATE_VIS basic_istream<_CharT, _Traits>::sentry
 {
     bool __ok_;
 
@@ -303,18 +333,9 @@ basic_istream<_CharT, _Traits>::sentry::sentry(basic_istream<_CharT, _Traits>& _
         __is.setstate(ios_base::failbit);
 }
 
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_istream<_CharT, _Traits>::basic_istream(basic_streambuf<char_type, traits_type>* __sb)
-    : __gc_(0)
-{
-    this->init(__sb);
-}
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_istream<_CharT, _Traits>::basic_istream(basic_istream&& __rhs)
     : __gc_(__rhs.__gc_)
 {
@@ -323,7 +344,6 @@ basic_istream<_CharT, _Traits>::basic_istream(basic_istream&& __rhs)
 }
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_istream<_CharT, _Traits>&
 basic_istream<_CharT, _Traits>::operator=(basic_istream&& __rhs)
 {
@@ -331,7 +351,7 @@ basic_istream<_CharT, _Traits>::operator=(basic_istream&& __rhs)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 basic_istream<_CharT, _Traits>::~basic_istream()
@@ -339,15 +359,6 @@ basic_istream<_CharT, _Traits>::~basic_istream()
 }
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-void
-basic_istream<_CharT, _Traits>::swap(basic_istream& __rhs)
-{
-    _VSTD::swap(__gc_, __rhs.__gc_);
-    basic_ios<char_type, traits_type>::swap(__rhs);
-}
-
-template <class _CharT, class _Traits>
 basic_istream<_CharT, _Traits>&
 basic_istream<_CharT, _Traits>::operator>>(unsigned short& __n)
 {
@@ -724,33 +735,6 @@ basic_istream<_CharT, _Traits>::operator>>(int& __n)
     return *this;
 }
 
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_istream<_CharT, _Traits>&
-basic_istream<_CharT, _Traits>::operator>>(basic_istream& (*__pf)(basic_istream&))
-{
-    return __pf(*this);
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_istream<_CharT, _Traits>&
-basic_istream<_CharT, _Traits>::operator>>(basic_ios<char_type, traits_type>&
-                                           (*__pf)(basic_ios<char_type, traits_type>&))
-{
-    __pf(*this);
-    return *this;
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_istream<_CharT, _Traits>&
-basic_istream<_CharT, _Traits>::operator>>(ios_base& (*__pf)(ios_base&))
-{
-    __pf(*this);
-    return *this;
-}
-
 template<class _CharT, class _Traits>
 basic_istream<_CharT, _Traits>&
 operator>>(basic_istream<_CharT, _Traits>& __is, _CharT* __s)
@@ -947,17 +931,6 @@ basic_istream<_CharT, _Traits>::get()
 }
 
 template<class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_istream<_CharT, _Traits>&
-basic_istream<_CharT, _Traits>::get(char_type& __c)
-{
-    int_type __ch = get();
-    if (__ch != traits_type::eof())
-        __c = traits_type::to_char_type(__ch);
-    return *this;
-}
-
-template<class _CharT, class _Traits>
 basic_istream<_CharT, _Traits>&
 basic_istream<_CharT, _Traits>::get(char_type* __s, streamsize __n, char_type __dlm)
 {
@@ -1006,14 +979,6 @@ basic_istream<_CharT, _Traits>::get(char_type* __s, streamsize __n, char_type __
 }
 
 template<class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_istream<_CharT, _Traits>&
-basic_istream<_CharT, _Traits>::get(char_type* __s, streamsize __n)
-{
-    return get(__s, __n, this->widen('\n'));
-}
-
-template<class _CharT, class _Traits>
 basic_istream<_CharT, _Traits>&
 basic_istream<_CharT, _Traits>::get(basic_streambuf<char_type, traits_type>& __sb,
                                     char_type __dlm)
@@ -1068,14 +1033,6 @@ basic_istream<_CharT, _Traits>::get(basic_streambuf<char_type, traits_type>& __s
 }
 
 template<class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_istream<_CharT, _Traits>&
-basic_istream<_CharT, _Traits>::get(basic_streambuf<char_type, traits_type>& __sb)
-{
-    return get(__sb, this->widen('\n'));
-}
-
-template<class _CharT, class _Traits>
 basic_istream<_CharT, _Traits>&
 basic_istream<_CharT, _Traits>::getline(char_type* __s, streamsize __n, char_type __dlm)
 {
@@ -1112,16 +1069,18 @@ basic_istream<_CharT, _Traits>::getline(char_type* __s, streamsize __n, char_typ
                 this->rdbuf()->sbumpc();
                 ++__gc_;
             }
-            if (__n > 0)
-                *__s = char_type();
             if (__gc_ == 0)
                __err |= ios_base::failbit;
             this->setstate(__err);
         }
+        if (__n > 0)
+            *__s = char_type();
 #ifndef _LIBCPP_NO_EXCEPTIONS
     }
     catch (...)
     {
+        if (__n > 0)
+            *__s = char_type();
         this->__set_badbit_and_consider_rethrow();
     }
 #endif  // _LIBCPP_NO_EXCEPTIONS
@@ -1129,14 +1088,6 @@ basic_istream<_CharT, _Traits>::getline(char_type* __s, streamsize __n, char_typ
 }
 
 template<class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_istream<_CharT, _Traits>&
-basic_istream<_CharT, _Traits>::getline(char_type* __s, streamsize __n)
-{
-    return getline(__s, __n, this->widen('\n'));
-}
-
-template<class _CharT, class _Traits>
 basic_istream<_CharT, _Traits>&
 basic_istream<_CharT, _Traits>::ignore(streamsize __n, int_type __dlm)
 {
@@ -1476,21 +1427,21 @@ ws(basic_istream<_CharT, _Traits>& __is)
     return __is;
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 basic_istream<_CharT, _Traits>&
-operator>>(basic_istream<_CharT, _Traits>&& __is, _Tp& __x)
+operator>>(basic_istream<_CharT, _Traits>&& __is, _Tp&& __x)
 {
-    __is >> __x;
+    __is >> _VSTD::forward<_Tp>(__x);
     return __is;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY basic_iostream
+class _LIBCPP_TEMPLATE_VIS basic_iostream
     : public basic_istream<_CharT, _Traits>,
       public basic_ostream<_CharT, _Traits>
 {
@@ -1503,41 +1454,36 @@ public:
     typedef typename traits_type::off_type off_type;
 
     // constructor/destructor
-    explicit basic_iostream(basic_streambuf<char_type, traits_type>* __sb);
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    explicit basic_iostream(basic_streambuf<char_type, traits_type>* __sb)
+      : basic_istream<_CharT, _Traits>(__sb)
+    {}
+
     virtual ~basic_iostream();
 protected:
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
+#ifndef _LIBCPP_CXX03_LANG
+    inline _LIBCPP_INLINE_VISIBILITY
     basic_iostream(basic_iostream&& __rhs);
-#endif
 
     // assign/swap
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
+    inline _LIBCPP_INLINE_VISIBILITY
     basic_iostream& operator=(basic_iostream&& __rhs);
 #endif
-    void swap(basic_iostream& __rhs);
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    void swap(basic_iostream& __rhs)
+    { basic_istream<char_type, traits_type>::swap(__rhs); }
 public:
 };
 
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_iostream<_CharT, _Traits>::basic_iostream(basic_streambuf<char_type, traits_type>* __sb)
-    : basic_istream<_CharT, _Traits>(__sb)
-{
-}
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_iostream<_CharT, _Traits>::basic_iostream(basic_iostream&& __rhs)
     : basic_istream<_CharT, _Traits>(_VSTD::move(__rhs))
 {
 }
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_iostream<_CharT, _Traits>&
 basic_iostream<_CharT, _Traits>::operator=(basic_iostream&& __rhs)
 {
@@ -1545,21 +1491,13 @@ basic_iostream<_CharT, _Traits>::operator=(basic_iostream&& __rhs)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 basic_iostream<_CharT, _Traits>::~basic_iostream()
 {
 }
 
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-void
-basic_iostream<_CharT, _Traits>::swap(basic_iostream& __rhs)
-{
-    basic_istream<char_type, traits_type>::swap(__rhs);
-}
-
 template<class _CharT, class _Traits, class _Allocator>
 basic_istream<_CharT, _Traits>&
 operator>>(basic_istream<_CharT, _Traits>& __is,
@@ -1670,7 +1608,7 @@ getline(basic_istream<_CharT, _Traits>& __is,
     return getline(__is, __str, __is.widen('\n'));
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template<class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1690,7 +1628,7 @@ getline(basic_istream<_CharT, _Traits>&& __is,
     return getline(__is, __str, __is.widen('\n'));
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, size_t _Size>
 basic_istream<_CharT, _Traits>&
@@ -1705,7 +1643,7 @@ operator>>(basic_istream<_CharT, _Traits>& __is, bitset<_Size>& __x)
         {
             basic_string<_CharT, _Traits> __str;
             const ctype<_CharT>& __ct = use_facet<ctype<_CharT> >(__is.getloc());
-            streamsize __c = 0;
+            size_t __c = 0;
             ios_base::iostate __err = ios_base::goodbit;
             _CharT __zero = __ct.widen('0');
             _CharT __one = __ct.widen('1');
@@ -1741,10 +1679,14 @@ operator>>(basic_istream<_CharT, _Traits>& __is, bitset<_Size>& __x)
     return __is;
 }
 
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_istream<char>)
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_istream<wchar_t>)
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_iostream<char>)
+#ifndef _LIBCPP_AVAILABILITY_NO_STREAMS_EXTERN_TEMPLATE
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_istream<char>)
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_istream<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_iostream<char>)
+#endif
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_ISTREAM
diff --git a/lib/libcxx/include/iterator b/lib/libcxx/include/iterator
index 0caabbb2ea1..8b887db037b 100644
--- a/lib/libcxx/include/iterator
+++ b/lib/libcxx/include/iterator
@@ -37,16 +37,6 @@ struct iterator_traits<T*>
     typedef random_access_iterator_tag iterator_category;
 };
 
-template<class T>
-struct iterator_traits<const T*>
-{
-    typedef ptrdiff_t difference_type;
-    typedef T value_type;
-    typedef const T* pointer;
-    typedef const T& reference;
-    typedef random_access_iterator_tag iterator_category;
-};
-
 template<class Category, class T, class Distance = ptrdiff_t,
          class Pointer = T*, class Reference = T&>
 struct iterator
@@ -64,14 +54,23 @@ struct forward_iterator_tag       : public input_iterator_tag         {};
 struct bidirectional_iterator_tag : public forward_iterator_tag       {};
 struct random_access_iterator_tag : public bidirectional_iterator_tag {};
 
+// 27.4.3, iterator operations
 // extension: second argument not conforming to C++03
-template <class InputIterator>
-void advance(InputIterator& i,
+template <class InputIterator>  // constexpr in C++17
+  constexpr void advance(InputIterator& i,
              typename iterator_traits<InputIterator>::difference_type n);
 
-template <class InputIterator>
-typename iterator_traits<InputIterator>::difference_type
-distance(InputIterator first, InputIterator last);
+template <class InputIterator>  // constexpr in C++17
+  constexpr typename iterator_traits<InputIterator>::difference_type
+    distance(InputIterator first, InputIterator last);
+
+template <class InputIterator>  // constexpr in C++17
+  constexpr InputIterator next(InputIterator x,
+typename iterator_traits<InputIterator>::difference_type n = 1);
+
+template <class BidirectionalIterator>  // constexpr in C++17
+  constexpr BidirectionalIterator prev(BidirectionalIterator x,
+    typename iterator_traits<BidirectionalIterator>::difference_type n = 1);    
 
 template <class Iterator>
 class reverse_iterator
@@ -89,57 +88,60 @@ public:
     typedef typename iterator_traits<Iterator>::reference       reference;
     typedef typename iterator_traits<Iterator>::pointer         pointer;
 
-    reverse_iterator();
-    explicit reverse_iterator(Iterator x);
-    template <class U> reverse_iterator(const reverse_iterator<U>& u);
-    Iterator base() const;
-    reference operator*() const;
-    pointer   operator->() const;
-    reverse_iterator& operator++();
-    reverse_iterator  operator++(int);
-    reverse_iterator& operator--();
-    reverse_iterator  operator--(int);
-    reverse_iterator  operator+ (difference_type n) const;
-    reverse_iterator& operator+=(difference_type n);
-    reverse_iterator  operator- (difference_type n) const;
-    reverse_iterator& operator-=(difference_type n);
-    reference         operator[](difference_type n) const;
+    constexpr reverse_iterator();
+    constexpr explicit reverse_iterator(Iterator x);
+    template <class U> constexpr reverse_iterator(const reverse_iterator<U>& u);
+    template <class U> constexpr reverse_iterator& operator=(const reverse_iterator<U>& u);
+    constexpr Iterator base() const;
+    constexpr reference operator*() const;
+    constexpr pointer   operator->() const;
+    constexpr reverse_iterator& operator++();
+    constexpr reverse_iterator  operator++(int);
+    constexpr reverse_iterator& operator--();
+    constexpr reverse_iterator  operator--(int);
+    constexpr reverse_iterator  operator+ (difference_type n) const;
+    constexpr reverse_iterator& operator+=(difference_type n);
+    constexpr reverse_iterator  operator- (difference_type n) const;
+    constexpr reverse_iterator& operator-=(difference_type n);
+    constexpr reference         operator[](difference_type n) const;
 };
 
 template <class Iterator1, class Iterator2>
-bool
+constexpr bool                          // constexpr in C++17
 operator==(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);
 
 template <class Iterator1, class Iterator2>
-bool
+constexpr bool                          // constexpr in C++17
 operator<(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);
 
 template <class Iterator1, class Iterator2>
-bool
+constexpr bool                          // constexpr in C++17
 operator!=(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);
 
 template <class Iterator1, class Iterator2>
-bool
+constexpr bool                          // constexpr in C++17
 operator>(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);
 
 template <class Iterator1, class Iterator2>
-bool
+constexpr bool                          // constexpr in C++17
 operator>=(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);
 
 template <class Iterator1, class Iterator2>
-bool
+constexpr bool                          // constexpr in C++17
 operator<=(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y);
 
 template <class Iterator1, class Iterator2>
-auto
+constexpr auto
 operator-(const reverse_iterator<Iterator1>& x, const reverse_iterator<Iterator2>& y)
--> decltype(__y.base() - __x.base());
+-> decltype(__y.base() - __x.base());   // constexpr in C++17
 
 template <class Iterator>
-reverse_iterator<Iterator>
-operator+(typename reverse_iterator<Iterator>::difference_type n, const reverse_iterator<Iterator>& x);
+constexpr reverse_iterator<Iterator>
+operator+(typename reverse_iterator<Iterator>::difference_type n, 
+          const reverse_iterator<Iterator>& x);   // constexpr in C++17
 
-template <class Iterator> reverse_iterator<Iterator> make_reverse_iterator(Iterator i); // C++14
+template <class Iterator>
+constexpr reverse_iterator<Iterator> make_reverse_iterator(Iterator i); // C++14, constexpr in C++17
 
 template <class Container>
 class back_insert_iterator
@@ -216,61 +218,64 @@ public:
     typedef typename iterator_traits<Iterator>::iterator_category iterator_category;
     typedef value_type&&                                          reference;
  
-    move_iterator();
-    explicit move_iterator(Iterator i);
-    template <class U> move_iterator(const move_iterator<U>& u);
-    template <class U> move_iterator& operator=(const move_iterator<U>& u);
-    iterator_type base() const;
-    reference operator*() const;
-    pointer operator->() const;
-    move_iterator& operator++();
-    move_iterator operator++(int);
-    move_iterator& operator--();
-    move_iterator operator--(int);
-    move_iterator operator+(difference_type n) const; 
-    move_iterator& operator+=(difference_type n); 
-    move_iterator operator-(difference_type n) const; 
-    move_iterator& operator-=(difference_type n); 
-    unspecified operator[](difference_type n) const;
+    constexpr move_iterator();  // all the constexprs are in C++17
+    constexpr explicit move_iterator(Iterator i);
+    template <class U>
+      constexpr move_iterator(const move_iterator<U>& u);
+    template <class U>
+      constexpr move_iterator& operator=(const move_iterator<U>& u);
+    constexpr iterator_type base() const;
+    constexpr reference operator*() const;
+    constexpr pointer operator->() const;
+    constexpr move_iterator& operator++();
+    constexpr move_iterator operator++(int);
+    constexpr move_iterator& operator--();
+    constexpr move_iterator operator--(int);
+    constexpr move_iterator operator+(difference_type n) const; 
+    constexpr move_iterator& operator+=(difference_type n); 
+    constexpr move_iterator operator-(difference_type n) const; 
+    constexpr move_iterator& operator-=(difference_type n); 
+    constexpr unspecified operator[](difference_type n) const;
 private:
     Iterator current; // exposition only
 };
 
 template <class Iterator1, class Iterator2>
-bool
+constexpr bool   // constexpr in C++17
 operator==(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
 
 template <class Iterator1, class Iterator2>
-bool
+constexpr bool   // constexpr in C++17
 operator!=(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
 
 template <class Iterator1, class Iterator2>
-bool
+constexpr bool   // constexpr in C++17
 operator<(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
 
 template <class Iterator1, class Iterator2>
-bool
+constexpr bool   // constexpr in C++17
 operator<=(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
 
 template <class Iterator1, class Iterator2>
-bool
+constexpr bool   // constexpr in C++17
 operator>(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
 
 template <class Iterator1, class Iterator2>
-bool
+constexpr bool   // constexpr in C++17
 operator>=(const move_iterator<Iterator1>& x, const move_iterator<Iterator2>& y);
 
 template <class Iterator1, class Iterator2>
-auto
+constexpr auto   // constexpr in C++17
 operator-(const move_iterator<Iterator1>& x,
           const move_iterator<Iterator2>& y) -> decltype(x.base() - y.base());
 
 template <class Iterator>
-move_iterator<Iterator> operator+(typename move_iterator<Iterator>::difference_type n, 
-                                     const move_iterator<Iterator>& x);
+constexpr move_iterator<Iterator> operator+(   // constexpr in C++17
+            typename move_iterator<Iterator>::difference_type n, 
+            const move_iterator<Iterator>& x);
 
-template <class Iterator>
-move_iterator<Iterator> make_move_iterator(const Iterator& i);
+template <class Iterator>   // constexpr in C++17
+constexpr  move_iterator<Iterator> make_move_iterator(const Iterator& i);
 
 
 template <class T, class charT = char, class traits = char_traits<charT>, class Distance = ptrdiff_t>
@@ -372,25 +377,25 @@ public:
     bool failed() const noexcept;
 };
 
-template <class C> auto begin(C& c) -> decltype(c.begin());
-template <class C> auto begin(const C& c) -> decltype(c.begin());
-template <class C> auto end(C& c) -> decltype(c.end());
-template <class C> auto end(const C& c) -> decltype(c.end());
-template <class T, size_t N> T* begin(T (&array)[N]);
-template <class T, size_t N> T* end(T (&array)[N]);
-
-template <class C> auto cbegin(const C& c) -> decltype(std::begin(c));        // C++14
-template <class C> auto cend(const C& c) -> decltype(std::end(c));            // C++14
-template <class C> auto rbegin(C& c) -> decltype(c.rbegin());                 // C++14
-template <class C> auto rbegin(const C& c) -> decltype(c.rbegin());           // C++14
-template <class C> auto rend(C& c) -> decltype(c.rend());                     // C++14
-template <class C> auto rend(const C& c) -> decltype(c.rend());               // C++14
-template <class E> reverse_iterator<const E*> rbegin(initializer_list<E> il); // C++14
-template <class E> reverse_iterator<const E*> rend(initializer_list<E> il);   // C++14
-template <class T, size_t N> reverse_iterator<T*> rbegin(T (&array)[N]);      // C++14
-template <class T, size_t N> reverse_iterator<T*> rend(T (&array)[N]);        // C++14
-template <class C> auto crbegin(const C& c) -> decltype(std::rbegin(c));      // C++14
-template <class C> auto crend(const C& c) -> decltype(std::rend(c));          // C++14
+template <class C> constexpr auto begin(C& c) -> decltype(c.begin());
+template <class C> constexpr auto begin(const C& c) -> decltype(c.begin());
+template <class C> constexpr auto end(C& c) -> decltype(c.end());
+template <class C> constexpr auto end(const C& c) -> decltype(c.end());
+template <class T, size_t N> constexpr T* begin(T (&array)[N]);
+template <class T, size_t N> constexpr T* end(T (&array)[N]);
+
+template <class C> auto constexpr cbegin(const C& c) -> decltype(std::begin(c));        // C++14
+template <class C> auto constexpr cend(const C& c) -> decltype(std::end(c));            // C++14
+template <class C> auto constexpr rbegin(C& c) -> decltype(c.rbegin());                 // C++14
+template <class C> auto constexpr rbegin(const C& c) -> decltype(c.rbegin());           // C++14
+template <class C> auto constexpr rend(C& c) -> decltype(c.rend());                     // C++14
+template <class C> constexpr auto rend(const C& c) -> decltype(c.rend());               // C++14
+template <class E> reverse_iterator<const E*> constexpr rbegin(initializer_list<E> il); // C++14
+template <class E> reverse_iterator<const E*> constexpr rend(initializer_list<E> il);   // C++14
+template <class T, size_t N> reverse_iterator<T*> constexpr rbegin(T (&array)[N]);      // C++14
+template <class T, size_t N> reverse_iterator<T*> constexpr rend(T (&array)[N]);        // C++14
+template <class C> constexpr auto crbegin(const C& c) -> decltype(std::rbegin(c));      // C++14
+template <class C> constexpr auto crend(const C& c) -> decltype(std::rend(c));          // C++14
 
 // 24.8, container access:
 template <class C> constexpr auto size(const C& c) -> decltype(c.size());         // C++17
@@ -425,11 +430,11 @@ template <class E> constexpr const E* data(initializer_list<E> il) noexcept;
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-struct _LIBCPP_TYPE_VIS_ONLY input_iterator_tag {};
-struct _LIBCPP_TYPE_VIS_ONLY output_iterator_tag {};
-struct _LIBCPP_TYPE_VIS_ONLY forward_iterator_tag       : public input_iterator_tag {};
-struct _LIBCPP_TYPE_VIS_ONLY bidirectional_iterator_tag : public forward_iterator_tag {};
-struct _LIBCPP_TYPE_VIS_ONLY random_access_iterator_tag : public bidirectional_iterator_tag {};
+struct _LIBCPP_TEMPLATE_VIS input_iterator_tag {};
+struct _LIBCPP_TEMPLATE_VIS output_iterator_tag {};
+struct _LIBCPP_TEMPLATE_VIS forward_iterator_tag       : public input_iterator_tag {};
+struct _LIBCPP_TEMPLATE_VIS bidirectional_iterator_tag : public forward_iterator_tag {};
+struct _LIBCPP_TEMPLATE_VIS random_access_iterator_tag : public bidirectional_iterator_tag {};
 
 template <class _Tp>
 struct __has_iterator_category
@@ -472,14 +477,14 @@ struct __iterator_traits<_Iter, true>
 //    the client expects instead of failing at compile time.
 
 template <class _Iter>
-struct _LIBCPP_TYPE_VIS_ONLY iterator_traits
+struct _LIBCPP_TEMPLATE_VIS iterator_traits
     : __iterator_traits<_Iter, __has_iterator_category<_Iter>::value> {};
 
 template<class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY iterator_traits<_Tp*>
+struct _LIBCPP_TEMPLATE_VIS iterator_traits<_Tp*>
 {
     typedef ptrdiff_t difference_type;
-    typedef typename remove_const<_Tp>::type value_type;
+    typedef typename remove_cv<_Tp>::type value_type;
     typedef _Tp* pointer;
     typedef _Tp& reference;
     typedef random_access_iterator_tag iterator_category;
@@ -508,12 +513,12 @@ struct __is_random_access_iterator : public __has_iterator_category_convertible_
 template <class _Tp>
 struct __is_exactly_input_iterator
     : public integral_constant<bool, 
-    	 __has_iterator_category_convertible_to<_Tp, input_iterator_tag>::value && 
-    	!__has_iterator_category_convertible_to<_Tp, forward_iterator_tag>::value> {};
+         __has_iterator_category_convertible_to<_Tp, input_iterator_tag>::value && 
+        !__has_iterator_category_convertible_to<_Tp, forward_iterator_tag>::value> {};
 
 template<class _Category, class _Tp, class _Distance = ptrdiff_t,
          class _Pointer = _Tp*, class _Reference = _Tp&>
-struct _LIBCPP_TYPE_VIS_ONLY iterator
+struct _LIBCPP_TEMPLATE_VIS iterator
 {
     typedef _Tp        value_type;
     typedef _Distance  difference_type;
@@ -523,7 +528,7 @@ struct _LIBCPP_TYPE_VIS_ONLY iterator
 };
 
 template <class _InputIter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 void __advance(_InputIter& __i,
              typename iterator_traits<_InputIter>::difference_type __n, input_iterator_tag)
 {
@@ -532,7 +537,7 @@ void __advance(_InputIter& __i,
 }
 
 template <class _BiDirIter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 void __advance(_BiDirIter& __i,
              typename iterator_traits<_BiDirIter>::difference_type __n, bidirectional_iterator_tag)
 {
@@ -545,7 +550,7 @@ void __advance(_BiDirIter& __i,
 }
 
 template <class _RandIter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 void __advance(_RandIter& __i,
              typename iterator_traits<_RandIter>::difference_type __n, random_access_iterator_tag)
 {
@@ -553,7 +558,7 @@ void __advance(_RandIter& __i,
 }
 
 template <class _InputIter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 void advance(_InputIter& __i,
              typename iterator_traits<_InputIter>::difference_type __n)
 {
@@ -561,7 +566,7 @@ void advance(_InputIter& __i,
 }
 
 template <class _InputIter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 typename iterator_traits<_InputIter>::difference_type
 __distance(_InputIter __first, _InputIter __last, input_iterator_tag)
 {
@@ -572,7 +577,7 @@ __distance(_InputIter __first, _InputIter __last, input_iterator_tag)
 }
 
 template <class _RandIter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 typename iterator_traits<_RandIter>::difference_type
 __distance(_RandIter __first, _RandIter __last, random_access_iterator_tag)
 {
@@ -580,7 +585,7 @@ __distance(_RandIter __first, _RandIter __last, random_access_iterator_tag)
 }
 
 template <class _InputIter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 typename iterator_traits<_InputIter>::difference_type
 distance(_InputIter __first, _InputIter __last)
 {
@@ -588,29 +593,43 @@ distance(_InputIter __first, _InputIter __last)
 }
 
 template <class _InputIter>
-inline _LIBCPP_INLINE_VISIBILITY
-_InputIter
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+typename enable_if
+<
+    __is_input_iterator<_InputIter>::value, 
+    _InputIter
+>::type
 next(_InputIter __x,
-     typename iterator_traits<_InputIter>::difference_type __n = 1,
-     typename enable_if<__is_input_iterator<_InputIter>::value>::type* = 0)
+     typename iterator_traits<_InputIter>::difference_type __n = 1)
 {
     _VSTD::advance(__x, __n);
     return __x;
 }
 
-template <class _BidiretionalIter>
-inline _LIBCPP_INLINE_VISIBILITY
-_BidiretionalIter
-prev(_BidiretionalIter __x,
-     typename iterator_traits<_BidiretionalIter>::difference_type __n = 1,
-     typename enable_if<__is_bidirectional_iterator<_BidiretionalIter>::value>::type* = 0)
+template <class _BidirectionalIter>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+typename enable_if
+<
+    __is_bidirectional_iterator<_BidirectionalIter>::value, 
+    _BidirectionalIter
+>::type
+prev(_BidirectionalIter __x,
+     typename iterator_traits<_BidirectionalIter>::difference_type __n = 1)
 {
     _VSTD::advance(__x, -__n);
     return __x;
 }
 
+
+template <class _Tp, class = void>
+struct __is_stashing_iterator : false_type {};
+
+template <class _Tp>
+struct __is_stashing_iterator<_Tp, typename __void_t<typename _Tp::__stashing_iterator_tag>::type>
+  : true_type {};
+
 template <class _Iter>
-class _LIBCPP_TYPE_VIS_ONLY reverse_iterator
+class _LIBCPP_TEMPLATE_VIS reverse_iterator
     : public iterator<typename iterator_traits<_Iter>::iterator_category,
                       typename iterator_traits<_Iter>::value_type,
                       typename iterator_traits<_Iter>::difference_type,
@@ -618,7 +637,12 @@ class _LIBCPP_TYPE_VIS_ONLY reverse_iterator
                       typename iterator_traits<_Iter>::reference>
 {
 private:
-    mutable _Iter __t;  // no longer used as of LWG #2360, not removed due to ABI break
+    /*mutable*/ _Iter __t;  // no longer used as of LWG #2360, not removed due to ABI break
+
+    static_assert(!__is_stashing_iterator<_Iter>::value,
+      "The specified iterator type cannot be used with reverse_iterator; "
+      "Using stashing iterators with reverse_iterator causes undefined behavior");
+
 protected:
     _Iter current;
 public:
@@ -627,33 +651,45 @@ public:
     typedef typename iterator_traits<_Iter>::reference       reference;
     typedef typename iterator_traits<_Iter>::pointer         pointer;
 
-    _LIBCPP_INLINE_VISIBILITY reverse_iterator() : current() {}
-    _LIBCPP_INLINE_VISIBILITY explicit reverse_iterator(_Iter __x) : __t(__x), current(__x) {}
-    template <class _Up> _LIBCPP_INLINE_VISIBILITY reverse_iterator(const reverse_iterator<_Up>& __u)
-        : __t(__u.base()), current(__u.base()) {}
-    _LIBCPP_INLINE_VISIBILITY _Iter base() const {return current;}
-    _LIBCPP_INLINE_VISIBILITY reference operator*() const {_Iter __tmp = current; return *--__tmp;}
-    _LIBCPP_INLINE_VISIBILITY pointer  operator->() const {return _VSTD::addressof(operator*());}
-    _LIBCPP_INLINE_VISIBILITY reverse_iterator& operator++() {--current; return *this;}
-    _LIBCPP_INLINE_VISIBILITY reverse_iterator  operator++(int)
-        {reverse_iterator __tmp(*this); --current; return __tmp;}
-    _LIBCPP_INLINE_VISIBILITY reverse_iterator& operator--() {++current; return *this;}
-    _LIBCPP_INLINE_VISIBILITY reverse_iterator  operator--(int)
-        {reverse_iterator __tmp(*this); ++current; return __tmp;}
-    _LIBCPP_INLINE_VISIBILITY reverse_iterator  operator+ (difference_type __n) const
-        {return reverse_iterator(current - __n);}
-    _LIBCPP_INLINE_VISIBILITY reverse_iterator& operator+=(difference_type __n)
-        {current -= __n; return *this;}
-    _LIBCPP_INLINE_VISIBILITY reverse_iterator  operator- (difference_type __n) const
-        {return reverse_iterator(current + __n);}
-    _LIBCPP_INLINE_VISIBILITY reverse_iterator& operator-=(difference_type __n)
-        {current += __n; return *this;}
-    _LIBCPP_INLINE_VISIBILITY reference         operator[](difference_type __n) const
-        {return *(*this + __n);}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reverse_iterator() : __t(), current() {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    explicit reverse_iterator(_Iter __x) : __t(__x), current(__x) {}
+    template <class _Up>
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+        reverse_iterator(const reverse_iterator<_Up>& __u) : __t(__u.base()), current(__u.base()) {}
+    template <class _Up>
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+        reverse_iterator& operator=(const reverse_iterator<_Up>& __u)
+            { __t = current = __u.base(); return *this; }
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    _Iter base() const {return current;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reference operator*() const {_Iter __tmp = current; return *--__tmp;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    pointer  operator->() const {return _VSTD::addressof(operator*());}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reverse_iterator& operator++() {--current; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reverse_iterator  operator++(int) {reverse_iterator __tmp(*this); --current; return __tmp;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reverse_iterator& operator--() {++current; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reverse_iterator  operator--(int) {reverse_iterator __tmp(*this); ++current; return __tmp;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reverse_iterator  operator+ (difference_type __n) const {return reverse_iterator(current - __n);}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reverse_iterator& operator+=(difference_type __n) {current -= __n; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reverse_iterator  operator- (difference_type __n) const {return reverse_iterator(current + __n);}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reverse_iterator& operator-=(difference_type __n) {current += __n; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reference         operator[](difference_type __n) const {return *(*this + __n);}
 };
 
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 bool
 operator==(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 {
@@ -661,7 +697,7 @@ operator==(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>&
 }
 
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 bool
 operator<(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 {
@@ -669,7 +705,7 @@ operator<(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& _
 }
 
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 bool
 operator!=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 {
@@ -677,7 +713,7 @@ operator!=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>&
 }
 
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 bool
 operator>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 {
@@ -685,7 +721,7 @@ operator>(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& _
 }
 
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 bool
 operator>=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 {
@@ -693,7 +729,7 @@ operator>=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>&
 }
 
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 bool
 operator<=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 {
@@ -702,7 +738,7 @@ operator<=(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>&
 
 #ifndef _LIBCPP_CXX03_LANG
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 auto
 operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& __y)
 -> decltype(__y.base() - __x.base())
@@ -720,7 +756,7 @@ operator-(const reverse_iterator<_Iter1>& __x, const reverse_iterator<_Iter2>& _
 #endif
 
 template <class _Iter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator<_Iter>
 operator+(typename reverse_iterator<_Iter>::difference_type __n, const reverse_iterator<_Iter>& __x)
 {
@@ -729,7 +765,7 @@ operator+(typename reverse_iterator<_Iter>::difference_type __n, const reverse_i
 
 #if _LIBCPP_STD_VER > 11
 template <class _Iter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator<_Iter> make_reverse_iterator(_Iter __i)
 {
     return reverse_iterator<_Iter>(__i);
@@ -737,7 +773,7 @@ reverse_iterator<_Iter> make_reverse_iterator(_Iter __i)
 #endif
 
 template <class _Container>
-class _LIBCPP_TYPE_VIS_ONLY back_insert_iterator
+class _LIBCPP_TEMPLATE_VIS back_insert_iterator
     : public iterator<output_iterator_tag,
                       void,
                       void,
@@ -752,10 +788,10 @@ public:
     _LIBCPP_INLINE_VISIBILITY explicit back_insert_iterator(_Container& __x) : container(_VSTD::addressof(__x)) {}
     _LIBCPP_INLINE_VISIBILITY back_insert_iterator& operator=(const typename _Container::value_type& __value_)
         {container->push_back(__value_); return *this;}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY back_insert_iterator& operator=(typename _Container::value_type&& __value_)
         {container->push_back(_VSTD::move(__value_)); return *this;}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY back_insert_iterator& operator*()     {return *this;}
     _LIBCPP_INLINE_VISIBILITY back_insert_iterator& operator++()    {return *this;}
     _LIBCPP_INLINE_VISIBILITY back_insert_iterator  operator++(int) {return *this;}
@@ -770,7 +806,7 @@ back_inserter(_Container& __x)
 }
 
 template <class _Container>
-class _LIBCPP_TYPE_VIS_ONLY front_insert_iterator
+class _LIBCPP_TEMPLATE_VIS front_insert_iterator
     : public iterator<output_iterator_tag,
                       void,
                       void,
@@ -785,10 +821,10 @@ public:
     _LIBCPP_INLINE_VISIBILITY explicit front_insert_iterator(_Container& __x) : container(_VSTD::addressof(__x)) {}
     _LIBCPP_INLINE_VISIBILITY front_insert_iterator& operator=(const typename _Container::value_type& __value_)
         {container->push_front(__value_); return *this;}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY front_insert_iterator& operator=(typename _Container::value_type&& __value_)
         {container->push_front(_VSTD::move(__value_)); return *this;}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY front_insert_iterator& operator*()     {return *this;}
     _LIBCPP_INLINE_VISIBILITY front_insert_iterator& operator++()    {return *this;}
     _LIBCPP_INLINE_VISIBILITY front_insert_iterator  operator++(int) {return *this;}
@@ -803,7 +839,7 @@ front_inserter(_Container& __x)
 }
 
 template <class _Container>
-class _LIBCPP_TYPE_VIS_ONLY insert_iterator
+class _LIBCPP_TEMPLATE_VIS insert_iterator
     : public iterator<output_iterator_tag,
                       void,
                       void,
@@ -820,10 +856,10 @@ public:
         : container(_VSTD::addressof(__x)), iter(__i) {}
     _LIBCPP_INLINE_VISIBILITY insert_iterator& operator=(const typename _Container::value_type& __value_)
         {iter = container->insert(iter, __value_); ++iter; return *this;}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY insert_iterator& operator=(typename _Container::value_type&& __value_)
         {iter = container->insert(iter, _VSTD::move(__value_)); ++iter; return *this;}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY insert_iterator& operator*()        {return *this;}
     _LIBCPP_INLINE_VISIBILITY insert_iterator& operator++()       {return *this;}
     _LIBCPP_INLINE_VISIBILITY insert_iterator& operator++(int)    {return *this;}
@@ -839,7 +875,7 @@ inserter(_Container& __x, typename _Container::iterator __i)
 
 template <class _Tp, class _CharT = char,
           class _Traits = char_traits<_CharT>, class _Distance = ptrdiff_t>
-class _LIBCPP_TYPE_VIS_ONLY istream_iterator
+class _LIBCPP_TEMPLATE_VIS istream_iterator
     : public iterator<input_iterator_tag, _Tp, _Distance, const _Tp*, const _Tp&>
 {
 public:
@@ -868,17 +904,39 @@ public:
     _LIBCPP_INLINE_VISIBILITY istream_iterator  operator++(int)
         {istream_iterator __t(*this); ++(*this); return __t;}
 
+    template <class _Up, class _CharU, class _TraitsU, class _DistanceU>
     friend _LIBCPP_INLINE_VISIBILITY
-    bool operator==(const istream_iterator& __x, const istream_iterator& __y)
-        {return __x.__in_stream_ == __y.__in_stream_;}
+    bool
+    operator==(const istream_iterator<_Up, _CharU, _TraitsU, _DistanceU>& __x,
+               const istream_iterator<_Up, _CharU, _TraitsU, _DistanceU>& __y);
 
+    template <class _Up, class _CharU, class _TraitsU, class _DistanceU>
     friend _LIBCPP_INLINE_VISIBILITY
-    bool operator!=(const istream_iterator& __x, const istream_iterator& __y)
-        {return !(__x == __y);}
+    bool
+    operator==(const istream_iterator<_Up, _CharU, _TraitsU, _DistanceU>& __x,
+               const istream_iterator<_Up, _CharU, _TraitsU, _DistanceU>& __y);
 };
 
+template <class _Tp, class _CharT, class _Traits, class _Distance>
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator==(const istream_iterator<_Tp, _CharT, _Traits, _Distance>& __x,
+           const istream_iterator<_Tp, _CharT, _Traits, _Distance>& __y)
+{
+    return __x.__in_stream_ == __y.__in_stream_;
+}
+
+template <class _Tp, class _CharT, class _Traits, class _Distance>
+inline _LIBCPP_INLINE_VISIBILITY
+bool
+operator!=(const istream_iterator<_Tp, _CharT, _Traits, _Distance>& __x,
+           const istream_iterator<_Tp, _CharT, _Traits, _Distance>& __y)
+{
+    return !(__x == __y);
+}
+
 template <class _Tp, class _CharT = char, class _Traits = char_traits<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY ostream_iterator
+class _LIBCPP_TEMPLATE_VIS ostream_iterator
     : public iterator<output_iterator_tag, void, void, void, void>
 {
 public:
@@ -889,9 +947,9 @@ private:
     ostream_type* __out_stream_;
     const char_type* __delim_;
 public:
-    _LIBCPP_INLINE_VISIBILITY ostream_iterator(ostream_type& __s)
+    _LIBCPP_INLINE_VISIBILITY ostream_iterator(ostream_type& __s) _NOEXCEPT
         : __out_stream_(_VSTD::addressof(__s)), __delim_(0) {}
-    _LIBCPP_INLINE_VISIBILITY ostream_iterator(ostream_type& __s, const _CharT* __delimiter)
+    _LIBCPP_INLINE_VISIBILITY ostream_iterator(ostream_type& __s, const _CharT* __delimiter) _NOEXCEPT
         : __out_stream_(_VSTD::addressof(__s)), __delim_(__delimiter) {}
     _LIBCPP_INLINE_VISIBILITY ostream_iterator& operator=(const _Tp& __value_)
         {
@@ -907,7 +965,7 @@ public:
 };
 
 template<class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY istreambuf_iterator
+class _LIBCPP_TEMPLATE_VIS istreambuf_iterator
     : public iterator<input_iterator_tag, _CharT,
                       typename _Traits::off_type, _CharT*,
                       _CharT>
@@ -950,7 +1008,6 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY char_type  operator*() const
         {return static_cast<char_type>(__sbuf_->sgetc());}
-    _LIBCPP_INLINE_VISIBILITY char_type* operator->() const {return nullptr;}
     _LIBCPP_INLINE_VISIBILITY istreambuf_iterator& operator++()
         {
             __sbuf_->sbumpc();
@@ -978,7 +1035,7 @@ bool operator!=(const istreambuf_iterator<_CharT,_Traits>& __a,
                 {return !__a.equal(__b);}
 
 template <class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY ostreambuf_iterator
+class _LIBCPP_TEMPLATE_VIS ostreambuf_iterator
     : public iterator<output_iterator_tag, void, void, void, void>
 {
 public:
@@ -1019,7 +1076,7 @@ public:
 };
 
 template <class _Iter>
-class _LIBCPP_TYPE_VIS_ONLY move_iterator
+class _LIBCPP_TEMPLATE_VIS move_iterator
 {
 private:
     _Iter __i;
@@ -1029,7 +1086,7 @@ public:
     typedef typename iterator_traits<iterator_type>::value_type value_type;
     typedef typename iterator_traits<iterator_type>::difference_type difference_type;
     typedef iterator_type pointer;
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     typedef typename iterator_traits<iterator_type>::reference __reference;
     typedef typename conditional<
             is_reference<__reference>::value,
@@ -1040,37 +1097,40 @@ public:
     typedef typename iterator_traits<iterator_type>::reference reference;
 #endif
 
-    _LIBCPP_INLINE_VISIBILITY move_iterator() : __i() {}
-    _LIBCPP_INLINE_VISIBILITY explicit move_iterator(_Iter __x) : __i(__x) {}
-    template <class _Up> _LIBCPP_INLINE_VISIBILITY move_iterator(const move_iterator<_Up>& __u)
-        : __i(__u.base()) {}
-    _LIBCPP_INLINE_VISIBILITY _Iter base() const {return __i;}
-    _LIBCPP_INLINE_VISIBILITY reference operator*() const {
-      return static_cast<reference>(*__i);
-    }
-    _LIBCPP_INLINE_VISIBILITY pointer  operator->() const { return __i;}
-    _LIBCPP_INLINE_VISIBILITY move_iterator& operator++() {++__i; return *this;}
-    _LIBCPP_INLINE_VISIBILITY move_iterator  operator++(int)
-        {move_iterator __tmp(*this); ++__i; return __tmp;}
-    _LIBCPP_INLINE_VISIBILITY move_iterator& operator--() {--__i; return *this;}
-    _LIBCPP_INLINE_VISIBILITY move_iterator  operator--(int)
-        {move_iterator __tmp(*this); --__i; return __tmp;}
-    _LIBCPP_INLINE_VISIBILITY move_iterator  operator+ (difference_type __n) const
-        {return move_iterator(__i + __n);}
-    _LIBCPP_INLINE_VISIBILITY move_iterator& operator+=(difference_type __n)
-        {__i += __n; return *this;}
-    _LIBCPP_INLINE_VISIBILITY move_iterator  operator- (difference_type __n) const
-        {return move_iterator(__i - __n);}
-    _LIBCPP_INLINE_VISIBILITY move_iterator& operator-=(difference_type __n)
-        {__i -= __n; return *this;}
-    _LIBCPP_INLINE_VISIBILITY reference         operator[](difference_type __n) const
-    {
-      return static_cast<reference>(__i[__n]);
-    }
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    move_iterator() : __i() {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    explicit move_iterator(_Iter __x) : __i(__x) {}
+    template <class _Up>
+      _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+      move_iterator(const move_iterator<_Up>& __u) : __i(__u.base()) {}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 _Iter base() const {return __i;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14 
+    reference operator*() const { return static_cast<reference>(*__i); }
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    pointer  operator->() const { return __i;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    move_iterator& operator++() {++__i; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    move_iterator  operator++(int) {move_iterator __tmp(*this); ++__i; return __tmp;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    move_iterator& operator--() {--__i; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    move_iterator  operator--(int) {move_iterator __tmp(*this); --__i; return __tmp;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    move_iterator  operator+ (difference_type __n) const {return move_iterator(__i + __n);}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    move_iterator& operator+=(difference_type __n) {__i += __n; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    move_iterator  operator- (difference_type __n) const {return move_iterator(__i - __n);}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    move_iterator& operator-=(difference_type __n) {__i -= __n; return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+    reference operator[](difference_type __n) const { return static_cast<reference>(__i[__n]); }
 };
 
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 bool
 operator==(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 {
@@ -1078,7 +1138,7 @@ operator==(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 }
 
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 bool
 operator<(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 {
@@ -1086,7 +1146,7 @@ operator<(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 }
 
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 bool
 operator!=(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 {
@@ -1094,7 +1154,7 @@ operator!=(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 }
 
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 bool
 operator>(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 {
@@ -1102,7 +1162,7 @@ operator>(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 }
 
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 bool
 operator>=(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 {
@@ -1110,7 +1170,7 @@ operator>=(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 }
 
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 bool
 operator<=(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 {
@@ -1119,7 +1179,7 @@ operator<=(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 
 #ifndef _LIBCPP_CXX03_LANG
 template <class _Iter1, class _Iter2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 auto
 operator-(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 -> decltype(__x.base() - __y.base())
@@ -1137,7 +1197,7 @@ operator-(const move_iterator<_Iter1>& __x, const move_iterator<_Iter2>& __y)
 #endif
 
 template <class _Iter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 move_iterator<_Iter>
 operator+(typename move_iterator<_Iter>::difference_type __n, const move_iterator<_Iter>& __x)
 {
@@ -1145,7 +1205,7 @@ operator+(typename move_iterator<_Iter>::difference_type __n, const move_iterato
 }
 
 template <class _Iter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 move_iterator<_Iter>
 make_move_iterator(_Iter __i)
 {
@@ -1159,56 +1219,58 @@ template <class _Iter> class __wrap_iter;
 template <class _Iter1, class _Iter2>
 _LIBCPP_INLINE_VISIBILITY
 bool
-operator==(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+operator==(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 
 template <class _Iter1, class _Iter2>
 _LIBCPP_INLINE_VISIBILITY
 bool
-operator<(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+operator<(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 
 template <class _Iter1, class _Iter2>
 _LIBCPP_INLINE_VISIBILITY
 bool
-operator!=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+operator!=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 
 template <class _Iter1, class _Iter2>
 _LIBCPP_INLINE_VISIBILITY
 bool
-operator>(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+operator>(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 
 template <class _Iter1, class _Iter2>
 _LIBCPP_INLINE_VISIBILITY
 bool
-operator>=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+operator>=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 
 template <class _Iter1, class _Iter2>
 _LIBCPP_INLINE_VISIBILITY
 bool
-operator<=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+operator<=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 
 #ifndef _LIBCPP_CXX03_LANG
 template <class _Iter1, class _Iter2>
 _LIBCPP_INLINE_VISIBILITY
 auto
-operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
+operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
 -> decltype(__x.base() - __y.base());
 #else
 template <class _Iter1, class _Iter2>
 _LIBCPP_INLINE_VISIBILITY
 typename __wrap_iter<_Iter1>::difference_type
-operator-(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+operator-(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 #endif
 
 template <class _Iter>
 _LIBCPP_INLINE_VISIBILITY
 __wrap_iter<_Iter>
-operator+(typename __wrap_iter<_Iter>::difference_type, __wrap_iter<_Iter>) _NOEXCEPT;
+operator+(typename __wrap_iter<_Iter>::difference_type, __wrap_iter<_Iter>) _NOEXCEPT_DEBUG;
 
 template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY copy(_Ip, _Ip, _Op);
 template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY copy_backward(_B1, _B1, _B2);
 template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY move(_Ip, _Ip, _Op);
 template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY move_backward(_B1, _B1, _B2);
 
+#if _LIBCPP_DEBUG_LEVEL < 2
+
 template <class _Tp>
 _LIBCPP_INLINE_VISIBILITY
 typename enable_if
@@ -1218,6 +1280,19 @@ typename enable_if
 >::type
 __unwrap_iter(__wrap_iter<_Tp*>);
 
+#else
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+typename enable_if
+<
+    is_trivially_copy_assignable<_Tp>::value,
+    __wrap_iter<_Tp*>
+>::type
+__unwrap_iter(__wrap_iter<_Tp*> __i);
+
+#endif
+
 template <class _Iter>
 class __wrap_iter
 {
@@ -1231,7 +1306,7 @@ public:
 private:
     iterator_type __i;
 public:
-    _LIBCPP_INLINE_VISIBILITY __wrap_iter() _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY __wrap_iter() _NOEXCEPT_DEBUG
 #if _LIBCPP_STD_VER > 11
                 : __i{}
 #endif
@@ -1241,7 +1316,7 @@ public:
 #endif
     }
     template <class _Up> _LIBCPP_INLINE_VISIBILITY __wrap_iter(const __wrap_iter<_Up>& __u,
-        typename enable_if<is_convertible<_Up, iterator_type>::value>::type* = 0) _NOEXCEPT
+        typename enable_if<is_convertible<_Up, iterator_type>::value>::type* = 0) _NOEXCEPT_DEBUG
         : __i(__u.base())
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1271,7 +1346,7 @@ public:
         __get_db()->__erase_i(this);
     }
 #endif
-    _LIBCPP_INLINE_VISIBILITY reference operator*() const _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY reference operator*() const _NOEXCEPT_DEBUG
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
         _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
@@ -1279,7 +1354,7 @@ public:
 #endif
         return *__i;
     }
-    _LIBCPP_INLINE_VISIBILITY pointer  operator->() const _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY pointer  operator->() const _NOEXCEPT_DEBUG
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
         _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
@@ -1287,7 +1362,7 @@ public:
 #endif
         return (pointer)_VSTD::addressof(*__i);
     }
-    _LIBCPP_INLINE_VISIBILITY __wrap_iter& operator++() _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY __wrap_iter& operator++() _NOEXCEPT_DEBUG
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
         _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
@@ -1296,9 +1371,9 @@ public:
         ++__i;
         return *this;
     }
-    _LIBCPP_INLINE_VISIBILITY __wrap_iter  operator++(int) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY __wrap_iter  operator++(int) _NOEXCEPT_DEBUG
         {__wrap_iter __tmp(*this); ++(*this); return __tmp;}
-    _LIBCPP_INLINE_VISIBILITY __wrap_iter& operator--() _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY __wrap_iter& operator--() _NOEXCEPT_DEBUG
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
         _LIBCPP_ASSERT(__get_const_db()->__decrementable(this),
@@ -1307,11 +1382,11 @@ public:
         --__i;
         return *this;
     }
-    _LIBCPP_INLINE_VISIBILITY __wrap_iter  operator--(int) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY __wrap_iter  operator--(int) _NOEXCEPT_DEBUG
         {__wrap_iter __tmp(*this); --(*this); return __tmp;}
-    _LIBCPP_INLINE_VISIBILITY __wrap_iter  operator+ (difference_type __n) const _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY __wrap_iter  operator+ (difference_type __n) const _NOEXCEPT_DEBUG
         {__wrap_iter __w(*this); __w += __n; return __w;}
-    _LIBCPP_INLINE_VISIBILITY __wrap_iter& operator+=(difference_type __n) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY __wrap_iter& operator+=(difference_type __n) _NOEXCEPT_DEBUG
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
         _LIBCPP_ASSERT(__get_const_db()->__addable(this, __n),
@@ -1320,11 +1395,11 @@ public:
         __i += __n;
         return *this;
     }
-    _LIBCPP_INLINE_VISIBILITY __wrap_iter  operator- (difference_type __n) const _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY __wrap_iter  operator- (difference_type __n) const _NOEXCEPT_DEBUG
         {return *this + (-__n);}
-    _LIBCPP_INLINE_VISIBILITY __wrap_iter& operator-=(difference_type __n) _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY __wrap_iter& operator-=(difference_type __n) _NOEXCEPT_DEBUG
         {*this += -__n; return *this;}
-    _LIBCPP_INLINE_VISIBILITY reference        operator[](difference_type __n) const _NOEXCEPT
+    _LIBCPP_INLINE_VISIBILITY reference        operator[](difference_type __n) const _NOEXCEPT_DEBUG
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
         _LIBCPP_ASSERT(__get_const_db()->__subscriptable(this, __n),
@@ -1333,7 +1408,7 @@ public:
         return __i[__n];
     }
 
-    _LIBCPP_INLINE_VISIBILITY iterator_type base() const _NOEXCEPT {return __i;}
+    _LIBCPP_INLINE_VISIBILITY iterator_type base() const _NOEXCEPT_DEBUG {return __i;}
 
 private:
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1342,66 +1417,67 @@ private:
         __get_db()->__insert_ic(this, __p);
     }
 #else
-    _LIBCPP_INLINE_VISIBILITY __wrap_iter(iterator_type __x) _NOEXCEPT : __i(__x) {}
+    _LIBCPP_INLINE_VISIBILITY __wrap_iter(iterator_type __x) _NOEXCEPT_DEBUG : __i(__x) {}
 #endif
 
     template <class _Up> friend class __wrap_iter;
     template <class _CharT, class _Traits, class _Alloc> friend class basic_string;
-    template <class _Tp, class _Alloc> friend class _LIBCPP_TYPE_VIS_ONLY vector;
+    template <class _Tp, class _Alloc> friend class _LIBCPP_TEMPLATE_VIS vector;
 
     template <class _Iter1, class _Iter2>
     friend
     bool
-    operator==(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+    operator==(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 
     template <class _Iter1, class _Iter2>
     friend
     bool
-    operator<(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+    operator<(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 
     template <class _Iter1, class _Iter2>
     friend
     bool
-    operator!=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+    operator!=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 
     template <class _Iter1, class _Iter2>
     friend
     bool
-    operator>(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+    operator>(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 
     template <class _Iter1, class _Iter2>
     friend
     bool
-    operator>=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+    operator>=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 
     template <class _Iter1, class _Iter2>
     friend
     bool
-    operator<=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+    operator<=(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 
 #ifndef _LIBCPP_CXX03_LANG
     template <class _Iter1, class _Iter2>
     friend
     auto
-    operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
+    operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
     -> decltype(__x.base() - __y.base());
 #else
     template <class _Iter1, class _Iter2>
     friend
     typename __wrap_iter<_Iter1>::difference_type
-    operator-(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT;
+    operator-(const __wrap_iter<_Iter1>&, const __wrap_iter<_Iter2>&) _NOEXCEPT_DEBUG;
 #endif
 
     template <class _Iter1>
     friend
     __wrap_iter<_Iter1>
-    operator+(typename __wrap_iter<_Iter1>::difference_type, __wrap_iter<_Iter1>) _NOEXCEPT;
+    operator+(typename __wrap_iter<_Iter1>::difference_type, __wrap_iter<_Iter1>) _NOEXCEPT_DEBUG;
 
     template <class _Ip, class _Op> friend _Op copy(_Ip, _Ip, _Op);
     template <class _B1, class _B2> friend _B2 copy_backward(_B1, _B1, _B2);
     template <class _Ip, class _Op> friend _Op move(_Ip, _Ip, _Op);
     template <class _B1, class _B2> friend _B2 move_backward(_B1, _B1, _B2);
 
+#if _LIBCPP_DEBUG_LEVEL < 2
     template <class _Tp>
     friend
     typename enable_if
@@ -1410,12 +1486,22 @@ private:
         _Tp*
     >::type
     __unwrap_iter(__wrap_iter<_Tp*>);
+#else
+  template <class _Tp>
+  inline _LIBCPP_INLINE_VISIBILITY
+  typename enable_if
+  <
+      is_trivially_copy_assignable<_Tp>::value,
+      __wrap_iter<_Tp*>
+  >::type
+  __unwrap_iter(__wrap_iter<_Tp*> __i);
+#endif
 };
 
 template <class _Iter1, class _Iter2>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-operator==(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
+operator==(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
 {
     return __x.base() == __y.base();
 }
@@ -1423,7 +1509,7 @@ operator==(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEX
 template <class _Iter1, class _Iter2>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-operator<(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
+operator<(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
 {
 #if _LIBCPP_DEBUG_LEVEL >= 2
     _LIBCPP_ASSERT(__get_const_db()->__less_than_comparable(&__x, &__y),
@@ -1435,7 +1521,7 @@ operator<(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXC
 template <class _Iter1, class _Iter2>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-operator!=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
+operator!=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
 {
     return !(__x == __y);
 }
@@ -1443,7 +1529,7 @@ operator!=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEX
 template <class _Iter1, class _Iter2>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-operator>(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
+operator>(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
 {
     return __y < __x;
 }
@@ -1451,7 +1537,7 @@ operator>(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXC
 template <class _Iter1, class _Iter2>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-operator>=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
+operator>=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
 {
     return !(__x < __y);
 }
@@ -1459,7 +1545,7 @@ operator>=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEX
 template <class _Iter1, class _Iter2>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-operator<=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
+operator<=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
 {
     return !(__y < __x);
 }
@@ -1467,7 +1553,7 @@ operator<=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEX
 template <class _Iter1>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-operator!=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT
+operator!=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT_DEBUG
 {
     return !(__x == __y);
 }
@@ -1475,7 +1561,7 @@ operator!=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEX
 template <class _Iter1>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-operator>(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT
+operator>(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT_DEBUG
 {
     return __y < __x;
 }
@@ -1483,7 +1569,7 @@ operator>(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXC
 template <class _Iter1>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-operator>=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT
+operator>=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT_DEBUG
 {
     return !(__x < __y);
 }
@@ -1491,7 +1577,7 @@ operator>=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEX
 template <class _Iter1>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-operator<=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT
+operator<=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEXCEPT_DEBUG
 {
     return !(__y < __x);
 }
@@ -1500,7 +1586,7 @@ operator<=(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter1>& __y) _NOEX
 template <class _Iter1, class _Iter2>
 inline _LIBCPP_INLINE_VISIBILITY
 auto
-operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
+operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
 -> decltype(__x.base() - __y.base())
 {
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1513,7 +1599,7 @@ operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXC
 template <class _Iter1, class _Iter2>
 inline _LIBCPP_INLINE_VISIBILITY
 typename __wrap_iter<_Iter1>::difference_type
-operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT
+operator-(const __wrap_iter<_Iter1>& __x, const __wrap_iter<_Iter2>& __y) _NOEXCEPT_DEBUG
 {
 #if _LIBCPP_DEBUG_LEVEL >= 2
     _LIBCPP_ASSERT(__get_const_db()->__less_than_comparable(&__x, &__y),
@@ -1527,7 +1613,7 @@ template <class _Iter>
 inline _LIBCPP_INLINE_VISIBILITY
 __wrap_iter<_Iter>
 operator+(typename __wrap_iter<_Iter>::difference_type __n,
-          __wrap_iter<_Iter> __x) _NOEXCEPT
+          __wrap_iter<_Iter> __x) _NOEXCEPT_DEBUG
 {
     __x += __n;
     return __x;
@@ -1535,19 +1621,19 @@ operator+(typename __wrap_iter<_Iter>::difference_type __n,
 
 template <class _Iter>
 struct __libcpp_is_trivial_iterator
-	: public _LIBCPP_BOOL_CONSTANT(is_pointer<_Iter>::value) {};
-	
+    : public _LIBCPP_BOOL_CONSTANT(is_pointer<_Iter>::value) {};
+    
 template <class _Iter>
 struct __libcpp_is_trivial_iterator<move_iterator<_Iter> >
-	: public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value) {};
+    : public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value) {};
 
 template <class _Iter>
 struct __libcpp_is_trivial_iterator<reverse_iterator<_Iter> >
-	: public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value) {};
+    : public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value) {};
 
 template <class _Iter>
 struct __libcpp_is_trivial_iterator<__wrap_iter<_Iter> >
-	: public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value) {};
+    : public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value) {};
 
 
 template <class _Tp, size_t _Np>
@@ -1566,10 +1652,10 @@ end(_Tp (&__array)[_Np])
     return __array + _Np;
 }
 
-#if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_TRAILING_RETURN)
+#if !defined(_LIBCPP_CXX03_LANG)
 
 template <class _Cp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 auto
 begin(_Cp& __c) -> decltype(__c.begin())
 {
@@ -1577,7 +1663,7 @@ begin(_Cp& __c) -> decltype(__c.begin())
 }
 
 template <class _Cp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 auto
 begin(const _Cp& __c) -> decltype(__c.begin())
 {
@@ -1585,7 +1671,7 @@ begin(const _Cp& __c) -> decltype(__c.begin())
 }
 
 template <class _Cp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 auto
 end(_Cp& __c) -> decltype(__c.end())
 {
@@ -1593,7 +1679,7 @@ end(_Cp& __c) -> decltype(__c.end())
 }
 
 template <class _Cp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 auto
 end(const _Cp& __c) -> decltype(__c.end())
 {
@@ -1603,28 +1689,28 @@ end(const _Cp& __c) -> decltype(__c.end())
 #if _LIBCPP_STD_VER > 11
 
 template <class _Tp, size_t _Np>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator<_Tp*> rbegin(_Tp (&__array)[_Np])
 {
     return reverse_iterator<_Tp*>(__array + _Np);
 }
 
 template <class _Tp, size_t _Np>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator<_Tp*> rend(_Tp (&__array)[_Np])
 {
     return reverse_iterator<_Tp*>(__array);
 }
 
 template <class _Ep>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator<const _Ep*> rbegin(initializer_list<_Ep> __il)
 {
     return reverse_iterator<const _Ep*>(__il.end());
 }
 
 template <class _Ep>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 reverse_iterator<const _Ep*> rend(initializer_list<_Ep> __il)
 {
     return reverse_iterator<const _Ep*>(__il.begin());
@@ -1645,42 +1731,42 @@ auto cend(const _Cp& __c) -> decltype(_VSTD::end(__c))
 }
 
 template <class _Cp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 auto rbegin(_Cp& __c) -> decltype(__c.rbegin())
 {
     return __c.rbegin();
 }
 
 template <class _Cp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 auto rbegin(const _Cp& __c) -> decltype(__c.rbegin())
 {
     return __c.rbegin();
 }
 
 template <class _Cp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 auto rend(_Cp& __c) -> decltype(__c.rend())
 {
     return __c.rend();
 }
 
 template <class _Cp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 auto rend(const _Cp& __c) -> decltype(__c.rend())
 {
     return __c.rend();
 }
 
 template <class _Cp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 auto crbegin(const _Cp& __c) -> decltype(_VSTD::rbegin(__c))
 {
     return _VSTD::rbegin(__c);
 }
 
 template <class _Cp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 auto crend(const _Cp& __c) -> decltype(_VSTD::rend(__c))
 {
     return _VSTD::rend(__c);
@@ -1689,7 +1775,7 @@ auto crend(const _Cp& __c) -> decltype(_VSTD::rend(__c))
 #endif
 
 
-#else  // !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_TRAILING_RETURN)
+#else  // defined(_LIBCPP_CXX03_LANG)
 
 template <class _Cp>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1723,34 +1809,70 @@ end(const _Cp& __c)
     return __c.end();
 }
 
-#endif  // !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_TRAILING_RETURN)
+#endif  // !defined(_LIBCPP_CXX03_LANG)
 
 #if _LIBCPP_STD_VER > 14
+
+// #if _LIBCPP_STD_VER > 11
+// template <>
+// struct _LIBCPP_TEMPLATE_VIS plus<void>
+// {
+//     template <class _T1, class _T2>
+//     _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+//     auto operator()(_T1&& __t, _T2&& __u) const
+//     _NOEXCEPT_(noexcept(_VSTD::forward<_T1>(__t) + _VSTD::forward<_T2>(__u)))
+//     -> decltype        (_VSTD::forward<_T1>(__t) + _VSTD::forward<_T2>(__u))
+//         { return        _VSTD::forward<_T1>(__t) + _VSTD::forward<_T2>(__u); }
+//     typedef void is_transparent;
+// };
+// #endif
+
 template <class _Cont>
-constexpr auto size(const _Cont& __c) -> decltype(__c.size()) { return __c.size(); }
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr auto size(const _Cont& __c)
+_NOEXCEPT_(noexcept(__c.size()))
+-> decltype        (__c.size())
+{ return            __c.size(); }
 
 template <class _Tp, size_t _Sz>
-constexpr size_t size(const _Tp (&__array)[_Sz]) noexcept { return _Sz; }
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr size_t size(const _Tp (&)[_Sz]) noexcept { return _Sz; }
 
 template <class _Cont>
-constexpr auto empty(const _Cont& __c) -> decltype(__c.empty()) { return __c.empty(); }
+_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY
+constexpr auto empty(const _Cont& __c)
+_NOEXCEPT_(noexcept(__c.empty()))
+-> decltype        (__c.empty())
+{ return            __c.empty(); }
 
 template <class _Tp, size_t _Sz>
-constexpr bool empty(const _Tp (&__array)[_Sz]) noexcept { return false; }
+_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool empty(const _Tp (&)[_Sz]) noexcept { return false; }
 
 template <class _Ep>
+_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY
 constexpr bool empty(initializer_list<_Ep> __il) noexcept { return __il.size() == 0; }
 
 template <class _Cont> constexpr
-auto data(_Cont& __c) -> decltype(__c.data()) { return __c.data(); }
+inline _LIBCPP_INLINE_VISIBILITY
+auto data(_Cont& __c)
+_NOEXCEPT_(noexcept(__c.data()))
+-> decltype        (__c.data())
+{ return            __c.data(); }
 
 template <class _Cont> constexpr
-auto data(const _Cont& __c) -> decltype(__c.data()) { return __c.data(); }
+inline _LIBCPP_INLINE_VISIBILITY
+auto data(const _Cont& __c)
+_NOEXCEPT_(noexcept(__c.data()))
+-> decltype        (__c.data()) 
+{ return            __c.data(); }
 
 template <class _Tp, size_t _Sz>
+inline _LIBCPP_INLINE_VISIBILITY
 constexpr _Tp* data(_Tp (&__array)[_Sz]) noexcept { return __array; }
 
 template <class _Ep>
+inline _LIBCPP_INLINE_VISIBILITY
 constexpr const _Ep* data(initializer_list<_Ep> __il) noexcept { return __il.begin(); }
 #endif
 
diff --git a/lib/libcxx/include/limits b/lib/libcxx/include/limits
index 80a1be40fe4..f530507f724 100644
--- a/lib/libcxx/include/limits
+++ b/lib/libcxx/include/limits
@@ -101,24 +101,25 @@ template<> class numeric_limits<cv long double>;
 }  // std
 
 */
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
-#endif
-
 #include <__config>
 #include <type_traits>
 
-#include <__undef_min_max>
-
-#if defined(_LIBCPP_MSVCRT)
-#include "support/win32/limits_win32.h"
+#if defined(_LIBCPP_COMPILER_MSVC)
+#include "support/win32/limits_msvc_win32.h"
 #endif // _LIBCPP_MSVCRT
 
 #if defined(__IBMCPP__)
 #include "support/ibm/limits.h"
 #endif // __IBMCPP__
 
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 enum float_round_style
@@ -182,14 +183,14 @@ protected:
     static _LIBCPP_CONSTEXPR const float_round_style round_style = round_toward_zero;
 };
 
-template <class _Tp, int digits, bool is_signed>
+template <class _Tp, int __digits, bool _IsSigned>
 struct __libcpp_compute_min
 {
-    static _LIBCPP_CONSTEXPR const _Tp value = _Tp(_Tp(1) << digits);
+    static _LIBCPP_CONSTEXPR const _Tp value = _Tp(_Tp(1) << __digits);
 };
 
-template <class _Tp, int digits>
-struct __libcpp_compute_min<_Tp, digits, false>
+template <class _Tp, int __digits>
+struct __libcpp_compute_min<_Tp, __digits, false>
 {
     static _LIBCPP_CONSTEXPR const _Tp value = _Tp(0);
 };
@@ -306,7 +307,7 @@ protected:
     static _LIBCPP_CONSTEXPR const bool is_signed = true;
     static _LIBCPP_CONSTEXPR const int  digits = __FLT_MANT_DIG__;
     static _LIBCPP_CONSTEXPR const int  digits10 = __FLT_DIG__;
-    static _LIBCPP_CONSTEXPR const int  max_digits10 = 2+(digits * 30103)/100000;
+    static _LIBCPP_CONSTEXPR const int  max_digits10 = 2+(digits * 30103l)/100000l;
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR type min() _NOEXCEPT {return __FLT_MIN__;}
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR type max() _NOEXCEPT {return __FLT_MAX__;}
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR type lowest() _NOEXCEPT {return -max();}
@@ -352,7 +353,7 @@ protected:
     static _LIBCPP_CONSTEXPR const bool is_signed = true;
     static _LIBCPP_CONSTEXPR const int  digits = __DBL_MANT_DIG__;
     static _LIBCPP_CONSTEXPR const int  digits10 = __DBL_DIG__;
-    static _LIBCPP_CONSTEXPR const int  max_digits10 = 2+(digits * 30103)/100000;
+    static _LIBCPP_CONSTEXPR const int  max_digits10 = 2+(digits * 30103l)/100000l;
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR type min() _NOEXCEPT {return __DBL_MIN__;}
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR type max() _NOEXCEPT {return __DBL_MAX__;}
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR type lowest() _NOEXCEPT {return -max();}
@@ -398,7 +399,7 @@ protected:
     static _LIBCPP_CONSTEXPR const bool is_signed = true;
     static _LIBCPP_CONSTEXPR const int  digits = __LDBL_MANT_DIG__;
     static _LIBCPP_CONSTEXPR const int  digits10 = __LDBL_DIG__;
-    static _LIBCPP_CONSTEXPR const int  max_digits10 = 2+(digits * 30103)/100000;
+    static _LIBCPP_CONSTEXPR const int  max_digits10 = 2+(digits * 30103l)/100000l;
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR type min() _NOEXCEPT {return __LDBL_MIN__;}
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR type max() _NOEXCEPT {return __LDBL_MAX__;}
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR type lowest() _NOEXCEPT {return -max();}
@@ -438,7 +439,7 @@ protected:
 };
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY numeric_limits
+class _LIBCPP_TEMPLATE_VIS numeric_limits
     : private __libcpp_numeric_limits<typename remove_cv<_Tp>::type>
 {
     typedef __libcpp_numeric_limits<typename remove_cv<_Tp>::type> __base;
@@ -531,7 +532,7 @@ template <class _Tp>
     _LIBCPP_CONSTEXPR const float_round_style numeric_limits<_Tp>::round_style;
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY numeric_limits<const _Tp>
+class _LIBCPP_TEMPLATE_VIS numeric_limits<const _Tp>
     : private numeric_limits<_Tp>
 {
     typedef numeric_limits<_Tp> __base;
@@ -624,7 +625,7 @@ template <class _Tp>
     _LIBCPP_CONSTEXPR const float_round_style numeric_limits<const _Tp>::round_style;
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY numeric_limits<volatile _Tp>
+class _LIBCPP_TEMPLATE_VIS numeric_limits<volatile _Tp>
     : private numeric_limits<_Tp>
 {
     typedef numeric_limits<_Tp> __base;
@@ -717,7 +718,7 @@ template <class _Tp>
     _LIBCPP_CONSTEXPR const float_round_style numeric_limits<volatile _Tp>::round_style;
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY numeric_limits<const volatile _Tp>
+class _LIBCPP_TEMPLATE_VIS numeric_limits<const volatile _Tp>
     : private numeric_limits<_Tp>
 {
     typedef numeric_limits<_Tp> __base;
@@ -811,4 +812,6 @@ template <class _Tp>
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_LIMITS
diff --git a/lib/libcxx/include/limits.h b/lib/libcxx/include/limits.h
new file mode 100644
index 00000000000..1867b104857
--- /dev/null
+++ b/lib/libcxx/include/limits.h
@@ -0,0 +1,65 @@
+// -*- C++ -*-
+//===--------------------------- limits.h ---------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_LIMITS_H
+#define _LIBCPP_LIMITS_H
+
+/*
+    limits.h synopsis
+
+Macros:
+
+    CHAR_BIT
+    SCHAR_MIN
+    SCHAR_MAX
+    UCHAR_MAX
+    CHAR_MIN
+    CHAR_MAX
+    MB_LEN_MAX
+    SHRT_MIN
+    SHRT_MAX
+    USHRT_MAX
+    INT_MIN
+    INT_MAX
+    UINT_MAX
+    LONG_MIN
+    LONG_MAX
+    ULONG_MAX
+    LLONG_MIN   // C99
+    LLONG_MAX   // C99
+    ULLONG_MAX  // C99
+
+*/
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+#ifndef __GNUC__
+#include_next <limits.h>
+#else
+// GCC header limits.h recursively includes itself through another header called
+// syslimits.h for some reason. This setup breaks down if we directly
+// #include_next GCC's limits.h (reasons not entirely clear to me). Therefore,
+// we manually re-create the necessary include sequence below:
+
+// Get the system limits.h defines (force recurse into the next level)
+#define _GCC_LIMITS_H_
+#define _GCC_NEXT_LIMITS_H
+#include_next <limits.h>
+
+// Get the ISO C defines
+#undef _GCC_LIMITS_H_
+#include_next <limits.h>
+#endif // __GNUC__
+
+#endif  // _LIBCPP_LIMITS_H
diff --git a/lib/libcxx/include/list b/lib/libcxx/include/list
index cff0a853eff..32e9a27bd2a 100644
--- a/lib/libcxx/include/list
+++ b/lib/libcxx/include/list
@@ -93,10 +93,10 @@ public:
     size_type max_size() const noexcept;
 
     template <class... Args>
-        void emplace_front(Args&&... args);
+        reference emplace_front(Args&&... args); // reference in C++17
     void pop_front();
     template <class... Args>
-        void emplace_back(Args&&... args);
+        reference emplace_back(Args&&... args);  // reference in C++17
     void pop_back();
     void push_front(const value_type& x);
     void push_front(value_type&& x);
@@ -177,14 +177,16 @@ template <class T, class Alloc>
 #include <algorithm>
 #include <type_traits>
 
-#include <__undef_min_max>
-
 #include <__debug>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Tp, class _VoidPtr> struct __list_node;
@@ -266,12 +268,12 @@ struct __list_node
     }
 };
 
-template <class _Tp, class _Alloc = allocator<_Tp> > class _LIBCPP_TYPE_VIS_ONLY list;
+template <class _Tp, class _Alloc = allocator<_Tp> > class _LIBCPP_TEMPLATE_VIS list;
 template <class _Tp, class _Alloc> class __list_imp;
-template <class _Tp, class _VoidPtr> class _LIBCPP_TYPE_VIS_ONLY __list_const_iterator;
+template <class _Tp, class _VoidPtr> class _LIBCPP_TEMPLATE_VIS __list_const_iterator;
 
 template <class _Tp, class _VoidPtr>
-class _LIBCPP_TYPE_VIS_ONLY __list_iterator
+class _LIBCPP_TEMPLATE_VIS __list_iterator
 {
     typedef __list_node_pointer_traits<_Tp, _VoidPtr> _NodeTraits;
     typedef typename _NodeTraits::__link_pointer __link_pointer;
@@ -394,7 +396,7 @@ public:
 };
 
 template <class _Tp, class _VoidPtr>
-class _LIBCPP_TYPE_VIS_ONLY __list_const_iterator
+class _LIBCPP_TEMPLATE_VIS __list_const_iterator
 {
     typedef __list_node_pointer_traits<_Tp, _VoidPtr> _NodeTraits;
     typedef typename _NodeTraits::__link_pointer __link_pointer;
@@ -479,7 +481,7 @@ public:
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
         _LIBCPP_ASSERT(__get_const_db()->__dereferenceable(this),
-                       "Attempted to dereference a non-dereferenceable list::iterator");
+                       "Attempted to dereference a non-dereferenceable list::const_iterator");
 #endif
         return pointer_traits<pointer>::pointer_to(__ptr_->__as_node()->__value_);
     }
@@ -571,6 +573,10 @@ protected:
         {return __size_alloc_.second();}
 
     _LIBCPP_INLINE_VISIBILITY
+    size_type __node_alloc_max_size() const _NOEXCEPT {
+        return __node_alloc_traits::max_size(__node_alloc());
+    }
+    _LIBCPP_INLINE_VISIBILITY
     static void __unlink_nodes(__link_pointer __f, __link_pointer __l) _NOEXCEPT;
 
     _LIBCPP_INLINE_VISIBILITY
@@ -622,9 +628,9 @@ protected:
 
     void swap(__list_imp& __c)
 #if _LIBCPP_STD_VER >= 14
-        _NOEXCEPT;
+        _NOEXCEPT_DEBUG;
 #else
-        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value || 
+        _NOEXCEPT_DEBUG_(!__alloc_traits::propagate_on_container_swap::value ||
                     __is_nothrow_swappable<allocator_type>::value);
 #endif
 
@@ -651,7 +657,7 @@ private:
         }
 
     _LIBCPP_INLINE_VISIBILITY
-    void __copy_assign_alloc(const __list_imp& __c, false_type)
+    void __copy_assign_alloc(const __list_imp&, false_type)
         {}
 
     _LIBCPP_INLINE_VISIBILITY
@@ -662,9 +668,16 @@ private:
         }
 
     _LIBCPP_INLINE_VISIBILITY
-    void __move_assign_alloc(__list_imp& __c, false_type)
+    void __move_assign_alloc(__list_imp&, false_type)
         _NOEXCEPT
         {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    void __invalidate_all_iterators() {
+#if _LIBCPP_DEBUG_LEVEL >= 2
+      __get_db()->__invalidate_all(this);
+#endif
+    }
 };
 
 // Unlink nodes [__f, __l]
@@ -720,21 +733,7 @@ __list_imp<_Tp, _Alloc>::clear() _NOEXCEPT
             __node_alloc_traits::destroy(__na, _VSTD::addressof(__np->__value_));
             __node_alloc_traits::deallocate(__na, __np, 1);
         }
-#if _LIBCPP_DEBUG_LEVEL >= 2
-        __c_node* __c = __get_db()->__find_c_and_lock(this);
-        for (__i_node** __p = __c->end_; __p != __c->beg_; )
-        {
-            --__p;
-            const_iterator* __i = static_cast<const_iterator*>((*__p)->__i_);
-            if (__i->__ptr_ != __l)
-            {
-                (*__p)->__c_ = nullptr;
-                if (--__c->end_ != __p)
-                    memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
-            }
-        }
-        __get_db()->unlock();
-#endif
+        __invalidate_all_iterators();
     }
 }
 
@@ -742,9 +741,9 @@ template <class _Tp, class _Alloc>
 void
 __list_imp<_Tp, _Alloc>::swap(__list_imp& __c)
 #if _LIBCPP_STD_VER >= 14
-        _NOEXCEPT
+        _NOEXCEPT_DEBUG
 #else
-        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value || 
+        _NOEXCEPT_DEBUG_(!__alloc_traits::propagate_on_container_swap::value ||
                     __is_nothrow_swappable<allocator_type>::value)
 #endif
 {
@@ -803,7 +802,7 @@ __list_imp<_Tp, _Alloc>::swap(__list_imp& __c)
 }
 
 template <class _Tp, class _Alloc /*= allocator<_Tp>*/>
-class _LIBCPP_TYPE_VIS_ONLY list
+class _LIBCPP_TEMPLATE_VIS list
     : private __list_imp<_Tp, _Alloc>
 {
     typedef __list_imp<_Tp, _Alloc> base;
@@ -863,11 +862,10 @@ public:
     list(const list& __c, const allocator_type& __a);
     _LIBCPP_INLINE_VISIBILITY
     list& operator=(const list& __c);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     list(initializer_list<value_type> __il);
     list(initializer_list<value_type> __il, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
     _LIBCPP_INLINE_VISIBILITY
     list(list&& __c)
         _NOEXCEPT_(is_nothrow_move_constructible<__node_allocator>::value);
@@ -878,33 +876,35 @@ public:
         _NOEXCEPT_(
             __node_alloc_traits::propagate_on_container_move_assignment::value &&
             is_nothrow_move_assignable<__node_allocator>::value);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
     _LIBCPP_INLINE_VISIBILITY
     list& operator=(initializer_list<value_type> __il)
         {assign(__il.begin(), __il.end()); return *this;}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
+    _LIBCPP_INLINE_VISIBILITY
+    void assign(initializer_list<value_type> __il)
+        {assign(__il.begin(), __il.end());}
+#endif  // _LIBCPP_CXX03_LANG
 
     template <class _InpIter>
         void assign(_InpIter __f, _InpIter __l,
              typename enable_if<__is_input_iterator<_InpIter>::value>::type* = 0);
     void assign(size_type __n, const value_type& __x);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-    _LIBCPP_INLINE_VISIBILITY
-    void assign(initializer_list<value_type> __il)
-        {assign(__il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
     _LIBCPP_INLINE_VISIBILITY
     allocator_type get_allocator() const _NOEXCEPT;
 
     _LIBCPP_INLINE_VISIBILITY
     size_type size() const _NOEXCEPT     {return base::__sz();}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool empty() const _NOEXCEPT         {return base::empty();}
     _LIBCPP_INLINE_VISIBILITY
     size_type max_size() const _NOEXCEPT
-        {return numeric_limits<difference_type>::max();}
+        {
+            return std::min<size_type>(
+                base::__node_alloc_max_size(),
+                numeric_limits<difference_type >::max());
+        }
 
     _LIBCPP_INLINE_VISIBILITY
           iterator begin() _NOEXCEPT        {return base::begin();}
@@ -963,40 +963,56 @@ public:
         return base::__end_.__prev_->__as_node()->__value_;
     }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     void push_front(value_type&& __x);
     void push_back(value_type&& __x);
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+
     template <class... _Args>
-       void emplace_front(_Args&&... __args);
+#if _LIBCPP_STD_VER > 14
+       reference emplace_front(_Args&&... __args);
+#else
+       void      emplace_front(_Args&&... __args);
+#endif
     template <class... _Args>
-        void emplace_back(_Args&&... __args);
+#if _LIBCPP_STD_VER > 14
+        reference emplace_back(_Args&&... __args);
+#else
+       void       emplace_back(_Args&&... __args);
+#endif
     template <class... _Args>
         iterator emplace(const_iterator __p, _Args&&... __args);
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+
     iterator insert(const_iterator __p, value_type&& __x);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
+    _LIBCPP_INLINE_VISIBILITY
+    iterator insert(const_iterator __p, initializer_list<value_type> __il)
+        {return insert(__p, __il.begin(), __il.end());}
+#endif  // _LIBCPP_CXX03_LANG
 
     void push_front(const value_type& __x);
     void push_back(const value_type& __x);
 
+#ifndef _LIBCPP_CXX03_LANG
+    template <class _Arg>
+    _LIBCPP_INLINE_VISIBILITY
+    void __emplace_back(_Arg&& __arg) { emplace_back(_VSTD::forward<_Arg>(__arg)); }
+#else
+    _LIBCPP_INLINE_VISIBILITY
+    void __emplace_back(value_type const& __arg) { push_back(__arg); }
+#endif
+
     iterator insert(const_iterator __p, const value_type& __x);
     iterator insert(const_iterator __p, size_type __n, const value_type& __x);
     template <class _InpIter>
         iterator insert(const_iterator __p, _InpIter __f, _InpIter __l,
              typename enable_if<__is_input_iterator<_InpIter>::value>::type* = 0);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-    _LIBCPP_INLINE_VISIBILITY
-    iterator insert(const_iterator __p, initializer_list<value_type> __il)
-        {return insert(__p, __il.begin(), __il.end());}
-#endif   // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
     _LIBCPP_INLINE_VISIBILITY
     void swap(list& __c)
 #if _LIBCPP_STD_VER >= 14
-        _NOEXCEPT
+        _NOEXCEPT_DEBUG
 #else
-        _NOEXCEPT_(!__node_alloc_traits::propagate_on_container_swap::value ||
+        _NOEXCEPT_DEBUG_(!__node_alloc_traits::propagate_on_container_swap::value ||
                    __is_nothrow_swappable<__node_allocator>::value)
 #endif
         {base::swap(__c);}
@@ -1013,22 +1029,18 @@ public:
     void resize(size_type __n, const value_type& __x);
 
     void splice(const_iterator __p, list& __c);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void splice(const_iterator __p, list&& __c) {splice(__p, __c);}
-#endif
-    void splice(const_iterator __p, list& __c, const_iterator __i);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     void splice(const_iterator __p, list&& __c, const_iterator __i)
         {splice(__p, __c, __i);}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    void splice(const_iterator __p, list& __c, const_iterator __f, const_iterator __l);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     void splice(const_iterator __p, list&& __c, const_iterator __f, const_iterator __l)
         {splice(__p, __c, __f, __l);}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif
+    void splice(const_iterator __p, list& __c, const_iterator __i);
+    void splice(const_iterator __p, list& __c, const_iterator __f, const_iterator __l);
 
     void remove(const value_type& __x);
     template <class _Pred> void remove_if(_Pred __pred);
@@ -1038,17 +1050,17 @@ public:
         void unique(_BinaryPred __binary_pred);
     _LIBCPP_INLINE_VISIBILITY
     void merge(list& __c);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void merge(list&& __c) {merge(__c);}
-#endif
-    template <class _Comp>
-        void merge(list& __c, _Comp __comp);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
     template <class _Comp>
     _LIBCPP_INLINE_VISIBILITY
         void merge(list&& __c, _Comp __comp) {merge(__c, __comp);}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif
+    template <class _Comp>
+        void merge(list& __c, _Comp __comp);
+
     _LIBCPP_INLINE_VISIBILITY
     void sort();
     template <class _Comp>
@@ -1059,6 +1071,16 @@ public:
 
     bool __invariants() const;
 
+    typedef __allocator_destructor<__node_allocator> __node_destructor;
+    typedef unique_ptr<__node, __node_destructor> __hold_pointer;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __hold_pointer __allocate_node(__node_allocator& __na) {
+      __node_pointer __p = __node_alloc_traits::allocate(__na, 1);
+      __p->__prev_ = nullptr;
+      return __hold_pointer(__p, __node_destructor(__na, 1));
+    }
+
 #if _LIBCPP_DEBUG_LEVEL >= 2
 
     bool __dereferenceable(const const_iterator* __i) const;
@@ -1137,7 +1159,7 @@ list<_Tp, _Alloc>::list(size_type __n)
     __get_db()->__insert_c(this);
 #endif
     for (; __n > 0; --__n)
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
         emplace_back();
 #else
         push_back(value_type());
@@ -1152,11 +1174,7 @@ list<_Tp, _Alloc>::list(size_type __n, const allocator_type& __a) : base(__a)
     __get_db()->__insert_c(this);
 #endif
     for (; __n > 0; --__n)
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
         emplace_back();
-#else
-        push_back(value_type());
-#endif
 }
 #endif
 
@@ -1190,7 +1208,7 @@ list<_Tp, _Alloc>::list(_InpIter __f, _InpIter __l,
     __get_db()->__insert_c(this);
 #endif
     for (; __f != __l; ++__f)
-        push_back(*__f);
+        __emplace_back(*__f);
 }
 
 template <class _Tp, class _Alloc>
@@ -1203,7 +1221,7 @@ list<_Tp, _Alloc>::list(_InpIter __f, _InpIter __l, const allocator_type& __a,
     __get_db()->__insert_c(this);
 #endif
     for (; __f != __l; ++__f)
-        push_back(*__f);
+        __emplace_back(*__f);
 }
 
 template <class _Tp, class _Alloc>
@@ -1230,7 +1248,7 @@ list<_Tp, _Alloc>::list(const list& __c, const allocator_type& __a)
         push_back(*__i);
 }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Alloc>
 list<_Tp, _Alloc>::list(initializer_list<value_type> __il, const allocator_type& __a)
@@ -1255,23 +1273,6 @@ list<_Tp, _Alloc>::list(initializer_list<value_type> __il)
         push_back(*__i);
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
-template <class _Tp, class _Alloc>
-inline
-list<_Tp, _Alloc>&
-list<_Tp, _Alloc>::operator=(const list& __c)
-{
-    if (this != &__c)
-    {
-        base::__copy_assign_alloc(__c);
-        assign(__c.begin(), __c.end());
-    }
-    return *this;
-}
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
 template <class _Tp, class _Alloc>
 inline
 list<_Tp, _Alloc>::list(list&& __c)
@@ -1337,7 +1338,20 @@ list<_Tp, _Alloc>::__move_assign(list& __c, true_type)
     splice(end(), __c);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
+
+template <class _Tp, class _Alloc>
+inline
+list<_Tp, _Alloc>&
+list<_Tp, _Alloc>::operator=(const list& __c)
+{
+    if (this != &__c)
+    {
+        base::__copy_assign_alloc(__c);
+        assign(__c.begin(), __c.end());
+    }
+    return *this;
+}
 
 template <class _Tp, class _Alloc>
 template <class _InpIter>
@@ -1353,6 +1367,9 @@ list<_Tp, _Alloc>::assign(_InpIter __f, _InpIter __l,
         insert(__e, __f, __l);
     else
         erase(__i, __e);
+#if _LIBCPP_DEBUG_LEVEL >= 2
+      __get_db()->__invalidate_all(this);
+#endif
 }
 
 template <class _Tp, class _Alloc>
@@ -1367,6 +1384,9 @@ list<_Tp, _Alloc>::assign(size_type __n, const value_type& __x)
         insert(__e, __n, __x);
     else
         erase(__i, __e);
+#if _LIBCPP_DEBUG_LEVEL >= 2
+      __get_db()->__invalidate_all(this);
+#endif
 }
 
 template <class _Tp, class _Alloc>
@@ -1387,9 +1407,7 @@ list<_Tp, _Alloc>::insert(const_iterator __p, const value_type& __x)
         " referring to this list");
 #endif
     __node_allocator& __na = base::__node_alloc();
-    typedef __allocator_destructor<__node_allocator> _Dp;
-    unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
-    __hold->__prev_ = 0;
+    __hold_pointer __hold = __allocate_node(__na);
     __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_), __x);
     __link_nodes(__p.__ptr_, __hold->__as_link(), __hold->__as_link());
     ++base::__sz();
@@ -1416,9 +1434,7 @@ list<_Tp, _Alloc>::insert(const_iterator __p, size_type __n, const value_type& _
     {
         size_type __ds = 0;
         __node_allocator& __na = base::__node_alloc();
-        typedef __allocator_destructor<__node_allocator> _Dp;
-        unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
-        __hold->__prev_ = 0;
+        __hold_pointer __hold = __allocate_node(__na);
         __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_), __x);
         ++__ds;
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1484,9 +1500,7 @@ list<_Tp, _Alloc>::insert(const_iterator __p, _InpIter __f, _InpIter __l,
     {
         size_type __ds = 0;
         __node_allocator& __na = base::__node_alloc();
-        typedef __allocator_destructor<__node_allocator> _Dp;
-        unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
-        __hold->__prev_ = 0;
+        __hold_pointer __hold = __allocate_node(__na);
         __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_), *__f);
         ++__ds;
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1539,8 +1553,7 @@ void
 list<_Tp, _Alloc>::push_front(const value_type& __x)
 {
     __node_allocator& __na = base::__node_alloc();
-    typedef __allocator_destructor<__node_allocator> _Dp;
-    unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
+    __hold_pointer __hold = __allocate_node(__na);
     __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_), __x);
     __link_pointer __nl = __hold->__as_link();
     __link_nodes_at_front(__nl, __nl);
@@ -1553,23 +1566,21 @@ void
 list<_Tp, _Alloc>::push_back(const value_type& __x)
 {
     __node_allocator& __na = base::__node_alloc();
-    typedef __allocator_destructor<__node_allocator> _Dp;
-    unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
+    __hold_pointer __hold = __allocate_node(__na);
     __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_), __x);
     __link_nodes_at_back(__hold.get()->__as_link(), __hold.get()->__as_link());
     ++base::__sz();
     __hold.release();
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Alloc>
 void
 list<_Tp, _Alloc>::push_front(value_type&& __x)
 {
     __node_allocator& __na = base::__node_alloc();
-    typedef __allocator_destructor<__node_allocator> _Dp;
-    unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
+    __hold_pointer __hold = __allocate_node(__na);
     __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_), _VSTD::move(__x));
     __link_nodes_at_front(__hold.get()->__as_link(), __hold.get()->__as_link());
     ++base::__sz();
@@ -1581,43 +1592,54 @@ void
 list<_Tp, _Alloc>::push_back(value_type&& __x)
 {
     __node_allocator& __na = base::__node_alloc();
-    typedef __allocator_destructor<__node_allocator> _Dp;
-    unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
+    __hold_pointer __hold = __allocate_node(__na);
     __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_), _VSTD::move(__x));
     __link_nodes_at_back(__hold.get()->__as_link(), __hold.get()->__as_link());
     ++base::__sz();
     __hold.release();
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
 template <class _Tp, class _Alloc>
 template <class... _Args>
+#if _LIBCPP_STD_VER > 14
+typename list<_Tp, _Alloc>::reference
+#else
 void
+#endif
 list<_Tp, _Alloc>::emplace_front(_Args&&... __args)
 {
     __node_allocator& __na = base::__node_alloc();
-    typedef __allocator_destructor<__node_allocator> _Dp;
-    unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
+    __hold_pointer __hold = __allocate_node(__na);
     __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_), _VSTD::forward<_Args>(__args)...);
     __link_nodes_at_front(__hold.get()->__as_link(), __hold.get()->__as_link());
     ++base::__sz();
+#if _LIBCPP_STD_VER > 14
+    return __hold.release()->__value_;
+#else
     __hold.release();
+#endif
 }
 
 template <class _Tp, class _Alloc>
 template <class... _Args>
+#if _LIBCPP_STD_VER > 14
+typename list<_Tp, _Alloc>::reference
+#else
 void
+#endif
 list<_Tp, _Alloc>::emplace_back(_Args&&... __args)
 {
     __node_allocator& __na = base::__node_alloc();
-    typedef __allocator_destructor<__node_allocator> _Dp;
-    unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
+    __hold_pointer __hold = __allocate_node(__na);
     __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_), _VSTD::forward<_Args>(__args)...);
     __link_pointer __nl = __hold->__as_link();
     __link_nodes_at_back(__nl, __nl);
     ++base::__sz();
+#if _LIBCPP_STD_VER > 14
+    return __hold.release()->__value_;
+#else
     __hold.release();
+#endif
 }
 
 template <class _Tp, class _Alloc>
@@ -1631,9 +1653,7 @@ list<_Tp, _Alloc>::emplace(const_iterator __p, _Args&&... __args)
         " referring to this list");
 #endif
     __node_allocator& __na = base::__node_alloc();
-    typedef __allocator_destructor<__node_allocator> _Dp;
-    unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
-    __hold->__prev_ = 0;
+    __hold_pointer __hold = __allocate_node(__na);
     __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_), _VSTD::forward<_Args>(__args)...);
     __link_pointer __nl = __hold.get()->__as_link();
     __link_nodes(__p.__ptr_, __nl, __nl);
@@ -1646,8 +1666,6 @@ list<_Tp, _Alloc>::emplace(const_iterator __p, _Args&&... __args)
 #endif
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-
 template <class _Tp, class _Alloc>
 typename list<_Tp, _Alloc>::iterator
 list<_Tp, _Alloc>::insert(const_iterator __p, value_type&& __x)
@@ -1658,9 +1676,7 @@ list<_Tp, _Alloc>::insert(const_iterator __p, value_type&& __x)
         " referring to this list");
 #endif
     __node_allocator& __na = base::__node_alloc();
-    typedef __allocator_destructor<__node_allocator> _Dp;
-    unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
-    __hold->__prev_ = 0;
+    __hold_pointer __hold = __allocate_node(__na);
     __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_), _VSTD::move(__x));
     __link_pointer __nl = __hold->__as_link();
     __link_nodes(__p.__ptr_, __nl, __nl);
@@ -1673,7 +1689,7 @@ list<_Tp, _Alloc>::insert(const_iterator __p, value_type&& __x)
 #endif
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Alloc>
 void
@@ -1751,15 +1767,15 @@ list<_Tp, _Alloc>::erase(const_iterator __p)
     --base::__sz();
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __c_node* __c = __get_db()->__find_c_and_lock(this);
-    for (__i_node** __p = __c->end_; __p != __c->beg_; )
+    for (__i_node** __ip = __c->end_; __ip != __c->beg_; )
     {
-        --__p;
-        iterator* __i = static_cast<iterator*>((*__p)->__i_);
+        --__ip;
+        iterator* __i = static_cast<iterator*>((*__ip)->__i_);
         if (__i->__ptr_ == __n)
         {
-            (*__p)->__c_ = nullptr;
-            if (--__c->end_ != __p)
-                memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
+            (*__ip)->__c_ = nullptr;
+            if (--__c->end_ != __ip)
+                memmove(__ip, __ip+1, (__c->end_ - __ip)*sizeof(__i_node*));
         }
     }
     __get_db()->unlock();
@@ -1782,6 +1798,9 @@ list<_Tp, _Alloc>::erase(const_iterator __f, const_iterator __l)
     _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__f) == this,
         "list::erase(iterator, iterator) called with an iterator not"
         " referring to this list");
+   _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__l) == this,
+        "list::erase(iterator, iterator) called with an iterator not"
+        " referring to this list");
 #endif
     if (__f != __l)
     {
@@ -1830,9 +1849,7 @@ list<_Tp, _Alloc>::resize(size_type __n)
         __n -= base::__sz();
         size_type __ds = 0;
         __node_allocator& __na = base::__node_alloc();
-        typedef __allocator_destructor<__node_allocator> _Dp;
-        unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
-        __hold->__prev_ = 0;
+        __hold_pointer __hold = __allocate_node(__na);
         __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_));
         ++__ds;
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1889,9 +1906,7 @@ list<_Tp, _Alloc>::resize(size_type __n, const value_type& __x)
         __n -= base::__sz();
         size_type __ds = 0;
         __node_allocator& __na = base::__node_alloc();
-        typedef __allocator_destructor<__node_allocator> _Dp;
-        unique_ptr<__node, _Dp> __hold(__node_alloc_traits::allocate(__na, 1), _Dp(__na, 1));
-        __hold->__prev_ = 0;
+        __hold_pointer __hold = __allocate_node(__na);
         __node_alloc_traits::construct(__na, _VSTD::addressof(__hold->__value_), __x);
         ++__ds;
         __link_pointer __nl = __hold.release()->__as_link();
@@ -1961,16 +1976,16 @@ list<_Tp, _Alloc>::splice(const_iterator __p, list& __c)
         __libcpp_db* __db = __get_db();
         __c_node* __cn1 = __db->__find_c_and_lock(this);
         __c_node* __cn2 = __db->__find_c(&__c);
-        for (__i_node** __p = __cn2->end_; __p != __cn2->beg_;)
+        for (__i_node** __ip = __cn2->end_; __ip != __cn2->beg_;)
         {
-            --__p;
-            iterator* __i = static_cast<iterator*>((*__p)->__i_);
+            --__ip;
+            iterator* __i = static_cast<iterator*>((*__ip)->__i_);
             if (__i->__ptr_ != __c.__end_as_link())
             {
-                __cn1->__add(*__p);
-                (*__p)->__c_ = __cn1;
-                if (--__cn2->end_ != __p)
-                    memmove(__p, __p+1, (__cn2->end_ - __p)*sizeof(__i_node*));
+                __cn1->__add(*__ip);
+                (*__ip)->__c_ = __cn1;
+                if (--__cn2->end_ != __ip)
+                    memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
             }
         }
         __db->unlock();
@@ -2004,16 +2019,16 @@ list<_Tp, _Alloc>::splice(const_iterator __p, list& __c, const_iterator __i)
         __libcpp_db* __db = __get_db();
         __c_node* __cn1 = __db->__find_c_and_lock(this);
         __c_node* __cn2 = __db->__find_c(&__c);
-        for (__i_node** __p = __cn2->end_; __p != __cn2->beg_;)
+        for (__i_node** __ip = __cn2->end_; __ip != __cn2->beg_;)
         {
-            --__p;
-            iterator* __j = static_cast<iterator*>((*__p)->__i_);
+            --__ip;
+            iterator* __j = static_cast<iterator*>((*__ip)->__i_);
             if (__j->__ptr_ == __f)
             {
-                __cn1->__add(*__p);
-                (*__p)->__c_ = __cn1;
-                if (--__cn2->end_ != __p)
-                    memmove(__p, __p+1, (__cn2->end_ - __p)*sizeof(__i_node*));
+                __cn1->__add(*__ip);
+                (*__ip)->__c_ = __cn1;
+                if (--__cn2->end_ != __ip)
+                    memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
             }
         }
         __db->unlock();
@@ -2058,19 +2073,19 @@ list<_Tp, _Alloc>::splice(const_iterator __p, list& __c, const_iterator __f, con
         __libcpp_db* __db = __get_db();
         __c_node* __cn1 = __db->__find_c_and_lock(this);
         __c_node* __cn2 = __db->__find_c(&__c);
-        for (__i_node** __p = __cn2->end_; __p != __cn2->beg_;)
+        for (__i_node** __ip = __cn2->end_; __ip != __cn2->beg_;)
         {
-            --__p;
-            iterator* __j = static_cast<iterator*>((*__p)->__i_);
+            --__ip;
+            iterator* __j = static_cast<iterator*>((*__ip)->__i_);
             for (__link_pointer __k = __f.__ptr_;
                                           __k != __l.__ptr_; __k = __k->__next_)
             {
                 if (__j->__ptr_ == __k)
                 {
-                    __cn1->__add(*__p);
-                    (*__p)->__c_ = __cn1;
-                    if (--__cn2->end_ != __p)
-                        memmove(__p, __p+1, (__cn2->end_ - __p)*sizeof(__i_node*));
+                    __cn1->__add(*__ip);
+                    (*__ip)->__c_ = __cn1;
+                    if (--__cn2->end_ != __ip)
+                        memmove(__ip, __ip+1, (__cn2->end_ - __ip)*sizeof(__i_node*));
                 }
             }
         }
@@ -2083,7 +2098,7 @@ template <class _Tp, class _Alloc>
 void
 list<_Tp, _Alloc>::remove(const value_type& __x)
 {
-    list<_Tp, _Alloc> __deleted_nodes; // collect the nodes we're removing
+    list<_Tp, _Alloc> __deleted_nodes(get_allocator()); // collect the nodes we're removing
     for (const_iterator __i = begin(), __e = end(); __i != __e;)
     {
         if (*__i == __x)
@@ -2328,14 +2343,14 @@ list<_Tp, _Alloc>::__decrementable(const const_iterator* __i) const
 
 template <class _Tp, class _Alloc>
 bool
-list<_Tp, _Alloc>::__addable(const const_iterator* __i, ptrdiff_t __n) const
+list<_Tp, _Alloc>::__addable(const const_iterator*, ptrdiff_t) const
 {
     return false;
 }
 
 template <class _Tp, class _Alloc>
 bool
-list<_Tp, _Alloc>::__subscriptable(const const_iterator* __i, ptrdiff_t __n) const
+list<_Tp, _Alloc>::__subscriptable(const const_iterator*, ptrdiff_t) const
 {
     return false;
 }
@@ -2401,4 +2416,6 @@ swap(list<_Tp, _Alloc>& __x, list<_Tp, _Alloc>& __y)
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_LIST
diff --git a/lib/libcxx/include/locale b/lib/libcxx/include/locale
index 3d804e86f4d..a86645d2cc4 100644
--- a/lib/libcxx/include/locale
+++ b/lib/libcxx/include/locale
@@ -192,14 +192,7 @@ template <class charT> class messages_byname;
 #endif
 #include <cstdlib>
 #include <ctime>
-#if defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
-#include <support/win32/locale_win32.h>
-#elif defined(_NEWLIB_VERSION)
-// FIXME: replace all the uses of _NEWLIB_VERSION with __NEWLIB__ preceded by an
-// include of <sys/cdefs.h> once https://sourceware.org/ml/newlib-cvs/2014-q3/msg00038.html
-// has had a chance to bake for a bit
-#include <support/newlib/xlocale.h>
-#endif
+#include <cstdio>
 #ifdef _LIBCPP_HAS_CATOPEN
 #include <nl_types.h>
 #endif
@@ -208,18 +201,20 @@ template <class charT> class messages_byname;
 #include <Availability.h>
 #endif
 
-#include <__undef_min_max>
-
-#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
-#pragma GCC system_header
-#endif
-
 #ifdef _LIBCPP_LOCALE__L_EXTENSIONS
 #include <__bsd_locale_defaults.h>
 #else
 #include <__bsd_locale_fallbacks.h>
 #endif
 
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #if defined(__APPLE__) || defined(__FreeBSD__)
@@ -233,9 +228,6 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 #define __cloc_defined
 #endif
 
-typedef _VSTD::remove_pointer<locale_t>::type __locale_struct;
-typedef _VSTD::unique_ptr<__locale_struct, decltype(&freelocale)> __locale_unique_ptr;
-
 // __scan_keyword
 // Scans [__b, __e) until a match is found in the basic_strings range
 //  [__kb, __ke) or until it can be shown that there is no match in [__kb, __ke).
@@ -380,19 +372,57 @@ template <class _CharT>
 struct __num_get
     : protected __num_get_base
 {
-    static string __stage2_int_prep(ios_base& __iob, _CharT* __atoms, _CharT& __thousands_sep);
     static string __stage2_float_prep(ios_base& __iob, _CharT* __atoms, _CharT& __decimal_point,
                                       _CharT& __thousands_sep);
-    static int __stage2_int_loop(_CharT __ct, int __base, char* __a, char*& __a_end,
-                  unsigned& __dc, _CharT __thousands_sep, const string& __grouping,
-                  unsigned* __g, unsigned*& __g_end, _CharT* __atoms);
+
     static int __stage2_float_loop(_CharT __ct, bool& __in_units, char& __exp,
                                    char* __a, char*& __a_end,
                                    _CharT __decimal_point, _CharT __thousands_sep,
                                    const string& __grouping, unsigned* __g,
                                    unsigned*& __g_end, unsigned& __dc, _CharT* __atoms);
+#ifndef _LIBCPP_ABI_OPTIMIZED_LOCALE_NUM_GET
+    static string __stage2_int_prep(ios_base& __iob, _CharT* __atoms, _CharT& __thousands_sep);
+    static int __stage2_int_loop(_CharT __ct, int __base, char* __a, char*& __a_end,
+                  unsigned& __dc, _CharT __thousands_sep, const string& __grouping,
+                  unsigned* __g, unsigned*& __g_end, _CharT* __atoms);
+
+#else
+    static string __stage2_int_prep(ios_base& __iob, _CharT& __thousands_sep)
+    {
+        locale __loc = __iob.getloc();
+        const numpunct<_CharT>& __np = use_facet<numpunct<_CharT> >(__loc);
+        __thousands_sep = __np.thousands_sep();
+        return __np.grouping();
+    }
+
+    const _CharT* __do_widen(ios_base& __iob, _CharT* __atoms) const
+    {
+      return __do_widen_p(__iob, __atoms);
+    }
+
+
+    static int __stage2_int_loop(_CharT __ct, int __base, char* __a, char*& __a_end,
+                  unsigned& __dc, _CharT __thousands_sep, const string& __grouping,
+                  unsigned* __g, unsigned*& __g_end, const _CharT* __atoms);
+private:
+    template<typename T>
+    const T* __do_widen_p(ios_base& __iob, T* __atoms) const
+    {
+      locale __loc = __iob.getloc();
+      use_facet<ctype<T> >(__loc).widen(__src, __src + 26, __atoms);
+      return __atoms;
+    }
+
+    const char* __do_widen_p(ios_base& __iob, char* __atoms) const
+    {
+      (void)__iob;
+      (void)__atoms;
+      return __src;
+    }
+#endif
 };
 
+#ifndef _LIBCPP_ABI_OPTIMIZED_LOCALE_NUM_GET
 template <class _CharT>
 string
 __num_get<_CharT>::__stage2_int_prep(ios_base& __iob, _CharT* __atoms, _CharT& __thousands_sep)
@@ -403,6 +433,7 @@ __num_get<_CharT>::__stage2_int_prep(ios_base& __iob, _CharT* __atoms, _CharT& _
     __thousands_sep = __np.thousands_sep();
     return __np.grouping();
 }
+#endif
 
 template <class _CharT>
 string
@@ -419,9 +450,16 @@ __num_get<_CharT>::__stage2_float_prep(ios_base& __iob, _CharT* __atoms, _CharT&
 
 template <class _CharT>
 int
+#ifndef _LIBCPP_ABI_OPTIMIZED_LOCALE_NUM_GET
 __num_get<_CharT>::__stage2_int_loop(_CharT __ct, int __base, char* __a, char*& __a_end,
                   unsigned& __dc, _CharT __thousands_sep, const string& __grouping,
                   unsigned* __g, unsigned*& __g_end, _CharT* __atoms)
+#else
+__num_get<_CharT>::__stage2_int_loop(_CharT __ct, int __base, char* __a, char*& __a_end,
+                  unsigned& __dc, _CharT __thousands_sep, const string& __grouping,
+                  unsigned* __g, unsigned*& __g_end, const _CharT* __atoms)
+
+#endif
 {
     if (__a_end == __a && (__ct == __atoms[24] || __ct == __atoms[25]))
     {
@@ -523,11 +561,11 @@ __num_get<_CharT>::__stage2_float_loop(_CharT __ct, bool& __in_units, char& __ex
     return 0;
 }
 
-_LIBCPP_EXTERN_TEMPLATE2(struct _LIBCPP_TYPE_VIS __num_get<char>)
-_LIBCPP_EXTERN_TEMPLATE2(struct _LIBCPP_TYPE_VIS __num_get<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(struct _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __num_get<char>)
+_LIBCPP_EXTERN_TEMPLATE2(struct _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __num_get<wchar_t>)
 
 template <class _CharT, class _InputIterator = istreambuf_iterator<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY num_get
+class _LIBCPP_TEMPLATE_VIS num_get
     : public locale::facet,
       private __num_get<_CharT>
 {
@@ -623,16 +661,19 @@ protected:
     ~num_get() {}
 
     template <class _Fp>
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
     iter_type __do_get_floating_point
                             (iter_type __b, iter_type __e, ios_base& __iob,
                              ios_base::iostate& __err, _Fp& __v) const;
 
     template <class _Signed>
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
     iter_type __do_get_signed
                             (iter_type __b, iter_type __e, ios_base& __iob,
                              ios_base::iostate& __err, _Signed& __v) const;
 
     template <class _Unsigned>
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
     iter_type __do_get_unsigned
                             (iter_type __b, iter_type __e, ios_base& __iob,
                              ios_base::iostate& __err, _Unsigned& __v) const;
@@ -779,6 +820,7 @@ long double __do_strtod<long double>(const char* __a, char** __p2) {
 }
 
 template <class _Tp>
+_LIBCPP_HIDDEN
 _Tp
 __num_get_float(const char* __a, const char* __a_end, ios_base::iostate& __err)
 {
@@ -853,9 +895,16 @@ num_get<_CharT, _InputIterator>::__do_get_signed(iter_type __b, iter_type __e,
     // Stage 1
     int __base = this->__get_base(__iob);
     // Stage 2
-    char_type __atoms[26];
     char_type __thousands_sep;
+    const int __atoms_size = 26;
+#ifdef _LIBCPP_ABI_OPTIMIZED_LOCALE_NUM_GET
+    char_type __atoms1[__atoms_size];
+    const char_type *__atoms = this->__do_widen(__iob, __atoms1);
+    string __grouping = this->__stage2_int_prep(__iob, __thousands_sep);
+#else
+    char_type __atoms[__atoms_size];
     string __grouping = this->__stage2_int_prep(__iob, __atoms, __thousands_sep);
+#endif
     string __buf;
     __buf.resize(__buf.capacity());
     char* __a = &__buf[0];
@@ -903,9 +952,16 @@ num_get<_CharT, _InputIterator>::__do_get_unsigned(iter_type __b, iter_type __e,
     // Stage 1
     int __base = this->__get_base(__iob);
     // Stage 2
-    char_type __atoms[26];
     char_type __thousands_sep;
+    const int __atoms_size = 26;
+#ifdef _LIBCPP_ABI_OPTIMIZED_LOCALE_NUM_GET
+    char_type __atoms1[__atoms_size];
+    const char_type *__atoms = this->__do_widen(__iob, __atoms1);
+    string __grouping = this->__stage2_int_prep(__iob, __thousands_sep);
+#else
+    char_type __atoms[__atoms_size];
     string __grouping = this->__stage2_int_prep(__iob, __atoms, __thousands_sep);
+#endif
     string __buf;
     __buf.resize(__buf.capacity());
     char* __a = &__buf[0];
@@ -1042,8 +1098,8 @@ num_get<_CharT, _InputIterator>::do_get(iter_type __b, iter_type __e,
     return __b;
 }
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS num_get<char>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS num_get<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS num_get<char>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS num_get<wchar_t>)
 
 struct _LIBCPP_TYPE_VIS __num_put_base
 {
@@ -1192,11 +1248,11 @@ __num_put<_CharT>::__widen_and_group_float(char* __nb, char* __np, char* __ne,
         __op = __ob + (__np - __nb);
 }
 
-_LIBCPP_EXTERN_TEMPLATE2(struct _LIBCPP_TYPE_VIS __num_put<char>)
-_LIBCPP_EXTERN_TEMPLATE2(struct _LIBCPP_TYPE_VIS __num_put<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(struct _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __num_put<char>)
+_LIBCPP_EXTERN_TEMPLATE2(struct _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __num_put<wchar_t>)
 
 template <class _CharT, class _OutputIterator = ostreambuf_iterator<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY num_put
+class _LIBCPP_TEMPLATE_VIS num_put
     : public locale::facet,
       private __num_put<_CharT>
 {
@@ -1398,6 +1454,7 @@ num_put<_CharT, _OutputIterator>::do_put(iter_type __s, ios_base& __iob,
     this->__format_int(__fmt+1, __len, true, __iob.flags());
     const unsigned __nbuf = (numeric_limits<long>::digits / 3)
                           + ((numeric_limits<long>::digits % 3) != 0)
+                          + ((__iob.flags() & ios_base::showbase) != 0)
                           + 2;
     char __nar[__nbuf];
     int __nc = __libcpp_snprintf_l(__nar, sizeof(__nar), _LIBCPP_GET_C_LOCALE, __fmt, __v);
@@ -1424,6 +1481,7 @@ num_put<_CharT, _OutputIterator>::do_put(iter_type __s, ios_base& __iob,
     this->__format_int(__fmt+1, __len, true, __iob.flags());
     const unsigned __nbuf = (numeric_limits<long long>::digits / 3)
                           + ((numeric_limits<long long>::digits % 3) != 0)
+                          + ((__iob.flags() & ios_base::showbase) != 0)
                           + 2;
     char __nar[__nbuf];
     int __nc = __libcpp_snprintf_l(__nar, sizeof(__nar), _LIBCPP_GET_C_LOCALE, __fmt, __v);
@@ -1450,6 +1508,7 @@ num_put<_CharT, _OutputIterator>::do_put(iter_type __s, ios_base& __iob,
     this->__format_int(__fmt+1, __len, false, __iob.flags());
     const unsigned __nbuf = (numeric_limits<unsigned long>::digits / 3)
                           + ((numeric_limits<unsigned long>::digits % 3) != 0)
+                          + ((__iob.flags() & ios_base::showbase) != 0)
                           + 1;
     char __nar[__nbuf];
     int __nc = __libcpp_snprintf_l(__nar, sizeof(__nar), _LIBCPP_GET_C_LOCALE, __fmt, __v);
@@ -1476,6 +1535,7 @@ num_put<_CharT, _OutputIterator>::do_put(iter_type __s, ios_base& __iob,
     this->__format_int(__fmt+1, __len, false, __iob.flags());
     const unsigned __nbuf = (numeric_limits<unsigned long long>::digits / 3)
                           + ((numeric_limits<unsigned long long>::digits % 3) != 0)
+                          + ((__iob.flags() & ios_base::showbase) != 0)
                           + 1;
     char __nar[__nbuf];
     int __nc = __libcpp_snprintf_l(__nar, sizeof(__nar), _LIBCPP_GET_C_LOCALE, __fmt, __v);
@@ -1621,8 +1681,8 @@ num_put<_CharT, _OutputIterator>::do_put(iter_type __s, ios_base& __iob,
     return __pad_and_output(__s, __o, __op, __oe, __iob, __fl);
 }
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS num_put<char>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS num_put<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS num_put<char>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS num_put<wchar_t>)
 
 template <class _CharT, class _InputIterator>
 _LIBCPP_HIDDEN
@@ -1664,7 +1724,7 @@ public:
 };
 
 template <class _CharT>
-class _LIBCPP_TYPE_VIS_ONLY __time_get_c_storage
+class _LIBCPP_TEMPLATE_VIS __time_get_c_storage
 {
 protected:
     typedef basic_string<_CharT> string_type;
@@ -1681,8 +1741,24 @@ protected:
     ~__time_get_c_storage() {}
 };
 
+template <> _LIBCPP_FUNC_VIS const string* __time_get_c_storage<char>::__weeks() const;
+template <> _LIBCPP_FUNC_VIS const string* __time_get_c_storage<char>::__months() const;
+template <> _LIBCPP_FUNC_VIS const string* __time_get_c_storage<char>::__am_pm() const;
+template <> _LIBCPP_FUNC_VIS const string& __time_get_c_storage<char>::__c() const;
+template <> _LIBCPP_FUNC_VIS const string& __time_get_c_storage<char>::__r() const;
+template <> _LIBCPP_FUNC_VIS const string& __time_get_c_storage<char>::__x() const;
+template <> _LIBCPP_FUNC_VIS const string& __time_get_c_storage<char>::__X() const;
+
+template <> _LIBCPP_FUNC_VIS const wstring* __time_get_c_storage<wchar_t>::__weeks() const;
+template <> _LIBCPP_FUNC_VIS const wstring* __time_get_c_storage<wchar_t>::__months() const;
+template <> _LIBCPP_FUNC_VIS const wstring* __time_get_c_storage<wchar_t>::__am_pm() const;
+template <> _LIBCPP_FUNC_VIS const wstring& __time_get_c_storage<wchar_t>::__c() const;
+template <> _LIBCPP_FUNC_VIS const wstring& __time_get_c_storage<wchar_t>::__r() const;
+template <> _LIBCPP_FUNC_VIS const wstring& __time_get_c_storage<wchar_t>::__x() const;
+template <> _LIBCPP_FUNC_VIS const wstring& __time_get_c_storage<wchar_t>::__X() const;
+
 template <class _CharT, class _InputIterator = istreambuf_iterator<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY time_get
+class _LIBCPP_TEMPLATE_VIS time_get
     : public locale::facet,
       public time_base,
       private __time_get_c_storage<_CharT>
@@ -2291,8 +2367,8 @@ time_get<_CharT, _InputIterator>::do_get(iter_type __b, iter_type __e,
     return __b;
 }
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS time_get<char>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS time_get<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS time_get<char>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS time_get<wchar_t>)
 
 class _LIBCPP_TYPE_VIS __time_get
 {
@@ -2305,7 +2381,7 @@ protected:
 };
 
 template <class _CharT>
-class _LIBCPP_TYPE_VIS_ONLY __time_get_storage
+class _LIBCPP_TEMPLATE_VIS __time_get_storage
     : public __time_get
 {
 protected:
@@ -2332,7 +2408,7 @@ private:
 };
 
 template <class _CharT, class _InputIterator = istreambuf_iterator<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY time_get_byname
+class _LIBCPP_TEMPLATE_VIS time_get_byname
     : public time_get<_CharT, _InputIterator>,
       private __time_get_storage<_CharT>
 {
@@ -2374,8 +2450,8 @@ private:
     virtual const string_type& __X() const      {return this->__X_;}
 };
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS time_get_byname<char>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS time_get_byname<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS time_get_byname<char>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS time_get_byname<wchar_t>)
 
 class _LIBCPP_TYPE_VIS __time_put
 {
@@ -2392,7 +2468,7 @@ protected:
 };
 
 template <class _CharT, class _OutputIterator = ostreambuf_iterator<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY time_put
+class _LIBCPP_TEMPLATE_VIS time_put
     : public locale::facet,
       private __time_put
 {
@@ -2487,11 +2563,11 @@ time_put<_CharT, _OutputIterator>::do_put(iter_type __s, ios_base&,
     return _VSTD::copy(__nb, __ne, __s);
 }
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS time_put<char>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS time_put<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS time_put<char>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS time_put<wchar_t>)
 
 template <class _CharT, class _OutputIterator = ostreambuf_iterator<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY time_put_byname
+class _LIBCPP_TEMPLATE_VIS time_put_byname
     : public time_put<_CharT, _OutputIterator>
 {
 public:
@@ -2508,8 +2584,8 @@ protected:
     ~time_put_byname() {}
 };
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS time_put_byname<char>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS time_put_byname<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS time_put_byname<char>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS time_put_byname<wchar_t>)
 
 // money_base
 
@@ -2525,7 +2601,7 @@ public:
 // moneypunct
 
 template <class _CharT, bool _International = false>
-class _LIBCPP_TYPE_VIS_ONLY moneypunct
+class _LIBCPP_TEMPLATE_VIS moneypunct
     : public locale::facet,
       public money_base
 {
@@ -2575,15 +2651,15 @@ template <class _CharT, bool _International>
 const bool
 moneypunct<_CharT, _International>::intl;
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS moneypunct<char, false>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS moneypunct<char, true>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS moneypunct<wchar_t, false>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS moneypunct<wchar_t, true>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS moneypunct<char, false>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS moneypunct<char, true>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS moneypunct<wchar_t, false>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS moneypunct<wchar_t, true>)
 
 // moneypunct_byname
 
 template <class _CharT, bool _International = false>
-class _LIBCPP_TYPE_VIS_ONLY moneypunct_byname
+class _LIBCPP_TEMPLATE_VIS moneypunct_byname
     : public moneypunct<_CharT, _International>
 {
 public:
@@ -2627,15 +2703,15 @@ private:
     void init(const char*);
 };
 
-template<> void moneypunct_byname<char, false>::init(const char*);
-template<> void moneypunct_byname<char, true>::init(const char*);
-template<> void moneypunct_byname<wchar_t, false>::init(const char*);
-template<> void moneypunct_byname<wchar_t, true>::init(const char*);
+template<> _LIBCPP_FUNC_VIS void moneypunct_byname<char, false>::init(const char*);
+template<> _LIBCPP_FUNC_VIS void moneypunct_byname<char, true>::init(const char*);
+template<> _LIBCPP_FUNC_VIS void moneypunct_byname<wchar_t, false>::init(const char*);
+template<> _LIBCPP_FUNC_VIS void moneypunct_byname<wchar_t, true>::init(const char*);
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS moneypunct_byname<char, false>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS moneypunct_byname<char, true>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS moneypunct_byname<wchar_t, false>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS moneypunct_byname<wchar_t, true>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS moneypunct_byname<char, false>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS moneypunct_byname<char, true>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS moneypunct_byname<wchar_t, false>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS moneypunct_byname<wchar_t, true>)
 
 // money_get
 
@@ -2691,11 +2767,11 @@ __money_get<_CharT>::__gather_info(bool __intl, const locale& __loc,
     }
 }
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS __money_get<char>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS __money_get<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __money_get<char>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __money_get<wchar_t>)
 
 template <class _CharT, class _InputIterator = istreambuf_iterator<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY money_get
+class _LIBCPP_TEMPLATE_VIS money_get
     : public locale::facet,
       private __money_get<_CharT>
 {
@@ -2821,7 +2897,7 @@ money_get<_CharT, _InputIterator>::__do_get(iter_type& __b, iter_type __e,
                     return false;
                 }
             }
-            // drop through
+            _LIBCPP_FALLTHROUGH();
         case money_base::none:
             if (__p != 3)
             {
@@ -3074,8 +3150,8 @@ money_get<_CharT, _InputIterator>::do_get(iter_type __b, iter_type __e,
     return __b;
 }
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS money_get<char>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS money_get<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS money_get<char>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS money_get<wchar_t>)
 
 // money_put
 
@@ -3249,11 +3325,11 @@ __money_put<_CharT>::__format(char_type* __mb, char_type*& __mi, char_type*& __m
         __mi = __mb;
 }
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS __money_put<char>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS __money_put<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __money_put<char>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __money_put<wchar_t>)
 
 template <class _CharT, class _OutputIterator = ostreambuf_iterator<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY money_put
+class _LIBCPP_TEMPLATE_VIS money_put
     : public locale::facet,
       private __money_put<_CharT>
 {
@@ -3402,8 +3478,8 @@ money_put<_CharT, _OutputIterator>::do_put(iter_type __s, bool __intl,
     return __pad_and_output(__s, __mb, __mi, __me, __iob, __fl);
 }
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS money_put<char>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS money_put<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS money_put<char>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS money_put<wchar_t>)
 
 // messages
 
@@ -3416,7 +3492,7 @@ public:
 };
 
 template <class _CharT>
-class _LIBCPP_TYPE_VIS_ONLY messages
+class _LIBCPP_TEMPLATE_VIS messages
     : public locale::facet,
       public messages_base
 {
@@ -3512,11 +3588,11 @@ messages<_CharT>::do_close(catalog __c) const
 #endif // _LIBCPP_HAS_CATOPEN
 }
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS messages<char>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS messages<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS messages<char>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS messages<wchar_t>)
 
 template <class _CharT>
-class _LIBCPP_TYPE_VIS_ONLY messages_byname
+class _LIBCPP_TEMPLATE_VIS messages_byname
     : public messages<_CharT>
 {
 public:
@@ -3536,13 +3612,13 @@ protected:
     ~messages_byname() {}
 };
 
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS messages_byname<char>)
-_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_TYPE_VIS messages_byname<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS messages_byname<char>)
+_LIBCPP_EXTERN_TEMPLATE2(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS messages_byname<wchar_t>)
 
 template<class _Codecvt, class _Elem = wchar_t,
          class _Wide_alloc = allocator<_Elem>,
          class _Byte_alloc = allocator<char> >
-class _LIBCPP_TYPE_VIS_ONLY wstring_convert
+class _LIBCPP_TEMPLATE_VIS wstring_convert
 {
 public:
     typedef basic_string<char, char_traits<char>, _Byte_alloc>   byte_string;
@@ -3566,7 +3642,7 @@ public:
     wstring_convert(_Codecvt* __pcvt, state_type __state);
     _LIBCPP_EXPLICIT_AFTER_CXX11 wstring_convert(const byte_string& __byte_err,
                     const wide_string& __wide_err = wide_string());
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_ALWAYS_INLINE
     wstring_convert(wstring_convert&& __wc);
 #endif
@@ -3625,7 +3701,7 @@ wstring_convert<_Codecvt, _Elem, _Wide_alloc, _Byte_alloc>::
     __cvtptr_ = new _Codecvt;
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template<class _Codecvt, class _Elem, class _Wide_alloc, class _Byte_alloc>
 inline
@@ -3639,7 +3715,7 @@ wstring_convert<_Codecvt, _Elem, _Wide_alloc, _Byte_alloc>::
     __wc.__cvtptr_ = nullptr;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template<class _Codecvt, class _Elem, class _Wide_alloc, class _Byte_alloc>
 wstring_convert<_Codecvt, _Elem, _Wide_alloc, _Byte_alloc>::~wstring_convert()
@@ -3701,10 +3777,10 @@ wstring_convert<_Codecvt, _Elem, _Wide_alloc, _Byte_alloc>::
         if (__r == codecvt_base::ok)
             return __ws;
     }
-#ifndef _LIBCPP_NO_EXCEPTIONS
+
     if (__wide_err_string_.empty())
-        throw range_error("wstring_convert: from_bytes error");
-#endif  // _LIBCPP_NO_EXCEPTIONS
+        __throw_range_error("wstring_convert: from_bytes error");
+
     return __wide_err_string_;
 }
 
@@ -3790,15 +3866,15 @@ wstring_convert<_Codecvt, _Elem, _Wide_alloc, _Byte_alloc>::
                 return __bs;
         }
     }
-#ifndef _LIBCPP_NO_EXCEPTIONS
+
     if (__byte_err_string_.empty())
-        throw range_error("wstring_convert: to_bytes error");
-#endif  // _LIBCPP_NO_EXCEPTIONS
+        __throw_range_error("wstring_convert: to_bytes error");
+
     return __byte_err_string_;
 }
 
 template <class _Codecvt, class _Elem = wchar_t, class _Tr = char_traits<_Elem> >
-class _LIBCPP_TYPE_VIS_ONLY wbuffer_convert
+class _LIBCPP_TEMPLATE_VIS wbuffer_convert
     : public basic_streambuf<_Elem, _Tr>
 {
 public:
@@ -3932,7 +4008,8 @@ wbuffer_convert<_Codecvt, _Elem, _Tr>::underflow()
             streamsize __nmemb = _VSTD::min(static_cast<streamsize>(this->egptr() - this->eback() - __unget_sz),
                                  static_cast<streamsize>(__extbufend_ - __extbufnext_));
             codecvt_base::result __r;
-            state_type __svs = __st_;
+            // FIXME: Do we ever need to restore the state here?
+            //state_type __svs = __st_;
             streamsize __nr = __bufptr_->sgetn(const_cast<char*>(__extbufnext_), __nmemb);
             if (__nr != 0)
             {
@@ -3943,7 +4020,8 @@ wbuffer_convert<_Codecvt, _Elem, _Tr>::underflow()
                                        this->egptr(), __inext);
                 if (__r == codecvt_base::noconv)
                 {
-                    this->setg((char_type*)__extbuf_, (char_type*)__extbuf_, (char_type*)__extbufend_);
+                    this->setg((char_type*)__extbuf_, (char_type*)__extbuf_, 
+                               (char_type*) const_cast<char *>(__extbufend_));
                     __c = *this->gptr();
                 }
                 else if (__inext != this->eback() + __unget_sz)
@@ -4031,8 +4109,8 @@ wbuffer_convert<_Codecvt, _Elem, _Tr>::overflow(int_type __c)
                         return traits_type::eof();
                     if (__r == codecvt_base::partial)
                     {
-                        this->setp((char_type*)__e, this->pptr());
-                        this->pbump(this->epptr() - this->pbase());
+                        this->setp(const_cast<char_type *>(__e), this->pptr());
+                        this->__pbump(this->epptr() - this->pbase());
                     }
                 }
                 else
@@ -4252,4 +4330,6 @@ wbuffer_convert<_Codecvt, _Elem, _Tr>::__close()
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_LOCALE
diff --git a/lib/libcxx/include/locale.h b/lib/libcxx/include/locale.h
new file mode 100644
index 00000000000..cad7b8b53eb
--- /dev/null
+++ b/lib/libcxx/include/locale.h
@@ -0,0 +1,45 @@
+// -*- C++ -*-
+//===---------------------------- locale.h --------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_LOCALE_H
+#define _LIBCPP_LOCALE_H
+
+/*
+    locale.h synopsis
+
+Macros:
+
+    LC_ALL
+    LC_COLLATE
+    LC_CTYPE
+    LC_MONETARY
+    LC_NUMERIC
+    LC_TIME
+
+Types:
+
+    lconv
+
+Functions:
+
+   setlocale
+   localeconv
+
+*/
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+#include_next <locale.h>
+
+#endif  // _LIBCPP_LOCALE_H
diff --git a/lib/libcxx/include/map b/lib/libcxx/include/map
index bdde949bc1e..95214938981 100644
--- a/lib/libcxx/include/map
+++ b/lib/libcxx/include/map
@@ -453,9 +453,7 @@ swap(multimap<Key, T, Compare, Allocator>& x,
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Key, class _CP, class _Compare,
-          bool = is_empty<_Compare>::value && !__libcpp_is_final<_Compare>::value
-         >
+template <class _Key, class _CP, class _Compare, bool _IsSmall>
 class __map_value_compare
     : private _Compare
 {
@@ -482,8 +480,8 @@ public:
     void swap(__map_value_compare&__y)
         _NOEXCEPT_(__is_nothrow_swappable<_Compare>::value)
     {
-        using _VSTD::swap;
-        swap(static_cast<const _Compare&>(*this), static_cast<const _Compare&>(__y));
+      using _VSTD::swap;
+      swap(static_cast<_Compare&>(*this), static_cast<_Compare&>(__y));
     }
 
 #if _LIBCPP_STD_VER > 11
@@ -533,7 +531,7 @@ public:
         using _VSTD::swap;
         swap(comp, __y.comp);
     }
-    
+
 #if _LIBCPP_STD_VER > 11
     template <typename _K2>
     _LIBCPP_INLINE_VISIBILITY
@@ -584,7 +582,7 @@ public:
           __second_constructed(false)
         {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     __map_node_destructor(__tree_node_destructor<allocator_type>&& __x) _NOEXCEPT
         : __na_(__x.__na_),
@@ -593,7 +591,7 @@ public:
         {
             __x.__value_constructed = false;
         }
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     void operator()(pointer __p) _NOEXCEPT
@@ -669,7 +667,7 @@ private:
    ~__value_type();
 };
 
-#endif
+#endif // _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 struct __extract_key_value_types;
@@ -682,7 +680,7 @@ struct __extract_key_value_types<__value_type<_Key, _Tp> >
 };
 
 template <class _TreeIterator>
-class _LIBCPP_TYPE_VIS_ONLY __map_iterator
+class _LIBCPP_TEMPLATE_VIS __map_iterator
 {
     typedef typename _TreeIterator::_NodeTypes                   _NodeTypes;
     typedef typename _TreeIterator::__pointer_traits             __pointer_traits;
@@ -730,18 +728,18 @@ public:
     friend _LIBCPP_INLINE_VISIBILITY
     bool operator==(const __map_iterator& __x, const __map_iterator& __y)
         {return __x.__i_ == __y.__i_;}
-    friend 
+    friend
     _LIBCPP_INLINE_VISIBILITY
     bool operator!=(const __map_iterator& __x, const __map_iterator& __y)
         {return __x.__i_ != __y.__i_;}
 
-    template <class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY map;
-    template <class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY multimap;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __map_const_iterator;
+    template <class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS map;
+    template <class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS multimap;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __map_const_iterator;
 };
 
 template <class _TreeIterator>
-class _LIBCPP_TYPE_VIS_ONLY __map_const_iterator
+class _LIBCPP_TEMPLATE_VIS __map_const_iterator
 {
     typedef typename _TreeIterator::_NodeTypes                   _NodeTypes;
     typedef typename _TreeIterator::__pointer_traits             __pointer_traits;
@@ -797,14 +795,14 @@ public:
     bool operator!=(const __map_const_iterator& __x, const __map_const_iterator& __y)
         {return __x.__i_ != __y.__i_;}
 
-    template <class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY map;
-    template <class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY multimap;
-    template <class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY __tree_const_iterator;
+    template <class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS map;
+    template <class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS multimap;
+    template <class, class, class> friend class _LIBCPP_TEMPLATE_VIS __tree_const_iterator;
 };
 
 template <class _Key, class _Tp, class _Compare = less<_Key>,
           class _Allocator = allocator<pair<const _Key, _Tp> > >
-class _LIBCPP_TYPE_VIS_ONLY map
+class _LIBCPP_TEMPLATE_VIS map
 {
 public:
     // types:
@@ -820,7 +818,7 @@ public:
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
 
-    class _LIBCPP_TYPE_VIS_ONLY value_compare
+    class _LIBCPP_TEMPLATE_VIS value_compare
         : public binary_function<value_type, value_type, bool>
     {
         friend class map;
@@ -895,7 +893,7 @@ public:
 
 #if _LIBCPP_STD_VER > 11
     template <class _InputIterator>
-    _LIBCPP_INLINE_VISIBILITY 
+    _LIBCPP_INLINE_VISIBILITY
     map(_InputIterator __f, _InputIterator __l, const allocator_type& __a)
         : map(__f, __l, key_compare(), __a) {}
 #endif
@@ -923,7 +921,7 @@ public:
             return *this;
         }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     map(map&& __m)
@@ -942,10 +940,6 @@ public:
             return *this;
         }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
     _LIBCPP_INLINE_VISIBILITY
     map(initializer_list<value_type> __il, const key_compare& __comp = key_compare())
         : __tree_(__vc(__comp))
@@ -961,7 +955,7 @@ public:
         }
 
 #if _LIBCPP_STD_VER > 11
-    _LIBCPP_INLINE_VISIBILITY 
+    _LIBCPP_INLINE_VISIBILITY
     map(initializer_list<value_type> __il, const allocator_type& __a)
         : map(__il, key_compare(), __a) {}
 #endif
@@ -973,7 +967,7 @@ public:
             return *this;
         }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     explicit map(const allocator_type& __a)
@@ -1018,7 +1012,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     const_reverse_iterator crend() const _NOEXCEPT {return rend();}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool      empty() const _NOEXCEPT {return __tree_.size() == 0;}
     _LIBCPP_INLINE_VISIBILITY
     size_type size() const _NOEXCEPT {return __tree_.size();}
@@ -1084,6 +1078,10 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     iterator insert(const_iterator __p,  value_type&& __v)
     {return __tree_.__insert_unique(__p.__i_, _VSTD::move(__v));}
+
+    _LIBCPP_INLINE_VISIBILITY
+    void insert(initializer_list<value_type> __il)
+        {insert(__il.begin(), __il.end());}
 #endif
 
     template <class _InputIterator>
@@ -1094,14 +1092,6 @@ public:
                 insert(__e.__i_, *__f);
         }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
-    _LIBCPP_INLINE_VISIBILITY
-    void insert(initializer_list<value_type> __il)
-        {insert(__il.begin(), __il.end());}
-
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 #if _LIBCPP_STD_VER > 14
 
     template <class... _Args>
@@ -1196,7 +1186,7 @@ public:
         return emplace_hint(__h, _VSTD::move(__k), _VSTD::forward<_Vp>(__v));
      }
 
-#endif
+#endif // _LIBCPP_STD_VER > 14
 
     _LIBCPP_INLINE_VISIBILITY
     iterator erase(const_iterator __p) {return __tree_.erase(__p.__i_);}
@@ -1297,6 +1287,7 @@ private:
     typedef typename __base::__node_allocator          __node_allocator;
     typedef typename __base::__node_pointer            __node_pointer;
     typedef typename __base::__node_base_pointer       __node_base_pointer;
+    typedef typename __base::__parent_pointer          __parent_pointer;
 
     typedef __map_node_destructor<__node_allocator> _Dp;
     typedef unique_ptr<__node, _Dp> __node_holder;
@@ -1304,67 +1295,10 @@ private:
 #ifdef _LIBCPP_CXX03_LANG
     __node_holder __construct_node_with_key(const key_type& __k);
 #endif
-
-    __node_base_pointer const&
-    __find_equal_key(__node_base_pointer& __parent, const key_type& __k) const;
-
-    _LIBCPP_INLINE_VISIBILITY
-    __node_base_pointer&
-    __find_equal_key(__node_base_pointer& __parent, const key_type& __k) {
-        map const* __const_this = this;
-        return const_cast<__node_base_pointer&>(
-            __const_this->__find_equal_key(__parent, __k));
-    }
 };
 
 
-// Find __k
-// Set __parent to parent of null leaf and
-//    return reference to null leaf iv __k does not exist.
-// If __k exists, set parent to node of __k and return reference to node of __k
-template <class _Key, class _Tp, class _Compare, class _Allocator>
-typename map<_Key, _Tp, _Compare, _Allocator>::__node_base_pointer const&
-map<_Key, _Tp, _Compare, _Allocator>::__find_equal_key(__node_base_pointer& __parent,
-                                                       const key_type& __k) const
-{
-    __node_pointer __nd = __tree_.__root();
-    if (__nd != nullptr)
-    {
-        while (true)
-        {
-            if (__tree_.value_comp().key_comp()(__k, __nd->__value_.__cc.first))
-            {
-                if (__nd->__left_ != nullptr)
-                    __nd = static_cast<__node_pointer>(__nd->__left_);
-                else
-                {
-                    __parent = static_cast<__node_base_pointer>(__nd);
-                    return __parent->__left_;
-                }
-            }
-            else if (__tree_.value_comp().key_comp()(__nd->__value_.__cc.first, __k))
-            {
-                if (__nd->__right_ != nullptr)
-                    __nd = static_cast<__node_pointer>(__nd->__right_);
-                else
-                {
-                    __parent = static_cast<__node_base_pointer>(__nd);
-                    return __parent->__right_;
-                }
-            }
-            else
-            {
-                __parent = static_cast<__node_base_pointer>(__nd);
-                return __parent;
-            }
-        }
-    }
-    __parent = static_cast<__node_base_pointer>(__tree_.__end_node());
-    return __parent->__left_;
-}
-
 #ifndef _LIBCPP_CXX03_LANG
-
 template <class _Key, class _Tp, class _Compare, class _Allocator>
 map<_Key, _Tp, _Compare, _Allocator>::map(map&& __m, const allocator_type& __a)
     : __tree_(_VSTD::move(__m.__tree_), typename __base::allocator_type(__a))
@@ -1378,10 +1312,27 @@ map<_Key, _Tp, _Compare, _Allocator>::map(map&& __m, const allocator_type& __a)
     }
 }
 
-#endif  // !_LIBCPP_CXX03_LANG
+template <class _Key, class _Tp, class _Compare, class _Allocator>
+_Tp&
+map<_Key, _Tp, _Compare, _Allocator>::operator[](const key_type& __k)
+{
+    return __tree_.__emplace_unique_key_args(__k,
+        _VSTD::piecewise_construct,
+        _VSTD::forward_as_tuple(__k),
+        _VSTD::forward_as_tuple()).first->__cc.second;
+}
 
+template <class _Key, class _Tp, class _Compare, class _Allocator>
+_Tp&
+map<_Key, _Tp, _Compare, _Allocator>::operator[](key_type&& __k)
+{
+    return __tree_.__emplace_unique_key_args(__k,
+        _VSTD::piecewise_construct,
+        _VSTD::forward_as_tuple(_VSTD::move(__k)),
+        _VSTD::forward_as_tuple()).first->__cc.second;
+}
 
-#ifdef _LIBCPP_CXX03_LANG
+#else // _LIBCPP_CXX03_LANG
 
 template <class _Key, class _Tp, class _Compare, class _Allocator>
 typename map<_Key, _Tp, _Compare, _Allocator>::__node_holder
@@ -1400,8 +1351,8 @@ template <class _Key, class _Tp, class _Compare, class _Allocator>
 _Tp&
 map<_Key, _Tp, _Compare, _Allocator>::operator[](const key_type& __k)
 {
-    __node_base_pointer __parent;
-    __node_base_pointer& __child = __find_equal_key(__parent, __k);
+    __parent_pointer __parent;
+    __node_base_pointer& __child = __tree_.__find_equal(__parent, __k);
     __node_pointer __r = static_cast<__node_pointer>(__child);
     if (__child == nullptr)
     {
@@ -1412,36 +1363,14 @@ map<_Key, _Tp, _Compare, _Allocator>::operator[](const key_type& __k)
     return __r->__value_.__cc.second;
 }
 
-#else
-
-template <class _Key, class _Tp, class _Compare, class _Allocator>
-_Tp&
-map<_Key, _Tp, _Compare, _Allocator>::operator[](const key_type& __k)
-{
-    return __tree_.__emplace_unique_key_args(__k,
-        _VSTD::piecewise_construct,
-        _VSTD::forward_as_tuple(__k),
-        _VSTD::forward_as_tuple()).first->__cc.second;
-}
-
-template <class _Key, class _Tp, class _Compare, class _Allocator>
-_Tp&
-map<_Key, _Tp, _Compare, _Allocator>::operator[](key_type&& __k)
-{
-    return __tree_.__emplace_unique_key_args(__k,
-        _VSTD::piecewise_construct,
-        _VSTD::forward_as_tuple(_VSTD::move(__k)),
-        _VSTD::forward_as_tuple()).first->__cc.second;
-}
-
-#endif  // !_LIBCPP_CXX03_LANG
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Key, class _Tp, class _Compare, class _Allocator>
 _Tp&
 map<_Key, _Tp, _Compare, _Allocator>::at(const key_type& __k)
 {
-    __node_base_pointer __parent;
-    __node_base_pointer& __child = __find_equal_key(__parent, __k);
+    __parent_pointer __parent;
+    __node_base_pointer& __child = __tree_.__find_equal(__parent, __k);
 #ifndef _LIBCPP_NO_EXCEPTIONS
     if (__child == nullptr)
         throw out_of_range("map::at:  key not found");
@@ -1453,8 +1382,8 @@ template <class _Key, class _Tp, class _Compare, class _Allocator>
 const _Tp&
 map<_Key, _Tp, _Compare, _Allocator>::at(const key_type& __k) const
 {
-    __node_base_pointer __parent;
-    __node_base_pointer __child = __find_equal_key(__parent, __k);
+    __parent_pointer __parent;
+    __node_base_pointer __child = __tree_.__find_equal(__parent, __k);
 #ifndef _LIBCPP_NO_EXCEPTIONS
     if (__child == nullptr)
         throw out_of_range("map::at:  key not found");
@@ -1529,7 +1458,7 @@ swap(map<_Key, _Tp, _Compare, _Allocator>& __x,
 
 template <class _Key, class _Tp, class _Compare = less<_Key>,
           class _Allocator = allocator<pair<const _Key, _Tp> > >
-class _LIBCPP_TYPE_VIS_ONLY multimap
+class _LIBCPP_TEMPLATE_VIS multimap
 {
 public:
     // types:
@@ -1545,7 +1474,7 @@ public:
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
 
-    class _LIBCPP_TYPE_VIS_ONLY value_compare
+    class _LIBCPP_TEMPLATE_VIS value_compare
         : public binary_function<value_type, value_type, bool>
     {
         friend class multimap;
@@ -1621,7 +1550,7 @@ public:
 
 #if _LIBCPP_STD_VER > 11
     template <class _InputIterator>
-    _LIBCPP_INLINE_VISIBILITY 
+    _LIBCPP_INLINE_VISIBILITY
     multimap(_InputIterator __f, _InputIterator __l, const allocator_type& __a)
         : multimap(__f, __l, key_compare(), __a) {}
 #endif
@@ -1650,7 +1579,7 @@ public:
             return *this;
         }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     multimap(multimap&& __m)
@@ -1669,10 +1598,6 @@ public:
             return *this;
         }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
     _LIBCPP_INLINE_VISIBILITY
     multimap(initializer_list<value_type> __il, const key_compare& __comp = key_compare())
         : __tree_(__vc(__comp))
@@ -1688,7 +1613,7 @@ public:
         }
 
 #if _LIBCPP_STD_VER > 11
-    _LIBCPP_INLINE_VISIBILITY 
+    _LIBCPP_INLINE_VISIBILITY
     multimap(initializer_list<value_type> __il, const allocator_type& __a)
         : multimap(__il, key_compare(), __a) {}
 #endif
@@ -1700,7 +1625,7 @@ public:
             return *this;
         }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     explicit multimap(const allocator_type& __a)
@@ -1744,7 +1669,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     const_reverse_iterator crend() const _NOEXCEPT {return rend();}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool empty() const _NOEXCEPT {return __tree_.size() == 0;}
     _LIBCPP_INLINE_VISIBILITY
     size_type size() const _NOEXCEPT {return __tree_.size();}
@@ -1793,6 +1718,11 @@ public:
     iterator insert(const_iterator __p, value_type&& __v)
         {return __tree_.__insert_multi(__p.__i_, _VSTD::move(__v));}
 
+
+    _LIBCPP_INLINE_VISIBILITY
+    void insert(initializer_list<value_type> __il)
+        {insert(__il.begin(), __il.end());}
+
 #endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
@@ -1810,14 +1740,6 @@ public:
                 __tree_.__insert_multi(__e.__i_, *__f);
         }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
-    _LIBCPP_INLINE_VISIBILITY
-    void insert(initializer_list<value_type> __il)
-        {insert(__il.begin(), __il.end());}
-
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
     _LIBCPP_INLINE_VISIBILITY
     iterator erase(const_iterator __p) {return __tree_.erase(__p.__i_);}
     _LIBCPP_INLINE_VISIBILITY
diff --git a/lib/libcxx/include/math.h b/lib/libcxx/include/math.h
index 20205544d51..8c30ba85d22 100644
--- a/lib/libcxx/include/math.h
+++ b/lib/libcxx/include/math.h
@@ -307,10 +307,7 @@ long double    truncl(long double x);
 extern "C++" {
 
 #include <type_traits>
-
-#ifdef _LIBCPP_MSVCRT
-#include "support/win32/math_win32.h"
-#endif
+#include <limits>
 
 // signbit
 
@@ -328,12 +325,50 @@ __libcpp_signbit(_A1 __lcpp_x) _NOEXCEPT
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
-typename std::enable_if<std::is_arithmetic<_A1>::value, bool>::type
+typename std::enable_if<std::is_floating_point<_A1>::value, bool>::type
 signbit(_A1 __lcpp_x) _NOEXCEPT
 {
     return __libcpp_signbit((typename std::__promote<_A1>::type)__lcpp_x);
 }
 
+template <class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename std::enable_if<
+    std::is_integral<_A1>::value && std::is_signed<_A1>::value, bool>::type
+signbit(_A1 __lcpp_x) _NOEXCEPT
+{ return __lcpp_x < 0; }
+
+template <class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename std::enable_if<
+    std::is_integral<_A1>::value && !std::is_signed<_A1>::value, bool>::type
+signbit(_A1) _NOEXCEPT
+{ return false; }
+
+#elif defined(_LIBCPP_MSVCRT)
+
+template <typename _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename std::enable_if<std::is_floating_point<_A1>::value, bool>::type
+signbit(_A1 __lcpp_x) _NOEXCEPT
+{
+  return ::signbit(static_cast<typename std::__promote<_A1>::type>(__lcpp_x));
+}
+
+template <class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename std::enable_if<
+    std::is_integral<_A1>::value && std::is_signed<_A1>::value, bool>::type
+signbit(_A1 __lcpp_x) _NOEXCEPT
+{ return __lcpp_x < 0; }
+
+template <class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename std::enable_if<
+    std::is_integral<_A1>::value && !std::is_signed<_A1>::value, bool>::type
+signbit(_A1) _NOEXCEPT
+{ return false; }
+
 #endif  // signbit
 
 // fpclassify
@@ -352,12 +387,34 @@ __libcpp_fpclassify(_A1 __lcpp_x) _NOEXCEPT
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
-typename std::enable_if<std::is_arithmetic<_A1>::value, int>::type
+typename std::enable_if<std::is_floating_point<_A1>::value, int>::type
 fpclassify(_A1 __lcpp_x) _NOEXCEPT
 {
     return __libcpp_fpclassify((typename std::__promote<_A1>::type)__lcpp_x);
 }
 
+template <class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename std::enable_if<std::is_integral<_A1>::value, int>::type
+fpclassify(_A1 __lcpp_x) _NOEXCEPT
+{ return __lcpp_x == 0 ? FP_ZERO : FP_NORMAL; }
+
+#elif defined(_LIBCPP_MSVCRT)
+
+template <typename _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename std::enable_if<std::is_floating_point<_A1>::value, bool>::type
+fpclassify(_A1 __lcpp_x) _NOEXCEPT
+{
+  return ::fpclassify(static_cast<typename std::__promote<_A1>::type>(__lcpp_x));
+}
+
+template <class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename std::enable_if<std::is_integral<_A1>::value, int>::type
+fpclassify(_A1 __lcpp_x) _NOEXCEPT
+{ return __lcpp_x == 0 ? FP_ZERO : FP_NORMAL; }
+
 #endif  // fpclassify
 
 // isfinite
@@ -376,12 +433,22 @@ __libcpp_isfinite(_A1 __lcpp_x) _NOEXCEPT
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
-typename std::enable_if<std::is_arithmetic<_A1>::value, bool>::type
+typename std::enable_if<
+    std::is_arithmetic<_A1>::value && std::numeric_limits<_A1>::has_infinity,
+    bool>::type
 isfinite(_A1 __lcpp_x) _NOEXCEPT
 {
     return __libcpp_isfinite((typename std::__promote<_A1>::type)__lcpp_x);
 }
 
+template <class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename std::enable_if<
+    std::is_arithmetic<_A1>::value && !std::numeric_limits<_A1>::has_infinity,
+    bool>::type
+isfinite(_A1) _NOEXCEPT
+{ return true; }
+
 #endif  // isfinite
 
 // isinf
@@ -400,12 +467,22 @@ __libcpp_isinf(_A1 __lcpp_x) _NOEXCEPT
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
-typename std::enable_if<std::is_arithmetic<_A1>::value, bool>::type
+typename std::enable_if<
+    std::is_arithmetic<_A1>::value && std::numeric_limits<_A1>::has_infinity,
+    bool>::type
 isinf(_A1 __lcpp_x) _NOEXCEPT
 {
     return __libcpp_isinf((typename std::__promote<_A1>::type)__lcpp_x);
 }
 
+template <class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename std::enable_if<
+    std::is_arithmetic<_A1>::value && !std::numeric_limits<_A1>::has_infinity,
+    bool>::type
+isinf(_A1) _NOEXCEPT
+{ return false; }
+
 #endif  // isinf
 
 // isnan
@@ -424,12 +501,18 @@ __libcpp_isnan(_A1 __lcpp_x) _NOEXCEPT
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
-typename std::enable_if<std::is_arithmetic<_A1>::value, bool>::type
+typename std::enable_if<std::is_floating_point<_A1>::value, bool>::type
 isnan(_A1 __lcpp_x) _NOEXCEPT
 {
     return __libcpp_isnan((typename std::__promote<_A1>::type)__lcpp_x);
 }
 
+template <class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename std::enable_if<std::is_integral<_A1>::value, bool>::type
+isnan(_A1) _NOEXCEPT
+{ return false; }
+
 #endif  // isnan
 
 // isnormal
@@ -448,12 +531,18 @@ __libcpp_isnormal(_A1 __lcpp_x) _NOEXCEPT
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
-typename std::enable_if<std::is_arithmetic<_A1>::value, bool>::type
+typename std::enable_if<std::is_floating_point<_A1>::value, bool>::type
 isnormal(_A1 __lcpp_x) _NOEXCEPT
 {
     return __libcpp_isnormal((typename std::__promote<_A1>::type)__lcpp_x);
 }
 
+template <class _A1>
+inline _LIBCPP_INLINE_VISIBILITY
+typename std::enable_if<std::is_integral<_A1>::value, bool>::type
+isnormal(_A1 __lcpp_x) _NOEXCEPT
+{ return __lcpp_x != 0; }
+
 #endif  // isnormal
 
 // isgreater
@@ -636,65 +725,63 @@ isunordered(_A1 __lcpp_x, _A2 __lcpp_y) _NOEXCEPT
 
 #endif  // isunordered
 
-#ifndef __sun__
-
 // abs
 
-#if !defined(_AIX)
+#if !(defined(_AIX) || defined(__sun__))
 inline _LIBCPP_INLINE_VISIBILITY
 float
-abs(float __lcpp_x) _NOEXCEPT {return fabsf(__lcpp_x);}
+abs(float __lcpp_x) _NOEXCEPT {return ::fabsf(__lcpp_x);}
 
 inline _LIBCPP_INLINE_VISIBILITY
 double
-abs(double __lcpp_x) _NOEXCEPT {return fabs(__lcpp_x);}
+abs(double __lcpp_x) _NOEXCEPT {return ::fabs(__lcpp_x);}
 
 inline _LIBCPP_INLINE_VISIBILITY
 long double
-abs(long double __lcpp_x) _NOEXCEPT {return fabsl(__lcpp_x);}
-#endif // !defined(_AIX)
+abs(long double __lcpp_x) _NOEXCEPT {return ::fabsl(__lcpp_x);}
+#endif // !(defined(_AIX) || defined(__sun__))
 
 // acos
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       acos(float __lcpp_x) _NOEXCEPT       {return acosf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double acos(long double __lcpp_x) _NOEXCEPT {return acosl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       acos(float __lcpp_x) _NOEXCEPT       {return ::acosf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double acos(long double __lcpp_x) _NOEXCEPT {return ::acosl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-acos(_A1 __lcpp_x) _NOEXCEPT {return acos((double)__lcpp_x);}
+acos(_A1 __lcpp_x) _NOEXCEPT {return ::acos((double)__lcpp_x);}
 
 // asin
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       asin(float __lcpp_x) _NOEXCEPT       {return asinf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double asin(long double __lcpp_x) _NOEXCEPT {return asinl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       asin(float __lcpp_x) _NOEXCEPT       {return ::asinf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double asin(long double __lcpp_x) _NOEXCEPT {return ::asinl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-asin(_A1 __lcpp_x) _NOEXCEPT {return asin((double)__lcpp_x);}
+asin(_A1 __lcpp_x) _NOEXCEPT {return ::asin((double)__lcpp_x);}
 
 // atan
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       atan(float __lcpp_x) _NOEXCEPT       {return atanf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double atan(long double __lcpp_x) _NOEXCEPT {return atanl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       atan(float __lcpp_x) _NOEXCEPT       {return ::atanf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double atan(long double __lcpp_x) _NOEXCEPT {return ::atanl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-atan(_A1 __lcpp_x) _NOEXCEPT {return atan((double)__lcpp_x);}
+atan(_A1 __lcpp_x) _NOEXCEPT {return ::atan((double)__lcpp_x);}
 
 // atan2
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       atan2(float __lcpp_y, float __lcpp_x) _NOEXCEPT             {return atan2f(__lcpp_y, __lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double atan2(long double __lcpp_y, long double __lcpp_x) _NOEXCEPT {return atan2l(__lcpp_y, __lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       atan2(float __lcpp_y, float __lcpp_x) _NOEXCEPT             {return ::atan2f(__lcpp_y, __lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double atan2(long double __lcpp_y, long double __lcpp_x) _NOEXCEPT {return ::atan2l(__lcpp_y, __lcpp_x);}
 #endif
 
 template <class _A1, class _A2>
@@ -710,86 +797,86 @@ atan2(_A1 __lcpp_y, _A2 __lcpp_x) _NOEXCEPT
     typedef typename std::__promote<_A1, _A2>::type __result_type;
     static_assert((!(std::is_same<_A1, __result_type>::value &&
                      std::is_same<_A2, __result_type>::value)), "");
-    return atan2((__result_type)__lcpp_y, (__result_type)__lcpp_x);
+    return ::atan2((__result_type)__lcpp_y, (__result_type)__lcpp_x);
 }
 
 // ceil
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       ceil(float __lcpp_x) _NOEXCEPT       {return ceilf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double ceil(long double __lcpp_x) _NOEXCEPT {return ceill(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       ceil(float __lcpp_x) _NOEXCEPT       {return ::ceilf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double ceil(long double __lcpp_x) _NOEXCEPT {return ::ceill(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-ceil(_A1 __lcpp_x) _NOEXCEPT {return ceil((double)__lcpp_x);}
+ceil(_A1 __lcpp_x) _NOEXCEPT {return ::ceil((double)__lcpp_x);}
 
 // cos
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       cos(float __lcpp_x) _NOEXCEPT       {return cosf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double cos(long double __lcpp_x) _NOEXCEPT {return cosl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       cos(float __lcpp_x) _NOEXCEPT       {return ::cosf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double cos(long double __lcpp_x) _NOEXCEPT {return ::cosl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-cos(_A1 __lcpp_x) _NOEXCEPT {return cos((double)__lcpp_x);}
+cos(_A1 __lcpp_x) _NOEXCEPT {return ::cos((double)__lcpp_x);}
 
 // cosh
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       cosh(float __lcpp_x) _NOEXCEPT       {return coshf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double cosh(long double __lcpp_x) _NOEXCEPT {return coshl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       cosh(float __lcpp_x) _NOEXCEPT       {return ::coshf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double cosh(long double __lcpp_x) _NOEXCEPT {return ::coshl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-cosh(_A1 __lcpp_x) _NOEXCEPT {return cosh((double)__lcpp_x);}
+cosh(_A1 __lcpp_x) _NOEXCEPT {return ::cosh((double)__lcpp_x);}
 
 // exp
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       exp(float __lcpp_x) _NOEXCEPT       {return expf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double exp(long double __lcpp_x) _NOEXCEPT {return expl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       exp(float __lcpp_x) _NOEXCEPT       {return ::expf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double exp(long double __lcpp_x) _NOEXCEPT {return ::expl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-exp(_A1 __lcpp_x) _NOEXCEPT {return exp((double)__lcpp_x);}
+exp(_A1 __lcpp_x) _NOEXCEPT {return ::exp((double)__lcpp_x);}
 
 // fabs
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       fabs(float __lcpp_x) _NOEXCEPT       {return fabsf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double fabs(long double __lcpp_x) _NOEXCEPT {return fabsl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       fabs(float __lcpp_x) _NOEXCEPT       {return ::fabsf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double fabs(long double __lcpp_x) _NOEXCEPT {return ::fabsl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-fabs(_A1 __lcpp_x) _NOEXCEPT {return fabs((double)__lcpp_x);}
+fabs(_A1 __lcpp_x) _NOEXCEPT {return ::fabs((double)__lcpp_x);}
 
 // floor
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       floor(float __lcpp_x) _NOEXCEPT       {return floorf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double floor(long double __lcpp_x) _NOEXCEPT {return floorl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       floor(float __lcpp_x) _NOEXCEPT       {return ::floorf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double floor(long double __lcpp_x) _NOEXCEPT {return ::floorl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-floor(_A1 __lcpp_x) _NOEXCEPT {return floor((double)__lcpp_x);}
+floor(_A1 __lcpp_x) _NOEXCEPT {return ::floor((double)__lcpp_x);}
 
 // fmod
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       fmod(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return fmodf(__lcpp_x, __lcpp_y);}
-inline _LIBCPP_INLINE_VISIBILITY long double fmod(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return fmodl(__lcpp_x, __lcpp_y);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       fmod(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return ::fmodf(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY long double fmod(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return ::fmodl(__lcpp_x, __lcpp_y);}
 #endif
 
 template <class _A1, class _A2>
@@ -805,69 +892,69 @@ fmod(_A1 __lcpp_x, _A2 __lcpp_y) _NOEXCEPT
     typedef typename std::__promote<_A1, _A2>::type __result_type;
     static_assert((!(std::is_same<_A1, __result_type>::value &&
                      std::is_same<_A2, __result_type>::value)), "");
-    return fmod((__result_type)__lcpp_x, (__result_type)__lcpp_y);
+    return ::fmod((__result_type)__lcpp_x, (__result_type)__lcpp_y);
 }
 
 // frexp
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       frexp(float __lcpp_x, int* __lcpp_e) _NOEXCEPT       {return frexpf(__lcpp_x, __lcpp_e);}
-inline _LIBCPP_INLINE_VISIBILITY long double frexp(long double __lcpp_x, int* __lcpp_e) _NOEXCEPT {return frexpl(__lcpp_x, __lcpp_e);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       frexp(float __lcpp_x, int* __lcpp_e) _NOEXCEPT       {return ::frexpf(__lcpp_x, __lcpp_e);}
+inline _LIBCPP_INLINE_VISIBILITY long double frexp(long double __lcpp_x, int* __lcpp_e) _NOEXCEPT {return ::frexpl(__lcpp_x, __lcpp_e);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-frexp(_A1 __lcpp_x, int* __lcpp_e) _NOEXCEPT {return frexp((double)__lcpp_x, __lcpp_e);}
+frexp(_A1 __lcpp_x, int* __lcpp_e) _NOEXCEPT {return ::frexp((double)__lcpp_x, __lcpp_e);}
 
 // ldexp
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       ldexp(float __lcpp_x, int __lcpp_e) _NOEXCEPT       {return ldexpf(__lcpp_x, __lcpp_e);}
-inline _LIBCPP_INLINE_VISIBILITY long double ldexp(long double __lcpp_x, int __lcpp_e) _NOEXCEPT {return ldexpl(__lcpp_x, __lcpp_e);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       ldexp(float __lcpp_x, int __lcpp_e) _NOEXCEPT       {return ::ldexpf(__lcpp_x, __lcpp_e);}
+inline _LIBCPP_INLINE_VISIBILITY long double ldexp(long double __lcpp_x, int __lcpp_e) _NOEXCEPT {return ::ldexpl(__lcpp_x, __lcpp_e);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-ldexp(_A1 __lcpp_x, int __lcpp_e) _NOEXCEPT {return ldexp((double)__lcpp_x, __lcpp_e);}
+ldexp(_A1 __lcpp_x, int __lcpp_e) _NOEXCEPT {return ::ldexp((double)__lcpp_x, __lcpp_e);}
 
 // log
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       log(float __lcpp_x) _NOEXCEPT       {return logf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double log(long double __lcpp_x) _NOEXCEPT {return logl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       log(float __lcpp_x) _NOEXCEPT       {return ::logf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double log(long double __lcpp_x) _NOEXCEPT {return ::logl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-log(_A1 __lcpp_x) _NOEXCEPT {return log((double)__lcpp_x);}
+log(_A1 __lcpp_x) _NOEXCEPT {return ::log((double)__lcpp_x);}
 
 // log10
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       log10(float __lcpp_x) _NOEXCEPT       {return log10f(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double log10(long double __lcpp_x) _NOEXCEPT {return log10l(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       log10(float __lcpp_x) _NOEXCEPT       {return ::log10f(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double log10(long double __lcpp_x) _NOEXCEPT {return ::log10l(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-log10(_A1 __lcpp_x) _NOEXCEPT {return log10((double)__lcpp_x);}
+log10(_A1 __lcpp_x) _NOEXCEPT {return ::log10((double)__lcpp_x);}
 
 // modf
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       modf(float __lcpp_x, float* __lcpp_y) _NOEXCEPT             {return modff(__lcpp_x, __lcpp_y);}
-inline _LIBCPP_INLINE_VISIBILITY long double modf(long double __lcpp_x, long double* __lcpp_y) _NOEXCEPT {return modfl(__lcpp_x, __lcpp_y);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       modf(float __lcpp_x, float* __lcpp_y) _NOEXCEPT             {return ::modff(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY long double modf(long double __lcpp_x, long double* __lcpp_y) _NOEXCEPT {return ::modfl(__lcpp_x, __lcpp_y);}
 #endif
 
 // pow
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       pow(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return powf(__lcpp_x, __lcpp_y);}
-inline _LIBCPP_INLINE_VISIBILITY long double pow(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return powl(__lcpp_x, __lcpp_y);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       pow(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return ::powf(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY long double pow(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return ::powl(__lcpp_x, __lcpp_y);}
 #endif
 
 template <class _A1, class _A2>
@@ -883,131 +970,119 @@ pow(_A1 __lcpp_x, _A2 __lcpp_y) _NOEXCEPT
     typedef typename std::__promote<_A1, _A2>::type __result_type;
     static_assert((!(std::is_same<_A1, __result_type>::value &&
                      std::is_same<_A2, __result_type>::value)), "");
-    return pow((__result_type)__lcpp_x, (__result_type)__lcpp_y);
+    return ::pow((__result_type)__lcpp_x, (__result_type)__lcpp_y);
 }
 
 // sin
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       sin(float __lcpp_x) _NOEXCEPT       {return sinf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double sin(long double __lcpp_x) _NOEXCEPT {return sinl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       sin(float __lcpp_x) _NOEXCEPT       {return ::sinf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double sin(long double __lcpp_x) _NOEXCEPT {return ::sinl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-sin(_A1 __lcpp_x) _NOEXCEPT {return sin((double)__lcpp_x);}
+sin(_A1 __lcpp_x) _NOEXCEPT {return ::sin((double)__lcpp_x);}
 
 // sinh
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       sinh(float __lcpp_x) _NOEXCEPT       {return sinhf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double sinh(long double __lcpp_x) _NOEXCEPT {return sinhl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       sinh(float __lcpp_x) _NOEXCEPT       {return ::sinhf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double sinh(long double __lcpp_x) _NOEXCEPT {return ::sinhl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-sinh(_A1 __lcpp_x) _NOEXCEPT {return sinh((double)__lcpp_x);}
+sinh(_A1 __lcpp_x) _NOEXCEPT {return ::sinh((double)__lcpp_x);}
 
 // sqrt
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       sqrt(float __lcpp_x) _NOEXCEPT       {return sqrtf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double sqrt(long double __lcpp_x) _NOEXCEPT {return sqrtl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       sqrt(float __lcpp_x) _NOEXCEPT       {return ::sqrtf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double sqrt(long double __lcpp_x) _NOEXCEPT {return ::sqrtl(__lcpp_x);}
 #endif
 
-#endif // __sun__
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-sqrt(_A1 __lcpp_x) _NOEXCEPT {return sqrt((double)__lcpp_x);}
-#ifndef __sun__
+sqrt(_A1 __lcpp_x) _NOEXCEPT {return ::sqrt((double)__lcpp_x);}
 
 // tan
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       tan(float __lcpp_x) _NOEXCEPT       {return tanf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double tan(long double __lcpp_x) _NOEXCEPT {return tanl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       tan(float __lcpp_x) _NOEXCEPT       {return ::tanf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double tan(long double __lcpp_x) _NOEXCEPT {return ::tanl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-tan(_A1 __lcpp_x) _NOEXCEPT {return tan((double)__lcpp_x);}
+tan(_A1 __lcpp_x) _NOEXCEPT {return ::tan((double)__lcpp_x);}
 
 // tanh
 
-#if !(defined(_LIBCPP_MSVCRT) || defined(_AIX))
-inline _LIBCPP_INLINE_VISIBILITY float       tanh(float __lcpp_x) _NOEXCEPT       {return tanhf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double tanh(long double __lcpp_x) _NOEXCEPT {return tanhl(__lcpp_x);}
+#if !(defined(_AIX) || defined(__sun__))
+inline _LIBCPP_INLINE_VISIBILITY float       tanh(float __lcpp_x) _NOEXCEPT       {return ::tanhf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double tanh(long double __lcpp_x) _NOEXCEPT {return ::tanhl(__lcpp_x);}
 #endif
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-tanh(_A1 __lcpp_x) _NOEXCEPT {return tanh((double)__lcpp_x);}
+tanh(_A1 __lcpp_x) _NOEXCEPT {return ::tanh((double)__lcpp_x);}
 
 // acosh
 
-#ifndef _LIBCPP_MSVCRT
-inline _LIBCPP_INLINE_VISIBILITY float       acosh(float __lcpp_x) _NOEXCEPT       {return acoshf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double acosh(long double __lcpp_x) _NOEXCEPT {return acoshl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       acosh(float __lcpp_x) _NOEXCEPT       {return ::acoshf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double acosh(long double __lcpp_x) _NOEXCEPT {return ::acoshl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-acosh(_A1 __lcpp_x) _NOEXCEPT {return acosh((double)__lcpp_x);}
-#endif
+acosh(_A1 __lcpp_x) _NOEXCEPT {return ::acosh((double)__lcpp_x);}
 
 // asinh
 
-#ifndef _LIBCPP_MSVCRT
-inline _LIBCPP_INLINE_VISIBILITY float       asinh(float __lcpp_x) _NOEXCEPT       {return asinhf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double asinh(long double __lcpp_x) _NOEXCEPT {return asinhl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       asinh(float __lcpp_x) _NOEXCEPT       {return ::asinhf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double asinh(long double __lcpp_x) _NOEXCEPT {return ::asinhl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-asinh(_A1 __lcpp_x) _NOEXCEPT {return asinh((double)__lcpp_x);}
-#endif
+asinh(_A1 __lcpp_x) _NOEXCEPT {return ::asinh((double)__lcpp_x);}
 
 // atanh
 
-#ifndef _LIBCPP_MSVCRT
-inline _LIBCPP_INLINE_VISIBILITY float       atanh(float __lcpp_x) _NOEXCEPT       {return atanhf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double atanh(long double __lcpp_x) _NOEXCEPT {return atanhl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       atanh(float __lcpp_x) _NOEXCEPT       {return ::atanhf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double atanh(long double __lcpp_x) _NOEXCEPT {return ::atanhl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-atanh(_A1 __lcpp_x) _NOEXCEPT {return atanh((double)__lcpp_x);}
-#endif
+atanh(_A1 __lcpp_x) _NOEXCEPT {return ::atanh((double)__lcpp_x);}
 
 // cbrt
 
-#ifndef _LIBCPP_MSVCRT
-inline _LIBCPP_INLINE_VISIBILITY float       cbrt(float __lcpp_x) _NOEXCEPT       {return cbrtf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double cbrt(long double __lcpp_x) _NOEXCEPT {return cbrtl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       cbrt(float __lcpp_x) _NOEXCEPT       {return ::cbrtf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double cbrt(long double __lcpp_x) _NOEXCEPT {return ::cbrtl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-cbrt(_A1 __lcpp_x) _NOEXCEPT {return cbrt((double)__lcpp_x);}
-#endif
+cbrt(_A1 __lcpp_x) _NOEXCEPT {return ::cbrt((double)__lcpp_x);}
 
 // copysign
 
-#if !defined(_VC_CRT_MAJOR_VERSION) || (_VC_CRT_MAJOR_VERSION < 12)
 inline _LIBCPP_INLINE_VISIBILITY float copysign(float __lcpp_x,
                                                 float __lcpp_y) _NOEXCEPT {
-  return copysignf(__lcpp_x, __lcpp_y);
+  return ::copysignf(__lcpp_x, __lcpp_y);
 }
 inline _LIBCPP_INLINE_VISIBILITY long double
 copysign(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {
-  return copysignl(__lcpp_x, __lcpp_y);
+  return ::copysignl(__lcpp_x, __lcpp_y);
 }
-#endif
 
 template <class _A1, class _A2>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1022,55 +1097,53 @@ copysign(_A1 __lcpp_x, _A2 __lcpp_y) _NOEXCEPT
     typedef typename std::__promote<_A1, _A2>::type __result_type;
     static_assert((!(std::is_same<_A1, __result_type>::value &&
                      std::is_same<_A2, __result_type>::value)), "");
-    return copysign((__result_type)__lcpp_x, (__result_type)__lcpp_y);
+    return ::copysign((__result_type)__lcpp_x, (__result_type)__lcpp_y);
 }
 
-#ifndef _LIBCPP_MSVCRT
-
 // erf
 
-inline _LIBCPP_INLINE_VISIBILITY float       erf(float __lcpp_x) _NOEXCEPT       {return erff(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double erf(long double __lcpp_x) _NOEXCEPT {return erfl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       erf(float __lcpp_x) _NOEXCEPT       {return ::erff(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double erf(long double __lcpp_x) _NOEXCEPT {return ::erfl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-erf(_A1 __lcpp_x) _NOEXCEPT {return erf((double)__lcpp_x);}
+erf(_A1 __lcpp_x) _NOEXCEPT {return ::erf((double)__lcpp_x);}
 
 // erfc
 
-inline _LIBCPP_INLINE_VISIBILITY float       erfc(float __lcpp_x) _NOEXCEPT       {return erfcf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double erfc(long double __lcpp_x) _NOEXCEPT {return erfcl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       erfc(float __lcpp_x) _NOEXCEPT       {return ::erfcf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double erfc(long double __lcpp_x) _NOEXCEPT {return ::erfcl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-erfc(_A1 __lcpp_x) _NOEXCEPT {return erfc((double)__lcpp_x);}
+erfc(_A1 __lcpp_x) _NOEXCEPT {return ::erfc((double)__lcpp_x);}
 
 // exp2
 
-inline _LIBCPP_INLINE_VISIBILITY float       exp2(float __lcpp_x) _NOEXCEPT       {return exp2f(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double exp2(long double __lcpp_x) _NOEXCEPT {return exp2l(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       exp2(float __lcpp_x) _NOEXCEPT       {return ::exp2f(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double exp2(long double __lcpp_x) _NOEXCEPT {return ::exp2l(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-exp2(_A1 __lcpp_x) _NOEXCEPT {return exp2((double)__lcpp_x);}
+exp2(_A1 __lcpp_x) _NOEXCEPT {return ::exp2((double)__lcpp_x);}
 
 // expm1
 
-inline _LIBCPP_INLINE_VISIBILITY float       expm1(float __lcpp_x) _NOEXCEPT       {return expm1f(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double expm1(long double __lcpp_x) _NOEXCEPT {return expm1l(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       expm1(float __lcpp_x) _NOEXCEPT       {return ::expm1f(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double expm1(long double __lcpp_x) _NOEXCEPT {return ::expm1l(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-expm1(_A1 __lcpp_x) _NOEXCEPT {return expm1((double)__lcpp_x);}
+expm1(_A1 __lcpp_x) _NOEXCEPT {return ::expm1((double)__lcpp_x);}
 
 // fdim
 
-inline _LIBCPP_INLINE_VISIBILITY float       fdim(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return fdimf(__lcpp_x, __lcpp_y);}
-inline _LIBCPP_INLINE_VISIBILITY long double fdim(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return fdiml(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY float       fdim(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return ::fdimf(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY long double fdim(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return ::fdiml(__lcpp_x, __lcpp_y);}
 
 template <class _A1, class _A2>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1085,13 +1158,13 @@ fdim(_A1 __lcpp_x, _A2 __lcpp_y) _NOEXCEPT
     typedef typename std::__promote<_A1, _A2>::type __result_type;
     static_assert((!(std::is_same<_A1, __result_type>::value &&
                      std::is_same<_A2, __result_type>::value)), "");
-    return fdim((__result_type)__lcpp_x, (__result_type)__lcpp_y);
+    return ::fdim((__result_type)__lcpp_x, (__result_type)__lcpp_y);
 }
 
 // fma
 
-inline _LIBCPP_INLINE_VISIBILITY float       fma(float __lcpp_x, float __lcpp_y, float __lcpp_z) _NOEXCEPT                   {return fmaf(__lcpp_x, __lcpp_y, __lcpp_z);}
-inline _LIBCPP_INLINE_VISIBILITY long double fma(long double __lcpp_x, long double __lcpp_y, long double __lcpp_z) _NOEXCEPT {return fmal(__lcpp_x, __lcpp_y, __lcpp_z);}
+inline _LIBCPP_INLINE_VISIBILITY float       fma(float __lcpp_x, float __lcpp_y, float __lcpp_z) _NOEXCEPT                   {return ::fmaf(__lcpp_x, __lcpp_y, __lcpp_z);}
+inline _LIBCPP_INLINE_VISIBILITY long double fma(long double __lcpp_x, long double __lcpp_y, long double __lcpp_z) _NOEXCEPT {return ::fmal(__lcpp_x, __lcpp_y, __lcpp_z);}
 
 template <class _A1, class _A2, class _A3>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1108,13 +1181,13 @@ fma(_A1 __lcpp_x, _A2 __lcpp_y, _A3 __lcpp_z) _NOEXCEPT
     static_assert((!(std::is_same<_A1, __result_type>::value &&
                      std::is_same<_A2, __result_type>::value &&
                      std::is_same<_A3, __result_type>::value)), "");
-    return fma((__result_type)__lcpp_x, (__result_type)__lcpp_y, (__result_type)__lcpp_z);
+    return ::fma((__result_type)__lcpp_x, (__result_type)__lcpp_y, (__result_type)__lcpp_z);
 }
 
 // fmax
 
-inline _LIBCPP_INLINE_VISIBILITY float       fmax(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return fmaxf(__lcpp_x, __lcpp_y);}
-inline _LIBCPP_INLINE_VISIBILITY long double fmax(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return fmaxl(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY float       fmax(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return ::fmaxf(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY long double fmax(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return ::fmaxl(__lcpp_x, __lcpp_y);}
 
 template <class _A1, class _A2>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1129,13 +1202,13 @@ fmax(_A1 __lcpp_x, _A2 __lcpp_y) _NOEXCEPT
     typedef typename std::__promote<_A1, _A2>::type __result_type;
     static_assert((!(std::is_same<_A1, __result_type>::value &&
                      std::is_same<_A2, __result_type>::value)), "");
-    return fmax((__result_type)__lcpp_x, (__result_type)__lcpp_y);
+    return ::fmax((__result_type)__lcpp_x, (__result_type)__lcpp_y);
 }
 
 // fmin
 
-inline _LIBCPP_INLINE_VISIBILITY float       fmin(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return fminf(__lcpp_x, __lcpp_y);}
-inline _LIBCPP_INLINE_VISIBILITY long double fmin(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return fminl(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY float       fmin(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return ::fminf(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY long double fmin(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return ::fminl(__lcpp_x, __lcpp_y);}
 
 template <class _A1, class _A2>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1150,13 +1223,13 @@ fmin(_A1 __lcpp_x, _A2 __lcpp_y) _NOEXCEPT
     typedef typename std::__promote<_A1, _A2>::type __result_type;
     static_assert((!(std::is_same<_A1, __result_type>::value &&
                      std::is_same<_A2, __result_type>::value)), "");
-    return fmin((__result_type)__lcpp_x, (__result_type)__lcpp_y);
+    return ::fmin((__result_type)__lcpp_x, (__result_type)__lcpp_y);
 }
 
 // hypot
 
-inline _LIBCPP_INLINE_VISIBILITY float       hypot(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return hypotf(__lcpp_x, __lcpp_y);}
-inline _LIBCPP_INLINE_VISIBILITY long double hypot(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return hypotl(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY float       hypot(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return ::hypotf(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY long double hypot(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return ::hypotl(__lcpp_x, __lcpp_y);}
 
 template <class _A1, class _A2>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1171,115 +1244,115 @@ hypot(_A1 __lcpp_x, _A2 __lcpp_y) _NOEXCEPT
     typedef typename std::__promote<_A1, _A2>::type __result_type;
     static_assert((!(std::is_same<_A1, __result_type>::value &&
                      std::is_same<_A2, __result_type>::value)), "");
-    return hypot((__result_type)__lcpp_x, (__result_type)__lcpp_y);
+    return ::hypot((__result_type)__lcpp_x, (__result_type)__lcpp_y);
 }
 
 // ilogb
 
-inline _LIBCPP_INLINE_VISIBILITY int ilogb(float __lcpp_x) _NOEXCEPT       {return ilogbf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY int ilogb(long double __lcpp_x) _NOEXCEPT {return ilogbl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY int ilogb(float __lcpp_x) _NOEXCEPT       {return ::ilogbf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY int ilogb(long double __lcpp_x) _NOEXCEPT {return ::ilogbl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, int>::type
-ilogb(_A1 __lcpp_x) _NOEXCEPT {return ilogb((double)__lcpp_x);}
+ilogb(_A1 __lcpp_x) _NOEXCEPT {return ::ilogb((double)__lcpp_x);}
 
 // lgamma
 
-inline _LIBCPP_INLINE_VISIBILITY float       lgamma(float __lcpp_x) _NOEXCEPT       {return lgammaf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double lgamma(long double __lcpp_x) _NOEXCEPT {return lgammal(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       lgamma(float __lcpp_x) _NOEXCEPT       {return ::lgammaf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double lgamma(long double __lcpp_x) _NOEXCEPT {return ::lgammal(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-lgamma(_A1 __lcpp_x) _NOEXCEPT {return lgamma((double)__lcpp_x);}
+lgamma(_A1 __lcpp_x) _NOEXCEPT {return ::lgamma((double)__lcpp_x);}
 
 // llrint
 
-inline _LIBCPP_INLINE_VISIBILITY long long llrint(float __lcpp_x) _NOEXCEPT       {return llrintf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long long llrint(long double __lcpp_x) _NOEXCEPT {return llrintl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long long llrint(float __lcpp_x) _NOEXCEPT       {return ::llrintf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long long llrint(long double __lcpp_x) _NOEXCEPT {return ::llrintl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, long long>::type
-llrint(_A1 __lcpp_x) _NOEXCEPT {return llrint((double)__lcpp_x);}
+llrint(_A1 __lcpp_x) _NOEXCEPT {return ::llrint((double)__lcpp_x);}
 
 // llround
 
-inline _LIBCPP_INLINE_VISIBILITY long long llround(float __lcpp_x) _NOEXCEPT       {return llroundf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long long llround(long double __lcpp_x) _NOEXCEPT {return llroundl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long long llround(float __lcpp_x) _NOEXCEPT       {return ::llroundf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long long llround(long double __lcpp_x) _NOEXCEPT {return ::llroundl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, long long>::type
-llround(_A1 __lcpp_x) _NOEXCEPT {return llround((double)__lcpp_x);}
+llround(_A1 __lcpp_x) _NOEXCEPT {return ::llround((double)__lcpp_x);}
 
 // log1p
 
-inline _LIBCPP_INLINE_VISIBILITY float       log1p(float __lcpp_x) _NOEXCEPT       {return log1pf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double log1p(long double __lcpp_x) _NOEXCEPT {return log1pl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       log1p(float __lcpp_x) _NOEXCEPT       {return ::log1pf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double log1p(long double __lcpp_x) _NOEXCEPT {return ::log1pl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-log1p(_A1 __lcpp_x) _NOEXCEPT {return log1p((double)__lcpp_x);}
+log1p(_A1 __lcpp_x) _NOEXCEPT {return ::log1p((double)__lcpp_x);}
 
 // log2
 
-inline _LIBCPP_INLINE_VISIBILITY float       log2(float __lcpp_x) _NOEXCEPT       {return log2f(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double log2(long double __lcpp_x) _NOEXCEPT {return log2l(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       log2(float __lcpp_x) _NOEXCEPT       {return ::log2f(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double log2(long double __lcpp_x) _NOEXCEPT {return ::log2l(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-log2(_A1 __lcpp_x) _NOEXCEPT {return log2((double)__lcpp_x);}
+log2(_A1 __lcpp_x) _NOEXCEPT {return ::log2((double)__lcpp_x);}
 
 // logb
 
-inline _LIBCPP_INLINE_VISIBILITY float       logb(float __lcpp_x) _NOEXCEPT       {return logbf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double logb(long double __lcpp_x) _NOEXCEPT {return logbl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       logb(float __lcpp_x) _NOEXCEPT       {return ::logbf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double logb(long double __lcpp_x) _NOEXCEPT {return ::logbl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-logb(_A1 __lcpp_x) _NOEXCEPT {return logb((double)__lcpp_x);}
+logb(_A1 __lcpp_x) _NOEXCEPT {return ::logb((double)__lcpp_x);}
 
 // lrint
 
-inline _LIBCPP_INLINE_VISIBILITY long lrint(float __lcpp_x) _NOEXCEPT       {return lrintf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long lrint(long double __lcpp_x) _NOEXCEPT {return lrintl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long lrint(float __lcpp_x) _NOEXCEPT       {return ::lrintf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long lrint(long double __lcpp_x) _NOEXCEPT {return ::lrintl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, long>::type
-lrint(_A1 __lcpp_x) _NOEXCEPT {return lrint((double)__lcpp_x);}
+lrint(_A1 __lcpp_x) _NOEXCEPT {return ::lrint((double)__lcpp_x);}
 
 // lround
 
-inline _LIBCPP_INLINE_VISIBILITY long lround(float __lcpp_x) _NOEXCEPT       {return lroundf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long lround(long double __lcpp_x) _NOEXCEPT {return lroundl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long lround(float __lcpp_x) _NOEXCEPT       {return ::lroundf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long lround(long double __lcpp_x) _NOEXCEPT {return ::lroundl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, long>::type
-lround(_A1 __lcpp_x) _NOEXCEPT {return lround((double)__lcpp_x);}
+lround(_A1 __lcpp_x) _NOEXCEPT {return ::lround((double)__lcpp_x);}
 
 // nan
 
 // nearbyint
 
-inline _LIBCPP_INLINE_VISIBILITY float       nearbyint(float __lcpp_x) _NOEXCEPT       {return nearbyintf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double nearbyint(long double __lcpp_x) _NOEXCEPT {return nearbyintl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       nearbyint(float __lcpp_x) _NOEXCEPT       {return ::nearbyintf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double nearbyint(long double __lcpp_x) _NOEXCEPT {return ::nearbyintl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-nearbyint(_A1 __lcpp_x) _NOEXCEPT {return nearbyint((double)__lcpp_x);}
+nearbyint(_A1 __lcpp_x) _NOEXCEPT {return ::nearbyint((double)__lcpp_x);}
 
 // nextafter
 
-inline _LIBCPP_INLINE_VISIBILITY float       nextafter(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return nextafterf(__lcpp_x, __lcpp_y);}
-inline _LIBCPP_INLINE_VISIBILITY long double nextafter(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return nextafterl(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY float       nextafter(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return ::nextafterf(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY long double nextafter(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return ::nextafterl(__lcpp_x, __lcpp_y);}
 
 template <class _A1, class _A2>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1294,23 +1367,23 @@ nextafter(_A1 __lcpp_x, _A2 __lcpp_y) _NOEXCEPT
     typedef typename std::__promote<_A1, _A2>::type __result_type;
     static_assert((!(std::is_same<_A1, __result_type>::value &&
                      std::is_same<_A2, __result_type>::value)), "");
-    return nextafter((__result_type)__lcpp_x, (__result_type)__lcpp_y);
+    return ::nextafter((__result_type)__lcpp_x, (__result_type)__lcpp_y);
 }
 
 // nexttoward
 
-inline _LIBCPP_INLINE_VISIBILITY float       nexttoward(float __lcpp_x, long double __lcpp_y) _NOEXCEPT       {return nexttowardf(__lcpp_x, __lcpp_y);}
-inline _LIBCPP_INLINE_VISIBILITY long double nexttoward(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return nexttowardl(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY float       nexttoward(float __lcpp_x, long double __lcpp_y) _NOEXCEPT       {return ::nexttowardf(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY long double nexttoward(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return ::nexttowardl(__lcpp_x, __lcpp_y);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-nexttoward(_A1 __lcpp_x, long double __lcpp_y) _NOEXCEPT {return nexttoward((double)__lcpp_x, __lcpp_y);}
+nexttoward(_A1 __lcpp_x, long double __lcpp_y) _NOEXCEPT {return ::nexttoward((double)__lcpp_x, __lcpp_y);}
 
 // remainder
 
-inline _LIBCPP_INLINE_VISIBILITY float       remainder(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return remainderf(__lcpp_x, __lcpp_y);}
-inline _LIBCPP_INLINE_VISIBILITY long double remainder(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return remainderl(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY float       remainder(float __lcpp_x, float __lcpp_y) _NOEXCEPT             {return ::remainderf(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY long double remainder(long double __lcpp_x, long double __lcpp_y) _NOEXCEPT {return ::remainderl(__lcpp_x, __lcpp_y);}
 
 template <class _A1, class _A2>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1325,13 +1398,13 @@ remainder(_A1 __lcpp_x, _A2 __lcpp_y) _NOEXCEPT
     typedef typename std::__promote<_A1, _A2>::type __result_type;
     static_assert((!(std::is_same<_A1, __result_type>::value &&
                      std::is_same<_A2, __result_type>::value)), "");
-    return remainder((__result_type)__lcpp_x, (__result_type)__lcpp_y);
+    return ::remainder((__result_type)__lcpp_x, (__result_type)__lcpp_y);
 }
 
 // remquo
 
-inline _LIBCPP_INLINE_VISIBILITY float       remquo(float __lcpp_x, float __lcpp_y, int* __lcpp_z) _NOEXCEPT             {return remquof(__lcpp_x, __lcpp_y, __lcpp_z);}
-inline _LIBCPP_INLINE_VISIBILITY long double remquo(long double __lcpp_x, long double __lcpp_y, int* __lcpp_z) _NOEXCEPT {return remquol(__lcpp_x, __lcpp_y, __lcpp_z);}
+inline _LIBCPP_INLINE_VISIBILITY float       remquo(float __lcpp_x, float __lcpp_y, int* __lcpp_z) _NOEXCEPT             {return ::remquof(__lcpp_x, __lcpp_y, __lcpp_z);}
+inline _LIBCPP_INLINE_VISIBILITY long double remquo(long double __lcpp_x, long double __lcpp_y, int* __lcpp_z) _NOEXCEPT {return ::remquol(__lcpp_x, __lcpp_y, __lcpp_z);}
 
 template <class _A1, class _A2>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1346,71 +1419,68 @@ remquo(_A1 __lcpp_x, _A2 __lcpp_y, int* __lcpp_z) _NOEXCEPT
     typedef typename std::__promote<_A1, _A2>::type __result_type;
     static_assert((!(std::is_same<_A1, __result_type>::value &&
                      std::is_same<_A2, __result_type>::value)), "");
-    return remquo((__result_type)__lcpp_x, (__result_type)__lcpp_y, __lcpp_z);
+    return ::remquo((__result_type)__lcpp_x, (__result_type)__lcpp_y, __lcpp_z);
 }
 
 // rint
 
-inline _LIBCPP_INLINE_VISIBILITY float       rint(float __lcpp_x) _NOEXCEPT       {return rintf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double rint(long double __lcpp_x) _NOEXCEPT {return rintl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       rint(float __lcpp_x) _NOEXCEPT       {return ::rintf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double rint(long double __lcpp_x) _NOEXCEPT {return ::rintl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-rint(_A1 __lcpp_x) _NOEXCEPT {return rint((double)__lcpp_x);}
+rint(_A1 __lcpp_x) _NOEXCEPT {return ::rint((double)__lcpp_x);}
 
 // round
 
-inline _LIBCPP_INLINE_VISIBILITY float       round(float __lcpp_x) _NOEXCEPT       {return roundf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double round(long double __lcpp_x) _NOEXCEPT {return roundl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       round(float __lcpp_x) _NOEXCEPT       {return ::roundf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double round(long double __lcpp_x) _NOEXCEPT {return ::roundl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-round(_A1 __lcpp_x) _NOEXCEPT {return round((double)__lcpp_x);}
+round(_A1 __lcpp_x) _NOEXCEPT {return ::round((double)__lcpp_x);}
 
 // scalbln
 
-inline _LIBCPP_INLINE_VISIBILITY float       scalbln(float __lcpp_x, long __lcpp_y) _NOEXCEPT       {return scalblnf(__lcpp_x, __lcpp_y);}
-inline _LIBCPP_INLINE_VISIBILITY long double scalbln(long double __lcpp_x, long __lcpp_y) _NOEXCEPT {return scalblnl(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY float       scalbln(float __lcpp_x, long __lcpp_y) _NOEXCEPT       {return ::scalblnf(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY long double scalbln(long double __lcpp_x, long __lcpp_y) _NOEXCEPT {return ::scalblnl(__lcpp_x, __lcpp_y);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-scalbln(_A1 __lcpp_x, long __lcpp_y) _NOEXCEPT {return scalbln((double)__lcpp_x, __lcpp_y);}
+scalbln(_A1 __lcpp_x, long __lcpp_y) _NOEXCEPT {return ::scalbln((double)__lcpp_x, __lcpp_y);}
 
 // scalbn
 
-inline _LIBCPP_INLINE_VISIBILITY float       scalbn(float __lcpp_x, int __lcpp_y) _NOEXCEPT       {return scalbnf(__lcpp_x, __lcpp_y);}
-inline _LIBCPP_INLINE_VISIBILITY long double scalbn(long double __lcpp_x, int __lcpp_y) _NOEXCEPT {return scalbnl(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY float       scalbn(float __lcpp_x, int __lcpp_y) _NOEXCEPT       {return ::scalbnf(__lcpp_x, __lcpp_y);}
+inline _LIBCPP_INLINE_VISIBILITY long double scalbn(long double __lcpp_x, int __lcpp_y) _NOEXCEPT {return ::scalbnl(__lcpp_x, __lcpp_y);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-scalbn(_A1 __lcpp_x, int __lcpp_y) _NOEXCEPT {return scalbn((double)__lcpp_x, __lcpp_y);}
+scalbn(_A1 __lcpp_x, int __lcpp_y) _NOEXCEPT {return ::scalbn((double)__lcpp_x, __lcpp_y);}
 
 // tgamma
 
-inline _LIBCPP_INLINE_VISIBILITY float       tgamma(float __lcpp_x) _NOEXCEPT       {return tgammaf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double tgamma(long double __lcpp_x) _NOEXCEPT {return tgammal(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       tgamma(float __lcpp_x) _NOEXCEPT       {return ::tgammaf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double tgamma(long double __lcpp_x) _NOEXCEPT {return ::tgammal(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-tgamma(_A1 __lcpp_x) _NOEXCEPT {return tgamma((double)__lcpp_x);}
+tgamma(_A1 __lcpp_x) _NOEXCEPT {return ::tgamma((double)__lcpp_x);}
 
 // trunc
 
-inline _LIBCPP_INLINE_VISIBILITY float       trunc(float __lcpp_x) _NOEXCEPT       {return truncf(__lcpp_x);}
-inline _LIBCPP_INLINE_VISIBILITY long double trunc(long double __lcpp_x) _NOEXCEPT {return truncl(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY float       trunc(float __lcpp_x) _NOEXCEPT       {return ::truncf(__lcpp_x);}
+inline _LIBCPP_INLINE_VISIBILITY long double trunc(long double __lcpp_x) _NOEXCEPT {return ::truncl(__lcpp_x);}
 
 template <class _A1>
 inline _LIBCPP_INLINE_VISIBILITY
 typename std::enable_if<std::is_integral<_A1>::value, double>::type
-trunc(_A1 __lcpp_x) _NOEXCEPT {return trunc((double)__lcpp_x);}
-
-#endif // !_LIBCPP_MSVCRT
-#endif // __sun__
+trunc(_A1 __lcpp_x) _NOEXCEPT {return ::trunc((double)__lcpp_x);}
 
 } // extern "C++"
 
diff --git a/lib/libcxx/include/memory b/lib/libcxx/include/memory
index 7a3281e1793..d6b427b941b 100644
--- a/lib/libcxx/include/memory
+++ b/lib/libcxx/include/memory
@@ -18,7 +18,7 @@ namespace std
 {
 
 struct allocator_arg_t { };
-constexpr allocator_arg_t allocator_arg = allocator_arg_t();
+inline constexpr allocator_arg_t allocator_arg = allocator_arg_t();
 
 template <class T, class Alloc> struct uses_allocator;
 
@@ -46,6 +46,9 @@ struct pointer_traits<T*>
     static pointer pointer_to(<details>) noexcept;
 };
 
+template <class T> constexpr T* to_address(T* p) noexcept; // C++20
+template <class Ptr> auto to_address(const Ptr& p) noexcept; // C++20
+
 template <class Alloc>
 struct allocator_traits
 {
@@ -81,8 +84,8 @@ struct allocator_traits
     template <class T> using rebind_alloc  = Alloc::rebind<U>::other | Alloc<T, Args...>;
     template <class T> using rebind_traits = allocator_traits<rebind_alloc<T>>;
 
-    static pointer allocate(allocator_type& a, size_type n);
-    static pointer allocate(allocator_type& a, size_type n, const_void_pointer hint);
+    static pointer allocate(allocator_type& a, size_type n);                          // [[nodiscard]] in C++20
+    static pointer allocate(allocator_type& a, size_type n, const_void_pointer hint); // [[nodiscard]] in C++20
 
     static void deallocate(allocator_type& a, pointer p, size_type n) noexcept;
 
@@ -164,6 +167,7 @@ template <class T> pair<T*,ptrdiff_t> get_temporary_buffer(ptrdiff_t n) noexcept
 template <class T> void               return_temporary_buffer(T* p) noexcept;
 
 template <class T> T* addressof(T& r) noexcept;
+template <class T> T* addressof(const T&& r) noexcept = delete;
 
 template <class InputIterator, class ForwardIterator>
 ForwardIterator
@@ -180,10 +184,37 @@ template <class ForwardIterator, class Size, class T>
 ForwardIterator
 uninitialized_fill_n(ForwardIterator first, Size n, const T& x);
 
-template <class Y> struct auto_ptr_ref {};
+template <class T>
+void destroy_at(T* location);
+
+template <class ForwardIterator>
+ void destroy(ForwardIterator first, ForwardIterator last);
+
+template <class ForwardIterator, class Size>
+ ForwardIterator destroy_n(ForwardIterator first, Size n);
+
+template <class InputIterator, class ForwardIterator>
+ ForwardIterator uninitialized_move(InputIterator first, InputIterator last, ForwardIterator result);
+
+template <class InputIterator, class Size, class ForwardIterator>
+ pair<InputIterator,ForwardIterator> uninitialized_move_n(InputIterator first, Size n, ForwardIterator result);
+
+template <class ForwardIterator>
+ void uninitialized_value_construct(ForwardIterator first, ForwardIterator last);
+
+template <class ForwardIterator, class Size>
+ ForwardIterator uninitialized_value_construct_n(ForwardIterator first, Size n);
+
+template <class ForwardIterator>
+ void uninitialized_default_construct(ForwardIterator first, ForwardIterator last);
+
+template <class ForwardIterator, class Size>
+ ForwardIterator uninitialized_default_construct_n(ForwardIterator first, Size n);
+
+template <class Y> struct auto_ptr_ref {};      // removed in C++17
 
 template<class X>
-class auto_ptr
+class auto_ptr                                  // removed in C++17
 {
 public:
     typedef X element_type;
@@ -242,7 +273,7 @@ public:
     template <class U, class E>
         unique_ptr(unique_ptr<U, E>&& u) noexcept;
     template <class U>
-        unique_ptr(auto_ptr<U>&& u) noexcept;
+        unique_ptr(auto_ptr<U>&& u) noexcept;       // removed in C++17
 
     // destructor
     ~unique_ptr();
@@ -356,6 +387,9 @@ template<class T, class... Args> unique_ptr<T> make_unique(Args&&... args);
 template<class T>                unique_ptr<T> make_unique(size_t n);           // C++14
 template<class T, class... Args> unspecified   make_unique(Args&&...) = delete; // C++14, T == U[N]
 
+template<class E, class T, class Y, class D>
+    basic_ostream<E, T>& operator<< (basic_ostream<E, T>& os, unique_ptr<Y, D> const& p);
+
 template<class T>
 class shared_ptr
 {
@@ -376,7 +410,7 @@ public:
     shared_ptr(shared_ptr&& r) noexcept;
     template<class Y> shared_ptr(shared_ptr<Y>&& r) noexcept;
     template<class Y> explicit shared_ptr(const weak_ptr<Y>& r);
-    template<class Y> shared_ptr(auto_ptr<Y>&& r);
+    template<class Y> shared_ptr(auto_ptr<Y>&& r);          // removed in C++17
     template <class Y, class D> shared_ptr(unique_ptr<Y, D>&& r);
     shared_ptr(nullptr_t) : shared_ptr() { }
 
@@ -388,7 +422,7 @@ public:
     template<class Y> shared_ptr& operator=(const shared_ptr<Y>& r) noexcept;
     shared_ptr& operator=(shared_ptr&& r) noexcept;
     template<class Y> shared_ptr& operator=(shared_ptr<Y>&& r);
-    template<class Y> shared_ptr& operator=(auto_ptr<Y>&& r);
+    template<class Y> shared_ptr& operator=(auto_ptr<Y>&& r); // removed in C++17
     template <class Y, class D> shared_ptr& operator=(unique_ptr<Y, D>&& r);
 
     // modifiers:
@@ -405,8 +439,8 @@ public:
     long use_count() const noexcept;
     bool unique() const noexcept;
     explicit operator bool() const noexcept;
-    template<class U> bool owner_before(shared_ptr<U> const& b) const;
-    template<class U> bool owner_before(weak_ptr<U> const& b) const;
+    template<class U> bool owner_before(shared_ptr<U> const& b) const noexcept;
+    template<class U> bool owner_before(weak_ptr<U> const& b) const noexcept;
 };
 
 // shared_ptr comparisons:
@@ -503,8 +537,8 @@ public:
     long use_count() const noexcept;
     bool expired() const noexcept;
     shared_ptr<T> lock() const noexcept;
-    template<class U> bool owner_before(shared_ptr<U> const& b) const;
-    template<class U> bool owner_before(weak_ptr<U> const& b) const;
+    template<class U> bool owner_before(shared_ptr<U> const& b) const noexcept;
+    template<class U> bool owner_before(weak_ptr<U> const& b) const noexcept;
 };
 
 // weak_ptr specialized algorithms:
@@ -518,9 +552,9 @@ struct owner_less<shared_ptr<T>>
     : binary_function<shared_ptr<T>, shared_ptr<T>, bool>
 {
     typedef bool result_type;
-    bool operator()(shared_ptr<T> const&, shared_ptr<T> const&) const;
-    bool operator()(shared_ptr<T> const&, weak_ptr<T> const&) const;
-    bool operator()(weak_ptr<T> const&, shared_ptr<T> const&) const;
+    bool operator()(shared_ptr<T> const&, shared_ptr<T> const&) const noexcept;
+    bool operator()(shared_ptr<T> const&, weak_ptr<T> const&) const noexcept;
+    bool operator()(weak_ptr<T> const&, shared_ptr<T> const&) const noexcept;
 };
 
 template<class T>
@@ -528,9 +562,24 @@ struct owner_less<weak_ptr<T>>
     : binary_function<weak_ptr<T>, weak_ptr<T>, bool>
 {
     typedef bool result_type;
-    bool operator()(weak_ptr<T> const&, weak_ptr<T> const&) const;
-    bool operator()(shared_ptr<T> const&, weak_ptr<T> const&) const;
-    bool operator()(weak_ptr<T> const&, shared_ptr<T> const&) const;
+    bool operator()(weak_ptr<T> const&, weak_ptr<T> const&) const noexcept;
+    bool operator()(shared_ptr<T> const&, weak_ptr<T> const&) const noexcept;
+    bool operator()(weak_ptr<T> const&, shared_ptr<T> const&) const noexcept;
+};
+
+template <>  // Added in C++14
+struct owner_less<void>
+{
+    template <class _Tp, class _Up>
+    bool operator()( shared_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) const noexcept;
+    template <class _Tp, class _Up>
+    bool operator()( shared_ptr<_Tp> const& __x,   weak_ptr<_Up> const& __y) const noexcept;
+    template <class _Tp, class _Up>
+    bool operator()(   weak_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) const noexcept;
+    template <class _Tp, class _Up>
+    bool operator()(   weak_ptr<_Tp> const& __x,   weak_ptr<_Up> const& __y) const noexcept;
+
+    typedef void is_transparent;
 };
 
 template<class T>
@@ -582,6 +631,9 @@ template <class T> struct hash;
 template <class T, class D> struct hash<unique_ptr<T, D> >;
 template <class T> struct hash<shared_ptr<T> >;
 
+template <class T, class Alloc>
+  inline constexpr bool uses_allocator_v = uses_allocator<T, Alloc>::value;
+
 // Pointer safety
 enum class pointer_safety { relaxed, preferred, strict };
 void declare_reachable(void *p);
@@ -610,21 +662,19 @@ void* align(size_t alignment, size_t size, void*& ptr, size_t& space);
 #include <tuple>
 #include <stdexcept>
 #include <cstring>
-#if defined(_LIBCPP_NO_EXCEPTIONS)
-    #include <cassert>
-#endif
-
+#include <cassert>
 #if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
 #  include <atomic>
 #endif
 
-#include <__undef_min_max>
-#include <__undef___deallocate>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _ValueType>
@@ -639,12 +689,24 @@ _ValueType __libcpp_relaxed_load(_ValueType const* __value) {
 #endif
 }
 
-// addressof moved to <__functional_base>
+template <class _ValueType>
+inline _LIBCPP_ALWAYS_INLINE
+_ValueType __libcpp_acquire_load(_ValueType const* __value) {
+#if !defined(_LIBCPP_HAS_NO_THREADS) && \
+    defined(__ATOMIC_ACQUIRE) &&        \
+    (__has_builtin(__atomic_load_n) || _GNUC_VER >= 407)
+    return __atomic_load_n(__value, __ATOMIC_ACQUIRE);
+#else
+    return *__value;
+#endif
+}
+
+// addressof moved to <type_traits>
 
 template <class _Tp> class allocator;
 
 template <>
-class _LIBCPP_TYPE_VIS_ONLY allocator<void>
+class _LIBCPP_TEMPLATE_VIS allocator<void>
 {
 public:
     typedef void*             pointer;
@@ -655,7 +717,7 @@ public:
 };
 
 template <>
-class _LIBCPP_TYPE_VIS_ONLY allocator<const void>
+class _LIBCPP_TEMPLATE_VIS allocator<const void>
 {
 public:
     typedef const void*       pointer;
@@ -667,16 +729,12 @@ public:
 
 // pointer_traits
 
+template <class _Tp, class = void>
+struct __has_element_type : false_type {};
+
 template <class _Tp>
-struct __has_element_type
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::element_type* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
-};
+struct __has_element_type<_Tp,
+              typename __void_t<typename _Tp::element_type>::type> : true_type {};
 
 template <class _Ptr, bool = __has_element_type<_Ptr>::value>
 struct __pointer_traits_element_type;
@@ -755,16 +813,12 @@ struct __pointer_traits_element_type<_Sp<_Tp, _A0, _A1, _A2>, false>
 
 #endif  // _LIBCPP_HAS_NO_VARIADICS
 
+template <class _Tp, class = void>
+struct __has_difference_type : false_type {};
+
 template <class _Tp>
-struct __has_difference_type
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::difference_type* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
-};
+struct __has_difference_type<_Tp,
+            typename __void_t<typename _Tp::difference_type>::type> : true_type {};
 
 template <class _Ptr, bool = __has_difference_type<_Ptr>::value>
 struct __pointer_traits_difference_type
@@ -792,7 +846,7 @@ public:
 template <class _Tp, class _Up, bool = __has_rebind<_Tp, _Up>::value>
 struct __pointer_traits_rebind
 {
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     typedef typename _Tp::template rebind<_Up> type;
 #else
     typedef typename _Tp::template rebind<_Up>::other type;
@@ -804,7 +858,7 @@ struct __pointer_traits_rebind
 template <template <class, class...> class _Sp, class _Tp, class ..._Args, class _Up>
 struct __pointer_traits_rebind<_Sp<_Tp, _Args...>, _Up, true>
 {
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     typedef typename _Sp<_Tp, _Args...>::template rebind<_Up> type;
 #else
     typedef typename _Sp<_Tp, _Args...>::template rebind<_Up>::other type;
@@ -822,7 +876,7 @@ struct __pointer_traits_rebind<_Sp<_Tp, _Args...>, _Up, false>
 template <template <class> class _Sp, class _Tp, class _Up>
 struct __pointer_traits_rebind<_Sp<_Tp>, _Up, true>
 {
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     typedef typename _Sp<_Tp>::template rebind<_Up> type;
 #else
     typedef typename _Sp<_Tp>::template rebind<_Up>::other type;
@@ -838,7 +892,7 @@ struct __pointer_traits_rebind<_Sp<_Tp>, _Up, false>
 template <template <class, class> class _Sp, class _Tp, class _A0, class _Up>
 struct __pointer_traits_rebind<_Sp<_Tp, _A0>, _Up, true>
 {
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     typedef typename _Sp<_Tp, _A0>::template rebind<_Up> type;
 #else
     typedef typename _Sp<_Tp, _A0>::template rebind<_Up>::other type;
@@ -855,7 +909,7 @@ template <template <class, class, class> class _Sp, class _Tp, class _A0,
                                          class _A1, class _Up>
 struct __pointer_traits_rebind<_Sp<_Tp, _A0, _A1>, _Up, true>
 {
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     typedef typename _Sp<_Tp, _A0, _A1>::template rebind<_Up> type;
 #else
     typedef typename _Sp<_Tp, _A0, _A1>::template rebind<_Up>::other type;
@@ -873,7 +927,7 @@ template <template <class, class, class, class> class _Sp, class _Tp, class _A0,
                                                 class _A1, class _A2, class _Up>
 struct __pointer_traits_rebind<_Sp<_Tp, _A0, _A1, _A2>, _Up, true>
 {
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     typedef typename _Sp<_Tp, _A0, _A1, _A2>::template rebind<_Up> type;
 #else
     typedef typename _Sp<_Tp, _A0, _A1, _A2>::template rebind<_Up>::other type;
@@ -890,18 +944,18 @@ struct __pointer_traits_rebind<_Sp<_Tp, _A0, _A1, _A2>, _Up, false>
 #endif  // _LIBCPP_HAS_NO_VARIADICS
 
 template <class _Ptr>
-struct _LIBCPP_TYPE_VIS_ONLY pointer_traits
+struct _LIBCPP_TEMPLATE_VIS pointer_traits
 {
     typedef _Ptr                                                     pointer;
     typedef typename __pointer_traits_element_type<pointer>::type    element_type;
     typedef typename __pointer_traits_difference_type<pointer>::type difference_type;
 
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     template <class _Up> using rebind = typename __pointer_traits_rebind<pointer, _Up>::type;
 #else
     template <class _Up> struct rebind
         {typedef typename __pointer_traits_rebind<pointer, _Up>::type other;};
-#endif  // _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#endif  // _LIBCPP_CXX03_LANG
 
 private:
     struct __nat {};
@@ -913,13 +967,13 @@ public:
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY pointer_traits<_Tp*>
+struct _LIBCPP_TEMPLATE_VIS pointer_traits<_Tp*>
 {
     typedef _Tp*      pointer;
     typedef _Tp       element_type;
     typedef ptrdiff_t difference_type;
 
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     template <class _Up> using rebind = _Up*;
 #else
     template <class _Up> struct rebind {typedef _Up* other;};
@@ -936,7 +990,7 @@ public:
 
 template <class _From, class _To>
 struct __rebind_pointer {
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     typedef typename pointer_traits<_From>::template rebind<_To>        type;
 #else
     typedef typename pointer_traits<_From>::template rebind<_To>::other type;
@@ -945,17 +999,12 @@ struct __rebind_pointer {
 
 // allocator_traits
 
-namespace __has_pointer_type_imp
-{
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::pointer* = 0);
-}
+template <class _Tp, class = void>
+struct __has_pointer_type : false_type {};
 
 template <class _Tp>
-struct __has_pointer_type
-    : public integral_constant<bool, sizeof(__has_pointer_type_imp::__test<_Tp>(0)) == 1>
-{
-};
+struct __has_pointer_type<_Tp,
+          typename __void_t<typename _Tp::pointer>::type> : true_type {};
 
 namespace __pointer_type_imp
 {
@@ -980,16 +1029,12 @@ struct __pointer_type
     typedef typename __pointer_type_imp::__pointer_type<_Tp, typename remove_reference<_Dp>::type>::type type;
 };
 
+template <class _Tp, class = void>
+struct __has_const_pointer : false_type {};
+
 template <class _Tp>
-struct __has_const_pointer
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::const_pointer* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
-};
+struct __has_const_pointer<_Tp,
+            typename __void_t<typename _Tp::const_pointer>::type> : true_type {};
 
 template <class _Tp, class _Ptr, class _Alloc, bool = __has_const_pointer<_Alloc>::value>
 struct __const_pointer
@@ -1000,23 +1045,19 @@ struct __const_pointer
 template <class _Tp, class _Ptr, class _Alloc>
 struct __const_pointer<_Tp, _Ptr, _Alloc, false>
 {
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     typedef typename pointer_traits<_Ptr>::template rebind<const _Tp> type;
 #else
     typedef typename pointer_traits<_Ptr>::template rebind<const _Tp>::other type;
 #endif
 };
 
+template <class _Tp, class = void>
+struct __has_void_pointer : false_type {};
+
 template <class _Tp>
-struct __has_void_pointer
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::void_pointer* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
-};
+struct __has_void_pointer<_Tp,
+               typename __void_t<typename _Tp::void_pointer>::type> : true_type {};
 
 template <class _Ptr, class _Alloc, bool = __has_void_pointer<_Alloc>::value>
 struct __void_pointer
@@ -1027,23 +1068,19 @@ struct __void_pointer
 template <class _Ptr, class _Alloc>
 struct __void_pointer<_Ptr, _Alloc, false>
 {
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     typedef typename pointer_traits<_Ptr>::template rebind<void> type;
 #else
     typedef typename pointer_traits<_Ptr>::template rebind<void>::other type;
 #endif
 };
 
+template <class _Tp, class = void>
+struct __has_const_void_pointer : false_type {};
+
 template <class _Tp>
-struct __has_const_void_pointer
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::const_void_pointer* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
-};
+struct __has_const_void_pointer<_Tp,
+            typename __void_t<typename _Tp::const_void_pointer>::type> : true_type {};
 
 template <class _Ptr, class _Alloc, bool = __has_const_void_pointer<_Alloc>::value>
 struct __const_void_pointer
@@ -1054,7 +1091,7 @@ struct __const_void_pointer
 template <class _Ptr, class _Alloc>
 struct __const_void_pointer<_Ptr, _Alloc, false>
 {
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     typedef typename pointer_traits<_Ptr>::template rebind<const void> type;
 #else
     typedef typename pointer_traits<_Ptr>::template rebind<const void>::other type;
@@ -1062,13 +1099,14 @@ struct __const_void_pointer<_Ptr, _Alloc, false>
 };
 
 template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
 _Tp*
 __to_raw_pointer(_Tp* __p) _NOEXCEPT
 {
     return __p;
 }
 
+#if _LIBCPP_STD_VER <= 17
 template <class _Pointer>
 inline _LIBCPP_INLINE_VISIBILITY
 typename pointer_traits<_Pointer>::element_type*
@@ -1076,17 +1114,48 @@ __to_raw_pointer(_Pointer __p) _NOEXCEPT
 {
     return _VSTD::__to_raw_pointer(__p.operator->());
 }
+#else
+template <class _Pointer>
+inline _LIBCPP_INLINE_VISIBILITY
+auto
+__to_raw_pointer(const _Pointer& __p) _NOEXCEPT
+-> decltype(pointer_traits<_Pointer>::to_address(__p))
+{
+    return pointer_traits<_Pointer>::to_address(__p);
+}
+
+template <class _Pointer, class... _None>
+inline _LIBCPP_INLINE_VISIBILITY
+auto
+__to_raw_pointer(const _Pointer& __p, _None...) _NOEXCEPT
+{
+    return _VSTD::__to_raw_pointer(__p.operator->());
+}
 
 template <class _Tp>
-struct __has_size_type
+inline _LIBCPP_INLINE_VISIBILITY constexpr
+_Tp*
+to_address(_Tp* __p) _NOEXCEPT
 {
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::size_type* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
-};
+    static_assert(!is_function_v<_Tp>, "_Tp is a function type");
+    return __p;
+}
+
+template <class _Pointer>
+inline _LIBCPP_INLINE_VISIBILITY
+auto
+to_address(const _Pointer& __p) _NOEXCEPT
+{
+    return _VSTD::__to_raw_pointer(__p);
+}
+#endif
+
+template <class _Tp, class = void>
+struct __has_size_type : false_type {};
+
+template <class _Tp>
+struct __has_size_type<_Tp,
+               typename __void_t<typename _Tp::size_type>::type> : true_type {};
 
 template <class _Alloc, class _DiffType, bool = __has_size_type<_Alloc>::value>
 struct __size_type
@@ -1100,16 +1169,13 @@ struct __size_type<_Alloc, _DiffType, true>
     typedef typename _Alloc::size_type type;
 };
 
+template <class _Tp, class = void>
+struct __has_propagate_on_container_copy_assignment : false_type {};
+
 template <class _Tp>
-struct __has_propagate_on_container_copy_assignment
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::propagate_on_container_copy_assignment* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
-};
+struct __has_propagate_on_container_copy_assignment<_Tp,
+    typename __void_t<typename _Tp::propagate_on_container_copy_assignment>::type>
+        : true_type {};
 
 template <class _Alloc, bool = __has_propagate_on_container_copy_assignment<_Alloc>::value>
 struct __propagate_on_container_copy_assignment
@@ -1123,16 +1189,13 @@ struct __propagate_on_container_copy_assignment<_Alloc, true>
     typedef typename _Alloc::propagate_on_container_copy_assignment type;
 };
 
+template <class _Tp, class = void>
+struct __has_propagate_on_container_move_assignment : false_type {};
+
 template <class _Tp>
-struct __has_propagate_on_container_move_assignment
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::propagate_on_container_move_assignment* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
-};
+struct __has_propagate_on_container_move_assignment<_Tp,
+           typename __void_t<typename _Tp::propagate_on_container_move_assignment>::type>
+               : true_type {};
 
 template <class _Alloc, bool = __has_propagate_on_container_move_assignment<_Alloc>::value>
 struct __propagate_on_container_move_assignment
@@ -1146,16 +1209,13 @@ struct __propagate_on_container_move_assignment<_Alloc, true>
     typedef typename _Alloc::propagate_on_container_move_assignment type;
 };
 
+template <class _Tp, class = void>
+struct __has_propagate_on_container_swap : false_type {};
+
 template <class _Tp>
-struct __has_propagate_on_container_swap
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::propagate_on_container_swap* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
-};
+struct __has_propagate_on_container_swap<_Tp,
+           typename __void_t<typename _Tp::propagate_on_container_swap>::type>
+               : true_type {};
 
 template <class _Alloc, bool = __has_propagate_on_container_swap<_Alloc>::value>
 struct __propagate_on_container_swap
@@ -1169,16 +1229,13 @@ struct __propagate_on_container_swap<_Alloc, true>
     typedef typename _Alloc::propagate_on_container_swap type;
 };
 
+template <class _Tp, class = void>
+struct __has_is_always_equal : false_type {};
+
 template <class _Tp>
-struct __has_is_always_equal
-{
-private:
-    struct __two {char __lx; char __lxx;};
-    template <class _Up> static __two __test(...);
-    template <class _Up> static char __test(typename _Up::is_always_equal* = 0);
-public:
-    static const bool value = sizeof(__test<_Tp>(0)) == 1;
-};
+struct __has_is_always_equal<_Tp,
+           typename __void_t<typename _Tp::is_always_equal>::type>
+               : true_type {};
 
 template <class _Alloc, bool = __has_is_always_equal<_Alloc>::value>
 struct __is_always_equal
@@ -1285,12 +1342,12 @@ struct __allocator_traits_rebind<_Alloc<_Tp, _A0, _A1, _A2>, _Up, false>
 
 #endif  // _LIBCPP_HAS_NO_VARIADICS
 
-#ifndef _LIBCPP_HAS_NO_ADVANCED_SFINAE
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Alloc, class _SizeType, class _ConstVoidPtr>
 auto
 __has_allocate_hint_test(_Alloc&& __a, _SizeType&& __sz, _ConstVoidPtr&& __p)
-    -> decltype(__a.allocate(__sz, __p), true_type());
+    -> decltype((void)__a.allocate(__sz, __p), true_type());
 
 template <class _Alloc, class _SizeType, class _ConstVoidPtr>
 auto
@@ -1301,14 +1358,14 @@ template <class _Alloc, class _SizeType, class _ConstVoidPtr>
 struct __has_allocate_hint
     : integral_constant<bool,
         is_same<
-            decltype(__has_allocate_hint_test(declval<_Alloc>(),
+            decltype(_VSTD::__has_allocate_hint_test(declval<_Alloc>(),
                                           declval<_SizeType>(),
                                           declval<_ConstVoidPtr>())),
             true_type>::value>
 {
 };
 
-#else  // _LIBCPP_HAS_NO_ADVANCED_SFINAE
+#else  // _LIBCPP_CXX03_LANG
 
 template <class _Alloc, class _SizeType, class _ConstVoidPtr>
 struct __has_allocate_hint
@@ -1316,9 +1373,9 @@ struct __has_allocate_hint
 {
 };
 
-#endif  // _LIBCPP_HAS_NO_ADVANCED_SFINAE
+#endif  // _LIBCPP_CXX03_LANG
 
-#if !defined(_LIBCPP_HAS_NO_ADVANCED_SFINAE) && !defined(_LIBCPP_HAS_NO_VARIADICS)
+#if !defined(_LIBCPP_CXX03_LANG)
 
 template <class _Alloc, class _Tp, class ..._Args>
 decltype(_VSTD::declval<_Alloc>().construct(_VSTD::declval<_Tp*>(),
@@ -1334,7 +1391,7 @@ template <class _Alloc, class _Pointer, class ..._Args>
 struct __has_construct
     : integral_constant<bool,
         is_same<
-            decltype(__has_construct_test(declval<_Alloc>(),
+            decltype(_VSTD::__has_construct_test(declval<_Alloc>(),
                                           declval<_Pointer>(),
                                           declval<_Args>()...)),
             true_type>::value>
@@ -1355,7 +1412,7 @@ template <class _Alloc, class _Pointer>
 struct __has_destroy
     : integral_constant<bool,
         is_same<
-            decltype(__has_destroy_test(declval<_Alloc>(),
+            decltype(_VSTD::__has_destroy_test(declval<_Alloc>(),
                                         declval<_Pointer>())),
             true_type>::value>
 {
@@ -1375,7 +1432,7 @@ template <class _Alloc>
 struct __has_max_size
     : integral_constant<bool,
         is_same<
-            decltype(__has_max_size_test(declval<_Alloc&>())),
+            decltype(_VSTD::__has_max_size_test(declval<_Alloc&>())),
             true_type>::value>
 {
 };
@@ -1394,12 +1451,12 @@ template <class _Alloc>
 struct __has_select_on_container_copy_construction
     : integral_constant<bool,
         is_same<
-            decltype(__has_select_on_container_copy_construction_test(declval<_Alloc&>())),
+            decltype(_VSTD::__has_select_on_container_copy_construction_test(declval<_Alloc&>())),
             true_type>::value>
 {
 };
 
-#else  // _LIBCPP_HAS_NO_ADVANCED_SFINAE
+#else  // _LIBCPP_CXX03_LANG
 
 #ifndef _LIBCPP_HAS_NO_VARIADICS
 
@@ -1437,7 +1494,7 @@ struct __has_select_on_container_copy_construction
 {
 };
 
-#endif  // _LIBCPP_HAS_NO_ADVANCED_SFINAE
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Alloc, class _Ptr, bool = __has_difference_type<_Alloc>::value>
 struct __alloc_traits_difference_type
@@ -1452,7 +1509,7 @@ struct __alloc_traits_difference_type<_Alloc, _Ptr, true>
 };
 
 template <class _Alloc>
-struct _LIBCPP_TYPE_VIS_ONLY allocator_traits
+struct _LIBCPP_TEMPLATE_VIS allocator_traits
 {
     typedef _Alloc                              allocator_type;
     typedef typename allocator_type::value_type value_type;
@@ -1474,23 +1531,23 @@ struct _LIBCPP_TYPE_VIS_ONLY allocator_traits
     typedef typename __is_always_equal<allocator_type>::type
                      is_always_equal;
 
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     template <class _Tp> using rebind_alloc =
                   typename __allocator_traits_rebind<allocator_type, _Tp>::type;
     template <class _Tp> using rebind_traits = allocator_traits<rebind_alloc<_Tp>>;
-#else  // _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#else  // _LIBCPP_CXX03_LANG
     template <class _Tp> struct rebind_alloc
         {typedef typename __allocator_traits_rebind<allocator_type, _Tp>::type other;};
     template <class _Tp> struct rebind_traits
         {typedef allocator_traits<typename rebind_alloc<_Tp>::other> other;};
-#endif  // _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#endif  // _LIBCPP_CXX03_LANG
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     static pointer allocate(allocator_type& __a, size_type __n)
         {return __a.allocate(__n);}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     static pointer allocate(allocator_type& __a, size_type __n, const_void_pointer __hint)
-        {return allocate(__a, __n, __hint,
+        {return __allocate(__a, __n, __hint,
             __has_allocate_hint<allocator_type, size_type, const_void_pointer>());}
 
     _LIBCPP_INLINE_VISIBILITY
@@ -1506,26 +1563,26 @@ struct _LIBCPP_TYPE_VIS_ONLY allocator_traits
 #else  // _LIBCPP_HAS_NO_VARIADICS
     template <class _Tp>
         _LIBCPP_INLINE_VISIBILITY
-        static void construct(allocator_type& __a, _Tp* __p)
+        static void construct(allocator_type&, _Tp* __p)
             {
                 ::new ((void*)__p) _Tp();
             }
     template <class _Tp, class _A0>
         _LIBCPP_INLINE_VISIBILITY
-        static void construct(allocator_type& __a, _Tp* __p, const _A0& __a0)
+        static void construct(allocator_type&, _Tp* __p, const _A0& __a0)
             {
                 ::new ((void*)__p) _Tp(__a0);
             }
     template <class _Tp, class _A0, class _A1>
         _LIBCPP_INLINE_VISIBILITY
-        static void construct(allocator_type& __a, _Tp* __p, const _A0& __a0,
+        static void construct(allocator_type&, _Tp* __p, const _A0& __a0,
                               const _A1& __a1)
             {
                 ::new ((void*)__p) _Tp(__a0, __a1);
             }
     template <class _Tp, class _A0, class _A1, class _A2>
         _LIBCPP_INLINE_VISIBILITY
-        static void construct(allocator_type& __a, _Tp* __p, const _A0& __a0,
+        static void construct(allocator_type&, _Tp* __p, const _A0& __a0,
                               const _A1& __a1, const _A2& __a2)
             {
                 ::new ((void*)__p) _Tp(__a0, __a1, __a2);
@@ -1544,7 +1601,7 @@ struct _LIBCPP_TYPE_VIS_ONLY allocator_traits
     _LIBCPP_INLINE_VISIBILITY
     static allocator_type
         select_on_container_copy_construction(const allocator_type& __a)
-            {return select_on_container_copy_construction(
+            {return __select_on_container_copy_construction(
                 __has_select_on_container_copy_construction<const allocator_type>(),
                 __a);}
 
@@ -1568,7 +1625,7 @@ struct _LIBCPP_TYPE_VIS_ONLY allocator_traits
              is_trivially_move_constructible<_Tp>::value,
             void
         >::type
-        __construct_forward(allocator_type& __a, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2)
+        __construct_forward(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2)
         {
             ptrdiff_t _Np = __end1 - __begin1;
             if (_Np > 0)
@@ -1598,7 +1655,7 @@ struct _LIBCPP_TYPE_VIS_ONLY allocator_traits
              is_trivially_move_constructible<_Tp>::value,
             void
         >::type
-        __construct_range_forward(allocator_type& __a, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2)
+        __construct_range_forward(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2)
         {
             typedef typename remove_const<_Tp>::type _Vp;
             ptrdiff_t _Np = __end1 - __begin1;
@@ -1632,7 +1689,7 @@ struct _LIBCPP_TYPE_VIS_ONLY allocator_traits
              is_trivially_move_constructible<_Tp>::value,
             void
         >::type
-        __construct_backward(allocator_type& __a, _Tp* __begin1, _Tp* __end1, _Tp*& __end2)
+        __construct_backward(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __end2)
         {
             ptrdiff_t _Np = __end1 - __begin1;
             __end2 -= _Np;
@@ -1643,11 +1700,11 @@ struct _LIBCPP_TYPE_VIS_ONLY allocator_traits
 private:
 
     _LIBCPP_INLINE_VISIBILITY
-    static pointer allocate(allocator_type& __a, size_type __n,
+    static pointer __allocate(allocator_type& __a, size_type __n,
         const_void_pointer __hint, true_type)
         {return __a.allocate(__n, __hint);}
     _LIBCPP_INLINE_VISIBILITY
-    static pointer allocate(allocator_type& __a, size_type __n,
+    static pointer __allocate(allocator_type& __a, size_type __n,
         const_void_pointer, false_type)
         {return __a.allocate(__n);}
 
@@ -1676,26 +1733,26 @@ private:
             }
 
     _LIBCPP_INLINE_VISIBILITY
-    static size_type __max_size(true_type, const allocator_type& __a)
+    static size_type __max_size(true_type, const allocator_type& __a) _NOEXCEPT
             {return __a.max_size();}
     _LIBCPP_INLINE_VISIBILITY
-    static size_type __max_size(false_type, const allocator_type&)
+    static size_type __max_size(false_type, const allocator_type&) _NOEXCEPT
             {return numeric_limits<size_type>::max() / sizeof(value_type);}
 
     _LIBCPP_INLINE_VISIBILITY
     static allocator_type
-        select_on_container_copy_construction(true_type, const allocator_type& __a)
+        __select_on_container_copy_construction(true_type, const allocator_type& __a)
             {return __a.select_on_container_copy_construction();}
     _LIBCPP_INLINE_VISIBILITY
     static allocator_type
-        select_on_container_copy_construction(false_type, const allocator_type& __a)
+        __select_on_container_copy_construction(false_type, const allocator_type& __a)
             {return __a;}
 };
 
 template <class _Traits, class _Tp>
 struct __rebind_alloc_helper
 {
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
     typedef typename _Traits::template rebind_alloc<_Tp>        type;
 #else
     typedef typename _Traits::template rebind_alloc<_Tp>::other type;
@@ -1705,7 +1762,7 @@ struct __rebind_alloc_helper
 // allocator
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY allocator
+class _LIBCPP_TEMPLATE_VIS allocator
 {
 public:
     typedef size_t            size_type;
@@ -1727,15 +1784,16 @@ public:
         {return _VSTD::addressof(__x);}
     _LIBCPP_INLINE_VISIBILITY const_pointer address(const_reference __x) const _NOEXCEPT
         {return _VSTD::addressof(__x);}
-    _LIBCPP_INLINE_VISIBILITY pointer allocate(size_type __n, allocator<void>::const_pointer = 0)
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY 
+    pointer allocate(size_type __n, allocator<void>::const_pointer = 0)
         {
         if (__n > max_size())
-            __libcpp_throw(length_error("allocator<T>::allocate(size_t n)"
-                                      " 'n' exceeds maximum supported size"));
+            __throw_length_error("allocator<T>::allocate(size_t n)"
+                                 " 'n' exceeds maximum supported size");
         return static_cast<pointer>(_VSTD::__allocate(__n * sizeof(_Tp)));
         }
     _LIBCPP_INLINE_VISIBILITY void deallocate(pointer __p, size_type) _NOEXCEPT
-        {_VSTD::__deallocate((void*)__p);}
+        {_VSTD::__libcpp_deallocate((void*)__p);}
     _LIBCPP_INLINE_VISIBILITY size_type max_size() const _NOEXCEPT
         {return size_type(~0) / sizeof(_Tp);}
 #if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
@@ -1803,7 +1861,7 @@ public:
 };
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY allocator<const _Tp>
+class _LIBCPP_TEMPLATE_VIS allocator<const _Tp>
 {
 public:
     typedef size_t            size_type;
@@ -1826,12 +1884,12 @@ public:
     _LIBCPP_INLINE_VISIBILITY pointer allocate(size_type __n, allocator<void>::const_pointer = 0)
     {
         if (__n > max_size())
-            __libcpp_throw(length_error("allocator<const T>::allocate(size_t n)"
-                                      " 'n' exceeds maximum supported size"));
+            __throw_length_error("allocator<const T>::allocate(size_t n)"
+                                 " 'n' exceeds maximum supported size");
         return static_cast<pointer>(_VSTD::__allocate(__n * sizeof(_Tp)));
     }
     _LIBCPP_INLINE_VISIBILITY void deallocate(pointer __p, size_type) _NOEXCEPT
-        {_VSTD::__deallocate((void*)__p);}
+        {_VSTD::__libcpp_deallocate((void*) const_cast<_Tp *>(__p));}
     _LIBCPP_INLINE_VISIBILITY size_type max_size() const _NOEXCEPT
         {return size_type(~0) / sizeof(_Tp);}
 #if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
@@ -1847,7 +1905,7 @@ public:
         void
         construct(pointer __p)
         {
-            ::new((void*)__p) _Tp();
+            ::new((void*) const_cast<_Tp *>(__p)) _Tp();
         }
 # if defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
 
@@ -1856,14 +1914,14 @@ public:
         void
         construct(pointer __p, _A0& __a0)
         {
-            ::new((void*)__p) _Tp(__a0);
+            ::new((void*) const_cast<_Tp *>(__p)) _Tp(__a0);
         }
     template <class _A0>
         _LIBCPP_INLINE_VISIBILITY
         void
         construct(pointer __p, const _A0& __a0)
         {
-            ::new((void*)__p) _Tp(__a0);
+            ::new((void*) const_cast<_Tp *>(__p)) _Tp(__a0);
         }
 # endif  // defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
     template <class _A0, class _A1>
@@ -1871,28 +1929,28 @@ public:
         void
         construct(pointer __p, _A0& __a0, _A1& __a1)
         {
-            ::new((void*)__p) _Tp(__a0, __a1);
+            ::new((void*) const_cast<_Tp *>(__p)) _Tp(__a0, __a1);
         }
     template <class _A0, class _A1>
         _LIBCPP_INLINE_VISIBILITY
         void
         construct(pointer __p, const _A0& __a0, _A1& __a1)
         {
-            ::new((void*)__p) _Tp(__a0, __a1);
+            ::new((void*) const_cast<_Tp *>(__p)) _Tp(__a0, __a1);
         }
     template <class _A0, class _A1>
         _LIBCPP_INLINE_VISIBILITY
         void
         construct(pointer __p, _A0& __a0, const _A1& __a1)
         {
-            ::new((void*)__p) _Tp(__a0, __a1);
+            ::new((void*) const_cast<_Tp *>(__p)) _Tp(__a0, __a1);
         }
     template <class _A0, class _A1>
         _LIBCPP_INLINE_VISIBILITY
         void
         construct(pointer __p, const _A0& __a0, const _A1& __a1)
         {
-            ::new((void*)__p) _Tp(__a0, __a1);
+            ::new((void*) const_cast<_Tp *>(__p)) _Tp(__a0, __a1);
         }
 #endif  // !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
     _LIBCPP_INLINE_VISIBILITY void destroy(pointer __p) {__p->~_Tp();}
@@ -1907,7 +1965,7 @@ inline _LIBCPP_INLINE_VISIBILITY
 bool operator!=(const allocator<_Tp>&, const allocator<_Up>&) _NOEXCEPT {return false;}
 
 template <class _OutputIterator, class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY raw_storage_iterator
+class _LIBCPP_TEMPLATE_VIS raw_storage_iterator
     : public iterator<output_iterator_tag,
                       _Tp,                                         // purposefully not C++03
                       ptrdiff_t,                                   // purposefully not C++03
@@ -1929,7 +1987,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY raw_storage_iterator  operator++(int)
         {raw_storage_iterator __t(*this); ++__x_; return __t;}
 #if _LIBCPP_STD_VER >= 14
-    _LIBCPP_INLINE_VISIBILITY _OutputIterator base() const { return __x_; } 
+    _LIBCPP_INLINE_VISIBILITY _OutputIterator base() const { return __x_; }
 #endif
 };
 
@@ -1960,6 +2018,7 @@ template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 void return_temporary_buffer(_Tp* __p) _NOEXCEPT {::operator delete(__p);}
 
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
 template <class _Tp>
 struct auto_ptr_ref
 {
@@ -1967,7 +2026,7 @@ struct auto_ptr_ref
 };
 
 template<class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY auto_ptr
+class _LIBCPP_TEMPLATE_VIS auto_ptr
 {
 private:
     _Tp* __ptr_;
@@ -2011,961 +2070,830 @@ public:
 };
 
 template <>
-class _LIBCPP_TYPE_VIS_ONLY auto_ptr<void>
+class _LIBCPP_TEMPLATE_VIS auto_ptr<void>
 {
 public:
     typedef void element_type;
 };
+#endif
 
-template <class _T1, class _T2, bool = is_same<typename remove_cv<_T1>::type,
-                                                     typename remove_cv<_T2>::type>::value,
-                                bool = is_empty<_T1>::value
-                                       && !__libcpp_is_final<_T1>::value,
-                                bool = is_empty<_T2>::value
-                                       && !__libcpp_is_final<_T2>::value
-         >
-struct __libcpp_compressed_pair_switch;
+template <class _Tp, int _Idx,
+          bool _CanBeEmptyBase =
+              is_empty<_Tp>::value && !__libcpp_is_final<_Tp>::value>
+struct __compressed_pair_elem {
+  typedef _Tp _ParamT;
+  typedef _Tp& reference;
+  typedef const _Tp& const_reference;
+
+#ifndef _LIBCPP_CXX03_LANG
+  _LIBCPP_INLINE_VISIBILITY constexpr __compressed_pair_elem() : __value_() {}
+
+  template <class _Up, class = typename enable_if<
+      !is_same<__compressed_pair_elem, typename decay<_Up>::type>::value
+  >::type>
+  _LIBCPP_INLINE_VISIBILITY
+  constexpr explicit
+  __compressed_pair_elem(_Up&& __u)
+      : __value_(_VSTD::forward<_Up>(__u)){};
+
+  template <class... _Args, size_t... _Indexes>
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+  __compressed_pair_elem(piecewise_construct_t, tuple<_Args...> __args,
+                         __tuple_indices<_Indexes...>)
+      : __value_(_VSTD::forward<_Args>(_VSTD::get<_Indexes>(__args))...) {}
+#else
+  _LIBCPP_INLINE_VISIBILITY __compressed_pair_elem() : __value_() {}
+  _LIBCPP_INLINE_VISIBILITY
+  __compressed_pair_elem(_ParamT __p) : __value_(std::forward<_ParamT>(__p)) {}
+#endif
 
-template <class _T1, class _T2, bool IsSame>
-struct __libcpp_compressed_pair_switch<_T1, _T2, IsSame, false, false> {enum {value = 0};};
+  _LIBCPP_INLINE_VISIBILITY reference __get() _NOEXCEPT { return __value_; }
+  _LIBCPP_INLINE_VISIBILITY
+  const_reference __get() const _NOEXCEPT { return __value_; }
 
-template <class _T1, class _T2, bool IsSame>
-struct __libcpp_compressed_pair_switch<_T1, _T2, IsSame, true, false>  {enum {value = 1};};
+private:
+  _Tp __value_;
+};
+
+template <class _Tp, int _Idx>
+struct __compressed_pair_elem<_Tp, _Idx, true> : private _Tp {
+  typedef _Tp _ParamT;
+  typedef _Tp& reference;
+  typedef const _Tp& const_reference;
+  typedef _Tp __value_type;
+
+#ifndef _LIBCPP_CXX03_LANG
+  _LIBCPP_INLINE_VISIBILITY constexpr __compressed_pair_elem() = default;
+
+  template <class _Up, class = typename enable_if<
+        !is_same<__compressed_pair_elem, typename decay<_Up>::type>::value
+  >::type>
+  _LIBCPP_INLINE_VISIBILITY
+  constexpr explicit
+  __compressed_pair_elem(_Up&& __u)
+      : __value_type(_VSTD::forward<_Up>(__u)){};
+
+  template <class... _Args, size_t... _Indexes>
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+  __compressed_pair_elem(piecewise_construct_t, tuple<_Args...> __args,
+                         __tuple_indices<_Indexes...>)
+      : __value_type(_VSTD::forward<_Args>(_VSTD::get<_Indexes>(__args))...) {}
+#else
+  _LIBCPP_INLINE_VISIBILITY __compressed_pair_elem() : __value_type() {}
+  _LIBCPP_INLINE_VISIBILITY
+  __compressed_pair_elem(_ParamT __p)
+      : __value_type(std::forward<_ParamT>(__p)) {}
+#endif
 
-template <class _T1, class _T2, bool IsSame>
-struct __libcpp_compressed_pair_switch<_T1, _T2, IsSame, false, true>  {enum {value = 2};};
+  _LIBCPP_INLINE_VISIBILITY reference __get() _NOEXCEPT { return *this; }
+  _LIBCPP_INLINE_VISIBILITY
+  const_reference __get() const _NOEXCEPT { return *this; }
+};
 
-template <class _T1, class _T2>
-struct __libcpp_compressed_pair_switch<_T1, _T2, false, true, true>    {enum {value = 3};};
+// Tag used to construct the second element of the compressed pair.
+struct __second_tag {};
 
 template <class _T1, class _T2>
-struct __libcpp_compressed_pair_switch<_T1, _T2, true, true, true>     {enum {value = 1};};
-
-template <class _T1, class _T2, unsigned = __libcpp_compressed_pair_switch<_T1, _T2>::value>
-class __libcpp_compressed_pair_imp;
+class __compressed_pair : private __compressed_pair_elem<_T1, 0>,
+                          private __compressed_pair_elem<_T2, 1> {
+  typedef __compressed_pair_elem<_T1, 0> _Base1;
+  typedef __compressed_pair_elem<_T2, 1> _Base2;
+
+  // NOTE: This static assert should never fire because __compressed_pair
+  // is *almost never* used in a scenario where it's possible for T1 == T2.
+  // (The exception is std::function where it is possible that the function
+  //  object and the allocator have the same type).
+  static_assert((!is_same<_T1, _T2>::value),
+    "__compressed_pair cannot be instantated when T1 and T2 are the same type; "
+    "The current implementation is NOT ABI-compatible with the previous "
+    "implementation for this configuration");
 
-template <class _T1, class _T2>
-class __libcpp_compressed_pair_imp<_T1, _T2, 0>
-{
-private:
-    _T1 __first_;
-    _T2 __second_;
 public:
-    typedef _T1 _T1_param;
-    typedef _T2 _T2_param;
-
-    typedef typename remove_reference<_T1>::type& _T1_reference;
-    typedef typename remove_reference<_T2>::type& _T2_reference;
-
-    typedef const typename remove_reference<_T1>::type& _T1_const_reference;
-    typedef const typename remove_reference<_T2>::type& _T2_const_reference;
-
-    _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp() : __first_(), __second_() {}
-    _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T1_param __t1)
-        : __first_(_VSTD::forward<_T1_param>(__t1)), __second_() {}
-    _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T2_param __t2)
-        : __first_(), __second_(_VSTD::forward<_T2_param>(__t2)) {}
-    _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp(_T1_param __t1, _T2_param __t2)
-        : __first_(_VSTD::forward<_T1_param>(__t1)), __second_(_VSTD::forward<_T2_param>(__t2)) {}
-
-#if defined(_LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS) && !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
-
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp(const __libcpp_compressed_pair_imp& __p)
-        _NOEXCEPT_(is_nothrow_copy_constructible<_T1>::value &&
-                   is_nothrow_copy_constructible<_T2>::value)
-        : __first_(__p.first()),
-          __second_(__p.second()) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp& operator=(const __libcpp_compressed_pair_imp& __p)
-        _NOEXCEPT_(is_nothrow_copy_assignable<_T1>::value &&
-                   is_nothrow_copy_assignable<_T2>::value)
-        {
-            __first_ = __p.first();
-            __second_ = __p.second();
-            return *this;
-        }
+#ifndef _LIBCPP_CXX03_LANG
+  template <bool _Dummy = true,
+      class = typename enable_if<
+          __dependent_type<is_default_constructible<_T1>, _Dummy>::value &&
+          __dependent_type<is_default_constructible<_T2>, _Dummy>::value
+      >::type
+  >
+  _LIBCPP_INLINE_VISIBILITY
+  constexpr __compressed_pair() {}
+
+  template <class _Tp, typename enable_if<!is_same<typename decay<_Tp>::type,
+                                                   __compressed_pair>::value,
+                                          bool>::type = true>
+  _LIBCPP_INLINE_VISIBILITY constexpr explicit
+  __compressed_pair(_Tp&& __t)
+      : _Base1(std::forward<_Tp>(__t)), _Base2() {}
+
+  template <class _Tp>
+  _LIBCPP_INLINE_VISIBILITY constexpr
+  __compressed_pair(__second_tag, _Tp&& __t)
+      : _Base1(), _Base2(std::forward<_Tp>(__t)) {}
+
+  template <class _U1, class _U2>
+  _LIBCPP_INLINE_VISIBILITY constexpr
+  __compressed_pair(_U1&& __t1, _U2&& __t2)
+      : _Base1(std::forward<_U1>(__t1)), _Base2(std::forward<_U2>(__t2)) {}
+
+  template <class... _Args1, class... _Args2>
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+  __compressed_pair(piecewise_construct_t __pc, tuple<_Args1...> __first_args,
+                    tuple<_Args2...> __second_args)
+      : _Base1(__pc, _VSTD::move(__first_args),
+               typename __make_tuple_indices<sizeof...(_Args1)>::type()),
+        _Base2(__pc, _VSTD::move(__second_args),
+               typename __make_tuple_indices<sizeof...(_Args2)>::type()) {}
 
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp(__libcpp_compressed_pair_imp&& __p)
-        _NOEXCEPT_(is_nothrow_move_constructible<_T1>::value &&
-                   is_nothrow_move_constructible<_T2>::value)
-        : __first_(_VSTD::forward<_T1>(__p.first())),
-          __second_(_VSTD::forward<_T2>(__p.second())) {}
+#else
+  _LIBCPP_INLINE_VISIBILITY
+  __compressed_pair() {}
 
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp& operator=(__libcpp_compressed_pair_imp&& __p)
-        _NOEXCEPT_(is_nothrow_move_assignable<_T1>::value &&
-                   is_nothrow_move_assignable<_T2>::value)
-        {
-            __first_ = _VSTD::forward<_T1>(__p.first());
-            __second_ = _VSTD::forward<_T2>(__p.second());
-            return *this;
-        }
+  _LIBCPP_INLINE_VISIBILITY explicit
+  __compressed_pair(_T1 __t1) : _Base1(_VSTD::forward<_T1>(__t1)) {}
 
-#endif  // defined(_LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS) && !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+  _LIBCPP_INLINE_VISIBILITY
+  __compressed_pair(__second_tag, _T2 __t2)
+      : _Base1(), _Base2(_VSTD::forward<_T2>(__t2)) {}
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+  _LIBCPP_INLINE_VISIBILITY
+  __compressed_pair(_T1 __t1, _T2 __t2)
+      : _Base1(_VSTD::forward<_T1>(__t1)), _Base2(_VSTD::forward<_T2>(__t2)) {}
+#endif
 
-    template <class... _Args1, class... _Args2, size_t... _I1, size_t... _I2>
-        _LIBCPP_INLINE_VISIBILITY
-        __libcpp_compressed_pair_imp(piecewise_construct_t __pc,
-                                     tuple<_Args1...> __first_args,
-                                     tuple<_Args2...> __second_args,
-                                     __tuple_indices<_I1...>,
-                                     __tuple_indices<_I2...>)
-            : __first_(_VSTD::forward<_Args1>(_VSTD::get<_I1>(__first_args))...),
-              __second_(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...)
-            {}
+  _LIBCPP_INLINE_VISIBILITY
+  typename _Base1::reference first() _NOEXCEPT {
+    return static_cast<_Base1&>(*this).__get();
+  }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+  _LIBCPP_INLINE_VISIBILITY
+  typename _Base1::const_reference first() const _NOEXCEPT {
+    return static_cast<_Base1 const&>(*this).__get();
+  }
 
-    _LIBCPP_INLINE_VISIBILITY _T1_reference       first() _NOEXCEPT       {return __first_;}
-    _LIBCPP_INLINE_VISIBILITY _T1_const_reference first() const _NOEXCEPT {return __first_;}
+  _LIBCPP_INLINE_VISIBILITY
+  typename _Base2::reference second() _NOEXCEPT {
+    return static_cast<_Base2&>(*this).__get();
+  }
 
-    _LIBCPP_INLINE_VISIBILITY _T2_reference       second() _NOEXCEPT       {return __second_;}
-    _LIBCPP_INLINE_VISIBILITY _T2_const_reference second() const _NOEXCEPT {return __second_;}
+  _LIBCPP_INLINE_VISIBILITY
+  typename _Base2::const_reference second() const _NOEXCEPT {
+    return static_cast<_Base2 const&>(*this).__get();
+  }
 
-    _LIBCPP_INLINE_VISIBILITY void swap(__libcpp_compressed_pair_imp& __x)
-        _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
-                   __is_nothrow_swappable<_T2>::value)
-    {
-        using _VSTD::swap;
-        swap(__first_, __x.__first_);
-        swap(__second_, __x.__second_);
-    }
+  _LIBCPP_INLINE_VISIBILITY
+  void swap(__compressed_pair& __x)
+    _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
+               __is_nothrow_swappable<_T2>::value)
+  {
+    using std::swap;
+    swap(first(), __x.first());
+    swap(second(), __x.second());
+  }
 };
 
 template <class _T1, class _T2>
-class __libcpp_compressed_pair_imp<_T1, _T2, 1>
-    : private _T1
-{
-private:
-    _T2 __second_;
-public:
-    typedef _T1 _T1_param;
-    typedef _T2 _T2_param;
-
-    typedef _T1&                                        _T1_reference;
-    typedef typename remove_reference<_T2>::type& _T2_reference;
-
-    typedef const _T1&                                        _T1_const_reference;
-    typedef const typename remove_reference<_T2>::type& _T2_const_reference;
-
-    _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp() : __second_() {}
-    _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T1_param __t1)
-        : _T1(_VSTD::forward<_T1_param>(__t1)), __second_() {}
-    _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T2_param __t2)
-        : __second_(_VSTD::forward<_T2_param>(__t2)) {}
-    _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp(_T1_param __t1, _T2_param __t2)
-        : _T1(_VSTD::forward<_T1_param>(__t1)), __second_(_VSTD::forward<_T2_param>(__t2)) {}
-
-#if defined(_LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS) && !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
-
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp(const __libcpp_compressed_pair_imp& __p)
-        _NOEXCEPT_(is_nothrow_copy_constructible<_T1>::value &&
-                   is_nothrow_copy_constructible<_T2>::value)
-        : _T1(__p.first()), __second_(__p.second()) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp& operator=(const __libcpp_compressed_pair_imp& __p)
-        _NOEXCEPT_(is_nothrow_copy_assignable<_T1>::value &&
-                   is_nothrow_copy_assignable<_T2>::value)
-        {
-            _T1::operator=(__p.first());
-            __second_ = __p.second();
-            return *this;
-        }
-
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp(__libcpp_compressed_pair_imp&& __p)
-        _NOEXCEPT_(is_nothrow_move_constructible<_T1>::value &&
-                   is_nothrow_move_constructible<_T2>::value)
-        : _T1(_VSTD::move(__p.first())), __second_(_VSTD::forward<_T2>(__p.second())) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp& operator=(__libcpp_compressed_pair_imp&& __p)
-        _NOEXCEPT_(is_nothrow_move_assignable<_T1>::value &&
-                   is_nothrow_move_assignable<_T2>::value)
-        {
-            _T1::operator=(_VSTD::move(__p.first()));
-            __second_ = _VSTD::forward<_T2>(__p.second());
-            return *this;
-        }
-
-#endif  // defined(_LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS) && !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
-
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
-    template <class... _Args1, class... _Args2, size_t... _I1, size_t... _I2>
-        _LIBCPP_INLINE_VISIBILITY
-        __libcpp_compressed_pair_imp(piecewise_construct_t __pc,
-                                     tuple<_Args1...> __first_args,
-                                     tuple<_Args2...> __second_args,
-                                     __tuple_indices<_I1...>,
-                                     __tuple_indices<_I2...>)
-            : _T1(_VSTD::forward<_Args1>(_VSTD::get<_I1>(__first_args))...),
-              __second_(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...)
-            {}
-
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-
-    _LIBCPP_INLINE_VISIBILITY _T1_reference       first() _NOEXCEPT       {return *this;}
-    _LIBCPP_INLINE_VISIBILITY _T1_const_reference first() const _NOEXCEPT {return *this;}
+inline _LIBCPP_INLINE_VISIBILITY
+void swap(__compressed_pair<_T1, _T2>& __x, __compressed_pair<_T1, _T2>& __y)
+    _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
+               __is_nothrow_swappable<_T2>::value) {
+  __x.swap(__y);
+}
 
-    _LIBCPP_INLINE_VISIBILITY _T2_reference       second() _NOEXCEPT       {return __second_;}
-    _LIBCPP_INLINE_VISIBILITY _T2_const_reference second() const _NOEXCEPT {return __second_;}
+// default_delete
 
-    _LIBCPP_INLINE_VISIBILITY void swap(__libcpp_compressed_pair_imp& __x)
-        _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
-                   __is_nothrow_swappable<_T2>::value)
-    {
-        using _VSTD::swap;
-        swap(__second_, __x.__second_);
-    }
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS default_delete {
+    static_assert(!is_function<_Tp>::value,
+                  "default_delete cannot be instantiated for function types");
+#ifndef _LIBCPP_CXX03_LANG
+  _LIBCPP_INLINE_VISIBILITY constexpr default_delete() noexcept = default;
+#else
+  _LIBCPP_INLINE_VISIBILITY default_delete() {}
+#endif
+  template <class _Up>
+  _LIBCPP_INLINE_VISIBILITY
+  default_delete(const default_delete<_Up>&,
+                 typename enable_if<is_convertible<_Up*, _Tp*>::value>::type* =
+                     0) _NOEXCEPT {}
+
+  _LIBCPP_INLINE_VISIBILITY void operator()(_Tp* __ptr) const _NOEXCEPT {
+    static_assert(sizeof(_Tp) > 0,
+                  "default_delete can not delete incomplete type");
+    static_assert(!is_void<_Tp>::value,
+                  "default_delete can not delete incomplete type");
+    delete __ptr;
+  }
 };
 
-template <class _T1, class _T2>
-class __libcpp_compressed_pair_imp<_T1, _T2, 2>
-    : private _T2
-{
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS default_delete<_Tp[]> {
 private:
-    _T1 __first_;
-public:
-    typedef _T1 _T1_param;
-    typedef _T2 _T2_param;
-
-    typedef typename remove_reference<_T1>::type& _T1_reference;
-    typedef _T2&                                        _T2_reference;
-
-    typedef const typename remove_reference<_T1>::type& _T1_const_reference;
-    typedef const _T2&                                        _T2_const_reference;
-
-    _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp() : __first_() {}
-    _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T1_param __t1)
-        : __first_(_VSTD::forward<_T1_param>(__t1)) {}
-    _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T2_param __t2)
-        : _T2(_VSTD::forward<_T2_param>(__t2)), __first_() {}
-    _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp(_T1_param __t1, _T2_param __t2)
-        _NOEXCEPT_(is_nothrow_move_constructible<_T1>::value &&
-                   is_nothrow_move_constructible<_T2>::value)
-        : _T2(_VSTD::forward<_T2_param>(__t2)), __first_(_VSTD::forward<_T1_param>(__t1)) {}
-
-#if defined(_LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS) && !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+  template <class _Up>
+  struct _EnableIfConvertible
+      : enable_if<is_convertible<_Up(*)[], _Tp(*)[]>::value> {};
 
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp(const __libcpp_compressed_pair_imp& __p)
-        _NOEXCEPT_(is_nothrow_copy_constructible<_T1>::value &&
-                   is_nothrow_copy_constructible<_T2>::value)
-        : _T2(__p.second()), __first_(__p.first()) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp& operator=(const __libcpp_compressed_pair_imp& __p)
-        _NOEXCEPT_(is_nothrow_copy_assignable<_T1>::value &&
-                   is_nothrow_copy_assignable<_T2>::value)
-        {
-            _T2::operator=(__p.second());
-            __first_ = __p.first();
-            return *this;
-        }
-
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp(__libcpp_compressed_pair_imp&& __p)
-        _NOEXCEPT_(is_nothrow_move_constructible<_T1>::value &&
-                   is_nothrow_move_constructible<_T2>::value)
-        : _T2(_VSTD::forward<_T2>(__p.second())), __first_(_VSTD::move(__p.first())) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp& operator=(__libcpp_compressed_pair_imp&& __p)
-        _NOEXCEPT_(is_nothrow_move_assignable<_T1>::value &&
-                   is_nothrow_move_assignable<_T2>::value)
-        {
-            _T2::operator=(_VSTD::forward<_T2>(__p.second()));
-            __first_ = _VSTD::move(__p.first());
-            return *this;
-        }
-
-#endif  // defined(_LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS) && !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+public:
+#ifndef _LIBCPP_CXX03_LANG
+  _LIBCPP_INLINE_VISIBILITY constexpr default_delete() noexcept = default;
+#else
+  _LIBCPP_INLINE_VISIBILITY default_delete() {}
+#endif
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+  template <class _Up>
+  _LIBCPP_INLINE_VISIBILITY
+  default_delete(const default_delete<_Up[]>&,
+                 typename _EnableIfConvertible<_Up>::type* = 0) _NOEXCEPT {}
+
+  template <class _Up>
+  _LIBCPP_INLINE_VISIBILITY
+  typename _EnableIfConvertible<_Up>::type
+  operator()(_Up* __ptr) const _NOEXCEPT {
+    static_assert(sizeof(_Tp) > 0,
+                  "default_delete can not delete incomplete type");
+    static_assert(!is_void<_Tp>::value,
+                  "default_delete can not delete void type");
+    delete[] __ptr;
+  }
+};
 
-    template <class... _Args1, class... _Args2, size_t... _I1, size_t... _I2>
-        _LIBCPP_INLINE_VISIBILITY
-        __libcpp_compressed_pair_imp(piecewise_construct_t __pc,
-                                     tuple<_Args1...> __first_args,
-                                     tuple<_Args2...> __second_args,
-                                     __tuple_indices<_I1...>,
-                                     __tuple_indices<_I2...>)
-            : _T2(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...),
-              __first_(_VSTD::forward<_Args1>(_VSTD::get<_I1>(__first_args))...)
-              
-            {}
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
 
-    _LIBCPP_INLINE_VISIBILITY _T1_reference       first() _NOEXCEPT       {return __first_;}
-    _LIBCPP_INLINE_VISIBILITY _T1_const_reference first() const _NOEXCEPT {return __first_;}
+#ifndef _LIBCPP_CXX03_LANG
+template <class _Deleter>
+struct __unique_ptr_deleter_sfinae {
+  static_assert(!is_reference<_Deleter>::value, "incorrect specialization");
+  typedef const _Deleter& __lval_ref_type;
+  typedef _Deleter&& __good_rval_ref_type;
+  typedef true_type __enable_rval_overload;
+};
 
-    _LIBCPP_INLINE_VISIBILITY _T2_reference       second() _NOEXCEPT       {return *this;}
-    _LIBCPP_INLINE_VISIBILITY _T2_const_reference second() const _NOEXCEPT {return *this;}
+template <class _Deleter>
+struct __unique_ptr_deleter_sfinae<_Deleter const&> {
+  typedef const _Deleter& __lval_ref_type;
+  typedef const _Deleter&& __bad_rval_ref_type;
+  typedef false_type __enable_rval_overload;
+};
 
-    _LIBCPP_INLINE_VISIBILITY void swap(__libcpp_compressed_pair_imp& __x)
-        _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
-                   __is_nothrow_swappable<_T2>::value)
-    {
-        using _VSTD::swap;
-        swap(__first_, __x.__first_);
-    }
+template <class _Deleter>
+struct __unique_ptr_deleter_sfinae<_Deleter&> {
+  typedef _Deleter& __lval_ref_type;
+  typedef _Deleter&& __bad_rval_ref_type;
+  typedef false_type __enable_rval_overload;
 };
+#endif // !defined(_LIBCPP_CXX03_LANG)
 
-template <class _T1, class _T2>
-class __libcpp_compressed_pair_imp<_T1, _T2, 3>
-    : private _T1,
-      private _T2
-{
+template <class _Tp, class _Dp = default_delete<_Tp> >
+class _LIBCPP_TEMPLATE_VIS unique_ptr {
 public:
-    typedef _T1 _T1_param;
-    typedef _T2 _T2_param;
-
-    typedef _T1& _T1_reference;
-    typedef _T2& _T2_reference;
+  typedef _Tp element_type;
+  typedef _Dp deleter_type;
+  typedef typename __pointer_type<_Tp, deleter_type>::type pointer;
 
-    typedef const _T1& _T1_const_reference;
-    typedef const _T2& _T2_const_reference;
+  static_assert(!is_rvalue_reference<deleter_type>::value,
+                "the specified deleter type cannot be an rvalue reference");
 
-    _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp() {}
-    _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T1_param __t1)
-        : _T1(_VSTD::forward<_T1_param>(__t1)) {}
-    _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T2_param __t2)
-        : _T2(_VSTD::forward<_T2_param>(__t2)) {}
-    _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp(_T1_param __t1, _T2_param __t2)
-        : _T1(_VSTD::forward<_T1_param>(__t1)), _T2(_VSTD::forward<_T2_param>(__t2)) {}
+private:
+  __compressed_pair<pointer, deleter_type> __ptr_;
 
-#if defined(_LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS) && !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+  struct __nat { int __for_bool_; };
 
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp(const __libcpp_compressed_pair_imp& __p)
-        _NOEXCEPT_(is_nothrow_copy_constructible<_T1>::value &&
-                   is_nothrow_copy_constructible<_T2>::value)
-        : _T1(__p.first()), _T2(__p.second()) {}
+#ifndef _LIBCPP_CXX03_LANG
+  typedef __unique_ptr_deleter_sfinae<_Dp> _DeleterSFINAE;
 
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp& operator=(const __libcpp_compressed_pair_imp& __p)
-        _NOEXCEPT_(is_nothrow_copy_assignable<_T1>::value &&
-                   is_nothrow_copy_assignable<_T2>::value)
-        {
-            _T1::operator=(__p.first());
-            _T2::operator=(__p.second());
-            return *this;
-        }
+  template <bool _Dummy>
+  using _LValRefType =
+      typename __dependent_type<_DeleterSFINAE, _Dummy>::__lval_ref_type;
 
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp(__libcpp_compressed_pair_imp&& __p)
-        _NOEXCEPT_(is_nothrow_move_constructible<_T1>::value &&
-                   is_nothrow_move_constructible<_T2>::value)
-        : _T1(_VSTD::move(__p.first())), _T2(_VSTD::move(__p.second())) {}
+  template <bool _Dummy>
+  using _GoodRValRefType =
+      typename __dependent_type<_DeleterSFINAE, _Dummy>::__good_rval_ref_type;
 
-    _LIBCPP_INLINE_VISIBILITY
-    __libcpp_compressed_pair_imp& operator=(__libcpp_compressed_pair_imp&& __p)
-        _NOEXCEPT_(is_nothrow_move_assignable<_T1>::value &&
-                   is_nothrow_move_assignable<_T2>::value)
-        {
-            _T1::operator=(_VSTD::move(__p.first()));
-            _T2::operator=(_VSTD::move(__p.second()));
-            return *this;
-        }
+  template <bool _Dummy>
+  using _BadRValRefType =
+      typename __dependent_type<_DeleterSFINAE, _Dummy>::__bad_rval_ref_type;
 
-#endif  // defined(_LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS) && !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+  template <bool _Dummy, class _Deleter = typename __dependent_type<
+                             __identity<deleter_type>, _Dummy>::type>
+  using _EnableIfDeleterDefaultConstructible =
+      typename enable_if<is_default_constructible<_Deleter>::value &&
+                         !is_pointer<_Deleter>::value>::type;
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+  template <class _ArgType>
+  using _EnableIfDeleterConstructible =
+      typename enable_if<is_constructible<deleter_type, _ArgType>::value>::type;
 
-    template <class... _Args1, class... _Args2, size_t... _I1, size_t... _I2>
-        _LIBCPP_INLINE_VISIBILITY
-        __libcpp_compressed_pair_imp(piecewise_construct_t __pc,
-                                     tuple<_Args1...> __first_args,
-                                     tuple<_Args2...> __second_args,
-                                     __tuple_indices<_I1...>,
-                                     __tuple_indices<_I2...>)
-            : _T1(_VSTD::forward<_Args1>(_VSTD::get<_I1>(__first_args))...),
-              _T2(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...)
-            {}
+  template <class _UPtr, class _Up>
+  using _EnableIfMoveConvertible = typename enable_if<
+      is_convertible<typename _UPtr::pointer, pointer>::value &&
+      !is_array<_Up>::value
+  >::type;
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+  template <class _UDel>
+  using _EnableIfDeleterConvertible = typename enable_if<
+      (is_reference<_Dp>::value && is_same<_Dp, _UDel>::value) ||
+      (!is_reference<_Dp>::value && is_convertible<_UDel, _Dp>::value)
+    >::type;
 
-    _LIBCPP_INLINE_VISIBILITY _T1_reference       first() _NOEXCEPT       {return *this;}
-    _LIBCPP_INLINE_VISIBILITY _T1_const_reference first() const _NOEXCEPT {return *this;}
+  template <class _UDel>
+  using _EnableIfDeleterAssignable = typename enable_if<
+      is_assignable<_Dp&, _UDel&&>::value
+    >::type;
 
-    _LIBCPP_INLINE_VISIBILITY _T2_reference       second() _NOEXCEPT       {return *this;}
-    _LIBCPP_INLINE_VISIBILITY _T2_const_reference second() const _NOEXCEPT {return *this;}
-
-    _LIBCPP_INLINE_VISIBILITY void swap(__libcpp_compressed_pair_imp&)
-        _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
-                   __is_nothrow_swappable<_T2>::value)
-    {
-    }
-};
-
-template <class _T1, class _T2>
-class __compressed_pair
-    : private __libcpp_compressed_pair_imp<_T1, _T2>
-{
-    typedef __libcpp_compressed_pair_imp<_T1, _T2> base;
 public:
-    typedef typename base::_T1_param _T1_param;
-    typedef typename base::_T2_param _T2_param;
-
-    typedef typename base::_T1_reference _T1_reference;
-    typedef typename base::_T2_reference _T2_reference;
+  template <bool _Dummy = true,
+            class = _EnableIfDeleterDefaultConstructible<_Dummy>>
+  _LIBCPP_INLINE_VISIBILITY
+  constexpr unique_ptr() noexcept : __ptr_(pointer()) {}
+
+  template <bool _Dummy = true,
+            class = _EnableIfDeleterDefaultConstructible<_Dummy>>
+  _LIBCPP_INLINE_VISIBILITY
+  constexpr unique_ptr(nullptr_t) noexcept : __ptr_(pointer()) {}
+
+  template <bool _Dummy = true,
+            class = _EnableIfDeleterDefaultConstructible<_Dummy>>
+  _LIBCPP_INLINE_VISIBILITY
+  explicit unique_ptr(pointer __p) noexcept : __ptr_(__p) {}
+
+  template <bool _Dummy = true,
+            class = _EnableIfDeleterConstructible<_LValRefType<_Dummy>>>
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(pointer __p, _LValRefType<_Dummy> __d) noexcept
+      : __ptr_(__p, __d) {}
+
+  template <bool _Dummy = true,
+            class = _EnableIfDeleterConstructible<_GoodRValRefType<_Dummy>>>
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(pointer __p, _GoodRValRefType<_Dummy> __d) noexcept
+      : __ptr_(__p, _VSTD::move(__d)) {
+    static_assert(!is_reference<deleter_type>::value,
+                  "rvalue deleter bound to reference");
+  }
 
-    typedef typename base::_T1_const_reference _T1_const_reference;
-    typedef typename base::_T2_const_reference _T2_const_reference;
+  template <bool _Dummy = true,
+            class = _EnableIfDeleterConstructible<_BadRValRefType<_Dummy>>>
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(pointer __p, _BadRValRefType<_Dummy> __d) = delete;
 
-    _LIBCPP_INLINE_VISIBILITY __compressed_pair() {}
-    _LIBCPP_INLINE_VISIBILITY explicit __compressed_pair(_T1_param __t1)
-        : base(_VSTD::forward<_T1_param>(__t1)) {}
-    _LIBCPP_INLINE_VISIBILITY explicit __compressed_pair(_T2_param __t2)
-        : base(_VSTD::forward<_T2_param>(__t2)) {}
-    _LIBCPP_INLINE_VISIBILITY __compressed_pair(_T1_param __t1, _T2_param __t2)
-        : base(_VSTD::forward<_T1_param>(__t1), _VSTD::forward<_T2_param>(__t2)) {}
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(unique_ptr&& __u) noexcept
+      : __ptr_(__u.release(), _VSTD::forward<deleter_type>(__u.get_deleter())) {
+  }
 
-#if defined(_LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS) && !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+  template <class _Up, class _Ep,
+      class = _EnableIfMoveConvertible<unique_ptr<_Up, _Ep>, _Up>,
+      class = _EnableIfDeleterConvertible<_Ep>
+  >
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT
+      : __ptr_(__u.release(), _VSTD::forward<_Ep>(__u.get_deleter())) {}
+
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
+  template <class _Up>
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(auto_ptr<_Up>&& __p,
+             typename enable_if<is_convertible<_Up*, _Tp*>::value &&
+                                    is_same<_Dp, default_delete<_Tp>>::value,
+                                __nat>::type = __nat()) _NOEXCEPT
+      : __ptr_(__p.release()) {}
+#endif
 
-    _LIBCPP_INLINE_VISIBILITY
-    __compressed_pair(const __compressed_pair& __p)
-        _NOEXCEPT_(is_nothrow_copy_constructible<_T1>::value &&
-                   is_nothrow_copy_constructible<_T2>::value)
-        : base(__p) {}
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr& operator=(unique_ptr&& __u) _NOEXCEPT {
+    reset(__u.release());
+    __ptr_.second() = _VSTD::forward<deleter_type>(__u.get_deleter());
+    return *this;
+  }
 
-    _LIBCPP_INLINE_VISIBILITY
-    __compressed_pair& operator=(const __compressed_pair& __p)
-        _NOEXCEPT_(is_nothrow_copy_assignable<_T1>::value &&
-                   is_nothrow_copy_assignable<_T2>::value)
-        {
-            base::operator=(__p);
-            return *this;
-        }
+  template <class _Up, class _Ep,
+      class = _EnableIfMoveConvertible<unique_ptr<_Up, _Ep>, _Up>,
+      class = _EnableIfDeleterAssignable<_Ep>
+  >
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr& operator=(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT {
+    reset(__u.release());
+    __ptr_.second() = _VSTD::forward<_Ep>(__u.get_deleter());
+    return *this;
+  }
 
-    _LIBCPP_INLINE_VISIBILITY
-    __compressed_pair(__compressed_pair&& __p)
-        _NOEXCEPT_(is_nothrow_move_constructible<_T1>::value &&
-                   is_nothrow_move_constructible<_T2>::value)
-        : base(_VSTD::move(__p)) {}
+#else  // _LIBCPP_CXX03_LANG
+private:
+  unique_ptr(unique_ptr&);
+  template <class _Up, class _Ep> unique_ptr(unique_ptr<_Up, _Ep>&);
 
-    _LIBCPP_INLINE_VISIBILITY
-    __compressed_pair& operator=(__compressed_pair&& __p)
-        _NOEXCEPT_(is_nothrow_move_assignable<_T1>::value &&
-                   is_nothrow_move_assignable<_T2>::value)
-        {
-            base::operator=(_VSTD::move(__p));
-            return *this;
-        }
+  unique_ptr& operator=(unique_ptr&);
+  template <class _Up, class _Ep> unique_ptr& operator=(unique_ptr<_Up, _Ep>&);
 
-#endif  // defined(_LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS) && !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+public:
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr() : __ptr_(pointer())
+  {
+    static_assert(!is_pointer<deleter_type>::value,
+                  "unique_ptr constructed with null function pointer deleter");
+    static_assert(is_default_constructible<deleter_type>::value,
+                  "unique_ptr::deleter_type is not default constructible");
+  }
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(nullptr_t) : __ptr_(pointer())
+  {
+    static_assert(!is_pointer<deleter_type>::value,
+                  "unique_ptr constructed with null function pointer deleter");
+  }
+  _LIBCPP_INLINE_VISIBILITY
+  explicit unique_ptr(pointer __p)
+      : __ptr_(_VSTD::move(__p)) {
+    static_assert(!is_pointer<deleter_type>::value,
+                  "unique_ptr constructed with null function pointer deleter");
+  }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+  _LIBCPP_INLINE_VISIBILITY
+  operator __rv<unique_ptr>() {
+    return __rv<unique_ptr>(*this);
+  }
 
-    template <class... _Args1, class... _Args2>
-        _LIBCPP_INLINE_VISIBILITY
-        __compressed_pair(piecewise_construct_t __pc, tuple<_Args1...> __first_args,
-                                                      tuple<_Args2...> __second_args)
-            : base(__pc, _VSTD::move(__first_args), _VSTD::move(__second_args),
-                   typename __make_tuple_indices<sizeof...(_Args1)>::type(),
-                   typename __make_tuple_indices<sizeof...(_Args2) >::type())
-            {}
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(__rv<unique_ptr> __u)
+      : __ptr_(__u->release(),
+               _VSTD::forward<deleter_type>(__u->get_deleter())) {}
+
+  template <class _Up, class _Ep>
+  _LIBCPP_INLINE_VISIBILITY
+  typename enable_if<
+      !is_array<_Up>::value &&
+          is_convertible<typename unique_ptr<_Up, _Ep>::pointer,
+                         pointer>::value &&
+          is_assignable<deleter_type&, _Ep&>::value,
+      unique_ptr&>::type
+  operator=(unique_ptr<_Up, _Ep> __u) {
+    reset(__u.release());
+    __ptr_.second() = _VSTD::forward<_Ep>(__u.get_deleter());
+    return *this;
+  }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(pointer __p, deleter_type __d)
+      : __ptr_(_VSTD::move(__p), _VSTD::move(__d)) {}
+#endif // _LIBCPP_CXX03_LANG
+
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
+  template <class _Up>
+  _LIBCPP_INLINE_VISIBILITY
+      typename enable_if<is_convertible<_Up*, _Tp*>::value &&
+                             is_same<_Dp, default_delete<_Tp> >::value,
+                         unique_ptr&>::type
+      operator=(auto_ptr<_Up> __p) {
+    reset(__p.release());
+    return *this;
+  }
+#endif
 
-    _LIBCPP_INLINE_VISIBILITY _T1_reference       first() _NOEXCEPT       {return base::first();}
-    _LIBCPP_INLINE_VISIBILITY _T1_const_reference first() const _NOEXCEPT {return base::first();}
+  _LIBCPP_INLINE_VISIBILITY
+  ~unique_ptr() { reset(); }
 
-    _LIBCPP_INLINE_VISIBILITY _T2_reference       second() _NOEXCEPT       {return base::second();}
-    _LIBCPP_INLINE_VISIBILITY _T2_const_reference second() const _NOEXCEPT {return base::second();}
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr& operator=(nullptr_t) _NOEXCEPT {
+    reset();
+    return *this;
+  }
 
-    _LIBCPP_INLINE_VISIBILITY void swap(__compressed_pair& __x)
-        _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
-                   __is_nothrow_swappable<_T2>::value)
-        {base::swap(__x);}
-};
+  _LIBCPP_INLINE_VISIBILITY
+  typename add_lvalue_reference<_Tp>::type
+  operator*() const {
+    return *__ptr_.first();
+  }
+  _LIBCPP_INLINE_VISIBILITY
+  pointer operator->() const _NOEXCEPT {
+    return __ptr_.first();
+  }
+  _LIBCPP_INLINE_VISIBILITY
+  pointer get() const _NOEXCEPT {
+    return __ptr_.first();
+  }
+  _LIBCPP_INLINE_VISIBILITY
+  deleter_type& get_deleter() _NOEXCEPT {
+    return __ptr_.second();
+  }
+  _LIBCPP_INLINE_VISIBILITY
+  const deleter_type& get_deleter() const _NOEXCEPT {
+    return __ptr_.second();
+  }
+  _LIBCPP_INLINE_VISIBILITY
+  _LIBCPP_EXPLICIT operator bool() const _NOEXCEPT {
+    return __ptr_.first() != nullptr;
+  }
 
-template <class _T1, class _T2>
-inline _LIBCPP_INLINE_VISIBILITY
-void
-swap(__compressed_pair<_T1, _T2>& __x, __compressed_pair<_T1, _T2>& __y)
-        _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
-                   __is_nothrow_swappable<_T2>::value)
-    {__x.swap(__y);}
-
-// __same_or_less_cv_qualified
-
-template <class _Ptr1, class _Ptr2,
-          bool = is_same<typename remove_cv<typename pointer_traits<_Ptr1>::element_type>::type,
-                         typename remove_cv<typename pointer_traits<_Ptr2>::element_type>::type
-                        >::value
-         >
-struct __same_or_less_cv_qualified_imp
-    : is_convertible<_Ptr1, _Ptr2> {};
-
-template <class _Ptr1, class _Ptr2>
-struct __same_or_less_cv_qualified_imp<_Ptr1, _Ptr2, false>
-    : false_type {};
-
-template <class _Ptr1, class _Ptr2, bool = is_pointer<_Ptr1>::value ||
-                                           is_same<_Ptr1, _Ptr2>::value ||
-                                           __has_element_type<_Ptr1>::value>
-struct __same_or_less_cv_qualified
-    : __same_or_less_cv_qualified_imp<_Ptr1, _Ptr2> {};
-
-template <class _Ptr1, class _Ptr2>
-struct __same_or_less_cv_qualified<_Ptr1, _Ptr2, false>
-    : false_type {};
+  _LIBCPP_INLINE_VISIBILITY
+  pointer release() _NOEXCEPT {
+    pointer __t = __ptr_.first();
+    __ptr_.first() = pointer();
+    return __t;
+  }
 
-// default_delete
+  _LIBCPP_INLINE_VISIBILITY
+  void reset(pointer __p = pointer()) _NOEXCEPT {
+    pointer __tmp = __ptr_.first();
+    __ptr_.first() = __p;
+    if (__tmp)
+      __ptr_.second()(__tmp);
+  }
 
-template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY default_delete
-{
-#ifndef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR default_delete() _NOEXCEPT = default;
-#else
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR default_delete() _NOEXCEPT {}
-#endif
-    template <class _Up>
-        _LIBCPP_INLINE_VISIBILITY default_delete(const default_delete<_Up>&,
-             typename enable_if<is_convertible<_Up*, _Tp*>::value>::type* = 0) _NOEXCEPT {}
-    _LIBCPP_INLINE_VISIBILITY void operator() (_Tp* __ptr) const _NOEXCEPT
-        {
-            static_assert(sizeof(_Tp) > 0, "default_delete can not delete incomplete type");
-            static_assert(!is_void<_Tp>::value, "default_delete can not delete incomplete type");
-            delete __ptr;
-        }
+  _LIBCPP_INLINE_VISIBILITY
+  void swap(unique_ptr& __u) _NOEXCEPT {
+    __ptr_.swap(__u.__ptr_);
+  }
 };
 
-template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY default_delete<_Tp[]>
-{
-public:
-#ifndef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR default_delete() _NOEXCEPT = default;
-#else
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR default_delete() _NOEXCEPT {}
-#endif
-    template <class _Up>
-        _LIBCPP_INLINE_VISIBILITY default_delete(const default_delete<_Up[]>&,
-             typename enable_if<__same_or_less_cv_qualified<_Up*, _Tp*>::value>::type* = 0) _NOEXCEPT {}
-    template <class _Up>
-        _LIBCPP_INLINE_VISIBILITY
-        void operator() (_Up* __ptr,
-                         typename enable_if<__same_or_less_cv_qualified<_Up*, _Tp*>::value>::type* = 0) const _NOEXCEPT
-        {
-            static_assert(sizeof(_Tp) > 0, "default_delete can not delete incomplete type");
-            static_assert(!is_void<_Tp>::value, "default_delete can not delete void type");
-            delete [] __ptr;
-        }
-};
 
-template <class _Tp, class _Dp = default_delete<_Tp> >
-class _LIBCPP_TYPE_VIS_ONLY unique_ptr
-{
+template <class _Tp, class _Dp>
+class _LIBCPP_TEMPLATE_VIS unique_ptr<_Tp[], _Dp> {
 public:
-    typedef _Tp element_type;
-    typedef _Dp deleter_type;
-    typedef typename __pointer_type<_Tp, deleter_type>::type pointer;
-private:
-    __compressed_pair<pointer, deleter_type> __ptr_;
+  typedef _Tp element_type;
+  typedef _Dp deleter_type;
+  typedef typename __pointer_type<_Tp, deleter_type>::type pointer;
 
-#ifdef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    unique_ptr(unique_ptr&);
-    template <class _Up, class _Ep>
-        unique_ptr(unique_ptr<_Up, _Ep>&);
-    unique_ptr& operator=(unique_ptr&);
-    template <class _Up, class _Ep>
-        unique_ptr& operator=(unique_ptr<_Up, _Ep>&);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-    struct __nat {int __for_bool_;};
+private:
+  __compressed_pair<pointer, deleter_type> __ptr_;
+
+  template <class _From>
+  struct _CheckArrayPointerConversion : is_same<_From, pointer> {};
+
+  template <class _FromElem>
+  struct _CheckArrayPointerConversion<_FromElem*>
+      : integral_constant<bool,
+          is_same<_FromElem*, pointer>::value ||
+            (is_same<pointer, element_type*>::value &&
+             is_convertible<_FromElem(*)[], element_type(*)[]>::value)
+      >
+  {};
+
+#ifndef _LIBCPP_CXX03_LANG
+  typedef __unique_ptr_deleter_sfinae<_Dp> _DeleterSFINAE;
+
+  template <bool _Dummy>
+  using _LValRefType =
+      typename __dependent_type<_DeleterSFINAE, _Dummy>::__lval_ref_type;
+
+  template <bool _Dummy>
+  using _GoodRValRefType =
+      typename __dependent_type<_DeleterSFINAE, _Dummy>::__good_rval_ref_type;
+
+  template <bool _Dummy>
+  using _BadRValRefType =
+      typename __dependent_type<_DeleterSFINAE, _Dummy>::__bad_rval_ref_type;
+
+  template <bool _Dummy, class _Deleter = typename __dependent_type<
+                             __identity<deleter_type>, _Dummy>::type>
+  using _EnableIfDeleterDefaultConstructible =
+      typename enable_if<is_default_constructible<_Deleter>::value &&
+                         !is_pointer<_Deleter>::value>::type;
+
+  template <class _ArgType>
+  using _EnableIfDeleterConstructible =
+      typename enable_if<is_constructible<deleter_type, _ArgType>::value>::type;
+
+  template <class _Pp>
+  using _EnableIfPointerConvertible = typename enable_if<
+      _CheckArrayPointerConversion<_Pp>::value
+  >::type;
+
+  template <class _UPtr, class _Up,
+        class _ElemT = typename _UPtr::element_type>
+  using _EnableIfMoveConvertible = typename enable_if<
+      is_array<_Up>::value &&
+      is_same<pointer, element_type*>::value &&
+      is_same<typename _UPtr::pointer, _ElemT*>::value &&
+      is_convertible<_ElemT(*)[], element_type(*)[]>::value
+    >::type;
+
+  template <class _UDel>
+  using _EnableIfDeleterConvertible = typename enable_if<
+      (is_reference<_Dp>::value && is_same<_Dp, _UDel>::value) ||
+      (!is_reference<_Dp>::value && is_convertible<_UDel, _Dp>::value)
+    >::type;
+
+  template <class _UDel>
+  using _EnableIfDeleterAssignable = typename enable_if<
+      is_assignable<_Dp&, _UDel&&>::value
+    >::type;
 
-    typedef       typename remove_reference<deleter_type>::type& _Dp_reference;
-    typedef const typename remove_reference<deleter_type>::type& _Dp_const_reference;
 public:
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR unique_ptr() _NOEXCEPT
-        : __ptr_(pointer())
-        {
-            static_assert(!is_pointer<deleter_type>::value,
-                "unique_ptr constructed with null function pointer deleter");
-        }
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT
-        : __ptr_(pointer())
-        {
-            static_assert(!is_pointer<deleter_type>::value,
-                "unique_ptr constructed with null function pointer deleter");
-        }
-    _LIBCPP_INLINE_VISIBILITY explicit unique_ptr(pointer __p) _NOEXCEPT
-        : __ptr_(_VSTD::move(__p))
-        {
-            static_assert(!is_pointer<deleter_type>::value,
-                "unique_ptr constructed with null function pointer deleter");
-        }
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(pointer __p, typename conditional<
-                                        is_reference<deleter_type>::value,
-                                        deleter_type,
-                                        typename add_lvalue_reference<const deleter_type>::type>::type __d)
-             _NOEXCEPT
-        : __ptr_(__p, __d) {}
-
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(pointer __p, typename remove_reference<deleter_type>::type&& __d)
-             _NOEXCEPT
-        : __ptr_(__p, _VSTD::move(__d))
-        {
-            static_assert(!is_reference<deleter_type>::value, "rvalue deleter bound to reference");
-        }
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(unique_ptr&& __u) _NOEXCEPT
-        : __ptr_(__u.release(), _VSTD::forward<deleter_type>(__u.get_deleter())) {}
-    template <class _Up, class _Ep>
-        _LIBCPP_INLINE_VISIBILITY
-        unique_ptr(unique_ptr<_Up, _Ep>&& __u,
-                   typename enable_if
-                      <
-                        !is_array<_Up>::value &&
-                         is_convertible<typename unique_ptr<_Up, _Ep>::pointer, pointer>::value &&
-                         is_convertible<_Ep, deleter_type>::value &&
-                         (
-                            !is_reference<deleter_type>::value ||
-                            is_same<deleter_type, _Ep>::value
-                         ),
-                         __nat
-                      >::type = __nat()) _NOEXCEPT
-            : __ptr_(__u.release(), _VSTD::forward<_Ep>(__u.get_deleter())) {}
-
-    template <class _Up>
-        _LIBCPP_INLINE_VISIBILITY unique_ptr(auto_ptr<_Up>&& __p,
-                typename enable_if<
-                                      is_convertible<_Up*, _Tp*>::value &&
-                                      is_same<_Dp, default_delete<_Tp> >::value,
-                                      __nat
-                                  >::type = __nat()) _NOEXCEPT
-            : __ptr_(__p.release())
-            {
-            }
-
-        _LIBCPP_INLINE_VISIBILITY unique_ptr& operator=(unique_ptr&& __u) _NOEXCEPT
-            {
-                reset(__u.release());
-                __ptr_.second() = _VSTD::forward<deleter_type>(__u.get_deleter());
-                return *this;
-            }
-
-        template <class _Up, class _Ep>
-            _LIBCPP_INLINE_VISIBILITY
-            typename enable_if
-            <
-                !is_array<_Up>::value &&
-                is_convertible<typename unique_ptr<_Up, _Ep>::pointer, pointer>::value &&
-                is_assignable<deleter_type&, _Ep&&>::value,
-                unique_ptr&
-            >::type
-            operator=(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT
-            {
-                reset(__u.release());
-                __ptr_.second() = _VSTD::forward<_Ep>(__u.get_deleter());
-                return *this;
-            }
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-    _LIBCPP_INLINE_VISIBILITY operator __rv<unique_ptr>()
-    {
-        return __rv<unique_ptr>(*this);
-    }
-
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(__rv<unique_ptr> __u)
-        : __ptr_(__u->release(), _VSTD::forward<deleter_type>(__u->get_deleter())) {}
-
-    template <class _Up, class _Ep>
-    _LIBCPP_INLINE_VISIBILITY
-    typename enable_if<
-        !is_array<_Up>::value &&
-        is_convertible<typename unique_ptr<_Up, _Ep>::pointer, pointer>::value &&
-        is_assignable<deleter_type&, _Ep&>::value,
-        unique_ptr&
-    >::type
-    operator=(unique_ptr<_Up, _Ep> __u)
-    {
-        reset(__u.release());
-        __ptr_.second() = _VSTD::forward<_Ep>(__u.get_deleter());
-        return *this;
-    }
-
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(pointer __p, deleter_type __d)
-        : __ptr_(_VSTD::move(__p), _VSTD::move(__d)) {}
-
-    template <class _Up>
-        _LIBCPP_INLINE_VISIBILITY
-                typename enable_if<
-                                      is_convertible<_Up*, _Tp*>::value &&
-                                      is_same<_Dp, default_delete<_Tp> >::value,
-                                      unique_ptr&
-                                  >::type
-        operator=(auto_ptr<_Up> __p)
-            {reset(__p.release()); return *this;}
+  template <bool _Dummy = true,
+            class = _EnableIfDeleterDefaultConstructible<_Dummy>>
+  _LIBCPP_INLINE_VISIBILITY
+  constexpr unique_ptr() noexcept : __ptr_(pointer()) {}
+
+  template <bool _Dummy = true,
+            class = _EnableIfDeleterDefaultConstructible<_Dummy>>
+  _LIBCPP_INLINE_VISIBILITY
+  constexpr unique_ptr(nullptr_t) noexcept : __ptr_(pointer()) {}
+
+  template <class _Pp, bool _Dummy = true,
+            class = _EnableIfDeleterDefaultConstructible<_Dummy>,
+            class = _EnableIfPointerConvertible<_Pp>>
+  _LIBCPP_INLINE_VISIBILITY
+  explicit unique_ptr(_Pp __p) noexcept
+      : __ptr_(__p) {}
+
+  template <class _Pp, bool _Dummy = true,
+            class = _EnableIfDeleterConstructible<_LValRefType<_Dummy>>,
+            class = _EnableIfPointerConvertible<_Pp>>
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(_Pp __p, _LValRefType<_Dummy> __d) noexcept
+      : __ptr_(__p, __d) {}
+
+  template <bool _Dummy = true,
+            class = _EnableIfDeleterConstructible<_LValRefType<_Dummy>>>
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(nullptr_t, _LValRefType<_Dummy> __d) noexcept
+      : __ptr_(nullptr, __d) {}
+
+  template <class _Pp, bool _Dummy = true,
+            class = _EnableIfDeleterConstructible<_GoodRValRefType<_Dummy>>,
+            class = _EnableIfPointerConvertible<_Pp>>
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(_Pp __p, _GoodRValRefType<_Dummy> __d) noexcept
+      : __ptr_(__p, _VSTD::move(__d)) {
+    static_assert(!is_reference<deleter_type>::value,
+                  "rvalue deleter bound to reference");
+  }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY ~unique_ptr() {reset();}
+  template <bool _Dummy = true,
+            class = _EnableIfDeleterConstructible<_GoodRValRefType<_Dummy>>>
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(nullptr_t, _GoodRValRefType<_Dummy> __d) noexcept
+      : __ptr_(nullptr, _VSTD::move(__d)) {
+    static_assert(!is_reference<deleter_type>::value,
+                  "rvalue deleter bound to reference");
+  }
 
-    _LIBCPP_INLINE_VISIBILITY unique_ptr& operator=(nullptr_t) _NOEXCEPT
-    {
-        reset();
-        return *this;
-    }
+  template <class _Pp, bool _Dummy = true,
+            class = _EnableIfDeleterConstructible<_BadRValRefType<_Dummy>>,
+            class = _EnableIfPointerConvertible<_Pp>>
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(_Pp __p, _BadRValRefType<_Dummy> __d) = delete;
 
-    _LIBCPP_INLINE_VISIBILITY typename add_lvalue_reference<_Tp>::type operator*() const
-        {return *__ptr_.first();}
-    _LIBCPP_INLINE_VISIBILITY pointer operator->() const _NOEXCEPT {return __ptr_.first();}
-    _LIBCPP_INLINE_VISIBILITY pointer get() const _NOEXCEPT {return __ptr_.first();}
-    _LIBCPP_INLINE_VISIBILITY       _Dp_reference get_deleter() _NOEXCEPT
-        {return __ptr_.second();}
-    _LIBCPP_INLINE_VISIBILITY _Dp_const_reference get_deleter() const _NOEXCEPT
-        {return __ptr_.second();}
-    _LIBCPP_INLINE_VISIBILITY
-        _LIBCPP_EXPLICIT operator bool() const _NOEXCEPT
-        {return __ptr_.first() != nullptr;}
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(unique_ptr&& __u) noexcept
+      : __ptr_(__u.release(), _VSTD::forward<deleter_type>(__u.get_deleter())) {
+  }
 
-    _LIBCPP_INLINE_VISIBILITY pointer release() _NOEXCEPT
-    {
-        pointer __t = __ptr_.first();
-        __ptr_.first() = pointer();
-        return __t;
-    }
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr& operator=(unique_ptr&& __u) noexcept {
+    reset(__u.release());
+    __ptr_.second() = _VSTD::forward<deleter_type>(__u.get_deleter());
+    return *this;
+  }
 
-    _LIBCPP_INLINE_VISIBILITY void reset(pointer __p = pointer()) _NOEXCEPT
-    {
-        pointer __tmp = __ptr_.first();
-        __ptr_.first() = __p;
-        if (__tmp)
-            __ptr_.second()(__tmp);
-    }
+  template <class _Up, class _Ep,
+      class = _EnableIfMoveConvertible<unique_ptr<_Up, _Ep>, _Up>,
+      class = _EnableIfDeleterConvertible<_Ep>
+  >
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(unique_ptr<_Up, _Ep>&& __u) noexcept
+      : __ptr_(__u.release(), _VSTD::forward<_Ep>(__u.get_deleter())) {
+  }
 
-    _LIBCPP_INLINE_VISIBILITY void swap(unique_ptr& __u) _NOEXCEPT
-        {__ptr_.swap(__u.__ptr_);}
-};
+  template <class _Up, class _Ep,
+      class = _EnableIfMoveConvertible<unique_ptr<_Up, _Ep>, _Up>,
+      class = _EnableIfDeleterAssignable<_Ep>
+  >
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr&
+  operator=(unique_ptr<_Up, _Ep>&& __u) noexcept {
+    reset(__u.release());
+    __ptr_.second() = _VSTD::forward<_Ep>(__u.get_deleter());
+    return *this;
+  }
 
-template <class _Tp, class _Dp>
-class _LIBCPP_TYPE_VIS_ONLY unique_ptr<_Tp[], _Dp>
-{
-public:
-    typedef _Tp element_type;
-    typedef _Dp deleter_type;
-    typedef typename __pointer_type<_Tp, deleter_type>::type pointer;
+#else // _LIBCPP_CXX03_LANG
 private:
-    __compressed_pair<pointer, deleter_type> __ptr_;
+  template <class _Up> explicit unique_ptr(_Up);
 
-#ifdef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    unique_ptr(unique_ptr&);
-    template <class _Up>
-        unique_ptr(unique_ptr<_Up>&);
-    unique_ptr& operator=(unique_ptr&);
-    template <class _Up>
-        unique_ptr& operator=(unique_ptr<_Up>&);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+  unique_ptr(unique_ptr&);
+  template <class _Up> unique_ptr(unique_ptr<_Up>&);
 
-    struct __nat {int __for_bool_;};
+  unique_ptr& operator=(unique_ptr&);
+  template <class _Up> unique_ptr& operator=(unique_ptr<_Up>&);
 
-    typedef       typename remove_reference<deleter_type>::type& _Dp_reference;
-    typedef const typename remove_reference<deleter_type>::type& _Dp_const_reference;
+  template <class _Up>
+  unique_ptr(_Up __u,
+             typename conditional<
+                 is_reference<deleter_type>::value, deleter_type,
+                 typename add_lvalue_reference<const deleter_type>::type>::type,
+             typename enable_if<is_convertible<_Up, pointer>::value,
+                                __nat>::type = __nat());
 public:
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR unique_ptr() _NOEXCEPT
-        : __ptr_(pointer())
-        {
-            static_assert(!is_pointer<deleter_type>::value,
-                "unique_ptr constructed with null function pointer deleter");
-        }
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT
-        : __ptr_(pointer())
-        {
-            static_assert(!is_pointer<deleter_type>::value,
-                "unique_ptr constructed with null function pointer deleter");
-        }
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    template <class _Pp>
-    _LIBCPP_INLINE_VISIBILITY explicit unique_ptr(_Pp __p,
-            typename enable_if<__same_or_less_cv_qualified<_Pp, pointer>::value, __nat>::type = __nat()) _NOEXCEPT
-        : __ptr_(__p)
-        {
-            static_assert(!is_pointer<deleter_type>::value,
-                "unique_ptr constructed with null function pointer deleter");
-        }
-
-    template <class _Pp>
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(_Pp __p, typename conditional<
-                                       is_reference<deleter_type>::value,
-                                       deleter_type,
-                                       typename add_lvalue_reference<const deleter_type>::type>::type __d,
-                                       typename enable_if<__same_or_less_cv_qualified<_Pp, pointer>::value, __nat>::type = __nat())
-             _NOEXCEPT
-        : __ptr_(__p, __d) {}
-
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(nullptr_t, typename conditional<
-                                       is_reference<deleter_type>::value,
-                                       deleter_type,
-                                       typename add_lvalue_reference<const deleter_type>::type>::type __d)
-             _NOEXCEPT
-        : __ptr_(pointer(), __d) {}
-
-    template <class _Pp>
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(_Pp __p,
-                                         typename remove_reference<deleter_type>::type&& __d,
-                                         typename enable_if<__same_or_less_cv_qualified<_Pp, pointer>::value, __nat>::type = __nat())
-             _NOEXCEPT
-        : __ptr_(__p, _VSTD::move(__d))
-        {
-            static_assert(!is_reference<deleter_type>::value, "rvalue deleter bound to reference");
-        }
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr() : __ptr_(pointer()) {
+    static_assert(!is_pointer<deleter_type>::value,
+                  "unique_ptr constructed with null function pointer deleter");
+  }
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(nullptr_t) : __ptr_(pointer()) {
+    static_assert(!is_pointer<deleter_type>::value,
+                  "unique_ptr constructed with null function pointer deleter");
+  }
 
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(nullptr_t, typename remove_reference<deleter_type>::type&& __d)
-             _NOEXCEPT
-        : __ptr_(pointer(), _VSTD::move(__d))
-        {
-            static_assert(!is_reference<deleter_type>::value, "rvalue deleter bound to reference");
-        }
+  _LIBCPP_INLINE_VISIBILITY
+  explicit unique_ptr(pointer __p) : __ptr_(__p) {
+    static_assert(!is_pointer<deleter_type>::value,
+                  "unique_ptr constructed with null function pointer deleter");
+  }
 
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(unique_ptr&& __u) _NOEXCEPT
-        : __ptr_(__u.release(), _VSTD::forward<deleter_type>(__u.get_deleter())) {}
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(pointer __p, deleter_type __d)
+      : __ptr_(__p, _VSTD::forward<deleter_type>(__d)) {}
 
-    _LIBCPP_INLINE_VISIBILITY unique_ptr& operator=(unique_ptr&& __u) _NOEXCEPT
-        {
-            reset(__u.release());
-            __ptr_.second() = _VSTD::forward<deleter_type>(__u.get_deleter());
-            return *this;
-        }
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(nullptr_t, deleter_type __d)
+      : __ptr_(pointer(), _VSTD::forward<deleter_type>(__d)) {}
 
-    template <class _Up, class _Ep>
-        _LIBCPP_INLINE_VISIBILITY
-        unique_ptr(unique_ptr<_Up, _Ep>&& __u,
-                   typename enable_if
-                            <
-                                is_array<_Up>::value &&
-                                __same_or_less_cv_qualified<typename unique_ptr<_Up, _Ep>::pointer, pointer>::value
-                                && is_convertible<_Ep, deleter_type>::value &&
-                                (
-                                    !is_reference<deleter_type>::value ||
-                                    is_same<deleter_type, _Ep>::value
-                                ),
-                                __nat
-                            >::type = __nat()
-                  ) _NOEXCEPT
-        : __ptr_(__u.release(), _VSTD::forward<deleter_type>(__u.get_deleter())) {}
-
-
-        template <class _Up, class _Ep>
-            _LIBCPP_INLINE_VISIBILITY
-            typename enable_if
-            <
-                is_array<_Up>::value &&
-                __same_or_less_cv_qualified<typename unique_ptr<_Up, _Ep>::pointer, pointer>::value &&
-                is_assignable<deleter_type&, _Ep&&>::value,
-                unique_ptr&
-            >::type
-            operator=(unique_ptr<_Up, _Ep>&& __u) _NOEXCEPT
-            {
-                reset(__u.release());
-                __ptr_.second() = _VSTD::forward<_Ep>(__u.get_deleter());
-                return *this;
-            }
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+  _LIBCPP_INLINE_VISIBILITY
+  operator __rv<unique_ptr>() {
+    return __rv<unique_ptr>(*this);
+  }
 
-    _LIBCPP_INLINE_VISIBILITY explicit unique_ptr(pointer __p)
-        : __ptr_(__p)
-        {
-            static_assert(!is_pointer<deleter_type>::value,
-                "unique_ptr constructed with null function pointer deleter");
-        }
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr(__rv<unique_ptr> __u)
+      : __ptr_(__u->release(),
+               _VSTD::forward<deleter_type>(__u->get_deleter())) {}
 
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(pointer __p, deleter_type __d)
-        : __ptr_(__p, _VSTD::forward<deleter_type>(__d)) {}
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr& operator=(__rv<unique_ptr> __u) {
+    reset(__u->release());
+    __ptr_.second() = _VSTD::forward<deleter_type>(__u->get_deleter());
+    return *this;
+  }
 
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(nullptr_t, deleter_type __d)
-        : __ptr_(pointer(), _VSTD::forward<deleter_type>(__d)) {}
+#endif // _LIBCPP_CXX03_LANG
 
-    _LIBCPP_INLINE_VISIBILITY operator __rv<unique_ptr>()
-    {
-        return __rv<unique_ptr>(*this);
-    }
+public:
+  _LIBCPP_INLINE_VISIBILITY
+  ~unique_ptr() { reset(); }
 
-    _LIBCPP_INLINE_VISIBILITY unique_ptr(__rv<unique_ptr> __u)
-        : __ptr_(__u->release(), _VSTD::forward<deleter_type>(__u->get_deleter())) {}
+  _LIBCPP_INLINE_VISIBILITY
+  unique_ptr& operator=(nullptr_t) _NOEXCEPT {
+    reset();
+    return *this;
+  }
 
-    _LIBCPP_INLINE_VISIBILITY unique_ptr& operator=(__rv<unique_ptr> __u)
-    {
-        reset(__u->release());
-        __ptr_.second() = _VSTD::forward<deleter_type>(__u->get_deleter());
-        return *this;
-    }
+  _LIBCPP_INLINE_VISIBILITY
+  typename add_lvalue_reference<_Tp>::type
+  operator[](size_t __i) const {
+    return __ptr_.first()[__i];
+  }
+  _LIBCPP_INLINE_VISIBILITY
+  pointer get() const _NOEXCEPT {
+    return __ptr_.first();
+  }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY ~unique_ptr() {reset();}
+  _LIBCPP_INLINE_VISIBILITY
+  deleter_type& get_deleter() _NOEXCEPT {
+    return __ptr_.second();
+  }
 
-    _LIBCPP_INLINE_VISIBILITY unique_ptr& operator=(nullptr_t) _NOEXCEPT
-    {
-        reset();
-        return *this;
-    }
+  _LIBCPP_INLINE_VISIBILITY
+  const deleter_type& get_deleter() const _NOEXCEPT {
+    return __ptr_.second();
+  }
+  _LIBCPP_INLINE_VISIBILITY
+  _LIBCPP_EXPLICIT operator bool() const _NOEXCEPT {
+    return __ptr_.first() != nullptr;
+  }
 
-    _LIBCPP_INLINE_VISIBILITY typename add_lvalue_reference<_Tp>::type operator[](size_t __i) const
-        {return __ptr_.first()[__i];}
-    _LIBCPP_INLINE_VISIBILITY pointer get() const _NOEXCEPT {return __ptr_.first();}
-    _LIBCPP_INLINE_VISIBILITY       _Dp_reference get_deleter() _NOEXCEPT
-        {return __ptr_.second();}
-    _LIBCPP_INLINE_VISIBILITY _Dp_const_reference get_deleter() const _NOEXCEPT
-        {return __ptr_.second();}
-    _LIBCPP_INLINE_VISIBILITY
-        _LIBCPP_EXPLICIT operator bool() const _NOEXCEPT
-        {return __ptr_.first() != nullptr;}
+  _LIBCPP_INLINE_VISIBILITY
+  pointer release() _NOEXCEPT {
+    pointer __t = __ptr_.first();
+    __ptr_.first() = pointer();
+    return __t;
+  }
 
-    _LIBCPP_INLINE_VISIBILITY pointer release() _NOEXCEPT
-    {
-        pointer __t = __ptr_.first();
-        __ptr_.first() = pointer();
-        return __t;
-    }
+  template <class _Pp>
+  _LIBCPP_INLINE_VISIBILITY
+  typename enable_if<
+      _CheckArrayPointerConversion<_Pp>::value
+  >::type
+  reset(_Pp __p) _NOEXCEPT {
+    pointer __tmp = __ptr_.first();
+    __ptr_.first() = __p;
+    if (__tmp)
+      __ptr_.second()(__tmp);
+  }
 
-    template <class _Pp>
-    _LIBCPP_INLINE_VISIBILITY
-    typename enable_if<__same_or_less_cv_qualified<_Pp, pointer>::value, void>::type
-    reset(_Pp __p) _NOEXCEPT
-    {
-        pointer __tmp = __ptr_.first();
-        __ptr_.first() = __p;
-        if (__tmp)
-            __ptr_.second()(__tmp);
-    }
-    _LIBCPP_INLINE_VISIBILITY void reset(nullptr_t = nullptr) _NOEXCEPT
-    {
-        pointer __tmp = __ptr_.first();
-        __ptr_.first() = nullptr;
-        if (__tmp)
-            __ptr_.second()(__tmp);
-    }
+  _LIBCPP_INLINE_VISIBILITY
+  void reset(nullptr_t = nullptr) _NOEXCEPT {
+    pointer __tmp = __ptr_.first();
+    __ptr_.first() = nullptr;
+    if (__tmp)
+      __ptr_.second()(__tmp);
+  }
 
-    _LIBCPP_INLINE_VISIBILITY void swap(unique_ptr& __u) {__ptr_.swap(__u.__ptr_);}
-private:
+  _LIBCPP_INLINE_VISIBILITY
+  void swap(unique_ptr& __u) _NOEXCEPT {
+    __ptr_.swap(__u.__ptr_);
+  }
 
-#ifdef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    template <class _Up>
-        explicit unique_ptr(_Up);
-    template <class _Up>
-        unique_ptr(_Up __u,
-                   typename conditional<
-                                       is_reference<deleter_type>::value,
-                                       deleter_type,
-                                       typename add_lvalue_reference<const deleter_type>::type>::type,
-                   typename enable_if
-                      <
-                         is_convertible<_Up, pointer>::value,
-                         __nat
-                      >::type = __nat());
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 };
 
 template <class _Tp, class _Dp>
@@ -3165,353 +3093,18 @@ template<class _Tp, class... _Args>
 
 #endif  // _LIBCPP_STD_VER > 11
 
-template <class _Size>
-inline _LIBCPP_INLINE_VISIBILITY
-_Size
-__loadword(const void* __p)
-{
-    _Size __r;
-    std::memcpy(&__r, __p, sizeof(__r));
-    return __r;
-}
-
-// We use murmur2 when size_t is 32 bits, and cityhash64 when size_t
-// is 64 bits.  This is because cityhash64 uses 64bit x 64bit
-// multiplication, which can be very slow on 32-bit systems.
-template <class _Size, size_t = sizeof(_Size)*__CHAR_BIT__>
-struct __murmur2_or_cityhash;
-
-template <class _Size>
-struct __murmur2_or_cityhash<_Size, 32>
-{
-    _Size operator()(const void* __key, _Size __len);
-};
-
-// murmur2
-template <class _Size>
-_Size
-__murmur2_or_cityhash<_Size, 32>::operator()(const void* __key, _Size __len) _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK 
-{
-    const _Size __m = 0x5bd1e995;
-    const _Size __r = 24;
-    _Size __h = __len;
-    const unsigned char* __data = static_cast<const unsigned char*>(__key);
-    for (; __len >= 4; __data += 4, __len -= 4)
-    {
-        _Size __k = __loadword<_Size>(__data);
-        __k *= __m;
-        __k ^= __k >> __r;
-        __k *= __m;
-        __h *= __m;
-        __h ^= __k;
-    }
-    switch (__len)
-    {
-    case 3:
-        __h ^= __data[2] << 16;
-    case 2:
-        __h ^= __data[1] << 8;
-    case 1:
-        __h ^= __data[0];
-        __h *= __m;
-    }
-    __h ^= __h >> 13;
-    __h *= __m;
-    __h ^= __h >> 15;
-    return __h;
-}
-
-template <class _Size>
-struct __murmur2_or_cityhash<_Size, 64>
-{
-    _Size operator()(const void* __key, _Size __len);
-
- private:
-  // Some primes between 2^63 and 2^64.
-  static const _Size __k0 = 0xc3a5c85c97cb3127ULL;
-  static const _Size __k1 = 0xb492b66fbe98f273ULL;
-  static const _Size __k2 = 0x9ae16a3b2f90404fULL;
-  static const _Size __k3 = 0xc949d7c7509e6557ULL;
-
-  static _Size __rotate(_Size __val, int __shift) {
-    return __shift == 0 ? __val : ((__val >> __shift) | (__val << (64 - __shift)));
-  }
-
-  static _Size __rotate_by_at_least_1(_Size __val, int __shift) {
-    return (__val >> __shift) | (__val << (64 - __shift));
-  }
-
-  static _Size __shift_mix(_Size __val) {
-    return __val ^ (__val >> 47);
-  }
-
-  static _Size __hash_len_16(_Size __u, _Size __v) {
-    const _Size __mul = 0x9ddfea08eb382d69ULL;
-    _Size __a = (__u ^ __v) * __mul;
-    __a ^= (__a >> 47);
-    _Size __b = (__v ^ __a) * __mul;
-    __b ^= (__b >> 47);
-    __b *= __mul;
-    return __b;
-  }
-
-  static _Size __hash_len_0_to_16(const char* __s, _Size __len) {
-    if (__len > 8) {
-      const _Size __a = __loadword<_Size>(__s);
-      const _Size __b = __loadword<_Size>(__s + __len - 8);
-      return __hash_len_16(__a, __rotate_by_at_least_1(__b + __len, __len)) ^ __b;
-    }
-    if (__len >= 4) {
-      const uint32_t __a = __loadword<uint32_t>(__s);
-      const uint32_t __b = __loadword<uint32_t>(__s + __len - 4);
-      return __hash_len_16(__len + (__a << 3), __b);
-    }
-    if (__len > 0) {
-      const unsigned char __a = __s[0];
-      const unsigned char __b = __s[__len >> 1];
-      const unsigned char __c = __s[__len - 1];
-      const uint32_t __y = static_cast<uint32_t>(__a) +
-                           (static_cast<uint32_t>(__b) << 8);
-      const uint32_t __z = __len + (static_cast<uint32_t>(__c) << 2);
-      return __shift_mix(__y * __k2 ^ __z * __k3) * __k2;
-    }
-    return __k2;
-  }
-
-  static _Size __hash_len_17_to_32(const char *__s, _Size __len) {
-    const _Size __a = __loadword<_Size>(__s) * __k1;
-    const _Size __b = __loadword<_Size>(__s + 8);
-    const _Size __c = __loadword<_Size>(__s + __len - 8) * __k2;
-    const _Size __d = __loadword<_Size>(__s + __len - 16) * __k0;
-    return __hash_len_16(__rotate(__a - __b, 43) + __rotate(__c, 30) + __d,
-                         __a + __rotate(__b ^ __k3, 20) - __c + __len);
-  }
-
-  // Return a 16-byte hash for 48 bytes.  Quick and dirty.
-  // Callers do best to use "random-looking" values for a and b.
-  static pair<_Size, _Size> __weak_hash_len_32_with_seeds(
-      _Size __w, _Size __x, _Size __y, _Size __z, _Size __a, _Size __b) {
-    __a += __w;
-    __b = __rotate(__b + __a + __z, 21);
-    const _Size __c = __a;
-    __a += __x;
-    __a += __y;
-    __b += __rotate(__a, 44);
-    return pair<_Size, _Size>(__a + __z, __b + __c);
-  }
-
-  // Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.
-  static pair<_Size, _Size> __weak_hash_len_32_with_seeds(
-      const char* __s, _Size __a, _Size __b) {
-    return __weak_hash_len_32_with_seeds(__loadword<_Size>(__s),
-                                         __loadword<_Size>(__s + 8),
-                                         __loadword<_Size>(__s + 16),
-                                         __loadword<_Size>(__s + 24),
-                                         __a,
-                                         __b);
-  }
-
-  // Return an 8-byte hash for 33 to 64 bytes.
-  static _Size __hash_len_33_to_64(const char *__s, size_t __len) {
-    _Size __z = __loadword<_Size>(__s + 24);
-    _Size __a = __loadword<_Size>(__s) +
-                (__len + __loadword<_Size>(__s + __len - 16)) * __k0;
-    _Size __b = __rotate(__a + __z, 52);
-    _Size __c = __rotate(__a, 37);
-    __a += __loadword<_Size>(__s + 8);
-    __c += __rotate(__a, 7);
-    __a += __loadword<_Size>(__s + 16);
-    _Size __vf = __a + __z;
-    _Size __vs = __b + __rotate(__a, 31) + __c;
-    __a = __loadword<_Size>(__s + 16) + __loadword<_Size>(__s + __len - 32);
-    __z += __loadword<_Size>(__s + __len - 8);
-    __b = __rotate(__a + __z, 52);
-    __c = __rotate(__a, 37);
-    __a += __loadword<_Size>(__s + __len - 24);
-    __c += __rotate(__a, 7);
-    __a += __loadword<_Size>(__s + __len - 16);
-    _Size __wf = __a + __z;
-    _Size __ws = __b + __rotate(__a, 31) + __c;
-    _Size __r = __shift_mix((__vf + __ws) * __k2 + (__wf + __vs) * __k0);
-    return __shift_mix(__r * __k0 + __vs) * __k2;
-  }
-};
-
-// cityhash64
-template <class _Size>
-_Size
-__murmur2_or_cityhash<_Size, 64>::operator()(const void* __key, _Size __len) _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK 
-{
-  const char* __s = static_cast<const char*>(__key);
-  if (__len <= 32) {
-    if (__len <= 16) {
-      return __hash_len_0_to_16(__s, __len);
-    } else {
-      return __hash_len_17_to_32(__s, __len);
-    }
-  } else if (__len <= 64) {
-    return __hash_len_33_to_64(__s, __len);
-  }
-
-  // For strings over 64 bytes we hash the end first, and then as we
-  // loop we keep 56 bytes of state: v, w, x, y, and z.
-  _Size __x = __loadword<_Size>(__s + __len - 40);
-  _Size __y = __loadword<_Size>(__s + __len - 16) +
-              __loadword<_Size>(__s + __len - 56);
-  _Size __z = __hash_len_16(__loadword<_Size>(__s + __len - 48) + __len,
-                          __loadword<_Size>(__s + __len - 24));
-  pair<_Size, _Size> __v = __weak_hash_len_32_with_seeds(__s + __len - 64, __len, __z);
-  pair<_Size, _Size> __w = __weak_hash_len_32_with_seeds(__s + __len - 32, __y + __k1, __x);
-  __x = __x * __k1 + __loadword<_Size>(__s);
-
-  // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
-  __len = (__len - 1) & ~static_cast<_Size>(63);
-  do {
-    __x = __rotate(__x + __y + __v.first + __loadword<_Size>(__s + 8), 37) * __k1;
-    __y = __rotate(__y + __v.second + __loadword<_Size>(__s + 48), 42) * __k1;
-    __x ^= __w.second;
-    __y += __v.first + __loadword<_Size>(__s + 40);
-    __z = __rotate(__z + __w.first, 33) * __k1;
-    __v = __weak_hash_len_32_with_seeds(__s, __v.second * __k1, __x + __w.first);
-    __w = __weak_hash_len_32_with_seeds(__s + 32, __z + __w.second,
-                                        __y + __loadword<_Size>(__s + 16));
-    std::swap(__z, __x);
-    __s += 64;
-    __len -= 64;
-  } while (__len != 0);
-  return __hash_len_16(
-      __hash_len_16(__v.first, __w.first) + __shift_mix(__y) * __k1 + __z,
-      __hash_len_16(__v.second, __w.second) + __x);
-}
-
-template <class _Tp, size_t = sizeof(_Tp) / sizeof(size_t)>
-struct __scalar_hash;
-
-template <class _Tp>
-struct __scalar_hash<_Tp, 0>
-    : public unary_function<_Tp, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(_Tp __v) const _NOEXCEPT
-    {
-        union
-        {
-            _Tp    __t;
-            size_t __a;
-        } __u;
-        __u.__a = 0;
-        __u.__t = __v;
-        return __u.__a;
-    }
-};
-
-template <class _Tp>
-struct __scalar_hash<_Tp, 1>
-    : public unary_function<_Tp, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(_Tp __v) const _NOEXCEPT
-    {
-        union
-        {
-            _Tp    __t;
-            size_t __a;
-        } __u;
-        __u.__t = __v;
-        return __u.__a;
-    }
-};
-
-template <class _Tp>
-struct __scalar_hash<_Tp, 2>
-    : public unary_function<_Tp, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(_Tp __v) const _NOEXCEPT
-    {
-        union
-        {
-            _Tp __t;
-            struct
-            {
-                size_t __a;
-                size_t __b;
-            } __s;
-        } __u;
-        __u.__t = __v;
-        return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
-    }
-};
-
-template <class _Tp>
-struct __scalar_hash<_Tp, 3>
-    : public unary_function<_Tp, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(_Tp __v) const _NOEXCEPT
-    {
-        union
-        {
-            _Tp __t;
-            struct
-            {
-                size_t __a;
-                size_t __b;
-                size_t __c;
-            } __s;
-        } __u;
-        __u.__t = __v;
-        return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
-    }
-};
-
-template <class _Tp>
-struct __scalar_hash<_Tp, 4>
-    : public unary_function<_Tp, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(_Tp __v) const _NOEXCEPT
-    {
-        union
-        {
-            _Tp __t;
-            struct
-            {
-                size_t __a;
-                size_t __b;
-                size_t __c;
-                size_t __d;
-            } __s;
-        } __u;
-        __u.__t = __v;
-        return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
-    }
-};
-
-template<class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY hash<_Tp*>
-    : public unary_function<_Tp*, size_t>
-{
-    _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(_Tp* __v) const _NOEXCEPT
-    {
-        union
-        {
-            _Tp* __t;
-            size_t __a;
-        } __u;
-        __u.__t = __v;
-        return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
-    }
-};
-
 template <class _Tp, class _Dp>
-struct _LIBCPP_TYPE_VIS_ONLY hash<unique_ptr<_Tp, _Dp> >
+#ifdef _LIBCPP_CXX03_LANG
+struct _LIBCPP_TEMPLATE_VIS hash<unique_ptr<_Tp, _Dp> >
+#else
+struct _LIBCPP_TEMPLATE_VIS hash<__enable_hash_helper<
+    unique_ptr<_Tp, _Dp>, typename unique_ptr<_Tp, _Dp>::pointer>>
+#endif
 {
     typedef unique_ptr<_Tp, _Dp> argument_type;
     typedef size_t               result_type;
     _LIBCPP_INLINE_VISIBILITY
-    result_type operator()(const argument_type& __ptr) const _NOEXCEPT
+    result_type operator()(const argument_type& __ptr) const
     {
         typedef typename argument_type::pointer pointer;
         return hash<pointer>()(__ptr.get());
@@ -3521,28 +3114,28 @@ struct _LIBCPP_TYPE_VIS_ONLY hash<unique_ptr<_Tp, _Dp> >
 struct __destruct_n
 {
 private:
-    size_t size;
+    size_t __size_;
 
     template <class _Tp>
     _LIBCPP_INLINE_VISIBILITY void __process(_Tp* __p, false_type) _NOEXCEPT
-        {for (size_t __i = 0; __i < size; ++__i, ++__p) __p->~_Tp();}
+        {for (size_t __i = 0; __i < __size_; ++__i, ++__p) __p->~_Tp();}
 
     template <class _Tp>
     _LIBCPP_INLINE_VISIBILITY void __process(_Tp*, true_type) _NOEXCEPT
         {}
 
     _LIBCPP_INLINE_VISIBILITY void __incr(false_type) _NOEXCEPT
-        {++size;}
+        {++__size_;}
     _LIBCPP_INLINE_VISIBILITY void __incr(true_type) _NOEXCEPT
         {}
 
     _LIBCPP_INLINE_VISIBILITY void __set(size_t __s, false_type) _NOEXCEPT
-        {size = __s;}
+        {__size_ = __s;}
     _LIBCPP_INLINE_VISIBILITY void __set(size_t, true_type) _NOEXCEPT
         {}
 public:
     _LIBCPP_INLINE_VISIBILITY explicit __destruct_n(size_t __s) _NOEXCEPT
-        : size(__s) {}
+        : __size_(__s) {}
 
     template <class _Tp>
     _LIBCPP_INLINE_VISIBILITY void __incr(_Tp*) _NOEXCEPT
@@ -3671,6 +3264,181 @@ uninitialized_fill_n(_ForwardIterator __f, _Size __n, const _Tp& __x)
     return __f;
 }
 
+#if _LIBCPP_STD_VER > 14
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+void destroy_at(_Tp* __loc) {
+    _LIBCPP_ASSERT(__loc, "null pointer given to destroy_at");
+    __loc->~_Tp();
+}
+
+template <class _ForwardIterator>
+inline _LIBCPP_INLINE_VISIBILITY
+void destroy(_ForwardIterator __first, _ForwardIterator __last) {
+    for (; __first != __last; ++__first)
+        _VSTD::destroy_at(_VSTD::addressof(*__first));
+}
+
+template <class _ForwardIterator, class _Size>
+inline _LIBCPP_INLINE_VISIBILITY
+_ForwardIterator destroy_n(_ForwardIterator __first, _Size __n) {
+    for (; __n > 0; (void)++__first, --__n)
+        _VSTD::destroy_at(_VSTD::addressof(*__first));
+    return __first;
+}
+
+template <class _ForwardIterator>
+inline _LIBCPP_INLINE_VISIBILITY
+void uninitialized_default_construct(_ForwardIterator __first, _ForwardIterator __last) {
+    using _Vt = typename iterator_traits<_ForwardIterator>::value_type;
+    auto __idx = __first;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try {
+#endif
+    for (; __idx != __last; ++__idx)
+        ::new((void*)_VSTD::addressof(*__idx)) _Vt;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    } catch (...) {
+        _VSTD::destroy(__first, __idx);
+        throw;
+    }
+#endif
+}
+
+template <class _ForwardIterator, class _Size>
+inline _LIBCPP_INLINE_VISIBILITY
+_ForwardIterator uninitialized_default_construct_n(_ForwardIterator __first, _Size __n) {
+    using _Vt = typename iterator_traits<_ForwardIterator>::value_type;
+    auto __idx = __first;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try {
+#endif
+    for (; __n > 0; (void)++__idx, --__n)
+        ::new((void*)_VSTD::addressof(*__idx)) _Vt;
+    return __idx;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    } catch (...) {
+        _VSTD::destroy(__first, __idx);
+        throw;
+    }
+#endif
+}
+
+
+template <class _ForwardIterator>
+inline _LIBCPP_INLINE_VISIBILITY
+void uninitialized_value_construct(_ForwardIterator __first, _ForwardIterator __last) {
+    using _Vt = typename iterator_traits<_ForwardIterator>::value_type;
+    auto __idx = __first;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try {
+#endif
+    for (; __idx != __last; ++__idx)
+        ::new((void*)_VSTD::addressof(*__idx)) _Vt();
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    } catch (...) {
+        _VSTD::destroy(__first, __idx);
+        throw;
+    }
+#endif
+}
+
+template <class _ForwardIterator, class _Size>
+inline _LIBCPP_INLINE_VISIBILITY
+_ForwardIterator uninitialized_value_construct_n(_ForwardIterator __first, _Size __n) {
+    using _Vt = typename iterator_traits<_ForwardIterator>::value_type;
+    auto __idx = __first;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try {
+#endif
+    for (; __n > 0; (void)++__idx, --__n)
+        ::new((void*)_VSTD::addressof(*__idx)) _Vt();
+    return __idx;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    } catch (...) {
+        _VSTD::destroy(__first, __idx);
+        throw;
+    }
+#endif
+}
+
+
+template <class _InputIt, class _ForwardIt>
+inline _LIBCPP_INLINE_VISIBILITY
+_ForwardIt uninitialized_move(_InputIt __first, _InputIt __last, _ForwardIt __first_res) {
+    using _Vt = typename iterator_traits<_ForwardIt>::value_type;
+    auto __idx = __first_res;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try {
+#endif
+    for (; __first != __last; (void)++__idx, ++__first)
+        ::new((void*)_VSTD::addressof(*__idx)) _Vt(std::move(*__first));
+    return __idx;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    } catch (...) {
+        _VSTD::destroy(__first_res, __idx);
+        throw;
+    }
+#endif
+}
+
+template <class _InputIt, class _Size, class _ForwardIt>
+inline _LIBCPP_INLINE_VISIBILITY
+pair<_InputIt, _ForwardIt>
+uninitialized_move_n(_InputIt __first, _Size __n, _ForwardIt __first_res) {
+    using _Vt = typename iterator_traits<_ForwardIt>::value_type;
+    auto __idx = __first_res;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try {
+#endif
+    for (; __n > 0; ++__idx, (void)++__first, --__n)
+        ::new((void*)_VSTD::addressof(*__idx)) _Vt(std::move(*__first));
+    return {__first, __idx};
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    } catch (...) {
+        _VSTD::destroy(__first_res, __idx);
+        throw;
+    }
+#endif
+}
+
+
+#endif // _LIBCPP_STD_VER > 14
+
+// NOTE: Relaxed and acq/rel atomics (for increment and decrement respectively)
+// should be sufficient for thread safety.
+// See https://bugs.llvm.org/show_bug.cgi?id=22803
+#if defined(__clang__) && __has_builtin(__atomic_add_fetch)          \
+                       && defined(__ATOMIC_RELAXED)                  \
+                       && defined(__ATOMIC_ACQ_REL)
+#   define _LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT
+#elif !defined(__clang__) && defined(_GNUC_VER) && _GNUC_VER >= 407
+#   define _LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT
+#endif
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY _Tp
+__libcpp_atomic_refcount_increment(_Tp& __t) _NOEXCEPT
+{
+#if defined(_LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT) && !defined(_LIBCPP_HAS_NO_THREADS)
+    return __atomic_add_fetch(&__t, 1, __ATOMIC_RELAXED);
+#else
+    return __t += 1;
+#endif
+}
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY _Tp
+__libcpp_atomic_refcount_decrement(_Tp& __t) _NOEXCEPT
+{
+#if defined(_LIBCPP_HAS_BUILTIN_ATOMIC_SUPPORT) && !defined(_LIBCPP_HAS_NO_THREADS)
+    return __atomic_add_fetch(&__t, -1, __ATOMIC_ACQ_REL);
+#else
+    return __t -= 1;
+#endif
+}
+
 class _LIBCPP_EXCEPTION_ABI bad_weak_ptr
     : public std::exception
 {
@@ -3679,7 +3447,17 @@ public:
     virtual const char* what() const  _NOEXCEPT;
 };
 
-template<class _Tp> class _LIBCPP_TYPE_VIS_ONLY weak_ptr;
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+void __throw_bad_weak_ptr()
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw bad_weak_ptr();
+#else
+    _VSTD::abort();
+#endif
+}
+
+template<class _Tp> class _LIBCPP_TEMPLATE_VIS weak_ptr;
 
 class _LIBCPP_TYPE_VIS __shared_count
 {
@@ -3697,8 +3475,24 @@ public:
     explicit __shared_count(long __refs = 0) _NOEXCEPT
         : __shared_owners_(__refs) {}
 
+#if defined(_LIBCPP_BUILDING_MEMORY) && \
+    defined(_LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS)
     void __add_shared() _NOEXCEPT;
     bool __release_shared() _NOEXCEPT;
+#else
+    _LIBCPP_INLINE_VISIBILITY
+    void __add_shared() _NOEXCEPT {
+      __libcpp_atomic_refcount_increment(__shared_owners_);
+    }
+    _LIBCPP_INLINE_VISIBILITY
+    bool __release_shared() _NOEXCEPT {
+      if (__libcpp_atomic_refcount_decrement(__shared_owners_) == -1) {
+        __on_zero_shared();
+        return true;
+      }
+      return false;
+    }
+#endif
     _LIBCPP_INLINE_VISIBILITY
     long use_count() const _NOEXCEPT {
         return __libcpp_relaxed_load(&__shared_owners_) + 1;
@@ -3719,9 +3513,26 @@ protected:
     virtual ~__shared_weak_count();
 
 public:
+#if defined(_LIBCPP_BUILDING_MEMORY) && \
+    defined(_LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS)
     void __add_shared() _NOEXCEPT;
     void __add_weak() _NOEXCEPT;
     void __release_shared() _NOEXCEPT;
+#else
+    _LIBCPP_INLINE_VISIBILITY
+    void __add_shared() _NOEXCEPT {
+      __shared_count::__add_shared();
+    }
+    _LIBCPP_INLINE_VISIBILITY
+    void __add_weak() _NOEXCEPT {
+      __libcpp_atomic_refcount_increment(__shared_weak_owners_);
+    }
+    _LIBCPP_INLINE_VISIBILITY
+    void __release_shared() _NOEXCEPT {
+      if (__shared_count::__release_shared())
+        __release_weak();
+    }
+#endif
     void __release_weak() _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     long use_count() const _NOEXCEPT {return __shared_count::use_count();}
@@ -3763,7 +3574,7 @@ template <class _Tp, class _Dp, class _Alloc>
 const void*
 __shared_ptr_pointer<_Tp, _Dp, _Alloc>::__get_deleter(const type_info& __t) const _NOEXCEPT
 {
-    return __t == typeid(_Dp) ? _VSTD::addressof(__data_.first().second()) : 0;
+    return __t == typeid(_Dp) ? _VSTD::addressof(__data_.first().second()) : nullptr;
 }
 
 #endif  // _LIBCPP_NO_RTTI
@@ -3857,13 +3668,26 @@ __shared_ptr_emplace<_Tp, _Alloc>::__on_zero_shared_weak() _NOEXCEPT
     __a.deallocate(_PTraits::pointer_to(*this), 1);
 }
 
-template<class _Tp> class _LIBCPP_TYPE_VIS_ONLY enable_shared_from_this;
+struct __shared_ptr_dummy_rebind_allocator_type;
+template <>
+class _LIBCPP_TEMPLATE_VIS allocator<__shared_ptr_dummy_rebind_allocator_type>
+{
+public:
+    template <class _Other>
+    struct rebind
+    {
+        typedef allocator<_Other> other;
+    };
+};
+
+template<class _Tp> class _LIBCPP_TEMPLATE_VIS enable_shared_from_this;
 
 template<class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY shared_ptr
+class _LIBCPP_TEMPLATE_VIS shared_ptr
 {
 public:
     typedef _Tp element_type;
+
 #if _LIBCPP_STD_VER > 14
     typedef weak_ptr<_Tp> weak_type;
 #endif
@@ -3894,17 +3718,18 @@ public:
     template<class _Yp>
         _LIBCPP_INLINE_VISIBILITY
         shared_ptr(const shared_ptr<_Yp>& __r,
-                   typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat>::type = __nat())
+                   typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type = __nat())
                        _NOEXCEPT;
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     shared_ptr(shared_ptr&& __r) _NOEXCEPT;
     template<class _Yp> _LIBCPP_INLINE_VISIBILITY  shared_ptr(shared_ptr<_Yp>&& __r,
-                   typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat>::type = __nat())
+                   typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type = __nat())
                        _NOEXCEPT;
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     template<class _Yp> explicit shared_ptr(const weak_ptr<_Yp>& __r,
-                   typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat>::type= __nat());
+                   typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type= __nat());
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     template<class _Yp>
         shared_ptr(auto_ptr<_Yp>&& __r,
@@ -3914,6 +3739,7 @@ public:
         shared_ptr(auto_ptr<_Yp> __r,
                    typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type = __nat());
 #endif
+#endif
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     template <class _Yp, class _Dp>
         shared_ptr(unique_ptr<_Yp, _Dp>&&,
@@ -3977,6 +3803,7 @@ public:
         >::type
         _LIBCPP_INLINE_VISIBILITY
         operator=(shared_ptr<_Yp>&& __r);
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
     template<class _Yp>
         _LIBCPP_INLINE_VISIBILITY
         typename enable_if
@@ -3986,7 +3813,9 @@ public:
             shared_ptr
         >::type&
         operator=(auto_ptr<_Yp>&& __r);
+#endif
 #else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
     template<class _Yp>
         _LIBCPP_INLINE_VISIBILITY
         typename enable_if
@@ -3997,6 +3826,7 @@ public:
         >::type
         operator=(auto_ptr<_Yp> __r);
 #endif
+#endif
     template <class _Yp, class _Dp>
         typename enable_if
         <
@@ -4056,11 +3886,11 @@ public:
     _LIBCPP_EXPLICIT operator bool() const _NOEXCEPT {return get() != 0;}
     template <class _Up>
         _LIBCPP_INLINE_VISIBILITY
-        bool owner_before(shared_ptr<_Up> const& __p) const
+        bool owner_before(shared_ptr<_Up> const& __p) const _NOEXCEPT
         {return __cntrl_ < __p.__cntrl_;}
     template <class _Up>
         _LIBCPP_INLINE_VISIBILITY
-        bool owner_before(weak_ptr<_Up> const& __p) const
+        bool owner_before(weak_ptr<_Up> const& __p) const _NOEXCEPT
         {return __cntrl_ < __p.__cntrl_;}
     _LIBCPP_INLINE_VISIBILITY
     bool
@@ -4071,7 +3901,9 @@ public:
     template <class _Dp>
         _LIBCPP_INLINE_VISIBILITY
         _Dp* __get_deleter() const _NOEXCEPT
-            {return (_Dp*)(__cntrl_ ? __cntrl_->__get_deleter(typeid(_Dp)) : 0);}
+            {return static_cast<_Dp*>(__cntrl_
+                    ? const_cast<void *>(__cntrl_->__get_deleter(typeid(_Dp)))
+                      : nullptr);}
 #endif  // _LIBCPP_NO_RTTI
 
 #ifndef _LIBCPP_HAS_NO_VARIADICS
@@ -4118,10 +3950,24 @@ public:
 #endif  // _LIBCPP_HAS_NO_VARIADICS
 
 private:
+    template <class _Yp, bool = is_function<_Yp>::value>
+        struct __shared_ptr_default_allocator
+        {
+            typedef allocator<_Yp> type;
+        };
+
+    template <class _Yp>
+        struct __shared_ptr_default_allocator<_Yp, true>
+        {
+            typedef allocator<__shared_ptr_dummy_rebind_allocator_type> type;
+        };
 
     template <class _Yp, class _OrigPtr>
         _LIBCPP_INLINE_VISIBILITY
-        void
+        typename enable_if<is_convertible<_OrigPtr*,
+                                          const enable_shared_from_this<_Yp>*
+        >::value,
+            void>::type
         __enable_weak_this(const enable_shared_from_this<_Yp>* __e,
                            _OrigPtr* __ptr) _NOEXCEPT
         {
@@ -4133,13 +3979,13 @@ private:
             }
         }
 
-    _LIBCPP_INLINE_VISIBILITY
-    void __enable_weak_this(const volatile void*, const volatile void*) _NOEXCEPT {}
+    _LIBCPP_INLINE_VISIBILITY void __enable_weak_this(...) _NOEXCEPT {}
 
-    template <class _Up> friend class _LIBCPP_TYPE_VIS_ONLY shared_ptr;
-    template <class _Up> friend class _LIBCPP_TYPE_VIS_ONLY weak_ptr;
+    template <class _Up> friend class _LIBCPP_TEMPLATE_VIS shared_ptr;
+    template <class _Up> friend class _LIBCPP_TEMPLATE_VIS weak_ptr;
 };
 
+
 template<class _Tp>
 inline
 _LIBCPP_CONSTEXPR
@@ -4165,8 +4011,9 @@ shared_ptr<_Tp>::shared_ptr(_Yp* __p,
     : __ptr_(__p)
 {
     unique_ptr<_Yp> __hold(__p);
-    typedef __shared_ptr_pointer<_Yp*, default_delete<_Yp>, allocator<_Yp> > _CntrlBlk;
-    __cntrl_ = new _CntrlBlk(__p, default_delete<_Yp>(), allocator<_Yp>());
+    typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
+    typedef __shared_ptr_pointer<_Yp*, default_delete<_Yp>, _AllocT > _CntrlBlk;
+    __cntrl_ = new _CntrlBlk(__p, default_delete<_Yp>(), _AllocT());
     __hold.release();
     __enable_weak_this(__p, __p);
 }
@@ -4181,8 +4028,9 @@ shared_ptr<_Tp>::shared_ptr(_Yp* __p, _Dp __d,
     try
     {
 #endif  // _LIBCPP_NO_EXCEPTIONS
-        typedef __shared_ptr_pointer<_Yp*, _Dp, allocator<_Yp> > _CntrlBlk;
-        __cntrl_ = new _CntrlBlk(__p, __d, allocator<_Yp>());
+        typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
+        typedef __shared_ptr_pointer<_Yp*, _Dp, _AllocT > _CntrlBlk;
+        __cntrl_ = new _CntrlBlk(__p, __d, _AllocT());
         __enable_weak_this(__p, __p);
 #ifndef _LIBCPP_NO_EXCEPTIONS
     }
@@ -4203,8 +4051,9 @@ shared_ptr<_Tp>::shared_ptr(nullptr_t __p, _Dp __d)
     try
     {
 #endif  // _LIBCPP_NO_EXCEPTIONS
-        typedef __shared_ptr_pointer<nullptr_t, _Dp, allocator<_Tp> > _CntrlBlk;
-        __cntrl_ = new _CntrlBlk(__p, __d, allocator<_Tp>());
+        typedef typename __shared_ptr_default_allocator<_Tp>::type _AllocT;
+        typedef __shared_ptr_pointer<nullptr_t, _Dp, _AllocT > _CntrlBlk;
+        __cntrl_ = new _CntrlBlk(__p, __d, _AllocT());
 #ifndef _LIBCPP_NO_EXCEPTIONS
     }
     catch (...)
@@ -4296,7 +4145,7 @@ template<class _Tp>
 template<class _Yp>
 inline
 shared_ptr<_Tp>::shared_ptr(const shared_ptr<_Yp>& __r,
-                            typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat>::type)
+                            typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type)
          _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
@@ -4321,7 +4170,7 @@ template<class _Tp>
 template<class _Yp>
 inline
 shared_ptr<_Tp>::shared_ptr(shared_ptr<_Yp>&& __r,
-                            typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat>::type)
+                            typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type)
          _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
@@ -4332,6 +4181,7 @@ shared_ptr<_Tp>::shared_ptr(shared_ptr<_Yp>&& __r,
 
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
 template<class _Tp>
 template<class _Yp>
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
@@ -4347,6 +4197,7 @@ shared_ptr<_Tp>::shared_ptr(auto_ptr<_Yp> __r,
     __enable_weak_this(__r.get(), __r.get());
     __r.release();
 }
+#endif
 
 template<class _Tp>
 template <class _Yp, class _Dp>
@@ -4370,8 +4221,9 @@ shared_ptr<_Tp>::shared_ptr(unique_ptr<_Yp, _Dp> __r,
     else
 #endif
     {
-        typedef __shared_ptr_pointer<_Yp*, _Dp, allocator<_Yp> > _CntrlBlk;
-        __cntrl_ = new _CntrlBlk(__r.get(), __r.get_deleter(), allocator<_Yp>());
+        typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
+        typedef __shared_ptr_pointer<_Yp*, _Dp, _AllocT > _CntrlBlk;
+        __cntrl_ = new _CntrlBlk(__r.get(), __r.get_deleter(), _AllocT());
         __enable_weak_this(__r.get(), __r.get());
     }
     __r.release();
@@ -4399,10 +4251,11 @@ shared_ptr<_Tp>::shared_ptr(unique_ptr<_Yp, _Dp> __r,
     else
 #endif
     {
+        typedef typename __shared_ptr_default_allocator<_Yp>::type _AllocT;
         typedef __shared_ptr_pointer<_Yp*,
                                      reference_wrapper<typename remove_reference<_Dp>::type>,
-                                     allocator<_Yp> > _CntrlBlk;
-        __cntrl_ = new _CntrlBlk(__r.get(), ref(__r.get_deleter()), allocator<_Yp>());
+                                     _AllocT > _CntrlBlk;
+        __cntrl_ = new _CntrlBlk(__r.get(), ref(__r.get_deleter()), _AllocT());
         __enable_weak_this(__r.get(), __r.get());
     }
     __r.release();
@@ -4415,6 +4268,7 @@ template<class ..._Args>
 shared_ptr<_Tp>
 shared_ptr<_Tp>::make_shared(_Args&& ...__args)
 {
+    static_assert( is_constructible<_Tp, _Args...>::value, "Can't construct object in make_shared" );
     typedef __shared_ptr_emplace<_Tp, allocator<_Tp> > _CntrlBlk;
     typedef allocator<_CntrlBlk> _A2;
     typedef __allocator_destructor<_A2> _D2;
@@ -4433,6 +4287,7 @@ template<class _Alloc, class ..._Args>
 shared_ptr<_Tp>
 shared_ptr<_Tp>::allocate_shared(const _Alloc& __a, _Args&& ...__args)
 {
+    static_assert( is_constructible<_Tp, _Args...>::value, "Can't construct object in allocate_shared" );
     typedef __shared_ptr_emplace<_Tp, _Alloc> _CntrlBlk;
     typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _A2;
     typedef __allocator_destructor<_A2> _D2;
@@ -4453,6 +4308,7 @@ template<class _Tp>
 shared_ptr<_Tp>
 shared_ptr<_Tp>::make_shared()
 {
+    static_assert((is_constructible<_Tp>::value), "Can't construct object in make_shared" );
     typedef __shared_ptr_emplace<_Tp, allocator<_Tp> > _CntrlBlk;
     typedef allocator<_CntrlBlk> _Alloc2;
     typedef __allocator_destructor<_Alloc2> _D2;
@@ -4471,6 +4327,7 @@ template<class _A0>
 shared_ptr<_Tp>
 shared_ptr<_Tp>::make_shared(_A0& __a0)
 {
+    static_assert((is_constructible<_Tp, _A0>::value), "Can't construct object in make_shared" );
     typedef __shared_ptr_emplace<_Tp, allocator<_Tp> > _CntrlBlk;
     typedef allocator<_CntrlBlk> _Alloc2;
     typedef __allocator_destructor<_Alloc2> _D2;
@@ -4489,6 +4346,7 @@ template<class _A0, class _A1>
 shared_ptr<_Tp>
 shared_ptr<_Tp>::make_shared(_A0& __a0, _A1& __a1)
 {
+    static_assert((is_constructible<_Tp, _A0, _A1>::value), "Can't construct object in make_shared" );
     typedef __shared_ptr_emplace<_Tp, allocator<_Tp> > _CntrlBlk;
     typedef allocator<_CntrlBlk> _Alloc2;
     typedef __allocator_destructor<_Alloc2> _D2;
@@ -4507,6 +4365,7 @@ template<class _A0, class _A1, class _A2>
 shared_ptr<_Tp>
 shared_ptr<_Tp>::make_shared(_A0& __a0, _A1& __a1, _A2& __a2)
 {
+    static_assert((is_constructible<_Tp, _A0, _A1, _A2>::value), "Can't construct object in make_shared" );
     typedef __shared_ptr_emplace<_Tp, allocator<_Tp> > _CntrlBlk;
     typedef allocator<_CntrlBlk> _Alloc2;
     typedef __allocator_destructor<_Alloc2> _D2;
@@ -4525,6 +4384,7 @@ template<class _Alloc>
 shared_ptr<_Tp>
 shared_ptr<_Tp>::allocate_shared(const _Alloc& __a)
 {
+    static_assert((is_constructible<_Tp>::value), "Can't construct object in allocate_shared" );
     typedef __shared_ptr_emplace<_Tp, _Alloc> _CntrlBlk;
     typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _Alloc2;
     typedef __allocator_destructor<_Alloc2> _D2;
@@ -4544,6 +4404,7 @@ template<class _Alloc, class _A0>
 shared_ptr<_Tp>
 shared_ptr<_Tp>::allocate_shared(const _Alloc& __a, _A0& __a0)
 {
+    static_assert((is_constructible<_Tp, _A0>::value), "Can't construct object in allocate_shared" );
     typedef __shared_ptr_emplace<_Tp, _Alloc> _CntrlBlk;
     typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _Alloc2;
     typedef __allocator_destructor<_Alloc2> _D2;
@@ -4563,6 +4424,7 @@ template<class _Alloc, class _A0, class _A1>
 shared_ptr<_Tp>
 shared_ptr<_Tp>::allocate_shared(const _Alloc& __a, _A0& __a0, _A1& __a1)
 {
+    static_assert((is_constructible<_Tp, _A0, _A1>::value), "Can't construct object in allocate_shared" );
     typedef __shared_ptr_emplace<_Tp, _Alloc> _CntrlBlk;
     typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _Alloc2;
     typedef __allocator_destructor<_Alloc2> _D2;
@@ -4582,6 +4444,7 @@ template<class _Alloc, class _A0, class _A1, class _A2>
 shared_ptr<_Tp>
 shared_ptr<_Tp>::allocate_shared(const _Alloc& __a, _A0& __a0, _A1& __a1, _A2& __a2)
 {
+    static_assert((is_constructible<_Tp, _A0, _A1, _A2>::value), "Can't construct object in allocate_shared" );
     typedef __shared_ptr_emplace<_Tp, _Alloc> _CntrlBlk;
     typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _Alloc2;
     typedef __allocator_destructor<_Alloc2> _D2;
@@ -4619,7 +4482,7 @@ template<class _Yp>
 inline
 typename enable_if
 <
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     shared_ptr<_Tp>&
 >::type
 shared_ptr<_Tp>::operator=(const shared_ptr<_Yp>& __r) _NOEXCEPT
@@ -4644,7 +4507,7 @@ template<class _Yp>
 inline
 typename enable_if
 <
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     shared_ptr<_Tp>&
 >::type
 shared_ptr<_Tp>::operator=(shared_ptr<_Yp>&& __r)
@@ -4653,13 +4516,14 @@ shared_ptr<_Tp>::operator=(shared_ptr<_Yp>&& __r)
     return *this;
 }
 
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
 template<class _Tp>
 template<class _Yp>
 inline
 typename enable_if
 <
     !is_array<_Yp>::value &&
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     shared_ptr<_Tp>
 >::type&
 shared_ptr<_Tp>::operator=(auto_ptr<_Yp>&& __r)
@@ -4667,6 +4531,7 @@ shared_ptr<_Tp>::operator=(auto_ptr<_Yp>&& __r)
     shared_ptr(_VSTD::move(__r)).swap(*this);
     return *this;
 }
+#endif
 
 template<class _Tp>
 template <class _Yp, class _Dp>
@@ -4674,7 +4539,8 @@ inline
 typename enable_if
 <
     !is_array<_Yp>::value &&
-    is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, _Tp*>::value,
+    is_convertible<typename unique_ptr<_Yp, _Dp>::pointer,
+                   typename shared_ptr<_Tp>::element_type*>::value,
     shared_ptr<_Tp>&
 >::type
 shared_ptr<_Tp>::operator=(unique_ptr<_Yp, _Dp>&& __r)
@@ -4685,13 +4551,14 @@ shared_ptr<_Tp>::operator=(unique_ptr<_Yp, _Dp>&& __r)
 
 #else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
+#if _LIBCPP_STD_VER <= 14 || defined(_LIBCPP_ENABLE_CXX17_REMOVED_AUTO_PTR)
 template<class _Tp>
 template<class _Yp>
 inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
 <
     !is_array<_Yp>::value &&
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     shared_ptr<_Tp>&
 >::type
 shared_ptr<_Tp>::operator=(auto_ptr<_Yp> __r)
@@ -4699,6 +4566,7 @@ shared_ptr<_Tp>::operator=(auto_ptr<_Yp> __r)
     shared_ptr(__r).swap(*this);
     return *this;
 }
+#endif
 
 template<class _Tp>
 template <class _Yp, class _Dp>
@@ -4706,7 +4574,8 @@ inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
 <
     !is_array<_Yp>::value &&
-    is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, _Tp*>::value,
+    is_convertible<typename unique_ptr<_Yp, _Dp>::pointer,
+                   typename shared_ptr<_Tp>::element_type*>::value,
     shared_ptr<_Tp>&
 >::type
 shared_ptr<_Tp>::operator=(unique_ptr<_Yp, _Dp> __r)
@@ -4739,7 +4608,7 @@ template<class _Yp>
 inline
 typename enable_if
 <
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     void
 >::type
 shared_ptr<_Tp>::reset(_Yp* __p)
@@ -4752,7 +4621,7 @@ template<class _Yp, class _Dp>
 inline
 typename enable_if
 <
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     void
 >::type
 shared_ptr<_Tp>::reset(_Yp* __p, _Dp __d)
@@ -4765,7 +4634,7 @@ template<class _Yp, class _Dp, class _Alloc>
 inline
 typename enable_if
 <
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     void
 >::type
 shared_ptr<_Tp>::reset(_Yp* __p, _Dp __d, _Alloc __a)
@@ -5070,7 +4939,7 @@ get_deleter(const shared_ptr<_Tp>& __p) _NOEXCEPT
 #endif  // _LIBCPP_NO_RTTI
 
 template<class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY weak_ptr
+class _LIBCPP_TEMPLATE_VIS weak_ptr
 {
 public:
     typedef _Tp element_type;
@@ -5148,15 +5017,15 @@ public:
     shared_ptr<_Tp> lock() const _NOEXCEPT;
     template<class _Up>
         _LIBCPP_INLINE_VISIBILITY
-        bool owner_before(const shared_ptr<_Up>& __r) const
+        bool owner_before(const shared_ptr<_Up>& __r) const _NOEXCEPT
         {return __cntrl_ < __r.__cntrl_;}
     template<class _Up>
         _LIBCPP_INLINE_VISIBILITY
-        bool owner_before(const weak_ptr<_Up>& __r) const
+        bool owner_before(const weak_ptr<_Up>& __r) const _NOEXCEPT
         {return __cntrl_ < __r.__cntrl_;}
 
-    template <class _Up> friend class _LIBCPP_TYPE_VIS_ONLY weak_ptr;
-    template <class _Up> friend class _LIBCPP_TYPE_VIS_ONLY shared_ptr;
+    template <class _Up> friend class _LIBCPP_TEMPLATE_VIS weak_ptr;
+    template <class _Up> friend class _LIBCPP_TEMPLATE_VIS shared_ptr;
 };
 
 template<class _Tp>
@@ -5330,16 +5199,12 @@ weak_ptr<_Tp>::reset() _NOEXCEPT
 template<class _Tp>
 template<class _Yp>
 shared_ptr<_Tp>::shared_ptr(const weak_ptr<_Yp>& __r,
-                            typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat>::type)
+                            typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type)
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_ ? __r.__cntrl_->lock() : __r.__cntrl_)
 {
     if (__cntrl_ == 0)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw bad_weak_ptr();
-#else
-        assert(!"bad_weak_ptr");
-#endif
+        __throw_bad_weak_ptr();
 }
 
 template<class _Tp>
@@ -5360,63 +5225,63 @@ template <class _Tp> struct owner_less;
 #endif
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY owner_less<shared_ptr<_Tp> >
+struct _LIBCPP_TEMPLATE_VIS owner_less<shared_ptr<_Tp> >
     : binary_function<shared_ptr<_Tp>, shared_ptr<_Tp>, bool>
 {
     typedef bool result_type;
     _LIBCPP_INLINE_VISIBILITY
-    bool operator()(shared_ptr<_Tp> const& __x, shared_ptr<_Tp> const& __y) const
+    bool operator()(shared_ptr<_Tp> const& __x, shared_ptr<_Tp> const& __y) const _NOEXCEPT
         {return __x.owner_before(__y);}
     _LIBCPP_INLINE_VISIBILITY
-    bool operator()(shared_ptr<_Tp> const& __x,   weak_ptr<_Tp> const& __y) const
+    bool operator()(shared_ptr<_Tp> const& __x,   weak_ptr<_Tp> const& __y) const _NOEXCEPT
         {return __x.owner_before(__y);}
     _LIBCPP_INLINE_VISIBILITY
-    bool operator()(  weak_ptr<_Tp> const& __x, shared_ptr<_Tp> const& __y) const
+    bool operator()(  weak_ptr<_Tp> const& __x, shared_ptr<_Tp> const& __y) const _NOEXCEPT
         {return __x.owner_before(__y);}
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY owner_less<weak_ptr<_Tp> >
+struct _LIBCPP_TEMPLATE_VIS owner_less<weak_ptr<_Tp> >
     : binary_function<weak_ptr<_Tp>, weak_ptr<_Tp>, bool>
 {
     typedef bool result_type;
     _LIBCPP_INLINE_VISIBILITY
-    bool operator()(  weak_ptr<_Tp> const& __x,   weak_ptr<_Tp> const& __y) const
+    bool operator()(  weak_ptr<_Tp> const& __x,   weak_ptr<_Tp> const& __y) const _NOEXCEPT
         {return __x.owner_before(__y);}
     _LIBCPP_INLINE_VISIBILITY
-    bool operator()(shared_ptr<_Tp> const& __x,   weak_ptr<_Tp> const& __y) const
+    bool operator()(shared_ptr<_Tp> const& __x,   weak_ptr<_Tp> const& __y) const _NOEXCEPT
         {return __x.owner_before(__y);}
     _LIBCPP_INLINE_VISIBILITY
-    bool operator()(  weak_ptr<_Tp> const& __x, shared_ptr<_Tp> const& __y) const
+    bool operator()(  weak_ptr<_Tp> const& __x, shared_ptr<_Tp> const& __y) const _NOEXCEPT
         {return __x.owner_before(__y);}
 };
 
 #if _LIBCPP_STD_VER > 14
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY owner_less<void>
+struct _LIBCPP_TEMPLATE_VIS owner_less<void>
 {
     template <class _Tp, class _Up>
     _LIBCPP_INLINE_VISIBILITY
-    bool operator()( shared_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) const
+    bool operator()( shared_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) const _NOEXCEPT
         {return __x.owner_before(__y);}
     template <class _Tp, class _Up>
     _LIBCPP_INLINE_VISIBILITY
-    bool operator()( shared_ptr<_Tp> const& __x,  weak_ptr<_Up> const& __y) const
+    bool operator()( shared_ptr<_Tp> const& __x,   weak_ptr<_Up> const& __y) const _NOEXCEPT
         {return __x.owner_before(__y);}
     template <class _Tp, class _Up>
     _LIBCPP_INLINE_VISIBILITY
-    bool operator()(   weak_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) const
+    bool operator()(   weak_ptr<_Tp> const& __x, shared_ptr<_Up> const& __y) const _NOEXCEPT
         {return __x.owner_before(__y);}
     template <class _Tp, class _Up>
     _LIBCPP_INLINE_VISIBILITY
-    bool operator()(   weak_ptr<_Tp> const& __x,   weak_ptr<_Up> const& __y) const
+    bool operator()(   weak_ptr<_Tp> const& __x,   weak_ptr<_Up> const& __y) const _NOEXCEPT
         {return __x.owner_before(__y);}
     typedef void is_transparent;
 };
 #endif
 
 template<class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY enable_shared_from_this
+class _LIBCPP_TEMPLATE_VIS enable_shared_from_this
 {
     mutable weak_ptr<_Tp> __weak_this_;
 protected:
@@ -5451,10 +5316,11 @@ public:
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY hash<shared_ptr<_Tp> >
+struct _LIBCPP_TEMPLATE_VIS hash<shared_ptr<_Tp> >
 {
     typedef shared_ptr<_Tp>      argument_type;
     typedef size_t               result_type;
+
     _LIBCPP_INLINE_VISIBILITY
     result_type operator()(const argument_type& __ptr) const _NOEXCEPT
     {
@@ -5485,7 +5351,8 @@ private:
     friend _LIBCPP_FUNC_VIS __sp_mut& __get_sp_mut(const void*);
 };
 
-_LIBCPP_FUNC_VIS __sp_mut& __get_sp_mut(const void*);
+_LIBCPP_FUNC_VIS _LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
+__sp_mut& __get_sp_mut(const void*);
 
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -5496,6 +5363,7 @@ atomic_is_lock_free(const shared_ptr<_Tp>*)
 }
 
 template <class _Tp>
+_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
 shared_ptr<_Tp>
 atomic_load(const shared_ptr<_Tp>* __p)
 {
@@ -5505,9 +5373,10 @@ atomic_load(const shared_ptr<_Tp>* __p)
     __m.unlock();
     return __q;
 }
-  
+
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
+_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
 shared_ptr<_Tp>
 atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order)
 {
@@ -5515,6 +5384,7 @@ atomic_load_explicit(const shared_ptr<_Tp>* __p, memory_order)
 }
 
 template <class _Tp>
+_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
 void
 atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
 {
@@ -5526,6 +5396,7 @@ atomic_store(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
 
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
+_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
 void
 atomic_store_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order)
 {
@@ -5533,6 +5404,7 @@ atomic_store_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order)
 }
 
 template <class _Tp>
+_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
 shared_ptr<_Tp>
 atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
 {
@@ -5542,9 +5414,10 @@ atomic_exchange(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r)
     __m.unlock();
     return __r;
 }
-  
+
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
+_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
 shared_ptr<_Tp>
 atomic_exchange_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order)
 {
@@ -5552,6 +5425,7 @@ atomic_exchange_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp> __r, memory_order
 }
 
 template <class _Tp>
+_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
 bool
 atomic_compare_exchange_strong(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w)
 {
@@ -5573,6 +5447,7 @@ atomic_compare_exchange_strong(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, share
 
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
+_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
 bool
 atomic_compare_exchange_weak(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_ptr<_Tp> __w)
 {
@@ -5581,6 +5456,7 @@ atomic_compare_exchange_weak(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v, shared_
 
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
+_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
 bool
 atomic_compare_exchange_strong_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v,
                                         shared_ptr<_Tp> __w, memory_order, memory_order)
@@ -5590,6 +5466,7 @@ atomic_compare_exchange_strong_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* _
 
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
+_LIBCPP_AVAILABILITY_ATOMIC_SHARED_PTR
 bool
 atomic_compare_exchange_weak_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v,
                                       shared_ptr<_Tp> __w, memory_order, memory_order)
@@ -5600,6 +5477,15 @@ atomic_compare_exchange_weak_explicit(shared_ptr<_Tp>* __p, shared_ptr<_Tp>* __v
 #endif  // !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
 
 //enum class
+#if defined(_LIBCPP_ABI_POINTER_SAFETY_ENUM_TYPE)
+# ifndef _LIBCPP_CXX03_LANG
+enum class pointer_safety : unsigned char {
+  relaxed,
+  preferred,
+  strict
+};
+# endif
+#else
 struct _LIBCPP_TYPE_VIS pointer_safety
 {
     enum __lx
@@ -5612,15 +5498,32 @@ struct _LIBCPP_TYPE_VIS pointer_safety
     __lx __v_;
 
     _LIBCPP_INLINE_VISIBILITY
+    pointer_safety() : __v_() {}
+
+    _LIBCPP_INLINE_VISIBILITY
     pointer_safety(__lx __v) : __v_(__v) {}
     _LIBCPP_INLINE_VISIBILITY
     operator int() const {return __v_;}
 };
+#endif
+
+#if !defined(_LIBCPP_ABI_POINTER_SAFETY_ENUM_TYPE) && \
+    defined(_LIBCPP_BUILDING_MEMORY)
+_LIBCPP_FUNC_VIS pointer_safety get_pointer_safety() _NOEXCEPT;
+#else
+// This function is only offered in C++03 under ABI v1.
+# if !defined(_LIBCPP_ABI_POINTER_SAFETY_ENUM_TYPE) || !defined(_LIBCPP_CXX03_LANG)
+inline _LIBCPP_INLINE_VISIBILITY
+pointer_safety get_pointer_safety() _NOEXCEPT {
+  return pointer_safety::relaxed;
+}
+# endif
+#endif
+
 
 _LIBCPP_FUNC_VIS void declare_reachable(void* __p);
 _LIBCPP_FUNC_VIS void declare_no_pointers(char* __p, size_t __n);
 _LIBCPP_FUNC_VIS void undeclare_no_pointers(char* __p, size_t __n);
-_LIBCPP_FUNC_VIS pointer_safety get_pointer_safety() _NOEXCEPT;
 _LIBCPP_FUNC_VIS void* __undeclare_reachable(void* __p);
 
 template <class _Tp>
@@ -5643,7 +5546,7 @@ void __swap_allocator(_Alloc & __a1, _Alloc & __a2)
     _NOEXCEPT_(__is_nothrow_swappable<_Alloc>::value)
 #endif
 {
-    __swap_allocator(__a1, __a2, 
+    __swap_allocator(__a1, __a2,
       integral_constant<bool, _VSTD::allocator_traits<_Alloc>::propagate_on_container_swap::value>());
 }
 
@@ -5665,7 +5568,7 @@ inline _LIBCPP_INLINE_VISIBILITY
 void __swap_allocator(_Alloc &, _Alloc &, false_type) _NOEXCEPT {}
 
 template <typename _Alloc, typename _Traits=allocator_traits<_Alloc> >
-struct __noexcept_move_assign_container : public integral_constant<bool, 
+struct __noexcept_move_assign_container : public integral_constant<bool,
     _Traits::propagate_on_container_move_assignment::value
 #if _LIBCPP_STD_VER > 14
         || _Traits::is_always_equal::value
@@ -5679,21 +5582,23 @@ struct __noexcept_move_assign_container : public integral_constant<bool,
 template <class _Tp, class _Alloc>
 struct __temp_value {
     typedef allocator_traits<_Alloc> _Traits;
-    
+
     typename aligned_storage<sizeof(_Tp), alignof(_Tp)>::type __v;
     _Alloc &__a;
 
     _Tp *__addr() { return reinterpret_cast<_Tp *>(addressof(__v)); }
     _Tp &   get() { return *__addr(); }
-        
+
     template<class... _Args>
     __temp_value(_Alloc &__alloc, _Args&& ... __args) : __a(__alloc)
     { _Traits::construct(__a, __addr(), _VSTD::forward<_Args>(__args)...); }
-    
+
     ~__temp_value() { _Traits::destroy(__a, __addr()); }
     };
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_MEMORY
diff --git a/lib/libcxx/include/module.modulemap b/lib/libcxx/include/module.modulemap
index 3fb7428411d..3194b5c9f2a 100644
--- a/lib/libcxx/include/module.modulemap
+++ b/lib/libcxx/include/module.modulemap
@@ -1,13 +1,224 @@
+// define the module for __config outside of the top level 'std' module
+// since __config may be included from C headers which may create an
+// include cycle.
+module std_config [system] [extern_c] {
+    header "__config"
+}
+
 module std [system] {
+  export std_config
   // FIXME: The standard does not require that each of these submodules
   // re-exports its imported modules. We should provide an alternative form of
   // export that issues a warning if a name from the submodule is used, and
   // use that to provide a 'strict mode' for libc++.
+
+  // Deprecated C-compatibility headers. These can all be included from within
+  // an 'extern "C"' context.
+  module depr [extern_c] {
+    // <assert.h> provided by C library.
+    module ctype_h {
+      header "ctype.h"
+      export *
+    }
+    module errno_h {
+      header "errno.h"
+      export *
+    }
+    // <fenv.h> provided by C library.
+    // <float.h> provided by compiler or C library.
+    module inttypes_h {
+      header "inttypes.h"
+      export stdint_h
+      export *
+    }
+    // <iso646.h> provided by compiler.
+    // <limits.h> provided by compiler or C library.
+    module locale_h {
+      header "locale.h"
+      export *
+    }
+    module math_h {
+      header "math.h"
+      export *
+    }
+    module setjmp_h {
+      header "setjmp.h"
+      export *
+    }
+    // FIXME: <stdalign.h> is missing.
+    // <signal.h> provided by C library.
+    // <stdarg.h> provided by compiler.
+    // <stdbool.h> provided by compiler.
+    module stddef_h {
+      // <stddef.h>'s __need_* macros require textual inclusion.
+      textual header "stddef.h"
+    }
+    module stdint_h {
+      header "stdint.h"
+      export *
+      // FIXME: This module only exists on OS X and for some reason the
+      // wildcard above doesn't export it.
+      export Darwin.C.stdint
+    }
+    module stdio_h {
+      // <stdio.h>'s __need_* macros require textual inclusion.
+      textual header "stdio.h"
+      export *
+      export Darwin.C.stdio
+    }
+    module stdlib_h {
+      // <stdlib.h>'s __need_* macros require textual inclusion.
+      textual header "stdlib.h"
+      export *
+    }
+    module string_h {
+      header "string.h"
+      export *
+    }
+    // FIXME: <uchar.h> is missing.
+    // <time.h> provided by C library.
+    module wchar_h {
+      // <wchar.h>'s __need_* macros require textual inclusion.
+      textual header "wchar.h"
+      export *
+    }
+    module wctype_h {
+      header "wctype.h"
+      export *
+    }
+  }
+
+  // <complex.h> and <tgmath.h> are not C headers in any real sense, do not
+  // allow their use in extern "C" contexts.
+  module complex_h {
+    header "complex.h"
+    export ccomplex
+    export *
+  }
+  module tgmath_h {
+    header "tgmath.h"
+    export ccomplex
+    export cmath
+    export *
+  }
+
+  // C compatibility headers.
+  module compat {
+    module cassert {
+      // <cassert>'s use of NDEBUG requires textual inclusion.
+      textual header "cassert"
+    }
+    module ccomplex {
+      header "ccomplex"
+      export complex
+      export *
+    }
+    module cctype {
+      header "cctype"
+      export *
+    }
+    module cerrno {
+      header "cerrno"
+      export *
+    }
+    module cfenv {
+      header "cfenv"
+      export *
+    }
+    module cfloat {
+      header "cfloat"
+      export *
+    }
+    module cinttypes {
+      header "cinttypes"
+      export cstdint
+      export *
+    }
+    module ciso646 {
+      header "ciso646"
+      export *
+    }
+    module climits {
+      header "climits"
+      export *
+    }
+    module clocale {
+      header "clocale"
+      export *
+    }
+    module cmath {
+      header "cmath"
+      export *
+    }
+    module csetjmp {
+      header "csetjmp"
+      export *
+    }
+    module csignal {
+      header "csignal"
+      export *
+    }
+    // FIXME: <cstdalign> is missing.
+    module cstdarg {
+      header "cstdarg"
+      export *
+    }
+    module cstdbool {
+      header "cstdbool"
+      export *
+    }
+    module cstddef {
+      header "cstddef"
+      export *
+    }
+    module cstdint {
+      header "cstdint"
+      export depr.stdint_h
+      export *
+    }
+    module cstdio {
+      header "cstdio"
+      export *
+    }
+    module cstdlib {
+      header "cstdlib"
+      export *
+    }
+    module cstring {
+      header "cstring"
+      export *
+    }
+    module ctgmath {
+      header "ctgmath"
+      export ccomplex
+      export cmath
+      export *
+    }
+    module ctime {
+      header "ctime"
+      export *
+    }
+    // FIXME: <cuchar> is missing.
+    module cwchar {
+      header "cwchar"
+      export depr.stdio_h
+      export *
+    }
+    module cwctype {
+      header "cwctype"
+      export *
+    }
+  }
+
   module algorithm {
     header "algorithm"
     export initializer_list
     export *
   }
+  module any {
+    header "any"
+    export *
+  }
   module array {
     header "array"
     export initializer_list
@@ -16,7 +227,6 @@ module std [system] {
   module atomic {
     header "atomic"
     export *
-    requires cplusplus11
   }
   module bitset {
     header "bitset"
@@ -25,118 +235,10 @@ module std [system] {
     export *
   }
   // No submodule for cassert. It fundamentally needs repeated, textual inclusion.
-  module ccomplex {
-    header "ccomplex"
-    export complex
-    export *
-  }
-  module cctype {
-    header "cctype"
-    export *
-  }
-  module cerrno {
-    header "cerrno"
-/*
-    export_macros    ECONNREFUSED, EIO,          ENODEV,      ENOTEMPTY,       ERANGE,
-      E2BIG,         ECONNRESET,   EISCONN,      ENOENT,      ENOTRECOVERABLE, EROFS,
-      EACCES,        EDEADLK,      EISDIR,       ENOEXEC,     ENOTSOCK,        ESPIPE,
-      EADDRINUSE,    EDESTADDRREQ, ELOOP,        ENOLCK,      ENOTSUP,         ESRCH,
-      EADDRNOTAVAIL, EDOM,         EMFILE,       ENOLINK,     ENOTTY,          ETIME,
-      EAFNOSUPPORT,  EEXIST,       EMLINK,       ENOMEM,      ENXIO,           ETIMEDOUT,
-      EAGAIN,        EFAULT,       EMSGSIZE,     ENOMSG,      EOPNOTSUPP,      ETXTBSY,
-      EALREADY,      EFBIG,        ENAMETOOLONG, ENOPROTOOPT, EOVERFLOW,       EWOULDBLOCK,
-      EBADF,         EHOSTUNREACH, ENETDOWN,     ENOSPC,      EOWNERDEAD,      EXDEV,
-      EBADMSG,       EIDRM,        ENETRESET,    ENOSR,       EPERM,           errno,
-      EBUSY,         EILSEQ,       ENETUNREACH,  ENOSTR,      EPIPE,
-      ECANCELED,     EINPROGRESS,  ENFILE,       ENOSYS,      EPROTO,
-      ECHILD,        EINTR,        ENOBUFS,      ENOTCONN,    EPROTONOSUPPORT,
-      ECONNABORTED,  EINVAL,       ENODATA,      ENOTDIR,     EPROTOTYPE
-*/
-    export *
-  }
-  module cfenv {
-    header "cfenv"
-/*
-    export_macros FE_ALL_EXCEPT, FE_DIVBYZERO, FE_INEXACT, FE_INVALID, FE_OVERFLOW,
-                  FE_UNDERFLOW, FE_DOWNWARD, FE_TONEAREST, FE_TOWARDZERO, FE_UPWARD,
-                  FE_DFL_ENV
-*/
-    export *
-  }
-  module cfloat {
-    header "cfloat"
-/*
-    export_macros FLT_EVAL_METHOD, FLT_RADIX, FLT_ROUNDS,
-                  FLT_DIG, FLT_EPSILON, FLT_MANT_DIG,
-                  FLT_MAX, FLT_MAX_10_EXP, FLT_MAX_EXP,
-                  FLT_MIN, FLT_MIN_10_EXP, FLT_MIN_EXP,
-                  DBL_DIG, DBL_EPSILON, DBL_MANT_DIG,
-                  DBL_MAX, DBL_MAX_10_EXP, DBL_MAX_EXP,
-                  DBL_MIN, DBL_MIN_10_EXP, DBL_MIN_EXP,
-                  LDBL_DIG, LDBL_EPSILON, LDBL_MANT_DIG,
-                  LDBL_MAX, LDBL_MAX_10_EXP, LDBL_MAX_EXP,
-                  LDBL_MIN, LDBL_MIN_10_EXP, LDBL_MIN_EXP
-*/
-    export *
-  }
   module chrono {
     header "chrono"
     export *
   }
-  module cinttypes {
-    header "cinttypes"
-    export cstdint
-/*
-    export_macros
-      PRId8, PRId16, PRId32, PRId64, PRIdFAST8, PRIdFAST16, PRIdFAST32, PRIdFAST64, PRIdLEAST8, PRIdLEAST16, PRIdLEAST32, PRIdLEAST64, PRIdMAX, PRIdPTR,
-      PRIi8, PRIi16, PRIi32, PRIi64, PRIiFAST8, PRIiFAST16, PRIiFAST32, PRIiFAST64, PRIiLEAST8, PRIiLEAST16, PRIiLEAST32, PRIiLEAST64, PRIiMAX, PRIiPTR,
-      PRIo8, PRIo16, PRIo32, PRIo64, PRIoFAST8, PRIoFAST16, PRIoFAST32, PRIoFAST64, PRIoLEAST8, PRIoLEAST16, PRIoLEAST32, PRIoLEAST64, PRIoMAX, PRIoPTR,
-      PRIu8, PRIu16, PRIu32, PRIu64, PRIuFAST8, PRIuFAST16, PRIuFAST32, PRIuFAST64, PRIuLEAST8, PRIuLEAST16, PRIuLEAST32, PRIuLEAST64, PRIuMAX, PRIuPTR,
-      PRIx8, PRIx16, PRIx32, PRIx64, PRIxFAST8, PRIxFAST16, PRIxFAST32, PRIxFAST64, PRIxLEAST8, PRIxLEAST16, PRIxLEAST32, PRIxLEAST64, PRIxMAX, PRIxPTR,
-      PRIX8, PRIX16, PRIX32, PRIX64, PRIXFAST8, PRIXFAST16, PRIXFAST32, PRIXFAST64, PRIXLEAST8, PRIXLEAST16, PRIXLEAST32, PRIXLEAST64, PRIXMAX, PRIXPTR,
-      SCNd8, SCNd16, SCNd32, SCNd64, SCNdFAST8, SCNdFAST16, SCNdFAST32, SCNdFAST64, SCNdLEAST8, SCNdLEAST16, SCNdLEAST32, SCNdLEAST64, SCNdMAX, SCNdPTR,
-      SCNi8, SCNi16, SCNi32, SCNi64, SCNiFAST8, SCNiFAST16, SCNiFAST32, SCNiFAST64, SCNiLEAST8, SCNiLEAST16, SCNiLEAST32, SCNiLEAST64, SCNiMAX, SCNiPTR,
-      SCNo8, SCNo16, SCNo32, SCNo64, SCNoFAST8, SCNoFAST16, SCNoFAST32, SCNoFAST64, SCNoLEAST8, SCNoLEAST16, SCNoLEAST32, SCNoLEAST64, SCNoMAX, SCNoPTR,
-      SCNu8, SCNu16, SCNu32, SCNu64, SCNuFAST8, SCNuFAST16, SCNuFAST32, SCNuFAST64, SCNuLEAST8, SCNuLEAST16, SCNuLEAST32, SCNuLEAST64, SCNuMAX, SCNuPTR,
-      SCNx8, SCNx16, SCNx32, SCNx64, SCNxFAST8, SCNxFAST16, SCNxFAST32, SCNxFAST64, SCNxLEAST8, SCNxLEAST16, SCNxLEAST32, SCNxLEAST64, SCNxMAX, SCNxPTR,
-      SCNX8, SCNX16, SCNX32, SCNX64, SCNXFAST8, SCNXFAST16, SCNXFAST32, SCNXFAST64, SCNXLEAST8, SCNXLEAST16, SCNXLEAST32, SCNXLEAST64, SCNXMAX, SCNXPTR
-*/
-    export *
-  }
-  module ciso646 {
-    header "ciso646"
-    export *
-  }
-  module climits {
-    header "climits"
-/*
-    export_macros CHAR_BIT,  CHAR_MIN,  CHAR_MAX,
-                  SCHAR_MIN, SCHAR_MAX, UCHAR_MAX,
-                  SHRT_MIN,  SHRT_MAX,  USHRT_MAX,
-                  INT_MIN,   INT_MAX,   UINT_MAX,
-                  LONG_MIN,  LONG_MAX,  ULONG_MAX,
-                  LLONG_MIN, LLONG_MAX, ULLONG_MAX,
-                  MB_LEN_MAX
-*/
-    export *
-  }
-  module clocale {
-    header "clocale"
-/*
-    export_macros LC_ALL, LC_COLLATE, LC_CTYPE, LC_MONETARY, LC_NUMERIC, LC_TIME, NULL
-*/
-    export *
-  }
-  module cmath {
-    header "cmath"
-/*
-    export_macros FP_FAST_FMA, FP_FAST_FMAF, FP_FAST_FMAL, FP_ILOGBO, FP_ILOGBNAN,
-                  FP_INFINITE, FP_NAN, FP_NORMAL, FP_SUBNORMAL, FP_ZERO,
-                  HUGE_VAL, HUGE_VALF, HUGE_VALL, INFINITY, NAN,
-                  MATH_ERRNO, MATH_ERREXCEPT, math_errhandling
-*/
-    export *
-  }
   module codecvt {
     header "codecvt"
     export *
@@ -149,108 +251,6 @@ module std [system] {
     header "condition_variable"
     export *
   }
-  module csetjmp {
-    header "csetjmp"
-/*
-    export_macros setjmp
-*/
-    export *
-  }
-  module csignal {
-    header "csignal"
-/*
-    export_macros SIGABRT, SIGFPE, SIGILL, SIGINT, SIGSEGV, SIGTERM,
-                  SIG_DFL, SIG_IGN, SIG_ERR
-*/
-    export *
-  }
-  module cstdarg {
-    header "cstdarg"
-/*
-    export_macros va_arg, va_start, va_end, va_copy
-*/
-    export *
-  }
-  module cstdbool {
-    header "cstdbool"
-/*
-    export_macros __bool_true_false_are_defined
-*/
-    export *
-  }
-  module cstddef {
-    header "cstddef"
-/*
-    export_macros NULL, offsetof
-*/
-    export *
-  }
-  module cstdint {
-    header "cstdint"
-/*
-    export_macros
-      INT_8_MIN, INT_8_MAX, UINT_8_MAX, INT_16_MIN, INT_16_MAX, UINT_16_MAX,
-      INT_32_MIN, INT_32_MAX, UINT_32_MAX, INT_64_MIN, INT_64_MAX, UINT_64_MAX,
-      INT_FAST8_MIN, INT_FAST8_MAX, UINT_FAST8_MAX, INT_FAST16_MIN, INT_FAST16_MAX, UINT_FAST16_MAX,
-      INT_FAST32_MIN, INT_FAST32_MAX, UINT_FAST32_MAX, INT_FAST64_MIN, INT_FAST64_MAX, UINT_FAST64_MAX,
-      INT_LEAST8_MIN, INT_LEAST8_MAX, UINT_LEAST8_MAX, INT_LEAST16_MIN, INT_LEAST16_MAX, UINT_LEAST16_MAX,
-      INT_LEAST32_MIN, INT_LEAST32_MAX, UINT_LEAST32_MAX, INT_LEAST64_MIN, INT_LEAST64_MAX, UINT_LEAST64_MAX,
-      INT_MAX_MIN, INT_MAX_MAX, UINT_MAX_MAX, INT_PTR_MIN, INT_PTR_MAX, UINT_PTR_MAX,
-      PTRDIFF_MIN, PTRDIFF_MAX, SIG_ATOMIC_MIN, SIG_ATOMIC_MAX, WCHAR_MIN, WCHAR_MAX, WINT_MIN, WINT_MAX,
-      SIZE_MAX
-*/
-    export *
-  }
-  module cstdio {
-    header "cstdio"
-/*
-    export_macros BUFSIZ, EOF, FILENAME_MAX, FOPEN_MAX, L_tmpnam, NULL,
-                  SEEK_CUR, SEEK_END, SEEK_SET, TMP_MAX, _IOFBF, _IOLBF,
-                  stdin, stdout, stderr
-*/
-    export *
-  }
-  module cstdlib {
-    header "cstdlib"
-/*
-    export_macros RAND_MAX
-*/
-    export *
-  }
-  module cstring {
-    header "cstring"
-/*
-    export_macros NULL
-*/
-    export *
-  }
-  module ctgmath {
-    header "ctgmath"
-    export ccomplex
-    export cmath
-    export *
-  }
-  module ctime {
-    header "ctime"
-/*
-    export_macros NULL, CLOCKS_PER_SEC
-*/
-    export *
-  }
-  module cwchar {
-    header "cwchar"
-/*
-    export_macros NULL, WCHAR_MAX, WCHAR_MIN, WEOF
-*/
-    export *
-  }
-  module cwctype {
-    header "cwctype"
-/*
-    export_macros WEOF
-*/
-    export *
-  }
   module deque {
     header "deque"
     export initializer_list
@@ -345,6 +345,10 @@ module std [system] {
     header "numeric"
     export *
   }
+  module optional {
+    header "optional"
+    export *
+  }
   module ostream {
     header "ostream"
     // FIXME: should re-export ios, streambuf?
@@ -399,11 +403,19 @@ module std [system] {
   module string {
     header "string"
     export initializer_list
+    export string_view
+    export __string
+    export *
+  }
+  module string_view {
+    header "string_view"
+    export initializer_list
+    export __string
     export *
   }
   module strstream {
     header "strstream"
-    requires !cplusplus11
+    export *
   }
   module system_error {
     header "system_error"
@@ -449,17 +461,16 @@ module std [system] {
     export initializer_list
     export *
   }
+  module variant {
+    header "variant"
+    export *
+  }
   module vector {
     header "vector"
     export initializer_list
     export *
   }
 
-  // FIXME: We don't have modules for the <foo.h> headers, because they might
-  // be included from the C library's headers, and that would create a #include
-  // cycle. For the same reason, we don't have a module for __config.
-  //module __config { header "__config" export * }
-
   // FIXME: These should be private.
   module __bit_reference { header "__bit_reference" export * }
   module __debug { header "__debug" export * }
@@ -470,8 +481,131 @@ module std [system] {
   module __split_buffer { header "__split_buffer" export * }
   module __sso_allocator { header "__sso_allocator" export * }
   module __std_stream { header "__std_stream" export * }
+  module __string { header "__string" export * }
   module __tree { header "__tree" export * }
   module __tuple { header "__tuple" export * }
-  module __undef_min_max { header "__undef_min_max" export * }
-  module __undef___deallocate { header "__undef___deallocate" export * }
+  module __undef_macros { header "__undef_macros" export * }
+
+  module experimental {
+    requires cplusplus11
+
+    module algorithm {
+      header "experimental/algorithm"
+      export *
+    }
+    module any {
+      header "experimental/any"
+      export *
+    }
+    module chrono {
+      header "experimental/chrono"
+      export *
+    }
+     module coroutine {
+      requires coroutines
+      header "experimental/coroutine"
+      export *
+    }
+    module deque {
+      header "experimental/deque"
+      export *
+    }
+    module dynarray {
+      header "experimental/dynarray"
+      export *
+    }
+    module filesystem {
+      header "experimental/filesystem"
+      export *
+    }
+    module forward_list {
+      header "experimental/forward_list"
+      export *
+    }
+    module functional {
+      header "experimental/functional"
+      export *
+    }
+    module iterator {
+      header "experimental/iterator"
+      export *
+    }
+    module list {
+      header "experimental/list"
+      export *
+    }
+    module map {
+      header "experimental/map"
+      export *
+    }
+    module memory_resource {
+      header "experimental/memory_resource"
+      export *
+    }
+    module numeric {
+      header "experimental/numeric"
+      export *
+    }
+    module optional {
+      header "experimental/optional"
+      export *
+    }
+    module propagate_const {
+      header "experimental/propagate_const"
+      export *
+    }
+    module ratio {
+      header "experimental/ratio"
+      export *
+    }
+    module regex {
+      header "experimental/regex"
+      export *
+    }
+    module set {
+      header "experimental/set"
+      export *
+    }
+    module string {
+      header "experimental/string"
+      export *
+    }
+    module string_view {
+      header "experimental/string_view"
+      export *
+    }
+    module system_error {
+      header "experimental/system_error"
+      export *
+    }
+    module tuple {
+      header "experimental/tuple"
+      export *
+    }
+    module type_traits {
+      header "experimental/type_traits"
+      export *
+    }
+    module unordered_map {
+      header "experimental/unordered_map"
+      export *
+    }
+    module unordered_set {
+      header "experimental/unordered_set"
+      export *
+    }
+    module utility {
+      header "experimental/utility"
+      export *
+    }
+    module vector {
+      header "experimental/vector"
+      export *
+    }
+    // FIXME these should be private
+    module __memory {
+      header "experimental/__memory"
+      export *
+    }
+  } // end experimental
 }
diff --git a/lib/libcxx/include/mutex b/lib/libcxx/include/mutex
index c047cf943e8..52e39b0fb1f 100644
--- a/lib/libcxx/include/mutex
+++ b/lib/libcxx/include/mutex
@@ -91,9 +91,9 @@ struct defer_lock_t {};
 struct try_to_lock_t {};
 struct adopt_lock_t {};
 
-constexpr defer_lock_t  defer_lock{};
-constexpr try_to_lock_t try_to_lock{};
-constexpr adopt_lock_t  adopt_lock{};
+inline constexpr defer_lock_t  defer_lock{};
+inline constexpr try_to_lock_t try_to_lock{};
+inline constexpr adopt_lock_t  adopt_lock{};
 
 template <class Mutex>
 class lock_guard
@@ -109,15 +109,17 @@ public:
     lock_guard& operator=(lock_guard const&) = delete;
 };
 
-template <class... MutexTypes> // Variadic lock_guard only provided in ABI V2.
-class lock_guard
+template <class... MutexTypes>
+class scoped_lock // C++17
 {
 public:
-    explicit lock_guard(MutexTypes&... m);
-    lock_guard(MutexTypes&... m, adopt_lock_t);
-    ~lock_guard();
-    lock_guard(lock_guard const&) = delete;
-    lock_guard& operator=(lock_guard const&) = delete;
+    using mutex_type = Mutex;  // If MutexTypes... consists of the single type Mutex
+
+    explicit scoped_lock(MutexTypes&... m);
+    scoped_lock(adopt_lock_t, MutexTypes&... m);
+    ~scoped_lock();
+    scoped_lock(scoped_lock const&) = delete;
+    scoped_lock& operator=(scoped_lock const&) = delete;
 private:
     tuple<MutexTypes&...> pm; // exposition only
 };
@@ -189,24 +191,26 @@ template<class Callable, class ...Args>
 #include <__mutex_base>
 #include <functional>
 #include <memory>
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 #include <tuple>
 #endif
 #include <__threading_support>
 
-#include <__undef_min_max>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #ifndef _LIBCPP_HAS_NO_THREADS
 
 class _LIBCPP_TYPE_VIS recursive_mutex
 {
-    __libcpp_mutex_t __m_;
+    __libcpp_recursive_mutex_t __m_;
 
 public:
      recursive_mutex();
@@ -221,7 +225,8 @@ public:
     bool try_lock() _NOEXCEPT;
     void unlock()  _NOEXCEPT;
 
-    typedef __libcpp_mutex_t* native_handle_type;
+    typedef __libcpp_recursive_mutex_t* native_handle_type;
+
     _LIBCPP_INLINE_VISIBILITY
     native_handle_type native_handle() {return &__m_;}
 };
@@ -247,6 +252,7 @@ public:
         bool try_lock_for(const chrono::duration<_Rep, _Period>& __d)
             {return try_lock_until(chrono::steady_clock::now() + __d);}
     template <class _Clock, class _Duration>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         bool try_lock_until(const chrono::time_point<_Clock, _Duration>& __t);
     void unlock() _NOEXCEPT;
 };
@@ -290,6 +296,7 @@ public:
         bool try_lock_for(const chrono::duration<_Rep, _Period>& __d)
             {return try_lock_until(chrono::steady_clock::now() + __d);}
     template <class _Clock, class _Duration>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         bool try_lock_until(const chrono::time_point<_Clock, _Duration>& __t);
     void unlock() _NOEXCEPT;
 };
@@ -338,7 +345,7 @@ try_lock(_L0& __l0, _L1& __l1)
     return 0;
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _L0, class _L1, class _L2, class... _L3>
 int
@@ -357,7 +364,7 @@ try_lock(_L0& __l0, _L1& __l1, _L2& __l2, _L3&... __l3)
     return __r;
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _L0, class _L1>
 void
@@ -386,7 +393,7 @@ lock(_L0& __l0, _L1& __l1)
     }
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _L0, class _L1, class _L2, class ..._L3>
 void
@@ -461,19 +468,96 @@ void __unlock(_L0& __l0, _L1& __l1, _L2& __l2, _L3&... __l3) {
     _VSTD::__unlock(__l2, __l3...);
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+#endif  // _LIBCPP_CXX03_LANG
+
+#if _LIBCPP_STD_VER > 14
+template <class ..._Mutexes>
+class _LIBCPP_TEMPLATE_VIS scoped_lock;
+
+template <>
+class _LIBCPP_TEMPLATE_VIS scoped_lock<> {
+public:
+    explicit scoped_lock() {}
+    ~scoped_lock() = default;
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit scoped_lock(adopt_lock_t) {}
+
+    scoped_lock(scoped_lock const&) = delete;
+    scoped_lock& operator=(scoped_lock const&) = delete;
+};
+
+template <class _Mutex>
+class _LIBCPP_TEMPLATE_VIS scoped_lock<_Mutex> {
+public:
+    typedef _Mutex  mutex_type;
+private:
+    mutex_type& __m_;
+public:
+    explicit scoped_lock(mutex_type & __m) _LIBCPP_THREAD_SAFETY_ANNOTATION(acquire_capability(__m))
+        : __m_(__m) {__m_.lock();}
+
+    ~scoped_lock() _LIBCPP_THREAD_SAFETY_ANNOTATION(release_capability()) {__m_.unlock();}
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit scoped_lock(adopt_lock_t, mutex_type& __m) _LIBCPP_THREAD_SAFETY_ANNOTATION(requires_capability(__m))
+        : __m_(__m) {}
+
+    scoped_lock(scoped_lock const&) = delete;
+    scoped_lock& operator=(scoped_lock const&) = delete;
+};
+
+template <class ..._MArgs>
+class _LIBCPP_TEMPLATE_VIS scoped_lock
+{
+    static_assert(sizeof...(_MArgs) > 1, "At least 2 lock types required");
+    typedef tuple<_MArgs&...> _MutexTuple;
+
+public:
+    _LIBCPP_INLINE_VISIBILITY
+    explicit scoped_lock(_MArgs&... __margs)
+      : __t_(__margs...)
+    {
+        _VSTD::lock(__margs...);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    scoped_lock(adopt_lock_t, _MArgs&... __margs)
+        : __t_(__margs...)
+    {
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    ~scoped_lock() {
+        typedef typename __make_tuple_indices<sizeof...(_MArgs)>::type _Indices;
+        __unlock_unpack(_Indices{}, __t_);
+    }
+
+    scoped_lock(scoped_lock const&) = delete;
+    scoped_lock& operator=(scoped_lock const&) = delete;
+
+private:
+    template <size_t ..._Indx>
+    _LIBCPP_INLINE_VISIBILITY
+    static void __unlock_unpack(__tuple_indices<_Indx...>, _MutexTuple& __mt) {
+        _VSTD::__unlock(_VSTD::get<_Indx>(__mt)...);
+    }
+
+    _MutexTuple __t_;
+};
 
+#endif // _LIBCPP_STD_VER > 14
 #endif // !_LIBCPP_HAS_NO_THREADS
 
-struct _LIBCPP_TYPE_VIS_ONLY once_flag;
+struct _LIBCPP_TEMPLATE_VIS once_flag;
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 
 template<class _Callable, class... _Args>
 _LIBCPP_INLINE_VISIBILITY
 void call_once(once_flag&, _Callable&&, _Args&&...);
 
-#else  // _LIBCPP_HAS_NO_VARIADICS
+#else  // _LIBCPP_CXX03_LANG
 
 template<class _Callable>
 _LIBCPP_INLINE_VISIBILITY
@@ -483,9 +567,9 @@ template<class _Callable>
 _LIBCPP_INLINE_VISIBILITY
 void call_once(once_flag&, const _Callable&);
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+#endif  // _LIBCPP_CXX03_LANG
 
-struct _LIBCPP_TYPE_VIS_ONLY once_flag
+struct _LIBCPP_TEMPLATE_VIS once_flag
 {
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR
@@ -497,11 +581,11 @@ private:
 
     unsigned long __state_;
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
     template<class _Callable, class... _Args>
     friend
     void call_once(once_flag&, _Callable&&, _Args&&...);
-#else  // _LIBCPP_HAS_NO_VARIADICS
+#else  // _LIBCPP_CXX03_LANG
     template<class _Callable>
     friend
     void call_once(once_flag&, _Callable&);
@@ -509,10 +593,10 @@ private:
     template<class _Callable>
     friend
     void call_once(once_flag&, const _Callable&);
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+#endif  // _LIBCPP_CXX03_LANG
 };
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Fp>
 class __call_once_param
@@ -567,14 +651,14 @@ __call_once_proxy(void* __vp)
 
 _LIBCPP_FUNC_VIS void __call_once(volatile unsigned long&, void*, void(*)(void*));
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 
 template<class _Callable, class... _Args>
 inline _LIBCPP_INLINE_VISIBILITY
 void
 call_once(once_flag& __flag, _Callable&& __func, _Args&&... __args)
 {
-    if (__libcpp_relaxed_load(&__flag.__state_) != ~0ul)
+    if (__libcpp_acquire_load(&__flag.__state_) != ~0ul)
     {
         typedef tuple<_Callable&&, _Args&&...> _Gp;
         _Gp __f(_VSTD::forward<_Callable>(__func), _VSTD::forward<_Args>(__args)...);
@@ -583,14 +667,14 @@ call_once(once_flag& __flag, _Callable&& __func, _Args&&... __args)
     }
 }
 
-#else  // _LIBCPP_HAS_NO_VARIADICS
+#else  // _LIBCPP_CXX03_LANG
 
 template<class _Callable>
 inline _LIBCPP_INLINE_VISIBILITY
 void
 call_once(once_flag& __flag, _Callable& __func)
 {
-    if (__libcpp_relaxed_load(&__flag.__state_) != ~0ul)
+    if (__libcpp_acquire_load(&__flag.__state_) != ~0ul)
     {
         __call_once_param<_Callable> __p(__func);
         __call_once(__flag.__state_, &__p, &__call_once_proxy<_Callable>);
@@ -602,72 +686,17 @@ inline _LIBCPP_INLINE_VISIBILITY
 void
 call_once(once_flag& __flag, const _Callable& __func)
 {
-    if (__flag.__state_ != ~0ul)
+    if (__libcpp_acquire_load(&__flag.__state_) != ~0ul)
     {
         __call_once_param<const _Callable> __p(__func);
         __call_once(__flag.__state_, &__p, &__call_once_proxy<const _Callable>);
     }
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-
-
-#if defined(_LIBCPP_ABI_VARIADIC_LOCK_GUARD) \
-    && !defined(_LIBCPP_CXX03_LANG)
-template <>
-class _LIBCPP_TYPE_VIS_ONLY lock_guard<> {
-public:
-    explicit lock_guard() {}
-    ~lock_guard() = default;
-
-    _LIBCPP_INLINE_VISIBILITY
-    explicit lock_guard(adopt_lock_t) {}
-
-    lock_guard(lock_guard const&) = delete;
-    lock_guard& operator=(lock_guard const&) = delete;
-};
-
-template <class ..._MArgs>
-class _LIBCPP_TYPE_VIS_ONLY lock_guard
-{
-    static_assert(sizeof...(_MArgs) >= 2, "At least 2 lock types required");
-    typedef tuple<_MArgs&...> _MutexTuple;
-
-public:
-    _LIBCPP_INLINE_VISIBILITY
-    explicit lock_guard(_MArgs&... __margs)
-      : __t_(__margs...)
-    {
-        _VSTD::lock(__margs...);
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    lock_guard(_MArgs&... __margs, adopt_lock_t)
-        : __t_(__margs...)
-    {
-    }
-
-    _LIBCPP_INLINE_VISIBILITY
-    ~lock_guard() {
-        typedef typename __make_tuple_indices<sizeof...(_MArgs)>::type _Indices;
-        __unlock_unpack(_Indices{}, __t_);
-    }
-
-    lock_guard(lock_guard const&) = delete;
-    lock_guard& operator=(lock_guard const&) = delete;
-
-private:
-    template <size_t ..._Indx>
-    _LIBCPP_INLINE_VISIBILITY
-    static void __unlock_unpack(__tuple_indices<_Indx...>, _MutexTuple& __mt) {
-        _VSTD::__unlock(_VSTD::get<_Indx>(__mt)...);
-    }
-
-    _MutexTuple __t_;
-};
-
-#endif // _LIBCPP_ABI_VARIADIC_LOCK_GUARD
+#endif  // _LIBCPP_CXX03_LANG
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_MUTEX
diff --git a/lib/libcxx/include/new b/lib/libcxx/include/new
index d2b2ae648b4..4e527501b1e 100644
--- a/lib/libcxx/include/new
+++ b/lib/libcxx/include/new
@@ -27,40 +27,61 @@ public:
     virtual const char* what() const noexcept;
 };
 
-class bad_array_length : public bad_alloc // C++14
+class bad_array_length : public bad_alloc // FIXME: Not part of C++
 {
 public:
     bad_array_length() noexcept;
 };
 
-class bad_array_new_length : public bad_alloc
+class bad_array_new_length : public bad_alloc // C++14
 {
 public:
     bad_array_new_length() noexcept;
 };
 
+enum class align_val_t : size_t {}; // C++17
 struct nothrow_t {};
 extern const nothrow_t nothrow;
 typedef void (*new_handler)();
 new_handler set_new_handler(new_handler new_p) noexcept;
 new_handler get_new_handler() noexcept;
 
+// 21.6.4, pointer optimization barrier
+template <class T> constexpr T* launder(T* p) noexcept; // C++17
 }  // std
 
-void* operator new(std::size_t size);                                   // replaceable
-void* operator new(std::size_t size, const std::nothrow_t&) noexcept;   // replaceable
+void* operator new(std::size_t size);                                   // replaceable, nodiscard in C++2a
+void* operator new(std::size_t size, std::align_val_t alignment);       // replaceable, C++17, nodiscard in C++2a
+void* operator new(std::size_t size, const std::nothrow_t&) noexcept;   // replaceable, nodiscard in C++2a
+void* operator new(std::size_t size, std::align_val_t alignment,
+                   const std::nothrow_t&) noexcept;                     // replaceable, C++17, nodiscard in C++2a
 void  operator delete(void* ptr) noexcept;                              // replaceable
 void  operator delete(void* ptr, std::size_t size) noexcept;            // replaceable, C++14
+void  operator delete(void* ptr, std::align_val_t alignment) noexcept;  // replaceable, C++17
+void  operator delete(void* ptr, std::size_t size,
+                      std::align_val_t alignment) noexcept;             // replaceable, C++17
 void  operator delete(void* ptr, const std::nothrow_t&) noexcept;       // replaceable
-
-void* operator new[](std::size_t size);                                 // replaceable
-void* operator new[](std::size_t size, const std::nothrow_t&) noexcept; // replaceable
+void  operator delete(void* ptr, std:align_val_t alignment,
+                      const std::nothrow_t&) noexcept;                  // replaceable, C++17
+
+void* operator new[](std::size_t size);                                 // replaceable, nodiscard in C++2a
+void* operator new[](std::size_t size,
+                     std::align_val_t alignment) noexcept;              // replaceable, C++17, nodiscard in C++2a
+void* operator new[](std::size_t size, const std::nothrow_t&) noexcept; // replaceable, nodiscard in C++2a
+void* operator new[](std::size_t size, std::align_val_t alignment,
+                     const std::nothrow_t&) noexcept;                   // replaceable, C++17, nodiscard in C++2a
 void  operator delete[](void* ptr) noexcept;                            // replaceable
 void  operator delete[](void* ptr, std::size_t size) noexcept;          // replaceable, C++14
+void  operator delete[](void* ptr,
+                        std::align_val_t alignment) noexcept;           // replaceable, C++17
+void  operator delete[](void* ptr, std::size_t size,
+                        std::align_val_t alignment) noexcept;           // replaceable, C++17
 void  operator delete[](void* ptr, const std::nothrow_t&) noexcept;     // replaceable
+void  operator delete[](void* ptr, std::align_val_t alignment,
+                        const std::nothrow_t&) noexcept;                // replaceable, C++17
 
-void* operator new  (std::size_t size, void* ptr) noexcept;
-void* operator new[](std::size_t size, void* ptr) noexcept;
+void* operator new  (std::size_t size, void* ptr) noexcept;             // nodiscard in C++2a
+void* operator new[](std::size_t size, void* ptr) noexcept;             // nodiscard in C++2a
 void  operator delete  (void* ptr, void*) noexcept;
 void  operator delete[](void* ptr, void*) noexcept;
 
@@ -69,16 +90,36 @@ void  operator delete[](void* ptr, void*) noexcept;
 #include <__config>
 #include <exception>
 #include <cstddef>
+#ifdef _LIBCPP_NO_EXCEPTIONS
+#include <cstdlib>
+#endif
 
-#include <__undef___deallocate>
+#if defined(_LIBCPP_ABI_MICROSOFT) && !defined(_LIBCPP_NO_VCRUNTIME)
+#include <new.h>
+#endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+#if !(defined(_LIBCPP_BUILDING_NEW) || _LIBCPP_STD_VER >= 14 || \
+    (defined(__cpp_sized_deallocation) && __cpp_sized_deallocation >= 201309))
+# define _LIBCPP_HAS_NO_SIZED_DEALLOCATION
+#endif
+
+#if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION) && \
+    (!(defined(_LIBCPP_BUILDING_NEW) || _LIBCPP_STD_VER > 14 || \
+    (defined(__cpp_aligned_new) && __cpp_aligned_new >= 201606)))
+# define _LIBCPP_HAS_NO_ALIGNED_ALLOCATION
+#endif
+
 namespace std  // purposefully not using versioning namespace
 {
 
+#if !defined(_LIBCPP_ABI_MICROSOFT) || defined(_LIBCPP_NO_VCRUNTIME)
+struct _LIBCPP_TYPE_VIS nothrow_t {};
+extern _LIBCPP_FUNC_VIS const nothrow_t nothrow;
+
 class _LIBCPP_EXCEPTION_ABI bad_alloc
     : public exception
 {
@@ -97,11 +138,18 @@ public:
     virtual const char* what() const _NOEXCEPT;
 };
 
-#if defined(_LIBCPP_BUILDING_NEW) || (_LIBCPP_STD_VER > 11)
+typedef void (*new_handler)();
+_LIBCPP_FUNC_VIS new_handler set_new_handler(new_handler) _NOEXCEPT;
+_LIBCPP_FUNC_VIS new_handler get_new_handler() _NOEXCEPT;
 
-class _LIBCPP_EXCEPTION_ABI bad_array_length
-    : public bad_alloc
-{
+#endif // !_LIBCPP_ABI_MICROSOFT || _LIBCPP_NO_VCRUNTIME
+
+_LIBCPP_NORETURN _LIBCPP_FUNC_VIS void __throw_bad_alloc();  // not in C++ spec
+
+#if defined(_LIBCPP_BUILDING_LIBRARY) || (_LIBCPP_STD_VER > 11)
+
+class _LIBCPP_EXCEPTION_ABI _LIBCPP_AVAILABILITY_BAD_ARRAY_LENGTH
+    bad_array_length : public bad_alloc {
 public:
     bad_array_length() _NOEXCEPT;
     virtual ~bad_array_length() _NOEXCEPT;
@@ -112,53 +160,65 @@ public:
 
 #endif  // defined(_LIBCPP_BUILDING_NEW) || (_LIBCPP_STD_VER > 11)
 
-_LIBCPP_FUNC_VIS void __throw_bad_alloc();  // not in C++ spec
-
-struct _LIBCPP_TYPE_VIS nothrow_t {};
-extern _LIBCPP_FUNC_VIS const nothrow_t nothrow;
-typedef void (*new_handler)();
-_LIBCPP_FUNC_VIS new_handler set_new_handler(new_handler) _NOEXCEPT;
-_LIBCPP_FUNC_VIS new_handler get_new_handler() _NOEXCEPT;
+#if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION) || _LIBCPP_STD_VER > 14
+#ifndef _LIBCPP_CXX03_LANG
+enum class _LIBCPP_ENUM_VIS align_val_t : size_t { };
+#else
+enum align_val_t { __zero = 0, __max = (size_t)-1 };
+#endif
+#endif
 
 }  // std
 
-#if defined(_WIN32) && !defined(cxx_EXPORTS)
-# define _LIBCPP_NEW_DELETE_VIS _LIBCPP_FUNC_VIS_ONLY
+#if defined(_LIBCPP_CXX03_LANG)
+#define _THROW_BAD_ALLOC throw(std::bad_alloc)
 #else
-# define _LIBCPP_NEW_DELETE_VIS _LIBCPP_FUNC_VIS
+#define _THROW_BAD_ALLOC
+#endif
+
+#if !defined(_LIBCPP_ABI_MICROSOFT) || defined(_LIBCPP_NO_VCRUNTIME)
+
+_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz) _THROW_BAD_ALLOC;
+_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz, const std::nothrow_t&) _NOEXCEPT _NOALIAS;
+_LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete(void* __p) _NOEXCEPT;
+_LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete(void* __p, const std::nothrow_t&) _NOEXCEPT;
+#ifndef _LIBCPP_HAS_NO_SIZED_DEALLOCATION
+_LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE void  operator delete(void* __p, std::size_t __sz) _NOEXCEPT;
 #endif
 
-_LIBCPP_NEW_DELETE_VIS void* operator new(std::size_t __sz)
-#if !__has_feature(cxx_noexcept)
-    throw(std::bad_alloc)
+_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz) _THROW_BAD_ALLOC;
+_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz, const std::nothrow_t&) _NOEXCEPT _NOALIAS;
+_LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete[](void* __p) _NOEXCEPT;
+_LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete[](void* __p, const std::nothrow_t&) _NOEXCEPT;
+#ifndef _LIBCPP_HAS_NO_SIZED_DEALLOCATION
+_LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE void  operator delete[](void* __p, std::size_t __sz) _NOEXCEPT;
 #endif
-;
-_LIBCPP_NEW_DELETE_VIS void* operator new(std::size_t __sz, const std::nothrow_t&) _NOEXCEPT _NOALIAS;
-_LIBCPP_NEW_DELETE_VIS void  operator delete(void* __p) _NOEXCEPT;
-_LIBCPP_NEW_DELETE_VIS void  operator delete(void* __p, const std::nothrow_t&) _NOEXCEPT;
-#if defined(_LIBCPP_BUILDING_NEW) || _LIBCPP_STD_VER >= 14 || \
-    (defined(__cpp_sized_deallocation) && __cpp_sized_deallocation >= 201309)
-_LIBCPP_NEW_DELETE_VIS void  operator delete(void* __p, std::size_t __sz) _NOEXCEPT;
+
+#ifndef _LIBCPP_HAS_NO_ALIGNED_ALLOCATION
+_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz, std::align_val_t) _THROW_BAD_ALLOC;
+_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new(std::size_t __sz, std::align_val_t, const std::nothrow_t&) _NOEXCEPT _NOALIAS;
+_LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete(void* __p, std::align_val_t) _NOEXCEPT;
+_LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete(void* __p, std::align_val_t, const std::nothrow_t&) _NOEXCEPT;
+#ifndef _LIBCPP_HAS_NO_SIZED_DEALLOCATION
+_LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE void  operator delete(void* __p, std::size_t __sz, std::align_val_t) _NOEXCEPT;
 #endif
 
-_LIBCPP_NEW_DELETE_VIS void* operator new[](std::size_t __sz)
-#if !__has_feature(cxx_noexcept)
-    throw(std::bad_alloc)
+_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz, std::align_val_t) _THROW_BAD_ALLOC;
+_LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_OVERRIDABLE_FUNC_VIS void* operator new[](std::size_t __sz, std::align_val_t, const std::nothrow_t&) _NOEXCEPT _NOALIAS;
+_LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete[](void* __p, std::align_val_t) _NOEXCEPT;
+_LIBCPP_OVERRIDABLE_FUNC_VIS void  operator delete[](void* __p, std::align_val_t, const std::nothrow_t&) _NOEXCEPT;
+#ifndef _LIBCPP_HAS_NO_SIZED_DEALLOCATION
+_LIBCPP_OVERRIDABLE_FUNC_VIS _LIBCPP_AVAILABILITY_SIZED_NEW_DELETE void  operator delete[](void* __p, std::size_t __sz, std::align_val_t) _NOEXCEPT;
 #endif
-;
-_LIBCPP_NEW_DELETE_VIS void* operator new[](std::size_t __sz, const std::nothrow_t&) _NOEXCEPT _NOALIAS;
-_LIBCPP_NEW_DELETE_VIS void  operator delete[](void* __p) _NOEXCEPT;
-_LIBCPP_NEW_DELETE_VIS void  operator delete[](void* __p, const std::nothrow_t&) _NOEXCEPT;
-#if defined(_LIBCPP_BUILDING_NEW) || _LIBCPP_STD_VER >= 14 || \
-    (defined(__cpp_sized_deallocation) && __cpp_sized_deallocation >= 201309)
-_LIBCPP_NEW_DELETE_VIS void  operator delete[](void* __p, std::size_t __sz) _NOEXCEPT;
 #endif
 
-inline _LIBCPP_INLINE_VISIBILITY void* operator new  (std::size_t, void* __p) _NOEXCEPT {return __p;}
-inline _LIBCPP_INLINE_VISIBILITY void* operator new[](std::size_t, void* __p) _NOEXCEPT {return __p;}
+_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY void* operator new  (std::size_t, void* __p) _NOEXCEPT {return __p;}
+_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY void* operator new[](std::size_t, void* __p) _NOEXCEPT {return __p;}
 inline _LIBCPP_INLINE_VISIBILITY void  operator delete  (void*, void*) _NOEXCEPT {}
 inline _LIBCPP_INLINE_VISIBILITY void  operator delete[](void*, void*) _NOEXCEPT {}
 
+#endif // !_LIBCPP_ABI_MICROSOFT || _LIBCPP_NO_VCRUNTIME
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 inline _LIBCPP_INLINE_VISIBILITY void *__allocate(size_t __size) {
@@ -169,7 +229,7 @@ inline _LIBCPP_INLINE_VISIBILITY void *__allocate(size_t __size) {
 #endif
 }
 
-inline _LIBCPP_INLINE_VISIBILITY void __deallocate(void *__ptr) {
+inline _LIBCPP_INLINE_VISIBILITY void __libcpp_deallocate(void *__ptr) {
 #ifdef _LIBCPP_HAS_NO_BUILTIN_OPERATOR_NEW_DELETE
   ::operator delete(__ptr);
 #else
@@ -177,6 +237,44 @@ inline _LIBCPP_INLINE_VISIBILITY void __deallocate(void *__ptr) {
 #endif
 }
 
+#ifdef _LIBCPP_BAD_ARRAY_LENGTH_DEFINED
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+#ifndef _LIBCPP_NO_EXCEPTIONS
+_LIBCPP_AVAILABILITY_BAD_ARRAY_LENGTH
+#endif
+void __throw_bad_array_length()
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw bad_array_length();
+#else
+	_VSTD::abort();
+#endif
+}
+#endif
+
+template <class _Tp>
+_LIBCPP_NODISCARD_AFTER_CXX17 inline 
+_LIBCPP_CONSTEXPR _Tp* __launder(_Tp* __p) _NOEXCEPT
+{
+    static_assert (!(is_function<_Tp>::value), "can't launder functions" );
+    static_assert (!(is_same<void, typename remove_cv<_Tp>::type>::value), "can't launder cv-void" );
+#ifdef _LIBCPP_COMPILER_HAS_BUILTIN_LAUNDER
+    return __builtin_launder(__p);
+#else
+    return __p;
+#endif
+}
+
+
+#if _LIBCPP_STD_VER > 14
+template <class _Tp>
+_LIBCPP_NODISCARD_AFTER_CXX17 inline _LIBCPP_INLINE_VISIBILITY
+constexpr _Tp* launder(_Tp* __p) noexcept
+{
+    return _VSTD::__launder(__p);
+}
+#endif
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_NEW
diff --git a/lib/libcxx/include/numeric b/lib/libcxx/include/numeric
index 21c3781ab6a..1b7d97c5be0 100644
--- a/lib/libcxx/include/numeric
+++ b/lib/libcxx/include/numeric
@@ -25,6 +25,18 @@ template <class InputIterator, class T, class BinaryOperation>
     T
     accumulate(InputIterator first, InputIterator last, T init, BinaryOperation binary_op);
 
+template<class InputIterator>
+    typename iterator_traits<InputIterator>::value_type
+    reduce(InputIterator first, InputIterator last);  // C++17
+
+template<class InputIterator, class T>
+    T
+    reduce(InputIterator first, InputIterator last, T init);  // C++17
+
+template<class InputIterator, class T, class BinaryOperation>
+    T
+    reduce(InputIterator first, InputIterator last, T init, BinaryOperation binary_op);  // C++17
+
 template <class InputIterator1, class InputIterator2, class T>
     T
     inner_product(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2, T init);
@@ -34,6 +46,23 @@ template <class InputIterator1, class InputIterator2, class T, class BinaryOpera
     inner_product(InputIterator1 first1, InputIterator1 last1, InputIterator2 first2,
                   T init, BinaryOperation1 binary_op1, BinaryOperation2 binary_op2);
 
+
+template<class InputIterator1, class InputIterator2, class T>
+    T
+    transform_reduce(InputIterator1 first1, InputIterator1 last1,
+                     InputIterator2 first2, T init);  // C++17
+                     
+template<class InputIterator1, class InputIterator2, class T, class BinaryOperation1, class BinaryOperation2>
+    T
+    transform_reduce(InputIterator1 first1, InputIterator1 last1,
+                     InputIterator2 first2, T init,
+                     BinaryOperation1 binary_op1, BinaryOperation2 binary_op2);  // C++17
+
+template<class InputIterator, class T, class BinaryOperation, class UnaryOperation>
+    T
+    transform_reduce(InputIterator first, InputIterator last, T init,
+                     BinaryOperation binary_op, UnaryOperation unary_op);  // C++17
+
 template <class InputIterator, class OutputIterator>
     OutputIterator
     partial_sum(InputIterator first, InputIterator last, OutputIterator result);
@@ -42,6 +71,52 @@ template <class InputIterator, class OutputIterator, class BinaryOperation>
     OutputIterator
     partial_sum(InputIterator first, InputIterator last, OutputIterator result, BinaryOperation binary_op);
 
+template<class InputIterator, class OutputIterator, class T>
+    OutputIterator
+    exclusive_scan(InputIterator first, InputIterator last,
+                   OutputIterator result, T init); // C++17
+                           
+template<class InputIterator, class OutputIterator, class T, class BinaryOperation>
+    OutputIterator
+    exclusive_scan(InputIterator first, InputIterator last, 
+                   OutputIterator result, T init, BinaryOperation binary_op); // C++17
+
+template<class InputIterator, class OutputIterator>
+    OutputIterator
+    inclusive_scan(InputIterator first, InputIterator last, OutputIterator result);  // C++17
+
+template<class InputIterator, class OutputIterator, class BinaryOperation>
+    OutputIterator
+    inclusive_scan(InputIterator first, InputIterator last,
+                   OutputIterator result, BinaryOperation binary_op);  // C++17
+
+template<class InputIterator, class OutputIterator, class BinaryOperation, class T>
+    OutputIterator
+    inclusive_scan(InputIterator first, InputIterator last,
+                   OutputIterator result, BinaryOperation binary_op, T init);  // C++17
+
+template<class InputIterator, class OutputIterator, class T,
+         class BinaryOperation, class UnaryOperation>
+    OutputIterator
+    transform_exclusive_scan(InputIterator first, InputIterator last,
+                             OutputIterator result, T init,
+                             BinaryOperation binary_op, UnaryOperation unary_op);  // C++17
+
+template<class InputIterator, class OutputIterator,
+         class BinaryOperation, class UnaryOperation>
+	OutputIterator
+	transform_inclusive_scan(InputIterator first, InputIterator last,
+                             OutputIterator result,
+                             BinaryOperation binary_op, UnaryOperation unary_op);  // C++17
+                                          
+template<class InputIterator, class OutputIterator,
+         class BinaryOperation, class UnaryOperation, class T>
+	OutputIterator
+	transform_inclusive_scan(InputIterator first, InputIterator last,
+                             OutputIterator result,
+                             BinaryOperation binary_op, UnaryOperation unary_op,
+                             T init);  // C++17
+
 template <class InputIterator, class OutputIterator>
     OutputIterator
     adjacent_difference(InputIterator first, InputIterator last, OutputIterator result);
@@ -53,17 +128,28 @@ template <class InputIterator, class OutputIterator, class BinaryOperation>
 template <class ForwardIterator, class T>
     void iota(ForwardIterator first, ForwardIterator last, T value);
 
+template <class M, class N>
+    constexpr common_type_t<M,N> gcd(M m, N n);    // C++17
+
+template <class M, class N>
+    constexpr common_type_t<M,N> lcm(M m, N n);    // C++17
+
 }  // std
 
 */
 
 #include <__config>
 #include <iterator>
+#include <limits> // for numeric_limits
+#include <functional>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _InputIterator, class _Tp>
@@ -86,6 +172,35 @@ accumulate(_InputIterator __first, _InputIterator __last, _Tp __init, _BinaryOpe
     return __init;
 }
 
+#if _LIBCPP_STD_VER > 14
+template <class _InputIterator, class _Tp, class _BinaryOp>
+inline _LIBCPP_INLINE_VISIBILITY
+_Tp
+reduce(_InputIterator __first, _InputIterator __last, _Tp __init, _BinaryOp __b)
+{
+    for (; __first != __last; ++__first)
+        __init = __b(__init, *__first);
+    return __init;
+}
+
+template <class _InputIterator, class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+_Tp
+reduce(_InputIterator __first, _InputIterator __last, _Tp __init)
+{
+    return _VSTD::reduce(__first, __last, __init, _VSTD::plus<>());
+}
+
+template <class _InputIterator>
+inline _LIBCPP_INLINE_VISIBILITY
+typename iterator_traits<_InputIterator>::value_type
+reduce(_InputIterator __first, _InputIterator __last)
+{
+    return _VSTD::reduce(__first, __last, 
+       typename iterator_traits<_InputIterator>::value_type{});
+}
+#endif
+
 template <class _InputIterator1, class _InputIterator2, class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 _Tp
@@ -107,6 +222,41 @@ inner_product(_InputIterator1 __first1, _InputIterator1 __last1, _InputIterator2
     return __init;
 }
 
+#if _LIBCPP_STD_VER > 14
+template <class _InputIterator, class _Tp, class _BinaryOp, class _UnaryOp>
+inline _LIBCPP_INLINE_VISIBILITY
+_Tp
+transform_reduce(_InputIterator __first, _InputIterator __last, 
+           _Tp __init,  _BinaryOp __b, _UnaryOp __u)
+{
+    for (; __first != __last; ++__first)
+        __init = __b(__init, __u(*__first));
+    return __init;
+}
+
+template <class _InputIterator1, class _InputIterator2, 
+          class _Tp, class _BinaryOp1, class _BinaryOp2>
+inline _LIBCPP_INLINE_VISIBILITY
+_Tp
+transform_reduce(_InputIterator1 __first1, _InputIterator1 __last1,
+                 _InputIterator2 __first2, _Tp __init,  _BinaryOp1 __b1, _BinaryOp2 __b2)
+{
+    for (; __first1 != __last1; ++__first1, (void) ++__first2)
+        __init = __b1(__init, __b2(*__first1, *__first2));
+    return __init;
+}
+
+template <class _InputIterator1, class _InputIterator2, class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+_Tp
+transform_reduce(_InputIterator1 __first1, _InputIterator1 __last1, 
+                 _InputIterator2 __first2, _Tp __init)
+{
+    return _VSTD::transform_reduce(__first1, __last1, __first2, __init, 
+                                   _VSTD::plus<>(), _VSTD::multiplies<>());
+}
+#endif
+
 template <class _InputIterator, class _OutputIterator>
 inline _LIBCPP_INLINE_VISIBILITY
 _OutputIterator
@@ -144,6 +294,117 @@ partial_sum(_InputIterator __first, _InputIterator __last, _OutputIterator __res
     return __result;
 }
 
+#if _LIBCPP_STD_VER > 14
+template <class _InputIterator, class _OutputIterator, class _Tp, class _BinaryOp>
+inline _LIBCPP_INLINE_VISIBILITY
+_OutputIterator
+exclusive_scan(_InputIterator __first, _InputIterator __last, 
+               _OutputIterator __result, _Tp __init, _BinaryOp __b)
+{
+    if (__first != __last)
+    {
+        _Tp __saved = __init;
+        do
+        {
+            __init = __b(__init, *__first);
+            *__result = __saved;
+            __saved = __init;
+            ++__result;
+        } while (++__first != __last);
+    }
+    return __result;
+}
+
+template <class _InputIterator, class _OutputIterator, class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+_OutputIterator
+exclusive_scan(_InputIterator __first, _InputIterator __last, 
+               _OutputIterator __result, _Tp __init)
+{
+    return _VSTD::exclusive_scan(__first, __last, __result, __init, _VSTD::plus<>());
+}
+
+template <class _InputIterator, class _OutputIterator, class _Tp, class _BinaryOp>
+_OutputIterator inclusive_scan(_InputIterator __first, _InputIterator __last, 
+                               _OutputIterator __result, _BinaryOp __b,  _Tp __init)
+{
+    for (; __first != __last; ++__first, (void) ++__result) {
+        __init = __b(__init, *__first);
+        *__result = __init;
+        }
+    return __result;
+}
+
+template <class _InputIterator, class _OutputIterator, class _BinaryOp>
+_OutputIterator inclusive_scan(_InputIterator __first, _InputIterator __last, 
+                               _OutputIterator __result, _BinaryOp __b)
+{
+    if (__first != __last) {
+        typename std::iterator_traits<_InputIterator>::value_type __init = *__first;
+        *__result++ = __init;
+        if (++__first != __last)
+            return _VSTD::inclusive_scan(__first, __last, __result, __b, __init);
+        }
+
+    return __result;
+}
+
+template <class _InputIterator, class _OutputIterator>
+_OutputIterator inclusive_scan(_InputIterator __first, _InputIterator __last, 
+                               _OutputIterator __result)
+{
+    return _VSTD::inclusive_scan(__first, __last, __result, std::plus<>());
+}
+
+template <class _InputIterator, class _OutputIterator, class _Tp, 
+          class _BinaryOp, class _UnaryOp>
+inline _LIBCPP_INLINE_VISIBILITY
+_OutputIterator
+transform_exclusive_scan(_InputIterator __first, _InputIterator __last, 
+                           _OutputIterator __result, _Tp __init,
+                           _BinaryOp __b, _UnaryOp __u)
+{
+    if (__first != __last)
+    {
+        _Tp __saved = __init;
+        do
+        {
+            __init = __b(__init, __u(*__first));
+            *__result = __saved;
+            __saved = __init;
+            ++__result;
+        } while (++__first != __last);
+    }
+    return __result;
+}
+
+template <class _InputIterator, class _OutputIterator, class _Tp, class _BinaryOp, class _UnaryOp>
+_OutputIterator transform_inclusive_scan(_InputIterator __first, _InputIterator __last, 
+                           _OutputIterator __result, _BinaryOp __b, _UnaryOp __u, _Tp __init)
+{
+    for (; __first != __last; ++__first, (void) ++__result) {
+        __init = __b(__init, __u(*__first));
+        *__result = __init;
+        }
+
+    return __result;
+}
+
+template <class _InputIterator, class _OutputIterator, class _BinaryOp, class _UnaryOp>
+_OutputIterator transform_inclusive_scan(_InputIterator __first, _InputIterator __last, 
+                               _OutputIterator __result, _BinaryOp __b, _UnaryOp __u)
+{
+    if (__first != __last) {
+        typename std::iterator_traits<_InputIterator>::value_type __init = __u(*__first);
+        *__result++ = __init;
+        if (++__first != __last)
+            return _VSTD::transform_inclusive_scan(__first, __last, __result, __b, __u, __init);
+        }
+    
+    return __result;
+}
+#endif
+
 template <class _InputIterator, class _OutputIterator>
 inline _LIBCPP_INLINE_VISIBILITY
 _OutputIterator
@@ -192,6 +453,74 @@ iota(_ForwardIterator __first, _ForwardIterator __last, _Tp __value_)
         *__first = __value_;
 }
 
+
+#if _LIBCPP_STD_VER > 14
+template <typename _Result, typename _Source, bool _IsSigned = is_signed<_Source>::value> struct __abs;
+
+template <typename _Result, typename _Source>
+struct __abs<_Result, _Source, true> {
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    _Result operator()(_Source __t) const noexcept
+    {
+    if (__t >= 0) return __t;
+    if (__t == numeric_limits<_Source>::min()) return -static_cast<_Result>(__t);
+    return -__t;
+    }
+};
+
+template <typename _Result, typename _Source>
+struct __abs<_Result, _Source, false> {
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    _Result operator()(_Source __t) const noexcept { return __t; }
+};
+
+
+template<class _Tp>
+_LIBCPP_CONSTEXPR _LIBCPP_HIDDEN
+_Tp __gcd(_Tp __m, _Tp __n)
+{
+    static_assert((!is_signed<_Tp>::value), "");
+    return __n == 0 ? __m : _VSTD::__gcd<_Tp>(__n, __m % __n);
+}
+
+
+template<class _Tp, class _Up>
+_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+common_type_t<_Tp,_Up>
+gcd(_Tp __m, _Up __n)
+{
+    static_assert((is_integral<_Tp>::value && is_integral<_Up>::value), "Arguments to gcd must be integer types");
+    static_assert((!is_same<typename remove_cv<_Tp>::type, bool>::value), "First argument to gcd cannot be bool" );
+    static_assert((!is_same<typename remove_cv<_Up>::type, bool>::value), "Second argument to gcd cannot be bool" );
+    using _Rp = common_type_t<_Tp,_Up>;
+    using _Wp = make_unsigned_t<_Rp>;
+    return static_cast<_Rp>(_VSTD::__gcd(
+        static_cast<_Wp>(__abs<_Rp, _Tp>()(__m)),
+        static_cast<_Wp>(__abs<_Rp, _Up>()(__n))));
+}
+
+template<class _Tp, class _Up>
+_LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+common_type_t<_Tp,_Up>
+lcm(_Tp __m, _Up __n)
+{
+    static_assert((is_integral<_Tp>::value && is_integral<_Up>::value), "Arguments to lcm must be integer types");
+    static_assert((!is_same<typename remove_cv<_Tp>::type, bool>::value), "First argument to lcm cannot be bool" );
+    static_assert((!is_same<typename remove_cv<_Up>::type, bool>::value), "Second argument to lcm cannot be bool" );
+    if (__m == 0 || __n == 0)
+        return 0;
+
+    using _Rp = common_type_t<_Tp,_Up>;
+    _Rp __val1 = __abs<_Rp, _Tp>()(__m) / _VSTD::gcd(__m, __n);
+    _Rp __val2 = __abs<_Rp, _Up>()(__n);
+    _LIBCPP_ASSERT((numeric_limits<_Rp>::max() / __val1 > __val2), "Overflow in lcm");
+    return __val1 * __val2;
+}
+
+#endif /* _LIBCPP_STD_VER > 14 */
+
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_NUMERIC
diff --git a/lib/libcxx/include/optional b/lib/libcxx/include/optional
new file mode 100644
index 00000000000..88fd6b5aba2
--- /dev/null
+++ b/lib/libcxx/include/optional
@@ -0,0 +1,1399 @@
+// -*- C++ -*-
+//===-------------------------- optional ----------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_OPTIONAL
+#define _LIBCPP_OPTIONAL
+
+/*
+    optional synopsis
+
+// C++1z
+
+namespace std {
+  // 23.6.3, optional for object types
+  template <class T> class optional;
+
+  // 23.6.4, no-value state indicator
+  struct nullopt_t{see below };
+  inline constexpr nullopt_t nullopt(unspecified );
+
+  // 23.6.5, class bad_optional_access
+  class bad_optional_access;
+
+  // 23.6.6, relational operators
+  template <class T, class U>
+  constexpr bool operator==(const optional<T>&, const optional<U>&);
+  template <class T, class U>
+  constexpr bool operator!=(const optional<T>&, const optional<U>&);
+  template <class T, class U>
+  constexpr bool operator<(const optional<T>&, const optional<U>&);
+  template <class T, class U>
+  constexpr bool operator>(const optional<T>&, const optional<U>&);
+  template <class T, class U>
+  constexpr bool operator<=(const optional<T>&, const optional<U>&);
+  template <class T, class U>
+  constexpr bool operator>=(const optional<T>&, const optional<U>&);
+
+  // 23.6.7 comparison with nullopt
+  template <class T> constexpr bool operator==(const optional<T>&, nullopt_t) noexcept;
+  template <class T> constexpr bool operator==(nullopt_t, const optional<T>&) noexcept;
+  template <class T> constexpr bool operator!=(const optional<T>&, nullopt_t) noexcept;
+  template <class T> constexpr bool operator!=(nullopt_t, const optional<T>&) noexcept;
+  template <class T> constexpr bool operator<(const optional<T>&, nullopt_t) noexcept;
+  template <class T> constexpr bool operator<(nullopt_t, const optional<T>&) noexcept;
+  template <class T> constexpr bool operator<=(const optional<T>&, nullopt_t) noexcept;
+  template <class T> constexpr bool operator<=(nullopt_t, const optional<T>&) noexcept;
+  template <class T> constexpr bool operator>(const optional<T>&, nullopt_t) noexcept;
+  template <class T> constexpr bool operator>(nullopt_t, const optional<T>&) noexcept;
+  template <class T> constexpr bool operator>=(const optional<T>&, nullopt_t) noexcept;
+  template <class T> constexpr bool operator>=(nullopt_t, const optional<T>&) noexcept;
+
+  // 23.6.8, comparison with T
+  template <class T, class U> constexpr bool operator==(const optional<T>&, const U&);
+  template <class T, class U> constexpr bool operator==(const T&, const optional<U>&);
+  template <class T, class U> constexpr bool operator!=(const optional<T>&, const U&);
+  template <class T, class U> constexpr bool operator!=(const T&, const optional<U>&);
+  template <class T, class U> constexpr bool operator<(const optional<T>&, const U&);
+  template <class T, class U> constexpr bool operator<(const T&, const optional<U>&);
+  template <class T, class U> constexpr bool operator<=(const optional<T>&, const U&);
+  template <class T, class U> constexpr bool operator<=(const T&, const optional<U>&);
+  template <class T, class U> constexpr bool operator>(const optional<T>&, const U&);
+  template <class T, class U> constexpr bool operator>(const T&, const optional<U>&);
+  template <class T, class U> constexpr bool operator>=(const optional<T>&, const U&);
+  template <class T, class U> constexpr bool operator>=(const T&, const optional<U>&);
+
+  // 23.6.9, specialized algorithms
+  template <class T> void swap(optional<T>&, optional<T>&) noexcept(see below );
+  template <class T> constexpr optional<see below > make_optional(T&&);
+  template <class T, class... Args>
+    constexpr optional<T> make_optional(Args&&... args);
+  template <class T, class U, class... Args>
+    constexpr optional<T> make_optional(initializer_list<U> il, Args&&... args);
+
+  // 23.6.10, hash support
+  template <class T> struct hash;
+  template <class T> struct hash<optional<T>>;
+
+  template <class T> class optional {
+  public:
+    using value_type = T;
+
+    // 23.6.3.1, constructors
+    constexpr optional() noexcept;
+    constexpr optional(nullopt_t) noexcept;
+    optional(const optional &);
+    optional(optional &&) noexcept(see below);
+    template <class... Args> constexpr explicit optional(in_place_t, Args &&...);
+    template <class U, class... Args>
+      constexpr explicit optional(in_place_t, initializer_list<U>, Args &&...);
+    template <class U = T>
+      constexpr EXPLICIT optional(U &&);
+    template <class U>
+      constexpr EXPLICIT optional(const optional<U> &);
+    template <class U>
+      constexpr EXPLICIT optional(optional<U> &&);
+
+    // 23.6.3.2, destructor
+    ~optional();
+
+    // 23.6.3.3, assignment
+    optional &operator=(nullopt_t) noexcept;
+    optional &operator=(const optional &);
+    optional &operator=(optional &&) noexcept(see below );
+    template <class U = T> optional &operator=(U &&);
+    template <class U> optional &operator=(const optional<U> &);
+    template <class U> optional &operator=(optional<U> &&);
+    template <class... Args> T& emplace(Args &&...);
+    template <class U, class... Args>
+      T& emplace(initializer_list<U>, Args &&...);
+
+    // 23.6.3.4, swap
+    void swap(optional &) noexcept(see below );
+
+    // 23.6.3.5, observers
+    constexpr T const *operator->() const;
+    constexpr T *operator->();
+    constexpr T const &operator*() const &;
+    constexpr T &operator*() &;
+    constexpr T &&operator*() &&;
+    constexpr const T &&operator*() const &&;
+    constexpr explicit operator bool() const noexcept;
+    constexpr bool has_value() const noexcept;
+    constexpr T const &value() const &;
+    constexpr T &value() &;
+    constexpr T &&value() &&;
+    constexpr const T &&value() const &&;
+    template <class U> constexpr T value_or(U &&) const &;
+    template <class U> constexpr T value_or(U &&) &&;
+
+    // 23.6.3.6, modifiers
+    void reset() noexcept;
+
+  private:
+    T *val; // exposition only
+  };
+} // namespace std
+
+*/
+
+#include <__config>
+#include <__debug>
+#include <__functional_base>
+#include <functional>
+#include <initializer_list>
+#include <new>
+#include <stdexcept>
+#include <type_traits>
+#include <utility>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
+namespace std  // purposefully not using versioning namespace
+{
+
+class _LIBCPP_EXCEPTION_ABI bad_optional_access
+    : public exception
+{
+public:
+    // Get the key function ~bad_optional_access() into the dylib
+    virtual ~bad_optional_access() _NOEXCEPT;
+    virtual const char* what() const _NOEXCEPT;
+};
+
+}  // std
+
+#if _LIBCPP_STD_VER > 14
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_NORETURN
+inline _LIBCPP_INLINE_VISIBILITY
+void __throw_bad_optional_access() {
+#ifndef _LIBCPP_NO_EXCEPTIONS
+        throw bad_optional_access();
+#else
+        _VSTD::abort();
+#endif
+}
+
+struct nullopt_t
+{
+    struct __secret_tag { _LIBCPP_INLINE_VISIBILITY explicit __secret_tag() = default; };
+    _LIBCPP_INLINE_VISIBILITY constexpr explicit nullopt_t(__secret_tag, __secret_tag) noexcept {}
+};
+
+_LIBCPP_INLINE_VAR constexpr nullopt_t nullopt{nullopt_t::__secret_tag{}, nullopt_t::__secret_tag{}};
+
+template <class _Tp, bool = is_trivially_destructible<_Tp>::value>
+struct __optional_destruct_base;
+
+template <class _Tp>
+struct __optional_destruct_base<_Tp, false>
+{
+    typedef _Tp value_type;
+    static_assert(is_object_v<value_type>,
+        "instantiation of optional with a non-object type is undefined behavior");
+    union
+    {
+        char __null_state_;
+        value_type __val_;
+    };
+    bool __engaged_;
+
+    _LIBCPP_INLINE_VISIBILITY
+    ~__optional_destruct_base()
+    {
+        if (__engaged_)
+            __val_.~value_type();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr __optional_destruct_base() noexcept
+        :  __null_state_(),
+           __engaged_(false) {}
+
+    template <class... _Args>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit __optional_destruct_base(in_place_t, _Args&&... __args)
+        :  __val_(_VSTD::forward<_Args>(__args)...),
+           __engaged_(true) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    void reset() noexcept
+    {
+        if (__engaged_)
+        {
+            __val_.~value_type();
+            __engaged_ = false;
+        }
+    }
+};
+
+template <class _Tp>
+struct __optional_destruct_base<_Tp, true>
+{
+    typedef _Tp value_type;
+    static_assert(is_object_v<value_type>,
+        "instantiation of optional with a non-object type is undefined behavior");
+    union
+    {
+        char __null_state_;
+        value_type __val_;
+    };
+    bool __engaged_;
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr __optional_destruct_base() noexcept
+        :  __null_state_(),
+           __engaged_(false) {}
+
+    template <class... _Args>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit __optional_destruct_base(in_place_t, _Args&&... __args)
+        :  __val_(_VSTD::forward<_Args>(__args)...),
+           __engaged_(true) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    void reset() noexcept
+    {
+        if (__engaged_)
+        {
+            __engaged_ = false;
+        }
+    }
+};
+
+template <class _Tp, bool = is_reference<_Tp>::value>
+struct __optional_storage_base : __optional_destruct_base<_Tp>
+{
+    using __base = __optional_destruct_base<_Tp>;
+    using value_type = _Tp;
+    using __base::__base;
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr bool has_value() const noexcept
+    {
+        return this->__engaged_;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type& __get() & noexcept
+    {
+        return this->__val_;
+    }
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr const value_type& __get() const& noexcept
+    {
+        return this->__val_;
+    }
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type&& __get() && noexcept
+    {
+        return _VSTD::move(this->__val_);
+    }
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr const value_type&& __get() const&& noexcept
+    {
+        return _VSTD::move(this->__val_);
+    }
+
+    template <class... _Args>
+    _LIBCPP_INLINE_VISIBILITY
+    void __construct(_Args&&... __args)
+    {
+        _LIBCPP_ASSERT(!has_value(), "__construct called for engaged __optional_storage");
+        ::new((void*)_VSTD::addressof(this->__val_)) value_type(_VSTD::forward<_Args>(__args)...);
+        this->__engaged_ = true;
+    }
+
+    template <class _That>
+    _LIBCPP_INLINE_VISIBILITY
+    void __construct_from(_That&& __opt)
+    {
+        if (__opt.has_value())
+            __construct(_VSTD::forward<_That>(__opt).__get());
+    }
+
+    template <class _That>
+    _LIBCPP_INLINE_VISIBILITY
+    void __assign_from(_That&& __opt)
+    {
+        if (this->__engaged_ == __opt.has_value())
+        {
+            if (this->__engaged_)
+                this->__val_ = _VSTD::forward<_That>(__opt).__get();
+        }
+        else
+        {
+            if (this->__engaged_)
+                this->reset();
+            else
+                __construct(_VSTD::forward<_That>(__opt).__get());
+        }
+    }
+};
+
+// optional<T&> is currently required ill-formed, however it may to be in the
+// future. For this reason it has already been implemented to ensure we can
+// make the change in an ABI compatible manner.
+template <class _Tp>
+struct __optional_storage_base<_Tp, true>
+{
+    using value_type = _Tp;
+    using __raw_type = remove_reference_t<_Tp>;
+    __raw_type* __value_;
+
+    template <class _Up>
+    static constexpr bool __can_bind_reference() {
+        using _RawUp = typename remove_reference<_Up>::type;
+        using _UpPtr = _RawUp*;
+        using _RawTp = typename remove_reference<_Tp>::type;
+        using _TpPtr = _RawTp*;
+        using _CheckLValueArg = integral_constant<bool,
+            (is_lvalue_reference<_Up>::value && is_convertible<_UpPtr, _TpPtr>::value)
+        ||  is_same<_RawUp, reference_wrapper<_RawTp>>::value
+        ||  is_same<_RawUp, reference_wrapper<typename remove_const<_RawTp>::type>>::value
+        >;
+        return (is_lvalue_reference<_Tp>::value && _CheckLValueArg::value)
+            || (is_rvalue_reference<_Tp>::value && !is_lvalue_reference<_Up>::value &&
+                is_convertible<_UpPtr, _TpPtr>::value);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr __optional_storage_base() noexcept
+        :  __value_(nullptr) {}
+
+    template <class _UArg>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit __optional_storage_base(in_place_t, _UArg&& __uarg)
+        :  __value_(_VSTD::addressof(__uarg))
+    {
+      static_assert(__can_bind_reference<_UArg>(),
+        "Attempted to construct a reference element in tuple from a "
+        "possible temporary");
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void reset() noexcept { __value_ = nullptr; }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr bool has_value() const noexcept
+      { return __value_ != nullptr; }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type& __get() const& noexcept
+      { return *__value_; }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type&& __get() const&& noexcept
+      { return _VSTD::forward<value_type>(*__value_); }
+
+    template <class _UArg>
+    _LIBCPP_INLINE_VISIBILITY
+    void __construct(_UArg&& __val)
+    {
+        _LIBCPP_ASSERT(!has_value(), "__construct called for engaged __optional_storage");
+        static_assert(__can_bind_reference<_UArg>(),
+            "Attempted to construct a reference element in tuple from a "
+            "possible temporary");
+        __value_ = _VSTD::addressof(__val);
+    }
+
+    template <class _That>
+    _LIBCPP_INLINE_VISIBILITY
+    void __construct_from(_That&& __opt)
+    {
+        if (__opt.has_value())
+            __construct(_VSTD::forward<_That>(__opt).__get());
+    }
+
+    template <class _That>
+    _LIBCPP_INLINE_VISIBILITY
+    void __assign_from(_That&& __opt)
+    {
+        if (has_value() == __opt.has_value())
+        {
+            if (has_value())
+                *__value_ = _VSTD::forward<_That>(__opt).__get();
+        }
+        else
+        {
+            if (has_value())
+                reset();
+            else
+                __construct(_VSTD::forward<_That>(__opt).__get());
+        }
+    }
+};
+
+template <class _Tp, bool = is_trivially_copy_constructible<_Tp>::value>
+struct __optional_copy_base : __optional_storage_base<_Tp>
+{
+    using __optional_storage_base<_Tp>::__optional_storage_base;
+};
+
+template <class _Tp>
+struct __optional_copy_base<_Tp, false> : __optional_storage_base<_Tp>
+{
+    using __optional_storage_base<_Tp>::__optional_storage_base;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_copy_base() = default;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_copy_base(const __optional_copy_base& __opt)
+    {
+        this->__construct_from(__opt);
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_copy_base(__optional_copy_base&&) = default;
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_copy_base& operator=(const __optional_copy_base&) = default;
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_copy_base& operator=(__optional_copy_base&&) = default;
+};
+
+template <class _Tp, bool = is_trivially_move_constructible<_Tp>::value>
+struct __optional_move_base : __optional_copy_base<_Tp>
+{
+    using __optional_copy_base<_Tp>::__optional_copy_base;
+};
+
+template <class _Tp>
+struct __optional_move_base<_Tp, false> : __optional_copy_base<_Tp>
+{
+    using value_type = _Tp;
+    using __optional_copy_base<_Tp>::__optional_copy_base;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_move_base() = default;
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_move_base(const __optional_move_base&) = default;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_move_base(__optional_move_base&& __opt)
+        noexcept(is_nothrow_move_constructible_v<value_type>)
+    {
+        this->__construct_from(_VSTD::move(__opt));
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_move_base& operator=(const __optional_move_base&) = default;
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_move_base& operator=(__optional_move_base&&) = default;
+};
+
+template <class _Tp, bool =
+    is_trivially_destructible<_Tp>::value &&
+    is_trivially_copy_constructible<_Tp>::value &&
+    is_trivially_copy_assignable<_Tp>::value>
+struct __optional_copy_assign_base : __optional_move_base<_Tp>
+{
+    using __optional_move_base<_Tp>::__optional_move_base;
+};
+
+template <class _Tp>
+struct __optional_copy_assign_base<_Tp, false> : __optional_move_base<_Tp>
+{
+    using __optional_move_base<_Tp>::__optional_move_base;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_copy_assign_base() = default;
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_copy_assign_base(const __optional_copy_assign_base&) = default;
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_copy_assign_base(__optional_copy_assign_base&&) = default;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_copy_assign_base& operator=(const __optional_copy_assign_base& __opt)
+    {
+        this->__assign_from(__opt);
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_copy_assign_base& operator=(__optional_copy_assign_base&&) = default;
+};
+
+template <class _Tp, bool =
+    is_trivially_destructible<_Tp>::value &&
+    is_trivially_move_constructible<_Tp>::value &&
+    is_trivially_move_assignable<_Tp>::value>
+struct __optional_move_assign_base : __optional_copy_assign_base<_Tp>
+{
+    using __optional_copy_assign_base<_Tp>::__optional_copy_assign_base;
+};
+
+template <class _Tp>
+struct __optional_move_assign_base<_Tp, false> : __optional_copy_assign_base<_Tp>
+{
+    using value_type = _Tp;
+    using __optional_copy_assign_base<_Tp>::__optional_copy_assign_base;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_move_assign_base() = default;
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_move_assign_base(const __optional_move_assign_base& __opt) = default;
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_move_assign_base(__optional_move_assign_base&&) = default;
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_move_assign_base& operator=(const __optional_move_assign_base&) = default;
+
+    _LIBCPP_INLINE_VISIBILITY
+    __optional_move_assign_base& operator=(__optional_move_assign_base&& __opt)
+        noexcept(is_nothrow_move_assignable_v<value_type> &&
+                 is_nothrow_move_constructible_v<value_type>)
+    {
+        this->__assign_from(_VSTD::move(__opt));
+        return *this;
+    }
+};
+
+template <class _Tp>
+using __optional_sfinae_ctor_base_t = __sfinae_ctor_base<
+    is_copy_constructible<_Tp>::value,
+    is_move_constructible<_Tp>::value
+>;
+
+template <class _Tp>
+using __optional_sfinae_assign_base_t = __sfinae_assign_base<
+    (is_copy_constructible<_Tp>::value && is_copy_assignable<_Tp>::value),
+    (is_move_constructible<_Tp>::value && is_move_assignable<_Tp>::value)
+>;
+
+template <class _Tp>
+class optional
+    : private __optional_move_assign_base<_Tp>
+    , private __optional_sfinae_ctor_base_t<_Tp>
+    , private __optional_sfinae_assign_base_t<_Tp>
+{
+    using __base = __optional_move_assign_base<_Tp>;
+public:
+    using value_type = _Tp;
+
+private:
+     // Disable the reference extension using this static assert.
+    static_assert(!is_same_v<value_type, in_place_t>,
+        "instantiation of optional with in_place_t is ill-formed");
+    static_assert(!is_same_v<__uncvref_t<value_type>, nullopt_t>,
+        "instantiation of optional with nullopt_t is ill-formed");
+    static_assert(!is_reference_v<value_type>,
+        "instantiation of optional with a reference type is ill-formed");
+    static_assert(is_destructible_v<value_type>,
+        "instantiation of optional with a non-destructible type is ill-formed");
+
+    // LWG2756: conditionally explicit conversion from _Up
+    struct _CheckOptionalArgsConstructor {
+      template <class _Up>
+      static constexpr bool __enable_implicit() {
+          return is_constructible_v<_Tp, _Up&&> &&
+                 is_convertible_v<_Up&&, _Tp>;
+      }
+
+      template <class _Up>
+      static constexpr bool __enable_explicit() {
+          return is_constructible_v<_Tp, _Up&&> &&
+                 !is_convertible_v<_Up&&, _Tp>;
+      }
+    };
+    template <class _Up>
+    using _CheckOptionalArgsCtor = conditional_t<
+        !is_same_v<decay_t<_Up>, in_place_t> &&
+        !is_same_v<decay_t<_Up>, optional>,
+        _CheckOptionalArgsConstructor,
+        __check_tuple_constructor_fail
+    >;
+    template <class _QualUp>
+    struct _CheckOptionalLikeConstructor {
+      template <class _Up, class _Opt = optional<_Up>>
+      using __check_constructible_from_opt = __lazy_or<
+          is_constructible<_Tp, _Opt&>,
+          is_constructible<_Tp, _Opt const&>,
+          is_constructible<_Tp, _Opt&&>,
+          is_constructible<_Tp, _Opt const&&>,
+          is_convertible<_Opt&, _Tp>,
+          is_convertible<_Opt const&, _Tp>,
+          is_convertible<_Opt&&, _Tp>,
+          is_convertible<_Opt const&&, _Tp>
+      >;
+      template <class _Up, class _Opt = optional<_Up>>
+      using __check_assignable_from_opt = __lazy_or<
+          is_assignable<_Tp&, _Opt&>,
+          is_assignable<_Tp&, _Opt const&>,
+          is_assignable<_Tp&, _Opt&&>,
+          is_assignable<_Tp&, _Opt const&&>
+      >;
+      template <class _Up, class _QUp = _QualUp>
+      static constexpr bool __enable_implicit() {
+          return is_convertible<_QUp, _Tp>::value &&
+              !__check_constructible_from_opt<_Up>::value;
+      }
+      template <class _Up, class _QUp = _QualUp>
+      static constexpr bool __enable_explicit() {
+          return !is_convertible<_QUp, _Tp>::value &&
+              !__check_constructible_from_opt<_Up>::value;
+      }
+      template <class _Up, class _QUp = _QualUp>
+      static constexpr bool __enable_assign() {
+          // Construction and assignability of _Qup to _Tp has already been
+          // checked.
+          return !__check_constructible_from_opt<_Up>::value &&
+              !__check_assignable_from_opt<_Up>::value;
+      }
+    };
+
+    template <class _Up, class _QualUp>
+    using _CheckOptionalLikeCtor = conditional_t<
+      __lazy_and<
+          __lazy_not<is_same<_Up, _Tp>>,
+          is_constructible<_Tp, _QualUp>
+      >::value,
+      _CheckOptionalLikeConstructor<_QualUp>,
+      __check_tuple_constructor_fail
+    >;
+    template <class _Up, class _QualUp>
+    using _CheckOptionalLikeAssign = conditional_t<
+      __lazy_and<
+          __lazy_not<is_same<_Up, _Tp>>,
+          is_constructible<_Tp, _QualUp>,
+          is_assignable<_Tp&, _QualUp>
+      >::value,
+      _CheckOptionalLikeConstructor<_QualUp>,
+      __check_tuple_constructor_fail
+    >;
+public:
+
+    _LIBCPP_INLINE_VISIBILITY constexpr optional() noexcept {}
+    _LIBCPP_INLINE_VISIBILITY constexpr optional(const optional&) = default;
+    _LIBCPP_INLINE_VISIBILITY constexpr optional(optional&&) = default;
+    _LIBCPP_INLINE_VISIBILITY constexpr optional(nullopt_t) noexcept {}
+
+    template <class... _Args, class = enable_if_t<
+        is_constructible_v<value_type, _Args...>>
+    >
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit optional(in_place_t, _Args&&... __args)
+        : __base(in_place, _VSTD::forward<_Args>(__args)...) {}
+
+    template <class _Up, class... _Args, class = enable_if_t<
+        is_constructible_v<value_type, initializer_list<_Up>&, _Args...>>
+    >
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit optional(in_place_t, initializer_list<_Up> __il, _Args&&... __args)
+        : __base(in_place, __il, _VSTD::forward<_Args>(__args)...) {}
+
+    template <class _Up = value_type, enable_if_t<
+        _CheckOptionalArgsCtor<_Up>::template __enable_implicit<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr optional(_Up&& __v)
+        : __base(in_place, _VSTD::forward<_Up>(__v)) {}
+
+    template <class _Up, enable_if_t<
+        _CheckOptionalArgsCtor<_Up>::template __enable_explicit<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit optional(_Up&& __v)
+        : __base(in_place, _VSTD::forward<_Up>(__v)) {}
+
+    // LWG2756: conditionally explicit conversion from const optional<_Up>&
+    template <class _Up, enable_if_t<
+        _CheckOptionalLikeCtor<_Up, _Up const&>::template __enable_implicit<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    optional(const optional<_Up>& __v)
+    {
+        this->__construct_from(__v);
+    }
+    template <class _Up, enable_if_t<
+        _CheckOptionalLikeCtor<_Up, _Up const&>::template __enable_explicit<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    explicit optional(const optional<_Up>& __v)
+    {
+        this->__construct_from(__v);
+    }
+
+    // LWG2756: conditionally explicit conversion from optional<_Up>&&
+    template <class _Up, enable_if_t<
+        _CheckOptionalLikeCtor<_Up, _Up &&>::template __enable_implicit<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    optional(optional<_Up>&& __v)
+    {
+        this->__construct_from(_VSTD::move(__v));
+    }
+    template <class _Up, enable_if_t<
+        _CheckOptionalLikeCtor<_Up, _Up &&>::template __enable_explicit<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    explicit optional(optional<_Up>&& __v)
+    {
+        this->__construct_from(_VSTD::move(__v));
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    optional& operator=(nullopt_t) noexcept
+    {
+        reset();
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY optional& operator=(const optional&) = default;
+    _LIBCPP_INLINE_VISIBILITY optional& operator=(optional&&) = default;
+
+    // LWG2756
+    template <class _Up = value_type,
+              class = enable_if_t
+                      <__lazy_and<
+                          integral_constant<bool,
+                              !is_same_v<decay_t<_Up>, optional> &&
+                              !(is_same_v<_Up, value_type> && is_scalar_v<value_type>)
+                          >,
+                          is_constructible<value_type, _Up>,
+                          is_assignable<value_type&, _Up>
+                      >::value>
+             >
+    _LIBCPP_INLINE_VISIBILITY
+    optional&
+    operator=(_Up&& __v)
+    {
+        if (this->has_value())
+            this->__get() = _VSTD::forward<_Up>(__v);
+        else
+            this->__construct(_VSTD::forward<_Up>(__v));
+        return *this;
+    }
+
+    // LWG2756
+    template <class _Up, enable_if_t<
+        _CheckOptionalLikeAssign<_Up, _Up const&>::template __enable_assign<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    optional&
+    operator=(const optional<_Up>& __v)
+    {
+        this->__assign_from(__v);
+        return *this;
+    }
+
+    // LWG2756
+    template <class _Up, enable_if_t<
+        _CheckOptionalLikeCtor<_Up, _Up &&>::template __enable_assign<_Up>()
+    , int> = 0>
+    _LIBCPP_INLINE_VISIBILITY
+    optional&
+    operator=(optional<_Up>&& __v)
+    {
+        this->__assign_from(_VSTD::move(__v));
+        return *this;
+    }
+
+    template <class... _Args,
+              class = enable_if_t
+                      <
+                          is_constructible_v<value_type, _Args...>
+                      >
+             >
+    _LIBCPP_INLINE_VISIBILITY
+    _Tp &
+    emplace(_Args&&... __args)
+    {
+        reset();
+        this->__construct(_VSTD::forward<_Args>(__args)...);
+        return this->__get();
+    }
+
+    template <class _Up, class... _Args,
+              class = enable_if_t
+                      <
+                          is_constructible_v<value_type, initializer_list<_Up>&, _Args...>
+                      >
+             >
+    _LIBCPP_INLINE_VISIBILITY
+    _Tp &
+    emplace(initializer_list<_Up> __il, _Args&&... __args)
+    {
+        reset();
+        this->__construct(__il, _VSTD::forward<_Args>(__args)...);
+        return this->__get();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    void swap(optional& __opt)
+        noexcept(is_nothrow_move_constructible_v<value_type> &&
+                 is_nothrow_swappable_v<value_type>)
+    {
+        if (this->has_value() == __opt.has_value())
+        {
+            using _VSTD::swap;
+            if (this->has_value())
+                swap(this->__get(), __opt.__get());
+        }
+        else
+        {
+            if (this->has_value())
+            {
+                __opt.__construct(_VSTD::move(this->__get()));
+                reset();
+            }
+            else
+            {
+                this->__construct(_VSTD::move(__opt.__get()));
+                __opt.reset();
+            }
+        }
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    add_pointer_t<value_type const>
+    operator->() const
+    {
+        _LIBCPP_ASSERT(this->has_value(), "optional operator-> called for disengaged value");
+#ifndef _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
+        return _VSTD::addressof(this->__get());
+#else
+        return __operator_arrow(__has_operator_addressof<value_type>{}, this->__get());
+#endif
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    add_pointer_t<value_type>
+    operator->()
+    {
+        _LIBCPP_ASSERT(this->has_value(), "optional operator-> called for disengaged value");
+#ifndef _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
+        return _VSTD::addressof(this->__get());
+#else
+        return __operator_arrow(__has_operator_addressof<value_type>{}, this->__get());
+#endif
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    const value_type&
+    operator*() const&
+    {
+        _LIBCPP_ASSERT(this->has_value(), "optional operator* called for disengaged value");
+        return this->__get();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    value_type&
+    operator*() &
+    {
+        _LIBCPP_ASSERT(this->has_value(), "optional operator* called for disengaged value");
+        return this->__get();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    value_type&&
+    operator*() &&
+    {
+        _LIBCPP_ASSERT(this->has_value(), "optional operator* called for disengaged value");
+        return _VSTD::move(this->__get());
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    const value_type&&
+    operator*() const&&
+    {
+        _LIBCPP_ASSERT(this->has_value(), "optional operator* called for disengaged value");
+        return _VSTD::move(this->__get());
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr explicit operator bool() const noexcept { return has_value(); }
+
+    using __base::has_value;
+    using __base::__get;
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type const& value() const&
+    {
+        if (!this->has_value())
+            __throw_bad_optional_access();
+        return this->__get();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type& value() &
+    {
+        if (!this->has_value())
+            __throw_bad_optional_access();
+        return this->__get();
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type&& value() &&
+    {
+        if (!this->has_value())
+            __throw_bad_optional_access();
+        return _VSTD::move(this->__get());
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type const&& value() const&&
+    {
+        if (!this->has_value())
+            __throw_bad_optional_access();
+        return _VSTD::move(this->__get());
+    }
+
+    template <class _Up>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type value_or(_Up&& __v) const&
+    {
+        static_assert(is_copy_constructible_v<value_type>,
+                      "optional<T>::value_or: T must be copy constructible");
+        static_assert(is_convertible_v<_Up, value_type>,
+                      "optional<T>::value_or: U must be convertible to T");
+        return this->has_value() ? this->__get() :
+                                  static_cast<value_type>(_VSTD::forward<_Up>(__v));
+    }
+
+    template <class _Up>
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr value_type value_or(_Up&& __v) &&
+    {
+        static_assert(is_move_constructible_v<value_type>,
+                      "optional<T>::value_or: T must be move constructible");
+        static_assert(is_convertible_v<_Up, value_type>,
+                      "optional<T>::value_or: U must be convertible to T");
+        return this->has_value() ? _VSTD::move(this->__get()) :
+                                  static_cast<value_type>(_VSTD::forward<_Up>(__v));
+    }
+
+    using __base::reset;
+
+private:
+    template <class _Up>
+    _LIBCPP_INLINE_VISIBILITY
+    static _Up*
+    __operator_arrow(true_type, _Up& __x)
+    {
+        return _VSTD::addressof(__x);
+    }
+
+    template <class _Up>
+    _LIBCPP_INLINE_VISIBILITY
+    static constexpr _Up*
+    __operator_arrow(false_type, _Up& __x)
+    {
+        return &__x;
+    }
+};
+
+// Comparisons between optionals
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() ==
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator==(const optional<_Tp>& __x, const optional<_Up>& __y)
+{
+    if (static_cast<bool>(__x) != static_cast<bool>(__y))
+        return false;
+    if (!static_cast<bool>(__x))
+        return true;
+    return *__x == *__y;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() !=
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator!=(const optional<_Tp>& __x, const optional<_Up>& __y)
+{
+    if (static_cast<bool>(__x) != static_cast<bool>(__y))
+        return true;
+    if (!static_cast<bool>(__x))
+        return false;
+    return *__x != *__y;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() <
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator<(const optional<_Tp>& __x, const optional<_Up>& __y)
+{
+    if (!static_cast<bool>(__y))
+        return false;
+    if (!static_cast<bool>(__x))
+        return true;
+    return *__x < *__y;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() >
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator>(const optional<_Tp>& __x, const optional<_Up>& __y)
+{
+    if (!static_cast<bool>(__x))
+        return false;
+    if (!static_cast<bool>(__y))
+        return true;
+    return *__x > *__y;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() <=
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator<=(const optional<_Tp>& __x, const optional<_Up>& __y)
+{
+    if (!static_cast<bool>(__x))
+        return true;
+    if (!static_cast<bool>(__y))
+        return false;
+    return *__x <= *__y;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() >=
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator>=(const optional<_Tp>& __x, const optional<_Up>& __y)
+{
+    if (!static_cast<bool>(__y))
+        return true;
+    if (!static_cast<bool>(__x))
+        return false;
+    return *__x >= *__y;
+}
+
+// Comparisons with nullopt
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator==(const optional<_Tp>& __x, nullopt_t) noexcept
+{
+    return !static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator==(nullopt_t, const optional<_Tp>& __x) noexcept
+{
+    return !static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator!=(const optional<_Tp>& __x, nullopt_t) noexcept
+{
+    return static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator!=(nullopt_t, const optional<_Tp>& __x) noexcept
+{
+    return static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator<(const optional<_Tp>&, nullopt_t) noexcept
+{
+    return false;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator<(nullopt_t, const optional<_Tp>& __x) noexcept
+{
+    return static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator<=(const optional<_Tp>& __x, nullopt_t) noexcept
+{
+    return !static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator<=(nullopt_t, const optional<_Tp>&) noexcept
+{
+    return true;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator>(const optional<_Tp>& __x, nullopt_t) noexcept
+{
+    return static_cast<bool>(__x);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator>(nullopt_t, const optional<_Tp>&) noexcept
+{
+    return false;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator>=(const optional<_Tp>&, nullopt_t) noexcept
+{
+    return true;
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+bool
+operator>=(nullopt_t, const optional<_Tp>& __x) noexcept
+{
+    return !static_cast<bool>(__x);
+}
+
+// Comparisons with T
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() ==
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator==(const optional<_Tp>& __x, const _Up& __v)
+{
+    return static_cast<bool>(__x) ? *__x == __v : false;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() ==
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator==(const _Tp& __v, const optional<_Up>& __x)
+{
+    return static_cast<bool>(__x) ? __v == *__x : false;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() !=
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator!=(const optional<_Tp>& __x, const _Up& __v)
+{
+    return static_cast<bool>(__x) ? *__x != __v : true;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() !=
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator!=(const _Tp& __v, const optional<_Up>& __x)
+{
+    return static_cast<bool>(__x) ? __v != *__x : true;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() <
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator<(const optional<_Tp>& __x, const _Up& __v)
+{
+    return static_cast<bool>(__x) ? *__x < __v : true;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() <
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator<(const _Tp& __v, const optional<_Up>& __x)
+{
+    return static_cast<bool>(__x) ? __v < *__x : false;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() <=
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator<=(const optional<_Tp>& __x, const _Up& __v)
+{
+    return static_cast<bool>(__x) ? *__x <= __v : true;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() <=
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator<=(const _Tp& __v, const optional<_Up>& __x)
+{
+    return static_cast<bool>(__x) ? __v <= *__x : false;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() >
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator>(const optional<_Tp>& __x, const _Up& __v)
+{
+    return static_cast<bool>(__x) ? *__x > __v : false;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() >
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator>(const _Tp& __v, const optional<_Up>& __x)
+{
+    return static_cast<bool>(__x) ? __v > *__x : true;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() >=
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator>=(const optional<_Tp>& __x, const _Up& __v)
+{
+    return static_cast<bool>(__x) ? *__x >= __v : false;
+}
+
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VISIBILITY constexpr
+enable_if_t<
+    is_convertible_v<decltype(_VSTD::declval<const _Tp&>() >=
+        _VSTD::declval<const _Up&>()), bool>,
+    bool
+>
+operator>=(const _Tp& __v, const optional<_Up>& __x)
+{
+    return static_cast<bool>(__x) ? __v >= *__x : true;
+}
+
+
+template <class _Tp>
+inline _LIBCPP_INLINE_VISIBILITY
+enable_if_t<
+    is_move_constructible_v<_Tp> && is_swappable_v<_Tp>,
+    void
+>
+swap(optional<_Tp>& __x, optional<_Tp>& __y) noexcept(noexcept(__x.swap(__y)))
+{
+    __x.swap(__y);
+}
+
+template <class _Tp>
+_LIBCPP_INLINE_VISIBILITY constexpr
+optional<decay_t<_Tp>> make_optional(_Tp&& __v)
+{
+    return optional<decay_t<_Tp>>(_VSTD::forward<_Tp>(__v));
+}
+
+template <class _Tp, class... _Args>
+_LIBCPP_INLINE_VISIBILITY constexpr
+optional<_Tp> make_optional(_Args&&... __args)
+{
+    return optional<_Tp>(in_place, _VSTD::forward<_Args>(__args)...);
+}
+
+template <class _Tp, class _Up, class... _Args>
+_LIBCPP_INLINE_VISIBILITY constexpr
+optional<_Tp> make_optional(initializer_list<_Up> __il,  _Args&&... __args)
+{
+    return optional<_Tp>(in_place, __il, _VSTD::forward<_Args>(__args)...);
+}
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS hash<
+    __enable_hash_helper<optional<_Tp>, remove_const_t<_Tp>>
+>
+{
+    typedef optional<_Tp> argument_type;
+    typedef size_t        result_type;
+
+    _LIBCPP_INLINE_VISIBILITY
+    result_type operator()(const argument_type& __opt) const
+    {
+        return static_cast<bool>(__opt) ? hash<remove_const_t<_Tp>>()(*__opt) : 0;
+    }
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif  // _LIBCPP_STD_VER > 14
+
+_LIBCPP_POP_MACROS
+
+#endif  // _LIBCPP_OPTIONAL
diff --git a/lib/libcxx/include/ostream b/lib/libcxx/include/ostream
index f55fd40856e..f3250a7080d 100644
--- a/lib/libcxx/include/ostream
+++ b/lib/libcxx/include/ostream
@@ -148,7 +148,7 @@ template <class charT, class traits, class T>
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY basic_ostream
+class _LIBCPP_TEMPLATE_VIS basic_ostream
     : virtual public basic_ios<_CharT, _Traits>
 {
 public:
@@ -160,22 +160,24 @@ public:
     typedef typename traits_type::off_type off_type;
 
     // 27.7.2.2 Constructor/destructor:
-    explicit basic_ostream(basic_streambuf<char_type, traits_type>* __sb);
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    explicit basic_ostream(basic_streambuf<char_type, traits_type>* __sb)
+    { this->init(__sb); }
     virtual ~basic_ostream();
 protected:
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
+#ifndef _LIBCPP_CXX03_LANG
+    inline _LIBCPP_INLINE_VISIBILITY
     basic_ostream(basic_ostream&& __rhs);
-#endif
 
     // 27.7.2.3 Assign/swap
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
+    inline _LIBCPP_INLINE_VISIBILITY
     basic_ostream& operator=(basic_ostream&& __rhs);
 #endif
-    void swap(basic_ostream& __rhs);
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    void swap(basic_ostream& __rhs)
+    { basic_ios<char_type, traits_type>::swap(__rhs); }
 
-#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+#ifndef _LIBCPP_CXX03_LANG
     basic_ostream           (const basic_ostream& __rhs) = delete;
     basic_ostream& operator=(const basic_ostream& __rhs) = delete;
 #else
@@ -185,13 +187,22 @@ protected:
 public:
 
     // 27.7.2.4 Prefix/suffix:
-    class _LIBCPP_TYPE_VIS_ONLY sentry;
+    class _LIBCPP_TEMPLATE_VIS sentry;
 
     // 27.7.2.6 Formatted output:
-    basic_ostream& operator<<(basic_ostream& (*__pf)(basic_ostream&));
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    basic_ostream& operator<<(basic_ostream& (*__pf)(basic_ostream&))
+    { return __pf(*this); }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
     basic_ostream& operator<<(basic_ios<char_type, traits_type>&
-                              (*__pf)(basic_ios<char_type,traits_type>&));
-    basic_ostream& operator<<(ios_base& (*__pf)(ios_base&));
+                              (*__pf)(basic_ios<char_type,traits_type>&))
+    { __pf(*this); return *this; }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    basic_ostream& operator<<(ios_base& (*__pf)(ios_base&))
+    { __pf(*this); return *this; }
+
     basic_ostream& operator<<(bool __n);
     basic_ostream& operator<<(short __n);
     basic_ostream& operator<<(unsigned short __n);
@@ -213,8 +224,11 @@ public:
     basic_ostream& flush();
 
     // 27.7.2.5 seeks:
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
     pos_type tellp();
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
     basic_ostream& seekp(pos_type __pos);
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
     basic_ostream& seekp(off_type __off, ios_base::seekdir __dir);
 
 protected:
@@ -223,7 +237,7 @@ protected:
 };
 
 template <class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY basic_ostream<_CharT, _Traits>::sentry
+class _LIBCPP_TEMPLATE_VIS basic_ostream<_CharT, _Traits>::sentry
 {
     bool __ok_;
     basic_ostream<_CharT, _Traits>& __os_;
@@ -274,24 +288,15 @@ basic_ostream<_CharT, _Traits>::sentry::~sentry()
     }
 }
 
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_ostream<_CharT, _Traits>::basic_ostream(basic_streambuf<char_type, traits_type>* __sb)
-{
-    this->init(__sb);
-}
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_ostream<_CharT, _Traits>::basic_ostream(basic_ostream&& __rhs)
 {
     this->move(__rhs);
 }
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_ostream<_CharT, _Traits>&
 basic_ostream<_CharT, _Traits>::operator=(basic_ostream&& __rhs)
 {
@@ -299,7 +304,7 @@ basic_ostream<_CharT, _Traits>::operator=(basic_ostream&& __rhs)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits>
 basic_ostream<_CharT, _Traits>::~basic_ostream()
@@ -307,41 +312,6 @@ basic_ostream<_CharT, _Traits>::~basic_ostream()
 }
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-void
-basic_ostream<_CharT, _Traits>::swap(basic_ostream& __rhs)
-{
-    basic_ios<char_type, traits_type>::swap(__rhs);
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_ostream<_CharT, _Traits>&
-basic_ostream<_CharT, _Traits>::operator<<(basic_ostream& (*__pf)(basic_ostream&))
-{
-    return __pf(*this);
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_ostream<_CharT, _Traits>&
-basic_ostream<_CharT, _Traits>::operator<<(basic_ios<char_type, traits_type>&
-                                           (*__pf)(basic_ios<char_type,traits_type>&))
-{
-    __pf(*this);
-    return *this;
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_ostream<_CharT, _Traits>&
-basic_ostream<_CharT, _Traits>::operator<<(ios_base& (*__pf)(ios_base&))
-{
-    __pf(*this);
-    return *this;
-}
-
-template <class _CharT, class _Traits>
 basic_ostream<_CharT, _Traits>&
 basic_ostream<_CharT, _Traits>::operator<<(basic_streambuf<char_type, traits_type>* __sb)
 {
@@ -989,7 +959,6 @@ basic_ostream<_CharT, _Traits>::flush()
 }
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
 typename basic_ostream<_CharT, _Traits>::pos_type
 basic_ostream<_CharT, _Traits>::tellp()
 {
@@ -999,7 +968,6 @@ basic_ostream<_CharT, _Traits>::tellp()
 }
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_ostream<_CharT, _Traits>&
 basic_ostream<_CharT, _Traits>::seekp(pos_type __pos)
 {
@@ -1013,7 +981,6 @@ basic_ostream<_CharT, _Traits>::seekp(pos_type __pos)
 }
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_ostream<_CharT, _Traits>&
 basic_ostream<_CharT, _Traits>::seekp(off_type __off, ios_base::seekdir __dir)
 {
@@ -1054,7 +1021,7 @@ flush(basic_ostream<_CharT, _Traits>& __os)
     return __os;
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Stream, class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1070,7 +1037,7 @@ operator<<(_Stream&& __os, const _Tp& __x)
     return _VSTD::move(__os);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template<class _CharT, class _Traits, class _Allocator>
 basic_ostream<_CharT, _Traits>&
@@ -1080,6 +1047,14 @@ operator<<(basic_ostream<_CharT, _Traits>& __os,
     return _VSTD::__put_character_sequence(__os, __str.data(), __str.size());
 }
 
+template<class _CharT, class _Traits>
+basic_ostream<_CharT, _Traits>&
+operator<<(basic_ostream<_CharT, _Traits>& __os,
+           const basic_string_view<_CharT, _Traits> __sv)
+{
+    return _VSTD::__put_character_sequence(__os, __sv.data(), __sv.size());
+}
+
 template <class _CharT, class _Traits>
 inline _LIBCPP_INLINE_VISIBILITY
 basic_ostream<_CharT, _Traits>&
@@ -1096,6 +1071,20 @@ operator<<(basic_ostream<_CharT, _Traits>& __os, shared_ptr<_Yp> const& __p)
     return __os << __p.get();
 }
 
+#ifndef _LIBCPP_HAS_NO_DECLTYPE
+template<class _CharT, class _Traits, class _Yp, class _Dp>
+inline _LIBCPP_INLINE_VISIBILITY
+typename enable_if
+<
+    is_same<void, typename __void_t<decltype(declval<basic_ostream<_CharT, _Traits>&>() << declval<_Yp>())>::type>::value,
+    basic_ostream<_CharT, _Traits>&
+>::type
+operator<<(basic_ostream<_CharT, _Traits>& __os, unique_ptr<_Yp, _Dp> const& __p)
+{
+    return __os << __p.get();
+}
+#endif
+
 template <class _CharT, class _Traits, size_t _Size>
 basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os, const bitset<_Size>& __x)
@@ -1105,8 +1094,10 @@ operator<<(basic_ostream<_CharT, _Traits>& __os, const bitset<_Size>& __x)
                          use_facet<ctype<_CharT> >(__os.getloc()).widen('1'));
 }
 
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_ostream<char>)
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_ostream<wchar_t>)
+#ifndef _LIBCPP_AVAILABILITY_NO_STREAMS_EXTERN_TEMPLATE
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_ostream<char>)
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_ostream<wchar_t>)
+#endif
 
 _LIBCPP_END_NAMESPACE_STD
 
diff --git a/lib/libcxx/include/queue b/lib/libcxx/include/queue
index c657b52f803..670fbb722ee 100644
--- a/lib/libcxx/include/queue
+++ b/lib/libcxx/include/queue
@@ -63,7 +63,7 @@ public:
 
     void push(const value_type& v);
     void push(value_type&& v);
-    template <class... Args> void emplace(Args&&... args);
+    template <class... Args> reference emplace(Args&&... args); // reference in C++17
     void pop();
 
     void swap(queue& q) noexcept(is_nothrow_swappable_v<Container>)
@@ -178,7 +178,7 @@ template <class T, class Container, class Compare>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Tp, class _Container = deque<_Tp> > class _LIBCPP_TYPE_VIS_ONLY queue;
+template <class _Tp, class _Container = deque<_Tp> > class _LIBCPP_TEMPLATE_VIS queue;
 
 template <class _Tp, class _Container>
 _LIBCPP_INLINE_VISIBILITY
@@ -191,7 +191,7 @@ bool
 operator< (const queue<_Tp, _Container>& __x,const queue<_Tp, _Container>& __y);
 
 template <class _Tp, class _Container /*= deque<_Tp>*/>
-class _LIBCPP_TYPE_VIS_ONLY queue
+class _LIBCPP_TEMPLATE_VIS queue
 {
 public:
     typedef _Container                               container_type;
@@ -213,29 +213,27 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     queue(const queue& __q) : c(__q.c) {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+    _LIBCPP_INLINE_VISIBILITY
+    queue& operator=(const queue& __q) {c = __q.c; return *this;}
+
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     queue(queue&& __q)
         _NOEXCEPT_(is_nothrow_move_constructible<container_type>::value)
         : c(_VSTD::move(__q.c)) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
     _LIBCPP_INLINE_VISIBILITY
-    queue& operator=(const queue& __q) {c = __q.c; return *this;}
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
     queue& operator=(queue&& __q)
         _NOEXCEPT_(is_nothrow_move_assignable<container_type>::value)
         {c = _VSTD::move(__q.c); return *this;}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     explicit queue(const container_type& __c)  : c(__c) {}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit queue(container_type&& __c) : c(_VSTD::move(__c)) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     template <class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         explicit queue(const _Alloc& __a,
@@ -254,7 +252,7 @@ public:
                        typename enable_if<uses_allocator<container_type,
                                                          _Alloc>::value>::type* = 0)
             : c(__c, __a) {}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     template <class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         queue(container_type&& __c, const _Alloc& __a,
@@ -268,9 +266,9 @@ public:
                                                          _Alloc>::value>::type* = 0)
             : c(_VSTD::move(__q.c), __a) {}
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool      empty() const {return c.empty();}
     _LIBCPP_INLINE_VISIBILITY
     size_type size() const  {return c.size();}
@@ -286,16 +284,19 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     void push(const value_type& __v) {c.push_back(__v);}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void push(value_type&& __v)      {c.push_back(_VSTD::move(__v));}
-#ifndef _LIBCPP_HAS_NO_VARIADICS
     template <class... _Args>
         _LIBCPP_INLINE_VISIBILITY
-        void emplace(_Args&&... __args)
-            {c.emplace_back(_VSTD::forward<_Args>(__args)...);}
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#if _LIBCPP_STD_VER > 14
+        reference emplace(_Args&&... __args)
+            { return c.emplace_back(_VSTD::forward<_Args>(__args)...);}
+#else
+        void     emplace(_Args&&... __args)
+            {        c.emplace_back(_VSTD::forward<_Args>(__args)...);}
+#endif
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void pop() {c.pop_front();}
 
@@ -381,14 +382,14 @@ swap(queue<_Tp, _Container>& __x, queue<_Tp, _Container>& __y)
 }
 
 template <class _Tp, class _Container, class _Alloc>
-struct _LIBCPP_TYPE_VIS_ONLY uses_allocator<queue<_Tp, _Container>, _Alloc>
+struct _LIBCPP_TEMPLATE_VIS uses_allocator<queue<_Tp, _Container>, _Alloc>
     : public uses_allocator<_Container, _Alloc>
 {
 };
 
 template <class _Tp, class _Container = vector<_Tp>,
           class _Compare = less<typename _Container::value_type> >
-class _LIBCPP_TYPE_VIS_ONLY priority_queue
+class _LIBCPP_TEMPLATE_VIS priority_queue
 {
 public:
     typedef _Container                               container_type;
@@ -413,32 +414,30 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     priority_queue(const priority_queue& __q) : c(__q.c), comp(__q.comp) {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+    _LIBCPP_INLINE_VISIBILITY
+    priority_queue& operator=(const priority_queue& __q)
+        {c = __q.c; comp = __q.comp; return *this;}
+
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     priority_queue(priority_queue&& __q)
         _NOEXCEPT_(is_nothrow_move_constructible<container_type>::value &&
                    is_nothrow_move_constructible<value_compare>::value)
         : c(_VSTD::move(__q.c)), comp(_VSTD::move(__q.comp)) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-    _LIBCPP_INLINE_VISIBILITY
-    priority_queue& operator=(const priority_queue& __q)
-        {c = __q.c; comp = __q.comp; return *this;}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     priority_queue& operator=(priority_queue&& __q)
         _NOEXCEPT_(is_nothrow_move_assignable<container_type>::value &&
                    is_nothrow_move_assignable<value_compare>::value)
         {c = _VSTD::move(__q.c); comp = _VSTD::move(__q.comp); return *this;}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     explicit priority_queue(const value_compare& __comp)
         : c(), comp(__comp) {}
     _LIBCPP_INLINE_VISIBILITY
     priority_queue(const value_compare& __comp, const container_type& __c);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit priority_queue(const value_compare& __comp, container_type&& __c);
 #endif
@@ -450,12 +449,12 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         priority_queue(_InputIter __f, _InputIter __l,
                        const value_compare& __comp, const container_type& __c);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     template <class _InputIter>
         _LIBCPP_INLINE_VISIBILITY
         priority_queue(_InputIter __f, _InputIter __l,
                        const value_compare& __comp, container_type&& __c);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     template <class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         explicit priority_queue(const _Alloc& __a,
@@ -477,7 +476,7 @@ public:
         priority_queue(const priority_queue& __q, const _Alloc& __a,
                        typename enable_if<uses_allocator<container_type,
                                                          _Alloc>::value>::type* = 0);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     template <class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         priority_queue(const value_compare& __comp, container_type&& __c,
@@ -489,9 +488,9 @@ public:
         priority_queue(priority_queue&& __q, const _Alloc& __a,
                        typename enable_if<uses_allocator<container_type,
                                                          _Alloc>::value>::type* = 0);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool            empty() const {return c.empty();}
     _LIBCPP_INLINE_VISIBILITY
     size_type       size() const  {return c.size();}
@@ -500,13 +499,13 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     void push(const value_type& __v);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void push(value_type&& __v);
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-    template <class... _Args> _LIBCPP_INLINE_VISIBILITY void emplace(_Args&&... __args);
-#endif
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+    template <class... _Args>
+    _LIBCPP_INLINE_VISIBILITY
+    void emplace(_Args&&... __args);
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void pop();
 
@@ -526,7 +525,7 @@ priority_queue<_Tp, _Container, _Compare>::priority_queue(const _Compare& __comp
     _VSTD::make_heap(c.begin(), c.end(), comp);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Container, class _Compare>
 inline
@@ -538,7 +537,7 @@ priority_queue<_Tp, _Container, _Compare>::priority_queue(const value_compare& _
     _VSTD::make_heap(c.begin(), c.end(), comp);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Container, class _Compare>
 template <class _InputIter>
@@ -564,7 +563,7 @@ priority_queue<_Tp, _Container, _Compare>::priority_queue(_InputIter __f, _Input
     _VSTD::make_heap(c.begin(), c.end(), comp);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Container, class _Compare>
 template <class _InputIter>
@@ -579,7 +578,7 @@ priority_queue<_Tp, _Container, _Compare>::priority_queue(_InputIter __f, _Input
     _VSTD::make_heap(c.begin(), c.end(), comp);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Container, class _Compare>
 template <class _Alloc>
@@ -630,7 +629,7 @@ priority_queue<_Tp, _Container, _Compare>::priority_queue(const priority_queue&
     _VSTD::make_heap(c.begin(), c.end(), comp);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Container, class _Compare>
 template <class _Alloc>
@@ -659,7 +658,7 @@ priority_queue<_Tp, _Container, _Compare>::priority_queue(priority_queue&& __q,
     _VSTD::make_heap(c.begin(), c.end(), comp);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Container, class _Compare>
 inline
@@ -670,7 +669,7 @@ priority_queue<_Tp, _Container, _Compare>::push(const value_type& __v)
     _VSTD::push_heap(c.begin(), c.end(), comp);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Container, class _Compare>
 inline
@@ -681,8 +680,6 @@ priority_queue<_Tp, _Container, _Compare>::push(value_type&& __v)
     _VSTD::push_heap(c.begin(), c.end(), comp);
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
 template <class _Tp, class _Container, class _Compare>
 template <class... _Args>
 inline
@@ -693,8 +690,7 @@ priority_queue<_Tp, _Container, _Compare>::emplace(_Args&&... __args)
     _VSTD::push_heap(c.begin(), c.end(), comp);
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Container, class _Compare>
 inline
@@ -732,7 +728,7 @@ swap(priority_queue<_Tp, _Container, _Compare>& __x,
 }
 
 template <class _Tp, class _Container, class _Compare, class _Alloc>
-struct _LIBCPP_TYPE_VIS_ONLY uses_allocator<priority_queue<_Tp, _Container, _Compare>, _Alloc>
+struct _LIBCPP_TEMPLATE_VIS uses_allocator<priority_queue<_Tp, _Container, _Compare>, _Alloc>
     : public uses_allocator<_Container, _Alloc>
 {
 };
diff --git a/lib/libcxx/include/random b/lib/libcxx/include/random
index 794bf7b3fd1..9073a5285b1 100644
--- a/lib/libcxx/include/random
+++ b/lib/libcxx/include/random
@@ -1646,12 +1646,14 @@ class piecewise_linear_distribution
 #include <istream>
 #include <ostream>
 
-#include <__undef_min_max>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 // __is_seed_sequence
@@ -1813,7 +1815,7 @@ struct __lce_ta<__a, __c, __m, (unsigned short)(~0), __b>
 };
 
 template <class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
-class _LIBCPP_TYPE_VIS_ONLY linear_congruential_engine;
+class _LIBCPP_TEMPLATE_VIS linear_congruential_engine;
 
 template <class _CharT, class _Traits,
           class _Up, _Up _Ap, _Up _Cp, _Up _Np>
@@ -1829,7 +1831,7 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
            linear_congruential_engine<_Up, _Ap, _Cp, _Np>& __x);
 
 template <class _UIntType, _UIntType __a, _UIntType __c, _UIntType __m>
-class _LIBCPP_TYPE_VIS_ONLY linear_congruential_engine
+class _LIBCPP_TEMPLATE_VIS linear_congruential_engine
 {
 public:
     // types
@@ -2011,49 +2013,49 @@ typedef minstd_rand                                       default_random_engine;
 template <class _UIntType, size_t __w, size_t __n, size_t __m, size_t __r,
           _UIntType __a, size_t __u, _UIntType __d, size_t __s,
           _UIntType __b, size_t __t, _UIntType __c, size_t __l, _UIntType __f>
-class _LIBCPP_TYPE_VIS_ONLY mersenne_twister_engine;
+class _LIBCPP_TEMPLATE_VIS mersenne_twister_engine;
 
-template <class _UI, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
-          _UI _Ap, size_t _Up, _UI _Dp, size_t _Sp,
-          _UI _Bp, size_t _Tp, _UI _Cp, size_t _Lp, _UI _Fp>
+template <class _UInt, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
+          _UInt _Ap, size_t _Up, _UInt _Dp, size_t _Sp,
+          _UInt _Bp, size_t _Tp, _UInt _Cp, size_t _Lp, _UInt _Fp>
 bool
-operator==(const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+operator==(const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                          _Bp, _Tp, _Cp, _Lp, _Fp>& __x,
-           const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+           const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                          _Bp, _Tp, _Cp, _Lp, _Fp>& __y);
 
-template <class _UI, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
-          _UI _Ap, size_t _Up, _UI _Dp, size_t _Sp,
-          _UI _Bp, size_t _Tp, _UI _Cp, size_t _Lp, _UI _Fp>
+template <class _UInt, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
+          _UInt _Ap, size_t _Up, _UInt _Dp, size_t _Sp,
+          _UInt _Bp, size_t _Tp, _UInt _Cp, size_t _Lp, _UInt _Fp>
 _LIBCPP_INLINE_VISIBILITY
 bool
-operator!=(const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+operator!=(const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                          _Bp, _Tp, _Cp, _Lp, _Fp>& __x,
-           const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+           const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                          _Bp, _Tp, _Cp, _Lp, _Fp>& __y);
 
 template <class _CharT, class _Traits,
-          class _UI, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
-          _UI _Ap, size_t _Up, _UI _Dp, size_t _Sp,
-          _UI _Bp, size_t _Tp, _UI _Cp, size_t _Lp, _UI _Fp>
+          class _UInt, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
+          _UInt _Ap, size_t _Up, _UInt _Dp, size_t _Sp,
+          _UInt _Bp, size_t _Tp, _UInt _Cp, size_t _Lp, _UInt _Fp>
 basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os,
-           const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+           const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                          _Bp, _Tp, _Cp, _Lp, _Fp>& __x);
 
 template <class _CharT, class _Traits,
-          class _UI, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
-          _UI _Ap, size_t _Up, _UI _Dp, size_t _Sp,
-          _UI _Bp, size_t _Tp, _UI _Cp, size_t _Lp, _UI _Fp>
+          class _UInt, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
+          _UInt _Ap, size_t _Up, _UInt _Dp, size_t _Sp,
+          _UInt _Bp, size_t _Tp, _UInt _Cp, size_t _Lp, _UInt _Fp>
 basic_istream<_CharT, _Traits>&
 operator>>(basic_istream<_CharT, _Traits>& __is,
-           mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+           mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                    _Bp, _Tp, _Cp, _Lp, _Fp>& __x);
 
 template <class _UIntType, size_t __w, size_t __n, size_t __m, size_t __r,
           _UIntType __a, size_t __u, _UIntType __d, size_t __s,
           _UIntType __b, size_t __t, _UIntType __c, size_t __l, _UIntType __f>
-class _LIBCPP_TYPE_VIS_ONLY mersenne_twister_engine
+class _LIBCPP_TEMPLATE_VIS mersenne_twister_engine
 {
 public:
     // types
@@ -2129,44 +2131,44 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     void discard(unsigned long long __z) {for (; __z; --__z) operator()();}
 
-    template <class _UI, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
-              _UI _Ap, size_t _Up, _UI _Dp, size_t _Sp,
-              _UI _Bp, size_t _Tp, _UI _Cp, size_t _Lp, _UI _Fp>
+    template <class _UInt, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
+              _UInt _Ap, size_t _Up, _UInt _Dp, size_t _Sp,
+              _UInt _Bp, size_t _Tp, _UInt _Cp, size_t _Lp, _UInt _Fp>
     friend
     bool
-    operator==(const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+    operator==(const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                              _Bp, _Tp, _Cp, _Lp, _Fp>& __x,
-               const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+               const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                              _Bp, _Tp, _Cp, _Lp, _Fp>& __y);
 
-    template <class _UI, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
-              _UI _Ap, size_t _Up, _UI _Dp, size_t _Sp,
-              _UI _Bp, size_t _Tp, _UI _Cp, size_t _Lp, _UI _Fp>
+    template <class _UInt, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
+              _UInt _Ap, size_t _Up, _UInt _Dp, size_t _Sp,
+              _UInt _Bp, size_t _Tp, _UInt _Cp, size_t _Lp, _UInt _Fp>
     friend
     bool
-    operator!=(const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+    operator!=(const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                              _Bp, _Tp, _Cp, _Lp, _Fp>& __x,
-               const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+               const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                              _Bp, _Tp, _Cp, _Lp, _Fp>& __y);
 
     template <class _CharT, class _Traits,
-              class _UI, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
-              _UI _Ap, size_t _Up, _UI _Dp, size_t _Sp,
-              _UI _Bp, size_t _Tp, _UI _Cp, size_t _Lp, _UI _Fp>
+              class _UInt, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
+              _UInt _Ap, size_t _Up, _UInt _Dp, size_t _Sp,
+              _UInt _Bp, size_t _Tp, _UInt _Cp, size_t _Lp, _UInt _Fp>
     friend
     basic_ostream<_CharT, _Traits>&
     operator<<(basic_ostream<_CharT, _Traits>& __os,
-               const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+               const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                              _Bp, _Tp, _Cp, _Lp, _Fp>& __x);
 
     template <class _CharT, class _Traits,
-              class _UI, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
-              _UI _Ap, size_t _Up, _UI _Dp, size_t _Sp,
-              _UI _Bp, size_t _Tp, _UI _Cp, size_t _Lp, _UI _Fp>
+              class _UInt, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
+              _UInt _Ap, size_t _Up, _UInt _Dp, size_t _Sp,
+              _UInt _Bp, size_t _Tp, _UInt _Cp, size_t _Lp, _UInt _Fp>
     friend
     basic_istream<_CharT, _Traits>&
     operator>>(basic_istream<_CharT, _Traits>& __is,
-               mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+               mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                        _Bp, _Tp, _Cp, _Lp, _Fp>& __x);
 private:
 
@@ -2306,6 +2308,7 @@ template <class _UIntType, size_t __w, size_t __n, size_t __m, size_t __r,
 void
 mersenne_twister_engine<_UIntType, __w, __n, __m, __r, __a, __u, __d, __s, __b,
     __t, __c, __l, __f>::seed(result_type __sd)
+    _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
 {   // __w >= 2
     __x_[0] = __sd & _Max;
     for (size_t __i = 1; __i < __n; ++__i)
@@ -2384,13 +2387,13 @@ mersenne_twister_engine<_UIntType, __w, __n, __m, __r, __a, __u, __d, __s, __b,
     return __z ^ __rshift<__l>(__z);
 }
 
-template <class _UI, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
-          _UI _Ap, size_t _Up, _UI _Dp, size_t _Sp,
-          _UI _Bp, size_t _Tp, _UI _Cp, size_t _Lp, _UI _Fp>
+template <class _UInt, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
+          _UInt _Ap, size_t _Up, _UInt _Dp, size_t _Sp,
+          _UInt _Bp, size_t _Tp, _UInt _Cp, size_t _Lp, _UInt _Fp>
 bool
-operator==(const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+operator==(const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                          _Bp, _Tp, _Cp, _Lp, _Fp>& __x,
-           const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+           const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                          _Bp, _Tp, _Cp, _Lp, _Fp>& __y)
 {
     if (__x.__i_ == __y.__i_)
@@ -2428,26 +2431,26 @@ operator==(const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp,
                        __x.__x_ + (_Np - (__y.__i_ + __j)));
 }
 
-template <class _UI, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
-          _UI _Ap, size_t _Up, _UI _Dp, size_t _Sp,
-          _UI _Bp, size_t _Tp, _UI _Cp, size_t _Lp, _UI _Fp>
+template <class _UInt, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
+          _UInt _Ap, size_t _Up, _UInt _Dp, size_t _Sp,
+          _UInt _Bp, size_t _Tp, _UInt _Cp, size_t _Lp, _UInt _Fp>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
-operator!=(const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+operator!=(const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                          _Bp, _Tp, _Cp, _Lp, _Fp>& __x,
-           const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+           const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                          _Bp, _Tp, _Cp, _Lp, _Fp>& __y)
 {
     return !(__x == __y);
 }
 
 template <class _CharT, class _Traits,
-          class _UI, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
-          _UI _Ap, size_t _Up, _UI _Dp, size_t _Sp,
-          _UI _Bp, size_t _Tp, _UI _Cp, size_t _Lp, _UI _Fp>
+          class _UInt, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
+          _UInt _Ap, size_t _Up, _UInt _Dp, size_t _Sp,
+          _UInt _Bp, size_t _Tp, _UInt _Cp, size_t _Lp, _UInt _Fp>
 basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os,
-           const mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+           const mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                          _Bp, _Tp, _Cp, _Lp, _Fp>& __x)
 {
     __save_flags<_CharT, _Traits> __lx(__os);
@@ -2463,17 +2466,17 @@ operator<<(basic_ostream<_CharT, _Traits>& __os,
 }
 
 template <class _CharT, class _Traits,
-          class _UI, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
-          _UI _Ap, size_t _Up, _UI _Dp, size_t _Sp,
-          _UI _Bp, size_t _Tp, _UI _Cp, size_t _Lp, _UI _Fp>
+          class _UInt, size_t _Wp, size_t _Np, size_t _Mp, size_t _Rp,
+          _UInt _Ap, size_t _Up, _UInt _Dp, size_t _Sp,
+          _UInt _Bp, size_t _Tp, _UInt _Cp, size_t _Lp, _UInt _Fp>
 basic_istream<_CharT, _Traits>&
 operator>>(basic_istream<_CharT, _Traits>& __is,
-           mersenne_twister_engine<_UI, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
+           mersenne_twister_engine<_UInt, _Wp, _Np, _Mp, _Rp, _Ap, _Up, _Dp, _Sp,
                                    _Bp, _Tp, _Cp, _Lp, _Fp>& __x)
 {
     __save_flags<_CharT, _Traits> __lx(__is);
     __is.flags(ios_base::dec | ios_base::skipws);
-    _UI __t[_Np];
+    _UInt __t[_Np];
     for (size_t __i = 0; __i < _Np; ++__i)
         __is >> __t[__i];
     if (!__is.fail())
@@ -2499,35 +2502,35 @@ typedef mersenne_twister_engine<uint_fast64_t, 64, 312, 156, 31,
 // subtract_with_carry_engine
 
 template<class _UIntType, size_t __w, size_t __s, size_t __r>
-class _LIBCPP_TYPE_VIS_ONLY subtract_with_carry_engine;
+class _LIBCPP_TEMPLATE_VIS subtract_with_carry_engine;
 
-template<class _UI, size_t _Wp, size_t _Sp, size_t _Rp>
+template<class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
 bool
 operator==(
-    const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __x,
-    const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __y);
+    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x,
+    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __y);
 
-template<class _UI, size_t _Wp, size_t _Sp, size_t _Rp>
+template<class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
 _LIBCPP_INLINE_VISIBILITY
 bool
 operator!=(
-    const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __x,
-    const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __y);
+    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x,
+    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __y);
 
 template <class _CharT, class _Traits,
-          class _UI, size_t _Wp, size_t _Sp, size_t _Rp>
+          class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
 basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os,
-           const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __x);
+           const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x);
 
 template <class _CharT, class _Traits,
-          class _UI, size_t _Wp, size_t _Sp, size_t _Rp>
+          class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
 basic_istream<_CharT, _Traits>&
 operator>>(basic_istream<_CharT, _Traits>& __is,
-           subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __x);
+           subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x);
 
 template<class _UIntType, size_t __w, size_t __s, size_t __r>
-class _LIBCPP_TYPE_VIS_ONLY subtract_with_carry_engine
+class _LIBCPP_TEMPLATE_VIS subtract_with_carry_engine
 {
 public:
     // types
@@ -2586,33 +2589,33 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     void discard(unsigned long long __z) {for (; __z; --__z) operator()();}
 
-    template<class _UI, size_t _Wp, size_t _Sp, size_t _Rp>
+    template<class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
     friend
     bool
     operator==(
-        const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __x,
-        const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __y);
+        const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x,
+        const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __y);
 
-    template<class _UI, size_t _Wp, size_t _Sp, size_t _Rp>
+    template<class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
     friend
     bool
     operator!=(
-        const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __x,
-        const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __y);
+        const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x,
+        const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __y);
 
     template <class _CharT, class _Traits,
-              class _UI, size_t _Wp, size_t _Sp, size_t _Rp>
+              class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
     friend
     basic_ostream<_CharT, _Traits>&
     operator<<(basic_ostream<_CharT, _Traits>& __os,
-               const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __x);
+               const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x);
 
     template <class _CharT, class _Traits,
-              class _UI, size_t _Wp, size_t _Sp, size_t _Rp>
+              class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
     friend
     basic_istream<_CharT, _Traits>&
     operator>>(basic_istream<_CharT, _Traits>& __is,
-               subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __x);
+               subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x);
 
 private:
 
@@ -2711,11 +2714,11 @@ subtract_with_carry_engine<_UIntType, __w, __s, __r>::operator()()
     return __xr;
 }
 
-template<class _UI, size_t _Wp, size_t _Sp, size_t _Rp>
+template<class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
 bool
 operator==(
-    const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __x,
-    const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __y)
+    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x,
+    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __y)
 {
     if (__x.__c_ != __y.__c_)
         return false;
@@ -2754,21 +2757,21 @@ operator==(
                        __x.__x_ + (_Rp - (__y.__i_ + __j)));
 }
 
-template<class _UI, size_t _Wp, size_t _Sp, size_t _Rp>
+template<class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
 operator!=(
-    const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __x,
-    const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __y)
+    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x,
+    const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __y)
 {
     return !(__x == __y);
 }
 
 template <class _CharT, class _Traits,
-          class _UI, size_t _Wp, size_t _Sp, size_t _Rp>
+          class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
 basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os,
-           const subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __x)
+           const subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x)
 {
     __save_flags<_CharT, _Traits> __lx(__os);
     __os.flags(ios_base::dec | ios_base::left);
@@ -2784,14 +2787,14 @@ operator<<(basic_ostream<_CharT, _Traits>& __os,
 }
 
 template <class _CharT, class _Traits,
-          class _UI, size_t _Wp, size_t _Sp, size_t _Rp>
+          class _UInt, size_t _Wp, size_t _Sp, size_t _Rp>
 basic_istream<_CharT, _Traits>&
 operator>>(basic_istream<_CharT, _Traits>& __is,
-           subtract_with_carry_engine<_UI, _Wp, _Sp, _Rp>& __x)
+           subtract_with_carry_engine<_UInt, _Wp, _Sp, _Rp>& __x)
 {
     __save_flags<_CharT, _Traits> __lx(__is);
     __is.flags(ios_base::dec | ios_base::skipws);
-    _UI __t[_Rp+1];
+    _UInt __t[_Rp+1];
     for (size_t __i = 0; __i < _Rp+1; ++__i)
         __is >> __t[__i];
     if (!__is.fail())
@@ -2810,13 +2813,14 @@ typedef subtract_with_carry_engine<uint_fast64_t, 48,  5, 12>     ranlux48_base;
 // discard_block_engine
 
 template<class _Engine, size_t __p, size_t __r>
-class _LIBCPP_TYPE_VIS_ONLY discard_block_engine
+class _LIBCPP_TEMPLATE_VIS discard_block_engine
 {
     _Engine __e_;
     int     __n_;
 
     static_assert(  0 <  __r, "discard_block_engine invalid parameters");
     static_assert(__r <= __p, "discard_block_engine invalid parameters");
+    static_assert(__r <= INT_MAX, "discard_block_engine invalid parameters");
 public:
     // types
     typedef typename _Engine::result_type result_type;
@@ -2825,7 +2829,7 @@ public:
     static _LIBCPP_CONSTEXPR const size_t block_size = __p;
     static _LIBCPP_CONSTEXPR const size_t used_block = __r;
 
-#ifdef _LIBCPP_HAS_NO_CONSTEXPR
+#ifdef _LIBCPP_CXX03_LANG
     static const result_type _Min = _Engine::_Min;
     static const result_type _Max = _Engine::_Max;
 #else
@@ -2844,11 +2848,11 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     explicit discard_block_engine(const _Engine& __e)
         : __e_(__e), __n_(0) {}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit discard_block_engine(_Engine&& __e)
         : __e_(_VSTD::move(__e)), __n_(0) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit discard_block_engine(result_type __sd) : __e_(__sd), __n_(0) {}
     template<class _Sseq>
@@ -2918,7 +2922,7 @@ template<class _Engine, size_t __p, size_t __r>
 typename discard_block_engine<_Engine, __p, __r>::result_type
 discard_block_engine<_Engine, __p, __r>::operator()()
 {
-    if (__n_ >= __r)
+    if (__n_ >= static_cast<int>(__r))
     {
         __e_.discard(__p - __r);
         __n_ = 0;
@@ -2983,15 +2987,15 @@ typedef discard_block_engine<ranlux48_base, 389, 11> ranlux48;
 // independent_bits_engine
 
 template<class _Engine, size_t __w, class _UIntType>
-class _LIBCPP_TYPE_VIS_ONLY independent_bits_engine
+class _LIBCPP_TEMPLATE_VIS independent_bits_engine
 {
-    template <class _UI, _UI _R0, size_t _Wp, size_t _Mp>
+    template <class _UInt, _UInt _R0, size_t _Wp, size_t _Mp>
     class __get_n
     {
-        static _LIBCPP_CONSTEXPR const size_t _Dt = numeric_limits<_UI>::digits;
+        static _LIBCPP_CONSTEXPR const size_t _Dt = numeric_limits<_UInt>::digits;
         static _LIBCPP_CONSTEXPR const size_t _Np = _Wp / _Mp + (_Wp % _Mp != 0);
         static _LIBCPP_CONSTEXPR const size_t _W0 = _Wp / _Np;
-        static _LIBCPP_CONSTEXPR const _UI _Y0 = _W0 >= _Dt ? 0 : (_R0 >> _W0) << _W0;
+        static _LIBCPP_CONSTEXPR const _UInt _Y0 = _W0 >= _Dt ? 0 : (_R0 >> _W0) << _W0;
     public:
         static _LIBCPP_CONSTEXPR const size_t value = _R0 - _Y0 > _Y0 / _Np ? _Np + 1 : _Np;
     };
@@ -3013,7 +3017,7 @@ private:
                 result_type,
                 _Engine_result_type
         >::type _Working_result_type;
-#ifdef _LIBCPP_HAS_NO_CONSTEXPR
+#ifdef _LIBCPP_CXX03_LANG
     static const _Working_result_type _Rp = _Engine::_Max - _Engine::_Min
                                           + _Working_result_type(1);
 #else
@@ -3054,11 +3058,11 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     explicit independent_bits_engine(const _Engine& __e)
         : __e_(__e) {}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit independent_bits_engine(_Engine&& __e)
         : __e_(_VSTD::move(__e)) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit independent_bits_engine(result_type __sd) : __e_(__sd) {}
     template<class _Sseq>
@@ -3090,33 +3094,33 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     const _Engine& base() const _NOEXCEPT {return __e_;}
 
-    template<class _Eng, size_t _Wp, class _UI>
+    template<class _Eng, size_t _Wp, class _UInt>
     friend
     bool
     operator==(
-        const independent_bits_engine<_Eng, _Wp, _UI>& __x,
-        const independent_bits_engine<_Eng, _Wp, _UI>& __y);
+        const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
+        const independent_bits_engine<_Eng, _Wp, _UInt>& __y);
 
-    template<class _Eng, size_t _Wp, class _UI>
+    template<class _Eng, size_t _Wp, class _UInt>
     friend
     bool
     operator!=(
-        const independent_bits_engine<_Eng, _Wp, _UI>& __x,
-        const independent_bits_engine<_Eng, _Wp, _UI>& __y);
+        const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
+        const independent_bits_engine<_Eng, _Wp, _UInt>& __y);
 
     template <class _CharT, class _Traits,
-              class _Eng, size_t _Wp, class _UI>
+              class _Eng, size_t _Wp, class _UInt>
     friend
     basic_ostream<_CharT, _Traits>&
     operator<<(basic_ostream<_CharT, _Traits>& __os,
-               const independent_bits_engine<_Eng, _Wp, _UI>& __x);
+               const independent_bits_engine<_Eng, _Wp, _UInt>& __x);
 
     template <class _CharT, class _Traits,
-              class _Eng, size_t _Wp, class _UI>
+              class _Eng, size_t _Wp, class _UInt>
     friend
     basic_istream<_CharT, _Traits>&
     operator>>(basic_istream<_CharT, _Traits>& __is,
-               independent_bits_engine<_Eng, _Wp, _UI>& __x);
+               independent_bits_engine<_Eng, _Wp, _UInt>& __x);
 
 private:
     _LIBCPP_INLINE_VISIBILITY
@@ -3178,40 +3182,40 @@ independent_bits_engine<_Engine, __w, _UIntType>::__eval(true_type)
     return _Sp;
 }
 
-template<class _Eng, size_t _Wp, class _UI>
+template<class _Eng, size_t _Wp, class _UInt>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
 operator==(
-    const independent_bits_engine<_Eng, _Wp, _UI>& __x,
-    const independent_bits_engine<_Eng, _Wp, _UI>& __y)
+    const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
+    const independent_bits_engine<_Eng, _Wp, _UInt>& __y)
 {
     return __x.base() == __y.base();
 }
 
-template<class _Eng, size_t _Wp, class _UI>
+template<class _Eng, size_t _Wp, class _UInt>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
 operator!=(
-    const independent_bits_engine<_Eng, _Wp, _UI>& __x,
-    const independent_bits_engine<_Eng, _Wp, _UI>& __y)
+    const independent_bits_engine<_Eng, _Wp, _UInt>& __x,
+    const independent_bits_engine<_Eng, _Wp, _UInt>& __y)
 {
     return !(__x == __y);
 }
 
 template <class _CharT, class _Traits,
-          class _Eng, size_t _Wp, class _UI>
+          class _Eng, size_t _Wp, class _UInt>
 basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os,
-           const independent_bits_engine<_Eng, _Wp, _UI>& __x)
+           const independent_bits_engine<_Eng, _Wp, _UInt>& __x)
 {
     return __os << __x.base();
 }
 
 template <class _CharT, class _Traits,
-          class _Eng, size_t _Wp, class _UI>
+          class _Eng, size_t _Wp, class _UInt>
 basic_istream<_CharT, _Traits>&
 operator>>(basic_istream<_CharT, _Traits>& __is,
-           independent_bits_engine<_Eng, _Wp, _UI>& __x)
+           independent_bits_engine<_Eng, _Wp, _UInt>& __x)
 {
     _Eng __e;
     __is >> __e;
@@ -3247,7 +3251,7 @@ public:
 };
 
 template<class _Engine, size_t __k>
-class _LIBCPP_TYPE_VIS_ONLY shuffle_order_engine
+class _LIBCPP_TEMPLATE_VIS shuffle_order_engine
 {
     static_assert(0 < __k, "shuffle_order_engine invalid parameters");
 public:
@@ -3263,7 +3267,7 @@ public:
     // engine characteristics
     static _LIBCPP_CONSTEXPR const size_t table_size = __k;
 
-#ifdef _LIBCPP_HAS_NO_CONSTEXPR
+#ifdef _LIBCPP_CXX03_LANG
     static const result_type _Min = _Engine::_Min;
     static const result_type _Max = _Engine::_Max;
 #else
@@ -3284,11 +3288,11 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     explicit shuffle_order_engine(const _Engine& __e)
         : __e_(__e) {__init();}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit shuffle_order_engine(_Engine&& __e)
         : __e_(_VSTD::move(__e)) {__init();}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit shuffle_order_engine(result_type __sd) : __e_(__sd) {__init();}
     template<class _Sseq>
@@ -3510,7 +3514,7 @@ private:
 
 // seed_seq
 
-class _LIBCPP_TYPE_VIS_ONLY seed_seq
+class _LIBCPP_TEMPLATE_VIS seed_seq
 {
 public:
     // types
@@ -3525,11 +3529,11 @@ public:
     // constructors
     _LIBCPP_INLINE_VISIBILITY
     seed_seq() _NOEXCEPT {}
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     template<class _Tp>
         _LIBCPP_INLINE_VISIBILITY
         seed_seq(initializer_list<_Tp> __il) {init(__il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     template<class _InputIterator>
         _LIBCPP_INLINE_VISIBILITY
@@ -3636,7 +3640,7 @@ generate_canonical(_URNG& __g)
 {
     const size_t _Dt = numeric_limits<_RealType>::digits;
     const size_t __b = _Dt < __bits ? _Dt : __bits;
-#ifdef _LIBCPP_HAS_NO_CONSTEXPR
+#ifdef _LIBCPP_CXX03_LANG
     const size_t __logR = __log2<uint64_t, _URNG::_Max - _URNG::_Min + uint64_t(1)>::value;
 #else
     const size_t __logR = __log2<uint64_t, _URNG::max() - _URNG::min() + uint64_t(1)>::value;
@@ -3687,13 +3691,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // uniform_real_distribution
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY uniform_real_distribution
+class _LIBCPP_TEMPLATE_VIS uniform_real_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         result_type __a_;
         result_type __b_;
@@ -3808,13 +3812,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 
 // bernoulli_distribution
 
-class _LIBCPP_TYPE_VIS_ONLY bernoulli_distribution
+class _LIBCPP_TEMPLATE_VIS bernoulli_distribution
 {
 public:
     // types
     typedef bool result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         double __p_;
     public:
@@ -3917,13 +3921,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is, bernoulli_distribution& __x)
 // binomial_distribution
 
 template<class _IntType = int>
-class _LIBCPP_TYPE_VIS_ONLY binomial_distribution
+class _LIBCPP_TEMPLATE_VIS binomial_distribution
 {
 public:
     // types
     typedef _IntType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         result_type __t_;
         double __p_;
@@ -3996,16 +4000,30 @@ public:
         {return !(__x == __y);}
 };
 
+#ifndef _LIBCPP_MSVCRT
+extern "C" double lgamma_r(double, int *);
+#endif
+
+inline _LIBCPP_INLINE_VISIBILITY double __libcpp_lgamma(double __d) {
+#if defined(_LIBCPP_MSVCRT)
+  return lgamma(__d);
+#else
+  int __sign;
+  return lgamma_r(__d, &__sign);
+#endif
+}
+
 template<class _IntType>
-binomial_distribution<_IntType>::param_type::param_type(result_type __t, double __p)
+binomial_distribution<_IntType>::param_type::param_type(const result_type __t, const double __p)
     : __t_(__t), __p_(__p)
 {
     if (0 < __p_ && __p_ < 1)
     {
         __r0_ = static_cast<result_type>((__t_ + 1) * __p_);
-        __pr_ = _VSTD::exp(_VSTD::lgamma(__t_ + 1.) - _VSTD::lgamma(__r0_ + 1.) -
-                          _VSTD::lgamma(__t_ - __r0_ + 1.) + __r0_ * _VSTD::log(__p_) +
-                          (__t_ - __r0_) * _VSTD::log(1 - __p_));
+        __pr_ = _VSTD::exp(__libcpp_lgamma(__t_ + 1.) -
+                           __libcpp_lgamma(__r0_ + 1.) -
+                           __libcpp_lgamma(__t_ - __r0_ + 1.) + __r0_ * _VSTD::log(__p_) +
+                           (__t_ - __r0_) * _VSTD::log(1 - __p_));
         __odds_ratio_ = __p_ / (1 - __p_);
     }
 }
@@ -4085,13 +4103,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // exponential_distribution
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY exponential_distribution
+class _LIBCPP_TEMPLATE_VIS exponential_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         result_type __lambda_;
     public:
@@ -4200,13 +4218,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // normal_distribution
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY normal_distribution
+class _LIBCPP_TEMPLATE_VIS normal_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         result_type __mean_;
         result_type __stddev_;
@@ -4368,13 +4386,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // lognormal_distribution
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY lognormal_distribution
+class _LIBCPP_TEMPLATE_VIS lognormal_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         normal_distribution<result_type> __nd_;
     public:
@@ -4493,13 +4511,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // poisson_distribution
 
 template<class _IntType = int>
-class _LIBCPP_TYPE_VIS_ONLY poisson_distribution
+class _LIBCPP_TEMPLATE_VIS poisson_distribution
 {
 public:
     // types
     typedef _IntType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         double __mean_;
         double __s_;
@@ -4724,13 +4742,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // weibull_distribution
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY weibull_distribution
+class _LIBCPP_TEMPLATE_VIS weibull_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         result_type __a_;
         result_type __b_;
@@ -4838,13 +4856,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 }
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY extreme_value_distribution
+class _LIBCPP_TEMPLATE_VIS extreme_value_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         result_type __a_;
         result_type __b_;
@@ -4959,13 +4977,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // gamma_distribution
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY gamma_distribution
+class _LIBCPP_TEMPLATE_VIS gamma_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         result_type __alpha_;
         result_type __beta_;
@@ -5131,13 +5149,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // negative_binomial_distribution
 
 template<class _IntType = int>
-class _LIBCPP_TYPE_VIS_ONLY negative_binomial_distribution
+class _LIBCPP_TEMPLATE_VIS negative_binomial_distribution
 {
 public:
     // types
     typedef _IntType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         result_type __k_;
         double __p_;
@@ -5266,13 +5284,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // geometric_distribution
 
 template<class _IntType = int>
-class _LIBCPP_TYPE_VIS_ONLY geometric_distribution
+class _LIBCPP_TEMPLATE_VIS geometric_distribution
 {
 public:
     // types
     typedef _IntType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         double __p_;
     public:
@@ -5368,13 +5386,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // chi_squared_distribution
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY chi_squared_distribution
+class _LIBCPP_TEMPLATE_VIS chi_squared_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         result_type __n_;
     public:
@@ -5474,13 +5492,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // cauchy_distribution
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY cauchy_distribution
+class _LIBCPP_TEMPLATE_VIS cauchy_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         result_type __a_;
         result_type __b_;
@@ -5597,13 +5615,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // fisher_f_distribution
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY fisher_f_distribution
+class _LIBCPP_TEMPLATE_VIS fisher_f_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         result_type __m_;
         result_type __n_;
@@ -5719,13 +5737,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // student_t_distribution
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY student_t_distribution
+class _LIBCPP_TEMPLATE_VIS student_t_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         result_type __n_;
     public:
@@ -5832,13 +5850,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // discrete_distribution
 
 template<class _IntType = int>
-class _LIBCPP_TYPE_VIS_ONLY discrete_distribution
+class _LIBCPP_TEMPLATE_VIS discrete_distribution
 {
 public:
     // types
     typedef _IntType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         vector<double> __p_;
     public:
@@ -5850,11 +5868,11 @@ public:
             _LIBCPP_INLINE_VISIBILITY
             param_type(_InputIterator __f, _InputIterator __l)
             : __p_(__f, __l) {__init();}
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
         _LIBCPP_INLINE_VISIBILITY
         param_type(initializer_list<double> __wl)
             : __p_(__wl.begin(), __wl.end()) {__init();}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
         template<class _UnaryOperation>
             param_type(size_t __nw, double __xmin, double __xmax,
                        _UnaryOperation __fw);
@@ -5897,11 +5915,11 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         discrete_distribution(_InputIterator __f, _InputIterator __l)
             : __p_(__f, __l) {}
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     discrete_distribution(initializer_list<double> __wl)
         : __p_(__wl) {}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
     template<class _UnaryOperation>
         _LIBCPP_INLINE_VISIBILITY
         discrete_distribution(size_t __nw, double __xmin, double __xmax,
@@ -6060,13 +6078,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // piecewise_constant_distribution
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY piecewise_constant_distribution
+class _LIBCPP_TEMPLATE_VIS piecewise_constant_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         vector<result_type> __b_;
         vector<result_type> __densities_;
@@ -6078,10 +6096,10 @@ public:
         template<class _InputIteratorB, class _InputIteratorW>
             param_type(_InputIteratorB __fB, _InputIteratorB __lB,
                        _InputIteratorW __fW);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
         template<class _UnaryOperation>
             param_type(initializer_list<result_type> __bl, _UnaryOperation __fw);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
         template<class _UnaryOperation>
             param_type(size_t __nw, result_type __xmin, result_type __xmax,
                        _UnaryOperation __fw);
@@ -6131,13 +6149,13 @@ public:
                                         _InputIteratorW __fW)
         : __p_(__fB, __lB, __fW) {}
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     template<class _UnaryOperation>
         _LIBCPP_INLINE_VISIBILITY
         piecewise_constant_distribution(initializer_list<result_type> __bl,
                                         _UnaryOperation __fw)
         : __p_(__bl, __fw) {}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     template<class _UnaryOperation>
         _LIBCPP_INLINE_VISIBILITY
@@ -6267,7 +6285,7 @@ piecewise_constant_distribution<_RealType>::param_type::param_type(
     }
 }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
 
 template<class _RealType>
 template<class _UnaryOperation>
@@ -6292,7 +6310,7 @@ piecewise_constant_distribution<_RealType>::param_type::param_type(
     }
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 template<class _RealType>
 template<class _UnaryOperation>
@@ -6383,13 +6401,13 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 // piecewise_linear_distribution
 
 template<class _RealType = double>
-class _LIBCPP_TYPE_VIS_ONLY piecewise_linear_distribution
+class _LIBCPP_TEMPLATE_VIS piecewise_linear_distribution
 {
 public:
     // types
     typedef _RealType result_type;
 
-    class _LIBCPP_TYPE_VIS_ONLY param_type
+    class _LIBCPP_TEMPLATE_VIS param_type
     {
         vector<result_type> __b_;
         vector<result_type> __densities_;
@@ -6401,10 +6419,10 @@ public:
         template<class _InputIteratorB, class _InputIteratorW>
             param_type(_InputIteratorB __fB, _InputIteratorB __lB,
                        _InputIteratorW __fW);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
         template<class _UnaryOperation>
             param_type(initializer_list<result_type> __bl, _UnaryOperation __fw);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
         template<class _UnaryOperation>
             param_type(size_t __nw, result_type __xmin, result_type __xmax,
                        _UnaryOperation __fw);
@@ -6454,13 +6472,13 @@ public:
                                       _InputIteratorW __fW)
         : __p_(__fB, __lB, __fW) {}
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     template<class _UnaryOperation>
         _LIBCPP_INLINE_VISIBILITY
         piecewise_linear_distribution(initializer_list<result_type> __bl,
                                       _UnaryOperation __fw)
         : __p_(__bl, __fw) {}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     template<class _UnaryOperation>
         _LIBCPP_INLINE_VISIBILITY
@@ -6594,7 +6612,7 @@ piecewise_linear_distribution<_RealType>::param_type::param_type(
     }
 }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
 
 template<class _RealType>
 template<class _UnaryOperation>
@@ -6619,7 +6637,7 @@ piecewise_linear_distribution<_RealType>::param_type::param_type(
     }
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 template<class _RealType>
 template<class _UnaryOperation>
@@ -6721,4 +6739,6 @@ operator>>(basic_istream<_CharT, _Traits>& __is,
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_RANDOM
diff --git a/lib/libcxx/include/ratio b/lib/libcxx/include/ratio
index 8f708ce478d..7ee5ec24517 100644
--- a/lib/libcxx/include/ratio
+++ b/lib/libcxx/include/ratio
@@ -63,17 +63,17 @@ typedef ratio<   1000000000000000000000, 1> zetta;  // not supported
 typedef ratio<1000000000000000000000000, 1> yotta;  // not supported
 
   // 20.11.5, ratio comparison
-  template <class R1, class R2> constexpr bool ratio_equal_v
+  template <class R1, class R2> inline constexpr bool ratio_equal_v
     = ratio_equal<R1, R2>::value;                                       // C++17
-  template <class R1, class R2> constexpr bool ratio_not_equal_v
+  template <class R1, class R2> inline constexpr bool ratio_not_equal_v
     = ratio_not_equal<R1, R2>::value;                                   // C++17
-  template <class R1, class R2> constexpr bool ratio_less_v
+  template <class R1, class R2> inline constexpr bool ratio_less_v
     = ratio_less<R1, R2>::value;                                        // C++17
-  template <class R1, class R2> constexpr bool ratio_less_equal_v
+  template <class R1, class R2> inline constexpr bool ratio_less_equal_v
     = ratio_less_equal<R1, R2>::value;                                  // C++17
-  template <class R1, class R2> constexpr bool ratio_greater_v
+  template <class R1, class R2> inline constexpr bool ratio_greater_v
     = ratio_greater<R1, R2>::value;                                     // C++17
-  template <class R1, class R2> constexpr bool ratio_greater_equal_v
+  template <class R1, class R2> inline constexpr bool ratio_greater_equal_v
     = ratio_greater_equal<R1, R2>::value;                               // C++17
 }
 */
@@ -83,12 +83,14 @@ typedef ratio<1000000000000000000000000, 1> yotta;  // not supported
 #include <climits>
 #include <type_traits>
 
-#include <__undef_min_max>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 // __static_gcd
@@ -244,7 +246,7 @@ public:
 };
 
 template <intmax_t _Num, intmax_t _Den = 1>
-class _LIBCPP_TYPE_VIS_ONLY ratio
+class _LIBCPP_TEMPLATE_VIS ratio
 {
     static_assert(__static_abs<_Num>::value >= 0, "ratio numerator is out of range");
     static_assert(_Den != 0, "ratio divide by 0");
@@ -300,18 +302,18 @@ public:
         >::type type;
 };
 
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _R1, class _R2> using ratio_multiply
                                     = typename __ratio_multiply<_R1, _R2>::type;
 
-#else  // _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#else  // _LIBCPP_CXX03_LANG
 
 template <class _R1, class _R2>
-struct _LIBCPP_TYPE_VIS_ONLY ratio_multiply
+struct _LIBCPP_TEMPLATE_VIS ratio_multiply
     : public __ratio_multiply<_R1, _R2>::type {};
 
-#endif  // _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _R1, class _R2>
 struct __ratio_divide
@@ -327,18 +329,18 @@ public:
         >::type type;
 };
 
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _R1, class _R2> using ratio_divide
                                       = typename __ratio_divide<_R1, _R2>::type;
 
-#else  // _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#else  // _LIBCPP_CXX03_LANG
 
 template <class _R1, class _R2>
-struct _LIBCPP_TYPE_VIS_ONLY ratio_divide
+struct _LIBCPP_TEMPLATE_VIS ratio_divide
     : public __ratio_divide<_R1, _R2>::type {};
 
-#endif  // _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _R1, class _R2>
 struct __ratio_add
@@ -362,18 +364,18 @@ public:
         >::type type;
 };
 
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _R1, class _R2> using ratio_add
                                          = typename __ratio_add<_R1, _R2>::type;
 
-#else  // _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#else  // _LIBCPP_CXX03_LANG
 
 template <class _R1, class _R2>
-struct _LIBCPP_TYPE_VIS_ONLY ratio_add
+struct _LIBCPP_TEMPLATE_VIS ratio_add
     : public __ratio_add<_R1, _R2>::type {};
 
-#endif  // _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _R1, class _R2>
 struct __ratio_subtract
@@ -397,27 +399,27 @@ public:
         >::type type;
 };
 
-#ifndef _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _R1, class _R2> using ratio_subtract
                                     = typename __ratio_subtract<_R1, _R2>::type;
 
-#else  // _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#else  // _LIBCPP_CXX03_LANG
 
 template <class _R1, class _R2>
-struct _LIBCPP_TYPE_VIS_ONLY ratio_subtract
+struct _LIBCPP_TEMPLATE_VIS ratio_subtract
     : public __ratio_subtract<_R1, _R2>::type {};
 
-#endif  // _LIBCPP_HAS_NO_TEMPLATE_ALIASES
+#endif  // _LIBCPP_CXX03_LANG
 
 // ratio_equal
 
 template <class _R1, class _R2>
-struct _LIBCPP_TYPE_VIS_ONLY ratio_equal
+struct _LIBCPP_TEMPLATE_VIS ratio_equal
     : public _LIBCPP_BOOL_CONSTANT((_R1::num == _R2::num && _R1::den == _R2::den)) {};
 
 template <class _R1, class _R2>
-struct _LIBCPP_TYPE_VIS_ONLY ratio_not_equal
+struct _LIBCPP_TEMPLATE_VIS ratio_not_equal
     : public _LIBCPP_BOOL_CONSTANT((!ratio_equal<_R1, _R2>::value)) {};
 
 // ratio_less
@@ -476,19 +478,19 @@ struct __ratio_less<_R1, _R2, -1LL, -1LL>
 };
 
 template <class _R1, class _R2>
-struct _LIBCPP_TYPE_VIS_ONLY ratio_less
+struct _LIBCPP_TEMPLATE_VIS ratio_less
     : public _LIBCPP_BOOL_CONSTANT((__ratio_less<_R1, _R2>::value)) {};
 
 template <class _R1, class _R2>
-struct _LIBCPP_TYPE_VIS_ONLY ratio_less_equal
+struct _LIBCPP_TEMPLATE_VIS ratio_less_equal
     : public _LIBCPP_BOOL_CONSTANT((!ratio_less<_R2, _R1>::value)) {};
 
 template <class _R1, class _R2>
-struct _LIBCPP_TYPE_VIS_ONLY ratio_greater
+struct _LIBCPP_TEMPLATE_VIS ratio_greater
     : public _LIBCPP_BOOL_CONSTANT((ratio_less<_R2, _R1>::value)) {};
 
 template <class _R1, class _R2>
-struct _LIBCPP_TYPE_VIS_ONLY ratio_greater_equal
+struct _LIBCPP_TEMPLATE_VIS ratio_greater_equal
     : public _LIBCPP_BOOL_CONSTANT((!ratio_less<_R1, _R2>::value)) {};
 
 template <class _R1, class _R2>
@@ -499,25 +501,33 @@ struct __ratio_gcd
 };
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _R1, class _R2> _LIBCPP_CONSTEXPR bool ratio_equal_v
+template <class _R1, class _R2>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool ratio_equal_v
     = ratio_equal<_R1, _R2>::value;
 
-template <class _R1, class _R2> _LIBCPP_CONSTEXPR bool ratio_not_equal_v
+template <class _R1, class _R2>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool ratio_not_equal_v
     = ratio_not_equal<_R1, _R2>::value;
 
-template <class _R1, class _R2> _LIBCPP_CONSTEXPR bool ratio_less_v
+template <class _R1, class _R2>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool ratio_less_v
     = ratio_less<_R1, _R2>::value;
 
-template <class _R1, class _R2> _LIBCPP_CONSTEXPR bool ratio_less_equal_v
+template <class _R1, class _R2>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool ratio_less_equal_v
     = ratio_less_equal<_R1, _R2>::value;
 
-template <class _R1, class _R2> _LIBCPP_CONSTEXPR bool ratio_greater_v
+template <class _R1, class _R2>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool ratio_greater_v
     = ratio_greater<_R1, _R2>::value;
 
-template <class _R1, class _R2> _LIBCPP_CONSTEXPR bool ratio_greater_equal_v
+template <class _R1, class _R2>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool ratio_greater_equal_v
     = ratio_greater_equal<_R1, _R2>::value;
 #endif
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_RATIO
diff --git a/lib/libcxx/include/regex b/lib/libcxx/include/regex
index 1139d8fb2a9..ff84b2738b7 100644
--- a/lib/libcxx/include/regex
+++ b/lib/libcxx/include/regex
@@ -127,6 +127,8 @@ class basic_regex
 public:
     // types:
     typedef charT                               value_type;
+    typedef traits                              traits_type;
+    typedef typename traits::string_type        string_type;
     typedef regex_constants::syntax_option_type flag_type;
     typedef typename traits::locale_type        locale_type;
 
@@ -145,7 +147,7 @@ public:
     // construct/copy/destroy:
     basic_regex();
     explicit basic_regex(const charT* p, flag_type f = regex_constants::ECMAScript);
-    basic_regex(const charT* p, size_t len, flag_type f);
+    basic_regex(const charT* p, size_t len, flag_type f = regex_constants::ECMAScript);
     basic_regex(const basic_regex&);
     basic_regex(basic_regex&&) noexcept;
     template <class ST, class SA>
@@ -762,14 +764,17 @@ typedef regex_token_iterator<wstring::const_iterator> wsregex_token_iterator;
 #include <memory>
 #include <vector>
 #include <deque>
-#include <cassert>
-
-#include <__undef_min_max>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
+#define _LIBCPP_REGEX_COMPLEXITY_FACTOR 4096
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace regex_constants
@@ -864,7 +869,8 @@ enum match_flag_type
     format_sed        = 1 << 8,
     format_no_copy    = 1 << 9,
     format_first_only = 1 << 10,
-    __no_update_pos   = 1 << 11
+    __no_update_pos   = 1 << 11,
+    __full_match      = 1 << 12
 };
 
 inline _LIBCPP_INLINE_VISIBILITY
@@ -957,18 +963,18 @@ public:
 };
 
 template <regex_constants::error_type _Ev>
-_LIBCPP_ALWAYS_INLINE
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
 void __throw_regex_error()
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS
     throw regex_error(_Ev);
 #else
-    assert(!"regex_error");
+    _VSTD::abort();
 #endif
 }
 
 template <class _CharT>
-struct _LIBCPP_TYPE_VIS_ONLY regex_traits
+struct _LIBCPP_TEMPLATE_VIS regex_traits
 {
 public:
     typedef _CharT                  char_type;
@@ -1285,11 +1291,11 @@ regex_traits<_CharT>::__regex_traits_value(wchar_t __ch, int __radix) const
 
 template <class _CharT> class __node;
 
-template <class _BidirectionalIterator> class _LIBCPP_TYPE_VIS_ONLY sub_match;
+template <class _BidirectionalIterator> class _LIBCPP_TEMPLATE_VIS sub_match;
 
 template <class _BidirectionalIterator,
           class _Allocator = allocator<sub_match<_BidirectionalIterator> > >
-class _LIBCPP_TYPE_VIS_ONLY match_results;
+class _LIBCPP_TEMPLATE_VIS match_results;
 
 template <class _CharT>
 struct __state
@@ -2403,17 +2409,28 @@ __bracket_expression<_CharT, _Traits>::__exec(__state& __s) const
                 goto __exit;
             }
         }
-        if (!__neg_chars_.empty())
+        // set of "__found" chars =
+        //   union(complement(union(__neg_chars_, __neg_mask_)),
+        //         other cases...)
+        //
+        // __neg_chars_ and __neg_mask_'d better be handled together, as there
+        // are no short circuit opportunities.
+        //
+        // In addition, when __neg_mask_/__neg_chars_ is empty, they should be
+        // treated as all ones/all chars.
         {
-            for (size_t __i = 0; __i < __neg_chars_.size(); ++__i)
-            {
-                if (__ch == __neg_chars_[__i])
-                    goto __is_neg_char;
-            }
+          const bool __in_neg_mask = (__neg_mask_ == 0) ||
+              __traits_.isctype(__ch, __neg_mask_);
+          const bool __in_neg_chars =
+              __neg_chars_.empty() ||
+              std::find(__neg_chars_.begin(), __neg_chars_.end(), __ch) !=
+              __neg_chars_.end();
+          if (!(__in_neg_mask || __in_neg_chars))
+          {
             __found = true;
             goto __exit;
+          }
         }
-__is_neg_char:
         if (!__ranges_.empty())
         {
             string_type __s2 = __collate_ ?
@@ -2445,11 +2462,6 @@ __is_neg_char:
             __found = true;
             goto __exit;
         }
-        if (__neg_mask_ && !__traits_.isctype(__ch, __neg_mask_))
-        {
-            __found = true;
-            goto __exit;
-        }
     }
     else
         __found = __negate_;  // force reject
@@ -2470,11 +2482,13 @@ __exit:
 template <class _CharT, class _Traits> class __lookahead;
 
 template <class _CharT, class _Traits = regex_traits<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY basic_regex
+class _LIBCPP_TEMPLATE_VIS basic_regex
 {
 public:
     // types:
     typedef _CharT                              value_type;
+    typedef _Traits                             traits_type;
+    typedef typename _Traits::string_type       string_type;
     typedef regex_constants::syntax_option_type flag_type;
     typedef typename _Traits::locale_type       locale_type;
 
@@ -2515,7 +2529,7 @@ public:
           __end_(0)
         {__parse(__p, __p + __traits_.length(__p));}
     _LIBCPP_INLINE_VISIBILITY
-    basic_regex(const value_type* __p, size_t __len, flag_type __f)
+    basic_regex(const value_type* __p, size_t __len, flag_type __f = regex_constants::ECMAScript)
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
           __end_(0)
         {__parse(__p, __p + __len);}
@@ -2535,14 +2549,14 @@ public:
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
           __end_(0)
         {__parse(__first, __last);}
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_regex(initializer_list<value_type> __il,
                 flag_type __f = regex_constants::ECMAScript)
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
           __end_(0)
         {__parse(__il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 //    ~basic_regex() = default;
 
@@ -2551,11 +2565,11 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     basic_regex& operator=(const value_type* __p)
         {return assign(__p);}
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_regex& operator=(initializer_list<value_type> __il)
         {return assign(__il);}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
     template <class _ST, class _SA>
         _LIBCPP_INLINE_VISIBILITY
         basic_regex& operator=(const basic_string<value_type, _ST, _SA>& __p)
@@ -2565,7 +2579,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     basic_regex& assign(const basic_regex& __that)
         {return *this = __that;}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_regex& assign(basic_regex&& __that) _NOEXCEPT
         {return *this = _VSTD::move(__that);}
@@ -2622,14 +2636,14 @@ public:
             return assign(basic_regex(__first, __last, __f));
         }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     basic_regex& assign(initializer_list<value_type> __il,
                         flag_type __f = regex_constants::ECMAScript)
         {return assign(__il.begin(), __il.end(), __f);}
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     // const operations:
     _LIBCPP_INLINE_VISIBILITY
@@ -2981,10 +2995,12 @@ __lookahead<_CharT, _Traits>::__exec(__state& __s) const
 {
     match_results<const _CharT*> __m;
     __m.__init(1 + __exp_.mark_count(), __s.__current_, __s.__last_);
-    bool __matched = __exp_.__match_at_start_ecma(__s.__current_, __s.__last_,
-                                                  __m,
-                                                  __s.__flags_ | regex_constants::match_continuous,
-                                                  __s.__at_first_ && __s.__current_ == __s.__first_);
+    bool __matched = __exp_.__match_at_start_ecma(
+        __s.__current_, __s.__last_,
+        __m,
+        (__s.__flags_ | regex_constants::match_continuous) &
+        ~regex_constants::__full_match,
+        __s.__at_first_ && __s.__current_ == __s.__first_);
     if (__matched != __invert_)
     {
         __s.__do_ = __state::__accept_but_not_consume;
@@ -3951,7 +3967,6 @@ basic_regex<_CharT, _Traits>::__parse_equivalence_class(_ForwardIterator __first
     if (__temp == __last)
         __throw_regex_error<regex_constants::error_brack>();
     // [__first, __temp) contains all text in [= ... =]
-    typedef typename _Traits::string_type string_type;
     string_type __collate_name =
         __traits_.lookup_collatename(__first, __temp);
     if (__collate_name.empty())
@@ -4049,6 +4064,8 @@ basic_regex<_CharT, _Traits>::__parse_DUP_COUNT(_ForwardIterator __first,
                  __first != __last && ( __val = __traits_.value(*__first, 10)) != -1;
                  ++__first)
             {
+                if (__c >= std::numeric_limits<int>::max() / 10)
+                    __throw_regex_error<regex_constants::error_badbrace>();
                 __c *= 10;
                 __c += __val;
             }
@@ -4308,9 +4325,14 @@ basic_regex<_CharT, _Traits>::__parse_decimal_escape(_ForwardIterator __first,
         else if ('1' <= *__first && *__first <= '9')
         {
             unsigned __v = *__first - '0';
-            for (++__first; '0' <= *__first && *__first <= '9'; ++__first)
+            for (++__first;
+                    __first != __last && '0' <= *__first && *__first <= '9'; ++__first)
+                {
+                if (__v >= std::numeric_limits<unsigned>::max() / 10)
+                    __throw_regex_error<regex_constants::error_backref>();
                 __v = 10 * __v + *__first - '0';
-            if (__v > mark_count())
+                }
+            if (__v == 0 || __v > mark_count())
                 __throw_regex_error<regex_constants::error_backref>();
             __push_back_ref(__v);
         }
@@ -4758,7 +4780,7 @@ typedef basic_regex<wchar_t> wregex;
 // sub_match
 
 template <class _BidirectionalIterator>
-class _LIBCPP_TYPE_VIS_ONLY sub_match
+class _LIBCPP_TEMPLATE_VIS sub_match
     : public pair<_BidirectionalIterator, _BidirectionalIterator>
 {
 public:
@@ -5181,7 +5203,7 @@ operator<<(basic_ostream<_CharT, _ST>& __os, const sub_match<_BiIter>& __m)
 }
 
 template <class _BidirectionalIterator, class _Allocator>
-class _LIBCPP_TYPE_VIS_ONLY match_results
+class _LIBCPP_TEMPLATE_VIS match_results
 {
 public:
     typedef _Allocator                                        allocator_type;
@@ -5218,11 +5240,11 @@ public:
 
     // size:
     _LIBCPP_INLINE_VISIBILITY
-    size_type size() const {return __matches_.size();}
+    size_type size() const _NOEXCEPT {return __matches_.size();}
     _LIBCPP_INLINE_VISIBILITY
-    size_type max_size() const {return __matches_.max_size();}
-    _LIBCPP_INLINE_VISIBILITY
-    bool empty() const {return size() == 0;}
+    size_type max_size() const _NOEXCEPT {return __matches_.max_size();}
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
+    bool empty() const _NOEXCEPT {return size() == 0;}
 
     // element access:
     _LIBCPP_INLINE_VISIBILITY
@@ -5255,15 +5277,15 @@ public:
     // format:
     template <class _OutputIter>
         _OutputIter
-        format(_OutputIter __out, const char_type* __fmt_first,
+        format(_OutputIter __output_iter, const char_type* __fmt_first,
                const char_type* __fmt_last,
                regex_constants::match_flag_type __flags = regex_constants::format_default) const;
     template <class _OutputIter, class _ST, class _SA>
         _LIBCPP_INLINE_VISIBILITY
         _OutputIter
-        format(_OutputIter __out, const basic_string<char_type, _ST, _SA>& __fmt,
+        format(_OutputIter __output_iter, const basic_string<char_type, _ST, _SA>& __fmt,
                regex_constants::match_flag_type __flags = regex_constants::format_default) const
-            {return format(__out, __fmt.data(), __fmt.data() + __fmt.size(), __flags);}
+            {return format(__output_iter, __fmt.data(), __fmt.data() + __fmt.size(), __flags);}
     template <class _ST, class _SA>
         _LIBCPP_INLINE_VISIBILITY
         basic_string<char_type, _ST, _SA>
@@ -5375,7 +5397,7 @@ match_results<_BidirectionalIterator, _Allocator>::__init(unsigned __s,
 template <class _BidirectionalIterator, class _Allocator>
 template <class _OutputIter>
 _OutputIter
-match_results<_BidirectionalIterator, _Allocator>::format(_OutputIter __out,
+match_results<_BidirectionalIterator, _Allocator>::format(_OutputIter __output_iter,
         const char_type* __fmt_first, const char_type* __fmt_last,
         regex_constants::match_flag_type __flags) const
 {
@@ -5384,27 +5406,27 @@ match_results<_BidirectionalIterator, _Allocator>::format(_OutputIter __out,
         for (; __fmt_first != __fmt_last; ++__fmt_first)
         {
             if (*__fmt_first == '&')
-                __out = _VSTD::copy(__matches_[0].first, __matches_[0].second,
-                                   __out);
+                __output_iter = _VSTD::copy(__matches_[0].first, __matches_[0].second,
+                                   __output_iter);
             else if (*__fmt_first == '\\' && __fmt_first + 1 != __fmt_last)
             {
                 ++__fmt_first;
                 if ('0' <= *__fmt_first && *__fmt_first <= '9')
                 {
                     size_t __i = *__fmt_first - '0';
-                    __out = _VSTD::copy((*this)[__i].first,
-                                        (*this)[__i].second, __out);
+                    __output_iter = _VSTD::copy((*this)[__i].first,
+                                        (*this)[__i].second, __output_iter);
                 }
                 else
                 {
-                    *__out = *__fmt_first;
-                    ++__out;
+                    *__output_iter = *__fmt_first;
+                    ++__output_iter;
                 }
             }
             else
             {
-                *__out = *__fmt_first;
-                ++__out;
+                *__output_iter = *__fmt_first;
+                ++__output_iter;
             }
         }
     }
@@ -5417,52 +5439,54 @@ match_results<_BidirectionalIterator, _Allocator>::format(_OutputIter __out,
                 switch (__fmt_first[1])
                 {
                 case '$':
-                    *__out = *++__fmt_first;
-                    ++__out;
+                    *__output_iter = *++__fmt_first;
+                    ++__output_iter;
                     break;
                 case '&':
                     ++__fmt_first;
-                    __out = _VSTD::copy(__matches_[0].first, __matches_[0].second,
-                                       __out);
+                    __output_iter = _VSTD::copy(__matches_[0].first, __matches_[0].second,
+                                       __output_iter);
                     break;
                 case '`':
                     ++__fmt_first;
-                    __out = _VSTD::copy(__prefix_.first, __prefix_.second, __out);
+                    __output_iter = _VSTD::copy(__prefix_.first, __prefix_.second, __output_iter);
                     break;
                 case '\'':
                     ++__fmt_first;
-                    __out = _VSTD::copy(__suffix_.first, __suffix_.second, __out);
+                    __output_iter = _VSTD::copy(__suffix_.first, __suffix_.second, __output_iter);
                     break;
                 default:
                     if ('0' <= __fmt_first[1] && __fmt_first[1] <= '9')
                     {
                         ++__fmt_first;
-                        size_t __i = *__fmt_first - '0';
+                        size_t __idx = *__fmt_first - '0';
                         if (__fmt_first + 1 != __fmt_last &&
                             '0' <= __fmt_first[1] && __fmt_first[1] <= '9')
                         {
                             ++__fmt_first;
-                            __i = 10 * __i + *__fmt_first - '0';
+                            if (__idx >= std::numeric_limits<size_t>::max() / 10)
+                                __throw_regex_error<regex_constants::error_escape>();
+                            __idx = 10 * __idx + *__fmt_first - '0';
                         }
-                        __out = _VSTD::copy((*this)[__i].first,
-                                            (*this)[__i].second, __out);
+                        __output_iter = _VSTD::copy((*this)[__idx].first,
+                                            (*this)[__idx].second, __output_iter);
                     }
                     else
                     {
-                        *__out = *__fmt_first;
-                        ++__out;
+                        *__output_iter = *__fmt_first;
+                        ++__output_iter;
                     }
                     break;
                 }
             }
             else
             {
-                *__out = *__fmt_first;
-                ++__out;
+                *__output_iter = *__fmt_first;
+                ++__output_iter;
             }
         }
     }
-    return __out;
+    return __output_iter;
 }
 
 template <class _BidirectionalIterator, class _Allocator>
@@ -5544,14 +5568,32 @@ basic_regex<_CharT, _Traits>::__match_at_start_ecma(
         __states.back().__node_ = __st;
         __states.back().__flags_ = __flags;
         __states.back().__at_first_ = __at_first;
+        int __counter = 0;
+        int __length = __last - __first;
         do
         {
+            ++__counter;
+            if (__counter % _LIBCPP_REGEX_COMPLEXITY_FACTOR == 0 &&
+                __counter / _LIBCPP_REGEX_COMPLEXITY_FACTOR >= __length)
+              __throw_regex_error<regex_constants::error_complexity>();
             __state& __s = __states.back();
             if (__s.__node_)
                 __s.__node_->__exec(__s);
             switch (__s.__do_)
             {
             case __state::__end_state:
+                if ((__flags & regex_constants::match_not_null) &&
+                    __s.__current_ == __first)
+                {
+                  __states.pop_back();
+                  break;
+                }
+                if ((__flags & regex_constants::__full_match) &&
+                    __s.__current_ != __last)
+                {
+                  __states.pop_back();
+                  break;
+                }
                 __m.__matches_[0].first = __first;
                 __m.__matches_[0].second = _VSTD::next(__first, __s.__current_ - __first);
                 __m.__matches_[0].matched = true;
@@ -5607,14 +5649,32 @@ basic_regex<_CharT, _Traits>::__match_at_start_posix_nosubs(
         __states.back().__flags_ = __flags;
         __states.back().__at_first_ = __at_first;
         bool __matched = false;
+        int __counter = 0;
+        int __length = __last - __first;
         do
         {
+            ++__counter;
+            if (__counter % _LIBCPP_REGEX_COMPLEXITY_FACTOR == 0 &&
+                __counter / _LIBCPP_REGEX_COMPLEXITY_FACTOR >= __length)
+              __throw_regex_error<regex_constants::error_complexity>();
             __state& __s = __states.back();
             if (__s.__node_)
                 __s.__node_->__exec(__s);
             switch (__s.__do_)
             {
             case __state::__end_state:
+                if ((__flags & regex_constants::match_not_null) &&
+                    __s.__current_ == __first)
+                {
+                  __states.pop_back();
+                  break;
+                }
+                if ((__flags & regex_constants::__full_match) &&
+                    __s.__current_ != __last)
+                {
+                  __states.pop_back();
+                  break;
+                }
                 if (!__matched || __highest_j < __s.__current_ - __s.__first_)
                     __highest_j = __s.__current_ - __s.__first_;
                 __matched = true;
@@ -5692,14 +5752,32 @@ basic_regex<_CharT, _Traits>::__match_at_start_posix_subs(
         __states.back().__at_first_ = __at_first;
         const _CharT* __current = __first;
         bool __matched = false;
+        int __counter = 0;
+        int __length = __last - __first;
         do
         {
+            ++__counter;
+            if (__counter % _LIBCPP_REGEX_COMPLEXITY_FACTOR == 0 &&
+                __counter / _LIBCPP_REGEX_COMPLEXITY_FACTOR >= __length)
+              __throw_regex_error<regex_constants::error_complexity>();
             __state& __s = __states.back();
             if (__s.__node_)
                 __s.__node_->__exec(__s);
             switch (__s.__do_)
             {
             case __state::__end_state:
+                if ((__flags & regex_constants::match_not_null) &&
+                    __s.__current_ == __first)
+                {
+                  __states.pop_back();
+                  break;
+                }
+                if ((__flags & regex_constants::__full_match) &&
+                    __s.__current_ != __last)
+                {
+                  __states.pop_back();
+                  break;
+                }
                 if (!__matched || __highest_j < __s.__current_ - __s.__first_)
                 {
                     __highest_j = __s.__current_ - __s.__first_;
@@ -5930,8 +6008,10 @@ regex_match(_BidirectionalIterator __first, _BidirectionalIterator __last,
             const basic_regex<_CharT, _Traits>& __e,
             regex_constants::match_flag_type __flags = regex_constants::match_default)
 {
-    bool __r = _VSTD::regex_search(__first, __last, __m, __e,
-                            __flags | regex_constants::match_continuous);
+    bool __r = _VSTD::regex_search(
+        __first, __last, __m, __e,
+        __flags | regex_constants::match_continuous |
+        regex_constants::__full_match);
     if (__r)
     {
         __r = !__m.suffix().matched;
@@ -6007,7 +6087,7 @@ regex_match(const basic_string<_CharT, _ST, _SA>& __s,
 template <class _BidirectionalIterator,
           class _CharT = typename iterator_traits<_BidirectionalIterator>::value_type,
           class _Traits = regex_traits<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY regex_iterator
+class _LIBCPP_TEMPLATE_VIS regex_iterator
 {
 public:
     typedef basic_regex<_CharT, _Traits>          regex_type;
@@ -6096,7 +6176,7 @@ regex_iterator<_BidirectionalIterator, _CharT, _Traits>::operator++()
 {
     __flags_ |= regex_constants::__no_update_pos;
     _BidirectionalIterator __start = __match_[0].second;
-    if (__match_.empty())
+    if (__match_[0].first == __match_[0].second)
     {
         if (__start == __end_)
         {
@@ -6126,7 +6206,7 @@ typedef regex_iterator<wstring::const_iterator> wsregex_iterator;
 template <class _BidirectionalIterator,
           class _CharT = typename iterator_traits<_BidirectionalIterator>::value_type,
           class _Traits = regex_traits<_CharT> >
-class _LIBCPP_TYPE_VIS_ONLY regex_token_iterator
+class _LIBCPP_TEMPLATE_VIS regex_token_iterator
 {
 public:
     typedef basic_regex<_CharT, _Traits>      regex_type;
@@ -6142,7 +6222,7 @@ private:
     _Position         __position_;
     const value_type* __result_;
     value_type        __suffix_;
-    ptrdiff_t         _N_;
+    ptrdiff_t         __n_;
     vector<int>       __subs_;
 
 public:
@@ -6169,7 +6249,7 @@ public:
                                      regex_constants::match_default) = delete;
 #endif
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     regex_token_iterator(_BidirectionalIterator __a, _BidirectionalIterator __b,
                          const regex_type& __re,
                          initializer_list<int> __submatches,
@@ -6183,7 +6263,7 @@ public:
                          regex_constants::match_flag_type __m =
                                        regex_constants::match_default) = delete;
 #endif
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
     template <size_t _Np>
         regex_token_iterator(_BidirectionalIterator __a,
                              _BidirectionalIterator __b,
@@ -6225,10 +6305,10 @@ public:
 private:
     void __init(_BidirectionalIterator __a, _BidirectionalIterator __b);
     void __establish_result () {
-        if (__subs_[_N_] == -1)
+        if (__subs_[__n_] == -1)
             __result_ = &__position_->prefix();
         else
-            __result_ = &(*__position_)[__subs_[_N_]];
+            __result_ = &(*__position_)[__subs_[__n_]];
         }       
 };
 
@@ -6237,7 +6317,7 @@ regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
     regex_token_iterator()
     : __result_(nullptr),
       __suffix_(),
-      _N_(0)
+      __n_(0)
 {
 }
 
@@ -6248,7 +6328,7 @@ regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
 {
     if (__position_ != _Position())
         __establish_result ();
-    else if (__subs_[_N_] == -1)
+    else if (__subs_[__n_] == -1)
     {
         __suffix_.matched = true;
         __suffix_.first = __a;
@@ -6265,7 +6345,7 @@ regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
                          const regex_type& __re, int __submatch,
                          regex_constants::match_flag_type __m)
     : __position_(__a, __b, __re, __m),
-      _N_(0),
+      __n_(0),
       __subs_(1, __submatch)
 {
     __init(__a, __b);
@@ -6277,13 +6357,13 @@ regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
                          const regex_type& __re, const vector<int>& __submatches,
                          regex_constants::match_flag_type __m)
     : __position_(__a, __b, __re, __m),
-      _N_(0),
+      __n_(0),
       __subs_(__submatches)
 {
     __init(__a, __b);
 }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _BidirectionalIterator, class _CharT, class _Traits>
 regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
@@ -6292,13 +6372,13 @@ regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
                          initializer_list<int> __submatches,
                          regex_constants::match_flag_type __m)
     : __position_(__a, __b, __re, __m),
-      _N_(0),
+      __n_(0),
       __subs_(__submatches)
 {
     __init(__a, __b);
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _BidirectionalIterator, class _CharT, class _Traits>
 template <size_t _Np>
@@ -6308,7 +6388,7 @@ regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
                              const int (&__submatches)[_Np],
                              regex_constants::match_flag_type __m)
     : __position_(__a, __b, __re, __m),
-      _N_(0),
+      __n_(0),
       __subs_(__submatches, __submatches + _Np)
 {
     __init(__a, __b);
@@ -6320,7 +6400,7 @@ regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
     : __position_(__x.__position_),
       __result_(__x.__result_),
       __suffix_(__x.__suffix_),
-      _N_(__x._N_),
+      __n_(__x.__n_),
       __subs_(__x.__subs_)
 {
     if (__x.__result_ == &__x.__suffix_)
@@ -6342,7 +6422,7 @@ regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
         else
             __result_ = __x.__result_;
         __suffix_ = __x.__suffix_;
-        _N_ = __x._N_;
+        __n_ = __x.__n_;
         __subs_ = __x.__subs_;
 
         if ( __result_ != nullptr && __result_ != &__suffix_ )
@@ -6365,7 +6445,7 @@ regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::
         return false;
     if (__result_ == &__suffix_ || __x.__result_ == &__x.__suffix_)
         return false;
-    return __position_ == __x.__position_ && _N_ == __x._N_ &&
+    return __position_ == __x.__position_ && __n_ == __x.__n_ &&
            __subs_ == __x.__subs_;
 }
 
@@ -6376,14 +6456,14 @@ regex_token_iterator<_BidirectionalIterator, _CharT, _Traits>::operator++()
     _Position __prev = __position_;
     if (__result_ == &__suffix_)
         __result_ = nullptr;
-    else if (_N_ + 1 < __subs_.size())
+    else if (static_cast<size_t>(__n_ + 1) < __subs_.size())
     {
-        ++_N_;
+        ++__n_;
         __establish_result();
     }
     else
     {
-        _N_ = 0;
+        __n_ = 0;
         ++__position_;
         if (__position_ != _Position())
             __establish_result();
@@ -6414,7 +6494,7 @@ typedef regex_token_iterator<wstring::const_iterator> wsregex_token_iterator;
 template <class _OutputIterator, class _BidirectionalIterator,
           class _Traits, class _CharT>
 _OutputIterator
-regex_replace(_OutputIterator __out,
+regex_replace(_OutputIterator __output_iter,
               _BidirectionalIterator __first, _BidirectionalIterator __last,
               const basic_regex<_CharT, _Traits>& __e, const _CharT* __fmt,
               regex_constants::match_flag_type __flags = regex_constants::match_default)
@@ -6425,7 +6505,7 @@ regex_replace(_OutputIterator __out,
     if (__i == __eof)
     {
         if (!(__flags & regex_constants::format_no_copy))
-            __out = _VSTD::copy(__first, __last, __out);
+            __output_iter = _VSTD::copy(__first, __last, __output_iter);
     }
     else
     {
@@ -6433,29 +6513,29 @@ regex_replace(_OutputIterator __out,
         for (size_t __len = char_traits<_CharT>::length(__fmt); __i != __eof; ++__i)
         {
             if (!(__flags & regex_constants::format_no_copy))
-                __out = _VSTD::copy(__i->prefix().first, __i->prefix().second, __out);
-            __out = __i->format(__out, __fmt, __fmt + __len, __flags);
+                __output_iter = _VSTD::copy(__i->prefix().first, __i->prefix().second, __output_iter);
+            __output_iter = __i->format(__output_iter, __fmt, __fmt + __len, __flags);
             __lm = __i->suffix();
             if (__flags & regex_constants::format_first_only)
                 break;
         }
         if (!(__flags & regex_constants::format_no_copy))
-            __out = _VSTD::copy(__lm.first, __lm.second, __out);
+            __output_iter = _VSTD::copy(__lm.first, __lm.second, __output_iter);
     }
-    return __out;
+    return __output_iter;
 }
 
 template <class _OutputIterator, class _BidirectionalIterator,
           class _Traits, class _CharT, class _ST, class _SA>
 inline _LIBCPP_INLINE_VISIBILITY
 _OutputIterator
-regex_replace(_OutputIterator __out,
+regex_replace(_OutputIterator __output_iter,
               _BidirectionalIterator __first, _BidirectionalIterator __last,
               const basic_regex<_CharT, _Traits>& __e,
               const basic_string<_CharT, _ST, _SA>& __fmt,
               regex_constants::match_flag_type __flags = regex_constants::match_default)
 {
-    return _VSTD::regex_replace(__out, __first, __last, __e, __fmt.c_str(), __flags);
+    return _VSTD::regex_replace(__output_iter, __first, __last, __e, __fmt.c_str(), __flags);
 }
 
 template <class _Traits, class _CharT, class _ST, class _SA, class _FST,
@@ -6518,4 +6598,6 @@ regex_replace(const _CharT* __s,
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_REGEX
diff --git a/lib/libcxx/include/scoped_allocator b/lib/libcxx/include/scoped_allocator
index 9436dac9c19..4760d946def 100644
--- a/lib/libcxx/include/scoped_allocator
+++ b/lib/libcxx/include/scoped_allocator
@@ -68,8 +68,8 @@ public:
     outer_allocator_type& outer_allocator() noexcept;
     const outer_allocator_type& outer_allocator() const noexcept;
 
-    pointer allocate(size_type n);
-    pointer allocate(size_type n, const_void_pointer hint);
+    pointer allocate(size_type n);                           // [[nodiscard]] in C++20
+    pointer allocate(size_type n, const_void_pointer hint);  // [[nodiscard]] in C++20
     void deallocate(pointer p, size_type n) noexcept;
 
     size_type max_size() const;
@@ -115,7 +115,7 @@ template <class OuterA1, class OuterA2, class... InnerAllocs>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_ADVANCED_SFINAE)
+#if !defined(_LIBCPP_CXX03_LANG)
 
 // scoped_allocator_adaptor
 
@@ -384,7 +384,7 @@ struct __outermost<_Alloc, true>
 };
 
 template <class _OuterAlloc, class... _InnerAllocs>
-class _LIBCPP_TYPE_VIS_ONLY scoped_allocator_adaptor<_OuterAlloc, _InnerAllocs...>
+class _LIBCPP_TEMPLATE_VIS scoped_allocator_adaptor<_OuterAlloc, _InnerAllocs...>
     : public __scoped_allocator_storage<_OuterAlloc, _InnerAllocs...>
 {
     typedef __scoped_allocator_storage<_OuterAlloc, _InnerAllocs...> base;
@@ -477,11 +477,11 @@ public:
     const outer_allocator_type& outer_allocator() const _NOEXCEPT
         {return base::outer_allocator();}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     pointer allocate(size_type __n)
         {return allocator_traits<outer_allocator_type>::
             allocate(outer_allocator(), __n);}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     pointer allocate(size_type __n, const_void_pointer __hint)
         {return allocator_traits<outer_allocator_type>::
             allocate(outer_allocator(), __n, __hint);}
@@ -498,8 +498,58 @@ public:
     template <class _Tp, class... _Args>
         _LIBCPP_INLINE_VISIBILITY
         void construct(_Tp* __p, _Args&& ...__args)
-            {__construct(__uses_alloc_ctor<_Tp, inner_allocator_type, _Args...>(),
+            {__construct(__uses_alloc_ctor<_Tp, inner_allocator_type&, _Args...>(),
                          __p, _VSTD::forward<_Args>(__args)...);}
+
+    template <class _T1, class _T2, class... _Args1, class... _Args2>
+    void construct(pair<_T1, _T2>* __p, piecewise_construct_t,
+                       tuple<_Args1...> __x, tuple<_Args2...> __y)
+    {
+        typedef __outermost<outer_allocator_type> _OM;
+        allocator_traits<typename _OM::type>::construct(
+            _OM()(outer_allocator()), __p, piecewise_construct
+          , __transform_tuple(
+              typename __uses_alloc_ctor<
+                  _T1, inner_allocator_type&, _Args1...
+              >::type()
+            , _VSTD::move(__x)
+            , typename __make_tuple_indices<sizeof...(_Args1)>::type{}
+          )
+          , __transform_tuple(
+              typename __uses_alloc_ctor<
+                  _T2, inner_allocator_type&, _Args2...
+              >::type()
+            , _VSTD::move(__y)
+            , typename __make_tuple_indices<sizeof...(_Args2)>::type{}
+          )
+        );
+    }
+
+    template <class _T1, class _T2>
+    void construct(pair<_T1, _T2>* __p)
+    { construct(__p, piecewise_construct, tuple<>{}, tuple<>{}); }
+
+    template <class _T1, class _T2, class _Up, class _Vp>
+    void construct(pair<_T1, _T2>* __p, _Up&& __x, _Vp&& __y) {
+        construct(__p, piecewise_construct,
+                  _VSTD::forward_as_tuple(_VSTD::forward<_Up>(__x)),
+                  _VSTD::forward_as_tuple(_VSTD::forward<_Vp>(__y)));
+    }
+
+    template <class _T1, class _T2, class _Up, class _Vp>
+    void construct(pair<_T1, _T2>* __p, const pair<_Up, _Vp>& __x) {
+        construct(__p, piecewise_construct,
+                  _VSTD::forward_as_tuple(__x.first),
+                  _VSTD::forward_as_tuple(__x.second));
+    }
+
+    template <class _T1, class _T2, class _Up, class _Vp>
+    void construct(pair<_T1, _T2>* __p, pair<_Up, _Vp>&& __x) {
+        construct(__p, piecewise_construct,
+                  _VSTD::forward_as_tuple(_VSTD::forward<_Up>(__x.first)),
+                  _VSTD::forward_as_tuple(_VSTD::forward<_Vp>(__x.second)));
+    }
+
     template <class _Tp>
         _LIBCPP_INLINE_VISIBILITY
         void destroy(_Tp* __p)
@@ -515,6 +565,7 @@ public:
 
 private:
 
+
     template <class _OuterA2,
               class = typename enable_if<
                         is_constructible<outer_allocator_type, _OuterA2>::value
@@ -545,9 +596,7 @@ private:
                 allocator_traits<typename _OM::type>::construct
                 (
                     _OM()(outer_allocator()),
-                    __p,
-                    allocator_arg,
-                    inner_allocator(),
+                    __p, allocator_arg, inner_allocator(),
                     _VSTD::forward<_Args>(__args)...
                 );
             }
@@ -566,6 +615,36 @@ private:
                 );
             }
 
+    template <class ..._Args, size_t ..._Idx>
+    _LIBCPP_INLINE_VISIBILITY
+    tuple<_Args&&...>
+    __transform_tuple(integral_constant<int, 0>, tuple<_Args...>&& __t,
+                      __tuple_indices<_Idx...>)
+    {
+        return _VSTD::forward_as_tuple(_VSTD::get<_Idx>(_VSTD::move(__t))...);
+    }
+
+    template <class ..._Args, size_t ..._Idx>
+    _LIBCPP_INLINE_VISIBILITY
+    tuple<allocator_arg_t, inner_allocator_type&, _Args&&...>
+    __transform_tuple(integral_constant<int, 1>, tuple<_Args...> && __t,
+                      __tuple_indices<_Idx...>)
+    {
+        using _Tup = tuple<allocator_arg_t, inner_allocator_type&, _Args&&...>;
+        return _Tup(allocator_arg, inner_allocator(),
+                    _VSTD::get<_Idx>(_VSTD::move(__t))...);
+    }
+
+    template <class ..._Args, size_t ..._Idx>
+    _LIBCPP_INLINE_VISIBILITY
+    tuple<_Args&&..., inner_allocator_type&>
+    __transform_tuple(integral_constant<int, 2>, tuple<_Args...> && __t,
+                      __tuple_indices<_Idx...>)
+    {
+        using _Tup = tuple<_Args&&..., inner_allocator_type&>;
+        return _Tup(_VSTD::get<_Idx>(_VSTD::move(__t))..., inner_allocator());
+    }
+
     template <class...> friend class __scoped_allocator_storage;
 };
 
@@ -597,7 +676,7 @@ operator!=(const scoped_allocator_adaptor<_OuterA1, _InnerAllocs...>& __a,
     return !(__a == __b);
 }
 
-#endif  // !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_ADVANCED_SFINAE)
+#endif  // !defined(_LIBCPP_CXX03_LANG)
 
 _LIBCPP_END_NAMESPACE_STD
 
diff --git a/lib/libcxx/include/set b/lib/libcxx/include/set
index ac69e085241..b4c6b2ef8c5 100644
--- a/lib/libcxx/include/set
+++ b/lib/libcxx/include/set
@@ -397,7 +397,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Key, class _Compare = less<_Key>,
           class _Allocator = allocator<_Key> >
-class _LIBCPP_TYPE_VIS_ONLY set
+class _LIBCPP_TEMPLATE_VIS set
 {
 public:
     // types:
@@ -486,12 +486,12 @@ public:
             return *this;
         }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     set(set&& __s)
         _NOEXCEPT_(is_nothrow_move_constructible<__base>::value)
         : __tree_(_VSTD::move(__s.__tree_)) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     explicit set(const allocator_type& __a)
@@ -504,11 +504,9 @@ public:
             insert(__s.begin(), __s.end());
         }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     set(set&& __s, const allocator_type& __a);
-#endif
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     _LIBCPP_INLINE_VISIBILITY
     set(initializer_list<value_type> __il, const value_compare& __comp = value_compare())
         : __tree_(__comp)
@@ -536,9 +534,7 @@ public:
             __tree_.__assign_unique(__il.begin(), __il.end());
             return *this;
         }
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     set& operator=(set&& __s)
         _NOEXCEPT_(is_nothrow_move_assignable<__base>::value)
@@ -546,7 +542,7 @@ public:
             __tree_ = _VSTD::move(__s.__tree_);
             return *this;
         }
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
           iterator begin() _NOEXCEPT       {return __tree_.begin();}
@@ -579,7 +575,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     const_reverse_iterator crend() const _NOEXCEPT {return rend();}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool empty() const _NOEXCEPT {return __tree_.size() == 0;}
     _LIBCPP_INLINE_VISIBILITY
     size_type size() const _NOEXCEPT {return __tree_.size();}
@@ -587,7 +583,7 @@ public:
     size_type max_size() const _NOEXCEPT {return __tree_.max_size();}
 
     // modifiers:
-#if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
+#ifndef _LIBCPP_CXX03_LANG
     template <class... _Args>
         _LIBCPP_INLINE_VISIBILITY
         pair<iterator, bool> emplace(_Args&&... __args)
@@ -596,23 +592,15 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         iterator emplace_hint(const_iterator __p, _Args&&... __args)
             {return __tree_.__emplace_hint_unique(__p, _VSTD::forward<_Args>(__args)...);}
-#endif  // !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
+#endif  // _LIBCPP_CXX03_LANG
+
     _LIBCPP_INLINE_VISIBILITY
     pair<iterator,bool> insert(const value_type& __v)
         {return __tree_.__insert_unique(__v);}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
-    pair<iterator,bool> insert(value_type&& __v)
-        {return __tree_.__insert_unique(_VSTD::move(__v));}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     iterator insert(const_iterator __p, const value_type& __v)
         {return __tree_.__insert_unique(__p, __v);}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
-    iterator insert(const_iterator __p, value_type&& __v)
-        {return __tree_.__insert_unique(__p, _VSTD::move(__v));}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
     template <class _InputIterator>
         _LIBCPP_INLINE_VISIBILITY
         void insert(_InputIterator __f, _InputIterator __l)
@@ -621,11 +609,19 @@ public:
                 __tree_.__insert_unique(__e, *__f);
         }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
+    _LIBCPP_INLINE_VISIBILITY
+    pair<iterator,bool> insert(value_type&& __v)
+        {return __tree_.__insert_unique(_VSTD::move(__v));}
+
+    _LIBCPP_INLINE_VISIBILITY
+    iterator insert(const_iterator __p, value_type&& __v)
+        {return __tree_.__insert_unique(__p, _VSTD::move(__v));}
+
     _LIBCPP_INLINE_VISIBILITY
     void insert(initializer_list<value_type> __il)
         {insert(__il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     iterator  erase(const_iterator __p) {return __tree_.erase(__p);}
@@ -672,7 +668,7 @@ public:
     template <typename _K2>
     _LIBCPP_INLINE_VISIBILITY
     typename enable_if<__is_transparent<_Compare, _K2>::value,size_type>::type
-    count(const _K2& __k)                  {return __tree_.__count_unique(__k);}
+    count(const _K2& __k) const                    {return __tree_.__count_unique(__k);}
 #endif
     _LIBCPP_INLINE_VISIBILITY
     iterator lower_bound(const key_type& __k)
@@ -727,7 +723,7 @@ public:
 #endif
 };
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Key, class _Compare, class _Allocator>
 set<_Key, _Compare, _Allocator>::set(set&& __s, const allocator_type& __a)
@@ -741,7 +737,7 @@ set<_Key, _Compare, _Allocator>::set(set&& __s, const allocator_type& __a)
     }
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Key, class _Compare, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -810,7 +806,7 @@ swap(set<_Key, _Compare, _Allocator>& __x,
 
 template <class _Key, class _Compare = less<_Key>,
           class _Allocator = allocator<_Key> >
-class _LIBCPP_TYPE_VIS_ONLY multiset
+class _LIBCPP_TEMPLATE_VIS multiset
 {
 public:
     // types:
@@ -901,12 +897,14 @@ public:
             return *this;
         }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     multiset(multiset&& __s)
         _NOEXCEPT_(is_nothrow_move_constructible<__base>::value)
         : __tree_(_VSTD::move(__s.__tree_)) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
+    multiset(multiset&& __s, const allocator_type& __a);
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     explicit multiset(const allocator_type& __a)
         : __tree_(__a) {}
@@ -916,11 +914,8 @@ public:
         {
             insert(__s.begin(), __s.end());
         }
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    multiset(multiset&& __s, const allocator_type& __a);
-#endif
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     multiset(initializer_list<value_type> __il, const value_compare& __comp = value_compare())
         : __tree_(__comp)
@@ -948,9 +943,7 @@ public:
             __tree_.__assign_multi(__il.begin(), __il.end());
             return *this;
         }
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     multiset& operator=(multiset&& __s)
         _NOEXCEPT_(is_nothrow_move_assignable<__base>::value)
@@ -958,7 +951,7 @@ public:
             __tree_ = _VSTD::move(__s.__tree_);
             return *this;
         }
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
           iterator begin() _NOEXCEPT       {return __tree_.begin();}
@@ -991,7 +984,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     const_reverse_iterator crend() const _NOEXCEPT {return rend();}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool empty() const _NOEXCEPT {return __tree_.size() == 0;}
     _LIBCPP_INLINE_VISIBILITY
     size_type size() const _NOEXCEPT {return __tree_.size();}
@@ -999,7 +992,7 @@ public:
     size_type max_size() const _NOEXCEPT {return __tree_.max_size();}
 
     // modifiers:
-#if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
+#ifndef _LIBCPP_CXX03_LANG
     template <class... _Args>
         _LIBCPP_INLINE_VISIBILITY
         iterator emplace(_Args&&... __args)
@@ -1008,23 +1001,15 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         iterator emplace_hint(const_iterator __p, _Args&&... __args)
             {return __tree_.__emplace_hint_multi(__p, _VSTD::forward<_Args>(__args)...);}
-#endif  // !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
+#endif  // _LIBCPP_CXX03_LANG
+
     _LIBCPP_INLINE_VISIBILITY
     iterator insert(const value_type& __v)
         {return __tree_.__insert_multi(__v);}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
-    iterator insert(value_type&& __v)
-        {return __tree_.__insert_multi(_VSTD::move(__v));}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     iterator insert(const_iterator __p, const value_type& __v)
         {return __tree_.__insert_multi(__p, __v);}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
-    iterator insert(const_iterator __p, value_type&& __v)
-        {return __tree_.__insert_multi(_VSTD::move(__v));}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
     template <class _InputIterator>
         _LIBCPP_INLINE_VISIBILITY
         void insert(_InputIterator __f, _InputIterator __l)
@@ -1033,11 +1018,19 @@ public:
                 __tree_.__insert_multi(__e, *__f);
         }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
+    _LIBCPP_INLINE_VISIBILITY
+    iterator insert(value_type&& __v)
+        {return __tree_.__insert_multi(_VSTD::move(__v));}
+
+    _LIBCPP_INLINE_VISIBILITY
+    iterator insert(const_iterator __p, value_type&& __v)
+        {return __tree_.__insert_multi(__p, _VSTD::move(__v));}
+
     _LIBCPP_INLINE_VISIBILITY
     void insert(initializer_list<value_type> __il)
         {insert(__il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     iterator  erase(const_iterator __p) {return __tree_.erase(__p);}
@@ -1140,7 +1133,7 @@ public:
 #endif
 };
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Key, class _Compare, class _Allocator>
 multiset<_Key, _Compare, _Allocator>::multiset(multiset&& __s, const allocator_type& __a)
@@ -1154,7 +1147,7 @@ multiset<_Key, _Compare, _Allocator>::multiset(multiset&& __s, const allocator_t
     }
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Key, class _Compare, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
diff --git a/lib/libcxx/include/shared_mutex b/lib/libcxx/include/shared_mutex
index 923fe07ab38..9cb81528cd9 100644
--- a/lib/libcxx/include/shared_mutex
+++ b/lib/libcxx/include/shared_mutex
@@ -125,12 +125,14 @@ template <class Mutex>
 
 #include <__config>
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 #if _LIBCPP_STD_VER > 11 || defined(_LIBCPP_BUILDING_SHARED_MUTEX)
 
 #include <__mutex_base>
 
-#include <__undef_min_max>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
@@ -141,7 +143,7 @@ template <class Mutex>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-struct _LIBCPP_TYPE_VIS __shared_mutex_base
+struct _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_SHARED_MUTEX __shared_mutex_base
 {
     mutex               __mut_;
     condition_variable  __gate1_;
@@ -173,11 +175,11 @@ struct _LIBCPP_TYPE_VIS __shared_mutex_base
 
 
 #if _LIBCPP_STD_VER > 14
-class _LIBCPP_TYPE_VIS shared_mutex
+class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_SHARED_MUTEX shared_mutex
 {
-	__shared_mutex_base __base;
+    __shared_mutex_base __base;
 public:
-    shared_mutex() : __base() {}
+    _LIBCPP_INLINE_VISIBILITY shared_mutex() : __base() {}
     _LIBCPP_INLINE_VISIBILITY ~shared_mutex() = default;
 
     shared_mutex(const shared_mutex&) = delete;
@@ -199,9 +201,9 @@ public:
 #endif
 
 
-class _LIBCPP_TYPE_VIS shared_timed_mutex
+class _LIBCPP_TYPE_VIS _LIBCPP_AVAILABILITY_SHARED_MUTEX shared_timed_mutex
 {
-	__shared_mutex_base __base;
+    __shared_mutex_base __base;
 public:
     shared_timed_mutex();
     _LIBCPP_INLINE_VISIBILITY ~shared_timed_mutex() = default;
@@ -220,6 +222,7 @@ public:
             return try_lock_until(chrono::steady_clock::now() + __rel_time);
         }
     template <class _Clock, class _Duration>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         bool
         try_lock_until(const chrono::time_point<_Clock, _Duration>& __abs_time);
     void unlock();
@@ -235,6 +238,7 @@ public:
             return try_lock_shared_until(chrono::steady_clock::now() + __rel_time);
         }
     template <class _Clock, class _Duration>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         bool
         try_lock_shared_until(const chrono::time_point<_Clock, _Duration>& __abs_time);
     void unlock_shared();
@@ -498,4 +502,6 @@ _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_STD_VER > 11
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_SHARED_MUTEX
diff --git a/lib/libcxx/include/sstream b/lib/libcxx/include/sstream
index 27ae78f9d45..b01f47b6872 100644
--- a/lib/libcxx/include/sstream
+++ b/lib/libcxx/include/sstream
@@ -175,18 +175,20 @@ typedef basic_stringstream<wchar_t> wstringstream;
 #include <istream>
 #include <string>
 
-#include <__undef_min_max>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 // basic_stringbuf
 
 template <class _CharT, class _Traits, class _Allocator>
-class _LIBCPP_TYPE_VIS_ONLY basic_stringbuf
+class _LIBCPP_TEMPLATE_VIS basic_stringbuf
     : public basic_streambuf<_CharT, _Traits>
 {
 public:
@@ -207,15 +209,15 @@ private:
 
 public:
     // 27.8.1.1 Constructors:
+    inline _LIBCPP_INLINE_VISIBILITY
     explicit basic_stringbuf(ios_base::openmode __wch = ios_base::in | ios_base::out);
+    inline _LIBCPP_INLINE_VISIBILITY
     explicit basic_stringbuf(const string_type& __s,
                              ios_base::openmode __wch = ios_base::in | ios_base::out);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     basic_stringbuf(basic_stringbuf&& __rhs);
-#endif
 
     // 27.8.1.2 Assign and swap:
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     basic_stringbuf& operator=(basic_stringbuf&& __rhs);
 #endif
     void swap(basic_stringbuf& __rhs);
@@ -231,30 +233,29 @@ protected:
     virtual int_type overflow (int_type __c = traits_type::eof());
     virtual pos_type seekoff(off_type __off, ios_base::seekdir __way,
                              ios_base::openmode __wch = ios_base::in | ios_base::out);
+    inline _LIBCPP_INLINE_VISIBILITY
     virtual pos_type seekpos(pos_type __sp,
                              ios_base::openmode __wch = ios_base::in | ios_base::out);
 };
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_stringbuf<_CharT, _Traits, _Allocator>::basic_stringbuf(ios_base::openmode __wch)
     : __hm_(0),
       __mode_(__wch)
 {
-    str(string_type());
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_stringbuf<_CharT, _Traits, _Allocator>::basic_stringbuf(const string_type& __s,
                              ios_base::openmode __wch)
-    : __hm_(0),
+    : __str_(__s.get_allocator()),
+      __hm_(0),
       __mode_(__wch)
 {
     str(__s);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
 basic_stringbuf<_CharT, _Traits, _Allocator>::basic_stringbuf(basic_stringbuf&& __rhs)
@@ -287,7 +288,7 @@ basic_stringbuf<_CharT, _Traits, _Allocator>::basic_stringbuf(basic_stringbuf&&
     if (__bout != -1)
     {
         this->setp(__p + __bout, __p + __eout);
-        this->pbump(__nout);
+        this->__pbump(__nout);
     }
     __hm_ = __hm == -1 ? nullptr : __p + __hm;
     __p = const_cast<char_type*>(__rhs.__str_.data());
@@ -330,7 +331,7 @@ basic_stringbuf<_CharT, _Traits, _Allocator>::operator=(basic_stringbuf&& __rhs)
     if (__bout != -1)
     {
         this->setp(__p + __bout, __p + __eout);
-        this->pbump(__nout);
+        this->__pbump(__nout);
     }
     else
         this->setp(nullptr, nullptr);
@@ -345,7 +346,7 @@ basic_stringbuf<_CharT, _Traits, _Allocator>::operator=(basic_stringbuf&& __rhs)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
 void
@@ -401,7 +402,7 @@ basic_stringbuf<_CharT, _Traits, _Allocator>::swap(basic_stringbuf& __rhs)
     if (__rbout != -1)
     {
         this->setp(__p + __rbout, __p + __reout);
-        this->pbump(__rnout);
+        this->__pbump(__rnout);
     }
     else
         this->setp(nullptr, nullptr);
@@ -414,7 +415,7 @@ basic_stringbuf<_CharT, _Traits, _Allocator>::swap(basic_stringbuf& __rhs)
     if (__lbout != -1)
     {
         __rhs.setp(__p + __lbout, __p + __leout);
-        __rhs.pbump(__lnout);
+        __rhs.__pbump(__lnout);
     }
     else
         __rhs.setp(nullptr, nullptr);
@@ -469,7 +470,15 @@ basic_stringbuf<_CharT, _Traits, _Allocator>::str(const string_type& __s)
         this->setp(const_cast<char_type*>(__str_.data()),
                    const_cast<char_type*>(__str_.data()) + __str_.size());
         if (__mode_ & (ios_base::app | ios_base::ate))
-            this->pbump(__sz);
+        {
+            while (__sz > INT_MAX)
+            {
+            	this->pbump(INT_MAX);
+            	__sz -= INT_MAX;
+            }
+            if (__sz > 0)
+            	this->pbump(__sz);
+    	}
     }
 }
 
@@ -534,7 +543,7 @@ basic_stringbuf<_CharT, _Traits, _Allocator>::overflow(int_type __c)
                 __str_.resize(__str_.capacity());
                 char_type* __p = const_cast<char_type*>(__str_.data());
                 this->setp(__p, __p + __str_.size());
-                this->pbump(__nout);
+                this->__pbump(__nout);
                 __hm_ = this->pbase() + __hm;
 #ifndef _LIBCPP_NO_EXCEPTIONS
             }
@@ -568,6 +577,7 @@ basic_stringbuf<_CharT, _Traits, _Allocator>::seekoff(off_type __off,
     if ((__wch & (ios_base::in | ios_base::out)) == (ios_base::in | ios_base::out)
         && __way == ios_base::cur)
         return pos_type(-1);
+    const ptrdiff_t __hm = __hm_ == nullptr ? 0 : __hm_ - __str_.data();
     off_type __noff;
     switch (__way)
     {
@@ -581,13 +591,13 @@ basic_stringbuf<_CharT, _Traits, _Allocator>::seekoff(off_type __off,
             __noff = this->pptr() - this->pbase();
         break;
     case ios_base::end:
-        __noff = __hm_ - __str_.data();
+        __noff = __hm;
         break;
     default:
         return pos_type(-1);
     }
     __noff += __off;
-    if (__noff < 0 || __hm_ - __str_.data() < __noff)
+    if (__noff < 0 || __hm < __noff)
         return pos_type(-1);
     if (__noff != 0)
     {
@@ -607,7 +617,6 @@ basic_stringbuf<_CharT, _Traits, _Allocator>::seekoff(off_type __off,
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 typename basic_stringbuf<_CharT, _Traits, _Allocator>::pos_type
 basic_stringbuf<_CharT, _Traits, _Allocator>::seekpos(pos_type __sp,
                                                       ios_base::openmode __wch)
@@ -618,7 +627,7 @@ basic_stringbuf<_CharT, _Traits, _Allocator>::seekpos(pos_type __sp,
 // basic_istringstream
 
 template <class _CharT, class _Traits, class _Allocator>
-class _LIBCPP_TYPE_VIS_ONLY basic_istringstream
+class _LIBCPP_TEMPLATE_VIS basic_istringstream
     : public basic_istream<_CharT, _Traits>
 {
 public:
@@ -636,25 +645,31 @@ private:
 
 public:
     // 27.8.2.1 Constructors:
+    inline _LIBCPP_INLINE_VISIBILITY
     explicit basic_istringstream(ios_base::openmode __wch = ios_base::in);
+    inline _LIBCPP_INLINE_VISIBILITY
     explicit basic_istringstream(const string_type& __s,
                                  ios_base::openmode __wch = ios_base::in);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
+    inline _LIBCPP_INLINE_VISIBILITY
     basic_istringstream(basic_istringstream&& __rhs);
 
     // 27.8.2.2 Assign and swap:
     basic_istringstream& operator=(basic_istringstream&& __rhs);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
+    inline _LIBCPP_INLINE_VISIBILITY
     void swap(basic_istringstream& __rhs);
 
     // 27.8.2.3 Members:
+    inline _LIBCPP_INLINE_VISIBILITY
     basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const;
+    inline _LIBCPP_INLINE_VISIBILITY
     string_type str() const;
+    inline _LIBCPP_INLINE_VISIBILITY
     void str(const string_type& __s);
 };
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_istringstream<_CharT, _Traits, _Allocator>::basic_istringstream(ios_base::openmode __wch)
     : basic_istream<_CharT, _Traits>(&__sb_),
       __sb_(__wch | ios_base::in)
@@ -662,7 +677,6 @@ basic_istringstream<_CharT, _Traits, _Allocator>::basic_istringstream(ios_base::
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_istringstream<_CharT, _Traits, _Allocator>::basic_istringstream(const string_type& __s,
                                                                       ios_base::openmode __wch)
     : basic_istream<_CharT, _Traits>(&__sb_),
@@ -670,10 +684,9 @@ basic_istringstream<_CharT, _Traits, _Allocator>::basic_istringstream(const stri
 {
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_istringstream<_CharT, _Traits, _Allocator>::basic_istringstream(basic_istringstream&& __rhs)
     : basic_istream<_CharT, _Traits>(_VSTD::move(__rhs)),
       __sb_(_VSTD::move(__rhs.__sb_))
@@ -690,12 +703,10 @@ basic_istringstream<_CharT, _Traits, _Allocator>::operator=(basic_istringstream&
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
-void
-basic_istringstream<_CharT, _Traits, _Allocator>::swap(basic_istringstream& __rhs)
+void basic_istringstream<_CharT, _Traits, _Allocator>::swap(basic_istringstream& __rhs)
 {
     basic_istream<char_type, traits_type>::swap(__rhs);
     __sb_.swap(__rhs.__sb_);
@@ -711,7 +722,6 @@ swap(basic_istringstream<_CharT, _Traits, _Allocator>& __x,
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_stringbuf<_CharT, _Traits, _Allocator>*
 basic_istringstream<_CharT, _Traits, _Allocator>::rdbuf() const
 {
@@ -719,7 +729,6 @@ basic_istringstream<_CharT, _Traits, _Allocator>::rdbuf() const
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_string<_CharT, _Traits, _Allocator>
 basic_istringstream<_CharT, _Traits, _Allocator>::str() const
 {
@@ -727,9 +736,7 @@ basic_istringstream<_CharT, _Traits, _Allocator>::str() const
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
-void
-basic_istringstream<_CharT, _Traits, _Allocator>::str(const string_type& __s)
+void basic_istringstream<_CharT, _Traits, _Allocator>::str(const string_type& __s)
 {
     __sb_.str(__s);
 }
@@ -737,7 +744,7 @@ basic_istringstream<_CharT, _Traits, _Allocator>::str(const string_type& __s)
 // basic_ostringstream
 
 template <class _CharT, class _Traits, class _Allocator>
-class _LIBCPP_TYPE_VIS_ONLY basic_ostringstream
+class _LIBCPP_TEMPLATE_VIS basic_ostringstream
     : public basic_ostream<_CharT, _Traits>
 {
 public:
@@ -755,25 +762,31 @@ private:
 
 public:
     // 27.8.2.1 Constructors:
+    inline _LIBCPP_INLINE_VISIBILITY
     explicit basic_ostringstream(ios_base::openmode __wch = ios_base::out);
+    inline _LIBCPP_INLINE_VISIBILITY
     explicit basic_ostringstream(const string_type& __s,
                                  ios_base::openmode __wch = ios_base::out);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
+    inline _LIBCPP_INLINE_VISIBILITY
     basic_ostringstream(basic_ostringstream&& __rhs);
 
     // 27.8.2.2 Assign and swap:
     basic_ostringstream& operator=(basic_ostringstream&& __rhs);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
+    inline _LIBCPP_INLINE_VISIBILITY
     void swap(basic_ostringstream& __rhs);
 
     // 27.8.2.3 Members:
+    inline _LIBCPP_INLINE_VISIBILITY
     basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const;
+    inline _LIBCPP_INLINE_VISIBILITY
     string_type str() const;
+    inline _LIBCPP_INLINE_VISIBILITY
     void str(const string_type& __s);
 };
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_ostringstream<_CharT, _Traits, _Allocator>::basic_ostringstream(ios_base::openmode __wch)
     : basic_ostream<_CharT, _Traits>(&__sb_),
       __sb_(__wch | ios_base::out)
@@ -781,7 +794,6 @@ basic_ostringstream<_CharT, _Traits, _Allocator>::basic_ostringstream(ios_base::
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_ostringstream<_CharT, _Traits, _Allocator>::basic_ostringstream(const string_type& __s,
                                                                       ios_base::openmode __wch)
     : basic_ostream<_CharT, _Traits>(&__sb_),
@@ -789,10 +801,9 @@ basic_ostringstream<_CharT, _Traits, _Allocator>::basic_ostringstream(const stri
 {
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_ostringstream<_CharT, _Traits, _Allocator>::basic_ostringstream(basic_ostringstream&& __rhs)
     : basic_ostream<_CharT, _Traits>(_VSTD::move(__rhs)),
       __sb_(_VSTD::move(__rhs.__sb_))
@@ -809,10 +820,9 @@ basic_ostringstream<_CharT, _Traits, _Allocator>::operator=(basic_ostringstream&
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 void
 basic_ostringstream<_CharT, _Traits, _Allocator>::swap(basic_ostringstream& __rhs)
 {
@@ -830,7 +840,6 @@ swap(basic_ostringstream<_CharT, _Traits, _Allocator>& __x,
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_stringbuf<_CharT, _Traits, _Allocator>*
 basic_ostringstream<_CharT, _Traits, _Allocator>::rdbuf() const
 {
@@ -838,7 +847,6 @@ basic_ostringstream<_CharT, _Traits, _Allocator>::rdbuf() const
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_string<_CharT, _Traits, _Allocator>
 basic_ostringstream<_CharT, _Traits, _Allocator>::str() const
 {
@@ -846,7 +854,6 @@ basic_ostringstream<_CharT, _Traits, _Allocator>::str() const
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 void
 basic_ostringstream<_CharT, _Traits, _Allocator>::str(const string_type& __s)
 {
@@ -856,7 +863,7 @@ basic_ostringstream<_CharT, _Traits, _Allocator>::str(const string_type& __s)
 // basic_stringstream
 
 template <class _CharT, class _Traits, class _Allocator>
-class _LIBCPP_TYPE_VIS_ONLY basic_stringstream
+class _LIBCPP_TEMPLATE_VIS basic_stringstream
     : public basic_iostream<_CharT, _Traits>
 {
 public:
@@ -874,25 +881,31 @@ private:
 
 public:
     // 27.8.2.1 Constructors:
+    inline _LIBCPP_INLINE_VISIBILITY
     explicit basic_stringstream(ios_base::openmode __wch = ios_base::in | ios_base::out);
+    inline _LIBCPP_INLINE_VISIBILITY
     explicit basic_stringstream(const string_type& __s,
                                 ios_base::openmode __wch = ios_base::in | ios_base::out);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
+    inline _LIBCPP_INLINE_VISIBILITY
     basic_stringstream(basic_stringstream&& __rhs);
 
     // 27.8.2.2 Assign and swap:
     basic_stringstream& operator=(basic_stringstream&& __rhs);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
+    inline _LIBCPP_INLINE_VISIBILITY
     void swap(basic_stringstream& __rhs);
 
     // 27.8.2.3 Members:
+    inline _LIBCPP_INLINE_VISIBILITY
     basic_stringbuf<char_type, traits_type, allocator_type>* rdbuf() const;
+    inline _LIBCPP_INLINE_VISIBILITY
     string_type str() const;
+    inline _LIBCPP_INLINE_VISIBILITY
     void str(const string_type& __s);
 };
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_stringstream<_CharT, _Traits, _Allocator>::basic_stringstream(ios_base::openmode __wch)
     : basic_iostream<_CharT, _Traits>(&__sb_),
       __sb_(__wch)
@@ -900,7 +913,6 @@ basic_stringstream<_CharT, _Traits, _Allocator>::basic_stringstream(ios_base::op
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_stringstream<_CharT, _Traits, _Allocator>::basic_stringstream(const string_type& __s,
                                                                     ios_base::openmode __wch)
     : basic_iostream<_CharT, _Traits>(&__sb_),
@@ -908,10 +920,9 @@ basic_stringstream<_CharT, _Traits, _Allocator>::basic_stringstream(const string
 {
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_stringstream<_CharT, _Traits, _Allocator>::basic_stringstream(basic_stringstream&& __rhs)
     : basic_iostream<_CharT, _Traits>(_VSTD::move(__rhs)),
       __sb_(_VSTD::move(__rhs.__sb_))
@@ -928,10 +939,9 @@ basic_stringstream<_CharT, _Traits, _Allocator>::operator=(basic_stringstream&&
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 void
 basic_stringstream<_CharT, _Traits, _Allocator>::swap(basic_stringstream& __rhs)
 {
@@ -949,7 +959,6 @@ swap(basic_stringstream<_CharT, _Traits, _Allocator>& __x,
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_stringbuf<_CharT, _Traits, _Allocator>*
 basic_stringstream<_CharT, _Traits, _Allocator>::rdbuf() const
 {
@@ -957,7 +966,6 @@ basic_stringstream<_CharT, _Traits, _Allocator>::rdbuf() const
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 basic_string<_CharT, _Traits, _Allocator>
 basic_stringstream<_CharT, _Traits, _Allocator>::str() const
 {
@@ -965,7 +973,6 @@ basic_stringstream<_CharT, _Traits, _Allocator>::str() const
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-inline _LIBCPP_INLINE_VISIBILITY
 void
 basic_stringstream<_CharT, _Traits, _Allocator>::str(const string_type& __s)
 {
@@ -974,4 +981,6 @@ basic_stringstream<_CharT, _Traits, _Allocator>::str(const string_type& __s)
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_SSTREAM
diff --git a/lib/libcxx/include/stack b/lib/libcxx/include/stack
index 48b3b0d16ec..0cb4c6ca925 100644
--- a/lib/libcxx/include/stack
+++ b/lib/libcxx/include/stack
@@ -55,7 +55,7 @@ public:
 
     void push(const value_type& x);
     void push(value_type&& x);
-    template <class... Args> void emplace(Args&&... args);
+    template <class... Args> reference emplace(Args&&... args); // reference in C++17
     void pop();
 
     void swap(stack& c) noexcept(is_nothrow_swappable_v<Container>)
@@ -91,7 +91,7 @@ template <class T, class Container>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Tp, class _Container = deque<_Tp> > class _LIBCPP_TYPE_VIS_ONLY stack;
+template <class _Tp, class _Container = deque<_Tp> > class _LIBCPP_TEMPLATE_VIS stack;
 
 template <class _Tp, class _Container>
 _LIBCPP_INLINE_VISIBILITY
@@ -104,7 +104,7 @@ bool
 operator< (const stack<_Tp, _Container>& __x, const stack<_Tp, _Container>& __y);
 
 template <class _Tp, class _Container /*= deque<_Tp>*/>
-class _LIBCPP_TYPE_VIS_ONLY stack
+class _LIBCPP_TEMPLATE_VIS stack
 {
 public:
     typedef _Container                               container_type;
@@ -126,29 +126,28 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     stack(const stack& __q) : c(__q.c) {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+    _LIBCPP_INLINE_VISIBILITY
+    stack& operator=(const stack& __q) {c = __q.c; return *this;}
+
+
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     stack(stack&& __q)
         _NOEXCEPT_(is_nothrow_move_constructible<container_type>::value)
         : c(_VSTD::move(__q.c)) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
     _LIBCPP_INLINE_VISIBILITY
-    stack& operator=(const stack& __q) {c = __q.c; return *this;}
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
     stack& operator=(stack&& __q)
         _NOEXCEPT_(is_nothrow_move_assignable<container_type>::value)
         {c = _VSTD::move(__q.c); return *this;}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
     _LIBCPP_INLINE_VISIBILITY
-    explicit stack(const container_type& __c) : c(__c) {}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY
     explicit stack(container_type&& __c) : c(_VSTD::move(__c)) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit stack(const container_type& __c) : c(__c) {}
+
     template <class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         explicit stack(const _Alloc& __a,
@@ -167,7 +166,7 @@ public:
               typename enable_if<uses_allocator<container_type,
                                                 _Alloc>::value>::type* = 0)
             : c(__s.c, __a) {}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     template <class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         stack(container_type&& __c, const _Alloc& __a,
@@ -180,9 +179,9 @@ public:
               typename enable_if<uses_allocator<container_type,
                                                 _Alloc>::value>::type* = 0)
             : c(_VSTD::move(__s.c), __a) {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool empty()     const      {return c.empty();}
     _LIBCPP_INLINE_VISIBILITY
     size_type size() const      {return c.size();}
@@ -193,16 +192,21 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     void push(const value_type& __v) {c.push_back(__v);}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void push(value_type&& __v) {c.push_back(_VSTD::move(__v));}
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+
     template <class... _Args>
         _LIBCPP_INLINE_VISIBILITY
-        void emplace(_Args&&... __args)
-        {c.emplace_back(_VSTD::forward<_Args>(__args)...);}
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#if _LIBCPP_STD_VER > 14
+        reference emplace(_Args&&... __args)
+        { return c.emplace_back(_VSTD::forward<_Args>(__args)...);}
+#else
+        void      emplace(_Args&&... __args)
+        {        c.emplace_back(_VSTD::forward<_Args>(__args)...);}
+#endif
+#endif  // _LIBCPP_CXX03_LANG
+
     _LIBCPP_INLINE_VISIBILITY
     void pop() {c.pop_back();}
 
@@ -286,7 +290,7 @@ swap(stack<_Tp, _Container>& __x, stack<_Tp, _Container>& __y)
 }
 
 template <class _Tp, class _Container, class _Alloc>
-struct _LIBCPP_TYPE_VIS_ONLY uses_allocator<stack<_Tp, _Container>, _Alloc>
+struct _LIBCPP_TEMPLATE_VIS uses_allocator<stack<_Tp, _Container>, _Alloc>
     : public uses_allocator<_Container, _Alloc>
 {
 };
diff --git a/lib/libcxx/include/stddef.h b/lib/libcxx/include/stddef.h
index 8841bbea297..faf8552d8ce 100644
--- a/lib/libcxx/include/stddef.h
+++ b/lib/libcxx/include/stddef.h
@@ -53,7 +53,8 @@ using std::nullptr_t;
 }
 
 // Re-use the compiler's <stddef.h> max_align_t where possible.
-#if !defined(__CLANG_MAX_ALIGN_T_DEFINED) && !defined(_GCC_MAX_ALIGN_T)
+#if !defined(__CLANG_MAX_ALIGN_T_DEFINED) && !defined(_GCC_MAX_ALIGN_T) && \
+    !defined(__DEFINED_max_align_t)
 typedef long double max_align_t;
 #endif
 
diff --git a/lib/libcxx/include/stdexcept b/lib/libcxx/include/stdexcept
index 4218b1398d8..95a96cc0767 100644
--- a/lib/libcxx/include/stdexcept
+++ b/lib/libcxx/include/stdexcept
@@ -45,22 +45,31 @@ public:
 #include <__config>
 #include <exception>
 #include <iosfwd>  // for string forward decl
+#ifdef _LIBCPP_NO_EXCEPTIONS
+#include <cstdlib>
+#endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
-#ifndef _LIBCPP___REFSTRING
 _LIBCPP_BEGIN_NAMESPACE_STD
-class _LIBCPP_HIDDEN __libcpp_refstring {
-#ifdef __clang__
-    const char *__imp_ __attribute__((__unused__)); // only clang emits a warning
-#else
-    const char *__imp_;
-#endif
+
+class _LIBCPP_HIDDEN __libcpp_refstring
+{
+    const char* __imp_;
+
+    bool __uses_refcount() const;
+public:
+    explicit __libcpp_refstring(const char* __msg);
+    __libcpp_refstring(const __libcpp_refstring& __s) _NOEXCEPT;
+    __libcpp_refstring& operator=(const __libcpp_refstring& __s) _NOEXCEPT;
+    ~__libcpp_refstring();
+
+    const char* c_str() const _NOEXCEPT {return __imp_;}
 };
+
 _LIBCPP_END_NAMESPACE_STD
-#endif
 
 namespace std  // purposefully not using versioning namespace
 {
@@ -171,4 +180,99 @@ public:
 
 }  // std
 
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// in the dylib
+_LIBCPP_NORETURN _LIBCPP_FUNC_VIS void __throw_runtime_error(const char*);
+
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+void __throw_logic_error(const char*__msg)
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw logic_error(__msg);
+#else
+    ((void)__msg);
+	  _VSTD::abort();
+#endif
+}
+
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+void __throw_domain_error(const char*__msg)
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw domain_error(__msg);
+#else
+    ((void)__msg);
+	  _VSTD::abort();
+#endif
+}
+
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+void __throw_invalid_argument(const char*__msg)
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw invalid_argument(__msg);
+#else
+    ((void)__msg);
+	  _VSTD::abort();
+#endif
+}
+
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+void __throw_length_error(const char*__msg)
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw length_error(__msg);
+#else
+    ((void)__msg);
+	  _VSTD::abort();
+#endif
+}
+
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+void __throw_out_of_range(const char*__msg)
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw out_of_range(__msg);
+#else
+    ((void)__msg);
+	  _VSTD::abort();
+#endif
+}
+
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+void __throw_range_error(const char*__msg)
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw range_error(__msg);
+#else
+    ((void)__msg);
+	  _VSTD::abort();
+#endif
+}
+
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+void __throw_overflow_error(const char*__msg)
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw overflow_error(__msg);
+#else
+    ((void)__msg);
+    _VSTD::abort();
+#endif
+}
+
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+void __throw_underflow_error(const char*__msg)
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw underflow_error(__msg);
+#else
+    ((void)__msg);
+    _VSTD::abort();
+#endif
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
 #endif  // _LIBCPP_STDEXCEPT
diff --git a/lib/libcxx/include/stdint.h b/lib/libcxx/include/stdint.h
new file mode 100644
index 00000000000..468f6cd97c2
--- /dev/null
+++ b/lib/libcxx/include/stdint.h
@@ -0,0 +1,121 @@
+// -*- C++ -*-
+//===---------------------------- stdint.h --------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STDINT_H
+#define _LIBCPP_STDINT_H
+
+/*
+    stdint.h synopsis
+
+Macros:
+
+    INT8_MIN
+    INT16_MIN
+    INT32_MIN
+    INT64_MIN
+
+    INT8_MAX
+    INT16_MAX
+    INT32_MAX
+    INT64_MAX
+
+    UINT8_MAX
+    UINT16_MAX
+    UINT32_MAX
+    UINT64_MAX
+
+    INT_LEAST8_MIN
+    INT_LEAST16_MIN
+    INT_LEAST32_MIN
+    INT_LEAST64_MIN
+
+    INT_LEAST8_MAX
+    INT_LEAST16_MAX
+    INT_LEAST32_MAX
+    INT_LEAST64_MAX
+
+    UINT_LEAST8_MAX
+    UINT_LEAST16_MAX
+    UINT_LEAST32_MAX
+    UINT_LEAST64_MAX
+
+    INT_FAST8_MIN
+    INT_FAST16_MIN
+    INT_FAST32_MIN
+    INT_FAST64_MIN
+
+    INT_FAST8_MAX
+    INT_FAST16_MAX
+    INT_FAST32_MAX
+    INT_FAST64_MAX
+
+    UINT_FAST8_MAX
+    UINT_FAST16_MAX
+    UINT_FAST32_MAX
+    UINT_FAST64_MAX
+
+    INTPTR_MIN
+    INTPTR_MAX
+    UINTPTR_MAX
+
+    INTMAX_MIN
+    INTMAX_MAX
+
+    UINTMAX_MAX
+
+    PTRDIFF_MIN
+    PTRDIFF_MAX
+
+    SIG_ATOMIC_MIN
+    SIG_ATOMIC_MAX
+
+    SIZE_MAX
+
+    WCHAR_MIN
+    WCHAR_MAX
+
+    WINT_MIN
+    WINT_MAX
+
+    INT8_C(value)
+    INT16_C(value)
+    INT32_C(value)
+    INT64_C(value)
+
+    UINT8_C(value)
+    UINT16_C(value)
+    UINT32_C(value)
+    UINT64_C(value)
+
+    INTMAX_C(value)
+    UINTMAX_C(value)
+
+*/
+
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+/* C99 stdlib (e.g. glibc < 2.18) does not provide macros needed
+   for C++11 unless __STDC_LIMIT_MACROS and __STDC_CONSTANT_MACROS
+   are defined
+*/
+#if defined(__cplusplus) && !defined(__STDC_LIMIT_MACROS)
+#   define __STDC_LIMIT_MACROS
+#endif
+#if defined(__cplusplus) && !defined(__STDC_CONSTANT_MACROS)
+#   define __STDC_CONSTANT_MACROS
+#endif
+
+#include_next <stdint.h>
+
+#endif  // _LIBCPP_STDINT_H
diff --git a/lib/libcxx/include/stdlib.h b/lib/libcxx/include/stdlib.h
index 12fd676a15f..f11c5e76226 100644
--- a/lib/libcxx/include/stdlib.h
+++ b/lib/libcxx/include/stdlib.h
@@ -97,10 +97,6 @@ void *aligned_alloc(size_t alignment, size_t size);                       // C11
 
 extern "C++" {
 
-#ifdef _LIBCPP_MSVCRT
-#include "support/win32/locale_win32.h"
-#endif // _LIBCPP_MSVCRT
-
 #undef abs
 #undef div
 #undef labs
diff --git a/lib/libcxx/include/streambuf b/lib/libcxx/include/streambuf
index 7544aaf179b..ea64f578045 100644
--- a/lib/libcxx/include/streambuf
+++ b/lib/libcxx/include/streambuf
@@ -116,10 +116,13 @@ protected:
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _CharT, class _Traits>
-class _LIBCPP_TYPE_VIS_ONLY basic_streambuf
+class _LIBCPP_TEMPLATE_VIS basic_streambuf
 {
 public:
     // types:
@@ -132,32 +135,96 @@ public:
     virtual ~basic_streambuf();
 
     // 27.6.2.2.1 locales:
-    locale pubimbue(const locale& __loc);
-    locale getloc() const;
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    locale pubimbue(const locale& __loc) {
+        imbue(__loc);
+        locale __r = __loc_;
+        __loc_ = __loc;
+        return __r;
+    }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    locale getloc() const { return __loc_; }
 
     // 27.6.2.2.2 buffer and positioning:
-    basic_streambuf* pubsetbuf(char_type* __s, streamsize __n);
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    basic_streambuf* pubsetbuf(char_type* __s, streamsize __n)
+    { return setbuf(__s, __n); }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
     pos_type pubseekoff(off_type __off, ios_base::seekdir __way,
-                        ios_base::openmode __which = ios_base::in | ios_base::out);
+                        ios_base::openmode __which = ios_base::in | ios_base::out)
+    { return seekoff(__off, __way, __which); }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
     pos_type pubseekpos(pos_type __sp,
-                        ios_base::openmode __which = ios_base::in | ios_base::out);
-    int pubsync();
+                        ios_base::openmode __which = ios_base::in | ios_base::out)
+    { return seekpos(__sp, __which); }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    int pubsync() { return sync(); }
 
     // Get and put areas:
     // 27.6.2.2.3 Get area:
-    streamsize in_avail();
-    int_type snextc();
-    int_type sbumpc();
-    int_type sgetc();
-    streamsize sgetn(char_type* __s, streamsize __n);
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    streamsize in_avail() {
+        if (__ninp_ < __einp_)
+            return static_cast<streamsize>(__einp_ - __ninp_);
+        return showmanyc();
+    }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    int_type snextc() {
+        if (sbumpc() == traits_type::eof())
+            return traits_type::eof();
+        return sgetc();
+    }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    int_type sbumpc() {
+        if (__ninp_ == __einp_)
+            return uflow();
+        return traits_type::to_int_type(*__ninp_++);
+    }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    int_type sgetc() {
+        if (__ninp_ == __einp_)
+            return underflow();
+        return traits_type::to_int_type(*__ninp_);
+    }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    streamsize sgetn(char_type* __s, streamsize __n)
+    { return xsgetn(__s, __n); }
 
     // 27.6.2.2.4 Putback:
-    int_type sputbackc(char_type __c);
-    int_type sungetc();
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    int_type sputbackc(char_type __c) {
+        if (__binp_ == __ninp_ || !traits_type::eq(__c, __ninp_[-1]))
+            return pbackfail(traits_type::to_int_type(__c));
+        return traits_type::to_int_type(*--__ninp_);
+    }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    int_type sungetc() {
+        if (__binp_ == __ninp_)
+          return pbackfail();
+        return traits_type::to_int_type(*--__ninp_);
+    }
 
     // 27.6.2.2.5 Put area:
-    int_type sputc(char_type __c);
-    streamsize sputn(const char_type* __s, streamsize __n);
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    int_type sputc(char_type __c) {
+        if (__nout_ == __eout_)
+            return overflow(traits_type::to_int_type(__c));
+        *__nout_++ = __c;
+        return traits_type::to_int_type(__c);
+    }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    streamsize sputn(const char_type* __s, streamsize __n)
+    { return xsputn(__s, __n); }
 
 protected:
     basic_streambuf();
@@ -169,15 +236,33 @@ protected:
     _LIBCPP_ALWAYS_INLINE char_type* eback() const {return __binp_;}
     _LIBCPP_ALWAYS_INLINE char_type* gptr()  const {return __ninp_;}
     _LIBCPP_ALWAYS_INLINE char_type* egptr() const {return __einp_;}
-    void gbump(int __n);
-    void setg(char_type* __gbeg, char_type* __gnext, char_type* __gend);
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    void gbump(int __n) { __ninp_ += __n; }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    void setg(char_type* __gbeg, char_type* __gnext, char_type* __gend) {
+        __binp_ = __gbeg;
+        __ninp_ = __gnext;
+        __einp_ = __gend;
+    }
 
     // 27.6.2.3.3 Put area:
     _LIBCPP_ALWAYS_INLINE char_type* pbase() const {return __bout_;}
     _LIBCPP_ALWAYS_INLINE char_type* pptr()  const {return __nout_;}
     _LIBCPP_ALWAYS_INLINE char_type* epptr() const {return __eout_;}
-    void pbump(int __n);
-    void setp(char_type* __pbeg, char_type* __pend);
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    void pbump(int __n) { __nout_ += __n; }
+
+    _LIBCPP_ALWAYS_INLINE
+    void __pbump(streamsize __n) { __nout_ += __n; }
+
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    void setp(char_type* __pbeg, char_type* __pend) {
+        __bout_ = __nout_ = __pbeg;
+        __eout_ = __pend;
+    }
 
     // 27.6.2.4 virtual functions:
     // 27.6.2.4.1 Locales:
@@ -220,147 +305,6 @@ basic_streambuf<_CharT, _Traits>::~basic_streambuf()
 }
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-locale
-basic_streambuf<_CharT, _Traits>::pubimbue(const locale& __loc)
-{
-    imbue(__loc);
-    locale __r = __loc_;
-    __loc_ = __loc;
-    return __r;
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-locale
-basic_streambuf<_CharT, _Traits>::getloc() const
-{
-    return __loc_;
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-basic_streambuf<_CharT, _Traits>*
-basic_streambuf<_CharT, _Traits>::pubsetbuf(char_type* __s, streamsize __n)
-{
-    return setbuf(__s, __n);
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-typename basic_streambuf<_CharT, _Traits>::pos_type
-basic_streambuf<_CharT, _Traits>::pubseekoff(off_type __off,
-                                             ios_base::seekdir __way,
-                                             ios_base::openmode __which)
-{
-    return seekoff(__off, __way, __which);
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-typename basic_streambuf<_CharT, _Traits>::pos_type
-basic_streambuf<_CharT, _Traits>::pubseekpos(pos_type __sp,
-                                             ios_base::openmode __which)
-{
-    return seekpos(__sp, __which);
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-int
-basic_streambuf<_CharT, _Traits>::pubsync()
-{
-    return sync();
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-streamsize
-basic_streambuf<_CharT, _Traits>::in_avail()
-{
-    if (__ninp_ < __einp_)
-        return static_cast<streamsize>(__einp_ - __ninp_);
-    return showmanyc();
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-typename basic_streambuf<_CharT, _Traits>::int_type
-basic_streambuf<_CharT, _Traits>::snextc()
-{
-    if (sbumpc() == traits_type::eof())
-        return traits_type::eof();
-    return sgetc();
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-typename basic_streambuf<_CharT, _Traits>::int_type
-basic_streambuf<_CharT, _Traits>::sbumpc()
-{
-    if (__ninp_ == __einp_)
-        return uflow();
-    return traits_type::to_int_type(*__ninp_++);
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-typename basic_streambuf<_CharT, _Traits>::int_type
-basic_streambuf<_CharT, _Traits>::sgetc()
-{
-    if (__ninp_ == __einp_)
-        return underflow();
-    return traits_type::to_int_type(*__ninp_);
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-streamsize
-basic_streambuf<_CharT, _Traits>::sgetn(char_type* __s, streamsize __n)
-{
-    return xsgetn(__s, __n);
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-typename basic_streambuf<_CharT, _Traits>::int_type
-basic_streambuf<_CharT, _Traits>::sputbackc(char_type __c)
-{
-    if (__binp_ == __ninp_ || !traits_type::eq(__c, __ninp_[-1]))
-        return pbackfail(traits_type::to_int_type(__c));
-    return traits_type::to_int_type(*--__ninp_);
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-typename basic_streambuf<_CharT, _Traits>::int_type
-basic_streambuf<_CharT, _Traits>::sungetc()
-{
-    if (__binp_ == __ninp_)
-        return pbackfail();
-    return traits_type::to_int_type(*--__ninp_);
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-typename basic_streambuf<_CharT, _Traits>::int_type
-basic_streambuf<_CharT, _Traits>::sputc(char_type __c)
-{
-    if (__nout_ == __eout_)
-        return overflow(traits_type::to_int_type(__c));
-    *__nout_++ = __c;
-    return traits_type::to_int_type(__c);
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-streamsize
-basic_streambuf<_CharT, _Traits>::sputn(const char_type* __s, streamsize __n)
-{
-    return xsputn(__s, __n);
-}
-
-template <class _CharT, class _Traits>
 basic_streambuf<_CharT, _Traits>::basic_streambuf()
     : __binp_(0),
       __ninp_(0),
@@ -411,42 +355,6 @@ basic_streambuf<_CharT, _Traits>::swap(basic_streambuf& __sb)
 }
 
 template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-void
-basic_streambuf<_CharT, _Traits>::gbump(int __n)
-{
-    __ninp_ += __n;
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-void
-basic_streambuf<_CharT, _Traits>::setg(char_type* __gbeg, char_type* __gnext,
-                                                          char_type* __gend)
-{
-    __binp_ = __gbeg;
-    __ninp_ = __gnext;
-    __einp_ = __gend;
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-void
-basic_streambuf<_CharT, _Traits>::pbump(int __n)
-{
-    __nout_ += __n;
-}
-
-template <class _CharT, class _Traits>
-inline _LIBCPP_INLINE_VISIBILITY
-void
-basic_streambuf<_CharT, _Traits>::setp(char_type* __pbeg, char_type* __pend)
-{
-    __bout_ = __nout_ = __pbeg;
-    __eout_ = __pend;
-}
-
-template <class _CharT, class _Traits>
 void
 basic_streambuf<_CharT, _Traits>::imbue(const locale&)
 {
@@ -499,7 +407,8 @@ basic_streambuf<_CharT, _Traits>::xsgetn(char_type* __s, streamsize __n)
     {
         if (__ninp_ < __einp_)
         {
-            const streamsize __len = _VSTD::min(__einp_ - __ninp_, __n - __i);
+            const streamsize __len = _VSTD::min(static_cast<streamsize>(INT_MAX),
+                                _VSTD::min(__einp_ - __ninp_, __n - __i));
             traits_type::copy(__s, __ninp_, __len);
             __s +=  __len;
             __i +=  __len;
@@ -574,12 +483,16 @@ basic_streambuf<_CharT, _Traits>::overflow(int_type)
     return traits_type::eof();
 }
 
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_streambuf<char>)
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_streambuf<wchar_t>)
+#ifndef _LIBCPP_AVAILABILITY_NO_STREAMS_EXTERN_TEMPLATE
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_streambuf<char>)
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_streambuf<wchar_t>)
 
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_ios<char>)
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_ios<wchar_t>)
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_ios<char>)
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_ios<wchar_t>)
+#endif
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_STEAMBUF
diff --git a/lib/libcxx/include/string b/lib/libcxx/include/string
index 786735f970f..f5d548965aa 100644
--- a/lib/libcxx/include/string
+++ b/lib/libcxx/include/string
@@ -101,7 +101,10 @@ public:
     basic_string(const basic_string& str, size_type pos,
                  const allocator_type& a = allocator_type());
     basic_string(const basic_string& str, size_type pos, size_type n,
-                 const Allocator& a = Allocator());             
+                 const Allocator& a = Allocator());
+    template<class T>
+        basic_string(const T& t, size_type pos, size_type n, const Allocator& a = Allocator()); // C++17
+    explicit basic_string(const basic_string_view<charT, traits> sv, const Allocator& a = Allocator());
     basic_string(const value_type* s, const allocator_type& a = allocator_type());
     basic_string(const value_type* s, size_type n, const allocator_type& a = allocator_type());
     basic_string(size_type n, value_type c, const allocator_type& a = allocator_type());
@@ -114,7 +117,10 @@ public:
 
     ~basic_string();
 
+    operator basic_string_view<charT, traits>() const noexcept;
+
     basic_string& operator=(const basic_string& str);
+    basic_string& operator=(basic_string_view<charT, traits> sv);
     basic_string& operator=(basic_string&& str)
         noexcept(
              allocator_type::propagate_on_container_move_assignment::value ||
@@ -158,12 +164,16 @@ public:
     reference       at(size_type n);
 
     basic_string& operator+=(const basic_string& str);
+    basic_string& operator+=(basic_string_view<charT, traits> sv);
     basic_string& operator+=(const value_type* s);
     basic_string& operator+=(value_type c);
     basic_string& operator+=(initializer_list<value_type>);
 
     basic_string& append(const basic_string& str);
+    basic_string& append(basic_string_view<charT, traits> sv);
     basic_string& append(const basic_string& str, size_type pos, size_type n=npos); //C++14
+    template <class T>
+        basic_string& append(const T& t, size_type pos, size_type n=npos); // C++17
     basic_string& append(const value_type* s, size_type n);
     basic_string& append(const value_type* s);
     basic_string& append(size_type n, value_type c);
@@ -179,8 +189,11 @@ public:
     const_reference back() const;
 
     basic_string& assign(const basic_string& str);
+    basic_string& assign(basic_string_view<charT, traits> sv);
     basic_string& assign(basic_string&& str);
     basic_string& assign(const basic_string& str, size_type pos, size_type n=npos); // C++14
+    template <class T>
+        basic_string& assign(const T& t, size_type pos, size_type n=npos); // C++17
     basic_string& assign(const value_type* s, size_type n);
     basic_string& assign(const value_type* s);
     basic_string& assign(size_type n, value_type c);
@@ -189,8 +202,11 @@ public:
     basic_string& assign(initializer_list<value_type>);
 
     basic_string& insert(size_type pos1, const basic_string& str);
+    basic_string& insert(size_type pos1, basic_string_view<charT, traits> sv);
     basic_string& insert(size_type pos1, const basic_string& str,
                          size_type pos2, size_type n);
+    template <class T>
+        basic_string& insert(size_type pos1, const T& t, size_type pos2, size_type n); // C++17
     basic_string& insert(size_type pos, const value_type* s, size_type n=npos); //C++14
     basic_string& insert(size_type pos, const value_type* s);
     basic_string& insert(size_type pos, size_type n, value_type c);
@@ -205,12 +221,17 @@ public:
     iterator      erase(const_iterator first, const_iterator last);
 
     basic_string& replace(size_type pos1, size_type n1, const basic_string& str);
+    basic_string& replace(size_type pos1, size_type n1, basic_string_view<charT, traits> sv);
     basic_string& replace(size_type pos1, size_type n1, const basic_string& str,
                           size_type pos2, size_type n2=npos); // C++14
+    template <class T>
+        basic_string& replace(size_type pos1, size_type n1, const T& t,
+                              size_type pos2, size_type n); // C++17
     basic_string& replace(size_type pos, size_type n1, const value_type* s, size_type n2);
     basic_string& replace(size_type pos, size_type n1, const value_type* s);
     basic_string& replace(size_type pos, size_type n1, size_type n2, value_type c);
     basic_string& replace(const_iterator i1, const_iterator i2, const basic_string& str);
+    basic_string& replace(const_iterator i1, const_iterator i2, basic_string_view<charT, traits> sv);
     basic_string& replace(const_iterator i1, const_iterator i2, const value_type* s, size_type n);
     basic_string& replace(const_iterator i1, const_iterator i2, const value_type* s);
     basic_string& replace(const_iterator i1, const_iterator i2, size_type n, value_type c);
@@ -232,43 +253,61 @@ public:
     allocator_type get_allocator() const noexcept;
 
     size_type find(const basic_string& str, size_type pos = 0) const noexcept;
+    size_type find(basic_string_view<charT, traits> sv, size_type pos = 0) const noexcept;
     size_type find(const value_type* s, size_type pos, size_type n) const noexcept;
     size_type find(const value_type* s, size_type pos = 0) const noexcept;
     size_type find(value_type c, size_type pos = 0) const noexcept;
 
     size_type rfind(const basic_string& str, size_type pos = npos) const noexcept;
+    size_type rfind(basic_string_view<charT, traits> sv, size_type pos = npos) const noexcept;
     size_type rfind(const value_type* s, size_type pos, size_type n) const noexcept;
     size_type rfind(const value_type* s, size_type pos = npos) const noexcept;
     size_type rfind(value_type c, size_type pos = npos) const noexcept;
 
     size_type find_first_of(const basic_string& str, size_type pos = 0) const noexcept;
+    size_type find_first_of(basic_string_view<charT, traits> sv, size_type pos = 0) const noexcept;
     size_type find_first_of(const value_type* s, size_type pos, size_type n) const noexcept;
     size_type find_first_of(const value_type* s, size_type pos = 0) const noexcept;
     size_type find_first_of(value_type c, size_type pos = 0) const noexcept;
 
     size_type find_last_of(const basic_string& str, size_type pos = npos) const noexcept;
+    size_type find_last_of(basic_string_view<charT, traits> sv, size_type pos = npos) const noexcept;
     size_type find_last_of(const value_type* s, size_type pos, size_type n) const noexcept;
     size_type find_last_of(const value_type* s, size_type pos = npos) const noexcept;
     size_type find_last_of(value_type c, size_type pos = npos) const noexcept;
 
     size_type find_first_not_of(const basic_string& str, size_type pos = 0) const noexcept;
+    size_type find_first_not_of(basic_string_view<charT, traits> sv, size_type pos = 0) const noexcept;
     size_type find_first_not_of(const value_type* s, size_type pos, size_type n) const noexcept;
     size_type find_first_not_of(const value_type* s, size_type pos = 0) const noexcept;
     size_type find_first_not_of(value_type c, size_type pos = 0) const noexcept;
 
     size_type find_last_not_of(const basic_string& str, size_type pos = npos) const noexcept;
+    size_type find_last_not_of(basic_string_view<charT, traits> sv, size_type pos = npos) const noexcept;
     size_type find_last_not_of(const value_type* s, size_type pos, size_type n) const noexcept;
     size_type find_last_not_of(const value_type* s, size_type pos = npos) const noexcept;
     size_type find_last_not_of(value_type c, size_type pos = npos) const noexcept;
 
     int compare(const basic_string& str) const noexcept;
+    int compare(basic_string_view<charT, traits> sv) const noexcept;
     int compare(size_type pos1, size_type n1, const basic_string& str) const;
+    int compare(size_type pos1, size_type n1, basic_string_view<charT, traits> sv) const;
     int compare(size_type pos1, size_type n1, const basic_string& str,
                 size_type pos2, size_type n2=npos) const; // C++14
+    template <class T>
+        int compare(size_type pos1, size_type n1, const T& t,
+                    size_type pos2, size_type n2=npos) const; // C++17
     int compare(const value_type* s) const noexcept;
     int compare(size_type pos1, size_type n1, const value_type* s) const;
     int compare(size_type pos1, size_type n1, const value_type* s, size_type n2) const;
 
+    bool starts_with(basic_string_view<charT, traits> sv) const noexcept; // C++2a
+    bool starts_with(charT c) const noexcept;                             // C++2a
+    bool starts_with(const charT* s) const;                               // C++2a
+    bool ends_with(basic_string_view<charT, traits> sv) const noexcept;   // C++2a
+    bool ends_with(charT c) const noexcept;                               // C++2a
+    bool ends_with(const charT* s) const;                                 // C++2a
+
     bool __invariants() const;
 };
 
@@ -435,6 +474,7 @@ basic_string<char32_t> operator "" s( const char32_t *str, size_t len ); // C++1
 */
 
 #include <__config>
+#include <string_view>
 #include <iosfwd>
 #include <cstring>
 #include <cstdio>  // For EOF.
@@ -450,11 +490,6 @@ basic_string<char32_t> operator "" s( const char32_t *str, size_t len ); // C++1
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
 #include <cstdint>
 #endif
-#if defined(_LIBCPP_NO_EXCEPTIONS)
-#include <cassert>
-#endif
-
-#include <__undef_min_max>
 
 #include <__debug>
 
@@ -462,12 +497,16 @@ basic_string<char32_t> operator "" s( const char32_t *str, size_t len ); // C++1
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 // fpos
 
 template <class _StateT>
-class _LIBCPP_TYPE_VIS_ONLY fpos
+class _LIBCPP_TEMPLATE_VIS fpos
 {
 private:
     _StateT __st_;
@@ -501,647 +540,6 @@ inline _LIBCPP_INLINE_VISIBILITY
 bool operator!=(const fpos<_StateT>& __x, const fpos<_StateT>& __y)
     {return streamoff(__x) != streamoff(__y);}
 
-// char_traits
-
-template <class _CharT>
-struct _LIBCPP_TYPE_VIS_ONLY char_traits
-{
-    typedef _CharT    char_type;
-    typedef int       int_type;
-    typedef streamoff off_type;
-    typedef streampos pos_type;
-    typedef mbstate_t state_type;
-
-    static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
-        {__c1 = __c2;}
-    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
-        {return __c1 == __c2;}
-    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
-        {return __c1 < __c2;}
-
-    static int              compare(const char_type* __s1, const char_type* __s2, size_t __n);
-    _LIBCPP_INLINE_VISIBILITY
-    static size_t           length(const char_type* __s);
-    _LIBCPP_INLINE_VISIBILITY
-    static const char_type* find(const char_type* __s, size_t __n, const char_type& __a);
-    static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n);
-    _LIBCPP_INLINE_VISIBILITY
-    static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n);
-    _LIBCPP_INLINE_VISIBILITY
-    static char_type*       assign(char_type* __s, size_t __n, char_type __a);
-
-    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
-        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
-    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
-        {return char_type(__c);}
-    static inline _LIBCPP_CONSTEXPR int_type  to_int_type(char_type __c) _NOEXCEPT
-        {return int_type(__c);}
-    static inline _LIBCPP_CONSTEXPR bool      eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
-        {return __c1 == __c2;}
-    static inline _LIBCPP_CONSTEXPR int_type  eof() _NOEXCEPT
-        {return int_type(EOF);}
-};
-
-template <class _CharT>
-int
-char_traits<_CharT>::compare(const char_type* __s1, const char_type* __s2, size_t __n)
-{
-    for (; __n; --__n, ++__s1, ++__s2)
-    {
-        if (lt(*__s1, *__s2))
-            return -1;
-        if (lt(*__s2, *__s1))
-            return 1;
-    }
-    return 0;
-}
-
-template <class _CharT>
-inline
-size_t
-char_traits<_CharT>::length(const char_type* __s)
-{
-    size_t __len = 0;
-    for (; !eq(*__s, char_type(0)); ++__s)
-        ++__len;
-    return __len;
-}
-
-template <class _CharT>
-inline
-const _CharT*
-char_traits<_CharT>::find(const char_type* __s, size_t __n, const char_type& __a)
-{
-    for (; __n; --__n)
-    {
-        if (eq(*__s, __a))
-            return __s;
-        ++__s;
-    }
-    return 0;
-}
-
-template <class _CharT>
-_CharT*
-char_traits<_CharT>::move(char_type* __s1, const char_type* __s2, size_t __n)
-{
-    char_type* __r = __s1;
-    if (__s1 < __s2)
-    {
-        for (; __n; --__n, ++__s1, ++__s2)
-            assign(*__s1, *__s2);
-    }
-    else if (__s2 < __s1)
-    {
-        __s1 += __n;
-        __s2 += __n;
-        for (; __n; --__n)
-            assign(*--__s1, *--__s2);
-    }
-    return __r;
-}
-
-template <class _CharT>
-inline
-_CharT*
-char_traits<_CharT>::copy(char_type* __s1, const char_type* __s2, size_t __n)
-{
-    _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
-    char_type* __r = __s1;
-    for (; __n; --__n, ++__s1, ++__s2)
-        assign(*__s1, *__s2);
-    return __r;
-}
-
-template <class _CharT>
-inline
-_CharT*
-char_traits<_CharT>::assign(char_type* __s, size_t __n, char_type __a)
-{
-    char_type* __r = __s;
-    for (; __n; --__n, ++__s)
-        assign(*__s, __a);
-    return __r;
-}
-
-// char_traits<char>
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY char_traits<char>
-{
-    typedef char      char_type;
-    typedef int       int_type;
-    typedef streamoff off_type;
-    typedef streampos pos_type;
-    typedef mbstate_t state_type;
-
-    static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
-        {__c1 = __c2;}
-    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
-            {return __c1 == __c2;}
-    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
-        {return (unsigned char)__c1 < (unsigned char)__c2;}
-
-    static inline int compare(const char_type* __s1, const char_type* __s2, size_t __n)
-        {return __n == 0 ? 0 : memcmp(__s1, __s2, __n);}
-    static inline size_t length(const char_type* __s) {return strlen(__s);}
-    static inline const char_type* find(const char_type* __s, size_t __n, const char_type& __a)
-        {return __n == 0 ? NULL : (const char_type*) memchr(__s, to_int_type(__a), __n);}
-    static inline char_type* move(char_type* __s1, const char_type* __s2, size_t __n)
-        {return __n == 0 ? __s1 : (char_type*) memmove(__s1, __s2, __n);}
-    static inline char_type* copy(char_type* __s1, const char_type* __s2, size_t __n)
-        {
-            _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
-            return __n == 0 ? __s1 : (char_type*)memcpy(__s1, __s2, __n);
-        }
-    static inline char_type* assign(char_type* __s, size_t __n, char_type __a)
-        {return __n == 0 ? __s : (char_type*)memset(__s, to_int_type(__a), __n);}
-
-    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
-        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
-    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
-        {return char_type(__c);}
-    static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
-        {return int_type((unsigned char)__c);}
-    static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
-        {return __c1 == __c2;}
-    static inline _LIBCPP_CONSTEXPR int_type  eof() _NOEXCEPT
-        {return int_type(EOF);}
-};
-
-// char_traits<wchar_t>
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY char_traits<wchar_t>
-{
-    typedef wchar_t   char_type;
-    typedef wint_t    int_type;
-    typedef streamoff off_type;
-    typedef streampos pos_type;
-    typedef mbstate_t state_type;
-
-    static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
-        {__c1 = __c2;}
-    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
-        {return __c1 == __c2;}
-    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
-        {return __c1 < __c2;}
-
-    static inline int compare(const char_type* __s1, const char_type* __s2, size_t __n)
-        {return __n == 0 ? 0 : wmemcmp(__s1, __s2, __n);}
-    static inline size_t length(const char_type* __s)
-        {return wcslen(__s);}
-    static inline const char_type* find(const char_type* __s, size_t __n, const char_type& __a)
-        {return __n == 0 ? NULL : (const char_type*)wmemchr(__s, __a, __n);}
-    static inline char_type* move(char_type* __s1, const char_type* __s2, size_t __n)
-        {return __n == 0 ? __s1 : (char_type*)wmemmove(__s1, __s2, __n);}
-    static inline char_type* copy(char_type* __s1, const char_type* __s2, size_t __n)
-        {
-            _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
-            return __n == 0 ? __s1 : (char_type*)wmemcpy(__s1, __s2, __n);
-        }
-    static inline char_type* assign(char_type* __s, size_t __n, char_type __a)
-        {return __n == 0 ? __s : (char_type*)wmemset(__s, __a, __n);}
-
-    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
-        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
-    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
-        {return char_type(__c);}
-    static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
-        {return int_type(__c);}
-    static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
-        {return __c1 == __c2;}
-    static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
-        {return int_type(WEOF);}
-};
-
-#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY char_traits<char16_t>
-{
-    typedef char16_t       char_type;
-    typedef uint_least16_t int_type;
-    typedef streamoff      off_type;
-    typedef u16streampos   pos_type;
-    typedef mbstate_t      state_type;
-
-    static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
-        {__c1 = __c2;}
-    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
-        {return __c1 == __c2;}
-    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
-        {return __c1 < __c2;}
-
-    _LIBCPP_INLINE_VISIBILITY
-    static int              compare(const char_type* __s1, const char_type* __s2, size_t __n);
-    _LIBCPP_INLINE_VISIBILITY
-    static size_t           length(const char_type* __s);
-    _LIBCPP_INLINE_VISIBILITY
-    static const char_type* find(const char_type* __s, size_t __n, const char_type& __a);
-    _LIBCPP_INLINE_VISIBILITY
-    static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n);
-    _LIBCPP_INLINE_VISIBILITY
-    static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n);
-    _LIBCPP_INLINE_VISIBILITY
-    static char_type*       assign(char_type* __s, size_t __n, char_type __a);
-
-    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
-        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
-    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
-        {return char_type(__c);}
-    static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
-        {return int_type(__c);}
-    static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
-        {return __c1 == __c2;}
-    static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
-        {return int_type(0xFFFF);}
-};
-
-inline
-int
-char_traits<char16_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n)
-{
-    for (; __n; --__n, ++__s1, ++__s2)
-    {
-        if (lt(*__s1, *__s2))
-            return -1;
-        if (lt(*__s2, *__s1))
-            return 1;
-    }
-    return 0;
-}
-
-inline
-size_t
-char_traits<char16_t>::length(const char_type* __s)
-{
-    size_t __len = 0;
-    for (; !eq(*__s, char_type(0)); ++__s)
-        ++__len;
-    return __len;
-}
-
-inline
-const char16_t*
-char_traits<char16_t>::find(const char_type* __s, size_t __n, const char_type& __a)
-{
-    for (; __n; --__n)
-    {
-        if (eq(*__s, __a))
-            return __s;
-        ++__s;
-    }
-    return 0;
-}
-
-inline
-char16_t*
-char_traits<char16_t>::move(char_type* __s1, const char_type* __s2, size_t __n)
-{
-    char_type* __r = __s1;
-    if (__s1 < __s2)
-    {
-        for (; __n; --__n, ++__s1, ++__s2)
-            assign(*__s1, *__s2);
-    }
-    else if (__s2 < __s1)
-    {
-        __s1 += __n;
-        __s2 += __n;
-        for (; __n; --__n)
-            assign(*--__s1, *--__s2);
-    }
-    return __r;
-}
-
-inline
-char16_t*
-char_traits<char16_t>::copy(char_type* __s1, const char_type* __s2, size_t __n)
-{
-    _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
-    char_type* __r = __s1;
-    for (; __n; --__n, ++__s1, ++__s2)
-        assign(*__s1, *__s2);
-    return __r;
-}
-
-inline
-char16_t*
-char_traits<char16_t>::assign(char_type* __s, size_t __n, char_type __a)
-{
-    char_type* __r = __s;
-    for (; __n; --__n, ++__s)
-        assign(*__s, __a);
-    return __r;
-}
-
-template <>
-struct _LIBCPP_TYPE_VIS_ONLY char_traits<char32_t>
-{
-    typedef char32_t       char_type;
-    typedef uint_least32_t int_type;
-    typedef streamoff      off_type;
-    typedef u32streampos   pos_type;
-    typedef mbstate_t      state_type;
-
-    static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
-        {__c1 = __c2;}
-    static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
-        {return __c1 == __c2;}
-    static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
-        {return __c1 < __c2;}
-
-    _LIBCPP_INLINE_VISIBILITY
-    static int              compare(const char_type* __s1, const char_type* __s2, size_t __n);
-    _LIBCPP_INLINE_VISIBILITY
-    static size_t           length(const char_type* __s);
-    _LIBCPP_INLINE_VISIBILITY
-    static const char_type* find(const char_type* __s, size_t __n, const char_type& __a);
-    _LIBCPP_INLINE_VISIBILITY
-    static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n);
-    _LIBCPP_INLINE_VISIBILITY
-    static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n);
-    _LIBCPP_INLINE_VISIBILITY
-    static char_type*       assign(char_type* __s, size_t __n, char_type __a);
-
-    static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
-        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
-    static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
-        {return char_type(__c);}
-    static inline _LIBCPP_CONSTEXPR int_type to_int_type(char_type __c) _NOEXCEPT
-        {return int_type(__c);}
-    static inline _LIBCPP_CONSTEXPR bool eq_int_type(int_type __c1, int_type __c2) _NOEXCEPT
-        {return __c1 == __c2;}
-    static inline _LIBCPP_CONSTEXPR int_type eof() _NOEXCEPT
-        {return int_type(0xFFFFFFFF);}
-};
-
-inline
-int
-char_traits<char32_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n)
-{
-    for (; __n; --__n, ++__s1, ++__s2)
-    {
-        if (lt(*__s1, *__s2))
-            return -1;
-        if (lt(*__s2, *__s1))
-            return 1;
-    }
-    return 0;
-}
-
-inline
-size_t
-char_traits<char32_t>::length(const char_type* __s)
-{
-    size_t __len = 0;
-    for (; !eq(*__s, char_type(0)); ++__s)
-        ++__len;
-    return __len;
-}
-
-inline
-const char32_t*
-char_traits<char32_t>::find(const char_type* __s, size_t __n, const char_type& __a)
-{
-    for (; __n; --__n)
-    {
-        if (eq(*__s, __a))
-            return __s;
-        ++__s;
-    }
-    return 0;
-}
-
-inline
-char32_t*
-char_traits<char32_t>::move(char_type* __s1, const char_type* __s2, size_t __n)
-{
-    char_type* __r = __s1;
-    if (__s1 < __s2)
-    {
-        for (; __n; --__n, ++__s1, ++__s2)
-            assign(*__s1, *__s2);
-    }
-    else if (__s2 < __s1)
-    {
-        __s1 += __n;
-        __s2 += __n;
-        for (; __n; --__n)
-            assign(*--__s1, *--__s2);
-    }
-    return __r;
-}
-
-inline
-char32_t*
-char_traits<char32_t>::copy(char_type* __s1, const char_type* __s2, size_t __n)
-{
-    _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
-    char_type* __r = __s1;
-    for (; __n; --__n, ++__s1, ++__s2)
-        assign(*__s1, *__s2);
-    return __r;
-}
-
-inline
-char32_t*
-char_traits<char32_t>::assign(char_type* __s, size_t __n, char_type __a)
-{
-    char_type* __r = __s;
-    for (; __n; --__n, ++__s)
-        assign(*__s, __a);
-    return __r;
-}
-
-#endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
-
-// helper fns for basic_string
-
-// __str_find
-template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
-inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_find(const _CharT *__p, _SizeT __sz, 
-             _CharT __c, _SizeT __pos) _NOEXCEPT
-{
-    if (__pos >= __sz)
-        return __npos;
-    const _CharT* __r = _Traits::find(__p + __pos, __sz - __pos, __c);
-    if (__r == 0)
-        return __npos;
-    return static_cast<_SizeT>(__r - __p);
-}
-
-template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
-inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_find(const _CharT *__p, _SizeT __sz, 
-       const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
-{
-    if (__pos > __sz || __sz - __pos < __n)
-        return __npos;
-    if (__n == 0)
-        return __pos;
-    const _CharT* __r = 
-        _VSTD::__search(__p + __pos, __p + __sz,
-                        __s, __s + __n, _Traits::eq,
-                        random_access_iterator_tag(), random_access_iterator_tag()).first;
-    if (__r == __p + __sz)
-        return __npos;
-    return static_cast<_SizeT>(__r - __p);
-}
-
-
-// __str_rfind
-
-template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
-inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_rfind(const _CharT *__p, _SizeT __sz, 
-              _CharT __c, _SizeT __pos) _NOEXCEPT
-{
-    if (__sz < 1)
-        return __npos;
-    if (__pos < __sz)
-        ++__pos;
-    else
-        __pos = __sz;
-    for (const _CharT* __ps = __p + __pos; __ps != __p;)
-    {
-        if (_Traits::eq(*--__ps, __c))
-            return static_cast<_SizeT>(__ps - __p);
-    }
-    return __npos;
-}
-
-template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
-inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_rfind(const _CharT *__p, _SizeT __sz, 
-        const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
-{
-    __pos = _VSTD::min(__pos, __sz);
-    if (__n < __sz - __pos)
-        __pos += __n;
-    else
-        __pos = __sz;
-    const _CharT* __r = _VSTD::__find_end(
-                  __p, __p + __pos, __s, __s + __n, _Traits::eq, 
-                        random_access_iterator_tag(), random_access_iterator_tag());
-    if (__n > 0 && __r == __p + __pos)
-        return __npos;
-    return static_cast<_SizeT>(__r - __p);
-}
-
-// __str_find_first_of
-template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
-inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_find_first_of(const _CharT *__p, _SizeT __sz,
-                const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
-{
-    if (__pos >= __sz || __n == 0)
-        return __npos;
-    const _CharT* __r = _VSTD::__find_first_of_ce
-        (__p + __pos, __p + __sz, __s, __s + __n, _Traits::eq );
-    if (__r == __p + __sz)
-        return __npos;
-    return static_cast<_SizeT>(__r - __p);
-}
-
-
-// __str_find_last_of
-template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
-inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_find_last_of(const _CharT *__p, _SizeT __sz,
-               const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
-    {
-    if (__n != 0)
-    {
-        if (__pos < __sz)
-            ++__pos;
-        else
-            __pos = __sz;
-        for (const _CharT* __ps = __p + __pos; __ps != __p;)
-        {
-            const _CharT* __r = _Traits::find(__s, __n, *--__ps);
-            if (__r)
-                return static_cast<_SizeT>(__ps - __p);
-        }
-    }
-    return __npos;
-}
-
-
-// __str_find_first_not_of
-template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
-inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_find_first_not_of(const _CharT *__p, _SizeT __sz,
-                    const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
-{
-    if (__pos < __sz)
-    {
-        const _CharT* __pe = __p + __sz;
-        for (const _CharT* __ps = __p + __pos; __ps != __pe; ++__ps)
-            if (_Traits::find(__s, __n, *__ps) == 0)
-                return static_cast<_SizeT>(__ps - __p);
-    }
-    return __npos;
-}
-
-
-template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
-inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_find_first_not_of(const _CharT *__p, _SizeT __sz,
-                          _CharT __c, _SizeT __pos) _NOEXCEPT
-{
-    if (__pos < __sz)
-    {
-        const _CharT* __pe = __p + __sz;
-        for (const _CharT* __ps = __p + __pos; __ps != __pe; ++__ps)
-            if (!_Traits::eq(*__ps, __c))
-                return static_cast<_SizeT>(__ps - __p);
-    }
-    return __npos;
-}
-
-
-// __str_find_last_not_of
-template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
-inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_find_last_not_of(const _CharT *__p, _SizeT __sz,
-                   const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
-{
-    if (__pos < __sz)
-        ++__pos;
-    else
-        __pos = __sz;
-    for (const _CharT* __ps = __p + __pos; __ps != __p;)
-        if (_Traits::find(__s, __n, *--__ps) == 0)
-            return static_cast<_SizeT>(__ps - __p);
-    return __npos;
-}
-
-
-template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
-inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_find_last_not_of(const _CharT *__p, _SizeT __sz,
-                         _CharT __c, _SizeT __pos) _NOEXCEPT
-{
-    if (__pos < __sz)
-        ++__pos;
-    else
-        __pos = __sz;
-    for (const _CharT* __ps = __p + __pos; __ps != __p;)
-        if (!_Traits::eq(*--__ps, __c))
-            return static_cast<_SizeT>(__ps - __p);
-    return __npos;
-}
-
-template<class _Ptr>
-size_t _LIBCPP_INLINE_VISIBILITY __do_string_hash(_Ptr __p, _Ptr __e)
-{
-    typedef typename iterator_traits<_Ptr>::value_type value_type;
-    return __murmur2_or_cityhash<size_t>()(__p, (__e-__p)*sizeof(value_type));
-}
-
 // basic_string
 
 template<class _CharT, class _Traits, class _Allocator>
@@ -1165,44 +563,31 @@ template<class _CharT, class _Traits, class _Allocator>
 basic_string<_CharT, _Traits, _Allocator>
 operator+(const basic_string<_CharT, _Traits, _Allocator>& __x, _CharT __y);
 
+_LIBCPP_EXTERN_TEMPLATE(_LIBCPP_FUNC_VIS string operator+<char, char_traits<char>, allocator<char> >(char const*, string const&))
+
 template <bool>
-class _LIBCPP_TYPE_VIS_ONLY __basic_string_common
+class _LIBCPP_TEMPLATE_VIS __basic_string_common
 {
 protected:
-    void __throw_length_error() const;
-    void __throw_out_of_range() const;
+    _LIBCPP_NORETURN void __throw_length_error() const;
+    _LIBCPP_NORETURN void __throw_out_of_range() const;
 };
 
 template <bool __b>
 void
 __basic_string_common<__b>::__throw_length_error() const
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    throw length_error("basic_string");
-#else
-    assert(!"basic_string length_error");
-#endif
+    _VSTD::__throw_length_error("basic_string");
 }
 
 template <bool __b>
 void
 __basic_string_common<__b>::__throw_out_of_range() const
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    throw out_of_range("basic_string");
-#else
-    assert(!"basic_string out_of_range");
-#endif
+    _VSTD::__throw_out_of_range("basic_string");
 }
 
-#ifdef _LIBCPP_MSVC
-#pragma warning( push )
-#pragma warning( disable: 4231 )
-#endif // _LIBCPP_MSVC
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS __basic_string_common<true>)
-#ifdef _LIBCPP_MSVC
-#pragma warning( pop )
-#endif // _LIBCPP_MSVC
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __basic_string_common<true>)
 
 #ifdef _LIBCPP_NO_EXCEPTIONS
 template <class _Iter>
@@ -1228,6 +613,11 @@ template <class _Iter>
 struct __libcpp_string_gets_noexcept_iterator
     : public _LIBCPP_BOOL_CONSTANT(__libcpp_is_trivial_iterator<_Iter>::value || __libcpp_string_gets_noexcept_iterator_impl<_Iter>::value) {};
 
+template <class _CharT, class _Traits, class _Tp>
+struct __can_be_converted_to_string_view : public _LIBCPP_BOOL_CONSTANT(
+    ( is_convertible<const _Tp&, basic_string_view<_CharT, _Traits> >::value &&
+     !is_convertible<const _Tp&, const _CharT*>::value)) {};
+
 #ifdef _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
 
 template <class _CharT, size_t = sizeof(_CharT)>
@@ -1244,13 +634,14 @@ struct __padding<_CharT, 1>
 #endif  // _LIBCPP_ABI_ALTERNATE_STRING_LAYOUT
 
 template<class _CharT, class _Traits, class _Allocator>
-class _LIBCPP_TYPE_VIS_ONLY basic_string
+class _LIBCPP_TEMPLATE_VIS basic_string
     : private __basic_string_common<true>
 {
 public:
     typedef basic_string                                 __self;
+    typedef basic_string_view<_CharT, _Traits>           __self_view;
     typedef _Traits                                      traits_type;
-    typedef typename traits_type::char_type              value_type;
+    typedef _CharT                                       value_type;
     typedef _Allocator                                   allocator_type;
     typedef allocator_traits<allocator_type>             __alloc_traits;
     typedef typename __alloc_traits::size_type           size_type;
@@ -1261,7 +652,7 @@ public:
     typedef typename __alloc_traits::const_pointer       const_pointer;
 
     static_assert(is_pod<value_type>::value, "Character type of basic_string must be a POD");
-    static_assert((is_same<_CharT, value_type>::value),
+    static_assert((is_same<_CharT, typename traits_type::char_type>::value),
                   "traits_type::char_type must be the same type as CharT");
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
@@ -1286,12 +677,12 @@ private:
         size_type __cap_;
     };
 
-#if _LIBCPP_BIG_ENDIAN
-    enum {__short_mask = 0x01};
-    enum {__long_mask  = 0x1ul};
+#ifdef _LIBCPP_BIG_ENDIAN
+    static const size_type __short_mask = 0x01;
+    static const size_type __long_mask  = 0x1ul;
 #else  // _LIBCPP_BIG_ENDIAN
-    enum {__short_mask = 0x80};
-    enum {__long_mask  = ~(size_type(~0) >> 1)};
+    static const size_type __short_mask = 0x80;
+    static const size_type __long_mask  = ~(size_type(~0) >> 1);
 #endif  // _LIBCPP_BIG_ENDIAN
 
     enum {__min_cap = (sizeof(__long) - 1)/sizeof(value_type) > 2 ?
@@ -1316,12 +707,12 @@ private:
         pointer   __data_;
     };
 
-#if _LIBCPP_BIG_ENDIAN
-    enum {__short_mask = 0x80};
-    enum {__long_mask  = ~(size_type(~0) >> 1)};
+#ifdef _LIBCPP_BIG_ENDIAN
+    static const size_type __short_mask = 0x80;
+    static const size_type __long_mask  = ~(size_type(~0) >> 1);
 #else  // _LIBCPP_BIG_ENDIAN
-    enum {__short_mask = 0x01};
-    enum {__long_mask  = 0x1ul};
+    static const size_type __short_mask = 0x01;
+    static const size_type __long_mask  = 0x1ul;
 #endif  // _LIBCPP_BIG_ENDIAN
 
     enum {__min_cap = (sizeof(__long) - 1)/sizeof(value_type) > 2 ?
@@ -1376,7 +767,7 @@ public:
     basic_string(const basic_string& __str);
     basic_string(const basic_string& __str, const allocator_type& __a);
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_string(basic_string&& __str)
 #if _LIBCPP_STD_VER <= 14
@@ -1387,50 +778,66 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     basic_string(basic_string&& __str, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    _LIBCPP_INLINE_VISIBILITY basic_string(const value_type* __s);
+#endif  // _LIBCPP_CXX03_LANG
+    _LIBCPP_INLINE_VISIBILITY basic_string(const _CharT* __s);
     _LIBCPP_INLINE_VISIBILITY
-    basic_string(const value_type* __s, const allocator_type& __a);
+    basic_string(const _CharT* __s, const _Allocator& __a);
     _LIBCPP_INLINE_VISIBILITY
-    basic_string(const value_type* __s, size_type __n);
+    basic_string(const _CharT* __s, size_type __n);
     _LIBCPP_INLINE_VISIBILITY
-    basic_string(const value_type* __s, size_type __n, const allocator_type& __a);
+    basic_string(const _CharT* __s, size_type __n, const _Allocator& __a);
     _LIBCPP_INLINE_VISIBILITY
-    basic_string(size_type __n, value_type __c);
+    basic_string(size_type __n, _CharT __c);
     _LIBCPP_INLINE_VISIBILITY
-    basic_string(size_type __n, value_type __c, const allocator_type& __a);
+    basic_string(size_type __n, _CharT __c, const _Allocator& __a);
     basic_string(const basic_string& __str, size_type __pos, size_type __n,
-                 const allocator_type& __a = allocator_type());
+                 const _Allocator& __a = _Allocator());
     _LIBCPP_INLINE_VISIBILITY
     basic_string(const basic_string& __str, size_type __pos,
-                 const allocator_type& __a = allocator_type());
+                 const _Allocator& __a = _Allocator());
+    template<class _Tp>
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+        basic_string(const _Tp& __t, size_type __pos, size_type __n,
+                     const allocator_type& __a = allocator_type(),
+                     typename enable_if<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value, void>::type* = 0);
+    _LIBCPP_INLINE_VISIBILITY explicit
+    basic_string(__self_view __sv);
+    _LIBCPP_INLINE_VISIBILITY
+    basic_string(__self_view __sv, const _Allocator& __a);
     template<class _InputIterator>
         _LIBCPP_INLINE_VISIBILITY
         basic_string(_InputIterator __first, _InputIterator __last);
     template<class _InputIterator>
         _LIBCPP_INLINE_VISIBILITY
         basic_string(_InputIterator __first, _InputIterator __last, const allocator_type& __a);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
-    basic_string(initializer_list<value_type> __il);
+    basic_string(initializer_list<_CharT> __il);
     _LIBCPP_INLINE_VISIBILITY
-    basic_string(initializer_list<value_type> __il, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+    basic_string(initializer_list<_CharT> __il, const _Allocator& __a);
+#endif  // _LIBCPP_CXX03_LANG
 
-    ~basic_string();
+    inline ~basic_string();
+
+    _LIBCPP_INLINE_VISIBILITY
+    operator __self_view() const _NOEXCEPT { return __self_view(data(), size()); }
 
     basic_string& operator=(const basic_string& __str);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
+#ifndef _LIBCPP_CXX03_LANG
+    template <class = void>
+#endif
+    _LIBCPP_INLINE_VISIBILITY
+    basic_string& operator=(__self_view __sv)  {return assign(__sv);}
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_string& operator=(basic_string&& __str)
         _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value));
+     _LIBCPP_INLINE_VISIBILITY
+    basic_string& operator=(initializer_list<value_type> __il) {return assign(__il.begin(), __il.size());}
 #endif
     _LIBCPP_INLINE_VISIBILITY basic_string& operator=(const value_type* __s) {return assign(__s);}
     basic_string& operator=(value_type __c);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-    _LIBCPP_INLINE_VISIBILITY
-    basic_string& operator=(initializer_list<value_type> __il) {return assign(__il.begin(), __il.size());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
 #if _LIBCPP_DEBUG_LEVEL >= 2
     _LIBCPP_INLINE_VISIBILITY
@@ -1496,52 +903,78 @@ public:
     void resize(size_type __n, value_type __c);
     _LIBCPP_INLINE_VISIBILITY void resize(size_type __n) {resize(__n, value_type());}
 
-    void reserve(size_type res_arg = 0);
+    void reserve(size_type __res_arg = 0);
     _LIBCPP_INLINE_VISIBILITY
     void shrink_to_fit() _NOEXCEPT {reserve();}
     _LIBCPP_INLINE_VISIBILITY
     void clear() _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY bool empty() const _NOEXCEPT {return size() == 0;}
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
+    bool empty() const _NOEXCEPT {return size() == 0;}
 
-    _LIBCPP_INLINE_VISIBILITY const_reference operator[](size_type __pos) const;
-    _LIBCPP_INLINE_VISIBILITY reference       operator[](size_type __pos);
+    _LIBCPP_INLINE_VISIBILITY const_reference operator[](size_type __pos) const _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY reference       operator[](size_type __pos)       _NOEXCEPT;
 
     const_reference at(size_type __n) const;
     reference       at(size_type __n);
 
     _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(const basic_string& __str) {return append(__str);}
-    _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(const value_type* __s)         {return append(__s);}
+    _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(__self_view __sv)          {return append(__sv);}
+    _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(const value_type* __s)     {return append(__s);}
     _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(value_type __c)            {push_back(__c); return *this;}
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY basic_string& operator+=(initializer_list<value_type> __il) {return append(__il);}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     basic_string& append(const basic_string& __str);
+    _LIBCPP_INLINE_VISIBILITY
+    basic_string& append(__self_view __sv) { return append(__sv.data(), __sv.size()); }
     basic_string& append(const basic_string& __str, size_type __pos, size_type __n=npos);
+    template <class _Tp>
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    typename enable_if
+        <
+            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
+            basic_string&
+        >::type
+                  append(const _Tp& __t, size_type __pos, size_type __n=npos);
     basic_string& append(const value_type* __s, size_type __n);
     basic_string& append(const value_type* __s);
     basic_string& append(size_type __n, value_type __c);
+    template <class _ForwardIterator>
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    basic_string& __append_forward_unsafe(_ForwardIterator, _ForwardIterator);
     template<class _InputIterator>
-        typename enable_if
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    typename enable_if
         <
             __is_exactly_input_iterator<_InputIterator>::value
                 || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
             basic_string&
         >::type
-        append(_InputIterator __first, _InputIterator __last);
+    _LIBCPP_INLINE_VISIBILITY
+    append(_InputIterator __first, _InputIterator __last) {
+      const basic_string __temp (__first, __last, __alloc());
+      append(__temp.data(), __temp.size());
+      return *this;
+    }
     template<class _ForwardIterator>
-        typename enable_if
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    typename enable_if
         <
             __is_forward_iterator<_ForwardIterator>::value
                 && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
             basic_string&
         >::type
-        append(_ForwardIterator __first, _ForwardIterator __last);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+    _LIBCPP_INLINE_VISIBILITY
+    append(_ForwardIterator __first, _ForwardIterator __last) {
+      return __append_forward_unsafe(__first, __last);
+    }
+
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_string& append(initializer_list<value_type> __il) {return append(__il.begin(), __il.size());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     void push_back(value_type __c);
     _LIBCPP_INLINE_VISIBILITY
@@ -1552,19 +985,30 @@ public:
     _LIBCPP_INLINE_VISIBILITY const_reference back() const;
 
     _LIBCPP_INLINE_VISIBILITY
+    basic_string& assign(__self_view __sv) { return assign(__sv.data(), __sv.size()); }
+    _LIBCPP_INLINE_VISIBILITY
     basic_string& assign(const basic_string& __str) { return *this = __str; }
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
-    basic_string& assign(basic_string&& str)
+    basic_string& assign(basic_string&& __str)
         _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value))
-        {*this = _VSTD::move(str); return *this;}
+        {*this = _VSTD::move(__str); return *this;}
 #endif
     basic_string& assign(const basic_string& __str, size_type __pos, size_type __n=npos);
+    template <class _Tp>
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    typename enable_if
+        <
+            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
+            basic_string&
+        >::type
+                  assign(const _Tp & __t, size_type __pos, size_type __n=npos);
     basic_string& assign(const value_type* __s, size_type __n);
     basic_string& assign(const value_type* __s);
     basic_string& assign(size_type __n, value_type __c);
     template<class _InputIterator>
-        typename enable_if
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    typename enable_if
         <
            __is_exactly_input_iterator<_InputIterator>::value
                 || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
@@ -1572,20 +1016,31 @@ public:
         >::type
         assign(_InputIterator __first, _InputIterator __last);
     template<class _ForwardIterator>
-        typename enable_if
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    typename enable_if
         <
             __is_forward_iterator<_ForwardIterator>::value
                  && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
             basic_string&
         >::type
         assign(_ForwardIterator __first, _ForwardIterator __last);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_string& assign(initializer_list<value_type> __il) {return assign(__il.begin(), __il.size());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     basic_string& insert(size_type __pos1, const basic_string& __str);
+    _LIBCPP_INLINE_VISIBILITY
+    basic_string& insert(size_type __pos1, __self_view __sv) { return insert(__pos1, __sv.data(), __sv.size()); }
+    template <class _Tp>
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    typename enable_if
+        <
+            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
+            basic_string&
+        >::type
+                  insert(size_type __pos1, const _Tp& __t, size_type __pos2, size_type __n=npos);
     basic_string& insert(size_type __pos1, const basic_string& __str, size_type __pos2, size_type __n=npos);
     basic_string& insert(size_type __pos, const value_type* __s, size_type __n);
     basic_string& insert(size_type __pos, const value_type* __s);
@@ -1594,7 +1049,8 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     iterator      insert(const_iterator __pos, size_type __n, value_type __c);
     template<class _InputIterator>
-        typename enable_if
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    typename enable_if
         <
            __is_exactly_input_iterator<_InputIterator>::value
                 || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
@@ -1602,18 +1058,19 @@ public:
         >::type
         insert(const_iterator __pos, _InputIterator __first, _InputIterator __last);
     template<class _ForwardIterator>
-        typename enable_if
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    typename enable_if
         <
             __is_forward_iterator<_ForwardIterator>::value
                  && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
             iterator
         >::type
         insert(const_iterator __pos, _ForwardIterator __first, _ForwardIterator __last);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     iterator insert(const_iterator __pos, initializer_list<value_type> __il)
                     {return insert(__pos, __il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     basic_string& erase(size_type __pos = 0, size_type __n = npos);
     _LIBCPP_INLINE_VISIBILITY
@@ -1623,30 +1080,43 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     basic_string& replace(size_type __pos1, size_type __n1, const basic_string& __str);
+    _LIBCPP_INLINE_VISIBILITY
+    basic_string& replace(size_type __pos1, size_type __n1, __self_view __sv) { return replace(__pos1, __n1, __sv.data(), __sv.size()); }
     basic_string& replace(size_type __pos1, size_type __n1, const basic_string& __str, size_type __pos2, size_type __n2=npos);
+    template <class _Tp>
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    typename enable_if
+        <
+            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
+            basic_string&
+        >::type
+                  replace(size_type __pos1, size_type __n1, const _Tp& __t, size_type __pos2, size_type __n2=npos);
     basic_string& replace(size_type __pos, size_type __n1, const value_type* __s, size_type __n2);
     basic_string& replace(size_type __pos, size_type __n1, const value_type* __s);
     basic_string& replace(size_type __pos, size_type __n1, size_type __n2, value_type __c);
     _LIBCPP_INLINE_VISIBILITY
     basic_string& replace(const_iterator __i1, const_iterator __i2, const basic_string& __str);
     _LIBCPP_INLINE_VISIBILITY
+    basic_string& replace(const_iterator __i1, const_iterator __i2, __self_view __sv) { return replace(__i1 - begin(), __i2 - __i1, __sv); }
+    _LIBCPP_INLINE_VISIBILITY
     basic_string& replace(const_iterator __i1, const_iterator __i2, const value_type* __s, size_type __n);
     _LIBCPP_INLINE_VISIBILITY
     basic_string& replace(const_iterator __i1, const_iterator __i2, const value_type* __s);
     _LIBCPP_INLINE_VISIBILITY
     basic_string& replace(const_iterator __i1, const_iterator __i2, size_type __n, value_type __c);
     template<class _InputIterator>
-        typename enable_if
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    typename enable_if
         <
             __is_input_iterator<_InputIterator>::value,
             basic_string&
         >::type
         replace(const_iterator __i1, const_iterator __i2, _InputIterator __j1, _InputIterator __j2);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_string& replace(const_iterator __i1, const_iterator __i2, initializer_list<value_type> __il)
         {return replace(__i1, __i2, __il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     size_type copy(value_type* __s, size_type __n, size_type __pos = 0) const;
     _LIBCPP_INLINE_VISIBILITY
@@ -1655,9 +1125,9 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     void swap(basic_string& __str)
 #if _LIBCPP_STD_VER >= 14
-        _NOEXCEPT;
+        _NOEXCEPT_DEBUG;
 #else
-        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value || 
+        _NOEXCEPT_DEBUG_(!__alloc_traits::propagate_on_container_swap::value ||
                     __is_nothrow_swappable<allocator_type>::value);
 #endif
 
@@ -1665,7 +1135,7 @@ public:
     const value_type* c_str() const _NOEXCEPT {return data();}
     _LIBCPP_INLINE_VISIBILITY
     const value_type* data() const _NOEXCEPT  {return _VSTD::__to_raw_pointer(__get_pointer());}
-#if _LIBCPP_STD_VER > 14
+#if _LIBCPP_STD_VER > 14 || defined(_LIBCPP_BUILDING_LIBRARY)
     _LIBCPP_INLINE_VISIBILITY
     value_type* data()             _NOEXCEPT  {return _VSTD::__to_raw_pointer(__get_pointer());}
 #endif
@@ -1675,6 +1145,8 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     size_type find(const basic_string& __str, size_type __pos = 0) const _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    size_type find(__self_view __sv, size_type __pos = 0) const _NOEXCEPT;
     size_type find(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     size_type find(const value_type* __s, size_type __pos = 0) const _NOEXCEPT;
@@ -1682,6 +1154,8 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     size_type rfind(const basic_string& __str, size_type __pos = npos) const _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    size_type rfind(__self_view __sv, size_type __pos = npos) const _NOEXCEPT;
     size_type rfind(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     size_type rfind(const value_type* __s, size_type __pos = npos) const _NOEXCEPT;
@@ -1689,6 +1163,8 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     size_type find_first_of(const basic_string& __str, size_type __pos = 0) const _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    size_type find_first_of(__self_view __sv, size_type __pos = 0) const _NOEXCEPT;
     size_type find_first_of(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     size_type find_first_of(const value_type* __s, size_type __pos = 0) const _NOEXCEPT;
@@ -1697,6 +1173,8 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     size_type find_last_of(const basic_string& __str, size_type __pos = npos) const _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    size_type find_last_of(__self_view __sv, size_type __pos = npos) const _NOEXCEPT;
     size_type find_last_of(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     size_type find_last_of(const value_type* __s, size_type __pos = npos) const _NOEXCEPT;
@@ -1705,6 +1183,8 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     size_type find_first_not_of(const basic_string& __str, size_type __pos = 0) const _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    size_type find_first_not_of(__self_view __sv, size_type __pos = 0) const _NOEXCEPT;
     size_type find_first_not_of(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     size_type find_first_not_of(const value_type* __s, size_type __pos = 0) const _NOEXCEPT;
@@ -1713,6 +1193,8 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     size_type find_last_not_of(const basic_string& __str, size_type __pos = npos) const _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    size_type find_last_not_of(__self_view __sv, size_type __pos = npos) const _NOEXCEPT;
     size_type find_last_not_of(const value_type* __s, size_type __pos, size_type __n) const _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
     size_type find_last_not_of(const value_type* __s, size_type __pos = npos) const _NOEXCEPT;
@@ -1722,12 +1204,50 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     int compare(const basic_string& __str) const _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
+    int compare(__self_view __sv) const _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY
+    int compare(size_type __pos1, size_type __n1, __self_view __sv) const;
+    _LIBCPP_INLINE_VISIBILITY
     int compare(size_type __pos1, size_type __n1, const basic_string& __str) const;
     int compare(size_type __pos1, size_type __n1, const basic_string& __str, size_type __pos2, size_type __n2=npos) const;
+    template <class _Tp>
+    inline _LIBCPP_INLINE_VISIBILITY
+        typename enable_if
+        <
+            __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
+            int
+        >::type
+        compare(size_type __pos1, size_type __n1, const _Tp& __t, size_type __pos2, size_type __n2=npos) const;
     int compare(const value_type* __s) const _NOEXCEPT;
     int compare(size_type __pos1, size_type __n1, const value_type* __s) const;
     int compare(size_type __pos1, size_type __n1, const value_type* __s, size_type __n2) const;
 
+#if _LIBCPP_STD_VER > 17
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool starts_with(__self_view __sv) const _NOEXCEPT
+    { return __self_view(data(), size()).starts_with(__sv); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool starts_with(value_type __c) const _NOEXCEPT
+    { return !empty() && _Traits::eq(front(), __c); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool starts_with(const value_type* __s) const _NOEXCEPT
+    { return starts_with(__self_view(__s)); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool ends_with(__self_view __sv) const _NOEXCEPT
+    { return __self_view(data(), size()).ends_with( __sv); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool ends_with(value_type __c) const _NOEXCEPT
+    { return !empty() && _Traits::eq(back(), __c); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool ends_with(const value_type* __s) const _NOEXCEPT
+    { return ends_with(__self_view(__s)); }
+#endif
+
     _LIBCPP_INLINE_VISIBILITY bool __invariants() const;
 
     _LIBCPP_INLINE_VISIBILITY
@@ -1755,7 +1275,7 @@ private:
 
     _LIBCPP_INLINE_VISIBILITY
     void __set_short_size(size_type __s) _NOEXCEPT
-#   if _LIBCPP_BIG_ENDIAN
+#   ifdef _LIBCPP_BIG_ENDIAN
         {__r_.first().__s.__size_ = (unsigned char)(__s << 1);}
 #   else
         {__r_.first().__s.__size_ = (unsigned char)(__s);}
@@ -1763,7 +1283,7 @@ private:
 
     _LIBCPP_INLINE_VISIBILITY
     size_type __get_short_size() const _NOEXCEPT
-#   if _LIBCPP_BIG_ENDIAN
+#   ifdef _LIBCPP_BIG_ENDIAN
         {return __r_.first().__s.__size_ >> 1;}
 #   else
         {return __r_.first().__s.__size_;}
@@ -1773,7 +1293,7 @@ private:
 
     _LIBCPP_INLINE_VISIBILITY
     void __set_short_size(size_type __s) _NOEXCEPT
-#   if _LIBCPP_BIG_ENDIAN
+#   ifdef _LIBCPP_BIG_ENDIAN
         {__r_.first().__s.__size_ = (unsigned char)(__s);}
 #   else
         {__r_.first().__s.__size_ = (unsigned char)(__s << 1);}
@@ -1781,7 +1301,7 @@ private:
 
     _LIBCPP_INLINE_VISIBILITY
     size_type __get_short_size() const _NOEXCEPT
-#   if _LIBCPP_BIG_ENDIAN
+#   ifdef _LIBCPP_BIG_ENDIAN
         {return __r_.first().__s.__size_;}
 #   else
         {return __r_.first().__s.__size_ >> 1;}
@@ -1847,11 +1367,15 @@ private:
                  __align_it<sizeof(value_type) < __alignment ?
                             __alignment/sizeof(value_type) : 1 > (__s+1)) - 1;}
 
+    inline
     void __init(const value_type* __s, size_type __sz, size_type __reserve);
+    inline
     void __init(const value_type* __s, size_type __sz);
+    inline
     void __init(size_type __n, value_type __c);
 
     template <class _InputIterator>
+    inline
     typename enable_if
     <
         __is_exactly_input_iterator<_InputIterator>::value,
@@ -1860,6 +1384,7 @@ private:
     __init(_InputIterator __first, _InputIterator __last);
 
     template <class _ForwardIterator>
+    inline
     typename enable_if
     <
         __is_forward_iterator<_ForwardIterator>::value,
@@ -1884,19 +1409,35 @@ private:
     _LIBCPP_INLINE_VISIBILITY
     void __copy_assign_alloc(const basic_string& __str, true_type)
         {
-            if (__alloc() != __str.__alloc())
+            if (__alloc() == __str.__alloc())
+                __alloc() = __str.__alloc();
+            else
             {
-                clear();
-                shrink_to_fit();
+                if (!__str.__is_long())
+                {
+                    clear();
+                    shrink_to_fit();
+                    __alloc() = __str.__alloc();
+                }
+                else
+                {
+                    allocator_type __a = __str.__alloc();
+                    pointer __p = __alloc_traits::allocate(__a, __str.__get_long_cap());
+                    clear();
+                    shrink_to_fit();
+                    __alloc() = _VSTD::move(__a);
+                    __set_long_pointer(__p);
+                    __set_long_cap(__str.__get_long_cap());
+                    __set_long_size(__str.size());
+                }
             }
-            __alloc() = __str.__alloc();
         }
 
     _LIBCPP_INLINE_VISIBILITY
     void __copy_assign_alloc(const basic_string&, false_type) _NOEXCEPT
         {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void __move_assign(basic_string& __str, false_type)
         _NOEXCEPT_(__alloc_traits::is_always_equal::value);
@@ -1999,7 +1540,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const allocator_type& __
 #else
         _NOEXCEPT
 #endif
-: __r_(__a)
+: __r_(__second_tag(), __a)
 {
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __get_db()->__insert_c(this);
@@ -2008,8 +1549,9 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const allocator_type& __
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-void
-basic_string<_CharT, _Traits, _Allocator>::__init(const value_type* __s, size_type __sz, size_type __reserve)
+void basic_string<_CharT, _Traits, _Allocator>::__init(const value_type* __s,
+                                                       size_type __sz,
+                                                       size_type __reserve)
 {
     if (__reserve > max_size())
         this->__throw_length_error();
@@ -2057,7 +1599,7 @@ basic_string<_CharT, _Traits, _Allocator>::__init(const value_type* __s, size_ty
 
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
-basic_string<_CharT, _Traits, _Allocator>::basic_string(const value_type* __s)
+basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s)
 {
     _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*) detected nullptr");
     __init(__s, traits_type::length(__s));
@@ -2068,8 +1610,8 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const value_type* __s)
 
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
-basic_string<_CharT, _Traits, _Allocator>::basic_string(const value_type* __s, const allocator_type& __a)
-    : __r_(__a)
+basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, const _Allocator& __a)
+    : __r_(__second_tag(), __a)
 {
     _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*, allocator) detected nullptr");
     __init(__s, traits_type::length(__s));
@@ -2080,7 +1622,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const value_type* __s, c
 
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
-basic_string<_CharT, _Traits, _Allocator>::basic_string(const value_type* __s, size_type __n)
+basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_type __n)
 {
     _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n) detected nullptr");
     __init(__s, __n);
@@ -2091,8 +1633,8 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const value_type* __s, s
 
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
-basic_string<_CharT, _Traits, _Allocator>::basic_string(const value_type* __s, size_type __n, const allocator_type& __a)
-    : __r_(__a)
+basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_type __n, const _Allocator& __a)
+    : __r_(__second_tag(), __a)
 {
     _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n, allocator) detected nullptr");
     __init(__s, __n);
@@ -2103,7 +1645,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const value_type* __s, s
 
 template <class _CharT, class _Traits, class _Allocator>
 basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str)
-    : __r_(__alloc_traits::select_on_container_copy_construction(__str.__alloc()))
+    : __r_(__second_tag(), __alloc_traits::select_on_container_copy_construction(__str.__alloc()))
 {
     if (!__str.__is_long())
         __r_.first().__r = __str.__r_.first().__r;
@@ -2115,8 +1657,9 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __st
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str, const allocator_type& __a)
-    : __r_(__a)
+basic_string<_CharT, _Traits, _Allocator>::basic_string(
+    const basic_string& __str, const allocator_type& __a)
+    : __r_(__second_tag(), __a)
 {
     if (!__str.__is_long())
         __r_.first().__r = __str.__r_.first().__r;
@@ -2127,7 +1670,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __st
 #endif
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -2150,7 +1693,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str)
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str, const allocator_type& __a)
-    : __r_(__a)
+    : __r_(__second_tag(), __a)
 {
     if (__str.__is_long() && __a != __str.__alloc()) // copy, not move
         __init(_VSTD::__to_raw_pointer(__str.__get_long_pointer()), __str.__get_long_size());
@@ -2166,7 +1709,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str, co
 #endif
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
 void
@@ -2194,7 +1737,7 @@ basic_string<_CharT, _Traits, _Allocator>::__init(size_type __n, value_type __c)
 
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
-basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, value_type __c)
+basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c)
 {
     __init(__n, __c);
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -2204,8 +1747,8 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, value_typ
 
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
-basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, value_type __c, const allocator_type& __a)
-    : __r_(__a)
+basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c, const _Allocator& __a)
+    : __r_(__second_tag(), __a)
 {
     __init(__n, __c);
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -2214,9 +1757,10 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, value_typ
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str, size_type __pos, size_type __n,
-                                                        const allocator_type& __a)
-    : __r_(__a)
+basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str,
+                                                        size_type __pos, size_type __n,
+                                                        const _Allocator& __a)
+    : __r_(__second_tag(), __a)
 {
     size_type __str_sz = __str.size();
     if (__pos > __str_sz)
@@ -2230,8 +1774,8 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __st
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str, size_type __pos,
-                                                        const allocator_type& __a)
-    : __r_(__a)
+                                                        const _Allocator& __a)
+    : __r_(__second_tag(), __a)
 {
     size_type __str_sz = __str.size();
     if (__pos > __str_sz)
@@ -2243,6 +1787,41 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __st
 }
 
 template <class _CharT, class _Traits, class _Allocator>
+template <class _Tp>
+basic_string<_CharT, _Traits, _Allocator>::basic_string(
+             const _Tp& __t, size_type __pos, size_type __n, const allocator_type& __a,
+             typename enable_if<__can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value, void>::type *)
+    : __r_(__second_tag(), __a)
+{
+    __self_view __sv = __self_view(__t).substr(__pos, __n);
+    __init(__sv.data(), __sv.size());
+#if _LIBCPP_DEBUG_LEVEL >= 2
+    __get_db()->__insert_c(this);
+#endif
+}
+
+template <class _CharT, class _Traits, class _Allocator>
+inline _LIBCPP_INLINE_VISIBILITY
+basic_string<_CharT, _Traits, _Allocator>::basic_string(__self_view __sv)
+{
+    __init(__sv.data(), __sv.size());
+#if _LIBCPP_DEBUG_LEVEL >= 2
+    __get_db()->__insert_c(this);
+#endif
+}
+
+template <class _CharT, class _Traits, class _Allocator>
+inline _LIBCPP_INLINE_VISIBILITY
+basic_string<_CharT, _Traits, _Allocator>::basic_string(__self_view __sv, const _Allocator& __a)
+    : __r_(__second_tag(), __a)
+{
+    __init(__sv.data(), __sv.size());
+#if _LIBCPP_DEBUG_LEVEL >= 2
+    __get_db()->__insert_c(this);
+#endif
+}
+
+template <class _CharT, class _Traits, class _Allocator>
 template <class _InputIterator>
 typename enable_if
 <
@@ -2316,7 +1895,7 @@ template<class _InputIterator>
 inline _LIBCPP_INLINE_VISIBILITY
 basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last,
                                                         const allocator_type& __a)
-    : __r_(__a)
+    : __r_(__second_tag(), __a)
 {
     __init(__first, __last);
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -2324,11 +1903,12 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first,
 #endif
 }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
-basic_string<_CharT, _Traits, _Allocator>::basic_string(initializer_list<value_type> __il)
+basic_string<_CharT, _Traits, _Allocator>::basic_string(
+    initializer_list<_CharT> __il)
 {
     __init(__il.begin(), __il.end());
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -2338,8 +1918,10 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(initializer_list<value_t
 
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
-basic_string<_CharT, _Traits, _Allocator>::basic_string(initializer_list<value_type> __il, const allocator_type& __a)
-    : __r_(__a)
+
+basic_string<_CharT, _Traits, _Allocator>::basic_string(
+    initializer_list<_CharT> __il, const _Allocator& __a)
+    : __r_(__second_tag(), __a)
 {
     __init(__il.begin(), __il.end());
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -2347,7 +1929,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(initializer_list<value_t
 #endif
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
 basic_string<_CharT, _Traits, _Allocator>::~basic_string()
@@ -2496,7 +2078,7 @@ basic_string<_CharT, _Traits, _Allocator>::operator=(const basic_string& __str)
     return *this;
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -2550,7 +2132,7 @@ typename enable_if
 >::type
 basic_string<_CharT, _Traits, _Allocator>::assign(_InputIterator __first, _InputIterator __last)
 {
-    basic_string __temp(__first, __last, __alloc());
+    const basic_string __temp(__first, __last, __alloc());
     assign(__temp.data(), __temp.size());
     return *this;
 }
@@ -2593,6 +2175,23 @@ basic_string<_CharT, _Traits, _Allocator>::assign(const basic_string& __str, siz
 }
 
 template <class _CharT, class _Traits, class _Allocator>
+template <class _Tp>
+typename enable_if
+<
+    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
+    basic_string<_CharT, _Traits, _Allocator>&
+>::type
+basic_string<_CharT, _Traits, _Allocator>::assign(const _Tp & __t, size_type __pos, size_type __n)
+{
+    __self_view __sv = __t;
+    size_type __sz = __sv.size();
+    if (__pos > __sz)
+        this->__throw_out_of_range();
+    return assign(__sv.data() + __pos, _VSTD::min(__n, __sz - __pos));
+}
+
+
+template <class _CharT, class _Traits, class _Allocator>
 basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::assign(const value_type* __s)
 {
@@ -2681,43 +2280,48 @@ basic_string<_CharT, _Traits, _Allocator>::push_back(value_type __c)
     traits_type::assign(*++__p, value_type());
 }
 
-template <class _CharT, class _Traits, class _Allocator>
-template<class _InputIterator>
-typename enable_if
-<
-    __is_exactly_input_iterator<_InputIterator>::value
-             || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
-    basic_string<_CharT, _Traits, _Allocator>&
->::type
-basic_string<_CharT, _Traits, _Allocator>::append(_InputIterator __first, _InputIterator __last)
+template <class _Tp>
+bool __ptr_in_range (const _Tp* __p, const _Tp* __first, const _Tp* __last)
 {
-	basic_string __temp (__first, __last, __alloc());
-	append(__temp.data(), __temp.size());
-    return *this;
+    return __first <= __p && __p < __last;
+}
+
+template <class _Tp1, class _Tp2>
+bool __ptr_in_range (const _Tp1*, const _Tp2*, const _Tp2*)
+{
+    return false;
 }
 
 template <class _CharT, class _Traits, class _Allocator>
 template<class _ForwardIterator>
-typename enable_if
-<
-    __is_forward_iterator<_ForwardIterator>::value
-          && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
-    basic_string<_CharT, _Traits, _Allocator>&
->::type
-basic_string<_CharT, _Traits, _Allocator>::append(_ForwardIterator __first, _ForwardIterator __last)
+basic_string<_CharT, _Traits, _Allocator>&
+basic_string<_CharT, _Traits, _Allocator>::__append_forward_unsafe(
+    _ForwardIterator __first, _ForwardIterator __last)
 {
+    static_assert(__is_forward_iterator<_ForwardIterator>::value,
+                  "function requires a ForwardIterator");
     size_type __sz = size();
     size_type __cap = capacity();
     size_type __n = static_cast<size_type>(_VSTD::distance(__first, __last));
     if (__n)
     {
-        if (__cap - __sz < __n)
-            __grow_by(__cap, __sz + __n - __cap, __sz, __sz, 0);
-        pointer __p = __get_pointer() + __sz;
-        for (; __first != __last; ++__p, ++__first)
-            traits_type::assign(*__p, *__first);
-        traits_type::assign(*__p, value_type());
-        __set_size(__sz + __n);
+        typedef typename iterator_traits<_ForwardIterator>::reference _CharRef;
+        _CharRef __tmp_ref = *__first;
+        if (__ptr_in_range(_VSTD::addressof(__tmp_ref), data(), data() + size()))
+        {
+            const basic_string __temp (__first, __last, __alloc());
+            append(__temp.data(), __temp.size());
+        }
+        else 
+        {
+            if (__cap - __sz < __n)
+                __grow_by(__cap, __sz + __n - __cap, __sz, __sz, 0);
+            pointer __p = __get_pointer() + __sz;
+            for (; __first != __last; ++__p, ++__first)
+                traits_type::assign(*__p, *__first);
+            traits_type::assign(*__p, value_type());
+            __set_size(__sz + __n);
+        }
     }
     return *this;
 }
@@ -2741,6 +2345,22 @@ basic_string<_CharT, _Traits, _Allocator>::append(const basic_string& __str, siz
 }
 
 template <class _CharT, class _Traits, class _Allocator>
+template <class _Tp>
+    typename enable_if
+    <
+        __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
+        basic_string<_CharT, _Traits, _Allocator>&
+    >::type
+basic_string<_CharT, _Traits, _Allocator>::append(const _Tp & __t, size_type __pos, size_type __n)
+{
+    __self_view __sv = __t;
+    size_type __sz = __sv.size();
+    if (__pos > __sz)
+        this->__throw_out_of_range();
+    return append(__sv.data() + __pos, _VSTD::min(__n, __sz - __pos));
+}
+
+template <class _CharT, class _Traits, class _Allocator>
 basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::append(const value_type* __s)
 {
@@ -2828,7 +2448,7 @@ basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, _InputIt
         "string::insert(iterator, range) called with an iterator not"
         " referring to this string");
 #endif
-    basic_string __temp(__first, __last, __alloc());
+    const basic_string __temp(__first, __last, __alloc());
     return insert(__pos, __temp.data(), __temp.data() + __temp.size());
 }
 
@@ -2848,11 +2468,19 @@ basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, _Forward
         " referring to this string");
 #endif
     size_type __ip = static_cast<size_type>(__pos - begin());
-    size_type __sz = size();
-    size_type __cap = capacity();
     size_type __n = static_cast<size_type>(_VSTD::distance(__first, __last));
     if (__n)
     {
+        typedef typename iterator_traits<_ForwardIterator>::reference _CharRef;
+        _CharRef __tmp_char = *__first;
+        if (__ptr_in_range(_VSTD::addressof(__tmp_char), data(), data() + size()))
+        {
+            const basic_string __temp(__first, __last, __alloc());
+            return insert(__pos, __temp.data(), __temp.data() + __temp.size());
+        }
+
+        size_type __sz = size();
+        size_type __cap = capacity();
         value_type* __p;
         if (__cap - __sz >= __n)
         {
@@ -2895,6 +2523,23 @@ basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos1, const basic_
 }
 
 template <class _CharT, class _Traits, class _Allocator>
+template <class _Tp>
+typename enable_if
+<
+    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
+    basic_string<_CharT, _Traits, _Allocator>&
+>::type
+basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos1, const _Tp& __t,
+                                                  size_type __pos2, size_type __n)
+{
+    __self_view __sv = __t;
+    size_type __str_sz = __sv.size();
+    if (__pos2 > __str_sz)
+        this->__throw_out_of_range();
+    return insert(__pos1, __sv.data() + __pos2, _VSTD::min(__n, __str_sz - __pos2));
+}
+
+template <class _CharT, class _Traits, class _Allocator>
 basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos, const value_type* __s)
 {
@@ -2948,6 +2593,7 @@ basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, size_typ
 template <class _CharT, class _Traits, class _Allocator>
 basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __n1, const value_type* __s, size_type __n2)
+    _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
 {
     _LIBCPP_ASSERT(__n2 == 0 || __s != nullptr, "string::replace received nullptr");
     size_type __sz = size();
@@ -2987,6 +2633,8 @@ basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __
         }
         traits_type::move(__p + __pos, __s, __n2);
 __finish:
+// __sz += __n2 - __n1; in this and the below function below can cause unsigned integer overflow,
+// but this is a safe operation, so we disable the check.
         __sz += __n2 - __n1;
         __set_size(__sz);
         __invalidate_iterators_past(__sz);
@@ -3000,6 +2648,7 @@ __finish:
 template <class _CharT, class _Traits, class _Allocator>
 basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __n1, size_type __n2, value_type __c)
+    _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
 {
     size_type __sz = size();
     if (__pos > __sz)
@@ -3040,7 +2689,7 @@ typename enable_if
 basic_string<_CharT, _Traits, _Allocator>::replace(const_iterator __i1, const_iterator __i2,
                                                    _InputIterator __j1, _InputIterator __j2)
 {
-    basic_string __temp(__j1, __j2, __alloc());
+    const basic_string __temp(__j1, __j2, __alloc());
     return this->replace(__i1, __i2, __temp);
 }
 
@@ -3064,6 +2713,23 @@ basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos1, size_type _
 }
 
 template <class _CharT, class _Traits, class _Allocator>
+template <class _Tp>
+typename enable_if
+<
+    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
+    basic_string<_CharT, _Traits, _Allocator>&
+>::type
+basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos1, size_type __n1, const _Tp& __t,
+                                                   size_type __pos2, size_type __n2)
+{
+    __self_view __sv = __t;
+    size_type __str_sz = __sv.size();
+    if (__pos2 > __str_sz)
+        this->__throw_out_of_range();
+    return replace(__pos1, __n1, __sv.data() + __pos2, _VSTD::min(__n2, __str_sz - __pos2));
+}
+
+template <class _CharT, class _Traits, class _Allocator>
 basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __n1, const value_type* __s)
 {
@@ -3238,7 +2904,7 @@ typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::max_size() const _NOEXCEPT
 {
     size_type __m = __alloc_traits::max_size(__alloc());
-#if _LIBCPP_BIG_ENDIAN
+#ifdef _LIBCPP_BIG_ENDIAN
     return (__m <= ~__long_mask ? __m : __m/2) - __alignment;
 #else
     return __m - __alignment;
@@ -3311,7 +2977,7 @@ basic_string<_CharT, _Traits, _Allocator>::reserve(size_type __res_arg)
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 typename basic_string<_CharT, _Traits, _Allocator>::const_reference
-basic_string<_CharT, _Traits, _Allocator>::operator[](size_type __pos) const
+basic_string<_CharT, _Traits, _Allocator>::operator[](size_type __pos) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__pos <= size(), "string index out of bounds");
     return *(data() + __pos);
@@ -3320,7 +2986,7 @@ basic_string<_CharT, _Traits, _Allocator>::operator[](size_type __pos) const
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 typename basic_string<_CharT, _Traits, _Allocator>::reference
-basic_string<_CharT, _Traits, _Allocator>::operator[](size_type __pos)
+basic_string<_CharT, _Traits, _Allocator>::operator[](size_type __pos) _NOEXCEPT
 {
     _LIBCPP_ASSERT(__pos <= size(), "string index out of bounds");
     return *(__get_pointer() + __pos);
@@ -3405,9 +3071,9 @@ inline _LIBCPP_INLINE_VISIBILITY
 void
 basic_string<_CharT, _Traits, _Allocator>::swap(basic_string& __str)
 #if _LIBCPP_STD_VER >= 14
-        _NOEXCEPT
+        _NOEXCEPT_DEBUG
 #else
-        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value || 
+        _NOEXCEPT_DEBUG_(!__alloc_traits::propagate_on_container_swap::value ||
                     __is_nothrow_swappable<allocator_type>::value)
 #endif
 {
@@ -3418,6 +3084,10 @@ basic_string<_CharT, _Traits, _Allocator>::swap(basic_string& __str)
         __get_db()->__invalidate_all(&__str);
     __get_db()->swap(this, &__str);
 #endif
+    _LIBCPP_ASSERT(
+        __alloc_traits::propagate_on_container_swap::value ||
+        __alloc_traits::is_always_equal::value ||
+        __alloc() == __str.__alloc(), "swapping non-equal allocators");
     _VSTD::swap(__r_.first(), __str.__r_.first());
     __swap_allocator(__alloc(), __str.__alloc());
 }
@@ -3440,7 +3110,7 @@ basic_string<_CharT, _Traits, _Allocator>::find(const value_type* __s,
                                                 size_type __n) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find(): received nullptr");
-    return _VSTD::__str_find<value_type, size_type, traits_type, npos>
+    return __str_find<value_type, size_type, traits_type, npos>
         (data(), size(), __s, __pos, __n);
 }
 
@@ -3450,18 +3120,28 @@ typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find(const basic_string& __str,
                                                 size_type __pos) const _NOEXCEPT
 {
-    return _VSTD::__str_find<value_type, size_type, traits_type, npos>
+    return __str_find<value_type, size_type, traits_type, npos>
         (data(), size(), __str.data(), __pos, __str.size());
 }
 
 template<class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 typename basic_string<_CharT, _Traits, _Allocator>::size_type
+basic_string<_CharT, _Traits, _Allocator>::find(__self_view __sv,
+                                                size_type __pos) const _NOEXCEPT
+{
+    return __str_find<value_type, size_type, traits_type, npos>
+        (data(), size(), __sv.data(), __pos, __sv.size());
+}
+
+template<class _CharT, class _Traits, class _Allocator>
+inline _LIBCPP_INLINE_VISIBILITY
+typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find(const value_type* __s,
                                                 size_type __pos) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__s != nullptr, "string::find(): received nullptr");
-    return _VSTD::__str_find<value_type, size_type, traits_type, npos>
+    return __str_find<value_type, size_type, traits_type, npos>
         (data(), size(), __s, __pos, traits_type::length(__s));
 }
 
@@ -3470,7 +3150,7 @@ typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find(value_type __c,
                                                 size_type __pos) const _NOEXCEPT
 {
-    return _VSTD::__str_find<value_type, size_type, traits_type, npos>
+    return __str_find<value_type, size_type, traits_type, npos>
         (data(), size(), __c, __pos);
 }
 
@@ -3483,7 +3163,7 @@ basic_string<_CharT, _Traits, _Allocator>::rfind(const value_type* __s,
                                                  size_type __n) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::rfind(): received nullptr");
-    return _VSTD::__str_rfind<value_type, size_type, traits_type, npos>
+    return __str_rfind<value_type, size_type, traits_type, npos>
         (data(), size(), __s, __pos, __n);
 }
 
@@ -3493,18 +3173,28 @@ typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::rfind(const basic_string& __str,
                                                  size_type __pos) const _NOEXCEPT
 {
-    return _VSTD::__str_rfind<value_type, size_type, traits_type, npos>
+    return __str_rfind<value_type, size_type, traits_type, npos>
         (data(), size(), __str.data(), __pos, __str.size());
 }
 
 template<class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 typename basic_string<_CharT, _Traits, _Allocator>::size_type
+basic_string<_CharT, _Traits, _Allocator>::rfind(__self_view __sv,
+                                                size_type __pos) const _NOEXCEPT
+{
+    return __str_rfind<value_type, size_type, traits_type, npos>
+        (data(), size(), __sv.data(), __pos, __sv.size());
+}
+
+template<class _CharT, class _Traits, class _Allocator>
+inline _LIBCPP_INLINE_VISIBILITY
+typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::rfind(const value_type* __s,
                                                  size_type __pos) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__s != nullptr, "string::rfind(): received nullptr");
-    return _VSTD::__str_rfind<value_type, size_type, traits_type, npos>
+    return __str_rfind<value_type, size_type, traits_type, npos>
         (data(), size(), __s, __pos, traits_type::length(__s));
 }
 
@@ -3513,7 +3203,7 @@ typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::rfind(value_type __c,
                                                  size_type __pos) const _NOEXCEPT
 {
-    return _VSTD::__str_rfind<value_type, size_type, traits_type, npos>
+    return __str_rfind<value_type, size_type, traits_type, npos>
         (data(), size(), __c, __pos);
 }
 
@@ -3526,7 +3216,7 @@ basic_string<_CharT, _Traits, _Allocator>::find_first_of(const value_type* __s,
                                                          size_type __n) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find_first_of(): received nullptr");
-    return _VSTD::__str_find_first_of<value_type, size_type, traits_type, npos>
+    return __str_find_first_of<value_type, size_type, traits_type, npos>
         (data(), size(), __s, __pos, __n);
 }
 
@@ -3536,18 +3226,28 @@ typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find_first_of(const basic_string& __str,
                                                          size_type __pos) const _NOEXCEPT
 {
-    return _VSTD::__str_find_first_of<value_type, size_type, traits_type, npos>
+    return __str_find_first_of<value_type, size_type, traits_type, npos>
         (data(), size(), __str.data(), __pos, __str.size());
 }
 
 template<class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 typename basic_string<_CharT, _Traits, _Allocator>::size_type
+basic_string<_CharT, _Traits, _Allocator>::find_first_of(__self_view __sv,
+                                                size_type __pos) const _NOEXCEPT
+{
+    return __str_find_first_of<value_type, size_type, traits_type, npos>
+        (data(), size(), __sv.data(), __pos, __sv.size());
+}
+
+template<class _CharT, class _Traits, class _Allocator>
+inline _LIBCPP_INLINE_VISIBILITY
+typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find_first_of(const value_type* __s,
                                                          size_type __pos) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__s != nullptr, "string::find_first_of(): received nullptr");
-    return _VSTD::__str_find_first_of<value_type, size_type, traits_type, npos>
+    return __str_find_first_of<value_type, size_type, traits_type, npos>
         (data(), size(), __s, __pos, traits_type::length(__s));
 }
 
@@ -3569,7 +3269,7 @@ basic_string<_CharT, _Traits, _Allocator>::find_last_of(const value_type* __s,
                                                         size_type __n) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find_last_of(): received nullptr");
-    return _VSTD::__str_find_last_of<value_type, size_type, traits_type, npos>
+    return __str_find_last_of<value_type, size_type, traits_type, npos>
         (data(), size(), __s, __pos, __n);
 }
 
@@ -3579,18 +3279,28 @@ typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find_last_of(const basic_string& __str,
                                                         size_type __pos) const _NOEXCEPT
 {
-    return _VSTD::__str_find_last_of<value_type, size_type, traits_type, npos>
+    return __str_find_last_of<value_type, size_type, traits_type, npos>
         (data(), size(), __str.data(), __pos, __str.size());
 }
 
 template<class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 typename basic_string<_CharT, _Traits, _Allocator>::size_type
+basic_string<_CharT, _Traits, _Allocator>::find_last_of(__self_view __sv,
+                                                size_type __pos) const _NOEXCEPT
+{
+    return __str_find_last_of<value_type, size_type, traits_type, npos>
+        (data(), size(), __sv.data(), __pos, __sv.size());
+}
+
+template<class _CharT, class _Traits, class _Allocator>
+inline _LIBCPP_INLINE_VISIBILITY
+typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find_last_of(const value_type* __s,
                                                         size_type __pos) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__s != nullptr, "string::find_last_of(): received nullptr");
-    return _VSTD::__str_find_last_of<value_type, size_type, traits_type, npos>
+    return __str_find_last_of<value_type, size_type, traits_type, npos>
         (data(), size(), __s, __pos, traits_type::length(__s));
 }
 
@@ -3612,7 +3322,7 @@ basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(const value_type* _
                                                              size_type __n) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find_first_not_of(): received nullptr");
-    return _VSTD::__str_find_first_not_of<value_type, size_type, traits_type, npos>
+    return __str_find_first_not_of<value_type, size_type, traits_type, npos>
         (data(), size(), __s, __pos, __n);
 }
 
@@ -3622,18 +3332,28 @@ typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(const basic_string& __str,
                                                              size_type __pos) const _NOEXCEPT
 {
-    return _VSTD::__str_find_first_not_of<value_type, size_type, traits_type, npos>
+    return __str_find_first_not_of<value_type, size_type, traits_type, npos>
         (data(), size(), __str.data(), __pos, __str.size());
 }
 
 template<class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 typename basic_string<_CharT, _Traits, _Allocator>::size_type
+basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(__self_view __sv,
+                                                size_type __pos) const _NOEXCEPT
+{
+    return __str_find_first_not_of<value_type, size_type, traits_type, npos>
+        (data(), size(), __sv.data(), __pos, __sv.size());
+}
+
+template<class _CharT, class _Traits, class _Allocator>
+inline _LIBCPP_INLINE_VISIBILITY
+typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(const value_type* __s,
                                                              size_type __pos) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__s != nullptr, "string::find_first_not_of(): received nullptr");
-    return _VSTD::__str_find_first_not_of<value_type, size_type, traits_type, npos>
+    return __str_find_first_not_of<value_type, size_type, traits_type, npos>
         (data(), size(), __s, __pos, traits_type::length(__s));
 }
 
@@ -3643,7 +3363,7 @@ typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find_first_not_of(value_type __c,
                                                              size_type __pos) const _NOEXCEPT
 {
-    return _VSTD::__str_find_first_not_of<value_type, size_type, traits_type, npos>
+    return __str_find_first_not_of<value_type, size_type, traits_type, npos>
         (data(), size(), __c, __pos);
 }
 
@@ -3656,7 +3376,7 @@ basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(const value_type* __
                                                             size_type __n) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string::find_last_not_of(): received nullptr");
-    return _VSTD::__str_find_last_not_of<value_type, size_type, traits_type, npos>
+    return __str_find_last_not_of<value_type, size_type, traits_type, npos>
         (data(), size(), __s, __pos, __n);
 }
 
@@ -3666,18 +3386,28 @@ typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(const basic_string& __str,
                                                             size_type __pos) const _NOEXCEPT
 {
-    return _VSTD::__str_find_last_not_of<value_type, size_type, traits_type, npos>
+    return __str_find_last_not_of<value_type, size_type, traits_type, npos>
         (data(), size(), __str.data(), __pos, __str.size());
 }
 
 template<class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 typename basic_string<_CharT, _Traits, _Allocator>::size_type
+basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(__self_view __sv,
+                                                size_type __pos) const _NOEXCEPT
+{
+    return __str_find_last_not_of<value_type, size_type, traits_type, npos>
+        (data(), size(), __sv.data(), __pos, __sv.size());
+}
+
+template<class _CharT, class _Traits, class _Allocator>
+inline _LIBCPP_INLINE_VISIBILITY
+typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(const value_type* __s,
                                                             size_type __pos) const _NOEXCEPT
 {
     _LIBCPP_ASSERT(__s != nullptr, "string::find_last_not_of(): received nullptr");
-    return _VSTD::__str_find_last_not_of<value_type, size_type, traits_type, npos>
+    return __str_find_last_not_of<value_type, size_type, traits_type, npos>
         (data(), size(), __s, __pos, traits_type::length(__s));
 }
 
@@ -3687,7 +3417,7 @@ typename basic_string<_CharT, _Traits, _Allocator>::size_type
 basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(value_type __c,
                                                             size_type __pos) const _NOEXCEPT
 {
-    return _VSTD::__str_find_last_not_of<value_type, size_type, traits_type, npos>
+    return __str_find_last_not_of<value_type, size_type, traits_type, npos>
         (data(), size(), __c, __pos);
 }
 
@@ -3696,11 +3426,11 @@ basic_string<_CharT, _Traits, _Allocator>::find_last_not_of(value_type __c,
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 int
-basic_string<_CharT, _Traits, _Allocator>::compare(const basic_string& __str) const _NOEXCEPT
+basic_string<_CharT, _Traits, _Allocator>::compare(__self_view __sv) const _NOEXCEPT
 {
     size_t __lhs_sz = size();
-    size_t __rhs_sz = __str.size();
-    int __result = traits_type::compare(data(), __str.data(),
+    size_t __rhs_sz = __sv.size();
+    int __result = traits_type::compare(data(), __sv.data(),
                                         _VSTD::min(__lhs_sz, __rhs_sz));
     if (__result != 0)
         return __result;
@@ -3714,6 +3444,47 @@ basic_string<_CharT, _Traits, _Allocator>::compare(const basic_string& __str) co
 template <class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 int
+basic_string<_CharT, _Traits, _Allocator>::compare(const basic_string& __str) const _NOEXCEPT
+{
+    return compare(__self_view(__str));
+}
+
+template <class _CharT, class _Traits, class _Allocator>
+int
+basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
+                                                   size_type __n1,
+                                                   const value_type* __s,
+                                                   size_type __n2) const
+{
+    _LIBCPP_ASSERT(__n2 == 0 || __s != nullptr, "string::compare(): received nullptr");
+    size_type __sz = size();
+    if (__pos1 > __sz || __n2 == npos)
+        this->__throw_out_of_range();
+    size_type __rlen = _VSTD::min(__n1, __sz - __pos1);
+    int __r = traits_type::compare(data() + __pos1, __s, _VSTD::min(__rlen, __n2));
+    if (__r == 0)
+    {
+        if (__rlen < __n2)
+            __r = -1;
+        else if (__rlen > __n2)
+            __r = 1;
+    }
+    return __r;
+}
+
+template <class _CharT, class _Traits, class _Allocator>
+inline _LIBCPP_INLINE_VISIBILITY
+int
+basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
+                                                   size_type __n1,
+                                                   __self_view __sv) const
+{
+    return compare(__pos1, __n1, __sv.data(), __sv.size());
+}
+
+template <class _CharT, class _Traits, class _Allocator>
+inline _LIBCPP_INLINE_VISIBILITY
+int
 basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
                                                    size_type __n1,
                                                    const basic_string& __str) const
@@ -3722,6 +3493,23 @@ basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
 }
 
 template <class _CharT, class _Traits, class _Allocator>
+template <class _Tp>
+typename enable_if
+<
+    __can_be_converted_to_string_view<_CharT, _Traits, _Tp>::value,
+    int
+>::type
+basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
+                                                   size_type __n1,
+                                                   const _Tp& __t,
+                                                   size_type __pos2,
+                                                   size_type __n2) const
+{
+    __self_view __sv = __t;
+    return __self_view(*this).substr(__pos1, __n1).compare(__sv.substr(__pos2, __n2));
+}
+
+template <class _CharT, class _Traits, class _Allocator>
 int
 basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
                                                    size_type __n1,
@@ -3729,11 +3517,7 @@ basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
                                                    size_type __pos2,
                                                    size_type __n2) const
 {
-    size_type __sz = __str.size();
-    if (__pos2 > __sz)
-        this->__throw_out_of_range();
-    return compare(__pos1, __n1, __str.data() + __pos2, _VSTD::min(__n2,
-                                                                  __sz - __pos2));
+        return compare(__pos1, __n1, __self_view(__str), __pos2, __n2);
 }
 
 template <class _CharT, class _Traits, class _Allocator>
@@ -3754,29 +3538,6 @@ basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
     return compare(__pos1, __n1, __s, traits_type::length(__s));
 }
 
-template <class _CharT, class _Traits, class _Allocator>
-int
-basic_string<_CharT, _Traits, _Allocator>::compare(size_type __pos1,
-                                                   size_type __n1,
-                                                   const value_type* __s,
-                                                   size_type __n2) const
-{
-    _LIBCPP_ASSERT(__n2 == 0 || __s != nullptr, "string::compare(): received nullptr");
-    size_type __sz = size();
-    if (__pos1 > __sz || __n2 == npos)
-        this->__throw_out_of_range();
-    size_type __rlen = _VSTD::min(__n1, __sz - __pos1);
-    int __r = traits_type::compare(data() + __pos1, __s, _VSTD::min(__rlen, __n2));
-    if (__r == 0)
-    {
-        if (__rlen < __n2)
-            __r = -1;
-        else if (__rlen > __n2)
-            __r = 1;
-    }
-    return __r;
-}
-
 // __invariants
 
 template<class _CharT, class _Traits, class _Allocator>
@@ -3854,8 +3615,6 @@ operator==(const basic_string<_CharT,_Traits,_Allocator>& __lhs,
     return __lhs.compare(0, _String::npos, __rhs, __rhs_len) == 0;
 }
 
-// operator!=
-
 template<class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
@@ -4060,7 +3819,7 @@ operator+(const basic_string<_CharT, _Traits, _Allocator>& __lhs, _CharT __rhs)
     return __r;
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template<class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -4120,7 +3879,7 @@ operator+(basic_string<_CharT, _Traits, _Allocator>&& __lhs, _CharT __rhs)
     return _VSTD::move(__lhs);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 // swap
 
@@ -4186,7 +3945,7 @@ template<class _CharT, class _Traits, class _Allocator>
                    basic_string<_CharT, _Traits, _Allocator>::npos;
 
 template<class _CharT, class _Traits, class _Allocator>
-struct _LIBCPP_TYPE_VIS_ONLY hash<basic_string<_CharT, _Traits, _Allocator> >
+struct _LIBCPP_TEMPLATE_VIS hash<basic_string<_CharT, _Traits, _Allocator> >
     : public unary_function<basic_string<_CharT, _Traits, _Allocator>, size_t>
 {
     size_t
@@ -4222,7 +3981,7 @@ basic_istream<_CharT, _Traits>&
 getline(basic_istream<_CharT, _Traits>& __is,
         basic_string<_CharT, _Traits, _Allocator>& __str);
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template<class _CharT, class _Traits, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -4236,7 +3995,7 @@ basic_istream<_CharT, _Traits>&
 getline(basic_istream<_CharT, _Traits>&& __is,
         basic_string<_CharT, _Traits, _Allocator>& __str);
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 #if _LIBCPP_DEBUG_LEVEL >= 2
 
@@ -4274,6 +4033,9 @@ basic_string<_CharT, _Traits, _Allocator>::__subscriptable(const const_iterator*
 
 #endif  // _LIBCPP_DEBUG_LEVEL >= 2
 
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_string<char>)
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_string<wchar_t>)
+
 #if _LIBCPP_STD_VER > 11 
 // Literal suffixes for basic_string [basic.string.literals]
 inline namespace literals
@@ -4307,10 +4069,8 @@ inline namespace literals
 }
 #endif
 
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_string<char>)
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS basic_string<wchar_t>)
-_LIBCPP_EXTERN_TEMPLATE(string operator+<char, char_traits<char>, allocator<char> >(char const*, string const&))
-
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_STRING
diff --git a/lib/libcxx/include/string_view b/lib/libcxx/include/string_view
new file mode 100644
index 00000000000..72cf816e8d5
--- /dev/null
+++ b/lib/libcxx/include/string_view
@@ -0,0 +1,825 @@
+// -*- C++ -*-
+//===------------------------ string_view ---------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_STRING_VIEW
+#define _LIBCPP_STRING_VIEW
+
+/*
+string_view synopsis
+
+namespace std {
+
+    // 7.2, Class template basic_string_view
+    template<class charT, class traits = char_traits<charT>>
+        class basic_string_view;
+
+    // 7.9, basic_string_view non-member comparison functions
+    template<class charT, class traits>
+    constexpr bool operator==(basic_string_view<charT, traits> x,
+                              basic_string_view<charT, traits> y) noexcept;
+    template<class charT, class traits>
+    constexpr bool operator!=(basic_string_view<charT, traits> x,
+                              basic_string_view<charT, traits> y) noexcept;
+    template<class charT, class traits>
+    constexpr bool operator< (basic_string_view<charT, traits> x,
+                                 basic_string_view<charT, traits> y) noexcept;
+    template<class charT, class traits>
+    constexpr bool operator> (basic_string_view<charT, traits> x,
+                              basic_string_view<charT, traits> y) noexcept;
+    template<class charT, class traits>
+    constexpr bool operator<=(basic_string_view<charT, traits> x,
+                                 basic_string_view<charT, traits> y) noexcept;
+    template<class charT, class traits>
+    constexpr bool operator>=(basic_string_view<charT, traits> x,
+                              basic_string_view<charT, traits> y) noexcept;
+    // see below, sufficient additional overloads of comparison functions
+
+    // 7.10, Inserters and extractors
+    template<class charT, class traits>
+      basic_ostream<charT, traits>&
+        operator<<(basic_ostream<charT, traits>& os,
+                   basic_string_view<charT, traits> str);
+
+    // basic_string_view typedef names
+    typedef basic_string_view<char> string_view;
+    typedef basic_string_view<char16_t> u16string_view;
+    typedef basic_string_view<char32_t> u32string_view;
+    typedef basic_string_view<wchar_t> wstring_view;
+
+    template<class charT, class traits = char_traits<charT>>
+    class basic_string_view {
+      public:
+      // types
+      typedef traits traits_type;
+      typedef charT value_type;
+      typedef charT* pointer;
+      typedef const charT* const_pointer;
+      typedef charT& reference;
+      typedef const charT& const_reference;
+      typedef implementation-defined const_iterator;
+      typedef const_iterator iterator;
+      typedef reverse_iterator<const_iterator> const_reverse_iterator;
+      typedef const_reverse_iterator reverse_iterator;
+      typedef size_t size_type;
+      typedef ptrdiff_t difference_type;
+      static constexpr size_type npos = size_type(-1);
+
+      // 7.3, basic_string_view constructors and assignment operators
+      constexpr basic_string_view() noexcept;
+      constexpr basic_string_view(const basic_string_view&) noexcept = default;
+      basic_string_view& operator=(const basic_string_view&) noexcept = default;
+      template<class Allocator>
+      constexpr basic_string_view(const charT* str);
+      constexpr basic_string_view(const charT* str, size_type len);
+
+      // 7.4, basic_string_view iterator support
+      constexpr const_iterator begin() const noexcept;
+      constexpr const_iterator end() const noexcept;
+      constexpr const_iterator cbegin() const noexcept;
+      constexpr const_iterator cend() const noexcept;
+      const_reverse_iterator rbegin() const noexcept;
+      const_reverse_iterator rend() const noexcept;
+      const_reverse_iterator crbegin() const noexcept;
+      const_reverse_iterator crend() const noexcept;
+
+      // 7.5, basic_string_view capacity
+      constexpr size_type size() const noexcept;
+      constexpr size_type length() const noexcept;
+      constexpr size_type max_size() const noexcept;
+      constexpr bool empty() const noexcept;
+
+      // 7.6, basic_string_view element access
+      constexpr const_reference operator[](size_type pos) const;
+      constexpr const_reference at(size_type pos) const;
+      constexpr const_reference front() const;
+      constexpr const_reference back() const;
+      constexpr const_pointer data() const noexcept;
+
+      // 7.7, basic_string_view modifiers
+      constexpr void remove_prefix(size_type n);
+      constexpr void remove_suffix(size_type n);
+      constexpr void swap(basic_string_view& s) noexcept;
+
+      size_type copy(charT* s, size_type n, size_type pos = 0) const;
+
+      constexpr basic_string_view substr(size_type pos = 0, size_type n = npos) const;
+      constexpr int compare(basic_string_view s) const noexcept;
+      constexpr int compare(size_type pos1, size_type n1, basic_string_view s) const;
+      constexpr int compare(size_type pos1, size_type n1,
+                            basic_string_view s, size_type pos2, size_type n2) const;
+      constexpr int compare(const charT* s) const;
+      constexpr int compare(size_type pos1, size_type n1, const charT* s) const;
+      constexpr int compare(size_type pos1, size_type n1,
+                            const charT* s, size_type n2) const;
+      constexpr size_type find(basic_string_view s, size_type pos = 0) const noexcept;
+      constexpr size_type find(charT c, size_type pos = 0) const noexcept;
+      constexpr size_type find(const charT* s, size_type pos, size_type n) const;
+      constexpr size_type find(const charT* s, size_type pos = 0) const;
+      constexpr size_type rfind(basic_string_view s, size_type pos = npos) const noexcept;
+      constexpr size_type rfind(charT c, size_type pos = npos) const noexcept;
+      constexpr size_type rfind(const charT* s, size_type pos, size_type n) const;
+      constexpr size_type rfind(const charT* s, size_type pos = npos) const;
+      constexpr size_type find_first_of(basic_string_view s, size_type pos = 0) const noexcept;
+      constexpr size_type find_first_of(charT c, size_type pos = 0) const noexcept;
+      constexpr size_type find_first_of(const charT* s, size_type pos, size_type n) const;
+      constexpr size_type find_first_of(const charT* s, size_type pos = 0) const;
+      constexpr size_type find_last_of(basic_string_view s, size_type pos = npos) const noexcept;
+      constexpr size_type find_last_of(charT c, size_type pos = npos) const noexcept;
+      constexpr size_type find_last_of(const charT* s, size_type pos, size_type n) const;
+      constexpr size_type find_last_of(const charT* s, size_type pos = npos) const;
+      constexpr size_type find_first_not_of(basic_string_view s, size_type pos = 0) const noexcept;
+      constexpr size_type find_first_not_of(charT c, size_type pos = 0) const noexcept;
+      constexpr size_type find_first_not_of(const charT* s, size_type pos, size_type n) const;
+      constexpr size_type find_first_not_of(const charT* s, size_type pos = 0) const;
+      constexpr size_type find_last_not_of(basic_string_view s, size_type pos = npos) const noexcept;
+      constexpr size_type find_last_not_of(charT c, size_type pos = npos) const noexcept;
+      constexpr size_type find_last_not_of(const charT* s, size_type pos, size_type n) const;
+      constexpr size_type find_last_not_of(const charT* s, size_type pos = npos) const;
+
+      constexpr bool starts_with(basic_string_view s) const noexcept; // C++2a
+      constexpr bool starts_with(charT c) const noexcept;             // C++2a
+      constexpr bool starts_with(const charT* s) const;               // C++2a
+      constexpr bool ends_with(basic_string_view s) const noexcept;   // C++2a
+      constexpr bool ends_with(charT c) const noexcept;               // C++2a
+      constexpr bool ends_with(const charT* s) const;                 // C++2a
+
+     private:
+      const_pointer data_;  // exposition only
+      size_type     size_;  // exposition only
+    };
+
+  // 7.11, Hash support
+  template <class T> struct hash;
+  template <> struct hash<string_view>;
+  template <> struct hash<u16string_view>;
+  template <> struct hash<u32string_view>;
+  template <> struct hash<wstring_view>;
+
+  constexpr basic_string_view<char>     operator "" sv( const char *str,     size_t len ) noexcept;
+  constexpr basic_string_view<wchar_t>  operator "" sv( const wchar_t *str,  size_t len ) noexcept;
+  constexpr basic_string_view<char16_t> operator "" sv( const char16_t *str, size_t len ) noexcept;
+  constexpr basic_string_view<char32_t> operator "" sv( const char32_t *str, size_t len ) noexcept;
+
+}  // namespace std
+
+
+*/
+
+#include <__config>
+#include <__string>
+#include <algorithm>
+#include <iterator>
+#include <limits>
+#include <stdexcept>
+#include <__debug>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template<class _CharT, class _Traits = char_traits<_CharT> >
+class _LIBCPP_TEMPLATE_VIS basic_string_view {
+public:
+    // types
+    typedef _Traits                                    traits_type;
+    typedef _CharT                                     value_type;
+    typedef _CharT*                                    pointer;
+    typedef const _CharT*                              const_pointer;
+    typedef _CharT&                                    reference;
+    typedef const _CharT&                              const_reference;
+    typedef const_pointer                              const_iterator; // See [string.view.iterators]
+    typedef const_iterator                             iterator;
+    typedef _VSTD::reverse_iterator<const_iterator>    const_reverse_iterator;
+    typedef const_reverse_iterator                     reverse_iterator;
+    typedef size_t                                     size_type;
+    typedef ptrdiff_t                                  difference_type;
+    static _LIBCPP_CONSTEXPR const size_type npos = -1; // size_type(-1);
+
+    static_assert(is_pod<value_type>::value, "Character type of basic_string_view must be a POD");
+    static_assert((is_same<_CharT, typename traits_type::char_type>::value),
+                  "traits_type::char_type must be the same type as CharT");
+
+    // [string.view.cons], construct/copy
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    basic_string_view() _NOEXCEPT : __data (nullptr), __size(0) {}
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    basic_string_view(const basic_string_view&) _NOEXCEPT = default;
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    basic_string_view& operator=(const basic_string_view&) _NOEXCEPT = default;
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    basic_string_view(const _CharT* __s, size_type __len) _NOEXCEPT
+        : __data(__s), __size(__len)
+    {
+// #if _LIBCPP_STD_VER > 11
+//         _LIBCPP_ASSERT(__len == 0 || __s != nullptr, "string_view::string_view(_CharT *, size_t): received nullptr");
+// #endif
+    }
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    basic_string_view(const _CharT* __s)
+        : __data(__s), __size(_Traits::length(__s)) {}
+
+    // [string.view.iterators], iterators
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    const_iterator begin()  const _NOEXCEPT { return cbegin(); }
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    const_iterator end()    const _NOEXCEPT { return cend(); }
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    const_iterator cbegin() const _NOEXCEPT { return __data; }
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    const_iterator cend()   const _NOEXCEPT { return __data + __size; }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX14 _LIBCPP_INLINE_VISIBILITY
+    const_reverse_iterator rbegin()   const _NOEXCEPT { return const_reverse_iterator(cend()); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX14 _LIBCPP_INLINE_VISIBILITY
+    const_reverse_iterator rend()     const _NOEXCEPT { return const_reverse_iterator(cbegin()); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX14 _LIBCPP_INLINE_VISIBILITY
+    const_reverse_iterator crbegin()  const _NOEXCEPT { return const_reverse_iterator(cend()); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX14 _LIBCPP_INLINE_VISIBILITY
+    const_reverse_iterator crend()    const _NOEXCEPT { return const_reverse_iterator(cbegin()); }
+
+    // [string.view.capacity], capacity
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    size_type size()     const _NOEXCEPT { return __size; }
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    size_type length()   const _NOEXCEPT { return __size; }
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    size_type max_size() const _NOEXCEPT { return numeric_limits<size_type>::max(); }
+
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    bool empty()         const _NOEXCEPT { return __size == 0; }
+
+    // [string.view.access], element access
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    const_reference operator[](size_type __pos) const _NOEXCEPT { return __data[__pos]; }
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    const_reference at(size_type __pos) const
+    {
+        return __pos >= size()
+            ? (__throw_out_of_range("string_view::at"), __data[0])
+            : __data[__pos];
+    }
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    const_reference front() const
+    {
+        return _LIBCPP_ASSERT(!empty(), "string_view::front(): string is empty"), __data[0];
+    }
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    const_reference back() const
+    {
+        return _LIBCPP_ASSERT(!empty(), "string_view::back(): string is empty"), __data[__size-1];
+    }
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    const_pointer data() const _NOEXCEPT { return __data; }
+
+    // [string.view.modifiers], modifiers:
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    void remove_prefix(size_type __n) _NOEXCEPT
+    {
+        _LIBCPP_ASSERT(__n <= size(), "remove_prefix() can't remove more than size()");
+        __data += __n;
+        __size -= __n;
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    void remove_suffix(size_type __n) _NOEXCEPT
+    {
+        _LIBCPP_ASSERT(__n <= size(), "remove_suffix() can't remove more than size()");
+        __size -= __n;
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    void swap(basic_string_view& __other) _NOEXCEPT
+    {
+        const value_type *__p = __data;
+        __data = __other.__data;
+        __other.__data = __p;
+
+        size_type __sz = __size;
+        __size = __other.__size;
+        __other.__size = __sz;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    size_type copy(_CharT* __s, size_type __n, size_type __pos = 0) const
+    {
+        if (__pos > size())
+            __throw_out_of_range("string_view::copy");
+        size_type __rlen = _VSTD::min(__n, size() - __pos);
+        _Traits::copy(__s, data() + __pos, __rlen);
+        return __rlen;
+    }
+
+    _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+    basic_string_view substr(size_type __pos = 0, size_type __n = npos) const
+    {
+        return __pos > size()
+            ? (__throw_out_of_range("string_view::substr"), basic_string_view())
+            : basic_string_view(data() + __pos, _VSTD::min(__n, size() - __pos));
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 int compare(basic_string_view __sv) const _NOEXCEPT
+    {
+        size_type __rlen = _VSTD::min( size(), __sv.size());
+        int __retval = _Traits::compare(data(), __sv.data(), __rlen);
+        if ( __retval == 0 ) // first __rlen chars matched
+            __retval = size() == __sv.size() ? 0 : ( size() < __sv.size() ? -1 : 1 );
+        return __retval;
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    int compare(size_type __pos1, size_type __n1, basic_string_view __sv) const
+    {
+        return substr(__pos1, __n1).compare(__sv);
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    int compare(                       size_type __pos1, size_type __n1, 
+                basic_string_view __sv, size_type __pos2, size_type __n2) const
+    {
+        return substr(__pos1, __n1).compare(__sv.substr(__pos2, __n2));
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    int compare(const _CharT* __s) const _NOEXCEPT
+    {
+        return compare(basic_string_view(__s));
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    int compare(size_type __pos1, size_type __n1, const _CharT* __s) const
+    {
+        return substr(__pos1, __n1).compare(basic_string_view(__s));
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    int compare(size_type __pos1, size_type __n1, const _CharT* __s, size_type __n2) const
+    {
+        return substr(__pos1, __n1).compare(basic_string_view(__s, __n2));
+    }
+
+    // find
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find(basic_string_view __s, size_type __pos = 0) const _NOEXCEPT
+    {
+        _LIBCPP_ASSERT(__s.size() == 0 || __s.data() != nullptr, "string_view::find(): received nullptr");
+        return __str_find<value_type, size_type, traits_type, npos>
+            (data(), size(), __s.data(), __pos, __s.size());
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find(_CharT __c, size_type __pos = 0) const _NOEXCEPT
+    {
+        return __str_find<value_type, size_type, traits_type, npos>
+            (data(), size(), __c, __pos);
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find(const _CharT* __s, size_type __pos, size_type __n) const
+    {
+        _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string_view::find(): received nullptr");
+        return __str_find<value_type, size_type, traits_type, npos>
+            (data(), size(), __s, __pos, __n);
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find(const _CharT* __s, size_type __pos = 0) const
+    {
+        _LIBCPP_ASSERT(__s != nullptr, "string_view::find(): received nullptr");
+        return __str_find<value_type, size_type, traits_type, npos>
+            (data(), size(), __s, __pos, traits_type::length(__s));
+    }
+
+    // rfind
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type rfind(basic_string_view __s, size_type __pos = npos) const _NOEXCEPT
+    {
+        _LIBCPP_ASSERT(__s.size() == 0 || __s.data() != nullptr, "string_view::find(): received nullptr");
+        return __str_rfind<value_type, size_type, traits_type, npos>
+            (data(), size(), __s.data(), __pos, __s.size());
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type rfind(_CharT __c, size_type __pos = npos) const _NOEXCEPT
+    {
+        return __str_rfind<value_type, size_type, traits_type, npos>
+            (data(), size(), __c, __pos);
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type rfind(const _CharT* __s, size_type __pos, size_type __n) const
+    {
+        _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string_view::rfind(): received nullptr");
+        return __str_rfind<value_type, size_type, traits_type, npos>
+            (data(), size(), __s, __pos, __n);
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type rfind(const _CharT* __s, size_type __pos=npos) const
+    {
+        _LIBCPP_ASSERT(__s != nullptr, "string_view::rfind(): received nullptr");
+        return __str_rfind<value_type, size_type, traits_type, npos>
+            (data(), size(), __s, __pos, traits_type::length(__s));
+    }
+
+    // find_first_of
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_first_of(basic_string_view __s, size_type __pos = 0) const _NOEXCEPT
+    {
+        _LIBCPP_ASSERT(__s.size() == 0 || __s.data() != nullptr, "string_view::find_first_of(): received nullptr");
+        return __str_find_first_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __s.data(), __pos, __s.size());
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_first_of(_CharT __c, size_type __pos = 0) const _NOEXCEPT
+    { return find(__c, __pos); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_first_of(const _CharT* __s, size_type __pos, size_type __n) const
+    {
+        _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string_view::find_first_of(): received nullptr");
+        return __str_find_first_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __s, __pos, __n);
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_first_of(const _CharT* __s, size_type __pos=0) const
+    {
+        _LIBCPP_ASSERT(__s != nullptr, "string_view::find_first_of(): received nullptr");
+        return __str_find_first_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __s, __pos, traits_type::length(__s));
+    }
+
+    // find_last_of
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_last_of(basic_string_view __s, size_type __pos=npos) const _NOEXCEPT
+    {
+        _LIBCPP_ASSERT(__s.size() == 0 || __s.data() != nullptr, "string_view::find_last_of(): received nullptr");
+        return __str_find_last_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __s.data(), __pos, __s.size());
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_last_of(_CharT __c, size_type __pos = npos) const _NOEXCEPT
+    { return rfind(__c, __pos); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_last_of(const _CharT* __s, size_type __pos, size_type __n) const
+    {
+        _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string_view::find_last_of(): received nullptr");
+        return __str_find_last_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __s, __pos, __n);
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_last_of(const _CharT* __s, size_type __pos=npos) const
+    {
+        _LIBCPP_ASSERT(__s != nullptr, "string_view::find_last_of(): received nullptr");
+        return __str_find_last_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __s, __pos, traits_type::length(__s));
+    }
+
+    // find_first_not_of
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_first_not_of(basic_string_view __s, size_type __pos=0) const _NOEXCEPT
+    {
+        _LIBCPP_ASSERT(__s.size() == 0 || __s.data() != nullptr, "string_view::find_first_not_of(): received nullptr");
+        return __str_find_first_not_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __s.data(), __pos, __s.size());
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_first_not_of(_CharT __c, size_type __pos=0) const _NOEXCEPT
+    {
+        return __str_find_first_not_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __c, __pos);
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_first_not_of(const _CharT* __s, size_type __pos, size_type __n) const
+    {
+        _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string_view::find_first_not_of(): received nullptr");
+        return __str_find_first_not_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __s, __pos, __n);
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_first_not_of(const _CharT* __s, size_type __pos=0) const
+    {
+        _LIBCPP_ASSERT(__s != nullptr, "string_view::find_first_not_of(): received nullptr");
+        return __str_find_first_not_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __s, __pos, traits_type::length(__s));
+    }
+
+    // find_last_not_of
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_last_not_of(basic_string_view __s, size_type __pos=npos) const _NOEXCEPT
+    {
+        _LIBCPP_ASSERT(__s.size() == 0 || __s.data() != nullptr, "string_view::find_last_not_of(): received nullptr");
+        return __str_find_last_not_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __s.data(), __pos, __s.size());
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_last_not_of(_CharT __c, size_type __pos=npos) const _NOEXCEPT
+    {
+        return __str_find_last_not_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __c, __pos);
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_last_not_of(const _CharT* __s, size_type __pos, size_type __n) const
+    {
+        _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "string_view::find_last_not_of(): received nullptr");
+        return __str_find_last_not_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __s, __pos, __n);
+    }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    size_type find_last_not_of(const _CharT* __s, size_type __pos=npos) const
+    {
+        _LIBCPP_ASSERT(__s != nullptr, "string_view::find_last_not_of(): received nullptr");
+        return __str_find_last_not_of<value_type, size_type, traits_type, npos>
+            (data(), size(), __s, __pos, traits_type::length(__s));
+    }
+
+#if _LIBCPP_STD_VER > 17
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool starts_with(basic_string_view __s) const _NOEXCEPT
+    { return size() >= __s.size() && compare(0, __s.size(), __s) == 0; }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool starts_with(value_type __c) const _NOEXCEPT
+    { return !empty() && _Traits::eq(front(), __c); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool starts_with(const value_type* __s) const _NOEXCEPT
+    { return starts_with(basic_string_view(__s)); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool ends_with(basic_string_view __s) const _NOEXCEPT
+    { return size() >= __s.size() && compare(size() - __s.size(), npos, __s) == 0; }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool ends_with(value_type __c) const _NOEXCEPT
+    { return !empty() && _Traits::eq(back(), __c); }
+
+    _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+    bool ends_with(const value_type* __s) const _NOEXCEPT
+    { return ends_with(basic_string_view(__s)); }
+#endif
+
+private:
+    const   value_type* __data;
+    size_type           __size;
+};
+
+
+// [string.view.comparison]
+// operator ==
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator==(basic_string_view<_CharT, _Traits> __lhs,
+                basic_string_view<_CharT, _Traits> __rhs) _NOEXCEPT
+{
+    if ( __lhs.size() != __rhs.size()) return false;
+    return __lhs.compare(__rhs) == 0;
+}
+
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator==(basic_string_view<_CharT, _Traits> __lhs,
+                typename common_type<basic_string_view<_CharT, _Traits> >::type __rhs) _NOEXCEPT
+{
+    if ( __lhs.size() != __rhs.size()) return false;
+    return __lhs.compare(__rhs) == 0;
+}
+
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator==(typename common_type<basic_string_view<_CharT, _Traits> >::type __lhs, 
+                basic_string_view<_CharT, _Traits> __rhs) _NOEXCEPT
+{
+    if ( __lhs.size() != __rhs.size()) return false;
+    return __lhs.compare(__rhs) == 0;
+}
+
+
+// operator !=
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator!=(basic_string_view<_CharT, _Traits> __lhs, basic_string_view<_CharT, _Traits> __rhs) _NOEXCEPT
+{
+    if ( __lhs.size() != __rhs.size())
+        return true;
+    return __lhs.compare(__rhs) != 0;
+}
+
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator!=(basic_string_view<_CharT, _Traits> __lhs,
+                typename common_type<basic_string_view<_CharT, _Traits> >::type __rhs) _NOEXCEPT
+{
+    if ( __lhs.size() != __rhs.size())
+        return true;
+    return __lhs.compare(__rhs) != 0;
+}
+
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator!=(typename common_type<basic_string_view<_CharT, _Traits> >::type __lhs, 
+                basic_string_view<_CharT, _Traits> __rhs) _NOEXCEPT
+{
+    if ( __lhs.size() != __rhs.size())
+        return true;
+    return __lhs.compare(__rhs) != 0;
+}
+
+
+// operator <
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator<(basic_string_view<_CharT, _Traits> __lhs, basic_string_view<_CharT, _Traits> __rhs) _NOEXCEPT
+{
+    return __lhs.compare(__rhs) < 0;
+}
+
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator<(basic_string_view<_CharT, _Traits> __lhs,
+                typename common_type<basic_string_view<_CharT, _Traits> >::type __rhs) _NOEXCEPT
+{
+    return __lhs.compare(__rhs) < 0;
+}
+
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator<(typename common_type<basic_string_view<_CharT, _Traits> >::type __lhs, 
+                basic_string_view<_CharT, _Traits> __rhs) _NOEXCEPT
+{
+    return __lhs.compare(__rhs) < 0;
+}
+
+
+// operator >
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator> (basic_string_view<_CharT, _Traits> __lhs, basic_string_view<_CharT, _Traits> __rhs) _NOEXCEPT
+{
+    return __lhs.compare(__rhs) > 0;
+}
+
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator>(basic_string_view<_CharT, _Traits> __lhs,
+                typename common_type<basic_string_view<_CharT, _Traits> >::type __rhs) _NOEXCEPT
+{
+    return __lhs.compare(__rhs) > 0;
+}
+
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator>(typename common_type<basic_string_view<_CharT, _Traits> >::type __lhs, 
+                basic_string_view<_CharT, _Traits> __rhs) _NOEXCEPT
+{
+    return __lhs.compare(__rhs) > 0;
+}
+
+
+// operator <=
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator<=(basic_string_view<_CharT, _Traits> __lhs, basic_string_view<_CharT, _Traits> __rhs) _NOEXCEPT
+{
+    return __lhs.compare(__rhs) <= 0;
+}
+
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator<=(basic_string_view<_CharT, _Traits> __lhs,
+                typename common_type<basic_string_view<_CharT, _Traits> >::type __rhs) _NOEXCEPT
+{
+    return __lhs.compare(__rhs) <= 0;
+}
+
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator<=(typename common_type<basic_string_view<_CharT, _Traits> >::type __lhs, 
+                basic_string_view<_CharT, _Traits> __rhs) _NOEXCEPT
+{
+    return __lhs.compare(__rhs) <= 0;
+}
+
+
+// operator >=
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator>=(basic_string_view<_CharT, _Traits> __lhs, basic_string_view<_CharT, _Traits> __rhs) _NOEXCEPT
+{
+    return __lhs.compare(__rhs) >= 0;
+}
+
+
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator>=(basic_string_view<_CharT, _Traits> __lhs,
+                typename common_type<basic_string_view<_CharT, _Traits> >::type __rhs) _NOEXCEPT
+{
+    return __lhs.compare(__rhs) >= 0;
+}
+
+template<class _CharT, class _Traits>
+_LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+bool operator>=(typename common_type<basic_string_view<_CharT, _Traits> >::type __lhs, 
+                basic_string_view<_CharT, _Traits> __rhs) _NOEXCEPT
+{
+    return __lhs.compare(__rhs) >= 0;
+}
+
+typedef basic_string_view<char>     string_view;
+typedef basic_string_view<char16_t> u16string_view;
+typedef basic_string_view<char32_t> u32string_view;
+typedef basic_string_view<wchar_t>  wstring_view;
+
+// [string.view.hash]
+template<class _CharT, class _Traits>
+struct _LIBCPP_TEMPLATE_VIS hash<basic_string_view<_CharT, _Traits> >
+    : public unary_function<basic_string_view<_CharT, _Traits>, size_t>
+{
+    size_t operator()(const basic_string_view<_CharT, _Traits> __val) const _NOEXCEPT;
+};
+
+template<class _CharT, class _Traits>
+size_t
+hash<basic_string_view<_CharT, _Traits> >::operator()(
+        const basic_string_view<_CharT, _Traits> __val) const _NOEXCEPT
+{
+    return __do_string_hash(__val.data(), __val.data() + __val.size());
+}
+
+
+#if _LIBCPP_STD_VER > 11 
+inline namespace literals
+{
+  inline namespace string_view_literals
+  {
+    inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    basic_string_view<char> operator "" sv(const char *__str, size_t __len) _NOEXCEPT
+    {
+        return basic_string_view<char> (__str, __len);
+    }
+
+    inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    basic_string_view<wchar_t> operator "" sv(const wchar_t *__str, size_t __len) _NOEXCEPT
+    {
+        return basic_string_view<wchar_t> (__str, __len);
+    }
+
+    inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    basic_string_view<char16_t> operator "" sv(const char16_t *__str, size_t __len) _NOEXCEPT
+    {
+        return basic_string_view<char16_t> (__str, __len);
+    }
+
+    inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    basic_string_view<char32_t> operator "" sv(const char32_t *__str, size_t __len) _NOEXCEPT
+    {
+        return basic_string_view<char32_t> (__str, __len);
+    }
+  }
+}
+#endif
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP_STRING_VIEW
diff --git a/lib/libcxx/include/strstream b/lib/libcxx/include/strstream
index 81eef2ab484..b00b9d830df 100644
--- a/lib/libcxx/include/strstream
+++ b/lib/libcxx/include/strstream
@@ -151,12 +151,12 @@ public:
     strstreambuf(unsigned char* __gnext, streamsize __n, unsigned char* __pbeg = 0);
     strstreambuf(const unsigned char* __gnext, streamsize __n);
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     strstreambuf(strstreambuf&& __rhs);
     _LIBCPP_INLINE_VISIBILITY
     strstreambuf& operator=(strstreambuf&& __rhs);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     virtual ~strstreambuf();
 
@@ -191,7 +191,7 @@ private:
     void __init(char* __gnext, streamsize __n, char* __pbeg);
 };
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 inline _LIBCPP_INLINE_VISIBILITY
 strstreambuf::strstreambuf(strstreambuf&& __rhs)
@@ -226,7 +226,7 @@ strstreambuf::operator=(strstreambuf&& __rhs)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 class _LIBCPP_TYPE_VIS istrstream
     : public istream
@@ -245,7 +245,7 @@ public:
     istrstream(char* __s, streamsize __n)
         : istream(&__sb_), __sb_(__s, __n) {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     istrstream(istrstream&& __rhs)
         : istream(_VSTD::move(__rhs)),
@@ -261,7 +261,7 @@ public:
         __sb_ = _VSTD::move(__rhs.__sb_);
         return *this;
     }
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     virtual ~istrstream();
 
@@ -294,7 +294,7 @@ public:
           __sb_(__s, __n, __s + (__mode & ios::app ? strlen(__s) : 0))
         {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     ostrstream(ostrstream&& __rhs)
         : ostream(_VSTD::move(__rhs)),
@@ -310,7 +310,7 @@ public:
         __sb_ = _VSTD::move(__rhs.__sb_);
         return *this;
     }
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     virtual ~ostrstream();
 
@@ -354,7 +354,7 @@ public:
           __sb_(__s, __n, __s + (__mode & ios::app ? strlen(__s) : 0))
         {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     strstream(strstream&& __rhs)
         : iostream(_VSTD::move(__rhs)),
@@ -370,7 +370,7 @@ public:
         __sb_ = _VSTD::move(__rhs.__sb_);
         return *this;
     }
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     virtual ~strstream();
 
diff --git a/lib/libcxx/include/support/android/locale_bionic.h b/lib/libcxx/include/support/android/locale_bionic.h
index 1365563ee48..482e2343358 100644
--- a/lib/libcxx/include/support/android/locale_bionic.h
+++ b/lib/libcxx/include/support/android/locale_bionic.h
@@ -11,7 +11,7 @@
 #ifndef _LIBCPP_SUPPORT_ANDROID_LOCALE_BIONIC_H
 #define _LIBCPP_SUPPORT_ANDROID_LOCALE_BIONIC_H
 
-#if defined(__ANDROID__)
+#if defined(__BIONIC__)
 
 #ifdef __cplusplus
 extern "C" {
@@ -27,5 +27,5 @@ extern "C" {
 #include <support/xlocale/__posix_l_fallback.h>
 #include <support/xlocale/__strtonum_fallback.h>
 
-#endif // defined(__ANDROID__)
+#endif // defined(__BIONIC__)
 #endif // _LIBCPP_SUPPORT_ANDROID_LOCALE_BIONIC_H
diff --git a/lib/libcxx/include/support/fuchsia/xlocale.h b/lib/libcxx/include/support/fuchsia/xlocale.h
new file mode 100644
index 00000000000..1de2fca28e2
--- /dev/null
+++ b/lib/libcxx/include/support/fuchsia/xlocale.h
@@ -0,0 +1,23 @@
+// -*- C++ -*-
+//===------------------- support/fuchsia/xlocale.h ------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_SUPPORT_FUCHSIA_XLOCALE_H
+#define _LIBCPP_SUPPORT_FUCHSIA_XLOCALE_H
+
+#if defined(__Fuchsia__)
+
+#include <cstdlib>
+#include <cwchar>
+#include <support/xlocale/__posix_l_fallback.h>
+#include <support/xlocale/__strtonum_fallback.h>
+
+#endif // defined(__Fuchsia__)
+
+#endif // _LIBCPP_SUPPORT_FUCHSIA_XLOCALE_H
diff --git a/lib/libcxx/include/support/win32/limits_msvc_win32.h b/lib/libcxx/include/support/win32/limits_msvc_win32.h
new file mode 100644
index 00000000000..1ab2e0b6dc1
--- /dev/null
+++ b/lib/libcxx/include/support/win32/limits_msvc_win32.h
@@ -0,0 +1,72 @@
+// -*- C++ -*-
+//===------------------ support/win32/limits_msvc_win32.h -----------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_SUPPORT_WIN32_LIMITS_MSVC_WIN32_H
+#define _LIBCPP_SUPPORT_WIN32_LIMITS_MSVC_WIN32_H
+
+#if !defined(_LIBCPP_MSVCRT)
+#error "This header complements the Microsoft C Runtime library, and should not be included otherwise."
+#endif
+#if defined(__clang__)
+#error "This header should only be included when using Microsofts C1XX frontend"
+#endif
+
+#include <limits.h> // CHAR_BIT
+#include <float.h> // limit constants
+#include <math.h> // HUGE_VAL
+#include <ymath.h> // internal MSVC header providing the needed functionality
+
+#define __CHAR_BIT__       CHAR_BIT
+
+#define __FLT_MANT_DIG__   FLT_MANT_DIG
+#define __FLT_DIG__        FLT_DIG
+#define __FLT_RADIX__      FLT_RADIX
+#define __FLT_MIN_EXP__    FLT_MIN_EXP
+#define __FLT_MIN_10_EXP__ FLT_MIN_10_EXP
+#define __FLT_MAX_EXP__    FLT_MAX_EXP
+#define __FLT_MAX_10_EXP__ FLT_MAX_10_EXP
+#define __FLT_MIN__        FLT_MIN
+#define __FLT_MAX__        FLT_MAX
+#define __FLT_EPSILON__    FLT_EPSILON
+// predefined by MinGW GCC
+#define __FLT_DENORM_MIN__ 1.40129846432481707092e-45F
+
+#define __DBL_MANT_DIG__   DBL_MANT_DIG
+#define __DBL_DIG__        DBL_DIG
+#define __DBL_RADIX__      DBL_RADIX
+#define __DBL_MIN_EXP__    DBL_MIN_EXP
+#define __DBL_MIN_10_EXP__ DBL_MIN_10_EXP
+#define __DBL_MAX_EXP__    DBL_MAX_EXP
+#define __DBL_MAX_10_EXP__ DBL_MAX_10_EXP
+#define __DBL_MIN__        DBL_MIN
+#define __DBL_MAX__        DBL_MAX
+#define __DBL_EPSILON__    DBL_EPSILON
+// predefined by MinGW GCC
+#define __DBL_DENORM_MIN__ double(4.94065645841246544177e-324L)
+
+#define __LDBL_MANT_DIG__   LDBL_MANT_DIG
+#define __LDBL_DIG__        LDBL_DIG
+#define __LDBL_RADIX__      LDBL_RADIX
+#define __LDBL_MIN_EXP__    LDBL_MIN_EXP
+#define __LDBL_MIN_10_EXP__ LDBL_MIN_10_EXP
+#define __LDBL_MAX_EXP__    LDBL_MAX_EXP
+#define __LDBL_MAX_10_EXP__ LDBL_MAX_10_EXP
+#define __LDBL_MIN__        LDBL_MIN
+#define __LDBL_MAX__        LDBL_MAX
+#define __LDBL_EPSILON__    LDBL_EPSILON
+// predefined by MinGW GCC
+#define __LDBL_DENORM_MIN__ 3.64519953188247460253e-4951L
+
+// __builtin replacements/workarounds
+#define __builtin_huge_vall()    _LInf._Long_double
+#define __builtin_nanl(__dummmy) _LNan._Long_double
+#define __builtin_nansl(__dummy) _LSnan._Long_double
+
+#endif // _LIBCPP_SUPPORT_WIN32_LIMITS_MSVC_WIN32_H
diff --git a/lib/libcxx/include/support/win32/locale_win32.h b/lib/libcxx/include/support/win32/locale_win32.h
index 7f3710ecc18..aebfff22ecf 100644
--- a/lib/libcxx/include/support/win32/locale_win32.h
+++ b/lib/libcxx/include/support/win32/locale_win32.h
@@ -11,13 +11,96 @@
 #ifndef _LIBCPP_SUPPORT_WIN32_LOCALE_WIN32_H
 #define _LIBCPP_SUPPORT_WIN32_LOCALE_WIN32_H
 
-// ctype mask table defined in msvcrt.dll
-extern "C" unsigned short  __declspec(dllimport) _ctype[];
-
-#include "support/win32/support.h"
-#include "support/win32/locale_mgmt_win32.h"
+#include <__config>
 #include <stdio.h>
-#include <memory>
+#include <xlocinfo.h> // _locale_t
+#include <__nullptr>
+
+#define LC_COLLATE_MASK _M_COLLATE
+#define LC_CTYPE_MASK _M_CTYPE
+#define LC_MONETARY_MASK _M_MONETARY
+#define LC_NUMERIC_MASK _M_NUMERIC
+#define LC_TIME_MASK _M_TIME
+#define LC_MESSAGES_MASK _M_MESSAGES
+#define LC_ALL_MASK (  LC_COLLATE_MASK \
+                     | LC_CTYPE_MASK \
+                     | LC_MESSAGES_MASK \
+                     | LC_MONETARY_MASK \
+                     | LC_NUMERIC_MASK \
+                     | LC_TIME_MASK )
+
+class locale_t {
+public:
+    locale_t()
+        : __locale(nullptr), __locale_str(nullptr) {}
+    locale_t(std::nullptr_t)
+        : __locale(nullptr), __locale_str(nullptr) {}
+    locale_t(_locale_t __locale, const char* __locale_str)
+        : __locale(__locale), __locale_str(__locale_str) {}
+
+    friend bool operator==(const locale_t& __left, const locale_t& __right) {
+        return __left.__locale == __right.__locale;
+    }
+
+    friend bool operator==(const locale_t& __left, int __right) {
+        return __left.__locale == nullptr && __right == 0;
+    }
+
+    friend bool operator==(const locale_t& __left, std::nullptr_t) {
+        return __left.__locale == nullptr;
+    }
+
+    friend bool operator==(int __left, const locale_t& __right) {
+        return __left == 0 && nullptr == __right.__locale;
+    }
+
+    friend bool operator==(std::nullptr_t, const locale_t& __right) {
+        return nullptr == __right.__locale;
+    }
+
+    friend bool operator!=(const locale_t& __left, const locale_t& __right) {
+        return !(__left == __right);
+    }
+
+    friend bool operator!=(const locale_t& __left, int __right) {
+        return !(__left == __right);
+    }
+
+    friend bool operator!=(const locale_t& __left, std::nullptr_t __right) {
+        return !(__left == __right);
+    }
+
+    friend bool operator!=(int __left, const locale_t& __right) {
+        return !(__left == __right);
+    }
+
+    friend bool operator!=(std::nullptr_t __left, const locale_t& __right) {
+        return !(__left == __right);
+    }
+
+    operator bool() const {
+        return __locale != nullptr;
+    }
+
+    const char* __get_locale() const { return __locale_str; }
+
+    operator _locale_t() const {
+        return __locale;
+    }
+private:
+    _locale_t __locale;
+    const char* __locale_str;
+};
+
+// Locale management functions
+#define freelocale _free_locale
+// FIXME: base currently unused. Needs manual work to construct the new locale
+locale_t newlocale( int mask, const char * locale, locale_t base );
+// uselocale can't be implemented on Windows because Windows allows partial modification
+// of thread-local locale and so _get_current_locale() returns a copy while uselocale does
+// not create any copies.
+// We can still implement raii even without uselocale though.
+
 
 lconv *localeconv_l( locale_t loc );
 size_t mbrlen_l( const char *__restrict s, size_t n,
@@ -34,22 +117,21 @@ size_t wcsnrtombs_l( char *__restrict dst, const wchar_t **__restrict src,
                      size_t nwc, size_t len, mbstate_t *__restrict ps, locale_t loc);
 wint_t btowc_l( int c, locale_t loc );
 int wctob_l( wint_t c, locale_t loc );
-typedef _VSTD::remove_pointer<locale_t>::type __locale_struct;
-typedef _VSTD::unique_ptr<__locale_struct, decltype(&uselocale)> __locale_raii;
-inline _LIBCPP_ALWAYS_INLINE
-decltype(MB_CUR_MAX) MB_CUR_MAX_L( locale_t __l )
-{
-  __locale_raii __current( uselocale(__l), uselocale );
-  return MB_CUR_MAX;
-}
+
+decltype(MB_CUR_MAX) MB_CUR_MAX_L( locale_t __l );
 
 // the *_l functions are prefixed on Windows, only available for msvcr80+, VS2005+
 #define mbtowc_l _mbtowc_l
 #define strtoll_l _strtoi64_l
 #define strtoull_l _strtoui64_l
-// FIXME: current msvcrt does not know about long double
-#define strtold_l _strtod_l
-
+#define strtod_l _strtod_l
+#if defined(_LIBCPP_MSVCRT)
+#define strtof_l _strtof_l
+#define strtold_l _strtold_l
+#else
+float strtof_l(const char*, char**, locale_t);
+long double strtold_l(const char*, char**, locale_t);
+#endif
 inline _LIBCPP_INLINE_VISIBILITY
 int
 islower_l(int c, _locale_t loc)
@@ -83,16 +165,18 @@ isupper_l(int c, _locale_t loc)
 #define iswxdigit_l _iswxdigit_l
 #define towupper_l _towupper_l
 #define towlower_l _towlower_l
+#if defined(__MINGW32__) && __MSVCRT_VERSION__ < 0x0800
+#define strftime_l( __s, __l, __f, __tm, __loc ) strftime( __s, __l, __f, __tm )
+#else
 #define strftime_l _strftime_l
+#endif
 #define sscanf_l( __s, __l, __f, ...) _sscanf_l( __s, __f, __l, __VA_ARGS__ )
-#define vsscanf_l( __s, __l, __f, ...) _sscanf_l( __s, __f, __l, __VA_ARGS__ )
 #define sprintf_l( __s, __l, __f, ... ) _sprintf_l( __s, __f, __l, __VA_ARGS__ )
 #define vsprintf_l( __s, __l, __f, ... ) _vsprintf_l( __s, __f, __l, __VA_ARGS__ )
 #define vsnprintf_l( __s, __n, __l, __f, ... ) _vsnprintf_l( __s, __n, __f, __l, __VA_ARGS__ )
-int snprintf_l(char *ret, size_t n, locale_t loc, const char *format, ...);
-int asprintf_l( char **ret, locale_t loc, const char *format, ... );
-int vasprintf_l( char **ret, locale_t loc, const char *format, va_list ap );
-
+_LIBCPP_FUNC_VIS int snprintf_l(char *ret, size_t n, locale_t loc, const char *format, ...);
+_LIBCPP_FUNC_VIS int asprintf_l( char **ret, locale_t loc, const char *format, ... );
+_LIBCPP_FUNC_VIS int vasprintf_l( char **ret, locale_t loc, const char *format, va_list ap );
 
 // not-so-pressing FIXME: use locale to determine blank characters
 inline int isblank_l( int c, locale_t /*loc*/ )
@@ -104,10 +188,4 @@ inline int iswblank_l( wint_t c, locale_t /*loc*/ )
     return ( c == L' ' || c == L'\t' );
 }
 
-#if defined(_LIBCPP_MSVCRT)
-inline int isblank( int c, locale_t /*loc*/ )
-{ return ( c == ' ' || c == '\t' ); }
-inline int iswblank( wint_t c, locale_t /*loc*/ )
-{ return ( c == L' ' || c == L'\t' ); }
-#endif // _LIBCPP_MSVCRT
 #endif // _LIBCPP_SUPPORT_WIN32_LOCALE_WIN32_H
diff --git a/lib/libcxx/include/support/xlocale/__posix_l_fallback.h b/lib/libcxx/include/support/xlocale/__posix_l_fallback.h
index 8bf9567ffc2..c893a67313c 100644
--- a/lib/libcxx/include/support/xlocale/__posix_l_fallback.h
+++ b/lib/libcxx/include/support/xlocale/__posix_l_fallback.h
@@ -124,11 +124,11 @@ inline _LIBCPP_ALWAYS_INLINE int tolower_l(int c, locale_t) {
   return ::tolower(c);
 }
 
-inline _LIBCPP_ALWAYS_INLINE int towupper_l(int c, locale_t) {
+inline _LIBCPP_ALWAYS_INLINE wint_t towupper_l(wint_t c, locale_t) {
   return ::towupper(c);
 }
 
-inline _LIBCPP_ALWAYS_INLINE int towlower_l(int c, locale_t) {
+inline _LIBCPP_ALWAYS_INLINE wint_t towlower_l(wint_t c, locale_t) {
   return ::towlower(c);
 }
 
diff --git a/lib/libcxx/include/system_error b/lib/libcxx/include/system_error
index 134bb327403..c577edceee8 100644
--- a/lib/libcxx/include/system_error
+++ b/lib/libcxx/include/system_error
@@ -46,6 +46,12 @@ template <class T> struct is_error_code_enum
 template <class T> struct is_error_condition_enum
     : public false_type {};
 
+template <class _Tp>
+inline constexpr size_t is_error_condition_enum_v = is_error_condition_enum<_Tp>::value; // C++17
+
+template <class _Tp>
+inline constexpr size_t is_error_code_enum_v = is_error_code_enum<_Tp>::value; // C++17
+
 class error_code
 {
 public:
@@ -213,6 +219,7 @@ bool operator!=(const error_condition& lhs, const error_code& rhs) noexcept;
 bool operator!=(const error_condition& lhs, const error_condition& rhs) noexcept;
 
 template <> struct hash<std::error_code>;
+template <> struct hash<std::error_condition>;
 
 }  // std
 
@@ -223,6 +230,7 @@ template <> struct hash<std::error_code>;
 #include <type_traits>
 #include <stdexcept>
 #include <__functional_base>
+#include <string>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
@@ -233,15 +241,25 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 // is_error_code_enum
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_error_code_enum
+struct _LIBCPP_TEMPLATE_VIS is_error_code_enum
     : public false_type {};
 
+#if _LIBCPP_STD_VER > 14
+template <class _Tp>
+_LIBCPP_INLINE_VAR constexpr size_t is_error_code_enum_v = is_error_code_enum<_Tp>::value;
+#endif
+
 // is_error_condition_enum
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_error_condition_enum
+struct _LIBCPP_TEMPLATE_VIS is_error_condition_enum
     : public false_type {};
 
+#if _LIBCPP_STD_VER > 14
+template <class _Tp>
+_LIBCPP_INLINE_VAR constexpr size_t is_error_condition_enum_v = is_error_condition_enum<_Tp>::value;
+#endif
+
 // Some error codes are not present on all platforms, so we provide equivalents
 // for them:
 
@@ -346,12 +364,12 @@ _LIBCPP_DECLARE_STRONG_ENUM(errc)
 _LIBCPP_DECLARE_STRONG_ENUM_EPILOG(errc)
 
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY is_error_condition_enum<errc>
+struct _LIBCPP_TEMPLATE_VIS is_error_condition_enum<errc>
     : true_type { };
 
 #ifdef _LIBCPP_HAS_NO_STRONG_ENUMS
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY is_error_condition_enum<errc::__lx>
+struct _LIBCPP_TEMPLATE_VIS is_error_condition_enum<errc::__lx>
     : true_type { };
 #endif
 
@@ -367,7 +385,8 @@ class _LIBCPP_TYPE_VIS error_category
 public:
     virtual ~error_category() _NOEXCEPT;
 
-#ifdef _LIBCPP_BUILDING_SYSTEM_ERROR
+#if defined(_LIBCPP_BUILDING_SYSTEM_ERROR) && \
+    defined(_LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS)
     error_category() _NOEXCEPT;
 #else
     _LIBCPP_ALWAYS_INLINE
@@ -603,7 +622,7 @@ operator!=(const error_condition& __x, const error_condition& __y) _NOEXCEPT
 {return !(__x == __y);}
 
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<error_code>
+struct _LIBCPP_TEMPLATE_VIS hash<error_code>
     : public unary_function<error_code, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -613,6 +632,17 @@ struct _LIBCPP_TYPE_VIS_ONLY hash<error_code>
     }
 };
 
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<error_condition>
+    : public unary_function<error_condition, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(const error_condition& __ec) const _NOEXCEPT
+    {
+        return static_cast<size_t>(__ec.value());
+    }
+};
+
 // system_error
 
 class _LIBCPP_TYPE_VIS system_error
@@ -635,7 +665,8 @@ private:
     static string __init(const error_code&, string);
 };
 
-_LIBCPP_FUNC_VIS void __throw_system_error(int ev, const char* what_arg);
+_LIBCPP_NORETURN _LIBCPP_FUNC_VIS
+void __throw_system_error(int ev, const char* what_arg);
 
 _LIBCPP_END_NAMESPACE_STD
 
diff --git a/lib/libcxx/include/thread b/lib/libcxx/include/thread
index 022021c5add..1b8dca394aa 100644
--- a/lib/libcxx/include/thread
+++ b/lib/libcxx/include/thread
@@ -95,15 +95,19 @@ void sleep_for(const chrono::duration<Rep, Period>& rel_time);
 #include <system_error>
 #include <chrono>
 #include <__mutex_base>
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 #include <tuple>
 #endif
 #include <__threading_support>
+#include <__debug>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 #define __STDCPP_THREADS__ __cplusplus
 
 #ifdef _LIBCPP_HAS_NO_THREADS
@@ -136,7 +140,7 @@ public:
 template <class _Tp>
 class __thread_specific_ptr
 {
-    __libcpp_tl_key __key_;
+    __libcpp_tls_key __key_;
 
      // Only __thread_local_data() may construct a __thread_specific_ptr
      // and only with _Tp == __thread_struct.
@@ -147,24 +151,24 @@ class __thread_specific_ptr
     __thread_specific_ptr(const __thread_specific_ptr&);
     __thread_specific_ptr& operator=(const __thread_specific_ptr&);
 
-    static void __at_thread_exit(void*);
+    static void _LIBCPP_TLS_DESTRUCTOR_CC __at_thread_exit(void*);
+
 public:
     typedef _Tp* pointer;
 
     ~__thread_specific_ptr();
 
     _LIBCPP_INLINE_VISIBILITY
-    pointer get() const {return static_cast<_Tp*>(__libcpp_tl_get(__key_));}
+    pointer get() const {return static_cast<_Tp*>(__libcpp_tls_get(__key_));}
     _LIBCPP_INLINE_VISIBILITY
     pointer operator*() const {return *get();}
     _LIBCPP_INLINE_VISIBILITY
     pointer operator->() const {return get();}
-    pointer release();
-    void reset(pointer __p = nullptr);
+    void set_pointer(pointer __p);
 };
 
 template <class _Tp>
-void
+void _LIBCPP_TLS_DESTRUCTOR_CC
 __thread_specific_ptr<_Tp>::__at_thread_exit(void* __p)
 {
     delete static_cast<pointer>(__p);
@@ -173,12 +177,10 @@ __thread_specific_ptr<_Tp>::__at_thread_exit(void* __p)
 template <class _Tp>
 __thread_specific_ptr<_Tp>::__thread_specific_ptr()
 {
-    int __ec = __libcpp_tl_create(
-        &__key_,
-        &__thread_specific_ptr::__at_thread_exit);
-    if (__ec)
-        __throw_system_error(__ec,
-                           "__thread_specific_ptr construction failed");
+  int __ec =
+      __libcpp_tls_create(&__key_, &__thread_specific_ptr::__at_thread_exit);
+  if (__ec)
+    __throw_system_error(__ec, "__thread_specific_ptr construction failed");
 }
 
 template <class _Tp>
@@ -191,21 +193,12 @@ __thread_specific_ptr<_Tp>::~__thread_specific_ptr()
 }
 
 template <class _Tp>
-typename __thread_specific_ptr<_Tp>::pointer
-__thread_specific_ptr<_Tp>::release()
-{
-    pointer __p = get();
-    __libcpp_tl_set(__key_, nullptr);
-    return __p;
-}
-
-template <class _Tp>
 void
-__thread_specific_ptr<_Tp>::reset(pointer __p)
+__thread_specific_ptr<_Tp>::set_pointer(pointer __p)
 {
-    pointer __p_old = get();
-    __libcpp_tl_set(__key_, __p);
-    delete __p_old;
+    _LIBCPP_ASSERT(get() == nullptr,
+                   "Attempting to overwrite thread local data");
+    __libcpp_tls_set(__key_, __p);
 }
 
 class _LIBCPP_TYPE_VIS thread;
@@ -220,7 +213,7 @@ _LIBCPP_INLINE_VISIBILITY __thread_id get_id() _NOEXCEPT;
 
 template<> struct hash<__thread_id>;
 
-class _LIBCPP_TYPE_VIS_ONLY __thread_id
+class _LIBCPP_TEMPLATE_VIS __thread_id
 {
     // FIXME: pthread_t is a pointer on Darwin but a long on Linux.
     // NULL is the no-thread value on Darwin.  Someone needs to check
@@ -263,15 +256,15 @@ private:
 
     friend __thread_id this_thread::get_id() _NOEXCEPT;
     friend class _LIBCPP_TYPE_VIS thread;
-    friend struct _LIBCPP_TYPE_VIS_ONLY hash<__thread_id>;
+    friend struct _LIBCPP_TEMPLATE_VIS hash<__thread_id>;
 };
 
 template<>
-struct _LIBCPP_TYPE_VIS_ONLY hash<__thread_id>
+struct _LIBCPP_TEMPLATE_VIS hash<__thread_id>
     : public unary_function<__thread_id, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
-    size_t operator()(__thread_id __v) const
+    size_t operator()(__thread_id __v) const _NOEXCEPT
     {
         return hash<__libcpp_thread_id>()(__v.__id_);
     }
@@ -300,32 +293,35 @@ public:
     typedef __libcpp_thread_t native_handle_type;
 
     _LIBCPP_INLINE_VISIBILITY
-    thread() _NOEXCEPT : __t_(0) {}
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+    thread() _NOEXCEPT : __t_(_LIBCPP_NULL_THREAD) {}
+#ifndef _LIBCPP_CXX03_LANG
     template <class _Fp, class ..._Args,
               class = typename enable_if
               <
                    !is_same<typename decay<_Fp>::type, thread>::value
               >::type
              >
+        _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         explicit thread(_Fp&& __f, _Args&&... __args);
-#else  // _LIBCPP_HAS_NO_VARIADICS
-    template <class _Fp> explicit thread(_Fp __f);
+#else  // _LIBCPP_CXX03_LANG
+    template <class _Fp>
+    _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
+    explicit thread(_Fp __f);
 #endif
     ~thread();
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
-    thread(thread&& __t) _NOEXCEPT : __t_(__t.__t_) {__t.__t_ = 0;}
+    thread(thread&& __t) _NOEXCEPT : __t_(__t.__t_) {__t.__t_ = _LIBCPP_NULL_THREAD;}
     _LIBCPP_INLINE_VISIBILITY
     thread& operator=(thread&& __t) _NOEXCEPT;
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     void swap(thread& __t) _NOEXCEPT {_VSTD::swap(__t_, __t.__t_);}
 
     _LIBCPP_INLINE_VISIBILITY
-    bool joinable() const _NOEXCEPT {return __t_ != 0;}
+    bool joinable() const _NOEXCEPT {return !__libcpp_thread_isnull(&__t_);}
     void join();
     void detach();
     _LIBCPP_INLINE_VISIBILITY
@@ -336,7 +332,7 @@ public:
     static unsigned hardware_concurrency() _NOEXCEPT;
 };
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _TSp, class _Fp, class ..._Args, size_t ..._Indices>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -351,7 +347,7 @@ void* __thread_proxy(void* __vp)
 {
     // _Fp = std::tuple< unique_ptr<__thread_struct>, Functor, Args...>
     std::unique_ptr<_Fp> __p(static_cast<_Fp*>(__vp));
-    __thread_local_data().reset(_VSTD::get<0>(*__p).release());
+    __thread_local_data().set_pointer(_VSTD::get<0>(*__p).release());
     typedef typename __make_tuple_indices<tuple_size<_Fp>::value, 2>::type _Index;
     __thread_execute(*__p, _Index());
     return nullptr;
@@ -376,7 +372,18 @@ thread::thread(_Fp&& __f, _Args&&... __args)
         __throw_system_error(__ec, "thread constructor failed");
 }
 
-#else  // _LIBCPP_HAS_NO_VARIADICS
+inline
+thread&
+thread::operator=(thread&& __t) _NOEXCEPT
+{
+    if (!__libcpp_thread_isnull(&__t_))
+        terminate();
+    __t_ = __t.__t_;
+    __t.__t_ = _LIBCPP_NULL_THREAD;
+    return *this;
+}
+
+#else  // _LIBCPP_CXX03_LANG
 
 template <class _Fp>
 struct __thread_invoke_pair {
@@ -392,7 +399,7 @@ template <class _Fp>
 void* __thread_proxy_cxx03(void* __vp)
 {
     std::unique_ptr<_Fp> __p(static_cast<_Fp*>(__vp));
-    __thread_local_data().reset(__p->__tsp_.release());
+    __thread_local_data().set_pointer(__p->__tsp_.release());
     (__p->__fn_)();
     return nullptr;
 }
@@ -411,22 +418,7 @@ thread::thread(_Fp __f)
         __throw_system_error(__ec, "thread constructor failed");
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-inline
-thread&
-thread::operator=(thread&& __t) _NOEXCEPT
-{
-    if (__t_ != 0)
-        terminate();
-    __t_ = __t.__t_;
-    __t.__t_ = 0;
-    return *this;
-}
-
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 inline _LIBCPP_INLINE_VISIBILITY
 void swap(thread& __x, thread& __y) _NOEXCEPT {__x.swap(__y);}
@@ -434,7 +426,7 @@ void swap(thread& __x, thread& __y) _NOEXCEPT {__x.swap(__y);}
 namespace this_thread
 {
 
-_LIBCPP_FUNC_VIS void sleep_for(const chrono::nanoseconds& ns);
+_LIBCPP_FUNC_VIS void sleep_for(const chrono::nanoseconds& __ns);
 
 template <class _Rep, class _Period>
 void
@@ -487,4 +479,6 @@ _LIBCPP_END_NAMESPACE_STD
 
 #endif // !_LIBCPP_HAS_NO_THREADS
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_THREAD
diff --git a/lib/libcxx/include/tuple b/lib/libcxx/include/tuple
index 6805d8c7635..31578d1557a 100644
--- a/lib/libcxx/include/tuple
+++ b/lib/libcxx/include/tuple
@@ -70,7 +70,7 @@ public:
     void swap(tuple&) noexcept(AND(swap(declval<T&>(), declval<T&>())...));
 };
 
-const unspecified ignore;
+inline constexpr unspecified ignore;
 
 template <class... T> tuple<V...>  make_tuple(T&&...); // constexpr in C++14
 template <class... T> tuple<ATypes...> forward_as_tuple(T&&...) noexcept; // constexpr in C++14
@@ -87,7 +87,7 @@ template <class T, class Tuple>
 template <class T> class tuple_size; // undefined
 template <class... T> class tuple_size<tuple<T...>>;
 template <class T>
- constexpr size_t tuple_size_v = tuple_size<T>::value; // C++17
+ inline constexpr size_t tuple_size_v = tuple_size<T>::value; // C++17
 template <size_t I, class T> class tuple_element; // undefined
 template <size_t I, class... T> class tuple_element<I, tuple<T...>>;
 template <size_t I, class T>
@@ -148,29 +148,8 @@ template <class... Types>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
 
-// tuple_size
-
-template <class ..._Tp>
-class _LIBCPP_TYPE_VIS_ONLY tuple_size<tuple<_Tp...> >
-    : public integral_constant<size_t, sizeof...(_Tp)>
-{
-};
-
-// tuple_element
-
-template <size_t _Ip, class ..._Tp>
-class _LIBCPP_TYPE_VIS_ONLY tuple_element<_Ip, tuple<_Tp...> >
-{
-public:
-    typedef typename tuple_element<_Ip, __tuple_types<_Tp...> >::type type;
-};
-
-#if _LIBCPP_STD_VER > 11
-template <size_t _Ip, class ..._Tp>
-using tuple_element_t = typename tuple_element <_Ip, _Tp...>::type;
-#endif
 
 // __tuple_leaf
 
@@ -190,33 +169,47 @@ void swap(__tuple_leaf<_Ip, _Hp, _Ep>& __x, __tuple_leaf<_Ip, _Hp, _Ep>& __y)
 template <size_t _Ip, class _Hp, bool>
 class __tuple_leaf
 {
-    _Hp value;
+    _Hp __value_;
+
+    template <class _Tp>
+    static constexpr bool __can_bind_reference() {
+        using _RawTp = typename remove_reference<_Tp>::type;
+        using _RawHp = typename remove_reference<_Hp>::type;
+        using _CheckLValueArg = integral_constant<bool,
+            is_lvalue_reference<_Tp>::value
+        ||  is_same<_RawTp, reference_wrapper<_RawHp>>::value
+        ||  is_same<_RawTp, reference_wrapper<typename remove_const<_RawHp>::type>>::value
+        >;
+        return  !is_reference<_Hp>::value
+            || (is_lvalue_reference<_Hp>::value && _CheckLValueArg::value)
+            || (is_rvalue_reference<_Hp>::value && !is_lvalue_reference<_Tp>::value);
+    }
 
     __tuple_leaf& operator=(const __tuple_leaf&);
 public:
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR __tuple_leaf()
-             _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) : value()
+             _NOEXCEPT_(is_nothrow_default_constructible<_Hp>::value) : __value_()
        {static_assert(!is_reference<_Hp>::value,
               "Attempted to default construct a reference element in a tuple");}
 
     template <class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         __tuple_leaf(integral_constant<int, 0>, const _Alloc&)
-            : value()
+            : __value_()
         {static_assert(!is_reference<_Hp>::value,
               "Attempted to default construct a reference element in a tuple");}
 
     template <class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a)
-            : value(allocator_arg_t(), __a)
+            : __value_(allocator_arg_t(), __a)
         {static_assert(!is_reference<_Hp>::value,
               "Attempted to default construct a reference element in a tuple");}
 
     template <class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a)
-            : value(__a)
+            : __value_(__a)
         {static_assert(!is_reference<_Hp>::value,
               "Attempted to default construct a reference element in a tuple");}
 
@@ -230,60 +223,30 @@ public:
             >
         _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
         explicit __tuple_leaf(_Tp&& __t) _NOEXCEPT_((is_nothrow_constructible<_Hp, _Tp>::value))
-            : value(_VSTD::forward<_Tp>(__t))
-        {static_assert(!is_reference<_Hp>::value ||
-                       (is_lvalue_reference<_Hp>::value &&
-                        (is_lvalue_reference<_Tp>::value ||
-                         is_same<typename remove_reference<_Tp>::type,
-                                 reference_wrapper<
-                                    typename remove_reference<_Hp>::type
-                                 >
-                                >::value)) ||
-                        (is_rvalue_reference<_Hp>::value &&
-                         !is_lvalue_reference<_Tp>::value),
+            : __value_(_VSTD::forward<_Tp>(__t))
+        {static_assert(__can_bind_reference<_Tp>(),
        "Attempted to construct a reference element in a tuple with an rvalue");}
 
     template <class _Tp, class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         explicit __tuple_leaf(integral_constant<int, 0>, const _Alloc&, _Tp&& __t)
-            : value(_VSTD::forward<_Tp>(__t))
-        {static_assert(!is_lvalue_reference<_Hp>::value ||
-                       (is_lvalue_reference<_Hp>::value &&
-                        (is_lvalue_reference<_Tp>::value ||
-                         is_same<typename remove_reference<_Tp>::type,
-                                 reference_wrapper<
-                                    typename remove_reference<_Hp>::type
-                                 >
-                                >::value)),
+            : __value_(_VSTD::forward<_Tp>(__t))
+        {static_assert(__can_bind_reference<_Tp>(),
        "Attempted to construct a reference element in a tuple with an rvalue");}
 
     template <class _Tp, class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         explicit __tuple_leaf(integral_constant<int, 1>, const _Alloc& __a, _Tp&& __t)
-            : value(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t))
-        {static_assert(!is_lvalue_reference<_Hp>::value ||
-                       (is_lvalue_reference<_Hp>::value &&
-                        (is_lvalue_reference<_Tp>::value ||
-                         is_same<typename remove_reference<_Tp>::type,
-                                 reference_wrapper<
-                                    typename remove_reference<_Hp>::type
-                                 >
-                                >::value)),
-       "Attempted to construct a reference element in a tuple with an rvalue");}
+            : __value_(allocator_arg_t(), __a, _VSTD::forward<_Tp>(__t))
+        {static_assert(!is_reference<_Hp>::value,
+            "Attempted to uses-allocator construct a reference element in a tuple");}
 
     template <class _Tp, class _Alloc>
         _LIBCPP_INLINE_VISIBILITY
         explicit __tuple_leaf(integral_constant<int, 2>, const _Alloc& __a, _Tp&& __t)
-            : value(_VSTD::forward<_Tp>(__t), __a)
-        {static_assert(!is_lvalue_reference<_Hp>::value ||
-                       (is_lvalue_reference<_Hp>::value &&
-                        (is_lvalue_reference<_Tp>::value ||
-                         is_same<typename remove_reference<_Tp>::type,
-                                 reference_wrapper<
-                                    typename remove_reference<_Hp>::type
-                                 >
-                                >::value)),
-       "Attempted to construct a reference element in a tuple with an rvalue");}
+            : __value_(_VSTD::forward<_Tp>(__t), __a)
+        {static_assert(!is_reference<_Hp>::value,
+           "Attempted to uses-allocator construct a reference element in a tuple");}
 
     __tuple_leaf(const __tuple_leaf& __t) = default;
     __tuple_leaf(__tuple_leaf&& __t) = default;
@@ -293,7 +256,7 @@ public:
         __tuple_leaf&
         operator=(_Tp&& __t) _NOEXCEPT_((is_nothrow_assignable<_Hp&, _Tp>::value))
         {
-            value = _VSTD::forward<_Tp>(__t);
+            __value_ = _VSTD::forward<_Tp>(__t);
             return *this;
         }
 
@@ -304,8 +267,8 @@ public:
         return 0;
     }
 
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11       _Hp& get()       _NOEXCEPT {return value;}
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const _Hp& get() const _NOEXCEPT {return value;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11       _Hp& get()       _NOEXCEPT {return __value_;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11 const _Hp& get() const _NOEXCEPT {return __value_;}
 };
 
 template <size_t _Ip, class _Hp>
@@ -403,7 +366,7 @@ struct __all_default_constructible<__tuple_types<_Tp...>>
 template<class _Indx, class ..._Tp> struct __tuple_impl;
 
 template<size_t ..._Indx, class ..._Tp>
-struct __tuple_impl<__tuple_indices<_Indx...>, _Tp...>
+struct _LIBCPP_DECLSPEC_EMPTY_BASES __tuple_impl<__tuple_indices<_Indx...>, _Tp...>
     : public __tuple_leaf<_Indx, _Tp>...
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -505,34 +468,20 @@ struct __tuple_impl<__tuple_indices<_Indx...>, _Tp...>
     }
 };
 
-template <bool _IsTuple, class _SizeTrait, size_t _Expected>
-struct __tuple_like_with_size_imp : false_type {};
-
-template <class _SizeTrait, size_t _Expected>
-struct __tuple_like_with_size_imp<true, _SizeTrait, _Expected>
-    : integral_constant<bool, _SizeTrait::value == _Expected> {};
 
-template <class _Tuple, size_t _ExpectedSize,
-          class _RawTuple = typename __uncvref<_Tuple>::type>
-using __tuple_like_with_size = __tuple_like_with_size_imp<
-                                   __tuple_like<_RawTuple>::value,
-                                   tuple_size<_RawTuple>, _ExpectedSize
-                              >;
-
-
-struct _LIBCPP_TYPE_VIS __check_tuple_constructor_fail {
-    template <class ...>
-    static constexpr bool __enable_explicit() { return false; }
-    template <class ...>
-    static constexpr bool __enable_implicit() { return false; }
-};
 
 template <class ..._Tp>
-class _LIBCPP_TYPE_VIS_ONLY tuple
+class _LIBCPP_TEMPLATE_VIS tuple
 {
-    typedef __tuple_impl<typename __make_tuple_indices<sizeof...(_Tp)>::type, _Tp...> base;
+    typedef __tuple_impl<typename __make_tuple_indices<sizeof...(_Tp)>::type, _Tp...> _BaseT;
+
+    _BaseT __base_;
 
-    base base_;
+#if defined(_LIBCPP_ENABLE_TUPLE_IMPLICIT_REDUCED_ARITY_EXTENSION)
+    static constexpr bool _EnableImplicitReducedArityExtension = true;
+#else
+    static constexpr bool _EnableImplicitReducedArityExtension = false;
+#endif
 
     template <class ..._Args>
     struct _PackExpandsToThisTuple : false_type {};
@@ -548,6 +497,11 @@ class _LIBCPP_TYPE_VIS_ONLY tuple
     struct _CheckArgsConstructor<true, _Dummy>
     {
         template <class ..._Args>
+        static constexpr bool __enable_default() {
+            return __all<is_default_constructible<_Args>::value...>::value;
+        }
+
+        template <class ..._Args>
         static constexpr bool __enable_explicit() {
             return
                 __tuple_constructible<
@@ -657,12 +611,15 @@ class _LIBCPP_TYPE_VIS_ONLY tuple
 public:
 
     template <bool _Dummy = true, class = typename enable_if<
-        __all<__dependent_type<is_default_constructible<_Tp>, _Dummy>::value...>::value
+        _CheckArgsConstructor<_Dummy>::template __enable_default<_Tp...>()
     >::type>
     _LIBCPP_INLINE_VISIBILITY
     _LIBCPP_CONSTEXPR tuple()
         _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}
 
+    tuple(tuple const&) = default;
+    tuple(tuple&&) = default;
+
     template <class _AllocArgT, class _Alloc, bool _Dummy = true, class = typename enable_if<
         __lazy_and<
             is_same<allocator_arg_t, _AllocArgT>,
@@ -671,7 +628,7 @@ public:
     >::type>
     _LIBCPP_INLINE_VISIBILITY
     tuple(_AllocArgT, _Alloc const& __a)
-      : base_(allocator_arg_t(), __a,
+      : __base_(allocator_arg_t(), __a,
                     __tuple_indices<>(), __tuple_types<>(),
                     typename __make_tuple_indices<sizeof...(_Tp), 0>::type(),
                     __tuple_types<_Tp...>()) {}
@@ -681,13 +638,13 @@ public:
                       <
                          _CheckArgsConstructor<
                             _Dummy
-                         >::template __enable_implicit<_Tp...>(),
+                         >::template __enable_implicit<_Tp const&...>(),
                          bool
                       >::type = false
         >
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     tuple(const _Tp& ... __t) _NOEXCEPT_((__all<is_nothrow_copy_constructible<_Tp>::value...>::value))
-        : base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
+        : __base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
                 typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
                 typename __make_tuple_indices<0>::type(),
                 typename __make_tuple_types<tuple, 0>::type(),
@@ -699,13 +656,13 @@ public:
                       <
                          _CheckArgsConstructor<
                             _Dummy
-                         >::template __enable_explicit<_Tp...>(),
+                         >::template __enable_explicit<_Tp const&...>(),
                          bool
                       >::type = false
         >
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     explicit tuple(const _Tp& ... __t) _NOEXCEPT_((__all<is_nothrow_copy_constructible<_Tp>::value...>::value))
-        : base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
+        : __base_(typename __make_tuple_indices<sizeof...(_Tp)>::type(),
                 typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
                 typename __make_tuple_indices<0>::type(),
                 typename __make_tuple_types<tuple, 0>::type(),
@@ -717,13 +674,13 @@ public:
                       <
                          _CheckArgsConstructor<
                             _Dummy
-                         >::template __enable_implicit<_Tp...>(),
+                         >::template __enable_implicit<_Tp const&...>(),
                          bool
                       >::type = false
         >
       _LIBCPP_INLINE_VISIBILITY
       tuple(allocator_arg_t, const _Alloc& __a, const _Tp& ... __t)
-        : base_(allocator_arg_t(), __a,
+        : __base_(allocator_arg_t(), __a,
                 typename __make_tuple_indices<sizeof...(_Tp)>::type(),
                 typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
                 typename __make_tuple_indices<0>::type(),
@@ -736,14 +693,14 @@ public:
                       <
                          _CheckArgsConstructor<
                             _Dummy
-                         >::template __enable_explicit<_Tp...>(),
+                         >::template __enable_explicit<_Tp const&...>(),
                          bool
                       >::type = false
         >
       _LIBCPP_INLINE_VISIBILITY
       explicit
       tuple(allocator_arg_t, const _Alloc& __a, const _Tp& ... __t)
-        : base_(allocator_arg_t(), __a,
+        : __base_(allocator_arg_t(), __a,
                 typename __make_tuple_indices<sizeof...(_Tp)>::type(),
                 typename __make_tuple_types<tuple, sizeof...(_Tp)>::type(),
                 typename __make_tuple_indices<0>::type(),
@@ -752,11 +709,17 @@ public:
                ) {}
 
     template <class ..._Up,
+              bool _PackIsTuple = _PackExpandsToThisTuple<_Up...>::value,
               typename enable_if
                       <
                          _CheckArgsConstructor<
-                             sizeof...(_Up) <= sizeof...(_Tp)
-                             && !_PackExpandsToThisTuple<_Up...>::value
+                             sizeof...(_Up) == sizeof...(_Tp)
+                             && !_PackIsTuple
+                         >::template __enable_implicit<_Up...>() ||
+                        _CheckArgsConstructor<
+                            _EnableImplicitReducedArityExtension
+                            && sizeof...(_Up) < sizeof...(_Tp)
+                            && !_PackIsTuple
                          >::template __enable_implicit<_Up...>(),
                          bool
                       >::type = false
@@ -764,7 +727,7 @@ public:
         _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
         tuple(_Up&&... __u)
             _NOEXCEPT_((
-                is_nothrow_constructible<base,
+                is_nothrow_constructible<_BaseT,
                     typename __make_tuple_indices<sizeof...(_Up)>::type,
                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type,
                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type,
@@ -772,7 +735,7 @@ public:
                     _Up...
                 >::value
             ))
-            : base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
+            : __base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
                     typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
@@ -784,7 +747,12 @@ public:
                          _CheckArgsConstructor<
                              sizeof...(_Up) <= sizeof...(_Tp)
                              && !_PackExpandsToThisTuple<_Up...>::value
-                         >::template __enable_explicit<_Up...>(),
+                         >::template __enable_explicit<_Up...>() ||
+                         _CheckArgsConstructor<
+                            !_EnableImplicitReducedArityExtension
+                            && sizeof...(_Up) < sizeof...(_Tp)
+                            && !_PackExpandsToThisTuple<_Up...>::value
+                         >::template __enable_implicit<_Up...>(),
                          bool
                       >::type = false
              >
@@ -792,7 +760,7 @@ public:
         explicit
         tuple(_Up&&... __u)
             _NOEXCEPT_((
-                is_nothrow_constructible<base,
+                is_nothrow_constructible<_BaseT,
                     typename __make_tuple_indices<sizeof...(_Up)>::type,
                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type,
                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type,
@@ -800,7 +768,7 @@ public:
                     _Up...
                 >::value
             ))
-            : base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
+            : __base_(typename __make_tuple_indices<sizeof...(_Up)>::type(),
                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
                     typename __make_tuple_types<tuple, sizeof...(_Tp), sizeof...(_Up)>::type(),
@@ -818,7 +786,7 @@ public:
              >
         _LIBCPP_INLINE_VISIBILITY
         tuple(allocator_arg_t, const _Alloc& __a, _Up&&... __u)
-            : base_(allocator_arg_t(), __a,
+            : __base_(allocator_arg_t(), __a,
                     typename __make_tuple_indices<sizeof...(_Up)>::type(),
                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
@@ -838,7 +806,7 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         explicit
         tuple(allocator_arg_t, const _Alloc& __a, _Up&&... __u)
-            : base_(allocator_arg_t(), __a,
+            : __base_(allocator_arg_t(), __a,
                     typename __make_tuple_indices<sizeof...(_Up)>::type(),
                     typename __make_tuple_types<tuple, sizeof...(_Up)>::type(),
                     typename __make_tuple_indices<sizeof...(_Tp), sizeof...(_Up)>::type(),
@@ -856,8 +824,8 @@ public:
                       >::type = false
              >
         _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<base, _Tuple>::value))
-            : base_(_VSTD::forward<_Tuple>(__t)) {}
+        tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<_BaseT, _Tuple>::value))
+            : __base_(_VSTD::forward<_Tuple>(__t)) {}
 
     template <class _Tuple,
               typename enable_if
@@ -871,8 +839,8 @@ public:
              >
         _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
         explicit
-        tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<base, _Tuple>::value))
-            : base_(_VSTD::forward<_Tuple>(__t)) {}
+        tuple(_Tuple&& __t) _NOEXCEPT_((is_nothrow_constructible<_BaseT, _Tuple>::value))
+            : __base_(_VSTD::forward<_Tuple>(__t)) {}
 
     template <class _Alloc, class _Tuple,
               typename enable_if
@@ -885,7 +853,7 @@ public:
              >
         _LIBCPP_INLINE_VISIBILITY
         tuple(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
-            : base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}
+            : __base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}
 
     template <class _Alloc, class _Tuple,
               typename enable_if
@@ -899,7 +867,26 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         explicit
         tuple(allocator_arg_t, const _Alloc& __a, _Tuple&& __t)
-            : base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}
+            : __base_(allocator_arg_t(), __a, _VSTD::forward<_Tuple>(__t)) {}
+
+    using _CanCopyAssign = __all<is_copy_assignable<_Tp>::value...>;
+    using _CanMoveAssign = __all<is_move_assignable<_Tp>::value...>;
+
+    _LIBCPP_INLINE_VISIBILITY
+    tuple& operator=(typename conditional<_CanCopyAssign::value, tuple, __nat>::type const& __t)
+        _NOEXCEPT_((__all<is_nothrow_copy_assignable<_Tp>::value...>::value))
+    {
+        __base_.operator=(__t.__base_);
+        return *this;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    tuple& operator=(typename conditional<_CanMoveAssign::value, tuple, __nat>::type&& __t)
+        _NOEXCEPT_((__all<is_nothrow_move_assignable<_Tp>::value...>::value))
+    {
+        __base_.operator=(static_cast<_BaseT&&>(__t.__base_));
+        return *this;
+    }
 
     template <class _Tuple,
               class = typename enable_if
@@ -909,19 +896,19 @@ public:
              >
         _LIBCPP_INLINE_VISIBILITY
         tuple&
-        operator=(_Tuple&& __t) _NOEXCEPT_((is_nothrow_assignable<base&, _Tuple>::value))
+        operator=(_Tuple&& __t) _NOEXCEPT_((is_nothrow_assignable<_BaseT&, _Tuple>::value))
         {
-            base_.operator=(_VSTD::forward<_Tuple>(__t));
+            __base_.operator=(_VSTD::forward<_Tuple>(__t));
             return *this;
         }
 
     _LIBCPP_INLINE_VISIBILITY
     void swap(tuple& __t) _NOEXCEPT_(__all<__is_nothrow_swappable<_Tp>::value...>::value)
-        {base_.swap(__t.base_);}
+        {__base_.swap(__t.__base_);}
 };
 
 template <>
-class _LIBCPP_TYPE_VIS_ONLY tuple<>
+class _LIBCPP_TEMPLATE_VIS tuple<>
 {
 public:
     _LIBCPP_INLINE_VISIBILITY
@@ -942,6 +929,16 @@ public:
     void swap(tuple&) _NOEXCEPT {}
 };
 
+#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+// NOTE: These are not yet standardized, but are required to simulate the
+// implicit deduction guide that should be generated had libc++ declared the
+// tuple-like constructors "correctly"
+template <class _Alloc, class ..._Args>
+tuple(allocator_arg_t, const _Alloc&, tuple<_Args...> const&) -> tuple<_Args...>;
+template <class _Alloc, class ..._Args>
+tuple(allocator_arg_t, const _Alloc&, tuple<_Args...>&&) -> tuple<_Args...>;
+#endif
+
 template <class ..._Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
@@ -961,7 +958,7 @@ typename tuple_element<_Ip, tuple<_Tp...> >::type&
 get(tuple<_Tp...>& __t) _NOEXCEPT
 {
     typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
-    return static_cast<__tuple_leaf<_Ip, type>&>(__t.base_).get();
+    return static_cast<__tuple_leaf<_Ip, type>&>(__t.__base_).get();
 }
 
 template <size_t _Ip, class ..._Tp>
@@ -970,7 +967,7 @@ const typename tuple_element<_Ip, tuple<_Tp...> >::type&
 get(const tuple<_Tp...>& __t) _NOEXCEPT
 {
     typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
-    return static_cast<const __tuple_leaf<_Ip, type>&>(__t.base_).get();
+    return static_cast<const __tuple_leaf<_Ip, type>&>(__t.__base_).get();
 }
 
 template <size_t _Ip, class ..._Tp>
@@ -980,7 +977,7 @@ get(tuple<_Tp...>&& __t) _NOEXCEPT
 {
     typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
     return static_cast<type&&>(
-             static_cast<__tuple_leaf<_Ip, type>&&>(__t.base_).get());
+             static_cast<__tuple_leaf<_Ip, type>&&>(__t.__base_).get());
 }
 
 template <size_t _Ip, class ..._Tp>
@@ -990,7 +987,7 @@ get(const tuple<_Tp...>&& __t) _NOEXCEPT
 {
     typedef typename tuple_element<_Ip, tuple<_Tp...> >::type type;
     return static_cast<const type&&>(
-             static_cast<const __tuple_leaf<_Ip, type>&&>(__t.base_).get());
+             static_cast<const __tuple_leaf<_Ip, type>&&>(__t.__base_).get());
 }
 
 #if _LIBCPP_STD_VER > 11
@@ -1015,10 +1012,10 @@ constexpr size_t __find_idx(size_t __i, const bool (&__matches)[_Nx]) {
 
 template <class _T1, class ..._Args>
 struct __find_exactly_one_checked {
-  static constexpr bool __matches[] = {is_same<_T1, _Args>::value...};
+    static constexpr bool __matches[sizeof...(_Args)] = {is_same<_T1, _Args>::value...};
     static constexpr size_t value = __find_detail::__find_idx(0, __matches);
-    static_assert (value != __not_found, "type not found in type list" );
-    static_assert(value != __ambiguous,"type occurs more than once in type list");
+    static_assert(value != __not_found, "type not found in type list" );
+    static_assert(value != __ambiguous, "type occurs more than once in type list");
 };
 
 template <class _T1>
@@ -1077,11 +1074,13 @@ template <class _Up>
 struct __ignore_t
 {
     template <class _Tp>
-        _LIBCPP_INLINE_VISIBILITY
-        const __ignore_t& operator=(_Tp&&) const {return *this;}
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    const __ignore_t& operator=(_Tp&&) const {return *this;}
 };
 
-namespace { const __ignore_t<unsigned char> ignore = __ignore_t<unsigned char>(); }
+namespace {
+  _LIBCPP_INLINE_VAR constexpr __ignore_t<unsigned char> ignore = __ignore_t<unsigned char>();
+}
 
 template <class _Tp>
 struct __make_tuple_return_impl
@@ -1353,7 +1352,7 @@ tuple_cat(_Tuple0&& __t0, _Tuples&&... __tpls)
 }
 
 template <class ..._Tp, class _Alloc>
-struct _LIBCPP_TYPE_VIS_ONLY uses_allocator<tuple<_Tp...>, _Alloc>
+struct _LIBCPP_TEMPLATE_VIS uses_allocator<tuple<_Tp...>, _Alloc>
     : true_type {};
 
 template <class _T1, class _T2>
@@ -1367,11 +1366,9 @@ pair<_T1, _T2>::pair(piecewise_construct_t,
 {
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-
 #if _LIBCPP_STD_VER > 14
 template <class _Tp>
-constexpr size_t tuple_size_v = tuple_size<_Tp>::value;
+_LIBCPP_INLINE_VAR constexpr size_t tuple_size_v = tuple_size<_Tp>::value;
 
 #define _LIBCPP_NOEXCEPT_RETURN(...) noexcept(noexcept(__VA_ARGS__)) { return __VA_ARGS__; }
 
@@ -1413,6 +1410,8 @@ _LIBCPP_NOEXCEPT_RETURN(
 
 #endif // _LIBCPP_STD_VER > 14
 
+#endif // !defined(_LIBCPP_CXX03_LANG)
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_TUPLE
diff --git a/lib/libcxx/include/type_traits b/lib/libcxx/include/type_traits
index 821a73c764d..eb443ee0abd 100644
--- a/lib/libcxx/include/type_traits
+++ b/lib/libcxx/include/type_traits
@@ -97,6 +97,7 @@ namespace std
     template <class T> struct is_polymorphic;
     template <class T> struct is_abstract;
     template <class T> struct is_final; // C++14
+    template <class T> struct is_aggregate; // C++17
 
     template <class T, class... Args> struct is_constructible;
     template <class T>                struct is_default_constructible;
@@ -131,30 +132,32 @@ namespace std
 
     template <class T> struct has_virtual_destructor;
 
+    template<class T> struct has_unique_object_representations;         // C++17
+
     // Relationships between types:
     template <class T, class U> struct is_same;
     template <class Base, class Derived> struct is_base_of;
     template <class From, class To> struct is_convertible;
 
-    template <class, class R = void> struct is_callable; // not defined
-    template <class Fn, class... ArgTypes, class R>
-      struct is_callable<Fn(ArgTypes...), R>;
+    template <class Fn, class... ArgTypes> struct is_invocable;
+    template <class R, class Fn, class... ArgTypes> struct is_invocable_r;
 
-    template <class, class R = void> struct is_nothrow_callable; // not defined
-    template <class Fn, class... ArgTypes, class R>
-      struct is_nothrow_callable<Fn(ArgTypes...), R>;
+    template <class Fn, class... ArgTypes> struct is_nothrow_invocable;
+    template <class R, class Fn, class... ArgTypes> struct is_nothrow_invocable_r;
 
     // Alignment properties and transformations:
     template <class T> struct alignment_of;
     template <size_t Len, size_t Align = most_stringent_alignment_requirement>
         struct aligned_storage;
     template <size_t Len, class... Types> struct aligned_union;
+    template <class T> struct remove_cvref; // C++20
 
     template <class T> struct decay;
     template <class... T> struct common_type;
     template <class T> struct underlying_type;
     template <class> class result_of; // undefined
     template <class Fn, class... ArgTypes> class result_of<Fn(ArgTypes...)>;
+    template <class Fn, class... ArgTypes> struct invoke_result;  // C++17
 
     // const-volatile modifications:
     template <class T>
@@ -202,6 +205,8 @@ namespace std
     template <std::size_t Len, class... Types>
       using aligned_union_t   = typename aligned_union<Len,Types...>::type;  // C++14
     template <class T>
+      using remove_cvref_t    = typename remove_cvref<T>::type;  // C++20
+    template <class T>
       using decay_t           = typename decay<T>::type;  // C++14
     template <bool b, class T=void>
       using enable_if_t       = typename enable_if<b,T>::type;  // C++14
@@ -211,174 +216,184 @@ namespace std
       using common_type_t     = typename common_type<T...>::type;  // C++14
     template <class T>
       using underlying_type_t = typename underlying_type<T>::type;  // C++14
-    template <class F, class... ArgTypes>
-      using result_of_t       = typename result_of<F(ArgTypes...)>::type;  // C++14
+    template <class T>
+      using result_of_t       = typename result_of<T>::type;  // C++14
+    template <class Fn, class... ArgTypes>
+      using invoke_result_t   = typename invoke_result<Fn, ArgTypes...>::type;  // C++17
 
     template <class...>
       using void_t = void;   // C++17
       
       // See C++14 20.10.4.1, primary type categories
-      template <class T> constexpr bool is_void_v
+      template <class T> inline constexpr bool is_void_v
         = is_void<T>::value;                                             // C++17
-      template <class T> constexpr bool is_null_pointer_v
+      template <class T> inline constexpr bool is_null_pointer_v
         = is_null_pointer<T>::value;                                     // C++17
-      template <class T> constexpr bool is_integral_v
+      template <class T> inline constexpr bool is_integral_v
         = is_integral<T>::value;                                         // C++17
-      template <class T> constexpr bool is_floating_point_v
+      template <class T> inline constexpr bool is_floating_point_v
         = is_floating_point<T>::value;                                   // C++17
-      template <class T> constexpr bool is_array_v
+      template <class T> inline constexpr bool is_array_v
         = is_array<T>::value;                                            // C++17
-      template <class T> constexpr bool is_pointer_v
+      template <class T> inline constexpr bool is_pointer_v
         = is_pointer<T>::value;                                          // C++17
-      template <class T> constexpr bool is_lvalue_reference_v
+      template <class T> inline constexpr bool is_lvalue_reference_v
         = is_lvalue_reference<T>::value;                                 // C++17
-      template <class T> constexpr bool is_rvalue_reference_v
+      template <class T> inline constexpr bool is_rvalue_reference_v
         = is_rvalue_reference<T>::value;                                 // C++17
-      template <class T> constexpr bool is_member_object_pointer_v
+      template <class T> inline constexpr bool is_member_object_pointer_v
         = is_member_object_pointer<T>::value;                            // C++17
-      template <class T> constexpr bool is_member_function_pointer_v
+      template <class T> inline constexpr bool is_member_function_pointer_v
         = is_member_function_pointer<T>::value;                          // C++17
-      template <class T> constexpr bool is_enum_v
+      template <class T> inline constexpr bool is_enum_v
         = is_enum<T>::value;                                             // C++17
-      template <class T> constexpr bool is_union_v
+      template <class T> inline constexpr bool is_union_v
         = is_union<T>::value;                                            // C++17
-      template <class T> constexpr bool is_class_v
+      template <class T> inline constexpr bool is_class_v
         = is_class<T>::value;                                            // C++17
-      template <class T> constexpr bool is_function_v
+      template <class T> inline constexpr bool is_function_v
         = is_function<T>::value;                                         // C++17
 
       // See C++14 20.10.4.2, composite type categories
-      template <class T> constexpr bool is_reference_v
+      template <class T> inline constexpr bool is_reference_v
         = is_reference<T>::value;                                        // C++17
-      template <class T> constexpr bool is_arithmetic_v
+      template <class T> inline constexpr bool is_arithmetic_v
         = is_arithmetic<T>::value;                                       // C++17
-      template <class T> constexpr bool is_fundamental_v
+      template <class T> inline constexpr bool is_fundamental_v
         = is_fundamental<T>::value;                                      // C++17
-      template <class T> constexpr bool is_object_v
+      template <class T> inline constexpr bool is_object_v
         = is_object<T>::value;                                           // C++17
-      template <class T> constexpr bool is_scalar_v
+      template <class T> inline constexpr bool is_scalar_v
         = is_scalar<T>::value;                                           // C++17
-      template <class T> constexpr bool is_compound_v
+      template <class T> inline constexpr bool is_compound_v
         = is_compound<T>::value;                                         // C++17
-      template <class T> constexpr bool is_member_pointer_v
+      template <class T> inline constexpr bool is_member_pointer_v
         = is_member_pointer<T>::value;                                   // C++17
 
       // See C++14 20.10.4.3, type properties
-      template <class T> constexpr bool is_const_v
+      template <class T> inline constexpr bool is_const_v
         = is_const<T>::value;                                            // C++17
-      template <class T> constexpr bool is_volatile_v
+      template <class T> inline constexpr bool is_volatile_v
         = is_volatile<T>::value;                                         // C++17
-      template <class T> constexpr bool is_trivial_v
+      template <class T> inline constexpr bool is_trivial_v
         = is_trivial<T>::value;                                          // C++17
-      template <class T> constexpr bool is_trivially_copyable_v
+      template <class T> inline constexpr bool is_trivially_copyable_v
         = is_trivially_copyable<T>::value;                               // C++17
-      template <class T> constexpr bool is_standard_layout_v
+      template <class T> inline constexpr bool is_standard_layout_v
         = is_standard_layout<T>::value;                                  // C++17
-      template <class T> constexpr bool is_pod_v
+      template <class T> inline constexpr bool is_pod_v
         = is_pod<T>::value;                                              // C++17
-      template <class T> constexpr bool is_literal_type_v
+      template <class T> inline constexpr bool is_literal_type_v
         = is_literal_type<T>::value;                                     // C++17
-      template <class T> constexpr bool is_empty_v
+      template <class T> inline constexpr bool is_empty_v
         = is_empty<T>::value;                                            // C++17
-      template <class T> constexpr bool is_polymorphic_v
+      template <class T> inline constexpr bool is_polymorphic_v
         = is_polymorphic<T>::value;                                      // C++17
-      template <class T> constexpr bool is_abstract_v
+      template <class T> inline constexpr bool is_abstract_v
         = is_abstract<T>::value;                                         // C++17
-      template <class T> constexpr bool is_final_v
+      template <class T> inline constexpr bool is_final_v
         = is_final<T>::value;                                            // C++17
-      template <class T> constexpr bool is_signed_v
+      template <class T> inline constexpr bool is_aggregate_v
+        = is_aggregate<T>::value;                                        // C++17
+      template <class T> inline constexpr bool is_signed_v
         = is_signed<T>::value;                                           // C++17
-      template <class T> constexpr bool is_unsigned_v
+      template <class T> inline constexpr bool is_unsigned_v
         = is_unsigned<T>::value;                                         // C++17
-      template <class T, class... Args> constexpr bool is_constructible_v
+      template <class T, class... Args> inline constexpr bool is_constructible_v
         = is_constructible<T, Args...>::value;                           // C++17
-      template <class T> constexpr bool is_default_constructible_v
+      template <class T> inline constexpr bool is_default_constructible_v
         = is_default_constructible<T>::value;                            // C++17
-      template <class T> constexpr bool is_copy_constructible_v
+      template <class T> inline constexpr bool is_copy_constructible_v
         = is_copy_constructible<T>::value;                               // C++17
-      template <class T> constexpr bool is_move_constructible_v
+      template <class T> inline constexpr bool is_move_constructible_v
         = is_move_constructible<T>::value;                               // C++17
-      template <class T, class U> constexpr bool is_assignable_v
+      template <class T, class U> inline constexpr bool is_assignable_v
         = is_assignable<T, U>::value;                                    // C++17
-      template <class T> constexpr bool is_copy_assignable_v
+      template <class T> inline constexpr bool is_copy_assignable_v
         = is_copy_assignable<T>::value;                                  // C++17
-      template <class T> constexpr bool is_move_assignable_v
+      template <class T> inline constexpr bool is_move_assignable_v
         = is_move_assignable<T>::value;                                  // C++17
-      template <class T, class U> constexpr bool is_swappable_with_v
+      template <class T, class U> inline constexpr bool is_swappable_with_v
         = is_swappable_with<T, U>::value;                                // C++17
-      template <class T> constexpr bool is_swappable_v
+      template <class T> inline constexpr bool is_swappable_v
         = is_swappable<T>::value;                                        // C++17
-      template <class T> constexpr bool is_destructible_v
+      template <class T> inline constexpr bool is_destructible_v
         = is_destructible<T>::value;                                     // C++17
-      template <class T, class... Args> constexpr bool is_trivially_constructible_v
+      template <class T, class... Args> inline constexpr bool is_trivially_constructible_v
         = is_trivially_constructible<T, Args...>::value;                 // C++17
-      template <class T> constexpr bool is_trivially_default_constructible_v
+      template <class T> inline constexpr bool is_trivially_default_constructible_v
         = is_trivially_default_constructible<T>::value;                  // C++17
-      template <class T> constexpr bool is_trivially_copy_constructible_v
+      template <class T> inline constexpr bool is_trivially_copy_constructible_v
         = is_trivially_copy_constructible<T>::value;                     // C++17
-      template <class T> constexpr bool is_trivially_move_constructible_v
+      template <class T> inline constexpr bool is_trivially_move_constructible_v
         = is_trivially_move_constructible<T>::value;                     // C++17
-      template <class T, class U> constexpr bool is_trivially_assignable_v
+      template <class T, class U> inline constexpr bool is_trivially_assignable_v
         = is_trivially_assignable<T, U>::value;                          // C++17
-      template <class T> constexpr bool is_trivially_copy_assignable_v
+      template <class T> inline constexpr bool is_trivially_copy_assignable_v
         = is_trivially_copy_assignable<T>::value;                        // C++17
-      template <class T> constexpr bool is_trivially_move_assignable_v
+      template <class T> inline constexpr bool is_trivially_move_assignable_v
         = is_trivially_move_assignable<T>::value;                        // C++17
-      template <class T> constexpr bool is_trivially_destructible_v
+      template <class T> inline constexpr bool is_trivially_destructible_v
         = is_trivially_destructible<T>::value;                           // C++17
-      template <class T, class... Args> constexpr bool is_nothrow_constructible_v
+      template <class T, class... Args> inline constexpr bool is_nothrow_constructible_v
         = is_nothrow_constructible<T, Args...>::value;                   // C++17
-      template <class T> constexpr bool is_nothrow_default_constructible_v
+      template <class T> inline constexpr bool is_nothrow_default_constructible_v
         = is_nothrow_default_constructible<T>::value;                    // C++17
-      template <class T> constexpr bool is_nothrow_copy_constructible_v
+      template <class T> inline constexpr bool is_nothrow_copy_constructible_v
         = is_nothrow_copy_constructible<T>::value;                       // C++17
-      template <class T> constexpr bool is_nothrow_move_constructible_v
+      template <class T> inline constexpr bool is_nothrow_move_constructible_v
         = is_nothrow_move_constructible<T>::value;                       // C++17
-      template <class T, class U> constexpr bool is_nothrow_assignable_v
+      template <class T, class U> inline constexpr bool is_nothrow_assignable_v
         = is_nothrow_assignable<T, U>::value;                            // C++17
-      template <class T> constexpr bool is_nothrow_copy_assignable_v
+      template <class T> inline constexpr bool is_nothrow_copy_assignable_v
         = is_nothrow_copy_assignable<T>::value;                          // C++17
-      template <class T> constexpr bool is_nothrow_move_assignable_v
+      template <class T> inline constexpr bool is_nothrow_move_assignable_v
         = is_nothrow_move_assignable<T>::value;                          // C++17
-      template <class T, class U> constexpr bool is_nothrow_swappable_with_v
+      template <class T, class U> inline constexpr bool is_nothrow_swappable_with_v
         = is_nothrow_swappable_with<T, U>::value;                       // C++17
-      template <class T> constexpr bool is_nothrow_swappable_v
+      template <class T> inline constexpr bool is_nothrow_swappable_v
         = is_nothrow_swappable<T>::value;                               // C++17
-      template <class T> constexpr bool is_nothrow_destructible_v
+      template <class T> inline constexpr bool is_nothrow_destructible_v
         = is_nothrow_destructible<T>::value;                             // C++17
-      template <class T> constexpr bool has_virtual_destructor_v
+      template <class T> inline constexpr bool has_virtual_destructor_v
         = has_virtual_destructor<T>::value;                              // C++17
+      template<class T> inline constexpr bool has_unique_object_representations_v // C++17
+        = has_unique_object_representations<T>::value;
 
       // See C++14 20.10.5, type property queries
-      template <class T> constexpr size_t alignment_of_v
+      template <class T> inline constexpr size_t alignment_of_v
         = alignment_of<T>::value;                                        // C++17
-      template <class T> constexpr size_t rank_v
+      template <class T> inline constexpr size_t rank_v
         = rank<T>::value;                                                // C++17
-      template <class T, unsigned I = 0> constexpr size_t extent_v
+      template <class T, unsigned I = 0> inline constexpr size_t extent_v
         = extent<T, I>::value;                                           // C++17
 
       // See C++14 20.10.6, type relations
-      template <class T, class U> constexpr bool is_same_v
+      template <class T, class U> inline constexpr bool is_same_v
         = is_same<T, U>::value;                                          // C++17
-      template <class Base, class Derived> constexpr bool is_base_of_v
+      template <class Base, class Derived> inline constexpr bool is_base_of_v
         = is_base_of<Base, Derived>::value;                              // C++17
-      template <class From, class To> constexpr bool is_convertible_v
+      template <class From, class To> inline constexpr bool is_convertible_v
         = is_convertible<From, To>::value;                               // C++17
-      template <class T, class R = void> constexpr bool is_callable_v
-        = is_callable<T, R>::value;                                      // C++17
-      template <class T, class R = void> constexpr bool is_nothrow_callable_v
-        = is_nothrow_callable<T, R>::value;                              // C++17
+      template <class Fn, class... ArgTypes> inline constexpr bool is_invocable_v
+        = is_invocable<Fn, ArgTypes...>::value;                          // C++17
+      template <class R, class Fn, class... ArgTypes> inline constexpr bool is_invocable_r_v
+        = is_invocable_r<R, Fn, ArgTypes...>::value;                     // C++17
+      template <class Fn, class... ArgTypes> inline constexpr bool is_nothrow_invocable_v
+        = is_nothrow_invocable<Fn, ArgTypes...>::value;                  // C++17
+      template <class R, class Fn, class... ArgTypes> inline constexpr bool is_nothrow_invocable_r_v
+        = is_nothrow_invocable_r<R, Fn, ArgTypes...>::value;             // C++17
 
       // [meta.logical], logical operator traits:
       template<class... B> struct conjunction;                           // C++17
       template<class... B> 
-        constexpr bool conjunction_v = conjunction<B...>::value;         // C++17
+        inline constexpr bool conjunction_v = conjunction<B...>::value;  // C++17
       template<class... B> struct disjunction;                           // C++17
       template<class... B>
-        constexpr bool disjunction_v = disjunction<B...>::value;         // C++17
+        inline constexpr bool disjunction_v = disjunction<B...>::value;  // C++17
       template<class B> struct negation;                                 // C++17
       template<class B> 
-        constexpr bool negation_v = negation<B>::value;                  // C++17
+        inline constexpr bool negation_v = negation<B>::value;           // C++17
 
 }
 
@@ -392,9 +407,9 @@ namespace std
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _T1, class _T2> struct _LIBCPP_TYPE_VIS_ONLY pair;
-template <class _Tp> class _LIBCPP_TYPE_VIS_ONLY reference_wrapper;
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY hash;
+template <class _T1, class _T2> struct _LIBCPP_TEMPLATE_VIS pair;
+template <class _Tp> class _LIBCPP_TEMPLATE_VIS reference_wrapper;
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS hash;
 
 template <class>
 struct __void_t { typedef void type; };
@@ -403,29 +418,29 @@ template <class _Tp>
 struct __identity { typedef _Tp type; };
 
 template <class _Tp, bool>
-struct _LIBCPP_TYPE_VIS_ONLY __dependent_type : public _Tp {};
+struct _LIBCPP_TEMPLATE_VIS __dependent_type : public _Tp {};
 
 template <bool _Bp, class _If, class _Then>
-    struct _LIBCPP_TYPE_VIS_ONLY conditional {typedef _If type;};
+    struct _LIBCPP_TEMPLATE_VIS conditional {typedef _If type;};
 template <class _If, class _Then>
-    struct _LIBCPP_TYPE_VIS_ONLY conditional<false, _If, _Then> {typedef _Then type;};
+    struct _LIBCPP_TEMPLATE_VIS conditional<false, _If, _Then> {typedef _Then type;};
 
 #if _LIBCPP_STD_VER > 11
 template <bool _Bp, class _If, class _Then> using conditional_t = typename conditional<_Bp, _If, _Then>::type;
 #endif
 
-template <bool, class _Tp> struct _LIBCPP_TYPE_VIS_ONLY __lazy_enable_if {};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY __lazy_enable_if<true, _Tp> {typedef typename _Tp::type type;};
+template <bool, class _Tp> struct _LIBCPP_TEMPLATE_VIS __lazy_enable_if {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS __lazy_enable_if<true, _Tp> {typedef typename _Tp::type type;};
 
-template <bool, class _Tp = void> struct _LIBCPP_TYPE_VIS_ONLY enable_if {};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY enable_if<true, _Tp> {typedef _Tp type;};
+template <bool, class _Tp = void> struct _LIBCPP_TEMPLATE_VIS enable_if {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS enable_if<true, _Tp> {typedef _Tp type;};
 
 #if _LIBCPP_STD_VER > 11
 template <bool _Bp, class _Tp = void> using enable_if_t = typename enable_if<_Bp, _Tp>::type;
 #endif
 
 // addressof
-#if __has_builtin(__builtin_addressof)
+#ifndef _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
 
 template <class _Tp>
 inline _LIBCPP_CONSTEXPR_AFTER_CXX14
@@ -443,10 +458,11 @@ inline _LIBCPP_NO_CFI _LIBCPP_INLINE_VISIBILITY
 _Tp*
 addressof(_Tp& __x) _NOEXCEPT
 {
-    return (_Tp*)&reinterpret_cast<const volatile char&>(__x);
+  return reinterpret_cast<_Tp *>(
+      const_cast<char *>(&reinterpret_cast<const volatile char &>(__x)));
 }
 
-#endif // __has_builtin(__builtin_addressof)
+#endif // _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
 
 #if defined(_LIBCPP_HAS_OBJC_ARC) && !defined(_LIBCPP_PREDEFINED_OBJC_ARC_ADDRESSOF)
 // Objective-C++ Automatic Reference Counting uses qualified pointers
@@ -488,12 +504,16 @@ addressof(__unsafe_unretained _Tp& __x) _NOEXCEPT
 }
 #endif
 
+#if !defined(_LIBCPP_CXX03_LANG)
+template <class _Tp> _Tp* addressof(const _Tp&&) noexcept = delete;
+#endif
+
 struct __two {char __lx[2];};
 
 // helper class:
 
 template <class _Tp, _Tp __v>
-struct _LIBCPP_TYPE_VIS_ONLY integral_constant
+struct _LIBCPP_TEMPLATE_VIS integral_constant
 {
     static _LIBCPP_CONSTEXPR const _Tp      value = __v;
     typedef _Tp               value_type;
@@ -520,7 +540,7 @@ using bool_constant = integral_constant<bool, __b>;
 typedef _LIBCPP_BOOL_CONSTANT(true)  true_type;
 typedef _LIBCPP_BOOL_CONSTANT(false) false_type;
 
-#if !defined(_LIBCPP_HAS_NO_VARIADICS)
+#if !defined(_LIBCPP_CXX03_LANG)
 
 // __lazy_and
 
@@ -595,47 +615,49 @@ struct __or_<_B0, _B1, _B2, _Bn...>
 template<class _Tp> 
 struct __not_ : conditional<_Tp::value, false_type, true_type>::type {};
 
-#endif // !defined(_LIBCPP_HAS_NO_VARIADICS)
+#endif // !defined(_LIBCPP_CXX03_LANG)
 
 // is_const
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_const            : public false_type {};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_const<_Tp const> : public true_type {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_const            : public false_type {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_const<_Tp const> : public true_type {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_const_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_const_v
     = is_const<_Tp>::value;
 #endif
 
 // is_volatile
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_volatile               : public false_type {};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_volatile<_Tp volatile> : public true_type {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_volatile               : public false_type {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_volatile<_Tp volatile> : public true_type {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_volatile_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_volatile_v
     = is_volatile<_Tp>::value;
 #endif
 
 // remove_const
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_const            {typedef _Tp type;};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_const<const _Tp> {typedef _Tp type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_const            {typedef _Tp type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_const<const _Tp> {typedef _Tp type;};
 #if _LIBCPP_STD_VER > 11
 template <class _Tp> using remove_const_t = typename remove_const<_Tp>::type;
 #endif
 
 // remove_volatile
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_volatile               {typedef _Tp type;};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_volatile<volatile _Tp> {typedef _Tp type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_volatile               {typedef _Tp type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_volatile<volatile _Tp> {typedef _Tp type;};
 #if _LIBCPP_STD_VER > 11
 template <class _Tp> using remove_volatile_t = typename remove_volatile<_Tp>::type;
 #endif
 
 // remove_cv
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_cv
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_cv
 {typedef typename remove_volatile<typename remove_const<_Tp>::type>::type type;};
 #if _LIBCPP_STD_VER > 11
 template <class _Tp> using remove_cv_t = typename remove_cv<_Tp>::type;
@@ -646,11 +668,12 @@ template <class _Tp> using remove_cv_t = typename remove_cv<_Tp>::type;
 template <class _Tp> struct __libcpp_is_void       : public false_type {};
 template <>          struct __libcpp_is_void<void> : public true_type {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_void
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_void
     : public __libcpp_is_void<typename remove_cv<_Tp>::type> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_void_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_void_v
     = is_void<_Tp>::value;
 #endif
 
@@ -659,15 +682,16 @@ template <class _Tp> _LIBCPP_CONSTEXPR bool is_void_v
 template <class _Tp> struct __is_nullptr_t_impl       : public false_type {};
 template <>          struct __is_nullptr_t_impl<nullptr_t> : public true_type {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY __is_nullptr_t
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS __is_nullptr_t
     : public __is_nullptr_t_impl<typename remove_cv<_Tp>::type> {};
 
 #if _LIBCPP_STD_VER > 11
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_null_pointer
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_null_pointer
     : public __is_nullptr_t_impl<typename remove_cv<_Tp>::type> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_null_pointer_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_null_pointer_v
     = is_null_pointer<_Tp>::value;
 #endif
 #endif
@@ -697,11 +721,12 @@ template <>          struct __libcpp_is_integral<__int128_t>         : public tr
 template <>          struct __libcpp_is_integral<__uint128_t>        : public true_type {};
 #endif
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_integral
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_integral
     : public __libcpp_is_integral<typename remove_cv<_Tp>::type> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_integral_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_integral_v
     = is_integral<_Tp>::value;
 #endif
 
@@ -712,25 +737,27 @@ template <>          struct __libcpp_is_floating_point<float>       : public tru
 template <>          struct __libcpp_is_floating_point<double>      : public true_type {};
 template <>          struct __libcpp_is_floating_point<long double> : public true_type {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_floating_point
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_floating_point
     : public __libcpp_is_floating_point<typename remove_cv<_Tp>::type> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_floating_point_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_floating_point_v
     = is_floating_point<_Tp>::value;
 #endif
 
 // is_array
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_array
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_array
     : public false_type {};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_array<_Tp[]>
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_array<_Tp[]>
     : public true_type {};
-template <class _Tp, size_t _Np> struct _LIBCPP_TYPE_VIS_ONLY is_array<_Tp[_Np]>
+template <class _Tp, size_t _Np> struct _LIBCPP_TEMPLATE_VIS is_array<_Tp[_Np]>
     : public true_type {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_array_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_array_v
     = is_array<_Tp>::value;
 #endif
 
@@ -739,57 +766,62 @@ template <class _Tp> _LIBCPP_CONSTEXPR bool is_array_v
 template <class _Tp> struct __libcpp_is_pointer       : public false_type {};
 template <class _Tp> struct __libcpp_is_pointer<_Tp*> : public true_type {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_pointer
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_pointer
     : public __libcpp_is_pointer<typename remove_cv<_Tp>::type> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_pointer_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_pointer_v
     = is_pointer<_Tp>::value;
 #endif
 
 // is_reference
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_lvalue_reference       : public false_type {};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_lvalue_reference<_Tp&> : public true_type {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_lvalue_reference       : public false_type {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_lvalue_reference<_Tp&> : public true_type {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_rvalue_reference        : public false_type {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_rvalue_reference        : public false_type {};
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_rvalue_reference<_Tp&&> : public true_type {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_rvalue_reference<_Tp&&> : public true_type {};
 #endif
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_reference        : public false_type {};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_reference<_Tp&>  : public true_type {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_reference        : public false_type {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_reference<_Tp&>  : public true_type {};
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_reference<_Tp&&> : public true_type {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_reference<_Tp&&> : public true_type {};
 #endif
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_reference_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_reference_v
     = is_reference<_Tp>::value;
 
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_lvalue_reference_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_lvalue_reference_v
     = is_lvalue_reference<_Tp>::value;
 
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_rvalue_reference_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_rvalue_reference_v
     = is_rvalue_reference<_Tp>::value;
 #endif
 // is_union
 
 #if __has_feature(is_union) || (_GNUC_VER >= 403)
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_union
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_union
     : public integral_constant<bool, __is_union(_Tp)> {};
 
 #else
 
 template <class _Tp> struct __libcpp_union : public false_type {};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_union
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_union
     : public __libcpp_union<typename remove_cv<_Tp>::type> {};
 
 #endif
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_union_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_union_v
     = is_union<_Tp>::value;
 #endif
 
@@ -797,7 +829,7 @@ template <class _Tp> _LIBCPP_CONSTEXPR bool is_union_v
 
 #if __has_feature(is_class) || (_GNUC_VER >= 403)
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_class
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_class
     : public integral_constant<bool, __is_class(_Tp)> {};
 
 #else
@@ -808,23 +840,25 @@ template <class _Tp> char  __test(int _Tp::*);
 template <class _Tp> __two __test(...);
 }
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_class
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_class
     : public integral_constant<bool, sizeof(__is_class_imp::__test<_Tp>(0)) == 1 && !is_union<_Tp>::value> {};
 
 #endif
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_class_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_class_v
     = is_class<_Tp>::value;
 #endif
 
 // is_same
 
-template <class _Tp, class _Up> struct _LIBCPP_TYPE_VIS_ONLY is_same           : public false_type {};
-template <class _Tp>            struct _LIBCPP_TYPE_VIS_ONLY is_same<_Tp, _Tp> : public true_type {};
+template <class _Tp, class _Up> struct _LIBCPP_TEMPLATE_VIS is_same           : public false_type {};
+template <class _Tp>            struct _LIBCPP_TEMPLATE_VIS is_same<_Tp, _Tp> : public true_type {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp, class _Up> _LIBCPP_CONSTEXPR bool is_same_v
+template <class _Tp, class _Up>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_same_v
     = is_same<_Tp, _Up>::value;
 #endif
 
@@ -850,11 +884,12 @@ struct __libcpp_is_function
     {};
 template <class _Tp> struct __libcpp_is_function<_Tp, true> : public false_type {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_function
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_function
     : public __libcpp_is_function<_Tp> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_function_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_function_v
     = is_function<_Tp>::value;
 #endif
 
@@ -877,11 +912,12 @@ template <class _Ret, class _Class>
 struct __libcpp_is_member_function_pointer<_Ret _Class::*>
     : public is_function<_Ret> {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_member_function_pointer
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_member_function_pointer
     : public __libcpp_is_member_function_pointer<typename remove_cv<_Tp>::type>::type {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_member_function_pointer_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_member_function_pointer_v
     = is_member_function_pointer<_Tp>::value;
 #endif
 
@@ -890,22 +926,24 @@ template <class _Tp> _LIBCPP_CONSTEXPR bool is_member_function_pointer_v
 template <class _Tp>            struct __libcpp_is_member_pointer             : public false_type {};
 template <class _Tp, class _Up> struct __libcpp_is_member_pointer<_Tp _Up::*> : public true_type {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_member_pointer
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_member_pointer
     : public __libcpp_is_member_pointer<typename remove_cv<_Tp>::type> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_member_pointer_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_member_pointer_v
     = is_member_pointer<_Tp>::value;
 #endif
 
 // is_member_object_pointer
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_member_object_pointer
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_member_object_pointer
     : public integral_constant<bool, is_member_pointer<_Tp>::value &&
                                     !is_member_function_pointer<_Tp>::value> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_member_object_pointer_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_member_object_pointer_v
     = is_member_object_pointer<_Tp>::value;
 #endif
 
@@ -913,12 +951,12 @@ template <class _Tp> _LIBCPP_CONSTEXPR bool is_member_object_pointer_v
 
 #if __has_feature(is_enum) || (_GNUC_VER >= 403)
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_enum
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_enum
     : public integral_constant<bool, __is_enum(_Tp)> {};
 
 #else
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_enum
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_enum
     : public integral_constant<bool, !is_void<_Tp>::value             &&
                                      !is_integral<_Tp>::value         &&
                                      !is_floating_point<_Tp>::value   &&
@@ -933,69 +971,75 @@ template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_enum
 #endif
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_enum_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_enum_v
     = is_enum<_Tp>::value;
 #endif
 
 // is_arithmetic
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_arithmetic
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_arithmetic
     : public integral_constant<bool, is_integral<_Tp>::value      ||
                                      is_floating_point<_Tp>::value> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_arithmetic_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_arithmetic_v
     = is_arithmetic<_Tp>::value;
 #endif
 
 // is_fundamental
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_fundamental
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_fundamental
     : public integral_constant<bool, is_void<_Tp>::value        ||
                                      __is_nullptr_t<_Tp>::value ||
                                      is_arithmetic<_Tp>::value> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_fundamental_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_fundamental_v
     = is_fundamental<_Tp>::value;
 #endif
 
 // is_scalar
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_scalar
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_scalar
     : public integral_constant<bool, is_arithmetic<_Tp>::value     ||
                                      is_member_pointer<_Tp>::value ||
                                      is_pointer<_Tp>::value        ||
                                      __is_nullptr_t<_Tp>::value    ||
                                      is_enum<_Tp>::value           > {};
 
-template <> struct _LIBCPP_TYPE_VIS_ONLY is_scalar<nullptr_t> : public true_type {};
+template <> struct _LIBCPP_TEMPLATE_VIS is_scalar<nullptr_t> : public true_type {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_scalar_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_scalar_v
     = is_scalar<_Tp>::value;
 #endif
 
 // is_object
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_object
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_object
     : public integral_constant<bool, is_scalar<_Tp>::value ||
                                      is_array<_Tp>::value  ||
                                      is_union<_Tp>::value  ||
                                      is_class<_Tp>::value  > {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_object_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_object_v
     = is_object<_Tp>::value;
 #endif
 
 // is_compound
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_compound
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_compound
     : public integral_constant<bool, !is_fundamental<_Tp>::value> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_compound_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_compound_v
     = is_compound<_Tp>::value;
 #endif
 
@@ -1022,7 +1066,7 @@ struct __add_const             {typedef _Tp type;};
 template <class _Tp>
 struct __add_const<_Tp, false> {typedef const _Tp type;};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY add_const
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_const
     {typedef typename __add_const<_Tp>::type type;};
 
 #if _LIBCPP_STD_VER > 11
@@ -1039,7 +1083,7 @@ struct __add_volatile             {typedef _Tp type;};
 template <class _Tp>
 struct __add_volatile<_Tp, false> {typedef volatile _Tp type;};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY add_volatile
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_volatile
     {typedef typename __add_volatile<_Tp>::type type;};
 
 #if _LIBCPP_STD_VER > 11
@@ -1048,7 +1092,7 @@ template <class _Tp> using add_volatile_t = typename add_volatile<_Tp>::type;
 
 // add_cv
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY add_cv
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_cv
     {typedef typename add_const<typename add_volatile<_Tp>::type>::type type;};
 
 #if _LIBCPP_STD_VER > 11
@@ -1057,10 +1101,10 @@ template <class _Tp> using add_cv_t = typename add_cv<_Tp>::type;
 
 // remove_reference
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_reference        {typedef _Tp type;};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_reference<_Tp&>  {typedef _Tp type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_reference        {typedef _Tp type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_reference<_Tp&>  {typedef _Tp type;};
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_reference<_Tp&&> {typedef _Tp type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_reference<_Tp&&> {typedef _Tp type;};
 #endif
 
 #if _LIBCPP_STD_VER > 11
@@ -1072,7 +1116,7 @@ template <class _Tp> using remove_reference_t = typename remove_reference<_Tp>::
 template <class _Tp, bool = __is_referenceable<_Tp>::value> struct __add_lvalue_reference_impl            { typedef _Tp  type; };
 template <class _Tp                                       > struct __add_lvalue_reference_impl<_Tp, true> { typedef _Tp& type; };
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY add_lvalue_reference
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_lvalue_reference
 {typedef typename __add_lvalue_reference_impl<_Tp>::type type;};
 
 #if _LIBCPP_STD_VER > 11
@@ -1084,7 +1128,7 @@ template <class _Tp> using add_lvalue_reference_t = typename add_lvalue_referenc
 template <class _Tp, bool = __is_referenceable<_Tp>::value> struct __add_rvalue_reference_impl            { typedef _Tp   type; };
 template <class _Tp                                       > struct __add_rvalue_reference_impl<_Tp, true> { typedef _Tp&& type; };
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY add_rvalue_reference
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_rvalue_reference
 {typedef typename __add_rvalue_reference_impl<_Tp>::type type;};
 
 #if _LIBCPP_STD_VER > 11
@@ -1122,12 +1166,28 @@ struct __unconstref {
     typedef typename remove_const<typename remove_reference<_Tp>::type>::type type;
 };
 
+#ifndef _LIBCPP_CXX03_LANG
+template <class _Tp>
+using __uncvref_t = typename __uncvref<_Tp>::type;
+#endif
+
 // __is_same_uncvref
 
 template <class _Tp, class _Up>
 struct __is_same_uncvref : is_same<typename __uncvref<_Tp>::type,
                                    typename __uncvref<_Up>::type> {};
 
+#if _LIBCPP_STD_VER > 17
+// aligned_union - same as __uncvref
+template <class _Tp>
+struct remove_cvref {
+    using type = remove_cv_t<remove_reference_t<_Tp>>;
+};
+
+template <class _Tp> using remove_cvref_t = typename remove_cvref<_Tp>::type;
+#endif
+
+
 struct __any
 {
     __any(...);
@@ -1135,11 +1195,11 @@ struct __any
 
 // remove_pointer
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_pointer                      {typedef _Tp type;};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_pointer<_Tp*>                {typedef _Tp type;};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_pointer<_Tp* const>          {typedef _Tp type;};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_pointer<_Tp* volatile>       {typedef _Tp type;};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_pointer<_Tp* const volatile> {typedef _Tp type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_pointer                      {typedef _Tp type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_pointer<_Tp*>                {typedef _Tp type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_pointer<_Tp* const>          {typedef _Tp type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_pointer<_Tp* volatile>       {typedef _Tp type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_pointer<_Tp* const volatile> {typedef _Tp type;};
 
 #if _LIBCPP_STD_VER > 11
 template <class _Tp> using remove_pointer_t = typename remove_pointer<_Tp>::type;
@@ -1155,7 +1215,7 @@ struct __add_pointer_impl
 template <class _Tp> struct __add_pointer_impl<_Tp, false> 
     {typedef _Tp type;};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY add_pointer
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_pointer
     {typedef typename __add_pointer_impl<_Tp>::type type;};
 
 #if _LIBCPP_STD_VER > 11
@@ -1175,10 +1235,11 @@ struct __libcpp_is_signed : public __libcpp_is_signed_impl<_Tp> {};
 
 template <class _Tp> struct __libcpp_is_signed<_Tp, false> : public false_type {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_signed : public __libcpp_is_signed<_Tp> {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_signed : public __libcpp_is_signed<_Tp> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_signed_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_signed_v
     = is_signed<_Tp>::value;
 #endif
 
@@ -1195,52 +1256,55 @@ struct __libcpp_is_unsigned : public __libcpp_is_unsigned_impl<_Tp> {};
 
 template <class _Tp> struct __libcpp_is_unsigned<_Tp, false> : public false_type {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_unsigned : public __libcpp_is_unsigned<_Tp> {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_unsigned : public __libcpp_is_unsigned<_Tp> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_unsigned_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_unsigned_v
     = is_unsigned<_Tp>::value;
 #endif
 
 // rank
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY rank
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS rank
     : public integral_constant<size_t, 0> {};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY rank<_Tp[]>
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS rank<_Tp[]>
     : public integral_constant<size_t, rank<_Tp>::value + 1> {};
-template <class _Tp, size_t _Np> struct _LIBCPP_TYPE_VIS_ONLY rank<_Tp[_Np]>
+template <class _Tp, size_t _Np> struct _LIBCPP_TEMPLATE_VIS rank<_Tp[_Np]>
     : public integral_constant<size_t, rank<_Tp>::value + 1> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR size_t rank_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR size_t rank_v
     = rank<_Tp>::value;
 #endif
 
 // extent
 
-template <class _Tp, unsigned _Ip = 0> struct _LIBCPP_TYPE_VIS_ONLY extent
+template <class _Tp, unsigned _Ip = 0> struct _LIBCPP_TEMPLATE_VIS extent
     : public integral_constant<size_t, 0> {};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY extent<_Tp[], 0>
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS extent<_Tp[], 0>
     : public integral_constant<size_t, 0> {};
-template <class _Tp, unsigned _Ip> struct _LIBCPP_TYPE_VIS_ONLY extent<_Tp[], _Ip>
+template <class _Tp, unsigned _Ip> struct _LIBCPP_TEMPLATE_VIS extent<_Tp[], _Ip>
     : public integral_constant<size_t, extent<_Tp, _Ip-1>::value> {};
-template <class _Tp, size_t _Np> struct _LIBCPP_TYPE_VIS_ONLY extent<_Tp[_Np], 0>
+template <class _Tp, size_t _Np> struct _LIBCPP_TEMPLATE_VIS extent<_Tp[_Np], 0>
     : public integral_constant<size_t, _Np> {};
-template <class _Tp, size_t _Np, unsigned _Ip> struct _LIBCPP_TYPE_VIS_ONLY extent<_Tp[_Np], _Ip>
+template <class _Tp, size_t _Np, unsigned _Ip> struct _LIBCPP_TEMPLATE_VIS extent<_Tp[_Np], _Ip>
     : public integral_constant<size_t, extent<_Tp, _Ip-1>::value> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp, unsigned _Ip = 0> _LIBCPP_CONSTEXPR size_t extent_v
+template <class _Tp, unsigned _Ip = 0>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR size_t extent_v
     = extent<_Tp, _Ip>::value;
 #endif
 
 // remove_extent
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_extent
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_extent
     {typedef _Tp type;};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_extent<_Tp[]>
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_extent<_Tp[]>
     {typedef _Tp type;};
-template <class _Tp, size_t _Np> struct _LIBCPP_TYPE_VIS_ONLY remove_extent<_Tp[_Np]>
+template <class _Tp, size_t _Np> struct _LIBCPP_TEMPLATE_VIS remove_extent<_Tp[_Np]>
     {typedef _Tp type;};
 
 #if _LIBCPP_STD_VER > 11
@@ -1249,11 +1313,11 @@ template <class _Tp> using remove_extent_t = typename remove_extent<_Tp>::type;
 
 // remove_all_extents
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_all_extents
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_all_extents
     {typedef _Tp type;};
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY remove_all_extents<_Tp[]>
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS remove_all_extents<_Tp[]>
     {typedef typename remove_all_extents<_Tp>::type type;};
-template <class _Tp, size_t _Np> struct _LIBCPP_TYPE_VIS_ONLY remove_all_extents<_Tp[_Np]>
+template <class _Tp, size_t _Np> struct _LIBCPP_TEMPLATE_VIS remove_all_extents<_Tp[_Np]>
     {typedef typename remove_all_extents<_Tp>::type type;};
 
 #if _LIBCPP_STD_VER > 11
@@ -1262,11 +1326,13 @@ template <class _Tp> using remove_all_extents_t = typename remove_all_extents<_T
 
 // decay
 
-template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY decay
-{
-private:
-    typedef typename remove_reference<_Tp>::type _Up;
+template <class _Up, bool>
+struct __decay {
+    typedef typename remove_cv<_Up>::type type;
+};
+
+template <class _Up>
+struct __decay<_Up, true> {
 public:
     typedef typename conditional
                      <
@@ -1281,56 +1347,71 @@ public:
                      >::type type;
 };
 
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS decay
+{
+private:
+    typedef typename remove_reference<_Tp>::type _Up;
+public:
+    typedef typename __decay<_Up, __is_referenceable<_Up>::value>::type type;
+};
+
 #if _LIBCPP_STD_VER > 11
 template <class _Tp> using decay_t = typename decay<_Tp>::type;
 #endif
 
 // is_abstract
 
-namespace __is_abstract_imp
-{
-template <class _Tp> char  __test(_Tp (*)[1]);
-template <class _Tp> __two __test(...);
-}
-
-template <class _Tp, bool = is_class<_Tp>::value>
-struct __libcpp_abstract : public integral_constant<bool, sizeof(__is_abstract_imp::__test<_Tp>(0)) != 1> {};
-
-template <class _Tp> struct __libcpp_abstract<_Tp, false> : public false_type {};
-
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_abstract : public __libcpp_abstract<_Tp> {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_abstract
+    : public integral_constant<bool, __is_abstract(_Tp)> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_abstract_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_abstract_v
     = is_abstract<_Tp>::value;
 #endif
 
 // is_final
 
 #if defined(_LIBCPP_HAS_IS_FINAL)
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS
 __libcpp_is_final : public integral_constant<bool, __is_final(_Tp)> {};
 #else
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS
 __libcpp_is_final : public false_type {};
 #endif
 
 #if defined(_LIBCPP_HAS_IS_FINAL) && _LIBCPP_STD_VER > 11
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS
 is_final : public integral_constant<bool, __is_final(_Tp)> {};
 #endif
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_final_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_final_v
     = is_final<_Tp>::value;
 #endif
 
+// is_aggregate
+#if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_IS_AGGREGATE)
+
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS
+is_aggregate : public integral_constant<bool, __is_aggregate(_Tp)> {};
+
+#if !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
+template <class _Tp>
+_LIBCPP_INLINE_VAR constexpr bool is_aggregate_v
+    = is_aggregate<_Tp>::value;
+#endif
+
+#endif // _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_IS_AGGREGATE)
+
 // is_base_of
 
 #ifdef _LIBCPP_HAS_IS_BASE_OF
 
 template <class _Bp, class _Dp>
-struct _LIBCPP_TYPE_VIS_ONLY is_base_of
+struct _LIBCPP_TEMPLATE_VIS is_base_of
     : public integral_constant<bool, __is_base_of(_Bp, _Dp)> {};
 
 #else  // _LIBCPP_HAS_IS_BASE_OF
@@ -1354,14 +1435,15 @@ template <class _Bp, class _Dp> __two __test(...);
 }
 
 template <class _Bp, class _Dp>
-struct _LIBCPP_TYPE_VIS_ONLY is_base_of
+struct _LIBCPP_TEMPLATE_VIS is_base_of
     : public integral_constant<bool, is_class<_Bp>::value &&
                                      sizeof(__is_base_of_imp::__test<_Bp, _Dp>(0)) == 2> {};
 
 #endif  // _LIBCPP_HAS_IS_BASE_OF
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Bp, class _Dp> _LIBCPP_CONSTEXPR bool is_base_of_v
+template <class _Bp, class _Dp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_base_of_v
     = is_base_of<_Bp, _Dp>::value;
 #endif
 
@@ -1369,7 +1451,7 @@ template <class _Bp, class _Dp> _LIBCPP_CONSTEXPR bool is_base_of_v
 
 #if __has_feature(is_convertible_to) && !defined(_LIBCPP_USE_IS_CONVERTIBLE_FALLBACK)
 
-template <class _T1, class _T2> struct _LIBCPP_TYPE_VIS_ONLY is_convertible
+template <class _T1, class _T2> struct _LIBCPP_TEMPLATE_VIS is_convertible
     : public integral_constant<bool, __is_convertible_to(_T1, _T2) &&
                                      !is_abstract<_T2>::value> {};
 
@@ -1441,7 +1523,7 @@ template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 1, 3> : public
 template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 2, 3> : public false_type {};
 template <class _T1, class _T2> struct __is_convertible<_T1, _T2, 3, 3> : public true_type {};
 
-template <class _T1, class _T2> struct _LIBCPP_TYPE_VIS_ONLY is_convertible
+template <class _T1, class _T2> struct _LIBCPP_TEMPLATE_VIS is_convertible
     : public __is_convertible<_T1, _T2>
 {
     static const size_t __complete_check1 = __is_convertible_check<_T1>::__v;
@@ -1451,7 +1533,8 @@ template <class _T1, class _T2> struct _LIBCPP_TYPE_VIS_ONLY is_convertible
 #endif  // __has_feature(is_convertible_to)
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _From, class _To> _LIBCPP_CONSTEXPR bool is_convertible_v
+template <class _From, class _To>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_convertible_v
     = is_convertible<_From, _To>::value;
 #endif
 
@@ -1460,7 +1543,7 @@ template <class _From, class _To> _LIBCPP_CONSTEXPR bool is_convertible_v
 #if __has_feature(is_empty) || (_GNUC_VER >= 407)
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_empty
+struct _LIBCPP_TEMPLATE_VIS is_empty
     : public integral_constant<bool, __is_empty(_Tp)> {};
 
 #else  // __has_feature(is_empty)
@@ -1482,21 +1565,22 @@ struct __libcpp_empty : public integral_constant<bool, sizeof(__is_empty1<_Tp>)
 
 template <class _Tp> struct __libcpp_empty<_Tp, false> : public false_type {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_empty : public __libcpp_empty<_Tp> {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_empty : public __libcpp_empty<_Tp> {};
 
 #endif  // __has_feature(is_empty)
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_empty_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_empty_v
     = is_empty<_Tp>::value;
 #endif
 
 // is_polymorphic
 
-#if __has_feature(is_polymorphic) || defined(_LIBCPP_MSVC)
+#if __has_feature(is_polymorphic) || defined(_LIBCPP_COMPILER_MSVC)
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_polymorphic
+struct _LIBCPP_TEMPLATE_VIS is_polymorphic
     : public integral_constant<bool, __is_polymorphic(_Tp)> {};
 
 #else
@@ -1506,13 +1590,14 @@ template<typename _Tp> char &__is_polymorphic_impl(
                        int>::type);
 template<typename _Tp> __two &__is_polymorphic_impl(...);
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_polymorphic
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_polymorphic
     : public integral_constant<bool, sizeof(__is_polymorphic_impl<_Tp>(0)) == 1> {};
 
 #endif // __has_feature(is_polymorphic)
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_polymorphic_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_polymorphic_v
     = is_polymorphic<_Tp>::value;
 #endif
 
@@ -1520,28 +1605,46 @@ template <class _Tp> _LIBCPP_CONSTEXPR bool is_polymorphic_v
 
 #if __has_feature(has_virtual_destructor) || (_GNUC_VER >= 403)
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY has_virtual_destructor
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS has_virtual_destructor
     : public integral_constant<bool, __has_virtual_destructor(_Tp)> {};
 
 #else
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY has_virtual_destructor
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS has_virtual_destructor
     : public false_type {};
 
 #endif
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool has_virtual_destructor_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool has_virtual_destructor_v
     = has_virtual_destructor<_Tp>::value;
 #endif
 
+// has_unique_object_representations
+
+#if _LIBCPP_STD_VER > 14 && defined(_LIBCPP_HAS_UNIQUE_OBJECT_REPRESENTATIONS)
+
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS has_unique_object_representations
+    : public integral_constant<bool, 
+       __has_unique_object_representations(remove_cv_t<remove_all_extents_t<_Tp>>)> {};
+
+#if !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool has_unique_object_representations_v
+    = has_unique_object_representations<_Tp>::value;
+#endif
+
+#endif
+
 // alignment_of
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY alignment_of
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS alignment_of
     : public integral_constant<size_t, __alignof__(_Tp)> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR size_t alignment_of_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR size_t alignment_of_v
     = alignment_of<_Tp>::value;
 #endif
 
@@ -1556,7 +1659,7 @@ struct __type_list
 
 struct __nat
 {
-#ifndef _LIBCPP_HAS_NO_DELETED_FUNCTIONS
+#ifndef _LIBCPP_CXX03_LANG
     __nat() = delete;
     __nat(const __nat&) = delete;
     __nat& operator=(const __nat&) = delete;
@@ -1630,7 +1733,7 @@ struct __find_max_align<__type_list<_Hp, _Tp>, _Len>
     : public integral_constant<size_t, __select_align<_Len, _Hp::value, __find_max_align<_Tp, _Len>::value>::value> {};
 
 template <size_t _Len, size_t _Align = __find_max_align<__all_types, _Len>::value>
-struct _LIBCPP_TYPE_VIS_ONLY aligned_storage
+struct _LIBCPP_TEMPLATE_VIS aligned_storage
 {
     typedef typename __find_pod<__all_types, _Align>::type _Aligner;
     static_assert(!is_void<_Aligner>::value, "");
@@ -1648,7 +1751,7 @@ template <size_t _Len, size_t _Align = __find_max_align<__all_types, _Len>::valu
 
 #define _CREATE_ALIGNED_STORAGE_SPECIALIZATION(n) \
 template <size_t _Len>\
-struct _LIBCPP_TYPE_VIS_ONLY aligned_storage<_Len, n>\
+struct _LIBCPP_TEMPLATE_VIS aligned_storage<_Len, n>\
 {\
     struct _ALIGNAS(n) type\
     {\
@@ -1670,10 +1773,10 @@ _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x400);
 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x800);
 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x1000);
 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x2000);
-// MSDN says that MSVC does not support alignment beyond 8192 (=0x2000)
-#if !defined(_LIBCPP_MSVC)
+// PE/COFF does not support alignment beyond 8192 (=0x2000)
+#if !defined(_LIBCPP_OBJECT_FORMAT_COFF)
 _CREATE_ALIGNED_STORAGE_SPECIALIZATION(0x4000);
-#endif // !_LIBCPP_MSVC
+#endif // !defined(_LIBCPP_OBJECT_FORMAT_COFF)
 
 #undef _CREATE_ALIGNED_STORAGE_SPECIALIZATION
 
@@ -1903,7 +2006,7 @@ template <> struct __make_signed<__uint128_t,        true> {typedef __int128_t t
 #endif
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY make_signed
+struct _LIBCPP_TEMPLATE_VIS make_signed
 {
     typedef typename __apply_cv<_Tp, typename __make_signed<typename remove_cv<_Tp>::type>::type>::type type;
 };
@@ -1936,7 +2039,7 @@ template <> struct __make_unsigned<__uint128_t,        true> {typedef __uint128_
 #endif
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY make_unsigned
+struct _LIBCPP_TEMPLATE_VIS make_unsigned
 {
     typedef typename __apply_cv<_Tp, typename __make_unsigned<typename remove_cv<_Tp>::type>::type>::type type;
 };
@@ -1948,21 +2051,28 @@ template <class _Tp> using make_unsigned_t = typename make_unsigned<_Tp>::type;
 #ifdef _LIBCPP_HAS_NO_VARIADICS
 
 template <class _Tp, class _Up = void, class _Vp = void>
-struct _LIBCPP_TYPE_VIS_ONLY common_type
+struct _LIBCPP_TEMPLATE_VIS common_type
 {
 public:
     typedef typename common_type<typename common_type<_Tp, _Up>::type, _Vp>::type type;
 };
 
+template <>
+struct _LIBCPP_TEMPLATE_VIS common_type<void, void, void>
+{
+public:
+    typedef void type;
+};
+
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY common_type<_Tp, void, void>
+struct _LIBCPP_TEMPLATE_VIS common_type<_Tp, void, void>
 {
 public:
-    typedef typename decay<_Tp>::type type;
+    typedef typename common_type<_Tp, _Tp>::type type;
 };
 
 template <class _Tp, class _Up>
-struct _LIBCPP_TYPE_VIS_ONLY common_type<_Tp, _Up, void>
+struct _LIBCPP_TEMPLATE_VIS common_type<_Tp, _Up, void>
 {
     typedef typename decay<decltype(
         true ? _VSTD::declval<_Tp>() : _VSTD::declval<_Up>()
@@ -1974,23 +2084,21 @@ struct _LIBCPP_TYPE_VIS_ONLY common_type<_Tp, _Up, void>
 // bullet 1 - sizeof...(Tp) == 0
 
 template <class ..._Tp>
-struct _LIBCPP_TYPE_VIS_ONLY common_type {};
+struct _LIBCPP_TEMPLATE_VIS common_type {};
 
 // bullet 2 - sizeof...(Tp) == 1
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY common_type<_Tp>
-{
-    typedef typename decay<_Tp>::type type;
-};
+struct _LIBCPP_TEMPLATE_VIS common_type<_Tp>
+    : public common_type<_Tp, _Tp> {};
 
 // bullet 3 - sizeof...(Tp) == 2
 
 template <class _Tp, class _Up, class = void>
-struct __common_type2 {};
+struct __common_type2_imp {};
 
 template <class _Tp, class _Up>
-struct __common_type2<_Tp, _Up,
+struct __common_type2_imp<_Tp, _Up,
     typename __void_t<decltype(
         true ? _VSTD::declval<_Tp>() : _VSTD::declval<_Up>()
     )>::type>
@@ -2000,8 +2108,18 @@ struct __common_type2<_Tp, _Up,
     )>::type type;
 };
 
+template <class _Tp, class _Up,
+          class _DTp = typename decay<_Tp>::type,
+          class _DUp = typename decay<_Up>::type>
+using __common_type2 =
+  typename conditional<
+    is_same<_Tp, _DTp>::value && is_same<_Up, _DUp>::value,
+    __common_type2_imp<_Tp, _Up>,
+    common_type<_DTp, _DUp>
+  >::type;
+
 template <class _Tp, class _Up>
-struct _LIBCPP_TYPE_VIS_ONLY common_type<_Tp, _Up>
+struct _LIBCPP_TEMPLATE_VIS common_type<_Tp, _Up>
     : __common_type2<_Tp, _Up> {};
 
 // bullet 4 - sizeof...(Tp) > 2
@@ -2011,17 +2129,25 @@ template <class ...Tp> struct __common_types;
 template <class, class = void>
 struct __common_type_impl {};
 
+template <class _Tp, class _Up>
+struct __common_type_impl<
+    __common_types<_Tp, _Up>,
+    typename __void_t<typename common_type<_Tp, _Up>::type>::type>
+{
+  typedef typename common_type<_Tp, _Up>::type type;
+};
+
 template <class _Tp, class _Up, class ..._Vp>
 struct __common_type_impl<__common_types<_Tp, _Up, _Vp...>,
     typename __void_t<typename common_type<_Tp, _Up>::type>::type>
+  : __common_type_impl<
+      __common_types<typename common_type<_Tp, _Up>::type, _Vp...> >
 {
-    typedef typename common_type<
-        typename common_type<_Tp, _Up>::type, _Vp...
-    >::type type;
+
 };
 
 template <class _Tp, class _Up, class ..._Vp>
-struct _LIBCPP_TYPE_VIS_ONLY common_type<_Tp, _Up, _Vp...>
+struct _LIBCPP_TEMPLATE_VIS common_type<_Tp, _Up, _Vp...>
     : __common_type_impl<__common_types<_Tp, _Up, _Vp...> > {};
 
 #if _LIBCPP_STD_VER > 11
@@ -2036,26 +2162,15 @@ template<typename, typename _Tp> struct __select_2nd { typedef _Tp type; };
 
 template <class _Tp, class _Arg>
 typename __select_2nd<decltype((_VSTD::declval<_Tp>() = _VSTD::declval<_Arg>())), true_type>::type
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-__is_assignable_test(_Tp&&, _Arg&&);
-#else
-__is_assignable_test(_Tp, _Arg&);
-#endif
+__is_assignable_test(int);
+
+template <class, class>
+false_type __is_assignable_test(...);
 
-template <class _Arg>
-false_type
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-__is_assignable_test(__any, _Arg&&);
-#else
-__is_assignable_test(__any, _Arg&);
-#endif
 
 template <class _Tp, class _Arg, bool = is_void<_Tp>::value || is_void<_Arg>::value>
 struct __is_assignable_imp
-    : public common_type
-        <
-            decltype(_VSTD::__is_assignable_test(declval<_Tp>(), declval<_Arg>()))
-        >::type {};
+    : public decltype((_VSTD::__is_assignable_test<_Tp, _Arg>(0))) {};
 
 template <class _Tp, class _Arg>
 struct __is_assignable_imp<_Tp, _Arg, true>
@@ -2068,33 +2183,36 @@ struct is_assignable
     : public __is_assignable_imp<_Tp, _Arg> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp, class _Arg> _LIBCPP_CONSTEXPR bool is_assignable_v
+template <class _Tp, class _Arg>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_assignable_v
     = is_assignable<_Tp, _Arg>::value;
 #endif
 
 // is_copy_assignable
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_copy_assignable
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_copy_assignable
     : public is_assignable<typename add_lvalue_reference<_Tp>::type,
                   typename add_lvalue_reference<typename add_const<_Tp>::type>::type> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_copy_assignable_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_copy_assignable_v
     = is_copy_assignable<_Tp>::value;
 #endif
 
 // is_move_assignable
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_move_assignable
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_move_assignable
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     : public is_assignable<typename add_lvalue_reference<_Tp>::type,
-                     const typename add_rvalue_reference<_Tp>::type> {};
+                           typename add_rvalue_reference<_Tp>::type> {};
 #else
     : public is_copy_assignable<_Tp> {};
 #endif
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_move_assignable_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_move_assignable_v
     = is_move_assignable<_Tp>::value;
 #endif
 
@@ -2157,7 +2275,8 @@ struct is_destructible<void>
     : public _VSTD::false_type {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_destructible_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_destructible_v
     = is_destructible<_Tp>::value;
 #endif
 
@@ -2166,7 +2285,7 @@ template <class _Tp> _LIBCPP_CONSTEXPR bool is_destructible_v
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
 template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
 typename remove_reference<_Tp>::type&&
 move(_Tp&& __t) _NOEXCEPT
 {
@@ -2175,7 +2294,7 @@ move(_Tp&& __t) _NOEXCEPT
 }
 
 template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
 _Tp&&
 forward(typename remove_reference<_Tp>::type& __t) _NOEXCEPT
 {
@@ -2183,12 +2302,12 @@ forward(typename remove_reference<_Tp>::type& __t) _NOEXCEPT
 }
 
 template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
 _Tp&&
 forward(typename remove_reference<_Tp>::type&& __t) _NOEXCEPT
 {
     static_assert(!is_lvalue_reference<_Tp>::value,
-                  "Can not forward an rvalue as an lvalue.");
+                  "can not forward an rvalue as an lvalue");
     return static_cast<_Tp&&>(__t);
 }
 
@@ -2852,7 +2971,7 @@ class __result_of<_Fn(_Tp, _A0, _A1, _A2), false, true>  // _Fn must be member p
 // result_of
 
 template <class _Fn>
-class _LIBCPP_TYPE_VIS_ONLY result_of<_Fn()>
+class _LIBCPP_TEMPLATE_VIS result_of<_Fn()>
     : public __result_of<_Fn(),
                          is_class<typename remove_reference<_Fn>::type>::value ||
                          is_function<typename remove_pointer<typename remove_reference<_Fn>::type>::type>::value,
@@ -2862,7 +2981,7 @@ class _LIBCPP_TYPE_VIS_ONLY result_of<_Fn()>
 };
 
 template <class _Fn, class _A0>
-class _LIBCPP_TYPE_VIS_ONLY result_of<_Fn(_A0)>
+class _LIBCPP_TEMPLATE_VIS result_of<_Fn(_A0)>
     : public __result_of<_Fn(_A0),
                          is_class<typename remove_reference<_Fn>::type>::value ||
                          is_function<typename remove_pointer<typename remove_reference<_Fn>::type>::type>::value,
@@ -2872,7 +2991,7 @@ class _LIBCPP_TYPE_VIS_ONLY result_of<_Fn(_A0)>
 };
 
 template <class _Fn, class _A0, class _A1>
-class _LIBCPP_TYPE_VIS_ONLY result_of<_Fn(_A0, _A1)>
+class _LIBCPP_TEMPLATE_VIS result_of<_Fn(_A0, _A1)>
     : public __result_of<_Fn(_A0, _A1),
                          is_class<typename remove_reference<_Fn>::type>::value ||
                          is_function<typename remove_pointer<typename remove_reference<_Fn>::type>::type>::value,
@@ -2882,7 +3001,7 @@ class _LIBCPP_TYPE_VIS_ONLY result_of<_Fn(_A0, _A1)>
 };
 
 template <class _Fn, class _A0, class _A1, class _A2>
-class _LIBCPP_TYPE_VIS_ONLY result_of<_Fn(_A0, _A1, _A2)>
+class _LIBCPP_TEMPLATE_VIS result_of<_Fn(_A0, _A1, _A2)>
     : public __result_of<_Fn(_A0, _A1, _A2),
                          is_class<typename remove_reference<_Fn>::type>::value ||
                          is_function<typename remove_pointer<typename remove_reference<_Fn>::type>::type>::value,
@@ -2900,135 +3019,132 @@ namespace __is_construct
 struct __nat {};
 }
 
-#if __has_feature(is_constructible)
-
-template <class _Tp, class ..._Args>
-struct _LIBCPP_TYPE_VIS_ONLY is_constructible
-    : public integral_constant<bool, __is_constructible(_Tp, _Args...)>
-    {};
-
-#else
-
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
-//      main is_constructible test
-
-template <class _Tp, class ..._Args>
-typename __select_2nd<decltype(_VSTD::move(_Tp(_VSTD::declval<_Args>()...))), true_type>::type
-__is_constructible_test(_Tp&&, _Args&& ...);
+#if !defined(_LIBCPP_CXX03_LANG) && (!__has_feature(is_constructible) || \
+    defined(_LIBCPP_TESTING_FALLBACK_IS_CONSTRUCTIBLE))
 
-template <class ..._Args>
-false_type
-__is_constructible_test(__any, _Args&& ...);
+template <class _Tp, class... _Args>
+struct __libcpp_is_constructible;
+
+template <class _To, class _From>
+struct __is_invalid_base_to_derived_cast {
+  static_assert(is_reference<_To>::value, "Wrong specialization");
+  using _RawFrom = __uncvref_t<_From>;
+  using _RawTo = __uncvref_t<_To>;
+  static const bool value = __lazy_and<
+        __lazy_not<is_same<_RawFrom, _RawTo>>,
+        is_base_of<_RawFrom, _RawTo>,
+        __lazy_not<__libcpp_is_constructible<_RawTo, _From>>
+  >::value;
+};
+
+template <class _To, class _From>
+struct __is_invalid_lvalue_to_rvalue_cast : false_type {
+  static_assert(is_reference<_To>::value, "Wrong specialization");
+};
+
+template <class _ToRef, class _FromRef>
+struct __is_invalid_lvalue_to_rvalue_cast<_ToRef&&, _FromRef&> {
+  using _RawFrom = __uncvref_t<_FromRef>;
+  using _RawTo = __uncvref_t<_ToRef>;
+  static const bool value = __lazy_and<
+      __lazy_not<is_function<_RawTo>>,
+      __lazy_or<
+        is_same<_RawFrom, _RawTo>,
+        is_base_of<_RawTo, _RawFrom>>
+    >::value;
+};
+
+struct __is_constructible_helper
+{
+    template <class _To>
+    static void __eat(_To);
+
+    // This overload is needed to work around a Clang bug that disallows
+    // static_cast<T&&>(e) for non-reference-compatible types.
+    // Example: static_cast<int&&>(declval<double>());
+    // NOTE: The static_cast implementation below is required to support
+    //  classes with explicit conversion operators.
+    template <class _To, class _From,
+              class = decltype(__eat<_To>(_VSTD::declval<_From>()))>
+    static true_type __test_cast(int);
+
+    template <class _To, class _From,
+              class = decltype(static_cast<_To>(_VSTD::declval<_From>()))>
+    static integral_constant<bool,
+        !__is_invalid_base_to_derived_cast<_To, _From>::value &&
+        !__is_invalid_lvalue_to_rvalue_cast<_To, _From>::value
+    > __test_cast(long);
 
-template <bool, class _Tp, class... _Args>
-struct __libcpp_is_constructible // false, _Tp is not a scalar
-    : public common_type
-             <
-                 decltype(__is_constructible_test(declval<_Tp>(), declval<_Args>()...))
-             >::type
-    {};
+    template <class, class>
+    static false_type __test_cast(...);
 
-//      function types are not constructible
+    template <class _Tp, class ..._Args,
+        class = decltype(_Tp(_VSTD::declval<_Args>()...))>
+    static true_type __test_nary(int);
+    template <class _Tp, class...>
+    static false_type __test_nary(...);
 
-template <class _Rp, class... _A1, class... _A2>
-struct __libcpp_is_constructible<false, _Rp(_A1...), _A2...>
-    : public false_type
-    {};
-
-//      handle scalars and reference types
+    template <class _Tp, class _A0, class = decltype(::new _Tp(_VSTD::declval<_A0>()))>
+    static is_destructible<_Tp> __test_unary(int);
+    template <class, class>
+    static false_type __test_unary(...);
+};
 
-//      Scalars are default constructible, references are not
+template <class _Tp, bool = is_void<_Tp>::value>
+struct __is_default_constructible
+    : decltype(__is_constructible_helper::__test_nary<_Tp>(0))
+{};
 
 template <class _Tp>
-struct __libcpp_is_constructible<true, _Tp>
-    : public is_scalar<_Tp>
-    {};
-
-//      Scalars and references are constructible from one arg if that arg is
-//          implicitly convertible to the scalar or reference.
+struct __is_default_constructible<_Tp, true> : false_type {};
 
 template <class _Tp>
-struct __is_constructible_ref
-{
-    true_type static __lxx(_Tp);
-    false_type static __lxx(...);
-};
-
-template <class _Tp, class _A0>
-struct __libcpp_is_constructible<true, _Tp, _A0>
-    : public common_type
-             <
-                 decltype(__is_constructible_ref<_Tp>::__lxx(declval<_A0>()))
-             >::type
-    {};
-
-//      Scalars and references are not constructible from multiple args.
-
-template <class _Tp, class _A0, class ..._Args>
-struct __libcpp_is_constructible<true, _Tp, _A0, _Args...>
-    : public false_type
-    {};
-
-//      Treat scalars and reference types separately
-
-template <bool, class _Tp, class... _Args>
-struct __is_constructible_void_check
-    : public __libcpp_is_constructible<is_scalar<_Tp>::value || is_reference<_Tp>::value,
-                                _Tp, _Args...>
-    {};
+struct __is_default_constructible<_Tp[], false> : false_type {};
 
-//      If any of T or Args is void, is_constructible should be false
+template <class _Tp, size_t _Nx>
+struct __is_default_constructible<_Tp[_Nx], false>
+    : __is_default_constructible<typename remove_all_extents<_Tp>::type>  {};
 
 template <class _Tp, class... _Args>
-struct __is_constructible_void_check<true, _Tp, _Args...>
-    : public false_type
-    {};
-
-template <class ..._Args> struct __contains_void;
-
-template <> struct __contains_void<> : false_type {};
-
-template <class _A0, class ..._Args>
-struct __contains_void<_A0, _Args...>
+struct __libcpp_is_constructible
 {
-    static const bool value = is_void<_A0>::value ||
-                              __contains_void<_Args...>::value;
+  static_assert(sizeof...(_Args) > 1, "Wrong specialization");
+  typedef decltype(__is_constructible_helper::__test_nary<_Tp, _Args...>(0))
+      type;
 };
 
-//      is_constructible entry point
-
-template <class _Tp, class... _Args>
-struct _LIBCPP_TYPE_VIS_ONLY is_constructible
-    : public __is_constructible_void_check<__contains_void<_Tp, _Args...>::value
-                                        || is_abstract<_Tp>::value,
-                                           _Tp, _Args...>
-    {};
-
-//      Array types are default constructible if their element type
-//      is default constructible
+template <class _Tp>
+struct __libcpp_is_constructible<_Tp> : __is_default_constructible<_Tp> {};
 
-template <class _Ap, size_t _Np>
-struct __libcpp_is_constructible<false, _Ap[_Np]>
-    : public is_constructible<typename remove_all_extents<_Ap>::type>
-    {};
+template <class _Tp, class _A0>
+struct __libcpp_is_constructible<_Tp, _A0>
+    : public decltype(__is_constructible_helper::__test_unary<_Tp, _A0>(0))
+{};
 
-//      Otherwise array types are not constructible by this syntax
+template <class _Tp, class _A0>
+struct __libcpp_is_constructible<_Tp&, _A0>
+    : public decltype(__is_constructible_helper::
+    __test_cast<_Tp&, _A0>(0))
+{};
 
-template <class _Ap, size_t _Np, class ..._Args>
-struct __libcpp_is_constructible<false, _Ap[_Np], _Args...>
-    : public false_type
-    {};
+template <class _Tp, class _A0>
+struct __libcpp_is_constructible<_Tp&&, _A0>
+    : public decltype(__is_constructible_helper::
+    __test_cast<_Tp&&, _A0>(0))
+{};
 
-//      Incomplete array types are not constructible
+#endif
 
-template <class _Ap, class ..._Args>
-struct __libcpp_is_constructible<false, _Ap[], _Args...>
-    : public false_type
+#if __has_feature(is_constructible)
+template <class _Tp, class ..._Args>
+struct _LIBCPP_TEMPLATE_VIS is_constructible
+    : public integral_constant<bool, __is_constructible(_Tp, _Args...)>
     {};
-
-#else  // _LIBCPP_HAS_NO_VARIADICS
-
+#elif !defined(_LIBCPP_CXX03_LANG)
+template <class _Tp, class... _Args>
+struct _LIBCPP_TEMPLATE_VIS is_constructible
+    : public __libcpp_is_constructible<_Tp, _Args...>::type {};
+#else
 // template <class T> struct is_constructible0;
 
 //      main is_constructible0 test
@@ -3056,6 +3172,14 @@ template <class _A0, class _A1>
 false_type
 __is_constructible2_test(__any, _A0&, _A1&);
 
+template <class _Tp, class _A0, class _A1, class _A2>
+decltype((_Tp(_VSTD::declval<_A0>(), _VSTD::declval<_A1>(), _VSTD::declval<_A2>()), true_type()))
+__is_constructible3_test(_Tp&, _A0&, _A1&, _A2&);
+
+template <class _A0, class _A1, class _A2>
+false_type
+__is_constructible3_test(__any, _A0&, _A1&, _A2&);
+
 template <bool, class _Tp>
 struct __is_constructible0_imp // false, _Tp is not a scalar
     : public common_type
@@ -3080,6 +3204,14 @@ struct __is_constructible2_imp // false, _Tp is not a scalar
              >::type
     {};
 
+template <bool, class _Tp, class _A0, class _A1, class _A2>
+struct __is_constructible3_imp // false, _Tp is not a scalar
+    : public common_type
+             <
+                 decltype(__is_constructible3_test(declval<_Tp&>(), declval<_A0>(), declval<_A1>(), declval<_A2>()))
+             >::type
+    {};
+
 //      handle scalars and reference types
 
 //      Scalars are default constructible, references are not
@@ -3099,6 +3231,11 @@ struct __is_constructible2_imp<true, _Tp, _A0, _A1>
     : public false_type
     {};
 
+template <class _Tp, class _A0, class _A1, class _A2>
+struct __is_constructible3_imp<true, _Tp, _A0, _A1, _A2>
+    : public false_type
+    {};
+
 //      Treat scalars and reference types separately
 
 template <bool, class _Tp>
@@ -3119,6 +3256,12 @@ struct __is_constructible2_void_check
                                 _Tp, _A0, _A1>
     {};
 
+template <bool, class _Tp, class _A0, class _A1, class _A2>
+struct __is_constructible3_void_check
+    : public __is_constructible3_imp<is_scalar<_Tp>::value || is_reference<_Tp>::value,
+                                _Tp, _A0, _A1, _A2>
+    {};
+
 //      If any of T or Args is void, is_constructible should be false
 
 template <class _Tp>
@@ -3136,21 +3279,28 @@ struct __is_constructible2_void_check<true, _Tp, _A0, _A1>
     : public false_type
     {};
 
+template <class _Tp, class _A0, class _A1, class _A2>
+struct __is_constructible3_void_check<true, _Tp, _A0, _A1, _A2>
+    : public false_type
+    {};
+
 //      is_constructible entry point
 
 template <class _Tp, class _A0 = __is_construct::__nat,
-                     class _A1 = __is_construct::__nat>
-struct _LIBCPP_TYPE_VIS_ONLY is_constructible
-    : public __is_constructible2_void_check<is_void<_Tp>::value
+                     class _A1 = __is_construct::__nat,
+                     class _A2 = __is_construct::__nat>
+struct _LIBCPP_TEMPLATE_VIS is_constructible
+    : public __is_constructible3_void_check<is_void<_Tp>::value
                                         || is_abstract<_Tp>::value
                                         || is_function<_Tp>::value
                                         || is_void<_A0>::value
-                                        || is_void<_A1>::value,
-                                           _Tp, _A0, _A1>
+                                        || is_void<_A1>::value
+                                        || is_void<_A2>::value,
+                                           _Tp, _A0, _A1, _A2>
     {};
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_constructible<_Tp, __is_construct::__nat, __is_construct::__nat>
+struct _LIBCPP_TEMPLATE_VIS is_constructible<_Tp, __is_construct::__nat, __is_construct::__nat>
     : public __is_constructible0_void_check<is_void<_Tp>::value
                                         || is_abstract<_Tp>::value
                                         || is_function<_Tp>::value,
@@ -3158,7 +3308,7 @@ struct _LIBCPP_TYPE_VIS_ONLY is_constructible<_Tp, __is_construct::__nat, __is_c
     {};
 
 template <class _Tp, class _A0>
-struct _LIBCPP_TYPE_VIS_ONLY is_constructible<_Tp, _A0, __is_construct::__nat>
+struct _LIBCPP_TEMPLATE_VIS is_constructible<_Tp, _A0, __is_construct::__nat>
     : public __is_constructible1_void_check<is_void<_Tp>::value
                                         || is_abstract<_Tp>::value
                                         || is_function<_Tp>::value
@@ -3166,6 +3316,16 @@ struct _LIBCPP_TYPE_VIS_ONLY is_constructible<_Tp, _A0, __is_construct::__nat>
                                            _Tp, _A0>
     {};
 
+template <class _Tp, class _A0, class _A1>
+struct _LIBCPP_TEMPLATE_VIS is_constructible<_Tp, _A0, _A1, __is_construct::__nat>
+    : public __is_constructible2_void_check<is_void<_Tp>::value
+                                        || is_abstract<_Tp>::value
+                                        || is_function<_Tp>::value
+                                        || is_void<_A0>::value
+                                        || is_void<_A1>::value,
+                                           _Tp, _A0, _A1>
+    {};
+
 //      Array types are default constructible if their element type
 //      is default constructible
 
@@ -3184,6 +3344,11 @@ struct __is_constructible2_imp<false, _Ap[_Np], _A0, _A1>
     : public false_type
     {};
 
+template <class _Ap, size_t _Np, class _A0, class _A1, class _A2>
+struct __is_constructible3_imp<false, _Ap[_Np], _A0, _A1, _A2>
+    : public false_type
+    {};
+
 //      Incomplete array types are not constructible
 
 template <class _Ap>
@@ -3201,42 +3366,50 @@ struct __is_constructible2_imp<false, _Ap[], _A0, _A1>
     : public false_type
     {};
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-#endif  // __has_feature(is_constructible)
+template <class _Ap, class _A0, class _A1, class _A2>
+struct __is_constructible3_imp<false, _Ap[], _A0, _A1, _A2>
+    : public false_type
+    {};
+
+#endif // __has_feature(is_constructible)
+
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
-template <class _Tp, class ..._Args> _LIBCPP_CONSTEXPR bool is_constructible_v
+template <class _Tp, class ..._Args>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_constructible_v
     = is_constructible<_Tp, _Args...>::value;
 #endif
 
 // is_default_constructible
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_default_constructible
+struct _LIBCPP_TEMPLATE_VIS is_default_constructible
     : public is_constructible<_Tp>
     {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_default_constructible_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_default_constructible_v
     = is_default_constructible<_Tp>::value;
 #endif
 
 // is_copy_constructible
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_copy_constructible
+struct _LIBCPP_TEMPLATE_VIS is_copy_constructible
     : public is_constructible<_Tp, 
                   typename add_lvalue_reference<typename add_const<_Tp>::type>::type> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_copy_constructible_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_copy_constructible_v
     = is_copy_constructible<_Tp>::value;
 #endif
 
 // is_move_constructible
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_move_constructible
+struct _LIBCPP_TEMPLATE_VIS is_move_constructible
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     : public is_constructible<_Tp, typename add_rvalue_reference<_Tp>::type>
 #else
@@ -3245,7 +3418,8 @@ struct _LIBCPP_TYPE_VIS_ONLY is_move_constructible
     {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_move_constructible_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_move_constructible_v
     = is_move_constructible<_Tp>::value;
 #endif
 
@@ -3256,7 +3430,7 @@ template <class _Tp> _LIBCPP_CONSTEXPR bool is_move_constructible_v
 #if __has_feature(is_trivially_constructible) || _GNUC_VER >= 501
 
 template <class _Tp, class... _Args>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible
     : integral_constant<bool, __is_trivially_constructible(_Tp, _Args...)>
 {
 };
@@ -3264,13 +3438,13 @@ struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible
 #else  // !__has_feature(is_trivially_constructible)
 
 template <class _Tp, class... _Args>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible
     : false_type
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp>
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp>
 #if __has_feature(has_trivial_constructor) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_trivial_constructor(_Tp)>
 #else
@@ -3281,22 +3455,22 @@ struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp>
 
 template <class _Tp>
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, _Tp&&>
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp&&>
 #else
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, _Tp>
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp>
 #endif
     : integral_constant<bool, is_scalar<_Tp>::value>
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, const _Tp&>
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, const _Tp&>
     : integral_constant<bool, is_scalar<_Tp>::value>
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, _Tp&>
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp&>
     : integral_constant<bool, is_scalar<_Tp>::value>
 {
 };
@@ -3307,7 +3481,7 @@ struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, _Tp&>
 
 template <class _Tp, class _A0 = __is_construct::__nat,
                      class _A1 = __is_construct::__nat>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible
     : false_type
 {
 };
@@ -3315,28 +3489,28 @@ struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible
 #if __has_feature(is_trivially_constructible) || _GNUC_VER >= 501
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, __is_construct::__nat,
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, __is_construct::__nat,
                                                        __is_construct::__nat>
     : integral_constant<bool, __is_trivially_constructible(_Tp)>
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, _Tp,
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp,
                                                        __is_construct::__nat>
     : integral_constant<bool, __is_trivially_constructible(_Tp, _Tp)>
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, const _Tp&,
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, const _Tp&,
                                                        __is_construct::__nat>
     : integral_constant<bool, __is_trivially_constructible(_Tp, const _Tp&)>
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, _Tp&,
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp&,
                                                        __is_construct::__nat>
     : integral_constant<bool, __is_trivially_constructible(_Tp, _Tp&)>
 {
@@ -3345,28 +3519,28 @@ struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, _Tp&,
 #else  // !__has_feature(is_trivially_constructible)
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, __is_construct::__nat,
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, __is_construct::__nat,
                                                        __is_construct::__nat>
     : integral_constant<bool, is_scalar<_Tp>::value>
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, _Tp,
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp,
                                                        __is_construct::__nat>
     : integral_constant<bool, is_scalar<_Tp>::value>
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, const _Tp&,
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, const _Tp&,
                                                        __is_construct::__nat>
     : integral_constant<bool, is_scalar<_Tp>::value>
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, _Tp&,
+struct _LIBCPP_TEMPLATE_VIS is_trivially_constructible<_Tp, _Tp&,
                                                        __is_construct::__nat>
     : integral_constant<bool, is_scalar<_Tp>::value>
 {
@@ -3377,35 +3551,38 @@ struct _LIBCPP_TYPE_VIS_ONLY is_trivially_constructible<_Tp, _Tp&,
 #endif  // _LIBCPP_HAS_NO_VARIADICS
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
-template <class _Tp, class... _Args> _LIBCPP_CONSTEXPR bool is_trivially_constructible_v
+template <class _Tp, class... _Args>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_trivially_constructible_v
     = is_trivially_constructible<_Tp, _Args...>::value;
 #endif
 
 // is_trivially_default_constructible
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_default_constructible
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_default_constructible
     : public is_trivially_constructible<_Tp>
     {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_trivially_default_constructible_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_trivially_default_constructible_v
     = is_trivially_default_constructible<_Tp>::value;
 #endif
 
 // is_trivially_copy_constructible
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_copy_constructible
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_copy_constructible
     : public is_trivially_constructible<_Tp, typename add_lvalue_reference<const _Tp>::type>
     {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_trivially_copy_constructible_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_trivially_copy_constructible_v
     = is_trivially_copy_constructible<_Tp>::value;
 #endif
 
 // is_trivially_move_constructible
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_move_constructible
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_move_constructible
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     : public is_trivially_constructible<_Tp, typename add_rvalue_reference<_Tp>::type>
 #else
@@ -3414,7 +3591,8 @@ template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_move_constructibl
     {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_trivially_move_constructible_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_trivially_move_constructible_v
     = is_trivially_move_constructible<_Tp>::value;
 #endif
 
@@ -3457,24 +3635,26 @@ struct is_trivially_assignable<_Tp&, _Tp&&>
 #endif  // !__has_feature(is_trivially_assignable)
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp, class _Arg> _LIBCPP_CONSTEXPR bool is_trivially_assignable_v
+template <class _Tp, class _Arg>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_trivially_assignable_v
     = is_trivially_assignable<_Tp, _Arg>::value;
 #endif
 
 // is_trivially_copy_assignable
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_copy_assignable
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_copy_assignable
     : public is_trivially_assignable<typename add_lvalue_reference<_Tp>::type,
                   typename add_lvalue_reference<typename add_const<_Tp>::type>::type> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_trivially_copy_assignable_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_trivially_copy_assignable_v
     = is_trivially_copy_assignable<_Tp>::value;
 #endif
 
 // is_trivially_move_assignable
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_move_assignable
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_move_assignable
     : public is_trivially_assignable<typename add_lvalue_reference<_Tp>::type,
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
                                      typename add_rvalue_reference<_Tp>::type>
@@ -3484,7 +3664,8 @@ template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_move_assignable
     {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_trivially_move_assignable_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_trivially_move_assignable_v
     = is_trivially_move_assignable<_Tp>::value;
 #endif
 
@@ -3492,7 +3673,7 @@ template <class _Tp> _LIBCPP_CONSTEXPR bool is_trivially_move_assignable_v
 
 #if __has_feature(has_trivial_destructor) || (_GNUC_VER >= 403)
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_destructible
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_destructible
     : public integral_constant<bool, is_destructible<_Tp>::value && __has_trivial_destructor(_Tp)> {};
 
 #else
@@ -3501,16 +3682,17 @@ template <class _Tp> struct __libcpp_trivial_destructor
     : public integral_constant<bool, is_scalar<_Tp>::value ||
                                      is_reference<_Tp>::value> {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_destructible
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_destructible
     : public __libcpp_trivial_destructor<typename remove_all_extents<_Tp>::type> {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_destructible<_Tp[]>
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_destructible<_Tp[]>
     : public false_type {};
 
 #endif
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_trivially_destructible_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_trivially_destructible_v
     = is_trivially_destructible<_Tp>::value;
 #endif
 
@@ -3518,7 +3700,7 @@ template <class _Tp> _LIBCPP_CONSTEXPR bool is_trivially_destructible_v
 
 #if 0
 template <class _Tp, class... _Args>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible
     : public integral_constant<bool, __is_nothrow_constructible(_Tp(_Args...))>
 {
 };
@@ -3553,13 +3735,13 @@ struct __libcpp_is_nothrow_constructible</*is constructible*/false, _IsReference
 };
 
 template <class _Tp, class... _Args>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible
     : __libcpp_is_nothrow_constructible<is_constructible<_Tp, _Args...>::value, is_reference<_Tp>::value, _Tp, _Args...>
 {
 };
 
 template <class _Tp, size_t _Ns>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp[_Ns]>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp[_Ns]>
     : __libcpp_is_nothrow_constructible<is_constructible<_Tp>::value, is_reference<_Tp>::value, _Tp>
 {
 };
@@ -3567,13 +3749,13 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp[_Ns]>
 #else  // __has_feature(cxx_noexcept)
 
 template <class _Tp, class... _Args>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible
     : false_type
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp>
 #if __has_feature(has_nothrow_constructor) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_constructor(_Tp)>
 #else
@@ -3584,9 +3766,9 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp>
 
 template <class _Tp>
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp&&>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, _Tp&&>
 #else
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, _Tp>
 #endif
 #if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
@@ -3597,7 +3779,7 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp>
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, const _Tp&>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, const _Tp&>
 #if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
 #else
@@ -3607,7 +3789,7 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, const _Tp&>
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp&>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, _Tp&>
 #if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
 #else
@@ -3622,13 +3804,13 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp&>
 
 template <class _Tp, class _A0 = __is_construct::__nat,
                      class _A1 = __is_construct::__nat>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible
     : false_type
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, __is_construct::__nat,
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, __is_construct::__nat,
                                                        __is_construct::__nat>
 #if __has_feature(has_nothrow_constructor) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_constructor(_Tp)>
@@ -3639,7 +3821,7 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, __is_construct::__nat
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp,
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, _Tp,
                                                        __is_construct::__nat>
 #if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
@@ -3650,7 +3832,7 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp,
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, const _Tp&,
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, const _Tp&,
                                                        __is_construct::__nat>
 #if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
@@ -3661,7 +3843,7 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, const _Tp&,
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp&,
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_constructible<_Tp, _Tp&,
                                                        __is_construct::__nat>
 #if __has_feature(has_nothrow_copy) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_copy(_Tp)>
@@ -3675,35 +3857,38 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_constructible<_Tp, _Tp&,
 #endif  // __has_feature(is_nothrow_constructible)
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
-template <class _Tp, class ..._Args> _LIBCPP_CONSTEXPR bool is_nothrow_constructible_v
+template <class _Tp, class ..._Args>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_nothrow_constructible_v
     = is_nothrow_constructible<_Tp, _Args...>::value;
 #endif
 
 // is_nothrow_default_constructible
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_default_constructible
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_nothrow_default_constructible
     : public is_nothrow_constructible<_Tp>
     {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_nothrow_default_constructible_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_nothrow_default_constructible_v
     = is_nothrow_default_constructible<_Tp>::value;
 #endif
 
 // is_nothrow_copy_constructible
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_copy_constructible
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_nothrow_copy_constructible
     : public is_nothrow_constructible<_Tp,
                   typename add_lvalue_reference<typename add_const<_Tp>::type>::type> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_nothrow_copy_constructible_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_nothrow_copy_constructible_v
     = is_nothrow_copy_constructible<_Tp>::value;
 #endif
 
 // is_nothrow_move_constructible
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_move_constructible
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_nothrow_move_constructible
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     : public is_nothrow_constructible<_Tp, typename add_rvalue_reference<_Tp>::type>
 #else
@@ -3712,7 +3897,8 @@ template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_move_constructible
     {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_nothrow_move_constructible_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_nothrow_move_constructible_v
     = is_nothrow_move_constructible<_Tp>::value;
 #endif
 
@@ -3735,7 +3921,7 @@ struct __libcpp_is_nothrow_assignable<true, _Tp, _Arg>
 };
 
 template <class _Tp, class _Arg>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_assignable
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_assignable
     : public __libcpp_is_nothrow_assignable<is_assignable<_Tp, _Arg>::value, _Tp, _Arg>
 {
 };
@@ -3743,11 +3929,11 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_assignable
 #else  // __has_feature(cxx_noexcept)
 
 template <class _Tp, class _Arg>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_assignable
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_assignable
     : public false_type {};
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_assignable<_Tp&, _Tp>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_assignable<_Tp&, _Tp>
 #if __has_feature(has_nothrow_assign) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
 #else
@@ -3755,7 +3941,7 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_assignable<_Tp&, _Tp>
 #endif
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_assignable<_Tp&, _Tp&>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_assignable<_Tp&, _Tp&>
 #if __has_feature(has_nothrow_assign) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
 #else
@@ -3763,7 +3949,7 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_assignable<_Tp&, _Tp&>
 #endif
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_assignable<_Tp&, const _Tp&>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_assignable<_Tp&, const _Tp&>
 #if __has_feature(has_nothrow_assign) || (_GNUC_VER >= 403)
     : integral_constant<bool, __has_nothrow_assign(_Tp)> {};
 #else
@@ -3785,24 +3971,26 @@ struct is_nothrow_assignable<_Tp&, _Tp&&>
 #endif  // __has_feature(cxx_noexcept)
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp, class _Arg> _LIBCPP_CONSTEXPR bool is_nothrow_assignable_v
+template <class _Tp, class _Arg>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_nothrow_assignable_v
     = is_nothrow_assignable<_Tp, _Arg>::value;
 #endif
 
 // is_nothrow_copy_assignable
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_copy_assignable
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_nothrow_copy_assignable
     : public is_nothrow_assignable<typename add_lvalue_reference<_Tp>::type,
                   typename add_lvalue_reference<typename add_const<_Tp>::type>::type> {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_nothrow_copy_assignable_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_nothrow_copy_assignable_v
     = is_nothrow_copy_assignable<_Tp>::value;
 #endif
 
 // is_nothrow_move_assignable
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_move_assignable
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_nothrow_move_assignable
     : public is_nothrow_assignable<typename add_lvalue_reference<_Tp>::type,
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
                                      typename add_rvalue_reference<_Tp>::type>
@@ -3812,7 +4000,8 @@ template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_move_assignable
     {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_nothrow_move_assignable_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_nothrow_move_assignable_v
     = is_nothrow_move_assignable<_Tp>::value;
 #endif
 
@@ -3835,19 +4024,19 @@ struct __libcpp_is_nothrow_destructible<true, _Tp>
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_destructible
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_destructible
     : public __libcpp_is_nothrow_destructible<is_destructible<_Tp>::value, _Tp>
 {
 };
 
 template <class _Tp, size_t _Ns>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_destructible<_Tp[_Ns]>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_destructible<_Tp[_Ns]>
     : public is_nothrow_destructible<_Tp>
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_destructible<_Tp&>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_destructible<_Tp&>
     : public true_type
 {
 };
@@ -3855,7 +4044,7 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_destructible<_Tp&>
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_destructible<_Tp&&>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_destructible<_Tp&&>
     : public true_type
 {
 };
@@ -3868,17 +4057,18 @@ template <class _Tp> struct __libcpp_nothrow_destructor
     : public integral_constant<bool, is_scalar<_Tp>::value ||
                                      is_reference<_Tp>::value> {};
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_destructible
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_nothrow_destructible
     : public __libcpp_nothrow_destructor<typename remove_all_extents<_Tp>::type> {};
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_destructible<_Tp[]>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_destructible<_Tp[]>
     : public false_type {};
 
 #endif
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_nothrow_destructible_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_nothrow_destructible_v
     = is_nothrow_destructible<_Tp>::value;
 #endif
 
@@ -3886,12 +4076,12 @@ template <class _Tp> _LIBCPP_CONSTEXPR bool is_nothrow_destructible_v
 
 #if __has_feature(is_pod) || (_GNUC_VER >= 403)
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_pod
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_pod
     : public integral_constant<bool, __is_pod(_Tp)> {};
 
 #else
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_pod
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_pod
     : public integral_constant<bool, is_trivially_default_constructible<_Tp>::value   &&
                                      is_trivially_copy_constructible<_Tp>::value      &&
                                      is_trivially_copy_assignable<_Tp>::value    &&
@@ -3900,13 +4090,14 @@ template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_pod
 #endif
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_pod_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_pod_v
     = is_pod<_Tp>::value;
 #endif
 
 // is_literal_type;
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_literal_type
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_literal_type
 #ifdef _LIBCPP_IS_LITERAL
     : public integral_constant<bool, _LIBCPP_IS_LITERAL(_Tp)>
 #else
@@ -3916,13 +4107,14 @@ template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_literal_type
     {};
     
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_literal_type_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_literal_type_v
     = is_literal_type<_Tp>::value;
 #endif
 
 // is_standard_layout;
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_standard_layout
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_standard_layout
 #if __has_feature(is_standard_layout) || (_GNUC_VER >= 407)
     : public integral_constant<bool, __is_standard_layout(_Tp)>
 #else
@@ -3931,13 +4123,14 @@ template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_standard_layout
     {};
     
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_standard_layout_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_standard_layout_v
     = is_standard_layout<_Tp>::value;
 #endif
 
 // is_trivially_copyable;
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_copyable
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivially_copyable
 #if __has_feature(is_trivially_copyable)
     : public integral_constant<bool, __is_trivially_copyable(_Tp)>
 #elif _GNUC_VER >= 501
@@ -3948,13 +4141,14 @@ template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivially_copyable
     {};
     
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_trivially_copyable_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_trivially_copyable_v
     = is_trivially_copyable<_Tp>::value;
 #endif
 
 // is_trivial;
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivial
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_trivial
 #if __has_feature(is_trivial) || _GNUC_VER >= 407
     : public integral_constant<bool, __is_trivial(_Tp)>
 #else
@@ -3964,7 +4158,8 @@ template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY is_trivial
     {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
-template <class _Tp> _LIBCPP_CONSTEXPR bool is_trivial_v
+template <class _Tp>
+_LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_trivial_v
     = is_trivial<_Tp>::value;
 #endif
 
@@ -4303,8 +4498,8 @@ struct __invokable_r
     using _Result = decltype(
         _VSTD::__invoke(_VSTD::declval<_Fp>(), _VSTD::declval<_Args>()...));
 
-    static const bool value =
-        conditional<
+    using type =
+        typename conditional<
             !is_same<_Result, __nat>::value,
             typename conditional<
                 is_void<_Ret>::value,
@@ -4312,7 +4507,8 @@ struct __invokable_r
                 is_convertible<_Result, _Ret>
             >::type,
             false_type
-        >::type::value;
+        >::type;
+    static const bool value = type::value;
 };
 
 template <class _Fp, class ..._Args>
@@ -4351,6 +4547,13 @@ using __nothrow_invokable_r =
     >;
 
 template <class _Fp, class ..._Args>
+using __nothrow_invokable =
+    __nothrow_invokable_r_imp<
+            __invokable<_Fp, _Args...>::value,
+            true, void, _Fp, _Args...
+    >;
+
+template <class _Fp, class ..._Args>
 struct __invoke_of
     : public enable_if<
         __invokable<_Fp, _Args...>::value,
@@ -4361,7 +4564,7 @@ struct __invoke_of
 // result_of
 
 template <class _Fp, class ..._Args>
-class _LIBCPP_TYPE_VIS_ONLY result_of<_Fp(_Args...)>
+class _LIBCPP_TEMPLATE_VIS result_of<_Fp(_Args...)>
     : public __invoke_of<_Fp, _Args...>
 {
 };
@@ -4372,30 +4575,52 @@ template <class _Tp> using result_of_t = typename result_of<_Tp>::type;
 
 #if _LIBCPP_STD_VER > 14
 
-// is_callable
+// invoke_result
+
+template <class _Fn, class... _Args>
+struct _LIBCPP_TEMPLATE_VIS invoke_result
+    : __invoke_of<_Fn, _Args...>
+{
+};
+
+template <class _Fn, class... _Args>
+using invoke_result_t = typename invoke_result<_Fn, _Args...>::type;
 
-template <class _Fn, class _Ret = void>
-struct _LIBCPP_TYPE_VIS_ONLY is_callable;
+// is_invocable
 
-template <class _Fn, class ..._Args, class _Ret>
-struct _LIBCPP_TYPE_VIS_ONLY is_callable<_Fn(_Args...), _Ret>
+template <class _Fn, class ..._Args>
+struct _LIBCPP_TEMPLATE_VIS is_invocable
+    : integral_constant<bool, __invokable<_Fn, _Args...>::value> {};
+
+template <class _Ret, class _Fn, class ..._Args>
+struct _LIBCPP_TEMPLATE_VIS is_invocable_r
     : integral_constant<bool, __invokable_r<_Ret, _Fn, _Args...>::value> {};
 
-template <class _Fn, class _Ret = void>
-constexpr bool is_callable_v = is_callable<_Fn, _Ret>::value;
+template <class _Fn, class ..._Args>
+_LIBCPP_INLINE_VAR constexpr bool is_invocable_v
+    = is_invocable<_Fn, _Args...>::value;
 
-// is_nothrow_callable
+template <class _Ret, class _Fn, class ..._Args>
+_LIBCPP_INLINE_VAR constexpr bool is_invocable_r_v
+    = is_invocable_r<_Ret, _Fn, _Args...>::value;
 
-template <class _Fn, class _Ret = void>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_callable;
+// is_nothrow_invocable
 
-template <class _Fn, class ..._Args, class _Ret>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_callable<_Fn(_Args...), _Ret>
-    : integral_constant<bool, __nothrow_invokable_r<_Ret, _Fn, _Args...>::value>
-{};
+template <class _Fn, class ..._Args>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_invocable
+    : integral_constant<bool, __nothrow_invokable<_Fn, _Args...>::value> {};
+
+template <class _Ret, class _Fn, class ..._Args>
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_invocable_r
+    : integral_constant<bool, __nothrow_invokable_r<_Ret, _Fn, _Args...>::value> {};
 
-template <class _Fn, class _Ret = void>
-constexpr bool is_nothrow_callable_v = is_nothrow_callable<_Fn, _Ret>::value;
+template <class _Fn, class ..._Args>
+_LIBCPP_INLINE_VAR constexpr bool is_nothrow_invocable_v
+    = is_nothrow_invocable<_Fn, _Args...>::value;
+
+template <class _Ret, class _Fn, class ..._Args>
+_LIBCPP_INLINE_VAR constexpr bool is_nothrow_invocable_r_v
+    = is_nothrow_invocable_r<_Ret, _Fn, _Args...>::value;
 
 #endif // _LIBCPP_STD_VER > 14
 
@@ -4406,7 +4631,7 @@ template <class _Tp> struct __is_nothrow_swappable;
 
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
-#ifndef _LIBCPP_HAS_NO_ADVANCED_SFINAE
+#ifndef _LIBCPP_CXX03_LANG
 typename enable_if
 <
     is_move_constructible<_Tp>::value &&
@@ -4499,13 +4724,13 @@ struct __is_nothrow_swappable
 #if _LIBCPP_STD_VER > 14
 
 template <class _Tp, class _Up>
-struct _LIBCPP_TYPE_VIS_ONLY is_swappable_with
+struct _LIBCPP_TEMPLATE_VIS is_swappable_with
     : public integral_constant<bool, __detail::__swappable_with<_Tp, _Up>::value>
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_swappable
+struct _LIBCPP_TEMPLATE_VIS is_swappable
     : public conditional<
         __is_referenceable<_Tp>::value,
         is_swappable_with<
@@ -4517,13 +4742,13 @@ struct _LIBCPP_TYPE_VIS_ONLY is_swappable
 };
 
 template <class _Tp, class _Up>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_swappable_with
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_swappable_with
     : public integral_constant<bool, __detail::__nothrow_swappable_with<_Tp, _Up>::value>
 {
 };
 
 template <class _Tp>
-struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_swappable
+struct _LIBCPP_TEMPLATE_VIS is_nothrow_swappable
     : public conditional<
         __is_referenceable<_Tp>::value,
         is_nothrow_swappable_with<
@@ -4535,16 +4760,20 @@ struct _LIBCPP_TYPE_VIS_ONLY is_nothrow_swappable
 };
 
 template <class _Tp, class _Up>
-constexpr bool is_swappable_with_v = is_swappable_with<_Tp, _Up>::value;
+_LIBCPP_INLINE_VAR constexpr bool is_swappable_with_v
+    = is_swappable_with<_Tp, _Up>::value;
 
 template <class _Tp>
-constexpr bool is_swappable_v = is_swappable<_Tp>::value;
+_LIBCPP_INLINE_VAR constexpr bool is_swappable_v
+    = is_swappable<_Tp>::value;
 
 template <class _Tp, class _Up>
-constexpr bool is_nothrow_swappable_with_v = is_nothrow_swappable_with<_Tp, _Up>::value;
+_LIBCPP_INLINE_VAR constexpr bool is_nothrow_swappable_with_v
+    = is_nothrow_swappable_with<_Tp, _Up>::value;
 
 template <class _Tp>
-constexpr bool is_nothrow_swappable_v = is_nothrow_swappable<_Tp>::value;
+_LIBCPP_INLINE_VAR constexpr bool is_nothrow_swappable_v
+    = is_nothrow_swappable<_Tp>::value;
 
 #endif // _LIBCPP_STD_VER > 14
 
@@ -4601,6 +4830,11 @@ long long __convert_to_integral(long long __val) { return __val; }
 inline _LIBCPP_INLINE_VISIBILITY
 unsigned long long __convert_to_integral(unsigned long long __val) {return __val; }
 
+template<typename _Fp>
+inline _LIBCPP_INLINE_VISIBILITY
+typename enable_if<is_floating_point<_Fp>::value, long long>::type
+ __convert_to_integral(_Fp __val) { return __val; }
+
 #ifndef _LIBCPP_HAS_NO_INT128
 inline _LIBCPP_INLINE_VISIBILITY
 __int128_t __convert_to_integral(__int128_t __val) { return __val; }
@@ -4614,7 +4848,7 @@ inline _LIBCPP_INLINE_VISIBILITY
 typename __sfinae_underlying_type<_Tp>::__promoted_type
 __convert_to_integral(_Tp __val) { return __val; }
 
-#ifndef _LIBCPP_HAS_NO_ADVANCED_SFINAE
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 struct __has_operator_addressof_member_imp
@@ -4646,23 +4880,31 @@ struct __has_operator_addressof
                                   || __has_operator_addressof_free_imp<_Tp>::value>
 {};
 
-#endif  // _LIBCPP_HAS_NO_ADVANCED_SFINAE
+#endif  // _LIBCPP_CXX03_LANG
 
 #if _LIBCPP_STD_VER > 14
+
+#define __cpp_lib_void_t 201411
 template <class...> using void_t = void;
 
 # ifndef _LIBCPP_HAS_NO_VARIADICS
 template <class... _Args>
 struct conjunction : __and_<_Args...> {};
-template<class... _Args> constexpr bool conjunction_v = conjunction<_Args...>::value;
+template<class... _Args>
+_LIBCPP_INLINE_VAR constexpr bool conjunction_v
+    = conjunction<_Args...>::value;
 
 template <class... _Args>
 struct disjunction : __or_<_Args...> {};
-template<class... _Args> constexpr bool disjunction_v = disjunction<_Args...>::value;
+template<class... _Args>
+_LIBCPP_INLINE_VAR constexpr bool disjunction_v
+    = disjunction<_Args...>::value;
 
 template <class _Tp>
 struct negation : __not_<_Tp> {};
-template<class _Tp> constexpr bool negation_v = negation<_Tp>::value;
+template<class _Tp>
+_LIBCPP_INLINE_VAR constexpr bool negation_v
+    = negation<_Tp>::value;
 # endif // _LIBCPP_HAS_NO_VARIADICS
 #endif  // _LIBCPP_STD_VER > 14
 
@@ -4701,4 +4943,35 @@ struct __can_extract_map_key<_ValTy, _Key, _Key, _RawValTy>
 
 _LIBCPP_END_NAMESPACE_STD
 
+#if _LIBCPP_STD_VER > 14
+// std::byte
+namespace std  // purposefully not versioned
+{
+template <class _Integer>
+  constexpr typename enable_if<is_integral_v<_Integer>, byte>::type &
+  operator<<=(byte& __lhs, _Integer __shift) noexcept
+  { return __lhs = __lhs << __shift; }
+  
+template <class _Integer>
+  constexpr typename enable_if<is_integral_v<_Integer>, byte>::type
+  operator<< (byte  __lhs, _Integer __shift) noexcept
+  { return static_cast<byte>(static_cast<unsigned char>(static_cast<unsigned int>(__lhs) << __shift)); }
+
+template <class _Integer>
+  constexpr typename enable_if<is_integral_v<_Integer>, byte>::type &
+  operator>>=(byte& __lhs, _Integer __shift) noexcept
+  { return __lhs = __lhs >> __shift; }
+
+template <class _Integer>
+  constexpr typename enable_if<is_integral_v<_Integer>, byte>::type
+  operator>> (byte  __lhs, _Integer __shift) noexcept
+  { return static_cast<byte>(static_cast<unsigned char>(static_cast<unsigned int>(__lhs) >> __shift)); }
+  
+template <class _Integer>
+  constexpr typename enable_if<is_integral_v<_Integer>, _Integer>::type
+  to_integer(byte __b) noexcept { return static_cast<_Integer>(__b); }
+
+}
+#endif
+
 #endif  // _LIBCPP_TYPE_TRAITS
diff --git a/lib/libcxx/include/typeindex b/lib/libcxx/include/typeindex
index d4d6ca96ba4..0565ca913e3 100644
--- a/lib/libcxx/include/typeindex
+++ b/lib/libcxx/include/typeindex
@@ -55,7 +55,7 @@ struct hash<type_index>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-class _LIBCPP_TYPE_VIS_ONLY type_index
+class _LIBCPP_TEMPLATE_VIS type_index
 {
     const type_info* __t_;
 public:
@@ -87,10 +87,10 @@ public:
     const char* name() const _NOEXCEPT {return __t_->name();}
 };
 
-template <class _Tp> struct _LIBCPP_TYPE_VIS_ONLY hash;
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS hash;
 
 template <>
-struct _LIBCPP_TYPE_VIS_ONLY hash<type_index>
+struct _LIBCPP_TEMPLATE_VIS hash<type_index>
     : public unary_function<type_index, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
diff --git a/lib/libcxx/include/typeinfo b/lib/libcxx/include/typeinfo
index 14ef77b31c3..7e8d3990ed9 100644
--- a/lib/libcxx/include/typeinfo
+++ b/lib/libcxx/include/typeinfo
@@ -61,11 +61,22 @@ public:
 #include <exception>
 #include <cstddef>
 #include <cstdint>
+#ifdef _LIBCPP_NO_EXCEPTIONS
+#include <cstdlib>
+#endif
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+#if !defined(_LIBCPP_ABI_MICROSOFT)
+#if defined(_LIBCPP_NONUNIQUE_RTTI_BIT)
+#define _LIBCPP_HAS_NONUNIQUE_TYPEINFO
+#else
+#define _LIBCPP_HAS_UNIQUE_TYPEINFO
+#endif
+#endif
+
 namespace std  // purposefully not using versioning namespace
 {
 
@@ -73,76 +84,119 @@ class _LIBCPP_EXCEPTION_ABI type_info
 {
     type_info& operator=(const type_info&);
     type_info(const type_info&);
+
+#if defined(_LIBCPP_HAS_NONUNIQUE_TYPEINFO)
+    _LIBCPP_INLINE_VISIBILITY
+    int __compare_nonunique_names(const type_info &__arg) const _NOEXCEPT
+    { return __builtin_strcmp(name(), __arg.name()); }
+#endif
+
+#if defined(_LIBCPP_ABI_MICROSOFT)
+    mutable struct {
+      const char *__undecorated_name;
+      const char __decorated_name[1];
+    } __data;
+
+    int __compare(const type_info &__rhs) const _NOEXCEPT;
+#endif // _LIBCPP_ABI_MICROSOFT
+
 protected:
-#ifndef _LIBCPP_NONUNIQUE_RTTI_BIT
-    const char* __type_name;
-#else
+#if !defined(_LIBCPP_ABI_MICROSOFT)
+#if defined(_LIBCPP_HAS_NONUNIQUE_TYPEINFO)
     // A const char* with the non-unique RTTI bit possibly set.
     uintptr_t __type_name;
-#endif
 
     _LIBCPP_INLINE_VISIBILITY
     explicit type_info(const char* __n)
-#ifndef _LIBCPP_NONUNIQUE_RTTI_BIT
-        : __type_name(__n) {}
+      : __type_name(reinterpret_cast<uintptr_t>(__n)) {}
 #else
-        : __type_name(reinterpret_cast<uintptr_t>(__n)) {}
+    const char *__type_name;
+
+    _LIBCPP_INLINE_VISIBILITY
+    explicit type_info(const char* __n) : __type_name(__n) {}
 #endif
+#endif // ! _LIBCPP_ABI_MICROSOFT
 
 public:
+    _LIBCPP_AVAILABILITY_TYPEINFO_VTABLE
     virtual ~type_info();
 
+#if defined(_LIBCPP_ABI_MICROSOFT)
+    const char *name() const _NOEXCEPT;
+
     _LIBCPP_INLINE_VISIBILITY
-    const char* name() const _NOEXCEPT
-#ifndef _LIBCPP_NONUNIQUE_RTTI_BIT
-        {return __type_name;}
+    bool before(const type_info& __arg) const _NOEXCEPT {
+      return __compare(__arg) < 0;
+    }
+
+    size_t hash_code() const _NOEXCEPT;
+
+    _LIBCPP_INLINE_VISIBILITY
+    bool operator==(const type_info& __arg) const _NOEXCEPT {
+      return __compare(__arg) == 0;
+    }
 #else
-        {return reinterpret_cast<const char*>(__type_name & ~_LIBCPP_NONUNIQUE_RTTI_BIT);}
-#endif
+#if defined(_LIBCPP_HAS_NONUNIQUE_TYPEINFO)
+    _LIBCPP_INLINE_VISIBILITY
+    const char* name() const _NOEXCEPT
+    {
+      return reinterpret_cast<const char*>(__type_name &
+                                           ~_LIBCPP_NONUNIQUE_RTTI_BIT);
+    }
 
     _LIBCPP_INLINE_VISIBILITY
     bool before(const type_info& __arg) const _NOEXCEPT
-#ifndef _LIBCPP_NONUNIQUE_RTTI_BIT
-        {return __type_name < __arg.__type_name;}
-#else
-        {if (!((__type_name & __arg.__type_name) & _LIBCPP_NONUNIQUE_RTTI_BIT))
-           return __type_name < __arg.__type_name;
-         return __compare_nonunique_names(__arg) < 0;}
-#endif
+    {
+      if (!((__type_name & __arg.__type_name) & _LIBCPP_NONUNIQUE_RTTI_BIT))
+        return __type_name < __arg.__type_name;
+      return __compare_nonunique_names(__arg) < 0;
+    }
 
     _LIBCPP_INLINE_VISIBILITY
     size_t hash_code() const _NOEXCEPT
-#ifndef _LIBCPP_NONUNIQUE_RTTI_BIT
-        {return *reinterpret_cast<const size_t*>(&__type_name);}
-#else
-        {if (!(__type_name & _LIBCPP_NONUNIQUE_RTTI_BIT)) return __type_name;
-         const char *__ptr = name();
-         size_t __hash = 5381;
-         while (unsigned char __c = static_cast<unsigned char>(*__ptr++))
-           __hash = (__hash * 33) ^ __c;
-         return __hash;}
-#endif
+    {
+      if (!(__type_name & _LIBCPP_NONUNIQUE_RTTI_BIT))
+        return __type_name;
+
+      const char* __ptr = name();
+      size_t __hash = 5381;
+      while (unsigned char __c = static_cast<unsigned char>(*__ptr++))
+        __hash = (__hash * 33) ^ __c;
+      return __hash;
+    }
 
     _LIBCPP_INLINE_VISIBILITY
     bool operator==(const type_info& __arg) const _NOEXCEPT
-#ifndef _LIBCPP_NONUNIQUE_RTTI_BIT
-        {return __type_name == __arg.__type_name;}
+    {
+      if (__type_name == __arg.__type_name)
+        return true;
+
+      if (!((__type_name & __arg.__type_name) & _LIBCPP_NONUNIQUE_RTTI_BIT))
+        return false;
+      return __compare_nonunique_names(__arg) == 0;
+    }
 #else
-        {if (__type_name == __arg.__type_name) return true;
-         if (!((__type_name & __arg.__type_name) & _LIBCPP_NONUNIQUE_RTTI_BIT))
-           return false;
-         return __compare_nonunique_names(__arg) == 0;}
-#endif
     _LIBCPP_INLINE_VISIBILITY
-    bool operator!=(const type_info& __arg) const _NOEXCEPT
-        {return !operator==(__arg);}
+    const char* name() const _NOEXCEPT
+    { return __type_name; }
 
-#ifdef _LIBCPP_NONUNIQUE_RTTI_BIT
-  private:
     _LIBCPP_INLINE_VISIBILITY
-    int __compare_nonunique_names(const type_info &__arg) const _NOEXCEPT
-        {return __builtin_strcmp(name(), __arg.name());}
+    bool before(const type_info& __arg) const _NOEXCEPT
+    { return __type_name < __arg.__type_name; }
+
+    _LIBCPP_INLINE_VISIBILITY
+    size_t hash_code() const _NOEXCEPT
+    { return reinterpret_cast<size_t>(__type_name); }
+
+    _LIBCPP_INLINE_VISIBILITY
+    bool operator==(const type_info& __arg) const _NOEXCEPT
+    { return __type_name == __arg.__type_name; }
 #endif
+#endif // _LIBCPP_ABI_MICROSOFT
+
+    _LIBCPP_INLINE_VISIBILITY
+    bool operator!=(const type_info& __arg) const _NOEXCEPT
+    { return !operator==(__arg); }
 };
 
 class _LIBCPP_EXCEPTION_ABI bad_cast
@@ -165,4 +219,16 @@ public:
 
 }  // std
 
+_LIBCPP_BEGIN_NAMESPACE_STD
+_LIBCPP_NORETURN inline _LIBCPP_ALWAYS_INLINE
+void __throw_bad_cast()
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw bad_cast();
+#else
+	_VSTD::abort();
+#endif
+}
+_LIBCPP_END_NAMESPACE_STD
+
 #endif  // __LIBCPP_TYPEINFO
diff --git a/lib/libcxx/include/unordered_map b/lib/libcxx/include/unordered_map
index 8d7edaf509c..725cb6af275 100644
--- a/lib/libcxx/include/unordered_map
+++ b/lib/libcxx/include/unordered_map
@@ -379,9 +379,7 @@ template <class Key, class T, class Hash, class Pred, class Alloc>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Key, class _Cp, class _Hash,
-          bool = is_empty<_Hash>::value && !__libcpp_is_final<_Hash>::value
-         >
+template <class _Key, class _Cp, class _Hash, bool _IsEmpty>
 class __unordered_map_hasher
     : private _Hash
 {
@@ -406,7 +404,7 @@ public:
         _NOEXCEPT_(__is_nothrow_swappable<_Hash>::value)
     {
         using _VSTD::swap;
-        swap(static_cast<const _Hash&>(*this), static_cast<const _Hash&>(__y));
+        swap(static_cast<_Hash&>(*this), static_cast<_Hash&>(__y));
     }
 };
 
@@ -449,9 +447,7 @@ swap(__unordered_map_hasher<_Key, _Cp, _Hash, __b>& __x,
     __x.swap(__y);
 }
 
-template <class _Key, class _Cp, class _Pred,
-          bool = is_empty<_Pred>::value && !__libcpp_is_final<_Pred>::value
-         >
+template <class _Key, class _Cp, class _Pred, bool _IsEmpty>
 class __unordered_map_equal
     : private _Pred
 {
@@ -479,7 +475,7 @@ public:
         _NOEXCEPT_(__is_nothrow_swappable<_Pred>::value)
     {
         using _VSTD::swap;
-        swap(static_cast<const _Pred&>(*this), static_cast<const _Pred&>(__y));
+        swap(static_cast<_Pred&>(*this), static_cast<_Pred&>(__y));
     }
 };
 
@@ -551,7 +547,7 @@ public:
           __second_constructed(false)
         {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     __hash_map_node_destructor(__hash_node_destructor<allocator_type>&& __x)
         _NOEXCEPT
@@ -561,7 +557,7 @@ public:
         {
             __x.__value_constructed = false;
         }
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#else  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     __hash_map_node_destructor(const __hash_node_destructor<allocator_type>& __x)
         : __na_(__x.__na_),
@@ -570,7 +566,7 @@ public:
         {
             const_cast<bool&>(__x.__value_constructed) = false;
         }
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     void operator()(pointer __p) _NOEXCEPT
@@ -641,7 +637,7 @@ private:
 #endif
 
 template <class _HashIterator>
-class _LIBCPP_TYPE_VIS_ONLY __hash_map_iterator
+class _LIBCPP_TEMPLATE_VIS __hash_map_iterator
 {
     _HashIterator __i_;
 
@@ -682,15 +678,15 @@ public:
         bool operator!=(const __hash_map_iterator& __x, const __hash_map_iterator& __y)
         {return __x.__i_ != __y.__i_;}
 
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY unordered_map;
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY unordered_multimap;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_const_iterator;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_const_local_iterator;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_map_const_iterator;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS unordered_map;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS unordered_multimap;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_const_iterator;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_const_local_iterator;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_map_const_iterator;
 };
 
 template <class _HashIterator>
-class _LIBCPP_TYPE_VIS_ONLY __hash_map_const_iterator
+class _LIBCPP_TEMPLATE_VIS __hash_map_const_iterator
 {
     _HashIterator __i_;
 
@@ -736,15 +732,15 @@ public:
         bool operator!=(const __hash_map_const_iterator& __x, const __hash_map_const_iterator& __y)
         {return __x.__i_ != __y.__i_;}
 
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY unordered_map;
-    template <class, class, class, class, class> friend class _LIBCPP_TYPE_VIS_ONLY unordered_multimap;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_const_iterator;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY __hash_const_local_iterator;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS unordered_map;
+    template <class, class, class, class, class> friend class _LIBCPP_TEMPLATE_VIS unordered_multimap;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_const_iterator;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS __hash_const_local_iterator;
 };
 
 template <class _Key, class _Tp, class _Hash = hash<_Key>, class _Pred = equal_to<_Key>,
           class _Alloc = allocator<pair<const _Key, _Tp> > >
-class _LIBCPP_TYPE_VIS_ONLY unordered_map
+class _LIBCPP_TEMPLATE_VIS unordered_map
 {
 public:
     // types
@@ -823,20 +819,18 @@ public:
     explicit unordered_map(const allocator_type& __a);
     unordered_map(const unordered_map& __u);
     unordered_map(const unordered_map& __u, const allocator_type& __a);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     unordered_map(unordered_map&& __u)
         _NOEXCEPT_(is_nothrow_move_constructible<__table>::value);
     unordered_map(unordered_map&& __u, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     unordered_map(initializer_list<value_type> __il);
     unordered_map(initializer_list<value_type> __il, size_type __n,
                   const hasher& __hf = hasher(), const key_equal& __eql = key_equal());
     unordered_map(initializer_list<value_type> __il, size_type __n,
                   const hasher& __hf, const key_equal& __eql,
                   const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 #if _LIBCPP_STD_VER > 11
     _LIBCPP_INLINE_VISIBILITY
     unordered_map(size_type __n, const allocator_type& __a)
@@ -879,21 +873,19 @@ public:
 #endif
         return *this;
     }
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     unordered_map& operator=(unordered_map&& __u)
         _NOEXCEPT_(is_nothrow_move_assignable<__table>::value);
-#endif
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     _LIBCPP_INLINE_VISIBILITY
     unordered_map& operator=(initializer_list<value_type> __il);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     allocator_type get_allocator() const _NOEXCEPT
         {return allocator_type(__table_.__node_alloc());}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool      empty() const _NOEXCEPT {return __table_.size() == 0;}
     _LIBCPP_INLINE_VISIBILITY
     size_type size() const _NOEXCEPT  {return __table_.size();}
@@ -922,6 +914,8 @@ public:
         _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__p) == this,
             "unordered_map::insert(const_iterator, const value_type&) called with an iterator not"
             " referring to this unordered_map");
+#else
+        ((void)__p);
 #endif
         return insert(__x).first;
     }
@@ -930,13 +924,11 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         void insert(_InputIterator __first, _InputIterator __last);
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void insert(initializer_list<value_type> __il)
         {insert(__il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
-#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     pair<iterator, bool> insert(value_type&& __x)
         {return __table_.__insert_unique(_VSTD::move(__x));}
@@ -946,6 +938,8 @@ public:
         _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__p) == this,
             "unordered_map::insert(const_iterator, const value_type&) called with an iterator not"
             " referring to this unordered_map");
+#else
+        ((void)__p);
 #endif
         return __table_.__insert_unique(_VSTD::move(__x)).first;
     }
@@ -965,6 +959,8 @@ public:
             _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__p) == this,
                 "unordered_map::insert(const_iterator, value_type&&) called with an iterator not"
                 " referring to this unordered_map");
+#else
+          ((void)__p);
 #endif
             return insert(_VSTD::forward<_Pp>(__x)).first;
         }
@@ -982,6 +978,8 @@ public:
         _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__p) == this,
             "unordered_map::emplace_hint(const_iterator, args...) called with an iterator not"
             " referring to this unordered_map");
+#else
+          ((void)__p);
 #endif
         return __table_.__emplace_unique(_VSTD::forward<_Args>(__args)...).first;
     }
@@ -1012,11 +1010,13 @@ public:
         iterator try_emplace(const_iterator __h, const key_type& __k, _Args&&... __args)
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
-        _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__p) == this,
+        _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__h) == this,
             "unordered_map::try_emplace(const_iterator, key, args...) called with an iterator not"
             " referring to this unordered_map");
+#else
+        ((void)__h);
 #endif
-            return try_emplace(__k, _VSTD::forward<_Args>(__args)...).first;
+        return try_emplace(__k, _VSTD::forward<_Args>(__args)...).first;
     }
 
     template <class... _Args>
@@ -1024,9 +1024,11 @@ public:
         iterator try_emplace(const_iterator __h, key_type&& __k, _Args&&... __args)
     {
 #if _LIBCPP_DEBUG_LEVEL >= 2
-        _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__p) == this,
+        _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__h) == this,
             "unordered_map::try_emplace(const_iterator, key, args...) called with an iterator not"
             " referring to this unordered_map");
+#else
+        ((void)__h);
 #endif
         return try_emplace(_VSTD::move(__k), _VSTD::forward<_Args>(__args)...).first;
     }
@@ -1057,18 +1059,20 @@ public:
 
     template <class _Vp>
         _LIBCPP_INLINE_VISIBILITY
-        iterator insert_or_assign(const_iterator __h, const key_type& __k, _Vp&& __v)
+        iterator insert_or_assign(const_iterator, const key_type& __k, _Vp&& __v)
      {
+          // FIXME: Add debug mode checking for the iterator input
           return insert_or_assign(__k, _VSTD::forward<_Vp>(__v)).first;
      }
 
     template <class _Vp>
         _LIBCPP_INLINE_VISIBILITY
-        iterator insert_or_assign(const_iterator __h, key_type&& __k, _Vp&& __v)
+        iterator insert_or_assign(const_iterator, key_type&& __k, _Vp&& __v)
      {
+        // FIXME: Add debug mode checking for the iterator input
         return insert_or_assign(_VSTD::move(__k), _VSTD::forward<_Vp>(__v)).first;
      }
-#endif
+#endif // _LIBCPP_STD_VER > 14
 
     _LIBCPP_INLINE_VISIBILITY
     iterator erase(const_iterator __p) {return __table_.erase(__p.__i_);}
@@ -1085,7 +1089,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     void swap(unordered_map& __u)
         _NOEXCEPT_(__is_nothrow_swappable<__table>::value)
-        {__table_.swap(__u.__table_);}
+        { __table_.swap(__u.__table_);}
 
     _LIBCPP_INLINE_VISIBILITY
     hasher hash_function() const
@@ -1267,7 +1271,7 @@ unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_map(
     insert(__u.begin(), __u.end());
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 inline
@@ -1304,10 +1308,6 @@ unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_map(
 #endif
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_map(
         initializer_list<value_type> __il)
@@ -1344,10 +1344,6 @@ unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_map(
     insert(__il.begin(), __il.end());
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 inline
 unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>&
@@ -1358,10 +1354,6 @@ unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator=(unordered_map&& __u)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 inline
 unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>&
@@ -1372,22 +1364,7 @@ unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator=(
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
-#ifdef _LIBCPP_CXX03_LANG
-template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
-typename unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::__node_holder
-unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::__construct_node_with_key(const key_type& __k)
-{
-    __node_allocator& __na = __table_.__node_alloc();
-    __node_holder __h(__node_traits::allocate(__na, 1), _Dp(__na));
-    __node_traits::construct(__na, _VSTD::addressof(__h->__value_.__cc.first), __k);
-    __h.get_deleter().__first_constructed = true;
-    __node_traits::construct(__na, _VSTD::addressof(__h->__value_.__cc.second));
-    __h.get_deleter().__second_constructed = true;
-    return _LIBCPP_EXPLICIT_MOVE(__h);  // explicitly moved for C++03
-}
-#endif
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 template <class _InputIterator>
@@ -1400,20 +1377,7 @@ unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::insert(_InputIterator __first,
         __table_.__insert_unique(*__first);
 }
 
-#ifdef _LIBCPP_CXX03_LANG
-template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
-_Tp&
-unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator[](const key_type& __k)
-{
-    iterator __i = find(__k);
-    if (__i != end())
-        return __i->second;
-    __node_holder __h = __construct_node_with_key(__k);
-    pair<iterator, bool> __r = __table_.__node_insert_unique(__h.get());
-    __h.release();
-    return __r.first->second;
-}
-#else
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 _Tp&
@@ -1432,8 +1396,35 @@ unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator[](key_type&& __k)
         std::piecewise_construct, std::forward_as_tuple(std::move(__k)),
                                   std::forward_as_tuple()).first->__cc.second;
 }
+#else // _LIBCPP_CXX03_LANG
+
+template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
+typename unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::__node_holder
+unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::__construct_node_with_key(const key_type& __k)
+{
+    __node_allocator& __na = __table_.__node_alloc();
+    __node_holder __h(__node_traits::allocate(__na, 1), _Dp(__na));
+    __node_traits::construct(__na, _VSTD::addressof(__h->__value_.__cc.first), __k);
+    __h.get_deleter().__first_constructed = true;
+    __node_traits::construct(__na, _VSTD::addressof(__h->__value_.__cc.second));
+    __h.get_deleter().__second_constructed = true;
+    return _LIBCPP_EXPLICIT_MOVE(__h);  // explicitly moved for C++03
+}
+
+template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
+_Tp&
+unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>::operator[](const key_type& __k)
+{
+    iterator __i = find(__k);
+    if (__i != end())
+        return __i->second;
+    __node_holder __h = __construct_node_with_key(__k);
+    pair<iterator, bool> __r = __table_.__node_insert_unique(__h.get());
+    __h.release();
+    return __r.first->second;
+}
 
-#endif  // !_LIBCPP_CXX03_MODE
+#endif  // _LIBCPP_CXX03_MODE
 
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 _Tp&
@@ -1499,7 +1490,7 @@ operator!=(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
 
 template <class _Key, class _Tp, class _Hash = hash<_Key>, class _Pred = equal_to<_Key>,
           class _Alloc = allocator<pair<const _Key, _Tp> > >
-class _LIBCPP_TYPE_VIS_ONLY unordered_multimap
+class _LIBCPP_TEMPLATE_VIS unordered_multimap
 {
 public:
     // types
@@ -1576,13 +1567,11 @@ public:
     explicit unordered_multimap(const allocator_type& __a);
     unordered_multimap(const unordered_multimap& __u);
     unordered_multimap(const unordered_multimap& __u, const allocator_type& __a);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     unordered_multimap(unordered_multimap&& __u)
         _NOEXCEPT_(is_nothrow_move_constructible<__table>::value);
     unordered_multimap(unordered_multimap&& __u, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     unordered_multimap(initializer_list<value_type> __il);
     unordered_multimap(initializer_list<value_type> __il, size_type __n,
                        const hasher& __hf = hasher(),
@@ -1590,7 +1579,7 @@ public:
     unordered_multimap(initializer_list<value_type> __il, size_type __n,
                        const hasher& __hf, const key_equal& __eql,
                        const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 #if _LIBCPP_STD_VER > 11
     _LIBCPP_INLINE_VISIBILITY
     unordered_multimap(size_type __n, const allocator_type& __a)
@@ -1633,21 +1622,19 @@ public:
 #endif
         return *this;
     }
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     unordered_multimap& operator=(unordered_multimap&& __u)
         _NOEXCEPT_(is_nothrow_move_assignable<__table>::value);
-#endif
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     _LIBCPP_INLINE_VISIBILITY
     unordered_multimap& operator=(initializer_list<value_type> __il);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     allocator_type get_allocator() const _NOEXCEPT
         {return allocator_type(__table_.__node_alloc());}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool      empty() const _NOEXCEPT {return __table_.size() == 0;}
     _LIBCPP_INLINE_VISIBILITY
     size_type size() const _NOEXCEPT  {return __table_.size();}
@@ -1678,13 +1665,10 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     void insert(_InputIterator __first, _InputIterator __last);
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void insert(initializer_list<value_type> __il)
         {insert(__il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
-#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     iterator insert(value_type&& __x) {return __table_.__insert_multi(_VSTD::move(__x));}
 
@@ -1902,7 +1886,7 @@ unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_multimap(
     insert(__u.begin(), __u.end());
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 inline
@@ -1941,10 +1925,6 @@ unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_multimap(
 #endif
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_multimap(
         initializer_list<value_type> __il)
@@ -1981,10 +1961,6 @@ unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>::unordered_multimap(
     insert(__il.begin(), __il.end());
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 inline
 unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>&
@@ -1995,10 +1971,6 @@ unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>::operator=(unordered_multima
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 inline
 unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>&
@@ -2009,7 +1981,7 @@ unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>::operator=(
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 
 
diff --git a/lib/libcxx/include/unordered_set b/lib/libcxx/include/unordered_set
index fb38b648a86..3ae024a45ee 100644
--- a/lib/libcxx/include/unordered_set
+++ b/lib/libcxx/include/unordered_set
@@ -333,7 +333,7 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <class _Value, class _Hash = hash<_Value>, class _Pred = equal_to<_Value>,
           class _Alloc = allocator<_Value> >
-class _LIBCPP_TYPE_VIS_ONLY unordered_set
+class _LIBCPP_TEMPLATE_VIS unordered_set
 {
 public:
     // types
@@ -408,13 +408,11 @@ public:
     explicit unordered_set(const allocator_type& __a);
     unordered_set(const unordered_set& __u);
     unordered_set(const unordered_set& __u, const allocator_type& __a);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     unordered_set(unordered_set&& __u)
         _NOEXCEPT_(is_nothrow_move_constructible<__table>::value);
     unordered_set(unordered_set&& __u, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     unordered_set(initializer_list<value_type> __il);
     unordered_set(initializer_list<value_type> __il, size_type __n,
                   const hasher& __hf = hasher(),
@@ -432,7 +430,7 @@ public:
                                   const hasher& __hf, const allocator_type& __a)
         : unordered_set(__il, __n, __hf, key_equal(), __a) {}
 #endif
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
     // ~unordered_set() = default;
     _LIBCPP_INLINE_VISIBILITY
     unordered_set& operator=(const unordered_set& __u)
@@ -440,21 +438,19 @@ public:
         __table_ = __u.__table_;
         return *this;
     }
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     unordered_set& operator=(unordered_set&& __u)
         _NOEXCEPT_(is_nothrow_move_assignable<__table>::value);
-#endif
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     _LIBCPP_INLINE_VISIBILITY
     unordered_set& operator=(initializer_list<value_type> __il);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     allocator_type get_allocator() const _NOEXCEPT
         {return allocator_type(__table_.__node_alloc());}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool      empty() const _NOEXCEPT {return __table_.size() == 0;}
     _LIBCPP_INLINE_VISIBILITY
     size_type size() const _NOEXCEPT  {return __table_.size();}
@@ -474,7 +470,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     const_iterator cend()   const _NOEXCEPT {return __table_.end();}
 
-#if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
+#ifndef _LIBCPP_CXX03_LANG
     template <class... _Args>
         _LIBCPP_INLINE_VISIBILITY
         pair<iterator, bool> emplace(_Args&&... __args)
@@ -493,51 +489,47 @@ public:
         iterator emplace_hint(const_iterator, _Args&&... __args)
             {return __table_.__emplace_unique(_VSTD::forward<_Args>(__args)...).first;}
 #endif
-#endif  // !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
-    _LIBCPP_INLINE_VISIBILITY
-    pair<iterator, bool> insert(const value_type& __x)
-        {return __table_.__insert_unique(__x);}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
     _LIBCPP_INLINE_VISIBILITY
     pair<iterator, bool> insert(value_type&& __x)
         {return __table_.__insert_unique(_VSTD::move(__x));}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
 #if _LIBCPP_DEBUG_LEVEL >= 2
-    iterator insert(const_iterator __p, const value_type& __x)
+    iterator insert(const_iterator __p, value_type&& __x)
         {
             _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__p) == this,
-                "unordered_set::insert(const_iterator, const value_type&) called with an iterator not"
+                "unordered_set::insert(const_iterator, value_type&&) called with an iterator not"
                 " referring to this unordered_set");
-            return insert(__x).first;
+            return insert(_VSTD::move(__x)).first;
         }
 #else
-    iterator insert(const_iterator, const value_type& __x)
-        {return insert(__x).first;}
+    iterator insert(const_iterator, value_type&& __x)
+        {return insert(_VSTD::move(__x)).first;}
 #endif
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+    _LIBCPP_INLINE_VISIBILITY
+    void insert(initializer_list<value_type> __il)
+        {insert(__il.begin(), __il.end());}
+#endif  // _LIBCPP_CXX03_LANG
+    _LIBCPP_INLINE_VISIBILITY
+    pair<iterator, bool> insert(const value_type& __x)
+        {return __table_.__insert_unique(__x);}
+
     _LIBCPP_INLINE_VISIBILITY
 #if _LIBCPP_DEBUG_LEVEL >= 2
-    iterator insert(const_iterator __p, value_type&& __x)
+    iterator insert(const_iterator __p, const value_type& __x)
         {
             _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__p) == this,
-                "unordered_set::insert(const_iterator, value_type&&) called with an iterator not"
+                "unordered_set::insert(const_iterator, const value_type&) called with an iterator not"
                 " referring to this unordered_set");
-            return insert(_VSTD::move(__x)).first;
+            return insert(__x).first;
         }
 #else
-    iterator insert(const_iterator, value_type&& __x)
-        {return insert(_VSTD::move(__x)).first;}
+    iterator insert(const_iterator, const value_type& __x)
+        {return insert(__x).first;}
 #endif
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     template <class _InputIterator>
         _LIBCPP_INLINE_VISIBILITY
         void insert(_InputIterator __first, _InputIterator __last);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-    _LIBCPP_INLINE_VISIBILITY
-    void insert(initializer_list<value_type> __il)
-        {insert(__il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
     _LIBCPP_INLINE_VISIBILITY
     iterator erase(const_iterator __p) {return __table_.erase(__p);}
@@ -717,7 +709,7 @@ unordered_set<_Value, _Hash, _Pred, _Alloc>::unordered_set(
     insert(__u.begin(), __u.end());
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Value, class _Hash, class _Pred, class _Alloc>
 inline
@@ -752,10 +744,6 @@ unordered_set<_Value, _Hash, _Pred, _Alloc>::unordered_set(
 #endif
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Value, class _Hash, class _Pred, class _Alloc>
 unordered_set<_Value, _Hash, _Pred, _Alloc>::unordered_set(
         initializer_list<value_type> __il)
@@ -792,10 +780,6 @@ unordered_set<_Value, _Hash, _Pred, _Alloc>::unordered_set(
     insert(__il.begin(), __il.end());
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
 template <class _Value, class _Hash, class _Pred, class _Alloc>
 inline
 unordered_set<_Value, _Hash, _Pred, _Alloc>&
@@ -806,10 +790,6 @@ unordered_set<_Value, _Hash, _Pred, _Alloc>::operator=(unordered_set&& __u)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Value, class _Hash, class _Pred, class _Alloc>
 inline
 unordered_set<_Value, _Hash, _Pred, _Alloc>&
@@ -820,7 +800,7 @@ unordered_set<_Value, _Hash, _Pred, _Alloc>::operator=(
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Value, class _Hash, class _Pred, class _Alloc>
 template <class _InputIterator>
@@ -873,7 +853,7 @@ operator!=(const unordered_set<_Value, _Hash, _Pred, _Alloc>& __x,
 
 template <class _Value, class _Hash = hash<_Value>, class _Pred = equal_to<_Value>,
           class _Alloc = allocator<_Value> >
-class _LIBCPP_TYPE_VIS_ONLY unordered_multiset
+class _LIBCPP_TEMPLATE_VIS unordered_multiset
 {
 public:
     // types
@@ -949,13 +929,11 @@ public:
     explicit unordered_multiset(const allocator_type& __a);
     unordered_multiset(const unordered_multiset& __u);
     unordered_multiset(const unordered_multiset& __u, const allocator_type& __a);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     unordered_multiset(unordered_multiset&& __u)
         _NOEXCEPT_(is_nothrow_move_constructible<__table>::value);
     unordered_multiset(unordered_multiset&& __u, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     unordered_multiset(initializer_list<value_type> __il);
     unordered_multiset(initializer_list<value_type> __il, size_type __n,
                        const hasher& __hf = hasher(),
@@ -971,7 +949,7 @@ public:
     unordered_multiset(initializer_list<value_type> __il, size_type __n, const hasher& __hf, const allocator_type& __a)
       : unordered_multiset(__il, __n, __hf, key_equal(), __a) {}
 #endif
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
     // ~unordered_multiset() = default;
     _LIBCPP_INLINE_VISIBILITY
     unordered_multiset& operator=(const unordered_multiset& __u)
@@ -979,20 +957,18 @@ public:
         __table_ = __u.__table_;
         return *this;
     }
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     unordered_multiset& operator=(unordered_multiset&& __u)
         _NOEXCEPT_(is_nothrow_move_assignable<__table>::value);
-#endif
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     unordered_multiset& operator=(initializer_list<value_type> __il);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     allocator_type get_allocator() const _NOEXCEPT
         {return allocator_type(__table_.__node_alloc());}
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool      empty() const _NOEXCEPT {return __table_.size() == 0;}
     _LIBCPP_INLINE_VISIBILITY
     size_type size() const _NOEXCEPT  {return __table_.size();}
@@ -1012,7 +988,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     const_iterator cend()   const _NOEXCEPT {return __table_.end();}
 
-#if !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
+#ifndef _LIBCPP_CXX03_LANG
     template <class... _Args>
         _LIBCPP_INLINE_VISIBILITY
         iterator emplace(_Args&&... __args)
@@ -1021,29 +997,27 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         iterator emplace_hint(const_iterator __p, _Args&&... __args)
             {return __table_.__emplace_hint_multi(__p, _VSTD::forward<_Args>(__args)...);}
-#endif  // !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES) && !defined(_LIBCPP_HAS_NO_VARIADICS)
-    _LIBCPP_INLINE_VISIBILITY
-    iterator insert(const value_type& __x) {return __table_.__insert_multi(__x);}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
     _LIBCPP_INLINE_VISIBILITY
     iterator insert(value_type&& __x) {return __table_.__insert_multi(_VSTD::move(__x));}
-#endif
-    _LIBCPP_INLINE_VISIBILITY
-    iterator insert(const_iterator __p, const value_type& __x)
-        {return __table_.__insert_multi(__p, __x);}
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     iterator insert(const_iterator __p, value_type&& __x)
         {return __table_.__insert_multi(__p, _VSTD::move(__x));}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-    template <class _InputIterator>
-        _LIBCPP_INLINE_VISIBILITY
-        void insert(_InputIterator __first, _InputIterator __last);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     _LIBCPP_INLINE_VISIBILITY
     void insert(initializer_list<value_type> __il)
         {insert(__il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
+
+    _LIBCPP_INLINE_VISIBILITY
+    iterator insert(const value_type& __x) {return __table_.__insert_multi(__x);}
+
+    _LIBCPP_INLINE_VISIBILITY
+    iterator insert(const_iterator __p, const value_type& __x)
+        {return __table_.__insert_multi(__p, __x);}
+
+    template <class _InputIterator>
+        _LIBCPP_INLINE_VISIBILITY
+        void insert(_InputIterator __first, _InputIterator __last);
 
     _LIBCPP_INLINE_VISIBILITY
     iterator erase(const_iterator __p) {return __table_.erase(__p);}
@@ -1224,7 +1198,7 @@ unordered_multiset<_Value, _Hash, _Pred, _Alloc>::unordered_multiset(
     insert(__u.begin(), __u.end());
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Value, class _Hash, class _Pred, class _Alloc>
 inline
@@ -1259,10 +1233,6 @@ unordered_multiset<_Value, _Hash, _Pred, _Alloc>::unordered_multiset(
 #endif
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Value, class _Hash, class _Pred, class _Alloc>
 unordered_multiset<_Value, _Hash, _Pred, _Alloc>::unordered_multiset(
         initializer_list<value_type> __il)
@@ -1299,10 +1269,6 @@ unordered_multiset<_Value, _Hash, _Pred, _Alloc>::unordered_multiset(
     insert(__il.begin(), __il.end());
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
 template <class _Value, class _Hash, class _Pred, class _Alloc>
 inline
 unordered_multiset<_Value, _Hash, _Pred, _Alloc>&
@@ -1314,10 +1280,6 @@ unordered_multiset<_Value, _Hash, _Pred, _Alloc>::operator=(
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Value, class _Hash, class _Pred, class _Alloc>
 inline
 unordered_multiset<_Value, _Hash, _Pred, _Alloc>&
@@ -1328,7 +1290,7 @@ unordered_multiset<_Value, _Hash, _Pred, _Alloc>::operator=(
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Value, class _Hash, class _Pred, class _Alloc>
 template <class _InputIterator>
diff --git a/lib/libcxx/include/utility b/lib/libcxx/include/utility
index 7b978ad3096..6fa2e15d144 100644
--- a/lib/libcxx/include/utility
+++ b/lib/libcxx/include/utility
@@ -99,7 +99,7 @@ void
 swap(pair<T1, T2>& x, pair<T1, T2>& y) noexcept(noexcept(x.swap(y)));
 
 struct piecewise_construct_t { };
-constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
+inline constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
 
 template <class T> class tuple_size;
 template <size_t I, class T> class tuple_element;
@@ -171,6 +171,25 @@ template<class... T>
 
 template<class T, class U=T>
     T exchange(T& obj, U&& new_value);
+
+// 20.2.7, in-place construction // C++17
+struct in_place_t {
+  explicit in_place_t() = default;
+};
+inline constexpr in_place_t in_place{};
+template <class T>
+  struct in_place_type_t {
+    explicit in_place_type_t() = default;
+  };
+template <class T>
+  inline constexpr in_place_type_t<T> in_place_type{};
+template <size_t I>
+  struct in_place_index_t {
+    explicit in_place_index_t() = default;
+  };
+template <size_t I>
+  inline constexpr in_place_index_t<I> in_place_index{};
+
 }  // std
 
 */
@@ -179,6 +198,10 @@ template<class T, class U=T>
 #include <__tuple>
 #include <type_traits>
 #include <initializer_list>
+#include <cstddef>
+#include <cstring>
+#include <cstdint>
+#include <__debug>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
@@ -249,14 +272,14 @@ swap(_Tp (&__a)[_Np], _Tp (&__b)[_Np]) _NOEXCEPT_(__is_nothrow_swappable<_Tp>::v
 
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 typename conditional
 <
     !is_nothrow_move_constructible<_Tp>::value && is_copy_constructible<_Tp>::value,
     const _Tp&,
     _Tp&&
 >::type
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#else  // _LIBCPP_CXX03_LANG
 const _Tp&
 #endif
 move_if_noexcept(_Tp& __x) _NOEXCEPT
@@ -269,15 +292,27 @@ template <class _Tp> constexpr add_const_t<_Tp>& as_const(_Tp& __t) noexcept { r
 template <class _Tp>                        void as_const(const _Tp&&) = delete;
 #endif
 
-struct _LIBCPP_TYPE_VIS_ONLY piecewise_construct_t { };
-#if defined(_LIBCPP_HAS_NO_CONSTEXPR) || defined(_LIBCPP_BUILDING_UTILITY)
+struct _LIBCPP_TEMPLATE_VIS piecewise_construct_t { };
+#if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_UTILITY)
 extern const piecewise_construct_t piecewise_construct;// = piecewise_construct_t();
 #else
-constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
+/* _LIBCPP_INLINE_VAR */ constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
+#endif
+
+#if defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
+struct __non_trivially_copyable_base {
+  _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
+  __non_trivially_copyable_base() _NOEXCEPT {}
+  _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
+  __non_trivially_copyable_base(__non_trivially_copyable_base const&) _NOEXCEPT {}
+};
 #endif
 
 template <class _T1, class _T2>
-struct _LIBCPP_TYPE_VIS_ONLY pair
+struct _LIBCPP_TEMPLATE_VIS pair
+#if defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
+: private __non_trivially_copyable_base
+#endif
 {
     typedef _T1 first_type;
     typedef _T2 second_type;
@@ -285,56 +320,179 @@ struct _LIBCPP_TYPE_VIS_ONLY pair
     _T1 first;
     _T2 second;
 
-#ifndef _LIBCPP_HAS_NO_DEFAULT_FUNCTION_TEMPLATE_ARGS
-    template <bool _Dummy = true, class = typename enable_if<
-        __dependent_type<is_default_constructible<_T1>, _Dummy>::value &&
-        __dependent_type<is_default_constructible<_T2>, _Dummy>::value
-      >::type>
+#if !defined(_LIBCPP_CXX03_LANG)
+    pair(pair const&) = default;
+    pair(pair&&) = default;
+#else
+  // Use the implicitly declared copy constructor in C++03
 #endif
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR pair() : first(), second() {}
 
-    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-    pair(const _T1& __x, const _T2& __y)
-        : first(__x), second(__y) {}
-
-    template<class _U1, class _U2>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        pair(const pair<_U1, _U2>& __p
-#ifndef _LIBCPP_HAS_NO_ADVANCED_SFINAE
-                 ,typename enable_if<is_convertible<const _U1&, _T1>::value &&
-                                    is_convertible<const _U2&, _T2>::value>::type* = 0
-#endif
-                                      )
-            : first(__p.first), second(__p.second) {}
+#ifdef _LIBCPP_CXX03_LANG
+    _LIBCPP_INLINE_VISIBILITY
+    pair() : first(), second() {}
 
-#if defined(_LIBCPP_DEPRECATED_ABI_DISABLE_PAIR_TRIVIAL_COPY_CTOR)
     _LIBCPP_INLINE_VISIBILITY
-    pair(const pair& __p)
-        _NOEXCEPT_(is_nothrow_copy_constructible<first_type>::value &&
-                   is_nothrow_copy_constructible<second_type>::value)
-        : first(__p.first),
-          second(__p.second)
-    {
-    }
+    pair(_T1 const& __t1, _T2 const& __t2) : first(__t1), second(__t2) {}
 
-# ifndef _LIBCPP_CXX03_LANG
+    template <class _U1, class _U2>
     _LIBCPP_INLINE_VISIBILITY
-    pair(pair&& __p) _NOEXCEPT_(is_nothrow_move_constructible<first_type>::value &&
-                                is_nothrow_move_constructible<second_type>::value)
-        : first(_VSTD::forward<first_type>(__p.first)),
-          second(_VSTD::forward<second_type>(__p.second))
-    {
+    pair(const pair<_U1, _U2>& __p) : first(__p.first), second(__p.second) {}
+
+    _LIBCPP_INLINE_VISIBILITY
+    pair& operator=(pair const& __p) {
+        first = __p.first;
+        second = __p.second;
+        return *this;
     }
-# endif
-#elif !defined(_LIBCPP_CXX03_LANG)
-    pair(pair const&) = default;
-    pair(pair&&) = default;
 #else
-  // Use the implicitly declared copy constructor in C++03
-#endif
+    template <bool _Val>
+    using _EnableB = typename enable_if<_Val, bool>::type;
+
+    struct _CheckArgs {
+      template <class _U1, class _U2>
+      static constexpr bool __enable_default() {
+          return is_default_constructible<_U1>::value
+              && is_default_constructible<_U2>::value;
+      }
+
+      template <class _U1, class _U2>
+      static constexpr bool __enable_explicit() {
+          return is_constructible<first_type, _U1>::value
+              && is_constructible<second_type, _U2>::value
+              && (!is_convertible<_U1, first_type>::value
+                  || !is_convertible<_U2, second_type>::value);
+      }
+
+      template <class _U1, class _U2>
+      static constexpr bool __enable_implicit() {
+          return is_constructible<first_type, _U1>::value
+              && is_constructible<second_type, _U2>::value
+              && is_convertible<_U1, first_type>::value
+              && is_convertible<_U2, second_type>::value;
+      }
+    };
+
+    template <bool _MaybeEnable>
+    using _CheckArgsDep = typename conditional<
+      _MaybeEnable, _CheckArgs, __check_tuple_constructor_fail>::type;
+
+    struct _CheckTupleLikeConstructor {
+        template <class _Tuple>
+        static constexpr bool __enable_implicit() {
+            return __tuple_convertible<_Tuple, pair>::value;
+        }
+
+        template <class _Tuple>
+        static constexpr bool __enable_explicit() {
+            return __tuple_constructible<_Tuple, pair>::value
+               && !__tuple_convertible<_Tuple, pair>::value;
+        }
+
+        template <class _Tuple>
+        static constexpr bool __enable_assign() {
+            return __tuple_assignable<_Tuple, pair>::value;
+        }
+    };
+
+    template <class _Tuple>
+    using _CheckTLC = typename conditional<
+        __tuple_like_with_size<_Tuple, 2>::value
+            && !is_same<typename decay<_Tuple>::type, pair>::value,
+        _CheckTupleLikeConstructor,
+        __check_tuple_constructor_fail
+    >::type;
+
+    template<bool _Dummy = true, _EnableB<
+            _CheckArgsDep<_Dummy>::template __enable_default<_T1, _T2>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    pair() : first(), second() {}
+
+    template <bool _Dummy = true, _EnableB<
+             _CheckArgsDep<_Dummy>::template __enable_explicit<_T1 const&, _T2 const&>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    explicit pair(_T1 const& __t1, _T2 const& __t2)
+        : first(__t1), second(__t2) {}
+
+    template<bool _Dummy = true, _EnableB<
+            _CheckArgsDep<_Dummy>::template __enable_implicit<_T1 const&, _T2 const&>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    pair(_T1 const& __t1, _T2 const& __t2)
+        : first(__t1), second(__t2) {}
+
+    template<class _U1, class _U2, _EnableB<
+             _CheckArgs::template __enable_explicit<_U1, _U2>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    explicit pair(_U1&& __u1, _U2&& __u2)
+        : first(_VSTD::forward<_U1>(__u1)), second(_VSTD::forward<_U2>(__u2)) {}
+
+    template<class _U1, class _U2, _EnableB<
+            _CheckArgs::template __enable_implicit<_U1, _U2>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    pair(_U1&& __u1, _U2&& __u2)
+        : first(_VSTD::forward<_U1>(__u1)), second(_VSTD::forward<_U2>(__u2)) {}
+
+    template<class _U1, class _U2, _EnableB<
+            _CheckArgs::template __enable_explicit<_U1 const&, _U2 const&>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    explicit pair(pair<_U1, _U2> const& __p)
+        : first(__p.first), second(__p.second) {}
+
+    template<class _U1, class _U2, _EnableB<
+            _CheckArgs::template __enable_implicit<_U1 const&, _U2 const&>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    pair(pair<_U1, _U2> const& __p)
+        : first(__p.first), second(__p.second) {}
+
+    template<class _U1, class _U2, _EnableB<
+            _CheckArgs::template __enable_explicit<_U1, _U2>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    explicit pair(pair<_U1, _U2>&&__p)
+        : first(_VSTD::forward<_U1>(__p.first)), second(_VSTD::forward<_U2>(__p.second)) {}
+
+    template<class _U1, class _U2, _EnableB<
+            _CheckArgs::template __enable_implicit<_U1, _U2>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    pair(pair<_U1, _U2>&& __p)
+        : first(_VSTD::forward<_U1>(__p.first)), second(_VSTD::forward<_U2>(__p.second)) {}
+
+    template<class _Tuple, _EnableB<
+            _CheckTLC<_Tuple>::template __enable_explicit<_Tuple>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    explicit pair(_Tuple&& __p)
+        : first(_VSTD::get<0>(_VSTD::forward<_Tuple>(__p))),
+          second(_VSTD::get<1>(_VSTD::forward<_Tuple>(__p))) {}
+
+    template<class _Tuple, _EnableB<
+            _CheckTLC<_Tuple>::template __enable_implicit<_Tuple>()
+    > = false>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    pair(_Tuple&& __p)
+        : first(_VSTD::get<0>(_VSTD::forward<_Tuple>(__p))),
+          second(_VSTD::get<1>(_VSTD::forward<_Tuple>(__p))) {}
+
+    template <class... _Args1, class... _Args2>
+    _LIBCPP_INLINE_VISIBILITY
+    pair(piecewise_construct_t __pc,
+         tuple<_Args1...> __first_args, tuple<_Args2...> __second_args)
+        : pair(__pc, __first_args, __second_args,
+                typename __make_tuple_indices<sizeof...(_Args1)>::type(),
+                typename __make_tuple_indices<sizeof...(_Args2) >::type()) {}
 
     _LIBCPP_INLINE_VISIBILITY
-    pair& operator=(const pair& __p)
+    pair& operator=(typename conditional<
+                        is_copy_assignable<first_type>::value &&
+                        is_copy_assignable<second_type>::value,
+                    pair, __nat>::type const& __p)
         _NOEXCEPT_(is_nothrow_copy_assignable<first_type>::value &&
                    is_nothrow_copy_assignable<second_type>::value)
     {
@@ -343,75 +501,30 @@ struct _LIBCPP_TYPE_VIS_ONLY pair
         return *this;
     }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-    template <class _U1, class _U2,
-              class = typename enable_if<is_convertible<_U1, first_type>::value &&
-                                         is_convertible<_U2, second_type>::value>::type>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        pair(_U1&& __u1, _U2&& __u2)
-            : first(_VSTD::forward<_U1>(__u1)),
-              second(_VSTD::forward<_U2>(__u2))
-            {}
-
-    template<class _U1, class _U2>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        pair(pair<_U1, _U2>&& __p,
-                 typename enable_if<is_convertible<_U1, _T1>::value &&
-                                    is_convertible<_U2, _T2>::value>::type* = 0)
-            : first(_VSTD::forward<_U1>(__p.first)),
-              second(_VSTD::forward<_U2>(__p.second)) {}
-
-    _LIBCPP_INLINE_VISIBILITY
-    pair&
-    operator=(pair&& __p) _NOEXCEPT_(is_nothrow_move_assignable<first_type>::value &&
-                                     is_nothrow_move_assignable<second_type>::value)
+    _LIBCPP_INLINE_VISIBILITY
+    pair& operator=(typename conditional<
+                        is_move_assignable<first_type>::value &&
+                        is_move_assignable<second_type>::value,
+                    pair, __nat>::type&& __p)
+        _NOEXCEPT_(is_nothrow_move_assignable<first_type>::value &&
+                   is_nothrow_move_assignable<second_type>::value)
     {
         first = _VSTD::forward<first_type>(__p.first);
         second = _VSTD::forward<second_type>(__p.second);
         return *this;
     }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
-    template<class _Tuple,
-             class = typename enable_if<__tuple_convertible<_Tuple, pair>::value>::type>
-        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
-        pair(_Tuple&& __p)
-            : first(_VSTD::forward<typename tuple_element<0,
-                                  typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<0>(__p))),
-              second(_VSTD::forward<typename tuple_element<1,
-                                   typename __make_tuple_types<_Tuple>::type>::type>(_VSTD::get<1>(__p)))
-            {}
-
-
-
-    template <class... _Args1, class... _Args2>
-        _LIBCPP_INLINE_VISIBILITY
-        pair(piecewise_construct_t __pc, tuple<_Args1...> __first_args,
-                                    tuple<_Args2...> __second_args)
-            : pair(__pc, __first_args, __second_args,
-                   typename __make_tuple_indices<sizeof...(_Args1)>::type(),
-                   typename __make_tuple_indices<sizeof...(_Args2) >::type())
-            {}
-
-    template <class _Tuple,
-              class = typename enable_if<__tuple_assignable<_Tuple, pair>::value>::type>
-        _LIBCPP_INLINE_VISIBILITY
-        pair&
-        operator=(_Tuple&& __p)
-        {
-            typedef typename __make_tuple_types<_Tuple>::type _TupleRef;
-            typedef typename tuple_element<0, _TupleRef>::type _U0;
-            typedef typename tuple_element<1, _TupleRef>::type _U1;
-            first  = _VSTD::forward<_U0>(_VSTD::get<0>(__p));
-            second = _VSTD::forward<_U1>(_VSTD::get<1>(__p));
-            return *this;
-        }
-
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+    template <class _Tuple, _EnableB<
+            _CheckTLC<_Tuple>::template __enable_assign<_Tuple>()
+     > = false>
+    _LIBCPP_INLINE_VISIBILITY
+    pair& operator=(_Tuple&& __p) {
+        first = _VSTD::get<0>(_VSTD::forward<_Tuple>(__p));
+        second = _VSTD::get<1>(_VSTD::forward<_Tuple>(__p));
+        return *this;
+    }
+#endif
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     void
     swap(pair& __p) _NOEXCEPT_(__is_nothrow_swappable<first_type>::value &&
@@ -423,15 +536,20 @@ struct _LIBCPP_TYPE_VIS_ONLY pair
     }
 private:
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+#ifndef _LIBCPP_CXX03_LANG
     template <class... _Args1, class... _Args2, size_t... _I1, size_t... _I2>
         _LIBCPP_INLINE_VISIBILITY
         pair(piecewise_construct_t,
              tuple<_Args1...>& __first_args, tuple<_Args2...>& __second_args,
              __tuple_indices<_I1...>, __tuple_indices<_I2...>);
-#endif  // _LIBCPP_HAS_NO_VARIADICS
+#endif
 };
 
+#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+template<class _T1, class _T2>
+pair(_T1, _T2) -> pair<_T1, _T2>;
+#endif // _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+
 template <class _T1, class _T2>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 bool
@@ -495,8 +613,7 @@ swap(pair<_T1, _T2>& __x, pair<_T1, _T2>& __y)
     __x.swap(__y);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 struct __make_pair_return_impl
@@ -525,7 +642,7 @@ make_pair(_T1&& __t1, _T2&& __t2)
                (_VSTD::forward<_T1>(__t1), _VSTD::forward<_T2>(__t2));
 }
 
-#else  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#else  // _LIBCPP_CXX03_LANG
 
 template <class _T1, class _T2>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -535,21 +652,27 @@ make_pair(_T1 __x, _T2 __y)
     return pair<_T1, _T2>(__x, __y);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _T1, class _T2>
-  class _LIBCPP_TYPE_VIS_ONLY tuple_size<pair<_T1, _T2> >
+  class _LIBCPP_TEMPLATE_VIS tuple_size<pair<_T1, _T2> >
     : public integral_constant<size_t, 2> {};
 
+template <size_t _Ip, class _T1, class _T2>
+class _LIBCPP_TEMPLATE_VIS tuple_element<_Ip, pair<_T1, _T2> >
+{
+    static_assert(_Ip < 2, "Index out of bounds in std::tuple_element<std::pair<T1, T2>>");
+};
+
 template <class _T1, class _T2>
-class _LIBCPP_TYPE_VIS_ONLY tuple_element<0, pair<_T1, _T2> >
+class _LIBCPP_TEMPLATE_VIS tuple_element<0, pair<_T1, _T2> >
 {
 public:
     typedef _T1 type;
 };
 
 template <class _T1, class _T2>
-class _LIBCPP_TYPE_VIS_ONLY tuple_element<1, pair<_T1, _T2> >
+class _LIBCPP_TEMPLATE_VIS tuple_element<1, pair<_T1, _T2> >
 {
 public:
     typedef _T2 type;
@@ -572,8 +695,7 @@ struct __get_pair<0>
     const _T1&
     get(const pair<_T1, _T2>& __p) _NOEXCEPT {return __p.first;}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
+#ifndef _LIBCPP_CXX03_LANG
     template <class _T1, class _T2>
     static
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
@@ -585,8 +707,7 @@ struct __get_pair<0>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     const _T1&&
     get(const pair<_T1, _T2>&& __p) _NOEXCEPT {return _VSTD::forward<const _T1>(__p.first);}
-
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 };
 
 template <>
@@ -604,8 +725,7 @@ struct __get_pair<1>
     const _T2&
     get(const pair<_T1, _T2>& __p) _NOEXCEPT {return __p.second;}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
+#ifndef _LIBCPP_CXX03_LANG
     template <class _T1, class _T2>
     static
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
@@ -617,8 +737,7 @@ struct __get_pair<1>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     const _T2&&
     get(const pair<_T1, _T2>&& __p) _NOEXCEPT {return _VSTD::forward<const _T2>(__p.second);}
-
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 };
 
 template <size_t _Ip, class _T1, class _T2>
@@ -637,8 +756,7 @@ get(const pair<_T1, _T2>& __p) _NOEXCEPT
     return __get_pair<_Ip>::get(__p);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
+#ifndef _LIBCPP_CXX03_LANG
 template <size_t _Ip, class _T1, class _T2>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename tuple_element<_Ip, pair<_T1, _T2> >::type&&
@@ -654,8 +772,7 @@ get(const pair<_T1, _T2>&& __p) _NOEXCEPT
 {
     return __get_pair<_Ip>::get(_VSTD::move(__p));
 }
-
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 #if _LIBCPP_STD_VER > 11
 template <class _T1, class _T2>
@@ -719,7 +836,7 @@ constexpr _T1 const && get(pair<_T2, _T1> const&& __p) _NOEXCEPT
 #if _LIBCPP_STD_VER > 11
 
 template<class _Tp, _Tp... _Ip>
-struct _LIBCPP_TYPE_VIS_ONLY integer_sequence
+struct _LIBCPP_TEMPLATE_VIS integer_sequence
 {
     typedef _Tp value_type;
     static_assert( is_integral<_Tp>::value,
@@ -782,6 +899,696 @@ _T1 exchange(_T1& __obj, _T2 && __new_value)
 }
 #endif  // _LIBCPP_STD_VER > 11
 
+#if _LIBCPP_STD_VER > 14
+
+struct _LIBCPP_TYPE_VIS in_place_t {
+    explicit in_place_t() = default;
+};
+_LIBCPP_INLINE_VAR constexpr in_place_t in_place{};
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS in_place_type_t {
+    explicit in_place_type_t() = default;
+};
+template <class _Tp>
+_LIBCPP_INLINE_VAR constexpr in_place_type_t<_Tp> in_place_type{};
+
+template <size_t _Idx>
+struct _LIBCPP_TYPE_VIS in_place_index_t {
+    explicit in_place_index_t() = default;
+};
+template <size_t _Idx>
+_LIBCPP_INLINE_VAR constexpr in_place_index_t<_Idx> in_place_index{};
+
+template <class _Tp> struct __is_inplace_type_imp : false_type {};
+template <class _Tp> struct __is_inplace_type_imp<in_place_type_t<_Tp>> : true_type {};
+
+template <class _Tp>
+using __is_inplace_type = __is_inplace_type_imp<__uncvref_t<_Tp>>;
+
+template <class _Tp> struct __is_inplace_index_imp : false_type {};
+template <size_t _Idx> struct __is_inplace_index_imp<in_place_index_t<_Idx>> : true_type {};
+
+template <class _Tp>
+using __is_inplace_index = __is_inplace_index_imp<__uncvref_t<_Tp>>;
+
+#endif // _LIBCPP_STD_VER > 14
+
+template <class _Arg, class _Result>
+struct _LIBCPP_TEMPLATE_VIS unary_function
+{
+    typedef _Arg    argument_type;
+    typedef _Result result_type;
+};
+
+template <class _Size>
+inline _LIBCPP_INLINE_VISIBILITY
+_Size
+__loadword(const void* __p)
+{
+    _Size __r;
+    std::memcpy(&__r, __p, sizeof(__r));
+    return __r;
+}
+
+// We use murmur2 when size_t is 32 bits, and cityhash64 when size_t
+// is 64 bits.  This is because cityhash64 uses 64bit x 64bit
+// multiplication, which can be very slow on 32-bit systems.
+template <class _Size, size_t = sizeof(_Size)*__CHAR_BIT__>
+struct __murmur2_or_cityhash;
+
+template <class _Size>
+struct __murmur2_or_cityhash<_Size, 32>
+{
+    inline _Size operator()(const void* __key, _Size __len)
+         _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK;
+};
+
+// murmur2
+template <class _Size>
+_Size
+__murmur2_or_cityhash<_Size, 32>::operator()(const void* __key, _Size __len)
+{
+    const _Size __m = 0x5bd1e995;
+    const _Size __r = 24;
+    _Size __h = __len;
+    const unsigned char* __data = static_cast<const unsigned char*>(__key);
+    for (; __len >= 4; __data += 4, __len -= 4)
+    {
+        _Size __k = __loadword<_Size>(__data);
+        __k *= __m;
+        __k ^= __k >> __r;
+        __k *= __m;
+        __h *= __m;
+        __h ^= __k;
+    }
+    switch (__len)
+    {
+    case 3:
+        __h ^= __data[2] << 16;
+    case 2:
+        __h ^= __data[1] << 8;
+    case 1:
+        __h ^= __data[0];
+        __h *= __m;
+    }
+    __h ^= __h >> 13;
+    __h *= __m;
+    __h ^= __h >> 15;
+    return __h;
+}
+
+template <class _Size>
+struct __murmur2_or_cityhash<_Size, 64>
+{
+    inline _Size operator()(const void* __key, _Size __len)  _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK;
+
+ private:
+  // Some primes between 2^63 and 2^64.
+  static const _Size __k0 = 0xc3a5c85c97cb3127ULL;
+  static const _Size __k1 = 0xb492b66fbe98f273ULL;
+  static const _Size __k2 = 0x9ae16a3b2f90404fULL;
+  static const _Size __k3 = 0xc949d7c7509e6557ULL;
+
+  static _Size __rotate(_Size __val, int __shift) {
+    return __shift == 0 ? __val : ((__val >> __shift) | (__val << (64 - __shift)));
+  }
+
+  static _Size __rotate_by_at_least_1(_Size __val, int __shift) {
+    return (__val >> __shift) | (__val << (64 - __shift));
+  }
+
+  static _Size __shift_mix(_Size __val) {
+    return __val ^ (__val >> 47);
+  }
+
+  static _Size __hash_len_16(_Size __u, _Size __v)
+     _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
+  {
+    const _Size __mul = 0x9ddfea08eb382d69ULL;
+    _Size __a = (__u ^ __v) * __mul;
+    __a ^= (__a >> 47);
+    _Size __b = (__v ^ __a) * __mul;
+    __b ^= (__b >> 47);
+    __b *= __mul;
+    return __b;
+  }
+
+  static _Size __hash_len_0_to_16(const char* __s, _Size __len)
+     _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
+  {
+    if (__len > 8) {
+      const _Size __a = __loadword<_Size>(__s);
+      const _Size __b = __loadword<_Size>(__s + __len - 8);
+      return __hash_len_16(__a, __rotate_by_at_least_1(__b + __len, __len)) ^ __b;
+    }
+    if (__len >= 4) {
+      const uint32_t __a = __loadword<uint32_t>(__s);
+      const uint32_t __b = __loadword<uint32_t>(__s + __len - 4);
+      return __hash_len_16(__len + (__a << 3), __b);
+    }
+    if (__len > 0) {
+      const unsigned char __a = __s[0];
+      const unsigned char __b = __s[__len >> 1];
+      const unsigned char __c = __s[__len - 1];
+      const uint32_t __y = static_cast<uint32_t>(__a) +
+                           (static_cast<uint32_t>(__b) << 8);
+      const uint32_t __z = __len + (static_cast<uint32_t>(__c) << 2);
+      return __shift_mix(__y * __k2 ^ __z * __k3) * __k2;
+    }
+    return __k2;
+  }
+
+  static _Size __hash_len_17_to_32(const char *__s, _Size __len)
+     _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
+  {
+    const _Size __a = __loadword<_Size>(__s) * __k1;
+    const _Size __b = __loadword<_Size>(__s + 8);
+    const _Size __c = __loadword<_Size>(__s + __len - 8) * __k2;
+    const _Size __d = __loadword<_Size>(__s + __len - 16) * __k0;
+    return __hash_len_16(__rotate(__a - __b, 43) + __rotate(__c, 30) + __d,
+                         __a + __rotate(__b ^ __k3, 20) - __c + __len);
+  }
+
+  // Return a 16-byte hash for 48 bytes.  Quick and dirty.
+  // Callers do best to use "random-looking" values for a and b.
+  static pair<_Size, _Size> __weak_hash_len_32_with_seeds(
+      _Size __w, _Size __x, _Size __y, _Size __z, _Size __a, _Size __b)
+        _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
+  {
+    __a += __w;
+    __b = __rotate(__b + __a + __z, 21);
+    const _Size __c = __a;
+    __a += __x;
+    __a += __y;
+    __b += __rotate(__a, 44);
+    return pair<_Size, _Size>(__a + __z, __b + __c);
+  }
+
+  // Return a 16-byte hash for s[0] ... s[31], a, and b.  Quick and dirty.
+  static pair<_Size, _Size> __weak_hash_len_32_with_seeds(
+      const char* __s, _Size __a, _Size __b)
+    _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
+  {
+    return __weak_hash_len_32_with_seeds(__loadword<_Size>(__s),
+                                         __loadword<_Size>(__s + 8),
+                                         __loadword<_Size>(__s + 16),
+                                         __loadword<_Size>(__s + 24),
+                                         __a,
+                                         __b);
+  }
+
+  // Return an 8-byte hash for 33 to 64 bytes.
+  static _Size __hash_len_33_to_64(const char *__s, size_t __len)
+    _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
+  {
+    _Size __z = __loadword<_Size>(__s + 24);
+    _Size __a = __loadword<_Size>(__s) +
+                (__len + __loadword<_Size>(__s + __len - 16)) * __k0;
+    _Size __b = __rotate(__a + __z, 52);
+    _Size __c = __rotate(__a, 37);
+    __a += __loadword<_Size>(__s + 8);
+    __c += __rotate(__a, 7);
+    __a += __loadword<_Size>(__s + 16);
+    _Size __vf = __a + __z;
+    _Size __vs = __b + __rotate(__a, 31) + __c;
+    __a = __loadword<_Size>(__s + 16) + __loadword<_Size>(__s + __len - 32);
+    __z += __loadword<_Size>(__s + __len - 8);
+    __b = __rotate(__a + __z, 52);
+    __c = __rotate(__a, 37);
+    __a += __loadword<_Size>(__s + __len - 24);
+    __c += __rotate(__a, 7);
+    __a += __loadword<_Size>(__s + __len - 16);
+    _Size __wf = __a + __z;
+    _Size __ws = __b + __rotate(__a, 31) + __c;
+    _Size __r = __shift_mix((__vf + __ws) * __k2 + (__wf + __vs) * __k0);
+    return __shift_mix(__r * __k0 + __vs) * __k2;
+  }
+};
+
+// cityhash64
+template <class _Size>
+_Size
+__murmur2_or_cityhash<_Size, 64>::operator()(const void* __key, _Size __len)
+{
+  const char* __s = static_cast<const char*>(__key);
+  if (__len <= 32) {
+    if (__len <= 16) {
+      return __hash_len_0_to_16(__s, __len);
+    } else {
+      return __hash_len_17_to_32(__s, __len);
+    }
+  } else if (__len <= 64) {
+    return __hash_len_33_to_64(__s, __len);
+  }
+
+  // For strings over 64 bytes we hash the end first, and then as we
+  // loop we keep 56 bytes of state: v, w, x, y, and z.
+  _Size __x = __loadword<_Size>(__s + __len - 40);
+  _Size __y = __loadword<_Size>(__s + __len - 16) +
+              __loadword<_Size>(__s + __len - 56);
+  _Size __z = __hash_len_16(__loadword<_Size>(__s + __len - 48) + __len,
+                          __loadword<_Size>(__s + __len - 24));
+  pair<_Size, _Size> __v = __weak_hash_len_32_with_seeds(__s + __len - 64, __len, __z);
+  pair<_Size, _Size> __w = __weak_hash_len_32_with_seeds(__s + __len - 32, __y + __k1, __x);
+  __x = __x * __k1 + __loadword<_Size>(__s);
+
+  // Decrease len to the nearest multiple of 64, and operate on 64-byte chunks.
+  __len = (__len - 1) & ~static_cast<_Size>(63);
+  do {
+    __x = __rotate(__x + __y + __v.first + __loadword<_Size>(__s + 8), 37) * __k1;
+    __y = __rotate(__y + __v.second + __loadword<_Size>(__s + 48), 42) * __k1;
+    __x ^= __w.second;
+    __y += __v.first + __loadword<_Size>(__s + 40);
+    __z = __rotate(__z + __w.first, 33) * __k1;
+    __v = __weak_hash_len_32_with_seeds(__s, __v.second * __k1, __x + __w.first);
+    __w = __weak_hash_len_32_with_seeds(__s + 32, __z + __w.second,
+                                        __y + __loadword<_Size>(__s + 16));
+    std::swap(__z, __x);
+    __s += 64;
+    __len -= 64;
+  } while (__len != 0);
+  return __hash_len_16(
+      __hash_len_16(__v.first, __w.first) + __shift_mix(__y) * __k1 + __z,
+      __hash_len_16(__v.second, __w.second) + __x);
+}
+
+template <class _Tp, size_t = sizeof(_Tp) / sizeof(size_t)>
+struct __scalar_hash;
+
+template <class _Tp>
+struct __scalar_hash<_Tp, 0>
+    : public unary_function<_Tp, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(_Tp __v) const _NOEXCEPT
+    {
+        union
+        {
+            _Tp    __t;
+            size_t __a;
+        } __u;
+        __u.__a = 0;
+        __u.__t = __v;
+        return __u.__a;
+    }
+};
+
+template <class _Tp>
+struct __scalar_hash<_Tp, 1>
+    : public unary_function<_Tp, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(_Tp __v) const _NOEXCEPT
+    {
+        union
+        {
+            _Tp    __t;
+            size_t __a;
+        } __u;
+        __u.__t = __v;
+        return __u.__a;
+    }
+};
+
+template <class _Tp>
+struct __scalar_hash<_Tp, 2>
+    : public unary_function<_Tp, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(_Tp __v) const _NOEXCEPT
+    {
+        union
+        {
+            _Tp __t;
+            struct
+            {
+                size_t __a;
+                size_t __b;
+            } __s;
+        } __u;
+        __u.__t = __v;
+        return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
+    }
+};
+
+template <class _Tp>
+struct __scalar_hash<_Tp, 3>
+    : public unary_function<_Tp, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(_Tp __v) const _NOEXCEPT
+    {
+        union
+        {
+            _Tp __t;
+            struct
+            {
+                size_t __a;
+                size_t __b;
+                size_t __c;
+            } __s;
+        } __u;
+        __u.__t = __v;
+        return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
+    }
+};
+
+template <class _Tp>
+struct __scalar_hash<_Tp, 4>
+    : public unary_function<_Tp, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(_Tp __v) const _NOEXCEPT
+    {
+        union
+        {
+            _Tp __t;
+            struct
+            {
+                size_t __a;
+                size_t __b;
+                size_t __c;
+                size_t __d;
+            } __s;
+        } __u;
+        __u.__t = __v;
+        return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
+    }
+};
+
+struct _PairT {
+  size_t first;
+  size_t second;
+};
+
+_LIBCPP_INLINE_VISIBILITY
+inline size_t __hash_combine(size_t __lhs, size_t __rhs) _NOEXCEPT {
+    typedef __scalar_hash<_PairT> _HashT;
+    const _PairT __p = {__lhs, __rhs};
+    return _HashT()(__p);
+}
+
+template<class _Tp>
+struct _LIBCPP_TEMPLATE_VIS hash<_Tp*>
+    : public unary_function<_Tp*, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(_Tp* __v) const _NOEXCEPT
+    {
+        union
+        {
+            _Tp* __t;
+            size_t __a;
+        } __u;
+        __u.__t = __v;
+        return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
+    }
+};
+
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<bool>
+    : public unary_function<bool, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(bool __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<char>
+    : public unary_function<char, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(char __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<signed char>
+    : public unary_function<signed char, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(signed char __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<unsigned char>
+    : public unary_function<unsigned char, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(unsigned char __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<char16_t>
+    : public unary_function<char16_t, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(char16_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<char32_t>
+    : public unary_function<char32_t, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(char32_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+#endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<wchar_t>
+    : public unary_function<wchar_t, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(wchar_t __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<short>
+    : public unary_function<short, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(short __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<unsigned short>
+    : public unary_function<unsigned short, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(unsigned short __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<int>
+    : public unary_function<int, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(int __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<unsigned int>
+    : public unary_function<unsigned int, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(unsigned int __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<long>
+    : public unary_function<long, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(long __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<unsigned long>
+    : public unary_function<unsigned long, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(unsigned long __v) const _NOEXCEPT {return static_cast<size_t>(__v);}
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<long long>
+    : public __scalar_hash<long long>
+{
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<unsigned long long>
+    : public __scalar_hash<unsigned long long>
+{
+};
+
+#ifndef _LIBCPP_HAS_NO_INT128
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<__int128_t>
+    : public __scalar_hash<__int128_t>
+{
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<__uint128_t>
+    : public __scalar_hash<__uint128_t>
+{
+};
+
+#endif
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<float>
+    : public __scalar_hash<float>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(float __v) const _NOEXCEPT
+    {
+        // -0.0 and 0.0 should return same hash
+       if (__v == 0)
+           return 0;
+        return __scalar_hash<float>::operator()(__v);
+    }
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<double>
+    : public __scalar_hash<double>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(double __v) const _NOEXCEPT
+    {
+        // -0.0 and 0.0 should return same hash
+       if (__v == 0)
+           return 0;
+        return __scalar_hash<double>::operator()(__v);
+    }
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<long double>
+    : public __scalar_hash<long double>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(long double __v) const _NOEXCEPT
+    {
+        // -0.0 and 0.0 should return same hash
+        if (__v == 0)
+            return 0;
+#if defined(__i386__)
+        // Zero out padding bits
+        union
+        {
+            long double __t;
+            struct
+            {
+                size_t __a;
+                size_t __b;
+                size_t __c;
+                size_t __d;
+            } __s;
+        } __u;
+        __u.__s.__a = 0;
+        __u.__s.__b = 0;
+        __u.__s.__c = 0;
+        __u.__s.__d = 0;
+        __u.__t = __v;
+        return __u.__s.__a ^ __u.__s.__b ^ __u.__s.__c ^ __u.__s.__d;
+#elif defined(__x86_64__)
+        // Zero out padding bits
+        union
+        {
+            long double __t;
+            struct
+            {
+                size_t __a;
+                size_t __b;
+            } __s;
+        } __u;
+        __u.__s.__a = 0;
+        __u.__s.__b = 0;
+        __u.__t = __v;
+        return __u.__s.__a ^ __u.__s.__b;
+#else
+        return __scalar_hash<long double>::operator()(__v);
+#endif
+    }
+};
+
+#if _LIBCPP_STD_VER > 11
+
+template <class _Tp, bool = is_enum<_Tp>::value>
+struct _LIBCPP_TEMPLATE_VIS __enum_hash
+    : public unary_function<_Tp, size_t>
+{
+    _LIBCPP_INLINE_VISIBILITY
+    size_t operator()(_Tp __v) const _NOEXCEPT
+    {
+        typedef typename underlying_type<_Tp>::type type;
+        return hash<type>{}(static_cast<type>(__v));
+    }
+};
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS __enum_hash<_Tp, false> {
+    __enum_hash() = delete;
+    __enum_hash(__enum_hash const&) = delete;
+    __enum_hash& operator=(__enum_hash const&) = delete;
+};
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS hash : public __enum_hash<_Tp>
+{
+};
+#endif
+
+#if _LIBCPP_STD_VER > 14
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<nullptr_t>
+  : public unary_function<nullptr_t, size_t>
+{
+  _LIBCPP_INLINE_VISIBILITY
+  size_t operator()(nullptr_t) const _NOEXCEPT {
+    return 662607004ull;
+  }
+};
+#endif
+
+#ifndef _LIBCPP_CXX03_LANG
+template <class _Key, class _Hash>
+using __check_hash_requirements = integral_constant<bool,
+    is_copy_constructible<_Hash>::value &&
+    is_move_constructible<_Hash>::value &&
+    __invokable_r<size_t, _Hash, _Key const&>::value
+>;
+
+template <class _Key, class _Hash = std::hash<_Key> >
+using __has_enabled_hash = integral_constant<bool,
+    __check_hash_requirements<_Key, _Hash>::value &&
+    is_default_constructible<_Hash>::value
+>;
+
+#if _LIBCPP_STD_VER > 14
+template <class _Type, class>
+using __enable_hash_helper_imp = _Type;
+
+template <class _Type, class ..._Keys>
+using __enable_hash_helper = __enable_hash_helper_imp<_Type,
+  typename enable_if<__all<__has_enabled_hash<_Keys>::value...>::value>::type
+>;
+#else
+template <class _Type, class ...>
+using __enable_hash_helper = _Type;
+#endif
+
+#endif // !_LIBCPP_CXX03_LANG
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_UTILITY
diff --git a/lib/libcxx/include/valarray b/lib/libcxx/include/valarray
index bde644e8719..ee61238a932 100644
--- a/lib/libcxx/include/valarray
+++ b/lib/libcxx/include/valarray
@@ -347,18 +347,19 @@ template <class T> unspecified2 end(const valarray<T>& v);
 #include <functional>
 #include <new>
 
-#include <__undef_min_max>
-#include <__undef___deallocate>
-
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template<class _Tp> class _LIBCPP_TYPE_VIS_ONLY valarray;
+template<class _Tp> class _LIBCPP_TEMPLATE_VIS valarray;
 
-class _LIBCPP_TYPE_VIS_ONLY slice
+class _LIBCPP_TEMPLATE_VIS slice
 {
     size_t __start_;
     size_t __size_;
@@ -383,11 +384,11 @@ public:
     _LIBCPP_INLINE_VISIBILITY size_t stride() const {return __stride_;}
 };
 
-template <class _Tp> class _LIBCPP_TYPE_VIS_ONLY slice_array;
+template <class _Tp> class _LIBCPP_TEMPLATE_VIS slice_array;
 class _LIBCPP_TYPE_VIS gslice;
-template <class _Tp> class _LIBCPP_TYPE_VIS_ONLY gslice_array;
-template <class _Tp> class _LIBCPP_TYPE_VIS_ONLY mask_array;
-template <class _Tp> class _LIBCPP_TYPE_VIS_ONLY indirect_array;
+template <class _Tp> class _LIBCPP_TEMPLATE_VIS gslice_array;
+template <class _Tp> class _LIBCPP_TEMPLATE_VIS mask_array;
+template <class _Tp> class _LIBCPP_TEMPLATE_VIS indirect_array;
 
 template <class _Tp>
 _LIBCPP_INLINE_VISIBILITY
@@ -673,7 +674,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     size_t size() const {return __size_;}
 
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY valarray;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS valarray;
 };
 
 template <class _ValExpr>
@@ -788,7 +789,7 @@ template<class _Tp>
 struct __is_val_expr<valarray<_Tp> > : true_type {};
 
 template<class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY valarray
+class _LIBCPP_TEMPLATE_VIS valarray
 {
 public:
     typedef _Tp value_type;
@@ -802,36 +803,32 @@ public:
     // construct/destroy:
     _LIBCPP_INLINE_VISIBILITY
     valarray() : __begin_(0), __end_(0) {}
-    _LIBCPP_INLINE_VISIBILITY
-    inline explicit valarray(size_t __n);
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
+    explicit valarray(size_t __n);
     _LIBCPP_INLINE_VISIBILITY
     valarray(const value_type& __x, size_t __n);
     valarray(const value_type* __p, size_t __n);
     valarray(const valarray& __v);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     valarray(valarray&& __v) _NOEXCEPT;
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     valarray(initializer_list<value_type> __il);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
     valarray(const slice_array<value_type>& __sa);
     valarray(const gslice_array<value_type>& __ga);
     valarray(const mask_array<value_type>& __ma);
     valarray(const indirect_array<value_type>& __ia);
-    inline _LIBCPP_INLINE_VISIBILITY
+    inline _LIBCPP_EXTERN_TEMPLATE_INLINE_VISIBILITY
     ~valarray();
 
     // assignment:
     valarray& operator=(const valarray& __v);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     valarray& operator=(valarray&& __v) _NOEXCEPT;
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
     _LIBCPP_INLINE_VISIBILITY
     valarray& operator=(initializer_list<value_type>);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     valarray& operator=(const value_type& __x);
     _LIBCPP_INLINE_VISIBILITY
@@ -862,32 +859,32 @@ public:
     __val_expr<__indirect_expr<const valarray&> > operator[](const gslice& __gs) const;
     _LIBCPP_INLINE_VISIBILITY
     gslice_array<value_type>   operator[](const gslice& __gs);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     __val_expr<__indirect_expr<const valarray&> > operator[](gslice&& __gs) const;
     _LIBCPP_INLINE_VISIBILITY
     gslice_array<value_type>                      operator[](gslice&& __gs);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     __val_expr<__mask_expr<const valarray&> >     operator[](const valarray<bool>& __vb) const;
     _LIBCPP_INLINE_VISIBILITY
     mask_array<value_type>                        operator[](const valarray<bool>& __vb);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     __val_expr<__mask_expr<const valarray&> >     operator[](valarray<bool>&& __vb) const;
     _LIBCPP_INLINE_VISIBILITY
     mask_array<value_type>                        operator[](valarray<bool>&& __vb);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     __val_expr<__indirect_expr<const valarray&> > operator[](const valarray<size_t>& __vs) const;
     _LIBCPP_INLINE_VISIBILITY
     indirect_array<value_type>                    operator[](const valarray<size_t>& __vs);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     __val_expr<__indirect_expr<const valarray&> > operator[](valarray<size_t>&& __vs) const;
     _LIBCPP_INLINE_VISIBILITY
     indirect_array<value_type>                    operator[](valarray<size_t>&& __vs);
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     // unary operators:
     valarray       operator+() const;
@@ -1028,12 +1025,12 @@ public:
     void     resize(size_t __n, value_type __x = value_type());
 
 private:
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY valarray;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY slice_array;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY gslice_array;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY mask_array;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS valarray;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS slice_array;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS gslice_array;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS mask_array;
     template <class> friend class __mask_expr;
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY indirect_array;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS indirect_array;
     template <class> friend class __indirect_expr;
     template <class> friend class __val_expr;
 
@@ -1147,7 +1144,7 @@ struct _BinaryOp<_Op, valarray<_Tp>, valarray<_Tp> >
 // slice_array
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY slice_array
+class _LIBCPP_TEMPLATE_VIS slice_array
 {
 public:
     typedef _Tp value_type;
@@ -1481,7 +1478,7 @@ public:
           __stride_(__stride)
         {__init(__start);}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     gslice(size_t __start, const valarray<size_t>&  __size,
@@ -1504,7 +1501,7 @@ public:
           __stride_(move(__stride))
         {__init(__start);}
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 //  gslice(const gslice&)            = default;
 //  gslice(gslice&&)                 = default;
@@ -1531,7 +1528,7 @@ private:
 // gslice_array
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY gslice_array
+class _LIBCPP_TEMPLATE_VIS gslice_array
 {
 public:
     typedef _Tp value_type;
@@ -1657,12 +1654,12 @@ private:
           __1d_(__gs.__1d_)
         {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
     gslice_array(gslice&& __gs, const valarray<value_type>& __v)
         : __vp_(const_cast<value_type*>(__v.__begin_)),
           __1d_(move(__gs.__1d_))
         {}
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     template <class> friend class valarray;
 };
@@ -1869,7 +1866,7 @@ gslice_array<_Tp>::operator=(const value_type& __x) const
 // mask_array
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY mask_array
+class _LIBCPP_TEMPLATE_VIS mask_array
 {
 public:
     typedef _Tp value_type;
@@ -2227,7 +2224,7 @@ public:
 // indirect_array
 
 template <class _Tp>
-class _LIBCPP_TYPE_VIS_ONLY indirect_array
+class _LIBCPP_TEMPLATE_VIS indirect_array
 {
 public:
     typedef _Tp value_type;
@@ -2354,7 +2351,7 @@ private:
           __1d_(__ia)
         {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     indirect_array(valarray<size_t>&& __ia, const valarray<value_type>& __v)
@@ -2362,7 +2359,7 @@ private:
           __1d_(move(__ia))
         {}
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
     template <class> friend class valarray;
 };
@@ -2573,7 +2570,7 @@ private:
           __1d_(__ia)
           {}
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
     _LIBCPP_INLINE_VISIBILITY
     __indirect_expr(valarray<size_t>&& __ia, const _RmExpr& __e)
@@ -2581,7 +2578,7 @@ private:
           __1d_(move(__ia))
           {}
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 public:
     _LIBCPP_INLINE_VISIBILITY
@@ -2591,7 +2588,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     size_t size() const {return __1d_.size();}
 
-    template <class> friend class _LIBCPP_TYPE_VIS_ONLY valarray;
+    template <class> friend class _LIBCPP_TEMPLATE_VIS valarray;
 };
 
 template<class _ValExpr>
@@ -2815,7 +2812,7 @@ valarray<_Tp>::valarray(const valarray& __v)
     }
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 inline
@@ -2826,10 +2823,6 @@ valarray<_Tp>::valarray(valarray&& __v) _NOEXCEPT
     __v.__begin_ = __v.__end_ = nullptr;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Tp>
 valarray<_Tp>::valarray(initializer_list<value_type> __il)
     : __begin_(0),
@@ -2856,7 +2849,7 @@ valarray<_Tp>::valarray(initializer_list<value_type> __il)
     }
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 valarray<_Tp>::valarray(const slice_array<value_type>& __sa)
@@ -2991,7 +2984,7 @@ valarray<_Tp>::operator=(const valarray& __v)
     return *this;
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 inline
@@ -3006,10 +2999,6 @@ valarray<_Tp>::operator=(valarray&& __v) _NOEXCEPT
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Tp>
 inline
 valarray<_Tp>&
@@ -3021,7 +3010,7 @@ valarray<_Tp>::operator=(initializer_list<value_type> __il)
     return *this;
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 inline
@@ -3133,7 +3122,7 @@ valarray<_Tp>::operator[](const gslice& __gs)
     return gslice_array<value_type>(__gs, *this);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 inline
@@ -3151,7 +3140,7 @@ valarray<_Tp>::operator[](gslice&& __gs)
     return gslice_array<value_type>(move(__gs), *this);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 inline
@@ -3169,7 +3158,7 @@ valarray<_Tp>::operator[](const valarray<bool>& __vb)
     return mask_array<value_type>(__vb, *this);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 inline
@@ -3187,7 +3176,7 @@ valarray<_Tp>::operator[](valarray<bool>&& __vb)
     return mask_array<value_type>(move(__vb), *this);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 inline
@@ -3205,7 +3194,7 @@ valarray<_Tp>::operator[](const valarray<size_t>& __vs)
     return indirect_array<value_type>(__vs, *this);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 inline
@@ -3223,7 +3212,7 @@ valarray<_Tp>::operator[](valarray<size_t>&& __vs)
     return indirect_array<value_type>(move(__vs), *this);
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Tp>
 valarray<_Tp>
@@ -3697,7 +3686,7 @@ valarray<_Tp>::resize(size_t __n, value_type __x)
     {
         while (__end_ != __begin_)
             (--__end_)->~value_type();
-        _VSTD::__deallocate(__begin_);
+        _VSTD::__libcpp_deallocate(__begin_);
         __begin_ = __end_ = nullptr;
     }
     if (__n)
@@ -4878,4 +4867,6 @@ end(const valarray<_Tp>& __v)
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_VALARRAY
diff --git a/lib/libcxx/include/variant b/lib/libcxx/include/variant
new file mode 100644
index 00000000000..987b8a7982d
--- /dev/null
+++ b/lib/libcxx/include/variant
@@ -0,0 +1,1594 @@
+// -*- C++ -*-
+//===------------------------------ variant -------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_VARIANT
+#define _LIBCPP_VARIANT
+
+/*
+   variant synopsis
+
+namespace std {
+
+  // 20.7.2, class template variant
+  template <class... Types>
+  class variant {
+  public:
+
+    // 20.7.2.1, constructors
+    constexpr variant() noexcept(see below);
+    variant(const variant&);
+    variant(variant&&) noexcept(see below);
+
+    template <class T> constexpr variant(T&&) noexcept(see below);
+
+    template <class T, class... Args>
+    constexpr explicit variant(in_place_type_t<T>, Args&&...);
+
+    template <class T, class U, class... Args>
+    constexpr explicit variant(
+        in_place_type_t<T>, initializer_list<U>, Args&&...);
+
+    template <size_t I, class... Args>
+    constexpr explicit variant(in_place_index_t<I>, Args&&...);
+
+    template <size_t I, class U, class... Args>
+    constexpr explicit variant(
+        in_place_index_t<I>, initializer_list<U>, Args&&...);
+
+    // 20.7.2.2, destructor
+    ~variant();
+
+    // 20.7.2.3, assignment
+    variant& operator=(const variant&);
+    variant& operator=(variant&&) noexcept(see below);
+
+    template <class T> variant& operator=(T&&) noexcept(see below);
+
+    // 20.7.2.4, modifiers
+    template <class T, class... Args>
+    T& emplace(Args&&...);
+
+    template <class T, class U, class... Args>
+    T& emplace(initializer_list<U>, Args&&...);
+
+    template <size_t I, class... Args>
+    variant_alternative_t<I, variant>& emplace(Args&&...);
+
+    template <size_t I, class U, class...  Args>
+    variant_alternative_t<I, variant>& emplace(initializer_list<U>, Args&&...);
+
+    // 20.7.2.5, value status
+    constexpr bool valueless_by_exception() const noexcept;
+    constexpr size_t index() const noexcept;
+
+    // 20.7.2.6, swap
+    void swap(variant&) noexcept(see below);
+  };
+
+  // 20.7.3, variant helper classes
+  template <class T> struct variant_size; // undefined
+
+  template <class T>
+  inline constexpr size_t variant_size_v = variant_size<T>::value;
+
+  template <class T> struct variant_size<const T>;
+  template <class T> struct variant_size<volatile T>;
+  template <class T> struct variant_size<const volatile T>;
+
+  template <class... Types>
+  struct variant_size<variant<Types...>>;
+
+  template <size_t I, class T> struct variant_alternative; // undefined
+
+  template <size_t I, class T>
+  using variant_alternative_t = typename variant_alternative<I, T>::type;
+
+  template <size_t I, class T> struct variant_alternative<I, const T>;
+  template <size_t I, class T> struct variant_alternative<I, volatile T>;
+  template <size_t I, class T> struct variant_alternative<I, const volatile T>;
+
+  template <size_t I, class... Types>
+  struct variant_alternative<I, variant<Types...>>;
+
+  inline constexpr size_t variant_npos = -1;
+
+  // 20.7.4, value access
+  template <class T, class... Types>
+  constexpr bool holds_alternative(const variant<Types...>&) noexcept;
+
+  template <size_t I, class... Types>
+  constexpr variant_alternative_t<I, variant<Types...>>&
+  get(variant<Types...>&);
+
+  template <size_t I, class... Types>
+  constexpr variant_alternative_t<I, variant<Types...>>&&
+  get(variant<Types...>&&);
+
+  template <size_t I, class... Types>
+  constexpr variant_alternative_t<I, variant<Types...>> const&
+  get(const variant<Types...>&);
+
+  template <size_t I, class... Types>
+  constexpr variant_alternative_t<I, variant<Types...>> const&&
+  get(const variant<Types...>&&);
+
+  template <class T, class...  Types>
+  constexpr T& get(variant<Types...>&);
+
+  template <class T, class... Types>
+  constexpr T&& get(variant<Types...>&&);
+
+  template <class T, class... Types>
+  constexpr const T& get(const variant<Types...>&);
+
+  template <class T, class... Types>
+  constexpr const T&& get(const variant<Types...>&&);
+
+  template <size_t I, class... Types>
+  constexpr add_pointer_t<variant_alternative_t<I, variant<Types...>>>
+  get_if(variant<Types...>*) noexcept;
+
+  template <size_t I, class... Types>
+  constexpr add_pointer_t<const variant_alternative_t<I, variant<Types...>>>
+  get_if(const variant<Types...>*) noexcept;
+
+  template <class T, class... Types>
+  constexpr add_pointer_t<T>
+  get_if(variant<Types...>*) noexcept;
+
+  template <class T, class... Types>
+  constexpr add_pointer_t<const T>
+  get_if(const variant<Types...>*) noexcept;
+
+  // 20.7.5, relational operators
+  template <class... Types>
+  constexpr bool operator==(const variant<Types...>&, const variant<Types...>&);
+
+  template <class... Types>
+  constexpr bool operator!=(const variant<Types...>&, const variant<Types...>&);
+
+  template <class... Types>
+  constexpr bool operator<(const variant<Types...>&, const variant<Types...>&);
+
+  template <class... Types>
+  constexpr bool operator>(const variant<Types...>&, const variant<Types...>&);
+
+  template <class... Types>
+  constexpr bool operator<=(const variant<Types...>&, const variant<Types...>&);
+
+  template <class... Types>
+  constexpr bool operator>=(const variant<Types...>&, const variant<Types...>&);
+
+  // 20.7.6, visitation
+  template <class Visitor, class... Variants>
+  constexpr see below visit(Visitor&&, Variants&&...);
+
+  // 20.7.7, class monostate
+  struct monostate;
+
+  // 20.7.8, monostate relational operators
+  constexpr bool operator<(monostate, monostate) noexcept;
+  constexpr bool operator>(monostate, monostate) noexcept;
+  constexpr bool operator<=(monostate, monostate) noexcept;
+  constexpr bool operator>=(monostate, monostate) noexcept;
+  constexpr bool operator==(monostate, monostate) noexcept;
+  constexpr bool operator!=(monostate, monostate) noexcept;
+
+  // 20.7.9, specialized algorithms
+  template <class... Types>
+  void swap(variant<Types...>&, variant<Types...>&) noexcept(see below);
+
+  // 20.7.10, class bad_variant_access
+  class bad_variant_access;
+
+  // 20.7.11, hash support
+  template <class T> struct hash;
+  template <class... Types> struct hash<variant<Types...>>;
+  template <> struct hash<monostate>;
+
+} // namespace std
+
+*/
+
+#include <__config>
+#include <__tuple>
+#include <array>
+#include <exception>
+#include <functional>
+#include <initializer_list>
+#include <new>
+#include <tuple>
+#include <type_traits>
+#include <utility>
+#include <limits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+namespace std { // explicitly not using versioning namespace
+
+class _LIBCPP_EXCEPTION_ABI bad_variant_access : public exception {
+public:
+  virtual const char* what() const _NOEXCEPT;
+};
+
+} // namespace std
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 14
+
+_LIBCPP_NORETURN
+inline _LIBCPP_INLINE_VISIBILITY
+void __throw_bad_variant_access() {
+#ifndef _LIBCPP_NO_EXCEPTIONS
+        throw bad_variant_access();
+#else
+        _VSTD::abort();
+#endif
+}
+
+template <class... _Types>
+class _LIBCPP_TEMPLATE_VIS variant;
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS variant_size;
+
+template <class _Tp>
+_LIBCPP_INLINE_VAR constexpr size_t variant_size_v = variant_size<_Tp>::value;
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS variant_size<const _Tp> : variant_size<_Tp> {};
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS variant_size<volatile _Tp> : variant_size<_Tp> {};
+
+template <class _Tp>
+struct _LIBCPP_TEMPLATE_VIS variant_size<const volatile _Tp>
+    : variant_size<_Tp> {};
+
+template <class... _Types>
+struct _LIBCPP_TEMPLATE_VIS variant_size<variant<_Types...>>
+    : integral_constant<size_t, sizeof...(_Types)> {};
+
+template <size_t _Ip, class _Tp>
+struct _LIBCPP_TEMPLATE_VIS variant_alternative;
+
+template <size_t _Ip, class _Tp>
+using variant_alternative_t = typename variant_alternative<_Ip, _Tp>::type;
+
+template <size_t _Ip, class _Tp>
+struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, const _Tp>
+    : add_const<variant_alternative_t<_Ip, _Tp>> {};
+
+template <size_t _Ip, class _Tp>
+struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, volatile _Tp>
+    : add_volatile<variant_alternative_t<_Ip, _Tp>> {};
+
+template <size_t _Ip, class _Tp>
+struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, const volatile _Tp>
+    : add_cv<variant_alternative_t<_Ip, _Tp>> {};
+
+template <size_t _Ip, class... _Types>
+struct _LIBCPP_TEMPLATE_VIS variant_alternative<_Ip, variant<_Types...>> {
+  static_assert(_Ip < sizeof...(_Types), "Index out of bounds in std::variant_alternative<>");
+  using type = __type_pack_element<_Ip, _Types...>;
+};
+
+_LIBCPP_INLINE_VAR constexpr size_t variant_npos = static_cast<size_t>(-1);
+
+constexpr int __choose_index_type(unsigned int __num_elem) {
+  if (__num_elem < std::numeric_limits<unsigned char>::max())
+    return 0;
+  if (__num_elem < std::numeric_limits<unsigned short>::max())
+    return 1;
+  return 2;
+}
+
+template <size_t _NumAlts>
+using __variant_index_t =
+#ifndef _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
+  unsigned int;
+#else
+  std::tuple_element_t<
+      __choose_index_type(_NumAlts),
+      std::tuple<unsigned char, unsigned short, unsigned int>
+  >;
+#endif
+
+template <class _IndexType>
+constexpr _IndexType __variant_npos = static_cast<_IndexType>(-1);
+
+namespace __find_detail {
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr size_t __find_index() {
+  constexpr bool __matches[] = {is_same_v<_Tp, _Types>...};
+  size_t __result = __not_found;
+  for (size_t __i = 0; __i < sizeof...(_Types); ++__i) {
+    if (__matches[__i]) {
+      if (__result != __not_found) {
+        return __ambiguous;
+      }
+      __result = __i;
+    }
+  }
+  return __result;
+}
+
+template <size_t _Index>
+struct __find_unambiguous_index_sfinae_impl
+    : integral_constant<size_t, _Index> {};
+
+template <>
+struct __find_unambiguous_index_sfinae_impl<__not_found> {};
+
+template <>
+struct __find_unambiguous_index_sfinae_impl<__ambiguous> {};
+
+template <class _Tp, class... _Types>
+struct __find_unambiguous_index_sfinae
+    : __find_unambiguous_index_sfinae_impl<__find_index<_Tp, _Types...>()> {};
+
+} // namespace __find_detail
+
+namespace __variant_detail {
+
+struct __valueless_t {};
+
+enum class _Trait { _TriviallyAvailable, _Available, _Unavailable };
+
+template <typename _Tp,
+          template <typename> class _IsTriviallyAvailable,
+          template <typename> class _IsAvailable>
+constexpr _Trait __trait =
+    _IsTriviallyAvailable<_Tp>::value
+        ? _Trait::_TriviallyAvailable
+        : _IsAvailable<_Tp>::value ? _Trait::_Available : _Trait::_Unavailable;
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr _Trait __common_trait(initializer_list<_Trait> __traits) {
+  _Trait __result = _Trait::_TriviallyAvailable;
+  for (_Trait __t : __traits) {
+    if (static_cast<int>(__t) > static_cast<int>(__result)) {
+      __result = __t;
+    }
+  }
+  return __result;
+}
+
+template <typename... _Types>
+struct __traits {
+  static constexpr _Trait __copy_constructible_trait =
+      __common_trait({__trait<_Types,
+                              is_trivially_copy_constructible,
+                              is_copy_constructible>...});
+
+  static constexpr _Trait __move_constructible_trait =
+      __common_trait({__trait<_Types,
+                              is_trivially_move_constructible,
+                              is_move_constructible>...});
+
+  static constexpr _Trait __copy_assignable_trait = __common_trait(
+      {__copy_constructible_trait,
+       __trait<_Types, is_trivially_copy_assignable, is_copy_assignable>...});
+
+  static constexpr _Trait __move_assignable_trait = __common_trait(
+      {__move_constructible_trait,
+       __trait<_Types, is_trivially_move_assignable, is_move_assignable>...});
+
+  static constexpr _Trait __destructible_trait = __common_trait(
+      {__trait<_Types, is_trivially_destructible, is_destructible>...});
+};
+
+namespace __access {
+
+struct __union {
+  template <class _Vp>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<0>) {
+    return _VSTD::forward<_Vp>(__v).__head;
+  }
+
+  template <class _Vp, size_t _Ip>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto&& __get_alt(_Vp&& __v, in_place_index_t<_Ip>) {
+    return __get_alt(_VSTD::forward<_Vp>(__v).__tail, in_place_index<_Ip - 1>);
+  }
+};
+
+struct __base {
+  template <size_t _Ip, class _Vp>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto&& __get_alt(_Vp&& __v) {
+    return __union::__get_alt(_VSTD::forward<_Vp>(__v).__data,
+                              in_place_index<_Ip>);
+  }
+};
+
+struct __variant {
+  template <size_t _Ip, class _Vp>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto&& __get_alt(_Vp&& __v) {
+    return __base::__get_alt<_Ip>(_VSTD::forward<_Vp>(__v).__impl);
+  }
+};
+
+} // namespace __access
+
+namespace __visitation {
+
+struct __base {
+  template <class _Visitor, class... _Vs>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr decltype(auto)
+  __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
+    constexpr auto __fdiagonal =
+        __make_fdiagonal<_Visitor&&,
+                         decltype(_VSTD::forward<_Vs>(__vs).__as_base())...>();
+    return __fdiagonal[__index](_VSTD::forward<_Visitor>(__visitor),
+                                _VSTD::forward<_Vs>(__vs).__as_base()...);
+  }
+
+  template <class _Visitor, class... _Vs>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor,
+                                              _Vs&&... __vs) {
+    constexpr auto __fmatrix =
+        __make_fmatrix<_Visitor&&,
+                       decltype(_VSTD::forward<_Vs>(__vs).__as_base())...>();
+    return __at(__fmatrix, __vs.index()...)(
+        _VSTD::forward<_Visitor>(__visitor),
+        _VSTD::forward<_Vs>(__vs).__as_base()...);
+  }
+
+private:
+  template <class _Tp>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr const _Tp& __at(const _Tp& __elem) { return __elem; }
+
+  template <class _Tp, size_t _Np, typename... _Indices>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto&& __at(const array<_Tp, _Np>& __elems,
+                               size_t __index, _Indices... __indices) {
+    return __at(__elems[__index], __indices...);
+  }
+
+  template <class _Fp, class... _Fs>
+  static constexpr void __std_visit_visitor_return_type_check() {
+    static_assert(
+        __all<is_same_v<_Fp, _Fs>...>::value,
+        "`std::visit` requires the visitor to have a single return type.");
+  }
+
+  template <class... _Fs>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto __make_farray(_Fs&&... __fs) {
+    __std_visit_visitor_return_type_check<decay_t<_Fs>...>();
+    using __result = array<common_type_t<decay_t<_Fs>...>, sizeof...(_Fs)>;
+    return __result{{_VSTD::forward<_Fs>(__fs)...}};
+  }
+
+  template <std::size_t... _Is>
+  struct __dispatcher {
+    template <class _Fp, class... _Vs>
+    inline _LIBCPP_INLINE_VISIBILITY
+    static constexpr decltype(auto) __dispatch(_Fp __f, _Vs... __vs) {
+        return __invoke_constexpr(
+            static_cast<_Fp>(__f),
+            __access::__base::__get_alt<_Is>(static_cast<_Vs>(__vs))...);
+    }
+  };
+
+  template <class _Fp, class... _Vs, size_t... _Is>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto __make_dispatch(index_sequence<_Is...>) {
+    return __dispatcher<_Is...>::template __dispatch<_Fp, _Vs...>;
+  }
+
+  template <size_t _Ip, class _Fp, class... _Vs>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto __make_fdiagonal_impl() {
+    return __make_dispatch<_Fp, _Vs...>(
+        index_sequence<(__identity<_Vs>{}, _Ip)...>{});
+  }
+
+  template <class _Fp, class... _Vs, size_t... _Is>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto __make_fdiagonal_impl(index_sequence<_Is...>) {
+    return __base::__make_farray(__make_fdiagonal_impl<_Is, _Fp, _Vs...>()...);
+  }
+
+  template <class _Fp, class _Vp, class... _Vs>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto __make_fdiagonal() {
+    constexpr size_t _Np = decay_t<_Vp>::__size();
+    static_assert(__all<(_Np == decay_t<_Vs>::__size())...>::value);
+    return __make_fdiagonal_impl<_Fp, _Vp, _Vs...>(make_index_sequence<_Np>{});
+  }
+
+  template <class _Fp, class... _Vs, size_t... _Is>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto __make_fmatrix_impl(index_sequence<_Is...> __is) {
+    return __make_dispatch<_Fp, _Vs...>(__is);
+  }
+
+  template <class _Fp, class... _Vs, size_t... _Is, size_t... _Js, class... _Ls>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto __make_fmatrix_impl(index_sequence<_Is...>,
+                                            index_sequence<_Js...>,
+                                            _Ls... __ls) {
+    return __base::__make_farray(__make_fmatrix_impl<_Fp, _Vs...>(
+        index_sequence<_Is..., _Js>{}, __ls...)...);
+  }
+
+  template <class _Fp, class... _Vs>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto __make_fmatrix() {
+    return __make_fmatrix_impl<_Fp, _Vs...>(
+        index_sequence<>{}, make_index_sequence<decay_t<_Vs>::__size()>{}...);
+  }
+};
+
+struct __variant {
+  template <class _Visitor, class... _Vs>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr decltype(auto)
+  __visit_alt_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
+    return __base::__visit_alt_at(__index,
+                                  _VSTD::forward<_Visitor>(__visitor),
+                                  _VSTD::forward<_Vs>(__vs).__impl...);
+  }
+
+  template <class _Visitor, class... _Vs>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr decltype(auto) __visit_alt(_Visitor&& __visitor,
+                                              _Vs&&... __vs) {
+    return __base::__visit_alt(_VSTD::forward<_Visitor>(__visitor),
+                               _VSTD::forward<_Vs>(__vs).__impl...);
+  }
+
+  template <class _Visitor, class... _Vs>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr decltype(auto)
+  __visit_value_at(size_t __index, _Visitor&& __visitor, _Vs&&... __vs) {
+    return __visit_alt_at(
+        __index,
+        __make_value_visitor(_VSTD::forward<_Visitor>(__visitor)),
+        _VSTD::forward<_Vs>(__vs)...);
+  }
+
+  template <class _Visitor, class... _Vs>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr decltype(auto) __visit_value(_Visitor&& __visitor,
+                                                _Vs&&... __vs) {
+    return __visit_alt(
+        __make_value_visitor(_VSTD::forward<_Visitor>(__visitor)),
+        _VSTD::forward<_Vs>(__vs)...);
+  }
+
+private:
+  template <class _Visitor, class... _Values>
+  static constexpr void __std_visit_exhaustive_visitor_check() {
+    static_assert(is_invocable_v<_Visitor, _Values...>,
+                  "`std::visit` requires the visitor to be exhaustive.");
+  }
+
+  template <class _Visitor>
+  struct __value_visitor {
+    template <class... _Alts>
+    inline _LIBCPP_INLINE_VISIBILITY
+    constexpr decltype(auto) operator()(_Alts&&... __alts) const {
+      __std_visit_exhaustive_visitor_check<
+          _Visitor,
+          decltype((_VSTD::forward<_Alts>(__alts).__value))...>();
+      return __invoke_constexpr(_VSTD::forward<_Visitor>(__visitor),
+                                _VSTD::forward<_Alts>(__alts).__value...);
+    }
+    _Visitor&& __visitor;
+  };
+
+  template <class _Visitor>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr auto __make_value_visitor(_Visitor&& __visitor) {
+    return __value_visitor<_Visitor>{_VSTD::forward<_Visitor>(__visitor)};
+  }
+};
+
+} // namespace __visitation
+
+template <size_t _Index, class _Tp>
+struct _LIBCPP_TEMPLATE_VIS __alt {
+  using __value_type = _Tp;
+
+  template <class... _Args>
+  inline _LIBCPP_INLINE_VISIBILITY
+  explicit constexpr __alt(in_place_t, _Args&&... __args)
+      : __value(_VSTD::forward<_Args>(__args)...) {}
+
+  __value_type __value;
+};
+
+template <_Trait _DestructibleTrait, size_t _Index, class... _Types>
+union _LIBCPP_TEMPLATE_VIS __union;
+
+template <_Trait _DestructibleTrait, size_t _Index>
+union _LIBCPP_TEMPLATE_VIS __union<_DestructibleTrait, _Index> {};
+
+#define _LIBCPP_VARIANT_UNION(destructible_trait, destructor)                  \
+  template <size_t _Index, class _Tp, class... _Types>                         \
+  union _LIBCPP_TEMPLATE_VIS __union<destructible_trait,                      \
+                                      _Index,                                  \
+                                      _Tp,                                     \
+                                      _Types...> {                             \
+  public:                                                                      \
+    inline _LIBCPP_INLINE_VISIBILITY                                           \
+    explicit constexpr __union(__valueless_t) noexcept : __dummy{} {}          \
+                                                                               \
+    template <class... _Args>                                                  \
+    inline _LIBCPP_INLINE_VISIBILITY                                           \
+    explicit constexpr __union(in_place_index_t<0>, _Args&&... __args)         \
+        : __head(in_place, _VSTD::forward<_Args>(__args)...) {}                \
+                                                                               \
+    template <size_t _Ip, class... _Args>                                      \
+    inline _LIBCPP_INLINE_VISIBILITY                                           \
+    explicit constexpr __union(in_place_index_t<_Ip>, _Args&&... __args)       \
+        : __tail(in_place_index<_Ip - 1>, _VSTD::forward<_Args>(__args)...) {} \
+                                                                               \
+    __union(const __union&) = default;                                         \
+    __union(__union&&) = default;                                              \
+                                                                               \
+    destructor                                                                 \
+                                                                               \
+    __union& operator=(const __union&) = default;                              \
+    __union& operator=(__union&&) = default;                                   \
+                                                                               \
+  private:                                                                     \
+    char __dummy;                                                              \
+    __alt<_Index, _Tp> __head;                                                 \
+    __union<destructible_trait, _Index + 1, _Types...> __tail;                 \
+                                                                               \
+    friend struct __access::__union;                                           \
+  }
+
+_LIBCPP_VARIANT_UNION(_Trait::_TriviallyAvailable, ~__union() = default;);
+_LIBCPP_VARIANT_UNION(_Trait::_Available, ~__union() {});
+_LIBCPP_VARIANT_UNION(_Trait::_Unavailable, ~__union() = delete;);
+
+#undef _LIBCPP_VARIANT_UNION
+
+template <_Trait _DestructibleTrait, class... _Types>
+class _LIBCPP_TEMPLATE_VIS __base {
+public:
+  using __index_t = __variant_index_t<sizeof...(_Types)>;
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  explicit constexpr __base(__valueless_t tag) noexcept
+      : __data(tag), __index(__variant_npos<__index_t>) {}
+
+  template <size_t _Ip, class... _Args>
+  inline _LIBCPP_INLINE_VISIBILITY
+  explicit constexpr __base(in_place_index_t<_Ip>, _Args&&... __args)
+      :
+        __data(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...),
+        __index(_Ip) {}
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  constexpr bool valueless_by_exception() const noexcept {
+    return index() == variant_npos;
+  }
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  constexpr size_t index() const noexcept {
+    return __index == __variant_npos<__index_t> ? variant_npos : __index;
+  }
+
+protected:
+  inline _LIBCPP_INLINE_VISIBILITY
+  constexpr auto&& __as_base() & { return *this; }
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  constexpr auto&& __as_base() && { return _VSTD::move(*this); }
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  constexpr auto&& __as_base() const & { return *this; }
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  constexpr auto&& __as_base() const && { return _VSTD::move(*this); }
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  static constexpr size_t __size() { return sizeof...(_Types); }
+
+  __union<_DestructibleTrait, 0, _Types...> __data;
+  __index_t __index;
+
+  friend struct __access::__base;
+  friend struct __visitation::__base;
+};
+
+template <class _Traits, _Trait = _Traits::__destructible_trait>
+class _LIBCPP_TEMPLATE_VIS __destructor;
+
+#define _LIBCPP_VARIANT_DESTRUCTOR(destructible_trait, destructor, destroy)    \
+  template <class... _Types>                                                   \
+  class _LIBCPP_TEMPLATE_VIS __destructor<__traits<_Types...>,                 \
+                                           destructible_trait>                 \
+      : public __base<destructible_trait, _Types...> {                         \
+    using __base_type = __base<destructible_trait, _Types...>;                 \
+    using __index_t = typename __base_type::__index_t;                         \
+                                                                               \
+  public:                                                                      \
+    using __base_type::__base_type;                                            \
+    using __base_type::operator=;                                              \
+                                                                               \
+    __destructor(const __destructor&) = default;                               \
+    __destructor(__destructor&&) = default;                                    \
+    destructor                                                                 \
+    __destructor& operator=(const __destructor&) = default;                    \
+    __destructor& operator=(__destructor&&) = default;                         \
+                                                                               \
+  protected:                                                                   \
+    inline _LIBCPP_INLINE_VISIBILITY                                           \
+    destroy                                                                    \
+  }
+
+_LIBCPP_VARIANT_DESTRUCTOR(
+    _Trait::_TriviallyAvailable,
+    ~__destructor() = default;,
+    void __destroy() noexcept { this->__index = __variant_npos<__index_t>; });
+
+_LIBCPP_VARIANT_DESTRUCTOR(
+    _Trait::_Available,
+    ~__destructor() { __destroy(); },
+    void __destroy() noexcept {
+      if (!this->valueless_by_exception()) {
+        __visitation::__base::__visit_alt(
+            [](auto& __alt) noexcept {
+              using __alt_type = decay_t<decltype(__alt)>;
+              __alt.~__alt_type();
+            },
+            *this);
+      }
+      this->__index = __variant_npos<__index_t>;
+    });
+
+_LIBCPP_VARIANT_DESTRUCTOR(
+    _Trait::_Unavailable,
+    ~__destructor() = delete;,
+    void __destroy() noexcept = delete;);
+
+#undef _LIBCPP_VARIANT_DESTRUCTOR
+
+template <class _Traits>
+class _LIBCPP_TEMPLATE_VIS __constructor : public __destructor<_Traits> {
+  using __base_type = __destructor<_Traits>;
+
+public:
+  using __base_type::__base_type;
+  using __base_type::operator=;
+
+protected:
+  template <size_t _Ip, class _Tp, class... _Args>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static _Tp& __construct_alt(__alt<_Ip, _Tp>& __a, _Args&&... __args) {
+    ::new ((void*)_VSTD::addressof(__a))
+        __alt<_Ip, _Tp>(in_place, _VSTD::forward<_Args>(__args)...);
+    return __a.__value;
+  }
+
+  template <class _Rhs>
+  inline _LIBCPP_INLINE_VISIBILITY
+  static void __generic_construct(__constructor& __lhs, _Rhs&& __rhs) {
+    __lhs.__destroy();
+    if (!__rhs.valueless_by_exception()) {
+      __visitation::__base::__visit_alt_at(
+          __rhs.index(),
+          [](auto& __lhs_alt, auto&& __rhs_alt) {
+            __construct_alt(
+                __lhs_alt,
+                _VSTD::forward<decltype(__rhs_alt)>(__rhs_alt).__value);
+          },
+          __lhs, _VSTD::forward<_Rhs>(__rhs));
+      __lhs.__index = __rhs.index();
+    }
+  }
+};
+
+template <class _Traits, _Trait = _Traits::__move_constructible_trait>
+class _LIBCPP_TEMPLATE_VIS __move_constructor;
+
+#define _LIBCPP_VARIANT_MOVE_CONSTRUCTOR(move_constructible_trait,             \
+                                         move_constructor)                     \
+  template <class... _Types>                                                   \
+  class _LIBCPP_TEMPLATE_VIS __move_constructor<__traits<_Types...>,          \
+                                                 move_constructible_trait>     \
+      : public __constructor<__traits<_Types...>> {                            \
+    using __base_type = __constructor<__traits<_Types...>>;                    \
+                                                                               \
+  public:                                                                      \
+    using __base_type::__base_type;                                            \
+    using __base_type::operator=;                                              \
+                                                                               \
+    __move_constructor(const __move_constructor&) = default;                   \
+    move_constructor                                                           \
+    ~__move_constructor() = default;                                           \
+    __move_constructor& operator=(const __move_constructor&) = default;        \
+    __move_constructor& operator=(__move_constructor&&) = default;             \
+  }
+
+_LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
+    _Trait::_TriviallyAvailable,
+    __move_constructor(__move_constructor&& __that) = default;);
+
+_LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
+    _Trait::_Available,
+    __move_constructor(__move_constructor&& __that) noexcept(
+        __all<is_nothrow_move_constructible_v<_Types>...>::value)
+        : __move_constructor(__valueless_t{}) {
+      this->__generic_construct(*this, _VSTD::move(__that));
+    });
+
+_LIBCPP_VARIANT_MOVE_CONSTRUCTOR(
+    _Trait::_Unavailable,
+    __move_constructor(__move_constructor&&) = delete;);
+
+#undef _LIBCPP_VARIANT_MOVE_CONSTRUCTOR
+
+template <class _Traits, _Trait = _Traits::__copy_constructible_trait>
+class _LIBCPP_TEMPLATE_VIS __copy_constructor;
+
+#define _LIBCPP_VARIANT_COPY_CONSTRUCTOR(copy_constructible_trait,             \
+                                         copy_constructor)                     \
+  template <class... _Types>                                                   \
+  class _LIBCPP_TEMPLATE_VIS __copy_constructor<__traits<_Types...>,          \
+                                                 copy_constructible_trait>     \
+      : public __move_constructor<__traits<_Types...>> {                       \
+    using __base_type = __move_constructor<__traits<_Types...>>;               \
+                                                                               \
+  public:                                                                      \
+    using __base_type::__base_type;                                            \
+    using __base_type::operator=;                                              \
+                                                                               \
+    copy_constructor                                                           \
+    __copy_constructor(__copy_constructor&&) = default;                        \
+    ~__copy_constructor() = default;                                           \
+    __copy_constructor& operator=(const __copy_constructor&) = default;        \
+    __copy_constructor& operator=(__copy_constructor&&) = default;             \
+  }
+
+_LIBCPP_VARIANT_COPY_CONSTRUCTOR(
+    _Trait::_TriviallyAvailable,
+    __copy_constructor(const __copy_constructor& __that) = default;);
+
+_LIBCPP_VARIANT_COPY_CONSTRUCTOR(
+    _Trait::_Available,
+    __copy_constructor(const __copy_constructor& __that)
+        : __copy_constructor(__valueless_t{}) {
+      this->__generic_construct(*this, __that);
+    });
+
+_LIBCPP_VARIANT_COPY_CONSTRUCTOR(
+    _Trait::_Unavailable,
+    __copy_constructor(const __copy_constructor&) = delete;);
+
+#undef _LIBCPP_VARIANT_COPY_CONSTRUCTOR
+
+template <class _Traits>
+class _LIBCPP_TEMPLATE_VIS __assignment : public __copy_constructor<_Traits> {
+  using __base_type = __copy_constructor<_Traits>;
+
+public:
+  using __base_type::__base_type;
+  using __base_type::operator=;
+
+  template <size_t _Ip, class... _Args>
+  inline _LIBCPP_INLINE_VISIBILITY
+  auto& __emplace(_Args&&... __args) {
+    this->__destroy();
+    auto& __res = this->__construct_alt(__access::__base::__get_alt<_Ip>(*this),
+                          _VSTD::forward<_Args>(__args)...);
+    this->__index = _Ip;
+    return __res;
+  }
+
+protected:
+  template <size_t _Ip, class _Tp, class _Arg>
+  inline _LIBCPP_INLINE_VISIBILITY
+  void __assign_alt(__alt<_Ip, _Tp>& __a, _Arg&& __arg) {
+    if (this->index() == _Ip) {
+      __a.__value = _VSTD::forward<_Arg>(__arg);
+    } else {
+      struct {
+        void operator()(true_type) const {
+          __this->__emplace<_Ip>(_VSTD::forward<_Arg>(__arg));
+        }
+        void operator()(false_type) const {
+          __this->__emplace<_Ip>(_Tp(_VSTD::forward<_Arg>(__arg)));
+        }
+        __assignment* __this;
+        _Arg&& __arg;
+      } __impl{this, _VSTD::forward<_Arg>(__arg)};
+      __impl(bool_constant<is_nothrow_constructible_v<_Tp, _Arg> ||
+                           !is_nothrow_move_constructible_v<_Tp>>{});
+    }
+  }
+
+  template <class _That>
+  inline _LIBCPP_INLINE_VISIBILITY
+  void __generic_assign(_That&& __that) {
+    if (this->valueless_by_exception() && __that.valueless_by_exception()) {
+      // do nothing.
+    } else if (__that.valueless_by_exception()) {
+      this->__destroy();
+    } else {
+      __visitation::__base::__visit_alt_at(
+          __that.index(),
+          [this](auto& __this_alt, auto&& __that_alt) {
+            this->__assign_alt(
+                __this_alt,
+                _VSTD::forward<decltype(__that_alt)>(__that_alt).__value);
+          },
+          *this, _VSTD::forward<_That>(__that));
+    }
+  }
+};
+
+template <class _Traits, _Trait = _Traits::__move_assignable_trait>
+class _LIBCPP_TEMPLATE_VIS __move_assignment;
+
+#define _LIBCPP_VARIANT_MOVE_ASSIGNMENT(move_assignable_trait,                 \
+                                        move_assignment)                       \
+  template <class... _Types>                                                   \
+  class _LIBCPP_TEMPLATE_VIS __move_assignment<__traits<_Types...>,           \
+                                                move_assignable_trait>         \
+      : public __assignment<__traits<_Types...>> {                             \
+    using __base_type = __assignment<__traits<_Types...>>;                     \
+                                                                               \
+  public:                                                                      \
+    using __base_type::__base_type;                                            \
+    using __base_type::operator=;                                              \
+                                                                               \
+    __move_assignment(const __move_assignment&) = default;                     \
+    __move_assignment(__move_assignment&&) = default;                          \
+    ~__move_assignment() = default;                                            \
+    __move_assignment& operator=(const __move_assignment&) = default;          \
+    move_assignment                                                            \
+  }
+
+_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
+    _Trait::_TriviallyAvailable,
+    __move_assignment& operator=(__move_assignment&& __that) = default;);
+
+_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
+    _Trait::_Available,
+    __move_assignment& operator=(__move_assignment&& __that) noexcept(
+        __all<(is_nothrow_move_constructible_v<_Types> &&
+               is_nothrow_move_assignable_v<_Types>)...>::value) {
+      this->__generic_assign(_VSTD::move(__that));
+      return *this;
+    });
+
+_LIBCPP_VARIANT_MOVE_ASSIGNMENT(
+    _Trait::_Unavailable,
+    __move_assignment& operator=(__move_assignment&&) = delete;);
+
+#undef _LIBCPP_VARIANT_MOVE_ASSIGNMENT
+
+template <class _Traits, _Trait = _Traits::__copy_assignable_trait>
+class _LIBCPP_TEMPLATE_VIS __copy_assignment;
+
+#define _LIBCPP_VARIANT_COPY_ASSIGNMENT(copy_assignable_trait,                 \
+                                        copy_assignment)                       \
+  template <class... _Types>                                                   \
+  class _LIBCPP_TEMPLATE_VIS __copy_assignment<__traits<_Types...>,           \
+                                                copy_assignable_trait>         \
+      : public __move_assignment<__traits<_Types...>> {                        \
+    using __base_type = __move_assignment<__traits<_Types...>>;                \
+                                                                               \
+  public:                                                                      \
+    using __base_type::__base_type;                                            \
+    using __base_type::operator=;                                              \
+                                                                               \
+    __copy_assignment(const __copy_assignment&) = default;                     \
+    __copy_assignment(__copy_assignment&&) = default;                          \
+    ~__copy_assignment() = default;                                            \
+    copy_assignment                                                            \
+    __copy_assignment& operator=(__copy_assignment&&) = default;               \
+  }
+
+_LIBCPP_VARIANT_COPY_ASSIGNMENT(
+    _Trait::_TriviallyAvailable,
+    __copy_assignment& operator=(const __copy_assignment& __that) = default;);
+
+_LIBCPP_VARIANT_COPY_ASSIGNMENT(
+    _Trait::_Available,
+    __copy_assignment& operator=(const __copy_assignment& __that) {
+      this->__generic_assign(__that);
+      return *this;
+    });
+
+_LIBCPP_VARIANT_COPY_ASSIGNMENT(
+    _Trait::_Unavailable,
+    __copy_assignment& operator=(const __copy_assignment&) = delete;);
+
+#undef _LIBCPP_VARIANT_COPY_ASSIGNMENT
+
+template <class... _Types>
+class _LIBCPP_TEMPLATE_VIS __impl
+    : public __copy_assignment<__traits<_Types...>> {
+  using __base_type = __copy_assignment<__traits<_Types...>>;
+
+public:
+  using __base_type::__base_type;
+  using __base_type::operator=;
+
+  template <size_t _Ip, class _Arg>
+  inline _LIBCPP_INLINE_VISIBILITY
+  void __assign(_Arg&& __arg) {
+    this->__assign_alt(__access::__base::__get_alt<_Ip>(*this),
+                       _VSTD::forward<_Arg>(__arg));
+  }
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  void __swap(__impl& __that)  {
+    if (this->valueless_by_exception() && __that.valueless_by_exception()) {
+      // do nothing.
+    } else if (this->index() == __that.index()) {
+      __visitation::__base::__visit_alt_at(
+          this->index(),
+          [](auto& __this_alt, auto& __that_alt) {
+            using _VSTD::swap;
+            swap(__this_alt.__value, __that_alt.__value);
+          },
+          *this,
+          __that);
+    } else {
+      __impl* __lhs = this;
+      __impl* __rhs = _VSTD::addressof(__that);
+      if (__lhs->__move_nothrow() && !__rhs->__move_nothrow()) {
+        _VSTD::swap(__lhs, __rhs);
+      }
+      __impl __tmp(_VSTD::move(*__rhs));
+#ifndef _LIBCPP_NO_EXCEPTIONS
+      // EXTENSION: When the move construction of `__lhs` into `__rhs` throws
+      // and `__tmp` is nothrow move constructible then we move `__tmp` back
+      // into `__rhs` and provide the strong exception safety guarentee.
+      try {
+        this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
+      } catch (...) {
+        if (__tmp.__move_nothrow()) {
+          this->__generic_construct(*__rhs, _VSTD::move(__tmp));
+        }
+        throw;
+      }
+#else
+      this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
+#endif
+      this->__generic_construct(*__lhs, _VSTD::move(__tmp));
+    }
+  }
+
+private:
+  inline _LIBCPP_INLINE_VISIBILITY
+  bool __move_nothrow() const {
+    constexpr bool __results[] = {is_nothrow_move_constructible_v<_Types>...};
+    return this->valueless_by_exception() || __results[this->index()];
+  }
+};
+
+template <class... _Types>
+struct __overload;
+
+template <>
+struct __overload<> { void operator()() const; };
+
+template <class _Tp, class... _Types>
+struct __overload<_Tp, _Types...> : __overload<_Types...> {
+  using __overload<_Types...>::operator();
+  __identity<_Tp> operator()(_Tp) const;
+};
+
+template <class _Tp, class... _Types>
+using __best_match_t = typename result_of_t<__overload<_Types...>(_Tp&&)>::type;
+
+} // __variant_detail
+
+template <class... _Types>
+class _LIBCPP_TEMPLATE_VIS variant
+    : private __sfinae_ctor_base<
+          __all<is_copy_constructible_v<_Types>...>::value,
+          __all<is_move_constructible_v<_Types>...>::value>,
+      private __sfinae_assign_base<
+          __all<(is_copy_constructible_v<_Types> &&
+                 is_copy_assignable_v<_Types>)...>::value,
+          __all<(is_move_constructible_v<_Types> &&
+                 is_move_assignable_v<_Types>)...>::value> {
+  static_assert(0 < sizeof...(_Types),
+                "variant must consist of at least one alternative.");
+
+  static_assert(__all<!is_array_v<_Types>...>::value,
+                "variant can not have an array type as an alternative.");
+
+  static_assert(__all<!is_reference_v<_Types>...>::value,
+                "variant can not have a reference type as an alternative.");
+
+  static_assert(__all<!is_void_v<_Types>...>::value,
+                "variant can not have a void type as an alternative.");
+
+  using __first_type = variant_alternative_t<0, variant>;
+
+public:
+  template <bool _Dummy = true,
+            enable_if_t<__dependent_type<is_default_constructible<__first_type>,
+                                         _Dummy>::value,
+                        int> = 0>
+  inline _LIBCPP_INLINE_VISIBILITY
+  constexpr variant() noexcept(is_nothrow_default_constructible_v<__first_type>)
+      : __impl(in_place_index<0>) {}
+
+  variant(const variant&) = default;
+  variant(variant&&) = default;
+
+  template <
+      class _Arg,
+      enable_if_t<!is_same_v<decay_t<_Arg>, variant>, int> = 0,
+      enable_if_t<!__is_inplace_type<decay_t<_Arg>>::value, int> = 0,
+      enable_if_t<!__is_inplace_index<decay_t<_Arg>>::value, int> = 0,
+      class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
+      size_t _Ip =
+          __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
+      enable_if_t<is_constructible_v<_Tp, _Arg>, int> = 0>
+  inline _LIBCPP_INLINE_VISIBILITY
+  constexpr variant(_Arg&& __arg) noexcept(
+      is_nothrow_constructible_v<_Tp, _Arg>)
+      : __impl(in_place_index<_Ip>, _VSTD::forward<_Arg>(__arg)) {}
+
+  template <size_t _Ip, class... _Args,
+            class = enable_if_t<(_Ip < sizeof...(_Types)), int>,
+            class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
+            enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
+  inline _LIBCPP_INLINE_VISIBILITY
+  explicit constexpr variant(
+      in_place_index_t<_Ip>,
+      _Args&&... __args) noexcept(is_nothrow_constructible_v<_Tp, _Args...>)
+      : __impl(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...) {}
+
+  template <
+      size_t _Ip,
+      class _Up,
+      class... _Args,
+      enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
+      class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
+      enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
+                  int> = 0>
+  inline _LIBCPP_INLINE_VISIBILITY
+  explicit constexpr variant(
+      in_place_index_t<_Ip>,
+      initializer_list<_Up> __il,
+      _Args&&... __args) noexcept(
+      is_nothrow_constructible_v<_Tp, initializer_list<_Up>&, _Args...>)
+      : __impl(in_place_index<_Ip>, __il, _VSTD::forward<_Args>(__args)...) {}
+
+  template <
+      class _Tp,
+      class... _Args,
+      size_t _Ip =
+          __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
+      enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
+  inline _LIBCPP_INLINE_VISIBILITY
+  explicit constexpr variant(in_place_type_t<_Tp>, _Args&&... __args) noexcept(
+      is_nothrow_constructible_v<_Tp, _Args...>)
+      : __impl(in_place_index<_Ip>, _VSTD::forward<_Args>(__args)...) {}
+
+  template <
+      class _Tp,
+      class _Up,
+      class... _Args,
+      size_t _Ip =
+          __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
+      enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
+                  int> = 0>
+  inline _LIBCPP_INLINE_VISIBILITY
+  explicit constexpr variant(
+      in_place_type_t<_Tp>,
+      initializer_list<_Up> __il,
+      _Args&&... __args) noexcept(
+      is_nothrow_constructible_v<_Tp, initializer_list< _Up>&, _Args...>)
+      : __impl(in_place_index<_Ip>, __il, _VSTD::forward<_Args>(__args)...) {}
+
+  ~variant() = default;
+
+  variant& operator=(const variant&) = default;
+  variant& operator=(variant&&) = default;
+
+  template <
+      class _Arg,
+      enable_if_t<!is_same_v<decay_t<_Arg>, variant>, int> = 0,
+      class _Tp = __variant_detail::__best_match_t<_Arg, _Types...>,
+      size_t _Ip =
+          __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
+      enable_if_t<is_assignable_v<_Tp&, _Arg> && is_constructible_v<_Tp, _Arg>,
+                  int> = 0>
+  inline _LIBCPP_INLINE_VISIBILITY
+  variant& operator=(_Arg&& __arg) noexcept(
+      is_nothrow_assignable_v<_Tp&, _Arg> &&
+      is_nothrow_constructible_v<_Tp, _Arg>) {
+    __impl.template __assign<_Ip>(_VSTD::forward<_Arg>(__arg));
+    return *this;
+  }
+
+  template <
+      size_t _Ip,
+      class... _Args,
+      enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
+      class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
+      enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
+  inline _LIBCPP_INLINE_VISIBILITY
+  _Tp& emplace(_Args&&... __args) {
+    return __impl.template __emplace<_Ip>(_VSTD::forward<_Args>(__args)...);
+  }
+
+  template <
+      size_t _Ip,
+      class _Up,
+      class... _Args,
+      enable_if_t<(_Ip < sizeof...(_Types)), int> = 0,
+      class _Tp = variant_alternative_t<_Ip, variant<_Types...>>,
+      enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
+                  int> = 0>
+  inline _LIBCPP_INLINE_VISIBILITY
+  _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) {
+    return __impl.template __emplace<_Ip>(__il, _VSTD::forward<_Args>(__args)...);
+  }
+
+  template <
+      class _Tp,
+      class... _Args,
+      size_t _Ip =
+          __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
+      enable_if_t<is_constructible_v<_Tp, _Args...>, int> = 0>
+  inline _LIBCPP_INLINE_VISIBILITY
+  _Tp& emplace(_Args&&... __args) {
+    return __impl.template __emplace<_Ip>(_VSTD::forward<_Args>(__args)...);
+  }
+
+  template <
+      class _Tp,
+      class _Up,
+      class... _Args,
+      size_t _Ip =
+          __find_detail::__find_unambiguous_index_sfinae<_Tp, _Types...>::value,
+      enable_if_t<is_constructible_v<_Tp, initializer_list<_Up>&, _Args...>,
+                  int> = 0>
+  inline _LIBCPP_INLINE_VISIBILITY
+  _Tp& emplace(initializer_list<_Up> __il, _Args&&... __args) {
+    return __impl.template __emplace<_Ip>(__il, _VSTD::forward<_Args>(__args)...);
+  }
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  constexpr bool valueless_by_exception() const noexcept {
+    return __impl.valueless_by_exception();
+  }
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  constexpr size_t index() const noexcept { return __impl.index(); }
+
+  template <
+      bool _Dummy = true,
+      enable_if_t<
+          __all<(
+              __dependent_type<is_move_constructible<_Types>, _Dummy>::value &&
+              __dependent_type<is_swappable<_Types>, _Dummy>::value)...>::value,
+          int> = 0>
+  inline _LIBCPP_INLINE_VISIBILITY
+  void swap(variant& __that) noexcept(
+      __all<(is_nothrow_move_constructible_v<_Types> &&
+             is_nothrow_swappable_v<_Types>)...>::value) {
+    __impl.__swap(__that.__impl);
+  }
+
+private:
+  __variant_detail::__impl<_Types...> __impl;
+
+  friend struct __variant_detail::__access::__variant;
+  friend struct __variant_detail::__visitation::__variant;
+};
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool __holds_alternative(const variant<_Types...>& __v) noexcept {
+  return __v.index() == _Ip;
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool holds_alternative(const variant<_Types...>& __v) noexcept {
+  return __holds_alternative<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
+}
+
+template <size_t _Ip, class _Vp>
+inline _LIBCPP_INLINE_VISIBILITY
+static constexpr auto&& __generic_get(_Vp&& __v) {
+  using __variant_detail::__access::__variant;
+  if (!__holds_alternative<_Ip>(__v)) {
+    __throw_bad_variant_access();
+  }
+  return __variant::__get_alt<_Ip>(_VSTD::forward<_Vp>(__v)).__value;
+}
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr variant_alternative_t<_Ip, variant<_Types...>>& get(
+    variant<_Types...>& __v) {
+  static_assert(_Ip < sizeof...(_Types));
+  static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
+  return __generic_get<_Ip>(__v);
+}
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr variant_alternative_t<_Ip, variant<_Types...>>&& get(
+    variant<_Types...>&& __v) {
+  static_assert(_Ip < sizeof...(_Types));
+  static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
+  return __generic_get<_Ip>(_VSTD::move(__v));
+}
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr const variant_alternative_t<_Ip, variant<_Types...>>& get(
+    const variant<_Types...>& __v) {
+  static_assert(_Ip < sizeof...(_Types));
+  static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
+  return __generic_get<_Ip>(__v);
+}
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr const variant_alternative_t<_Ip, variant<_Types...>>&& get(
+    const variant<_Types...>&& __v) {
+  static_assert(_Ip < sizeof...(_Types));
+  static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
+  return __generic_get<_Ip>(_VSTD::move(__v));
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr _Tp& get(variant<_Types...>& __v) {
+  static_assert(!is_void_v<_Tp>);
+  return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr _Tp&& get(variant<_Types...>&& __v) {
+  static_assert(!is_void_v<_Tp>);
+  return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(
+      _VSTD::move(__v));
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr const _Tp& get(const variant<_Types...>& __v) {
+  static_assert(!is_void_v<_Tp>);
+  return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr const _Tp&& get(const variant<_Types...>&& __v) {
+  static_assert(!is_void_v<_Tp>);
+  return _VSTD::get<__find_exactly_one_t<_Tp, _Types...>::value>(
+      _VSTD::move(__v));
+}
+
+template <size_t _Ip, class _Vp>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr auto* __generic_get_if(_Vp* __v) noexcept {
+  using __variant_detail::__access::__variant;
+  return __v && __holds_alternative<_Ip>(*__v)
+             ? _VSTD::addressof(__variant::__get_alt<_Ip>(*__v).__value)
+             : nullptr;
+}
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr add_pointer_t<variant_alternative_t<_Ip, variant<_Types...>>>
+get_if(variant<_Types...>* __v) noexcept {
+  static_assert(_Ip < sizeof...(_Types));
+  static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
+  return __generic_get_if<_Ip>(__v);
+}
+
+template <size_t _Ip, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr add_pointer_t<const variant_alternative_t<_Ip, variant<_Types...>>>
+get_if(const variant<_Types...>* __v) noexcept {
+  static_assert(_Ip < sizeof...(_Types));
+  static_assert(!is_void_v<variant_alternative_t<_Ip, variant<_Types...>>>);
+  return __generic_get_if<_Ip>(__v);
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr add_pointer_t<_Tp>
+get_if(variant<_Types...>* __v) noexcept {
+  static_assert(!is_void_v<_Tp>);
+  return _VSTD::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
+}
+
+template <class _Tp, class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr add_pointer_t<const _Tp>
+get_if(const variant<_Types...>* __v) noexcept {
+  static_assert(!is_void_v<_Tp>);
+  return _VSTD::get_if<__find_exactly_one_t<_Tp, _Types...>::value>(__v);
+}
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator==(const variant<_Types...>& __lhs,
+                          const variant<_Types...>& __rhs) {
+  using __variant_detail::__visitation::__variant;
+  if (__lhs.index() != __rhs.index()) return false;
+  if (__lhs.valueless_by_exception()) return true;
+  return __variant::__visit_value_at(__lhs.index(), equal_to<>{}, __lhs, __rhs);
+}
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator!=(const variant<_Types...>& __lhs,
+                          const variant<_Types...>& __rhs) {
+  using __variant_detail::__visitation::__variant;
+  if (__lhs.index() != __rhs.index()) return true;
+  if (__lhs.valueless_by_exception()) return false;
+  return __variant::__visit_value_at(
+      __lhs.index(), not_equal_to<>{}, __lhs, __rhs);
+}
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator<(const variant<_Types...>& __lhs,
+                         const variant<_Types...>& __rhs) {
+  using __variant_detail::__visitation::__variant;
+  if (__rhs.valueless_by_exception()) return false;
+  if (__lhs.valueless_by_exception()) return true;
+  if (__lhs.index() < __rhs.index()) return true;
+  if (__lhs.index() > __rhs.index()) return false;
+  return __variant::__visit_value_at(__lhs.index(), less<>{}, __lhs, __rhs);
+}
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator>(const variant<_Types...>& __lhs,
+                         const variant<_Types...>& __rhs) {
+  using __variant_detail::__visitation::__variant;
+  if (__lhs.valueless_by_exception()) return false;
+  if (__rhs.valueless_by_exception()) return true;
+  if (__lhs.index() > __rhs.index()) return true;
+  if (__lhs.index() < __rhs.index()) return false;
+  return __variant::__visit_value_at(__lhs.index(), greater<>{}, __lhs, __rhs);
+}
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator<=(const variant<_Types...>& __lhs,
+                          const variant<_Types...>& __rhs) {
+  using __variant_detail::__visitation::__variant;
+  if (__lhs.valueless_by_exception()) return true;
+  if (__rhs.valueless_by_exception()) return false;
+  if (__lhs.index() < __rhs.index()) return true;
+  if (__lhs.index() > __rhs.index()) return false;
+  return __variant::__visit_value_at(
+      __lhs.index(), less_equal<>{}, __lhs, __rhs);
+}
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator>=(const variant<_Types...>& __lhs,
+                          const variant<_Types...>& __rhs) {
+  using __variant_detail::__visitation::__variant;
+  if (__rhs.valueless_by_exception()) return true;
+  if (__lhs.valueless_by_exception()) return false;
+  if (__lhs.index() > __rhs.index()) return true;
+  if (__lhs.index() < __rhs.index()) return false;
+  return __variant::__visit_value_at(
+      __lhs.index(), greater_equal<>{}, __lhs, __rhs);
+}
+
+template <class _Visitor, class... _Vs>
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr decltype(auto) visit(_Visitor&& __visitor, _Vs&&... __vs) {
+  using __variant_detail::__visitation::__variant;
+  bool __results[] = {__vs.valueless_by_exception()...};
+  for (bool __result : __results) {
+    if (__result) {
+      __throw_bad_variant_access();
+    }
+  }
+  return __variant::__visit_value(_VSTD::forward<_Visitor>(__visitor),
+                                  _VSTD::forward<_Vs>(__vs)...);
+}
+
+struct _LIBCPP_TEMPLATE_VIS monostate {};
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator<(monostate, monostate) noexcept { return false; }
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator>(monostate, monostate) noexcept { return false; }
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator<=(monostate, monostate) noexcept { return true; }
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator>=(monostate, monostate) noexcept { return true; }
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator==(monostate, monostate) noexcept { return true; }
+
+inline _LIBCPP_INLINE_VISIBILITY
+constexpr bool operator!=(monostate, monostate) noexcept { return false; }
+
+template <class... _Types>
+inline _LIBCPP_INLINE_VISIBILITY
+auto swap(variant<_Types...>& __lhs,
+          variant<_Types...>& __rhs) noexcept(noexcept(__lhs.swap(__rhs)))
+    -> decltype(__lhs.swap(__rhs)) {
+  __lhs.swap(__rhs);
+}
+
+template <class... _Types>
+struct _LIBCPP_TEMPLATE_VIS hash<
+    __enable_hash_helper<variant<_Types...>, remove_const_t<_Types>...>> {
+  using argument_type = variant<_Types...>;
+  using result_type = size_t;
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  result_type operator()(const argument_type& __v) const {
+    using __variant_detail::__visitation::__variant;
+    size_t __res =
+        __v.valueless_by_exception()
+               ? 299792458 // Random value chosen by the universe upon creation
+               : __variant::__visit_alt(
+                     [](const auto& __alt) {
+                       using __alt_type = decay_t<decltype(__alt)>;
+                       using __value_type = remove_const_t<
+                         typename __alt_type::__value_type>;
+                       return hash<__value_type>{}(__alt.__value);
+                     },
+                     __v);
+    return __hash_combine(__res, hash<size_t>{}(__v.index()));
+  }
+};
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS hash<monostate> {
+  using argument_type = monostate;
+  using result_type = size_t;
+
+  inline _LIBCPP_INLINE_VISIBILITY
+  result_type operator()(const argument_type&) const _NOEXCEPT {
+    return 66740831; // return a fundamentally attractive random value.
+  }
+};
+
+#endif  // _LIBCPP_STD_VER > 14
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif  // _LIBCPP_VARIANT
diff --git a/lib/libcxx/include/vector b/lib/libcxx/include/vector
index 021bbfb6643..54b1e8831d5 100644
--- a/lib/libcxx/include/vector
+++ b/lib/libcxx/include/vector
@@ -99,7 +99,7 @@ public:
     void push_back(const value_type& x);
     void push_back(value_type&& x);
     template <class... Args>
-        void emplace_back(Args&&... args);
+        reference emplace_back(Args&&... args); // reference in C++17
     void pop_back();
 
     template <class... Args> iterator emplace(const_iterator position, Args&&... args);
@@ -218,7 +218,7 @@ public:
     const_reference back() const;
 
     void push_back(const value_type& x);
-    template <class... Args> void emplace_back(Args&&... args);  // C++14
+    template <class... Args> reference emplace_back(Args&&... args);  // C++14; reference in C++17
     void pop_back();
 
     template <class... Args> iterator emplace(const_iterator position, Args&&... args);  // C++14
@@ -275,14 +275,16 @@ void swap(vector<T,Allocator>& x, vector<T,Allocator>& y)
 #include <__split_buffer>
 #include <__functional_base>
 
-#include <__undef_min_max>
-
 #include <__debug>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <bool>
@@ -290,40 +292,25 @@ class __vector_base_common
 {
 protected:
     _LIBCPP_ALWAYS_INLINE __vector_base_common() {}
-    void __throw_length_error() const;
-    void __throw_out_of_range() const;
+    _LIBCPP_NORETURN void __throw_length_error() const;
+    _LIBCPP_NORETURN void __throw_out_of_range() const;
 };
 
 template <bool __b>
 void
 __vector_base_common<__b>::__throw_length_error() const
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    throw length_error("vector");
-#else
-    assert(!"vector length_error");
-#endif
+    _VSTD::__throw_length_error("vector");
 }
 
 template <bool __b>
 void
 __vector_base_common<__b>::__throw_out_of_range() const
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    throw out_of_range("vector");
-#else
-    assert(!"vector out_of_range");
-#endif
+    _VSTD::__throw_out_of_range("vector");
 }
 
-#ifdef _LIBCPP_MSVC
-#pragma warning( push )
-#pragma warning( disable: 4231 )
-#endif // _LIBCPP_MSVC
-_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_TYPE_VIS __vector_base_common<true>)
-#ifdef _LIBCPP_MSVC
-#pragma warning( pop )
-#endif // _LIBCPP_MSVC
+_LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS __vector_base_common<true>)
 
 template <class _Tp, class _Allocator>
 class __vector_base
@@ -421,8 +408,10 @@ inline _LIBCPP_INLINE_VISIBILITY
 void
 __vector_base<_Tp, _Allocator>::__destruct_at_end(pointer __new_last) _NOEXCEPT
 {
-    while (__new_last != __end_)
-        __alloc_traits::destroy(__alloc(), _VSTD::__to_raw_pointer(--__end_));
+    pointer __soon_to_be_end = __end_;
+    while (__new_last != __soon_to_be_end)
+        __alloc_traits::destroy(__alloc(), _VSTD::__to_raw_pointer(--__soon_to_be_end));
+    __end_ = __new_last;
 }
 
 template <class _Tp, class _Allocator>
@@ -455,7 +444,7 @@ __vector_base<_Tp, _Allocator>::~__vector_base()
 }
 
 template <class _Tp, class _Allocator /* = allocator<_Tp> */>
-class _LIBCPP_TYPE_VIS_ONLY vector
+class _LIBCPP_TEMPLATE_VIS vector
     : private __vector_base<_Tp, _Allocator>
 {
 private:
@@ -533,12 +522,7 @@ public:
                                  is_constructible<
                                     value_type,
                                     typename iterator_traits<_ForwardIterator>::reference>::value>::type* = 0);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-    _LIBCPP_INLINE_VISIBILITY
-    vector(initializer_list<value_type> __il);
-    _LIBCPP_INLINE_VISIBILITY
-    vector(initializer_list<value_type> __il, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
 #if _LIBCPP_DEBUG_LEVEL >= 2
     _LIBCPP_INLINE_VISIBILITY
     ~vector()
@@ -551,7 +535,14 @@ public:
     vector(const vector& __x, const allocator_type& __a);
     _LIBCPP_INLINE_VISIBILITY
     vector& operator=(const vector& __x);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
+#ifndef _LIBCPP_CXX03_LANG
+    _LIBCPP_INLINE_VISIBILITY
+    vector(initializer_list<value_type> __il);
+
+    _LIBCPP_INLINE_VISIBILITY
+    vector(initializer_list<value_type> __il, const allocator_type& __a);
+
     _LIBCPP_INLINE_VISIBILITY
     vector(vector&& __x)
 #if _LIBCPP_STD_VER > 14
@@ -559,17 +550,18 @@ public:
 #else
         _NOEXCEPT_(is_nothrow_move_constructible<allocator_type>::value);
 #endif
+
     _LIBCPP_INLINE_VISIBILITY
     vector(vector&& __x, const allocator_type& __a);
     _LIBCPP_INLINE_VISIBILITY
     vector& operator=(vector&& __x)
         _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value));
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
     _LIBCPP_INLINE_VISIBILITY
     vector& operator=(initializer_list<value_type> __il)
         {assign(__il.begin(), __il.end()); return *this;}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
+#endif  // !_LIBCPP_CXX03_LANG
 
     template <class _InputIterator>
         typename enable_if
@@ -594,11 +586,12 @@ public:
         assign(_ForwardIterator __first, _ForwardIterator __last);
 
     void assign(size_type __n, const_reference __u);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void assign(initializer_list<value_type> __il)
         {assign(__il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif
 
     _LIBCPP_INLINE_VISIBILITY
     allocator_type get_allocator() const _NOEXCEPT
@@ -641,7 +634,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     size_type capacity() const _NOEXCEPT
         {return __base::capacity();}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool empty() const _NOEXCEPT
         {return this->__begin_ == this->__end_;}
     size_type max_size() const _NOEXCEPT;
@@ -681,26 +674,42 @@ public:
     const value_type* data() const _NOEXCEPT
         {return _VSTD::__to_raw_pointer(this->__begin_);}
 
+#ifdef _LIBCPP_CXX03_LANG
+    _LIBCPP_INLINE_VISIBILITY
+    void __emplace_back(const value_type& __x) { push_back(__x); }
+#else
+    template <class _Arg>
+    _LIBCPP_INLINE_VISIBILITY
+    void __emplace_back(_Arg&& __arg) {
+      emplace_back(_VSTD::forward<_Arg>(__arg));
+    }
+#endif
+
     _LIBCPP_INLINE_VISIBILITY void push_back(const_reference __x);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY void push_back(value_type&& __x);
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+
     template <class... _Args>
         _LIBCPP_INLINE_VISIBILITY
-        void emplace_back(_Args&&... __args);
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#if _LIBCPP_STD_VER > 14
+        reference emplace_back(_Args&&... __args);
+#else
+        void      emplace_back(_Args&&... __args);
+#endif
+#endif // !_LIBCPP_CXX03_LANG
+
     _LIBCPP_INLINE_VISIBILITY
     void pop_back();
 
     iterator insert(const_iterator __position, const_reference __x);
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+
+#ifndef _LIBCPP_CXX03_LANG
     iterator insert(const_iterator __position, value_type&& __x);
-#ifndef _LIBCPP_HAS_NO_VARIADICS
     template <class... _Args>
         iterator emplace(const_iterator __position, _Args&&... __args);
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // !_LIBCPP_CXX03_LANG
+
     iterator insert(const_iterator __position, size_type __n, const_reference __x);
     template <class _InputIterator>
         typename enable_if
@@ -723,11 +732,12 @@ public:
             iterator
         >::type
         insert(const_iterator __position, _ForwardIterator __first, _ForwardIterator __last);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     iterator insert(const_iterator __position, initializer_list<value_type> __il)
         {return insert(__position, __il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif
 
     _LIBCPP_INLINE_VISIBILITY iterator erase(const_iterator __position);
     iterator erase(const_iterator __first, const_iterator __last);
@@ -746,9 +756,9 @@ public:
 
     void swap(vector&)
 #if _LIBCPP_STD_VER >= 14
-        _NOEXCEPT;
+        _NOEXCEPT_DEBUG;
 #else
-        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value || 
+        _NOEXCEPT_DEBUG_(!__alloc_traits::propagate_on_container_swap::value ||
                     __is_nothrow_swappable<allocator_type>::value);
 #endif
 
@@ -765,6 +775,7 @@ public:
 
 private:
     _LIBCPP_INLINE_VISIBILITY void __invalidate_all_iterators();
+    _LIBCPP_INLINE_VISIBILITY void __invalidate_iterators_past(pointer __new_last);
     void allocate(size_type __n);
     void deallocate() _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY size_type __recommend(size_type __new_size) const;
@@ -794,65 +805,59 @@ private:
     _LIBCPP_INLINE_VISIBILITY
     void __destruct_at_end(pointer __new_last) _NOEXCEPT
     {
-#if _LIBCPP_DEBUG_LEVEL >= 2
-        __c_node* __c = __get_db()->__find_c_and_lock(this);
-        for (__i_node** __p = __c->end_; __p != __c->beg_; )
-        {
-            --__p;
-            const_iterator* __i = static_cast<const_iterator*>((*__p)->__i_);
-            if (__i->base() > __new_last)
-            {
-                (*__p)->__c_ = nullptr;
-                if (--__c->end_ != __p)
-                    memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
-            }
-        }
-        __get_db()->unlock();
-#endif
+        __invalidate_iterators_past(__new_last);
         size_type __old_size = size();
         __base::__destruct_at_end(__new_last);
         __annotate_shrink(__old_size);
     }
-    template <class _Up>
-        void
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
-        __push_back_slow_path(_Up&& __x);
-#else
-        __push_back_slow_path(_Up& __x);
-#endif
-#if !defined(_LIBCPP_HAS_NO_VARIADICS) && !defined(_LIBCPP_HAS_NO_RVALUE_REFERENCES)
+
+#ifndef _LIBCPP_CXX03_LANG
+    template <class _Up> void __push_back_slow_path(_Up&& __x);
+
     template <class... _Args>
-        void
-        __emplace_back_slow_path(_Args&&... __args);
+    void __emplace_back_slow_path(_Args&&... __args);
+#else
+    template <class _Up> void __push_back_slow_path(_Up& __x);
 #endif
+
     // The following functions are no-ops outside of AddressSanitizer mode.
     // We call annotatations only for the default Allocator because other allocators
     // may not meet the AddressSanitizer alignment constraints.
     // See the documentation for __sanitizer_annotate_contiguous_container for more details.
-    void __annotate_contiguous_container
-    (const void *__beg, const void *__end, const void *__old_mid, const void *__new_mid) const
-    {
 #ifndef _LIBCPP_HAS_NO_ASAN
+    void __annotate_contiguous_container(const void *__beg, const void *__end,
+                                         const void *__old_mid,
+                                         const void *__new_mid) const
+    {
+
       if (__beg && is_same<allocator_type, __default_allocator_type>::value)
         __sanitizer_annotate_contiguous_container(__beg, __end, __old_mid, __new_mid);
-#endif
     }
-
-    void __annotate_new(size_type __current_size) const
-    {
+#else
+    _LIBCPP_INLINE_VISIBILITY
+    void __annotate_contiguous_container(const void*, const void*, const void*,
+                                         const void*) const {}
+#endif
+    _LIBCPP_INLINE_VISIBILITY
+    void __annotate_new(size_type __current_size) const {
       __annotate_contiguous_container(data(), data() + capacity(),
                                       data() + capacity(), data() + __current_size);
     }
-    void __annotate_delete() const
-    {
+
+    _LIBCPP_INLINE_VISIBILITY
+    void __annotate_delete() const {
       __annotate_contiguous_container(data(), data() + capacity(),
                                       data() + size(), data() + capacity());
     }
+
+    _LIBCPP_INLINE_VISIBILITY
     void __annotate_increase(size_type __n) const
     {
       __annotate_contiguous_container(data(), data() + capacity(),
                                       data() + size(), data() + size() + __n);
     }
+
+    _LIBCPP_INLINE_VISIBILITY
     void __annotate_shrink(size_type __old_size) const
     {
       __annotate_contiguous_container(data(), data() + capacity(),
@@ -877,8 +882,9 @@ private:
     };
 #else
     struct __RAII_IncreaseAnnotator {
-      inline __RAII_IncreaseAnnotator(const vector &, size_type __n = 1) {}
-      inline void __done() {}
+      _LIBCPP_INLINE_VISIBILITY
+      __RAII_IncreaseAnnotator(const vector &, size_type = 1) {}
+      _LIBCPP_INLINE_VISIBILITY void __done() {}
     };
 #endif
 
@@ -949,7 +955,8 @@ template <class _Tp, class _Allocator>
 typename vector<_Tp, _Allocator>::size_type
 vector<_Tp, _Allocator>::max_size() const _NOEXCEPT
 {
-    return _VSTD::min<size_type>(__alloc_traits::max_size(this->__alloc()), numeric_limits<size_type>::max() / 2);  // end() >= begin(), always
+    return _VSTD::min<size_type>(__alloc_traits::max_size(this->__alloc()),
+                                 numeric_limits<difference_type>::max());
 }
 
 //  Precondition:  __new_size > capacity()
@@ -1132,7 +1139,7 @@ vector<_Tp, _Allocator>::vector(_InputIterator __first,
     __get_db()->__insert_c(this);
 #endif
     for (; __first != __last; ++__first)
-        push_back(*__first);
+        __emplace_back(*__first);
 }
 
 template <class _Tp, class _Allocator>
@@ -1149,7 +1156,7 @@ vector<_Tp, _Allocator>::vector(_InputIterator __first, _InputIterator __last, c
     __get_db()->__insert_c(this);
 #endif
     for (; __first != __last; ++__first)
-        push_back(*__first);
+        __emplace_back(*__first);
 }
 
 template <class _Tp, class _Allocator>
@@ -1222,7 +1229,7 @@ vector<_Tp, _Allocator>::vector(const vector& __x, const allocator_type& __a)
     }
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1269,8 +1276,6 @@ vector<_Tp, _Allocator>::vector(vector&& __x, const allocator_type& __a)
     }
 }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Tp, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 vector<_Tp, _Allocator>::vector(initializer_list<value_type> __il)
@@ -1300,8 +1305,6 @@ vector<_Tp, _Allocator>::vector(initializer_list<value_type> __il, const allocat
     }
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
-
 template <class _Tp, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
 vector<_Tp, _Allocator>&
@@ -1343,7 +1346,7 @@ vector<_Tp, _Allocator>::__move_assign(vector& __c, true_type)
 #endif
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // !_LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1373,7 +1376,7 @@ vector<_Tp, _Allocator>::assign(_InputIterator __first, _InputIterator __last)
 {
     clear();
     for (; __first != __last; ++__first)
-        push_back(*__first);
+        __emplace_back(*__first);
 }
 
 template <class _Tp, class _Allocator>
@@ -1411,6 +1414,7 @@ vector<_Tp, _Allocator>::assign(_ForwardIterator __first, _ForwardIterator __las
         allocate(__recommend(__new_size));
         __construct_at_end(__first, __last, __new_size);
     }
+    __invalidate_all_iterators();
 }
 
 template <class _Tp, class _Allocator>
@@ -1432,6 +1436,7 @@ vector<_Tp, _Allocator>::assign(size_type __n, const_reference __u)
         allocate(__recommend(static_cast<size_type>(__n)));
         __construct_at_end(__n, __u);
     }
+    __invalidate_all_iterators();
 }
 
 template <class _Tp, class _Allocator>
@@ -1563,7 +1568,7 @@ vector<_Tp, _Allocator>::shrink_to_fit() _NOEXCEPT
 template <class _Tp, class _Allocator>
 template <class _Up>
 void
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 vector<_Tp, _Allocator>::__push_back_slow_path(_Up&& __x)
 #else
 vector<_Tp, _Allocator>::__push_back_slow_path(_Up& __x)
@@ -1594,7 +1599,7 @@ vector<_Tp, _Allocator>::push_back(const_reference __x)
         __push_back_slow_path(__x);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -1614,8 +1619,6 @@ vector<_Tp, _Allocator>::push_back(value_type&& __x)
         __push_back_slow_path(_VSTD::move(__x));
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
 template <class _Tp, class _Allocator>
 template <class... _Args>
 void
@@ -1632,7 +1635,11 @@ vector<_Tp, _Allocator>::__emplace_back_slow_path(_Args&&... __args)
 template <class _Tp, class _Allocator>
 template <class... _Args>
 inline
+#if _LIBCPP_STD_VER > 14
+typename vector<_Tp, _Allocator>::reference
+#else
 void
+#endif
 vector<_Tp, _Allocator>::emplace_back(_Args&&... __args)
 {
     if (this->__end_ < this->__end_cap())
@@ -1646,10 +1653,12 @@ vector<_Tp, _Allocator>::emplace_back(_Args&&... __args)
     }
     else
         __emplace_back_slow_path(_VSTD::forward<_Args>(__args)...);
+#if _LIBCPP_STD_VER > 14
+    return this->back();
+#endif
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // !_LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 inline
@@ -1674,8 +1683,9 @@ vector<_Tp, _Allocator>::erase(const_iterator __position)
         "vector::erase(iterator) called with a non-dereferenceable iterator");
     difference_type __ps = __position - cbegin();
     pointer __p = this->__begin_ + __ps;
-    iterator __r = __make_iter(__p);
     this->__destruct_at_end(_VSTD::move(__p + 1, this->__end_, __p));
+    this->__invalidate_iterators_past(__p-1);
+    iterator __r = __make_iter(__p);
     return __r;
 }
 
@@ -1687,12 +1697,17 @@ vector<_Tp, _Allocator>::erase(const_iterator __first, const_iterator __last)
     _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__first) == this,
         "vector::erase(iterator,  iterator) called with an iterator not"
         " referring to this vector");
+    _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__last) == this,
+        "vector::erase(iterator,  iterator) called with an iterator not"
+        " referring to this vector");
 #endif
     _LIBCPP_ASSERT(__first <= __last, "vector::erase(first, last) called with invalid range");
     pointer __p = this->__begin_ + (__first - begin());
-    iterator __r = __make_iter(__p);
-    if (__first != __last)
+    if (__first != __last) {
         this->__destruct_at_end(_VSTD::move(__p + (__last - __first), this->__end_, __p));
+        this->__invalidate_iterators_past(__p - 1);
+    }
+    iterator __r = __make_iter(__p);
     return __r;
 }
 
@@ -1748,7 +1763,7 @@ vector<_Tp, _Allocator>::insert(const_iterator __position, const_reference __x)
     return __make_iter(__p);
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 typename vector<_Tp, _Allocator>::iterator
@@ -1787,8 +1802,6 @@ vector<_Tp, _Allocator>::insert(const_iterator __position, value_type&& __x)
     return __make_iter(__p);
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
 template <class _Tp, class _Allocator>
 template <class... _Args>
 typename vector<_Tp, _Allocator>::iterator
@@ -1828,8 +1841,7 @@ vector<_Tp, _Allocator>::emplace(const_iterator __position, _Args&&... __args)
     return __make_iter(__p);
 }
 
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // !_LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Allocator>
 typename vector<_Tp, _Allocator>::iterator
@@ -2013,9 +2025,9 @@ template <class _Tp, class _Allocator>
 void
 vector<_Tp, _Allocator>::swap(vector& __x)
 #if _LIBCPP_STD_VER >= 14
-    _NOEXCEPT
+    _NOEXCEPT_DEBUG
 #else
-    _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value || 
+    _NOEXCEPT_DEBUG_(!__alloc_traits::propagate_on_container_swap::value ||
                 __is_nothrow_swappable<allocator_type>::value)
 #endif
 {
@@ -2026,7 +2038,7 @@ vector<_Tp, _Allocator>::swap(vector& __x)
     _VSTD::swap(this->__begin_, __x.__begin_);
     _VSTD::swap(this->__end_, __x.__end_);
     _VSTD::swap(this->__end_cap(), __x.__end_cap());
-    __swap_allocator(this->__alloc(), __x.__alloc(), 
+    __swap_allocator(this->__alloc(), __x.__alloc(),
         integral_constant<bool,__alloc_traits::propagate_on_container_swap::value>());
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __get_db()->swap(this, &__x);
@@ -2098,6 +2110,28 @@ vector<_Tp, _Allocator>::__invalidate_all_iterators()
 #endif  // _LIBCPP_DEBUG_LEVEL >= 2
 }
 
+
+template <class _Tp, class _Allocator>
+inline _LIBCPP_INLINE_VISIBILITY
+void
+vector<_Tp, _Allocator>::__invalidate_iterators_past(pointer __new_last) {
+#if _LIBCPP_DEBUG_LEVEL >= 2
+  __c_node* __c = __get_db()->__find_c_and_lock(this);
+  for (__i_node** __p = __c->end_; __p != __c->beg_; ) {
+    --__p;
+    const_iterator* __i = static_cast<const_iterator*>((*__p)->__i_);
+    if (__i->base() > __new_last) {
+      (*__p)->__c_ = nullptr;
+      if (--__c->end_ != __p)
+        memmove(__p, __p+1, (__c->end_ - __p)*sizeof(__i_node*));
+    }
+  }
+  __get_db()->unlock();
+#else
+  ((void)__new_last);
+#endif
+}
+
 // vector<bool>
 
 template <class _Allocator> class vector<bool, _Allocator>;
@@ -2111,7 +2145,7 @@ struct __has_storage_type<vector<bool, _Allocator> >
 };
 
 template <class _Allocator>
-class _LIBCPP_TYPE_VIS_ONLY vector<bool, _Allocator>
+class _LIBCPP_TEMPLATE_VIS vector<bool, _Allocator>
     : private __vector_base_common<true>
 {
 public:
@@ -2199,12 +2233,11 @@ public:
     vector(const vector& __v);
     vector(const vector& __v, const allocator_type& __a);
     vector& operator=(const vector& __v);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
+#ifndef _LIBCPP_CXX03_LANG
     vector(initializer_list<value_type> __il);
     vector(initializer_list<value_type> __il, const allocator_type& __a);
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     vector(vector&& __v)
 #if _LIBCPP_STD_VER > 14
@@ -2216,12 +2249,12 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     vector& operator=(vector&& __v)
         _NOEXCEPT_((__noexcept_move_assign_container<_Allocator, __alloc_traits>::value));
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
     _LIBCPP_INLINE_VISIBILITY
     vector& operator=(initializer_list<value_type> __il)
         {assign(__il.begin(), __il.end()); return *this;}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
+#endif  // !_LIBCPP_CXX03_LANG
 
     template <class _InputIterator>
         typename enable_if
@@ -2240,11 +2273,12 @@ public:
         assign(_ForwardIterator __first, _ForwardIterator __last);
 
     void assign(size_type __n, const value_type& __x);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     void assign(initializer_list<value_type> __il)
         {assign(__il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif
 
     _LIBCPP_INLINE_VISIBILITY allocator_type get_allocator() const _NOEXCEPT
         {return allocator_type(this->__alloc());}
@@ -2256,7 +2290,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     size_type size() const _NOEXCEPT
         {return __size_;}
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_AFTER_CXX17 _LIBCPP_INLINE_VISIBILITY
     bool empty() const _NOEXCEPT
         {return __size_ == 0;}
     void reserve(size_type __n);
@@ -2314,8 +2348,17 @@ public:
     void push_back(const value_type& __x);
 #if _LIBCPP_STD_VER > 11
     template <class... _Args>
-    _LIBCPP_INLINE_VISIBILITY void emplace_back(_Args&&... __args)
-        { push_back ( value_type ( _VSTD::forward<_Args>(__args)... )); }
+#if _LIBCPP_STD_VER > 14
+    _LIBCPP_INLINE_VISIBILITY reference emplace_back(_Args&&... __args)
+#else
+    _LIBCPP_INLINE_VISIBILITY void      emplace_back(_Args&&... __args)
+#endif
+    {
+        push_back ( value_type ( _VSTD::forward<_Args>(__args)... ));
+#if _LIBCPP_STD_VER > 14
+        return this->back();
+#endif
+    }
 #endif
 
     _LIBCPP_INLINE_VISIBILITY void pop_back() {--__size_;}
@@ -2344,11 +2387,12 @@ public:
             iterator
         >::type
         insert(const_iterator __position, _ForwardIterator __first, _ForwardIterator __last);
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+
+#ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     iterator insert(const_iterator __position, initializer_list<value_type> __il)
         {return insert(__position, __il.begin(), __il.end());}
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif
 
     _LIBCPP_INLINE_VISIBILITY iterator erase(const_iterator __position);
     iterator erase(const_iterator __first, const_iterator __last);
@@ -2360,7 +2404,7 @@ public:
 #if _LIBCPP_STD_VER >= 14
         _NOEXCEPT;
 #else
-        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value || 
+        _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value ||
                     __is_nothrow_swappable<allocator_type>::value);
 #endif
     static void swap(reference __x, reference __y) _NOEXCEPT { _VSTD::swap(__x, __y); }
@@ -2448,7 +2492,7 @@ private:
     friend class __bit_iterator<vector, false>;
     friend class __bit_iterator<vector, true>;
     friend struct __bit_array<vector>;
-    friend struct _LIBCPP_TYPE_VIS_ONLY hash<vector>;
+    friend struct _LIBCPP_TEMPLATE_VIS hash<vector>;
 };
 
 template <class _Allocator>
@@ -2708,7 +2752,7 @@ vector<bool, _Allocator>::vector(_ForwardIterator __first, _ForwardIterator __la
     }
 }
 
-#ifndef _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Allocator>
 vector<bool, _Allocator>::vector(initializer_list<value_type> __il)
@@ -2738,7 +2782,7 @@ vector<bool, _Allocator>::vector(initializer_list<value_type> __il, const alloca
     }
 }
 
-#endif  // _LIBCPP_HAS_NO_GENERALIZED_INITIALIZERS
+#endif  // _LIBCPP_CXX03_LANG
 
 template <class _Allocator>
 vector<bool, _Allocator>::~vector()
@@ -2795,7 +2839,7 @@ vector<bool, _Allocator>::operator=(const vector& __v)
     return *this;
 }
 
-#ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#ifndef _LIBCPP_CXX03_LANG
 
 template <class _Allocator>
 inline _LIBCPP_INLINE_VISIBILITY
@@ -2870,7 +2914,7 @@ vector<bool, _Allocator>::__move_assign(vector& __c, true_type)
     __c.__cap() = __c.__size_ = 0;
 }
 
-#endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
+#endif  // !_LIBCPP_CXX03_LANG
 
 template <class _Allocator>
 void
@@ -2891,6 +2935,7 @@ vector<bool, _Allocator>::assign(size_type __n, const value_type& __x)
         }
         _VSTD::fill_n(begin(), __n, __x);
     }
+  __invalidate_all_iterators();
 }
 
 template <class _Allocator>
@@ -2918,7 +2963,9 @@ typename enable_if
 vector<bool, _Allocator>::assign(_ForwardIterator __first, _ForwardIterator __last)
 {
     clear();
-    difference_type __n = _VSTD::distance(__first, __last);
+    difference_type __ns = _VSTD::distance(__first, __last);
+    _LIBCPP_ASSERT(__ns >= 0, "invalid range specified");
+    const size_t __n = static_cast<size_type>(__ns);
     if (__n)
     {
         if (__n > capacity())
@@ -3097,7 +3144,9 @@ typename enable_if
 >::type
 vector<bool, _Allocator>::insert(const_iterator __position, _ForwardIterator __first, _ForwardIterator __last)
 {
-    difference_type __n = _VSTD::distance(__first, __last);
+    const difference_type __n_signed = _VSTD::distance(__first, __last);
+    _LIBCPP_ASSERT(__n_signed >= 0, "invalid range specified");
+    const size_type __n = static_cast<size_type>(__n_signed);
     iterator __r;
     size_type __c = capacity();
     if (__n <= __c && size() <= __c - __n)
@@ -3148,14 +3197,14 @@ vector<bool, _Allocator>::swap(vector& __x)
 #if _LIBCPP_STD_VER >= 14
     _NOEXCEPT
 #else
-    _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value || 
+    _NOEXCEPT_(!__alloc_traits::propagate_on_container_swap::value ||
                 __is_nothrow_swappable<allocator_type>::value)
 #endif
 {
     _VSTD::swap(this->__begin_, __x.__begin_);
     _VSTD::swap(this->__size_, __x.__size_);
     _VSTD::swap(this->__cap(), __x.__cap());
-    __swap_allocator(this->__alloc(), __x.__alloc(), 
+    __swap_allocator(this->__alloc(), __x.__alloc(),
         integral_constant<bool, __alloc_traits::propagate_on_container_swap::value>());
 }
 
@@ -3246,7 +3295,7 @@ vector<bool, _Allocator>::__hash_code() const _NOEXCEPT
 }
 
 template <class _Allocator>
-struct _LIBCPP_TYPE_VIS_ONLY hash<vector<bool, _Allocator> >
+struct _LIBCPP_TEMPLATE_VIS hash<vector<bool, _Allocator> >
     : public unary_function<vector<bool, _Allocator>, size_t>
 {
     _LIBCPP_INLINE_VISIBILITY
@@ -3314,4 +3363,6 @@ swap(vector<_Tp, _Allocator>& __x, vector<_Tp, _Allocator>& __y)
 
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_VECTOR
diff --git a/lib/libcxx/include/wchar.h b/lib/libcxx/include/wchar.h
index c0c6ef754fb..f74fe6ddcff 100644
--- a/lib/libcxx/include/wchar.h
+++ b/lib/libcxx/include/wchar.h
@@ -125,6 +125,10 @@ size_t wcsrtombs(char* restrict dst, const wchar_t** restrict src, size_t len,
 #  if __GLIBC_PREREQ(2, 10)
 #    define _LIBCPP_WCHAR_H_HAS_CONST_OVERLOADS 1
 #  endif
+#elif defined(_LIBCPP_MSVCRT)
+#  if defined(_CRT_CONST_CORRECT_OVERLOADS)
+#    define _LIBCPP_WCHAR_H_HAS_CONST_OVERLOADS 1
+#  endif
 #endif
 
 #if defined(__cplusplus) && !defined(_LIBCPP_WCHAR_H_HAS_CONST_OVERLOADS) && defined(_LIBCPP_PREFERRED_OVERLOAD)
@@ -166,9 +170,12 @@ inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_PREFERRED_OVERLOAD
 }
 #endif
 
-#if defined(__cplusplus) && (defined(_LIBCPP_MSVCRT) || defined(__MINGW32__))
-extern "C++" {
-#include <support/win32/support.h> // pull in *swprintf defines
+#if defined(__cplusplus) && defined(_LIBCPP_MSVCRT_LIKE)
+extern "C" {
+size_t mbsnrtowcs(wchar_t *__restrict dst, const char **__restrict src,
+                  size_t nmc, size_t len, mbstate_t *__restrict ps);
+size_t wcsnrtombs(char *__restrict dst, const wchar_t **__restrict src,
+                  size_t nwc, size_t len, mbstate_t *__restrict ps);
 }  // extern "C++"
 #endif  // __cplusplus && _LIBCPP_MSVCRT