import of libc++ 6.0.0

43 files changed, 2711 insertions, 1185 deletions

diff --git a/lib/libcxx/src/algorithm.cpp b/lib/libcxx/src/algorithm.cpp
index e9752b0653e..f036eb7abe1 100644
--- a/lib/libcxx/src/algorithm.cpp
+++ b/lib/libcxx/src/algorithm.cpp
@@ -48,7 +48,7 @@ template bool __insertion_sort_incomplete<__less<long double>&, long double*>(lo
 template unsigned __sort5<__less<long double>&, long double*>(long double*, long double*, long double*, long double*, long double*, __less<long double>&);
 
 #ifndef _LIBCPP_HAS_NO_THREADS
-static __libcpp_mutex_t __rs_mut = _LIBCPP_MUTEX_INITIALIZER;
+_LIBCPP_SAFE_STATIC static __libcpp_mutex_t __rs_mut = _LIBCPP_MUTEX_INITIALIZER;
 #endif
 unsigned __rs_default::__c_ = 0;
 
diff --git a/lib/libcxx/src/any.cpp b/lib/libcxx/src/any.cpp
index f7768457890..45b2337eb35 100644
--- a/lib/libcxx/src/any.cpp
+++ b/lib/libcxx/src/any.cpp
@@ -7,12 +7,17 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "any"
 #include "experimental/any"
 
-_LIBCPP_BEGIN_NAMESPACE_LFTS
-
+namespace std {
 const char* bad_any_cast::what() const _NOEXCEPT {
     return "bad any cast";
 }
+}
 
+_LIBCPP_BEGIN_NAMESPACE_LFTS
+const char* bad_any_cast::what() const _NOEXCEPT {
+    return "bad any cast";
+}
 _LIBCPP_END_NAMESPACE_LFTS
diff --git a/lib/libcxx/src/chrono.cpp b/lib/libcxx/src/chrono.cpp
index 62149fbf420..d0e184ad32f 100644
--- a/lib/libcxx/src/chrono.cpp
+++ b/lib/libcxx/src/chrono.cpp
@@ -12,14 +12,45 @@
 #include "system_error"  // __throw_system_error
 #include <time.h>        // clock_gettime, CLOCK_MONOTONIC and CLOCK_REALTIME
 
-#if !defined(CLOCK_REALTIME)
-#include <sys/time.h>        // for gettimeofday and timeval
+#if (__APPLE__)
+#if defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__)
+#if __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ >= 101200
+#define _LIBCXX_USE_CLOCK_GETTIME
+#endif
+#elif defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__)
+#if __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ >= 100000
+#define _LIBCXX_USE_CLOCK_GETTIME
+#endif
+#elif defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__)
+#if __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ >= 100000
+#define _LIBCXX_USE_CLOCK_GETTIME
+#endif
+#elif defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__)
+#if __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ >= 30000
+#define _LIBCXX_USE_CLOCK_GETTIME
+#endif
+#endif // __ENVIRONMENT_.*_VERSION_MIN_REQUIRED__
+#else
+#define _LIBCXX_USE_CLOCK_GETTIME
+#endif // __APPLE__
+
+#if defined(_LIBCPP_WIN32API)
+#define WIN32_LEAN_AND_MEAN
+#define VC_EXTRA_LEAN
+#include <windows.h>
+#if _WIN32_WINNT >= _WIN32_WINNT_WIN8
+#include <winapifamily.h>
 #endif
+#else
+#if !defined(CLOCK_REALTIME) || !defined(_LIBCXX_USE_CLOCK_GETTIME)
+#include <sys/time.h>        // for gettimeofday and timeval
+#endif // !defined(CLOCK_REALTIME)
+#endif // defined(_LIBCPP_WIN32API)
 
-#if !defined(_LIBCPP_HAS_NO_MONOTONIC_CLOCK) && !defined(CLOCK_MONOTONIC)
+#if !defined(_LIBCPP_HAS_NO_MONOTONIC_CLOCK)
 #if __APPLE__
 #include <mach/mach_time.h>  // mach_absolute_time, mach_timebase_info_data_t
-#else
+#elif !defined(_LIBCPP_WIN32API) && !defined(CLOCK_MONOTONIC)
 #error "Monotonic clock not implemented"
 #endif
 #endif
@@ -36,16 +67,42 @@ const bool system_clock::is_steady;
 system_clock::time_point
 system_clock::now() _NOEXCEPT
 {
-#ifdef CLOCK_REALTIME
+#if defined(_LIBCPP_WIN32API)
+  // FILETIME is in 100ns units
+  using filetime_duration =
+      _VSTD::chrono::duration<__int64,
+                              _VSTD::ratio_multiply<_VSTD::ratio<100, 1>,
+                                                    nanoseconds::period>>;
+
+  // The Windows epoch is Jan 1 1601, the Unix epoch Jan 1 1970.
+  static _LIBCPP_CONSTEXPR const seconds nt_to_unix_epoch{11644473600};
+
+  FILETIME ft;
+#if _WIN32_WINNT >= _WIN32_WINNT_WIN8
+#if WINAPI_FAMILY_PARTITION(WINAPI_PARTITION_DESKTOP)
+  GetSystemTimePreciseAsFileTime(&ft);
+#else
+  GetSystemTimeAsFileTime(&ft);
+#endif
+#else
+  GetSystemTimeAsFileTime(&ft);
+#endif
+
+  filetime_duration d{(static_cast<__int64>(ft.dwHighDateTime) << 32) |
+                       static_cast<__int64>(ft.dwLowDateTime)};
+  return time_point(duration_cast<duration>(d - nt_to_unix_epoch));
+#else
+#if defined(_LIBCXX_USE_CLOCK_GETTIME) && defined(CLOCK_REALTIME)
     struct timespec tp;
     if (0 != clock_gettime(CLOCK_REALTIME, &tp))
         __throw_system_error(errno, "clock_gettime(CLOCK_REALTIME) failed");
     return time_point(seconds(tp.tv_sec) + microseconds(tp.tv_nsec / 1000));
-#else  // !CLOCK_REALTIME
+#else
     timeval tv;
     gettimeofday(&tv, 0);
     return time_point(seconds(tv.tv_sec) + microseconds(tv.tv_usec));
-#endif  // CLOCK_REALTIME
+#endif // _LIBCXX_USE_CLOCK_GETTIME && CLOCK_REALTIME
+#endif
 }
 
 time_t
@@ -69,19 +126,20 @@ system_clock::from_time_t(time_t t) _NOEXCEPT
 
 const bool steady_clock::is_steady;
 
-#ifdef CLOCK_MONOTONIC
+#if defined(__APPLE__)
 
+// Darwin libc versions >= 1133 provide ns precision via CLOCK_UPTIME_RAW
+#if defined(_LIBCXX_USE_CLOCK_GETTIME) && defined(CLOCK_UPTIME_RAW)
 steady_clock::time_point
 steady_clock::now() _NOEXCEPT
 {
     struct timespec tp;
-    if (0 != clock_gettime(CLOCK_MONOTONIC, &tp))
-        __throw_system_error(errno, "clock_gettime(CLOCK_MONOTONIC) failed");
+    if (0 != clock_gettime(CLOCK_UPTIME_RAW, &tp))
+        __throw_system_error(errno, "clock_gettime(CLOCK_UPTIME_RAW) failed");
     return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec));
 }
 
-#elif defined(__APPLE__)
-
+#else
 //   mach_absolute_time() * MachInfo.numer / MachInfo.denom is the number of
 //   nanoseconds since the computer booted up.  MachInfo.numer and MachInfo.denom
 //   are run time constants supplied by the OS.  This clock has no relationship
@@ -90,8 +148,6 @@ steady_clock::now() _NOEXCEPT
 // MachInfo.numer / MachInfo.denom is often 1 on the latest equipment.  Specialize
 //   for that case as an optimization.
 
-#pragma GCC visibility push(hidden)
-
 static
 steady_clock::rep
 steady_simplified()
@@ -129,14 +185,46 @@ init_steady_clock()
     return &steady_full;
 }
 
-#pragma GCC visibility pop
-
 steady_clock::time_point
 steady_clock::now() _NOEXCEPT
 {
     static FP fp = init_steady_clock();
     return time_point(duration(fp()));
 }
+#endif // defined(_LIBCXX_USE_CLOCK_GETTIME) && defined(CLOCK_UPTIME_RAW)
+
+#elif defined(_LIBCPP_WIN32API)
+
+steady_clock::time_point
+steady_clock::now() _NOEXCEPT
+{
+  static LARGE_INTEGER freq;
+  static BOOL initialized = FALSE;
+  if (!initialized)
+    initialized = QueryPerformanceFrequency(&freq); // always succceeds
+
+  LARGE_INTEGER counter;
+  QueryPerformanceCounter(&counter);
+  return time_point(duration(counter.QuadPart * nano::den / freq.QuadPart));
+}
+
+#elif defined(CLOCK_MONOTONIC)
+
+// On Apple platforms only CLOCK_UPTIME_RAW or mach_absolute_time are able to
+// time functions in the nanosecond range. Thus, they are the only acceptable
+// implementations of steady_clock.
+#ifdef __APPLE__
+#error "Never use CLOCK_MONOTONIC for steady_clock::now on Apple platforms"
+#endif
+
+steady_clock::time_point
+steady_clock::now() _NOEXCEPT
+{
+    struct timespec tp;
+    if (0 != clock_gettime(CLOCK_MONOTONIC, &tp))
+        __throw_system_error(errno, "clock_gettime(CLOCK_MONOTONIC) failed");
+    return time_point(seconds(tp.tv_sec) + nanoseconds(tp.tv_nsec));
+}
 
 #else
 #error "Monotonic clock not implemented"
diff --git a/lib/libcxx/src/condition_variable.cpp b/lib/libcxx/src/condition_variable.cpp
index bfb4bf3925f..2200aefb804 100644
--- a/lib/libcxx/src/condition_variable.cpp
+++ b/lib/libcxx/src/condition_variable.cpp
@@ -14,7 +14,7 @@
 #include "condition_variable"
 #include "thread"
 #include "system_error"
-#include "cassert"
+#include "__undef_macros"
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
@@ -79,6 +79,12 @@ condition_variable::__do_timed_wait(unique_lock<mutex>& lk,
 void
 notify_all_at_thread_exit(condition_variable& cond, unique_lock<mutex> lk)
 {
+    auto& tl_ptr = __thread_local_data();
+    // If this thread was not created using std::thread then it will not have
+    // previously allocated.
+    if (tl_ptr.get() == nullptr) {
+        tl_ptr.set_pointer(new __thread_struct);
+    }
     __thread_local_data()->notify_all_at_thread_exit(&cond, lk.release());
 }
 
diff --git a/lib/libcxx/src/debug.cpp b/lib/libcxx/src/debug.cpp
index b1a16e6e72d..f2fc1ceb495 100644
--- a/lib/libcxx/src/debug.cpp
+++ b/lib/libcxx/src/debug.cpp
@@ -7,16 +7,79 @@
 //
 //===----------------------------------------------------------------------===//
 
-#define _LIBCPP_DEBUG 1
 #include "__config"
 #include "__debug"
 #include "functional"
 #include "algorithm"
+#include "string"
+#include "cstdio"
 #include "__hash_table"
 #include "mutex"
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+static std::string make_what_str(__libcpp_debug_info const& info) {
+  string msg = info.__file_;
+  msg += ":" + to_string(info.__line_) + ": _LIBCPP_ASSERT '";
+  msg += info.__pred_;
+  msg += "' failed. ";
+  msg += info.__msg_;
+  return msg;
+}
+
+_LIBCPP_SAFE_STATIC __libcpp_debug_function_type
+    __libcpp_debug_function = __libcpp_abort_debug_function;
+
+bool __libcpp_set_debug_function(__libcpp_debug_function_type __func) {
+  __libcpp_debug_function = __func;
+  return true;
+}
+
+_LIBCPP_NORETURN void __libcpp_abort_debug_function(__libcpp_debug_info const& info) {
+  std::fprintf(stderr, "%s\n", make_what_str(info).c_str());
+  std::abort();
+}
+
+_LIBCPP_NORETURN void __libcpp_throw_debug_function(__libcpp_debug_info const& info) {
+#ifndef _LIBCPP_NO_EXCEPTIONS
+  throw __libcpp_debug_exception(info);
+#else
+  __libcpp_abort_debug_function(info);
+#endif
+}
+
+struct __libcpp_debug_exception::__libcpp_debug_exception_imp {
+  __libcpp_debug_info __info_;
+  std::string __what_str_;
+};
+
+__libcpp_debug_exception::__libcpp_debug_exception() _NOEXCEPT
+    : __imp_(nullptr) {
+}
+
+__libcpp_debug_exception::__libcpp_debug_exception(
+    __libcpp_debug_info const& info) : __imp_(new __libcpp_debug_exception_imp)
+{
+  __imp_->__info_ = info;
+  __imp_->__what_str_ = make_what_str(info);
+}
+__libcpp_debug_exception::__libcpp_debug_exception(
+    __libcpp_debug_exception const& other) : __imp_(nullptr) {
+  if (other.__imp_)
+    __imp_ = new __libcpp_debug_exception_imp(*other.__imp_);
+}
+
+__libcpp_debug_exception::~__libcpp_debug_exception() _NOEXCEPT {
+  if (__imp_)
+    delete __imp_;
+}
+
+const char* __libcpp_debug_exception::what() const _NOEXCEPT {
+  if (__imp_)
+    return __imp_->__what_str_.c_str();
+  return "__libcpp_debug_exception";
+}
+
 _LIBCPP_FUNC_VIS
 __libcpp_db*
 __get_db()
@@ -152,11 +215,8 @@ __libcpp_db::__insert_c(void* __c)
         size_t nc = __next_prime(2*static_cast<size_t>(__cend_ - __cbeg_) + 1);
         __c_node** cbeg = static_cast<__c_node**>(calloc(nc, sizeof(void*)));
         if (cbeg == nullptr)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-            throw bad_alloc();
-#else
-            abort();
-#endif
+            __throw_bad_alloc();
+
         for (__c_node** p = __cbeg_; p != __cend_; ++p)
         {
             __c_node* q = *p;
@@ -178,11 +238,8 @@ __libcpp_db::__insert_c(void* __c)
     __c_node* r = __cbeg_[hc] =
       static_cast<__c_node*>(malloc(sizeof(__c_node)));
     if (__cbeg_[hc] == nullptr)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw bad_alloc();
-#else
-        abort();
-#endif
+        __throw_bad_alloc();
+
     r->__c_ = __c;
     r->__next_ = p;
     ++__csz_;
@@ -475,11 +532,8 @@ __c_node::__add(__i_node* i)
         __i_node** beg =
            static_cast<__i_node**>(malloc(nc * sizeof(__i_node*)));
         if (beg == nullptr)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-            throw bad_alloc();
-#else
-            abort();
-#endif
+            __throw_bad_alloc();
+
         if (nc > 1)
             memcpy(beg, beg_, nc/2*sizeof(__i_node*));
         free(beg_);
@@ -501,11 +555,8 @@ __libcpp_db::__insert_iterator(void* __i)
         size_t nc = __next_prime(2*static_cast<size_t>(__iend_ - __ibeg_) + 1);
         __i_node** ibeg = static_cast<__i_node**>(calloc(nc, sizeof(void*)));
         if (ibeg == nullptr)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-            throw bad_alloc();
-#else
-            abort();
-#endif
+            __throw_bad_alloc();
+
         for (__i_node** p = __ibeg_; p != __iend_; ++p)
         {
             __i_node* q = *p;
@@ -527,11 +578,8 @@ __libcpp_db::__insert_iterator(void* __i)
     __i_node* r = __ibeg_[hi] =
       static_cast<__i_node*>(malloc(sizeof(__i_node)));
     if (r == nullptr)
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw bad_alloc();
-#else
-        abort();
-#endif
+        __throw_bad_alloc();
+
     ::new(r) __i_node(__i, p, nullptr);
     ++__isz_;
     return r;
diff --git a/lib/libcxx/src/exception.cpp b/lib/libcxx/src/exception.cpp
index e172f642d48..3d2dcfd5b10 100644
--- a/lib/libcxx/src/exception.cpp
+++ b/lib/libcxx/src/exception.cpp
@@ -6,304 +6,32 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
-#include <stdlib.h>
-#include <stdio.h>
 
 #include "exception"
 #include "new"
+#include "typeinfo"
 
-#if defined(__APPLE__) && !defined(LIBCXXRT)
+#if defined(LIBCXXRT) || defined(LIBCXX_BUILDING_LIBCXXABI) || \
+  (defined(__APPLE__) && !defined(_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY))
   #include <cxxabi.h>
-
   using namespace __cxxabiv1;
   #define HAVE_DEPENDENT_EH_ABI 1
-  #ifndef _LIBCPPABI_VERSION
-    using namespace __cxxabiapple;
-    // On Darwin, there are two STL shared libraries and a lower level ABI
-    // shared library.  The globals holding the current terminate handler and
-    // current unexpected handler are in the ABI library.
-    #define __terminate_handler  __cxxabiapple::__cxa_terminate_handler
-    #define __unexpected_handler __cxxabiapple::__cxa_unexpected_handler
-  #endif  // _LIBCPPABI_VERSION
-#elif defined(LIBCXXRT) || defined(LIBCXX_BUILDING_LIBCXXABI)
-  #include <cxxabi.h>
-  using namespace __cxxabiv1;
-  #if defined(LIBCXXRT) || defined(_LIBCPPABI_VERSION)
-    #define HAVE_DEPENDENT_EH_ABI 1
-  #endif
-#elif !defined(__GLIBCXX__) // defined(LIBCXX_BUILDING_LIBCXXABI)
-  static std::terminate_handler  __terminate_handler;
-  static std::unexpected_handler __unexpected_handler;
-#endif // defined(LIBCXX_BUILDING_LIBCXXABI)
-
-namespace std
-{
-
-#if !defined(LIBCXXRT) && !defined(_LIBCPPABI_VERSION) && !defined(__GLIBCXX__)
-
-// libcxxrt provides implementations of these functions itself.
-unexpected_handler
-set_unexpected(unexpected_handler func) _NOEXCEPT
-{
-    return __sync_lock_test_and_set(&__unexpected_handler, func);
-}
-
-unexpected_handler
-get_unexpected() _NOEXCEPT
-{
-    return __sync_fetch_and_add(&__unexpected_handler, (unexpected_handler)0);
-}
-
-_LIBCPP_NORETURN
-void
-unexpected()
-{
-    (*get_unexpected())();
-    // unexpected handler should not return
-    terminate();
-}
-
-terminate_handler
-set_terminate(terminate_handler func) _NOEXCEPT
-{
-    return __sync_lock_test_and_set(&__terminate_handler, func);
-}
-
-terminate_handler
-get_terminate() _NOEXCEPT
-{
-    return __sync_fetch_and_add(&__terminate_handler, (terminate_handler)0);
-}
-
-#ifndef __EMSCRIPTEN__ // We provide this in JS
-_LIBCPP_NORETURN
-void
-terminate() _NOEXCEPT
-{
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    try
-    {
-#endif  // _LIBCPP_NO_EXCEPTIONS
-        (*get_terminate())();
-        // handler should not return
-        fprintf(stderr, "terminate_handler unexpectedly returned\n");
-        ::abort();
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    }
-    catch (...)
-    {
-        // handler should not throw exception
-        fprintf(stderr, "terminate_handler unexpectedly threw an exception\n");
-        ::abort();
-    }
-#endif  // _LIBCPP_NO_EXCEPTIONS
-}
-#endif // !__EMSCRIPTEN__
-#endif // !defined(LIBCXXRT) && !defined(_LIBCPPABI_VERSION)
-
-#if !defined(LIBCXXRT) && !defined(__GLIBCXX__) && !defined(__EMSCRIPTEN__)
-bool uncaught_exception() _NOEXCEPT { return uncaught_exceptions() > 0; }
-
-int uncaught_exceptions() _NOEXCEPT
-{
-#if defined(__APPLE__) || defined(_LIBCPPABI_VERSION)
-   // on Darwin, there is a helper function so __cxa_get_globals is private
-# if _LIBCPPABI_VERSION > 1101
-    return __cxa_uncaught_exceptions();
-# else
-    return __cxa_uncaught_exception() ? 1 : 0;
-# endif
-#else  // __APPLE__
-#   if defined(_MSC_VER) && ! defined(__clang__)
-        _LIBCPP_WARNING("uncaught_exceptions not yet implemented")
-#   else
-#       warning uncaught_exception not yet implemented
-#   endif
-    fprintf(stderr, "uncaught_exceptions not yet implemented\n");
-    ::abort();
-#endif  // __APPLE__
-}
-
-
-#ifndef _LIBCPPABI_VERSION
-
-exception::~exception() _NOEXCEPT
-{
-}
-
-const char* exception::what() const _NOEXCEPT
-{
-  return "std::exception";
-}
-
-#endif  // _LIBCPPABI_VERSION
-#endif //LIBCXXRT
-#if !defined(_LIBCPPABI_VERSION) && !defined(__GLIBCXX__)
-
-bad_exception::~bad_exception() _NOEXCEPT
-{
-}
-
-const char* bad_exception::what() const _NOEXCEPT
-{
-  return "std::bad_exception";
-}
-
 #endif
 
-#if defined(__GLIBCXX__)
-
-// libsupc++ does not implement the dependent EH ABI and the functionality
-// it uses to implement std::exception_ptr (which it declares as an alias of
-// std::__exception_ptr::exception_ptr) is not directly exported to clients. So
-// we have little choice but to hijack std::__exception_ptr::exception_ptr's
-// (which fortunately has the same layout as our std::exception_ptr) copy
-// constructor, assignment operator and destructor (which are part of its
-// stable ABI), and its rethrow_exception(std::__exception_ptr::exception_ptr)
-// function.
-
-namespace __exception_ptr
-{
-
-struct exception_ptr
-{
-    void* __ptr_;
-
-    exception_ptr(const exception_ptr&) _NOEXCEPT;
-    exception_ptr& operator=(const exception_ptr&) _NOEXCEPT;
-    ~exception_ptr() _NOEXCEPT;
-};
-
-}
-
-_LIBCPP_NORETURN void rethrow_exception(__exception_ptr::exception_ptr);
-
-#endif
-
-exception_ptr::~exception_ptr() _NOEXCEPT
-{
-#if HAVE_DEPENDENT_EH_ABI
-    __cxa_decrement_exception_refcount(__ptr_);
-#elif defined(__GLIBCXX__)
-    reinterpret_cast<__exception_ptr::exception_ptr*>(this)->~exception_ptr();
-#else
-#   if defined(_MSC_VER) && ! defined(__clang__)
-        _LIBCPP_WARNING("exception_ptr not yet implemented")
-#   else
-#       warning exception_ptr not yet implemented
-#   endif
-    fprintf(stderr, "exception_ptr not yet implemented\n");
-    ::abort();
-#endif
-}
-
-exception_ptr::exception_ptr(const exception_ptr& other) _NOEXCEPT
-    : __ptr_(other.__ptr_)
-{
-#if HAVE_DEPENDENT_EH_ABI
-    __cxa_increment_exception_refcount(__ptr_);
-#elif defined(__GLIBCXX__)
-    new (reinterpret_cast<void*>(this)) __exception_ptr::exception_ptr(
-        reinterpret_cast<const __exception_ptr::exception_ptr&>(other));
-#else
-#   if defined(_MSC_VER) && ! defined(__clang__)
-        _LIBCPP_WARNING("exception_ptr not yet implemented")
-#   else
-#       warning exception_ptr not yet implemented
-#   endif
-    fprintf(stderr, "exception_ptr not yet implemented\n");
-    ::abort();
-#endif
-}
-
-exception_ptr& exception_ptr::operator=(const exception_ptr& other) _NOEXCEPT
-{
-#if HAVE_DEPENDENT_EH_ABI
-    if (__ptr_ != other.__ptr_)
-    {
-        __cxa_increment_exception_refcount(other.__ptr_);
-        __cxa_decrement_exception_refcount(__ptr_);
-        __ptr_ = other.__ptr_;
-    }
-    return *this;
-#elif defined(__GLIBCXX__)
-    *reinterpret_cast<__exception_ptr::exception_ptr*>(this) =
-        reinterpret_cast<const __exception_ptr::exception_ptr&>(other);
-    return *this;
-#else
-#   if defined(_MSC_VER) && ! defined(__clang__)
-        _LIBCPP_WARNING("exception_ptr not yet implemented")
-#   else
-#       warning exception_ptr not yet implemented
-#   endif
-    fprintf(stderr, "exception_ptr not yet implemented\n");
-    ::abort();
-#endif
-}
-
-nested_exception::nested_exception() _NOEXCEPT
-    : __ptr_(current_exception())
-{
-}
-
-#if !defined(__GLIBCXX__)
-
-nested_exception::~nested_exception() _NOEXCEPT
-{
-}
-
-#endif
-
-_LIBCPP_NORETURN
-void
-nested_exception::rethrow_nested() const
-{
-    if (__ptr_ == nullptr)
-        terminate();
-    rethrow_exception(__ptr_);
-}
-
-#if !defined(__GLIBCXX__)
-
-exception_ptr current_exception() _NOEXCEPT
-{
-#if HAVE_DEPENDENT_EH_ABI
-    // be nicer if there was a constructor that took a ptr, then
-    // this whole function would be just:
-    //    return exception_ptr(__cxa_current_primary_exception());
-    exception_ptr ptr;
-    ptr.__ptr_ = __cxa_current_primary_exception();
-    return ptr;
-#else
-#   if defined(_MSC_VER) && ! defined(__clang__)
-        _LIBCPP_WARNING( "exception_ptr not yet implemented" )
-#   else
-#       warning exception_ptr not yet implemented
-#   endif
-    fprintf(stderr, "exception_ptr not yet implemented\n");
-    ::abort();
-#endif
-}
-
-#endif  // !__GLIBCXX__
-
-_LIBCPP_NORETURN
-void rethrow_exception(exception_ptr p)
-{
-#if HAVE_DEPENDENT_EH_ABI
-    __cxa_rethrow_primary_exception(p.__ptr_);
-    // if p.__ptr_ is NULL, above returns so we terminate
-    terminate();
+#if defined(_LIBCPP_ABI_MICROSOFT)
+#include "support/runtime/exception_msvc.ipp"
+#include "support/runtime/exception_pointer_msvc.ipp"
+#elif defined(_LIBCPPABI_VERSION)
+#include "support/runtime/exception_libcxxabi.ipp"
+#include "support/runtime/exception_pointer_cxxabi.ipp"
+#elif defined(LIBCXXRT)
+#include "support/runtime/exception_libcxxrt.ipp"
+#include "support/runtime/exception_pointer_cxxabi.ipp"
 #elif defined(__GLIBCXX__)
-    rethrow_exception(reinterpret_cast<__exception_ptr::exception_ptr&>(p));
+#include "support/runtime/exception_glibcxx.ipp"
+#include "support/runtime/exception_pointer_glibcxx.ipp"
 #else
-#   if defined(_MSC_VER) && ! defined(__clang__)
-        _LIBCPP_WARNING("exception_ptr not yet implemented")
-#   else
-#       warning exception_ptr not yet implemented
-#   endif
-    fprintf(stderr, "exception_ptr not yet implemented\n");
-    ::abort();
+#include "include/atomic_support.h"
+#include "support/runtime/exception_fallback.ipp"
+#include "support/runtime/exception_pointer_unimplemented.ipp"
 #endif
-}
-} // std
diff --git a/lib/libcxx/src/experimental/filesystem/directory_iterator.cpp b/lib/libcxx/src/experimental/filesystem/directory_iterator.cpp
index fa217ba7a12..a552fdc4461 100644
--- a/lib/libcxx/src/experimental/filesystem/directory_iterator.cpp
+++ b/lib/libcxx/src/experimental/filesystem/directory_iterator.cpp
@@ -1,28 +1,32 @@
+//===------------------ directory_iterator.cpp ----------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
 #include "experimental/filesystem"
+#include "__config"
+#if defined(_LIBCPP_WIN32API)
+#define WIN32_LEAN_AND_MEAN
+#include <Windows.h>
+#else
 #include <dirent.h>
+#endif
 #include <errno.h>
 
 _LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL_FILESYSTEM
 
 namespace { namespace detail {
 
+#if !defined(_LIBCPP_WIN32API)
 inline error_code capture_errno() {
     _LIBCPP_ASSERT(errno, "Expected errno to be non-zero");
     return error_code{errno, std::generic_category()};
 }
-
-template <class ...Args>
-inline bool capture_error_or_throw(std::error_code* user_ec,
-                                   const char* msg, Args&&... args)
-{
-    std::error_code my_ec = capture_errno();
-    if (user_ec) {
-        *user_ec = my_ec;
-        return true;
-    }
-    __libcpp_throw(filesystem_error(msg, std::forward<Args>(args)..., my_ec));
-    return false;
-}
+#endif
 
 template <class ...Args>
 inline bool set_or_throw(std::error_code& my_ec,
@@ -33,29 +37,91 @@ inline bool set_or_throw(std::error_code& my_ec,
         *user_ec = my_ec;
         return true;
     }
-    __libcpp_throw(filesystem_error(msg, std::forward<Args>(args)..., my_ec));
+    __throw_filesystem_error(msg, std::forward<Args>(args)..., my_ec);
     return false;
 }
 
-typedef path::string_type string_type;
-
-
-inline string_type posix_readdir(DIR *dir_stream, error_code& ec) {
+#if !defined(_LIBCPP_WIN32API)
+inline path::string_type posix_readdir(DIR *dir_stream, error_code& ec) {
     struct dirent* dir_entry_ptr = nullptr;
     errno = 0; // zero errno in order to detect errors
+    ec.clear();
     if ((dir_entry_ptr = ::readdir(dir_stream)) == nullptr) {
-        ec = capture_errno();
+        if (errno)
+          ec = capture_errno();
         return {};
     } else {
-        ec.clear();
         return dir_entry_ptr->d_name;
     }
 }
+#endif
 
 }}                                                       // namespace detail
 
 using detail::set_or_throw;
 
+#if defined(_LIBCPP_WIN32API)
+class __dir_stream {
+public:
+  __dir_stream() = delete;
+  __dir_stream& operator=(const __dir_stream&) = delete;
+
+  __dir_stream(__dir_stream&& __ds) noexcept
+      : __stream_(__ds.__stream_), __root_(std::move(__ds.__root_)),
+        __entry_(std::move(__ds.__entry_)) {
+    __ds.__stream_ = INVALID_HANDLE_VALUE;
+  }
+
+  __dir_stream(const path& root, directory_options opts, error_code& ec)
+      : __stream_(INVALID_HANDLE_VALUE), __root_(root) {
+    __stream_ = ::FindFirstFile(root.c_str(), &__data_);
+    if (__stream_ == INVALID_HANDLE_VALUE) {
+      ec = error_code(::GetLastError(), std::generic_category());
+      const bool ignore_permission_denied =
+          bool(opts & directory_options::skip_permission_denied);
+      if (ignore_permission_denied && ec.value() == ERROR_ACCESS_DENIED)
+        ec.clear();
+      return;
+    }
+  }
+
+  ~__dir_stream() noexcept {
+    if (__stream_ == INVALID_HANDLE_VALUE)
+      return;
+    close();
+  }
+
+  bool good() const noexcept { return __stream_ != INVALID_HANDLE_VALUE; }
+
+  bool advance(error_code& ec) {
+    while (::FindNextFile(__stream_, &__data_)) {
+      if (!strcmp(__data_.cFileName, ".") || strcmp(__data_.cFileName, ".."))
+        continue;
+      __entry_.assign(__root_ / __data_.cFileName);
+      return true;
+    }
+    ec = error_code(::GetLastError(), std::generic_category());
+    close();
+    return false;
+  }
+
+private:
+  std::error_code close() noexcept {
+    std::error_code ec;
+    if (!::FindClose(__stream_))
+      ec = error_code(::GetLastError(), std::generic_category());
+    __stream_ = INVALID_HANDLE_VALUE;
+    return ec;
+  }
+
+  HANDLE __stream_{INVALID_HANDLE_VALUE};
+  WIN32_FIND_DATA __data_;
+
+public:
+  path __root_;
+  directory_entry __entry_;
+};
+#else
 class __dir_stream {
 public:
     __dir_stream() = delete;
@@ -117,6 +183,7 @@ public:
     path __root_;
     directory_entry __entry_;
 };
+#endif
 
 // directory_iterator
 
@@ -149,7 +216,7 @@ directory_iterator& directory_iterator::__increment(error_code *ec)
 
 }
 
-directory_entry const& directory_iterator::__deref() const {
+directory_entry const& directory_iterator::__dereference() const {
     _LIBCPP_ASSERT(__imp_, "Attempting to dereference an invalid iterator");
     return __imp_->__entry_;
 }
@@ -195,7 +262,7 @@ int recursive_directory_iterator::depth() const {
     return __imp_->__stack_.size() - 1;
 }
 
-const directory_entry& recursive_directory_iterator::__deref() const {
+const directory_entry& recursive_directory_iterator::__dereference() const {
     return __imp_->__stack_.top().__entry_;
 }
 
@@ -229,24 +296,43 @@ void recursive_directory_iterator::__advance(error_code* ec) {
 }
 
 bool recursive_directory_iterator::__try_recursion(error_code *ec) {
-
     bool rec_sym =
         bool(options() & directory_options::follow_directory_symlink);
+
     auto& curr_it = __imp_->__stack_.top();
 
-    if (is_directory(curr_it.__entry_.status()) &&
-        (!is_symlink(curr_it.__entry_.symlink_status()) || rec_sym))
-    {
-        std::error_code m_ec;
+    bool skip_rec = false;
+    std::error_code m_ec;
+    if (!rec_sym) {
+      file_status st = curr_it.__entry_.symlink_status(m_ec);
+      if (m_ec && status_known(st))
+        m_ec.clear();
+      if (m_ec || is_symlink(st) || !is_directory(st))
+        skip_rec = true;
+    } else {
+      file_status st = curr_it.__entry_.status(m_ec);
+      if (m_ec && status_known(st))
+        m_ec.clear();
+      if (m_ec || !is_directory(st))
+        skip_rec = true;
+    }
+
+    if (!skip_rec) {
         __dir_stream new_it(curr_it.__entry_.path(), __imp_->__options_, m_ec);
         if (new_it.good()) {
             __imp_->__stack_.push(_VSTD::move(new_it));
             return true;
         }
-        if (m_ec) {
-            __imp_.reset();
-            set_or_throw(m_ec, ec,
-                               "recursive_directory_iterator::operator++()");
+    }
+    if (m_ec) {
+        const bool allow_eacess = bool(__imp_->__options_
+            & directory_options::skip_permission_denied);
+        if (m_ec.value() == EACCES && allow_eacess) {
+          if (ec) ec->clear();
+        } else {
+          __imp_.reset();
+          set_or_throw(m_ec, ec,
+                       "recursive_directory_iterator::operator++()");
         }
     }
     return false;
diff --git a/lib/libcxx/src/experimental/filesystem/filesystem_time_helper.h b/lib/libcxx/src/experimental/filesystem/filesystem_time_helper.h
new file mode 100644
index 00000000000..a60fdef5f0d
--- /dev/null
+++ b/lib/libcxx/src/experimental/filesystem/filesystem_time_helper.h
@@ -0,0 +1,173 @@
+//===----------------------------------------------------------------------===////
+//
+//                     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 FILESYSTEM_TIME_HELPER_H
+#define FILESYSTEM_TIME_HELPER_H
+
+#include "experimental/__config"
+#include "chrono"
+#include "cstdlib"
+#include "climits"
+
+#include <unistd.h>
+#include <sys/stat.h>
+#if !defined(UTIME_OMIT)
+#include <sys/time.h> // for ::utimes as used in __last_write_time
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL_FILESYSTEM
+
+namespace time_detail { namespace {
+
+using namespace chrono;
+
+template <class FileTimeT,
+          bool IsFloat = is_floating_point<typename FileTimeT::rep>::value>
+struct fs_time_util_base {
+  static constexpr auto max_seconds =
+      duration_cast<seconds>(FileTimeT::duration::max()).count();
+
+  static constexpr auto max_nsec =
+      duration_cast<nanoseconds>(FileTimeT::duration::max() -
+                                 seconds(max_seconds))
+          .count();
+
+  static constexpr auto min_seconds =
+      duration_cast<seconds>(FileTimeT::duration::min()).count();
+
+  static constexpr auto min_nsec_timespec =
+      duration_cast<nanoseconds>(
+          (FileTimeT::duration::min() - seconds(min_seconds)) + seconds(1))
+          .count();
+
+  // Static assert that these values properly round trip.
+  static_assert((seconds(min_seconds) +
+                 duration_cast<microseconds>(nanoseconds(min_nsec_timespec))) -
+                        duration_cast<microseconds>(seconds(1)) ==
+                    FileTimeT::duration::min(),
+                "");
+};
+
+template <class FileTimeT>
+struct fs_time_util_base<FileTimeT, true> {
+  static const long long max_seconds;
+  static const long long max_nsec;
+  static const long long min_seconds;
+  static const long long min_nsec_timespec;
+};
+
+template <class FileTimeT>
+const long long fs_time_util_base<FileTimeT, true>::max_seconds =
+    duration_cast<seconds>(FileTimeT::duration::max()).count();
+
+template <class FileTimeT>
+const long long fs_time_util_base<FileTimeT, true>::max_nsec =
+    duration_cast<nanoseconds>(FileTimeT::duration::max() -
+                               seconds(max_seconds))
+        .count();
+
+template <class FileTimeT>
+const long long fs_time_util_base<FileTimeT, true>::min_seconds =
+    duration_cast<seconds>(FileTimeT::duration::min()).count();
+
+template <class FileTimeT>
+const long long fs_time_util_base<FileTimeT, true>::min_nsec_timespec =
+    duration_cast<nanoseconds>((FileTimeT::duration::min() -
+                                seconds(min_seconds)) +
+                               seconds(1))
+        .count();
+
+template <class FileTimeT, class TimeT, class TimeSpecT>
+struct fs_time_util : fs_time_util_base<FileTimeT> {
+  using Base = fs_time_util_base<FileTimeT>;
+  using Base::max_nsec;
+  using Base::max_seconds;
+  using Base::min_nsec_timespec;
+  using Base::min_seconds;
+
+public:
+  template <class CType, class ChronoType>
+  static bool checked_set(CType* out, ChronoType time) {
+    using Lim = numeric_limits<CType>;
+    if (time > Lim::max() || time < Lim::min())
+      return false;
+    *out = static_cast<CType>(time);
+    return true;
+  }
+
+  static _LIBCPP_CONSTEXPR_AFTER_CXX11 bool is_representable(TimeSpecT tm) {
+    if (tm.tv_sec >= 0) {
+      return (tm.tv_sec < max_seconds) ||
+             (tm.tv_sec == max_seconds && tm.tv_nsec <= max_nsec);
+    } else if (tm.tv_sec == (min_seconds - 1)) {
+      return tm.tv_nsec >= min_nsec_timespec;
+    } else {
+      return (tm.tv_sec >= min_seconds);
+    }
+  }
+
+  static _LIBCPP_CONSTEXPR_AFTER_CXX11 bool is_representable(FileTimeT tm) {
+    auto secs = duration_cast<seconds>(tm.time_since_epoch());
+    auto nsecs = duration_cast<nanoseconds>(tm.time_since_epoch() - secs);
+    if (nsecs.count() < 0) {
+      secs = secs + seconds(1);
+      nsecs = nsecs + seconds(1);
+    }
+    using TLim = numeric_limits<TimeT>;
+    if (secs.count() >= 0)
+      return secs.count() <= TLim::max();
+    return secs.count() >= TLim::min();
+  }
+
+  static _LIBCPP_CONSTEXPR_AFTER_CXX11 FileTimeT
+  convert_timespec(TimeSpecT tm) {
+    auto adj_msec = duration_cast<microseconds>(nanoseconds(tm.tv_nsec));
+    if (tm.tv_sec >= 0) {
+      auto Dur = seconds(tm.tv_sec) + microseconds(adj_msec);
+      return FileTimeT(Dur);
+    } else if (duration_cast<microseconds>(nanoseconds(tm.tv_nsec)).count() ==
+               0) {
+      return FileTimeT(seconds(tm.tv_sec));
+    } else { // tm.tv_sec < 0
+      auto adj_subsec =
+          duration_cast<microseconds>(seconds(1) - nanoseconds(tm.tv_nsec));
+      auto Dur = seconds(tm.tv_sec + 1) - adj_subsec;
+      return FileTimeT(Dur);
+    }
+  }
+
+  template <class SubSecDurT, class SubSecT>
+  static bool set_times_checked(TimeT* sec_out, SubSecT* subsec_out,
+                                FileTimeT tp) {
+    using namespace chrono;
+    auto dur = tp.time_since_epoch();
+    auto sec_dur = duration_cast<seconds>(dur);
+    auto subsec_dur = duration_cast<SubSecDurT>(dur - sec_dur);
+    // The tv_nsec and tv_usec fields must not be negative so adjust accordingly
+    if (subsec_dur.count() < 0) {
+      if (sec_dur.count() > min_seconds) {
+        sec_dur -= seconds(1);
+        subsec_dur += seconds(1);
+      } else {
+        subsec_dur = SubSecDurT::zero();
+      }
+    }
+    return checked_set(sec_out, sec_dur.count()) &&
+           checked_set(subsec_out, subsec_dur.count());
+  }
+};
+
+} // end namespace
+} // end namespace time_detail
+
+using time_detail::fs_time_util;
+
+_LIBCPP_END_NAMESPACE_EXPERIMENTAL_FILESYSTEM
+
+#endif // FILESYSTEM_TIME_HELPER_H
diff --git a/lib/libcxx/src/experimental/filesystem/operations.cpp b/lib/libcxx/src/experimental/filesystem/operations.cpp
index 369996fcbe6..662fa7b8626 100644
--- a/lib/libcxx/src/experimental/filesystem/operations.cpp
+++ b/lib/libcxx/src/experimental/filesystem/operations.cpp
@@ -15,6 +15,8 @@
 #include "cstdlib"
 #include "climits"
 
+#include "filesystem_time_helper.h"
+
 #include <unistd.h>
 #include <sys/stat.h>
 #include <sys/statvfs.h>
@@ -35,12 +37,9 @@ namespace detail { namespace  {
 using value_type = path::value_type;
 using string_type = path::string_type;
 
-
-
 inline std::error_code capture_errno() {
-    _LIBCPP_ASSERT(errno, "Expected errno to be non-zero");
-    std::error_code m_ec(errno, std::generic_category());
-    return m_ec;
+  _LIBCPP_ASSERT(errno, "Expected errno to be non-zero");
+  return std::error_code(errno, std::generic_category());
 }
 
 void set_or_throw(std::error_code const& m_ec, std::error_code* ec,
@@ -51,7 +50,7 @@ void set_or_throw(std::error_code const& m_ec, std::error_code* ec,
     } else {
         string msg_s("std::experimental::filesystem::");
         msg_s += msg;
-        __libcpp_throw(filesystem_error(msg_s, p, p2, m_ec));
+        __throw_filesystem_error(msg_s, p, p2, m_ec);
     }
 }
 
@@ -183,20 +182,20 @@ void __copy(const path& from, const path& to, copy_options options,
     const bool sym_status2 = bool(options &
         copy_options::copy_symlinks);
 
-    std::error_code m_ec;
+    std::error_code m_ec1;
     struct ::stat f_st = {};
     const file_status f = sym_status || sym_status2
-                                     ? detail::posix_lstat(from, f_st, &m_ec)
-                                     : detail::posix_stat(from,  f_st, &m_ec);
-    if (m_ec)
-        return set_or_throw(m_ec, ec, "copy", from, to);
+                                     ? detail::posix_lstat(from, f_st, &m_ec1)
+                                     : detail::posix_stat(from,  f_st, &m_ec1);
+    if (m_ec1)
+        return set_or_throw(m_ec1, ec, "copy", from, to);
 
     struct ::stat t_st = {};
-    const file_status t = sym_status ? detail::posix_lstat(to, t_st, &m_ec)
-                                     : detail::posix_stat(to, t_st, &m_ec);
+    const file_status t = sym_status ? detail::posix_lstat(to, t_st, &m_ec1)
+                                     : detail::posix_stat(to, t_st, &m_ec1);
 
     if (not status_known(t))
-        return set_or_throw(m_ec, ec, "copy", from, to);
+        return set_or_throw(m_ec1, ec, "copy", from, to);
 
     if (!exists(f) || is_other(f) || is_other(t)
         || (is_directory(f) && is_regular_file(t))
@@ -236,12 +235,11 @@ void __copy(const path& from, const path& to, copy_options options,
         }
         return;
     }
-    else if (is_directory(f)) {
-        if (not bool(copy_options::recursive & options) &&
-            bool(copy_options::__in_recursive_copy & options))
-        {
-            return;
-        }
+    else if (is_directory(f) && bool(copy_options::create_symlinks & options)) {
+        return set_or_throw(make_error_code(errc::is_a_directory), ec, "copy");
+    }
+    else if (is_directory(f) && (bool(copy_options::recursive & options) ||
+             copy_options::none == options)) {
 
         if (!exists(t)) {
             // create directory to with attributes from 'from'.
@@ -251,9 +249,9 @@ void __copy(const path& from, const path& to, copy_options options,
         directory_iterator it = ec ? directory_iterator(from, *ec)
                                    : directory_iterator(from);
         if (ec && *ec) { return; }
-        std::error_code m_ec;
-        for (; it != directory_iterator(); it.increment(m_ec)) {
-            if (m_ec) return set_or_throw(m_ec, ec, "copy", from, to);
+        std::error_code m_ec2;
+        for (; it != directory_iterator(); it.increment(m_ec2)) {
+            if (m_ec2) return set_or_throw(m_ec2, ec, "copy", from, to);
             __copy(it->path(), to / it->path().filename(),
                    options | copy_options::__in_recursive_copy, ec);
             if (ec && *ec) { return; }
@@ -283,6 +281,10 @@ bool __copy_file(const path& from, const path& to, copy_options options,
     }
 
     const bool to_exists = exists(to_st);
+    if (to_exists && !is_regular_file(to_st)) {
+        set_or_throw(make_error_code(errc::not_supported), ec, "copy_file", from, to);
+        return false;
+    }
     if (to_exists && bool(copy_options::skip_existing & options)) {
         return false;
     }
@@ -303,6 +305,8 @@ bool __copy_file(const path& from, const path& to, copy_options options,
         set_or_throw(make_error_code(errc::file_exists), ec, "copy", from, to);
         return false;
     }
+
+    _LIBCPP_UNREACHABLE();
 }
 
 void __copy_symlink(const path& existing_symlink, const path& new_symlink,
@@ -424,17 +428,20 @@ void __current_path(const path& p, std::error_code *ec) {
 
 bool __equivalent(const path& p1, const path& p2, std::error_code *ec)
 {
+    auto make_unsupported_error = [&]() {
+      set_or_throw(make_error_code(errc::not_supported), ec,
+                     "equivalent", p1, p2);
+      return false;
+    };
     std::error_code ec1, ec2;
     struct ::stat st1 = {};
     struct ::stat st2 = {};
     auto s1 = detail::posix_stat(p1.native(), st1, &ec1);
+    if (!exists(s1))
+      return make_unsupported_error();
     auto s2 = detail::posix_stat(p2.native(), st2, &ec2);
-
-    if ((!exists(s1) && !exists(s2)) || (is_other(s1) && is_other(s2))) {
-        set_or_throw(make_error_code(errc::not_supported), ec,
-                     "equivalent", p1, p2);
-        return false;
-    }
+    if (!exists(s2))
+      return make_unsupported_error();
     if (ec) ec->clear();
     return (st1.st_dev == st2.st_dev && st1.st_ino == st2.st_ino);
 }
@@ -476,55 +483,50 @@ bool __fs_is_empty(const path& p, std::error_code *ec)
     std::error_code m_ec;
     struct ::stat pst;
     auto st = detail::posix_stat(p, pst, &m_ec);
-    if (is_directory(st))
-        return directory_iterator(p) == directory_iterator{};
+    if (m_ec) {
+        set_or_throw(m_ec, ec, "is_empty", p);
+        return false;
+    }
+    else if (!is_directory(st) && !is_regular_file(st)) {
+        m_ec = make_error_code(errc::not_supported);
+        set_or_throw(m_ec, ec, "is_empty");
+        return false;
+    }
+    else if (is_directory(st)) {
+        auto it = ec ? directory_iterator(p, *ec) : directory_iterator(p);
+        if (ec && *ec)
+            return false;
+        return it == directory_iterator{};
+    }
     else if (is_regular_file(st))
         return static_cast<std::uintmax_t>(pst.st_size) == 0;
-    // else
-    set_or_throw(m_ec, ec, "is_empty", p);
-    return false;
+
+    _LIBCPP_UNREACHABLE();
 }
 
 
 namespace detail { namespace {
 
-template <class CType, class ChronoType>
-bool checked_set(CType* out, ChronoType time) {
-    using Lim = numeric_limits<CType>;
-    if (time > Lim::max() || time < Lim::min())
-        return false;
-    *out = static_cast<CType>(time);
-    return true;
-}
-
-constexpr long long min_seconds = file_time_type::duration::min().count()
-    / file_time_type::period::den;
-
-template <class SubSecDurT, class SubSecT>
-bool set_times_checked(time_t* sec_out, SubSecT* subsec_out, file_time_type tp) {
-    using namespace chrono;
-    auto dur = tp.time_since_epoch();
-    auto sec_dur = duration_cast<seconds>(dur);
-    auto subsec_dur = duration_cast<SubSecDurT>(dur - sec_dur);
-    // The tv_nsec and tv_usec fields must not be negative so adjust accordingly
-    if (subsec_dur.count() < 0) {
-        if (sec_dur.count() > min_seconds) {
+using TimeSpec = struct timespec;
+using StatT =  struct stat;
 
-            sec_dur -= seconds(1);
-            subsec_dur += seconds(1);
-        } else {
-            subsec_dur = SubSecDurT::zero();
-        }
-    }
-    return checked_set(sec_out, sec_dur.count())
-        && checked_set(subsec_out, subsec_dur.count());
-}
+#if defined(__APPLE__)
+TimeSpec extract_mtime(StatT const& st) { return st.st_mtimespec; }
+__attribute__((unused)) // Suppress warning
+TimeSpec extract_atime(StatT const& st) { return st.st_atimespec; }
+#else
+TimeSpec extract_mtime(StatT const& st) { return st.st_mtim; }
+__attribute__((unused)) // Suppress warning
+TimeSpec extract_atime(StatT const& st) { return st.st_atim; }
+#endif
 
 }} // end namespace detail
 
+using FSTime = fs_time_util<file_time_type, time_t, struct timespec>;
 
 file_time_type __last_write_time(const path& p, std::error_code *ec)
 {
+    using namespace ::std::chrono;
     std::error_code m_ec;
     struct ::stat st;
     detail::posix_stat(p, st, &m_ec);
@@ -533,7 +535,13 @@ file_time_type __last_write_time(const path& p, std::error_code *ec)
         return file_time_type::min();
     }
     if (ec) ec->clear();
-    return file_time_type::clock::from_time_t(st.st_mtime);
+    auto ts = detail::extract_mtime(st);
+    if (!FSTime::is_representable(ts)) {
+        set_or_throw(error_code(EOVERFLOW, generic_category()), ec,
+                     "last_write_time", p);
+        return file_time_type::min();
+    }
+    return FSTime::convert_timespec(ts);
 }
 
 void __last_write_time(const path& p, file_time_type new_time,
@@ -554,10 +562,11 @@ void __last_write_time(const path& p, file_time_type new_time,
         set_or_throw(m_ec, ec, "last_write_time", p);
         return;
     }
+    auto atime = detail::extract_atime(st);
     struct ::timeval tbuf[2];
-    tbuf[0].tv_sec = st.st_atime;
-    tbuf[0].tv_usec = 0;
-    const bool overflowed = !detail::set_times_checked<microseconds>(
+    tbuf[0].tv_sec = atime.tv_sec;
+    tbuf[0].tv_usec = duration_cast<microseconds>(nanoseconds(atime.tv_nsec)).count();
+    const bool overflowed = !FSTime::set_times_checked<microseconds>(
         &tbuf[1].tv_sec, &tbuf[1].tv_usec, new_time);
 
     if (overflowed) {
@@ -573,7 +582,7 @@ void __last_write_time(const path& p, file_time_type new_time,
     tbuf[0].tv_sec = 0;
     tbuf[0].tv_nsec = UTIME_OMIT;
 
-    const bool overflowed = !detail::set_times_checked<nanoseconds>(
+    const bool overflowed = !FSTime::set_times_checked<nanoseconds>(
         &tbuf[1].tv_sec, &tbuf[1].tv_nsec, new_time);
     if (overflowed) {
         set_or_throw(make_error_code(errc::invalid_argument),
@@ -701,7 +710,7 @@ void __rename(const path& from, const path& to, std::error_code *ec) {
 }
 
 void __resize_file(const path& p, std::uintmax_t size, std::error_code *ec) {
-    if (::truncate(p.c_str(), static_cast<long>(size)) == -1)
+    if (::truncate(p.c_str(), static_cast<::off_t>(size)) == -1)
         set_or_throw(ec, "resize_file", p);
     else if (ec)
         ec->clear();
@@ -720,7 +729,7 @@ space_info __space(const path& p, std::error_code *ec) {
     // Multiply with overflow checking.
     auto do_mult = [&](std::uintmax_t& out, std::uintmax_t other) {
       out = other * m_svfs.f_frsize;
-      if (out / other != m_svfs.f_frsize || other == 0)
+      if (other == 0 || out / other != m_svfs.f_frsize)
           out = static_cast<std::uintmax_t>(-1);
     };
     do_mult(si.capacity, m_svfs.f_blocks);
@@ -742,23 +751,28 @@ path __system_complete(const path& p, std::error_code *ec) {
     return absolute(p, current_path());
 }
 
-path __temp_directory_path(std::error_code *ec) {
-    const char* env_paths[] = {"TMPDIR", "TMP", "TEMP", "TEMPDIR"};
-    const char* ret = nullptr;
-    for (auto & ep : env_paths)  {
-        if ((ret = std::getenv(ep)))
-            break;
-    }
-    path p(ret ? ret : "/tmp");
-    std::error_code m_ec;
-    if (is_directory(p, m_ec)) {
-        if (ec) ec->clear();
-        return p;
-    }
+path __temp_directory_path(std::error_code* ec) {
+  const char* env_paths[] = {"TMPDIR", "TMP", "TEMP", "TEMPDIR"};
+  const char* ret = nullptr;
+
+  for (auto& ep : env_paths)
+    if ((ret = std::getenv(ep)))
+      break;
+  if (ret == nullptr)
+    ret = "/tmp";
+
+  path p(ret);
+  std::error_code m_ec;
+  if (!exists(p, m_ec) || !is_directory(p, m_ec)) {
     if (!m_ec || m_ec == make_error_code(errc::no_such_file_or_directory))
-        m_ec = make_error_code(errc::not_a_directory);
+      m_ec = make_error_code(errc::not_a_directory);
     set_or_throw(m_ec, ec, "temp_directory_path");
     return {};
+  }
+
+  if (ec)
+    ec->clear();
+  return p;
 }
 
 // An absolute path is composed according to the table in [fs.op.absolute].
diff --git a/lib/libcxx/src/experimental/filesystem/path.cpp b/lib/libcxx/src/experimental/filesystem/path.cpp
index 38c449832f6..dd4026cfe13 100644
--- a/lib/libcxx/src/experimental/filesystem/path.cpp
+++ b/lib/libcxx/src/experimental/filesystem/path.cpp
@@ -7,241 +7,284 @@
 //
 //===----------------------------------------------------------------------===//
 #include "experimental/filesystem"
-#include "experimental/string_view"
+#include "string_view"
 #include "utility"
 
-_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL_FILESYSTEM
-
-_LIBCPP_CONSTEXPR path::value_type path::preferred_separator;
-
 namespace { namespace parser
 {
+using namespace std;
+using namespace std::experimental::filesystem;
+
+using string_view_t = path::__string_view;
+using string_view_pair = pair<string_view_t, string_view_t>;
+using PosPtr = path::value_type const*;
+
+struct PathParser {
+  enum ParserState : unsigned char {
+    // Zero is a special sentinel value used by default constructed iterators.
+    PS_BeforeBegin = 1,
+    PS_InRootName,
+    PS_InRootDir,
+    PS_InFilenames,
+    PS_InTrailingSep,
+    PS_AtEnd
+  };
 
-using string_type = string_view;
-using value_type = path::value_type;
-
-using string_view_pair = pair<string_view, string_view>;
-
-// status reporting
-constexpr size_t npos = static_cast<size_t>(-1);
-
-inline bool good(size_t pos) { return pos != npos; }
-
-// lexical elements
-constexpr value_type preferred_separator = path::preferred_separator;
-constexpr value_type const * preferred_separator_str = "/";
-constexpr value_type const * dot = ".";
-
-// forward //
-bool is_separator(string_type const &, size_t);
-bool is_root_name(const string_type&, size_t);
-bool is_root_directory(string_type const &, size_t);
-bool is_trailing_separator(string_type const &, size_t);
-
-size_t start_of(string_type const &, size_t);
-size_t end_of(string_type const &, size_t);
-
-size_t root_name_start(const string_type& s);
-size_t root_name_end(const string_type&);
-
-size_t root_directory_start(string_type const &);
-size_t root_directory_end(string_type const &);
+  const string_view_t Path;
+  string_view_t RawEntry;
+  ParserState State;
 
-string_view_pair separate_filename(string_type const &);
-string_view extract_raw(string_type const &, size_t);
-string_view extract_preferred(string_type const &, size_t);
+private:
+  PathParser(string_view_t P, ParserState State) noexcept
+      : Path(P), State(State) {}
 
-inline bool is_separator(const string_type& s, size_t pos) {
-    return (pos < s.size() && s[pos] == preferred_separator);
-}
+public:
+  PathParser(string_view_t P, string_view_t E, unsigned char S)
+      : Path(P), RawEntry(E), State(static_cast<ParserState>(S)) {
+    // S cannot be '0' or PS_BeforeBegin.
+  }
 
-inline bool is_root_name(const string_type& s, size_t pos) {
-  return good(pos) && pos == 0 ? root_name_start(s) == pos : false;
-}
+  static PathParser CreateBegin(string_view_t P) noexcept {
+    PathParser PP(P, PS_BeforeBegin);
+    PP.increment();
+    return PP;
+  }
 
-inline bool is_root_directory(const string_type& s, size_t pos) {
-    return good(pos) ? root_directory_start(s) == pos : false;
-}
+  static PathParser CreateEnd(string_view_t P) noexcept {
+    PathParser PP(P, PS_AtEnd);
+    return PP;
+  }
 
-inline bool is_trailing_separator(const string_type& s, size_t pos) {
-    return (pos < s.size() && is_separator(s, pos) &&
-            end_of(s, pos) == s.size()-1 &&
-            !is_root_directory(s, pos) && !is_root_name(s, pos));
-}
+  PosPtr peek() const noexcept {
+    auto TkEnd = getNextTokenStartPos();
+    auto End = getAfterBack();
+    return TkEnd == End ? nullptr : TkEnd;
+  }
 
-size_t start_of(const string_type& s, size_t pos) {
-    if (pos >= s.size()) return npos;
-    bool in_sep = (s[pos] == preferred_separator);
-    while (pos - 1 < s.size() &&
-        (s[pos-1] == preferred_separator) == in_sep)
-    { --pos; }
-    if (pos == 2 && !in_sep && s[0] == preferred_separator &&
-        s[1] == preferred_separator)
-    { return 0; }
-    return pos;
-}
+  void increment() noexcept {
+    const PosPtr End = getAfterBack();
+    const PosPtr Start = getNextTokenStartPos();
+    if (Start == End)
+      return makeState(PS_AtEnd);
+
+    switch (State) {
+    case PS_BeforeBegin: {
+      PosPtr TkEnd = consumeSeparator(Start, End);
+      // If we consumed exactly two separators we have a root name.
+      if (TkEnd && TkEnd == Start + 2) {
+        // FIXME Do we need to consume a name or is '//' a root name on its own?
+        // what about '//.', '//..', '//...'?
+        auto NameEnd = consumeName(TkEnd, End);
+        if (NameEnd)
+          TkEnd = NameEnd;
+        return makeState(PS_InRootName, Start, TkEnd);
+      }
+      else if (TkEnd)
+        return makeState(PS_InRootDir, Start, TkEnd);
+      else
+        return makeState(PS_InFilenames, Start, consumeName(Start, End));
+    }
 
-size_t end_of(const string_type& s, size_t pos) {
-    if (pos >= s.size()) return npos;
-    // special case for root name
-    if (pos == 0 && is_root_name(s, pos)) return root_name_end(s);
-    bool in_sep = (s[pos] == preferred_separator);
-    while (pos + 1 < s.size() && (s[pos+1] == preferred_separator) == in_sep)
-    { ++pos; }
-    return pos;
-}
+    case PS_InRootName:
+      return makeState(PS_InRootDir, Start, consumeSeparator(Start, End));
+    case PS_InRootDir:
+      return makeState(PS_InFilenames, Start, consumeName(Start, End));
+
+    case PS_InFilenames: {
+      PosPtr SepEnd = consumeSeparator(Start, End);
+      if (SepEnd != End) {
+        PosPtr TkEnd = consumeName(SepEnd, End);
+        if (TkEnd)
+          return makeState(PS_InFilenames, SepEnd, TkEnd);
+      }
+      return makeState(PS_InTrailingSep, Start, SepEnd);
+    }
 
-inline size_t root_name_start(const string_type& s) {
-    return good(root_name_end(s)) ? 0 : npos;
-}
+    case PS_InTrailingSep:
+      return makeState(PS_AtEnd);
 
-size_t root_name_end(const string_type& s) {
-    if (s.size() < 2 || s[0] != preferred_separator
-        || s[1] != preferred_separator) {
-        return npos;
+    case PS_AtEnd:
+      _LIBCPP_UNREACHABLE();
     }
-    if (s.size() == 2) {
-        return 1;
+  }
+
+  void decrement() noexcept {
+    const PosPtr REnd = getBeforeFront();
+    const PosPtr RStart = getCurrentTokenStartPos() - 1;
+
+    switch (State) {
+    case PS_AtEnd: {
+      // Try to consume a trailing separator or root directory first.
+      if (PosPtr SepEnd = consumeSeparator(RStart, REnd)) {
+        if (SepEnd == REnd)
+          return makeState((RStart == REnd + 2) ? PS_InRootName : PS_InRootDir,
+                           Path.data(), RStart + 1);
+        // Check if we're seeing the root directory separator
+        auto PP = CreateBegin(Path);
+        bool InRootDir = PP.State == PS_InRootName &&
+            &PP.RawEntry.back() == SepEnd;
+        return makeState(InRootDir ? PS_InRootDir : PS_InTrailingSep,
+                         SepEnd + 1, RStart + 1);
+      } else {
+        PosPtr TkStart = consumeName(RStart, REnd);
+        if (TkStart == REnd + 2 && consumeSeparator(TkStart, REnd) == REnd)
+          return makeState(PS_InRootName, Path.data(), RStart + 1);
+        else
+          return makeState(PS_InFilenames, TkStart + 1, RStart + 1);
+      }
     }
-    size_t index = 2; // current position
-    if (s[index] == preferred_separator) {
-        return npos;
+    case PS_InTrailingSep:
+      return makeState(PS_InFilenames, consumeName(RStart, REnd) + 1, RStart + 1);
+    case PS_InFilenames: {
+      PosPtr SepEnd = consumeSeparator(RStart, REnd);
+      if (SepEnd == REnd)
+        return makeState((RStart == REnd + 2) ? PS_InRootName : PS_InRootDir,
+                         Path.data(), RStart + 1);
+      PosPtr TkEnd = consumeName(SepEnd, REnd);
+      if (TkEnd == REnd + 2 && consumeSeparator(TkEnd, REnd) == REnd)
+        return makeState(PS_InRootDir, SepEnd + 1, RStart + 1);
+      return makeState(PS_InFilenames, TkEnd + 1, SepEnd + 1);
     }
-    while (index + 1 < s.size() && s[index+1] != preferred_separator) {
-        ++index;
+    case PS_InRootDir:
+      return makeState(PS_InRootName, Path.data(), RStart + 1);
+    case PS_InRootName:
+    case PS_BeforeBegin:
+      _LIBCPP_UNREACHABLE();
     }
-    return index;
-}
-
-size_t root_directory_start(const string_type& s) {
-    size_t e = root_name_end(s);
-    if (!good(e))
-    return is_separator(s, 0) ? 0 : npos;
-    return is_separator(s, e + 1) ? e + 1 : npos;
-}
-
-size_t root_directory_end(const string_type& s) {
-    size_t st = root_directory_start(s);
-    if (!good(st)) return npos;
-    size_t index = st;
-    while (index + 1 < s.size() && s[index + 1] == preferred_separator)
-      { ++index; }
-    return index;
-}
-
-string_view_pair separate_filename(string_type const & s) {
-    if (s == "." || s == ".." || s.empty()) return string_view_pair{s, ""};
-    auto pos = s.find_last_of('.');
-    if (pos == string_type::npos) return string_view_pair{s, string_view{}};
-    return string_view_pair{s.substr(0, pos), s.substr(pos)};
-}
-
-inline string_view extract_raw(const string_type& s, size_t pos) {
-    size_t end_i = end_of(s, pos);
-    if (!good(end_i)) return string_view{};
-    return string_view(s).substr(pos, end_i - pos + 1);
-}
-
-string_view extract_preferred(const string_type& s, size_t pos) {
-    string_view raw = extract_raw(s, pos);
-    if (raw.empty())
-        return raw;
-    if (is_trailing_separator(s, pos))
-        return string_view{dot};
-    if (is_separator(s, pos) && !is_root_name(s, pos))
-        return string_view(preferred_separator_str);
-    return raw;
-}
-
-}} // namespace parser
-
-
-////////////////////////////////////////////////////////////////////////////////
-//                            path_view_iterator
-////////////////////////////////////////////////////////////////////////////////
-namespace {
-
-struct path_view_iterator {
-  const string_view __s_;
-  size_t __pos_;
+  }
 
-  explicit path_view_iterator(string_view const& __s) : __s_(__s), __pos_(__s_.empty() ? parser::npos : 0) {}
-  explicit path_view_iterator(string_view const& __s, size_t __p) : __s_(__s), __pos_(__p) {}
+  /// \brief Return a view with the "preferred representation" of the current
+  ///   element. For example trailing separators are represented as a '.'
+  string_view_t operator*() const noexcept {
+    switch (State) {
+    case PS_BeforeBegin:
+    case PS_AtEnd:
+      return "";
+    case PS_InRootDir:
+      return "/";
+    case PS_InTrailingSep:
+      return ".";
+    case PS_InRootName:
+    case PS_InFilenames:
+      return RawEntry;
+    }
+    _LIBCPP_UNREACHABLE();
+  }
 
-  string_view operator*() const {
-    return parser::extract_preferred(__s_, __pos_);
+  explicit operator bool() const noexcept {
+    return State != PS_BeforeBegin && State != PS_AtEnd;
   }
 
-  path_view_iterator& operator++() {
+  PathParser& operator++() noexcept {
     increment();
     return *this;
   }
 
-  path_view_iterator& operator--() {
+  PathParser& operator--() noexcept {
     decrement();
     return *this;
   }
 
-  void increment() {
-    if (__pos_ == parser::npos) return;
-    while (! set_position(parser::end_of(__s_, __pos_)+1))
-        ;
-    return;
+private:
+  void makeState(ParserState NewState, PosPtr Start, PosPtr End) noexcept {
+    State = NewState;
+    RawEntry = string_view_t(Start, End - Start);
+  }
+  void makeState(ParserState NewState) noexcept {
+    State = NewState;
+    RawEntry = {};
   }
 
-  void decrement() {
-    if (__pos_ == 0) {
-      set_position(0);
-    }
-    else if (__pos_ == parser::npos) {
-      auto const str_size = __s_.size();
-      set_position(parser::start_of(
-          __s_, str_size != 0 ? str_size - 1 : str_size));
-    } else {
-      while (!set_position(parser::start_of(__s_, __pos_-1)))
-        ;
-    }
+  PosPtr getAfterBack() const noexcept {
+    return Path.data() + Path.size();
+  }
+
+  PosPtr getBeforeFront() const noexcept {
+    return Path.data() - 1;
   }
 
-  bool set_position(size_t pos) {
-    if (pos >= __s_.size()) {
-      __pos_ = parser::npos;
-    } else {
-      __pos_ = pos;
+  /// \brief Return a pointer to the first character after the currently
+  ///   lexed element.
+  PosPtr getNextTokenStartPos() const noexcept {
+    switch (State) {
+    case PS_BeforeBegin:
+      return Path.data();
+    case PS_InRootName:
+    case PS_InRootDir:
+    case PS_InFilenames:
+      return &RawEntry.back() + 1;
+    case PS_InTrailingSep:
+    case PS_AtEnd:
+      return getAfterBack();
     }
-    return valid_iterator_position();
+    _LIBCPP_UNREACHABLE();
   }
 
-  bool valid_iterator_position() const {
-    if (__pos_ == parser::npos) return true; // end position is valid
-    return (!parser::is_separator      (__s_, __pos_) ||
-          parser::is_root_directory    (__s_, __pos_) ||
-          parser::is_trailing_separator(__s_, __pos_) ||
-          parser::is_root_name         (__s_, __pos_));
+  /// \brief Return a pointer to the first character in the currently lexed
+  ///   element.
+  PosPtr getCurrentTokenStartPos() const noexcept {
+    switch (State) {
+    case PS_BeforeBegin:
+    case PS_InRootName:
+      return &Path.front();
+    case PS_InRootDir:
+    case PS_InFilenames:
+    case PS_InTrailingSep:
+      return &RawEntry.front();
+    case PS_AtEnd:
+      return &Path.back() + 1;
+    }
+    _LIBCPP_UNREACHABLE();
   }
 
-  bool is_end() const { return __pos_ == parser::npos; }
+  PosPtr consumeSeparator(PosPtr P, PosPtr End) const noexcept {
+    if (P == End || *P != '/')
+      return nullptr;
+    const int Inc = P < End ? 1 : -1;
+    P += Inc;
+    while (P != End && *P == '/')
+      P += Inc;
+    return P;
+  }
 
-  inline bool operator==(path_view_iterator const& __p) {
-      return __pos_ == __p.__pos_;
+  PosPtr consumeName(PosPtr P, PosPtr End) const noexcept {
+    if (P == End || *P == '/')
+      return nullptr;
+    const int Inc = P < End ? 1 : -1;
+    P += Inc;
+    while (P != End && *P != '/')
+      P += Inc;
+    return P;
   }
 };
 
-path_view_iterator pbegin(path const& p) {
-    return path_view_iterator(p.native());
+string_view_pair separate_filename(string_view_t const & s) {
+    if (s == "." || s == ".." || s.empty()) return string_view_pair{s, ""};
+    auto pos = s.find_last_of('.');
+    if (pos == string_view_t::npos)
+        return string_view_pair{s, string_view_t{}};
+    return string_view_pair{s.substr(0, pos), s.substr(pos)};
 }
 
-path_view_iterator pend(path const& p) {
-    path_view_iterator __p(p.native());
-    __p.__pos_ = parser::npos;
-    return __p;
+string_view_t createView(PosPtr S, PosPtr E) noexcept {
+  return {S, static_cast<size_t>(E - S) + 1};
 }
 
-} // end namespace
+}} // namespace parser
+
+_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL_FILESYSTEM
+
+using parser::string_view_t;
+using parser::string_view_pair;
+using parser::PathParser;
+using parser::createView;
+
 ///////////////////////////////////////////////////////////////////////////////
 //                            path definitions
 ///////////////////////////////////////////////////////////////////////////////
 
+constexpr path::value_type path::preferred_separator;
+
 path & path::replace_extension(path const & replacement)
 {
     path p = extension();
@@ -260,131 +303,145 @@ path & path::replace_extension(path const & replacement)
 ///////////////////////////////////////////////////////////////////////////////
 // path.decompose
 
-string_view path::__root_name() const
+string_view_t path::__root_name() const
 {
-    return parser::is_root_name(__pn_, 0)
-      ? parser::extract_preferred(__pn_, 0)
-      : string_view{};
+    auto PP = PathParser::CreateBegin(__pn_);
+    if (PP.State == PathParser::PS_InRootName)
+      return *PP;
+    return {};
 }
 
-string_view path::__root_directory() const
+string_view_t path::__root_directory() const
 {
-    auto start_i = parser::root_directory_start(__pn_);
-    if(!parser::good(start_i)) {
-        return {};
-    }
-    return parser::extract_preferred(__pn_, start_i);
+    auto PP = PathParser::CreateBegin(__pn_);
+    if (PP.State == PathParser::PS_InRootName)
+      ++PP;
+    if (PP.State == PathParser::PS_InRootDir)
+      return *PP;
+    return {};
 }
 
-string_view path::__relative_path() const
+string_view_t path::__root_path_raw() const
 {
-    if (empty()) {
-        return {__pn_};
-    }
-    auto end_i = parser::root_directory_end(__pn_);
-    if (not parser::good(end_i)) {
-        end_i = parser::root_name_end(__pn_);
+    auto PP = PathParser::CreateBegin(__pn_);
+    if (PP.State == PathParser::PS_InRootName) {
+      auto NextCh = PP.peek();
+      if (NextCh && *NextCh == '/') {
+        ++PP;
+        return createView(__pn_.data(), &PP.RawEntry.back());
+      }
+      return PP.RawEntry;
     }
-    if (not parser::good(end_i)) {
-        return {__pn_};
-    }
-    return string_view(__pn_).substr(end_i+1);
+    if (PP.State == PathParser::PS_InRootDir)
+      return *PP;
+    return {};
 }
 
-string_view path::__parent_path() const
+string_view_t path::__relative_path() const
 {
-    if (empty() || pbegin(*this) == --pend(*this)) {
-        return {};
-    }
-    auto end_it = --(--pend(*this));
-    auto end_i = parser::end_of(__pn_, end_it.__pos_);
-    return string_view(__pn_).substr(0, end_i+1);
+    auto PP = PathParser::CreateBegin(__pn_);
+    while (PP.State <= PathParser::PS_InRootDir)
+      ++PP;
+    if (PP.State == PathParser::PS_AtEnd)
+      return {};
+    return createView(PP.RawEntry.data(), &__pn_.back());
 }
 
-string_view path::__filename() const
+string_view_t path::__parent_path() const
 {
-    return empty() ? string_view{} : *--pend(*this);
+    if (empty())
+      return {};
+    auto PP = PathParser::CreateEnd(__pn_);
+    --PP;
+    if (PP.RawEntry.data() == __pn_.data())
+      return {};
+    --PP;
+    return createView(__pn_.data(), &PP.RawEntry.back());
 }
 
-string_view path::__stem() const
+string_view_t path::__filename() const
+{
+    if (empty()) return {};
+    return *(--PathParser::CreateEnd(__pn_));
+}
+
+string_view_t path::__stem() const
 {
     return parser::separate_filename(__filename()).first;
 }
 
-string_view path::__extension() const
+string_view_t path::__extension() const
 {
     return parser::separate_filename(__filename()).second;
 }
 
 ////////////////////////////////////////////////////////////////////////////
 // path.comparisons
-int path::__compare(const value_type* __s) const {
-    path_view_iterator thisIter(this->native());
-    path_view_iterator sIter(__s);
-    while (!thisIter.is_end() && !sIter.is_end()) {
-        int res = (*thisIter).compare(*sIter);
+int path::__compare(string_view_t __s) const {
+    auto PP = PathParser::CreateBegin(__pn_);
+    auto PP2 = PathParser::CreateBegin(__s);
+    while (PP && PP2) {
+        int res = (*PP).compare(*PP2);
         if (res != 0) return res;
-        ++thisIter; ++sIter;
+        ++PP; ++PP2;
     }
-    if (thisIter.is_end() && sIter.is_end())
+    if (PP.State == PP2.State && PP.State == PathParser::PS_AtEnd)
         return 0;
-    if (thisIter.is_end())
+    if (PP.State == PathParser::PS_AtEnd)
         return -1;
     return 1;
 }
 
 ////////////////////////////////////////////////////////////////////////////
 // path.nonmembers
-size_t hash_value(const path& __p) _NOEXCEPT {
-  path_view_iterator thisIter(__p.native());
-  struct HashPairT {
-    size_t first;
-    size_t second;
-  };
-  HashPairT hp = {0, 0};
-  std::hash<string_view> hasher;
-  std::__scalar_hash<decltype(hp)> pair_hasher;
-  while (!thisIter.is_end()) {
-    hp.second = hasher(*thisIter);
-    hp.first = pair_hasher(hp);
-    ++thisIter;
+size_t hash_value(const path& __p) noexcept {
+  auto PP = PathParser::CreateBegin(__p.native());
+  size_t hash_value = 0;
+  std::hash<string_view_t> hasher;
+  while (PP) {
+    hash_value = __hash_combine(hash_value, hasher(*PP));
+    ++PP;
   }
-  return hp.first;
+  return hash_value;
 }
 
 ////////////////////////////////////////////////////////////////////////////
 // path.itr
 path::iterator path::begin() const
 {
-    path_view_iterator pit = pbegin(*this);
+    auto PP = PathParser::CreateBegin(__pn_);
     iterator it;
     it.__path_ptr_ = this;
-    it.__pos_ = pit.__pos_;
-    it.__elem_.__assign_view(*pit);
+    it.__state_ = PP.State;
+    it.__entry_ = PP.RawEntry;
+    it.__stashed_elem_.__assign_view(*PP);
     return it;
 }
 
 path::iterator path::end() const
 {
     iterator it{};
+    it.__state_ = PathParser::PS_AtEnd;
     it.__path_ptr_ = this;
-    it.__pos_ = parser::npos;
     return it;
 }
 
 path::iterator& path::iterator::__increment() {
-  path_view_iterator it(__path_ptr_->native(), __pos_);
-  it.increment();
-  __pos_ = it.__pos_;
-  __elem_.__assign_view(*it);
+  static_assert(__at_end == PathParser::PS_AtEnd, "");
+  PathParser PP(__path_ptr_->native(), __entry_, __state_);
+  ++PP;
+  __state_ = PP.State;
+  __entry_ = PP.RawEntry;
+  __stashed_elem_.__assign_view(*PP);
   return *this;
 }
 
 path::iterator& path::iterator::__decrement() {
-  path_view_iterator it(__path_ptr_->native(), __pos_);
-  it.decrement();
-  __pos_ = it.__pos_;
-  __elem_.__assign_view(*it);
+  PathParser PP(__path_ptr_->native(), __entry_, __state_);
+  --PP;
+  __state_ = PP.State;
+  __entry_ = PP.RawEntry;
+  __stashed_elem_.__assign_view(*PP);
   return *this;
 }
 
diff --git a/lib/libcxx/src/experimental/memory_resource.cpp b/lib/libcxx/src/experimental/memory_resource.cpp
index c01eb0823ba..c4dc1ca894a 100644
--- a/lib/libcxx/src/experimental/memory_resource.cpp
+++ b/lib/libcxx/src/experimental/memory_resource.cpp
@@ -23,7 +23,7 @@ _LIBCPP_BEGIN_NAMESPACE_LFTS_PMR
 
 // new_delete_resource()
 
-class _LIBCPP_TYPE_VIS_ONLY __new_delete_memory_resource_imp
+class _LIBCPP_TYPE_VIS __new_delete_memory_resource_imp
     : public memory_resource
 {
 public:
@@ -34,7 +34,7 @@ protected:
         { return __allocate(__size); }
 
     virtual void do_deallocate(void * __p, size_t, size_t)
-        { __deallocate(__p); }
+        { _VSTD::__libcpp_deallocate(__p); }
 
     virtual bool do_is_equal(memory_resource const & __other) const _NOEXCEPT
         { return &__other == this; }
@@ -42,7 +42,7 @@ protected:
 
 // null_memory_resource()
 
-class _LIBCPP_TYPE_VIS_ONLY __null_memory_resource_imp
+class _LIBCPP_TYPE_VIS __null_memory_resource_imp
     : public memory_resource
 {
 public:
@@ -50,11 +50,7 @@ public:
 
 protected:
     virtual void* do_allocate(size_t, size_t) {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        throw std::bad_alloc();
-#else
-        abort();
-#endif
+        __throw_bad_alloc();
     }
     virtual void do_deallocate(void *, size_t, size_t) {}
     virtual bool do_is_equal(memory_resource const & __other) const _NOEXCEPT
@@ -74,7 +70,10 @@ union ResourceInitHelper {
 };
 // When compiled in C++14 this initialization should be a constant expression.
 // Only in C++11 is "init_priority" needed to ensure initialization order.
-ResourceInitHelper res_init __attribute__((init_priority (101)));
+#if _LIBCPP_STD_VER > 11
+_LIBCPP_SAFE_STATIC
+#endif
+ResourceInitHelper res_init  __attribute__((init_priority (101)));
 
 } // end namespace
 
@@ -93,7 +92,7 @@ static memory_resource *
 __default_memory_resource(bool set = false, memory_resource * new_res = nullptr) _NOEXCEPT
 {
 #ifndef _LIBCPP_HAS_NO_ATOMIC_HEADER
-    static atomic<memory_resource*> __res =
+    _LIBCPP_SAFE_STATIC static atomic<memory_resource*> __res =
         ATOMIC_VAR_INIT(&res_init.resources.new_delete_res);
     if (set) {
         new_res = new_res ? new_res : new_delete_resource();
@@ -106,7 +105,7 @@ __default_memory_resource(bool set = false, memory_resource * new_res = nullptr)
             &__res, memory_order::memory_order_acquire);
     }
 #elif !defined(_LIBCPP_HAS_NO_THREADS)
-    static memory_resource * res = &res_init.resources.new_delete_res;
+    _LIBCPP_SAFE_STATIC static memory_resource * res = &res_init.resources.new_delete_res;
     static mutex res_lock;
     if (set) {
         new_res = new_res ? new_res : new_delete_resource();
@@ -119,7 +118,7 @@ __default_memory_resource(bool set = false, memory_resource * new_res = nullptr)
         return res;
     }
 #else
-    static memory_resource* res = &res_init.resources.new_delete_res;
+    _LIBCPP_SAFE_STATIC static memory_resource* res = &res_init.resources.new_delete_res;
     if (set) {
         new_res = new_res ? new_res : new_delete_resource();
         memory_resource * old_res = res;
@@ -141,4 +140,4 @@ memory_resource * set_default_resource(memory_resource * __new_res) _NOEXCEPT
     return __default_memory_resource(true, __new_res);
 }
 
-_LIBCPP_END_NAMESPACE_LFTS_PMR
\ No newline at end of file
+_LIBCPP_END_NAMESPACE_LFTS_PMR
diff --git a/lib/libcxx/src/functional.cpp b/lib/libcxx/src/functional.cpp
new file mode 100644
index 00000000000..5c2646f01b2
--- /dev/null
+++ b/lib/libcxx/src/functional.cpp
@@ -0,0 +1,26 @@
+//===----------------------- functional.cpp -------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+#include "functional"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#ifdef _LIBCPP_ABI_BAD_FUNCTION_CALL_KEY_FUNCTION
+bad_function_call::~bad_function_call() _NOEXCEPT
+{
+}
+
+const char*
+bad_function_call::what() const _NOEXCEPT
+{
+    return "std::bad_function_call";
+}
+#endif
+
+_LIBCPP_END_NAMESPACE_STD
diff --git a/lib/libcxx/src/include/atomic_support.h b/lib/libcxx/src/include/atomic_support.h
index 8b719c5f221..ccd8d78d3d7 100644
--- a/lib/libcxx/src/include/atomic_support.h
+++ b/lib/libcxx/src/include/atomic_support.h
@@ -16,6 +16,7 @@
 #if defined(__clang__) && __has_builtin(__atomic_load_n)             \
                        && __has_builtin(__atomic_store_n)            \
                        && __has_builtin(__atomic_add_fetch)          \
+                       && __has_builtin(__atomic_exchange_n)         \
                        && __has_builtin(__atomic_compare_exchange_n) \
                        && defined(__ATOMIC_RELAXED)                  \
                        && defined(__ATOMIC_CONSUME)                  \
@@ -29,7 +30,7 @@
 #endif
 
 #if !defined(_LIBCPP_HAS_ATOMIC_BUILTINS) && !defined(_LIBCPP_HAS_NO_THREADS)
-# if defined(_MSC_VER) && !defined(__clang__)
+# if defined(_LIBCPP_WARNING)
     _LIBCPP_WARNING("Building libc++ without __atomic builtins is unsupported")
 # else
 #   warning Building libc++ without __atomic builtins is unsupported
@@ -45,7 +46,7 @@ namespace {
 enum __libcpp_atomic_order {
     _AO_Relaxed = __ATOMIC_RELAXED,
     _AO_Consume = __ATOMIC_CONSUME,
-    _AO_Aquire  = __ATOMIC_ACQUIRE,
+    _AO_Acquire = __ATOMIC_ACQUIRE,
     _AO_Release = __ATOMIC_RELEASE,
     _AO_Acq_Rel = __ATOMIC_ACQ_REL,
     _AO_Seq     = __ATOMIC_SEQ_CST
@@ -84,6 +85,14 @@ _ValueType __libcpp_atomic_add(_ValueType* __val, _AddType __a,
 
 template <class _ValueType>
 inline _LIBCPP_INLINE_VISIBILITY
+_ValueType __libcpp_atomic_exchange(_ValueType* __target,
+                                    _ValueType __value, int __order = _AO_Seq)
+{
+    return __atomic_exchange_n(__target, __value, __order);
+}
+
+template <class _ValueType>
+inline _LIBCPP_INLINE_VISIBILITY
 bool __libcpp_atomic_compare_exchange(_ValueType* __val,
     _ValueType* __expected, _ValueType __after,
     int __success_order = _AO_Seq,
@@ -137,6 +146,16 @@ _ValueType __libcpp_atomic_add(_ValueType* __val, _AddType __a,
 
 template <class _ValueType>
 inline _LIBCPP_INLINE_VISIBILITY
+_ValueType __libcpp_atomic_exchange(_ValueType* __target,
+                                    _ValueType __value, int __order = _AO_Seq)
+{
+    _ValueType old = *__target;
+    *__target = __value;
+    return old;
+}
+
+template <class _ValueType>
+inline _LIBCPP_INLINE_VISIBILITY
 bool __libcpp_atomic_compare_exchange(_ValueType* __val,
     _ValueType* __expected, _ValueType __after,
     int = 0, int = 0)
diff --git a/lib/libcxx/src/include/config_elast.h b/lib/libcxx/src/include/config_elast.h
index 9d6a76b0c00..4c4d853c2a6 100644
--- a/lib/libcxx/src/include/config_elast.h
+++ b/lib/libcxx/src/include/config_elast.h
@@ -10,7 +10,9 @@
 #ifndef _LIBCPP_CONFIG_ELAST
 #define _LIBCPP_CONFIG_ELAST
 
-#if defined(_WIN32)
+#include <__config>
+
+#if defined(_LIBCPP_MSVCRT)
 #include <stdlib.h>
 #else
 #include <errno.h>
@@ -20,14 +22,16 @@
 #define _LIBCPP_ELAST ELAST
 #elif defined(_NEWLIB_VERSION)
 #define _LIBCPP_ELAST __ELASTERROR
-#elif defined(__linux__)
+#elif defined(__Fuchsia__)
+// No _LIBCPP_ELAST needed on Fuchsia
+#elif defined(__linux__) || defined(_LIBCPP_HAS_MUSL_LIBC)
 #define _LIBCPP_ELAST 4095
 #elif defined(__APPLE__)
 // No _LIBCPP_ELAST needed on Apple
 #elif defined(__sun__)
 #define _LIBCPP_ELAST ESTALE
-#elif defined(_WIN32)
-#define _LIBCPP_ELAST _sys_nerr
+#elif defined(_LIBCPP_MSVCRT)
+#define _LIBCPP_ELAST (_sys_nerr - 1)
 #else
 // Warn here so that the person doing the libcxx port has an easier time:
 #warning ELAST for this platform not yet implemented
diff --git a/lib/libcxx/src/include/refstring.h b/lib/libcxx/src/include/refstring.h
new file mode 100644
index 00000000000..702f2b7388d
--- /dev/null
+++ b/lib/libcxx/src/include/refstring.h
@@ -0,0 +1,128 @@
+//===------------------------ __refstring ---------------------------------===//
+//
+//                     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_REFSTRING_H
+#define _LIBCPP_REFSTRING_H
+
+#include <__config>
+#include <stdexcept>
+#include <cstddef>
+#include <cstring>
+#ifdef __APPLE__
+#include <dlfcn.h>
+#include <mach-o/dyld.h>
+#endif
+#include "atomic_support.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace __refstring_imp { namespace {
+typedef int count_t;
+
+struct _Rep_base {
+    std::size_t len;
+    std::size_t cap;
+    count_t     count;
+};
+
+inline _Rep_base* rep_from_data(const char *data_) noexcept {
+    char *data = const_cast<char *>(data_);
+    return reinterpret_cast<_Rep_base *>(data - sizeof(_Rep_base));
+}
+
+inline char * data_from_rep(_Rep_base *rep) noexcept {
+    char *data = reinterpret_cast<char *>(rep);
+    return data + sizeof(*rep);
+}
+
+#if defined(__APPLE__)
+inline
+const char* compute_gcc_empty_string_storage() _NOEXCEPT
+{
+    void* handle = dlopen("/usr/lib/libstdc++.6.dylib", RTLD_NOLOAD);
+    if (handle == nullptr)
+        return nullptr;
+    void* sym = dlsym(handle, "_ZNSs4_Rep20_S_empty_rep_storageE");
+    if (sym == nullptr)
+        return nullptr;
+    return data_from_rep(reinterpret_cast<_Rep_base *>(sym));
+}
+
+inline
+const char*
+get_gcc_empty_string_storage() _NOEXCEPT
+{
+    static const char* p = compute_gcc_empty_string_storage();
+    return p;
+}
+#endif
+
+}} // namespace __refstring_imp
+
+using namespace __refstring_imp;
+
+inline
+__libcpp_refstring::__libcpp_refstring(const char* msg) {
+    std::size_t len = strlen(msg);
+    _Rep_base* rep = static_cast<_Rep_base *>(::operator new(sizeof(*rep) + len + 1));
+    rep->len = len;
+    rep->cap = len;
+    rep->count = 0;
+    char *data = data_from_rep(rep);
+    std::memcpy(data, msg, len + 1);
+    __imp_ = data;
+}
+
+inline
+__libcpp_refstring::__libcpp_refstring(const __libcpp_refstring &s) _NOEXCEPT
+    : __imp_(s.__imp_)
+{
+    if (__uses_refcount())
+        __libcpp_atomic_add(&rep_from_data(__imp_)->count, 1);
+}
+
+inline
+__libcpp_refstring& __libcpp_refstring::operator=(__libcpp_refstring const& s) _NOEXCEPT {
+    bool adjust_old_count = __uses_refcount();
+    struct _Rep_base *old_rep = rep_from_data(__imp_);
+    __imp_ = s.__imp_;
+    if (__uses_refcount())
+        __libcpp_atomic_add(&rep_from_data(__imp_)->count, 1);
+    if (adjust_old_count)
+    {
+        if (__libcpp_atomic_add(&old_rep->count, count_t(-1)) < 0)
+        {
+            ::operator delete(old_rep);
+        }
+    }
+    return *this;
+}
+
+inline
+__libcpp_refstring::~__libcpp_refstring() {
+    if (__uses_refcount()) {
+        _Rep_base* rep = rep_from_data(__imp_);
+        if (__libcpp_atomic_add(&rep->count, count_t(-1)) < 0) {
+            ::operator delete(rep);
+        }
+    }
+}
+
+inline
+bool __libcpp_refstring::__uses_refcount() const {
+#ifdef __APPLE__
+    return __imp_ != get_gcc_empty_string_storage();
+#else
+    return true;
+#endif
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif //_LIBCPP_REFSTRING_H
diff --git a/lib/libcxx/src/ios.cpp b/lib/libcxx/src/ios.cpp
index 23e3ee0ca04..0f1d88e378f 100644
--- a/lib/libcxx/src/ios.cpp
+++ b/lib/libcxx/src/ios.cpp
@@ -22,22 +22,23 @@
 #include "new"
 #include "streambuf"
 #include "string"
+#include "__undef_macros"
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template class basic_ios<char>;
-template class basic_ios<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_ios<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_ios<wchar_t>;
 
-template class basic_streambuf<char>;
-template class basic_streambuf<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_streambuf<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_streambuf<wchar_t>;
 
-template class basic_istream<char>;
-template class basic_istream<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_istream<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_istream<wchar_t>;
 
-template class basic_ostream<char>;
-template class basic_ostream<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_ostream<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_ostream<wchar_t>;
 
-template class basic_iostream<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_iostream<char>;
 
 class _LIBCPP_HIDDEN __iostream_category
     : public __do_message
diff --git a/lib/libcxx/src/iostream.cpp b/lib/libcxx/src/iostream.cpp
index e073aec6ead..2b47cf25b64 100644
--- a/lib/libcxx/src/iostream.cpp
+++ b/lib/libcxx/src/iostream.cpp
@@ -11,35 +11,71 @@
 #include "string"
 #include "new"
 
+#define _str(s) #s
+#define str(s) _str(s)
+#define _LIBCPP_NAMESPACE_STR str(_LIBCPP_NAMESPACE)
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 #ifndef _LIBCPP_HAS_NO_STDIN
-_ALIGNAS_TYPE (istream)  _LIBCPP_FUNC_VIS char cin [sizeof(istream)];
-_ALIGNAS_TYPE (__stdinbuf<char> ) static char __cin [sizeof(__stdinbuf <char>)];
+_ALIGNAS_TYPE (istream) _LIBCPP_FUNC_VIS char cin[sizeof(istream)]
+#if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
+__asm__("?cin@" _LIBCPP_NAMESPACE_STR "@std@@3V?$basic_istream@DU?$char_traits@D@" _LIBCPP_NAMESPACE_STR "@std@@@12@A")
+#endif
+;
+_ALIGNAS_TYPE (__stdinbuf<char> ) static char __cin[sizeof(__stdinbuf <char>)];
 static mbstate_t mb_cin;
-_ALIGNAS_TYPE (wistream) _LIBCPP_FUNC_VIS char wcin [sizeof(wistream)];
-_ALIGNAS_TYPE (__stdinbuf<wchar_t> ) static char __wcin [sizeof(__stdinbuf <wchar_t>)];
+_ALIGNAS_TYPE (wistream) _LIBCPP_FUNC_VIS char wcin[sizeof(wistream)]
+#if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
+__asm__("?wcin@" _LIBCPP_NAMESPACE_STR "@std@@3V?$basic_istream@_WU?$char_traits@_W@" _LIBCPP_NAMESPACE_STR "@std@@@12@A")
+#endif
+;
+_ALIGNAS_TYPE (__stdinbuf<wchar_t> ) static char __wcin[sizeof(__stdinbuf <wchar_t>)];
 static mbstate_t mb_wcin;
 #endif
 
 #ifndef _LIBCPP_HAS_NO_STDOUT
-_ALIGNAS_TYPE (ostream)  _LIBCPP_FUNC_VIS char cout[sizeof(ostream)];
+_ALIGNAS_TYPE (ostream) _LIBCPP_FUNC_VIS char cout[sizeof(ostream)]
+#if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
+__asm__("?cout@" _LIBCPP_NAMESPACE_STR "@std@@3V?$basic_ostream@DU?$char_traits@D@" _LIBCPP_NAMESPACE_STR "@std@@@12@A")
+#endif
+;
 _ALIGNAS_TYPE (__stdoutbuf<char>) static char __cout[sizeof(__stdoutbuf<char>)];
 static mbstate_t mb_cout;
-_ALIGNAS_TYPE (wostream) _LIBCPP_FUNC_VIS char wcout[sizeof(wostream)];
+_ALIGNAS_TYPE (wostream) _LIBCPP_FUNC_VIS char wcout[sizeof(wostream)]
+#if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
+__asm__("?wcout@" _LIBCPP_NAMESPACE_STR "@std@@3V?$basic_ostream@_WU?$char_traits@_W@" _LIBCPP_NAMESPACE_STR "@std@@@12@A")
+#endif
+;
 _ALIGNAS_TYPE (__stdoutbuf<wchar_t>) static char __wcout[sizeof(__stdoutbuf<wchar_t>)];
 static mbstate_t mb_wcout;
 #endif
 
-_ALIGNAS_TYPE (ostream)  _LIBCPP_FUNC_VIS char cerr[sizeof(ostream)];
+_ALIGNAS_TYPE (ostream) _LIBCPP_FUNC_VIS char cerr[sizeof(ostream)]
+#if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
+__asm__("?cerr@" _LIBCPP_NAMESPACE_STR "@std@@3V?$basic_ostream@DU?$char_traits@D@" _LIBCPP_NAMESPACE_STR "@std@@@12@A")
+#endif
+;
 _ALIGNAS_TYPE (__stdoutbuf<char>) static char __cerr[sizeof(__stdoutbuf<char>)];
 static mbstate_t mb_cerr;
-_ALIGNAS_TYPE (wostream) _LIBCPP_FUNC_VIS char wcerr[sizeof(wostream)];
+_ALIGNAS_TYPE (wostream) _LIBCPP_FUNC_VIS char wcerr[sizeof(wostream)]
+#if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
+__asm__("?wcerr@" _LIBCPP_NAMESPACE_STR "@std@@3V?$basic_ostream@_WU?$char_traits@_W@" _LIBCPP_NAMESPACE_STR "@std@@@12@A")
+#endif
+;
 _ALIGNAS_TYPE (__stdoutbuf<wchar_t>) static char __wcerr[sizeof(__stdoutbuf<wchar_t>)];
 static mbstate_t mb_wcerr;
 
-_ALIGNAS_TYPE (ostream)  _LIBCPP_FUNC_VIS char clog[sizeof(ostream)];
-_ALIGNAS_TYPE (wostream) _LIBCPP_FUNC_VIS char wclog[sizeof(wostream)];
+_ALIGNAS_TYPE (ostream) _LIBCPP_FUNC_VIS char clog[sizeof(ostream)]
+#if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
+__asm__("?clog@" _LIBCPP_NAMESPACE_STR "@std@@3V?$basic_ostream@DU?$char_traits@D@" _LIBCPP_NAMESPACE_STR "@std@@@12@A")
+#endif
+;
+_ALIGNAS_TYPE (wostream) _LIBCPP_FUNC_VIS char wclog[sizeof(wostream)]
+#if defined(_LIBCPP_ABI_MICROSOFT) && defined(__clang__)
+__asm__("?wclog@" _LIBCPP_NAMESPACE_STR "@std@@3V?$basic_ostream@_WU?$char_traits@_W@" _LIBCPP_NAMESPACE_STR "@std@@@12@A")
+#endif
+;
 
 ios_base::Init __start_std_streams;
 
diff --git a/lib/libcxx/src/locale.cpp b/lib/libcxx/src/locale.cpp
index da2fd11678d..a6cb0e97d12 100644
--- a/lib/libcxx/src/locale.cpp
+++ b/lib/libcxx/src/locale.cpp
@@ -24,15 +24,20 @@
 #endif
 #include "clocale"
 #include "cstring"
+#if defined(_LIBCPP_MSVCRT)
+#define _CTYPE_DISABLE_MACROS
+#endif
 #include "cwctype"
 #include "__sso_allocator"
 #if defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
 #include "support/win32/locale_win32.h"
-#elif !defined(__ANDROID__)
+#elif !defined(__BIONIC__)
 #include <langinfo.h>
 #endif
 #include <stdlib.h>
 #include <stdio.h>
+#include "include/atomic_support.h"
+#include "__undef_macros"
 
 // On Linux, wint_t and wchar_t have different signed-ness, and this causes
 // lots of noise in the build log, but no bugs that I know of. 
@@ -42,6 +47,24 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+struct __libcpp_unique_locale {
+  __libcpp_unique_locale(const char* nm) : __loc_(newlocale(LC_ALL_MASK, nm, 0)) {}
+
+  ~__libcpp_unique_locale() {
+    if (__loc_)
+      freelocale(__loc_);
+  }
+
+  explicit operator bool() const { return __loc_; }
+
+  locale_t& get() { return __loc_; }
+
+  locale_t __loc_;
+private:
+  __libcpp_unique_locale(__libcpp_unique_locale const&);
+  __libcpp_unique_locale& operator=(__libcpp_unique_locale const&);
+};
+
 #ifdef __cloc_defined
 locale_t __cloc() {
   // In theory this could create a race condition. In practice
@@ -65,8 +88,8 @@ T&
 make(A0 a0)
 {
     static typename aligned_storage<sizeof(T)>::type buf;
-    ::new (&buf) T(a0);
-    return *reinterpret_cast<T*>(&buf);
+    auto *obj = ::new (&buf) T(a0);
+    return *obj;
 }
 
 template <class T, class A0, class A1>
@@ -85,8 +108,8 @@ T&
 make(A0 a0, A1 a1, A2 a2)
 {
     static typename aligned_storage<sizeof(T)>::type buf;
-    ::new (&buf) T(a0, a1, a2);
-    return *reinterpret_cast<T*>(&buf);
+    auto *obj = ::new (&buf) T(a0, a1, a2);
+    return *obj;
 }
 
 template <typename T, size_t N>
@@ -107,6 +130,16 @@ countof(const T * const begin, const T * const end)
     return static_cast<size_t>(end - begin);
 }
 
+_LIBCPP_NORETURN static void __throw_runtime_error(const string &msg)
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw runtime_error(msg);
+#else
+    (void)msg;
+    _VSTD::abort();
+#endif
+}
+
 }
 
 #if defined(_AIX)
@@ -127,7 +160,7 @@ class _LIBCPP_HIDDEN locale::__imp
     : public facet
 {
     enum {N = 28};
-#if defined(_LIBCPP_MSVC)
+#if defined(_LIBCPP_COMPILER_MSVC)
 // FIXME: MSVC doesn't support aligned parameters by value.
 // I can't get the __sso_allocator to work here
 // for MSVC I think for this reason.
@@ -467,8 +500,8 @@ locale::__imp::make_global()
 {
     // only one thread can get in here and it only gets in once
     static aligned_storage<sizeof(locale)>::type buf;
-    ::new (&buf) locale(locale::classic());
-    return *reinterpret_cast<locale*>(&buf);
+    auto *obj = ::new (&buf) locale(locale::classic());
+    return *obj;
 }
 
 locale&
@@ -566,10 +599,8 @@ locale::global(const locale& loc)
     locale& g = __global();
     locale r = g;
     g = loc;
-#ifndef __CloudABI__
     if (g.name() != "*")
         setlocale(LC_ALL, g.name().c_str());
-#endif
     return r;
 }
 
@@ -637,7 +668,7 @@ locale::id::__get()
 void
 locale::id::__init()
 {
-    __id_ = __sync_add_and_fetch(&__next_id, 1);
+    __id_ = __libcpp_atomic_add(&__next_id, 1);
 }
 
 // template <> class collate_byname<char>
@@ -646,22 +677,18 @@ collate_byname<char>::collate_byname(const char* n, size_t refs)
     : collate<char>(refs),
       __l(newlocale(LC_ALL_MASK, n, 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__l == 0)
-        throw runtime_error("collate_byname<char>::collate_byname"
+        __throw_runtime_error("collate_byname<char>::collate_byname"
                             " failed to construct for " + string(n));
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 collate_byname<char>::collate_byname(const string& name, size_t refs)
     : collate<char>(refs),
       __l(newlocale(LC_ALL_MASK, name.c_str(), 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__l == 0)
-        throw runtime_error("collate_byname<char>::collate_byname"
+        __throw_runtime_error("collate_byname<char>::collate_byname"
                             " failed to construct for " + name);
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 collate_byname<char>::~collate_byname()
@@ -698,22 +725,18 @@ collate_byname<wchar_t>::collate_byname(const char* n, size_t refs)
     : collate<wchar_t>(refs),
       __l(newlocale(LC_ALL_MASK, n, 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__l == 0)
-        throw runtime_error("collate_byname<wchar_t>::collate_byname(size_t refs)"
+        __throw_runtime_error("collate_byname<wchar_t>::collate_byname(size_t refs)"
                             " failed to construct for " + string(n));
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 collate_byname<wchar_t>::collate_byname(const string& name, size_t refs)
     : collate<wchar_t>(refs),
       __l(newlocale(LC_ALL_MASK, name.c_str(), 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__l == 0)
-        throw runtime_error("collate_byname<wchar_t>::collate_byname(size_t refs)"
+        __throw_runtime_error("collate_byname<wchar_t>::collate_byname(size_t refs)"
                             " failed to construct for " + name);
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 collate_byname<wchar_t>::~collate_byname()
@@ -1106,9 +1129,7 @@ ctype<char>::classic_table()  _NOEXCEPT
 #elif __sun__
     return __ctype_mask;
 #elif defined(_LIBCPP_MSVCRT) || defined(__MINGW32__)
-    return _ctype+1; // internal ctype mask table defined in msvcrt.dll
-// This is assumed to be safe, which is a nonsense assumption because we're
-// going to end up dereferencing it later...
+    return __pctype_func();
 #elif defined(__EMSCRIPTEN__)
     return *__ctype_b_loc();
 #elif defined(_NEWLIB_VERSION)
@@ -1172,22 +1193,18 @@ ctype_byname<char>::ctype_byname(const char* name, size_t refs)
     : ctype<char>(0, false, refs),
       __l(newlocale(LC_ALL_MASK, name, 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__l == 0)
-        throw runtime_error("ctype_byname<char>::ctype_byname"
+        __throw_runtime_error("ctype_byname<char>::ctype_byname"
                             " failed to construct for " + string(name));
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 ctype_byname<char>::ctype_byname(const string& name, size_t refs)
     : ctype<char>(0, false, refs),
       __l(newlocale(LC_ALL_MASK, name.c_str(), 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__l == 0)
-        throw runtime_error("ctype_byname<char>::ctype_byname"
+        __throw_runtime_error("ctype_byname<char>::ctype_byname"
                             " failed to construct for " + name);
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 ctype_byname<char>::~ctype_byname()
@@ -1229,22 +1246,18 @@ ctype_byname<wchar_t>::ctype_byname(const char* name, size_t refs)
     : ctype<wchar_t>(refs),
       __l(newlocale(LC_ALL_MASK, name, 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__l == 0)
-        throw runtime_error("ctype_byname<wchar_t>::ctype_byname"
+        __throw_runtime_error("ctype_byname<wchar_t>::ctype_byname"
                             " failed to construct for " + string(name));
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 ctype_byname<wchar_t>::ctype_byname(const string& name, size_t refs)
     : ctype<wchar_t>(refs),
       __l(newlocale(LC_ALL_MASK, name.c_str(), 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__l == 0)
-        throw runtime_error("ctype_byname<wchar_t>::ctype_byname"
+        __throw_runtime_error("ctype_byname<wchar_t>::ctype_byname"
                             " failed to construct for " + name);
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 ctype_byname<wchar_t>::~ctype_byname()
@@ -1504,11 +1517,9 @@ codecvt<wchar_t, char, mbstate_t>::codecvt(const char* nm, size_t refs)
     : locale::facet(refs),
       __l(newlocale(LC_ALL_MASK, nm, 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__l == 0)
-        throw runtime_error("codecvt_byname<wchar_t, char, mbstate_t>::codecvt_byname"
+        __throw_runtime_error("codecvt_byname<wchar_t, char, mbstate_t>::codecvt_byname"
                             " failed to construct for " + string(nm));
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 codecvt<wchar_t, char, mbstate_t>::~codecvt()
@@ -3255,7 +3266,7 @@ __codecvt_utf8<wchar_t>::do_out(state_type&,
     const intern_type* frm, const intern_type* frm_end, const intern_type*& frm_nxt,
     extern_type* to, extern_type* to_end, extern_type*& to_nxt) const
 {
-#if _WIN32
+#if defined(_LIBCPP_SHORT_WCHAR)
     const uint16_t* _frm = reinterpret_cast<const uint16_t*>(frm);
     const uint16_t* _frm_end = reinterpret_cast<const uint16_t*>(frm_end);
     const uint16_t* _frm_nxt = _frm;
@@ -3267,7 +3278,7 @@ __codecvt_utf8<wchar_t>::do_out(state_type&,
     uint8_t* _to = reinterpret_cast<uint8_t*>(to);
     uint8_t* _to_end = reinterpret_cast<uint8_t*>(to_end);
     uint8_t* _to_nxt = _to;
-#if _WIN32
+#if defined(_LIBCPP_SHORT_WCHAR)
     result r = ucs2_to_utf8(_frm, _frm_end, _frm_nxt, _to, _to_end, _to_nxt,
                             _Maxcode_, _Mode_);
 #else
@@ -3287,7 +3298,7 @@ __codecvt_utf8<wchar_t>::do_in(state_type&,
     const uint8_t* _frm = reinterpret_cast<const uint8_t*>(frm);
     const uint8_t* _frm_end = reinterpret_cast<const uint8_t*>(frm_end);
     const uint8_t* _frm_nxt = _frm;
-#if _WIN32
+#if defined(_LIBCPP_SHORT_WCHAR)
     uint16_t* _to = reinterpret_cast<uint16_t*>(to);
     uint16_t* _to_end = reinterpret_cast<uint16_t*>(to_end);
     uint16_t* _to_nxt = _to;
@@ -4191,6 +4202,54 @@ __widen_from_utf8<32>::~__widen_from_utf8()
 {
 }
 
+
+static bool checked_string_to_wchar_convert(wchar_t& dest,
+                                            const char* ptr,
+                                            locale_t loc) {
+  if (*ptr == '\0')
+    return false;
+  mbstate_t mb = {};
+  wchar_t out;
+  size_t ret = __libcpp_mbrtowc_l(&out, ptr, strlen(ptr), &mb, loc);
+  if (ret == static_cast<size_t>(-1) || ret == static_cast<size_t>(-2)) {
+    return false;
+  }
+  dest = out;
+  return true;
+}
+
+static bool checked_string_to_char_convert(char& dest,
+                                           const char* ptr,
+                                           locale_t __loc) {
+  if (*ptr == '\0')
+    return false;
+  if (!ptr[1]) {
+    dest = *ptr;
+    return true;
+  }
+  // First convert the MBS into a wide char then attempt to narrow it using
+  // wctob_l.
+  wchar_t wout;
+  if (!checked_string_to_wchar_convert(wout, ptr, __loc))
+    return false;
+  int res;
+  if ((res = __libcpp_wctob_l(wout, __loc)) != char_traits<char>::eof()) {
+    dest = res;
+    return true;
+  }
+  // FIXME: Work around specific multibyte sequences that we can reasonable
+  // translate into a different single byte.
+  switch (wout) {
+  case L'\u00A0': // non-breaking space
+    dest = ' ';
+    return true;
+  default:
+    return false;
+  }
+  _LIBCPP_UNREACHABLE();
+}
+
+
 // numpunct<char> && numpunct<wchar_t>
 
 locale::id numpunct< char  >::id;
@@ -4256,17 +4315,16 @@ numpunct_byname<char>::__init(const char* nm)
 {
     if (strcmp(nm, "C") != 0)
     {
-        __locale_unique_ptr loc(newlocale(LC_ALL_MASK, nm, 0), freelocale);
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        if (loc == nullptr)
-            throw runtime_error("numpunct_byname<char>::numpunct_byname"
+        __libcpp_unique_locale loc(nm);
+        if (!loc)
+            __throw_runtime_error("numpunct_byname<char>::numpunct_byname"
                                 " failed to construct for " + string(nm));
-#endif  // _LIBCPP_NO_EXCEPTIONS
+
         lconv* lc = __libcpp_localeconv_l(loc.get());
-        if (*lc->decimal_point)
-            __decimal_point_ = *lc->decimal_point;
-        if (*lc->thousands_sep)
-            __thousands_sep_ = *lc->thousands_sep;
+        checked_string_to_char_convert(__decimal_point_, lc->decimal_point,
+                                       loc.get());
+        checked_string_to_char_convert(__thousands_sep_, lc->thousands_sep,
+                                       loc.get());
         __grouping_ = lc->grouping;
         // localization for truename and falsename is not available
     }
@@ -4295,19 +4353,18 @@ numpunct_byname<wchar_t>::__init(const char* nm)
 {
     if (strcmp(nm, "C") != 0)
     {
-        __locale_unique_ptr loc(newlocale(LC_ALL_MASK, nm, 0), freelocale);
-#ifndef _LIBCPP_NO_EXCEPTIONS
-        if (loc == nullptr)
-            throw runtime_error("numpunct_byname<char>::numpunct_byname"
+        __libcpp_unique_locale loc(nm);
+        if (!loc)
+            __throw_runtime_error("numpunct_byname<wchar_t>::numpunct_byname"
                                 " failed to construct for " + string(nm));
-#endif  // _LIBCPP_NO_EXCEPTIONS
+
         lconv* lc = __libcpp_localeconv_l(loc.get());
-        if (*lc->decimal_point)
-            __decimal_point_ = *lc->decimal_point;
-        if (*lc->thousands_sep)
-            __thousands_sep_ = *lc->thousands_sep;
+        checked_string_to_wchar_convert(__decimal_point_, lc->decimal_point,
+                                        loc.get());
+        checked_string_to_wchar_convert(__thousands_sep_, lc->thousands_sep,
+                                        loc.get());
         __grouping_ = lc->grouping;
-        // locallization for truename and falsename is not available
+        // localization for truename and falsename is not available
     }
 }
 
@@ -4703,21 +4760,17 @@ __time_get_c_storage<wchar_t>::__r() const
 __time_get::__time_get(const char* nm)
     : __loc_(newlocale(LC_ALL_MASK, nm, 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__loc_ == 0)
-        throw runtime_error("time_get_byname"
+        __throw_runtime_error("time_get_byname"
                             " failed to construct for " + string(nm));
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 __time_get::__time_get(const string& nm)
     : __loc_(newlocale(LC_ALL_MASK, nm.c_str(), 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__loc_ == 0)
-        throw runtime_error("time_get_byname"
+        __throw_runtime_error("time_get_byname"
                             " failed to construct for " + nm);
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 __time_get::~__time_get()
@@ -5363,21 +5416,17 @@ __time_get_storage<wchar_t>::__do_date_order() const
 __time_put::__time_put(const char* nm)
     : __loc_(newlocale(LC_ALL_MASK, nm, 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__loc_ == 0)
-        throw runtime_error("time_put_byname"
+        __throw_runtime_error("time_put_byname"
                             " failed to construct for " + string(nm));
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 __time_put::__time_put(const string& nm)
     : __loc_(newlocale(LC_ALL_MASK, nm.c_str(), 0))
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
     if (__loc_ == 0)
-        throw runtime_error("time_put_byname"
+        __throw_runtime_error("time_put_byname"
                             " failed to construct for " + nm);
-#endif  // _LIBCPP_NO_EXCEPTIONS
 }
 
 __time_put::~__time_put()
@@ -5791,21 +5840,21 @@ void
 moneypunct_byname<char, false>::init(const char* nm)
 {
     typedef moneypunct<char, false> base;
-    __locale_unique_ptr loc(newlocale(LC_ALL_MASK, nm, 0), freelocale);
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    if (loc == nullptr)
-        throw runtime_error("moneypunct_byname"
+    __libcpp_unique_locale loc(nm);
+    if (!loc)
+        __throw_runtime_error("moneypunct_byname"
                             " failed to construct for " + string(nm));
-#endif  // _LIBCPP_NO_EXCEPTIONS
+
     lconv* lc = __libcpp_localeconv_l(loc.get());
-    if (*lc->mon_decimal_point)
-        __decimal_point_ = *lc->mon_decimal_point;
-    else
-        __decimal_point_ = base::do_decimal_point();
-    if (*lc->mon_thousands_sep)
-        __thousands_sep_ = *lc->mon_thousands_sep;
-    else
-        __thousands_sep_ = base::do_thousands_sep();
+    if (!checked_string_to_char_convert(__decimal_point_,
+                                        lc->mon_decimal_point,
+                                        loc.get()))
+      __decimal_point_ = base::do_decimal_point();
+    if (!checked_string_to_char_convert(__thousands_sep_,
+                                        lc->mon_thousands_sep,
+                                        loc.get()))
+      __thousands_sep_ = base::do_thousands_sep();
+
     __grouping_ = lc->mon_grouping;
     __curr_symbol_ = lc->currency_symbol;
     if (lc->frac_digits != CHAR_MAX)
@@ -5835,21 +5884,20 @@ void
 moneypunct_byname<char, true>::init(const char* nm)
 {
     typedef moneypunct<char, true> base;
-    __locale_unique_ptr loc(newlocale(LC_ALL_MASK, nm, 0), freelocale);
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    if (loc == nullptr)
-        throw runtime_error("moneypunct_byname"
+    __libcpp_unique_locale loc(nm);
+    if (!loc)
+        __throw_runtime_error("moneypunct_byname"
                             " failed to construct for " + string(nm));
-#endif  // _LIBCPP_NO_EXCEPTIONS
+
     lconv* lc = __libcpp_localeconv_l(loc.get());
-    if (*lc->mon_decimal_point)
-        __decimal_point_ = *lc->mon_decimal_point;
-    else
-        __decimal_point_ = base::do_decimal_point();
-    if (*lc->mon_thousands_sep)
-        __thousands_sep_ = *lc->mon_thousands_sep;
-    else
-        __thousands_sep_ = base::do_thousands_sep();
+    if (!checked_string_to_char_convert(__decimal_point_,
+                                        lc->mon_decimal_point,
+                                        loc.get()))
+      __decimal_point_ = base::do_decimal_point();
+    if (!checked_string_to_char_convert(__thousands_sep_,
+                                        lc->mon_thousands_sep,
+                                        loc.get()))
+      __thousands_sep_ = base::do_thousands_sep();
     __grouping_ = lc->mon_grouping;
     __curr_symbol_ = lc->int_curr_symbol;
     if (lc->int_frac_digits != CHAR_MAX)
@@ -5896,21 +5944,19 @@ void
 moneypunct_byname<wchar_t, false>::init(const char* nm)
 {
     typedef moneypunct<wchar_t, false> base;
-    __locale_unique_ptr loc(newlocale(LC_ALL_MASK, nm, 0), freelocale);
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    if (loc == nullptr)
-        throw runtime_error("moneypunct_byname"
+    __libcpp_unique_locale loc(nm);
+    if (!loc)
+        __throw_runtime_error("moneypunct_byname"
                             " failed to construct for " + string(nm));
-#endif  // _LIBCPP_NO_EXCEPTIONS
     lconv* lc = __libcpp_localeconv_l(loc.get());
-    if (*lc->mon_decimal_point)
-        __decimal_point_ = static_cast<wchar_t>(*lc->mon_decimal_point);
-    else
-        __decimal_point_ = base::do_decimal_point();
-    if (*lc->mon_thousands_sep)
-        __thousands_sep_ = static_cast<wchar_t>(*lc->mon_thousands_sep);
-    else
-        __thousands_sep_ = base::do_thousands_sep();
+    if (!checked_string_to_wchar_convert(__decimal_point_,
+                                         lc->mon_decimal_point,
+                                         loc.get()))
+      __decimal_point_ = base::do_decimal_point();
+    if (!checked_string_to_wchar_convert(__thousands_sep_,
+                                         lc->mon_thousands_sep,
+                                         loc.get()))
+      __thousands_sep_ = base::do_thousands_sep();
     __grouping_ = lc->mon_grouping;
     wchar_t wbuf[100];
     mbstate_t mb = {0};
@@ -5963,21 +6009,20 @@ void
 moneypunct_byname<wchar_t, true>::init(const char* nm)
 {
     typedef moneypunct<wchar_t, true> base;
-    __locale_unique_ptr loc(newlocale(LC_ALL_MASK, nm, 0), freelocale);
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    if (loc == nullptr)
-        throw runtime_error("moneypunct_byname"
+    __libcpp_unique_locale loc(nm);
+    if (!loc)
+        __throw_runtime_error("moneypunct_byname"
                             " failed to construct for " + string(nm));
-#endif  // _LIBCPP_NO_EXCEPTIONS
+
     lconv* lc = __libcpp_localeconv_l(loc.get());
-    if (*lc->mon_decimal_point)
-        __decimal_point_ = static_cast<wchar_t>(*lc->mon_decimal_point);
-    else
-        __decimal_point_ = base::do_decimal_point();
-    if (*lc->mon_thousands_sep)
-        __thousands_sep_ = static_cast<wchar_t>(*lc->mon_thousands_sep);
-    else
-        __thousands_sep_ = base::do_thousands_sep();
+    if (!checked_string_to_wchar_convert(__decimal_point_,
+                                         lc->mon_decimal_point,
+                                         loc.get()))
+      __decimal_point_ = base::do_decimal_point();
+    if (!checked_string_to_wchar_convert(__thousands_sep_,
+                                         lc->mon_thousands_sep,
+                                         loc.get()))
+      __thousands_sep_ = base::do_thousands_sep();
     __grouping_ = lc->mon_grouping;
     wchar_t wbuf[100];
     mbstate_t mb = {0};
@@ -6050,69 +6095,68 @@ void __throw_runtime_error(const char* msg)
     throw runtime_error(msg);
 #else
     (void)msg;
+    _VSTD::abort();
 #endif
 }
 
-template class collate<char>;
-template class collate<wchar_t>;
-
-template class num_get<char>;
-template class num_get<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS collate<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS collate<wchar_t>;
 
-template struct __num_get<char>;
-template struct __num_get<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS num_get<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS num_get<wchar_t>;
 
-template class num_put<char>;
-template class num_put<wchar_t>;
+template struct _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __num_get<char>;
+template struct _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __num_get<wchar_t>;
 
-template struct __num_put<char>;
-template struct __num_put<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS num_put<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS num_put<wchar_t>;
 
-template class time_get<char>;
-template class time_get<wchar_t>;
+template struct _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __num_put<char>;
+template struct _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __num_put<wchar_t>;
 
-template class time_get_byname<char>;
-template class time_get_byname<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS time_get<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS time_get<wchar_t>;
 
-template class time_put<char>;
-template class time_put<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS time_get_byname<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS time_get_byname<wchar_t>;
 
-template class time_put_byname<char>;
-template class time_put_byname<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS time_put<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS time_put<wchar_t>;
 
-template class moneypunct<char, false>;
-template class moneypunct<char, true>;
-template class moneypunct<wchar_t, false>;
-template class moneypunct<wchar_t, true>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS time_put_byname<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS time_put_byname<wchar_t>;
 
-template class moneypunct_byname<char, false>;
-template class moneypunct_byname<char, true>;
-template class moneypunct_byname<wchar_t, false>;
-template class moneypunct_byname<wchar_t, true>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS moneypunct<char, false>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS moneypunct<char, true>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS moneypunct<wchar_t, false>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS moneypunct<wchar_t, true>;
 
-template class money_get<char>;
-template class money_get<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS moneypunct_byname<char, false>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS moneypunct_byname<char, true>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS moneypunct_byname<wchar_t, false>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS moneypunct_byname<wchar_t, true>;
 
-template class __money_get<char>;
-template class __money_get<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS money_get<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS money_get<wchar_t>;
 
-template class money_put<char>;
-template class money_put<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __money_get<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __money_get<wchar_t>;
 
-template class __money_put<char>;
-template class __money_put<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS money_put<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS money_put<wchar_t>;
 
-template class messages<char>;
-template class messages<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __money_put<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __money_put<wchar_t>;
 
-template class messages_byname<char>;
-template class messages_byname<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS messages<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS messages<wchar_t>;
 
-template class codecvt_byname<char, char, mbstate_t>;
-template class codecvt_byname<wchar_t, char, mbstate_t>;
-template class codecvt_byname<char16_t, char, mbstate_t>;
-template class codecvt_byname<char32_t, char, mbstate_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS messages_byname<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS messages_byname<wchar_t>;
 
-template class __vector_base_common<true>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS codecvt_byname<char, char, mbstate_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS codecvt_byname<wchar_t, char, mbstate_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS codecvt_byname<char16_t, char, mbstate_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS codecvt_byname<char32_t, char, mbstate_t>;
 
 _LIBCPP_END_NAMESPACE_STD
diff --git a/lib/libcxx/src/memory.cpp b/lib/libcxx/src/memory.cpp
index 15e947fc0ff..4e0d3af9167 100644
--- a/lib/libcxx/src/memory.cpp
+++ b/lib/libcxx/src/memory.cpp
@@ -17,28 +17,6 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-namespace
-{
-
-// NOTE: Relaxed and acq/rel atomics (for increment and decrement respectively)
-// should be sufficient for thread safety.
-// See https://llvm.org/bugs/show_bug.cgi?id=22803
-template <class T>
-inline T
-increment(T& t) _NOEXCEPT
-{
-    return __libcpp_atomic_add(&t, 1, _AO_Relaxed);
-}
-
-template <class T>
-inline T
-decrement(T& t) _NOEXCEPT
-{
-    return __libcpp_atomic_add(&t, -1, _AO_Acq_Rel);
-}
-
-}  // namespace
-
 const allocator_arg_t allocator_arg = allocator_arg_t();
 
 bad_weak_ptr::~bad_weak_ptr() _NOEXCEPT {}
@@ -53,16 +31,21 @@ __shared_count::~__shared_count()
 {
 }
 
+__shared_weak_count::~__shared_weak_count()
+{
+}
+
+#if defined(_LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS)
 void
 __shared_count::__add_shared() _NOEXCEPT
 {
-    increment(__shared_owners_);
+    __libcpp_atomic_refcount_increment(__shared_owners_);
 }
 
 bool
 __shared_count::__release_shared() _NOEXCEPT
 {
-    if (decrement(__shared_owners_) == -1)
+    if (__libcpp_atomic_refcount_decrement(__shared_owners_) == -1)
     {
         __on_zero_shared();
         return true;
@@ -70,10 +53,6 @@ __shared_count::__release_shared() _NOEXCEPT
     return false;
 }
 
-__shared_weak_count::~__shared_weak_count()
-{
-}
-
 void
 __shared_weak_count::__add_shared() _NOEXCEPT
 {
@@ -83,7 +62,7 @@ __shared_weak_count::__add_shared() _NOEXCEPT
 void
 __shared_weak_count::__add_weak() _NOEXCEPT
 {
-    increment(__shared_weak_owners_);
+    __libcpp_atomic_refcount_increment(__shared_weak_owners_);
 }
 
 void
@@ -93,10 +72,40 @@ __shared_weak_count::__release_shared() _NOEXCEPT
         __release_weak();
 }
 
+#endif // _LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS
+
 void
 __shared_weak_count::__release_weak() _NOEXCEPT
 {
-    if (decrement(__shared_weak_owners_) == -1)
+    // NOTE: The acquire load here is an optimization of the very
+    // common case where a shared pointer is being destructed while
+    // having no other contended references.
+    //
+    // BENEFIT: We avoid expensive atomic stores like XADD and STREX
+    // in a common case.  Those instructions are slow and do nasty
+    // things to caches.
+    //
+    // IS THIS SAFE?  Yes.  During weak destruction, if we see that we
+    // are the last reference, we know that no-one else is accessing
+    // us. If someone were accessing us, then they would be doing so
+    // while the last shared / weak_ptr was being destructed, and
+    // that's undefined anyway.
+    //
+    // If we see anything other than a 0, then we have possible
+    // contention, and need to use an atomicrmw primitive.
+    // The same arguments don't apply for increment, where it is legal
+    // (though inadvisable) to share shared_ptr references between
+    // threads, and have them all get copied at once.  The argument
+    // also doesn't apply for __release_shared, because an outstanding
+    // weak_ptr::lock() could read / modify the shared count.
+    if (__libcpp_atomic_load(&__shared_weak_owners_, _AO_Acquire) == 0)
+    {
+        // no need to do this store, because we are about
+        // to destroy everything.
+        //__libcpp_atomic_store(&__shared_weak_owners_, -1, _AO_Release);
+        __on_zero_shared_weak();
+    }
+    else if (__libcpp_atomic_refcount_decrement(__shared_weak_owners_) == -1)
         __on_zero_shared_weak();
 }
 
@@ -111,7 +120,7 @@ __shared_weak_count::lock() _NOEXCEPT
                                              object_owners+1))
             return this;
     }
-    return 0;
+    return nullptr;
 }
 
 #if !defined(_LIBCPP_NO_RTTI) || !defined(_LIBCPP_BUILD_STATIC)
@@ -119,15 +128,15 @@ __shared_weak_count::lock() _NOEXCEPT
 const void*
 __shared_weak_count::__get_deleter(const type_info&) const _NOEXCEPT
 {
-    return 0;
+    return nullptr;
 }
 
 #endif  // _LIBCPP_NO_RTTI
 
 #if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
 
-static const std::size_t __sp_mut_count = 16;
-static __libcpp_mutex_t mut_back_imp[__sp_mut_count] =
+_LIBCPP_SAFE_STATIC static const std::size_t __sp_mut_count = 16;
+_LIBCPP_SAFE_STATIC static __libcpp_mutex_t mut_back[__sp_mut_count] =
 {
     _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER,
     _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER,
@@ -135,8 +144,6 @@ static __libcpp_mutex_t mut_back_imp[__sp_mut_count] =
     _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER, _LIBCPP_MUTEX_INITIALIZER
 };
 
-static mutex* mut_back = reinterpret_cast<std::mutex*>(mut_back_imp);
-
 _LIBCPP_CONSTEXPR __sp_mut::__sp_mut(void* p) _NOEXCEPT
    : __lx(p)
 {
@@ -145,13 +152,13 @@ _LIBCPP_CONSTEXPR __sp_mut::__sp_mut(void* p) _NOEXCEPT
 void
 __sp_mut::lock() _NOEXCEPT
 {
-    mutex& m = *static_cast<mutex*>(__lx);
+    auto m = static_cast<__libcpp_mutex_t*>(__lx);
     unsigned count = 0;
-    while (!m.try_lock())
+    while (!__libcpp_mutex_trylock(m))
     {
         if (++count > 16)
         {
-            m.lock();
+            __libcpp_mutex_lock(m);
             break;
         }
         this_thread::yield();
@@ -161,13 +168,13 @@ __sp_mut::lock() _NOEXCEPT
 void
 __sp_mut::unlock() _NOEXCEPT
 {
-    static_cast<mutex*>(__lx)->unlock();
+    __libcpp_mutex_unlock(static_cast<__libcpp_mutex_t*>(__lx));
 }
 
 __sp_mut&
 __get_sp_mut(const void* p)
 {
-    static __sp_mut muts[__sp_mut_count] 
+    static __sp_mut muts[__sp_mut_count]
     {
         &mut_back[ 0], &mut_back[ 1], &mut_back[ 2], &mut_back[ 3],
         &mut_back[ 4], &mut_back[ 5], &mut_back[ 6], &mut_back[ 7],
@@ -194,11 +201,12 @@ undeclare_no_pointers(char*, size_t)
 {
 }
 
-pointer_safety
-get_pointer_safety() _NOEXCEPT
+#if !defined(_LIBCPP_ABI_POINTER_SAFETY_ENUM_TYPE)
+pointer_safety get_pointer_safety() _NOEXCEPT
 {
     return pointer_safety::relaxed;
 }
+#endif
 
 void*
 __undeclare_reachable(void* p)
diff --git a/lib/libcxx/src/mutex.cpp b/lib/libcxx/src/mutex.cpp
index 9f808ca5076..c36bd5549da 100644
--- a/lib/libcxx/src/mutex.cpp
+++ b/lib/libcxx/src/mutex.cpp
@@ -11,8 +11,8 @@
 #include "mutex"
 #include "limits"
 #include "system_error"
-#include "cassert"
 #include "include/atomic_support.h"
+#include "__undef_macros"
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 #ifndef _LIBCPP_HAS_NO_THREADS
@@ -37,7 +37,7 @@ mutex::lock()
 bool
 mutex::try_lock() _NOEXCEPT
 {
-    return __libcpp_mutex_trylock(&__m_) == 0;
+    return __libcpp_mutex_trylock(&__m_);
 }
 
 void
@@ -45,7 +45,7 @@ mutex::unlock() _NOEXCEPT
 {
     int ec = __libcpp_mutex_unlock(&__m_);
     (void)ec;
-    assert(ec == 0);
+    _LIBCPP_ASSERT(ec == 0, "call to mutex::unlock failed");
 }
 
 // recursive_mutex
@@ -59,15 +59,15 @@ recursive_mutex::recursive_mutex()
 
 recursive_mutex::~recursive_mutex()
 {
-    int e = __libcpp_mutex_destroy(&__m_);
+    int e = __libcpp_recursive_mutex_destroy(&__m_);
     (void)e;
-    assert(e == 0);
+    _LIBCPP_ASSERT(e == 0, "call to ~recursive_mutex() failed");
 }
 
 void
 recursive_mutex::lock()
 {
-    int ec = __libcpp_mutex_lock(&__m_);
+    int ec = __libcpp_recursive_mutex_lock(&__m_);
     if (ec)
         __throw_system_error(ec, "recursive_mutex lock failed");
 }
@@ -75,15 +75,15 @@ recursive_mutex::lock()
 void
 recursive_mutex::unlock() _NOEXCEPT
 {
-    int e = __libcpp_mutex_unlock(&__m_);
+    int e = __libcpp_recursive_mutex_unlock(&__m_);
     (void)e;
-    assert(e == 0);
+    _LIBCPP_ASSERT(e == 0, "call to recursive_mutex::unlock() failed");
 }
 
 bool
 recursive_mutex::try_lock() _NOEXCEPT
 {
-    return __libcpp_mutex_trylock(&__m_) == 0;
+    return __libcpp_recursive_mutex_trylock(&__m_);
 }
 
 // timed_mutex
@@ -195,13 +195,10 @@ recursive_timed_mutex::unlock() _NOEXCEPT
 // keep in sync with:  7741191.
 
 #ifndef _LIBCPP_HAS_NO_THREADS
-static __libcpp_mutex_t mut = _LIBCPP_MUTEX_INITIALIZER;
-static __libcpp_condvar_t cv = _LIBCPP_CONDVAR_INITIALIZER;
+_LIBCPP_SAFE_STATIC static __libcpp_mutex_t mut = _LIBCPP_MUTEX_INITIALIZER;
+_LIBCPP_SAFE_STATIC static __libcpp_condvar_t cv = _LIBCPP_CONDVAR_INITIALIZER;
 #endif
 
-/// NOTE: Changes to flag are done via relaxed atomic stores
-///       even though the accesses are protected by a mutex because threads
-///       just entering 'call_once` concurrently read from flag.
 void
 __call_once(volatile unsigned long& flag, void* arg, void(*func)(void*))
 {
@@ -238,7 +235,7 @@ __call_once(volatile unsigned long& flag, void* arg, void(*func)(void*))
             __libcpp_mutex_unlock(&mut);
             func(arg);
             __libcpp_mutex_lock(&mut);
-            __libcpp_relaxed_store(&flag, ~0ul);
+            __libcpp_atomic_store(&flag, ~0ul, _AO_Release);
             __libcpp_mutex_unlock(&mut);
             __libcpp_condvar_broadcast(&cv);
 #ifndef _LIBCPP_NO_EXCEPTIONS
diff --git a/lib/libcxx/src/new.cpp b/lib/libcxx/src/new.cpp
index f4f73d86803..e228a0d83d8 100644
--- a/lib/libcxx/src/new.cpp
+++ b/lib/libcxx/src/new.cpp
@@ -12,37 +12,61 @@
 #include <stdlib.h>
 
 #include "new"
+#include "include/atomic_support.h"
 
-#if defined(__APPLE__) && !defined(LIBCXXRT)
-    #include <cxxabi.h>
-
-    #ifndef _LIBCPPABI_VERSION
-        // On Darwin, there are two STL shared libraries and a lower level ABI
-        // shared library.  The global holding the current new handler is
-        // in the ABI library and named __cxa_new_handler.
-        #define __new_handler __cxxabiapple::__cxa_new_handler
-    #endif
-#else  // __APPLE__
-    #if defined(LIBCXXRT) || defined(LIBCXX_BUILDING_LIBCXXABI)
-        #include <cxxabi.h>
-    #endif  // defined(LIBCXX_BUILDING_LIBCXXABI)
-    #if !defined(_LIBCPPABI_VERSION) && !defined(__GLIBCXX__)
-        static std::new_handler __new_handler;
-    #endif  // _LIBCPPABI_VERSION
+#if defined(_LIBCPP_ABI_MICROSOFT)
+#if defined(_LIBCPP_NO_VCRUNTIME)
+#include "support/runtime/new_handler_fallback.ipp"
+#endif
+#elif defined(LIBCXX_BUILDING_LIBCXXABI)
+#include <cxxabi.h>
+#elif defined(LIBCXXRT)
+#include <cxxabi.h>
+#include "support/runtime/new_handler_fallback.ipp"
+#elif defined(__GLIBCXX__)
+// nothing todo
+#else
+# if defined(__APPLE__) && !defined(_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY)
+#   include <cxxabi.h> // FIXME: remove this once buildit is gone.
+# else
+#   include "support/runtime/new_handler_fallback.ipp"
+# endif
 #endif
 
+namespace std
+{
+
 #ifndef __GLIBCXX__
+const nothrow_t nothrow = {};
+#endif
+
+#ifndef LIBSTDCXX
+
+void
+__throw_bad_alloc()
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    throw bad_alloc();
+#else
+    _VSTD::abort();
+#endif
+}
+
+#endif // !LIBSTDCXX
+
+}  // std
+
+#if !defined(__GLIBCXX__) &&                                                   \
+    (!defined(_LIBCPP_ABI_MICROSOFT) || defined(_LIBCPP_NO_VCRUNTIME)) &&      \
+    !defined(_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS)
 
 // Implement all new and delete operators as weak definitions
 // in this shared library, so that they can be overridden by programs
 // that define non-weak copies of the functions.
 
-_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+_LIBCPP_WEAK
 void *
-operator new(std::size_t size)
-#if !__has_feature(cxx_noexcept)
-    throw(std::bad_alloc)
-#endif
+operator new(std::size_t size) _THROW_BAD_ALLOC
 {
     if (size == 0)
         size = 1;
@@ -64,7 +88,7 @@ operator new(std::size_t size)
     return p;
 }
 
-_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+_LIBCPP_WEAK
 void*
 operator new(size_t size, const std::nothrow_t&) _NOEXCEPT
 {
@@ -83,17 +107,14 @@ operator new(size_t size, const std::nothrow_t&) _NOEXCEPT
     return p;
 }
 
-_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+_LIBCPP_WEAK
 void*
-operator new[](size_t size)
-#if !__has_feature(cxx_noexcept)
-    throw(std::bad_alloc)
-#endif
+operator new[](size_t size) _THROW_BAD_ALLOC
 {
     return ::operator new(size);
 }
 
-_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+_LIBCPP_WEAK
 void*
 operator new[](size_t size, const std::nothrow_t&) _NOEXCEPT
 {
@@ -112,7 +133,7 @@ operator new[](size_t size, const std::nothrow_t&) _NOEXCEPT
     return p;
 }
 
-_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+_LIBCPP_WEAK
 void
 operator delete(void* ptr) _NOEXCEPT
 {
@@ -120,130 +141,166 @@ operator delete(void* ptr) _NOEXCEPT
         ::free(ptr);
 }
 
-_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+_LIBCPP_WEAK
 void
 operator delete(void* ptr, const std::nothrow_t&) _NOEXCEPT
 {
     ::operator delete(ptr);
 }
 
-_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+_LIBCPP_WEAK
 void
 operator delete(void* ptr, size_t) _NOEXCEPT
 {
     ::operator delete(ptr);
 }
 
-_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+_LIBCPP_WEAK
 void
 operator delete[] (void* ptr) _NOEXCEPT
 {
     ::operator delete(ptr);
 }
 
-_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+_LIBCPP_WEAK
 void
 operator delete[] (void* ptr, const std::nothrow_t&) _NOEXCEPT
 {
     ::operator delete[](ptr);
 }
 
-_LIBCPP_WEAK _LIBCPP_NEW_DELETE_VIS
+_LIBCPP_WEAK
 void
 operator delete[] (void* ptr, size_t) _NOEXCEPT
 {
     ::operator delete[](ptr);
 }
 
-#endif // !__GLIBCXX__
+#if !defined(_LIBCPP_HAS_NO_ALIGNED_ALLOCATION)
 
-namespace std
+_LIBCPP_WEAK
+void *
+operator new(std::size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC
 {
-
-#ifndef __GLIBCXX__
-const nothrow_t nothrow = {};
+    if (size == 0)
+        size = 1;
+    if (static_cast<size_t>(alignment) < sizeof(void*))
+      alignment = std::align_val_t(sizeof(void*));
+    void* p;
+#if defined(_LIBCPP_MSVCRT_LIKE)
+    while ((p = _aligned_malloc(size, static_cast<size_t>(alignment))) == nullptr)
+#else
+    while (::posix_memalign(&p, static_cast<size_t>(alignment), size) != 0)
 #endif
-
-#ifndef _LIBCPPABI_VERSION
-
-#ifndef __GLIBCXX__
-
-new_handler
-set_new_handler(new_handler handler) _NOEXCEPT
-{
-    return __sync_lock_test_and_set(&__new_handler, handler);
-}
-
-new_handler
-get_new_handler() _NOEXCEPT
-{
-    return __sync_fetch_and_add(&__new_handler, nullptr);
-}
-
-#endif // !__GLIBCXX__
-
-#ifndef LIBCXXRT
-
-bad_alloc::bad_alloc() _NOEXCEPT
-{
+    {
+        // If posix_memalign fails and there is a new_handler,
+        // call it to try free up memory.
+        std::new_handler nh = std::get_new_handler();
+        if (nh)
+            nh();
+        else {
+#ifndef _LIBCPP_NO_EXCEPTIONS
+            throw std::bad_alloc();
+#else
+            p = nullptr; // posix_memalign doesn't initialize 'p' on failure
+            break;
+#endif
+        }
+    }
+    return p;
 }
 
-#ifndef __GLIBCXX__
-
-bad_alloc::~bad_alloc() _NOEXCEPT
+_LIBCPP_WEAK
+void*
+operator new(size_t size, std::align_val_t alignment, const std::nothrow_t&) _NOEXCEPT
 {
+    void* p = 0;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try
+    {
+#endif  // _LIBCPP_NO_EXCEPTIONS
+        p = ::operator new(size, alignment);
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    }
+    catch (...)
+    {
+    }
+#endif  // _LIBCPP_NO_EXCEPTIONS
+    return p;
 }
 
-const char*
-bad_alloc::what() const _NOEXCEPT
+_LIBCPP_WEAK
+void*
+operator new[](size_t size, std::align_val_t alignment) _THROW_BAD_ALLOC
 {
-    return "std::bad_alloc";
+    return ::operator new(size, alignment);
 }
 
-#endif // !__GLIBCXX__
-
-bad_array_new_length::bad_array_new_length() _NOEXCEPT
+_LIBCPP_WEAK
+void*
+operator new[](size_t size, std::align_val_t alignment, const std::nothrow_t&) _NOEXCEPT
 {
+    void* p = 0;
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try
+    {
+#endif  // _LIBCPP_NO_EXCEPTIONS
+        p = ::operator new[](size, alignment);
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    }
+    catch (...)
+    {
+    }
+#endif  // _LIBCPP_NO_EXCEPTIONS
+    return p;
 }
 
-bad_array_new_length::~bad_array_new_length() _NOEXCEPT
+_LIBCPP_WEAK
+void
+operator delete(void* ptr, std::align_val_t) _NOEXCEPT
 {
+    if (ptr)
+#if defined(_LIBCPP_MSVCRT_LIKE)
+        ::_aligned_free(ptr);
+#else
+        ::free(ptr);
+#endif
 }
 
-const char*
-bad_array_new_length::what() const _NOEXCEPT
+_LIBCPP_WEAK
+void
+operator delete(void* ptr, std::align_val_t alignment, const std::nothrow_t&) _NOEXCEPT
 {
-    return "bad_array_new_length";
+    ::operator delete(ptr, alignment);
 }
 
-#endif //LIBCXXRT
-
-const char*
-bad_array_length::what() const _NOEXCEPT
+_LIBCPP_WEAK
+void
+operator delete(void* ptr, size_t, std::align_val_t alignment) _NOEXCEPT
 {
-    return "bad_array_length";
+    ::operator delete(ptr, alignment);
 }
 
-bad_array_length::bad_array_length() _NOEXCEPT
+_LIBCPP_WEAK
+void
+operator delete[] (void* ptr, std::align_val_t alignment) _NOEXCEPT
 {
+    ::operator delete(ptr, alignment);
 }
 
-bad_array_length::~bad_array_length() _NOEXCEPT
+_LIBCPP_WEAK
+void
+operator delete[] (void* ptr, std::align_val_t alignment, const std::nothrow_t&) _NOEXCEPT
 {
+    ::operator delete[](ptr, alignment);
 }
 
-#endif // _LIBCPPABI_VERSION
-
-#ifndef LIBSTDCXX
-
+_LIBCPP_WEAK
 void
-__throw_bad_alloc()
+operator delete[] (void* ptr, size_t, std::align_val_t alignment) _NOEXCEPT
 {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-    throw bad_alloc();
-#endif
+    ::operator delete[](ptr, alignment);
 }
 
-#endif // !LIBSTDCXX
-
-}  // std
+#endif // !_LIBCPP_HAS_NO_ALIGNED_ALLOCATION
+#endif // !__GLIBCXX__ && (!_LIBCPP_ABI_MICROSOFT || _LIBCPP_NO_VCRUNTIME) && !_LIBCPP_DISABLE_NEW_DELETE_DEFINITIONS
diff --git a/lib/libcxx/src/optional.cpp b/lib/libcxx/src/optional.cpp
index 8c5dd76d86d..2877d175bc1 100644
--- a/lib/libcxx/src/optional.cpp
+++ b/lib/libcxx/src/optional.cpp
@@ -7,18 +7,22 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "optional"
 #include "experimental/optional"
 
-_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
+namespace std
+{
 
-#ifdef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
+bad_optional_access::~bad_optional_access() _NOEXCEPT = default;
 
-bad_optional_access::~bad_optional_access() _NOEXCEPT {}
+const char* bad_optional_access::what() const _NOEXCEPT {
+  return "bad_optional_access";
+  }
 
-#else
+} // std
 
-bad_optional_access::~bad_optional_access() _NOEXCEPT = default;
+_LIBCPP_BEGIN_NAMESPACE_EXPERIMENTAL
 
-#endif
+bad_optional_access::~bad_optional_access() _NOEXCEPT = default;
 
 _LIBCPP_END_NAMESPACE_EXPERIMENTAL
diff --git a/lib/libcxx/src/random.cpp b/lib/libcxx/src/random.cpp
index 4ab424eaa6e..4a2468368d0 100644
--- a/lib/libcxx/src/random.cpp
+++ b/lib/libcxx/src/random.cpp
@@ -7,6 +7,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include <__config>
+
 #if defined(_LIBCPP_USING_WIN32_RANDOM)
 // Must be defined before including stdlib.h to enable rand_s().
 #define _CRT_RAND_S
@@ -23,7 +25,9 @@
 #include <stdio.h>
 #include <stdlib.h>
 
-#if defined(_LIBCPP_USING_DEV_RANDOM)
+#if defined(_LIBCPP_USING_GETENTROPY)
+#include <sys/random.h>
+#elif defined(_LIBCPP_USING_DEV_RANDOM)
 #include <fcntl.h>
 #include <unistd.h>
 #elif defined(_LIBCPP_USING_NACL_RANDOM)
@@ -33,7 +37,30 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if defined(_LIBCPP_USING_ARC4_RANDOM)
+#if defined(_LIBCPP_USING_GETENTROPY)
+
+random_device::random_device(const string& __token)
+{
+    if (__token != "/dev/urandom")
+        __throw_system_error(ENOENT, ("random device not supported " + __token).c_str());
+}
+
+random_device::~random_device()
+{
+}
+
+unsigned
+random_device::operator()()
+{
+    unsigned r;
+    size_t n = sizeof(r);
+    int err = getentropy(&r, n);
+    if (err)
+        __throw_system_error(errno, "random_device getentropy failed");
+    return r;
+}
+
+#elif defined(_LIBCPP_USING_ARC4_RANDOM)
 
 random_device::random_device(const string& __token)
 {
diff --git a/lib/libcxx/src/stdexcept.cpp b/lib/libcxx/src/stdexcept.cpp
index 0a08bfec27e..5e06e521e40 100644
--- a/lib/libcxx/src/stdexcept.cpp
+++ b/lib/libcxx/src/stdexcept.cpp
@@ -7,19 +7,21 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "__refstring"
 #include "stdexcept"
 #include "new"
 #include "string"
 #include "system_error"
+#include "include/refstring.h"
 
 /* For _LIBCPPABI_VERSION */
-#if defined(LIBCXX_BUILDING_LIBCXXABI) || defined(__APPLE__) || defined(LIBCXXRT)
+#if !defined(_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY) && \
+    (defined(LIBCXX_BUILDING_LIBCXXABI) || defined(__APPLE__) || defined(LIBCXXRT))
 #include <cxxabi.h>
 #endif
 
 static_assert(sizeof(std::__libcpp_refstring) == sizeof(const char *), "");
 
+
 namespace std  // purposefully not using versioning namespace
 {
 
diff --git a/lib/libcxx/src/string.cpp b/lib/libcxx/src/string.cpp
index d3f29df639f..d7ebdd3e5c9 100644
--- a/lib/libcxx/src/string.cpp
+++ b/lib/libcxx/src/string.cpp
@@ -13,17 +13,14 @@
 #include "cerrno"
 #include "limits"
 #include "stdexcept"
-#ifdef _LIBCPP_MSVCRT
-#include "support/win32/support.h"
-#endif // _LIBCPP_MSVCRT
 #include <stdio.h>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template class __basic_string_common<true>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __basic_string_common<true>;
 
-template class basic_string<char>;
-template class basic_string<wchar_t>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_string<char>;
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS basic_string<wchar_t>;
 
 template
     string
@@ -40,7 +37,7 @@ void throw_helper( const string& msg )
     throw T( msg );
 #else
     fprintf(stderr, "%s\n", msg.c_str());
-    abort();
+    _VSTD::abort();
 #endif
 }
 
@@ -430,7 +427,7 @@ get_swprintf()
 #ifndef _LIBCPP_MSVCRT
     return swprintf;
 #else
-    return static_cast<int (__cdecl*)(wchar_t* __restrict, size_t, const wchar_t*__restrict, ...)>(swprintf);
+    return static_cast<int (__cdecl*)(wchar_t* __restrict, size_t, const wchar_t*__restrict, ...)>(_snwprintf);
 #endif
 }
 
diff --git a/lib/libcxx/src/strstream.cpp b/lib/libcxx/src/strstream.cpp
index 0e2d7ff21bb..8b8521f76af 100644
--- a/lib/libcxx/src/strstream.cpp
+++ b/lib/libcxx/src/strstream.cpp
@@ -11,7 +11,9 @@
 #include "algorithm"
 #include "climits"
 #include "cstring"
+#include "cstdlib"
 #include "__debug"
+#include "__undef_macros"
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
@@ -184,7 +186,7 @@ strstreambuf::overflow(int_type __c)
         }
         setg(buf, buf + ninp, buf + einp);
         setp(buf + einp, buf + new_size);
-        pbump(static_cast<int>(nout));
+        __pbump(nout);
         __strmode_ |= __allocated;
     }
     *pptr() = static_cast<char>(__c);
@@ -266,6 +268,8 @@ strstreambuf::seekoff(off_type __off, ios_base::seekdir __way, ios_base::openmod
         case ios::end:
             newoff = seekhigh - eback();
             break;
+        default:
+            _LIBCPP_UNREACHABLE();
         }
         newoff += __off;
         if (0 <= newoff && newoff <= seekhigh - eback())
@@ -278,7 +282,7 @@ strstreambuf::seekoff(off_type __off, ios_base::seekdir __way, ios_base::openmod
                 // min(pbase, newpos), newpos, epptr()
                 __off = epptr() - newpos;
                 setp(min(pbase(), newpos), epptr());
-                pbump(static_cast<int>((epptr() - pbase()) - __off));
+                __pbump((epptr() - pbase()) - __off);
             }
             __p = newoff;
         }
@@ -308,7 +312,7 @@ strstreambuf::seekpos(pos_type __sp, ios_base::openmode __which)
                     // min(pbase, newpos), newpos, epptr()
                     off_type temp = epptr() - newpos;
                     setp(min(pbase(), newpos), epptr());
-                    pbump(static_cast<int>((epptr() - pbase()) - temp));
+                    __pbump((epptr() - pbase()) - temp);
                 }
                 __p = newoff;
             }
diff --git a/lib/libcxx/src/support/runtime/exception_fallback.ipp b/lib/libcxx/src/support/runtime/exception_fallback.ipp
new file mode 100644
index 00000000000..664e7f48c09
--- /dev/null
+++ b/lib/libcxx/src/support/runtime/exception_fallback.ipp
@@ -0,0 +1,181 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+#include <cstdio>
+
+namespace std {
+
+_LIBCPP_SAFE_STATIC static std::terminate_handler  __terminate_handler;
+_LIBCPP_SAFE_STATIC static std::unexpected_handler __unexpected_handler;
+
+
+// libcxxrt provides implementations of these functions itself.
+unexpected_handler
+set_unexpected(unexpected_handler func) _NOEXCEPT
+{
+  return __libcpp_atomic_exchange(&__unexpected_handler, func);
+}
+
+unexpected_handler
+get_unexpected() _NOEXCEPT
+{
+  return __libcpp_atomic_load(&__unexpected_handler);
+
+}
+
+_LIBCPP_NORETURN
+void unexpected()
+{
+    (*get_unexpected())();
+    // unexpected handler should not return
+    terminate();
+}
+
+terminate_handler
+set_terminate(terminate_handler func) _NOEXCEPT
+{
+  return __libcpp_atomic_exchange(&__terminate_handler, func);
+}
+
+terminate_handler
+get_terminate() _NOEXCEPT
+{
+  return __libcpp_atomic_load(&__terminate_handler);
+}
+
+#ifndef __EMSCRIPTEN__ // We provide this in JS
+_LIBCPP_NORETURN
+void
+terminate() _NOEXCEPT
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try
+    {
+#endif  // _LIBCPP_NO_EXCEPTIONS
+        (*get_terminate())();
+        // handler should not return
+        fprintf(stderr, "terminate_handler unexpectedly returned\n");
+        ::abort();
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    }
+    catch (...)
+    {
+        // handler should not throw exception
+        fprintf(stderr, "terminate_handler unexpectedly threw an exception\n");
+        ::abort();
+    }
+#endif  // _LIBCPP_NO_EXCEPTIONS
+}
+#endif // !__EMSCRIPTEN__
+
+#if !defined(__EMSCRIPTEN__)
+bool uncaught_exception() _NOEXCEPT { return uncaught_exceptions() > 0; }
+
+int uncaught_exceptions() _NOEXCEPT
+{
+#warning uncaught_exception not yet implemented
+  fprintf(stderr, "uncaught_exceptions not yet implemented\n");
+  ::abort();
+}
+#endif // !__EMSCRIPTEN__
+
+
+exception::~exception() _NOEXCEPT
+{
+}
+
+const char* exception::what() const _NOEXCEPT
+{
+  return "std::exception";
+}
+
+bad_exception::~bad_exception() _NOEXCEPT
+{
+}
+
+const char* bad_exception::what() const _NOEXCEPT
+{
+  return "std::bad_exception";
+}
+
+
+bad_alloc::bad_alloc() _NOEXCEPT
+{
+}
+
+bad_alloc::~bad_alloc() _NOEXCEPT
+{
+}
+
+const char*
+bad_alloc::what() const _NOEXCEPT
+{
+    return "std::bad_alloc";
+}
+
+bad_array_new_length::bad_array_new_length() _NOEXCEPT
+{
+}
+
+bad_array_new_length::~bad_array_new_length() _NOEXCEPT
+{
+}
+
+const char*
+bad_array_new_length::what() const _NOEXCEPT
+{
+    return "bad_array_new_length";
+}
+
+
+bad_array_length::bad_array_length() _NOEXCEPT
+{
+}
+
+bad_array_length::~bad_array_length() _NOEXCEPT
+{
+}
+
+const char*
+bad_array_length::what() const _NOEXCEPT
+{
+    return "bad_array_length";
+}
+
+
+bad_cast::bad_cast() _NOEXCEPT
+{
+}
+
+bad_typeid::bad_typeid() _NOEXCEPT
+{
+}
+
+bad_cast::~bad_cast() _NOEXCEPT
+{
+}
+
+const char*
+bad_cast::what() const _NOEXCEPT
+{
+  return "std::bad_cast";
+}
+
+bad_typeid::~bad_typeid() _NOEXCEPT
+{
+}
+
+const char*
+bad_typeid::what() const _NOEXCEPT
+{
+  return "std::bad_typeid";
+}
+
+} // namespace std
diff --git a/lib/libcxx/src/support/runtime/exception_glibcxx.ipp b/lib/libcxx/src/support/runtime/exception_glibcxx.ipp
new file mode 100644
index 00000000000..0f78932f6f9
--- /dev/null
+++ b/lib/libcxx/src/support/runtime/exception_glibcxx.ipp
@@ -0,0 +1,38 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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 __GLIBCXX__
+#error header can only be used when targeting libstdc++ or libsupc++
+#endif
+
+namespace std {
+
+bad_alloc::bad_alloc() _NOEXCEPT
+{
+}
+
+bad_array_new_length::bad_array_new_length() _NOEXCEPT
+{
+}
+
+bad_array_length::bad_array_length() _NOEXCEPT
+{
+}
+
+
+bad_cast::bad_cast() _NOEXCEPT
+{
+}
+
+bad_typeid::bad_typeid() _NOEXCEPT
+{
+}
+
+} // namespace std
diff --git a/lib/libcxx/src/support/runtime/exception_libcxxabi.ipp b/lib/libcxx/src/support/runtime/exception_libcxxabi.ipp
new file mode 100644
index 00000000000..c3dcf1ec591
--- /dev/null
+++ b/lib/libcxx/src/support/runtime/exception_libcxxabi.ipp
@@ -0,0 +1,28 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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 _LIBCPPABI_VERSION
+#error this header can only be used with libc++abi
+#endif
+
+namespace std {
+
+bool uncaught_exception() _NOEXCEPT { return uncaught_exceptions() > 0; }
+
+int uncaught_exceptions() _NOEXCEPT
+{
+# if _LIBCPPABI_VERSION > 1101
+    return __cxa_uncaught_exceptions();
+# else
+    return __cxa_uncaught_exception() ? 1 : 0;
+# endif
+}
+
+} // namespace std
diff --git a/lib/libcxx/src/support/runtime/exception_libcxxrt.ipp b/lib/libcxx/src/support/runtime/exception_libcxxrt.ipp
new file mode 100644
index 00000000000..6d9e0cff58d
--- /dev/null
+++ b/lib/libcxx/src/support/runtime/exception_libcxxrt.ipp
@@ -0,0 +1,41 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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 LIBCXXRT
+#error this header may only be used when targeting libcxxrt
+#endif
+
+namespace std {
+
+bad_exception::~bad_exception() _NOEXCEPT
+{
+}
+
+const char* bad_exception::what() const _NOEXCEPT
+{
+  return "std::bad_exception";
+}
+
+
+bad_array_length::bad_array_length() _NOEXCEPT
+{
+}
+
+bad_array_length::~bad_array_length() _NOEXCEPT
+{
+}
+
+const char*
+bad_array_length::what() const _NOEXCEPT
+{
+    return "bad_array_length";
+}
+
+} // namespace std
diff --git a/lib/libcxx/src/support/runtime/exception_msvc.ipp b/lib/libcxx/src/support/runtime/exception_msvc.ipp
new file mode 100644
index 00000000000..d5bf5b726ea
--- /dev/null
+++ b/lib/libcxx/src/support/runtime/exception_msvc.ipp
@@ -0,0 +1,190 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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_ABI_MICROSOFT
+#error this header can only be used when targeting the MSVC ABI
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#if !defined(_ACRTIMP)
+#define _ACRTIMP __declspec(dllimport)
+#endif
+
+#if !defined(_VCRTIMP)
+#define _VCRTIMP __declspec(dllimport)
+#endif
+
+#if !defined(__CRTDECL)
+#define __CRTDECL __cdecl
+#endif
+
+extern "C" {
+typedef void (__CRTDECL* terminate_handler)();
+_ACRTIMP terminate_handler __cdecl set_terminate(
+    terminate_handler _NewTerminateHandler) throw();
+_ACRTIMP terminate_handler __cdecl _get_terminate();
+
+typedef void (__CRTDECL* unexpected_handler)();
+_VCRTIMP unexpected_handler __cdecl set_unexpected(
+    unexpected_handler _NewUnexpectedHandler) throw();
+_VCRTIMP unexpected_handler __cdecl _get_unexpected();
+
+_VCRTIMP int __cdecl __uncaught_exceptions();
+}
+
+namespace std {
+
+unexpected_handler
+set_unexpected(unexpected_handler func) _NOEXCEPT {
+  return ::set_unexpected(func);
+}
+
+unexpected_handler get_unexpected() _NOEXCEPT {
+  return ::_get_unexpected();
+}
+
+_LIBCPP_NORETURN
+void unexpected() {
+    (*get_unexpected())();
+    // unexpected handler should not return
+    terminate();
+}
+
+terminate_handler set_terminate(terminate_handler func) _NOEXCEPT {
+  return ::set_terminate(func);
+}
+
+terminate_handler get_terminate() _NOEXCEPT {
+  return ::_get_terminate();
+}
+
+_LIBCPP_NORETURN
+void terminate() _NOEXCEPT
+{
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    try
+    {
+#endif  // _LIBCPP_NO_EXCEPTIONS
+        (*get_terminate())();
+        // handler should not return
+        fprintf(stderr, "terminate_handler unexpectedly returned\n");
+        ::abort();
+#ifndef _LIBCPP_NO_EXCEPTIONS
+    }
+    catch (...)
+    {
+        // handler should not throw exception
+        fprintf(stderr, "terminate_handler unexpectedly threw an exception\n");
+        ::abort();
+    }
+#endif  // _LIBCPP_NO_EXCEPTIONS
+}
+
+bool uncaught_exception() _NOEXCEPT { return uncaught_exceptions() > 0; }
+
+int uncaught_exceptions() _NOEXCEPT {
+    return __uncaught_exceptions();
+}
+
+bad_array_length::bad_array_length() _NOEXCEPT
+{
+}
+
+bad_array_length::~bad_array_length() _NOEXCEPT
+{
+}
+
+const char*
+bad_array_length::what() const _NOEXCEPT
+{
+    return "bad_array_length";
+}
+
+bad_cast::bad_cast() _NOEXCEPT
+{
+}
+
+bad_cast::~bad_cast() _NOEXCEPT
+{
+}
+
+const char *
+bad_cast::what() const _NOEXCEPT
+{
+  return "std::bad_cast";
+}
+
+bad_typeid::bad_typeid() _NOEXCEPT
+{
+}
+
+bad_typeid::~bad_typeid() _NOEXCEPT
+{
+}
+
+const char *
+bad_typeid::what() const _NOEXCEPT
+{
+  return "std::bad_typeid";
+}
+
+#if defined(_LIBCPP_NO_VCRUNTIME)
+exception::~exception() _NOEXCEPT
+{
+}
+
+const char* exception::what() const _NOEXCEPT
+{
+  return "std::exception";
+}
+
+
+bad_exception::~bad_exception() _NOEXCEPT
+{
+}
+
+const char* bad_exception::what() const _NOEXCEPT
+{
+  return "std::bad_exception";
+}
+
+
+bad_alloc::bad_alloc() _NOEXCEPT
+{
+}
+
+bad_alloc::~bad_alloc() _NOEXCEPT
+{
+}
+
+const char*
+bad_alloc::what() const _NOEXCEPT
+{
+    return "std::bad_alloc";
+}
+
+bad_array_new_length::bad_array_new_length() _NOEXCEPT
+{
+}
+
+bad_array_new_length::~bad_array_new_length() _NOEXCEPT
+{
+}
+
+const char*
+bad_array_new_length::what() const _NOEXCEPT
+{
+    return "bad_array_new_length";
+}
+#endif // _LIBCPP_NO_VCRUNTIME
+
+} // namespace std
diff --git a/lib/libcxx/src/support/runtime/exception_pointer_cxxabi.ipp b/lib/libcxx/src/support/runtime/exception_pointer_cxxabi.ipp
new file mode 100644
index 00000000000..dfac8648c49
--- /dev/null
+++ b/lib/libcxx/src/support/runtime/exception_pointer_cxxabi.ipp
@@ -0,0 +1,74 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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 HAVE_DEPENDENT_EH_ABI
+#error this header may only be used with libc++abi or libcxxrt
+#endif
+
+namespace std {
+
+exception_ptr::~exception_ptr() _NOEXCEPT {
+  __cxa_decrement_exception_refcount(__ptr_);
+}
+
+exception_ptr::exception_ptr(const exception_ptr& other) _NOEXCEPT
+    : __ptr_(other.__ptr_)
+{
+    __cxa_increment_exception_refcount(__ptr_);
+}
+
+exception_ptr& exception_ptr::operator=(const exception_ptr& other) _NOEXCEPT
+{
+    if (__ptr_ != other.__ptr_)
+    {
+        __cxa_increment_exception_refcount(other.__ptr_);
+        __cxa_decrement_exception_refcount(__ptr_);
+        __ptr_ = other.__ptr_;
+    }
+    return *this;
+}
+
+nested_exception::nested_exception() _NOEXCEPT
+    : __ptr_(current_exception())
+{
+}
+
+nested_exception::~nested_exception() _NOEXCEPT
+{
+}
+
+_LIBCPP_NORETURN
+void
+nested_exception::rethrow_nested() const
+{
+    if (__ptr_ == nullptr)
+        terminate();
+    rethrow_exception(__ptr_);
+}
+
+exception_ptr current_exception() _NOEXCEPT
+{
+    // be nicer if there was a constructor that took a ptr, then
+    // this whole function would be just:
+    //    return exception_ptr(__cxa_current_primary_exception());
+    exception_ptr ptr;
+    ptr.__ptr_ = __cxa_current_primary_exception();
+    return ptr;
+}
+
+_LIBCPP_NORETURN
+void rethrow_exception(exception_ptr p)
+{
+    __cxa_rethrow_primary_exception(p.__ptr_);
+    // if p.__ptr_ is NULL, above returns so we terminate
+    terminate();
+}
+
+} // namespace std
diff --git a/lib/libcxx/src/support/runtime/exception_pointer_glibcxx.ipp b/lib/libcxx/src/support/runtime/exception_pointer_glibcxx.ipp
new file mode 100644
index 00000000000..9d20dfe4862
--- /dev/null
+++ b/lib/libcxx/src/support/runtime/exception_pointer_glibcxx.ipp
@@ -0,0 +1,78 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// libsupc++ does not implement the dependent EH ABI and the functionality
+// it uses to implement std::exception_ptr (which it declares as an alias of
+// std::__exception_ptr::exception_ptr) is not directly exported to clients. So
+// we have little choice but to hijack std::__exception_ptr::exception_ptr's
+// (which fortunately has the same layout as our std::exception_ptr) copy
+// constructor, assignment operator and destructor (which are part of its
+// stable ABI), and its rethrow_exception(std::__exception_ptr::exception_ptr)
+// function.
+
+namespace std {
+
+namespace __exception_ptr
+{
+
+struct exception_ptr
+{
+    void* __ptr_;
+
+    exception_ptr(const exception_ptr&) _NOEXCEPT;
+    exception_ptr& operator=(const exception_ptr&) _NOEXCEPT;
+    ~exception_ptr() _NOEXCEPT;
+};
+
+}
+
+_LIBCPP_NORETURN void rethrow_exception(__exception_ptr::exception_ptr);
+
+exception_ptr::~exception_ptr() _NOEXCEPT
+{
+    reinterpret_cast<__exception_ptr::exception_ptr*>(this)->~exception_ptr();
+}
+
+exception_ptr::exception_ptr(const exception_ptr& other) _NOEXCEPT
+    : __ptr_(other.__ptr_)
+{
+    new (reinterpret_cast<void*>(this)) __exception_ptr::exception_ptr(
+        reinterpret_cast<const __exception_ptr::exception_ptr&>(other));
+}
+
+exception_ptr& exception_ptr::operator=(const exception_ptr& other) _NOEXCEPT
+{
+    *reinterpret_cast<__exception_ptr::exception_ptr*>(this) =
+        reinterpret_cast<const __exception_ptr::exception_ptr&>(other);
+    return *this;
+}
+
+nested_exception::nested_exception() _NOEXCEPT
+    : __ptr_(current_exception())
+{
+}
+
+
+_LIBCPP_NORETURN
+void
+nested_exception::rethrow_nested() const
+{
+    if (__ptr_ == nullptr)
+        terminate();
+    rethrow_exception(__ptr_);
+}
+
+_LIBCPP_NORETURN
+void rethrow_exception(exception_ptr p)
+{
+    rethrow_exception(reinterpret_cast<__exception_ptr::exception_ptr&>(p));
+}
+
+} // namespace std
diff --git a/lib/libcxx/src/support/runtime/exception_pointer_msvc.ipp b/lib/libcxx/src/support/runtime/exception_pointer_msvc.ipp
new file mode 100644
index 00000000000..5ca7519a600
--- /dev/null
+++ b/lib/libcxx/src/support/runtime/exception_pointer_msvc.ipp
@@ -0,0 +1,101 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#if !defined(_CRTIMP2_PURE)
+#define _CRTIMP2_PURE __declspec(dllimport)
+#endif
+
+#if !defined(__CLRCALL_PURE_OR_CDECL)
+#define __CLRCALL_PURE_OR_CDECL __cdecl
+#endif
+
+_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL __ExceptionPtrCreate(void*);
+_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL __ExceptionPtrDestroy(void*);
+_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL __ExceptionPtrCopy(void*,
+                                                              const void*);
+_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL
+__ExceptionPtrAssign(void*, const void*);
+_CRTIMP2_PURE bool __CLRCALL_PURE_OR_CDECL
+__ExceptionPtrCompare(const void*, const void*);
+_CRTIMP2_PURE bool __CLRCALL_PURE_OR_CDECL
+__ExceptionPtrToBool(const void*);
+_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL __ExceptionPtrSwap(void*, void*);
+_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL
+__ExceptionPtrCurrentException(void*);
+[[noreturn]] _CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL
+__ExceptionPtrRethrow(const void*);
+_CRTIMP2_PURE void __CLRCALL_PURE_OR_CDECL
+__ExceptionPtrCopyException(void*, const void*, const void*);
+
+namespace std {
+
+exception_ptr::exception_ptr() _NOEXCEPT { __ExceptionPtrCreate(this); }
+exception_ptr::exception_ptr(nullptr_t) _NOEXCEPT { __ExceptionPtrCreate(this); }
+
+exception_ptr::exception_ptr(const exception_ptr& __other) _NOEXCEPT {
+  __ExceptionPtrCopy(this, &__other);
+}
+exception_ptr& exception_ptr::operator=(const exception_ptr& __other) _NOEXCEPT {
+  __ExceptionPtrAssign(this, &__other);
+  return *this;
+}
+
+exception_ptr& exception_ptr::operator=(nullptr_t) _NOEXCEPT {
+  exception_ptr dummy;
+  __ExceptionPtrAssign(this, &dummy);
+  return *this;
+}
+
+exception_ptr::~exception_ptr() _NOEXCEPT { __ExceptionPtrDestroy(this); }
+
+exception_ptr::operator bool() const _NOEXCEPT {
+  return __ExceptionPtrToBool(this);
+}
+
+bool operator==(const exception_ptr& __x, const exception_ptr& __y) _NOEXCEPT {
+  return __ExceptionPtrCompare(&__x, &__y);
+}
+
+
+void swap(exception_ptr& lhs, exception_ptr& rhs) _NOEXCEPT {
+  __ExceptionPtrSwap(&rhs, &lhs);
+}
+
+exception_ptr __copy_exception_ptr(void* __except, const void* __ptr) {
+  exception_ptr __ret = nullptr;
+  if (__ptr)
+    __ExceptionPtrCopyException(&__ret, __except, __ptr);
+  return __ret;
+}
+
+exception_ptr current_exception() _NOEXCEPT {
+  exception_ptr __ret;
+  __ExceptionPtrCurrentException(&__ret);
+  return __ret;
+}
+
+_LIBCPP_NORETURN
+void rethrow_exception(exception_ptr p) { __ExceptionPtrRethrow(&p); }
+
+nested_exception::nested_exception() _NOEXCEPT : __ptr_(current_exception()) {}
+
+nested_exception::~nested_exception() _NOEXCEPT {}
+
+_LIBCPP_NORETURN
+void nested_exception::rethrow_nested() const {
+  if (__ptr_ == nullptr)
+    terminate();
+  rethrow_exception(__ptr_);
+}
+
+} // namespace std
diff --git a/lib/libcxx/src/support/runtime/exception_pointer_unimplemented.ipp b/lib/libcxx/src/support/runtime/exception_pointer_unimplemented.ipp
new file mode 100644
index 00000000000..21c182c8597
--- /dev/null
+++ b/lib/libcxx/src/support/runtime/exception_pointer_unimplemented.ipp
@@ -0,0 +1,80 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+#include <stdio.h>
+#include <stdlib.h>
+
+namespace std {
+
+exception_ptr::~exception_ptr() _NOEXCEPT
+{
+#  warning exception_ptr not yet implemented
+  fprintf(stderr, "exception_ptr not yet implemented\n");
+  ::abort();
+}
+
+exception_ptr::exception_ptr(const exception_ptr& other) _NOEXCEPT
+    : __ptr_(other.__ptr_)
+{
+#  warning exception_ptr not yet implemented
+  fprintf(stderr, "exception_ptr not yet implemented\n");
+  ::abort();
+}
+
+exception_ptr& exception_ptr::operator=(const exception_ptr& other) _NOEXCEPT
+{
+#  warning exception_ptr not yet implemented
+  fprintf(stderr, "exception_ptr not yet implemented\n");
+  ::abort();
+}
+
+nested_exception::nested_exception() _NOEXCEPT
+    : __ptr_(current_exception())
+{
+}
+
+#if !defined(__GLIBCXX__)
+
+nested_exception::~nested_exception() _NOEXCEPT
+{
+}
+
+#endif
+
+_LIBCPP_NORETURN
+void
+nested_exception::rethrow_nested() const
+{
+#  warning exception_ptr not yet implemented
+  fprintf(stderr, "exception_ptr not yet implemented\n");
+  ::abort();
+#if 0
+  if (__ptr_ == nullptr)
+      terminate();
+  rethrow_exception(__ptr_);
+#endif // FIXME
+}
+
+exception_ptr current_exception() _NOEXCEPT
+{
+#  warning exception_ptr not yet implemented
+  fprintf(stderr, "exception_ptr not yet implemented\n");
+  ::abort();
+}
+
+_LIBCPP_NORETURN
+void rethrow_exception(exception_ptr p)
+{
+#  warning exception_ptr not yet implemented
+  fprintf(stderr, "exception_ptr not yet implemented\n");
+  ::abort();
+}
+
+} // namespace std
diff --git a/lib/libcxx/src/support/runtime/new_handler_fallback.ipp b/lib/libcxx/src/support/runtime/new_handler_fallback.ipp
new file mode 100644
index 00000000000..ec3f52354ca
--- /dev/null
+++ b/lib/libcxx/src/support/runtime/new_handler_fallback.ipp
@@ -0,0 +1,27 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+namespace std {
+
+_LIBCPP_SAFE_STATIC static std::new_handler __new_handler;
+
+new_handler
+set_new_handler(new_handler handler) _NOEXCEPT
+{
+    return __libcpp_atomic_exchange(&__new_handler, handler);
+}
+
+new_handler
+get_new_handler() _NOEXCEPT
+{
+    return __libcpp_atomic_load(&__new_handler);
+}
+
+} // namespace std
diff --git a/lib/libcxx/src/support/solaris/xlocale.cpp b/lib/libcxx/src/support/solaris/xlocale.cpp
new file mode 100644
index 00000000000..6eaf317c768
--- /dev/null
+++ b/lib/libcxx/src/support/solaris/xlocale.cpp
@@ -0,0 +1,69 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifdef __sun__
+
+#include "support/solaris/xlocale.h"
+#include <stdarg.h>
+#include <stdio.h>
+#include <sys/localedef.h>
+
+extern "C" {
+
+int isxdigit_l(int __c, locale_t __l) {
+    return isxdigit(__c);
+}
+
+int iswxdigit_l(wint_t __c, locale_t __l) {
+    return isxdigit(__c);
+}
+
+// FIXME: This disregards the locale, which is Very Wrong
+#define vsnprintf_l(__s, __n, __l, __format, __va)  \
+    vsnprintf(__s, __n, __format, __va) 
+
+int snprintf_l(char *__s, size_t __n, locale_t __l, const char *__format, ...)
+{
+  va_list __va;
+  va_start(__va, __format);
+  int __res = vsnprintf_l(__s, __n , __l, __format, __va);
+  va_end(__va);
+  return __res;
+}
+
+int asprintf_l(char **__s, locale_t __l, const char *__format, ...) {
+  va_list __va;
+  va_start(__va, __format);
+  // FIXME:
+  int __res = vasprintf(__s, __format, __va);
+  va_end(__va);
+  return __res;
+}
+
+int sscanf_l(const char *__s, locale_t __l, const char *__format, ...) {
+  va_list __va;
+  va_start(__va, __format);
+  // FIXME:
+  int __res = vsscanf(__s, __format, __va);
+  va_end(__va);
+  return __res;
+}
+
+size_t mbrtowc_l(wchar_t *__pwc, const char *__pmb,
+                 size_t __max, mbstate_t *__ps, locale_t __loc) {
+  return mbrtowc(__pwc, __pmb, __max, __ps);
+}
+
+struct lconv *localeconv_l(locale_t __l) {
+  return localeconv();
+}
+
+};
+
+#endif // __sun__
diff --git a/lib/libcxx/src/support/win32/locale_win32.cpp b/lib/libcxx/src/support/win32/locale_win32.cpp
index 5a43743470d..fdca7efff06 100644
--- a/lib/libcxx/src/support/win32/locale_win32.cpp
+++ b/lib/libcxx/src/support/win32/locale_win32.cpp
@@ -10,79 +10,83 @@
 
 #include <locale>
 #include <cstdarg> // va_start, va_end
+#include <memory>
+#include <type_traits>
+
+using std::__libcpp_locale_guard;
 
 // FIXME: base currently unused. Needs manual work to construct the new locale
 locale_t newlocale( int mask, const char * locale, locale_t /*base*/ )
 {
-    return _create_locale( mask, locale );
+    return {_create_locale( LC_ALL, locale ), locale};
 }
-locale_t uselocale( locale_t newloc )
+
+decltype(MB_CUR_MAX) MB_CUR_MAX_L( locale_t __l )
 {
-    locale_t old_locale = _get_current_locale();
-    if ( newloc == NULL )
-        return old_locale;
-    // uselocale sets the thread's locale by definition, so unconditionally use thread-local locale
-    _configthreadlocale( _ENABLE_PER_THREAD_LOCALE );
-    // uselocale sets all categories
-    setlocale( LC_ALL, newloc->locinfo->lc_category[LC_ALL].locale );
-    // uselocale returns the old locale_t
-    return old_locale;
+#if defined(_LIBCPP_MSVCRT)
+  return ___mb_cur_max_l_func(__l);
+#else
+  __libcpp_locale_guard __current(__l);
+  return MB_CUR_MAX;
+#endif
 }
+
+
 lconv *localeconv_l( locale_t loc )
 {
-    __locale_raii __current( uselocale(loc), uselocale );
+    __libcpp_locale_guard __current(loc);
     return localeconv();
 }
 size_t mbrlen_l( const char *__restrict s, size_t n,
                  mbstate_t *__restrict ps, locale_t loc )
 {
-    __locale_raii __current( uselocale(loc), uselocale );
+    __libcpp_locale_guard __current(loc);
     return mbrlen( s, n, ps );
 }
 size_t mbsrtowcs_l( wchar_t *__restrict dst, const char **__restrict src,
                     size_t len, mbstate_t *__restrict ps, locale_t loc )
 {
-    __locale_raii __current( uselocale(loc), uselocale );
+    __libcpp_locale_guard __current(loc);
     return mbsrtowcs( dst, src, len, ps );
 }
 size_t wcrtomb_l( char *__restrict s, wchar_t wc, mbstate_t *__restrict ps,
                   locale_t loc )
 {
-    __locale_raii __current( uselocale(loc), uselocale );
+    __libcpp_locale_guard __current(loc);
     return wcrtomb( s, wc, ps );
 }
 size_t mbrtowc_l( wchar_t *__restrict pwc, const char *__restrict s,
                   size_t n, mbstate_t *__restrict ps, locale_t loc )
 {
-    __locale_raii __current( uselocale(loc), uselocale );
+    __libcpp_locale_guard __current(loc);
     return mbrtowc( pwc, s, n, ps );
 }
 size_t mbsnrtowcs_l( wchar_t *__restrict dst, const char **__restrict src,
                      size_t nms, size_t len, mbstate_t *__restrict ps, locale_t loc )
 {
-    __locale_raii __current( uselocale(loc), uselocale );
+    __libcpp_locale_guard __current(loc);
     return mbsnrtowcs( dst, src, nms, len, ps );
 }
 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 )
 {
-    __locale_raii __current( uselocale(loc), uselocale );
+    __libcpp_locale_guard __current(loc);
     return wcsnrtombs( dst, src, nwc, len, ps );
 }
 wint_t btowc_l( int c, locale_t loc )
 {
-    __locale_raii __current( uselocale(loc), uselocale );
+    __libcpp_locale_guard __current(loc);
     return btowc( c );
 }
 int wctob_l( wint_t c, locale_t loc )
 {
-    __locale_raii __current( uselocale(loc), uselocale );
+    __libcpp_locale_guard __current(loc);
     return wctob( c );
 }
 
 int snprintf_l(char *ret, size_t n, locale_t loc, const char *format, ...)
 {
-    __locale_raii __current( uselocale(loc), uselocale );
+    __libcpp_locale_guard __current(loc);
     va_list ap;
     va_start( ap, format );
     int result = vsnprintf( ret, n, format, ap );
@@ -100,6 +104,18 @@ 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 )
 {
-    __locale_raii __current( uselocale(loc), uselocale );
+    __libcpp_locale_guard __current(loc);
     return vasprintf( ret, format, ap );
 }
+
+#if !defined(_LIBCPP_MSVCRT)
+float strtof_l(const char* nptr, char** endptr, locale_t loc) {
+  __libcpp_locale_guard __current(loc);
+  return strtof(nptr, endptr);
+}
+
+long double strtold_l(const char* nptr, char** endptr, locale_t loc) {
+  __libcpp_locale_guard __current(loc);
+  return strtold(nptr, endptr);
+}
+#endif
diff --git a/lib/libcxx/src/support/win32/support.cpp b/lib/libcxx/src/support/win32/support.cpp
index e989681a6d5..dbd1c4c418a 100644
--- a/lib/libcxx/src/support/win32/support.cpp
+++ b/lib/libcxx/src/support/win32/support.cpp
@@ -15,17 +15,6 @@
 #include <cstring> // strcpy, wcsncpy
 #include <cwchar>  // mbstate_t
 
-// Some of these functions aren't standard or if they conform, the name does not.
-
-int asprintf(char **sptr, const char *__restrict format, ...)
-{
-    va_list ap;
-    va_start(ap, format);
-    int result;
-    result = vasprintf(sptr, format, ap);
-    va_end(ap);
-    return result;
-}
 
 // Like sprintf, but when return value >= 0 it returns
 // a pointer to a malloc'd string in *sptr.
diff --git a/lib/libcxx/src/system_error.cpp b/lib/libcxx/src/system_error.cpp
index 87f35ae37f3..72623ea6bc8 100644
--- a/lib/libcxx/src/system_error.cpp
+++ b/lib/libcxx/src/system_error.cpp
@@ -17,9 +17,9 @@
 #include "cstring"
 #include "cstdio"
 #include "cstdlib"
-#include "cassert"
 #include "string"
 #include "string.h"
+#include "__debug"
 
 #if defined(__ANDROID__)
 #include <android/api-level.h>
@@ -29,9 +29,11 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 // class error_category
 
+#if defined(_LIBCPP_DEPRECATED_ABI_LEGACY_LIBRARY_DEFINITIONS_FOR_INLINE_FUNCTIONS)
 error_category::error_category() _NOEXCEPT
 {
 }
+#endif
 
 error_category::~error_category() _NOEXCEPT
 {
@@ -55,6 +57,7 @@ error_category::equivalent(const error_code& code, int condition) const _NOEXCEP
     return *this == code.category() && code.value() == condition;
 }
 
+#if !defined(_LIBCPP_HAS_NO_THREADS)
 namespace {
 
 //  GLIBC also uses 1024 as the maximum buffer size internally.
@@ -62,40 +65,69 @@ constexpr size_t strerror_buff_size = 1024;
 
 string do_strerror_r(int ev);
 
-#if defined(__linux__) && !defined(_LIBCPP_HAS_MUSL_LIBC)                      \
-    && (!defined(__ANDROID__) || __ANDROID_API__ >= 23)
-// GNU Extended version
+#if defined(_LIBCPP_MSVCRT_LIKE)
 string do_strerror_r(int ev) {
-    char buffer[strerror_buff_size];
-    char* ret = ::strerror_r(ev, buffer, strerror_buff_size);
-    return string(ret);
+  char buffer[strerror_buff_size];
+  if (::strerror_s(buffer, strerror_buff_size, ev) == 0)
+    return string(buffer);
+  std::snprintf(buffer, strerror_buff_size, "unknown error %d", ev);
+  return string(buffer);
 }
 #else
-// POSIX version
+
+// Only one of the two following functions will be used, depending on
+// the return type of strerror_r:
+
+// For the GNU variant, a char* return value:
+__attribute__((unused)) const char *
+handle_strerror_r_return(char *strerror_return, char *buffer) {
+  // GNU always returns a string pointer in its return value. The
+  // string might point to either the input buffer, or a static
+  // buffer, but we don't care which.
+  return strerror_return;
+}
+
+// For the POSIX variant: an int return value.
+__attribute__((unused)) const char *
+handle_strerror_r_return(int strerror_return, char *buffer) {
+  // The POSIX variant either:
+  // - fills in the provided buffer and returns 0
+  // - returns a positive error value, or
+  // - returns -1 and fills in errno with an error value.
+  if (strerror_return == 0)
+    return buffer;
+
+  // Only handle EINVAL. Other errors abort.
+  int new_errno = strerror_return == -1 ? errno : strerror_return;
+  if (new_errno == EINVAL)
+    return "";
+
+  _LIBCPP_ASSERT(new_errno == ERANGE, "unexpected error from ::strerror_r");
+  // FIXME maybe? 'strerror_buff_size' is likely to exceed the
+  // maximum error size so ERANGE shouldn't be returned.
+  std::abort();
+}
+
+// This function handles both GNU and POSIX variants, dispatching to
+// one of the two above functions.
 string do_strerror_r(int ev) {
     char buffer[strerror_buff_size];
+    // Preserve errno around the call. (The C++ standard requires that
+    // system_error functions not modify errno).
     const int old_errno = errno;
-    int ret;
-    if ((ret = ::strerror_r(ev, buffer, strerror_buff_size)) != 0) {
-        // If `ret == -1` then the error is specified using `errno`, otherwise
-        // `ret` represents the error.
-        const int new_errno = ret == -1 ? errno : ret;
-        errno = old_errno;
-        if (new_errno == EINVAL) {
-            std::snprintf(buffer, strerror_buff_size, "Unknown error %d", ev);
-            return string(buffer);
-        } else {
-            assert(new_errno == ERANGE);
-            // FIXME maybe? 'strerror_buff_size' is likely to exceed the
-            // maximum error size so ERANGE shouldn't be returned.
-            std::abort();
-        }
+    const char *error_message = handle_strerror_r_return(
+        ::strerror_r(ev, buffer, strerror_buff_size), buffer);
+    // If we didn't get any message, print one now.
+    if (!error_message[0]) {
+      std::snprintf(buffer, strerror_buff_size, "Unknown error %d", ev);
+      error_message = buffer;
     }
-    return string(buffer);
+    errno = old_errno;
+    return string(error_message);
 }
 #endif
-
 } // end namespace
+#endif
 
 string
 __do_message::message(int ev) const
@@ -258,6 +290,7 @@ __throw_system_error(int ev, const char* what_arg)
 #else
     (void)ev;
     (void)what_arg;
+    _VSTD::abort();
 #endif
 }
 
diff --git a/lib/libcxx/src/typeinfo.cpp b/lib/libcxx/src/typeinfo.cpp
index 5c0a609b5e5..0cb193b77d9 100644
--- a/lib/libcxx/src/typeinfo.cpp
+++ b/lib/libcxx/src/typeinfo.cpp
@@ -6,63 +6,52 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
-#include <stdlib.h>
-
-#if defined(__APPLE__) || defined(LIBCXXRT) ||                                 \
-    defined(LIBCXX_BUILDING_LIBCXXABI)
-#include <cxxabi.h>
-#endif
 
 #include "typeinfo"
 
-#if !defined(LIBCXXRT) && !defined(_LIBCPPABI_VERSION)
+#if defined(_LIBCPP_ABI_MICROSOFT)
+#include <string.h>
 
-std::bad_cast::bad_cast() _NOEXCEPT
-{
+int std::type_info::__compare(const type_info &__rhs) const _NOEXCEPT {
+  if (&__data == &__rhs.__data)
+    return 0;
+  return strcmp(&__data.__decorated_name[1], &__rhs.__data.__decorated_name[1]);
 }
 
-std::bad_typeid::bad_typeid() _NOEXCEPT
-{
+const char *std::type_info::name() const _NOEXCEPT {
+  // TODO(compnerd) cache demangled &__data.__decorated_name[1]
+  return &__data.__decorated_name[1];
 }
 
-#ifndef __GLIBCXX__
+size_t std::type_info::hash_code() const _NOEXCEPT {
+#if defined(_WIN64)
+  constexpr size_t fnv_offset_basis = 14695981039346656037ull;
+  constexpr size_t fnv_prime = 10995116282110ull;
+#else
+  constexpr size_t fnv_offset_basis = 2166136261ull;
+  constexpr size_t fnv_prime = 16777619ull;
+#endif
 
-std::bad_cast::~bad_cast() _NOEXCEPT
-{
-}
+  size_t value = fnv_offset_basis;
+  for (const char* c = &__data.__decorated_name[1]; *c; ++c) {
+    value ^= static_cast<size_t>(static_cast<unsigned char>(*c));
+    value *= fnv_prime;
+  }
 
-const char*
-std::bad_cast::what() const _NOEXCEPT
-{
-  return "std::bad_cast";
-}
+#if defined(_WIN64)
+  value ^= value >> 32;
+#endif
 
-std::bad_typeid::~bad_typeid() _NOEXCEPT
-{
+  return value;
 }
-
-const char*
-std::bad_typeid::what() const _NOEXCEPT
+#endif // _LIBCPP_ABI_MICROSOFT
+
+// FIXME: Remove __APPLE__ default here once buildit is gone.
+// FIXME: Remove the _LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY configuration.
+#if (!defined(LIBCXX_BUILDING_LIBCXXABI) && !defined(LIBCXXRT) &&              \
+     !defined(__GLIBCXX__) && !defined(__APPLE__)) ||                          \
+    defined(_LIBCPP_BUILDING_HAS_NO_ABI_LIBRARY)
+std::type_info::~type_info()
 {
-  return "std::bad_typeid";
 }
-
-#ifdef __APPLE__
-  // On Darwin, the cxa_bad_* functions cannot be in the lower level library
-  // because bad_cast and bad_typeid are defined in his higher level library
-  void __cxxabiv1::__cxa_bad_typeid()
-  {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-     throw std::bad_typeid();
 #endif
-  }
-  void __cxxabiv1::__cxa_bad_cast()
-  {
-#ifndef _LIBCPP_NO_EXCEPTIONS
-      throw std::bad_cast();
-#endif
-  }
-#endif
-
-#endif  // !__GLIBCXX__
-#endif  // !LIBCXXRT && !_LIBCPPABI_VERSION
diff --git a/lib/libcxx/src/variant.cpp b/lib/libcxx/src/variant.cpp
new file mode 100644
index 00000000000..5bb508c3f46
--- /dev/null
+++ b/lib/libcxx/src/variant.cpp
@@ -0,0 +1,18 @@
+//===------------------------ variant.cpp ---------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+#include "variant"
+
+namespace std {
+
+const char* bad_variant_access::what() const noexcept {
+  return "bad_variant_access";
+}
+
+}  // namespace std
diff --git a/lib/libcxx/src/vector.cpp b/lib/libcxx/src/vector.cpp
new file mode 100644
index 00000000000..300adaed5f4
--- /dev/null
+++ b/lib/libcxx/src/vector.cpp
@@ -0,0 +1,16 @@
+//===------------------------- vector.cpp ---------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+#include "vector"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+template class _LIBCPP_CLASS_TEMPLATE_INSTANTIATION_VIS __vector_base_common<true>;
+
+_LIBCPP_END_NAMESPACE_STD