Import libc++ 7.0.1.

1 files changed, 314 insertions, 34 deletions

diff --git a/lib/libcxx/include/fstream b/lib/libcxx/include/fstream
index f57908c8dfa..332b4747c1a 100644
--- a/lib/libcxx/include/fstream
+++ b/lib/libcxx/include/fstream
@@ -38,6 +38,7 @@ public:
     bool is_open() const;
     basic_filebuf* open(const char* s, ios_base::openmode mode);
     basic_filebuf* open(const string& s, ios_base::openmode mode);
+    basic_filebuf* open(const filesystem::path& p, ios_base::openmode mode); // C++17
     basic_filebuf* close();
 
 protected:
@@ -77,6 +78,8 @@ public:
     basic_ifstream();
     explicit basic_ifstream(const char* s, ios_base::openmode mode = ios_base::in);
     explicit basic_ifstream(const string& s, ios_base::openmode mode = ios_base::in);
+    explicit basic_ifstream(const filesystem::path& p,
+                            ios_base::openmode mode = ios_base::in); // C++17
     basic_ifstream(basic_ifstream&& rhs);
 
     basic_ifstream& operator=(basic_ifstream&& rhs);
@@ -86,6 +89,8 @@ public:
     bool is_open() const;
     void open(const char* s, ios_base::openmode mode = ios_base::in);
     void open(const string& s, ios_base::openmode mode = ios_base::in);
+    void open(const filesystem::path& s, ios_base::openmode mode = ios_base::in); // C++17
+
     void close();
 };
 
@@ -110,6 +115,8 @@ public:
     basic_ofstream();
     explicit basic_ofstream(const char* s, ios_base::openmode mode = ios_base::out);
     explicit basic_ofstream(const string& s, ios_base::openmode mode = ios_base::out);
+    explicit basic_ofstream(const filesystem::path& p,
+                            ios_base::openmode mode = ios_base::out); // C++17
     basic_ofstream(basic_ofstream&& rhs);
 
     basic_ofstream& operator=(basic_ofstream&& rhs);
@@ -119,6 +126,9 @@ public:
     bool is_open() const;
     void open(const char* s, ios_base::openmode mode = ios_base::out);
     void open(const string& s, ios_base::openmode mode = ios_base::out);
+    void open(const filesystem::path& p,
+              ios_base::openmode mode = ios_base::out); // C++17
+
     void close();
 };
 
@@ -143,6 +153,8 @@ public:
     basic_fstream();
     explicit basic_fstream(const char* s, ios_base::openmode mode = ios_base::in|ios_base::out);
     explicit basic_fstream(const string& s, ios_base::openmode mode = ios_base::in|ios_base::out);
+    explicit basic_fstream(const filesystem::path& p,
+                           ios_base::openmode mode = ios_base::in|ios_base::out); C++17
     basic_fstream(basic_fstream&& rhs);
 
     basic_fstream& operator=(basic_fstream&& rhs);
@@ -152,6 +164,9 @@ public:
     bool is_open() const;
     void open(const char* s, ios_base::openmode mode = ios_base::in|ios_base::out);
     void open(const string& s, ios_base::openmode mode = ios_base::in|ios_base::out);
+    void open(const filesystem::path& s,
+              ios_base::openmode mode = ios_base::in|ios_base::out); // C++17
+
     void close();
 };
 
@@ -170,6 +185,8 @@ typedef basic_fstream<wchar_t> wfstream;
 #include <istream>
 #include <__locale>
 #include <cstdio>
+#include <cstdlib>
+#include <filesystem>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
@@ -212,12 +229,28 @@ public:
     bool is_open() const;
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
     basic_filebuf* open(const char* __s, ios_base::openmode __mode);
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    basic_filebuf* open(const wchar_t* __s, ios_base::openmode __mode);
+#endif
     _LIBCPP_INLINE_VISIBILITY
     basic_filebuf* open(const string& __s, ios_base::openmode __mode);
+
+#if _LIBCPP_STD_VER >= 17
+    _LIBCPP_INLINE_VISIBILITY
+    basic_filebuf* open(const _VSTD_FS::path& __p, ios_base::openmode __mode) {
+      return open(__p.c_str(), __mode);
+    }
+#endif
+    _LIBCPP_INLINE_VISIBILITY
+    basic_filebuf* __open(int __fd, ios_base::openmode __mode);
 #endif
     basic_filebuf* close();
 
-protected:
+    _LIBCPP_INLINE_VISIBILITY
+    inline static const char*
+    __make_mdstring(ios_base::openmode __mode) _NOEXCEPT;
+
+  protected:
     // 27.9.1.5 Overridden virtual functions:
     virtual int_type underflow();
     virtual int_type pbackfail(int_type __c = traits_type::eof());
@@ -231,25 +264,25 @@ protected:
     virtual void imbue(const locale& __loc);
 
 private:
-    char*       __extbuf_;
-    const char* __extbufnext_;
-    const char* __extbufend_;
-    char __extbuf_min_[8];
-    size_t __ebs_;
-    char_type* __intbuf_;
-    size_t __ibs_;
-    FILE* __file_;
-    const codecvt<char_type, char, state_type>* __cv_;
-    state_type __st_;
-    state_type __st_last_;
-    ios_base::openmode __om_;
-    ios_base::openmode __cm_;
-    bool __owns_eb_;
-    bool __owns_ib_;
-    bool __always_noconv_;
-
-    bool __read_mode();
-    void __write_mode();
+  char* __extbuf_;
+  const char* __extbufnext_;
+  const char* __extbufend_;
+  char __extbuf_min_[8];
+  size_t __ebs_;
+  char_type* __intbuf_;
+  size_t __ibs_;
+  FILE* __file_;
+  const codecvt<char_type, char, state_type>* __cv_;
+  state_type __st_;
+  state_type __st_last_;
+  ios_base::openmode __om_;
+  ios_base::openmode __cm_;
+  bool __owns_eb_;
+  bool __owns_ib_;
+  bool __always_noconv_;
+
+  bool __read_mode();
+  void __write_mode();
 };
 
 template <class _CharT, class _Traits>
@@ -470,6 +503,46 @@ basic_filebuf<_CharT, _Traits>::is_open() const
     return __file_ != 0;
 }
 
+template <class _CharT, class _Traits>
+const char* basic_filebuf<_CharT, _Traits>::__make_mdstring(
+    ios_base::openmode __mode) _NOEXCEPT {
+  switch (__mode & ~ios_base::ate) {
+  case ios_base::out:
+  case ios_base::out | ios_base::trunc:
+    return "w";
+  case ios_base::out | ios_base::app:
+  case ios_base::app:
+    return "a";
+  case ios_base::in:
+    return "r";
+  case ios_base::in | ios_base::out:
+    return "r+";
+  case ios_base::in | ios_base::out | ios_base::trunc:
+    return "w+";
+  case ios_base::in | ios_base::out | ios_base::app:
+  case ios_base::in | ios_base::app:
+    return "a+";
+  case ios_base::out | ios_base::binary:
+  case ios_base::out | ios_base::trunc | ios_base::binary:
+    return "wb";
+  case ios_base::out | ios_base::app | ios_base::binary:
+  case ios_base::app | ios_base::binary:
+    return "ab";
+  case ios_base::in | ios_base::binary:
+    return "rb";
+  case ios_base::in | ios_base::out | ios_base::binary:
+    return "r+b";
+  case ios_base::in | ios_base::out | ios_base::trunc | ios_base::binary:
+    return "w+b";
+  case ios_base::in | ios_base::out | ios_base::app | ios_base::binary:
+  case ios_base::in | ios_base::app | ios_base::binary:
+    return "a+b";
+  default:
+    return nullptr;
+  }
+  _LIBCPP_UNREACHABLE();
+}
+
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
 template <class _CharT, class _Traits>
 basic_filebuf<_CharT, _Traits>*
@@ -478,51 +551,104 @@ basic_filebuf<_CharT, _Traits>::open(const char* __s, ios_base::openmode __mode)
     basic_filebuf<_CharT, _Traits>* __rt = 0;
     if (__file_ == 0)
     {
+      if (const char* __mdstr = __make_mdstring(__mode)) {
         __rt = this;
-        const char* __mdstr;
+        __file_ = fopen(__s, __mdstr);
+        if (__file_) {
+          __om_ = __mode;
+          if (__mode & ios_base::ate) {
+            if (fseek(__file_, 0, SEEK_END)) {
+              fclose(__file_);
+              __file_ = 0;
+              __rt = 0;
+            }
+          }
+        } else
+          __rt = 0;
+      }
+    }
+    return __rt;
+}
+
+template <class _CharT, class _Traits>
+_LIBCPP_INLINE_VISIBILITY basic_filebuf<_CharT, _Traits>*
+basic_filebuf<_CharT, _Traits>::__open(int __fd, ios_base::openmode __mode) {
+  basic_filebuf<_CharT, _Traits>* __rt = 0;
+  if (__file_ == 0) {
+    if (const char* __mdstr = __make_mdstring(__mode)) {
+      __rt = this;
+      __file_ = fdopen(__fd, __mdstr);
+      if (__file_) {
+        __om_ = __mode;
+        if (__mode & ios_base::ate) {
+          if (fseek(__file_, 0, SEEK_END)) {
+            fclose(__file_);
+            __file_ = 0;
+            __rt = 0;
+          }
+        }
+      } else
+        __rt = 0;
+    }
+  }
+  return __rt;
+}
+
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+// This is basically the same as the char* overload except that it uses _wfopen
+// and long mode strings.
+template <class _CharT, class _Traits>
+basic_filebuf<_CharT, _Traits>*
+basic_filebuf<_CharT, _Traits>::open(const wchar_t* __s, ios_base::openmode __mode)
+{
+    basic_filebuf<_CharT, _Traits>* __rt = 0;
+    if (__file_ == 0)
+    {
+        __rt = this;
+        const wchar_t* __mdstr;
         switch (__mode & ~ios_base::ate)
         {
         case ios_base::out:
         case ios_base::out | ios_base::trunc:
-            __mdstr = "w";
+            __mdstr = L"w";
             break;
         case ios_base::out | ios_base::app:
         case ios_base::app:
-            __mdstr = "a";
+            __mdstr = L"a";
             break;
         case ios_base::in:
-            __mdstr = "r";
+            __mdstr = L"r";
             break;
         case ios_base::in | ios_base::out:
-            __mdstr = "r+";
+            __mdstr = L"r+";
             break;
         case ios_base::in | ios_base::out | ios_base::trunc:
-            __mdstr = "w+";
+            __mdstr = L"w+";
             break;
         case ios_base::in | ios_base::out | ios_base::app:
         case ios_base::in | ios_base::app:
-            __mdstr = "a+";
+            __mdstr = L"a+";
             break;
         case ios_base::out | ios_base::binary:
         case ios_base::out | ios_base::trunc | ios_base::binary:
-            __mdstr = "wb";
+            __mdstr = L"wb";
             break;
         case ios_base::out | ios_base::app | ios_base::binary:
         case ios_base::app | ios_base::binary:
-            __mdstr = "ab";
+            __mdstr = L"ab";
             break;
         case ios_base::in | ios_base::binary:
-            __mdstr = "rb";
+            __mdstr = L"rb";
             break;
         case ios_base::in | ios_base::out | ios_base::binary:
-            __mdstr = "r+b";
+            __mdstr = L"r+b";
             break;
         case ios_base::in | ios_base::out | ios_base::trunc | ios_base::binary:
-            __mdstr = "w+b";
+            __mdstr = L"w+b";
             break;
         case ios_base::in | ios_base::out | ios_base::app | ios_base::binary:
         case ios_base::in | ios_base::app | ios_base::binary:
-            __mdstr = "a+b";
+            __mdstr = L"a+b";
             break;
         default:
             __rt = 0;
@@ -530,7 +656,7 @@ basic_filebuf<_CharT, _Traits>::open(const char* __s, ios_base::openmode __mode)
         }
         if (__rt)
         {
-            __file_ = fopen(__s, __mdstr);
+            __file_ = _wfopen(__s, __mdstr);
             if (__file_)
             {
                 __om_ = __mode;
@@ -550,6 +676,7 @@ basic_filebuf<_CharT, _Traits>::open(const char* __s, ios_base::openmode __mode)
     }
     return __rt;
 }
+#endif
 
 template <class _CharT, class _Traits>
 inline
@@ -1017,8 +1144,17 @@ public:
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
     _LIBCPP_INLINE_VISIBILITY
     explicit basic_ifstream(const char* __s, ios_base::openmode __mode = ios_base::in);
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    _LIBCPP_INLINE_VISIBILITY
+    explicit basic_ifstream(const wchar_t* __s, ios_base::openmode __mode = ios_base::in);
+#endif
     _LIBCPP_INLINE_VISIBILITY
     explicit basic_ifstream(const string& __s, ios_base::openmode __mode = ios_base::in);
+#if _LIBCPP_STD_VER >= 17
+    _LIBCPP_INLINE_VISIBILITY
+    explicit basic_ifstream(const filesystem::path& __p, ios_base::openmode __mode = ios_base::in)
+      : basic_ifstream(__p.c_str(), __mode) {}
+#endif // _LIBCPP_STD_VER >= 17
 #endif
 #ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
@@ -1036,7 +1172,20 @@ public:
     bool is_open() const;
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
     void open(const char* __s, ios_base::openmode __mode = ios_base::in);
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    void open(const wchar_t* __s, ios_base::openmode __mode = ios_base::in);
+#endif
     void open(const string& __s, ios_base::openmode __mode = ios_base::in);
+#if _LIBCPP_STD_VER >= 17
+    _LIBCPP_INLINE_VISIBILITY
+    void open(const filesystem::path& __p,
+              ios_base::openmode __mode = ios_base::in) {
+      return open(__p.c_str(), __mode);
+    }
+#endif // _LIBCPP_STD_VER >= 17
+
+    _LIBCPP_INLINE_VISIBILITY
+    void __open(int __fd, ios_base::openmode __mode);
 #endif
     _LIBCPP_INLINE_VISIBILITY
     void close();
@@ -1062,6 +1211,17 @@ basic_ifstream<_CharT, _Traits>::basic_ifstream(const char* __s, ios_base::openm
         this->setstate(ios_base::failbit);
 }
 
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+template <class _CharT, class _Traits>
+inline
+basic_ifstream<_CharT, _Traits>::basic_ifstream(const wchar_t* __s, ios_base::openmode __mode)
+    : basic_istream<char_type, traits_type>(&__sb_)
+{
+    if (__sb_.open(__s, __mode | ios_base::in) == 0)
+        this->setstate(ios_base::failbit);
+}
+#endif
+
 template <class _CharT, class _Traits>
 inline
 basic_ifstream<_CharT, _Traits>::basic_ifstream(const string& __s, ios_base::openmode __mode)
@@ -1139,6 +1299,18 @@ basic_ifstream<_CharT, _Traits>::open(const char* __s, ios_base::openmode __mode
         this->setstate(ios_base::failbit);
 }
 
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+template <class _CharT, class _Traits>
+void
+basic_ifstream<_CharT, _Traits>::open(const wchar_t* __s, ios_base::openmode __mode)
+{
+    if (__sb_.open(__s, __mode | ios_base::in))
+        this->clear();
+    else
+        this->setstate(ios_base::failbit);
+}
+#endif
+
 template <class _CharT, class _Traits>
 void
 basic_ifstream<_CharT, _Traits>::open(const string& __s, ios_base::openmode __mode)
@@ -1148,6 +1320,15 @@ basic_ifstream<_CharT, _Traits>::open(const string& __s, ios_base::openmode __mo
     else
         this->setstate(ios_base::failbit);
 }
+
+template <class _CharT, class _Traits>
+void basic_ifstream<_CharT, _Traits>::__open(int __fd,
+                                             ios_base::openmode __mode) {
+  if (__sb_.__open(__fd, __mode | ios_base::in))
+    this->clear();
+  else
+    this->setstate(ios_base::failbit);
+}
 #endif
 
 template <class _CharT, class _Traits>
@@ -1176,8 +1357,19 @@ public:
     basic_ofstream();
     _LIBCPP_INLINE_VISIBILITY
     explicit basic_ofstream(const char* __s, ios_base::openmode __mode = ios_base::out);
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    _LIBCPP_INLINE_VISIBILITY
+    explicit basic_ofstream(const wchar_t* __s, ios_base::openmode __mode = ios_base::out);
+#endif
     _LIBCPP_INLINE_VISIBILITY
     explicit basic_ofstream(const string& __s, ios_base::openmode __mode = ios_base::out);
+
+#if _LIBCPP_STD_VER >= 17
+    _LIBCPP_INLINE_VISIBILITY
+    explicit basic_ofstream(const filesystem::path& __p, ios_base::openmode __mode = ios_base::out)
+      : basic_ofstream(__p.c_str(), __mode) {}
+#endif // _LIBCPP_STD_VER >= 17
+
 #ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
     basic_ofstream(basic_ofstream&& __rhs);
@@ -1194,7 +1386,19 @@ public:
     bool is_open() const;
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
     void open(const char* __s, ios_base::openmode __mode = ios_base::out);
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    void open(const wchar_t* __s, ios_base::openmode __mode = ios_base::out);
+#endif
     void open(const string& __s, ios_base::openmode __mode = ios_base::out);
+
+#if _LIBCPP_STD_VER >= 17
+    _LIBCPP_INLINE_VISIBILITY
+    void open(const filesystem::path& __p, ios_base::openmode __mode = ios_base::out)
+    { return open(__p.c_str(), __mode); }
+#endif // _LIBCPP_STD_VER >= 17
+
+    _LIBCPP_INLINE_VISIBILITY
+    void __open(int __fd, ios_base::openmode __mode);
 #endif
     _LIBCPP_INLINE_VISIBILITY
     void close();
@@ -1220,6 +1424,17 @@ basic_ofstream<_CharT, _Traits>::basic_ofstream(const char* __s, ios_base::openm
         this->setstate(ios_base::failbit);
 }
 
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+template <class _CharT, class _Traits>
+inline
+basic_ofstream<_CharT, _Traits>::basic_ofstream(const wchar_t* __s, ios_base::openmode __mode)
+    : basic_ostream<char_type, traits_type>(&__sb_)
+{
+    if (__sb_.open(__s, __mode | ios_base::out) == 0)
+        this->setstate(ios_base::failbit);
+}
+#endif
+
 template <class _CharT, class _Traits>
 inline
 basic_ofstream<_CharT, _Traits>::basic_ofstream(const string& __s, ios_base::openmode __mode)
@@ -1297,6 +1512,18 @@ basic_ofstream<_CharT, _Traits>::open(const char* __s, ios_base::openmode __mode
         this->setstate(ios_base::failbit);
 }
 
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+template <class _CharT, class _Traits>
+void
+basic_ofstream<_CharT, _Traits>::open(const wchar_t* __s, ios_base::openmode __mode)
+{
+    if (__sb_.open(__s, __mode | ios_base::out))
+        this->clear();
+    else
+        this->setstate(ios_base::failbit);
+}
+#endif
+
 template <class _CharT, class _Traits>
 void
 basic_ofstream<_CharT, _Traits>::open(const string& __s, ios_base::openmode __mode)
@@ -1306,6 +1533,15 @@ basic_ofstream<_CharT, _Traits>::open(const string& __s, ios_base::openmode __mo
     else
         this->setstate(ios_base::failbit);
 }
+
+template <class _CharT, class _Traits>
+void basic_ofstream<_CharT, _Traits>::__open(int __fd,
+                                             ios_base::openmode __mode) {
+  if (__sb_.__open(__fd, __mode | ios_base::out))
+    this->clear();
+  else
+    this->setstate(ios_base::failbit);
+}
 #endif
 
 template <class _CharT, class _Traits>
@@ -1335,8 +1571,19 @@ public:
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
     _LIBCPP_INLINE_VISIBILITY
     explicit basic_fstream(const char* __s, ios_base::openmode __mode = ios_base::in | ios_base::out);
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    _LIBCPP_INLINE_VISIBILITY
+    explicit basic_fstream(const wchar_t* __s, ios_base::openmode __mode = ios_base::in | ios_base::out);
+#endif
     _LIBCPP_INLINE_VISIBILITY
     explicit basic_fstream(const string& __s, ios_base::openmode __mode = ios_base::in | ios_base::out);
+
+#if _LIBCPP_STD_VER >= 17
+    _LIBCPP_INLINE_VISIBILITY
+    explicit basic_fstream(const filesystem::path& __p, ios_base::openmode __mode = ios_base::in | ios_base::out)
+      : basic_fstream(__p.c_str(), __mode) {}
+#endif // _LIBCPP_STD_VER >= 17
+
 #endif
 #ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
@@ -1354,7 +1601,17 @@ public:
     bool is_open() const;
 #ifndef _LIBCPP_HAS_NO_GLOBAL_FILESYSTEM_NAMESPACE
     void open(const char* __s, ios_base::openmode __mode = ios_base::in | ios_base::out);
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    void open(const wchar_t* __s, ios_base::openmode __mode = ios_base::in | ios_base::out);
+#endif
     void open(const string& __s, ios_base::openmode __mode = ios_base::in | ios_base::out);
+
+#if _LIBCPP_STD_VER >= 17
+    _LIBCPP_INLINE_VISIBILITY
+    void open(const filesystem::path& __p, ios_base::openmode __mode = ios_base::in|ios_base::out)
+    { return open(__p.c_str(), __mode); }
+#endif // _LIBCPP_STD_VER >= 17
+
 #endif
     _LIBCPP_INLINE_VISIBILITY
     void close();
@@ -1380,6 +1637,17 @@ basic_fstream<_CharT, _Traits>::basic_fstream(const char* __s, ios_base::openmod
         this->setstate(ios_base::failbit);
 }
 
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+template <class _CharT, class _Traits>
+inline
+basic_fstream<_CharT, _Traits>::basic_fstream(const wchar_t* __s, ios_base::openmode __mode)
+    : basic_iostream<char_type, traits_type>(&__sb_)
+{
+    if (__sb_.open(__s, __mode) == 0)
+        this->setstate(ios_base::failbit);
+}
+#endif
+
 template <class _CharT, class _Traits>
 inline
 basic_fstream<_CharT, _Traits>::basic_fstream(const string& __s, ios_base::openmode __mode)
@@ -1457,6 +1725,18 @@ basic_fstream<_CharT, _Traits>::open(const char* __s, ios_base::openmode __mode)
         this->setstate(ios_base::failbit);
 }
 
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+template <class _CharT, class _Traits>
+void
+basic_fstream<_CharT, _Traits>::open(const wchar_t* __s, ios_base::openmode __mode)
+{
+    if (__sb_.open(__s, __mode))
+        this->clear();
+    else
+        this->setstate(ios_base::failbit);
+}
+#endif
+
 template <class _CharT, class _Traits>
 void
 basic_fstream<_CharT, _Traits>::open(const string& __s, ios_base::openmode __mode)