Index: include/__config
===================================================================
--- include/__config
+++ include/__config
@@ -247,6 +247,7 @@
 #  if (defined(_M_AMD64) || defined(__x86_64__)) || (defined(_M_ARM) || defined(__arm__))
 #    define _LIBCPP_HAS_BITSCAN64
 #  endif
+#  define _LIBCPP_HAS_OPEN_WITH_WCHAR
 # if defined(_LIBCPP_MSVCRT)
 #   define _LIBCPP_HAS_QUICK_EXIT
 # endif
Index: include/fstream
===================================================================
--- include/fstream
+++ include/fstream
@@ -212,6 +212,9 @@
     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);
 #endif
@@ -551,6 +554,90 @@
     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 = L"w";
+            break;
+        case ios_base::out | ios_base::app:
+        case ios_base::app:
+            __mdstr = L"a";
+            break;
+        case ios_base::in:
+            __mdstr = L"r";
+            break;
+        case ios_base::in | ios_base::out:
+            __mdstr = L"r+";
+            break;
+        case ios_base::in | ios_base::out | ios_base::trunc:
+            __mdstr = L"w+";
+            break;
+        case ios_base::in | ios_base::out | ios_base::app:
+        case ios_base::in | ios_base::app:
+            __mdstr = L"a+";
+            break;
+        case ios_base::out | ios_base::binary:
+        case ios_base::out | ios_base::trunc | ios_base::binary:
+            __mdstr = L"wb";
+            break;
+        case ios_base::out | ios_base::app | ios_base::binary:
+        case ios_base::app | ios_base::binary:
+            __mdstr = L"ab";
+            break;
+        case ios_base::in | ios_base::binary:
+            __mdstr = L"rb";
+            break;
+        case ios_base::in | ios_base::out | ios_base::binary:
+            __mdstr = L"r+b";
+            break;
+        case ios_base::in | ios_base::out | ios_base::trunc | ios_base::binary:
+            __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 = L"a+b";
+            break;
+        default:
+            __rt = 0;
+            break;
+        }
+        if (__rt)
+        {
+            __file_ = _wfopen(__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;
+}
+#endif
+
 template <class _CharT, class _Traits>
 inline
 basic_filebuf<_CharT, _Traits>*
@@ -1017,6 +1104,10 @@
 #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);
 #endif
@@ -1036,6 +1127,9 @@
     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);
 #endif
     _LIBCPP_INLINE_VISIBILITY
@@ -1062,6 +1156,17 @@
         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 +1244,18 @@
         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)
@@ -1176,6 +1293,10 @@
     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);
 #ifndef _LIBCPP_CXX03_LANG
@@ -1194,6 +1315,9 @@
     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);
 #endif
     _LIBCPP_INLINE_VISIBILITY
@@ -1220,6 +1344,17 @@
         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 +1432,18 @@
         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)
@@ -1335,6 +1482,10 @@
 #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);
 #endif
@@ -1354,6 +1505,9 @@
     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);
 #endif
     _LIBCPP_INLINE_VISIBILITY
@@ -1380,6 +1534,17 @@
         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 +1622,18 @@
         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)
Index: test/libcxx/input.output/file.streams/fstreams/fstream.cons/wchar_pointer.pass.cpp
===================================================================
--- test/libcxx/input.output/file.streams/fstreams/fstream.cons/wchar_pointer.pass.cpp
+++ test/libcxx/input.output/file.streams/fstreams/fstream.cons/wchar_pointer.pass.cpp
@@ -0,0 +1,46 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// <fstream>
+
+// template <class charT, class traits = char_traits<charT> >
+// class basic_fstream
+
+// explicit basic_fstream(const wchar_t* s, ios_base::openmode mode = ios_base::in | ios_base::out);
+
+#include <fstream>
+#include <cassert>
+#include "platform_support.h"
+
+int main()
+{
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    std::wstring temp = get_wide_temp_file_name();
+    {
+        std::fstream fs(temp.c_str(), std::ios_base::in | std::ios_base::out
+                                                | std::ios_base::trunc);
+        double x = 0;
+        fs << 3.25;
+        fs.seekg(0);
+        fs >> x;
+        assert(x == 3.25);
+    }
+    _wremove(temp.c_str());
+    {
+        std::wfstream fs(temp.c_str(), std::ios_base::in | std::ios_base::out
+                                                 | std::ios_base::trunc);
+        double x = 0;
+        fs << 3.25;
+        fs.seekg(0);
+        fs >> x;
+        assert(x == 3.25);
+    }
+    _wremove(temp.c_str());
+#endif
+}
Index: test/libcxx/input.output/file.streams/fstreams/fstream.members/open_wchar_pointer.pass.cpp
===================================================================
--- test/libcxx/input.output/file.streams/fstreams/fstream.members/open_wchar_pointer.pass.cpp
+++ test/libcxx/input.output/file.streams/fstreams/fstream.members/open_wchar_pointer.pass.cpp
@@ -0,0 +1,52 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// <fstream>
+
+// template <class charT, class traits = char_traits<charT> >
+// class basic_fstream
+
+// void open(const wchar_t* s, ios_base::openmode mode = ios_base::in|ios_base::out);
+
+#include <fstream>
+#include <cassert>
+#include "platform_support.h"
+
+int main()
+{
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    std::wstring temp = get_wide_temp_file_name();
+    {
+        std::fstream fs;
+        assert(!fs.is_open());
+        fs.open(temp.c_str(), std::ios_base::in | std::ios_base::out
+                                        | std::ios_base::trunc);
+        assert(fs.is_open());
+        double x = 0;
+        fs << 3.25;
+        fs.seekg(0);
+        fs >> x;
+        assert(x == 3.25);
+    }
+    _wremove(temp.c_str());
+    {
+        std::wfstream fs;
+        assert(!fs.is_open());
+        fs.open(temp.c_str(), std::ios_base::in | std::ios_base::out
+                                        | std::ios_base::trunc);
+        assert(fs.is_open());
+        double x = 0;
+        fs << 3.25;
+        fs.seekg(0);
+        fs >> x;
+        assert(x == 3.25);
+    }
+    _wremove(temp.c_str());
+#endif
+}
Index: test/libcxx/input.output/file.streams/fstreams/ifstream.cons/test.dat
===================================================================
--- test/libcxx/input.output/file.streams/fstreams/ifstream.cons/test.dat
+++ test/libcxx/input.output/file.streams/fstreams/ifstream.cons/test.dat
@@ -0,0 +1 @@
+3.25
\ No newline at end of file
Index: test/libcxx/input.output/file.streams/fstreams/ifstream.cons/wchar_pointer.pass.cpp
===================================================================
--- test/libcxx/input.output/file.streams/fstreams/ifstream.cons/wchar_pointer.pass.cpp
+++ test/libcxx/input.output/file.streams/fstreams/ifstream.cons/wchar_pointer.pass.cpp
@@ -0,0 +1,42 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// <fstream>
+
+// template <class charT, class traits = char_traits<charT> >
+// class basic_ifstream
+
+// explicit basic_ifstream(const wchar_t* s, ios_base::openmode mode = ios_base::in);
+
+#include <fstream>
+#include <cassert>
+
+int main()
+{
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    {
+        std::ifstream fs(L"test.dat");
+        double x = 0;
+        fs >> x;
+        assert(x == 3.25);
+    }
+    // std::ifstream(const wchar_t*, std::ios_base::openmode) is tested in
+    // test/libcxx/input.output/file.streams/fstreams/ofstream.cons/wchar_pointer.pass.cpp
+    // which creates writable files.
+    {
+        std::wifstream fs(L"test.dat");
+        double x = 0;
+        fs >> x;
+        assert(x == 3.25);
+    }
+    // std::wifstream(const wchar_t*, std::ios_base::openmode) is tested in
+    // test/libcxx/input.output/file.streams/fstreams/ofstream.cons/wchar_pointer.pass.cpp
+    // which creates writable files.
+#endif
+}
Index: test/libcxx/input.output/file.streams/fstreams/ifstream.members/open_wchar_pointer.pass.cpp
===================================================================
--- test/libcxx/input.output/file.streams/fstreams/ifstream.members/open_wchar_pointer.pass.cpp
+++ test/libcxx/input.output/file.streams/fstreams/ifstream.members/open_wchar_pointer.pass.cpp
@@ -0,0 +1,48 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// <fstream>
+
+// template <class charT, class traits = char_traits<charT> >
+// class basic_ifstream
+
+// void open(const wchar_t* s, ios_base::openmode mode = ios_base::in);
+
+#include <fstream>
+#include <cassert>
+
+int main()
+{
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    {
+        std::ifstream fs;
+        assert(!fs.is_open());
+        char c = 'a';
+        fs >> c;
+        assert(fs.fail());
+        assert(c == 'a');
+        fs.open(L"test.dat");
+        assert(fs.is_open());
+        fs >> c;
+        assert(c == 'r');
+    }
+    {
+        std::wifstream fs;
+        assert(!fs.is_open());
+        wchar_t c = L'a';
+        fs >> c;
+        assert(fs.fail());
+        assert(c == L'a');
+        fs.open(L"test.dat");
+        assert(fs.is_open());
+        fs >> c;
+        assert(c == L'r');
+    }
+#endif
+}
Index: test/libcxx/input.output/file.streams/fstreams/ifstream.members/test.dat
===================================================================
--- test/libcxx/input.output/file.streams/fstreams/ifstream.members/test.dat
+++ test/libcxx/input.output/file.streams/fstreams/ifstream.members/test.dat
@@ -0,0 +1 @@
+r
\ No newline at end of file
Index: test/libcxx/input.output/file.streams/fstreams/ofstream.cons/wchar_pointer.pass.cpp
===================================================================
--- test/libcxx/input.output/file.streams/fstreams/ofstream.cons/wchar_pointer.pass.cpp
+++ test/libcxx/input.output/file.streams/fstreams/ofstream.cons/wchar_pointer.pass.cpp
@@ -0,0 +1,60 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// <fstream>
+
+// template <class charT, class traits = char_traits<charT> >
+// class basic_ofstream
+
+// explicit basic_ofstream(const wchar_t* s, ios_base::openmode mode = ios_base::out);
+
+#include <fstream>
+#include <cassert>
+#include "platform_support.h"
+
+int main()
+{
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    std::wstring temp = get_wide_temp_file_name();
+    {
+        std::ofstream fs(temp.c_str());
+        fs << 3.25;
+    }
+    {
+        std::ifstream fs(temp.c_str());
+        double x = 0;
+        fs >> x;
+        assert(x == 3.25);
+    }
+    {
+        std::ifstream fs(temp.c_str(), std::ios_base::out);
+        double x = 0;
+        fs >> x;
+        assert(x == 3.25);
+    }
+    _wremove(temp.c_str());
+    {
+        std::wofstream fs(temp.c_str());
+        fs << 3.25;
+    }
+    {
+        std::wifstream fs(temp.c_str());
+        double x = 0;
+        fs >> x;
+        assert(x == 3.25);
+    }
+    {
+        std::wifstream fs(temp.c_str(), std::ios_base::out);
+        double x = 0;
+        fs >> x;
+        assert(x == 3.25);
+    }
+    _wremove(temp.c_str());
+#endif
+}
Index: test/libcxx/input.output/file.streams/fstreams/ofstream.members/open_wchar_pointer.pass.cpp
===================================================================
--- test/libcxx/input.output/file.streams/fstreams/ofstream.members/open_wchar_pointer.pass.cpp
+++ test/libcxx/input.output/file.streams/fstreams/ofstream.members/open_wchar_pointer.pass.cpp
@@ -0,0 +1,60 @@
+//===----------------------------------------------------------------------===//
+//
+//                     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.
+//
+//===----------------------------------------------------------------------===//
+
+// <fstream>
+
+// template <class charT, class traits = char_traits<charT> >
+// class basic_ofstream
+
+// void open(const wchar_t* s, ios_base::openmode mode = ios_base::out);
+
+#include <fstream>
+#include <cassert>
+#include "platform_support.h"
+
+int main()
+{
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+    std::wstring temp = get_wide_temp_file_name();
+    {
+        std::ofstream fs;
+        assert(!fs.is_open());
+        char c = 'a';
+        fs << c;
+        assert(fs.fail());
+        fs.open(temp.c_str());
+        assert(fs.is_open());
+        fs << c;
+    }
+    {
+        std::ifstream fs(temp.c_str());
+        char c = 0;
+        fs >> c;
+        assert(c == 'a');
+    }
+    _wremove(temp.c_str());
+    {
+        std::wofstream fs;
+        assert(!fs.is_open());
+        wchar_t c = L'a';
+        fs << c;
+        assert(fs.fail());
+        fs.open(temp.c_str());
+        assert(fs.is_open());
+        fs << c;
+    }
+    {
+        std::wifstream fs(temp.c_str());
+        wchar_t c = 0;
+        fs >> c;
+        assert(c == L'a');
+    }
+    _wremove(temp.c_str());
+#endif
+}
Index: test/support/platform_support.h
===================================================================
--- test/support/platform_support.h
+++ test/support/platform_support.h
@@ -54,6 +54,8 @@
 
 #include <stdio.h>
 #include <stdlib.h>
+#include <codecvt>
+#include <locale>
 #include <string>
 #if defined(_WIN32) || defined(__MINGW32__)
 #include <io.h> // _mktemp_s
@@ -97,6 +99,16 @@
     return Name;
 #endif
 }
+
+#ifdef _LIBCPP_HAS_OPEN_WITH_WCHAR
+inline
+std::wstring get_wide_temp_file_name()
+{
+    return std::wstring_convert<std::codecvt_utf8_utf16<wchar_t> >().from_bytes(
+        get_temp_file_name());
+}
+#endif // _LIBCPP_HAS_OPEN_WITH_WCHAR
+
 #endif // __CloudABI__
 
 #endif // PLATFORM_SUPPORT_H