Use std::error_code instead of llvm::error_code.

The idea of this patch is to turn llvm/Support/system_error.h into a
transitional header that just brings in the erorr_code api to the llvm
namespace. I will remove it shortly afterwards.

The cases where the general idea needed some tweaking:

* std::errc is a namespace in msvc, so we cannot use "using std::errc". I could
add an #ifdef, but there were not that many uses, so I just added std:: to
them in this patch.

* Template specialization had to be moved to the std namespace in this
patch set already.

* The msvc implementation of default_error_condition doesn't seem to
provide the same transformations as we need. Not too surprising since
the standard doesn't actually say what "equivalent" means. I fixed the
problem by keeping our old mapping and using it at error_code
construction time.

Despite these shortcomings I think this is still a good thing. Some reasons:

* The different implementations of system_error might improve over time.
* It removes 925 lines of code from llvm already.
* It removes 6313 bytes from the text segment of the clang binary when
it is built with gcc and 2816 bytes when building with clang and
libstdc++.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@210687 91177308-0d34-0410-b5e6-96231b3b80d8

15 files changed, 147 insertions, 328 deletions

diff --git a/lib/Object/Error.cpp b/lib/Object/Error.cpp
index 6bcc6f9a78..a373cff195 100644
--- a/lib/Object/Error.cpp
+++ b/lib/Object/Error.cpp
@@ -50,7 +50,7 @@ std::string _object_error_category::message(int EV) const {
 error_condition _object_error_category::default_error_condition(int EV) const {
   if (static_cast<object_error>(EV) == object_error::success)
     return error_condition();
-  return errc::invalid_argument;
+  return std::errc::invalid_argument;
 }
 
 const error_category &object::object_category() {
diff --git a/lib/ProfileData/InstrProf.cpp b/lib/ProfileData/InstrProf.cpp
index 94a79e9ed0..eed517df05 100644
--- a/lib/ProfileData/InstrProf.cpp
+++ b/lib/ProfileData/InstrProf.cpp
@@ -55,7 +55,7 @@ class InstrProfErrorCategoryType : public error_category {
   error_condition default_error_condition(int EV) const LLVM_NOEXCEPT override {
     if (static_cast<instrprof_error>(EV) == instrprof_error::success)
       return error_condition();
-    return errc::invalid_argument;
+    return std::errc::invalid_argument;
   }
 };
 }
diff --git a/lib/Support/CMakeLists.txt b/lib/Support/CMakeLists.txt
index 7f93a6c595..9febb84f2b 100644
--- a/lib/Support/CMakeLists.txt
+++ b/lib/Support/CMakeLists.txt
@@ -83,13 +83,13 @@ add_llvm_library(LLVMSupport
   RWMutex.cpp
   SearchForAddressOfSpecialSymbol.cpp
   Signals.cpp
-  system_error.cpp
   TargetRegistry.cpp
   ThreadLocal.cpp
   Threading.cpp
   TimeValue.cpp
   Valgrind.cpp
   Watchdog.cpp
+  WindowsError.cpp
 
   ADDITIONAL_HEADERS
   Unix/Host.inc
@@ -100,7 +100,6 @@ add_llvm_library(LLVMSupport
   Unix/Program.inc
   Unix/RWMutex.inc
   Unix/Signals.inc
-  Unix/system_error.inc
   Unix/ThreadLocal.inc
   Unix/TimeValue.inc
   Unix/Watchdog.inc
@@ -113,7 +112,6 @@ add_llvm_library(LLVMSupport
   Windows/Program.inc
   Windows/RWMutex.inc
   Windows/Signals.inc
-  Windows/system_error.inc
   Windows/ThreadLocal.inc
   Windows/TimeValue.inc
   Windows/Watchdog.inc
diff --git a/lib/Support/FileOutputBuffer.cpp b/lib/Support/FileOutputBuffer.cpp
index 5f74d00c6b..b869054338 100644
--- a/lib/Support/FileOutputBuffer.cpp
+++ b/lib/Support/FileOutputBuffer.cpp
@@ -51,7 +51,7 @@ error_code FileOutputBuffer::create(StringRef FilePath,
       if (EC)
         return EC;
       else
-        return make_error_code(errc::operation_not_permitted);
+        return make_error_code(std::errc::operation_not_permitted);
   }
 
   // Delete target file.
diff --git a/lib/Support/LockFileManager.cpp b/lib/Support/LockFileManager.cpp
index 05e75cff1a..2b7fc812d5 100644
--- a/lib/Support/LockFileManager.cpp
+++ b/lib/Support/LockFileManager.cpp
@@ -114,7 +114,7 @@ LockFileManager::LockFileManager(StringRef FileName)
     if (Out.has_error()) {
       // We failed to write out PID, so make up an excuse, remove the
       // unique lock file, and fail.
-      Error = make_error_code(errc::no_space_on_device);
+      Error = make_error_code(std::errc::no_space_on_device);
       sys::fs::remove(UniqueLockFileName.c_str());
       return;
     }
@@ -127,7 +127,7 @@ LockFileManager::LockFileManager(StringRef FileName)
     if (!EC)
       return;
 
-    if (EC != errc::file_exists) {
+    if (EC != std::errc::file_exists) {
       Error = EC;
       return;
     }
diff --git a/lib/Support/MemoryBuffer.cpp b/lib/Support/MemoryBuffer.cpp
index b7298090db..1f69326a1d 100644
--- a/lib/Support/MemoryBuffer.cpp
+++ b/lib/Support/MemoryBuffer.cpp
@@ -361,7 +361,7 @@ static error_code getOpenFileImpl(int FD, const char *Filename,
   if (!Buf) {
     // Failed to create a buffer. The only way it can fail is if
     // new(std::nothrow) returns 0.
-    return make_error_code(errc::not_enough_memory);
+    return make_error_code(std::errc::not_enough_memory);
   }
 
   std::unique_ptr<MemoryBuffer> SB(Buf);
diff --git a/lib/Support/Path.cpp b/lib/Support/Path.cpp
index 76bee47984..a9ac88e5d3 100644
--- a/lib/Support/Path.cpp
+++ b/lib/Support/Path.cpp
@@ -204,7 +204,7 @@ retry_random_path:
     if (error_code EC =
             sys::fs::openFileForWrite(Twine(ResultPath.begin()), ResultFD,
                                       sys::fs::F_RW | sys::fs::F_Excl, Mode)) {
-      if (EC == errc::file_exists)
+      if (EC == std::errc::file_exists)
         goto retry_random_path;
       return EC;
     }
@@ -224,7 +224,7 @@ retry_random_path:
 
   case FS_Dir: {
     if (error_code EC = sys::fs::create_directory(ResultPath.begin(), false)) {
-      if (EC == errc::file_exists)
+      if (EC == std::errc::file_exists)
         goto retry_random_path;
       return EC;
     }
@@ -829,7 +829,7 @@ error_code create_directories(const Twine &Path, bool IgnoreExisting) {
   error_code EC = create_directory(P, IgnoreExisting);
   // If we succeeded, or had any error other than the parent not existing, just
   // return it.
-  if (EC != errc::no_such_file_or_directory)
+  if (EC != std::errc::no_such_file_or_directory)
     return EC;
 
   // We failed because of a no_such_file_or_directory, try to create the
@@ -896,7 +896,7 @@ error_code has_magic(const Twine &path, const Twine &magic, bool &result) {
   SmallString<32> Buffer;
 
   if (error_code ec = get_magic(path, Magic.size(), Buffer)) {
-    if (ec == errc::value_too_large) {
+    if (ec == std::errc::value_too_large) {
       // Magic.size() > file_size(Path).
       result = false;
       return error_code();
@@ -1043,7 +1043,7 @@ error_code has_magic(const Twine &path, const Twine &magic, bool &result) {
 error_code identify_magic(const Twine &path, file_magic &result) {
   SmallString<32> Magic;
   error_code ec = get_magic(path, Magic.capacity(), Magic);
-  if (ec && ec != errc::value_too_large)
+  if (ec && ec != std::errc::value_too_large)
     return ec;
 
   result = identify_magic(Magic);
diff --git a/lib/Support/Unix/Path.inc b/lib/Support/Unix/Path.inc
index 11ea10e120..ef291db52d 100644
--- a/lib/Support/Unix/Path.inc
+++ b/lib/Support/Unix/Path.inc
@@ -317,7 +317,7 @@ error_code remove(const Twine &path, bool IgnoreNonExisting) {
   // effectively prevents LLVM from erasing things like /dev/null, any block
   // special file, or other things that aren't "regular" files.
   if (!S_ISREG(buf.st_mode) && !S_ISDIR(buf.st_mode) && !S_ISLNK(buf.st_mode))
-    return make_error_code(errc::operation_not_permitted);
+    return make_error_code(std::errc::operation_not_permitted);
 
   if (::remove(p.begin()) == -1) {
     if (errno != ENOENT || !IgnoreNonExisting)
@@ -402,7 +402,7 @@ static error_code fillStatus(int StatRet, const struct stat &Status,
                              file_status &Result) {
   if (StatRet != 0) {
     error_code ec(errno, generic_category());
-    if (ec == errc::no_such_file_or_directory)
+    if (ec == std::errc::no_such_file_or_directory)
       Result = file_status(file_type::file_not_found);
     else
       Result = file_status(file_type::status_error);
@@ -466,7 +466,7 @@ error_code setLastModificationAndAccessTime(int FD, TimeValue Time) {
   return error_code();
 #else
 #warning Missing futimes() and futimens()
-  return make_error_code(errc::not_supported);
+  return make_error_code(std::errc::not_supported);
 #endif
 }
 
@@ -510,7 +510,7 @@ mapped_file_region::mapped_file_region(const Twine &path,
   , Mapping() {
   // Make sure that the requested size fits within SIZE_T.
   if (length > std::numeric_limits<size_t>::max()) {
-    ec = make_error_code(errc::invalid_argument);
+    ec = make_error_code(std::errc::invalid_argument);
     return;
   }
 
@@ -539,7 +539,7 @@ mapped_file_region::mapped_file_region(int fd,
   , Mapping() {
   // Make sure that the requested size fits within SIZE_T.
   if (length > std::numeric_limits<size_t>::max()) {
-    ec = make_error_code(errc::invalid_argument);
+    ec = make_error_code(std::errc::invalid_argument);
     return;
   }
 
@@ -645,7 +645,7 @@ error_code get_magic(const Twine &path, uint32_t len,
     if (std::feof(file) != 0) {
       std::fclose(file);
       result.set_size(size);
-      return make_error_code(errc::value_too_large);
+      return make_error_code(std::errc::value_too_large);
     }
   }
   std::fclose(file);
diff --git a/lib/Support/Unix/system_error.inc b/lib/Support/Unix/system_error.inc
deleted file mode 100644
index 681e919edb..0000000000
--- a/lib/Support/Unix/system_error.inc
+++ /dev/null
@@ -1,34 +0,0 @@
-//===- llvm/Support/Unix/system_error.inc - Unix error_code ------*- C++ -*-===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file provides the Unix specific implementation of the error_code
-// and error_condition classes.
-//
-//===----------------------------------------------------------------------===//
-
-//===----------------------------------------------------------------------===//
-//=== WARNING: Implementation here must contain only generic UNIX code that
-//===          is guaranteed to work on *all* UNIX variants.
-//===----------------------------------------------------------------------===//
-
-using namespace llvm;
-
-std::string
-_system_error_category::message(int ev) const {
-  return _do_message::message(ev);
-}
-
-error_condition
-_system_error_category::default_error_condition(int ev) const {
-#ifdef ELAST
-  if (ev > ELAST)
-    return error_condition(ev, system_category());
-#endif  // ELAST
-  return error_condition(ev, generic_category());
-}
diff --git a/lib/Support/Windows/Path.inc b/lib/Support/Windows/Path.inc
index a819156871..fb484778e6 100644
--- a/lib/Support/Windows/Path.inc
+++ b/lib/Support/Windows/Path.inc
@@ -17,6 +17,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/ADT/STLExtras.h"
+#include "llvm/Support/WindowsError.h"
 #include <fcntl.h>
 #include <io.h>
 #include <sys/stat.h>
@@ -45,7 +46,7 @@ using llvm::sys::windows::UTF8ToUTF16;
 using llvm::sys::windows::UTF16ToUTF8;
 
 static error_code windows_error(DWORD E) {
-  return error_code(E, system_category());
+  return mapWindowsError(E);
 }
 
 static error_code TempDir(SmallVectorImpl<char> &Result) {
@@ -193,7 +194,7 @@ error_code remove(const Twine &path, bool IgnoreNonExisting) {
 
   file_status ST;
   if (error_code EC = status(path, ST)) {
-    if (EC != errc::no_such_file_or_directory || !IgnoreNonExisting)
+    if (EC != std::errc::no_such_file_or_directory || !IgnoreNonExisting)
       return EC;
     return error_code();
   }
@@ -205,14 +206,14 @@ error_code remove(const Twine &path, bool IgnoreNonExisting) {
   if (ST.type() == file_type::directory_file) {
     if (!::RemoveDirectoryW(c_str(path_utf16))) {
       error_code EC = windows_error(::GetLastError());
-      if (EC != errc::no_such_file_or_directory || !IgnoreNonExisting)
+      if (EC != std::errc::no_such_file_or_directory || !IgnoreNonExisting)
         return EC;
     }
     return error_code();
   }
   if (!::DeleteFileW(c_str(path_utf16))) {
     error_code EC = windows_error(::GetLastError());
-    if (EC != errc::no_such_file_or_directory || !IgnoreNonExisting)
+    if (EC != std::errc::no_such_file_or_directory || !IgnoreNonExisting)
       return EC;
   }
   return error_code();
@@ -516,7 +517,7 @@ error_code mapped_file_region::init(int FD, bool CloseFD, uint64_t Offset) {
         _close(FileDescriptor);
     } else
       ::CloseHandle(FileHandle);
-    return make_error_code(errc::invalid_argument);
+    return make_error_code(std::errc::invalid_argument);
   }
 
   DWORD flprotect;
@@ -652,7 +653,7 @@ mapped_file_region::mapped_file_region(int fd,
     if (closefd)
       _close(FileDescriptor);
     FileDescriptor = 0;
-    ec = make_error_code(errc::bad_file_descriptor);
+    ec = make_error_code(std::errc::bad_file_descriptor);
     return;
   }
 
@@ -815,7 +816,7 @@ error_code openFileForRead(const Twine &Name, int &ResultFD) {
     if (LastError != ERROR_ACCESS_DENIED)
       return EC;
     if (is_directory(Name))
-      return make_error_code(errc::is_a_directory);
+      return make_error_code(std::errc::is_a_directory);
     return EC;
   }
 
@@ -867,7 +868,7 @@ error_code openFileForWrite(const Twine &Name, int &ResultFD,
     if (LastError != ERROR_ACCESS_DENIED)
       return EC;
     if (is_directory(Name))
-      return make_error_code(errc::is_a_directory);
+      return make_error_code(std::errc::is_a_directory);
     return EC;
   }
 
diff --git a/lib/Support/Windows/Process.inc b/lib/Support/Windows/Process.inc
index 9707cf103f..0be871c695 100644
--- a/lib/Support/Windows/Process.inc
+++ b/lib/Support/Windows/Process.inc
@@ -13,6 +13,7 @@
 
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/WindowsError.h"
 #include <malloc.h>
 
 // The Windows.h header must be after LLVM and standard headers.
@@ -180,7 +181,7 @@ Optional<std::string> Process::GetEnv(StringRef Name) {
 }
 
 static error_code windows_error(DWORD E) {
-  return error_code(E, system_category());
+  return mapWindowsError(E);
 }
 
 error_code
diff --git a/lib/Support/Windows/system_error.inc b/lib/Support/Windows/system_error.inc
deleted file mode 100644
index 89492efad3..0000000000
--- a/lib/Support/Windows/system_error.inc
+++ /dev/null
@@ -1,141 +0,0 @@
-//===- llvm/Support/Win32/system_error.inc - Windows error_code --*- C++ -*-===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This file provides the Windows specific implementation of the error_code
-// and error_condition classes.
-//
-//===----------------------------------------------------------------------===//
-
-//===----------------------------------------------------------------------===//
-//=== WARNING: Implementation here must contain only generic Windows code that
-//===          is guaranteed to work on *all* Windows variants.
-//===----------------------------------------------------------------------===//
-
-#include <windows.h>
-#include <winerror.h>
-
-using namespace llvm;
-
-std::string
-_system_error_category::message(int ev) const {
-  LPVOID lpMsgBuf = 0;
-  DWORD retval = ::FormatMessageA(
-    FORMAT_MESSAGE_ALLOCATE_BUFFER |
-    FORMAT_MESSAGE_FROM_SYSTEM |
-    FORMAT_MESSAGE_IGNORE_INSERTS,
-    NULL,
-    ev,
-    MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), // Default language
-    (LPSTR) &lpMsgBuf,
-    0,
-    NULL);
-  if (retval == 0) {
-    ::LocalFree(lpMsgBuf);
-    return std::string("Unknown error");
-  }
-
-  std::string str( static_cast<LPCSTR>(lpMsgBuf) );
-  ::LocalFree(lpMsgBuf);
-
-  while (str.size()
-     && (str[str.size()-1] == '\n' || str[str.size()-1] == '\r'))
-    str.erase( str.size()-1 );
-  if (str.size() && str[str.size()-1] == '.')
-    str.erase( str.size()-1 );
-  return str;
-}
-
-// I'd rather not double the line count of the following.
-#define MAP_ERR_TO_COND(x, y) case x: return make_error_condition(errc::y)
-
-error_condition
-_system_error_category::default_error_condition(int ev) const {
-  switch (ev) {
-  // Windows system -> posix_errno decode table  ---------------------------//
-  // see WinError.h comments for descriptions of errors
-  MAP_ERR_TO_COND(ERROR_ACCESS_DENIED,       permission_denied);
-  MAP_ERR_TO_COND(ERROR_ALREADY_EXISTS,      file_exists);
-  MAP_ERR_TO_COND(ERROR_BAD_UNIT,            no_such_device);
-  MAP_ERR_TO_COND(ERROR_BUFFER_OVERFLOW,     filename_too_long);
-  MAP_ERR_TO_COND(ERROR_BUSY,                device_or_resource_busy);
-  MAP_ERR_TO_COND(ERROR_BUSY_DRIVE,          device_or_resource_busy);
-  MAP_ERR_TO_COND(ERROR_CANNOT_MAKE,         permission_denied);
-  MAP_ERR_TO_COND(ERROR_CANTOPEN,            io_error);
-  MAP_ERR_TO_COND(ERROR_CANTREAD,            io_error);
-  MAP_ERR_TO_COND(ERROR_CANTWRITE,           io_error);
-  MAP_ERR_TO_COND(ERROR_CURRENT_DIRECTORY,   permission_denied);
-  MAP_ERR_TO_COND(ERROR_DEV_NOT_EXIST,       no_such_device);
-  MAP_ERR_TO_COND(ERROR_DEVICE_IN_USE,       device_or_resource_busy);
-  MAP_ERR_TO_COND(ERROR_DIR_NOT_EMPTY,       directory_not_empty);
-  MAP_ERR_TO_COND(ERROR_DIRECTORY,           invalid_argument);
-  MAP_ERR_TO_COND(ERROR_DISK_FULL,           no_space_on_device);
-  MAP_ERR_TO_COND(ERROR_FILE_EXISTS,         file_exists);
-  MAP_ERR_TO_COND(ERROR_FILE_NOT_FOUND,      no_such_file_or_directory);
-  MAP_ERR_TO_COND(ERROR_HANDLE_DISK_FULL,    no_space_on_device);
-  MAP_ERR_TO_COND(ERROR_HANDLE_EOF,          value_too_large);
-  MAP_ERR_TO_COND(ERROR_INVALID_ACCESS,      permission_denied);
-  MAP_ERR_TO_COND(ERROR_INVALID_DRIVE,       no_such_device);
-  MAP_ERR_TO_COND(ERROR_INVALID_FUNCTION,    function_not_supported);
-  MAP_ERR_TO_COND(ERROR_INVALID_HANDLE,      invalid_argument);
-  MAP_ERR_TO_COND(ERROR_INVALID_NAME,        invalid_argument);
-  MAP_ERR_TO_COND(ERROR_LOCK_VIOLATION,      no_lock_available);
-  MAP_ERR_TO_COND(ERROR_LOCKED,              no_lock_available);
-  MAP_ERR_TO_COND(ERROR_NEGATIVE_SEEK,       invalid_argument);
-  MAP_ERR_TO_COND(ERROR_NOACCESS,            permission_denied);
-  MAP_ERR_TO_COND(ERROR_NOT_ENOUGH_MEMORY,   not_enough_memory);
-  MAP_ERR_TO_COND(ERROR_NOT_READY,           resource_unavailable_try_again);
-  MAP_ERR_TO_COND(ERROR_NOT_SAME_DEVICE,     cross_device_link);
-  MAP_ERR_TO_COND(ERROR_OPEN_FAILED,         io_error);
-  MAP_ERR_TO_COND(ERROR_OPEN_FILES,          device_or_resource_busy);
-  MAP_ERR_TO_COND(ERROR_OPERATION_ABORTED,   operation_canceled);
-  MAP_ERR_TO_COND(ERROR_OUTOFMEMORY,         not_enough_memory);
-  MAP_ERR_TO_COND(ERROR_PATH_NOT_FOUND,      no_such_file_or_directory);
-  MAP_ERR_TO_COND(ERROR_BAD_NETPATH,         no_such_file_or_directory);
-  MAP_ERR_TO_COND(ERROR_READ_FAULT,          io_error);
-  MAP_ERR_TO_COND(ERROR_RETRY,               resource_unavailable_try_again);
-  MAP_ERR_TO_COND(ERROR_SEEK,                io_error);
-  MAP_ERR_TO_COND(ERROR_SHARING_VIOLATION,   permission_denied);
-  MAP_ERR_TO_COND(ERROR_TOO_MANY_OPEN_FILES, too_many_files_open);
-  MAP_ERR_TO_COND(ERROR_WRITE_FAULT,         io_error);
-  MAP_ERR_TO_COND(ERROR_WRITE_PROTECT,       permission_denied);
-  MAP_ERR_TO_COND(ERROR_SEM_TIMEOUT,         timed_out);
-  MAP_ERR_TO_COND(WSAEACCES,                 permission_denied);
-  MAP_ERR_TO_COND(WSAEADDRINUSE,             address_in_use);
-  MAP_ERR_TO_COND(WSAEADDRNOTAVAIL,          address_not_available);
-  MAP_ERR_TO_COND(WSAEAFNOSUPPORT,           address_family_not_supported);
-  MAP_ERR_TO_COND(WSAEALREADY,               connection_already_in_progress);
-  MAP_ERR_TO_COND(WSAEBADF,                  bad_file_descriptor);
-  MAP_ERR_TO_COND(WSAECONNABORTED,           connection_aborted);
-  MAP_ERR_TO_COND(WSAECONNREFUSED,           connection_refused);
-  MAP_ERR_TO_COND(WSAECONNRESET,             connection_reset);
-  MAP_ERR_TO_COND(WSAEDESTADDRREQ,           destination_address_required);
-  MAP_ERR_TO_COND(WSAEFAULT,                 bad_address);
-  MAP_ERR_TO_COND(WSAEHOSTUNREACH,           host_unreachable);
-  MAP_ERR_TO_COND(WSAEINPROGRESS,            operation_in_progress);
-  MAP_ERR_TO_COND(WSAEINTR,                  interrupted);
-  MAP_ERR_TO_COND(WSAEINVAL,                 invalid_argument);
-  MAP_ERR_TO_COND(WSAEISCONN,                already_connected);
-  MAP_ERR_TO_COND(WSAEMFILE,                 too_many_files_open);
-  MAP_ERR_TO_COND(WSAEMSGSIZE,               message_size);
-  MAP_ERR_TO_COND(WSAENAMETOOLONG,           filename_too_long);
-  MAP_ERR_TO_COND(WSAENETDOWN,               network_down);
-  MAP_ERR_TO_COND(WSAENETRESET,              network_reset);
-  MAP_ERR_TO_COND(WSAENETUNREACH,            network_unreachable);
-  MAP_ERR_TO_COND(WSAENOBUFS,                no_buffer_space);
-  MAP_ERR_TO_COND(WSAENOPROTOOPT,            no_protocol_option);
-  MAP_ERR_TO_COND(WSAENOTCONN,               not_connected);
-  MAP_ERR_TO_COND(WSAENOTSOCK,               not_a_socket);
-  MAP_ERR_TO_COND(WSAEOPNOTSUPP,             operation_not_supported);
-  MAP_ERR_TO_COND(WSAEPROTONOSUPPORT,        protocol_not_supported);
-  MAP_ERR_TO_COND(WSAEPROTOTYPE,             wrong_protocol_type);
-  MAP_ERR_TO_COND(WSAETIMEDOUT,              timed_out);
-  MAP_ERR_TO_COND(WSAEWOULDBLOCK,            operation_would_block);
-  default: return error_condition(ev, system_category());
-  }
-}
diff --git a/lib/Support/WindowsError.cpp b/lib/Support/WindowsError.cpp
new file mode 100644
index 0000000000..59c575ff9e
--- /dev/null
+++ b/lib/Support/WindowsError.cpp
@@ -0,0 +1,115 @@
+//===-- WindowsError.cpp - Support for mapping windows errors to posix-----===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+//  This file implements a mapping from windows errors to posix ones.
+//  The standard doesn't define what the equivalence is from system
+//  errors to generic ones. The one implemented in msvc is too conservative
+//  for llvm, so we do an extra mapping when constructing an error_code
+//  from an windows error. This allows the rest of llvm to simple checks
+//  like "EC == std::errc::file_exists" and have it work on both posix and
+//  windows.
+//
+//===----------------------------------------------------------------------===//
+
+#ifdef _MSC_VER
+
+#include <winerror.h>
+
+#include "llvm/Support/WindowsError.h"
+
+// I'd rather not double the line count of the following.
+#define MAP_ERR_TO_COND(x, y)                                                  \
+  case x:                                                                      \
+    return std::make_error_code(std::errc::y)
+
+std::error_code llvm::mapWindowsError(unsigned EV) {
+  switch (EV) {
+    MAP_ERR_TO_COND(ERROR_ACCESS_DENIED, permission_denied);
+    MAP_ERR_TO_COND(ERROR_ALREADY_EXISTS, file_exists);
+    MAP_ERR_TO_COND(ERROR_BAD_UNIT, no_such_device);
+    MAP_ERR_TO_COND(ERROR_BUFFER_OVERFLOW, filename_too_long);
+    MAP_ERR_TO_COND(ERROR_BUSY, device_or_resource_busy);
+    MAP_ERR_TO_COND(ERROR_BUSY_DRIVE, device_or_resource_busy);
+    MAP_ERR_TO_COND(ERROR_CANNOT_MAKE, permission_denied);
+    MAP_ERR_TO_COND(ERROR_CANTOPEN, io_error);
+    MAP_ERR_TO_COND(ERROR_CANTREAD, io_error);
+    MAP_ERR_TO_COND(ERROR_CANTWRITE, io_error);
+    MAP_ERR_TO_COND(ERROR_CURRENT_DIRECTORY, permission_denied);
+    MAP_ERR_TO_COND(ERROR_DEV_NOT_EXIST, no_such_device);
+    MAP_ERR_TO_COND(ERROR_DEVICE_IN_USE, device_or_resource_busy);
+    MAP_ERR_TO_COND(ERROR_DIR_NOT_EMPTY, directory_not_empty);
+    MAP_ERR_TO_COND(ERROR_DIRECTORY, invalid_argument);
+    MAP_ERR_TO_COND(ERROR_DISK_FULL, no_space_on_device);
+    MAP_ERR_TO_COND(ERROR_FILE_EXISTS, file_exists);
+    MAP_ERR_TO_COND(ERROR_FILE_NOT_FOUND, no_such_file_or_directory);
+    MAP_ERR_TO_COND(ERROR_HANDLE_DISK_FULL, no_space_on_device);
+    MAP_ERR_TO_COND(ERROR_HANDLE_EOF, value_too_large);
+    MAP_ERR_TO_COND(ERROR_INVALID_ACCESS, permission_denied);
+    MAP_ERR_TO_COND(ERROR_INVALID_DRIVE, no_such_device);
+    MAP_ERR_TO_COND(ERROR_INVALID_FUNCTION, function_not_supported);
+    MAP_ERR_TO_COND(ERROR_INVALID_HANDLE, invalid_argument);
+    MAP_ERR_TO_COND(ERROR_INVALID_NAME, invalid_argument);
+    MAP_ERR_TO_COND(ERROR_LOCK_VIOLATION, no_lock_available);
+    MAP_ERR_TO_COND(ERROR_LOCKED, no_lock_available);
+    MAP_ERR_TO_COND(ERROR_NEGATIVE_SEEK, invalid_argument);
+    MAP_ERR_TO_COND(ERROR_NOACCESS, permission_denied);
+    MAP_ERR_TO_COND(ERROR_NOT_ENOUGH_MEMORY, not_enough_memory);
+    MAP_ERR_TO_COND(ERROR_NOT_READY, resource_unavailable_try_again);
+    MAP_ERR_TO_COND(ERROR_NOT_SAME_DEVICE, cross_device_link);
+    MAP_ERR_TO_COND(ERROR_OPEN_FAILED, io_error);
+    MAP_ERR_TO_COND(ERROR_OPEN_FILES, device_or_resource_busy);
+    MAP_ERR_TO_COND(ERROR_OPERATION_ABORTED, operation_canceled);
+    MAP_ERR_TO_COND(ERROR_OUTOFMEMORY, not_enough_memory);
+    MAP_ERR_TO_COND(ERROR_PATH_NOT_FOUND, no_such_file_or_directory);
+    MAP_ERR_TO_COND(ERROR_BAD_NETPATH, no_such_file_or_directory);
+    MAP_ERR_TO_COND(ERROR_READ_FAULT, io_error);
+    MAP_ERR_TO_COND(ERROR_RETRY, resource_unavailable_try_again);
+    MAP_ERR_TO_COND(ERROR_SEEK, io_error);
+    MAP_ERR_TO_COND(ERROR_SHARING_VIOLATION, permission_denied);
+    MAP_ERR_TO_COND(ERROR_TOO_MANY_OPEN_FILES, too_many_files_open);
+    MAP_ERR_TO_COND(ERROR_WRITE_FAULT, io_error);
+    MAP_ERR_TO_COND(ERROR_WRITE_PROTECT, permission_denied);
+    MAP_ERR_TO_COND(ERROR_SEM_TIMEOUT, timed_out);
+    MAP_ERR_TO_COND(WSAEACCES, permission_denied);
+    MAP_ERR_TO_COND(WSAEADDRINUSE, address_in_use);
+    MAP_ERR_TO_COND(WSAEADDRNOTAVAIL, address_not_available);
+    MAP_ERR_TO_COND(WSAEAFNOSUPPORT, address_family_not_supported);
+    MAP_ERR_TO_COND(WSAEALREADY, connection_already_in_progress);
+    MAP_ERR_TO_COND(WSAEBADF, bad_file_descriptor);
+    MAP_ERR_TO_COND(WSAECONNABORTED, connection_aborted);
+    MAP_ERR_TO_COND(WSAECONNREFUSED, connection_refused);
+    MAP_ERR_TO_COND(WSAECONNRESET, connection_reset);
+    MAP_ERR_TO_COND(WSAEDESTADDRREQ, destination_address_required);
+    MAP_ERR_TO_COND(WSAEFAULT, bad_address);
+    MAP_ERR_TO_COND(WSAEHOSTUNREACH, host_unreachable);
+    MAP_ERR_TO_COND(WSAEINPROGRESS, operation_in_progress);
+    MAP_ERR_TO_COND(WSAEINTR, interrupted);
+    MAP_ERR_TO_COND(WSAEINVAL, invalid_argument);
+    MAP_ERR_TO_COND(WSAEISCONN, already_connected);
+    MAP_ERR_TO_COND(WSAEMFILE, too_many_files_open);
+    MAP_ERR_TO_COND(WSAEMSGSIZE, message_size);
+    MAP_ERR_TO_COND(WSAENAMETOOLONG, filename_too_long);
+    MAP_ERR_TO_COND(WSAENETDOWN, network_down);
+    MAP_ERR_TO_COND(WSAENETRESET, network_reset);
+    MAP_ERR_TO_COND(WSAENETUNREACH, network_unreachable);
+    MAP_ERR_TO_COND(WSAENOBUFS, no_buffer_space);
+    MAP_ERR_TO_COND(WSAENOPROTOOPT, no_protocol_option);
+    MAP_ERR_TO_COND(WSAENOTCONN, not_connected);
+    MAP_ERR_TO_COND(WSAENOTSOCK, not_a_socket);
+    MAP_ERR_TO_COND(WSAEOPNOTSUPP, operation_not_supported);
+    MAP_ERR_TO_COND(WSAEPROTONOSUPPORT, protocol_not_supported);
+    MAP_ERR_TO_COND(WSAEPROTOTYPE, wrong_protocol_type);
+    MAP_ERR_TO_COND(WSAETIMEDOUT, timed_out);
+    MAP_ERR_TO_COND(WSAEWOULDBLOCK, operation_would_block);
+  default:
+    return std::error_code(EV, std::system_category());
+  }
+}
+
+#endif
diff --git a/lib/Support/YAMLTraits.cpp b/lib/Support/YAMLTraits.cpp
index 20f8b245c9..ed80eac76a 100644
--- a/lib/Support/YAMLTraits.cpp
+++ b/lib/Support/YAMLTraits.cpp
@@ -74,7 +74,7 @@ bool Input::setCurrentDocument() {
     Node *N = DocIterator->getRoot();
     if (!N) {
       assert(Strm->failed() && "Root is NULL iff parsing failed");
-      EC = make_error_code(errc::invalid_argument);
+      EC = make_error_code(std::errc::invalid_argument);
       return false;
     }
 
@@ -124,7 +124,7 @@ bool Input::preflightKey(const char *Key, bool Required, bool, bool &UseDefault,
   // nodes are present.
   if (!CurrentNode) {
     if (Required)
-      EC = make_error_code(errc::invalid_argument);
+      EC = make_error_code(std::errc::invalid_argument);
     return false;
   }
 
@@ -300,7 +300,7 @@ void Input::setError(HNode *hnode, const Twine &message) {
 
 void Input::setError(Node *node, const Twine &message) {
   Strm->printError(node, message);
-  EC = make_error_code(errc::invalid_argument);
+  EC = make_error_code(std::errc::invalid_argument);
 }
 
 Input::HNode *Input::createHNodes(Node *N) {
diff --git a/lib/Support/system_error.cpp b/lib/Support/system_error.cpp
deleted file mode 100644
index 46b501eea0..0000000000
--- a/lib/Support/system_error.cpp
+++ /dev/null
@@ -1,121 +0,0 @@
-//===---------------------- system_error.cpp ------------------------------===//
-//
-//                     The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-//
-// This was lifted from libc++ and modified for C++03.
-//
-//===----------------------------------------------------------------------===//
-
-#include "llvm/Support/system_error.h"
-#include "llvm/Support/Errno.h"
-#include <cstring>
-#include <string>
-
-namespace llvm {
-
-// class error_category
-
-error_category::error_category() {
-}
-
-error_category::~error_category() {
-}
-
-error_condition
-error_category::default_error_condition(int ev) const {
-  return error_condition(ev, *this);
-}
-
-bool
-error_category::equivalent(int code, const error_condition& condition) const {
-  return default_error_condition(code) == condition;
-}
-
-bool
-error_category::equivalent(const error_code& code, int condition) const {
-  return *this == code.category() && code.value() == condition;
-}
-
-std::string
-_do_message::message(int ev) const {
-  return std::string(sys::StrError(ev));
-}
-
-class _generic_error_category : public _do_message {
-public:
-  const char* name() const LLVM_NOEXCEPT override;
-  std::string message(int ev) const override;
-};
-
-const char*
-_generic_error_category::name() const {
-  return "generic";
-}
-
-std::string
-_generic_error_category::message(int ev) const {
-#ifdef ELAST
-  if (ev > ELAST)
-    return std::string("unspecified generic_category error");
-#endif  // ELAST
-  return _do_message::message(ev);
-}
-
-const error_category&
-generic_category() {
-  static _generic_error_category s;
-  return s;
-}
-
-class _system_error_category : public _do_message {
-public:
-  const char* name() const LLVM_NOEXCEPT override;
-  std::string message(int ev) const override;
-  error_condition default_error_condition(int ev) const override;
-};
-
-const char*
-_system_error_category::name() const {
-  return "system";
-}
-
-// std::string _system_error_category::message(int ev) const {
-// Is in Platform/system_error.inc
-
-// error_condition _system_error_category::default_error_condition(int ev) const
-// Is in Platform/system_error.inc
-
-const error_category&
-system_category() {
-  static _system_error_category s;
-  return s;
-}
-
-// error_condition
-
-std::string
-error_condition::message() const {
-  return _cat_->message(_val_);
-}
-
-// error_code
-
-std::string
-error_code::message() const {
-  return _cat_->message(_val_);
-}
-
-} // end namespace llvm
-
-// Include the truly platform-specific parts of this class.
-#if defined(LLVM_ON_UNIX)
-#include "Unix/system_error.inc"
-#endif
-#if defined(LLVM_ON_WIN32)
-#include "Windows/system_error.inc"
-#endif