Bug 43965 - Value of _MSVC_LANG doesn't match MSVC++ VS2019 /std:c++latest mode

[Manna]

Summary

The patch adds correct value of _MSVC_LANG to match with MSVC++ VS2019 /std:c++latest mode.

Bugzilla - Bug 43965
https://bugs.llvm.org/show_bug.cgi?id=43965

The value for a MS specific macro differs from Microsoft starting with VS2019 in /std:c++latest mode.

-bash-4.2$ cat msvclang.cpp
_MSVC_LANG

-bash-4.2$ cl /std:c++latest -E msvclang.cpp
Microsoft (R) C/C++ Optimizing Compiler Version 19.20.27508.1 for x64
Copyright (C) Microsoft Corporation.  All rights reserved.

/std:c++latest is provided as a preview of language features from the latest C++
working draft, and we're eager to hear about bugs and suggestions for improvements.
However, note that these features are provided as-is without support, and subject
to changes or removal as the working draft evolves. See
https://go.microsoft.com/fwlink/?linkid=2045807 for details.

msvclang.cpp

201705L

-bash-4.2$ clang-cl /std:c++latest -E  msvclang.cpp
201704L

[rnk]

lgtm, do you need someone to push this?

[Manna]

In D70996#1769590, @rnk wrote:

lgtm, do you need someone to push this?

Thanks Reid. Could you please push the changes?

Thanks,
Soumi

clang/lib/Basic/Targets/OSTargets.cpp

if (Opts.MSCompatibilityVersion) {
     // FIXME We cannot encode the revision information into 32-bits
     Builder.defineMacro("_MSC_BUILD", Twine(1));
 
     if (Opts.CPlusPlus11 && Opts.isCompatibleWithMSVC(LangOptions::MSVC2015))
       Builder.defineMacro("_HAS_CHAR16_T_LANGUAGE_SUPPORT", Twine(1));
 
     if (Opts.isCompatibleWithMSVC(LangOptions::MSVC2015)) {
       if (Opts.CPlusPlus2a)
-        Builder.defineMacro("_MSVC_LANG", "201704L");
+        Builder.defineMacro("_MSVC_LANG", "201705L");
       else if (Opts.CPlusPlus17)
         Builder.defineMacro("_MSVC_LANG", "201703L");
       else if (Opts.CPlusPlus14)
         Builder.defineMacro("_MSVC_LANG", "201402L");
     }
   }
 
   if (Opts.MicrosoftExt) {

clang/test/Preprocessor/predefined-win-macros.c

 // CHECK-MS: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_4 1
 // CHECK-MS: #define __GCC_HAVE_SYNC_COMPARE_AND_SWAP_8 1
 // CHECK-MS-NOT: GNU
 // CHECK-MS-NOT: GXX
 
 // RUN: %clang_cc1 %s -x c++ -E -dM -triple i686-pc-win32 -fms-extensions -fms-compatibility \
 // RUN:     -fms-compatibility-version=19.00 -std=c++2a -o - | FileCheck -match-full-lines %s --check-prefix=CHECK-MS-CPP2A
 // CHECK-MS-CPP2A: #define _MSC_VER 1900
-// CHECK-MS-CPP2A: #define _MSVC_LANG 201704L
+// CHECK-MS-CPP2A: #define _MSVC_LANG 201705L
 
 // RUN: %clang_cc1 -triple i386-windows %s -E -dM -o - \
 // RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-X86-WIN
 
 // CHECK-X86-WIN-NOT: #define WIN32 1
 // CHECK-X86-WIN-NOT: #define WIN64 1
 // CHECK-X86-WIN-NOT: #define WINNT 1
 // CHECK-X86-WIN: #define _WIN32 1