[clang] [clang-cl]: Add /std:c++23preview and update _MSVC_LANG for C++23 (PR #112378)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang-driver

Author: Hans (zmodem)

<details>
<summary>Changes</summary>

As discussed in https://discourse.llvm.org/t/clang-cl-adding-std-c-23preview/82553

---
Full diff: https://github.com/llvm/llvm-project/pull/112378.diff


5 Files Affected:

- (modified) clang/include/clang/Driver/Options.td (+1-1) 
- (modified) clang/lib/Basic/Targets/OSTargets.cpp (+1-2) 
- (modified) clang/lib/Driver/ToolChains/Clang.cpp (+1) 
- (modified) clang/test/Driver/cl-options.c (+3) 
- (modified) clang/test/Preprocessor/predefined-win-macros.c (+1-1) 


``````````diff
diff --git a/clang/include/clang/Driver/Options.td b/clang/include/clang/Driver/Options.td
index 6491e9ac73ce99..3390367173a29d 100644
--- a/clang/include/clang/Driver/Options.td
+++ b/clang/include/clang/Driver/Options.td
@@ -8526,7 +8526,7 @@ def _SLASH_execution_charset : CLCompileJoined<"execution-charset:">,
   HelpText<"Set runtime encoding, supports only UTF-8">,
   Alias<fexec_charset_EQ>;
 def _SLASH_std : CLCompileJoined<"std:">,
-  HelpText<"Set language version (c++14,c++17,c++20,c++latest,c11,c17)">;
+  HelpText<"Set language version (c++14,c++17,c++20,c++23preview,c++latest,c11,c17)">;
 def _SLASH_U : CLJoinedOrSeparate<"U">, HelpText<"Undefine macro">,
   MetaVarName<"<macro>">, Alias<U>;
 def _SLASH_validate_charset : CLFlag<"validate-charset">,
diff --git a/clang/lib/Basic/Targets/OSTargets.cpp b/clang/lib/Basic/Targets/OSTargets.cpp
index b56e2c7ca9c494..ff4d2df163e613 100644
--- a/clang/lib/Basic/Targets/OSTargets.cpp
+++ b/clang/lib/Basic/Targets/OSTargets.cpp
@@ -215,8 +215,7 @@ static void addVisualCDefines(const LangOptions &Opts, MacroBuilder &Builder) {
 
     if (Opts.isCompatibleWithMSVC(LangOptions::MSVC2015)) {
       if (Opts.CPlusPlus23)
-        // TODO update to the proper value.
-        Builder.defineMacro("_MSVC_LANG", "202004L");
+        Builder.defineMacro("_MSVC_LANG", "202302L");
       else if (Opts.CPlusPlus20)
         Builder.defineMacro("_MSVC_LANG", "202002L");
       else if (Opts.CPlusPlus17)
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 9d2f7a8960b45f..ca8f10c337e1e9 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7217,6 +7217,7 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                              .Case("c++17", "-std=c++17")
                              .Case("c++20", "-std=c++20")
                              // TODO add c++23 and c++26 when MSVC supports it.
+                             .Case("c++23preview", "-std=c++23")
                              .Case("c++latest", "-std=c++26")
                              .Default("");
       if (LanguageStandard.empty())
diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index 48d281bcd447e7..8191fda97788c1 100644
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -605,6 +605,9 @@
 // RUN: %clang_cl -fmsc-version=1900 -TP -std:c++20 -### -- %s 2>&1 | FileCheck -check-prefix=STDCXX20 %s
 // STDCXX20: -std=c++20
 
+// RUN: %clang_cl -fmsc-version=1900 -TP -std:c++23preview -### -- %s 2>&1 | FileCheck -check-prefix=STDCXX23PREVIEW %s
+// STDCXX23PREVIEW: -std=c++23
+
 // RUN: %clang_cl -fmsc-version=1900 -TP -std:c++latest -### -- %s 2>&1 | FileCheck -check-prefix=STDCXXLATEST %s
 // STDCXXLATEST: -std=c++26
 
diff --git a/clang/test/Preprocessor/predefined-win-macros.c b/clang/test/Preprocessor/predefined-win-macros.c
index 7d29e45c7d5ac6..e7988501afa689 100644
--- a/clang/test/Preprocessor/predefined-win-macros.c
+++ b/clang/test/Preprocessor/predefined-win-macros.c
@@ -56,7 +56,7 @@
 // RUN: %clang_cc1 %s -x c++ -E -dM -triple i686-pc-win32 -fms-extensions -fms-compatibility \
 // RUN:     -fms-compatibility-version=19.00 -std=c++23 -o - | FileCheck -match-full-lines %s --check-prefix=CHECK-MS-CPP2B
 // CHECK-MS-CPP2B: #define _MSC_VER 1900
-// CHECK-MS-CPP2B: #define _MSVC_LANG 202004L
+// CHECK-MS-CPP2B: #define _MSVC_LANG 202302L
 
 // RUN: %clang_cc1 -triple i386-windows %s -E -dM -o - \
 // RUN:   | FileCheck -match-full-lines %s --check-prefix=CHECK-X86-WIN

``````````

</details>


https://github.com/llvm/llvm-project/pull/112378