[clang] [clang-cl] Support /stdc:latest (PR #147284)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Aaron Ballman (AaronBallman)

<details>
<summary>Changes</summary>

cl.exe has /stdc:latest, analogous to /stdc++:latest, which sets the language mode to the latest standard. For C, that's C23. This adds support for the option.

Fixes #<!-- -->147233

---
Full diff: https://github.com/llvm/llvm-project/pull/147284.diff


3 Files Affected:

- (modified) clang/docs/ReleaseNotes.rst (+3-1) 
- (modified) clang/lib/Driver/ToolChains/Clang.cpp (+2) 
- (modified) clang/test/Driver/cl-options.c (+6) 


``````````diff
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 3d893e0aa8e2c..2052b43f48070 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -248,7 +248,9 @@ C Language Changes
   not valid in C++.
 - The ``[[clang::assume()]]`` attribute is now correctly recognized in C. The
   ``__attribute__((assume()))`` form has always been supported, so the fix is
-  specific to the attribute syntax used.
+  specific to the attribute syntax used.'
+- The ``clang-cl`` driver now recognizes ``/stdc:latest`` and sets the language
+  mode to C23. #GH147233
 
 C2y Feature Support
 ^^^^^^^^^^^^^^^^^^^
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index fea4ee909ff46..8a30b7ea8144a 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -7201,6 +7201,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
       LanguageStandard = llvm::StringSwitch<StringRef>(StdArg->getValue())
                              .Case("c11", "-std=c11")
                              .Case("c17", "-std=c17")
+                             // TODO: add c23 when MSVC supports it.
+                             .Case("clatest", "-std=c23")
                              .Default("");
       if (LanguageStandard.empty())
         D.Diag(clang::diag::warn_drv_unused_argument)
diff --git a/clang/test/Driver/cl-options.c b/clang/test/Driver/cl-options.c
index eb079895a0a88..57e16e8795a28 100644
--- a/clang/test/Driver/cl-options.c
+++ b/clang/test/Driver/cl-options.c
@@ -362,6 +362,12 @@
 // RUN: %clang_cl -c -### /std:c11 -- %s 2>&1 | FileCheck -check-prefix CHECK-C11 %s
 // CHECK-C11: -std=c11
 
+// RUN: %clang_cl -c -### /std:c17 -- %s 2>&1 | FileCheck -check-prefix CHECK-C17 %s
+// CHECK-C17: -std=c17
+
+// RUN: %clang_cl -c -### /std:clatest -- %s 2>&1 | FileCheck -check-prefix CHECK-CLATEST %s
+// CHECK-CLATEST: -std=c23
+
 // For some warning ids, we can map from MSVC warning to Clang warning.
 // RUN: %clang_cl -wd4005 -wd4100 -wd4910 -wd4996 -wd12345678 -### -- %s 2>&1 | FileCheck -check-prefix=Wno %s
 // Wno: "-cc1"

``````````

</details>


https://github.com/llvm/llvm-project/pull/147284