Define __STDC_NO_THREADS__ when targeting windows-msvc (PR48704)

MSVC's libc doesn't provide thread.h, so we should set the macro to indicate that. We could just set it in C mode, but I noticed that Darwin sets it unconditionally, so perhaps we should do the same here. Differential revision: https://reviews.llvm.org/D112081
llvm · Dec 16, 2021 · bbc690c · bbc690c
1 parent 8285522
commit bbc690c
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diff --git a/clang/lib/Basic/Targets/OSTargets.cpp b/clang/lib/Basic/Targets/OSTargets.cpp
@@ -203,6 +203,7 @@ static void addVisualCDefines(const LangOptions &Opts, MacroBuilder &Builder) {
   }
 
   Builder.defineMacro("_INTEGRAL_MAX_BITS", "64");
+  Builder.defineMacro("__STDC_NO_THREADS__");
 
   // Starting with VS 2022 17.1, MSVC predefines the below macro to inform
   // users of the execution character set defined at compile time.

diff --git a/clang/test/Preprocessor/init.c b/clang/test/Preprocessor/init.c
@@ -195,6 +195,7 @@
 // MSEXT-NOT:#define _NATIVE_WCHAR_T_DEFINED 1
 // MSEXT-NOT:#define _WCHAR_T_DEFINED 1
 // MSEXT:#define _MSVC_EXECUTION_CHARACTER_SET 65001
+// MSEXT:#define __STDC_NO_THREADS__ 1
 //
 //
 // RUN: %clang_cc1 -x c++ -fms-extensions -triple i686-pc-win32 -E -dM < /dev/null | FileCheck -match-full-lines -check-prefix MSEXT-CXX %s