llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT--> @llvm/pr-subscribers-platform-windows Author: A. Jiang (frederick-vs-ja) <details> <summary>Changes</summary> This patch makes Clang predefine `_CRT_USE_BUILTIN_OFFSETOF` in MS-compatible modes. The macro can make the `offsetof` provided by MS UCRT's `<stddef.h>` to select the `__builtin_offsetof` version, so with it Clang (Clang-cl) can directly consume UCRT's `offsetof`. MSVC predefines the macro as `1` since at least VS 2017 19.14, but I think it's also OK to define it in "older" compatible modes. Fixes #<!-- -->59689. --- Full diff: https://github.com/llvm/llvm-project/pull/127568.diff 3 Files Affected: - (modified) clang/lib/Basic/Targets/OSTargets.cpp (+2) - (added) clang/test/Sema/offsetof-ucrt.c (+16) - (added) clang/test/SemaCXX/offsetof-ucrt.cpp (+16) ``````````diff diff --git a/clang/lib/Basic/Targets/OSTargets.cpp b/clang/lib/Basic/Targets/OSTargets.cpp index 8af6623e5cb15..2e57c286c9a16 100644 --- a/clang/lib/Basic/Targets/OSTargets.cpp +++ b/clang/lib/Basic/Targets/OSTargets.cpp @@ -220,6 +220,8 @@ static void addVisualCDefines(const LangOptions &Opts, MacroBuilder &Builder) { Builder.defineMacro("_MSC_FULL_VER", Twine(Opts.MSCompatibilityVersion)); // FIXME We cannot encode the revision information into 32-bits Builder.defineMacro("_MSC_BUILD", Twine(1)); + // https://github.com/llvm/llvm-project/issues/59689 + Builder.defineMacro("_CRT_USE_BUILTIN_OFFSETOF", Twine(1)); if (Opts.CPlusPlus11 && Opts.isCompatibleWithMSVC(LangOptions::MSVC2015)) Builder.defineMacro("_HAS_CHAR16_T_LANGUAGE_SUPPORT", Twine(1)); diff --git a/clang/test/Sema/offsetof-ucrt.c b/clang/test/Sema/offsetof-ucrt.c new file mode 100644 index 0000000000000..0f21b317c1ff2 --- /dev/null +++ b/clang/test/Sema/offsetof-ucrt.c @@ -0,0 +1,16 @@ +// RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -verify -fms-compatibility + +typedef __typeof__(sizeof(0)) size_t; + +#if defined _MSC_VER && !defined _CRT_USE_BUILTIN_OFFSETOF +#ifdef __cplusplus +#define offsetof(s,m) ((::size_t)&reinterpret_cast<char const volatile&>((((s*)0)->m))) +#else +#define offsetof(s,m) ((size_t)&(((s*)0)->m)) +#endif +#else +#define offsetof(s,m) __builtin_offsetof(s,m) +#endif + +struct S { int a; }; +_Static_assert(offsetof(struct S, a) == 0, ""); diff --git a/clang/test/SemaCXX/offsetof-ucrt.cpp b/clang/test/SemaCXX/offsetof-ucrt.cpp new file mode 100644 index 0000000000000..425e0e7f88f37 --- /dev/null +++ b/clang/test/SemaCXX/offsetof-ucrt.cpp @@ -0,0 +1,16 @@ +// RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -verify -fms-compatibility + +typedef __typeof__(sizeof(0)) size_t; + +#if defined _MSC_VER && !defined _CRT_USE_BUILTIN_OFFSETOF +#ifdef __cplusplus +#define offsetof(s,m) ((::size_t)&reinterpret_cast<char const volatile&>((((s*)0)->m))) +#else +#define offsetof(s,m) ((size_t)&(((s*)0)->m)) +#endif +#else +#define offsetof(s,m) __builtin_offsetof(s,m) +#endif + +struct S { int a; }; +_Static_assert(offsetof(S, a) == 0, ""); `````````` </details> https://github.com/llvm/llvm-project/pull/127568 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
