Author: A. Jiang Date: 2025-03-13T14:02:44+08:00 New Revision: 6abe19ac587d36edf202830cbbceecfd1a55f191
URL: https://github.com/llvm/llvm-project/commit/6abe19ac587d36edf202830cbbceecfd1a55f191 DIFF: https://github.com/llvm/llvm-project/commit/6abe19ac587d36edf202830cbbceecfd1a55f191.diff LOG: [clang] Predefine `_CRT_USE_BUILTIN_OFFSETOF` in MS-compatible modes (#127568) 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. Added: clang/test/Sema/offsetof-ucrt.c clang/test/SemaCXX/offsetof-ucrt.cpp Modified: clang/docs/ReleaseNotes.rst clang/lib/Basic/Targets/OSTargets.cpp Removed: ################################################################################ diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 36215af5bc7b0..e587c6c7b74f2 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -358,6 +358,10 @@ Android Support Windows Support ^^^^^^^^^^^^^^^ +- Clang now defines ``_CRT_USE_BUILTIN_OFFSETOF`` macro in MSVC-compatible mode, + which makes ``offsetof`` provided by Microsoft's ``<stddef.h>`` to be defined + correctly. (#GH59689) + LoongArch Support ^^^^^^^^^^^^^^^^^ diff --git a/clang/lib/Basic/Targets/OSTargets.cpp b/clang/lib/Basic/Targets/OSTargets.cpp index 8af6623e5cb15..e744e84a5b079 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)); + // Exposed by MSVC, used in their stddef.h. + 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..05c3d87ce66ca --- /dev/null +++ b/clang/test/Sema/offsetof-ucrt.c @@ -0,0 +1,28 @@ +// RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -verify -fms-compatibility +// RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -verify +// expected-no-diagnostics + +typedef __typeof__(sizeof(0)) size_t; + +#ifdef _MSC_VER +#ifndef _CRT_USE_BUILTIN_OFFSETOF +#error _CRT_USE_BUILTIN_OFFSETOF should be predefined in MSVC-compatible modes. +#endif +#else +#ifdef _CRT_USE_BUILTIN_OFFSETOF +#error _CRT_USE_BUILTIN_OFFSETOF should not be predefined in non-MSVC-compatible modes. +#endif +#endif + +#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..95437554c4665 --- /dev/null +++ b/clang/test/SemaCXX/offsetof-ucrt.cpp @@ -0,0 +1,28 @@ +// RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -verify -fms-compatibility +// RUN: %clang_cc1 %s -triple i686-pc-win32 -fsyntax-only -verify +// expected-no-diagnostics + +typedef __typeof__(sizeof(0)) size_t; + +#ifdef _MSC_VER +#ifndef _CRT_USE_BUILTIN_OFFSETOF +#error _CRT_USE_BUILTIN_OFFSETOF should be predefined in MSVC-compatible modes. +#endif +#else +#ifdef _CRT_USE_BUILTIN_OFFSETOF +#error _CRT_USE_BUILTIN_OFFSETOF should not be predefined in non-MSVC-compatible modes. +#endif +#endif + +#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, ""); _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
