From f49bb1505b854253b4f993ca9b95836bde37feb5 Mon Sep 17 00:00:00 2001 From: Khem Raj Date: Tue, 24 Jan 2023 17:54:33 -0800 Subject: [PATCH] [ruby/fiddle] fiddle: Use C11 _Alignof to define ALIGN_OF when possible (https://github.com/ruby/fiddle/pull/120) WG14 N2350 made very clear that it is an UB having type definitions within "offsetof" [1]. This patch enhances the implementation of macro ALIGN_OF to use builtin "_Alignof" to avoid undefined behavior when using std=c11 or newer clang 16+ has started to flag this [2] Fixes build when using -std >= gnu11 and using clang16+ Older compilers gcc < 4.9 or clang < 8 has buggy _Alignof even though it may support C11, exclude those compiler versions [1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm [2] https://reviews.llvm.org/D133574 Signed-off-by: Khem Raj https://github.com/ruby/fiddle/commit/ad6c9aa826 --- ext/fiddle/fiddle.h | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) diff --git a/ext/fiddle/fiddle.h b/ext/fiddle/fiddle.h index 10eb9ceedb..684b943d30 100644 --- a/ext/fiddle/fiddle.h +++ b/ext/fiddle/fiddle.h @@ -196,7 +196,17 @@ #endif #define TYPE_UINTPTR_T (-TYPE_INTPTR_T) -#define ALIGN_OF(type) offsetof(struct {char align_c; type align_x;}, align_x) +/* GCC releases before GCC 4.9 had a bug in _Alignof. See GCC bug 52023 + . + clang versions < 8.0.0 have the same bug. */ +#if (!defined(__STDC_VERSION__) || __STDC_VERSION__ < 201112 \ + || (defined(__GNUC__) && __GNUC__ < 4 + (__GNUC_MINOR__ < 9) \ + && !defined(__clang__)) \ + || (defined(__clang__) && __clang_major__ < 8)) +# define ALIGN_OF(type) offsetof(struct {char align_c; type align_x;}, align_x) +#else +# define ALIGN_OF(type) _Alignof(type) +#endif #define ALIGN_VOIDP ALIGN_OF(void*) #define ALIGN_CHAR ALIGN_OF(char)