| From 6b3c202b46b9312c5bb0789145f13d8086e70948 Mon Sep 17 00:00:00 2001 |
| From: Khem Raj <raj.khem@gmail.com> |
| Date: Sun, 15 Jan 2023 02:34:17 -0800 |
| Subject: [PATCH] fiddle: Use C11 _Alignof to define ALIGN_OF when possible |
| |
| 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 |
| |
| Upstream-Status: Submitted [https://github.com/ruby/fiddle/pull/120] |
| Signed-off-by: Khem Raj <raj.khem@gmail.com> |
| --- |
| 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 10eb9ce..ffb395e 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 |
| + <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=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) |
| -- |
| 2.39.0 |
| |