Andrew Geissler | c5535c9 | 2023-01-27 16:10:19 -0600 | [diff] [blame^] | 1 | From 4089affd371e6d62dd8c1e57b344f8cc329005ea Mon Sep 17 00:00:00 2001 |
| 2 | From: Khem Raj <raj.khem@gmail.com> |
| 3 | Date: Sat, 14 Jan 2023 23:11:08 -0800 |
| 4 | Subject: [PATCH] Define alignof using _Alignof when using C11 or newer |
| 5 | |
| 6 | WG14 N2350 made very clear that it is an UB having type definitions |
| 7 | within "offsetof" [1]. This patch enhances the implementation of macro |
| 8 | alignof_slot to use builtin "_Alignof" to avoid undefined behavior on |
| 9 | when using std=c11 or newer |
| 10 | |
| 11 | clang 16+ has started to flag this [2] |
| 12 | |
| 13 | Fixes build when using -std >= gnu11 and using clang16+ |
| 14 | |
| 15 | Older compilers gcc < 4.9 or clang < 8 has buggy _Alignof even though it |
| 16 | may support C11, exclude those compilers too |
| 17 | |
| 18 | [1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm |
| 19 | [2] https://reviews.llvm.org/D133574 |
| 20 | |
| 21 | Upstream-Status: Submitted [https://groups.google.com/g/opkg-devel/c/gjcQPZgT_jI] |
| 22 | Signed-off-by: Khem Raj <raj.khem@gmail.com> |
| 23 | --- |
| 24 | libopkg/md5.c | 10 ++++++++++ |
| 25 | 1 file changed, 10 insertions(+) |
| 26 | |
| 27 | diff --git a/libopkg/md5.c b/libopkg/md5.c |
| 28 | index 981b9b8..ccb645e 100644 |
| 29 | --- a/libopkg/md5.c |
| 30 | +++ b/libopkg/md5.c |
| 31 | @@ -237,7 +237,17 @@ void md5_process_bytes(const void *buffer, size_t len, struct md5_ctx *ctx) |
| 32 | /* Process available complete blocks. */ |
| 33 | if (len >= 64) { |
| 34 | #if !_STRING_ARCH_unaligned |
| 35 | +/* GCC releases before GCC 4.9 had a bug in _Alignof. See GCC bug 52023 |
| 36 | + <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52023>. |
| 37 | + clang versions < 8.0.0 have the same bug. */ |
| 38 | +#if (!defined __STDC_VERSION__ || __STDC_VERSION__ < 201112 \ |
| 39 | + || (defined __GNUC__ && __GNUC__ < 4 + (__GNUC_MINOR__ < 9) \ |
| 40 | + && !defined __clang__) \ |
| 41 | + || (defined __clang__ && __clang_major__ < 8)) |
| 42 | #define alignof(type) offsetof (struct { char c; type x; }, x) |
| 43 | +#else |
| 44 | +#define alignof(type) _Alignof(type) |
| 45 | +#endif |
| 46 | #define UNALIGNED_P(p) (((size_t) p) % alignof (uint32_t) != 0) |
| 47 | if (UNALIGNED_P(buffer)) |
| 48 | while (len > 64) { |
| 49 | -- |
| 50 | 2.39.0 |
| 51 | |