| Message ID | 20230118083236.24418-1-raj.khem@gmail.com (mailing list archive) |
|---|---|
| State | Accepted, archived |
| Delegated to: | Jes Sorensen |
| Headers | show |
| Series | Define alignof using _Alignof when using C11 or newer | expand |
On 1/18/23 03:32, Khem Raj wrote: > WG14 N2350 made very clear that it is an UB having type definitions > within "offsetof" [1]. This patch enhances the implementation of macro > alignof_slot to use builtin "_Alignof" to avoid undefined behavior on > 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 compilers too > > [1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm > [2] https://reviews.llvm.org/D133574 > > Upstream-Status: Pending > Signed-off-by: Khem Raj <raj.khem@gmail.com> > --- > sha1.c | 12 +++++++++++- > 1 file changed, 11 insertions(+), 1 deletion(-) Applied, Thanks, Jes
diff --git a/sha1.c b/sha1.c index 89b32f4..1e4ad5d 100644 --- a/sha1.c +++ b/sha1.c @@ -229,7 +229,17 @@ sha1_process_bytes (const void *buffer, size_t len, struct sha1_ctx *ctx) if (len >= 64) { #if !_STRING_ARCH_unaligned -# define alignof(type) offsetof (struct { char c; type x; }, 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 alignof(type) offsetof (struct { char c; type x; }, x) +# else +# define alignof(type) _Alignof(type) +# endif # define UNALIGNED_P(p) (((size_t) p) % alignof (sha1_uint32) != 0) if (UNALIGNED_P (buffer)) while (len > 64)
WG14 N2350 made very clear that it is an UB having type definitions within "offsetof" [1]. This patch enhances the implementation of macro alignof_slot to use builtin "_Alignof" to avoid undefined behavior on 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 compilers too [1] https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2350.htm [2] https://reviews.llvm.org/D133574 Upstream-Status: Pending Signed-off-by: Khem Raj <raj.khem@gmail.com> --- sha1.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)