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| author | Jonathan Wakely <jwakely@redhat.com> | 2021-10-06 20:05:48 +0100 |
|---|---|---|
| committer | Jonathan Wakely <jwakely@redhat.com> | 2021-10-21 00:19:20 +0100 |
| commit | 8a9a59311551e833ca064de44ac23b193e1b704d (patch) | |
| tree | 1d91ec3b267277e45d849261406337c1c4fa5a3f /stdlib | |
| parent | aa783f9a7b774d67487daa9376095738aef5cf88 (diff) | |
| download | glibc-8a9a59311551e833ca064de44ac23b193e1b704d.tar.gz glibc-8a9a59311551e833ca064de44ac23b193e1b704d.tar.xz glibc-8a9a59311551e833ca064de44ac23b193e1b704d.zip | |
Add alloc_align attribute to memalign et al
GCC 4.9.0 added the alloc_align attribute to say that a function argument specifies the alignment of the returned pointer. Clang supports the attribute too. Using the attribute can allow a compiler to generate better code if it knows the returned pointer has a minimum alignment. See https://gcc.gnu.org/PR60092 for more details. GCC implicitly knows the semantics of aligned_alloc and posix_memalign, but not the obsolete memalign. As a result, GCC generates worse code when memalign is used, compared to aligned_alloc. Clang knows about aligned_alloc and memalign, but not posix_memalign. This change adds a new __attribute_alloc_align__ macro to <sys/cdefs.h> and then uses it on memalign (where it helps GCC) and aligned_alloc (where GCC and Clang already know the semantics, but it doesn't hurt) and xposix_memalign. It can't be used on posix_memalign because that doesn't return a pointer (the allocated pointer is returned via a void** parameter instead). Unlike the alloc_size attribute, alloc_align only allows a single argument. That means the new __attribute_alloc_align__ macro doesn't really need to be used with double parentheses to protect a comma between its arguments. For consistency with __attribute_alloc_size__ this patch defines it the same way, so that double parentheses are required. Signed-off-by: Jonathan Wakely <jwakely@redhat.com> Reviewed-by: Carlos O'Donell <carlos@redhat.com> Tested-by: Carlos O'Donell <carlos@redhat.com>
Diffstat (limited to 'stdlib')
| -rw-r--r-- | stdlib/stdlib.h | 4 |
1 files changed, 3 insertions, 1 deletions
diff --git a/stdlib/stdlib.h b/stdlib/stdlib.h index 74c00eee73..1feb381211 100644 --- a/stdlib/stdlib.h +++ b/stdlib/stdlib.h @@ -1,4 +1,5 @@ /* Copyright (C) 1991-2021 Free Software Foundation, Inc. + Copyright The GNU Toolchain Authors. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or @@ -589,7 +590,8 @@ extern int posix_memalign (void **__memptr, size_t __alignment, size_t __size) #ifdef __USE_ISOC11 /* ISO C variant of aligned allocation. */ extern void *aligned_alloc (size_t __alignment, size_t __size) - __THROW __attribute_malloc__ __attribute_alloc_size__ ((2)) __wur; + __THROW __attribute_malloc__ __attribute_alloc_align__ ((1)) + __attribute_alloc_size__ ((2)) __wur; #endif /* Abort execution and generate a core-dump. */ |