aligned_alloc: conform to C17

This patch adds the strict checking for power-of-two alignments
in aligned_alloc(), and updates the manual accordingly.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
This commit is contained in:
DJ Delorie 2023-03-21 00:46:43 -04:00
parent cea74a4a24
commit d1417176a3
6 changed files with 117 additions and 7 deletions

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@ -44,11 +44,13 @@ tests := mallocbug tst-malloc tst-valloc tst-calloc tst-obstack \
tst-safe-linking \
tst-mallocalign1 \
tst-memalign-2 \
tst-memalign-3
tst-memalign-3 \
tst-aligned-alloc
tests-static := \
tst-interpose-static-nothread \
tst-interpose-static-thread
tst-interpose-static-thread \
tst-aligned-alloc-static
# Test for the malloc_set_state symbol removed in glibc 2.25.
ifeq ($(have-GLIBC_2.23)$(build-shared),yesyes)

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@ -299,7 +299,14 @@ __debug_memalign (size_t alignment, size_t bytes)
return _debug_mid_memalign (alignment, bytes, RETURN_ADDRESS (0));
}
strong_alias (__debug_memalign, memalign)
strong_alias (__debug_memalign, aligned_alloc)
static void *
__debug_aligned_alloc (size_t alignment, size_t bytes)
{
if (!powerof2 (alignment) || alignment == 0)
return NULL;
return _debug_mid_memalign (alignment, bytes, RETURN_ADDRESS (0));
}
strong_alias (__debug_aligned_alloc, aligned_alloc)
static void *
__debug_pvalloc (size_t bytes)

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@ -3528,6 +3528,29 @@ __libc_memalign (size_t alignment, size_t bytes)
void *address = RETURN_ADDRESS (0);
return _mid_memalign (alignment, bytes, address);
}
libc_hidden_def (__libc_memalign)
/* For ISO C17. */
void *
weak_function
aligned_alloc (size_t alignment, size_t bytes)
{
if (!__malloc_initialized)
ptmalloc_init ();
/* Similar to memalign, but starting with ISO C17 the standard
requires an error for alignments that are not supported by the
implementation. Valid alignments for the current implementation
are non-negative powers of two. */
if (!powerof2 (alignment) || alignment == 0)
{
__set_errno (EINVAL);
return 0;
}
void *address = RETURN_ADDRESS (0);
return _mid_memalign (alignment, bytes, address);
}
static void *
_mid_memalign (size_t alignment, size_t bytes, void *address)
@ -3618,9 +3641,6 @@ _mid_memalign (size_t alignment, size_t bytes, void *address)
ar_ptr == arena_for_chunk (mem2chunk (p)));
return tag_new_usable (p);
}
/* For ISO C11. */
weak_alias (__libc_memalign, aligned_alloc)
libc_hidden_def (__libc_memalign)
void *
__libc_valloc (size_t bytes)

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@ -0,0 +1 @@
#include "tst-aligned-alloc.c"

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@ -0,0 +1,80 @@
/* Test for C17 alignment requirements.
Copyright (C) 2023 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.
The GNU C Library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with the GNU C Library; if not, see
<https://www.gnu.org/licenses/>. */
#include <errno.h>
#include <malloc.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <libc-diag.h>
#include <support/check.h>
static int
do_test (void)
{
void *p1;
void *p2;
void *p3;
void *p4;
void *p5;
errno = 0;
/* The implementation supports alignments that are non-negative powers of 2.
We test 5 distinct conditions here:
- A non-negative power of 2 alignment e.g. 64.
- A degenerate zero power of 2 alignment e.g. 1.
- A non-power-of-2 alignment e.g. 65.
- A zero alignment.
- A corner case SIZE_MAX / 2 + 1 alignment.
*/
p1 = aligned_alloc (64, 64);
if (p1 == NULL)
FAIL_EXIT1 ("aligned_alloc(64, 64) failed");
p2 = aligned_alloc (1, 64);
if (p2 == NULL)
FAIL_EXIT1 ("aligned_alloc(1, 64) failed");
p3 = aligned_alloc (65, 64);
if (p3 != NULL)
FAIL_EXIT1 ("aligned_alloc(65, 64) did not fail");
p4 = aligned_alloc (0, 64);
if (p4 != NULL)
FAIL_EXIT1 ("aligned_alloc(0, 64) did not fail");
/* This is an alignment like 0x80000000...UL */
p5 = aligned_alloc (SIZE_MAX / 2 + 1, 64);
if (p5 != NULL)
FAIL_EXIT1 ("aligned_alloc(SIZE_MAX/2+1, 64) did not fail");
free (p1);
free (p2);
return 0;
}
#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"

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@ -995,7 +995,7 @@ power of two than that, use @code{aligned_alloc} or @code{posix_memalign}.
@c Alias to memalign.
The @code{aligned_alloc} function allocates a block of @var{size} bytes whose
address is a multiple of @var{alignment}. The @var{alignment} must be a
power of two and @var{size} must be a multiple of @var{alignment}.
power of two.
The @code{aligned_alloc} function returns a null pointer on error and sets
@code{errno} to one of the following values: