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Return requested size for malloc_usable_size when MALLOC_CHECK_ > 0

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[BZ #1349]

malloc_usable_size returns the usable size in an allocated chunk,
which may be >= the requested size. In the case of MALLOC_CHECK_ being
exported to > 0 however, only the requested size is usable, since a
magic value is written at the end of the request size to trap writes
beyond request bounds. Hence, when MALLOC_CHECK_ is exported to > 0,
malloc_usable_size() should return the request size.
This commit is contained in:
Siddhesh Poyarekar
2012-09-05 21:49:00 +05:30
parent 4d038ae316
commit 6ef9cc37f0
6 changed files with 100 additions and 9 deletions
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49
malloc/tst-malloc-usable.c Normal file
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/* Ensure that malloc_usable_size returns the request size with
MALLOC_CHECK_ exported to a positive value.
Copyright (C) 2012 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
<http://www.gnu.org/licenses/>. */
#include <malloc.h>
#include <string.h>
#include <stdio.h>
static int
do_test (void)
{
size_t usable_size;
void *p = malloc (7);
if (!p)
{
printf ("memory allocation failed\n");
return 1;
}
usable_size = malloc_usable_size (p);
if (usable_size != 7)
{
printf ("malloc_usable_size: expected 7 but got %zu\n", usable_size);
return 1;
}
memset (p, 0, usable_size);
free (p);
return 0;
}
#define TEST_FUNCTION do_test ()
#include "../test-skeleton.c"