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/*
* Replacement for a missing reallocarray.
*
* Provides the same functionality as the OpenBSD library function
* reallocarray for those systems that don't have it. This function is the
* same as realloc, but takes the size arguments in the same form as calloc
* and checks for overflow so that the caller doesn't need to.
*
* The canonical version of this file is maintained in the rra-c-util package,
* which can be found at <https://www.eyrie.org/~eagle/software/rra-c-util/>.
*
* Written by Russ Allbery <eagle@eyrie.org>
* Copyright 2017 Russ Allbery <eagle@eyrie.org>
* Copyright 2014
* The Board of Trustees of the Leland Stanford Junior University
*
* Copying and distribution of this file, with or without modification, are
* permitted in any medium without royalty provided the copyright notice and
* this notice are preserved. This file is offered as-is, without any
* warranty.
*
* SPDX-License-Identifier: FSFAP
*/
#include <config.h>
#include <portable/system.h>
#include <errno.h>
/*
* If we're running the test suite, rename reallocarray to avoid conflicts
* with the system version. #undef it first because some systems may define
* it to another name.
*/
#if TESTING
# undef reallocarray
# define reallocarray test_reallocarray
void *test_reallocarray(void *, size_t, size_t);
#endif
/*
* nmemb * size cannot overflow if both are smaller than sqrt(SIZE_MAX). We
* can calculate that value statically by using 2^(sizeof(size_t) * 8) as the
* value of SIZE_MAX and then taking the square root, which gives
* 2^(sizeof(size_t) * 4). Compute the exponentiation with shift.
*/
#define CHECK_THRESHOLD (1UL << (sizeof(size_t) * 4))
void *
reallocarray(void *ptr, size_t nmemb, size_t size)
{
if (nmemb >= CHECK_THRESHOLD || size >= CHECK_THRESHOLD)
if (nmemb > 0 && SIZE_MAX / nmemb <= size) {
errno = ENOMEM;
return NULL;
}
/* Avoid a zero-size allocation. */
if (nmemb == 0 || size == 0) {
nmemb = 1;
size = 1;
}
return realloc(ptr, nmemb * size);
}
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