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/* xalloc-oversized.h -- memory allocation size checking
Copyright (C) 1990-2000, 2003-2004, 2006-2016 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
#ifndef XALLOC_OVERSIZED_H_
#define XALLOC_OVERSIZED_H_
#include <stddef.h>
#ifndef __has_builtin
# define __has_builtin(x) 0
#endif
/* Return 1 if an array of N objects, each of size S, cannot exist due
to size arithmetic overflow. S must be positive and N must be
nonnegative. This is a macro, not a function, so that it
works correctly even when SIZE_MAX < N.
By gnulib convention, SIZE_MAX represents overflow in size
calculations, so the conservative dividend to use here is
SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value.
However, malloc (SIZE_MAX) fails on all known hosts where
sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for
exactly-SIZE_MAX allocations on such hosts; this avoids a test and
branch when S is known to be 1. */
#if 5 <= __GNUC__ || __has_builtin (__builtin_mul_overflow)
# define xalloc_oversized(n, s) \
({ size_t __xalloc_size; __builtin_mul_overflow (n, s, &__xalloc_size); })
#else
# define xalloc_oversized(n, s) \
((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))
#endif
#endif /* !XALLOC_OVERSIZED_H_ */
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