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/* xalloc-oversized.h -- memory allocation size checking
Copyright (C) 1990-2000, 2003-2004, 2006-2020 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 <https://www.gnu.org/licenses/>. */
#ifndef XALLOC_OVERSIZED_H_
#define XALLOC_OVERSIZED_H_
#include <stddef.h>
#include <stdint.h>
/* True if N * S would overflow in a size_t calculation,
or would generate a value larger than PTRDIFF_MAX.
This expands to a constant expression if N and S are both constants.
By gnulib convention, SIZE_MAX represents overflow in size
calculations, so the conservative size_t-based dividend to use here
is SIZE_MAX - 1. */
#define __xalloc_oversized(n, s) \
((size_t) (PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX - 1) / (s) < (n))
#if PTRDIFF_MAX < SIZE_MAX
typedef ptrdiff_t __xalloc_count_type;
#else
typedef size_t __xalloc_count_type;
#endif
/* Return 1 if an array of N objects, each of size S, cannot exist
reliably due to size or ptrdiff_t 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. */
#if 7 <= __GNUC__
# define xalloc_oversized(n, s) \
__builtin_mul_overflow_p (n, s, (__xalloc_count_type) 1)
#elif 5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__
# define xalloc_oversized(n, s) \
(__builtin_constant_p (n) && __builtin_constant_p (s) \
? __xalloc_oversized (n, s) \
: ({ __xalloc_count_type __xalloc_count; \
__builtin_mul_overflow (n, s, &__xalloc_count); }))
/* Other compilers use integer division; this may be slower but is
more portable. */
#else
# define xalloc_oversized(n, s) __xalloc_oversized (n, s)
#endif
#endif /* !XALLOC_OVERSIZED_H_ */
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