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61 lines
2.3 KiB
C
61 lines
2.3 KiB
C
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/* xalloc-oversized.h -- memory allocation size checking
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Copyright (C) 1990-2000, 2003-2004, 2006-2020 Free Software Foundation, Inc.
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>. */
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#ifndef XALLOC_OVERSIZED_H_
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#define XALLOC_OVERSIZED_H_
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#include <stddef.h>
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#include <stdint.h>
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/* True if N * S would overflow in a size_t calculation,
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or would generate a value larger than PTRDIFF_MAX.
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This expands to a constant expression if N and S are both constants.
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By gnulib convention, SIZE_MAX represents overflow in size
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calculations, so the conservative size_t-based dividend to use here
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is SIZE_MAX - 1. */
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#define __xalloc_oversized(n, s) \
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((size_t) (PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX - 1) / (s) < (n))
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#if PTRDIFF_MAX < SIZE_MAX
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typedef ptrdiff_t __xalloc_count_type;
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#else
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typedef size_t __xalloc_count_type;
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#endif
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/* Return 1 if an array of N objects, each of size S, cannot exist
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reliably due to size or ptrdiff_t arithmetic overflow. S must be
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positive and N must be nonnegative. This is a macro, not a
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function, so that it works correctly even when SIZE_MAX < N. */
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#if 7 <= __GNUC__
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# define xalloc_oversized(n, s) \
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__builtin_mul_overflow_p (n, s, (__xalloc_count_type) 1)
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#elif 5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__
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# define xalloc_oversized(n, s) \
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(__builtin_constant_p (n) && __builtin_constant_p (s) \
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? __xalloc_oversized (n, s) \
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: ({ __xalloc_count_type __xalloc_count; \
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__builtin_mul_overflow (n, s, &__xalloc_count); }))
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/* Other compilers use integer division; this may be slower but is
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more portable. */
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#else
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# define xalloc_oversized(n, s) __xalloc_oversized (n, s)
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#endif
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#endif /* !XALLOC_OVERSIZED_H_ */
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