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68 lines
2.5 KiB
68 lines
2.5 KiB
/* xalloc-oversized.h -- memory allocation size checking |
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Copyright (C) 1990-2000, 2003-2004, 2006-2017 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 <http://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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/* Default for (non-Clang) compilers that lack __has_builtin. */ |
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#ifndef __has_builtin |
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# define __has_builtin(x) 0 |
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#endif |
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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__ || __has_builtin (__builtin_add_overflow_p) |
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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__ \ |
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|| (__has_builtin (__builtin_mul_overflow) \ |
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&& __has_builtin (__builtin_constant_p))) \ |
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&& !__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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