| 1 | /* xalloc-oversized.h -- memory allocation size checking
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| 2 |
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| 3 | Copyright (C) 1990-2000, 2003-2004, 2006-2021 Free Software Foundation, Inc.
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| 4 |
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| 5 | This file is free software: you can redistribute it and/or modify
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| 6 | it under the terms of the GNU Lesser General Public License as
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| 7 | published by the Free Software Foundation; either version 2.1 of the
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| 8 | License, or (at your option) any later version.
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| 9 |
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| 10 | This file is distributed in the hope that it will be useful,
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| 11 | but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 12 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 13 | GNU Lesser General Public License for more details.
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| 14 |
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| 15 | You should have received a copy of the GNU Lesser General Public License
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| 16 | along with this program. If not, see <https://www.gnu.org/licenses/>. */
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| 17 |
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| 18 | #ifndef XALLOC_OVERSIZED_H_
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| 19 | #define XALLOC_OVERSIZED_H_
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| 20 |
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| 21 | #include <stddef.h>
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| 22 | #include <stdint.h>
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| 23 |
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| 24 | /* True if N * S does not fit into both ptrdiff_t and size_t.
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| 25 | N and S should be nonnegative and free of side effects.
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| 26 | This expands to a constant expression if N and S are both constants.
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| 27 | By gnulib convention, SIZE_MAX represents overflow in size_t
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| 28 | calculations, so the conservative size_t-based dividend to use here
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| 29 | is SIZE_MAX - 1. */
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| 30 | #define __xalloc_oversized(n, s) \
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| 31 | ((s) != 0 \
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| 32 | && ((size_t) (PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX - 1) / (s) \
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| 33 | < (n)))
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| 34 |
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| 35 | /* Return 1 if and only if an array of N objects, each of size S,
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| 36 | cannot exist reliably because its total size in bytes would exceed
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| 37 | MIN (PTRDIFF_MAX, SIZE_MAX - 1).
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| 38 |
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| 39 | N and S should be nonnegative and free of side effects.
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| 40 |
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| 41 | Warning: (xalloc_oversized (N, S) ? NULL : malloc (N * S)) can
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| 42 | misbehave if N and S are both narrower than ptrdiff_t and size_t,
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| 43 | and can be rewritten as (xalloc_oversized (N, S) ? NULL
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| 44 | : malloc (N * (size_t) S)).
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| 45 |
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| 46 | This is a macro, not a function, so that it works even if an
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| 47 | argument exceeds MAX (PTRDIFF_MAX, SIZE_MAX). */
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| 48 | #if 7 <= __GNUC__ && !defined __clang__ && PTRDIFF_MAX < SIZE_MAX
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| 49 | # define xalloc_oversized(n, s) \
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| 50 | __builtin_mul_overflow_p (n, s, (ptrdiff_t) 1)
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| 51 | #elif (5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__ \
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| 52 | && PTRDIFF_MAX < SIZE_MAX)
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| 53 | # define xalloc_oversized(n, s) \
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| 54 | (__builtin_constant_p (n) && __builtin_constant_p (s) \
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| 55 | ? __xalloc_oversized (n, s) \
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| 56 | : ({ ptrdiff_t __xalloc_count; \
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| 57 | __builtin_mul_overflow (n, s, &__xalloc_count); }))
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| 58 |
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| 59 | /* Other compilers use integer division; this may be slower but is
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| 60 | more portable. */
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| 61 | #else
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| 62 | # define xalloc_oversized(n, s) __xalloc_oversized (n, s)
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| 63 | #endif
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| 64 |
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| 65 | #endif /* !XALLOC_OVERSIZED_H_ */
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