1: /* xalloc-oversized.h -- memory allocation size checking
2:
3: Copyright (C) 1990-2000, 2003-2004, 2006-2019 Free Software Foundation, Inc.
4:
5: This program is free software: you can redistribute it and/or modify
6: it under the terms of the GNU General Public License as published by
7: the Free Software Foundation; either version 3 of the License, or
8: (at your option) any later version.
9:
10: This program is distributed in the hope that it will be useful,
11: but WITHOUT ANY WARRANTY; without even the implied warranty of
12: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13: GNU General Public License for more details.
14:
15: You should have received a copy of the GNU General Public License
16: along with this program. If not, see <https://www.gnu.org/licenses/>. */
17:
18: #ifndef XALLOC_OVERSIZED_H_
19: #define XALLOC_OVERSIZED_H_
20:
21: #include <stddef.h>
22: #include <stdint.h>
23:
24: /* True if N * S would overflow in a size_t calculation,
25: or would generate a value larger than PTRDIFF_MAX.
26: This expands to a constant expression if N and S are both constants.
27: By gnulib convention, SIZE_MAX represents overflow in size
28: calculations, so the conservative size_t-based dividend to use here
29: is SIZE_MAX - 1. */
30: #define __xalloc_oversized(n, s) \
31: ((size_t) (PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX - 1) / (s) < (n))
32:
33: #if PTRDIFF_MAX < SIZE_MAX
34: typedef ptrdiff_t __xalloc_count_type;
35: #else
36: typedef size_t __xalloc_count_type;
37: #endif
38:
39: /* Return 1 if an array of N objects, each of size S, cannot exist
40: reliably due to size or ptrdiff_t arithmetic overflow. S must be
41: positive and N must be nonnegative. This is a macro, not a
42: function, so that it works correctly even when SIZE_MAX < N. */
43:
44: #if 7 <= __GNUC__
45: # define xalloc_oversized(n, s) \
46: __builtin_mul_overflow_p (n, s, (__xalloc_count_type) 1)
47: #elif 5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__
48: # define xalloc_oversized(n, s) \
49: (__builtin_constant_p (n) && __builtin_constant_p (s) \
50: ? __xalloc_oversized (n, s) \
51: : ({ __xalloc_count_type __xalloc_count; \
52: __builtin_mul_overflow (n, s, &__xalloc_count); }))
53:
54: /* Other compilers use integer division; this may be slower but is
55: more portable. */
56: #else
57: # define xalloc_oversized(n, s) __xalloc_oversized (n, s)
58: #endif
59:
60: #endif /* !XALLOC_OVERSIZED_H_ */
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