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1 | /* xalloc-oversized.h -- memory allocation size checking |
2 | ||
5df4cba6 | 3 | Copyright (C) 1990-2000, 2003-2004, 2006-2020 Free Software Foundation, Inc. |
c0c3707f CB |
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_ */ |