gsasl  1.10.0
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xalloc-oversized.h
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1 /* xalloc-oversized.h -- memory allocation size checking
2 
3  Copyright (C) 1990-2000, 2003-2004, 2006-2021 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__ && !defined __clang__
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_ */
size_t __xalloc_count_type