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-rw-r--r--gl/xalloc-oversized.h79
1 files changed, 53 insertions, 26 deletions
diff --git a/gl/xalloc-oversized.h b/gl/xalloc-oversized.h
index a971c78..5dbdfb5 100644
--- a/gl/xalloc-oversized.h
+++ b/gl/xalloc-oversized.h
@@ -1,38 +1,65 @@
1/* xalloc-oversized.h -- memory allocation size checking 1/* xalloc-oversized.h -- memory allocation size checking
2 2
3 Copyright (C) 1990-2000, 2003-2004, 2006-2013 Free Software Foundation, Inc. 3 Copyright (C) 1990-2000, 2003-2004, 2006-2023 Free Software Foundation, Inc.
4 4
5 This program is free software: you can redistribute it and/or modify 5 This file is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by 6 it under the terms of the GNU Lesser General Public License as
7 the Free Software Foundation; either version 3 of the License, or 7 published by the Free Software Foundation; either version 2.1 of the
8 (at your option) any later version. 8 License, or (at your option) any later version.
9 9
10 This program is distributed in the hope that it will be useful, 10 This file is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of 11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 GNU General Public License for more details. 13 GNU Lesser General Public License for more details.
14 14
15 You should have received a copy of the GNU General Public License 15 You should have received a copy of the GNU Lesser General Public License
16 along with this program. If not, see <http://www.gnu.org/licenses/>. */ 16 along with this program. If not, see <https://www.gnu.org/licenses/>. */
17 17
18#ifndef XALLOC_OVERSIZED_H_ 18#ifndef XALLOC_OVERSIZED_H_
19# define XALLOC_OVERSIZED_H_ 19#define XALLOC_OVERSIZED_H_
20 20
21# include <stddef.h> 21#include <stddef.h>
22 22#include <stdint.h>
23/* Return 1 if an array of N objects, each of size S, cannot exist due 23
24 to size arithmetic overflow. S must be positive and N must be 24/* True if N * S does not fit into both ptrdiff_t and size_t.
25 nonnegative. This is a macro, not a function, so that it 25 N and S should be nonnegative and free of side effects.
26 works correctly even when SIZE_MAX < N. 26 This expands to a constant expression if N and S are both constants.
27 27 By gnulib convention, SIZE_MAX represents overflow in size_t
28 By gnulib convention, SIZE_MAX represents overflow in size 28 calculations, so the conservative size_t-based dividend to use here
29 calculations, so the conservative dividend to use here is 29 is SIZE_MAX - 1. */
30 SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value. 30#define __xalloc_oversized(n, s) \
31 However, malloc (SIZE_MAX) fails on all known hosts where 31 ((s) != 0 \
32 sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for 32 && ((size_t) (PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX - 1) / (s) \
33 exactly-SIZE_MAX allocations on such hosts; this avoids a test and 33 < (n)))
34 branch when S is known to be 1. */ 34
35/* Return 1 if and only if an array of N objects, each of size S,
36 cannot exist reliably because its total size in bytes would exceed
37 MIN (PTRDIFF_MAX, SIZE_MAX - 1).
38
39 N and S should be nonnegative and free of side effects.
40
41 Warning: (xalloc_oversized (N, S) ? NULL : malloc (N * S)) can
42 misbehave if N and S are both narrower than ptrdiff_t and size_t,
43 and can be rewritten as (xalloc_oversized (N, S) ? NULL
44 : malloc (N * (size_t) S)).
45
46 This is a macro, not a function, so that it works even if an
47 argument exceeds MAX (PTRDIFF_MAX, SIZE_MAX). */
48#if 7 <= __GNUC__ && !defined __clang__ && PTRDIFF_MAX < SIZE_MAX
35# define xalloc_oversized(n, s) \ 49# define xalloc_oversized(n, s) \
36 ((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n)) 50 __builtin_mul_overflow_p (n, s, (ptrdiff_t) 1)
51#elif (5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__ \
52 && PTRDIFF_MAX < SIZE_MAX)
53# define xalloc_oversized(n, s) \
54 (__builtin_constant_p (n) && __builtin_constant_p (s) \
55 ? __xalloc_oversized (n, s) \
56 : ({ ptrdiff_t __xalloc_count; \
57 __builtin_mul_overflow (n, s, &__xalloc_count); }))
58
59/* Other compilers use integer division; this may be slower but is
60 more portable. */
61#else
62# define xalloc_oversized(n, s) __xalloc_oversized (n, s)
63#endif
37 64
38#endif /* !XALLOC_OVERSIZED_H_ */ 65#endif /* !XALLOC_OVERSIZED_H_ */