dhcpd-pools  2.28
ISC dhcpd lease usage analyser
xalloc-oversized.h
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1 /* xalloc-oversized.h -- memory allocation size checking
2 
3  Copyright (C) 1990-2000, 2003-2004, 2006-2015 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 <http://www.gnu.org/licenses/>. */
17 
18 #ifndef XALLOC_OVERSIZED_H_
19 #define XALLOC_OVERSIZED_H_
20 
21 #include <stddef.h>
22 
23 #ifndef __has_builtin
24 # define __has_builtin(x) 0
25 #endif
26 
27 /* Return 1 if an array of N objects, each of size S, cannot exist due
28  to size arithmetic overflow. S must be positive and N must be
29  nonnegative. This is a macro, not a function, so that it
30  works correctly even when SIZE_MAX < N.
31 
32  By gnulib convention, SIZE_MAX represents overflow in size
33  calculations, so the conservative dividend to use here is
34  SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value.
35  However, malloc (SIZE_MAX) fails on all known hosts where
36  sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for
37  exactly-SIZE_MAX allocations on such hosts; this avoids a test and
38  branch when S is known to be 1. */
39 #if 5 <= __GNUC__ || __has_builtin (__builtin_mul_overflow)
40 # define xalloc_oversized(n, s) \
41  ({ size_t __xalloc_size; __builtin_mul_overflow (n, s, &__xalloc_size); })
42 #else
43 # define xalloc_oversized(n, s) \
44  ((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))
45 #endif
46 
47 #endif /* !XALLOC_OVERSIZED_H_ */