1/* xalloc-oversized.h -- memory allocation size checking
2
3   Copyright (C) 1990-2000, 2003-2004, 2006-2012 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/* Return 1 if an array of N objects, each of size S, cannot exist due
24   to size arithmetic overflow.  S must be positive and N must be
25   nonnegative.  This is a macro, not a function, so that it
26   works correctly even when SIZE_MAX < N.
27
28   By gnulib convention, SIZE_MAX represents overflow in size
29   calculations, so the conservative dividend to use here is
30   SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value.
31   However, malloc (SIZE_MAX) fails on all known hosts where
32   sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for
33   exactly-SIZE_MAX allocations on such hosts; this avoids a test and
34   branch when S is known to be 1.  */
35# define xalloc_oversized(n, s) \
36    ((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))
37
38#endif /* !XALLOC_OVERSIZED_H_ */
39