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