1 /* xalloc-oversized.h -- memory allocation size checking 2 3 Copyright (C) 1990-2000, 2003-2004, 2006-2020 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__ 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_ */ 61