1/* -*- buffer-read-only: t -*- vi: set ro: */ 2/* DO NOT EDIT! GENERATED AUTOMATICALLY! */ 3#line 1 4/* xsize.h -- Checked size_t computations. 5 6 Copyright (C) 2003, 2008, 2009, 2010 Free Software Foundation, Inc. 7 8 This program is free software; you can redistribute it and/or modify 9 it under the terms of the GNU General Public License as published by 10 the Free Software Foundation; either version 3, or (at your option) 11 any later version. 12 13 This program is distributed in the hope that it will be useful, 14 but WITHOUT ANY WARRANTY; without even the implied warranty of 15 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 16 GNU General Public License for more details. 17 18 You should have received a copy of the GNU General Public License 19 along with this program; if not, write to the Free Software Foundation, 20 Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */ 21 22#ifndef _XSIZE_H 23#define _XSIZE_H 24 25/* Get size_t. */ 26#include <stddef.h> 27 28/* Get SIZE_MAX. */ 29#include <limits.h> 30#if HAVE_STDINT_H 31# include <stdint.h> 32#endif 33 34/* The size of memory objects is often computed through expressions of 35 type size_t. Example: 36 void* p = malloc (header_size + n * element_size). 37 These computations can lead to overflow. When this happens, malloc() 38 returns a piece of memory that is way too small, and the program then 39 crashes while attempting to fill the memory. 40 To avoid this, the functions and macros in this file check for overflow. 41 The convention is that SIZE_MAX represents overflow. 42 malloc (SIZE_MAX) is not guaranteed to fail -- think of a malloc 43 implementation that uses mmap --, it's recommended to use size_overflow_p() 44 or size_in_bounds_p() before invoking malloc(). 45 The example thus becomes: 46 size_t size = xsum (header_size, xtimes (n, element_size)); 47 void *p = (size_in_bounds_p (size) ? malloc (size) : NULL); 48*/ 49 50/* Convert an arbitrary value >= 0 to type size_t. */ 51#define xcast_size_t(N) \ 52 ((N) <= SIZE_MAX ? (size_t) (N) : SIZE_MAX) 53 54/* Sum of two sizes, with overflow check. */ 55static inline size_t 56#if __GNUC__ >= 3 57__attribute__ ((__pure__)) 58#endif 59xsum (size_t size1, size_t size2) 60{ 61 size_t sum = size1 + size2; 62 return (sum >= size1 ? sum : SIZE_MAX); 63} 64 65/* Sum of three sizes, with overflow check. */ 66static inline size_t 67#if __GNUC__ >= 3 68__attribute__ ((__pure__)) 69#endif 70xsum3 (size_t size1, size_t size2, size_t size3) 71{ 72 return xsum (xsum (size1, size2), size3); 73} 74 75/* Sum of four sizes, with overflow check. */ 76static inline size_t 77#if __GNUC__ >= 3 78__attribute__ ((__pure__)) 79#endif 80xsum4 (size_t size1, size_t size2, size_t size3, size_t size4) 81{ 82 return xsum (xsum (xsum (size1, size2), size3), size4); 83} 84 85/* Maximum of two sizes, with overflow check. */ 86static inline size_t 87#if __GNUC__ >= 3 88__attribute__ ((__pure__)) 89#endif 90xmax (size_t size1, size_t size2) 91{ 92 /* No explicit check is needed here, because for any n: 93 max (SIZE_MAX, n) == SIZE_MAX and max (n, SIZE_MAX) == SIZE_MAX. */ 94 return (size1 >= size2 ? size1 : size2); 95} 96 97/* Multiplication of a count with an element size, with overflow check. 98 The count must be >= 0 and the element size must be > 0. 99 This is a macro, not an inline function, so that it works correctly even 100 when N is of a wider type and N > SIZE_MAX. */ 101#define xtimes(N, ELSIZE) \ 102 ((N) <= SIZE_MAX / (ELSIZE) ? (size_t) (N) * (ELSIZE) : SIZE_MAX) 103 104/* Check for overflow. */ 105#define size_overflow_p(SIZE) \ 106 ((SIZE) == SIZE_MAX) 107/* Check against overflow. */ 108#define size_in_bounds_p(SIZE) \ 109 ((SIZE) != SIZE_MAX) 110 111#endif /* _XSIZE_H */ 112