/* xsize.h -- Checked size_t computations.
- Copyright (C) 2003 Free Software Foundation, Inc.
+ Copyright (C) 2003, 2008 Free Software Foundation, Inc.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software Foundation,
- Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
+ Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
#ifndef _XSIZE_H
#define _XSIZE_H
To avoid this, the functions and macros in this file check for overflow.
The convention is that SIZE_MAX represents overflow.
malloc (SIZE_MAX) is not guaranteed to fail -- think of a malloc
- implementation that uses mmap --, it's recommended to use SIZE_OVERFLOW_P
- before invoking malloc().
+ implementation that uses mmap --, it's recommended to use size_overflow_p()
+ or size_in_bounds_p() before invoking malloc().
The example thus becomes:
size_t size = xsum (header_size, xtimes (n, element_size));
- void *p = (!SIZE_OVERFLOW_P (size) ? malloc (size) : NULL);
+ void *p = (size_in_bounds_p (size) ? malloc (size) : NULL);
*/
/* Convert an arbitrary value >= 0 to type size_t. */
/* Sum of two sizes, with overflow check. */
static inline size_t
+#if __GNUC__ >= 3
+__attribute__ ((__pure__))
+#endif
xsum (size_t size1, size_t size2)
{
size_t sum = size1 + size2;
/* Sum of three sizes, with overflow check. */
static inline size_t
+#if __GNUC__ >= 3
+__attribute__ ((__pure__))
+#endif
xsum3 (size_t size1, size_t size2, size_t size3)
{
return xsum (xsum (size1, size2), size3);
/* Sum of four sizes, with overflow check. */
static inline size_t
+#if __GNUC__ >= 3
+__attribute__ ((__pure__))
+#endif
xsum4 (size_t size1, size_t size2, size_t size3, size_t size4)
{
return xsum (xsum (xsum (size1, size2), size3), size4);
}
+/* Maximum of two sizes, with overflow check. */
+static inline size_t
+#if __GNUC__ >= 3
+__attribute__ ((__pure__))
+#endif
+xmax (size_t size1, size_t size2)
+{
+ /* No explicit check is needed here, because for any n:
+ max (SIZE_MAX, n) == SIZE_MAX and max (n, SIZE_MAX) == SIZE_MAX. */
+ return (size1 >= size2 ? size1 : size2);
+}
+
/* Multiplication of a count with an element size, with overflow check.
The count must be >= 0 and the element size must be > 0.
This is a macro, not an inline function, so that it works correctly even
- when N is of a wider tupe and N > SIZE_MAX. */
+ when N is of a wider type and N > SIZE_MAX. */
#define xtimes(N, ELSIZE) \
((N) <= SIZE_MAX / (ELSIZE) ? (size_t) (N) * (ELSIZE) : SIZE_MAX)