xsize.h File Reference

#include <stddef.h>
#include <limits.h>

Include dependency graph for xsize.h:

This graph shows which files directly or indirectly include this file:

Go to the source code of this file.

Macros
#define	XSIZE_INLINE   _GL_INLINE
	xsize.h – Checked size_t computations. More...
#define	xcast_size_t(N)    ((N) <= SIZE_MAX ? (size_t) (N) : SIZE_MAX)
	The size of memory objects is often computed through expressions of type size_t. More...
#define	xtimes(N, ELSIZE)    ((N) <= SIZE_MAX / (ELSIZE) ? (size_t) (N) * (ELSIZE) : SIZE_MAX)
	Multiplication of a count with an element size, with overflow check. More...
#define	size_overflow_p(SIZE)    ((SIZE) == SIZE_MAX)
	Check for overflow. More...
#define	size_in_bounds_p(SIZE)    ((SIZE) != SIZE_MAX)
	Check against overflow. More...

Functions
XSIZE_INLINE size_t	xsum (size_t size1, size_t size2)
	Sum of two sizes, with overflow check. More...
XSIZE_INLINE size_t	xsum3 (size_t size1, size_t size2, size_t size3)
	Sum of three sizes, with overflow check. More...
XSIZE_INLINE size_t	xsum4 (size_t size1, size_t size2, size_t size3, size_t size4)
	Sum of four sizes, with overflow check. More...
XSIZE_INLINE size_t	xmax (size_t size1, size_t size2)
	Maximum of two sizes, with overflow check. More...

Macro Definition Documentation

size_in_bounds_p

#define size_in_bounds_p

(

SIZE

)

((SIZE) != SIZE_MAX)

Check against overflow.

Definition at line 112 of file xsize.h.

size_overflow_p

#define size_overflow_p

(

SIZE

)

((SIZE) == SIZE_MAX)

Check for overflow.

Definition at line 109 of file xsize.h.

xcast_size_t

#define xcast_size_t

(

N

)

((N) <= SIZE_MAX ? (size_t) (N) : SIZE_MAX)

The size of memory objects is often computed through expressions of type size_t.

Example: void* p = malloc (header_size + n * element_size). These computations can lead to overflow. When this happens, malloc() returns a piece of memory that is way too small, and the program then crashes while attempting to fill the memory. 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() 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_in_bounds_p (size) ? malloc (size) : NULL); Convert an arbitrary value >= 0 to type size_t.

Definition at line 55 of file xsize.h.

XSIZE_INLINE

#define XSIZE_INLINE   _GL_INLINE

xsize.h – Checked size_t computations.

Copyright (C) 2003, 2008-2014 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 the Free Software Foundation; either version 3, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, see http://www.gnu.org/licenses/.
Get size_t.
Get SIZE_MAX.

Definition at line 35 of file xsize.h.

xtimes

#define xtimes	(		N,
			ELSIZE
	)		((N) <= SIZE_MAX / (ELSIZE) ? (size_t) (N) * (ELSIZE) : SIZE_MAX)

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 a function, so that it works correctly even when N is of a wider type and N > SIZE_MAX.

Definition at line 105 of file xsize.h.

Function Documentation

xmax()

XSIZE_INLINE size_t xmax	(	size_t	size1,
		size_t	size2
	)

Maximum of two sizes, with overflow check.

No explicit check is needed here, because for any n: max (SIZE_MAX, n) == SIZE_MAX and max (n, SIZE_MAX) == SIZE_MAX.

Definition at line 94 of file xsize.h.

{
  /* 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);
}

Referenced by VASNPRINTF().

Here is the caller graph for this function:

xsum()

XSIZE_INLINE size_t xsum	(	size_t	size1,
		size_t	size2
	)

Sum of two sizes, with overflow check.

Definition at line 63 of file xsize.h.

{
  size_t sum = size1 + size2;
  return (sum >= size1 ? sum : SIZE_MAX);
}

References SIZE_MAX, and sum().

Referenced by MAX_ROOM_NEEDED(), PRINTF_PARSE(), VASNPRINTF(), xsum3(), and xsum4().

Here is the call graph for this function:

Here is the caller graph for this function:

xsum3()

XSIZE_INLINE size_t xsum3	(	size_t	size1,
		size_t	size2,
		size_t	size3
	)

Sum of three sizes, with overflow check.

Definition at line 74 of file xsize.h.

{
  return xsum (xsum (size1, size2), size3);
}

References xsum().

Referenced by VASNPRINTF().

Here is the call graph for this function:

Here is the caller graph for this function:

xsum4()

XSIZE_INLINE size_t xsum4	(	size_t	size1,
		size_t	size2,
		size_t	size3,
		size_t	size4
	)

Sum of four sizes, with overflow check.

Definition at line 84 of file xsize.h.

{
  return xsum (xsum (xsum (size1, size2), size3), size4);
}

References xsum().

Referenced by VASNPRINTF().

Here is the call graph for this function:

Here is the caller graph for this function: