path: root/lib/xalloc.h

/* xalloc.h -- malloc with out-of-memory checking

   Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   1999, 2000, 2003, 2004, 2006, 2007, 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
   the Free Software Foundation; either version 3 of the License, 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/>.  */

#ifndef XALLOC_H_
# define XALLOC_H_

# include <stddef.h>


# ifdef __cplusplus
extern "C" {
# endif


# ifndef __attribute__
#  if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 8)
#   define __attribute__(x)
#  endif
# endif

# ifndef ATTRIBUTE_NORETURN
#  define ATTRIBUTE_NORETURN __attribute__ ((__noreturn__))
# endif

/* This function is always triggered when memory is exhausted.
   It must be defined by the application, either explicitly
   or by using gnulib's xalloc-die module.  This is the
   function to call when one wants the program to die because of a
   memory allocation failure.  */
extern void xalloc_die (void) ATTRIBUTE_NORETURN;

void *xmalloc (size_t s);
void *xzalloc (size_t s);
void *xcalloc (size_t n, size_t s);
void *xrealloc (void *p, size_t s);
void *x2realloc (void *p, size_t *pn);
void *xmemdup (void const *p, size_t s);
char *xstrdup (char const *str);

/* Return 1 if an array of N objects, each of size S, cannot exist due
   to size arithmetic overflow.  S must be positive and N must be
   nonnegative.  This is a macro, not an inline function, so that it
   works correctly even when SIZE_MAX < N.

   By gnulib convention, SIZE_MAX represents overflow in size
   calculations, so the conservative dividend to use here is
   SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value.
   However, malloc (SIZE_MAX) fails on all known hosts where
   sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for
   exactly-SIZE_MAX allocations on such hosts; this avoids a test and
   branch when S is known to be 1.  */
# define xalloc_oversized(n, s) \
    ((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))


/* In the following macros, T must be an elementary or structure/union or
   typedef'ed type, or a pointer to such a type.  To apply one of the
   following macros to a function pointer or array type, you need to typedef
   it first and use the typedef name.  */

/* Allocate an object of type T dynamically, with error checking.  */
/* extern t *XMALLOC (typename t); */
# define XMALLOC(t) ((t *) xmalloc (sizeof (t)))

/* Allocate memory for N elements of type T, with error checking.  */
/* extern t *XNMALLOC (size_t n, typename t); */
# define XNMALLOC(n, t) \
    ((t *) (sizeof (t) == 1 ? xmalloc (n) : xnmalloc (n, sizeof (t))))

/* Allocate an object of type T dynamically, with error checking,
   and zero it.  */
/* extern t *XZALLOC (typename t); */
# define XZALLOC(t) ((t *) xzalloc (sizeof (t)))

/* Allocate memory for N elements of type T, with error checking,
   and zero it.  */
/* extern t *XCALLOC (size_t n, typename t); */
# define XCALLOC(n, t) \
    ((t *) (sizeof (t) == 1 ? xzalloc (n) : xcalloc (n, sizeof (t))))


# if HAVE_INLINE
#  define static_inline static inline
# else
   void *xnmalloc (size_t n, size_t s);
   void *xnrealloc (void *p, size_t n, size_t s);
   void *x2nrealloc (void *p, size_t *pn, size_t s);
   char *xcharalloc (size_t n);
# endif

# ifdef static_inline

/* Allocate an array of N objects, each with S bytes of memory,
   dynamically, with error checking.  S must be nonzero.  */

static_inline void *
xnmalloc (size_t n, size_t s)
{
  if (xalloc_oversized (n, s))
    xalloc_die ();
  return xmalloc (n * s);
}

/* Change the size of an allocated block of memory P to an array of N
   objects each of S bytes, with error checking.  S must be nonzero.  */

static_inline void *
xnrealloc (void *p, size_t n, size_t s)
{
  if (xalloc_oversized (n, s))
    xalloc_die ();
  return xrealloc (p, n * s);
}

/* If P is null, allocate a block of at least *PN such objects;
   otherwise, reallocate P so that it contains more than *PN objects
   each of S bytes.  *PN must be nonzero unless P is null, and S must
   be nonzero.  Set *PN to the new number of objects, and return the
   pointer to the new block.  *PN is never set to zero, and the
   returned pointer is never null.

   Repeated reallocations are guaranteed to make progress, either by
   allocating an initial block with a nonzero size, or by allocating a
   larger block.

   In the following implementation, nonzero sizes are increased by a
   factor of approximately 1.5 so that repeated reallocations have
   O(N) overall cost rather than O(N**2) cost, but the
   specification for this function does not guarantee that rate.

   Here is an example of use:

     int *p = NULL;
     size_t used = 0;
     size_t allocated = 0;

     void
     append_int (int value)
       {
	 if (used == allocated)
	   p = x2nrealloc (p, &allocated, sizeof *p);
	 p[used++] = value;
       }

   This causes x2nrealloc to allocate a block of some nonzero size the
   first time it is called.

   To have finer-grained control over the initial size, set *PN to a
   nonzero value before calling this function with P == NULL.  For
   example:

     int *p = NULL;
     size_t used = 0;
     size_t allocated = 0;
     size_t allocated1 = 1000;

     void
     append_int (int value)
       {
	 if (used == allocated)
	   {
	     p = x2nrealloc (p, &allocated1, sizeof *p);
	     allocated = allocated1;
	   }
	 p[used++] = value;
       }

   */

static_inline void *
x2nrealloc (void *p, size_t *pn, size_t s)
{
  size_t n = *pn;

  if (! p)
    {
      if (! n)
	{
	  /* The approximate size to use for initial small allocation
	     requests, when the invoking code specifies an old size of
	     zero.  64 bytes is the largest "small" request for the
	     GNU C library malloc.  */
	  enum { DEFAULT_MXFAST = 64 };

	  n = DEFAULT_MXFAST / s;
	  n += !n;
	}
    }
  else
    {
      /* Set N = ceil (1.5 * N) so that progress is made if N == 1.
	 Check for overflow, so that N * S stays in size_t range.
	 The check is slightly conservative, but an exact check isn't
	 worth the trouble.  */
      if ((size_t) -1 / 3 * 2 / s <= n)
	xalloc_die ();
      n += (n + 1) / 2;
    }

  *pn = n;
  return xrealloc (p, n * s);
}

/* Return a pointer to a new buffer of N bytes.  This is like xmalloc,
   except it returns char *.  */

static_inline char *
xcharalloc (size_t n)
{
  return XNMALLOC (n, char);
}

# endif

# ifdef __cplusplus
}

/* C++ does not allow conversions from void * to other pointer types
   without a cast.  Use templates to work around the problem when
   possible.  */

template <typename T> inline T *
xrealloc (T *p, size_t s)
{
  return (T *) xrealloc ((void *) p, s);
}

template <typename T> inline T *
xnrealloc (T *p, size_t n, size_t s)
{
  return (T *) xnrealloc ((void *) p, n, s);
}

template <typename T> inline T *
x2realloc (T *p, size_t *pn)
{
  return (T *) x2realloc ((void *) p, pn);
}

template <typename T> inline T *
x2nrealloc (T *p, size_t *pn, size_t s)
{
  return (T *) x2nrealloc ((void *) p, pn, s);
}

template <typename T> inline T *
xmemdup (T const *p, size_t s)
{
  return (T *) xmemdup ((void const *) p, s);
}

# endif


#endif /* !XALLOC_H_ */