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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, 2009, 2010 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

# ifndef ATTRIBUTE_MALLOC
#  if __GNUC__ >= 3
#   define ATTRIBUTE_MALLOC __attribute__ ((__malloc__))
#  else
#   define ATTRIBUTE_MALLOC
#  endif
# 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) ATTRIBUTE_MALLOC;
void *xzalloc (size_t s) ATTRIBUTE_MALLOC;
void *xcalloc (size_t n, size_t s) ATTRIBUTE_MALLOC;
void *xrealloc (void *p, size_t s);
void *x2realloc (void *p, size_t *pn);
void *xmemdup (void const *p, size_t s) ATTRIBUTE_MALLOC;
char *xstrdup (char const *str) ATTRIBUTE_MALLOC;

/* 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) ATTRIBUTE_MALLOC;
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) ATTRIBUTE_MALLOC;
# 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) ATTRIBUTE_MALLOC;
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) ATTRIBUTE_MALLOC;
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_ */

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