lib/xalloc.h

   1 /* xalloc.h -- malloc with out-of-memory checking
   2
   3    Copyright (C) 1990, 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998,
   4    1999, 2000, 2003, 2004, 2006 Free Software Foundation, Inc.
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software Foundation,
  18    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  19
  20 #ifndef XALLOC_H_
  21 # define XALLOC_H_
  22
  23 # include <stddef.h>
  24
  25
  26 # ifdef __cplusplus
  27 extern "C" {
  28 # endif
  29
  30
  31 # ifndef __attribute__
  32 #  if __GNUC__ < 2 || (__GNUC__ == 2 && __GNUC_MINOR__ < 8) || __STRICT_ANSI__
  33 #   define __attribute__(x)
  34 #  endif
  35 # endif
  36
  37 # ifndef ATTRIBUTE_NORETURN
  38 #  define ATTRIBUTE_NORETURN __attribute__ ((__noreturn__))
  39 # endif
  40
  41 /* This function is always triggered when memory is exhausted.
  42    It must be defined by the application, either explicitly
  43    or by using gnulib's xalloc-die module.  This is the
  44    function to call when one wants the program to die because of a
  45    memory allocation failure.  */
  46 extern void xalloc_die (void) ATTRIBUTE_NORETURN;
  47
  48 void *xmalloc (size_t s);
  49 void *xzalloc (size_t s);
  50 void *xcalloc (size_t n, size_t s);
  51 void *xrealloc (void *p, size_t s);
  52 void *x2realloc (void *p, size_t *pn);
  53 void *xmemdup (void const *p, size_t s);
  54 char *xstrdup (char const *str);
  55
  56 /* Return 1 if an array of N objects, each of size S, cannot exist due
  57    to size arithmetic overflow.  S must be positive and N must be
  58    nonnegative.  This is a macro, not an inline function, so that it
  59    works correctly even when SIZE_MAX < N.
  60
  61    By gnulib convention, SIZE_MAX represents overflow in size
  62    calculations, so the conservative dividend to use here is
  63    SIZE_MAX - 1, since SIZE_MAX might represent an overflowed value.
  64    However, malloc (SIZE_MAX) fails on all known hosts where
  65    sizeof (ptrdiff_t) <= sizeof (size_t), so do not bother to test for
  66    exactly-SIZE_MAX allocations on such hosts; this avoids a test and
  67    branch when S is known to be 1.  */
  68 # define xalloc_oversized(n, s) \
  69     ((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))
  70
  71
  72 /* In the following macros, T must be an elementary or structure/union or
  73    typedef'ed type, or a pointer to such a type.  To apply one of the
  74    following macros to a function pointer or array type, you need to typedef
  75    it first and use the typedef name.  */
  76
  77 /* Allocate an object of type T dynamically, with error checking.  */
  78 /* extern t *XMALLOC (typename t); */
  79 # define XMALLOC(t) ((t *) xmalloc (sizeof (t)))
  80
  81 /* Allocate memory for N elements of type T, with error checking.  */
  82 /* extern t *XNMALLOC (size_t n, typename t); */
  83 # define XNMALLOC(n, t) \
  84     ((t *) (sizeof (t) == 1 ? xmalloc (n) : xnmalloc (n, sizeof (t))))
  85
  86 /* Allocate an object of type T dynamically, with error checking,
  87    and zero it.  */
  88 /* extern t *XZALLOC (typename t); */
  89 # define XZALLOC(t) ((t *) xzalloc (sizeof (t)))
  90
  91 /* Allocate memory for N elements of type T, with error checking,
  92    and zero it.  */
  93 /* extern t *XCALLOC (size_t n, typename t); */
  94 # define XCALLOC(n, t) \
  95     ((t *) (sizeof (t) == 1 ? xzalloc (n) : xcalloc (n, sizeof (t))))
  96
  97
  98 # if HAVE_INLINE
  99 #  define static_inline static inline
 100 # else
 101    void *xnmalloc (size_t n, size_t s);
 102    void *xnrealloc (void *p, size_t n, size_t s);
 103    void *x2nrealloc (void *p, size_t *pn, size_t s);
 104    char *xcharalloc (size_t n);
 105 # endif
 106
 107 # ifdef static_inline
 108
 109 /* Allocate an array of N objects, each with S bytes of memory,
 110    dynamically, with error checking.  S must be nonzero.  */
 111
 112 static_inline void *
 113 xnmalloc (size_t n, size_t s)
 114 {
 115   if (xalloc_oversized (n, s))
 116     xalloc_die ();
 117   return xmalloc (n * s);
 118 }
 119
 120 /* Change the size of an allocated block of memory P to an array of N
 121    objects each of S bytes, with error checking.  S must be nonzero.  */
 122
 123 static_inline void *
 124 xnrealloc (void *p, size_t n, size_t s)
 125 {
 126   if (xalloc_oversized (n, s))
 127     xalloc_die ();
 128   return xrealloc (p, n * s);
 129 }
 130
 131 /* If P is null, allocate a block of at least *PN such objects;
 132    otherwise, reallocate P so that it contains more than *PN objects
 133    each of S bytes.  *PN must be nonzero unless P is null, and S must
 134    be nonzero.  Set *PN to the new number of objects, and return the
 135    pointer to the new block.  *PN is never set to zero, and the
 136    returned pointer is never null.
 137
 138    Repeated reallocations are guaranteed to make progress, either by
 139    allocating an initial block with a nonzero size, or by allocating a
 140    larger block.
 141
 142    In the following implementation, nonzero sizes are doubled so that
 143    repeated reallocations have O(N log N) overall cost rather than
 144    O(N**2) cost, but the specification for this function does not
 145    guarantee that sizes are doubled.
 146
 147    Here is an example of use:
 148
 149      int *p = NULL;
 150      size_t used = 0;
 151      size_t allocated = 0;
 152
 153      void
 154      append_int (int value)
 155        {
 156          if (used == allocated)
 157            p = x2nrealloc (p, &allocated, sizeof *p);
 158          p[used++] = value;
 159        }
 160
 161    This causes x2nrealloc to allocate a block of some nonzero size the
 162    first time it is called.
 163
 164    To have finer-grained control over the initial size, set *PN to a
 165    nonzero value before calling this function with P == NULL.  For
 166    example:
 167
 168      int *p = NULL;
 169      size_t used = 0;
 170      size_t allocated = 0;
 171      size_t allocated1 = 1000;
 172
 173      void
 174      append_int (int value)
 175        {
 176          if (used == allocated)
 177            {
 178              p = x2nrealloc (p, &allocated1, sizeof *p);
 179              allocated = allocated1;
 180            }
 181          p[used++] = value;
 182        }
 183
 184    */
 185
 186 static_inline void *
 187 x2nrealloc (void *p, size_t *pn, size_t s)
 188 {
 189   size_t n = *pn;
 190
 191   if (! p)
 192     {
 193       if (! n)
 194         {
 195           /* The approximate size to use for initial small allocation
 196              requests, when the invoking code specifies an old size of
 197              zero.  64 bytes is the largest "small" request for the
 198              GNU C library malloc.  */
 199           enum { DEFAULT_MXFAST = 64 };
 200
 201           n = DEFAULT_MXFAST / s;
 202           n += !n;
 203         }
 204     }
 205   else
 206     {
 207       if (((size_t) -1) / 2 / s < n)
 208         xalloc_die ();
 209       n *= 2;
 210     }
 211
 212   *pn = n;
 213   return xrealloc (p, n * s);
 214 }
 215
 216 /* Return a pointer to a new buffer of N bytes.  This is like xmalloc,
 217    except it returns char *.  */
 218
 219 static_inline char *
 220 xcharalloc (size_t n)
 221 {
 222   return XNMALLOC (n, char);
 223 }
 224
 225 # endif
 226
 227 # ifdef __cplusplus
 228 }
 229
 230 /* C++ does not allow conversions from void * to other pointer types
 231    without a cast.  Use templates to work around the problem when
 232    possible.  */
 233
 234 template <typename T> inline T *
 235 xrealloc (T *p, size_t s)
 236 {
 237   return (T *) xrealloc ((void *) p, s);
 238 }
 239
 240 template <typename T> inline T *
 241 xnrealloc (T *p, size_t n, size_t s)
 242 {
 243   return (T *) xnrealloc ((void *) p, n, s);
 244 }
 245
 246 template <typename T> inline T *
 247 x2realloc (T *p, size_t *pn)
 248 {
 249   return (T *) x2realloc ((void *) p, pn);
 250 }
 251
 252 template <typename T> inline T *
 253 x2nrealloc (T *p, size_t *pn, size_t s)
 254 {
 255   return (T *) x2nrealloc ((void *) p, pn, s);
 256 }
 257
 258 template <typename T> inline T *
 259 xmemdup (T const *p, size_t s)
 260 {
 261   return (T *) xmemdup ((void const *) p, s);
 262 }
 263
 264 # endif
 265
 266
 267 #endif /* !XALLOC_H_ */