release/src/router/libiconv/srclib/malloca.h

   1 /* Safe automatic memory allocation.
   2    Copyright (C) 2003-2007, 2009-2011 Free Software Foundation, Inc.
   3    Written by Bruno Haible <bruno@clisp.org>, 2003.
   4
   5    This program is free software; you can redistribute it and/or modify
   6    it under the terms of the GNU General Public License as published by
   7    the Free Software Foundation; either version 3, or (at your option)
   8    any later version.
   9
  10    This program is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13    GNU General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program; if not, write to the Free Software Foundation,
  17    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  18
  19 #ifndef _MALLOCA_H
  20 #define _MALLOCA_H
  21
  22 #include <alloca.h>
  23 #include <stddef.h>
  24 #include <stdlib.h>
  25
  26
  27 #ifdef __cplusplus
  28 extern "C" {
  29 #endif
  30
  31
  32 /* safe_alloca(N) is equivalent to alloca(N) when it is safe to call
  33    alloca(N); otherwise it returns NULL.  It either returns N bytes of
  34    memory allocated on the stack, that lasts until the function returns,
  35    or NULL.
  36    Use of safe_alloca should be avoided:
  37      - inside arguments of function calls - undefined behaviour,
  38      - in inline functions - the allocation may actually last until the
  39        calling function returns.
  40 */
  41 #if HAVE_ALLOCA
  42 /* The OS usually guarantees only one guard page at the bottom of the stack,
  43    and a page size can be as small as 4096 bytes.  So we cannot safely
  44    allocate anything larger than 4096 bytes.  Also care for the possibility
  45    of a few compiler-allocated temporary stack slots.
  46    This must be a macro, not an inline function.  */
  47 # define safe_alloca(N) ((N) < 4032 ? alloca (N) : NULL)
  48 #else
  49 # define safe_alloca(N) ((void) (N), NULL)
  50 #endif
  51
  52 /* malloca(N) is a safe variant of alloca(N).  It allocates N bytes of
  53    memory allocated on the stack, that must be freed using freea() before
  54    the function returns.  Upon failure, it returns NULL.  */
  55 #if HAVE_ALLOCA
  56 # define malloca(N) \
  57   ((N) < 4032 - sa_increment                                        \
  58    ? (void *) ((char *) alloca ((N) + sa_increment) + sa_increment) \
  59    : mmalloca (N))
  60 #else
  61 # define malloca(N) \
  62   mmalloca (N)
  63 #endif
  64 extern void * mmalloca (size_t n);
  65
  66 /* Free a block of memory allocated through malloca().  */
  67 #if HAVE_ALLOCA
  68 extern void freea (void *p);
  69 #else
  70 # define freea free
  71 #endif
  72
  73 /* nmalloca(N,S) is an overflow-safe variant of malloca (N * S).
  74    It allocates an array of N objects, each with S bytes of memory,
  75    on the stack.  S must be positive and N must be nonnegative.
  76    The array must be freed using freea() before the function returns.  */
  77 #if 1
  78 /* Cf. the definition of xalloc_oversized.  */
  79 # define nmalloca(n, s) \
  80     ((n) > (size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) \
  81      ? NULL \
  82      : malloca ((n) * (s)))
  83 #else
  84 extern void * nmalloca (size_t n, size_t s);
  85 #endif
  86
  87
  88 #ifdef __cplusplus
  89 }
  90 #endif
  91
  92
  93 /* ------------------- Auxiliary, non-public definitions ------------------- */
  94
  95 /* Determine the alignment of a type at compile time.  */
  96 #if defined __GNUC__
  97 # define sa_alignof __alignof__
  98 #elif defined __cplusplus
  99   template <class type> struct sa_alignof_helper { char __slot1; type __slot2; };
 100 # define sa_alignof(type) offsetof (sa_alignof_helper<type>, __slot2)
 101 #elif defined __hpux
 102   /* Work around a HP-UX 10.20 cc bug with enums constants defined as offsetof
 103      values.  */
 104 # define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8)
 105 #elif defined _AIX
 106   /* Work around an AIX 3.2.5 xlc bug with enums constants defined as offsetof
 107      values.  */
 108 # define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8)
 109 #else
 110 # define sa_alignof(type) offsetof (struct { char __slot1; type __slot2; }, __slot2)
 111 #endif
 112
 113 enum
 114 {
 115 /* The desired alignment of memory allocations is the maximum alignment
 116    among all elementary types.  */
 117   sa_alignment_long = sa_alignof (long),
 118   sa_alignment_double = sa_alignof (double),
 119 #if HAVE_LONG_LONG_INT
 120   sa_alignment_longlong = sa_alignof (long long),
 121 #endif
 122   sa_alignment_longdouble = sa_alignof (long double),
 123   sa_alignment_max = ((sa_alignment_long - 1) | (sa_alignment_double - 1)
 124 #if HAVE_LONG_LONG_INT
 125                       | (sa_alignment_longlong - 1)
 126 #endif
 127                       | (sa_alignment_longdouble - 1)
 128                      ) + 1,
 129 /* The increment that guarantees room for a magic word must be >= sizeof (int)
 130    and a multiple of sa_alignment_max.  */
 131   sa_increment = ((sizeof (int) + sa_alignment_max - 1) / sa_alignment_max) * sa_alignment_max
 132 };
 133
 134 #endif /* _MALLOCA_H */