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libiconv 1.16

    1: /* Safe automatic memory allocation.
    2:    Copyright (C) 2003-2007, 2009-2019 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, see <https://www.gnu.org/licenses/>.  */
   17: 
   18: #ifndef _MALLOCA_H
   19: #define _MALLOCA_H
   20: 
   21: #include <alloca.h>
   22: #include <stddef.h>
   23: #include <stdlib.h>
   24: #include <stdint.h>
   25: 
   26: #include "xalloc-oversized.h"
   27: 
   28: 
   29: #ifdef __cplusplus
   30: extern "C" {
   31: #endif
   32: 
   33: 
   34: /* safe_alloca(N) is equivalent to alloca(N) when it is safe to call
   35:    alloca(N); otherwise it returns NULL.  It either returns N bytes of
   36:    memory allocated on the stack, that lasts until the function returns,
   37:    or NULL.
   38:    Use of safe_alloca should be avoided:
   39:      - inside arguments of function calls - undefined behaviour,
   40:      - in inline functions - the allocation may actually last until the
   41:        calling function returns.
   42: */
   43: #if HAVE_ALLOCA
   44: /* The OS usually guarantees only one guard page at the bottom of the stack,
   45:    and a page size can be as small as 4096 bytes.  So we cannot safely
   46:    allocate anything larger than 4096 bytes.  Also care for the possibility
   47:    of a few compiler-allocated temporary stack slots.
   48:    This must be a macro, not a function.  */
   49: # define safe_alloca(N) ((N) < 4032 ? alloca (N) : NULL)
   50: #else
   51: # define safe_alloca(N) ((void) (N), NULL)
   52: #endif
   53: 
   54: /* malloca(N) is a safe variant of alloca(N).  It allocates N bytes of
   55:    memory allocated on the stack, that must be freed using freea() before
   56:    the function returns.  Upon failure, it returns NULL.  */
   57: #if HAVE_ALLOCA
   58: # define malloca(N) \
   59:   ((N) < 4032 - (2 * sa_alignment_max - 1)                                   \
   60:    ? (void *) (((uintptr_t) (char *) alloca ((N) + 2 * sa_alignment_max - 1) \
   61:                 + (2 * sa_alignment_max - 1))                                \
   62:                & ~(uintptr_t)(2 * sa_alignment_max - 1))                     \
   63:    : mmalloca (N))
   64: #else
   65: # define malloca(N) \
   66:   mmalloca (N)
   67: #endif
   68: extern void * mmalloca (size_t n);
   69: 
   70: /* Free a block of memory allocated through malloca().  */
   71: #if HAVE_ALLOCA
   72: extern void freea (void *p);
   73: #else
   74: # define freea free
   75: #endif
   76: 
   77: /* nmalloca(N,S) is an overflow-safe variant of malloca (N * S).
   78:    It allocates an array of N objects, each with S bytes of memory,
   79:    on the stack.  S must be positive and N must be nonnegative.
   80:    The array must be freed using freea() before the function returns.  */
   81: #define nmalloca(n, s) (xalloc_oversized (n, s) ? NULL : malloca ((n) * (s)))
   82: 
   83: 
   84: #ifdef __cplusplus
   85: }
   86: #endif
   87: 
   88: 
   89: /* ------------------- Auxiliary, non-public definitions ------------------- */
   90: 
   91: /* Determine the alignment of a type at compile time.  */
   92: #if defined __GNUC__ || defined __IBM__ALIGNOF__
   93: # define sa_alignof __alignof__
   94: #elif defined __cplusplus
   95:   template <class type> struct sa_alignof_helper { char __slot1; type __slot2; };
   96: # define sa_alignof(type) offsetof (sa_alignof_helper<type>, __slot2)
   97: #elif defined __hpux
   98:   /* Work around a HP-UX 10.20 cc bug with enums constants defined as offsetof
   99:      values.  */
  100: # define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8)
  101: #elif defined _AIX
  102:   /* Work around an AIX 3.2.5 xlc bug with enums constants defined as offsetof
  103:      values.  */
  104: # define sa_alignof(type) (sizeof (type) <= 4 ? 4 : 8)
  105: #else
  106: # define sa_alignof(type) offsetof (struct { char __slot1; type __slot2; }, __slot2)
  107: #endif
  108: 
  109: enum
  110: {
  111: /* The desired alignment of memory allocations is the maximum alignment
  112:    among all elementary types.  */
  113:   sa_alignment_long = sa_alignof (long),
  114:   sa_alignment_double = sa_alignof (double),
  115: #if HAVE_LONG_LONG_INT
  116:   sa_alignment_longlong = sa_alignof (long long),
  117: #endif
  118:   sa_alignment_longdouble = sa_alignof (long double),
  119:   sa_alignment_max = ((sa_alignment_long - 1) | (sa_alignment_double - 1)
  120: #if HAVE_LONG_LONG_INT
  121:                       | (sa_alignment_longlong - 1)
  122: #endif
  123:                       | (sa_alignment_longdouble - 1)
  124:                      ) + 1
  125: };
  126: 
  127: #endif /* _MALLOCA_H */