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Annotation of embedaddon/libiconv/srclib/malloca.h, revision 1.1

1.1     ! misho       1: /* Safe automatic memory allocation.
        !             2:    Copyright (C) 2003-2007 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 */