include/alloca.h

   1 /* Copyright (C) 1992, 1996, 1997, 1998, 1999 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #ifndef _ALLOCA_H
  19 #define _ALLOCA_H       1
  20
  21 #include <features.h>
  22
  23 #define __need_size_t
  24 #include <stddef.h>
  25
  26 __BEGIN_DECLS
  27
  28 /* Remove any previous definitions.  */
  29 #undef  alloca
  30
  31 /* Allocate a block that will be freed when the calling function exits.  */
  32 extern void *alloca (size_t __size) __THROW;
  33
  34 #ifdef  __GNUC__
  35 # define alloca(size)   __builtin_alloca (size)
  36 #endif /* GCC.  */
  37
  38 #ifdef _LIBC
  39 # define __MAX_ALLOCA_CUTOFF    65536
  40
  41 # include <bits/stackinfo.h>
  42 # ifdef _STACK_GROWS_DOWN
  43 #  define extend_alloca(buf, len, newlen) \
  44    (__typeof (buf)) ({ size_t __newlen = (newlen);                            \
  45                       char *__newbuf = alloca (__newlen);                     \
  46                       if (__newbuf + __newlen == (char *) buf)                \
  47                         len += __newlen;                                      \
  48                       else                                                    \
  49                         len = __newlen;                                       \
  50                       __newbuf; })
  51 # elif defined _STACK_GROWS_UP
  52 #  define extend_alloca(buf, len, newlen) \
  53    (__typeof (buf)) ({ size_t __newlen = (newlen);                            \
  54                       char *__newbuf = alloca (__newlen);                     \
  55                       char *__buf = (buf);                                    \
  56                       if (__buf + __newlen == __newbuf)                       \
  57                         {                                                     \
  58                           len += __newlen;                                    \
  59                           __newbuf = __buf;                                   \
  60                         }                                                     \
  61                       else                                                    \
  62                         len = __newlen;                                       \
  63                       __newbuf; })
  64 # else
  65 #  error unknown stack
  66 #  define extend_alloca(buf, len, newlen) \
  67    alloca (((len) = (newlen)))
  68 # endif
  69
  70 extern int __libc_alloca_cutoff (size_t size);
  71 #endif
  72
  73 __END_DECLS
  74
  75 #endif /* alloca.h */