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, write to the Free
  16    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  17    02111-1307 USA.  */
  18
  19 #ifndef _ALLOCA_H
  20 #define _ALLOCA_H       1
  21
  22 #include <features.h>
  23
  24 #define __need_size_t
  25 #include <stddef.h>
  26
  27 __BEGIN_DECLS
  28
  29 /* Remove any previous definitions.  */
  30 #undef  alloca
  31
  32 /* Allocate a block that will be freed when the calling function exits.  */
  33 extern void *alloca (size_t __size) __THROW;
  34
  35 #ifdef  __GNUC__
  36 # define alloca(size)   __builtin_alloca (size)
  37 #endif /* GCC.  */
  38
  39 #ifdef _LIBC
  40 # define __MAX_ALLOCA_CUTOFF    65536
  41
  42 # include <bits/stackinfo.h>
  43 # ifdef _STACK_GROWS_DOWN
  44 #  define extend_alloca(buf, len, newlen) \
  45    (__typeof (buf)) ({ size_t __newlen = (newlen);                            \
  46                       char *__newbuf = alloca (__newlen);                     \
  47                       if (__newbuf + __newlen == (char *) buf)                \
  48                         len += __newlen;                                      \
  49                       else                                                    \
  50                         len = __newlen;                                       \
  51                       __newbuf; })
  52 # elif defined _STACK_GROWS_UP
  53 #  define extend_alloca(buf, len, newlen) \
  54    (__typeof (buf)) ({ size_t __newlen = (newlen);                            \
  55                       char *__newbuf = alloca (__newlen);                     \
  56                       char *__buf = (buf);                                    \
  57                       if (__buf + __newlen == __newbuf)                       \
  58                         {                                                     \
  59                           len += __newlen;                                    \
  60                           __newbuf = __buf;                                   \
  61                         }                                                     \
  62                       else                                                    \
  63                         len = __newlen;                                       \
  64                       __newbuf; })
  65 # else
  66 #  error unknown stack
  67 #  define extend_alloca(buf, len, newlen) \
  68    alloca (((len) = (newlen)))
  69 # endif
  70 #endif
  71
  72 __END_DECLS
  73
  74 #endif /* alloca.h */