lib/alloca.in.h

   1 /* Memory allocation on the stack.
   2
   3    Copyright (C) 1995, 1999, 2001-2004, 2006-2018 Free Software Foundation,
   4    Inc.
   5
   6    This program is free software; you can redistribute it and/or modify it
   7    under the terms of the GNU General Public License as published
   8    by the Free Software Foundation; either version 3, or (at your option)
   9    any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public
  17    License along with this program; if not, see
  18    <https://www.gnu.org/licenses/>.
  19   */
  20
  21 /* Avoid using the symbol _ALLOCA_H here, as Bison assumes _ALLOCA_H
  22    means there is a real alloca function.  */
  23 #ifndef _GL_ALLOCA_H
  24 #define _GL_ALLOCA_H
  25
  26 /* alloca (N) returns a pointer to N bytes of memory
  27    allocated on the stack, which will last until the function returns.
  28    Use of alloca should be avoided:
  29      - inside arguments of function calls - undefined behaviour,
  30      - in inline functions - the allocation may actually last until the
  31        calling function returns,
  32      - for huge N (say, N >= 65536) - you never know how large (or small)
  33        the stack is, and when the stack cannot fulfill the memory allocation
  34        request, the program just crashes.
  35  */
  36
  37 #ifndef alloca
  38 # ifdef __GNUC__
  39 #  define alloca __builtin_alloca
  40 # elif defined _AIX
  41 #  define alloca __alloca
  42 # elif defined _MSC_VER
  43 #  include <malloc.h>
  44 #  define alloca _alloca
  45 # elif defined __DECC && defined __VMS
  46 #  define alloca __ALLOCA
  47 # elif defined __TANDEM && defined _TNS_E_TARGET
  48 #  ifdef  __cplusplus
  49 extern "C"
  50 #  endif
  51 void *_alloca (unsigned short);
  52 #  pragma intrinsic (_alloca)
  53 #  define alloca _alloca
  54 # elif defined __MVS__
  55 #  include <stdlib.h>
  56 # else
  57 #  include <stddef.h>
  58 #  ifdef  __cplusplus
  59 extern "C"
  60 #  endif
  61 void *alloca (size_t);
  62 # endif
  63 #endif
  64
  65 #endif /* _GL_ALLOCA_H */