lib/alloca.in.h

   1 /* Memory allocation on the stack.
   2
   3    Copyright (C) 1995, 1999, 2001-2004, 2006-2020 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 2, 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   /* Some version of mingw have an <alloca.h> that causes trouble when
  39      included after 'alloca' gets defined as a macro.  As a workaround,
  40      include this <alloca.h> first and define 'alloca' as a macro afterwards
  41      if needed.  */
  42 # if defined __GNUC__ && (defined _WIN32 && ! defined __CYGWIN__) && @HAVE_ALLOCA_H@
  43 #  include_next <alloca.h>
  44 # endif
  45 #endif
  46 #ifndef alloca
  47 # if defined __GNUC__ || (__clang_major__ >= 4)
  48 #  define alloca __builtin_alloca
  49 # elif defined _AIX
  50 #  define alloca __alloca
  51 # elif defined _MSC_VER
  52 #  include <malloc.h>
  53 #  define alloca _alloca
  54 # elif defined __DECC && defined __VMS
  55 #  define alloca __ALLOCA
  56 # elif defined __TANDEM && defined _TNS_E_TARGET
  57 #  ifdef  __cplusplus
  58 extern "C"
  59 #  endif
  60 void *_alloca (unsigned short);
  61 #  pragma intrinsic (_alloca)
  62 #  define alloca _alloca
  63 # elif defined __MVS__
  64 #  include <stdlib.h>
  65 # else
  66 #  include <stddef.h>
  67 #  ifdef  __cplusplus
  68 extern "C"
  69 #  endif
  70 void *alloca (size_t);
  71 # endif
  72 #endif
  73
  74 #endif /* _GL_ALLOCA_H */