1  /* Memory allocation on the stack.
       2  
       3     Copyright (C) 1995, 1999, 2001-2004, 2006-2021 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    /* 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 */