lib/alloca.in.h

   1 /* Memory allocation on the stack.
   2
   3    Copyright (C) 1995, 1999, 2001-2004, 2006-2024 Free Software Foundation,
   4    Inc.
   5
   6    This file is free software: you can redistribute it and/or modify
   7    it under the terms of the GNU Lesser General Public License as
   8    published by the Free Software Foundation; either version 2.1 of the
   9    License, or (at your option) any later version.
  10
  11    This file 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
  14    GNU Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public License
  17    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  18
  19 /* Avoid using the symbol _ALLOCA_H here, as Bison assumes _ALLOCA_H
  20    means there is a real alloca function.  */
  21 #ifndef _GL_ALLOCA_H
  22 #define _GL_ALLOCA_H
  23
  24 /* alloca (N) returns a pointer to N bytes of memory
  25    allocated on the stack, which will last until the function returns.
  26    Use of alloca should be avoided:
  27      - inside arguments of function calls - undefined behaviour,
  28      - in inline functions - the allocation may actually last until the
  29        calling function returns,
  30      - for huge N (say, N >= 65536) - you never know how large (or small)
  31        the stack is, and when the stack cannot fulfill the memory allocation
  32        request, the program just crashes.
  33  */
  34
  35 #ifndef alloca
  36   /* Some version of mingw have an <alloca.h> that causes trouble when
  37      included after 'alloca' gets defined as a macro.  As a workaround,
  38      include this <alloca.h> first and define 'alloca' as a macro afterwards
  39      if needed.  */
  40 # if defined __GNUC__ && (defined _WIN32 && ! defined __CYGWIN__) && @HAVE_ALLOCA_H@
  41 #  include_next <alloca.h>
  42 # endif
  43 #endif
  44 #ifndef alloca
  45 # if defined __GNUC__ || (__clang_major__ >= 4)
  46 #  define alloca __builtin_alloca
  47 # elif defined _AIX
  48 #  define alloca __alloca
  49 # elif defined _MSC_VER
  50 #  include <malloc.h>
  51 #  define alloca _alloca
  52 # elif defined __DECC && defined __VMS
  53 #  define alloca __ALLOCA
  54 # elif defined __TANDEM && defined _TNS_E_TARGET
  55 #  ifdef  __cplusplus
  56 extern "C"
  57 #  endif
  58 void *_alloca (unsigned short);
  59 #  pragma intrinsic (_alloca)
  60 #  define alloca _alloca
  61 # elif defined __MVS__
  62 #  include <stdlib.h>
  63 # else
  64 #  include <stddef.h>
  65 #  ifdef  __cplusplus
  66 extern "C"
  67 #  endif
  68 void *alloca (size_t);
  69 # endif
  70 #endif
  71
  72 #endif /* _GL_ALLOCA_H */