##### http://autoconf-archive.cryp.to/ax_check_define.html
#
# SYNOPSIS
#
#   AC_CHECK_DEFINE([symbol], [ACTION-IF-FOUND], [ACTION-IF-NOT])
#   AX_CHECK_DEFINE([includes],[symbol], [ACTION-IF-FOUND], [ACTION-IF-NOT])
#
# DESCRIPTION
#
#   Complements AC_CHECK_FUNC but it does not check for a function but
#   for a define to exist. Consider a usage like:
#
#    AC_CHECK_DEFINE(__STRICT_ANSI__, CFLAGS="$CFLAGS -D_XOPEN_SOURCE=500")
#
# LAST MODIFICATION
#
#   2006-10-13
#
# COPYLEFT
#
#   Copyright (c) 2006 Guido U. Draheim <guidod@gmx.de>
#
#   This program is free software; you can redistribute it and/or
#   modify it under the terms of the GNU General Public License as
#   published by the Free Software Foundation; either version 2 of the
#   License, or (at your option) any later version.
#
#   This program is distributed in the hope that it will be useful, but
#   WITHOUT ANY WARRANTY; without even the implied warranty of
#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
#   General Public License for more details.
#
#   You should have received a copy of the GNU General Public License
#   along with this program; if not, write to the Free Software
#   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA
#   02111-1307, USA.
#
#   As a special exception, the respective Autoconf Macro's copyright
#   owner gives unlimited permission to copy, distribute and modify the
#   configure scripts that are the output of Autoconf when processing
#   the Macro. You need not follow the terms of the GNU General Public
#   License when using or distributing such scripts, even though
#   portions of the text of the Macro appear in them. The GNU General
#   Public License (GPL) does govern all other use of the material that
#   constitutes the Autoconf Macro.
#
#   This special exception to the GPL applies to versions of the
#   Autoconf Macro released by the Autoconf Macro Archive. When you
#   make and distribute a modified version of the Autoconf Macro, you
#   may extend this special exception to the GPL to apply to your
#   modified version as well.

AC_DEFUN([AC_CHECK_DEFINED],[
AS_VAR_PUSHDEF([ac_var],[ac_cv_defined_$1])dnl
AC_CACHE_CHECK([for $1 defined], ac_var,
AC_TRY_COMPILE(,[
  #ifdef $1
  int ok;
  #else
  choke me
  #endif
],AS_VAR_SET(ac_var, yes),AS_VAR_SET(ac_var, no)))
AS_IF([test AS_VAR_GET(ac_var) != "no"], [$2], [$3])dnl
AS_VAR_POPDEF([ac_var])dnl
])

AC_DEFUN([AX_CHECK_DEFINED],[
AS_VAR_PUSHDEF([ac_var],[ac_cv_defined_$2])dnl
AC_CACHE_CHECK([for $1 defined], ac_var,
AC_TRY_COMPILE($1,[
  #ifndef $2
  int ok;
  #else
  choke me
  #endif
],AS_VAR_SET(ac_var, yes),AS_VAR_SET(ac_var, no)))
AS_IF([test AS_VAR_GET(ac_var) != "no"], [$3], [$4])dnl
AS_VAR_POPDEF([ac_var])dnl
])

AC_DEFUN([AX_CHECK_FUNC],
[AS_VAR_PUSHDEF([ac_var], [ac_cv_func_$2])dnl
AC_CACHE_CHECK([for $2], ac_var,
dnl AC_LANG_FUNC_LINK_TRY
[AC_LINK_IFELSE([AC_LANG_PROGRAM([$1
                #undef $2
                char $2 ();],[
                char (*f) () = $2;
                return f != $2; ])],
                [AS_VAR_SET(ac_var, yes)],
                [AS_VAR_SET(ac_var, no)])])
AS_IF([test AS_VAR_GET(ac_var) = yes], [$3], [$4])dnl
AS_VAR_POPDEF([ac_var])dnl
])# AC_CHECK_FUNC