# Check for flexible array member support.

# Copyright (C) 2006 Free Software Foundation, Inc.

# 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, 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., 51 Franklin Street, Fifth Floor, Boston, MA
# 02110-1301, USA.

# Written by Paul Eggert.

AC_DEFUN([AC_C_FLEXIBLE_ARRAY_MEMBER],
[
  AC_CACHE_CHECK([for flexible array member],
    ac_cv_c_flexmember,
    [AC_COMPILE_IFELSE(
       [AC_LANG_PROGRAM(
	  [[#include <stdlib.h>
	    #include <stdio.h>
	    #include <stddef.h>
	    struct s { int n; double d[]; };]],
	  [[int m = getchar ();
	    struct s *p = malloc (offsetof (struct s, d)
				  + m * sizeof (double));
	    p->d[0] = 0.0;
	    return p->d != (double *) NULL;]])],
       [ac_cv_c_flexmember=yes],
       [ac_cv_c_flexmember=no])])
  if test $ac_cv_c_flexmember = yes; then
    AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [],
      [Define to nothing if C supports flexible array members, and to
       1 if it does not.  That way, with a declaration like `struct s
       { int n; double d@<:@FLEXIBLE_ARRAY_MEMBER@:>@; };', the struct hack
       can be used with pre-C99 compilers.
       When computing the size of such an object, don't use 'sizeof (struct s)'
       as it overestimates the size.  Use 'offsetof (struct s, d)' instead.
       Don't use 'offsetof (struct s, d@<:@0@:>@)', as this doesn't work with
       MSVC and with C++ compilers.])
  else
    AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], 1)
  fi
])