1 # Check for flexible array member support.
3 # Copyright (C) 2006 Free Software Foundation, Inc.
5 # This program is free software; you can redistribute it and/or modify
6 # it under the terms of the GNU General Public License as published by
7 # the Free Software Foundation; either version 2, or (at your option)
10 # This program is distributed in the hope that it will be useful,
11 # but WITHOUT ANY WARRANTY; without even the implied warranty of
12 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
13 # GNU General Public License for more details.
15 # You should have received a copy of the GNU General Public License
16 # along with this program; if not, write to the Free Software
17 # Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
20 # Written by Paul Eggert.
22 AC_DEFUN([AC_C_FLEXIBLE_ARRAY_MEMBER],
24 AC_CACHE_CHECK([for flexible array member],
31 struct s { int n; double d[]; };]],
33 struct s *p = malloc (offsetof (struct s, d)
34 + m * sizeof (double));
36 return p->d != (double *) NULL;]])],
37 [ac_cv_c_flexmember=yes],
38 [ac_cv_c_flexmember=no])])
39 if test $ac_cv_c_flexmember = yes; then
40 AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], [],
41 [Define to nothing if C supports flexible array members, and to
42 1 if it does not. That way, with a declaration like `struct s
43 { int n; double d@<:@FLEXIBLE_ARRAY_MEMBER@:>@; };', the struct hack
44 can be used with pre-C99 compilers.
45 When computing the size of such an object, don't use 'sizeof (struct s)'
46 as it overestimates the size. Use 'offsetof (struct s, d)' instead.
47 Don't use 'offsetof (struct s, d@<:@0@:>@)', as this doesn't work with
48 MSVC and with C++ compilers.])
50 AC_DEFINE([FLEXIBLE_ARRAY_MEMBER], 1)