--- /dev/null
+# Check whether free (NULL) is supposed to work.
+
+# Copyright (C) 2003 Free Software Foundation, Inc.
+
+# This file is free software, distributed under the terms of the GNU
+# General Public License. As a special exception to the GNU General
+# Public License, this file may be distributed as part of a program
+# that contains a configuration script generated by Autoconf, under
+# the same distribution terms as the rest of that program.
+
+# Written by Paul Eggert.
+
+# We can't test for free (NULL) even at runtime, since it might
+# happen to "work" for our test program, but not in general. So, be
+# conservative and use feature tests for relatively modern hosts,
+# where free (NULL) is known to work. This costs a bit of
+# performance on some older hosts, but we can fix that later if
+# needed.
+
+AC_DEFUN([gl_FUNC_FREE],
+[
+ AC_CHECK_HEADERS_ONCE(unistd.h)
+ AC_CACHE_CHECK([whether free (NULL) is known to work],
+ [gl_cv_func_free],
+ [AC_COMPILE_IFELSE(
+ [AC_LANG_PROGRAM(
+ [[@%:@if HAVE_UNISTD_H
+ @%:@include <unistd.h>
+ @%:@endif]],
+ [[@%:@if _POSIX_VERSION < 199009L && \
+ (defined unix || defined _unix || defined _unix_ \
+ || defined __unix || defined __unix__)
+ @%:@error "'free (NULL)' is not known to work"
+ @%:@endif]])],
+ [gl_cv_func_free=yes],
+ [gl_cv_func_free=no])])
+
+ if test $gl_cv_func_free = yes; then
+ AC_LIBOBJ(free)
+ AC_DEFINE(free, rpl_free,
+ [Define to rpl_free if the replacement function should be used.])
+ fi
+])
+
+# Prerequisites of lib/free.c.
+AC_DEFUN([gl_PREREQ_FREE], [:])