1dnl Provide AC_USE_SYSTEM_EXTENSIONS for old autoconf machines.
2AC_DEFUN([ACX_USE_SYSTEM_EXTENSIONS],[
3  ifdef([AC_USE_SYSTEM_EXTENSIONS],[
4    AC_USE_SYSTEM_EXTENSIONS
5  ],[
6    AC_BEFORE([$0], [AC_COMPILE_IFELSE])
7    AC_BEFORE([$0], [AC_RUN_IFELSE])
8
9    AC_REQUIRE([AC_GNU_SOURCE])
10    AC_REQUIRE([AC_AIX])
11    AC_REQUIRE([AC_MINIX])
12
13    AH_VERBATIM([__EXTENSIONS__],
14[/* Enable extensions on Solaris.  */
15#ifndef __EXTENSIONS__
16# undef __EXTENSIONS__
17#endif
18#ifndef _POSIX_PTHREAD_SEMANTICS
19# undef _POSIX_PTHREAD_SEMANTICS
20#endif
21#ifndef _TANDEM_SOURCE
22# undef _TANDEM_SOURCE
23#endif])
24    AC_CACHE_CHECK([whether it is safe to define __EXTENSIONS__],
25      [ac_cv_safe_to_define___extensions__],
26      [AC_COMPILE_IFELSE(
27         [AC_LANG_PROGRAM([
28#           define __EXTENSIONS__ 1
29            AC_INCLUDES_DEFAULT])],
30         [ac_cv_safe_to_define___extensions__=yes],
31         [ac_cv_safe_to_define___extensions__=no])])
32    test $ac_cv_safe_to_define___extensions__ = yes &&
33      AC_DEFINE([__EXTENSIONS__])
34    AC_DEFINE([_POSIX_PTHREAD_SEMANTICS])
35    AC_DEFINE([_TANDEM_SOURCE])
36  ])
37])
38