|  | dnl Provide AC_USE_SYSTEM_EXTENSIONS for old autoconf machines. | 
|  | AC_DEFUN([ACX_USE_SYSTEM_EXTENSIONS],[ | 
|  | ifdef([AC_USE_SYSTEM_EXTENSIONS],[ | 
|  | AC_USE_SYSTEM_EXTENSIONS | 
|  | ],[ | 
|  | AC_BEFORE([$0], [AC_COMPILE_IFELSE]) | 
|  | AC_BEFORE([$0], [AC_RUN_IFELSE]) | 
|  |  | 
|  | AC_REQUIRE([AC_GNU_SOURCE]) | 
|  | AC_REQUIRE([AC_AIX]) | 
|  | AC_REQUIRE([AC_MINIX]) | 
|  |  | 
|  | AH_VERBATIM([__EXTENSIONS__], | 
|  | [/* Enable extensions on Solaris.  */ | 
|  | #ifndef __EXTENSIONS__ | 
|  | # undef __EXTENSIONS__ | 
|  | #endif | 
|  | #ifndef _POSIX_PTHREAD_SEMANTICS | 
|  | # undef _POSIX_PTHREAD_SEMANTICS | 
|  | #endif | 
|  | #ifndef _TANDEM_SOURCE | 
|  | # undef _TANDEM_SOURCE | 
|  | #endif]) | 
|  | AC_CACHE_CHECK([whether it is safe to define __EXTENSIONS__], | 
|  | [ac_cv_safe_to_define___extensions__], | 
|  | [AC_COMPILE_IFELSE( | 
|  | [AC_LANG_PROGRAM([ | 
|  | #           define __EXTENSIONS__ 1 | 
|  | AC_INCLUDES_DEFAULT])], | 
|  | [ac_cv_safe_to_define___extensions__=yes], | 
|  | [ac_cv_safe_to_define___extensions__=no])]) | 
|  | test $ac_cv_safe_to_define___extensions__ = yes && | 
|  | AC_DEFINE([__EXTENSIONS__]) | 
|  | AC_DEFINE([_POSIX_PTHREAD_SEMANTICS]) | 
|  | AC_DEFINE([_TANDEM_SOURCE]) | 
|  | ]) | 
|  | ]) |