Index: trunk/psLib/configure.ac
===================================================================
--- trunk/psLib/configure.ac	(revision 3835)
+++ trunk/psLib/configure.ac	(revision 3886)
@@ -35,15 +35,7 @@
 AC_LANG(C)
 AC_PROG_CC
-AC_GNU_SOURCE
-dnl Setup CFLAGS with project-particulars
-AC_MSG_CHECKING([C99 flag])
-if test "$GCC" == "yes"
-then
-CFLAGS="${CFLAGS=} -std=gnu99"
-AC_MSG_RESULT([-std=gnu99])
-else
-CFLAGS="${CFLAGS=} -std=c99"
-AC_MSG_RESULT([-std=c99])
-fi
+
+dnl enable POSIX/XSI and C99 compliance
+CFLAGS="${CFLAGS=} -D_XOPEN_SOURCE=600 -D_POSIX_C_SOURCE=200112L -std=c99"
 
 AC_LANG_PUSH(Fortran)