+/* Enable extensions on AIX 3, Interix. */
+#ifndef _ALL_SOURCE
+/* # undef _ALL_SOURCE */
+#endif
+/* Enable GNU extensions on systems that have them. */
+#ifndef _GNU_SOURCE
+/* # undef _GNU_SOURCE */
+#endif
+/* Enable threading extensions on Solaris. */
+#ifndef _POSIX_PTHREAD_SEMANTICS
+/* # undef _POSIX_PTHREAD_SEMANTICS */
+#endif
+/* Enable extensions on HP NonStop. */
+#ifndef _TANDEM_SOURCE
+/* # undef _TANDEM_SOURCE */
+#endif
+/* Enable general extensions on Solaris. */
+#ifndef __EXTENSIONS__
+/* # undef __EXTENSIONS__ */
+#endif
+