+/* Enable extensions on AIX 3, Interix. */
+#ifndef _ALL_SOURCE
+# undef _ALL_SOURCE
+#endif
+/* Enable general extensions on OS X. */
+#ifndef _DARWIN_C_SOURCE
+# undef _DARWIN_C_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 X/Open extensions if necessary. HP-UX 11.11 defines
+ mbstate_t only if _XOPEN_SOURCE is defined to 500, regardless of
+ whether compiling with -Ae or -D_HPUX_SOURCE=1. */
+#ifndef _XOPEN_SOURCE
+# undef _XOPEN_SOURCE
+#endif
+/* Enable general extensions on Solaris. */
+#ifndef __EXTENSIONS__
+# undef __EXTENSIONS__
+#endif
+
+