--- a/include/sys/cdefs.h
+++ b/include/sys/cdefs.h
@@ -40,3 +40,7 @@
 #ifndef __COPYRIGHT
 #define __COPYRIGHT(arg)	static const char copyright[] __attribute__((__unused__)) = arg
 #endif
+
+#ifndef __dead
+#define	__dead	__attribute__((__noreturn__))
+#endif

.