--- Net2/sys/cdefs.h	2018/04/24 18:03:58	1.1
+++ Net2/sys/cdefs.h	2018/04/24 18:16:39	1.1.1.2
@@ -30,11 +30,12 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- *	@(#)cdefs.h	7.6 (Berkeley) 5/4/91
+ *	from: @(#)cdefs.h	7.6 (Berkeley) 5/4/91
+ *	cdefs.h,v 1.4 1993/05/26 14:52:56 cgd Exp
  */
 
-#ifndef	_CDEFS_H_
-#define	_CDEFS_H_
+#ifndef	_SYS_CDEFS_H_
+#define	_SYS_CDEFS_H_
 
 #if defined(__cplusplus)
 #define	__BEGIN_DECLS	extern "C" {
@@ -75,4 +76,20 @@
 #endif	/* !__GNUC__ */
 #endif	/* !(__STDC__ || __cplusplus) */
 
-#endif /* !_CDEFS_H_ */
+/*
+ * GCC has extensions for declaring functions as `pure' (always returns
+ * the same value given the same inputs, i.e., has no external state and
+ * no side effects) and `dead' (nonreturning).  These mainly affect
+ * optimization and warnings.  Unfortunately, GCC complains if these are
+ * used under strict ANSI mode (`gcc -ansi -pedantic'), hence we need to
+ * define them only if compiling without this.
+ */
+#if defined(__GNUC__) && !defined(__STRICT_ANSI__)
+#define __dead __volatile
+#define __pure __const
+#else
+#define __dead
+#define __pure
+#endif
+
+#endif /* !_SYS_CDEFS_H_ */