3373 gcc >= 4.5 concerns about offsetof()

@@ -34,11 +34,15 @@
 #include <sys/nsctl/dsw.h>
 #include <sys/nsctl/dsw_dev.h>
 
 #include <sys/nsctl/nsvers.h>
 
-#define offsetof(s, m)  ((size_t)(&((s *)0)->m))
+#if defined(__GNUC__)
+#define offsetof(s, m)  __builtin_offsetof(s, m)
+#else
+#define offsetof(s, m)  ((size_t)(&(((s *)0)->m)))
+#endif
 
 
 const mdb_bitmask_t bi_flags_bits[] = {
         { "DSW_GOLDEN", DSW_GOLDEN, DSW_GOLDEN },
         { "DSW_COPYINGP", DSW_COPYINGP, DSW_COPYINGP },