3373 gcc >= 4.5 concerns about offsetof()

@@ -2415,11 +2415,15 @@
         return (0);
 }
 
 
 #ifndef offsetof
-#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
 #endif
 
 /*
  * re-write the size of the current partition
  */