3373 gcc >= 4.5 concerns about offsetof()
Portions contributed by: Igor Pashev <pashev.igor@gmail.com>

@@ -48,10 +48,16 @@
  * Calculate size of a shared ring, given the total available space for the
  * ring and indexes (_sz), and the name tag of the request/response structure.
  * A ring contains as many entries as will fit, rounded down to the nearest 
  * power of two (so we can mask with (size-1) to loop around).
  */
+#define __CONST_RING_SIZE(_s, _sz) \
+    (__RD32(((_sz) - offsetof(struct _s##_sring, ring)) / \
+       sizeof(((struct _s##_sring *)0)->ring[0])))
+/*
+ * The same for passing in an actual pointer instead of a name tag.
+ */
 #define __RING_SIZE(_s, _sz) \
     (__RD32(((_sz) - (long)(_s)->ring + (long)(_s)) / sizeof((_s)->ring[0])))
 
 /*
  * Macros to make the correct C datatypes for a new kind of ring.