+extern StgWord RTS_VAR(flip);
+
+// extract the retainer set field from c
+#define RSET(c) ((c)->header.prof.hp.rs)
+
+#define isRetainerSetFieldValid(c) \
+ ((((StgWord)(c)->header.prof.hp.rs & 1) ^ flip) == 0)
+
+static inline RetainerSet *
+retainerSetOf( StgClosure *c )
+{
+ ASSERT( isRetainerSetFieldValid(c) );
+ // StgWord has the same size as pointers, so the following type
+ // casting is okay.
+ return (RetainerSet *)((StgWord)RSET(c) ^ flip);
+}
+
+// Used by Storage.c:memInventory()