- struct weak_pointer *wp = weak_pointers;
- /* Push the weak pointer onto the list of weak pointers.
- * Do I have to watch for duplicates? Originally this was
- * part of trans_weak_pointer but that didn't work in the
- * case where the WP was in a promoted region.
+ /* Since we overwrite the 'next' field, we have to make
+ * sure not to do so for pointers already in the list.
+ * Instead of searching the list of weak_pointers each
+ * time, we ensure that next is always NULL when the weak
+ * pointer isn't in the list, and not NULL otherwise.
+ * Since we can't use NULL to denote end of list, we
+ * use a pointer back to the same weak_pointer.