Fix crasher for when an object's __del__ creates a new weakref to itself.
Patch only fixes new-style classes; classic classes still buggy.
Closes bug #1377858. Already backported.
diff --git a/Objects/weakrefobject.c b/Objects/weakrefobject.c
index 826f571..a404f29 100644
--- a/Objects/weakrefobject.c
+++ b/Objects/weakrefobject.c
@@ -57,6 +57,9 @@
PyWeakref_GET_OBJECT(self));
if (*list == self)
+ /* If 'self' is the end of the list (and thus self->wr_next == NULL)
+ then the weakref list itself (and thus the value of *list) will
+ end up being set to NULL. */
*list = self->wr_next;
self->wr_object = Py_None;
if (self->wr_prev != NULL)