Issue 3110: Crash with weakref subclass,
seen after a "import multiprocessing.reduction"
An instance of a weakref subclass can have attributes.
If such a weakref holds the only strong reference to the object,
deleting the weakref will delete the object. In this case,
the callback must not be called, because the ref object is being deleted!
Backport of r34309
diff --git a/Misc/NEWS b/Misc/NEWS
index cdc3f9c..27c12c1 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,9 @@
Core and builtins
-----------------
+- Issue #3100: Corrected a crash on deallocation of a subclassed weakref which
+ holds the last (strong) reference to its referent.
+
- Issue #1686386: Tuple's tp_repr did not take into account the possibility of
having a self-referential tuple, which is possible from C code. Nor did
object's tp_str consider that a type's tp_str could do something that could