New submission from Jeroen Demeyer <j.deme...@ugent.be>:
When designing an extension type subclassing an existing type, it makes sense to call the tp_dealloc of the base class from the tp_dealloc of the subclass. Now suppose that I'm subclassing "list" which uses the trashcan mechanism. Then it can happen that the tp_dealloc of list puts this object in the trashcan, even though the tp_dealloc of the subclass has already been called. Then the tp_dealloc of the subclass may be called multiple times, which is unsafe (tp_dealloc is expected to be called exactly once). To solve this, the trashcan mechanism should be disabled when tp_dealloc is called from a subclass. Interestingly, subtype_dealloc also solves this in a much more involved way (see the "Q. Why the bizarre (net-zero) manipulation of _PyRuntime.trash_delete_nesting around the trashcan macros?") in Objects/typeobject.c ---------- components: Interpreter Core messages: 335405 nosy: jdemeyer, pitrou, scoder priority: normal severity: normal status: open title: tp_dealloc trashcan shouldn't be called for subclasses versions: Python 2.7, Python 3.7, Python 3.8 _______________________________________ Python tracker <rep...@bugs.python.org> <https://bugs.python.org/issue35983> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
