On 15 June 2013 03:34, Antoine Pitrou <solip...@pitrou.net> wrote: > On Wed, 5 Jun 2013 09:10:54 -0700 > Benjamin Peterson <benja...@python.org> wrote: >> I (and Guido) are accepting PEP 442 (Safe object finalization) on the >> condition that finalizers are only ever called once globally. > > Ok, so there's an issue with that condition: it can't be upholded on > non-GC objects. Creating a non-GC object is quite obscure and rare, > though, since it requires basically a class with no __dict__ and an > empty __slots__: > > class C: > __slots__ = () > survivors = [] > > def __del__(self): > self.survivors.append(self) > > > In this case, a C instance's __del__ will be called every time > destruction is attempted, not only once. Is that a realistic problem?
So, to trigger that __del__() method a second time, such an object would have to be: 1. Defined in the first place (the use cases for stateless objects with destructors seem rare...) 2. Hanging off a reference cycle 3. Which then gets resurrected If it isn't easy to fix by changing the way such classes are constructed by typeobject.c (i.e. force them to be GC-aware when they define a __del__ method, since they may still be hanging off the edge of a reference cycle, even if they can't form one themselves), I'd say chalk it up as a CPython wart and not worry about it for now. As far as the test_subtype_resurrection failure goes, I think the associated comment says it all: "(On non-CPython implementations, however, __del__ is typically not called again.)" The test should just be rewritten to check that __del__ is only called once in the face of resurrection. Cheers, Nick. -- Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia _______________________________________________ Python-Dev mailing list Python-Dev@python.org http://mail.python.org/mailman/listinfo/python-dev Unsubscribe: http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
