On Sun, 04 Aug 2013 17:59:57 +0200 Stefan Behnel <stefan...@behnel.de> wrote: > > I continued my implementation and found that calling up the base type > > hierarchy is essentially the same code as calling up the hierarchy for > > tp_dealloc(), so that was easy to adapt to in Cython and is also more > > efficient than a generic loop (because it can usually benefit from > > inlining). So I'm personally ok with leaving the super type calling code to > > the user side, even though manual implementers may not be entirely happy. > > > > I think it should get explicitly documented how subtypes should deal with a > > tp_finalize() in (one of the) super types. It's not entirely trivial > > because the tp_finalize slot is not guaranteed to be filled for a super > > type IIUC, as opposed to tp_dealloc. I assume the recursive invariant that > > PyType_Ready() copies it would still hold, though.
Not only it could be NULL (if no upper type has a finalizer), but it could also not exist at all (if Py_TPFLAGS_HAVE_FINALIZE isn't in tp_flags). If an API is needed to make this easier then why not. But I'm not sure anyone else than Cython really has such concerns. Usually, the class hierarchy for C extension types is known at compile-time and therefore you know exactly which upper finalizers to call. > Hmm, it seems to me by now that the only safe way of handling this is to > let each tp_dealloc() level in the hierarchy call tp_finalize() through > PyObject_CallFinalizerFromDealloc(), instead of calling up the stack in > tp_finalize(). Otherwise, it's a bit fragile for arbitrary tp_dealloc() > functions in base types and subtypes. I'm not following you. Why is it "a bit fragile" to call the base tp_finalize from a derived tp_finalize? It should actually be totally safe, since tp_finalize is a regular function called in a safe environment (unlike tp_dealloc and tp_del). Regards Antoine. _______________________________________________ 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
