[Python-Dev] weak refs in descriptors (http://bugs.python.org/issue17950)

Joao S. O. Bueno jsbueno at python.org.br
Mon May 13 15:35:00 CEST 2013

On 13 May 2013 10:20, Maciej Fijalkowski <fijall at gmail.com> wrote:
> On Mon, May 13, 2013 at 1:49 PM, Kristján Valur Jónsson
> <kristjan at ccpgames.com> wrote:
>> Hello python-dev.
>> I‘m working on a patch to remove reference cycles from heap-allocated
>> classes:  http://bugs.python.org/issue17950
>> Part of the patch involves making sure that descriptors in the class
>> dictionary don’t contain strong references to the class itself.
>> This is item 2) in the defect description.
>> I have implemented this via weak references and hit no issues at all when
>> running the test suite.
>> But I’d like to ask the oracle if there is anything I may be overlooking
>> with this approach?  Any hidden problems we might encounter?
>> K
> Hi Kristjan
> The strong reference there is a feature. Descriptors keep the class
> alive if somehow the class disappears and the descriptor itself does
> not. Please don't change language semantics (yes, this is a change in
> semantics), just because the test suite passes - I can assure you
> there are people doing convoluted stuff that expect this to work.
+1 for it being an expected behavior.

So I think it would be a nice thing to write a test that breaks under
this condition


> Cheers,
> fijal
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