[issue17936] O(n**2) behaviour when adding/removing classes

[Antoine Pitrou]

Antoine Pitrou added the comment:

I think the logic is slightly wrong in remove_subclass. When you encounter Py_None, you can't be sure it's the weakref for the current type; theoretically, it could be any other one (depending on oddities in cleanup order, cycle collection, etc.). So you have to continue walking the list.

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Python tracker <report at bugs.python.org>
<http://bugs.python.org/issue17936>
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