[issue38006] Crash in remove() weak reference callback of weakref.WeakValueDictionary at Python exit

[STINNER Victor]

STINNER Victor <vstinner at python.org> added the comment:

> Is the behavior of tp_clear the key to this bug?

Once func_clear(my_func) is called, calling my_func() will crash: my_func() is unsuable.

Because of a complex dance involving borrowed references, the function is called *after* it's cleared.

Pablo's PR 15645 works around the problem by detecting this very specific case: call a function "after it's cleared" (while it's being garbage collected in practice).

Honestly, I'm still not sure how *exactly* the bug is triggered. I tried but failed to reproduce the initial cffi crash. reproducer.tar.gz is still a giant piece of code. I failed to simplify it to a few objects.

According to Pablo, gc_crash.py is a *different* (but similar) bug.

I would only be confident in approving a fix once I would be confident that I understood *exactly* how the initial bug (reproducer.tar.gz) occurred.

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue38006>
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