[Python-Dev] Debugging opportunity :-) (original) (raw)

Thomas Wouters thomas at python.org
Sat Apr 15 01:11:42 CEST 2006

On 4/15/06, Thomas Wouters <thomas at python.org> wrote:

(I first thought the problem was caused by gendealloc doing 'PyDECREF(gen->genframe)' instead of 'frame = gen->genframe; gen->genframe = NULL; PyDECREF(frame)', but that isn't the case. It should do it that way, I believe, but it's not the cause of this crash.)

fixes the crash.Ah, found the problem. After I hit 'send', I realized I hadn't checked frameobject's tp_clear, and sure enough, it calls Py_XDECREF in-place. That explains why the first generator object gets dealloced twice, although it doesn't explain why it doesn't blow up when it reaches a negative refcount. Fixing frameobject and genobject to both use Py_CLEAR() makes both the 'minimal' testcase and test_generators work. Your testcase also stops leaking, but alas, test_generators still leaks 255 references..... WTF-time for me, meaning I hit the sack and not think about it until next week :)

I'll upload a patch to Tim's bugreport after I remove my debugging cruft. All tp_clear/tp_traverse methods should really always use Py_CLEAR/Py_VISIT. I guess revisiting all tp_clear and tp_traverse methods is well worth putting on the TODO list,

Bad-pun'ly y'rs,

Thomas Wouters <thomas at python.org>

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