Author vstinner
Recipients ned.deily, vstinner, yselivanov
Date 2018-06-07.23:44:54
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Message-id <1528415094.5.0.592728768989.issue33803@psf.upfronthosting.co.za>
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test_asyncio started to crash in https://github.com/python/cpython/pull/7487

I debugged the crash with Yury: _PyHAMT_New() triggers indirectly a GC collection at "o->h_root = hamt_node_bitmap_new(0);". Problem: the object that is being created is already tracked by the GC, whereas its h_root field is not set. Then the GC does crash because the field is a random pointer.

hamt_alloc() must initialize h_root and h_count before tracking the object in the GC.

Thinking about the GC when writing an object constructor is hard :-(

Maybe we should add a debug option to trigger the GC more often to make such random bug more likely. contextvars has been implemented a few months ago, and we only spotted the bug a few days before Python 3.7.0 final release...
History
Date User Action Args
2018-06-07 23:44:54vstinnersetrecipients: + vstinner, ned.deily, yselivanov
2018-06-07 23:44:54vstinnersetmessageid: <1528415094.5.0.592728768989.issue33803@psf.upfronthosting.co.za>
2018-06-07 23:44:54vstinnerlinkissue33803 messages
2018-06-07 23:44:54vstinnercreate