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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Failed assertion in `Python/legacy_tracing.c:431` on a free-threading build","articleBody":"# Crash report\n\n### What happened?\n\nIt's possible to cause an abort on `!_PyMem_IsPtrFreed(tstate)` while running with `PYTHON_GIL=0` by calling the following code:\n```python\nimport threading\n\ndef errback(*args, **kw):\n    raise ValueError('error')\n\nfor x in range(200):\n    threading._start_joinable_thread(errback)\n    try:\n        threading.setprofile_all_threads(\"\")\n    except:\n        pass\n```\nAbort message:\n```\npython: Python/legacy_tracing.c:431: is_tstate_valid: Assertion `!_PyMem_IsPtrFreed(tstate)' failed.\nAborted\n```\nNot sure this isn't an expected failure mode.\nFound using [fusil](https://github.com/devdanzin/fusil) by @vstinner.\n\n### CPython versions tested on:\n\n3.13, 3.14, CPython main branch\n\n### Operating systems tested on:\n\nLinux\n\n### Output from running 'python -VV' on the command line:\n\nPython 3.14.0a2+ experimental free-threading build (heads/main-dirty:a13e94d84bf, Nov 23 2024, 07:16:19) [GCC 11.4.0]","author":{"url":"https://github.com/devdanzin","@type":"Person","name":"devdanzin"},"datePublished":"2024-11-24T18:51:30.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":10},"url":"https://github.com/127235/cpython/issues/127235"}