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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"SIGSEGV with generators in free-threaded build","articleBody":"# Crash report\r\n\r\n### What happened?\r\n\r\nTrying to iterate on a generator from multiple threads under the free-threaded build results in a segmentation fault.\r\n\r\nHere is a minimal repro:\r\n```python\r\nimport concurrent.futures\r\n\r\n\r\ndef gen():\r\n    while True:\r\n        yield\r\n\r\n\r\nit = gen()\r\nwith concurrent.futures.ThreadPoolExecutor() as executor:\r\n    while True:\r\n        _ = executor.submit(lambda: next(it))\r\n```\r\n\r\nThe issue seems to be specific to generators as other kinds of iterators work well in parallel.\r\n\r\n### CPython versions tested on:\r\n\r\nCPython main branch\r\n\r\n### Operating systems tested on:\r\n\r\nLinux\r\n\r\n### Output from running 'python -VV' on the command line:\r\n\r\nPython 3.14.0a0 experimental free-threading build (heads/main:c3b6dbff2c, Jun 10 2024, 16:54:16) [GCC 11.4.0]\r\n\r\n\u003c!-- gh-linked-prs --\u003e\r\n### Linked PRs\r\n* gh-120327\r\n* gh-142599\n* gh-142995\n* gh-143022\n* gh-143112\n* gh-143128\n* gh-144291\n* gh-144292\n* gh-144409\n\u003c!-- /gh-linked-prs --\u003e\r\n","author":{"url":"https://github.com/rostan-t","@type":"Person","name":"rostan-t"},"datePublished":"2024-06-10T14:59:56.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":9},"url":"https://github.com/120321/cpython/issues/120321"}