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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Data race in `functools.partial` in Python 3.14","articleBody":"# Bug report\n\nSeen by @ngoldbaum in NumPy in https://github.com/numpy/numpy/pull/30653#issuecomment-3755762506\n\n```\nWARNING: ThreadSanitizer: data race (pid=15392)\n  Read of size 8 at 0x00010b6de6f8 by thread T325:\n    #0 object_vacall call.c:820 (libpython3.14t.dylib:arm64+0x8e0f4)\n    #1 PyObject_CallFunctionObjArgs call.c:927 (libpython3.14t.dylib:arm64+0x8e49c)\n    #2 array_str \u003cnull\u003e (_multiarray_umath.cpython-314t-darwin.so:arm64+0x254dd8)\n    #3 PyObject_Str object.c:822 (libpython3.14t.dylib:arm64+0x13834c)\n...\n\n  Previous write of size 8 at 0x00010b6de6f8 by thread T327:\n    #0 partial_vectorcall_fallback _functoolsmodule.c:378 (libpython3.14t.dylib:arm64+0x424f94)\n    #1 partial_vectorcall _functoolsmodule.c:393 (libpython3.14t.dylib:arm64+0x4248dc)\n    #2 object_vacall call.c:820 (libpython3.14t.dylib:arm64+0x8e110)\n    #3 PyObject_CallFunctionObjArgs call.c:927 (libpython3.14t.dylib:arm64+0x8e49c)\n```\n\nThe relevant code is:\n\nhttps://github.com/python/cpython/blob/1241432150f6342e3d38c5a80a19c8c157a4ebe8/Modules/_functoolsmodule.c#L373-L381\n\nThe assignemnt `pto-\u003evectorcall = NULL` leads to a data race in the free threading build.\n\nThis is fixed in main. We should fix it in 3.14 by guarding that assignment with an `#ifndef Py_GIL_DISABLED`\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-143882\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/colesbury","@type":"Person","name":"colesbury"},"datePublished":"2026-01-15T18:01:50.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/143880/cpython/issues/143880"}