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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Type object's ob_type does not get set when tp_bases is set before PyType_Ready","articleBody":"\u003c!--\r\n  If you're new to Python and you're not sure whether what you're experiencing is a bug, the CPython issue tracker is not\r\n  the right place to seek help. Consider the following options instead:\r\n\r\n  - reading the Python tutorial: https://docs.python.org/3/tutorial/\r\n  - posting in the \"Users\" category on discuss.python.org: https://discuss.python.org/c/users/7\r\n  - emailing the Python-list mailing list: https://mail.python.org/mailman/listinfo/python-list\r\n  - searching our issue tracker (https://github.com/python/cpython/issues) to see if\r\n    your problem has already been reported\r\n--\u003e\r\n\r\n# Bug report\r\n\r\nThis came up while testing numpy on 3.12. A bug report has been filed on numpy/numpy#23766. It's happening due to #103912, which introduced [an additional check for `tp_bases` not being NULL](https://github.com/python/cpython/blob/cfa517d5a68bae24cbe8d9fe6b8e0d4935e507d2/Objects/typeobject.c#L6977) in `type_ready_set_bases`, which is called from `PyType_Ready`.\r\n\r\nnumpy sets `tp_bases` manually before calling `PyType_Ready`, which means that the afore-mentioned check succeeds, and so, [the line that sets `ob_type`](https://github.com/python/cpython/blob/cfa517d5a68bae24cbe8d9fe6b8e0d4935e507d2/Objects/typeobject.c#L7012) does not get executed (it used to before #103912), which leads to a segmentation fault [later on, when trying to set `mro`](https://github.com/python/cpython/blob/cfa517d5a68bae24cbe8d9fe6b8e0d4935e507d2/Objects/typeobject.c#L2152).\r\n\r\nThis looks like a bug, but I'm not sure whether that's expected and numpy should be adjusted. If the latter is true, should a note be added in the `What's new` document?\r\n\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-105122\n* gh-105211\n* gh-105225\n* gh-105248\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/lysnikolaou","@type":"Person","name":"lysnikolaou"},"datePublished":"2023-05-18T15:50:50.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":14},"url":"https://github.com/104614/cpython/issues/104614"}