René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"incompatible behaviour between 3.12.0rc1 and previous versions in ctypes","articleBody":"\u003c!--\r\n  New to Python? The issue tracker isn't the right place to get help.\r\n  Consider instead:\r\n\r\n  - reading the Python tutorial: https://docs.python.org/3/tutorial/\r\n  - posting at https://discuss.python.org/c/users/7\r\n  - emailing https://mail.python.org/mailman/listinfo/python-list\r\n--\u003e\r\n\r\n# Bug report\r\nTesting out 3.12.0rc1 on NumPy, we came across numpy/numpy#24399. I have distilled this down to a reproducer that fails on 3.12.0rc1, but passes on previous versions.\r\n## Checklist\r\n\r\n\u003c!-- Bugs in third-party projects (e.g. `requests`) do not belong in the CPython issue tracker --\u003e\r\n\r\n- [x] I am confident this is a bug in CPython, not a bug in a third-party project\r\n- [x] I have searched the CPython issue tracker, and am confident this bug has not been reported before\r\n\r\n## A clear and concise description of the bug\r\n\r\n```py\r\nfrom ctypes import Structure, pointer, c_int16, cast, POINTER\r\n\r\nclass Struct(Structure):\r\n    _fields_ = [('a', c_int16)]\r\n\r\nStruct3 = 3 * Struct\r\n\r\nc_array = (2 * Struct3)(\r\n    Struct3(Struct(a=1), Struct(a=2), Struct(a=3)),\r\n    Struct3(Struct(a=4), Struct(a=5), Struct(a=6))\r\n)\r\n\r\nassert c_array[0][0].a == 1\r\n\r\np_obj = cast(pointer(c_array), POINTER(pointer(c_array)._type_))\r\nobj = p_obj.contents\r\n# Works on 3.12, obj is 2d\r\nassert obj[0][0].a == 1\r\n\r\np_obj = cast(pointer(c_array[0]), POINTER(pointer(c_array)._type_))\r\nobj = p_obj.contents\r\n# Fails on 3.12.0rc1, but works on 3.11 and earlier: obj is not 2d\r\nassert obj[0][0].a == 1\r\n\r\n```\r\n\r\n\r\n\r\n# Your environment\r\n\r\n\u003c!-- Include all relevant details about the environment you experienced the bug in --\u003e\r\n\r\n- CPython versions tested on: 3.12rc1\r\n- Operating system and architecture: ubuntu 22.04\r\n\r\n\u003c!--\r\nYou can freely edit this form. Remove any lines you believe are unnecessary.\r\n--\u003e\r\n\r\nEdit: 3.12rc1 -\u003e 3.12.0rc1\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-108222\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/mattip","@type":"Person","name":"mattip"},"datePublished":"2023-08-14T12:37:01.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":9},"url":"https://github.com/107940/cpython/issues/107940"}