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Author vstinner
Recipients Mark.Shannon, vstinner
Date 2022-01-12.15:33:01
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <>
C extensions written for Python 3.10 and older which access directly to the PyFrameObject.f_back member build successfully on Python 3.11, but they can fail because f_back must not be read directly. f_back can be NULL even if the frame has an outer frame.

PyFrame_GetBack(PyFrameObject *frame)
    assert(frame != NULL);
    PyFrameObject *back = frame->f_back;
    if (back == NULL && frame->f_frame->previous != NULL) {
        back = _PyFrame_GetFrameObject(frame->f_frame->previous);
    return back;

I suggest to remove or "hide" this member from the structure. For example, rename "f_back" to "_f_back" to advice developers to not access it directly.

See also bpo-46355: Document PyFrameObject and PyThreadState changes.
Date User Action Args
2022-01-12 15:33:01vstinnersetrecipients: + vstinner, Mark.Shannon
2022-01-12 15:33:01vstinnersetmessageid: <>
2022-01-12 15:33:01vstinnerlinkissue46356 messages
2022-01-12 15:33:01vstinnercreate