René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Segfault on frame.f_back when frame is created with PyFrame_New()","articleBody":"Python segfaults when frame.f_back is accessed on a frame created with PyFrame_New() c api. Calling the PyFrame_GetBack() c api also segfaults, at least in debug builds and on win32 (it depends on the contents of uninitialized memory). Tested with 3.11.0 and git 3.11 branch as of Nov 4, 2022\r\n\r\nCause is that the -\u003eprevious field of the _PyInterpreterFrame is never set to NULL and when PyFrame_GetBack() runs, it tries to dereference the pointer value of -\u003eprevious and segfaults. A test case using ctypes is attached.\r\n\r\nAdding a frame-\u003eprevious = NULL; line to init_frame() in frameobject.c fixes this, though I don't know if it's the best place for it.\r\n\r\n[f_back_segfault.py.txt](https://github.com/python/cpython/files/9942212/f_back_segfault.py.txt)\r\n\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-100182\n* gh-100478\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/jpe","@type":"Person","name":"jpe"},"datePublished":"2022-11-04T22:01:16.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":7},"url":"https://github.com/99110/cpython/issues/99110"}