René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Missing Py_SetStackPointer call in LIST_APPEND","articleBody":"# Bug report\n\n### Bug description:\n\nIn a debug build:\n```python\nimport _testcapi\n_testcapi.set_nomemory(2)\nresult = [f'1{x}' for x in range(1)]\n```\n\n```\nAssertion failed: (tstate-\u003ecurrent_frame == NULL || tstate-\u003ecurrent_frame-\u003estackpointer != NULL), function _Py_Dealloc, file object.c, line 3298.\nfish: Job 1, './python.exe test.py' terminated by signal SIGABRT (Abort)\n```\n\n`LIST_APPEND` op calls `_PyList_AppendTakeRef` without setting the stack frame, `_PyList_AppendTakeRef` calls `_PyList_AppendTakeRefListResize` with a stolen ref to `newitem`.  If the list resize fails, then `newitem` is decref'd, which can cause a dealloc, which triggers the above assert on a debug build.\n\nUnless there is a performance impact, then I'm assuming this is just a case of calling Py_SetStackPointer at the appropriate point?\n\nPython 3.16.0a0 (heads/main-dirty:29a920e, Jun  9 2026, 00:36:55) [Clang 22.1.6 ]\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\nLinux\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-151538\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/stestagg","@type":"Person","name":"stestagg"},"datePublished":"2026-06-09T01:02:22.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/151119/cpython/issues/151119"}