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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"genericaliasobject.c: Two NULL dereference bugs","articleBody":"# Bug report\n\n### Bug description:\n\nParent: https://github.com/python/cpython/issues/146102\n\nhttps://gist.github.com/devdanzin/266ca45099796a2373866a07447d5ebf\n\n\n## Summary\n\n1. `ga_vectorcall` (line 653): `PyVectorcall_Function(alias-\u003eorigin)` can return NULL, immediately called as function pointer → segfault.\n2. `_Py_make_parameters` (line 243-245): After `_PyTuple_Resize` fails, `parameters` is NULL but `Py_DECREF(parameters)` is called → crash.\n\n## Fix\n\n1. Add NULL check and fallback to `PyObject_Vectorcall`.\n2. Change `Py_DECREF(parameters)` to `Py_XDECREF(parameters)` at line 245.\n\n### CPython versions tested on:\n\nCPython main branch\n\n### Operating systems tested on:\n\n_No response_\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-148226\n* gh-148705\n* gh-148712\n* gh-148717\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/prakashsellathurai","@type":"Person","name":"prakashsellathurai"},"datePublished":"2026-04-07T14:40:26.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":0},"url":"https://github.com/148222/cpython/issues/148222"}