gh-142606: Fix extra NULL arguments passed to PyObject_CallFunction #142607
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This PR fixes incorrect calls to PyObject_CallFunction where an extra NULL argument was passed despite the format string already specifying the complete argument list. PyObject_CallFunction does not use a NULL terminator; it relies solely on the format string to determine how many arguments to read. Providing more arguments than required results in undefined behavior due to va_list misalignment. The affected calls: - PyImport_Import() — "OOOOi" was given 6 arguments instead of 5 - deque_copy() — "Oi" was given 3 arguments instead of 2 Both have been corrected by removing the superfluous NULL. No functional changes beyond fixing the API misuse. Signed-off-by: Yongtao Huang <[email protected]>
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Dec 12, 2025
Misc/NEWS.d/next/Library/2025-12-11-23-57-20.gh-issue-142606.Xd3xTx.rst
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…d3xTx.rst Co-authored-by: AN Long <[email protected]>
Misc/NEWS.d/next/Library/2025-12-11-23-57-20.gh-issue-142606.Xd3xTx.rst
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I don't think this is undefined behaviour. Could you give an example where this breaks, or clarify where a C standard disallows unused varargs? |
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Agree, sorry for that. Close it. |
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This PR fixes incorrect calls to PyObject_CallFunction where an extra NULL argument was passed despite the format string already specifying the complete argument list.
PyObject_CallFunction does not use a NULL terminator; it relies solely on the format string to determine how many arguments to read. Providing more arguments than required results in undefined behavior due to va_list misalignment.
The affected calls:
Both have been corrected by removing the superfluous NULL. No functional changes beyond fixing the API misuse.