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[3.14] gh-159739: Keep generic alias arguments alive while formatting errors (GH-159981) - #160021
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…errors (pythonGH-159981) When a generic alias contains a list of parameters and an object claiming to be an unpacked type-variable tuple returns a non-tuple from `__typing_subst__`, the error path frees the temporary argument tuple before reading it to format a `TypeError`. That use-after-free can crash the interpreter instead of reporting the invalid substitution. (cherry picked from commit 9c649db) Co-authored-by: Jelle Zijlstra <jelle@openai.com>
This was referenced Oct 21, 2026
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When a generic alias contains a list of parameters and an object claiming to be an unpacked type-variable tuple returns a non-tuple from
__typing_subst__, the error path frees the temporary argument tuple before reading it to format aTypeError. That use-after-free can crash the interpreter instead of reporting the invalid substitution.(cherry picked from commit 9c649db)
Co-authored-by: Jelle Zijlstra jelle@openai.com