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[3.15] gh-159739: Keep the instance type alive during ABC subclass checks (GH-160198) - #160489
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JelleZijlstra merged 1 commit intoOct 24, 2026
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…ass checks (pythonGH-160198) When an instance advertises a __class__ different from its actual type, ABCMeta.__instancecheck__ performs two subclass checks. The first callback can change the instance's actual type and allow its old type to be collected before the second check, causing a crash. Keep the original type alive through both checks. Backport to 3.15 and 3.14. (cherry picked from commit dcbc453) Co-authored-by: Jelle Zijlstra <jelle@openai.com>
This was referenced Oct 23, 2026
JelleZijlstra
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October 23, 2026 20:35
JelleZijlstra
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October 24, 2026 20:44
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When an instance advertises a class different from its actual type, ABCMeta.instancecheck performs two subclass checks. The first callback can change the instance's actual type and allow its old type to be collected before the second check, causing a crash. Keep the original type alive through both checks. Backport to 3.15 and 3.14.
(cherry picked from commit dcbc453)
Co-authored-by: Jelle Zijlstra jelle@openai.com
Backport of #160198 to 3.15.
Carry over the subclass-callback lifetime fix and its regression test, adapting the test imports to the release branch.
Ran
test_abcon a 3.15 build.