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Our `all_instances_except_of_type` strategy sometimes yields class objects like `str`. When `test_from_rnc_input_bad_1` passes `str` to `RelaxNG.from_rnc_string`, rnc2rng makes an unbound `str.splitlines()` call with no arguments. That should just throw `TypeError` that’s caught by the test. But in CPython 3.11 and 3.12, the specialized `CALL` instructions for `METH_FASTCALL` methods like `str.splitlines` forgot to check for a missing `self` argument, so such a call may read past the end of the stack and segfault: python/cpython#131998 This seems to be the root cause for the uninvestigated Python 3.11/3.12 crash that motivated disabling the test in commit 8ecf09c. Prevent such crashes by excluding class objects from this strategy altogether on affected versions. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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This test was skipped in 8ecf09c due to an uninvestigated crash on Python 3.11 and 3.12, and later marked as an expected failure on GitHub Actions instead. The crash was CPython gh-131998, which the previous commit avoids by no longer passing class objects to the code under test. An expected failure marker couldn't have caught a segfault anyway, and would hide genuine failures of this test on GitHub. Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
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Owner
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Wow, million thanks for tracking it down, I always lacked the motivation to delve into rabbit hole myself. Just one small question though, does the problem only happens within GitHub actions? |
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No. It’s nondeterministic so there may be environmental factors that make it more or less likely, but I was able to reproduce the crash several times while running the tests locally. |
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Our
all_instances_except_of_typestrategy sometimes yields class objects likestr. Whentest_from_rnc_input_bad_1passesstrtoRelaxNG.from_rnc_string, rnc2rng makes an unboundstr.splitlines()call with no arguments. That should just throwTypeErrorthat’s caught by the test. But in CPython 3.11 and 3.12, the specializedCALLinstructions forMETH_FASTCALLmethods likestr.splitlinesforgot to check for a missingselfargument, so such a call may read past the end of the stack and segfault:This seems to be the root cause for the uninvestigated Python 3.11/3.12 crash that motivated disabling the test in commit 8ecf09c. Prevent such crashes by excluding class objects from this strategy altogether on affected versions.