[issue40696] exception chain cycles cause hangs (was "Exception handling with "await" can hang in Python3.9.0b1")

[Chris Jerdonek]

Chris Jerdonek <chris.jerdonek at gmail.com> added the comment:

Good to hear, Mariusz! And thanks for the report!

Also, as discussed above, I'm leaving this issue open (and retitling) until the following more general issue is fixed:

try:
    raise RuntimeError
except Exception as exc:
    print(f'handling: {exc!r}')
    exc.__context__ = exc
    raise ValueError  # hangs

As I mentioned above, I believe this is because _PyErr_SetObject() only checks for cycles that involve the exception being raised. In this case, the cycle involves the exception one further down:
ValueError -> RuntimeError -> RuntimeError -> RuntimeError -> ...

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title: Exception handling with "await" can hang in Python3.9.0b1 -> exception chain cycles cause hangs  (was "Exception handling with "await" can hang in Python3.9.0b1")

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue40696>
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