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

[Serhiy Storchaka]

Serhiy Storchaka <storchaka+cpython at gmail.com> added the comment:

In issue25782 two different solutions for general problem was proposed.

    When trying to raise the exception H,
        F -> G -> H -> I -> NULL
    with Yury's patch you would get
        H -> NULL
    and with my path you would get
        H -> F -> G -> I -> NULL

The issue was closed because we did not have realistic example when raising exception from the __context__ list would be reasonable and the more concrete original issue was fixed in other way. Now we have other example of creating cycles with __context__, so we can reopen yhat issue and decide what solution is better.

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