[New-bugs-announce] [issue31416] assertion failures in warn_explicit() in case of a bad warnings.filters or warnings.defaultaction

[Oren Milman]

New submission from Oren Milman:

The following code causes an assertion failure in warn_explicit() (in
Python/_warnings.c):

import warnings
warnings.filters = [(None, None, Warning, None, 0)]
warnings.warn_explicit(message='foo', category=Warning, filename='bar',
                       lineno=1)

this is because warn_explicit() assumes that get_filter() returned a string,
and passes the return value (of get_filter()) to _PyUnicode_EqualToASCIIString(),
which asserts it received a string.


In addition, get_filter() might return warnings.defaultaction, and so the
following code also causes an assertion failure in warn_explicit():

import warnings
warnings.defaultaction = None
warnings.filters = []
warnings.warn_explicit(message='foo', category=Warning, filename='bar',
                       lineno=1)

----------
components: Extension Modules
messages: 301867
nosy: Oren Milman
priority: normal
severity: normal
status: open
title: assertion failures in warn_explicit() in case of a bad warnings.filters or warnings.defaultaction
type: crash
versions: Python 3.7

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue31416>
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