[New-bugs-announce] [issue42208] Using logging or warnings during Python finalization does crash Python

[STINNER Victor]

New submission from STINNER Victor <vstinner at python.org>:

If you apply attached logging.patch, Python crash using attached crash.py:

$ echo|./python -i crash.py
>>>
>>> 
python: Python/_warnings.c:872: setup_context: Assertion `globals != NULL' failed.
Abandon (core dumped)


Attached logging.patch is a fix for bpo-26789: logging.FileHandler keeps a reference to the builtin open() function.

Attached crash.py does crash because of an unclosed file. It happens after PyInterpreterState_Clear(), in finalize_interp_clear():

    /* Last explicit GC collection */
    _PyGC_CollectNoFail();

setup_context() of Python/_warings.c does crash because tstate->interp->sysdict is NULL at this point.

Moreover, _io.TextIOWrapper.__init__() fails to import the locale module (to call locale.getpreferredencoding(), since the encoding is None) and picks the "ascii" encoding.

Moreover, even if I work around all these issues, _warnings.showwarnings() logs "lost sys.stderr" into stderr because, again, tstate->interp->sysdict is NULL at this point (and so sys.stderr no longer exists).

It looks like a bug in finalize_interp_clear() which triggers a garbage collection, whereas Python is no longer usable.

--

The logging module does automatically close files at exit using:

   atexit.register(shutdown)

But crash.py, a new file is opened by a logging handler after logging.shutdown() is called. Maybe another problem is that the logging module does not clear logger handlers, or prevent handlers to log more message, after shutdown() is called.

----------
components: Interpreter Core
files: logging.patch
keywords: patch
messages: 379974
nosy: vstinner
priority: normal
severity: normal
status: open
title: Using logging or warnings during Python finalization does crash Python
versions: Python 3.10
Added file: https://bugs.python.org/file49553/logging.patch

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<https://bugs.python.org/issue42208>
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