New submission from Min RK:
PyImport_GetModuleDict: no module dictionary! can be raised during interpreter
shutdown if a `__del__` method results in a warning. This only happens on
Python 3.5.
The prompting case is IPython 4.0.2 and traitlets 4.1.0. An IPython
ExtensionManager calls `self.shell.on_trait_change` during its `__del__` to
unregister a listener. That `on_trait_change` method is deprecated, and tries
to display a DeprecationWarning. The call to `warnings.warn results in:
Fatal Python error: PyImport_GetModuleDict: no module dictionary!
There appear to be races involved, because the crash happens with inconsistent
frequency, sometimes quite rarely.
I've tried to put together a simple minimal test case, but I cannot reproduce
the crash outside of IPython. I can, however, reproduce inconsistent behavior
where a UserWarning displayed during `__del__` sometimes fails with
ImportError: import of 'linecache' halted; None in sys.modules
and sometimes the exact same code succeeds, showing the error:
~/dev/tmp/del-warn/a.py:9: DeprecationWarning: I don't cleanup anymore
self.b.cleanup()
and sometimes it shows the warning but not the frame
~/dev/tmp/del-warn/a.py:9: DeprecationWarning: I don't cleanup anymore
----------
components: Interpreter Core
messages: 258586
nosy: minrk
priority: normal
severity: normal
status: open
title: PyImport_GetModuleDict: no module dictionary! when `__del__` triggers a
warning
type: crash
versions: Python 3.5
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Python tracker <[email protected]>
<http://bugs.python.org/issue26153>
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