Mark Dickinson <[email protected]> added the comment:
Here's a cut-down example, at the prompt:
Python 3.9.2 (default, Mar 31 2021, 05:47:22)
[Clang 11.0.3 (clang-1103.0.32.62)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import signal
>>> class App: pass
...
>>> def create_app():
... app = App()
... signal.signal(signal.SIGINT, signal.SIG_DFL)
...
>>> create_app()
At this point, since the App() instance was local to create_app, and wasn't
returned, I'd expect there to be no App objects alive in the system. But it
turns out there's still an App object being kept alive:
>>> import gc
>>> [obj for obj in gc.get_objects() if type(obj) is App]
[<__main__.App object at 0x10acb3d90>]
The cause is a call to _int_to_enum in signal.py which attempts to coerce the
default signal handler to an element of Handlers. That coercion fails, leaving
an exception
ValueError('<built-in function default_int_handler> is not a valid Handlers')
The traceback on that exception leads to the frame containing the call to
Enum.__new__, which in turn contains a reference ve_exc back to the exception.
[In the real code, App was a wx.App object, and the App.__init__ method played
the role of create_app.]
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Python tracker <[email protected]>
<https://bugs.python.org/issue42248>
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