New submission from Antoine Pitrou:
This is a tricky issue I'm sometimes seeing when running Numba's test suite,
and I can't seem to write a reproducer. Somtimes I'm seeing the following
messages:
Exception ignored in: <function
_OverloadedBase._make_finalizer.<locals>.finalizer at 0x7f1466487c80>
Traceback (most recent call last):
File "/home/antoine/numba/numba/dispatcher.py", line 59, in finalizer
if shutting_down():
NameError: free variable 'shutting_down' referenced before assignment in
enclosing scope
So what does it correspond to? The code is here:
https://github.com/numba/numba/blob/master/numba/dispatcher.py#L47
Basically, there's no way 'shutting_down' can be referenced before
assignment... except if it has been cleared. And the only thing which can clear
it here is the GC (namely, cell objects' tp_clear() method).
I'm not sure what the exact trigger for reproduction is. It does have to
feature a reference cycle involving the closure; perhaps the trashcan mechanism
comes into play as well. Also, the closure must be invoked on collection of
something in the cycle, so a weakref callback could be nice.
----------
messages: 225012
nosy: pitrou, tim.peters
priority: normal
severity: normal
status: open
title: cell object cleared too early?
versions: Python 3.4, Python 3.5
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Python tracker <rep...@bugs.python.org>
<http://bugs.python.org/issue22164>
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