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Jul 1, 2009, 8:46 AM
Post #2 of 4
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[issue6395] Add Pickle Support to the codecs Module
[In reply to]
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New submission from ThomasH <thomas.bugzilla [at] gmx>:
I recently ran into an infinite recursion trying to unpickle a
codecs.StreamWriter object (I presume the issue would be the same for a
StreamReader).
Here is the end of the stack trace:
File "/sw/lib/python2.5/codecs.py", line 330, in __getattr__
return getattr(self.stream, name)
File "/sw/lib/python2.5/codecs.py", line 330, in __getattr__
return getattr(self.stream, name)
File "/sw/lib/python2.5/codecs.py", line 330, in __getattr__
return getattr(self.stream, name)
RuntimeError: maximum recursion depth exceeded
The issue is the same under Python2.6 but the error output has changed
(see http://bugs.python.org/issue5508).
The problem is that the codecs module tries to delegate member lookup to
the underlying stream. But after unpickling, "self.stream" is not
defined, so the reference to self.stream in __getattr__ itself leads to
an invocation of __getattr__ - hence the recursion loop.
Using tools from the Pickle protocol, like __getstate__/__setstate__,
could help degrade codecs objects gracefully during pickle/unpickle
cycles. E.g. it might be enough to provide a dummy self.stream through
__setstate__.
----------
components: Library (Lib)
messages: 89985
nosy: ThomasH
severity: normal
status: open
title: Add Pickle Support to the codecs Module
type: crash
versions: Python 2.5, Python 2.6
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<http://bugs.python.org/issue6395>
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