[Patches] [ python-Patches-954922 ] Fix for 754449: hiding exc in threading during interp shutdn

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Patches item #954922, was opened at 2004-05-16 14:43
Message generated for change (Comment added) made by tim_one
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Category: Library (Lib)
Group: Python 2.4
Status: Open
Resolution: None
Priority: 5
Submitted By: Brett Cannon (bcannon)
Assigned to: Nobody/Anonymous (nobody)
Summary: Fix for 754449: hiding exc in threading during interp shutdn

Initial Comment:
Decided to start a fresh tracker item for this patch since I already 
attempted to close bug 754449 once before and I want to make 
sure the two fixes stay separate.

Someone emailed me a program whose testing suite could reliably 
reproduce the problem as reported in the bug report (for a quck 
refresher, basically if someone leaves a threading.Thread instance 
running while the interpreter is being shutdown and an exception is 
raised in the thread then that exception will cause  *another* 
exception in the subsequent attempt to report the exception from 
the thread because all globals have been set to None at that point).  
The previous fix that I checked in turned out not to be thorough 
enough (still needed, though).  I am currently waiting for the 
person who emailed me the triggering code to let me know if I can 
publish how to cause the error.

Attached is a patch to remove all instances of accessing globals 
(just as if I was writing a __del__ method for threading.Thread) by 
storing copies of sys.stderr, sys.exc_info, and sys.tracebacklimit.  
All of this is so that a decent approximation of a traceback print-
out can occur without having to call the 'traceback' module since its 
functions depend a lot on each other.

I mainly need someone else who is more familiar with dealing with 
tracebacks to make sure that I have not done something stupid and 
to make sure this is the best way to handle things.

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>Comment By: Tim Peters (tim_one)
Date: 2004-07-01 23:04

Message:
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Brett, it looks like self.__stderr is never given a value -- the 
__init__ code here binds a *local* vrbl __stderr to 
_sys.stderr.  If so, that tells me the bulk of the patch hasn't 
actually been exercised (else it would have raised 
AttributeError trying to print to self.__stderr).

To simplify it more, I think it would be fine to ignore 
sys.tracebacklimit.  A Google search shows that virtually the 
only use of sys.tracebacklimit in real life is the use made of it 
here:  passively accessing its value to simulate what it would 
have done if anyone had ever bothered to set it (of which I 
couldn't find even one example).

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Comment By: Brett Cannon (bcannon)
Date: 2004-07-01 00:33

Message:
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Uploading a new version of the patch to store one of the variables in the 
class instead of the instance since it it never expected to change.  Also 
changed the comment.

Still waiting for someone else to take a look at this code before I check it 
in.

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Comment By: Brett Cannon (bcannon)
Date: 2004-05-17 00:37

Message:
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Just posted how to reproduce the bug using the in-dev version of mnet as 
a post to the bug tracker item.

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https://sourceforge.net/tracker/?func=detail&atid=305470&aid=954922&group_id=5470