[Python-Dev] [ 654866 ] pickle and cPickle not equivalent

[Patrick K. O'Brien]

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I'd like to call attention to a bug report I just submitted to SF 
concerning a potentially serious problem with the c-version of pickle.

In short, I think I discovered a situation where cPickle is not doing 
the right thing in terms of storing a reference to a previously pickled 
class instance (using Pickler, of course). It looks like its doing a 
put of a new instance, then a get of the original instances dictionary, 
rather than a get of the original instance. On the other hand, pickle 
does the right thing.

I think this is a pretty serious problem, but I'm out of my league when 
it comes to debugging the c-version of pickle. I'm also basing my 
assessment on a minimal understanding of the pickle source code 
combined with looking at two pickle files, one created using pickle, 
the other using cPickle, with no other changes to the program that 
produced them. I understand that cosmetic differences are to be 
expected. But the difference I see is more substantial.

I attached the two pickle files to the SF bug report, but I can't tell 
if they got through so I'm attaching them here as well. If anyone can 
help track this down, I'd really appreciate it. If more detail is 
needed, or a simple code example would help, I'll be happy to do that.

Thanks.

-- 
Patrick K. O'Brien
Orbtech      http://www.orbtech.com/web/pobrien
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"Your source for Python programming expertise."
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