[Stackless] exceptions.TypeError: arg 5 (closure) expected cell, found stackless._wrap.cell when unpickling stackless thread

Richard Tew richard.m.tew at gmail.com
Fri Oct 9 20:21:28 CEST 2009

On Fri, Oct 9, 2009 at 10:38 PM, Crispin Wellington
<retrogradeorbit at gmail.com> wrote:
> I have written a server that contains stackless threads. When the server
> shuts down these threads are serialised to disk. This all happens without
> incident and I end up with a reasonably sized file per pickled object.
> When I go to deserialise them I hit a problem. I get this...
> -------------------
>       File
> "/home/cwellington/Development/yabi/yabi-be-twisted/trunk/TaskManager/Tasklets.py",
> line 54, in load
>         task = pickle.loads(data)
>       File "/usr/local/stackless/lib/python2.6/pickle.py", line 1415, in
> loads
>         return Unpickler(file).load()
>       File "/usr/local/stackless/lib/python2.6/pickle.py", line 898, in load
>         dispatch[key](self)
>       File "/usr/local/stackless/lib/python2.6/pickle.py", line 1258, in
> load_build
>         setstate(state)
>     exceptions.TypeError: arg 5 (closure) expected cell, found
> stackless._wrap.cell
> --------------------
> I think this might be a bug. The arguments are being passed back into the
> constructor of the stackless._wrap.function and the constructor is throwing
> that exception. So in essence, the __reduce__ or __reduce_ex__ functions are
> creating instatiation values that do not work on reinstantiation.
> I changed pickle.py to print out some debug. setstate is... <built-in method
> __setstate__ of stackless._wrap.function object at 0x21ca0c8> and (state)[4]
> is... (<cell at 0x2605f30: empty>, <cell at 0x2940718: list object at
> 0x259f518>, <cell at 0x2940670: str object at 0x2940768>, <cell at
> 0x2940750: str object at 0x29407d8>, <cell at 0x29407c0: int object at
> 0x25cd338>)
> These all seem to be "cell" objects. Why aren't they (stackless._wrap.cell)
> recognised as "cells"?
> I can provide a pickletools.dis() dump of the pickle stream if wanted.
> Using Stackless Python 2.6.2 on 64 bit linux (x86_64).
> Can anybody help me decode my objects? or even find a way to encode them so
> the are decodable? Is this a bug, or am I doing it wrong?

It definitely looks like a bug.  If you can provide the smallest
possible reproduction case, it would help us look into it and we could
add it to the test suite as a regression test.

If you want your objects back in the meantime, you might try compiling
2.6 with the relevant code raising these errors commented out.


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