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<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>This has been fixed in the stackless trunk, and merged into 2.6,
3.0, 3.1 and py3k in revisions 75377-75381<o:p></o:p></span></p>

<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>K<o:p></o:p></span></p>

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<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> stackless-bounces@stackless.com
[mailto:stackless-bounces@stackless.com] <b>On Behalf Of </b>Kristján Valur
Jónsson<br>
<b>Sent:</b> 12. október 2009 11:19<br>
<b>To:</b> Crispin Wellington; Richard Tew<br>
<b>Cc:</b> stackless@stackless.com<br>
<b>Subject:</b> Re: [Stackless] exceptions.TypeError: arg 5 (closure) expected
cell, found stackless._wrap.cell when unpickling stackless thread<o:p></o:p></span></p>

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<p class=MsoNormal><o:p>&nbsp;</o:p></p>

<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Ok, I understand the issue.<o:p></o:p></span></p>

<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Cell objects potentially can be part in a cycle.&nbsp; Therefore
for pickling, the three argument __reduce__ protocol is used, with an initial
&#8218;new&#8216;, followed by a &#8218;setstate&#8216; later.<o:p></o:p></span></p>

<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>Only in the &#8218;setstate&#8216; call will the type of the
object be changed from the special &#8222;_wrap&#8220; type.&nbsp; But
precisely because a reference cycle is being constructed, a fresh cell is being
inserted into a function, before having had its state set, and the function
constructor balks at this.<o:p></o:p></span></p>

<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>I see no way around this using the current wrapped pickle
technique except to fix the test in the function object.&nbsp; Once I have
created a simple regression test, I will submit a fix.<o:p></o:p></span></p>

<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p>&nbsp;</o:p></span></p>

<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'>K<o:p></o:p></span></p>

<p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";
color:#1F497D'><o:p>&nbsp;</o:p></span></p>

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<p class=MsoNormal><b><span lang=EN-US style='font-size:10.0pt;font-family:
"Tahoma","sans-serif"'>From:</span></b><span lang=EN-US style='font-size:10.0pt;
font-family:"Tahoma","sans-serif"'> stackless-bounces@stackless.com
[mailto:stackless-bounces@stackless.com] <b>On Behalf Of </b>Crispin Wellington<br>
<b>Sent:</b> 12. október 2009 05:27<br>
<b>To:</b> Richard Tew<br>
<b>Cc:</b> stackless@stackless.com<br>
<b>Subject:</b> Re: [Stackless] exceptions.TypeError: arg 5 (closure) expected
cell, found stackless._wrap.cell when unpickling stackless thread<o:p></o:p></span></p>

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<p class=MsoNormal><o:p>&nbsp;</o:p></p>

<p class=MsoNormal style='margin-bottom:12.0pt'>OK. I boiled down the code to a
small snippet that triggers the bug. It is a bug that is exposed through my use
of Twisted. If i create a factory, and then two callbacks that are closures,
each callback setting thread level variables. Then I add the callbacks to the
factory's deferred, and then I sleep the threadlet forever.<br>
<br>
Initiate the tasklet, pickle it, then unpickle it, and BAM, you have your
error:<br>
<br>
$ /usr/local/stackless/bin/python break-stackless.py<br>
Traceback (most recent call last):<br>
&nbsp; File &quot;break-stackless.py&quot;, line 47, in &lt;module&gt;<br>
&nbsp;&nbsp;&nbsp; test()<br>
&nbsp; File &quot;break-stackless.py&quot;, line 37, in test<br>
&nbsp;&nbsp;&nbsp; obj =&nbsp; pickle.loads(data)<br>
&nbsp; File &quot;/usr/local/stackless/lib/python2.6/pickle.py&quot;, line
1409, in loads<br>
&nbsp;&nbsp;&nbsp; return Unpickler(file).load()<br>
&nbsp; File &quot;/usr/local/stackless/lib/python2.6/pickle.py&quot;, line 893,
in load<br>
&nbsp;&nbsp;&nbsp; dispatch[key](self)<br>
&nbsp; File &quot;/usr/local/stackless/lib/python2.6/pickle.py&quot;, line
1252, in load_build<br>
&nbsp;&nbsp;&nbsp; setstate(state)<br>
TypeError: arg 5 (closure) expected cell, found stackless._wrap.cell<br>
<br>
The code is....<br>
<br>
-----------------------------<br>
<br>
import stackless<br>
import pickle<br>
<br>
from twisted.web import client<br>
<br>
def tasklet():<br>
&nbsp;&nbsp;&nbsp; # create an example state<br>
&nbsp;&nbsp;&nbsp; factory = client.HTTPClientFactory(&quot;<a
href="http://www.google.com/">http://www.google.com/</a>&quot;, agent =
&quot;stackless/1.0&quot; )<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <br>
&nbsp;&nbsp;&nbsp; get_complete = [False]<br>
&nbsp;&nbsp;&nbsp; get_failed = [False]<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <br>
&nbsp;&nbsp;&nbsp; def _doFailure(data):<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; get_failed[0] = factory.status<br>
&nbsp;&nbsp;&nbsp; <br>
&nbsp;&nbsp;&nbsp; def _doSuccess(data):<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; get_complete[0] = factory.status<br>
&nbsp;&nbsp;&nbsp; <br>
&nbsp;&nbsp;&nbsp; factory.deferred.addCallback(_doSuccess).addErrback(_doFailure)<br>
&nbsp;&nbsp;&nbsp; <br>
&nbsp;&nbsp;&nbsp; while True:<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; stackless.schedule()<br>
<br>
def test():<br>
&nbsp;&nbsp;&nbsp; # run the task<br>
&nbsp;&nbsp;&nbsp; task = stackless.tasklet(tasklet)<br>
&nbsp;&nbsp;&nbsp; task.setup()<br>
&nbsp;&nbsp;&nbsp; task.run()<br>
&nbsp;&nbsp;&nbsp; <br>
&nbsp;&nbsp;&nbsp; # pump once<br>
&nbsp;&nbsp;&nbsp; stackless.schedule()<br>
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; <br>
&nbsp;&nbsp;&nbsp; # now serialise<br>
&nbsp;&nbsp;&nbsp; data = pickle.dumps(task)<br>
&nbsp;&nbsp;&nbsp; <br>
&nbsp;&nbsp;&nbsp; # now deserialise<br>
&nbsp;&nbsp;&nbsp; obj =&nbsp; pickle.loads(data)<br>
&nbsp;&nbsp;&nbsp; <br>
&nbsp;&nbsp;&nbsp; # resume<br>
&nbsp;&nbsp;&nbsp; task.kill()<br>
&nbsp;&nbsp;&nbsp; obj.insert()<br>
&nbsp;&nbsp;&nbsp; <br>
&nbsp;&nbsp;&nbsp; # pump again<br>
&nbsp;&nbsp;&nbsp; stackless.schedule()<br>
&nbsp;&nbsp;&nbsp;&nbsp; <br>
if __name__==&quot;__main__&quot;:<br>
&nbsp;&nbsp;&nbsp; test()<br>
<br>
-----------------------<br>
<br>
If code formatting is an issue, I've attached the code to the email as a
file...<br>
<br>
Can anyone shed any light on this bug?<br>
<br>
Kind Regards<br>
<br>
Crispin<o:p></o:p></p>

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<p class=MsoNormal>On Sat, Oct 10, 2009 at 2:21 AM, Richard Tew &lt;<a
href="mailto:richard.m.tew@gmail.com">richard.m.tew@gmail.com</a>&gt; wrote:<o:p></o:p></p>

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<p class=MsoNormal style='margin-bottom:12.0pt'>On Fri, Oct 9, 2009 at 10:38
PM, Crispin Wellington<br>
&lt;<a href="mailto:retrogradeorbit@gmail.com">retrogradeorbit@gmail.com</a>&gt;
wrote:<br>
&gt; I have written a server that contains stackless threads. When the server<br>
&gt; shuts down these threads are serialised to disk. This all happens without<br>
&gt; incident and I end up with a reasonably sized file per pickled object.<br>
&gt;<br>
&gt; When I go to deserialise them I hit a problem. I get this...<br>
&gt; -------------------<br>
&gt; &nbsp;&nbsp;&nbsp; &nbsp; File<br>
&gt; &quot;/home/cwellington/Development/yabi/yabi-be-twisted/trunk/TaskManager/Tasklets.py&quot;,<br>
&gt; line 54, in load<br>
&gt; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; task = pickle.loads(data)<br>
&gt; &nbsp;&nbsp;&nbsp; &nbsp; File
&quot;/usr/local/stackless/lib/python2.6/pickle.py&quot;, line 1415, in<br>
&gt; loads<br>
&gt; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; return Unpickler(file).load()<br>
&gt; &nbsp;&nbsp;&nbsp; &nbsp; File &quot;/usr/local/stackless/lib/python2.6/pickle.py&quot;,
line 898, in load<br>
&gt; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; dispatch[key](self)<br>
&gt; &nbsp;&nbsp;&nbsp; &nbsp; File
&quot;/usr/local/stackless/lib/python2.6/pickle.py&quot;, line 1258, in<br>
&gt; load_build<br>
&gt; &nbsp;&nbsp;&nbsp; &nbsp;&nbsp;&nbsp; setstate(state)<br>
&gt; &nbsp;&nbsp;&nbsp; exceptions.TypeError: arg 5 (closure) expected cell,
found<br>
&gt; stackless._wrap.cell<br>
&gt; --------------------<br>
&gt;<br>
&gt; I think this might be a bug. The arguments are being passed back into the<br>
&gt; constructor of the stackless._wrap.function and the constructor is
throwing<br>
&gt; that exception. So in essence, the __reduce__ or __reduce_ex__ functions
are<br>
&gt; creating instatiation values that do not work on reinstantiation.<br>
&gt;<br>
&gt; I changed pickle.py to print out some debug. setstate is... &lt;built-in
method<br>
&gt; __setstate__ of stackless._wrap.function object at 0x21ca0c8&gt; and
(state)[4]<br>
&gt; is... (&lt;cell at 0x2605f30: empty&gt;, &lt;cell at 0x2940718: list
object at<br>
&gt; 0x259f518&gt;, &lt;cell at 0x2940670: str object at 0x2940768&gt;,
&lt;cell at<br>
&gt; 0x2940750: str object at 0x29407d8&gt;, &lt;cell at 0x29407c0: int object
at<br>
&gt; 0x25cd338&gt;)<br>
&gt;<br>
&gt; These all seem to be &quot;cell&quot; objects. Why aren't they
(stackless._wrap.cell)<br>
&gt; recognised as &quot;cells&quot;?<br>
&gt;<br>
&gt; I can provide a pickletools.dis() dump of the pickle stream if wanted.<br>
&gt;<br>
&gt; Using Stackless Python 2.6.2 on 64 bit linux (x86_64).<br>
&gt;<br>
&gt; Can anybody help me decode my objects? or even find a way to encode them
so<br>
&gt; the are decodable? Is this a bug, or am I doing it wrong?<o:p></o:p></p>

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<p class=MsoNormal>It definitely looks like a bug. &nbsp;If you can provide the
smallest<br>
possible reproduction case, it would help us look into it and we could<br>
add it to the test suite as a regression test.<br>
<br>
If you want your objects back in the meantime, you might try compiling<br>
2.6 with the relevant code raising these errors commented out.<br>
<span style='color:#888888'><br>
Richard.</span><o:p></o:p></p>

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<p class=MsoNormal><o:p>&nbsp;</o:p></p>

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