[Stackless] PySide violates Python API - PyQt does not!

Christian Tismer tismer at stackless.com
Sat Dec 8 04:45:20 CET 2012


Resent with a clearer subject line

This comes from the stackless mailing list. 

PySide directly uses the threadstate structure of Cpython, which
is a protocol violation. See below...

Am 08.12.2012 um 01:49 schrieb Christian Tismer <tismer at stackless.com>:

> Hi friends,
> 
> this evening, I looked a bit into shiboken, the module that is used
> for creating python interfaces for PySide, and now I'm
> pretty confident that I found a reason that is creating some issues.
> 
> libshiboken has an include file called sbkpython.h, and this includes
> python.h from the installed python.
> 
> And now we come to the interesting stuff:
> 
> There is threadstatesaver.h and threadstatesaver.cpp !
> The latter has code like:
> 
> void ThreadStateSaver::save()
> {
>     if (PyEval_ThreadsInitialized())
>         m_threadState = PyEval_SaveThread();
> }
> 
> But that code uses the threadstate definition from the cpython threadstate
> module, instead of the different (at least larger) structure in stackless
> threadstate. ;-)
> 
> IOW., things *might* work if pyside is built against stackless python
> instead of CPython.
> 
> Today I looked at a simple PySide script and a larger one - they both used
> multiple threads for startup. No idea if this code is involved there,
> python did not use threads, but I could imagine that is at least a time 
> bomb.
> 
> 
> Now, the question is: how to resolve this?
> ------------------------------------------
> 
> One way that needs testing is if PySide works ok on stackless
> when built from source. I could write an installer for this case.
> 
> The other question is: can we change stackless in a way that works
> with PySide compiled for CPython?
> 
> That would mean: tstate must stay completely unchanged in size.
> I guess the extra info that we use would neet to be put into a
> different structure, and the linkage back to tstate is a little trick,
> at least.
> 
> Another way would be to add a patch to libshiboken, that checks the
> real size of tstate dynamically. This would be an easier patch, although
> I think that at the moment it is not so easy to get anything into pyside,
> quickly.
> 
> I would like to get your opinion.
> And I definately want to make stackless work with pyside.
> 
> The source code can be inspected here:
> 
> http://qt.gitorious.org/pyside/shiboken/trees/master
> 
> cheers - chris
> 
> [cross-posting to the pyside list]
> 
> -- 
> Christian Tismer             :^)   <mailto:tismer at stackless.com>
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