[Stackless] PySide progress! At least a good reason to crash

Christian Tismer tismer at stackless.com
Sat Dec 8 01:49:23 CET 2012

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 

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,

I would like to get your opinion.
And I definately want to make stackless work with pyside.

The source code can be inspected here:


cheers - chris

[cross-posting to the pyside list]

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