[C++-sig] Deriving Python function from C++ base class with pure virtual function

[Jonathan Brandmeyer]

On Thu, 2004-12-02 at 08:34 -0800, Paul F. Kunz wrote:
> >>>>> On Sun, 14 Nov 2004 17:35:14 -0500, Jonathan Brandmeyer <jbrandmeyer at earthlink.net> said:
> 
> > See the PEP 311 interface PyGILState_Ensure()/PyGILState_Release(),
> > which you will use to wrap around the callback function in your C++
> > code.  This interface solves the thread bootstrap problem.
> > Furthermore, the lock is recursive, so locking the GIL is safe when
> > you already have the lock.
> 
>    I tried this with Boost-1.32.0 and Python 2.4 as follows...
> 
> double
> FunctionWrap::
> operator () ( double x ) const
> {
>   PyGILState_STATE state = PyGILState_Ensure ();
>   double value =  call_method < double, double > ( m_self, "valueAt", x );
>   PyGILState_Release ( state );
> 
>   return value;
> }

This isn't safe since call_method() can throw, which would prevent
releasing the GIL.  I made a small lock class that calls
PyGILState_Ensure() in its constructor, and PyGILState_Release() in the
destructor for this purpose.

> I still get SIGSEGV with different traceback as follows...
> 
[snipped]
>    Any suggestions?

Execute PyExec_InitThreads() in your module initialization function, and
see if that helps (it does for me).  Python does not do this
automatically.

HTH,
-Jonathan