[C++-sig] Threading support ?

[Dave Hawkes]

A useful facility in boost would be the ability for the user to 'plug-in'
code to support the Python GIL. Using the call policies precall/postcall
facilty would possibly be one way that this could be achieved when calling
c++ code from Python, though this is not ideal as it would be difficult to
make it exception proof. Also there is not similar support when calling from
c++ to python.

What I think is needed is a way of specifying a user defined class to be
defined inline with the call, much as the converter is in the code snippet
from boost below:

template<class R>
typename converter::return_from_python<R>::result_type
call(PyObject*callable,boost::type<R>* =0)
{
    converter::return_from_python<R>converter;
    return converter(
        PyEval_CallFunction(
            callable,const_cast<char*>("(" ")")));
}


In fact, by providing a specialised converter its constructor/destructor
could manage the GIL, but this is not really very practical.

Any ideas for supporting the GIL within boost, without adding overhead where
it's not needed?

Dave Hawkes