[C++-sig] Re: boost::python and threads

[David Abrahams]

Vladimir Vukicevic <vladimir at pobox.com> writes:

> David Abrahams wrote:
>
>> Vladimir, In addition to my earlier responses I'd like to point you
>> at this
>> posting from Patrick Hartling.
>> http://article.gmane.org/gmane.comp.python.c++/2833
>>
>>I'd really
>>like to get all these threading issues squared away in Boost.Python,
>>and I especially hope that since threading is so important in lua that
>>threading integration will benefit from the luabind discussions.  In
>>any case, proposals for patches to the Boost.Python core are very
>>much appreciated.
>>  
> Thanks for the article pointer.. I see what you meant by the guard
> class earlier.  Patrick seems to have basically implemented (in a
> fairly elegant way!) what the Python 2.3 PyGILStateEnsure/Release
> functions do; my patches to call.hpp and call_method.hpp do virtually
> the same thing, by creating a call_method_with_gil that one can use in
> wrappers instead of call_method.
>
> The difficulty seems to be calling from python into C++, in invoke.hpp. My patch took a first stab at it, but I didn't look closely enough -- 
> the arguments passed to f() in the invoke() calls are all arg
> converters.  What I'd really like to have happen is for a function
> foo, to have an invoke() and an invoke_helper, where the invoke_helper
> has the exact same signature as foo but inserts Py_BEGIN_ALLOW_THREADS
> and Py_END_ALLOW_THREADS around the actual call to foo() (or, more
> accurately, the pointer to foo).  This can't happen in the actual
> invoke() call, as my patch attempts to do, because the arg converters
> need to use Python API calls (oops!).  I'm working on adding an
> invoke_helper which will do the two-step invocation, but I need to
> study the to_python interface in more detail.

I think the key here is to find a way to wrap the wrapped (member)
function pointer f in a function *adapter* which does
Py_BEGIN_ALLOW_THREADS/Py_END_ALLOW_THREADS.

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com