Re: [pygccxml-development] Parameter passing, ownership semantics

[Gustavo C. <gjc...@gm...>]

On 2/22/07, Roman Yakovenko <rom...@gm...> wrote:
>
> On 2/22/07, Gustavo Carneiro <gjc...@gm...> wrote:
> >   That wiki entry didn't apply anymore probably due to changing
> > boost::python interfaces, but it provided very useful clues.  I managed
> to
> > get it working 100% correctly using another hack.  Here's the diff of
> the
> > manual changes I made to the wrapper:
> >
> > --- ns3.cpp     2007-02-21 23:46:44.000000000 +0000
> > +++ ns3-working.cpp      2007-02-21 23:44:34.000000000 +0000
> > @@ -9,19 +9,32 @@
> >   namespace bp = boost::python;
> >
> >   struct EventImpl_wrapper : ns3::EventImpl, bp::wrapper< ns3::EventImpl
> > {
> > +    ~EventImpl_wrapper() {
> >  +        if (this->pyobj) {
> > +            Py_DECREF(this->pyobj);
> > +            this->pyobj = 0;
> >  +        }
> > +
> >  +    }
> >
> >      EventImpl_wrapper()
> >      : ns3::EventImpl()
> >  -      , bp::wrapper< ns3::EventImpl >(){
> > -        // null constructor
> >  +      , bp::wrapper< ns3::EventImpl > (), pyobj(0) {
> >
> >      }
> >
> >      virtual void Notify(  ){
> >  +        if (!this->pyobj) {
> > +            this->pyobj =
> > bp::detail::wrapper_base_::get_owner(*this);
> >  +            Py_INCREF(this->pyobj);
> > +        }
> >           bp::override func_Notify = this->get_override( "Notify" );
> >           func_Notify(  );
> >      }
> >
> > +protected:
> >  +    PyObject *pyobj;
> > +
> >   };
> >
> >  static void Schedule_b8544467c482930a621aca2e7ac87dca(
> > std::auto_ptr< ::ns3::EventImpl > event ){
> >
>
> Hi Gustavo. I tested the code you post and it doesn't work for me :-(.
> I also doesn't understand how it works for you. You should increment
> reference
> on the object before you pass it "Schedule" member function, otherwise
> you get same "Segmentation fault". Am I missing something?
> I can avoid it by commenting the destructor code.


  You are right.  In my case it worked due to a bug in my code.  I forgot to
make ~EventImpl() virtual, and so ~EventImpl_wrapper() was never called! :P

  I hate C++ :(

Also I added new functionality, which allows you to implement the patch:
>
> http://pygccxml.svn.sourceforge.net/viewvc/pygccxml/pyplusplus_dev/unittests/transfer_ownership_tester.py?view=markup
>
> http://pygccxml.svn.sourceforge.net/viewvc/pygccxml/pyplusplus_dev/unittests/data/transfer_ownership_to_be_exported.hpp?view=markup


  Thanks, it works perfectly! :-)

-- 
Gustavo J. A. M. Carneiro
"The universe is always one step beyond logic."