Hi Holger, Adding checks for override and default implementation fixed the issue. - Thank you!
Best, Ernie. On Mon, Mar 16, 2015 at 2:04 AM, Holger Joukl <holger.jo...@lbbw.de> wrote: > > Hi Ernie, > > > When I tries to use class exposed as ’wrapper’ as substitute for C > > ++ original class i am getting a segfault error (see example below). > > Is there is something wrong with a way i create a wrapper-class or > > it is not intended to work as substitute for a base class? > > I haven't tried your code sample but you'd normally just expose the > wrapper class *instead* of the original class, with the name of "A". > > Python users don't need to know about the wrapper class intricacies. > > If you expose a non-pure-virtual method you should also add the > default implementation, just as you cited from > > http://www.boost.org/doc/libs/1_57_0/libs/python/doc/tutorial/doc/html/python/exposing.html#python.class_virtual_functions > (necessary to avoid infinite recursion if your Python override > implementation calls the > C++ base class method) > > I.e. something like (untested! Stick closely to the tutorial if in doubt) > > #include <iostream> > #include <boost/python.hpp> > > class A > { > public: > virtual ~A() { std::cout << "A destructor for object: " << this << > std::endl; } > > virtual void info() { std::cout << "C++ A info for object" << this > << std::endl; } > }; > > > struct A_Wrapper : A, boost::python::wrapper<A> > { > void info( > { > if (override info_override = this->get_override("info")) { > return info_override(); > } > return A::info(); > } > > void default_info() { return this->A::info(); } > }; > > > BOOST_PYTHON_MODULE(subclass) > { > boost::python::class_<A_Wrapper, boost::noncopyable>("A", > boost::python::init <>() ) > .def("info", &A::info, &A_Wrapper::default_info) > ; > } > > So the wrapper class provides you with the callback-ability to Python and > this is the one to expose. > > As per the segfault you get: I guess that this might stem from your not > calling the boost::python::wrapper<A> base class constructor in your > A_Wapper > constructor (note how I didn't provide a constructor for the wrapper > class): > > A_Wrapper() : A() {} // <-- not calling all base constructors here > > Again, haven't actually tried it. > > Holger > > Landesbank Baden-Wuerttemberg > Anstalt des oeffentlichen Rechts > Hauptsitze: Stuttgart, Karlsruhe, Mannheim, Mainz > HRA 12704 > Amtsgericht Stuttgart > _______________________________________________ > Cplusplus-sig mailing list > Cplusplus-sig@python.org > https://mail.python.org/mailman/listinfo/cplusplus-sig
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