Re: [Boost-users] Problem using serialization::xml_archive with polymrphic classes

Subject: Re: [Boost-users] Problem using serialization::xml_archive with polymrphic classes
From: przemyslaw.sliwa_at_[hidden]
Date: 2010-09-02 10:47:18

Hello,

thanks for help with this. This has fixed the problem. However, I have got 
a much more complicated example which fails. 
I have a simple inheritance structure with 4 classes, they derive 
a->b->c->d nothing complex. say a is the mose base and d is the most 
derived class, Each class has got a virtual destructor. I can easily 
serialize object of type d but I cannot do this with a pointer to a this 
class. Basicaly invoking in the code 

        std::vector<b*>         tmpCcys;
        ar & boost::serialization::make_nvp("currencyEvents", tmpCcys);

does not work at all! I can get to the point 

            // retrieve the true type of the object pointed to
            // if this assertion fails its an error in this library
            assert(NULL != this_type);

            const boost::serialization::extended_type_info * true_type =
                i.get_derived_extended_type_info(t);

            // note:if this exception is thrown, be sure that derived 
pointer
            // is either registered or exported.
            if(NULL == true_type){
                boost::serialization::throw_exception(
                    archive_exception(
                        archive_exception::unregistered_class,
                        true_type->get_debug_info()
                    )
                );
            }

in the oserializer.hpp where each element of the vector is dumped to the 
archive but call to i.get_derived_extended_type_info(t) throws an 
exception of an unknown type. It is not archive or event std::exception 
onlt catch(...) {...} can handle it and therefore it is not possible to 
see what is going on. The data under t looks fine but 

    const extended_type_info *
    get_derived_extended_type_info(const T & t) const {
        // note: this implementation - based on usage of typeid (rtti)
        // only does something if the class has at least one virtual 
function.
        BOOST_STATIC_WARNING(boost::is_polymorphic<T>::value);
        return 
 typeid_system::extended_type_info_typeid_0::get_extended_type_info(
                typeid(t)
            );
    }

simply throws something which is not possible to handle correctly. I 
cannot step into typeid(t) on windows and VC++2005. As mentioned i have no 
problems at all with serializing object. Serializing pointers deos not 
work att all! I am exporting the class using 

BOOST_CLASS_EXPORT_GUID(d, "CurrencyEvent")

I have to mention that the most base class is a template and I export it 
as well using

BOOST_CLASS_EXPORT_GUID(a<Currency>, "EventCurrency")
BOOST_CLASS_EXPORT_GUID(a<CurrencyCouple>, "EventCurrencyCouple")

similar 

BOOST_CLASS_EXPORT_GUID(b, "BaseCurrencyEvent")
BOOST_CLASS_EXPORT_GUID(c, "RealCurrencyEvent")

the classes a,b,c and d are within a namespace Events and defined/declared 
within a dll but this should not be a problem at all since I can serialize 
objects of the most derived class. 

Could someone help me with this issue? 

Thanks a lot in advance

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