Boost Serialization via base pointer to derived class [duplicate]

Answer 1

I must admit I am not familiar with this boost package, but I copied and compiled the code, which produced the same result as the OP mentioned

Realizing that we are using polymorphism, I added a public: virtual ~A(){}; in class A. Also, oa.register_type<B>(); is added in main according to the document, and output became:

A!
B!

According to the specification, a class is a polymorphic class only when declares or inherits a virtual function. For non-polymorphic classed, maybe polymorphism just does not work.

EDIT:

Putting the BOOST_CLASS_EXPORT(B); in B.cpp instead of B.h seems to solve this problem of redefinition.

EDIT:

Checked the expansion result of BOOST_CLASS_EXPORT(B) (reformatted):

namespace boost {
    namespace serialization {
        template<> struct guid_defined<B> : boost::mpl::true_ {};
        template<> inline const char * guid<B>(){ return "B"; }
    }
}
namespace boost {
    namespace archive {
        namespace detail {
            namespace { // NOTE
                template<> struct init_guid< B > {
                    static guid_initializer< B > const & g;
                };
                guid_initializer< B > const & init_guid< B >::g = ::boost::serialization::singleton< guid_initializer< B > >::get_mutable_instance().export_guid();
            }
        }
    }
}

And for the line marked with NOTE: for boost 1.42 used an anonymous namespace is used, which will be no problem if it is put into multiple cpp files or put into a header file (tested in ubuntu with g++, using the boost package come along with Ubuntu). However, in boost 1.48, namespace extra_detail is used, which would cause problems when put into multiple cpp files (tested in windows with VS2010, using boost downloaded from homepage).