I'm having a lot of trouble getting serialization of derived classes through a base pointer working across dlls. I have the following: DLL (data_types.dll) code: stdafx.h: #pragma once #include "targetver.h" #define WIN32_LEAN_AND_MEAN // Exclude rarely-used stuff from Windows headers // Windows Header Files: #include <windows.h> #pragma warning(disable: 4308) #include "boost/archive/polymorphic_iarchive.hpp" #include "boost/archive/polymorphic_oarchive.hpp" #include "boost/serialization/nvp.hpp" Base.h: #pragma once #include "boost/serialization/export.hpp" class __declspec(dllexport) Base { friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version); public: Base() {} virtual ~Base() {} int i; }; BOOST_SERIALIZATION_ASSUME_ABSTRACT(Base); // Doesn't make a difference. BOOST_CLASS_EXPORT_KEY(Base); Base.cpp: #include "stdafx.h" #include "Base.h" template<class Archive> void Base::serialize(Archive& ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(i); } BOOST_CLASS_EXPORT_IMPLEMENT(Base); template void __declspec(dllexport) Base::serialize(boost::archive::polymorphic_iarchive& ar, const unsigned int version); template void __declspec(dllexport) Base::serialize(boost::archive::polymorphic_oarchive& ar, const unsigned int version); Derived.h: #include "Base.h" class __declspec(dllexport) Derived : public Base { friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version); public: Derived() {} Derived(int num) : j(num) {} int j; }; BOOST_CLASS_EXPORT_KEY(Derived); Derived.cpp: #include "stdafx.h" #include "Derived.h" template<class Archive> void Derived::serialize(Archive& ar, const unsigned int version) { ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Base); ar & BOOST_SERIALIZATION_NVP(j); } BOOST_CLASS_EXPORT_IMPLEMENT(Derived); template void __declspec(dllexport) Derived::serialize(boost::archive::polymorphic_iarchive& ar, const unsigned int version); template void __declspec(dllexport) Derived::serialize(boost::archive::polymorphic_oarchive& ar, const unsigned int version); My exe links against the DLL and contains the following: #include "stdafx.h" #include "boost/archive/polymorphic_xml_iarchive.hpp" #include "boost/archive/polymorphic_xml_oarchive.hpp" #include "data_types/Derived.h" #include <fstream> int _tmain(int argc, _TCHAR* argv[]) { std::ofstream f("c:\\test.xml"); boost::archive::polymorphic_xml_oarchive xml(f); Base* b = new Derived(123); xml & BOOST_SERIALIZATION_NVP(b); delete b; return 0; } When serializing this fails with unregistered_class even though I export both Base and Derived. Jeremy