My application that works with 1.32 is failing to link with 1.33 RC1 due to boost::serialization::void_cast_register (specialised for my classes) being an unresolved external. In my case the void_cast_register call and the BOOST_CLASS_EXPORT macro are in one module while the serialization is done in another module, with all modules linked in one application. The code below also shows this problem, however if I add an archive class and header to the example then it will compile and link ok. Obviously this is when serialization is in the same module as the void_cast_register call. Any suggestions about what I need to add to make the application link? Richard ************************************************************************ ******* #pragma hdrstop #include #include #include #pragma link "libboost_serialization-bcb-mt-d-1_33.lib" class Z { public: virtual void DoSomething() =0; }; BOOST_IS_ABSTRACT(Z) class A : public Z { public: void DoSomething(){}; private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned intversion) { ar & boost::serialization::make_nvp("A", m_A); } int m_A; }; class B : public Z { public: void DoSomething(){}; private: friend class boost::serialization::access; template<class Archive> void serialize(Archive & ar, const unsigned intversion) { ar & boost::serialization::make_nvp("B", m_B); } int m_B; }; BOOST_CLASS_EXPORT(A) BOOST_CLASS_EXPORT(B) int main(int argc, char* argv[]) { boost::serialization::void_cast_register(0,0); boost::serialization::void_cast_register(0,0); return 0; } Errors: [Linker Error] Unresolved external 'const boost::serialization::void_cast_detail::void_caster& boost::serialization::void_cast_register(const A *, const Z *)' referenced from D:\PROJECTS\...\SOURCE\TEST\BUILD\MAIN.OBJ [Linker Error] Unresolved external 'const boost::serialization::void_cast_detail::void_caster& boost::serialization::void_cast_register(const B *, const Z *)' referenced from D:\PROJECTS\...\SOURCE\TEST\BUILD\MAIN.OBJ