Hello, I want to add serialization support to the Eigen2 matrix class. It works well (at least at compile time) until I try to serialize a shared_ptr. boost::shared_ptr<MatrixXd> shape; template <typename Archive> void serialize(Archive& ar, const unsigned int version) { ar & BOOST_SERIALIZATION_NVP(shape); }; I receive a long error message that begins with the first error: /usr/local/include/boost/type_traits/has_new_operator.hpp: In instantiation of 'boost::detail::has_new_operator_impl >': /usr/local/include/boost/type_traits/has_new_operator.hpp:109: instantiated from 'boost::has_new_operator >' /usr/local/include/boost/mpl/if.hpp:67: instantiated from 'boost::mpl::if_ >, boost ::mpl ::identity >::has_new_operator>, boost ::mpl ::identity >::doesnt_have_new_operator> >' /usr/local/include/boost/mpl/eval_if.hpp:37: instantiated from 'boost::mpl::eval_if >, boost ::mpl ::identity >::has_new_operator>, boost ::mpl ::identity >::doesnt_have_new_operator> >' /usr/local/include/boost/archive/detail/iserializer.hpp:235: instantiated from 'static T* boost::archive::detail::heap_allocator<T>::invoke() [with T = Eigen::Matrix]' /usr/local/include/boost/archive/detail/iserializer.hpp:278: instantiated from 'void boost::archive::detail::pointer_iserializer::load_object_ptr(boost::archive::detail::basic_iarchive&, void*&, unsigned int) const [with Archive = boost::archive::xml_iarchive, T = Eigen::Matrix]' BodySchema.cpp:110: instantiated from here /usr/local/include/boost/type_traits/has_new_operator.hpp:85: error: call of overloaded 'check_sig(int)' is ambiguous Has anybody a hint for me what is missing in the matrix class? second, could anybody please explain to me what BOOST_SERIALIZATION_SHARED_PTR does and when I have to use it (only saw it in the demo file). Thank you, Best regards Stefan