Hello, I am encountering the following warning when using virtual base class pointer to serialize a derived class. The same warning is displayed for all sample test programs that come with the serialization library. The compiler used is g++ version 3.4.3. /vob/adc/router/thirdparty/boost/boost/type_traits/is_virtual_base_of.hp p:56: warning: direct base `TestBase' inaccessible in `boost::detail::is_virtual_base_of_impl<TestBase, TestType1, mpl_::bool_< true> >::X' due to ambiguity Can you recommend any workarounds...or if this has been addressed. Thanks Sulakshan V #include <boost/archive/xml_oarchive.hpp> #include <boost/archive/xml_iarchive.hpp> #include <boost/serialization/nvp.hpp> #include <boost/serialization/base_object.hpp> #include <boost/serialization/type_info_implementation.hpp> #include <boost/serialization/export.hpp> #include <boost/serialization/extended_type_info_no_rtti.hpp> #include <boost/archive/archive_exception.hpp> #include <boost/archive/basic_xml_archive.hpp> #include <fstream> class TestBase { public: TestBase() : m_baseInt(111) {} virtual ~TestBase() {} virtual const char* get_key() const = 0; private: friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int) { ar & boost::serialization::make_nvp("BaseInt", m_baseInt); } int m_baseInt; }; BOOST_SERIALIZATION_ASSUME_ABSTRACT(TestBase) BOOST_CLASS_TYPE_INFO(TestBase, extended_type_info_no_rtti<TestBase>) BOOST_CLASS_EXPORT(TestBase) class TestType1 : public TestBase { public: TestType1() : m_int(666), m_float(777.f) {} virtual const char* get_key() const; private: friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version) { ar & boost::serialization::make_nvp("TestBase", boost::serialization::base_object<TestBase>(*this)); ar & boost::serialization::make_nvp("Type1Int", m_int); ar & boost::serialization::make_nvp("Type1Float", m_float); } int m_int; float m_float; }; BOOST_CLASS_TYPE_INFO(TestType1, extended_type_info_no_rtti<TestType1>) BOOST_CLASS_EXPORT(TestType1) const char* TestType1::get_key() const { return boost::serialization::type_info_implementation<TestType1>::type::get_con st_instance().get_key(); } class TestType2 : public TestBase { public: TestType2() : m_int(222), m_float(333.f) {} virtual const char* get_key() const; private: friend class boost::serialization::access; template<class Archive> void serialize(Archive& ar, const unsigned int version) { ar & boost::serialization::make_nvp("TestBase", boost::serialization::base_object<TestBase>(*this)); ar & boost::serialization::make_nvp("Type2Int", m_int); ar & boost::serialization::make_nvp("Type2Float", m_float); } int m_int; float m_float; }; BOOST_CLASS_TYPE_INFO(TestType2, extended_type_info_no_rtti<TestType2>) BOOST_CLASS_EXPORT(TestType2) const char* TestType2::get_key() const { return boost::serialization::type_info_implementation<TestType2>::type::get_con st_instance().get_key(); } int main(int argc, char** argv[]) { //Create new file std::ofstream testTypeOFS("TestType.xml"); boost::archive::xml_oarchive testOutXML(testTypeOFS); TestType1* pT1 = new TestType1; TestType2* pT2 = new TestType2; testOutXML << boost::serialization::make_nvp("TestType1", pT1); testOutXML << boost::serialization::make_nvp("TestType2", pT2); testTypeOFS.close(); delete pT1; delete pT2; //Load the file back in to extract a derived type. std::ifstream testTypeIFS("TestType.xml"); boost::archive::xml_iarchive testInXML(testTypeIFS); TestBase* pTB = NULL; try { testInXML >> boost::serialization::make_nvp("TestBase", pTB); } catch(boost::archive::archive_exception& ex) { std::cout << "Archive Exception: " << ex.code << "-" << ex.what() << std::endl; char exitNotice; std::cin >> exitNotice; } testTypeIFS.close(); return 0; } /vob/adc/router/thirdparty/boost/boost/type_traits/is_virtual_base_of.hp p:56: warning: direct base `TestBase' inaccessible in `boost::detail::is_virtual_base_of_impl<TestBase, TestType2, mpl_::bool_< true> >::X' due to ambiguity /vob/adc/router/thirdparty/boost/boost/type_traits/is_virtual_base_of.hp p: In instantiation of `boost::detail::is_virtual_base_of_impl<TestBase, TestType1, mpl_::bool_< true> >::X': /vob/adc/router/thirdparty/boost/boost/type_traits/is_virtual_base_of.hp p:70: instantiated from `boost::detail::is_virtual_base_of_impl<TestBase, TestType1, mpl_::bool_< true> >' /vob/adc/router/thirdparty/boost/boost/type_traits/is_virtual_base_of.hp p:78: instantiated from `boost::detail::is_virtual_base_of_impl2<TestBase, TestType1>' /vob/adc/router/thirdparty/boost/boost/type_traits/is_virtual_base_of.hp p:87: instantiated from `boost::is_virtual_base_of<TestBase, TestType1>' /vob/adc/router/thirdparty/boost/boost/mpl/if.hpp:67: instantiated from `boost::mpl::if_<boost::is_virtual_base_of<TestBase, TestType1>, boost::mpl::identity<boost::serialization::void_cast_detail::void_caster _virtual_base<TestType1, TestBase> >, boost::mpl::identity<boost::serialization::void_cast_detail::void_caster _primitive<TestType1, TestBase> > >' /vob/adc/router/thirdparty/boost/boost/mpl/eval_if.hpp:37: instantiated from `boost::mpl::eval_if<boost::is_virtual_base_of<TestBase, TestType1>, boost::mpl::identity<boost::serialization::void_cast_detail::void_caster _virtual_base<TestType1, TestBase> >, boost::mpl::identity<boost::serialization::void_cast_detail::void_caster _primitive<TestType1, TestBase> > >' /vob/adc/router/thirdparty/boost/boost/serialization/void_cast.hpp:271: instantiated from `const boost::serialization::void_cast_detail::void_caster& boost::serialization::void_cast_register(const Derived*, const Base*) [with Derived = TestType1, Base = TestBase]' /vob/adc/router/thirdparty/boost/boost/serialization/base_object.hpp:68: instantiated from `static const void* boost::serialization::detail::base_register<Base, Derived>::polymorphic::invoke() [with Base = TestBase, Derived = TestType1]' /vob/adc/router/thirdparty/boost/boost/serialization/base_object.hpp:82: instantiated from `static const void* boost::serialization::detail::base_register<Base, Derived>::invoke() [with Base = TestBase, Derived = TestType1]' /vob/adc/router/thirdparty/boost/boost/serialization/base_object.hpp:104 : instantiated from `typename boost::serialization::detail::base_cast<B, D>::type& boost::serialization::base_object(Derived&) [with Base = TestBase, Derived = TestType1]' x.cpp:48: instantiated from `void TestType1::serialize(Archive&, unsigned int) [with Archive = boost::archive::xml_iarchive]' /vob/adc/router/thirdparty/boost/boost/serialization/access.hpp:118: instantiated from `static void boost::serialization::access::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::xml_iarchive, T = TestType1]' /vob/adc/router/thirdparty/boost/boost/serialization/serialization.hpp:7 4: instantiated from `void boost::serialization::serialize(Archive&, T&, unsigned int) [with Archive = boost::archive::xml_iarchive, T = TestType1]' /vob/adc/router/thirdparty/boost/boost/serialization/serialization.hpp:1 33: instantiated from `void boost::serialization::serialize_adl(Archive&, T&, unsigned int) [with Archive = boost::archive::xml_iarchive, T = TestType1]' /vob/adc/router/thirdparty/boost/boost/archive/detail/iserializer.hpp:18 2: instantiated from `void boost::archive::detail::iserializer<Archive, T>::load_object_data(boost::archive::detail::basic_iarchive&, void*, unsigned int) const [with Archive = boost::archive::xml_iarchive, T = TestType1]' x.cpp:93: instantiated from here /vob/adc/router/thirdparty/boost/boost/type_traits/is_virtual_base_of.hp p:56: warning: direct base `TestBase' inaccessible in `boost::detail::is_virtual_base_of_impl<TestBase, TestType1, mpl_::bool_< true> >::X' due to ambiguity