Hello, we have a problem when serializing weak_ptr. The second example below produces invalid XML where the same attributes appears two times with different values. It appears that both save and load using boost::serialization works, but other tools complains about the XML code being invalid. The example has been tested using Boost 1.33.1 in Visual Studio 2005. Anders Edin, Sidec Technologies AB #include <iostream> #include <boost/shared_ptr.hpp> #include <boost/weak_ptr.hpp> #include <boost/archive/xml_oarchive.hpp> #include <boost/serialization/access.hpp> #include <boost/serialization/version.hpp> #include <boost/serialization/base_object.hpp> #include <boost/serialization/shared_ptr.hpp> #include <boost/serialization/weak_ptr.hpp> class A { public: A() {} virtual ~A() {} virtual void set_self(boost::shared_ptr<A> s) { self_ = s; } virtual boost::shared_ptr<A> get_self() const { return self_.lock(); } private: friend boost::serialization::access; template <typename Archive> void serialize(Archive& archive, const unsigned int file_version) { archive & boost::serialization::make_nvp("self_", self_); } boost::weak_ptr<A> self_; }; BOOST_CLASS_VERSION(A, 1); class B: public A { public: B(): value_(3) {} virtual ~B() {} private: friend boost::serialization::access; template <typename Archive> void serialize(Archive& archive, const unsigned int file_version) { archive & BOOST_SERIALIZATION_BASE_OBJECT_NVP(A); archive & boost::serialization::make_nvp("value_", value_); } int value_; }; BOOST_CLASS_VERSION(B, 1); int main(int argc, char* argv[]) { // First example // This test object points to itself boost::shared_ptr<A> a(new A()); a->set_self(a); { boost::archive::xml_oarchive archive(std::cout); archive << boost::serialization::make_nvp("A", a); } std::cout<<std::endl; // Second example // This test object also points to itself, but by pointing to its base class boost::shared_ptr<B> b(new B()); b->set_self(b); { boost::archive::xml_oarchive archive(std::cout); archive << boost::serialization::make_nvp("B", b); } return 0; } /* Output from running the program in Visual Studio 2005 using boost 1.33.1 * The first example works as expected * The second example produces invalid XML with attributes having two values in self_ <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> <!DOCTYPE boost_serialization> <boost_serialization signature="serialization::archive" version="3"> <A class_id="0" tracking_level="0" version="1"> <px class_id="1" tracking_level="1" version="1" object_id="_0"> <self_ class_id="2" tracking_level="0" version="0"> <px class_id_reference="1" object_id_reference="_0"></px> </self_> </px> </A> </boost_serialization> <?xml version="1.0" encoding="UTF-8" standalone="yes" ?> <!DOCTYPE boost_serialization> <boost_serialization signature="serialization::archive" version="3"> <B class_id="0" tracking_level="0" version="1"> <px class_id="1" tracking_level="1" version="1" object_id="_0"> <A class_id="2" tracking_level="1" version="1" object_id="_1"> <self_ class_id="3" tracking_level="0" version="0" class_id="4" tracking_level="0" version="1"> <px class_id_reference="1" object_id_reference="_0"></px> </self_> </A> <value_>3</value_> </px> </B> </boost_serialization> */