I'm trying to serialize a class with a non-default constructor and static const data members, so I have to override boost::serialization::save_construct_data() and load_construct_data(). I am getting a linking error:the static members referred to in save_construct_data() cannot be found ("undefined reference"). #include <boost/archive/tmpdir.hpp> #include <boost/archive/xml_iarchive.hpp> #include <boost/archive/xml_oarchive.hpp> // forward declarations class A; namespace boost { namespace serialization { template<class Archive> inline void save_construct_data(Archive &ar, const A *t, const unsigned int file_version); } } class A { friend class boost::serialization::access; // friend function (omitting load_construct_data() for brevity) template<class Archive> friend void save_construct_data(Archive &ar, const A *t, const unsigned int file_version); public: static const int var1 = 1; static const int var2 = 2; template<class Archive> void serialize(Archive & ar, const unsigned int file_version) { // do nothing }; } // overridden Boost function namespace boost { namespace serialization { template<class Archive> inline void save_construct_data( Archive &ar, const A *t, const unsigned int file_version) { // link errors happen at both of these two lines ("undefined reference" of var1, var2). ar << boost::serialization::make_nvp("var1", ::A::var1); ar << boost::serialization::make_nvp("var2", t->var2); }; }} // namespace… This puzzles me since I thought that static members have external linkage. This question seems to be more about namespaces than it is about Boost::Serialization, but I post here because some Serialization user must have run into it. Thanks, Kurt