c++ - boost unordered_map serialization says 'serialize' missing even with appropriate includes -

i've got simple class unordered map , serialize function:

#include <boost/unordered_map.hpp> #include <boost/serialization/unordered_map.hpp>  class to_serialize {   boost::unordered_map<int, int> m_map; public:   friend class boost::serialization::access;   template<class archive>   void serialize(archive & ar, const unsigned int) {     ar & m_map;   } }; 

now try create ts object , serialize it:

#include <fstream> #include <boost/archive/binary_iarchive.hpp> #include <boost/archive/binary_oarchive.hpp> #include "ts.cpp"  int main() {   to_serialize ts;   std::ofstream ofs("saved.bin");   {     boost::archive::binary_oarchive oa(ofs);     oa << ts;   }   ofs.close(); } 

this fails compile, with:

boost/serialization/access.hpp:116:9: error: 'class boost::unordered::unordered_map<int, int>' has no member named 'serialize' 

i don't understand i'm missing here? boost/serialization/unordered_map.hpp seems declare , define serialize function unordered map, guess that's not enough?

it looks answer simple -- boost implements serialization of stl unordered_map, not own boost::unordered_map version :(.