This looks to be a C++ code instantiation issue. Lookup explicit instantiation in your C++ reference. Look at the demo - polymorphic archives which tests separate code compilation. Good Luck Robert Ramey Cheok Yan Cheng wrote:

I am using VC++ 2003. I realize that when I provide the code defination for save and load on cpp file, the following error will occur:

animal error LNK2019: unresolved external symbol "private: void __thiscall cat::save<class boost::archive::text_oarchive>(class boost::archive::text_oarchive &,unsigned int)const " (??$save@Vtext_oarchive@archive@boost@@@cat@@ABEXAAVtext_oarchive@archive@boost@@I@Z) referenced in function "public: static void __cdecl boost::serialization::access::member_save(class boost::archive::text_oarchive &,class cat const &,unsigned int)" (??$member_save@Vtext_oarchive@archive@boost@@$$CBVcat@@@access@serialization@boost@@SAXAAVtext_oarchive@archive@2@ABVcat@@I@Z)

------ cat.h ------ #ifndef CAT_H #define CAT_H

#include #include

class cat { private: friend class boost::serialization::access; template<class Archive> void save(Archive & ar, const unsigned int version) const; template<class Archive> void load(Archive & ar, const unsigned int version); BOOST_SERIALIZATION_SPLIT_MEMBER() };

#endif

------- cat.cpp ------- #include "cat.h"

template<class Archive> void cat::save(Archive & ar, const unsigned int version) const { }

template<class Archive> void cat::load(Archive & ar, const unsigned int version) { }

*** try adding the following here #include #include // explicit instantiation template cat::save(boost::archive::text_oarchive ar, const unsigned int version) const; template cat::load(boost::archive::text_oarchive ar, const unsigned int version) ;

-------- main.cpp -------- #include <iostream> #include <cassert> #include <string> #include <sstream> #include <fstream> #include #include #include "cat.h"

int main() { const cat c;

// make an archive std::ofstream ofs("test"); boost::archive::text_oarchive oa(ofs); oa << c; }

However, if I remove cat.cpp file during compilation and having the code defination at header file as follow, the code compiled with no problem. May I know how I can put my serialization code at cpp file instead of header file? Thank you very much!

The reason I want to do so is that I need to perform class forwarding in certain classes. Due to the reason class forwarding unable to provide a full information of a class at header level, serialization code can only be written in cpp file level.

------ cat.h ------ #ifndef CAT_H #define CAT_H

#include #include

class cat { private: friend class boost::serialization::access; template<class Archive> void save(Archive & ar, const unsigned int version) const{} template<class Archive> void load(Archive & ar, const unsigned int version) {} BOOST_SERIALIZATION_SPLIT_MEMBER() };

#endif

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