Can anyone tell me what is wrong with the following code: #include <iomanip> #include <iostream> #include <fstream> #include <string> #include #include #include #include #include #include #include *class* ResData{ *friend* *class* boost::serialization::access; *friend* std::ostream& *operator*<<(std::ostream &os, const ResData& rD); *private*: std::string resName; int seqNum; int insNum; float sAS; *public*: ResData(); ResData(std::string, int, int); std::string getResName() const { *return* resName;} int getSeqNum() const { *return* seqNum;} int getInsNum() const { *return* insNum;} float getSAS() const { *return* sAS;} void setSAS(float sASP) { sAS = sASP;} *template*<*class* Archive> void serialize(Archive&, const unsigned int); }; std::ostream& *operator*<<(std::ostream& os, const ResData& rD){ *return* os << rD.getResName() << rD.getSeqNum() << rD.getInsNum() << rD.getSAS(); } int main(){ std::ofstream oFSBS("/home/Seb/Code/testData/results.dat"); boost::archive::text_oarchive oA(oFSBS); ResData temp("TEST", 1, 1); temp.setSAS(5555); oA << temp; oFSBS.close(); } I get the following error upon compilation: /usr/include/boost/archive/detail/oserializer.hpp: In function ‘void boost::archive::save(Archive&, T&) [with Archive = boost::archive::text_oarchive, T = ResData]’: /usr/include/boost/archive/basic_text_oarchive.hpp:78: instantiated from ‘void boost::archive::basic_text_oarchive<Archive>::save_override(T&, int) [with T = ResData, Archive = boost::archive::text_oarchive]’ /usr/include/boost/archive/detail/interface_oarchive.hpp:85: instantiated from ‘Archive& boost::archive::detail::interface_oarchive<Archive>::operator<<(T&) [with T = ResData, Archive = boost::archive::text_oarchive]’ test.cpp:54: instantiated from here /usr/include/boost/archive/detail/oserializer.hpp:566: error: invalid application of ‘sizeof’ to incomplete type ‘boost::STATIC_ASSERTION_FAILURE