OK, so it looks like posting from nabble loses the raw-tag stuff... The optional.hpp comment: // It is an inherent limitation to the serialization of optional.hpp // that the underlying type must be either a pointer or must have a // default constructor. It's possible that this could change sometime // in the future, but for now, one will have to work around it. This can // be done by serialization the optional<T> as optional<T *> BOOST_STATIC_ASSERT( boost::serialization::detail::is_default_constructible<T>::value || boost::is_pointer<T>::value ); The code snippet: #include <boost/serialization/string.hpp> #include <boost/serialization/optional.hpp> #include <boost/archive/text_iarchive.hpp> #include <boost/archive/text_oarchive.hpp> #include <fstream> int main(int argc, char *argv[]) { (void)argc; (void)argv; typedef boost::archive::text_oarchive oarchive_type; typedef boost::archive::text_iarchive iarchive_type; std::ios_base::openmode flags = std::ios_base::openmode(); { std::ofstream ofs("/tmp/tmp.bin", std::ios::out | flags); boost::optional<std::string> s = std::string("hello"); oarchive_type oa(ofs); oa << s; } { std::ifstream ifs("/tmp/tmp.bin", std::ios::in | flags); boost::optional<std::string> s; iarchive_type ia(ifs); // # ERROR # ia >> s; } } -- Sent from: http://boost.2283326.n4.nabble.com/Boost-Users-f2553780.html