Because there's no polymorphic_text_oarchive.cpp counterpart,
I think this is in the src directory. It should be pre-compiled into the library so you never actually see it. The portable binary archive is an example, so it's not included in the library.
There is no polymorphic_text_oarchive.cpp or polymorphic_text_iarchive.cpp in the boost 1.42 source. A search in the source for "polymorphic*archive.cpp" only reveals: ./libs/serialization/example/polymorphic_portable_binary_iarchive.cpp ./libs/serialization/example/polymorphic_portable_binary_oarchive.cpp ./libs/serialization/src/polymorphic_iarchive.cpp ./libs/serialization/src/polymorphic_oarchive.cpp And the latter 2 files basically only have these explicitly instantiations: template class archive_serializer_map<polymorphic_iarchive>; template class archive_serializer_map<polymorphic_oarchive>; Which I don't believe should be replicated in polymorphic_portable_binary_iarchive.cpp or polymorphic_portable_binary_oarchive.cpp since in the boost source code there is no explicit instantiations of the following forms: template archive_serializer_map<polymorphic_text_iarchive> template archive_serializer_map<polymorphic_text_oarchive> ... etc. BTW, why are you using explicit instantiations with seperate template .cpp files? It becomes a management nightmare keeping track of what needs to be explicitly instantiated in large projects. They're templates, so why not just have everything in headers? An additional advantage being that code is only generated for code that's used (implicitly instantiated) by the client. -Mostafa