[boost] question re autolink

"These macros will be undef'ed at the end of the header, further this header has no include guards - so be sure to include it only once from your library!" What is the rationale for the above? What happens if its violated. I'm sort of struggling implementind a dll version of the serialization library with autolink. The basic difficulty is that I would like to have the dlls mirror the structure of the the static libraries. That is libboost_serialization.lib libboost_wserializaton.lib depends on theabove wserialization.dll is both autolinked and uses serializaton.dll so Its kind of confusing. Robert Ramey