[boost] [serialization]Thread-safety of serialization lib

There are many places in serialization library that use a pattern like the following: static oserializer & instantiate(){ static oserializer instance; return instance; } AFAIK, not all compilers guarantee the initialization of a function level (or class member level) static variable is thread-safe. If I understand the code correctly, this essentially means that simultaneously serializing objects of the same type is not thread-safe. Am I missing something here? Thanks, Sean