Hi all, The typeof library defines some templates in the unnamed namespace. This was done to avoid ODR violations in certain contexts (although it introduces them in other contexts). The unnamed namespace used now is: boost::type_of::<unnamed> It turnes out MSVC 7.1 and 8.0 cannot handle this kind of namespace correctly in conjunction with precompiled headers. Specifically, if a template is defined inside such a namespace in the precompiled header, it cannot be specialized outside this precompiled header (for typeof this means types cannot be registered outside pch). The problem can be worked around by using a different kind of unnamed namespace, like, for example: <unnamed>::boost_typeof (<unnamed>::boost::type_of introduces ambiguity in some contexts) This kind of unnamed namespace can be handled correctly by both MS compilers, with respect to pch, but I don't believe it satisfies the Boost naming convention. OTOH, if no other solution is found, this is the only way we can achieve typeof compliance with pch, while still staying in the unnamed namespace. Thoughts? Regards, Arkadiy