http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57684
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- Yes, because std::unique_ptr has a special exception that says it can be instantiated with incomplete types, so that should work OK (like your case where the static member is a raw pointer, which prevents unordered_map being instantiated when base<> is instantiated. I hope for GCC 4.9 we can make unordered_map support incomplete types again, so the original code would work, but it doesn't support them currently, which is allowed by the standard.
