[boost] make_shared and allocate_shared for classes with private constructors

I have some classes that derive from enable_shared_from_this which I've given private constructors and static creation methods which return a shared_ptr. This prevents someone from using the class inappropriately. It seems obvious that at a minimum using make_shared internally here would be an improvement. Unfortunately this requires that make_shared be made a friend for every arity and probably won't work with the variadic template implementation of make_shared. Is it possible to make declaring friendship for make_shared and allocate_shared simpler? I thinking something like serialization does with friend class boost::serialization::access. Thanks, -- Michael Marcin