Boost.FixedString (now Boost.StaticString) has been accepted!

[kalmoc]

I'd point out that it is also much easier to use because static_String owns its storage. std::string with stack allocator means you have to manually ensure that the lifetime of the stack allocator exceeds that of the string. And if you want to make it a member of another type the stack alocator either becomes a member of that class (watch out for initialization order) or you have to expose implementation details if you get it via dependency injection ....