unique_ptr is usually the feature people mention if looking for a reason why C++11 is not just C++98/03 plus syntactic sugar, because it requires move semantics

unique_ptr is usually the feature people mention if looking for a reason why C++11 is not just C++98/03 plus syntactic sugar, because it requires move semantics which was introduced with C++11; that's why I directly pointed to Boost.Move, which offers move semantics including a unique_ptr version compatible with C++98/03. Only in C++14 (or 17, I don't remember, have to look up) they added a feature for which no C++98/03 implementation is known/possible, but most people are not even aware of it (so that one feature is barely the justification of "modern").