basic_ostringstream& operator=(basic_ostringstream&& rhs);
Effects: Move assigns the base and members of *this from the base and corresponding members of rhs.
void swap(basic_ostringstream& rhs);
Effects: Exchanges the state of *this and rhs by calling basic_ostream<charT, traits>::swap(rhs) and sb.swap(rhs.sb).
template <class charT, class traits, class Allocator>
void swap(basic_ostringstream<charT, traits, Allocator>& x,
basic_ostringstream<charT, traits, Allocator>& y);