std::basic_ios::set_rdbuf

Sets the associated stream buffer to sb without clearing its error state.

This member function is protected: it is called by the move constructors of the derived streams such as std::basic_ofstream or std::basic_istringstream, as the final step after constructing the base class and after moving the stream buffer: only the most derived stream class knows how to correctly move the stream buffer, but std::basic_ios needs to be made aware of the stream's new location so that its public member functions can access it.