Effects: Constructs an object of class basic_fstream<charT,traits>, initializing the base class with basic_iostream(&sb) and initializing sb with basic_filebuf<charT,traits>().
explicit basic_fstream(const char* s,
ios_base::openmode mode = ios_base::in|ios_base::out);
Effects: Constructs an object of class basic_fstream<charT, traits>, initializing the base class with basic_iostream(&sb) and initializing sb with basic_filebuf<charT, traits>(). Then calls rdbuf()->open(s, mode). If that function returns a null pointer, calls setstate(failbit).
explicit basic_fstream(const string& s,
ios_base::openmode mode = ios_base::in|ios_base::out);
Effects: the same as basic_fstream(s.c_str(), mode);
basic_fstream(basic_fstream&& rhs);
Effects: Move constructs from the rvalue rhs. This is accomplished by move constructing the base class, and the contained basic_filebuf. Next basic_istream<charT,traits>::set_rdbuf(&sb) is called to install the contained basic_filebuf.