explicit basic_ostringstream(ios_base::openmode which = ios_base::out);
Effects: Constructs an object of class basic_ostringstream, initializing the base class with basic_ostream(&sb) and initializing sb with basic_stringbuf<charT, traits, Allocator>(which | ios_base::out)) ([stringbuf.cons]).
explicit basic_ostringstream(
const basic_string<charT,traits,Allocator>& str,
ios_base::openmode which = ios_base::out);
Effects: Constructs an object of class basic_ostringstream<charT, traits>, initializing the base class with basic_ostream(&sb) and initializing sb with basic_stringbuf<charT, traits, Allocator>(str, which | ios_base::out)) ([stringbuf.cons]).
basic_ostringstream(basic_ostringstream&& rhs);
Effects: Move constructs from the rvalue rhs. This is accomplished by move constructing the base class, and the contained basic_stringbuf. Next basic_ostream<charT,traits>::set_rdbuf(&sb) is called to install the contained basic_stringbuf.