After the object wcin is initialized, wcin.tie() returns &wcout. Its state is otherwise the same as required for basic_ios<wchar_t>::init ([basic.ios.cons]).
The object wcout controls output to a stream buffer associated with the object stdout, declared in <cstdio> ([c.files]).
The object wcerr controls output to a stream buffer associated with the object stderr, declared in <cstdio> ([c.files]).
After the object wcerr is initialized, wcerr.flags() & unitbuf is nonzero and wcerr.tie() returns &wcout. Its state is otherwise the same as required for basic_ios<wchar_t>::init ([basic.ios.cons]).