[wide.stream.objects]
31 Input/output library [input.output]
31.4 Standard iostream objects [iostream.objects]
31.4.4 Wide stream objects [wide.stream.objects]
The object wcin controls input from a stream buffer associated with the object stdin, declared in .
After the object wcin is initialized, wcin.tie() returns &wcout.
The object wcout controls output to a stream buffer associated with the object stdout, declared in .
The object wcerr controls output to a stream buffer associated with the object stderr, declared in .
After the object wcerr is initialized, wcerr.flags() & unitbuf is nonzero and wcerr.tie() returns &wcout.
The object wclog controls output to a stream buffer associated with the object stderr, declared in .