Windows 10 RS4 supports locale ".utf8" already, I wonder why setlocale doesn't make fmt::print with L-string work?

[denchat]

Now we can do this std way on Windows 10 v1803 or later

std::setlocale(LC_ALL, "en_US.utf8");
wprintf(L"zß水");

but fmt::print still do need this :

_setmode( _fileno(stdout), _O_WTEXT );

Otherwise, it only prints 'z'.

I wonder why? Is there some performance hits to support setlocale like wprintf?

[denchat]

I just realize this works without _setmode

fmt::print(std::wcout,L"zß水\n");

Shouldn't fmt::print select wcout seemlessly? Why?
Is fmt::print with _setmode faster than fmt::print(std::wcout ?

[vitaut]

I wonder why?

As a library function print shouldn't be changing the global locale, because this could mess up user assumptions. This should be done on the application level.

Shouldn't fmt::print select wcout seemlessly?

Last time I checked writing via iostreams added nontrivial overhead. But you can easily write a formatting function that writes to wcout instead of stdout by default yourself.