[RFC] Add new C.UTF-8 locale.

[Joseph Myers]

On Mon, 29 Jun 2020, Florian Weimer via Libc-alpha wrote:

> This refers to the entries for <UD800>, not the multibyte sequences.
> I think we should aim for consistency between strcoll and wcscoll even
> for invalid sequences.

It's not clear what consistency means for byte sequences that cannot be 
converted from narrow to wide characters or vice versa.  strcoll and 
wcscoll have no way to report errors for such invalid byte sequences (so I 
suppose it's implicitly undefined behavior).

-- 
Joseph S. Myers
joseph@codesourcery.com