Hello,

I wanted to bring this new LWG issue to your attention.
https://cplusplus.github.io/LWG/issue3576

The author asks whether the fill character of std::format is

   - a code unit
   - a code point
   - a grapheme cluster

This might be an abi breaking thing, and implementation disagrees already
apparently.

My gut feeling is that it needs to at least be a codepoint.
I do not know if there are any concerns with allowing a grapheme in terms
of implementation or performance. There is definitively some motivation,
especially for non-nfc format strings.

This sort of issue illustrates my point that using the term character in
the standard can be problematic!

Thanks,
Have a great week,

Corentin