>  Add support for multibyte charsets in the "tolower" and "toupper" awk
>  functions.
Thank you for this.

>  Code contributed by Aleksey Cheusov in PR#36394, and slightly
>  tweaked for closer-to-KNF conventions by me.
               ^^^^^^^^^^^^^
               what's this?

>  Also slightly improved checks
>  of error returns.
And especially for this ;-)

Minor note. According to man page wcrtomb cannot return (size_t) -2.

-- 
Best regards, Aleksey Cheusov.