GNU diff-2.7.7 is not multibyte locale aware

[Bruno Haible]

Hi,

With GNU diff 2.7.7, trying to make side-by-side differences, the middle
column does not look right. This happens when the file contains UTF-8
non-ASCII characters. This is with glibc 2.2.90, and I have the environment
variable LC_CTYPE set to an UTF-8 locale.

$ uname -srm
Linux 2.4.10-4GB i686
$ diff --version|head -1
diff (GNU diffutils) 2.7.7
$ cat text
aeiou
äeiou
äeioü
äeioüvß
äeiöüwß
aeiou
$ diff -y --width=24 -t text text
aeiou         aeiou
äeiou          äeiou
äeioü           äeioü
äeioüvß          äeioüvß
äeiöüwß           äeiöüwß
aeiou         aeiou

This is not side-by-side. None of the code that deals with widths in
io.c, side.c, util.c is multibyte aware! Neither are the ISSPACE calls
in io.c, sdiff.c, util.c!

Bruno