I think I've mentioned it before, but the isspace() and similar man pages used to warn that they made sense only if ascii. So the recommendation was to always

I think I've mentioned it before, but the isspace() and similar man pages used to warn that they made sense only if ascii. So the recommendation was to always do (isascii() && iswhatever()). With the advent of locales they seem to have just omitted this rather than put in a warning or hint.