You can just check "is it UTF-8 encoded?". Then it doesn't matter when a new code point is added, it would still be correctly encoded. You could make this a c

You can just check "is it UTF-8 encoded?". Then it doesn't matter when a new code point is added, it would still be correctly encoded. You could make this a configurable kernel option; when enabled, filenames can only be created when they encode with UTF-8. The next big problem is control characters. But really, the only people who need control characters embedded in filenames are people breaking into computers using them. It doesn't matter if you use a GUI or a CUI, people generally don't embed newlines, or escape, or tabs in filenames. The leading "-" is probably more controversial, but the POSIX standard specifically notes such filenames as nonstandard.