Re: JFS default behavior (was: UTF-8 in file systems? xfs/extfs/etc.)

[Jamie Lokier <jamie@shareable.org>]

John Bradford wrote:
> > Definitely a good reason.  It seem many assume file names are a local thing,
> > but this is not so. Now consider the case with an external firewire
> > disk or memory stick created on a machine with iso-8859-1 as the system character
> > set and e.g xfs as the file system. What happens when I hook it up to a new redhat
> > installation that thinks file names are best stored as utf8? Most non-ascii
> > file names aren't even legal in utf8.
> 
> Another thing to consider is that you can encode the same character in
> several ways using utf8,

No, you can't.  Only the shortest encoding of a character is valid
UTF-8, and any program which claims to comply with Unicode is
_required_ to reject all other encodings, citing security as the main
reason.

That means any code which transcodes UTF-8 to another encoding (such
as iso-8859-1) must reject the non-minimal forms as invalid
characters, in whatever way that is done.

If there's any transcoding code in Linux which doesn't do that, it's a
potential security hole and should be fixed.

> so two filenames could have different byte strings, but evaluate to
> the same set of unicode characters.

That's true in some other encodings I think (the iso-2022 ones), but
not UTF-8.

-- Jamie