bug#81606: Mojibake with UTF-8 file names

> Date: Sun, 16 Aug 2026 13:19:05 +0000
> Cc: [email protected], [email protected]
> From: Werner LEMBERG <[email protected]>
> 
> >>   Non-ASCII characters in the name of of the master file must use
> >>   the same encoding as the current input file itself.  To make this
> >>   actually work, set the @code{coding} local variable accordingly;
> >>   in most cases, you want to use UTF-8 encoding.  Example:
> > 
> > This doesn't work, I think: the encoding of the current file is not
> > known when latexenc looks for the name of the main file.  That was
> > the reason for the original problem in this bug.  Or what am I
> > missing?
> 
> If a master file `foo` is specified in the local variables block,
> AUCTeX checks whether it is exists, otherwise it gets created.  This
> string `foo` must be given in the encoding specified by the `coding`
> cookie.

But this is trivially correct: any non-ASCII text in a file which has
a 'coding:' cookie _must_ be encoded in the encoding specified by
'coding:".  Right?  The cookie guarantees that the entire file,
including the Local Variables section, uses that single encoding.

Moreover, if there is a 'coding:' cookie, there's no need for
latexenc.el to look for anything else to determine the encoding.  In
fact, latexenc.el is not needed at all in this case, because the
'coding:' cookie is processed and acted upon by default when a file is
visited by Emacs.

> In other words, the encoding *is* known; the user should
> specify it explicitly so that Emacs doesn't select the wrong encoding
> accidentally.

If you want to require the 'coding:' cookie in all cases, that's fine,
but then latexenc.el is not needed at all, see above.