bug#12291: [rev 109796] wrong UTF-8 handling

[Eli Zaretskii <eliz@gnu.org>]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: 12291@debbugs.gnu.org,  Curtis Smith <smithcu@gvsu.edu>, Eli Zaretskii
>  <eliz@gnu.org>
> Date: Thu, 27 Jan 2022 17:32:53 +0100
> 
>              position: 1 of 2 (0%), column: 0
>             character:  (displayed as ) (codepoint 1266142, #o4650736, #x1351de)
>               charset: emacs (Full Emacs charset (excluding eight bit chars))
> code point in charset: 0x1351DE
>                syntax: w 	which means: word
>              category: L:Strong L2R
>              to input: type "C-x 8 RET 1351de"
> 
> So Emacs now displays more accurate information about the utf-8
> sequence.
> 
> It was pointed out that this sequence is outside the Unicode range,
> which only extends up to U+10FFFF, and that Emacs should perhaps display
> this as a number of raw bytes instead.  Is that something we still want
> to pursue, or is Emacs behaving like we want to here?  Eli?

This is the expected behavior.  The raw bytes start at #x3FFF00, so
#x1351de is some character code reserved for characters not unified with
Unicode (some CJK encodings have them).  Interpreting them as raw
bytes would be counter-productive.

I'm not sure what was Werner's problem with this, so maybe let him
chime in and explain more.