bug#27270: display-raw-bytes-as-hex generates ambiguous output for Emacs strings

[Paul Eggert]

On 4/23/22 07:00, Lars Ingebrigtsen wrote:
> we've had this format for half a decade now, and this doesn't
> really seem to be a problem in practice

Not surprising, since most people don't set display-raw-bytes-as-hex. 
But that doesn't mean it's not a problem. Quoting bugs can be issues 
even if they're unlikely to occur at random. (Think SQL injection. :-)


> I tend to think that introducing a new syntax just to fix it
> isn't worth it.

That's fine, so let's fix the problem as originally suggested. That is, 
display the string returned by (format "%c%c" #x9e #x66) as "\x9e\x66" 
(equivalent to (concat "\x9e" "\x66") which is correct) instead of as 
"\x9ef" (equivalent to "\N{BENGALI DIGIT NINE}" which is wrong).

This fixes the problem and doesn't introduce new syntax.