bug#31676: 27.0.50; More helpful error message for unescaped character literals

[Philipp Stephani <p.stephani2@gmail.com>]

Am Sa., 9. Juni 2018 um 19:31 Uhr schrieb Eli Zaretskii <eliz@gnu.org>:
>
> > From: Philipp Stephani <p.stephani2@gmail.com>
> > Date: Sat, 9 Jun 2018 19:12:30 +0200
> > Cc: larsi@gnus.org, 31676@debbugs.gnu.org
> >
> >  Sounds okay, but can you tell why you implemented
> >  lread--unescaped-character-literals in C?  If that's because you need
> >  to call it from load_warn_unescaped_character_literals, then C
> >  functions can call Lisp functions with no problems, we have several
> >  examples of that in the sources.  AFAICT, the C implementation is just
> >  a "transliteration" of straightforward Lisp code, so it reads strange.
> >
> > The function uses an uninterned variable, so it has to be in C. I think that's slightly better than interning the
> > variable and having some Lisp function access it (the latter would have one additional internal symbol).
>
> Why does it need an uninterned variable?

It doesn't need to be uninterned, but it's cleaner that way because no
other code can access the variable.

>  And if it does, why cannot
> it create a symbol that is not in obarray?

That's what the patch does.