bug#62009: 29.0.60; Emacs crashes on setf symbol-name

[Eli Zaretskii <eliz@gnu.org>]

> From: Robert Pluim <rpluim@gmail.com>
> Cc: Gregory Heytings <gregory@heytings.org>,  Philip Kaludercic
>  <philipk@posteo.net>,  michael_heerdegen@web.de,
>   monnier@iro.umontreal.ca,  62009@debbugs.gnu.org,  Eli Zaretskii
>  <eliz@gnu.org>,  Augusto Stoffel <arstoffel@gmail.com>
> Date: Fri, 10 Mar 2023 12:30:48 +0100
> 
> diff --git a/src/lisp.h b/src/lisp.h
> index 1276285e2f2..80bbb047824 100644
> --- a/src/lisp.h
> +++ b/src/lisp.h
> @@ -1685,6 +1685,8 @@ SREF (Lisp_Object string, ptrdiff_t index)
>  INLINE void
>  SSET (Lisp_Object string, ptrdiff_t index, unsigned char new)
>  {
> +  if (XSTRING (string)->u.s.size_byte == -2)
> +    Fsignal (Qsetting_constant, string);

"Setting constant" is misleading.

And again, why do that at all?  It's a waste of cycles, incurred on
_everyone_, for an extremely rare use case that is explicitly
discouraged.  We are not the TSA, and should not adopt their policy of
punishing the innocent 99.99% on behalf of a handful of villains.