bug#66117: 30.0.50; `find-buffer-visiting' is slow when opening large number of buffers

[Eli Zaretskii]

> Cc: dmitry@gutov.dev, 66117@debbugs.gnu.org, mattias.engdegard@gmail.com,
>  monnier@iro.umontreal.ca
> Date: Sun, 17 Dec 2023 12:36:59 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> 
> Maybe I'm confused, but won't this change have at least _some_ effect
> on Lisp programs?  For example, what about this fragment from the
> ELisp manual, which describes the effect of
> make-variable-buffer-local:
> 
>      A peculiar wrinkle of this feature is that binding the variable
>      (with ‘let’ or other binding constructs) does not create a
>      buffer-local binding for it.  Only setting the variable (with ‘set’
>      or ‘setq’), while the variable does not have a ‘let’-style binding
>      that was made in the current buffer, does so.
> 
> Will this case work the same after the change as it did before?

Also, re this part of the patch:

> +  DEFVAR_LISP ("case-fold-search", Vcase_fold_search,
> +            doc: /* Non-nil if searches and matches should ignore case.  */);
> +  Vcase_fold_search = Qt;
> +  DEFSYM (Qcase_fold_search, "case-fold-search");
> +  Fmake_variable_buffer_local (Qcase_fold_search);

Which value does this set to t -- the global default?  Isn't that
different from what we had before?