bug#58558: 29.0.50; re-search-forward is slow in some buffers

[Stephen Berman]

On Wed, 12 Apr 2023 17:30:36 +0300 Eli Zaretskii <eliz@gnu.org> wrote:

>> From: Stefan Monnier <monnier@iro.umontreal.ca>
>> Cc:  Ihor Radchenko <yantar92@posteo.net>, Eli Zaretskii <eliz@gnu.org>,
>>   larsi@gnus.org,  58558@debbugs.gnu.org
>> Date: Wed, 12 Apr 2023 10:06:03 -0400
>> 
>> > 1. emacs -Q
>> > 2. M-: (require 'cc-langs) <RET>
>> > 3. C-x b asd <RET>
>> > 4. M-: parse-sexp-lookup-properties <RET> => t
>> >
>> > On Emacs 28, (4) yields nil.
>> 
>> I suspect that the patch below might fix the immediate problem.
>> Of course, setting `parse-sexp-lookup-properties` should not have such
>> a major performance impact, so maybe we should keep digging into
>> the problem.
>
> Also, that code was there in Emacs 28 as well, so how come it suddenly
> has this effect now?

Note that, with emacs-28 -Q, `C-h v parse-sexp-lookup-properties' ==>

  parse-sexp-lookup-properties is a variable defined in ‘C source code’.
  
  Its value is nil

while with emacs-29 -Q, `C-h v parse-sexp-lookup-properties' ==>

  parse-sexp-lookup-properties is a variable defined in ‘C source code’.
  
  Its value is t
  Local in buffer *scratch*; global value is nil

Steve Berman