Subject: bug#42267: Fontification takes a long time when an equation contains a double prime

From: Arash Esbati <[email-masked]>
Date: Wed, 08 Jul 2020 22:22:59 +0200

Hi Najib,

Najib Idrissi-Kaïtouni <[email-masked]> writes:

> I would guess that Auctex thinks '' is the end of a quote and is
> looking for the (nonexistent) double backtick `` that would be the
> beginning of it. I tried to get a backtrace with gdb and it's not
> exactly clear which precise function is to blame, but it was always as
> part of the fontification. As a test, I filled a buffer with some
> lipsum and put an equation at the bottom. Without '' everything is
> fine, as soon as there is a '' in the equation things start to
> noticeably slow down.

Can you please share this test file so others can load it and see if the
behavior is reproducible?

> I am currently using the latest version, 12.2.4, and Emacs
> 27.0.91. The behavior is fairly recent, although I couldn't say if it
> started with this release precisely, it may have started more than a
> week ago.

AUCTeX's fontification for math went through a bigger overhaul.  Please
share the file and a recipe (preferably starting with `emacs -Q') how to
trigger your obeservation, that would help a lot.

Thanks in advance, Arash