Subject: bug#25682: 25.1; font-lock: fontifying too slow in some modes on very long lines

From: Lars Ingebrigtsen <[email-masked]>
Date: Thu, 31 Oct 2019 18:07:53 +0100

Ryan B <[email-masked]> writes:

> here are steps that reproduce this, with gnu emacs 25.1.1 on mac os x:
>
> 1. put the single long line under the === below (18572 chars long) into a file
> 2. run emacs -Q
> 3. type C-x C-f <filename> RET to open the file
> 4. type M-x compilation-mode RET
>
> this consistently hangs emacs for 9-10s for me on modern hardware, a 2014
> retina macbook pro.

The example was corrupted in transit (line-folded), so I've included a
fixed-up version as an attachment here.

Running M-x compilation-mode takes about five seconds for me, but this
laptop is pretty fast.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no