Subject: bug#43631: 28.0.50; CC Mode multiline strings grinds performance to a halt

From: Dmitry Gutov <[email-masked]>
Date: Sat, 26 Sep 2020 22:43:05 +0300

On 26.09.2020 19:17, Eli Zaretskii wrote:
> But I'm confused why the "fast" profile starts with
> font-lock-fontify-region, whereas the "slow" profile doesn't have
> font-lock-fontify-region anywhere...

Because CC Mode doesn't use syntax-propertize-function (most major modes 
do, so we're used to seeing "slow" syntax analysis being done inside 
font-lock-fontify-region because it calls s-p-f).

CC Mode applies syntax properties inside before/after-change-functions, 
and the "slow" profile reflects that: c-before-change is featured 
prominently.