Subject: bug#43558: [PATCH]: Fix (forward-comment 1) when end delimiter is escaped.

From: Dmitry Gutov <[email-masked]>
Date: Sun, 22 Nov 2020 22:39:08 +0200

On 22.11.2020 20:19, Alan Mackenzie wrote:
> Hello, Dmitry.
> 
> On Sun, Nov 22, 2020 at 19:46:24 +0200, Dmitry Gutov wrote:
>> On 22.11.2020 19:08, Alan Mackenzie wrote:
>>> Really?  Are there any other programming language modes whose comments
>>> syntax.c cannot handle without syntax-table text properties?
> 
>> Ruby is just one example.
> 
> Thanks.
> 
> I've just searched the web for that.  Ruby has block comment delimiters
> =begin and =end.
> 
> It would be possible to handle these in syntax.c, but somewhat clumsy
> and awkward.

Just like the C comments syntax discussed here.

> Presumably ruby-mode handles these with syntax-table text properties
> applied to the = sign and the terminating d, which is a little clumsy,
> but not too bad, at the Lisp level.

This is just two more regexps to search for (and propertize). I don't 
expect that the slowdown from them is in any way perceptible.

And the general point is that the Emacs syntax table structure doesn't 
necessarily have to mirror the syntax of the C language.