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From: Lars Ingebrigtsen <larsi@gnus.org>
To: Eli Zaretskii <eliz@gnu.org>
Cc: 53203@debbugs.gnu.org, Colin <my.old.email.sucked@gmail.com>
Subject: bug#53203: Comment with lots of color codes crashes or hangs emacs in scss-mode
Date: Thu, 13 Jan 2022 08:00:18 +0100	[thread overview]
Message-ID: <87wnj486il.fsf@gnus.org> (raw)
In-Reply-To: <83r19d5c1i.fsf@gnu.org> (Eli Zaretskii's message of "Wed, 12 Jan 2022 15:16:57 +0200")

Eli Zaretskii <eliz@gnu.org> writes:

> It seems to infloop in JIT font-lock, and the culprit seems to be this
> part of font-lock-keywords:
>
>        ;; Even though pseudo-elements should be prefixed by ::, a
>        ;; single colon is accepted for backward compatibility.
>        "\\(?:\\(:" (regexp-opt (append css-pseudo-class-ids
>                                        css-pseudo-element-ids)
>                                t)

Trying to understand the regexp used for scss here, I think that bit is
somewhat innocuous -- it just matches those words.

       ;; Even though pseudo-elements should be prefixed by ::, a
       ;; single colon is accepted for backward compatibility.
       "\\(?:\\(:" (regexp-opt (append css-pseudo-class-ids
                                       css-pseudo-element-ids)
                               t)
       "\\|::" (regexp-opt css-pseudo-element-ids t) "\\)"

But then we get:

       "\\(?:([^)]+)\\)?"
       (if (not sassy)
           "[^:{}()\n]*"
         (concat "[^:{}()\n#]*\\(?:" scss--hash-re "[^:{}()\n#]*\\)*"))
       "\\)*"

Which is a whole lot of backtracking, presumably exacerbated by the
previous ids bit of the regexp.

But I've repressed all I once knew about the scss language -- what is it
really trying to match here?  Anybody?

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





  reply	other threads:[~2022-01-13  7:00 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-12  7:20 bug#53203: Comment with lots of color codes crashes or hangs emacs in scss-mode Colin
2022-01-12 13:16 ` Eli Zaretskii
2022-01-13  7:00   ` Lars Ingebrigtsen [this message]
2022-01-13  8:58     ` Eli Zaretskii
2022-05-14 10:34     ` Simen Heggestøyl
2022-05-14 12:02       ` Lars Ingebrigtsen
2022-05-14 12:38       ` Lars Ingebrigtsen
2022-05-14 13:30         ` Lars Ingebrigtsen
2022-05-14 15:33           ` Lars Ingebrigtsen
2022-05-15 10:45             ` Simen Heggestøyl
2022-05-15 12:14               ` Lars Ingebrigtsen
2022-05-15 14:46                 ` Simen Heggestøyl

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