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bug#19873: Ill-formed regular expression is constructed in forward-parag
From: |
Marcin Borkowski |
Subject: |
bug#19873: Ill-formed regular expression is constructed in forward-paragraph. |
Date: |
Sun, 26 Feb 2017 17:44:51 +0100 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.0.50 (gnu/linux) |
On 2015-02-15, at 10:31, Alan Mackenzie <acm@muc.de> wrote:
> Hello, Emacs!
>
> In forward-paragraph, L37, a regular expression is constructed as
> follows:
>
> (let* ...
> (sp-parstart (concat "^[ \t]*\\(?:" parstart "\\|" parsep "\\)"))
> ...)
>
> . Here parstart and parsep are, more or less,
> paragraph-{start,separate}.
>
> The problem is that parstart and parsep themselves are likely to begin
> with "[ \t]*" (the default values certainly do), so we have two
> consecutive matchers for an arbitrary amount of whitespace. This causes
> the regexp engine to run very slowly when a line starts with lots of WS
> but doesn't match.
>
> This problem seems to be the cause of bug # 19846 (where holding down the
> spacebar inside a C comment causes Emacs to seize up when auto-fill mode
> is enabled).
Hi Alan, hi all,
I put this bug on my todo-list some time ago and decided now to revisit
it.
I'm wondering what could be done about it. First of all, my Emacs has
this as paragraph-start:
"\\|[ ]*$"
and this as paragraph-separate:
"[ ]*$"
and frankly speaking, I'm not sure why they differ at all (by default).
Also, even though forward-paragraph checks for "^" at their beginning,
they actually don't begin with that character (again, by default).
My first thought is to add a check whether paragraph-start and
paragraph-sep match something like
"^\\^?\\[[[:space:]]+\\][+*]?"
and if yes, make parstart/parsep equal to them, but without the matching
part.
WDYT?
--
Marcin Borkowski
http://octd.wmi.amu.edu.pl/en/Marcin_Borkowski
Faculty of Mathematics and Computer Science
Adam Mickiewicz University
- bug#19873: Ill-formed regular expression is constructed in forward-paragraph.,
Marcin Borkowski <=