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From: jan via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
To: Paul Eggert <eggert@cs.ucla.edu>
Cc: 41155@debbugs.gnu.org
Subject: bug#41155: 26.3; regexp 99% locks up emacs
Date: Tue, 12 May 2020 23:28:43 +0100	[thread overview]
Message-ID: <CADJx9Ld7XJcdi8kh-Jtg9gwNEMiErmUcXY9G-O=Mjis0N20m1Q@mail.gmail.com> (raw)
In-Reply-To: <facf01fc-7347-d550-4927-641f76f3e1ef@cs.ucla.edu>

I'm not sure that's the whole issue though

1. C-g does not break out.   If emacs simply hands off to a
C-language-based regex engine and waits for it to return then that
*may* be inevitable but I don't know.

2. I've done a bit of experimenting just now and something doesn't add
up, I'll try to reproduce that tomorrow, draw some conclusions and
post here.

Thanks for the feedback. And the equation solver weirdness, which I'll
read in detail later!

thanks

jan

On 12/05/2020, Paul Eggert <eggert@cs.ucla.edu> wrote:
>> I originally put it down to the regexp being clearly pathalogical
>
> Yes, that's pretty much it. Emacs uses a backtracking matcher and its worst
> case
> performance is exponential. You can even use the matcher to solve
> Diophantine
> integer equations ... verrrryy slowly; see:
>
> http://blog.stevenlevithan.com/archives/algebra-with-regexes
>
> So, don't do that. (Or if you *do* want to do that, fix the matcher - but
> good
> luck with that....)
>





  reply	other threads:[~2020-05-12 22:28 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-09 17:31 bug#41155: 26.3; regexp 99% locks up emacs jan via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-05-12 20:56 ` Paul Eggert
2020-05-12 22:28   ` jan via Bug reports for GNU Emacs, the Swiss army knife of text editors [this message]
2020-05-13  9:11     ` jan via Bug reports for GNU Emacs, the Swiss army knife of text editors
2020-05-14  4:46       ` Paul Eggert

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