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Re: Fixing ill-conditioned regular expressions. Proof of concept.


From: Alan Mackenzie
Subject: Re: Fixing ill-conditioned regular expressions. Proof of concept.
Date: Mon, 23 Feb 2015 22:42:45 +0000
User-agent: Mutt/1.5.22 (2013-10-16)

Hi, Paul.

On Mon, Feb 23, 2015 at 02:19:03PM -0800, Paul Eggert wrote:
> On 02/23/2015 12:21 PM, Alan Mackenzie wrote:
> > basically, I've got little idea about regexp engines.

> That's OK, if you prefer a source-to-source transformation then you can 
> use that instead, but the point is that this should be done for all uses 
> of the regexp code, not just for some of them.

Brilliant idea!  Why not call fix-re from within
re-search-forward/backward, looking-at, ...  With its cache, the extra
runtime will be negligible.  After a bit of tidying up, debugging,
handling of \{..\}, proper testing, ....

> The Emacs regexp code isn't Perl-inspired, as far as I know.  It's an 
> old copy of the glibc code, with a lot of hacks.  The glibc version 
> mutated quite a bit when it added i18n support, and Emacs's version has 
> mutated in different ways.

Ah, right.

-- 
Alan Mackenzie (Nuremberg, Germany).



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