Re: bug#40634: Massive pattern list handling with -E format seems very slow since 2.28.

[Jim Meyering]

On Sun, Sep 13, 2020 at 7:03 PM Paul Eggert <eggert@cs.ucla.edu> wrote:
> On 9/11/20 11:41 PM, Jim Meyering wrote:
> >> https://bugs.gnu.org/40634#32
> >>
> >> I'll try to take a look at the later patch.
> >
> > Oh! Glad you spotted that.
>
> I took a look and the basic idea sounds good though I admit I did not check
> every detail. While looking into it I found some opportunities for 
> improvements,
> plus I found what appear to be some longstanding bugs in the area, one of 
> which
> causes a grep test failure on Solaris (and I suspect the bug is also on
> GNU/Linux but the grep tests don't catch it). I installed the attached patches
> into Gnulib, updated grep to point to the new Gnulib version, and added a note
> in grep's NEWS file about this.
>
> Patch 1 is what Norihiro Tanaka proposed in Bug#40634#32, except I edited the
> commit message. Patch 2 consists of minor cleanups and performance tweaks for
> Patch 1. (Patches 3 and 4 are omitted as they were installed by others into
> Gnulib at about the same time I was installing these.) Patch 5 fixes a
> dfa-heap-overrun failure on Solaris that appears to be a longstanding bug
> exposed by Patch 1 when running on Solaris. Patch 6 merely cleans up code near
> Patch 5. Patch 7 fixes the use of an uninitialized constraint, which I
> discovered while debugging Patch 5 under Valgrind; this also appears to be a
> longstandiung bug.
>
> Coming up with test cases for all these bugs would be pretty tricky, 
> unfortunately.

Wow! Thank you!