Re: [PATCH 2/3] grep: stop "using" a custom JIT stack with PCRE v2

From: Carlo Arenas <carenas@gmail.com>
Date: Jul 25, 2019, 05:11 UTC
Message-ID: <CAPUEspjj+fG8QDmf=bZXktfpLgkgiu34HTjKLhm-cmEE04FE-A@mail.gmail.com>
In-Reply-To: <87imrr6vv2.fsf@evledraar.gmail.com>

On Wed, Jul 24, 2019 at 1:20 PM Ævar Arnfjörð Bjarmason <avarab@gmail.com> wrote:

Show 8 quoted lines

> On Wed, Jul 24 2019, Junio C Hamano wrote:
> >
> > Does everybody use pcre2 with JIT with Git these days, or only those
> > who want to live near the bleeding edge?
>
> My informal survey of various package recipies suggests that all the big
> *nix distros are using it by default now, so we have a lot of users in
> the wild, including in the just-released Debian stable.

FWIW neither OpenBSD or NetBSD enable JIT, and the git that comes with Xcode (AKA Apple Git) doesn't either, while still using PCRE1

Show 7 quoted lines

> > In any case, if we were not "using" the custom stack anyway for v2,
> > this change does not hurt anybody, possibly other than those who
> > will learn about pcre2 support by reading this message and experiments
> > with larger patterns.  And it should be simple to wire it back if it
> > becomes necessary later.
>
> *nod*

the following pattern fails unless 1MB stack is available:

  '^([/](?!/)|[^/])*~/.*'

the workaround implemented in GNU grep (that uses PCRE1) and the related discussion[1] are a very interesting read

Carlo

[1] https://www.mail-archive.com/bug-grep@gnu.org/msg05763.html