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Re: PCRE2 support?

Mark Mielke
September 19, 2018 03:20AM
On Tue, Sep 18, 2018 at 11:55 AM Maxim Dounin <mdounin@mdounin.ru> wrote:

> On Tue, Sep 18, 2018 at 08:12:20AM -0400, Thomas Ward wrote:
> > Downstream in Ubuntu, it has been proposed to demote pcre3 and
> > use pcre2 instead as it is newer.
> > https://trac.nginx.org/nginx/ticket/720 shows it was marked 4
> > years ago that NGINX does not support pcre2. Are there any
> > plans to use pcre2 instead of pcre3?
> There are no immediate plans.
> When we last checked, there were no problems with PCRE, but PCRE2
> wasn't available in most distributions we support, making the
> switch mostly meaningless.

I think there have been changes since then. PCRE2 was new in 2015, but
isn't new in 2018.

RHEL 7 (and clones) include libpcre2. I think this is a pretty wide set of
machines right here. I believe Ubuntu 16.04 LTS has libpcre2 which is
another wide set. Fedora has had it for a while now. I think that unless
you go to older releases, all major distributions should have PCRE2 by now.

I build haproxy with PCRE2 support.

One that was interesting to me, is that Git recently (April, 2018?)
switched to building with PCRE2 by default when "USE_LIBPCRE=Yes" was


I'm not sure about meaningless from a functionality perspective. All new
features are going into PCRE2. PCRE is a stable branched with only bug
fixes and security problems fixed. The newest features, including
performance improvements, are all in PCRE2. I believe the reason it is
"PCRE2-10" instead of "PCRE-10", is because of API changes, and the
opportunity to improve or fix previous API decisions. This then becomes the
basis for all future development free of the PCRE API shackles.

> Also, it looks like PCRE2 is still not supported even by Exim,
> which is the parent project of PCRE and PCRE2:
> https://bugs.exim.org/show_bug.cgi?id=1878

I don't think Exim should be the measure:

"PCRE was originally written for the Exim MTA https://www.exim.org/, but
is now used by many high-profile open source projects, including Apache
https://httpd.apache.org/, PHP http://www.php.net/, KDE
https://www.kde.org/, Postfix http://www.postfix.org/, and Nmap
https://nmap.org/. PCRE has also found its way into some well known
commercial products, like Apple Safari https://www.apple.com/safari/.
Some other interesting projects using PCRE include Chicken
http://www.call-with-current-continuation.org/, Ferite
http://www.ferite.org/, Onyx http://www.canonware.com/onyx/, Hypermail
http://www.hypermail-project.org/, Leafnode
http://leafnode.sourceforge.net/, Askemos http://www.askemos.org/,
Wenlin http://www.wenlin.com/, and 8th http://8th-dev.com/."

This list is also far from complete. PCRE and PCRE2 are widely used, and
PCRE2 is where all current improvement is occurring. Anybody waiting for
Exim, will probably be among the very last to switch.

As such, adding PCRE2 support to nginx looks premature.

Before writing the above, I was debating with myself about when the right
time to add support for a new component release is. For some projects and
some components, it will be more important than others. For example,
OpenSSL 1.1.1 with TLSv1.3 support might be considered premature for some
projects to support, and yet Nginx supports this newly released version
long before OpenSSL 1.1.1 is readily available in a majority of
distributions that you support. I think in this case, OpenSSL 1.1.1 is of
strategic importance to Nginx, and this ensured it was on the roadmap.
(However, it still seems to be missing an ability to configure the cipher
suite... :-) )

I don't know if PCRE2 belongs on this roadmap. I think there have been
significant improvements with the JIT compilation that could prove useful
for higher performance evaluation of regular expressions with Nginx, but I
personally don't have this requirement, so if after considering all of the
above - you still felt it was premature, I wouldn't raise any concern
personally. I just want to make sure this is an informed position. :-)

Mark Mielke <mark.mielke@gmail.com>
nginx-devel mailing list
Subject Author Views Posted

PCRE2 support?

Thomas Ward 709 September 18, 2018 08:14AM

Re: PCRE2 support?

Maxim Dounin 396 September 18, 2018 11:56AM

Re: PCRE2 support?

Mark Mielke 2124 September 19, 2018 03:20AM

Re: PCRE2 support?

Thomas Ward 353 January 24, 2019 10:24AM

Re: PCRE2 support?

Maxim Dounin 352 January 24, 2019 01:22PM

Re: PCRE2 support?

PGNet Dev 350 January 24, 2019 01:48PM

Re: PCRE2 support?

Maxim Dounin 669 January 24, 2019 07:14PM

Re: PCRE2 support?

Dipl. Ing. Sergey Brester 248 October 18, 2021 02:44AM

Re: PCRE2 support?

Maxim Dounin 413 October 18, 2021 09:48AM

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