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Date: Fri, 24 Jul 2015 15:14:05 +0700
Message-ID: <CAEZPtU6bfHzQmBq6HLP+d8v214=P1ZYW76ih7srX2GbVWoW2Tw@mail.gmail.com>
To: Adam Harvey <aharvey@php.net>
Cc: Christoph Becker <cmbecker69@gmx.de>, PHP internals <internals@lists.php.net>
Content-Type: multipart/alternative; boundary=001a114017347b12d1051b9a9666
Subject: Re: [PHP-DEV] PCRE JIT stack size limit
From: pierre.php@gmail.com (Pierre Joye)

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On Jul 24, 2015 10:34 AM, "Adam Harvey" <aharvey@php.net> wrote:
>
> On 23 July 2015 at 11:47, Christoph Becker <cmbecker69@gmx.de> wrote:
> <snip great explanation, thanks>
> > Therefore I tend to prefer a new ini setting (say, pcre.jitstack_limit).
> >  That would mean, however, to add yet another ini setting, of which
> > there are already so many.
>
> I'm not a big fan of that, although it's at least in the spirit of
> what configuration settings are meant to be used for.
>
> What if we added the PCRE_ERROR_JIT_STACKLIMIT error constant to those
> exposed to userland so that it's more easily noticed via
> preg_last_error(), and adding a modifier that can be used to disable
> the JIT on a per-pattern basis (by setting PCRE_NO_START_OPTIMIZE,
> which admittedly disables other stuff too, but at least the regex will
> run)? At least then users could check the error when the regex fails
> and re-run the regex without the JIT if they chose to.
>
> How likely is the average user to hit this, do you think?

I  am not sure we have accurate numbers or can have. It really depends on
the expressions. A simple one can exhaust the stack as much as a apparently
more complex expressions.

I have to say that the default stack we use now on windows has reduced the
amount of bug reports. I do not think we can eliminate it and increase it
too much may bring some bad side effects as well.

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