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Date: Mon, 15 May 2017 17:05:31 +0200
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Subject: Re: [PHP-DEV] BC break in master (7.2) - Distinguish betweenunmatched
 subpatterns and empty matches in preg_*()
From: cmbecker69@gmx.de ("Christoph M. Becker")

On 15.05.2017 at 12:12, Pierre Joye wrote:

> On Mon, May 15, 2017 at 1:57 PM, Nicolas Grekas
> <nicolas.grekas@gmail.com> wrote:
>
>> in master, feature request https://bugs.php.net/61780 has been implemented
>> and merged into master thanks to https://github.com/php/php-src/pull/1303
>>
>> But as noted in the PR and even in the UPGRADING file, this is a BC break:
>>   . preg_match() and other PCRE functions now distinguish between unmatched
>>     subpatterns and empty matches by reporting NULL and "" (empty string),
>>     respectively. Formerly, either was reported as empty string.
>>
>> While trying to run Symfony's test suite against 7.2, we noticed that this
>> BC break is hitting several components badly. If Symfony is hit, there will
>> be many more userland code impacted for sure.
>>
>> As written explicitly in the releasing policy of php-src, BC breaks must
>> not happen in minor versions. Therefore, I'm kindly but strongly asking for
>> this BC break to be reconsidered and removed.
> 
> I agree that a minimum 5 years old possible bug, quite small, causing
> BC breaks is not good. As far as the fix is critical or justified, I
> think it is sometimes ok to break BC for edge cases. However I do not
> see this is not the case here.
> 
> @RMs revert for 7.2 and re evaluate for later?

I'm not against reverting the commit, but if we want to postpone this
change to PHP 8, I suggest not to set unmatched subpatterns at all,
then.  The current solution has been an attempt to keep the BC break
small, but that apparently has failed.

-- 
Christoph M. Becker