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Re: [perl #124256] Regex loop for \K in lookbehind

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Karl Williamson
April 28, 2015 20:29
Re: [perl #124256] Regex loop for \K in lookbehind
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On 04/28/2015 06:40 AM, demerphq wrote:
> On 28 April 2015 at 13:14,  <> wrote:
>> On Mon, 27 Apr 2015, James E Keenan via RT wrote:
>>>> I think this is a similar bug to the one I have just
>>>> fixed in PCRE.
>>> Can you provide a link to that fix?
>>> Thank you very much.
>> Not very easily (I'd have to check the SVN manual to figure out how to
>> search for stuff - I'm a very simple user) and in any case the fix was
>> different for PCRE1 and PCRE2. The bug was in the test programs pcretest
>> and pcre2test rather than in the library itself (which only does single
>> matches). Here is a comment from pcre2test.c:
>>      However, even after matching a non-empty string, there is still one
>>      tricky case. If a pattern contains \K within a lookbehind assertion at the
>>      start, the end of the matched string can be at the offset where the match
>>      started. In the case of a normal /g iteration without special action, this
>>      leads to a loop that keeps on returning the same substring.
>> The code now checks for this case and advances the /g loop by one
>> character, just as it does for matching an empty string.
> Sounds like we have the same problem in Perl.
> Karl, if you dont see a way to fix this then let me know and I will pick it up.
> Cheers,
> yves

I haven't ever looked at the \K code; I was hoping someone else would 
look at this.

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