627609 - Empty group matching fails on /((a|)+b)+/.exec('bb')

Status: RESOLVED FIXED

(Core :: JavaScript Engine, defect)

Description

[Chris Leary [:cdleary] (not checking bugmail)]

dmandelin and I thought through this example in talking over the patch for bug 599854. We need a more robust way of tracking parens with valid empty group matches.

Comment 1

[David Mandelin [:dmandelin]]

Attachment: Patch

Comment 2

[Chris Leary [:cdleary] (not checking bugmail)]

Comment on attachment 506578 [details] [diff] [review]
Patch

This is clearly the right way to do it: if I knew what I was doing a little more when we first imported PCRE or we had a test case like this one, maybe I would have found this solution. :-)

Quantified assertions are invalid in the ES5 spec, although the ES3 grammar seems to allow it, which would calls into question examples like |/(?=foo)+/.exec('foofoo')|.

Can atOptionalBracket fall off the beginning of the pattern? If not, we should put a comment as to why the negative indexing is safe.

IRL we talked about whether BRAMINZERO was needed as a case within atOptionalBracket, but it doesn't seem so: if you lazy match my matching the empty string this situation should be equivalent to not executing the regexp within the lazy match at all. A comment about this within the atOptionalBracket would be nice.

Comment 3

[David Mandelin [:dmandelin]]

http://hg.mozilla.org/tracemonkey/rev/9f58085a9081

Comment 4

[Chris Leary [:cdleary] (not checking bugmail)]

cdleary-bot mozilla-central merge info:
http://hg.mozilla.org/mozilla-central/rev/9f58085a9081
http://hg.mozilla.org/mozilla-central/rev/0f340f13b171
http://hg.mozilla.org/mozilla-central/rev/68e341f7ac4e