Bug 119191 – Regular expressions with ".?" expressions at the start and the end match the entire string

• Status: RESOLVED
• Resolution: FIXED
• Component: JavaScriptCore

[Till Schneidereit]

STR:

Execute the following code in JSC:

'abcdefghijk'.match('.?e.?')

Expected result:
def

Actual result:
abcdefghijk


This also happens in SpiderMonkey, so it's almost guaranteed to be a Yarr issue.

[Till Schneidereit]

For SpiderMonkey, this regressed between two Yarr imports we did: 86639 was good, 130234 is bad.

[Sukolsak Sakshuwong]

Created attachment 344084 [details]
Patch

[Sukolsak Sakshuwong]

The benchmark results are at https://gist.github.com/sukolsak/da11c94998776a4dfb3340f12f7b7688. The patch doesn't seem to cause a significant slowdown. I can think of a way to optimize these cases (/.?abc.*/, /.*abc.?/, /.{0,4}abc.*/, etc), which involves storing the quantifiers of the leading and trailing dots in the DotStarEnclosure. But I'm not sure if we should do it.

[EWS Watchlist]

Comment on attachment 344084 [details]
Patch

Attachment 344084 [details] did not pass win-ews (win):
Output: https://webkit-queues.webkit.org/results/8410946

New failing tests:
http/tests/security/canvas-remote-read-remote-video-redirect.html
http/tests/security/video-poster-cross-origin-crash2.html

[EWS Watchlist]

Created attachment 344094 [details]
Archive of layout-test-results from ews205 for win-future

The attached test failures were seen while running run-webkit-tests on the win-ews.
Bot: ews205  Port: win-future  Platform: CYGWIN_NT-6.1-2.9.0-0.318-5-3-x86_64-64bit

[Michael Saboff]

Comment on attachment 344084 [details]
Patch

r=me

[Sukolsak Sakshuwong]

Thanks!

I ran some additional benchmark tests. (Thanks rniwa and yusukesuzuki for the help!). Here are the results.

Without the patch:
    RexBench         23.00 +- 1.71ms
    JetStream Score  203.41 +- 37.830

With the patch:
    RexBench         23.19 +- 3.13ms
    JetStream Score  200.63 +- 41.824

[Sukolsak Sakshuwong]

Created attachment 344156 [details]
Patch for landing

[WebKit Commit Bot]

Comment on attachment 344156 [details]
Patch for landing

Clearing flags on attachment: 344156

Committed r233453: <https://trac.webkit.org/changeset/233453>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Radar WebKit Bug Importer]

<rdar://problem/41750698>