Bug 55479 – Begin Characters Optimization Causes YARR Interpreter Errors

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

[Michael Saboff]

This issue was found while investigating https://bugs.webkit.org/show_bug.cgi?id=54978.

The temporary resolution to that defect was to disable the setting up of the begin characters optimization.

It appears that the begin characters code is not properly setting up the data.  From the original bug, it appears that the regular expression:
    /<((\/([^>]+)>)|(([^>]+)>))/
correctly finds '<p>' from the string '<p>This content should not appear as HTML <strong>source</strong>.</p>' when run via the interpreter.  If one adds (ABC>) as an alternative to the regular expression:
    /<((ABC>)|(\/([^>]+)>)|(([^>]+)>))/
then the interpreter doesn't find '<p>' in the subject string.

Walking through the code, the setupBeginChars() method determines that the first expression (w/o the (ABC>)) is not a candidate for the begin characters optimization.  The setupBeginChars() determines that the second expression is a candidate for the begin characters optimization and it looks for the strings "<A" and "</" which come from the first two alternatives. The last alternative isn't included in the optimization strings.

[Peter Varga]

Created attachment 84418 [details]
proposed patch

Thanks for the report. I fixed the bug and upload some additional test cases.

[Peter Varga]

Created attachment 84419 [details]
proposed patch v1.1

regexp-alternatives.js layout test's expected file is fixed.

[Peter Varga]

Created attachment 84432 [details]
proposed patch v1.2

Extend the layout test to force the testing of the YARR Interpreter.

[Michael Saboff]

Comment on attachment 84432 [details]
proposed patch v1.2

Looks good.   Thanks for addressing this quickly.

[WebKit Review Bot]

Comment on attachment 84432 [details]
proposed patch v1.2

Rejecting attachment 84432 [details] from review queue.

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[Oliver Hunt]

Comment on attachment 84432 [details]
proposed patch v1.2

r=me

[WebKit Commit Bot]

Comment on attachment 84432 [details]
proposed patch v1.2

Clearing flags on attachment: 84432

Committed r80217: <http://trac.webkit.org/changeset/80217>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.