Bug 101839 – REGRESSION(r133971): Causes WebProcess to hang at 100% on www.apple.com (Requested by kling on #webkit).

• Component: New Bugs
• Status: RESOLVED FIXED

[WebKit Review Bot]

http://trac.webkit.org/changeset/133971 broke the build:
Causes WebProcess to hang at 100% on www.apple.com (Requested by kling on #webkit).

This is an automatic bug report generated by the sheriff-bot. If this bug
report was created because of a flaky test, please file a bug for the flaky
test (if we don't already have one on file) and dup this bug against that bug
so that we can track how often these flaky tests case pain.

"Only you can prevent forest fires." -- Smokey the Bear

[WebKit Review Bot]

Created attachment 173451 [details]
ROLLOUT of r133971

Any committer can land this patch automatically by marking it commit-queue+.  The commit-queue will build and test the patch before landing to ensure that the rollout will be successful.  This process takes approximately 15 minutes.

If you would like to land the rollout faster, you can use the following command:

  webkit-patch land-attachment ATTACHMENT_ID

where ATTACHMENT_ID is the ID of this attachment.

[WebKit Review Bot]

Comment on attachment 173451 [details]
ROLLOUT of r133971

Clearing flags on attachment: 173451

Committed r134157: <http://trac.webkit.org/changeset/134157>

[WebKit Review Bot]

All reviewed patches have been landed.  Closing bug.

[Filip Pizlo]

Wow, sorry for the massive breakage!

The bug is that the way I wrote the DFG's optimizations of statements of the form:

if (foo) blah

!foo

I forgot that the empty string evaluates to false in these contexts, and instead wrote the optimization to assume that if I have a string then it's always true.

The fix is to change the optimization to exclude strings from the object-isn't-false optimization.