[webkit-dev] Odd behavior with instrumentation of WebKit

Darin Adler darin at apple.com
Tue Mar 15 15:31:06 PDT 2011

On Mar 15, 2011, at 8:16 AM, Gregor Richards wrote:

> We maintain an instrumented branch of WebKit to do various dynamic measurements of JavaScript. One of our changes which should have no semantic effect on the behavior of JS is actually causing a visible change in the behavior of (at least) http://about.com/ . The visible difference is that the menus don't work, and the underlying reason seems to be that Array.prototype.slice is (rather inexplicably) being rewritten to undefined, causing further code to fail. I've worked the issue down to a single line

It’s good that you reduced your JavaScript changes down to a single line. Next step would be to make a local copy of the about.com site, reproduce the bug with that, and then reduce it as well. Once you do that it you can get to the bottom of it quickly.

    -- Darin

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