XMLHttpRequest is not a function under JavaScriptCore / Safari

[msridhar]

Currently, record-replay of jQuery 2.0.2 works fine on Chrome, but not in PhantomJS. The issue in PhantomJS is that for Safari's Webkit (JavaScriptCore), typeof XMLHttpRequest (and various other native functions) is object rather than function. (This behavior remains even for the most recent version of Safari.) This leads to replay errors for scripts like:

var xhrSupported = new XMLHttpRequest();

During replay, we get the error:

/Users/m.sridharan/git-repos/jalangi/src/js/analysis.js:703
                throw tmp;
                      ^
TypeError: object is not a function
    at callAsNativeConstructor (/Users/m.sridharan/git-repos/jalangi/src/js/analysis.js:441:24)
    at callAsConstructor (/Users/m.sridharan/git-repos/jalangi/src/js/analysis.js:463:27)
    at invokeFun (/Users/m.sridharan/git-repos/jalangi/src/js/analysis.js:525:31)
    at /Users/m.sridharan/git-repos/jalangi/src/js/analysis.js:618:24
    at Object.<anonymous> (/private/tmp/foo2_jalangi_.js:13:257)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Module.require (module.js:364:17)

The code change attached to this pull request "fixes" the problem, by special-casing the function test for XMLHttpRequest. But, it's a total hack. Unfortunately, I can't think of a more general way to detect and address this issue.

Is there a better way to fix this problem?

[msridhar]

Updated the pull request title to reflect the underlying issue with JavaScriptCore. This one is lower priority for the moment since we mostly gave up on PhantomJS, but it may bite us again in the future.