[Webkit-unassigned] [Bug 40012] New: Callable objects created via JavaScriptCore API cannot be used as Geolocation callbacks

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=40012

           Summary: Callable objects created via JavaScriptCore API cannot
                    be used as Geolocation callbacks
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebCore JavaScript
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: ap at webkit.org
                CC: sam at webkit.org, barraclough at apple.com


Geolocation specification requires that only "Function objects" can be used for Geolocation callbacks. We currently require the callback to inherit from JSFunction, which is almost definitely incorrect, because this doesn't include functions created via API.

In JSC, there are two ways to check for being callable:
1) Check callData return value. That's the closest to just trying to call the object, but it includes RegExp objects, which we may or may not want to exclude;
2) Check that className is "Function". That seems to match the current WebIDL text best, but it doesn't cover objects created via API.

The reason for the spec requirement is reportedly to disallow objects with handleEvent property, and that makes sense, because the callbacks aren't events. But Geolocation shouldn't really be different from Database or other APIs that have callbacks. Web APIs don't check for callback argument types upfront (I actually suspect that a JS object can even become callable - or cease to be callable - at some point after creation, making upfront checks inadequate).

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