[Webkit-unassigned] [Bug 154009] New: GetValueFunc/PutValueFunc should not take both slotBase and thisValue

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=154009

            Bug ID: 154009
           Summary: GetValueFunc/PutValueFunc should not take both
                    slotBase and thisValue
    Classification: Unclassified
           Product: WebKit
           Version: Other
          Hardware: Unspecified
                OS: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: JavaScriptCore
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: barraclough at apple.com

In JavaScript there are two types of properties - regular value properties, and accessor properties. One difference between these is how they are reflected by getOwnPropertyDescriptor, and another is what object they operate on in the case of a prototype access. If you access a value property of a prototype object it return a value pertinent to the prototype, but in the case of a prototype object returning an accessor, then the accessor function is applied to the base object of the access.

JSC supports special 'custom' properties implemented as a c++ callback, and these custom properties can be used to implement either value- or accessor-like behavior. getOwnPropertyDescriptor behavior is selected via the CustomAccessor attribute. Value- or accessor-like object selection is current supported by passing both the slotBase and the thisValue to the callback,and hoping it uses the right one. This is probably inefficient, bug-prone, and leads to crazy like JSBoundSlotBaseFunction.

Instead, just pass one thisValue to the callback functions, consistent with CustomAccessor.

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