Status: New
Owner: ----
New issue 2075 by [email protected]: Implement AccessorInfo.IsInstanceOf()
http://code.google.com/p/v8/issues/detail?id=2075
Currently a DOM attribute is defined on a DOM object, but the Web IDL spec
requires that a DOM attribute should be defined on the prototype chain.
If we define the DOM attribute on the prototype chain, the V8 binding needs
to check whether the DOM attribute is implemented in 'this'. For example,
consider the following case:
var xhr = new XMLHttpRequest();
xhr.__proto__ = HTMLElement.prototype;
xhr.lang; // Crash!!
To avoid such kind of crash, the V8 binding needs to insert
the "instance-of" check, like this:
static v8::Handle<v8::Value> langAttrGetter(v8::Local<v8::String> name,
const v8::AccessorInfo& info)
{
if (!V8HTMLElement::GetTemplate()->HasInstance(info.This())) /*
The "instance-of" check. This checks whether 'lang' is defined on 'this'. */
return throwError(V8Proxy::TypeError);
Element* imp = V8Element::toNative(info.This());
return v8ExternalString(imp->getAttribute(HTMLNames::langAttr));
}
This works correctly. However, doing the "instance-of" check in the V8
binding side is too heavy. Considering the fact that V8 already knows the
result of the "instance-of" check before calling back langAttrGetter(), V8
can include the result of the "instance-of" check into AccessorInfo. In
other words, we want AccessorInfo.IsInstanceOf().
For more details (viewable from google internal only):
https://docs.google.com/a/google.com/document/d/1ldrDdfcwij5_juqvRpI_Rq20SgWiR88c4DUFvkQ0olU/edit
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