What's the intended use case of this option?
On Tuesday, February 27, 2018 at 4:21:03 PM UTC-8, Ben Noordhuis wrote:
>
> On Tue, Feb 27, 2018 at 5:49 AM, A.M. <cis7...@gmail.com <javascript:>>
> wrote:
> > Calling `SetWeak` like this:
> >
> > global_handle.SetWeak(parameter, &X::WeakCallback,
> > v8::WeakCallbackType::kInternalFields);
> >
> > , against a handle that contains an object with internal fields calls
> > `X::WeakCallback` with the parameter and both internal fields of
> > `v8::WeakCallbackInfo<v8::Global<v8::Object>>` always return `NULL`.
> >
> > Looking at
> > `v8::internal::GlobalHandles::Node::PostGarbageCollectionProcessing`,
> which
> > calls the weak callback, those internal fields are always `NULL`:
> >
> > void* embedder_fields[v8::kEmbedderFieldsInWeakCallback] = {nullptr,
> >
> nullptr};
> > v8::WeakCallbackInfo<void>
> data(reinterpret_cast<v8::Isolate*>(isolate),
> > parameter(), embedder_fields,
> nullptr);
> > weak_callback_(data);
> >
> >
> > Is that some experimental feature or there's some way to make object's
> > internal fields available within the weak callback?
> >
> > Thanks
>
> You're looking at the wrong code.
> GlobalHandles::Node::PostGarbageCollectionProcessing() only deals with
> weak handles, not phantom handles.
>
> WeakCallbackType::kInternalFields creates a phantom handle (confusing,
> I know) and those are dispatched in
> GlobalHandles::PostGarbageCollectionProcessing().
>
> IIRC, it's a two-pass system: first pass should reset the persistent
> handle, second pass is the real finalizer. Preempting the question of
> why it works that way: I don't know. :-)
>
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