On Tue, Jun 10, 2025 at 12:30 AM 蔡曜丞（つむぎ） <[email protected]> wrote:
> Hi,
>
> I'm updating v8 from v10.2.154.26 to v 12.4.254.
> I found out kFinalizer is deprecated in the newer version so I have to
> rework the weakcall back part in my implementation.
> When I simply change the kFinalizer in to kParameter in my SetWeak call,
> the program crashes when I calles SetAlignedPointerInInternalField in the
> destructor of my class under certain circumstance.
> I'm wondering what's the correct way to use internal field, and the reason
> why it's crashing if I change WeakCallbackType from kFinalizer to
> kParameter.
>
> The following is some code segment of my implementation.
>
> class A {
> v8::Persistent<v8::Object> mObject;
> }
>
> A::~A ()
> {
> if ( !mObject.IsEmpty() )
> mObject.ClearWeak();
> mObject.Reset();
> }
>
> void
> A::Wrap (v8::Local<v8::Object> const &object)
> {
> object->SetAlignedPointerInInternalField(0, this);
> mObject.Reset(v8::Isolate::GetCurrent(), object);
> }
>
> B::B() :A() {}
>
> B::~B()
> {
> if (!mObject.IsEmpty() && GetRuntime()->IsValid())
> {
> v8::Local<v8::Object> obj =
> v8::Local<v8::Object>::New(v8::Isolate::GetCurrent(), mObject);
>
I don't think a generic object has internal fields... all of my objects
that have internal fields came from a FunctionTemplate which looks like
volumeTemplate = FunctionTemplate::New( isolate, New );
volumeTemplate->SetClassName( String::NewFromUtf8Literal( isolate,
"sack.vfs.Volume" ) );
volumeTemplate->InstanceTemplate()->SetInternalFieldCount( 1 ); // 1
required for wrap
...
save the function (or use getfunction later to get the constructor
function instance
c->volConstructor.Reset( isolate, volumeTemplate->GetFunction(
isolate->GetCurrentContext() ).ToLocalChecked() );
get the constructor function
Local<Function> cons = Local<Function>::New( isolate, c->volConstructor
);
// and then make an instance of that - this new object will have an
internal field allocated for it.
MaybeLocal<Object> mo = cons->NewInstance( context, argc, argv );
> obj->SetAlignedPointerInInternalField(0, NULL); // Crashes here,
> seems obj is already collected, Is this needed to prevent dangling pointer?
> }
> }
>
> C::C()
> :B()
> {
> v8::Local<v8::Object> target =
> Initialize()->GetFunction(ctx).ToLocalChecked()
> ->NewInstance(ctx).ToLocalChecked();
>
> Wrap(target);
> mObject.SetWeak(this, WeakCallback, v8::WeakCallbackType::kParameter);
> // Was kFinalizer in previous version, no crash.
> }
>
> C::~C()
> {
> mObject.ClearWeak();
> }
>
> void
> B::WeakCallback(const v8::WeakCallbackInfo<C>& data)
> {
> C* self = data.GetParameter();
> self->EarlyComplete();
> delete self;
> }
>
> --
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>
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