[vm/ffi] Disallow adding finalizers to Pointer #45071
Description
We should disallow Pointer in Dart_NewWeakPersistentHandle and Dart_NewFinalizableHandle.
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Pointers do not have identity. We might want to optimize them to just be integers later.
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Also the nested structs and inline arrays representation does not keep original pointers alive:
class Foo extends Struct {
external Bar bar;
}
class Bar extends Struct {
Int32()
external int a;
}
void main(){
Pointer<Foo> fooPointer = calloc();
// Attach native finalizer to `fooPointer` using `Dart_NewWeakPersistentHandle` or `Dart_NewFinalizableHandle`.
Foo foo = fooPointer.ref;
Bar bar = foo.bar;
// GC
bar.a; // undefined behavior.
}This is a breaking change.