nodejs / nodejs/node-addon-api
Supporting circular references that can be garbage collected.
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- Dominant language
- C++
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Description
In JavaScript I can make two objects that reference each other and they'll still be GCed.
function makeObjectsThatReferenceEachOtherButLeakNoReferences() {
const a = new Uint8Array(1024);
const b = new Uint8Array(1024);
a.other = b; // make them reference each other
b.other = a;
}
makeObjectsThatReferenceEachOtherButLeakNoReferences();
In the code above, even though a circular reference was created, JavaScript will see there is no path from root and garbage collect the objects.
Is it possible to do the same in C++ Napi. If I make a class
class MyClass : public Napi::ObjectWrap<MyClass> {
...
Napi::Reference<Napi::Object> storedObjectRef_;
};
And I manage to make 2 instanced of MyClass and set storedObjectRef_ so they point to each other, AFAICT these objects will never be garbage collected.
Is there a solution?
Note: I know I could add some function close or whatever to null out storedObjectRef_ but that's not really the question I'm asking. I'm trying to reproduce JS garbage collecting circular references.
One idea I guess, which appears to work, is I could add a JS property to MyClass. So instead of Napi::Reference<Napi::Object> storageObjectRef_ I'd use Get, Set as in
this->Value().Set("storageObjectRef", otherObject);
but unfortunately that's visible externally which I don't want. I could use a symbol but those are inspectable too. Though it might be better than nothing if there is no other solutions.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
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Research direction
Start with the Napi::ObjectWrap and Napi::Reference usage shown in the issue, then investigate how Node-API handles native references and garbage collection for mutually referencing objects. Done means establishing whether collectible circular references are supported and documenting or proposing the required API-level approach; the issue does not name a source file or test.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- cpp, nodejs
- Domain
- backend
- Issue type
- Feature
- Difficulty
- 5/5
- Estimated time
- Over a week
- Activity status
- Stale
- Clarity
- Needs clarification
- Newbie friendliness
- 25/100