Why doesn't my Chrome Profiler show proper retaining paths for my objects, and why are my objects never released?

Question

I am trying to debug memory leaks in my webapp.

I take snapshots of the heap and compare different heaps.

I found out that some of my objects are being references somewhere. However, all of my objects are being retained through objects that looks internal to me, eg:

As you can see, this SectionNavView object is being referenced by a few methods that I have created: cleanUp, hide, isShown, etc. using my local variable that, but these methods are being referenced from something that I do not control: idToWrappedObject. Sometimes, there's another intermediary - a injectedScript object.

If my objects are only being referenced form internal V8 references, shouldn't they be released before the profiler takes a snapshot during its GC?

Answer 1

This simply means that you've used console.log. So the VM keeps a reference to your objects in order to allow you to inspect them later. You can either stop using the console or just clear it every time you take a heap snapshot.

You can reproduce it with the following steps:

1. Open new tab
2. Open console (clear it, if there is anything)
3. Take heap snapshot 1
4. Type console.log({ foo:'bar' }) in the console
5. Take heap snapshot 2
6. Clear the console
7. Take heap snapshot 3

Then view the results:

1. Open the comparison view between snapshot 2 and snapshot 1; you'll find the { foo: 'bar' } object

   

2. Open the comparison view between snapshot 3 and snapshot 2; you'll find the same object now displays a delta of -1, meaning it was garbage-collected after you cleared the console

   

Finally, you may also see "Global handles" and then "GC roots" in the retaining tree paths, beside _idToWrappedObject and InjectedScript. I'm not sure how this applies to the definition of GC roots but clearing the console does allow garbage collection.