finalizer

If the app thread holds a monitor when the finalizer is called, that would usually make the finalizer block until the app exits the monitor.

Another thing not mentioned in the article is that if you implement a finalizer your code becomes multithreaded.

A finalizer is an appropriate vehicle for performing this task, assuming the native peer holds no critical resources.

Once you have a finalizer your disposer needs to become thread-safe (and lock-free, you must never use a mutex in a finalizer).

But in that world, relying on something like a finalizer is impossible since your object will never be collected -- ever.

To make this work, the JIT would need to perform escape analysis on the finalizer too (since the finalizer can make an object escape).

It turned out that the finalizer queue is pretty low priority, so event subscriptions weren’t getting disposed by the finalizer until there was time to do so.

Even then, though, you would have to think carefully about all the subtle ramifications, like the consequences running a finalizer on an application thread instead of the finalizer thread.

Another problem is resurrection, where the finalizer creates a new reference to self or another finalized object.

[1] Which creates a reference-counted cycle containing the thing-to-be-forgotten, ensuring the finalizer is never called.

Rust always has unwinding, and the finalizer can just call `abort` to make this as linear as you can.

Secondly, he needs GC to trigger code that mutates the no-longer-referring object; the finalizer runs in the no-longer-referred-to object.

When I think I need one, I ask myself the following question: "Am I hacking on the core framework?" If the answer is no, then I probably shouldn't be writing a finalizer.

"it is possible that the finalizer and constructor are running concurrently."

In the languages you mention (and most other languages with a "with" or "IDisposable" equivalent), the "close" equivalent, or even the finalizer, can be called on objects that still have valid references to them hidden in another object or thread.

SafeHandle inherits CriticalFinalizerObject which triggers special GC treatment of the finalizer.