It incurs some cost, but whether it is higher is very debatable. This is very much workload dependent. A smart compiler can elide most reference updates.

No it can't, not in Swift's current implementation.

https://github.com/ixy-languages/ixy-languages

It would seem that the Swift compiler is far from smart[1].

[1]: <https://media.ccc.de/v/35c3-9670-safe_and_secure_drivers_in_...

Apple's ARC is not a GC in the classic sense. It doesn't stop the world and mark/sweep all of active memory. It's got "retain" and "release" calls automatically inserted and elided by the compiler to track reference counts at runtime, and when they hit zero, invoke a destructor. That's not even close to what most people think of when they think "gc". Of course it's not free, but it's deterministic.

I think you are being borderline pedantic here. ARC _is_ GC in the classic sense: https://en.wikipedia.org/wiki/Garbage_collection_(computer_s...

I agree with you that most people tend to associate GC with something more advanced nowadays, like mark and sweep as you said in another comment, but it seems pointless to argue that ARC is not a form of GC.

You're using a hearsay, folklore definition of GC, not a CS one.

Refcounting in the presence of threads is usually non-deterministic too.

It is non deterministic, but at a much different scale.