> Note that Rust doesn't fix this problem. Rust just encodes the assumption of pre-known lifetimes much more strongly in the language. If you're not in such a domain then you have to fall back to refcounting, which is (a) slow and (b) easy to get wrong such that you leak anyway. Early versions of Rust used refcounting for everything and iirc they found anywhere between 10-15% of the resulting binaries was refcounting instructions!

Well, modern idiomatic Rust only uses Arc/Rc on the few objects where it's needed, so the overhead of reference count adjustment is so tiny as to never show up. You typically only see reference count traffic be expensive when either (a) everything is reference counted, as in ancient Rust; or (b) on super-inefficient implementations of reference counting, as in COM where AddRef() and Release() are virtual calls.