Tail Recursion, Objective-C, and ARC
The problem is revealed: there is work to be done after the recursive call: automatic reference counting inserted a release call for the value returned from
node.next. If we were writing this with manual retain/release, one wouldn’t insert any memory management calls into this at all, because-nextreturns an autoreleased object. However when this is compiled under ARC, calls toobjc_retainAutoreleasedReturnValueandobjc_releaseare inserted to allow for another optimization — having the return value skip the autorelease pool entirely. Unfortunately in this case, it conflicts with tail call optimization.[…]
In an ARC environment, tail call optimization (and thus tail recursion) is too fragile. Don’t rely on it.
