Swift Deinitialization of Globals

Question

My Swift globals are not getting deinitialized.

class Person {
  let name: String
  init(name: String) {
    self.name = name
    println("\(name) is being initialized")
  }
  deinit {
    println("\(name) is being deinitialized")
  }
}

func local() {
  let person = Person(name: "Local")
}

local()

var personp: Person? = Person(name: "Optional Global")
personp = nil

var person = Person(name: "Global")

I am running this in a standalone binary (because apparently the playground has issues with deinit) with optimizations disabled, using Xcode6-Beta3:

> xcrun swift -O0 arc.swift && ./arc
Local is being initialized
Local is being deinitialized
Optional Global is being initialized
Optional Global is being deinitialized
Global is being initialized

Note the missing Global is being deinitialized.

I can't even figure out if this is expected behaviour or a bug, so if it is the former then references to the relevant legalese will be appreciated.

Answer 1

it looks fine to me... on ending the app nothing is deallocated - there is no point

---

deinit is only meant to FREE memory and remove observers and stuff - upon ending the process though, this is kinda 'useless' as the process memory 'will be wiped' anyways

==>

SO:

never put anything but memory management / observer related stuff in deinit

If you need a dedicated stop method - write one and call it explicitly before quitting the process

Answer 2

Think of the last line of code as:

var personp: Person? = Person(name: "Optional Global")
personp = nil

var person = Person(name: "Global")

exit(0)

Since person is never set to another value, ARC never decreases the retain count before the exit.

Swift works like a C program in that execution simply terminates and then all memory allocated to the process is returned in one sweep.

This is very different from in-execution memory handling which relies on in-process events to free memory. Since all execution of the program has completely stopped, there is no thread to run the deinit.

So in conclusion, this is just as it should be.