[SR-2500] deinit not called for singletons

[karwa]

Previous ID	SR-2500
Radar	None
Original Reporter	@karwa
Type	Bug
Status	Reopened
Resolution

Environment

Swift 5d21c2a

Additional Detail from JIRA

Votes	1
Component/s
Labels	Bug
Assignee	None
Priority	Medium

md5: 87c3da070e6443586ce467201d6d37fc

Issue Description:

class A {
          static let shared = A()
          private init() {}
          deinit { print("deinit called") }
}
print("\(A.shared)")

Output:

test.A

Expected Output:

test.A
deinit called

Basically I would expect that, at the end of the program, the singleton's deinit would be called. Am I wrong to expect that?

[karwa]

OK, doesn't matter, but I think we should have a way to clean up global resources from singletons on application termination.

[karwa]

Hmm... I don't know, I'd like to reopen this to ask how to achieve a similar functionality. For example, in C++ you could write:

class SingletonTest {
private:
  SingletonTest() {}
  ~SingletonTest() {
    std::cout << "Destructing!!" << std::endl;
  }

public:
  static SingletonTest& get_instance()  {
    static SingletonTest instance;
    return instance;
  }
};

To create a lazily-initialised singleton that will be destructed on exit; but we can't have static locals in Swift. So how would I create a singleton which has some external resources (e.g. temporary files) and cleans them up properly on exit?