> On Mar 31, 2016, at 3:58 PM, Patrick Pijnappel via swift-dev
> <swift-dev@swift.org> wrote:
>
> In trying to implement a COW type, but I'm running into problems with
> isUniqueReferenced breaking in even fairly simple cases. For example (with
> -O) the code below prints "bar: false", commenting out the print in test()
> makes it print "bar: true", and removing the var parameter var foo: Foo and
> using var foo = foo instead breaks it again. Am I doing something wrong here?
>
> class FooStorage { var x: Int = 0 }
>
> struct Foo { var storage = FooStorage() }
>
> func bar(var foo: Foo) {
> print("bar: \(isUniquelyReferencedNonObjC(&foo.storage))")
> }
>
> func test() {
> var foo = Foo()
> print("test: \(isUniquelyReferencedNonObjC(&foo.storage))")
> bar(foo)
> }
>
> test()
You're not doing anything wrong, this is just the ARC optimizer at work. `foo`
inside `test` is dead after the call to `bar`, so ownership is transferred
directly to `bar`'s parameter.
-Joe
_______________________________________________
swift-dev mailing list
swift-dev@swift.org
https://lists.swift.org/mailman/listinfo/swift-dev
