`OSAtomicCompareAndSwap64Barrier`, `OSAtomicIncrement64Barrier`, `OSAtomicDecrement64Barrier` are deprecated

[dworak]

[neakor]

I can't reproduce this with Xcode 10. How do I reproduce this?

[dworak]

Set the deployment target to iOS 10.0

[neakor]

@dworak here's the PR (#26) that addresses the deprecated APIs in AtomicInt. I'll follow up with another one for AtomicReference.