Concurrency: Introduce a CheckedContinuation adapter.
#35188
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| if let c = continuation { | ||
| c.resume(returning: x) | ||
| // Clear out the continuation so we don't try to resume again | ||
| continuation = nil |
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Perhaps CheckedContinuation should be thread-safe? Here we use an ordinary write to clear out the continuation once its fired, which could be racy in some of the most remarkable misuses of continuations, something like:
var cont : CheckedContinuation<Void>? = nil
func capture() async {
await withCheckedContinuation { k in cont = k }
}
func access() async {
async let x = cont!.resume(returning: ())
async let y = cont!.resume(returning: ())
}
To help catch runtime issues adopting `withUnsafeContinuation`, such as callback-based APIs that misleadingly invoke their callback multiple times and/or not at all, provide a couple of classes that can take ownership of a fresh `UnsafeContinuation` or `UnsafeThrowingContinuation`, and log attempts to resume the continuation multiple times or discard the object without ever resuming the continuation.
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@kavon Alright, I made it thread-safe by doing an atomic xchg with null when we take the continuation. @slavapestov I also made the type resilient so we can use more clever mechanisms for checking if we get them later. |
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To help catch runtime issues adopting
withUnsafeContinuation, such as callback-based APIs that misleadinglyinvoke their callback multiple times and/or not at all, provide a couple of classes that can take ownership of
a fresh
UnsafeContinuationorUnsafeThrowingContinuation, and log attempts to resume the continuation multiple timesor discard the object without ever resuming the continuation.