[Concurrency] Don't pass negative times to the Dispatch code. #81335
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Dispatch uses unsigned times, and cannot cope with times before its clock started. As such, passing negative times from Swift through to the C++ code results in large unsigned values, which then causes us to wait forever. This is undesirable. rdar://148899609
…och. Add a test to check that attempting to `Task.sleep(until:)` passing a time before the start of the Dispatch clocks works and doesn't wait forever. rdar://148899609
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Explanation: If you ask |
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@swift-ci Please test |
| func clamp(_ components: (seconds: Int64, attoseconds: Int64)) | ||
| -> (seconds: Int64, attoseconds: Int64) { | ||
| if components.seconds < 0 | ||
| || components.seconds == 0 && components.attoseconds < 0 { |
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Does a time with positive seconds and negative attoseconds actually make sense?
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:-) All three of us worried about that. It might make sense, but it can't happen because these components are calculated from a 128-bit attosecond count in Swift.Duration — so you could never end up with positive seconds and negative attoseconds.
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Dispatch uses unsigned times, and cannot cope with times before its clock started. As such, passing negative times from Swift through to the C++ code results in large unsigned values, which then causes us to wait forever. This is undesirable.
rdar://148899609