I have seen other questions dealing with “Capture of … with non-sendable type ‘…’ in an isolated closure” error, but none of them talk about autoreleasepool.

The relevant code:

Error appears in this part:

Self.workQueue.async {
            
    autoreleasepool {
        // Error in the following line:
        self.doWork(pixelBuffer: pixelBuffer, completion: completion)
    }
}

The error verbatim is:

Capture of ‘pixelBuffer’ with non-sendable type ‘CVPixelBuffer’ (aka ‘CVBuffer’) in an isolated closure; this is an error in the Swift 6 language mode

Class ‘CVBuffer’ does not conform to the ‘Sendable’ protocol (CoreVideo.CVBuffer)

The workqueue is defined as:

private static let workQueue = DispatchQueue(
    label: "...",
    qos: .userInitiated,
    autoreleaseFrequency: .workItem, // switching from default .never
    target: .global(qos: .userInitiated)
)

and doWork is defined as a private extension to the same class with signature

func doWork(pixelBuffer: CVPixelBuffer, completion: @escaping (SomeResult?, Error?) -> Void)

I can resolve the error if I remove autoreleasepool, i.e. this won’t produce any error:

Self.workQueue.async {
    self.doWork(pixelBuffer: pixelBuffer, completion: completion)
}

But the autoreleasepool was introduced as a fix for memory leak, related to doWork processing of the frames.

So now I am trying to understand what changed, and how to adjust to new requirements.

To be clear I am not looking for solution to this issue (it may require bigger refactoring, than fits one question). I am looking for explanation / guidance on:

• What this error in conjunction with autoreleasepool means
• What would be a correct way to use CVPixelBuffer / CVBuffer with autoreleasepool?

Thanks in advance.