XPC connection interrupted

An XPC connection is interrupted when the remote process terminates. This can happen for abnormal reasons (for example, the remote process crashing) and for normal reasons (the system terminating the remote process to recover memory). If you’re using XPC directly, which is typically only done on macOS [1], you must be prepared to handle either eventuality.

However, it seems that you’re on iOS, in which case you rarely use XPC directly but rather use it via some framework, and it’s the framework’s responsibility to handle interruptions. So the actual problem here is a bit of a mystery.

You wrote:

I am getting this error, "XPC connection interrupted" and caused my app to crash.

Please post the crash report you got.

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Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

[1] XPC is available on iOS starting with iOS 11, but the only supported use case is custom calls to file providers, which is a pretty obscure part of the system. If you’re using XPC directly, please do let me know.

'NSWindow drag regions should only be invalidated on the Main Thread!'

Something in your process is calling AppKit from a secondary thread. It’s hard to say what because you’ve posted a truncated backtrace. What does the full backtrace look like?

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Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"

Oh, you’re running this within an XPC Service! That’s a critical tibit.

Consider this snippet from your crash report:

Crashed Thread: 4  Dispatch queue: com.apple.main-thread

What’s weird about this is that the main queue is being run by thread 4. In normal application code, the main queue is always run by the main thread, that is, thread 0.

The reason this is happening is that you’re inside an XPC Service. By default an XPC Service’s main thread calls

dispatch_main

This is nice because it saves resources. If the XPC Service is dormant, there’s no point leaving a thread lying around doing nothing.

It’s weird because of its impact on main queue operations. When you dispatch something to the main queue, you expect it to run on the main thread, but here there’s no main thread to run the main queue. Instead, Dispatch temporarily assigns some other worker thread to run your main queue work. Main queue work is still serialised, it’s just not running on the main thread.

The problem comes when you call AppKit, which has all sorts of ‘must run on the main thread’ checks. In situation like this these checks will fail, throwing an exception that terminates your XPC Service process.

Fortunately there’s an easy fix: Configure your XPC Service to not call

dispatch_main

RunLoopType

NSRunLoop

xpcservice.plist

Share and Enjoy
—
Quinn “The Eskimo!”
Apple Developer Relations, Developer Technical Support, Core OS/Hardware

let myEmail = "eskimo" + "1" + "@apple.com"