withCheckedContinuation crashes on Xcode 16 RC

[MarkVillacampa]

Description

I can reproduce on Xcode 16 RC and Xcode 16.1 beta, but ONLY when running the app as "Designed for iPhone/iPad" on macOS Sonoma, and ONLY in debug mode (crash goes away in release mode).

I cannot reproduce by running on iOS 17 or 18 neither device nor simulator, and cannot reproduce either when running on macOS Sequoia beta.

Some developers have reported the issue also reproduces when installing the app via TestFlight on an iOS 18 device.

Original issue: RevenueCat/purchases-ios#4177

FB14855530

Reproduction

_ = try await withCheckedContinuation { continuation in
    continuation.resume(returning: true)
}

Stack dump

Thread 0 Crashed:
0   asdfsadf.debug.dylib          	       0x102551354 withCheckedContinuation<A>(isolation:function:_:) + 232
1   asdfsadf.debug.dylib          	       0x102551135 closure #1 in closure #2 in ContentView.body.getter + 1 (ContentView.swift:21)
2   asdfsadf.debug.dylib          	       0x102552299 partial apply for closure #1 in closure #2 in ContentView.body.getter + 1
3   libswift_Concurrency.dylib    	       0x2548aa0f9 completeTaskWithClosure(swift::AsyncContext*, swift::SwiftError*) + 1

Expected behavior

It doesnt crash

Environment

Xcode 16.1 beta 1

Apple Swift version 6.0 (swiftlang-6.0.0.7.6 clang-1600.0.24.1)
Target: arm64-apple-macosx14.0

Additional information

No response

[MarkVillacampa]

Quick update:

• Crash is still reproducible in Xcode 16 beta 6.
• The crash happens with withCheckedThrowingContinuation as well:

_ = try await withCheckedThrowingContinuation { continuation in
    continuation.resume(returning: true)
}

[mszyszylo]

Same issue for me.

I'm on Xcode 16.1 beta.

App crashes like @MarkVillacampa described with only iOS 18 simulators.

Thread 1: EXC_BAD_ACCESS (code=1, address=0x4)

[MarkVillacampa]

The crash is still present in Xcode 16 RC when running a Debug build as "Designed for iPad/iPhone" on macOS Sonoma

[random-yang]

Has anyone posted a question on the Apple Developer Forum, and is there a final solution to the problem?

[kiran-nayak-cheq]

+1. Any update on this?

[random-yang]

@kiran-nayak-cheq
Looks like the issue has been fixed in the updated version?
https://developer.apple.com/forums/thread/761580
https://forums.developer.apple.com/forums/thread/762682?page=1#803104022

[guidedways]

We're seeing this for our publicly released apps using Xcode version 16.0 (16A242d) (published, final updates to App Store, not debug versions) where random users are seeing persistent crashes at launch and the stack traces are vague. We see the following in each of them though:

9   libswift_Concurrency.dylib    	       0x26737e8a5 completeTaskWithClosure(swift::AsyncContext*, swift::SwiftError*) + 1

We are personally unable to reproduce this in any environment (debug / release) or on any OS. The users experiencing this range from being on macOS 11 to macOS 15, and iOS 16 / 18. It could potentially be affecting all operating system versions but we are unable to say this with certainty. We are using Xcode 16 to compile our apps using Swift v5 (5.10, not 6). The last update posted from Xcode 15 does not exhibit this issue.