Mango Snippets » #10

iOS: Fixing a Crash on Launch Issue on Apple Silicon Macs

My iOS app Mango Baby is made available for Apple Silicon Macs. Ever since macOS Sonoma, it would crash on launch.

A similar crash on launch issue happened for the release of macOS Ventura. It was because the ActivityKit is not available on macOS. I fixed it by protecting calls to the ActivityKit APIs against isiOSAppOnMac at runtime. But apparently a new issue has appeared for macOS Sonoma.

Attempt 1

First I asked on Mastodon, and Matt Massicotte very kindly provided tips and walked me through the debugging process.

TIP: For crashes on launch, Apple-captured crash logs are much more helpful than Crashlytics. They can be accessed in Xcode following these instructions.

Through the crash logs, I discovered the following stacktrace:

Termination Reason: Namespace DYLD, Code 1 Library missing
Library not loaded: /System/Library/Frameworks/ActivityKit.framework/ActivityKit
Referenced from: <9B5A3687-FF24-3E38-9007-1DE6A69EFEEB> /Volumes/VOLUME/*/
Reason: tried: '/System/105Support/System/Library/Frameworks/ActivityKit.framework/ActivityKit'
(terminated at launch; ignore backtrace)

Thread Crashed:
0 dyld 0x0000000189391b48 __abort_with_payload + 8
1 dyld 0x000000018939e108 abort_with_payload_wrapper_internal + 104 (terminate_with_reason.c:102)
2 dyld 0x000000018939e13c abort_with_payload + 16 (terminate_with_reason.c:124)
3 dyld 0x0000000189325518 dyld4::halt(char const, dyld4::StructuredError const*) + 304 (DyldProcessConfig.cpp: 2890)
4 dyld 0x00000001893221e8 dyld4::prepare(dyld4::APIs&, dyld3::Mach0Analyzer const) + 3884 (dyldMain.cpp:0)
5 dyld 0x0000000189320f44 start + 1948 (dyldMain.cpp:1238)

Then I remembered that I had to weak link the ActivityKit framework in order to make Mango Baby continue available on Macs. This is done by adding -weak_framework ActivityKit to Other Linker Flags. But this stacktrace is from my BabyWidget app extension for widgets, and I didn't have the flag for my Widget target. I submitted an update along with other features.

Since I didn't know any way of testing iOS apps running on Macs, I didn't verify the fix. And it turns out Mango Baby is still crashing.

Attempt 2

Later I learned from Franklin on Threads that you can enable the Test iPhone and iPad Apps on Apple Silicon Macs option on App Store Connect. Then, you can at least use TestFlight to test your iOS app running on Mac. This still isn't ideal, but it's already 100 times better than nothing.

I checked new crash logs again, and they look like:

Exception Subtype: KERN_INVALID_ADDRESS at 0x0000000000000000
Exception Codes: 0x0000000000000001, 0x0000000000000000

Thread 0 Crashed::  Dispatch queue:
0   ???                           	       0x0 ???
1   Baby                          	       0x102c75b1c closure #1 in closure #1 in closure #1 in closure #2 in AppModel.init(storage:) + 32 (AppModel.swift:488) [inlined]
2   Baby                          	       0x102c75b1c partial apply for closure #1 in closure #1 in closure #1 in closure #2 in AppModel.init(storage:) + 60
3   SwiftUI                       	       0x1c96f4c38 0x1c7d86000 + 26668088
4   SwiftUI                       	       0x1c96f4f28 0x1c7d86000 + 26668840
5   libswiftCore.dylib            	       0x190f6025c withExtendedLifetime<A, B>(_:_:) + 28
6   SwiftUI                       	       0x1c96f3420 0x1c7d86000 + 26661920
7   SwiftUI                       	       0x1c96f2f74 0x1c7d86000 + 26660724

Thread 0 crashed with ARM Thread State (64-bit):
    x0: 0x0000000000000000   x1: 0x0000000000000000   x2: 0x0000000000000103   x3: 0x0000600000296400
    x4: 0x0000000000000000   x5: 0x0000000000002760   x6: 0x00000001d94074e8   x7: 0x00000000ffffffff
    x8: 0x000000016d4658f0   x9: 0x000000016d465910  x10: 0x0000000000002760  x11: 0x00000000982478cd
   x12: 0x00000000000007fb  x13: 0x00000000000007fd  x14: 0x00000000984480d3  x15: 0x00000000000000d3
   x16: 0x0000000000000000  x17: 0x00000001d98d6c30  x18: 0x0000000000000000  x19: 0x000000016d4659d0
   x20: 0x000000016d465950  x21: 0x0000600002336710  x22: 0x00006000039a3020  x23: 0x0000000000000000
   x24: 0x000000016d465930  x25: 0x000000010372ebe8  x26: 0x00000001d98d3ec8  x27: 0x000000000000000f
   x28: 0x0000000000000000   fp: 0x000000016d465d90   lr: 0x0000000102c4ca70
    sp: 0x000000016d4658f0   pc: 0x0000000000000000 cpsr: 0x20001000
   far: 0x0000000000000000  esr: 0x82000006 (Instruction Abort) Translation fault

Binary Images:
0x102998000 - 0x1035b3fff com.mangoumbrella.Baby (2023.12) <ca277200-885e-3b08-8ee2-93648cc69108> /private/var/folders/*/

Following this helpful Investigating memory access crashes article from Apple, I ran the following command to discover the exact line it's crahsing:

$ atos -arch arm64 -o atos -arch arm64 -o /Applications/Mango\ -l 0x102998000 0x0000000102c4ca70
closure #2 in AppModel.processRemoteRecordEvents(events:) (in Baby) (AppModel.swift:1009)

And the line is:

if !ProcessInfo.processInfo.isiOSAppOnMac {
    LiveActivitiesManager.shared.syncAll()  // Crash here.

This doesn't make sense to me since this line shouldn't execute at all. It's protected by the isiOSAppOnMac check, and all the ActivityKit API calls are isolated in my LiveActivitiesManager class.

My only guess right now is that this might have something to do with branch predictions and the runtime will load the instructions even if they aren't executed at runtime in the end. With this guess, I have one solution in my mind: introduce a Protocol and two concrete classes for all my ActivityKit related functions. Something like:

protocol LiveActivitiesManagerProtocol {
    func syncAll()

class LiveActivitiesManager {
    static let shared: LiveActivitiesManagerProtocol = {
        if ProcessInfo.processInfo.isiOSAppOnMac {
            return NoopLiveActivitiesManager()
        } else {
            return RealLiveActivitiesManager()

fileprivate class NoopLiveActivitiesManager: LiveActivitiesManagerProtocol {
    func syncAll() {}

fileprivate class RealLiveActivitiesManager: LiveActivitiesManagerProtocol {
    func syncAll() {
        // Use ActivityKit APIs.

This code is now released in Mango Baby v2023.14 and it no longer crashes on Sonoma.