SwiftUI App crashes in main method on Startup (macOS 11)

Question

Created Feb ’21

Replies 3

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Hi,
my app sees quite a lot of crashes (crash report below) and I have no clue how to debug the problem any further.

The problems seems only to occur on macOS 11. Is there anyone als having this kind of problems? Are there fixes/workarounds?

The source code of my app is open source if anyone would like to have a look into it.

Code Block OS Version: macOS 11.2.2 (20D80)
Report Version: 104
Exception Type: EXC_BAD_INSTRUCTION (SIGILL)
Exception Codes: ILL_NOOP at 0x00007fff2ca430f4
Crashed Thread: 0
Application Specific Information:
Fatal error > SwiftUI
Thread 0 Crashed:
0   libswiftCore.dylib              0xfffe591310f4      _assertionFailure
1   SwiftUI                         0xfffe8516c6fc      ViewCache.commitPlacedChildren
2   SwiftUI                         0xfffe850727f4      IncrementalChildPlacements.updateValue
3   SwiftUI                         0xfffe8512890e      Attribute.init<T>
4   AttributeGraph                  0xfffe8625b17e      AG::Graph::UpdateStack::update
5   AttributeGraph                  0xfffe8625b607      AG::Graph::update_attribute
6   AttributeGraph                  0xfffe862638f2      AG::Subgraph::update
7   SwiftUI                         0xfffe85463679      GraphHost.runTransaction
8   SwiftUI                         0xfffe85464bce      GraphHost.runTransaction
9   SwiftUI                         0xfffe85463ec8      GraphHost.flushTransactions
10  SwiftUI                         0xfffe85464b6e      GraphHost.asyncTransaction<T>
11  SwiftUI                         0xfffe85464738      @callee_guaranteed
12  SwiftUI                         0xfffe84d172b0      ViewGraphDelegate.updateGraph<T>
13  SwiftUI                         0xfffe853201b9      ViewRendererHost.updateViewGraph<T>
14  SwiftUI                         0xfffe8531e2a8      ViewRendererHost.updateViewGraph<T>
15  SwiftUI                         0xfffe85329e98      NSHostingView<T>
16  SwiftUI                         0xfffe84d12f06      ViewGraphDelegate.updateGraph<T>
17  SwiftUI                         0xfffe84d17258      NSHostingView<T>
18  SwiftUI                         0xfffe85464b49      GraphHost.init
19  SwiftUI                         0xfffe84d18c9b      @callee_guaranteed
20  SwiftUI                         0xfffe8537a250      @callee_guaranteed
21  SwiftUI                         0xfffe85377ee5      NSRunLoop.flushObservers
22  SwiftUI                         0xfffe8537a198      NSRunLoop.addObserver
23  SwiftUI                         0xfffe853755fd      @callee_guaranteed
24  libswiftObjectiveC.dylib        0xfffe66ed2d9d      autoreleasepool<T>
25  SwiftUI                         0xfffe8537a182      NSRunLoop.addObserver
26  SwiftUI                         0xfffe8537a1ca      NSRunLoop.addObserver
27  CoreFoundation                  0xfffe40ab4dac      __CFRUNLOOP_IS_CALLING_OUT_TO_AN_OBSERVER_CALLBACK_FUNCTION__
28  CoreFoundation                  0xfffe40ab4c3c      __CFRunLoopDoObservers
29  CoreFoundation                  0xfffe40ab3745      CFRunLoopRunSpecific
30  HIToolbox                       0xfffe5101162f      RunCurrentEventLoopInMode
31  HIToolbox                       0xfffe5101142b      ReceiveNextEventCommon
32  HIToolbox                       0xfffe5101114e      _BlockUntilNextEventMatchingListInModeWithFilter
33  AppKit                          0xfffe45b349b0      _DPSNextEvent
34  AppKit                          0xfffe45b33176      -[NSApplication(NSEvent) _nextEventMatchingEventMask:untilDate:inMode:dequeue:]
35  AppKit                          0xfffe45b25689      -[NSApplication run]
36  AppKit                          0xfffe45af996e      NSApplicationMain
37  SwiftUI                         0xfffe84ab59f3      runApp
38  SwiftUI                         0xfffe8534c791      runApp<T>
39  SwiftUI                         0xfffe84ecb09c      App.main
40  PDFArchiver                     0x2067699b0         [inlined] PDFArchiverApp.$main
41  PDFArchiver                     0x2067699b0         main
42  libdyld.dylib                   0xfffe40967620      start

Crash Report

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Answer 1

Alex Silva OP

May ’21

Hi! Working with SwiftUI that same issue happened to us when having lists (using ForEach) with the same id. Imagine that you have a ForEach to present a list of people, if you use as id the name of the person, can happen that several people have John as id.
Be careful if you are mocking those items, that was what happened to us. We were mocking Models with the same id.

Hope it helps!

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Answer 2

BrentESR OP

May ’21

It would be nice if these crash logs included which view was having this issue.

From what I have seen, this error seems to be related specifically to ForEach and list's with duplicate IDs. However without any idea of which list this is happening in, it's incredibly difficult to debug.

A lot of swiftUI crashes are incredibly hard to debug. I hope there are some improvements in this regard with this in iOS 15.

0

Answer 3

imthath_m OP

Aug ’23

This no longer results in a crash. I get the following message in the console, when multiple elements have the id as nil inside a List.

ForEach<Array<ArrayData>, Optional<Int>, Text>: the ID nil occurs multiple times within the collection, this will give undefined results!

Make sure the identifiers are unique, if not multiple views will look the same but it will not crash.

0