_dispatch_assert_queue_fail under iOS 16.4.1. Don't understand the error.

Question

m.schokols OP

Created May ’23

Replies 3

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Views 2.2k

Participants 4

Since updating to iOS 16.4.1, our app crashes randomly with the following error message.

Exception Codes: 0x0000000000000001, 0x0000000199d542c0
Termination Reason: SIGNAL 5 Trace&#x2F;BPT trap: 5
Terminating Process: exc handler [499]

Triggered by Thread:  2

Thread 2 Crashed:
0   libdispatch.dylib             	       0x199d542c0 _dispatch_assert_queue_fail + 120
1   libdispatch.dylib             	       0x199d54248 dispatch_assert_queue + 196
2   UIKitCore                     	       0x1949c870c -[UIImageView _mainQ_beginLoadingIfApplicable] + 88
3   UIKitCore                     	       0x19495db34 -[UIImageView setHidden:] + 68
4   UIKitCore                     	       0x19492f128 -[UIButtonLegacyVisualProvider _updateImageView] + 372
5   UIKitCore                     	       0x19492ed78 -[UIButtonLegacyVisualProvider layoutSubviews] + 116
6   UIKitCore                     	       0x19492ecc4 -[UIButton layoutSubviews] + 40
7   UIKitCore                     	       0x1948fbef4 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 1920
8   QuartzCore                    	       0x193db64ac CA::Layer::layout_if_needed(CA::Transaction*) + 500
9   QuartzCore                    	       0x193dc9a28 CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 148
10  QuartzCore                    	       0x193ddae54 CA::Context::commit_transaction(CA::Transaction*, double, double*) + 444
11  QuartzCore                    	       0x193e0a3c0 CA::Transaction::commit() + 648
12  QuartzCore                    	       0x193e54b08 CA::Transaction::release_thread(void*) + 228
13  libsystem_pthread.dylib       	       0x1f2214b9c _pthread_tsd_cleanup + 620
14  libsystem_pthread.dylib       	       0x1f2217560 _pthread_exit + 84
15  libsystem_pthread.dylib       	       0x1f22140cc _pthread_wqthread_exit + 80
16  libsystem_pthread.dylib       	       0x1f2213e64 _pthread_wqthread + 424
17  libsystem_pthread.dylib       	       0x1f2213b7c start_wqthread + 8

I have trouble interpreting where our error lies within the exception. Can anyone give me a hint as to what kind of problem this might be?

Kind regards

Answered by Frameworks Engineer in 752540022

The most likely cause is that you manipulated a UIButton from a secondary thread, and now that the thread is exiting, Core Animation is committing a transaction due to your manipulation, resulting in this eventual assertion.

Boost

Answer 1

DTS Engineer OP

Apple

May ’23

So the immediate cause of this crash is a Dispatch queue assert. UIImageView, in frame 2, has called dispatch_assert_queue to assert that it’s on the main queue. It isn’t on the main queue, and thus Dispatch has trapped.

As to why it’s doing this from a secondary queue, that’s very much a UIKit question and thus kinda outside of my area of expertise. I’ve added the UIKit tag to your thread to see if that might garner some other eyes.

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Answer 2

Frameworks Engineer OP

Apple

May ’23

Accepted Answer

The most likely cause is that you manipulated a UIButton from a secondary thread, and now that the thread is exiting, Core Animation is committing a transaction due to your manipulation, resulting in this eventual assertion.

1

Answer 3

Frameworks Engineer OP

Apple

May ’23

You are accessing a UIKit API from a secondary thread. You can try reproducing the error with the Main Thread Checker enabled (In your scheme -> Diagnostics -> Main Thread Checker).

1