iOS app crash at -[UIView _wrappedProcessTraitChanges:withBehavior:] + 1288 (UIView.m:0)

Hello Apple engineers, could you help me understand whether this crash is a UIKit bug or something in our code that causes it. Based on the documentation it is an invalid fetch instruction, that's why I suspect UIKit.

I've found a similar crash here on the forums reported a year ago, it seemed to be a UIKit bug - https://forums.developer.apple.com/forums/thread/729448.

I've attached the full crash report (the app name was replaced with <Redacted>):

Thread 0 Crashed:
0 libobjc.A.dylib 0x000000019daf7c20 objc_msgSend + 32 (:-1)
1 UIKitCore 0x00000001a3020c50 -[UIView _wrappedProcessTraitChanges:withBehavior:] + 1288 (UIView.m:0)
2 UIKitCore 0x00000001a3020720 -[UIView _processChangesFromOldTraits:toCurrentTraits:withBehavior:] + 196 (UIView.m:7840)
3 UIKitCore 0x00000001a3020618 -[UIView _updateTraitCollectionAndProcessChangesWithBehavior:previousCollection:] + 112 (UIView.m:7831)
4 UIKitCore 0x00000001a2fa90c0 -[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 944 (UIView.m:19850)
5 QuartzCore 0x00000001a22dfc28 CA::Layer::layout_if_needed(CA::Transaction*) + 496 (CALayer.mm:10944)
6 QuartzCore 0x00000001a22df7b4 CA::Layer::layout_and_display_if_needed(CA::Transaction*) + 148 (CALayer.mm:2638)
7 QuartzCore 0x00000001a2336914 CA::Context::commit_transaction(CA::Transaction*, double, double*) + 472 (CAContextInternal.mm:2613)
8 QuartzCore 0x00000001a22b57c4 CA::Transaction::commit() + 648 (CATransactionInternal.mm:420)
9 QuartzCore 0x00000001a22f8a0c CA::Transaction::flush_as_runloop_observer(bool) + 88 (CATransactionInternal.mm:928)
10 UIKitCore 0x00000001a303f568 _UIApplicationFlushCATransaction + 52 (UIApplication.m:3326)
11 UIKitCore 0x00000001a303cb64 __setupUpdateSequence_block_invoke_2 + 332 (_UIUpdateScheduler.m:1652)
12 UIKitCore 0x00000001a303c9d8 _UIUpdateSequenceRun + 84 (_UIUpdateSequence.mm:136)
13 UIKitCore 0x00000001a303c628 schedulerStepScheduledMainSection + 172 (_UIUpdateScheduler.m:1171)
14 UIKitCore 0x00000001a303d59c runloopSourceCallback + 92 (_UIUpdateScheduler.m:1334)
15 CoreFoundation 0x00000001a080c328 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 28 (CFRunLoop.c:1970)
16 CoreFoundation 0x00000001a080c2bc __CFRunLoopDoSource0 + 176 (CFRunLoop.c:2014)
17 CoreFoundation 0x00000001a0809dc0 __CFRunLoopDoSources0 + 244 (CFRunLoop.c:2051)
18 CoreFoundation 0x00000001a0808fbc __CFRunLoopRun + 840 (CFRunLoop.c:2969)
19 CoreFoundation 0x00000001a0808830 CFRunLoopRunSpecific + 588 (CFRunLoop.c:3434)
20 GraphicsServices 0x00000001ec7e81c4 GSEventRunModal + 164 (GSEvent.c:2196)
21 UIKitCore 0x00000001a336eeb0 -[UIApplication _run] + 816 (UIApplication.m:3844)
22 UIKitCore 0x00000001a341d5b4 UIApplicationMain + 340 (UIApplication.m:5496)
23 UIKitCore 0x00000001a3757fa8 UIApplicationMain(_:_:_:_:) + 104 (UIKit.swift:565)
24 <Redacted> 0x00000001028bde64 specialized static UIApplicationDelegate.main() + 28 (/<compiler-generated>:16)
25 <Redacted> 0x00000001028bde64 static AppDelegate.$main() + 28 (AppDelegate.swift:0)
26 <Redacted> 0x00000001028bde64 main + 116
27 dyld 0x00000001c61f6ec8 start + 2724 (dyldMain.cpp:1334)

I made a mistake in my text above saying it's an invalid instruction fetch, documentation clearly says it's an invalid memory fetch because pc counter's value is different from the exception address.

We've found the culprit, it was a 3d-party SDK we use to record screen sessions. After downgrading to the previous SDK version the crash is gone. That SDK does a lot of method swizzling using Obj-C runtime and tracks all UI interactions, at the same time it's not open-source, so it's hard to say what was the reason.

iOS app crash at -[UIView _wrappedProcessTraitChanges:withBehavior:] + 1288 (UIView.m:0)
 
 
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