FB14569448
Since iOS 18 beta came out, our app has been failing at some point when a view controller is dismissed and it appears the main thread ends up looping in layout logic and logs the following to the console. The app hangs until it's terminated due to a memory overallocation issue.
Anyone else seen this?
<_UINavigationBarItemStackEntry: 0x302ac73f0> normalLayout[active]=0x1391ad880 searchLayout=0x0 item=<UINavigationItem: 0x13913a080> style=navigator: Ignoring unexpected nonmatching counterpart: (null) This is an internal UIKit bug. Snapshotting a view (0x1391e7c00, _UIButtonBarStackView) that has not been rendered at least once requires afterScreenUpdates:YES.
frame #0: 0x000000019bb07000 libobjc.A.dylibobjc_msgSend frame #1: 0x00000001a0fb4224 UIKitCore-[UIView(AdditionalLayoutSupport) _updateConstraintsIfNeededCollectingViews:forSecondPass:] + 144
frame #2: 0x00000001c270a030 CoreAutoLayout-[NSISEngine withBehaviors:performModifications:] + 84 frame #3: 0x00000001a0fe5424 UIKitCore__100-[UIView(AdditionalLayoutSupport) _updateConstraintsIfNeededWithViewForVariableChangeNotifications:]_block_invoke + 120
frame #4: 0x00000001a0fe3ae0 UIKitCore-[UIView(AdditionalLayoutSupport) _withUnsatisfiableConstraintsLoggingSuspendedIfEngineDelegateExists:] + 112 frame #5: 0x00000001a0fe2b4c UIKitCore-[UIView(AdditionalLayoutSupport) _updateConstraintsIfNeededWithViewForVariableChangeNotifications:] + 172
frame #6: 0x00000001a0fa9e90 UIKitCore-[UIView _updateConstraintsAtEngineLevelIfNeededWithViewForVariableChangeNotifications:] + 400 frame #7: 0x00000001a0fa9a18 UIKitCore-[UIView _updateConstraintsAsNecessaryAndApplyLayoutFromEngine] + 312
frame #8: 0x00000001a0fa97a4 UIKitCore-[UIView(Hierarchy) layoutSubviews] + 204 frame #9: 0x00000001a124fa78 UIKitCore-[_UIButtonBarStackView layoutSubviews] + 56
frame #10: 0x00000001a0f6430c UIKitCore-[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 2492 frame #11: 0x00000001a029d8d0 QuartzCoreCA::Layer::layout_if_needed(CA::Transaction*) + 496
frame #12: 0x00000001a0fa81d0 UIKitCore-[UIView(Hierarchy) layoutBelowIfNeeded] + 300 frame #13: 0x00000001a1843fa4 UIKitCore-[_UINavigationBarTransitionContextCrossfade _prepareContentView] + 132
frame #14: 0x00000001a18443bc UIKitCore-[_UINavigationBarTransitionContextCrossfade prepare] + 84 frame #15: 0x00000001a184e59c UIKitCore-[_UINavigationBarVisualProviderModernIOS _performAnimationWithTransitionCompletion:transition:] + 1524
frame #16: 0x00000001a180f938 UIKitCore-[UINavigationBar _popNavigationItemWithTransitionAssistant:] + 220 frame #17: 0x00000001a180f5f8 UIKitCore-[UINavigationBar _popNavigationItemWithTransition:] + 224
frame #18: 0x00000001a13bec9c UIKitCore-[UINavigationBar _setItemsUpToItem:transition:] + 240 frame #19: 0x00000001a13be76c UIKitCore-[UIViewController _removeNavigationItemsFromNavigationController:transition:] + 232
frame #20: 0x00000001a19c9dc0 UIKitCore__89-[UINavigationController _immediatelyApplyViewControllers:transition:animated:operation:]_block_invoke_3 + 800 frame #21: 0x00000001a19d0b2c UIKitCore__98-[UINavigationController _shouldSkipHostedRefreshControlUpdateSchedulingDeferredUpdateIfNecessary]_block_invoke + 40
frame #22: 0x00000001a19d7574 UIKitCore-[UINavigationController transitionConductor:didStartDeferredTransition:context:] + 792 frame #23: 0x00000001a21c9600 UIKitCore-[_UIViewControllerTransitionConductor startDeferredTransitionIfNeeded] + 688
frame #24: 0x00000001a10ab040 UIKitCore-[UINavigationController __viewWillLayoutSubviews] + 84 frame #25: 0x00000001a1350bcc UIKitCore-[UILayoutContainerView layoutSubviews] + 172
frame #26: 0x00000001a0f6430c UIKitCore-[UIView(CALayerDelegate) layoutSublayersOfLayer:] + 2492 frame #27: 0x00000001a029d8d0 QuartzCoreCA::Layer::layout_if_needed(CA::Transaction*) + 496
frame #28: 0x00000001a029d45c QuartzCoreCA::Layer::layout_and_display_if_needed(CA::Transaction*) + 148 frame #29: 0x00000001a02f64e0 QuartzCoreCA::Context::commit_transaction(CA::Transaction*, double, double*) + 472
frame #30: 0x00000001a02736c4 QuartzCoreCA::Transaction::commit() + 648 frame #31: 0x00000001a02b6584 QuartzCoreCA::Transaction::flush_as_runloop_observer(bool) + 88
frame #32: 0x00000001a1002c3c UIKitCore_UIApplicationFlushCATransaction + 52 frame #33: 0x00000001a10002dc UIKitCore_UIUpdateSequenceRun + 84
frame #34: 0x00000001a0ffff2c UIKitCoreschedulerStepScheduledMainSection + 172 frame #35: 0x00000001a1000df0 UIKitCorerunloopSourceCallback + 92
frame #36: 0x000000019e7edf90 CoreFoundation__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 28 frame #37: 0x000000019e7edf24 CoreFoundation__CFRunLoopDoSource0 + 176
frame #38: 0x000000019e7eba10 CoreFoundation__CFRunLoopDoSources0 + 244 frame #39: 0x000000019e7eac14 CoreFoundation__CFRunLoopRun + 840
frame #40: 0x000000019e7ea4c8 CoreFoundationCFRunLoopRunSpecific + 572 frame #41: 0x00000001eb06d1c4 GraphicsServicesGSEventRunModal + 164
frame #42: 0x00000001a1334a90 UIKitCore-[UIApplication _run] + 816 frame #43: 0x00000001a13e2d1c UIKitCoreUIApplicationMain + 340
frame #44: 0x000000010038ca7c LabWare Developmentmain at AppDelegate.swift:31:7 frame #45: 0x00000001c4f4e9b4 dyldstart + 2724
Your backtrace doesn't match the debug log you saw, but does imply a sequence of events that would explain your hang.
Specifically this kind of hang can happen if you put the same bar button item (or same custom view) in two different UINavigationBars. You end up in a layout loop because each bar will try to do layout and as a course of doing that layout invalidate the layout of the other navigation bar.
Its kind of like two children fighting over a toy.
The log you saw is something that can happen when a navigation item moves from one navigation bar to another, hence why it implies the possibility described above.
Its certainly possible that there is a bug in UIKit here too, but the bug report as written doesn't have enough information for us to make progress – we'd need a sample project or reproduction steps in order to continue the investigation.