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Crash after migration from 4.21 to UE4.22

I have some blueprint widgets (classes which is inherited from UserWidget) in my project. And there are no issues with these widgets in UE4.21. But behaviour in UE4.22 is pretty strange. I can open, edit and save any of them. I don't see any warnings or errors. But after each attempt to compile any of my blueprint widgets I get crash of UE4 Editor with the following stack trace:

LoginId:c0fa6c0f7c4f16874904ae83f30f612d EpicAccountId:e0d09450f0ea45f383a6cb4183d3c7ce

 Assertion failed: Existing.Linker->ExportMap[Existing.LinkerIndex].Object==this [File:/Users/build/Build/++UE4/Sync/Engine/Source/Runtime/CoreUObject/Private/UObject/UObjectLinker.cpp] [Line: 107]
 FGenericPlatformMisc::RaiseException(unsigned int) Address = 0x101fcd35b (filename not found) [in UE4Editor-Core.dylib]
 FMacErrorOutputDevice::Serialize(wchar_t const*, ELogVerbosity::Type, FName const&) Address = 0x10210d87d (filename not found) [in UE4Editor-Core.dylib]
 FOutputDevice::LogfImpl(wchar_t const*, ...) Address = 0x1021e1019 (filename not found) [in UE4Editor-Core.dylib]
 FDebug::AssertFailed(char const*, char const*, int, wchar_t const*, ...) Address = 0x102175a53 (filename not found) [in UE4Editor-Core.dylib]
 FDebug::CheckVerifyFailedImpl(char const*, char const*, int, wchar_t const*, ...) Address = 0x102175867 (filename not found) [in UE4Editor-Core.dylib]
 UObject::SetLinker(FLinkerLoad*, int, bool) Address = 0x1030b7906 (filename not found) [in UE4Editor-CoreUObject.dylib]
 UObject::BeginDestroy() Address = 0x102f9285e (filename not found) [in UE4Editor-CoreUObject.dylib]
 UObject::ConditionalBeginDestroy() Address = 0x102fa1dc7 (filename not found) [in UE4Editor-CoreUObject.dylib]
 UnhashUnreachableObjects(bool, float) Address = 0x102f2008a (filename not found) [in UE4Editor-CoreUObject.dylib]
 CollectGarbageInternal(EObjectFlags, bool) Address = 0x102f2255b (filename not found) [in UE4Editor-CoreUObject.dylib]
 CollectGarbage(EObjectFlags, bool) Address = 0x102f2465f (filename not found) [in UE4Editor-CoreUObject.dylib]
 FBlueprintCompilationManagerImpl::CompileSynchronouslyImpl(FBPCompileRequest const&) Address = 0x111fa080e (filename not found) [in UE4Editor-Kismet.dylib]
 FKismetEditorUtilities::CompileBlueprint(UBlueprint*, EBlueprintCompileOptions, FCompilerResultsLog*) Address = 0x10c1e22c8 (filename not found) [in UE4Editor-UnrealEd.dylib]
 FBlueprintEditor::Compile() Address = 0x11210b5ee (filename not found) [in UE4Editor-Kismet.dylib]
 TBaseSPMethodDelegateInstance<false, FBlueprintEditor, (ESPMode)0, TTypeWrapper<void> ()>::Execute() const Address = 0x112163f2d (filename not found) [in UE4Editor-Kismet.dylib]
 TBaseSPMethodDelegateInstance<false, FBlueprintEditor, (ESPMode)0, void ()>::ExecuteIfSafe() const Address = 0x112163fcb (filename not found) [in UE4Editor-Kismet.dylib]
 FUICommandList::ExecuteAction(TSharedRef<FUICommandInfo const, (ESPMode)0>) const Address = 0x103d915f4 (filename not found) [in UE4Editor-Slate.dylib]
 SToolBarButtonBlock::OnClicked() Address = 0x103e71a2a (filename not found) [in UE4Editor-Slate.dylib]
 TBaseSPMethodDelegateInstance<false, SToolBarButtonBlock, (ESPMode)0, FReply ()>::Execute() const Address = 0x103ec5093 (filename not found) [in UE4Editor-Slate.dylib]
 SButton::OnMouseButtonUp(FGeometry const&, FPointerEvent const&) Address = 0x103f1389c (filename not found) [in UE4Editor-Slate.dylib]
 FSlateApplication::RoutePointerUpEvent(FWidgetPath const&, FPointerEvent const&) Address = 0x103d6ce26 (filename not found) [in UE4Editor-Slate.dylib]
 FSlateApplication::ProcessMouseButtonUpEvent(FPointerEvent const&) Address = 0x103d26d44 (filename not found) [in UE4Editor-Slate.dylib]
 FSlateApplication::OnMouseUp(EMouseButtons::Type, FVector2D) Address = 0x103d75066 (filename not found) [in UE4Editor-Slate.dylib]
 FMacApplication::ProcessMouseUpEvent(FDeferredMacEvent const&, TSharedPtr<FMacWindow, (ESPMode)0>) Address = 0x103c9084a (filename not found) [in UE4Editor-ApplicationCore.dylib]
 FMacApplication::ProcessEvent(FDeferredMacEvent const&) Address = 0x103c8a208 (filename not found) [in UE4Editor-ApplicationCore.dylib]
 FMacApplication::ProcessDeferredEvents(float) Address = 0x103c89f5f (filename not found) [in UE4Editor-ApplicationCore.dylib]
 FSlateApplication::TickPlatform(float) Address = 0x103d46665 (filename not found) [in UE4Editor-Slate.dylib]
 FSlateApplication::Tick(ESlateTickType) Address = 0x103d45f5b (filename not found) [in UE4Editor-Slate.dylib]
 FEngineLoop::Tick() Address = 0x101e91ec0 (filename not found) [in UE4Editor]
 GuardedMain(wchar_t const*) Address = 0x101e9ab48 (filename not found) [in UE4Editor]
 -[UE4AppDelegate runGameThread:] Address = 0x101ea4c8e (filename not found) [in UE4Editor]
 -[FCocoaGameThread main] Address = 0x10210c891 (filename not found) [in UE4Editor-Core.dylib]
 Unknown() Address = 0x7fff41a8987e (filename not found) [in Foundation]
 _pthread_body Address = 0x7fff6bea42eb (filename not found) [in libsystem_pthread.dylib]
 _pthread_start Address = 0x7fff6bea7249 (filename not found) [in libsystem_pthread.dylib]
 thread_start Address = 0x7fff6bea340d (filename not found) [in libsystem_pthread.dylib]
Product Version: UE 4.22
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asked May 15 '19 at 09:10 AM in Bug Reports

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33 3 5

avatar image Jeff A ♦♦ STAFF May 15 '19 at 02:45 PM


We've recently made a switch to a new bug reporting method using a more structured form. Please visit the link below for more details and report the issue using the new Bug Submission Form. Feel free to continue to use this thread for community discussion around the issue.



avatar image Tapocheck May 16 '19 at 05:06 PM

UE4 callstack is useless (it's not possible to understand what really happens and why it happens), your support is absolutely useless too. It's not a first time when answer from your support is just "I can't reproduce that" and after hours of research I can confirm that it's a problem of your editor (not of my own blueprints). Oh my god, it's a worst editor ever (believe me, I saw much of them - some of them was really uncomfortable and ugly, but they at least didn't have so many bugs).

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3 answers: sort voted first

Well, for me it was a problem of Canvas Panel with 5 buttons (every button has text). I don't know which parts are significant here. The only way to fix the problem was to remove all children from Canvas Panel, save and compile blueprint, and finally add buttons back. More interesting thing here is that after UE4 editor relaunch the problem come back.

My current solution is avoid of Canvas Panel using. Replacing a panel with a grid helps me. And I hope my answer helps someone else. Support still can't reproduce the problem even with my assets.

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answered May 17 '19 at 05:36 PM

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Appodeal Inc
31 2 1

avatar image Tapocheck May 18 '19 at 04:32 AM

Thanks for the answer! I'll try

avatar image Tapocheck May 18 '19 at 12:54 PM

I have many widgets with Canvas panel as a parent widget, but I found a problem only in one of them. This is strange. Anyway, thank you very much! You save a lot of my time. But UE4 support is useless.

avatar image supple_hands May 27 '19 at 07:58 PM

So i'm running into a similar issue, however when I try to compile or delete the suspect widget, the engine crashes. When I replace the canvas with a grid, then save, then compile, it crashes. Any ideas?

Update* So I manually went into the windows folder structure and deleted the UASSET file for the widget. This fixed the issue. I should mention that for me, I did not upgrade from 4.21 -> 4.22 for my project. This was probably a result of the recent upgrade from 4.22.1 -> 4.22.2.

It might not even be related to upgrading as the widget was created after upgrading. This might just be a bug that occurs under very specific conditions (of which I have no clue).

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The same here...

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answered May 15 '19 at 01:20 PM

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6 1

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We are having the same problem here. Seems to be a regression in the way UE4 deals with circular blueprint class references. We worked around the issue by cleaning up our reference graphs by using blueprint interfaces and splitting some manager-type classes into base/implementation.

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answered Jun 12 '19 at 01:46 PM

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132 2 3 5

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