Description

This is a longstanding and common UMG crash that has affected more than 200 users since at least the 4.15 release.

User Descriptions

  • I was working in the UI and undid several last changes in quick succession. This was moving and scaling UI widgets. These were set to span the full width, with a fixed offset. My interaction which I was undoing had been dragging such a widget around.
  • crash when using UI Blueprint

Source Context

 367       	inline TBaseDelegate& operator=(const TBaseDelegate& Other)
  368       	{
  369       		if (&Other != this)
  370       		{
  371       			// this down-cast is OK! allows for managing invocation list in the base class without requiring virtual functions
  372       			TDelegateInstanceInterface* OtherInstance = Other.GetDelegateInstanceProtected();
  373       
  374       			if (OtherInstance != nullptr)
  375       			{
  376       				OtherInstance->CreateCopy(*this);
  377       			}
  378       			else
  379       			{
  380 ***** 				Unbind();
  381       			}
  382       		}
  383       
  384       		return *this;
  385       	}
Steps to Reproduce

repro steps currently unknown

Callstack
Access violation - code c0000005 (first/second chance not available)

UE4Editor_UMG!TBaseDelegate<FMargin>::operator=() [delegatesignatureimpl.inl:381]
UE4Editor_UMG!UCanvasPanelSlot::SetOffsets() [canvaspanelslot.cpp:190]
UE4Editor_UMG!UCanvasPanelSlot::SynchronizeProperties() [canvaspanelslot.cpp:301]
UE4Editor_CoreUObject!UObject::PostEditUndo() [obj.cpp:530]
UE4Editor_UnrealEd!FTransaction::Apply() [editortransaction.cpp:506]
UE4Editor_UnrealEd!UTransBuffer::Undo() [editortransaction.cpp:874]
UE4Editor_Kismet!TBaseSPMethodDelegateInstance<0,FBlueprintEditor,0,TTypeWrapper<void> __cdecl() [delegateinstancesimpl.h:327]
UE4Editor_Kismet!TBaseSPMethodDelegateInstance<0,FBlueprintEditor,0,void __cdecl() [delegateinstancesimpl.h:434]
UE4Editor_Slate!FUICommandList::ConditionalProcessCommandBindings() [uicommandlist.cpp:216]
UE4Editor_Slate!FUICommandList::ProcessCommandBindings() [uicommandlist.cpp:160]
UE4Editor_UnrealEd!FBaseToolkit::ProcessCommandBindings() [basetoolkit.cpp:74]
UE4Editor_UnrealEd!SStandaloneAssetEditorToolkitHost::OnKeyDown() [sstandaloneasseteditortoolkithost.cpp:324]
UE4Editor_Slate!<lambda_2afcd964c763e269e2d1a63f3a72f846>::operator() [slateapplication.cpp:4771]
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FBubblePolicy,FKeyEvent,<lambda_2afcd964c763e269e2d1a63f3a72f846> >() [slateapplication.cpp:232]
UE4Editor_Slate!FEventRouter::RouteAlongFocusPath<FEventRouter::FBubblePolicy,<lambda_2afcd964c763e269e2d1a63f3a72f846>,FKeyEvent>() [slateapplication.cpp:214]
UE4Editor_Slate!FSlateApplication::ProcessKeyDownEvent() [slateapplication.cpp:4769]
UE4Editor_Slate!FSlateApplication::OnKeyDown() [slateapplication.cpp:4681]
UE4Editor_Core!FWindowsApplication::ProcessDeferredMessage() [windowsapplication.cpp:1553]
UE4Editor_Core!FWindowsApplication::DeferMessage() [windowsapplication.cpp:2161]
UE4Editor_Core!FWindowsApplication::ProcessMessage() [windowsapplication.cpp:881]
UE4Editor_Core!FWindowsApplication::AppWndProc() [windowsapplication.cpp:721]
user32!UserCallWinProcCheckWow()
user32!DispatchMessageWorker()
UE4Editor_Core!FWindowsPlatformMisc::PumpMessages() [windowsplatformmisc.cpp:1009]
UE4Editor!FEngineLoop::Tick() [launchengineloop.cpp:3151]
UE4Editor!GuardedMain() [launch.cpp:166]
UE4Editor!GuardedMainWrapper() [launchwindows.cpp:134]
UE4Editor!WinMain() [launchwindows.cpp:210]
UE4Editor!__scrt_common_main_seh() [exe_common.inl:253]
kernel32!BaseThreadInitThunk()
ntdll!RtlUserThreadStart()

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Cannot Reproduce
ComponentUE - Editor - UI Systems
Affects Versions4.154.164.174.184.19
CreatedAug 29, 2017
ResolvedApr 9, 2019
UpdatedJul 14, 2020
View Jira Issue