Unreal Engine Issues and Bug Tracker (UE-50764)

Description

REGRESSION: Can be certain as this testing was blocked by [Link Removed]

Through a specific chain of events (see repro), it's possible to have a non-actor as the value for an Actor Class Reference, and there is no error indicating that this isn't valid, nor is the field cleared.

Once it's in this state, performing some actions can cause a crash (see callstack).

Steps to Reproduce

Open QAGame in editor.
Open the level blueprint.
Add a variable.
Set the type to Object > Object Reference.
Compile.
Set the Default Value to 256Cube.
Compile again.
Change the variable type to Actor > Soft Object Reference.
Compile. Note there's an error with the Default Value.
Change the Variable Type to Actor > Class Reference.
Compile.

RESULT
Note that 256Cube is accepted as the Default Value with no error. A few actions can result in a crash, such as:

Changing/Clearing Default Value
Changing Variable Type

Callstack

Assertion failed: ObjectA == nullptr || ObjectA->IsA<UClass>() [File:D:\Build\++UE4+Release-4.18+Compile\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\PropertyClass.cpp] [Line: 156]

UE4Editor_CoreUObject!UClassProperty::Identical() propertyclass.cpp:157 
UE4Editor_CoreUObject!UStruct::SerializeTaggedProperties() class.cpp:1122 
UE4Editor_CoreUObject!UObject::SerializeScriptProperties() obj.cpp:1276 
UE4Editor_CoreUObject!UObject::Serialize() obj.cpp:1210 
UE4Editor_Engine!AActor::Serialize() actor.cpp:559 
UE4Editor_Engine!FCPFUOWriter::FCPFUOWriter() unrealengine.cpp:11900 
UE4Editor_Engine!UEngine::CopyPropertiesForUnrelatedObjects() unrealengine.cpp:12009 
UE4Editor_UnrealEd!ReplaceActorHelper() kismetreinstanceutilities.cpp:1776 
UE4Editor_UnrealEd!FBlueprintCompileReinstancer::ReplaceInstancesOfClass_Inner() kismetreinstanceutilities.cpp:1969 
UE4Editor_UnrealEd!FBlueprintCompileReinstancer::BatchReplaceInstancesOfClass() kismetreinstanceutilities.cpp:1474 
UE4Editor_Kismet!FBlueprintCompilationManagerImpl::FlushReinstancingQueueImpl() blueprintcompilationmanager.cpp:1041 
UE4Editor_Kismet!FBlueprintCompilationManagerImpl::CompileSynchronouslyImpl() blueprintcompilationmanager.cpp:200 
UE4Editor_UnrealEd!FKismetEditorUtilities::CompileBlueprint() kismet2.cpp:745 
UE4Editor_Kismet!FBlueprintEditor::Compile() blueprinteditor.cpp:3181 
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::ExecuteAction() uicommandlist.cpp:97 
UE4Editor_Slate!SToolBarButtonBlock::OnClicked() stoolbarbuttonblock.cpp:300 
UE4Editor_Slate!TMemberFunctionCaller<SToolBarButtonBlock,FReply() delegateinstanceinterface.h:165 
UE4Editor_Slate!UE4Tuple_Private::TTupleImpl<TIntegerSequence<unsigned int> >::ApplyAfter<TMemberFunctionCaller<SToolBarButtonBlock,FReply() tuple.h:497 
UE4Editor_Slate!TBaseSPMethodDelegateInstance<0,SToolBarButtonBlock,0,FReply __cdecl() delegateinstancesimpl.h:327 
UE4Editor_Slate!TBaseDelegate<FReply>::Execute() delegatesignatureimpl.inl:537 
UE4Editor_Slate!SButton::OnMouseButtonUp() sbutton.cpp:282 
UE4Editor_Slate!<lambda_1002768c627006711ef2f351a87ec0e7>::operator() slateapplication.cpp:5263 
UE4Editor_Slate!FEventRouter::Route<FReply,FEventRouter::FToLeafmostPolicy,FPointerEvent,<lambda_1002768c627006711ef2f351a87ec0e7> >() slateapplication.cpp:234 
UE4Editor_Slate!FSlateApplication::RoutePointerUpEvent() slateapplication.cpp:5252 
UE4Editor_Slate!FSlateApplication::ProcessMouseButtonUpEvent() slateapplication.cpp:5750 
UE4Editor_Slate!FSlateApplication::OnMouseUp() slateapplication.cpp:5730 
UE4Editor_ApplicationCore!FWindowsApplication::ProcessDeferredMessage() windowsapplication.cpp:1725 
UE4Editor_ApplicationCore!FWindowsApplication::DeferMessage() windowsapplication.cpp:2171 
UE4Editor_ApplicationCore!FWindowsApplication::ProcessMessage() windowsapplication.cpp:888 
UE4Editor_ApplicationCore!FWindowsApplication::AppWndProc() windowsapplication.cpp:725 
user32!<Unknown> 
user32!<Unknown> 
UE4Editor_ApplicationCore!FWindowsPlatformApplicationMisc::PumpMessages() windowsplatformapplicationmisc.cpp:129 
UE4Editor!FEngineLoop::Tick() launchengineloop.cpp:3220 
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!<Unknown> 
ntdll!<Unknown>

Community References

Fix UE-51650

i have this problem UE4CC-Windows-58DC12AF4B97F057BD108FBFF569B2E9_0000

Delay nodes occasionally don't fire the "Completed" output in a nativized build

An error occurred while trying to generate project files !?

Undefined sysmbol: typeinfo for AActor when cross-compile linux dedicated server on windows

I am not able to find world outliner how to enable it?

Installer 4.10 failed with error code R-1603

Error UE5 5.0.3

[4.18] Visual Studio opens unnecessary windows when adding a new C++ class via the editor's interface

I can't open my map from the editor.

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Fixed

Component	UE - Gameplay - Blueprint
Affects Versions	4.18
Target Fix	4.18

Fix Commit	3680243
Release Commit	3680243

Created	Oct 4, 2017
Resolved	Oct 4, 2017
Updated	Apr 27, 2018

View Jira Issue

UE-50764

Actor Class Reference can take invalid Value, can lead to crash

Actor Class Reference can take invalid Value, can lead to crash

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