Subclass of UHierarchicalInstancedStaticMeshComponent causes crash on Hot-Reload

Serr72 · May 12, 2017, 11:00am

Engine version: 4.15.2

Steps to reproduce:

Create Basic code c++ project
Add c++ subclass of UHierarchicalInstancedStaticMeshComponent
Add property to your GameModeBase class (or any other class, but not to hierarchical instanced mesh subclass we created in step 2 ), this is just to trigger hot reload:

public:
UPROPERTY(EditAnywhere, BlueprintReadWrite)
int32 TestProperty;

4 Compile project in editor

5 Crash:

Assertion failed: IsValid() [File:D:\Build\++UE4+Release-4.15+Compile\Sync\Engine\Source\Runtime\Core\Public\Templates/SharedPointer.h] [Line: 826] 

UE4Editor_Core!FDebug::AssertFailed() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\private\misc\assertionmacros.cpp:349]
UE4Editor_Engine!UHierarchicalInstancedStaticMeshComponent::Serialize() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\engine\private\hierarchicalinstancedstaticmesh.cpp:1796]
UE4Editor_CoreUObject!FFindReferencersArchive::ResetPotentialReferencer() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\serialization\findreferencersarchive.cpp:90]
UE4Editor_UnrealEd!TFindObjectReferencers<UObject>::TFindObjectReferencers<UObject>() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\public\serialization\findobjectreferencers.h:49]
UE4Editor_UnrealEd!FReplaceReferenceHelper::FindAndReplaceReferences() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\unrealed\private\kismet2\kismetreinstanceutilities.cpp:81]
UE4Editor_UnrealEd!FBlueprintCompileReinstancer::ReplaceInstancesOfClass_Inner() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\unrealed\private\kismet2\kismetreinstanceutilities.cpp:1937]
UE4Editor_UnrealEd!FBlueprintCompileReinstancer::ReplaceInstancesOfClass() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\unrealed\private\kismet2\kismetreinstanceutilities.cpp:1476]
UE4Editor_UnrealEd!FBlueprintCompileReinstancer::ReinstanceInner() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\unrealed\private\kismet2\kismetreinstanceutilities.cpp:682]
UE4Editor_UnrealEd!FBlueprintCompileReinstancer::ReinstanceObjects() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\unrealed\private\kismet2\kismetreinstanceutilities.cpp:913]
UE4Editor_HotReload!FHotReloadModule::ReinstanceClass() [d:\build\++ue4+release-4.15+compile\sync\engine\source\developer\hotreload\private\hotreload.cpp:1271]
UE4Editor_HotReload!FHotReloadModule::ReinstanceClasses() [d:\build\++ue4+release-4.15+compile\sync\engine\source\developer\hotreload\private\hotreload.cpp:1254]
UE4Editor_HotReload!TBaseRawMethodDelegateInstance<0,FHotReloadModule,void __cdecl(void)>::ExecuteIfSafe() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:648]
UE4Editor_CoreUObject!TBaseMulticastDelegate<void>::Broadcast() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:937]
UE4Editor_CoreUObject!UClassReplaceHotReloadClasses() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\uobjectbase.cpp:720]
UE4Editor_CoreUObject!ProcessNewlyLoadedUObjects() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\coreuobject\private\uobject\uobjectbase.cpp:858]
UE4Editor_CoreUObject!TBaseStaticDelegateInstance<void __cdecl(void)>::ExecuteIfSafe() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:1027]
UE4Editor_Core!TBaseMulticastDelegate<void>::Broadcast() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:937]
UE4Editor_Core!FModuleManager::LoadModuleWithFailureReason() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\private\modules\modulemanager.cpp:471]
UE4Editor_Core!FModuleManager::LoadModule() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\private\modules\modulemanager.cpp:330]
UE4Editor_HotReload!FHotReloadModule::DoHotReloadInternal() [d:\build\++ue4+release-4.15+compile\sync\engine\source\developer\hotreload\private\hotreload.cpp:856]
UE4Editor_HotReload!UE4Function_Private::TFunctionRefCaller<<lambda_845f9b2944b03bbc30be1e1f4a8d7f4b>,void __cdecl(TMap<FString,FString,FDefaultSetAllocator,TDefaultMapKeyFuncs<FString,FString,0> > const & __ptr64,bool,enum ECompilationResult::Type)>::Call() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\core\public\templates\function.h:245]
UE4Editor_HotReload!FHotReloadModule::CheckForFinishedModuleDLLCompile() [d:\build\++ue4+release-4.15+compile\sync\engine\source\developer\hotreload\private\hotreload.cpp:1916]
UE4Editor_HotReload!FHotReloadModule::Tick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\developer\hotreload\private\hotreload.cpp:594]
UE4Editor_UnrealEd!UEditorEngine::Tick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\unrealed\private\editorengine.cpp:1236]
UE4Editor_UnrealEd!UUnrealEdEngine::Tick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\editor\unrealed\private\unrealedengine.cpp:391]
UE4Editor!FEngineLoop::Tick() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\launch\private\launchengineloop.cpp:3025]
UE4Editor!GuardedMain() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\launch\private\launch.cpp:166]
UE4Editor!GuardedMainWrapper() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:134]
UE4Editor!WinMain() [d:\build\++ue4+release-4.15+compile\sync\engine\source\runtime\launch\private\windows\launchwindows.cpp:210]
UE4Editor!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:264]
kernel32

anonymous_user_2b03d27c · May 15, 2017, 6:17pm

Hey -

Thank you for submitting a bug report. I have reproduced this issue and logged a report for it here Unreal Engine Issues and Bug Tracker (UE-45028) . You can track the report’s status as the issue is reviewed by our development staff. Please be aware that this issue may not be prioritized or fixed soon.

Cheers

Serr72 · May 16, 2017, 2:08am

Alright, thank you for your response. Probably worth mentioning that because of this bug you can’t use hot reload if you have custom c++ Foliage Component (as UFoliageInstancedStaticMeshComponent is subclass of HISM Component)

VSZ · August 11, 2017, 1:03pm

Hi , my project has started running into this issue as well and it’s hampering productivity quite a bit as I essentially can’t hot-reload anymore.

Hoping that community interest on this can be bumped up. I see that UE-35710 has been backlogged while UE-45028 is still open; hopeful that one of those will be taken up.

Some additional info: I’ve used custom HISMs for a very long time now but never had this issue until recently. If I mange to figure out what triggered this issue I’ll post back with a comment.

anonymous_user_2b03d27c · August 11, 2017, 2:16pm

Hey -

I have updated UE-45028 to indicate this is still affecting the community and that it still occurs in 4.17 as well.

VSZ · August 13, 2017, 7:07am

I found a workaround which I quickly wanted to share!

I migrated my HISM subclass to a separate gameplay module and now refer that module from by primary game module’s Build.cs. With this setup I can hotreload again, which is a big relief.

If you’re new to setting up gameplay modules check out this doc and/or use any of Epic’s modules or a simple plugin module as reference.

Hope this tidbit helps someone in the same situation

Rainbow.Warrior · April 20, 2018, 10:32am

Issue still occurs in 4.19 … Dear Unreal, plz fix.

I tried 's fix, and it still seems to crash

anonymous_user_13754250 · November 4, 2018, 8:08pm

4.19.2 this bug happens to me too. It crashes when I compile from editor, then if I restart the editor and compile again it works fine…unfortunately this is a routine that I have to do every single time I want to compile from editor (crash, restart and compile)

anonymous_user_31f993d3 · December 14, 2018, 10:31pm

I ran into this in UE 4.20.

It looks like the bug is that, when scanning for references after hot reloading, it’s dereferencing “ClusterTreePtr” - which is null for the class default object.

My workaround for now is to override “Serialize()” like so:

void UMyDerivedHISMComponent::Serialize(FArchive& Ar)
{
	bool hasTempClusterTreePtr = false;
	if (Ar.IsObjectReferenceCollector() && !ClusterTreePtr.IsValid())
	{
		ClusterTreePtr = MakeShareable(new TArray<FClusterNode>);
		hasTempClusterTreePtr = true;
	}

	Super::Serialize(Ar);

	if (hasTempClusterTreePtr)
	{
		ClusterTreePtr = nullptr;
	}
}

XynanXDB · January 17, 2020, 2:50pm

Even in 4.24.1, the bug still exists.