Unreal Engine Issues and Bug Tracker (UE-35870)

Description

Changing class code causes class instance placed in the viewport to produce the warning message shown below upon hot reload. Also reported that callstack occurs but does not crash the editor. The warning message has been reproduced internally with steps listed, callstack has not occurred internally.

REGRESSION:
Yes, this warning message does not appear in 4.12.5 after hot reload.

Working CL: 3039270
Broken CL: 3136830

*Editor Warning Message*

LogUObjectGlobals:Warning: Guid referenced by StaticMeshComponent /Game/Test.Test:PersistentLevel.MyActor_1.staticMesh is already used by StaticMeshComponent /Game/Test.Test:PersistentLevel.MyActor_2.staticMesh, which should never happen in the editor but could happen at runtime with duplicate level loading or PIE

Steps to Reproduce

Open UE4 Editor (any project)
Add code to project based on actor (MyActor)

Add the following to MyActor.h

UPROPERTY(Category = Rendering, VisibleDefaultsOnly, BlueprintReadOnly)
	class UStaticMeshComponent* StaticMesh;

UPROPERTY(EditAnywhere)
	int asd = 3;

Add the following to MyActor.cpp

StaticMesh = CreateDefaultSubobject<UStaticMeshComponent>(TEXT("staticMesh"));
RootComponent = StaticMesh;

static ConstructorHelpers::FObjectFinder<UStaticMesh> assetMesh(
TEXT("StaticMesh'/Engine/BasicShapes/Cube.Cube'"));

if (assetMesh.Succeeded())
{
	StaticMesh->SetStaticMesh(assetMesh.Object);
}

Compile
In the Editor, add instance of MyActor into the viewport
In VS, change "asd = 3" to "asd = 0"
Use the editor compile button to preform a hot reload

Result:
Warning printed in description appears in the output log after hot reload completes

Callstack

LogHotReload: New module detected: UE4Editor-SimpleCar1-3314.dll
 LogHotReload: Starting Hot-Reload from IDE
 LogHotReload: Re-instancing TriggerShape after hot-reload.
 LogStats: FPlatformStackWalk::StackWalkAndDump -  3.064 s
 LogOutputDevice:Error: === Handled ensure: ===
 LogOutputDevice:Error: Ensure condition failed: bArchetypeReinstanced [File:F:\WORK\UnrealEngine\Engine\Source\Editor\UnrealEd\Private\Kismet2\KismetReinstanceUtilities.cpp] [Line: 1556]
 LogOutputDevice:Error: Reinstancing non-actor (/Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian10.CapsuleTrigger); failed to resolve archetype object - property values may be lost.
 LogOutputDevice:Error: Stack: 
 LogOutputDevice:Error: UE4Editor-Core.dll!FWindowsPlatformStackWalk::StackWalkAndDump() [f:\work\unrealengine\engine\source\runtime\core\private\windows\windowsplatformstackwalk.cpp:183]
 LogOutputDevice:Error: UE4Editor-Core.dll!FDebug::EnsureFailed() [f:\work\unrealengine\engine\source\runtime\core\private\misc\outputdevice.cpp:297]
 LogOutputDevice:Error: UE4Editor-Core.dll!FDebug::OptionallyLogFormattedEnsureMessageReturningFalse() [f:\work\unrealengine\engine\source\runtime\core\private\misc\outputdevice.cpp:432]
 LogOutputDevice:Error: UE4Editor-UnrealEd.dll!FBlueprintCompileReinstancer::ReplaceInstancesOfClass_Inner() [f:\work\unrealengine\engine\source\editor\unrealed\private\kismet2\kismetreinstanceutilities.cpp:1556]
 LogOutputDevice:Error: UE4Editor-UnrealEd.dll!FBlueprintCompileReinstancer::ReplaceInstancesOfClass() [f:\work\unrealengine\engine\source\editor\unrealed\private\kismet2\kismetreinstanceutilities.cpp:1305]
 LogOutputDevice:Error: UE4Editor-UnrealEd.dll!FBlueprintCompileReinstancer::ReinstanceInner() [f:\work\unrealengine\engine\source\editor\unrealed\private\kismet2\kismetreinstanceutilities.cpp:599]
 LogOutputDevice:Error: UE4Editor-UnrealEd.dll!FBlueprintCompileReinstancer::ReinstanceObjects() [f:\work\unrealengine\engine\source\editor\unrealed\private\kismet2\kismetreinstanceutilities.cpp:761]
 LogOutputDevice:Error: UE4Editor-HotReload.dll!FHotReloadModule::ReinstanceClass() [f:\work\unrealengine\engine\source\developer\hotreload\private\hotreload.cpp:1232]
 LogOutputDevice:Error: UE4Editor-HotReload.dll!FHotReloadModule::ReinstanceClasses() [f:\work\unrealengine\engine\source\developer\hotreload\private\hotreload.cpp:1219]
 LogOutputDevice:Error: UE4Editor-HotReload.dll!TBaseRawMethodDelegateInstance<0,FHotReloadModule,void __cdecl(void)>::ExecuteIfSafe() [f:\work\unrealengine\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:638]
 LogOutputDevice:Error: UE4Editor-CoreUObject.dll!UClassReplaceHotReloadClasses() [f:\work\unrealengine\engine\source\runtime\coreuobject\private\uobject\uobjectbase.cpp:688]
 LogOutputDevice:Error: UE4Editor-CoreUObject.dll!ProcessNewlyLoadedUObjects() [f:\work\unrealengine\engine\source\runtime\coreuobject\private\uobject\uobjectbase.cpp:835]
 LogOutputDevice:Error: UE4Editor-CoreUObject.dll!TBaseStaticDelegateInstance<void __cdecl(void)>::ExecuteIfSafe() [f:\work\unrealengine\engine\source\runtime\core\public\delegates\delegateinstancesimpl.h:1017]
 LogOutputDevice:Error: UE4Editor-Core.dll!TBaseMulticastDelegate<void>::Broadcast() [f:\work\unrealengine\engine\source\runtime\core\public\delegates\delegatesignatureimpl.inl:921]
 LogOutputDevice:Error: UE4Editor-Core.dll!FModuleManager::LoadModuleWithFailureReason() [f:\work\unrealengine\engine\source\runtime\core\private\modules\modulemanager.cpp:461]
 LogOutputDevice:Error: UE4Editor-Core.dll!FModuleManager::LoadModule() [f:\work\unrealengine\engine\source\runtime\core\private\modules\modulemanager.cpp:322]
 LogOutputDevice:Error: UE4Editor-HotReload.dll!FHotReloadModule::DoHotReloadInternal() [f:\work\unrealengine\engine\source\developer\hotreload\private\hotreload.cpp:828]
 LogOutputDevice:Error: UE4Editor-HotReload.dll!FHotReloadModule::DoHotReloadFromIDE() [f:\work\unrealengine\engine\source\developer\hotreload\private\hotreload.cpp:1453]
 LogOutputDevice:Error: UE4Editor-HotReload.dll!FHotReloadModule::Tick() [f:\work\unrealengine\engine\source\developer\hotreload\private\hotreload.cpp:1386]
 LogOutputDevice:Error: UE4Editor-Core.dll!FTicker::Tick() [f:\work\unrealengine\engine\source\runtime\core\private\containers\ticker.cpp:79]
 LogOutputDevice:Error: UE4Editor.exe!FEngineLoop::Tick() [f:\work\unrealengine\engine\source\runtime\launch\private\launchengineloop.cpp:2938]
 LogOutputDevice:Error: UE4Editor.exe!GuardedMain() [f:\work\unrealengine\engine\source\runtime\launch\private\launch.cpp:156]
 LogOutputDevice:Error: UE4Editor.exe!GuardedMainWrapper() [f:\work\unrealengine\engine\source\runtime\launch\private\windows\launchwindows.cpp:126]
 LogOutputDevice:Error: UE4Editor.exe!WinMain() [f:\work\unrealengine\engine\source\runtime\launch\private\windows\launchwindows.cpp:202]
 LogOutputDevice:Error: UE4Editor.exe!__scrt_common_main_seh() [f:\dd\vctools\crt\vcstartup\src\startup\exe_common.inl:264]
 LogOutputDevice:Error: KERNEL32.DLL
 LogOutputDevice:Error: ntdll.dll
 LogOutputDevice:Error: ntdll.dll
 LogStats:                SubmitErrorReport -  0.000 s
 LogStats:                    SendNewReport -  0.422 s
 LogStats:             FDebug::EnsureFailed -  3.489 s
 LogUObjectGlobals:Warning: Guid referenced by TriggerShape /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian16.CapsuleTrigger is already used by TriggerShape /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian16.TriggerShape_6, which should never happen in the editor but could happen at runtime with duplicate lev
 el loading or PIE
 LogUObjectGlobals:Warning: Guid referenced by TriggerShape /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian20.CapsuleTrigger is already used by TriggerShape /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian20.TriggerShape_11, which should never happen in the editor but could happen at runtime with duplicate le
 vel loading or PIE
 LogHotReload: Re-instancing Pedestrian after hot-reload.
 LogUObjectGlobals:Warning: Guid referenced by ArrowComponent /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian16.arrow is already used by ArrowComponent /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian_7.arrow, which should never happen in the editor but could happen at runtime with duplicate level loading or 
 PIE
 LogUObjectGlobals:Warning: Guid referenced by SkeletalMeshComponent /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian16.SkelMesh is already used by SkeletalMeshComponent /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian_7.SkelMesh, which should never happen in the editor but could happen at runtime with duplica
 te level loading or PIE
 LogUObjectGlobals:Warning: Guid referenced by PedestrianMovementComponent /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian16.PedestrianMovementComp is already used by PedestrianMovementComponent /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian_7.PedestrianMovementComp, which should never happen in the editor 
 but could happen at runtime with duplicate level loading or PIE
 LogUObjectGlobals:Warning: Guid referenced by ArrowComponent /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian20.arrow is already used by ArrowComponent /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian_12.arrow, which should never happen in the editor but could happen at runtime with duplicate level loading or
  PIE
 LogUObjectGlobals:Warning: Guid referenced by SkeletalMeshComponent /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian20.SkelMesh is already used by SkeletalMeshComponent /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian_12.SkelMesh, which should never happen in the editor but could happen at runtime with duplic
 ate level loading or PIE
 LogUObjectGlobals:Warning: Guid referenced by PedestrianMovementComponent /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian20.PedestrianMovementComp is already used by PedestrianMovementComponent /Game/Maps/VehicleExampleMap.VehicleExampleMap:PersistentLevel.Pedestrian_12.PedestrianMovementComp, which should never happen in the editor
  but could happen at runtime with duplicate level loading or PIE
 LogContentBrowser: Native class hierarchy updated for 'SimpleCar1' in 0.0015 seconds. Added 12 classes and 3 folders.
 Display: HotReload successful (2 functions remapped  0 scriptstructs remapped)
 LogContentBrowser: Native class hierarchy populated in 0.0096 seconds. Added 2168 classes and 436 folders.
 Display: HotReload took  4.8s.

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Won't Fix

Component	UE - Gameplay - Blueprint
Affects Versions	4.13

Created	Sep 12, 2016
Resolved	Aug 18, 2021
Updated	Aug 18, 2021

View Jira Issue

UE-35870

Build Warning when HotReloading - LogUObjectGlobals:Warning: Guid is already used by

Build Warning when HotReloading - LogUObjectGlobals:Warning: Guid is already used by

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