UE 5.5.4 MulticastDelegateBase, MassSimulationSubsystem Unhandled Exception

Development Programming & Scripting
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1

Unreal Editor crashes during map loading at approximately 96% progress, with an EXCEPTION_ACCESS_VIOLATION error in TMulticastDelegateBase::CompactInvocationList() called from UMassSimulationSubsystem::BeginDestroy(). The crash occurs during garbage collection (Collect Garbage) when loading the default map at editor startup. The issue is intermittent. It is not mitigated by any attempted fixes, including clearing caches.

Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0xffffffffffffffff

UnrealEditor_MassSimulation!TMulticastDelegateBase::CompactInvocationList() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Delegates\MulticastDelegateBase.h:347]
UnrealEditor_MassSimulation!TMulticastDelegateBase::RemoveDelegateInstance() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Delegates\MulticastDelegateBase.h:310]
UnrealEditor_MassSimulation!UMassSimulationSubsystem::BeginDestroy() [D:\build++UE5\Sync\Engine\Plugins\Runtime\MassGameplay\Source\MassSimulation\Private\MassSimulationSubsystem.cpp:60]
UnrealEditor_CoreUObject!UObject::ConditionalBeginDestroy() [D:\build++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\Obj.cpp:1220]
UnrealEditor_CoreUObject!UnhashUnreachableObjects() [D:\build++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\GarbageCollection.cpp:5928]
UnrealEditor_CoreUObject!UE::GC::PostCollectGarbageImpl<1>() [D:\build++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\GarbageCollection.cpp:5547]
UnrealEditor_CoreUObject!UE::GC::FReachabilityAnalysisState::PerformReachabilityAnalysisAndConditionallyPurgeGarbage() [D:\build++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\GarbageCollection.cpp:5746]
UnrealEditor_CoreUObject!CollectGarbage() [D:\build++UE5\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\GarbageCollection.cpp:5986]
UnrealEditor_UnrealEd!UEditorEngine::Cleanse() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\EditorEngine.cpp:2820]
UnrealEditor_UnrealEd!UEditorEngine::EditorDestroyWorld() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\EditorServer.cpp:2060]
UnrealEditor_UnrealEd!UEditorEngine::Map_Load() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\EditorServer.cpp:2456]
UnrealEditor_UnrealEd!UEditorEngine::HandleMapCommand() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\EditorServer.cpp:6213]
UnrealEditor_UnrealEd!UEditorEngine::Exec_Editor() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\EditorServer.cpp:5674]
UnrealEditor_Core!FExec::Exec() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Private\Misc\Exec.cpp:18]
UnrealEditor_Engine!UEngine::Exec() [D:\build++UE5\Sync\Engine\Source\Runtime\Engine\Private\UnrealEngine.cpp:5027]
UnrealEditor_UnrealEd!UUnrealEdEngine::Exec() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\UnrealEdSrv.cpp:662]
UnrealEditor_UnrealEd!FEditorFileUtils::LoadMap() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\FileHelpers.cpp:2952]
UnrealEditor_UnrealEd!FEditorFileUtils::LoadDefaultMapAtStartup() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\FileHelpers.cpp:4958]
UnrealEditor_UnrealEd!FUnrealEdMisc::OnInit() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\UnrealEdMisc.cpp:375]
UnrealEditor_UnrealEd!EditorInit() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\UnrealEdGlobals.cpp:137]
UnrealEditor!GuardedMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:166]
UnrealEditor!GuardedMainWrapper() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:123]
UnrealEditor!LaunchWindowsStartup() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:277]
UnrealEditor!WinMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:317]
UnrealEditor!__scrt_common_main_seh() [D:\a_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
kernel32
ntdll

Plugins Enabled: MassEntity, MassGameplay.

Is the problem known? Where can I write and attach files with logs about it?

2

Hi there @Namidaa2

Welcome back to the forum! If you disable Mass Sim, does the issue still happen?

3

Hi! How can I manually disable the Mass Sim? The problem goes away if you disable autoregistration for all processors in all modules, after re-enabling autoregistration, the exception no longer occurs, I don’t understand why, nothing else has changed, git diff is empty

4

At the moment, I suspect that the problem may be in LiveCoding, I no longer use it and the exception no longer occurs… for now

5

Sorry for the late reply. Post got lost in my replies. Did you find a solution to this?

6

it’s hard to say, as if the problem is complex. currently, I’m getting stable crashes when using EMassProcessingPhase::MAX. just replacing it with FrameEnd or PostPhysics