Since UE5.4, it has been reported that if there's a class derived from UEditorUtilitySubsystem, the program crashes when the editor exits. This is because the code added in CL30853505 accesses freed memory.
In void UEditorUtilitySubsystem::Initialize(FSubsystemCollectionBase& Collection), the following code receives RunTaskCommandObject.
RunTaskCommandObject = IConsoleManager::Get().RegisterConsoleCommand( TEXT("RunTask"), TEXT(""), FConsoleCommandWithWorldArgsAndOutputDeviceDelegate::CreateUObject(this, &UEditorUtilitySubsystem::RunTaskCommand), ECVF_Default );
But if you create a subclass of EditorUtilitySubsystem, void UEditorUtilitySubsystem::Initialize(FSubsystemCollectionBase& Collection) is called multiple times and it causes duplicate command registration. To prevent this duplicate registration, Engine\Source\Runtime\Core\Private\HAL\ConsoleManager.cpp(2830) releases redundant objects and keep the last one;
// Replace console command with the new one and release the existing one. // This should be safe, because we don't have FindConsoleVariable equivalent for commands. ConsoleObjects.Add( Name, Cmd ); ExistingCmd->Release();
This results make the pointer owned by early initialized UEditorUtilitSubsystem a dangling pointer.
And now, when the editor exits, void UEditorUtilitySubsystem::Deinitialize() calls UnregisterConsoleObject with this dangling pointer;
IConsoleManager::Get().UnregisterConsoleObject(RunTaskCommandObject);
This ends up to call FString FConsoleManager::FindConsoleObjectName(const IConsoleObject* InVar) const and hit dangling pointer access added by CL30853505;
// if we didn't find one, and it has a parent, then give that a try >;if (InVar->GetParentObject() != nullptr)
The repro project is available from the attachment. Just open the project then close the editor.
Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0xffffffff00000028 UnrealEditor_Core!FConsoleManager::FindConsoleObjectName() [D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Private\HAL\ConsoleManager.cpp:2888] UnrealEditor_Core!FConsoleManager::UnregisterConsoleObject() [D:\build\++UE5\Sync\Engine\Source\Runtime\Core\Private\HAL\ConsoleManager.cpp:2116] UnrealEditor_Blutility!UEditorUtilitySubsystem::Deinitialize() [D:\build\++UE5\Sync\Engine\Source\Editor\Blutility\Private\EditorUtilitySubsystem.cpp:103] UnrealEditor_Engine!FSubsystemCollectionBase::Deinitialize() [D:\build\++UE5\Sync\Engine\Source\Runtime\Engine\Private\Subsystems\SubsystemCollection.cpp:201] UnrealEditor_UnrealEd!UEditorEngine::PreExit() [D:\build\++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\EditorEngine.cpp:1471] UnrealEditor!FEngineLoop::Exit() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:5087] UnrealEditor!GuardedMain() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:194] UnrealEditor!GuardedMainWrapper() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:118] UnrealEditor!LaunchWindowsStartup() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:258] UnrealEditor!WinMain() [D:\build\++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:298] UnrealEditor!__scrt_common_main_seh() [D:\a\_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288] kernel32 ntdll
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There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-218181 in the post.
| 0 |
| Component | UE - Editor - UI Systems - UMG |
|---|---|
| Affects Versions | 5.4 |
| Target Fix | 5.5 |
| Fix Commit | 34744557 |
|---|
| Created | Jun 18, 2024 |
|---|---|
| Resolved | Jun 28, 2024 |
| Updated | Jul 21, 2024 |