5.6 UE: Mutable crashes when compiling our Character BP

Development Pipeline & Plugins
, ,
1

-

2

Steps to Reproduce
Hello,

After updating from 5.5 to 5.6, running the Editor, whenever we try to compile or save our the character BP we get this crash:

Unhandled Exception: EXCEPTION_ACCESS_VIOLATION reading address 0x0000000000000030

UnrealEditor_CustomizableObject!UCustomizableObjectSystem::TickInternal() [C:\MyProject\Engine\Plugins\Mutable\Source\CustomizableObject\Private\MuCO\CustomizableObjectSystem.cpp:3997]
UnrealEditor_Engine!FStreamingManagerCollection::UpdateResourceStreaming() [C:\MyProject\Engine\Source\Runtime\Engine\Private\ContentStreaming.cpp:908]
UnrealEditor_Engine!IStreamingManager::Tick() [C:\MyProject\Engine\Source\Runtime\Engine\Private\ContentStreaming.cpp:741]
UnrealEditor_Engine!FStreamingManagerCollection::Tick()

UCustomizableObjectInstanceUsage has a member:

UPROPERTY(Instanced)
TObjectPtr<UCustomizableObjectInstanceUsagePrivate> Private;

Private turns out to be nullptr, but the current flow seems to not contemplate this case.

Functions like this assumes it’s valid:

USkeletalMeshComponent* UCustomizableObjectInstanceUsage::GetAttachParent() const
{
	if (UCustomizableSkeletalComponent* CustomizableSkeletalComponent = GetPrivate()->GetCustomizableSkeletalComponent())
	{
		return Cast<USkeletalMeshComponent>(CustomizableSkeletalComponent->GetAttachParent());
	}
	else if(UsedSkeletalMeshComponent.IsValid())
	{
		return UsedSkeletalMeshComponent.Get();
	}


	return nullptr;
}

We’ve been working with Mutable since 4.27, and this is the first time facing this crash.

Any idea?

Thank you.

3

Do you have your editor set to localized to your language? There’s a bug with localization that provokes a crash that has been fixed in 5.6.1.

4

Hello Alexei,

I’d say that’s not our case:

[Image Removed]Thanks.

5

Did you port this actor BP from 5.5?

It could be a backward compatibility issue. To confirm, try creating a new actor and adding the same structure (components, CO instances, etc.) and compiling/saving.