ECS types sometimes destruct before GameObjects leading to exceptions on shutdown

Unity Engine
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1

I have some GameObjects that create entities, which they destroy in their OnDestroy handler. This works just fine, except when the game is shutting down, about 20% of the time, the EntityManager will have already been deallocated by the time OnDestroy runs. This results in shutdown errors like these:

InvalidOperationException: The Unity.Entities.EntityManager has been deallocated, it is not allowed to access it
Unity.Collections.LowLevel.Unsafe.AtomicSafetyHandle.CheckWriteAndThrowNoEarlyOut (Unity.Collections.LowLevel.Unsafe.AtomicSafetyHandle handle) (at <fad2bd984a474a969b1042b2d70ac590>:0)
Unity.Collections.LowLevel.Unsafe.AtomicSafetyHandle.CheckWriteAndThrow (Unity.Collections.LowLevel.Unsafe.AtomicSafetyHandle handle) (at /Users/builduser/buildslave/unity/build/Runtime/Export/Jobs/AtomicSafetyHandle.bindings.cs:162)
Unity.Entities.EntityManager.GetCheckedEntityDataAccess () (at Library/PackageCache/com.unity.entities@0.11.1-preview.4/Unity.Entities/EntityManager.cs:70)
Unity.Entities.EntityManager.DestroyEntityInternal (Unity.Entities.Entity* entities, System.Int32 count) (at Library/PackageCache/com.unity.entities@0.11.1-preview.4/Unity.Entities/EntityManagerCreateDestroyEntities.cs:341)
Unity.Entities.EntityManager.DestroyEntity (Unity.Collections.NativeArray`1[T] entities) (at Library/PackageCache/com.unity.entities@0.11.1-preview.4/Unity.Entities/EntityManagerCreateDestroyEntities.cs:140)

I wonder if ECS objects should not destruct before GameObjects do on shutdown?

Full disclosure: my mind has been warped by 15 years of C++, so apologies if this makes no sense in your memory-managed, sci-fi future world, where you always label your references and the Garbage Collector deallocates things when it feels like it, on its way from the farmer’s market while snacking on organic goji berries.

2

Snark aside, would someone mind commenting on how Unity expects Entities get destroyed? Is doing that from OnDestroy on MonoBehaviors a no-no?

3

you can use “world.IsCreated” before trying to access the EntityManager on OnDestroy to ensure that the EntityManager is still valid

4

Cool, seems to work. It seems weird, though, that there are types you are responsible for destroying sometimes, but not other times. If the ECS stuff got destructed strictly after GameObjects on shutdown, you wouldn’t need branching teardown. Is that a reasonable feature request?