Burst UnmanagedCallersOnly

[astral lily]

The burst 1.8.8 changelog mentions the UnmanagedCallersOnly attribute, which as far as I can tell it's only part of .net 5+. Is there a way to use this attribute in Unity? I'm currently using 2022.2 so i guess this might have been added in 2023?

[naive quiver]

Not part of 2022.2 but we'll see where the future goes 2023+. As it has already landed in our version of mono:
https://github.com/Unity-Technologies/mono/pull/1772

[errant depot]

So the official answer is no, UnmanagedCallersOnly is not supported in Unity yet, even in Unity 2023 versions. With that said, it might work, let me explain:

We're currently working to bring CoreCLR and new .NET support to Unity. The UnmanagedCallersOnly attribute is a big part of that, allowing us to get excellent performance for code that crosses the native/managed boundary. So we are iteratively implementing support in Burst, IL2CPP, and Mono as we need it. Once there is a Unity release will full CoreCLR support, UnmanagedCallersOnly will also be fully supported. So you're seeing some implementation details of our current development work leak here. I would hold off until we have a full release though, as the current support is only what we need now, so there may be cases where it doesn't work completely.

[light coral]

🤔 So in future call method from managed land to unmanaged dots land will near to zero overhead?