If you know rust, the Godot rust bindings for GDExtension are also really good and let you use any Rust library in Godot (including tokio and async rust if you really want) https://godot-rust.github.io/

So it requires writing a CMake script, some python, and some weird C++ code.

A bit tedious but that's how it goes.

Static linking libstdc++ with -fvisibility=hidden saved me on Linux, though it bit me the day I needed exceptions to cross the boundary.

Just don't forget the versioning script needed on at least Linux. It's either that or build with the same older distro Godot uses, so you have a matching libstdc++ version. You can link with a newer stdlibc++ but you will need a linker versioning script that hides your impl from the dynamic linker so you don't get random ghosts in your machine.

> // Copy the position of every entity into the MultiMesh buffer

So, is a zero-copy impossible due to world (C++ vs Godot) boundaries?