Tracking issue: Godot 4.0 port of Foreigner

[follower]

Current status

• I've been intermittently following the development of GDExtension (the replacement for GDNative in Godot 4.0) since pre-alpha days.
• While there has been some recent improvement/forward motion, GDExtension has seemed relatively low in development priority, and currently it still seems neither fully baked nor completely documented. So there seemed limited benefit/opportunity for beginning a port of Foreigner to 4.0 in the pre-beta days.
• While still incomplete, GDExtension development does now seem to be at a point where initial exploratory development of an extension/add-on is possible in order to get familiar with the new feature.

A vision for Foreigner/FFI & Godot 4.0

• [TODO]

Known differences between Godot 3.x & 4.0 likely to impact Foreigner

• [TODO]

Useful GDExtension-related links for future reference

• GDExtension examples & documentation:

  • Initial introduction blog post (includes example walkthrough):

    • "Introducing GDNative's successor, GDExtension"

    • Mentions options for chat locations related to GDExtensions in "Where to go from here" section at end of post.

  • C++ Bindings/"SDK":

    • Repo: https://github.com/godotengine/godot-cpp/

    • Of particular note:

      • https://github.com/godotengine/godot-cpp/#versioning
      • "[IMPORTANT] godot-cpp commits to use to match official 4.0 beta releases #874"
      • Somewhat vague but useful "Getting Started with GDExtension" information: https://github.com/godotengine/godot-cpp/#getting-started
      • Example GDExtension: https://github.com/godotengine/godot-cpp/tree/master/test

  • https://github.com/godotengine/godot-headers:

    • Note (as @ 14 October 2022): "A pure C sample project is currently not available."
    • https://github.com/godotengine/godot-headers/blob/master/godot/gdnative_interface.h

  • Core implementation/headers:

    • core/extension/*

      • https://github.com/godotengine/godot/blob/master/core/extension/gdnative_interface.h
        • GDNativeInterface struct: https://github.com/godotengine/godot/blob/926429392a73a0c2261bc4ed4503c99025842d7c/core/extension/gdnative_interface.h#L384-L558
        • Entry point function prototype: https://github.com/godotengine/godot/blob/926429392a73a0c2261bc4ed4503c99025842d7c/core/extension/gdnative_interface.h#L581-L585
      • https://github.com/godotengine/godot/blob/master/core/extension/gdnative_interface.cpp
      • https://github.com/godotengine/godot/blob/master/core/extension/native_extension.h
      • https://github.com/godotengine/godot/blob/master/core/extension/native_extension.cpp

    • Original initial PR: " Implement native extension system (GDExtension) #49744 "

• Informative examples & issues related to GDExtension & Godot 4.0 ports in other projects:

  • https://github.com/GodotVR/godot_xr_reference

    • Note: "It is important to build debug builds as the editor requires debug builds to run."

  • "Summator Example from Custom Modules made with the GDExtension system in Godot 4": https://github.com/paddy-exe/GDExtensionSummator

  • https://github.com/Zylann/godot_voxel (master branch now targets Godot 4.0)

    • "Porting [godot_voxel] to GDExtension #333" (Tracking issue for the project port)

      • This issue includes a comprehensive overview of the Godot 4.0/GDExtension/module porting process & is essential reading.

    • "GDExtension issues tracker #442" (Tracking issue for GDExtension technology/feature itself.)

      • Even more essential reading--documents a wealth of GDExtension-related knowledge & current issues. (i.e. if you only read one GDExtension-related issue today, it should probably be that one. :D )

    • Documents build process: https://voxel-tools.readthedocs.io/en/latest/module_development/#gdextension

  • https://github.com/nonunknown/gdextension-creator (untested)

  • Godot 4 + GDExtension support godot-rust/gdnative#824

• Hey, wait a minute, that name looks familiar: Godot crashes when using cast_to on a node that precedes GDNative node in tree godotengine/godot-cpp#860 :D

[fire]

Hi, I am looking into this because https://github.com/metacall/core says libffi is the how they expose C++.