Geode Rust CXX

This is an example repo of a project that implements interop between Rust and C++ within a Geode mod. Rust can be called from C++ and vice versa.

It makes use of CXX to handle the bindings and codegen.

Prerequisites

Before this project will build, there are a few things required.

NOTE:

• This project has only been tested on windows so for the time being the prerequisites only target windows.

It compiles with both MSVC and Clang (tested on Clang 17.0.1).

Windows

• Windows 10/11 SDK (depends on your current OS)

• Adding the i686-pc-windows-msvc toolchain:

  rustup target add --toolchain stable-x86_64-pc-windows-msvc i686-pc-windows-msvc

Usage

Building the mod works like building a normal Geode mod. CMake should automatically handle building the Rust crate and linking, and the build.rs inside the crate invokes CXX which takes care of the rest.

NOTE:

• If you get linker errors on the first build, you may need to manually build the crate first in which case run the command below:

  cargo build --release

  Subsequent builds should then compile without issue.

Configuration

• Inside the root CMakeLists.txt are two variables: GEODE_PROJECT_NAME and RUST_CRATE_NAME. These are pretty self explanatory but make sure to change them to whatever you name the folders.
• Don't forget to update the neccessary information in the mod.json, about.md and other files, for your geode mod.
• If you plan to change the folder structure, don't forget to change everywhere that would be affected, especially the call to setup_geode_cxx

Potential issues

Mismatch detected for 'RuntimeLibrary': value 'MDd_DynamicDebug' doesn't match value 'MD_DynamicRelease' in cmake_pch.obj / lld-link: error: /failifmismatch: mismatch detected for 'RuntimeLibrary':

This means you haven't selected RelWithDebInfo as the build variant for the Geode mod.

setup_geode_cxx

This is the function that handles building the crate, linking the static Rust library with the Geode library, as well as linking all the required static native libraries, and other bits and pieces.

The arguments to this function are as follows:

Name	Required	Description
GEODE_PROJ_NAME	Yes	Name of the Geode mod folder
RUST_CRATE_DIR	Yes	Directory of the Rust crate
RUSTC_TARGET_TRIPLE	Yes	Rust compilation target. Must match the one used in .cargo/config.toml
RUST_CRATE_NAME	Yes	Name of the Rust crate.
CARGO_MANIFEST	No	Path to the Cargo.toml beloning to the crate.
CARGO_TARGET_DIR	No	Path to the output target folder of the crate.
CARGO_BIN	No	Path to the cargo executable.
CARGO_BUILD_PROFILE	No	The profile to build the crate with. Defaults to release. Any custom profile still needs to build like release would as a Geode mod is always built in release.