Export to Android

Exporting with gdext for Godot requires some of the same pieces that are required for building Godot from source. Specifically, the Android SDK Command Line Tools and JDK 17 as mentioned in Godot's documentation here.

Once you have those installed, you then need to follow Godot's instructions for setting up the build system here.

To find the jdk and nkd versions that are needed, reference the Godot configuration that your version of Godot is using. For example:

• master branch
• 4.2.2-stable tag

Compiling

The environment variable CLANG_PATH is used by bindgen's clang-sys dependency. See also clang-sys documentation

Set the environment variable CLANG_PATH to point to Android's build of clang. Example:

export CLANG_PATH=\
"{androidCliDirectory}/{androidCliVersion}/ndk/{ndkVersion}/toolchains/llvm/prebuilt/{hostMachineOs}/bin/clang"

Then set the CARGO_TARGET_{shoutTargetTriple}_LINKER to point to the Android linker for the Android triple you are targeting. The {shoutTargetTriple} should be in SHOUT_CASE so that a triple such as aarch64-linux-android becomes AARCH64_LINUX_ANDROID. You need to compile your gdext library for each Android triple individually. Possible targets can be found by running:

rustup target list

You can find the linkers in the Android CLI directory at:

{androidCliDirectory}/{androidCliVersion}/ndk/{ndkVersion}/toolchains/llvm/prebuilt/
{hostMachineOs}/bin/{targetTriple}{androidVersion}

As of writing this, the tested triples are:

Notice how the environment variables are in all-caps and the triple's "-" is replaced with "_".

Make sure to add all of the triples you want to support to rustup via:

rustup target add {targetTriple}

Example:

rustup target add aarch64-linux-android

A complete example

Putting it all together, here is an example compiling for aarch64-linux-android. This is also probably the most common Android target, as of the writing of this.

Assuming the following things:

1. Android CLI is installed in the $HOME folder.
2. Godot is still relying on Android NDK version 23.2.8568313. Check here.
3. The downloaded Android CLI version is: 11076708_latest (update this to be the version you downloaded).
4. This is being run on Linux. Change the linux-x86_64 folder in CLANG_PATH and CARGO_TARGET_AARCH64_LINUX_ANDROID_LINKER to be your host machine's operating system.
5. You are targeting Android version 34.

And here is what the commands look like running from a bash shell:

rustup target add aarch64-linux-android

export CLANG_PATH="$HOME/android-cli/11076708_latest/ndk/23.2.8568313/toolchains/llvm/prebuilt/linux-x86_64/bin/clang"
export CARGO_TARGET_AARCH64_LINUX_ANDROID_LINKER=\
"$HOME/android-cli/11076708_latest/ndk/23.2.8568313/toolchains/llvm/prebuilt/linux-x86_64/bin/aarch64-linux-android34-clang"

cargo build --target=aarch64-linux-android

And then you should find a built version of your GDExtension library in:

target/aarch64-linux-android/debug/{YourCrate}.so

Make sure to update your .gdextension file to point to the compiled lib. Example:

android.debug.arm64="res://path/to/rust/lib/target/aarch64-linux-android/debug/{YourCrate}.so