v79 / KNWorld

Kotlin Native for Pi

KNWorld - Experiments in Cross-Compilation

This is a test project for Kotlin Native. I've written a simple Kotlin program (inspired by the code at https://kotlinlang.org/docs/tutorials/native/using-intellij-idea.html) and modified it to work. My goal is to cross-compile from Windows to Raspberry Pi.

Sources

I've duplicated the source code in src\main\nativeMain and src\mainPiMain - the only difference is the output, which states whether the compilation was from native or pi.

Gradle

I've modified build.gradle.kts a little, as the examples on Kotlin's website did not work for me. I have added a new target called Pi, like this:

 linuxArm32Hfp("Pi") {
        binaries {
            executable {
                entryPoint = "main"
            }
        }
    }

Compilation

To build the 'native' binary (i.e. an executable for the machine you are currently running), just run gradle nativeBinaries.

To build for the Raspberry Pi, execute gradle PiBinaries.

The resulting executable file called 'KNWorld.kexe' can be found in build\bin\native\releaseExecutable and build\bin\Pi\releaseExecutable.

Copy the Pi version of KNWorld.kexe to your Raspberry Pi. I've even added extra steps to verify this is a Linux binary build from my host - Windows - machine.

pi@raspberrypi:~/PiShare $ uname -a
Linux raspberrypi 5.4.72-v7l+ #1356 SMP Thu Oct 22 13:57:51 BST 2020 armv7l GNU/Linux
pi@raspberrypi:~/PiShare $
pi@raspberrypi:~/PiShare $ file KNWorld.kexe
KNWorld.kexe: ELF 32-bit LSB executable, ARM, EABI5 version 1 (SYSV), dynamically linked, interpreter /lib/ld-linux-armhf.so.3, for GNU/Linux 2.6.32, BuildID[xxHash]=a487af0917a9a720, not stripped
pi@raspberrypi:~/PiShare $ ./KNWorld.kexe
PiMain: Hello, enter your name:
Liam Davison
Your name contains 11 letters
Your name contains 9 unique letters
pi@raspberrypi:~/PiShare $

Voila, cross-compilation from MS Windows X64 to Raspbian ARM 32Hfp Pi code. No Windows Subsystem for Linux was used in this code.

The next step is to start integrating C libraries from the Pi into the build process, but that's tearing my hair out and is, apparently, not possible from Windows.