Development guide

Right now, the best documentation of the development setup is in the AGENTS.md file.

Simple WASM build

The best way to build is using Nix, which builds a WASM blob which can then be run using NodeJS.

In order:

nix-build -I nixpkgs=channel:nixpkgs-unstable npm i node run-wasm.js

To build the WASM and run it under NodeJS.

This (and other workflows) have only been tested on my Macbook Air, so while there’s nothing highly system-dependent about the setup, because of the odd toolchains involved it’s likely that methodologies other than Nix won’t work without some tweaking.

Meson

The operating system is configured using Meson, and there are a variety of options which allow changing out drivers and the default “kernel program” (which sequence of things to do on startup)

meson setup build-riscv —cross-file=cross/riscv32.txt

and

meson setup build-wasm —cross-file=cross/wasm.txt

Will setup the build directory for a particular target.

Each target should set reasonable defaults: appropriate drivers, and a main sequence that gives you a functional shell. meson.build has full details on options.

And then

meson compile -C build-riscv -v

or

meson compile -C build-wasm -v

There are various shortcuts for building and running the operating system in the Justfile:

just —list

QEMU and WASM harnesses

On RISC-V, Otium currently runs under QEMU. The script tools/run-qemu-riscv.sh (just run-riscv as a shortcut).

On WASM, the NodeJS harness (node run-wasm.js) will run the operating system using SDL to provide graphics and device support.

Filesystem

Both harnesses will read the fs-in directory in the source tree to create the initial filesystem and try to push the results out to fs-out at the end