Zeo

Zeo compiles a whole Ruby program to native code. It reads the source with Prism, analyzes the entire program at once, lowers it to Cranelift IR, and links libzeo.a — Zeo's own Ruby runtime, written in Rust and compiled ahead of time: the object model, the core classes, the dispatcher, threads, fibers, and the reference-counted heap. There is no interpreter to boot and no JIT to warm up. The machine that runs the binary needs no Ruby.

$ cat hello.rb
puts [1, 2, 3].map { |x| x * 2 }.sum
$ zeo hello.rb          # runs it, like `ruby hello.rb`
12
$ zeo -o hello hello.rb # or write a native binary
$ ./hello
12

Every test compares Zeo's output with real Ruby 4.0.6, byte for byte.

Status

Experimental, and moving fast. Read Limitations before depending on it.

The corpus (test/) runs green, each program compared with real Ruby on stdout, stderr and the exit status. Every module, method, constant and visibility that Ruby 4.0.6 reaches has a Zeo answer, so what remains is behavioural, not missing surface.

Every known difference is recorded: in Compatibility when a user can see it, in test/divergences/ when it is deliberate, and in test/gaps/ when it is not fixed yet.

Install

The first release is not cut yet, so today the way in is a build from source (below). The release will ship three ways: cargo install zeo, gem install zeo (a per-platform gem that carries the binary), and a relocatable tarball:

$ tar xzf zeo-<version>-<triple>.tar.gz -C /usr/local

Building a binary needs a linker (cc) on the machine, the same requirement any native toolchain has.

Build it yourself

$ git clone https://github.com/ryanseys/zeo && cd zeo
$ cargo xtask deps    # Gemfile.lock -> vendor/, no ruby needed
$ cargo build
$ cargo nextest run

Ruby is needed for one thing only: recording a test's answer. Getting started walks the whole loop.

Documentation

docs/ is the map. The pages people reach for first:

• Getting started — clone to first test
• CLI reference — every verb and flag
• Architecture — what happens between hello.rb and hello
• Compatibility — library by library
• Performance — measured, with the method beside it

Contributing

Issues and pull requests are welcome. A bug report is most useful as the smallest .rb that shows it, what ruby printed, what zeo printed, and zeo --version; the issue template asks for exactly that. The one rule that matters: keep every difference from Ruby visible.

1. Check each new behaviour against real Ruby.
2. Leave a comment at the site of any difference you accept.
3. If a user can observe it, add a row to Compatibility and a note under test/gaps/.

CONTRIBUTING.md has the conventions.

License

MIT (LICENSE-MIT) or Apache 2.0 (LICENSE-APACHE), at your option.