Rust Call Lean

A tiny example of calling Lean's FFI from Rust with Nix.

This is based on:

• Lean4 Reverse FFI
• Lean4 FFI
• Rustonomicon FFI
• Rust Bindgen
• Rust Bindgen Static Functions

Usage

Since the entire environment was built on Nix flakes, the easiest way to run the executable is via Nix:

$ nix run .#caller

For interactive development, one can also drop into a develop shell:

$ nix develop

and then execute

$ cargo run

Execution without Nix is possible.

This project has been tested on Linux and Mac OS.

Structure

The project has 2 parts:

1. Callee, a Lean library
2. Caller, a Rust executable

Caller is dependent on Callee and requires it along with Lean to be present in the environment for linking. Specifically the following environment variables must be set:

• CALLEE_PATH: Path to a directory containing libCallee.so
• LEAN_ROOT: Path to a directory such that $LEAN_ROOT/include has lean headers and $LEAN_ROOT/lib has the leanshared library
• Clang path must be set so clang-sys can find it
• Clang executable must be present in PATH