cbindgen  

This project can be used to generate C bindings for Rust code. It is currently being developed to support creating bindings for WebRender, but has been designed to support any project.

Features

• Builds bindings for a crate, its mods, its dependent crates, and their mods
• Only the necessary types for exposed functions are given bindings
• Can specify annotations for controlling some aspects of binding
• Generic structs can be exposed using type IntFoo = Foo<i32>;
• Customizable formatting, can be used in C or C++ projects

Use

Command line

cbindgen crate/ -o crate/bindings.h

See cbindgen --help for more options.

build.rs

cbindgen can also be used in build scripts. How this fits into compiling the native code depends on your project.

Here's an example build.rs script:

extern crate cbindgen;

use std::env;
use cbindgen::{Config, Library};

fn main() {
    let root = env::var("CARGO_MANIFEST_DIR").unwrap();
    let config = Config::from_root_or_default(&root);

    Library::load(&root, &config)
        .generate().unwrap()
        .write_to_file("bindings.h");
}

Examples

See tests/ for some examples of rust source that can be handled.

How it works

1. All the structs, enums, type aliases, and functions that are representable in C are gathered
2. A dependency graph is built using the extern "C" functions as roots
   • This removes unneeded types from the bindings and sorts the structs that depend on each other
3. Some code generation is done to specialize generics that are specified as type aliases
4. The items are printed in dependency order in C syntax

Future work

1. Add a validation step to catch common issues
2. Better support for types with fully specified names
3. Better support for finding dependencies managed by Cargo
4. Support for generating a FFI interface for a Struct+Impl
5. ...