| # Rust FFI |
| |
| This document tries to provide guidance for C++/Rust FFI. |
| CLs to improve this guidance are welcomed. |
| |
| ## General guidance |
| |
| Chromium recommends using [the `cxx` crate](https://cxx.rs/) for C++/Rust FFI. |
| For introductory guidance, please see |
| [the `cxx` chapter](https://google.github.io/comprehensive-rust/chromium/interoperability-with-cpp.html) |
| in the Chromium day of the Comprehensive Rust course. |
| |
| Chromium also supports the following tools: |
| |
| * [`bindgen`](https://rust-lang.github.io/rust-bindgen/) - see |
| `//build/rust/rust_bindgen.gni` for usage instructions. |
| |
| At this point Chromium's `//build/rust/*.gni` templates do not support other FFI |
| tools like: |
| |
| * [`cbindgen`](https://github.com/mozilla/cbindgen) |
| * [`crubit`](https://github.com/google/crubit) |
| |
| ### `cxx` guidance |
| |
| #### Best practices |
| |
| * Generate C++ side of bindings into a project-specific or crate-specific |
| `namespace`. For example: `#[cxx::bridge(namespace = "some_cpp_namespace")]`. |
| * Maintain binding declarations in a **single** `#[cxx::bridge]` declaration. |
| `cxx` supports reusing types across multiple `bridge`s, but there are some |
| rough edges. |
| |
| #### Suggestions |
| |
| TODO: Provide some examples or suggestions on how to structure FFI bindings |
| (even if these suggestions wouldn't necessarily rise to the level of "best |
| practices"). |
