Code Formatting

bindgen uses rustfmt to format the emitted bindings. This section describes how to adjust the rustfmt behavior when being used from bindgen.

Passing a rustfmt.toml configuration file

rustfmt should automatically use any rustfmt.toml file that is present in the directory from where bindgen will be run. If you want to use a configuration file that has a different name or that is in a different directory you can use the --rustfmt-configuration-file flag or the Builder::rustfmt_configuration_file method.

Using a nightly release of rustfmt

If the rustfmt command does not correspond to a nightly release of rustfmt but you have rustup available, you can use nightly by following these steps:

When using bindgen as a CLI application

Use rustup run to run bindgen:

$ rustup run nightly bindgen [ARGS]

When using bindgen as a library

Take the output of the following command:

$ rustup which rustfmt --toolchain=nightly

and pass it to Builder::with_rustfmt:

use bindgen::Builder;
use std::process::Command;

fn main() {
    let output = Command::new("rustup")
        .args(["which", "rustfmt", "--toolchain", "nightly"])
        .output()
        .expect("Could not spawn `rustup` command");

    assert!(
        output.status.success(),
        "Unsuccessful status code when running `rustup`: {:?}",
        output
    );

    let rustfmt_path =
        String::from_utf8(output.stdout).expect("The `rustfmt` path is not valid `utf-8`");

    let bindings = Builder::default()
        .header("path/to/input.h")
        .with_rustfmt(rustfmt_path)
        .generate()
        .expect("Could not generate bindings");

    bindings
        .write_to_file("path/to/output.rs")
        .expect("Could not write bindings");
}

These two methods also apply to any other toolchain available in your system.