Cross compilation

Cross-compile with the cross tool.

Cross compilation

Rust can compile on one machine for another platform. A target is named with a triple: arch-vendor-system-abi. The standard library is downloaded for the target; linking needs a suitable linker:

$ rustup target add aarch64-unknown-linux-gnu
$ cargo build --release --target aarch64-unknown-linux-gnu

# .cargo/config.toml
[target.aarch64-unknown-linux-gnu]
linker = "aarch64-linux-gnu-gcc"

The cross tool reduces this to a single command, using containers that already hold the needed linker and libraries.

Code per target

Code can look at the target's properties with cfg:

#[cfg(target_os = "windows")]
const AYRAC: char = '\\';
#[cfg(not(target_os = "windows"))]
const AYRAC: char = '/';

println!("{}", usize::BITS);                         // 64 on a 64-bit system
println!("{}", cfg!(target_pointer_width = "64"));   // true
println!("{}", std::env::consts::OS);               // "linux", "windows", ..

rustc --print cfg --target <triple> lists all cfg values of a target.

Exercise Target information

Print usize::BITS and cfg!(target_pointer_width = "64") separated by a space (64-bit exercise environment).

Show example solution

fn main() {
    println!("{} {}", usize::BITS, cfg!(target_pointer_width = "64"));
}

Test yourself

What is the advantage of the <code>x86_64-unknown-linux-musl</code> target?
- No advantage
- It produces a fully statically linked binary independent of the glibc version
- It's always faster
- It runs on Windows
Show answer

It produces a fully statically linked binary independent of the glibc version — It's often chosen for single-file distribution and small containers.

Add a target

$ rustup target ____ aarch64-unknown-linux-gnu

Show answer

$ rustup target add aarch64-unknown-linux-gnu

Triple and platform

x86_64-pc-windows-msvc

Windows
aarch64-apple-darwin

Apple Silicon macOS
x86_64-unknown-linux-musl

Static Linux
wasm32-unknown-unknown

WebAssembly

Next lesson: Linker

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