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 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.