Cross-Compilation and Portability

Rust is a low-level system programming language that shines in many areas such as performance, memory safety, and concurrency. Although Rust is a relatively new language, it boasts impressive cross-compilation capabilities. This means that you can use it to write code on one platform and then compile it to be run on a different platform.

Cross-compilation is invaluable for systems programming work, where code often gets written on desktops or laptops but then needs to run on embedded devices, servers, or other types of systems. Moreover, Rust prides itself on the portability of its code. Rust programs can run on a wide array of systems without modifications – indeed, the Rust compiler produces binary executables that are self-contained and do not have external dependencies.

In this tutorial chapter, we shall explore cross-compilation in Rust, focusing on how to set up your workspace, compile, and deploy your application to different platforms. For our code examples throughout this tutorial, we'll be building the ever-popular "Hello, World!" in Rust and deploying it to fictional systems, "Starship Enterprise" and "Death Star."

First, we need to ensure that we have Rust installed on our development machine. You can get Rust by visiting their official website and following the installation instructions for your operating system.

$ curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh

Now, we can create our project folder and navigate into it:

$ mkdir hello_world && cd hello_world

Let's initialize our Rust project:

$ cargo init

This command will create a new Rust project with a main.rs file and a Cargo.toml file in your current directory. Let's keep things simple and edit the main.rs file using your preferred text editor to look like this:

fn main() {
    println!("Hello, World!");
}

To run this program, you would normally use the command:

$ cargo run

This will compile and run your program on your development machine. However, we want to compile it into a format that can be run on the "Starship Enterprise" and "Death Star."

To be able to cross-compile a Rust program, you first need to install the corresponding "standard library" for the target platform. The Rust project maintains a list of supported targets, including options for various versions of Windows, macOS, Android, iOS, and many types of Unix, as well as more specialized targets including the SpaceX Starship and the Death Star.

To add a new target, you use the rustup target add command followed by the name of the target. For instance, to add support for the "Starship Enterprise", you would run:

$ rustup target add x86_64-unknown-linux-gnu

To add support for the Death Star:

$ rustup target add arm-unknown-deathstar-eabi

After running this command, the standard library for your target platforms is installed, and you can use Rust's toolchain to compile for these targets.

To cross-compile your program, you use the cargo build command with the --target option followed by the name of the target. To cross-compile our "Hello, World!" program for the Starship Enterprise, you would run:

$ cargo build --target=x86_64-unknown-linux-gnu

To cross-compile it for the Death Star:

$ cargo build --target=arm-unknown-deathstar-eabi

If everything done correctly, these commands generate the binary files called hello_world in the directory target/x86_64-unknown-linux-gnu/debug/ and target/arm-unknown-deathstar-eabi/debug/ respectively.

Keep in mind that although the cargo build command will usually catch any code that is not portable between platforms, it cannot catch everything. In particular, most if not all system-specific behavior is defined in crates (Rust’s term for libraries) that come from the system itself, and those crates have to be written with portability in mind.

In conclusion, the Rust programming language offers extensive support for cross-compiling to a wide range of systems. By using a combination of cargo build and rustup target add, you can write code once in Rust and then compile it to run on virtually any platform.

While the capacity to cross-compile is a vital feature of any systems programming language, the true strength of Rust lies in the language's dedication to enabling developers to write code that is safe, concurrent and practical. This includes features such as its strong compile-time checks of memory safety and data race conditions, its rich type system that prevents many common errors, and its ergonomic syntax and design that make it a joy to use for all kinds of projects.

That is an overview of cross-compilation in Rust. In the next chapter, we will delve deeper into concurrent programming in Rust.