Bare Metal Rust

Introduction#

The Rust Standard Library (std) is compiled against only a handful of architectures. So, to compile to other architectures (that LLVM supports), Rust programs could opt not to use the entire std, and instead use just the portable subset of it, known as The Core Library (core).

#![no_std] Hello, World!

#![feature(start, libc, lang_items)]
#![no_std]
#![no_main]

// The libc crate allows importing functions from C.
extern crate libc;

// A list of C functions that are being imported
extern {
    pub fn printf(format: *const u8, ...) -> i32;
}

#[no_mangle]
// The main function, with its input arguments ignored, and an exit status is returned
pub extern fn main(_nargs: i32, _args: *const *const u8) -> i32 {
    // Print "Hello, World" to stdout using printf
    unsafe { 
        printf(b"Hello, World!\n" as *const u8);
    }

    // Exit with a return status of 0.
    0
}

#[lang = "eh_personality"] extern fn eh_personality() {}
#[lang = "panic_fmt"] extern fn panic_fmt() -> ! { panic!() }