Simple C programming bootstrap file in Rust

main.rs

#![feature(start, libc, lang_items)]
#![no_std]
#![no_main]
#![feature(rustc_private)]
extern crate libc;

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

#[lang = "eh_personality"]
extern fn eh_personality() {}

#[panic_handler]
fn panic(_info: &core::panic::PanicInfo) -> ! {
    loop {}
}

// Code starts below

#[no_mangle]
pub extern fn main(_nargs: i32, _args: *const *const u8) -> i32 {
    unsafe {
        printf(b"Hello, World!\n" as *const u8);
    }
    return 0
}

This creates a 14k executable, linked to libc

Background reading: https://fasterthanli.me/series/making-our-own-executable-packer/part-12