Minimal no_std example for M1 Mac

Cargo.toml

[package]
name = "rust-nostd-helloworld"
version = "0.1.0"
edition = "2021"

[dependencies]

config.toml

[profile.dev]
panic = "abort"

[profile.release]
panic = "abort"

[target.aarch64-apple-darwin]
linker = "clang"
rustflags = ["-C", "link-args=-e __start -nostartfiles -fuse-ld=mold"]

main.rs

#![no_std]
#![no_main]
#![feature(lang_items)]

use core::panic::PanicInfo;

#[no_mangle]
pub extern "C" fn _start() -> usize {
    let sys_message = "Hello world from no_std!\n";
    say_hello(sys_message);
    0
}

#[link(name = "c")]
extern "C" {
    fn write(fd: u32, buf: *const u8, count: usize) -> i32;
}

fn say_hello(message: &str) {
    let msg_ptr = message.as_ptr();
    let len = message.len();
    let _ = unsafe { write(1, msg_ptr, len) };
}

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

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