tests/pass/no_std.rs

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

// Plumbing to let us use `writeln!` to host stdout:

extern "Rust" {
    fn miri_write_to_stdout(bytes: &[u8]);
}

struct Host;

use core::fmt::Write;

impl Write for Host {
    fn write_str(&mut self, s: &str) -> core::fmt::Result {
        unsafe {
            miri_write_to_stdout(s.as_bytes());
        }
        Ok(())
    }
}

// Aaaand the test:

#[start]
fn start(_: isize, _: *const *const u8) -> isize {
    writeln!(Host, "hello, world!").unwrap();
    0
}

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

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