rs

hello.rs

// enable features required for a "no stdlib" build
#![feature(no_std, core, lang_items)]

// generate a static library (.a)
#![crate_type="staticlib"]

// do not link libstd
#![no_std]

// link libcore
extern crate core;

// export `yotz` as C-callable
#[no_mangle]
pub extern fn yotz(a: i32) -> i32 {
    a * 2
}

// runtime support functions normally provided by libstd
#[lang = "stack_exhausted"] extern fn stack_exhausted() {}
#[lang = "eh_personality"] extern fn eh_personality() {}
#[lang = "panic_fmt"] fn panic_fmt() -> ! { loop {} }

Makefile

RFLAGS=
RFLAGS+= --target=x86_64-unknown-linux-musl
RFLAGS+= -C lto -C opt-level=3 -C link-args=-s -C no-redzone=yes

libhello.a: hello.rs Makefile
	rustc $(RFLAGS) hello.rs