Process 20814 stopped
* thread #1, name = 'test_app', stop reason = breakpoint 3.1
    frame #0: 0x00007ffff7fe846a JIT(0x736320)`fib(n=0) at fib.rs:3:16
   1   	#[no_mangle]
   2   	pub extern "C" fn fib(n: u32) -> u32 {
-> 3   	    let mut a = 1;
   4   	    let mut b = 1;
   5   	    for _ in 0..n {
   6   	        let t = a;
   7   	        a = b;