Conditional compilation/execution

debugmacro.rs

fn mutate(x: &mut int) -> int {
    let ret = x.clone();
    *x += 100;
    ret
}

fn main() {
    let mut x = -5;

    x += 5;

    debug!("Original value of x: %d", mutate(&mut x));

    println!("Final value of x: {0:d}", x);
}

// Compilation command: 
rustc test.rs --cfg debug

// Execution command A:
RUST_LOG=test=4 ./test

// Execution result A:
Original value of x: 0
Final value of x: 100

// Execution command B:
./test

// Execution result B:
Final value of x: 0