Macro dont_panic::dont_panic

macro_rules! dont_panic {
    () => { ... };
    ($msg:expr) => { ... };
    ($fmt:expr, $($arg:tt)+) => { ... };
}

This macro doesn't panic. Instead it tries to call non-existing function. If the compiler can prove it can't be called an optimizes it away, the code will compile just fine. Else you get linking error.

This should be used only in cases you are absolutely sure are OK and optimizable by compiler.