Panic handler
Speaking of panic, we want to add our own panic handler. Normally, if the program panics, it will crash and invoke the default panic handler, which prints a stack trace about the error. We'll need more than that, so we change the panic handler to our own:
///////////////////////////////////////////////////////////////////////////////
//
// Panic handler
//
///////////////////////////////////////////////////////////////////////////////
pub const panic = std.debug.FullPanic(crashed);
fn crashed(msg: []const u8, trace: ?usize) noreturn {
std.debug.defaultPanic(msg, trace);
}
Since we don't need it for anything yet, what it does is simply to call the default panic handler, passing the same arguments it receives.
You may have noticed that strange return type: noreturn. It means the
function doesn't simply return anything, like a void would do, it doesn't
return at all. This is so because when this function is called, our program has
crashed already, and it couldn't return any value anyway. You shouldn't worry
about it because it's the first and last time we'll see it in our program.
When the program encounters an error at runtime, depending on the kind of error, two things may happen:
- the program crashes (best case)
- the program keeps running, but its state is corrupted (worst case)
In the second case really nasty things can happen, so we want to avoid bugs at all costs. In safe release modes (Debug and ReleaseSafe), events that would normally cause a crash or undefined behavior cause panic instead. The program terminates and you get a meaningful stack trace of what has caused the error.