gistfile1.rs

#![feature(rt)]
#![feature(unmarked_api)]

use std::thread;
use std::any::Any;
use std::rt::unwind::set_panic_handler;

fn main() {
  // Use the default handler
  panic!("Something's wrong"); // Prints "thread '<main>' panicked at 'Something's wrong', /Users/yohai/code/panic_handlers_test.rs:10"

  // Or... (comment out the code above)

  set_panic_handler(simple_handler);
  panic!("Something's wrong"); // Prints "A thread panicked: Something's wrong"
  //

  // Or... (comment out the code above)
  set_panic_handler(silent_handler);
  panic!("Something's wrong (but you'll never see this message)"); // Prints nothing
}

fn silent_handler(_msg: &(Any + Send), _file: &'static str, _line: u32) {}

fn simple_handler(obj: &(Any + Send), _file: &'static str, _line: u32) {
  let msg = match obj.downcast_ref::<&'static str>() {
      Some(s) => *s,
      None => match obj.downcast_ref::<String>() {
          Some(s) => &s[..],
          None => "Box<Any>",
      }
  };

  println!("A thread panicked: {}", &*msg);
}