How can I cause a panic on a thread to immediately end the main thread?

I tried to force my code to stop processing when any of threads panicked. The only more-or-less clear solution without using unstable features was to use Drop trait implemented on some struct. This can lead to a resource leak, but in my scenario I'm ok with this.

use std::process;
use std::thread;
use std::time::Duration;


static THREAD_ERROR_CODE: i32 = 0x1;
static NUM_THREADS: u32 = 17;
static PROBE_SLEEP_MILLIS: u64 = 500;

struct PoisonPill;

impl Drop for PoisonPill {
    fn drop(&mut self) {
        if thread::panicking() {
            println!("dropped while unwinding");
            process::exit(THREAD_ERROR_CODE);
        }
    }
}

fn main() {
    let mut thread_handles = vec![];

    for i in 0..NUM_THREADS {
        thread_handles.push(thread::spawn(move || {
            let b = PoisonPill;
            thread::sleep(Duration::from_millis(PROBE_SLEEP_MILLIS));
            if i % 2 == 0 {
                println!("kill {}", i);
                panic!();
            }
            println!("this is thread number {}", i);
        }));
    }

    for handle in thread_handles {
        let _ = handle.join();
    }
}

No matter how b = PoisonPill leaves it's scope, normal or after panic!, its Drop method kicks in. You can distinguish if the caller panicked using thread::panicking and take some action — in my case killing the process.

Updated for Rust 1.10+, see revision history for the previous version of the answer

good point, in go the main thread doesn't get unwound, the program just crashes, but the original panic is reported. This is in fact the behavior I want (although ideally resources would get cleaned up properly everywhere).

This you can achieve with the recently stable std::panic::set_hook() function. With it, you can set a hook which prints the panic info and then exits the whole process, something like this:

use std::thread;
use std::panic;
use std::process;

fn main() {
    // take_hook() returns the default hook in case when a custom one is not set
    let orig_hook = panic::take_hook();
    panic::set_hook(Box::new(move |panic_info| {
        // invoke the default handler and exit the process
        orig_hook(panic_info);
        process::exit(1);
    }));

    thread::spawn(move || {
        panic!("something bad happened");
    }).join();

    // this line won't ever be invoked because of process::exit()
    println!("Won't be printed");
}

Try commenting the set_hook() call out, and you'll see that the println!() line gets executed.

However, this approach, due to the use of process::exit(), will not allow resources allocated by other threads to be freed. In fact, I'm not sure that Go runtime allows this as well; it is likely that it uses the same approach with aborting the process.