Random silent crashes possibly related to ScheduleRunnerPlugin

[ashneverdawn]

I have this weird issue where bevy will randomly crash silently.
The issue tends to happen sooner the higher the framerate is set to.

use bevy::{app::ScheduleRunnerPlugin, prelude::*};
use std::time::{Duration, Instant};

fn main() {
  App::build()
    .add_plugin(ScheduleRunnerPlugin::run_loop(Duration::from_secs_f64(1.0 / 120.0)))
    .add_resource(Timer(Instant::now(), 0))
    .add_system(bevy_update.system())
    .run();
  println!("bevy shutdown unexpectedly!");
}
pub struct Timer(Instant, u64);
pub fn bevy_update(mut timer: ResMut<Timer>) {
  let elapsed = Instant::now().duration_since(timer.0).as_secs();
  if elapsed != timer.1 && elapsed % 3 == 0 {
    timer.1 = elapsed;
    println!("seconds elapsed: {}", elapsed);
  }
}

Tested on master:
at 240fps, I get it 1-5 secs in.
at 120fps, 10-30 secs in.
at 60fps, 30-60 secs in.
at 30fps, it happened 255 secs in.

This was tested on an old 2014 macbook pro, so if you're on a more recent machine, you may have to up the framerate to successfully reproduce it in a timely manner.

Note: What I refer to as "framerate" is from this line:

    .add_plugin(ScheduleRunnerPlugin::run_loop(Duration::from_secs_f64(1.0 / 120.0)))

[DJMcNab]

I've got it
If your tick takes longer than the wait duration, the schedule runner exits, because the exit condition of tick doesn't determine between no wait and app exit requested, which is clearly wrong.

bevy/crates/bevy_app/src/schedule_runner.rs

Line 97 in 4081142

while let Some(delay) = tick(&mut app, wait) {