Restarting macOS Apps Automatically on Crash
Normally apps crash because of bugs introduced by the developer, but in my experience, there are cases where crashes can be out of the developer’s control. […] After we reach a certain confidence in the app stability, we can explore some ways to have the app restart automatically when the inevitable crash happens.
[…]
So with a few lines of XML, we can have launchd start our app and keep it alive on crashes.
[…]
[A signal handler] is the method I use in Lunar and Clop and it is reliable enough while also being easy to use and compatible with old macOS versions.
[…]
If the app is mostly a menubar utility sitting in background, it could be useful to detect and recover from app hangs. […] We can periodically schedule a ping on the main thread, and if the ping is not received for
nseconds, an app hang happened.
Previously:
Update (2023-09-06): Quinn:
If you’re in a signal handler there’s a very limited list of stuff you can safely call. This list doesn’t include such useful things as
malloc, or the Swift or Objective-C runtimes.[…]
Think very carefully before installing a signal handler for any purpose. And if your goal is to catch crashes, read this first.
I personally do not see much risk in Panaitiu’s signal handler that only uses Objective-C to get the main bundle’s path and then start a helper task to relaunch it. That said, it could perhaps stash the path at launch and use a C function instead of Process to respawn.
In terms of trying to recover from signals, I'd be remiss if I didn't also mention Fish's epic regression investigation as a cautionary tale: https://ridiculousfish.com/blog/posts/The-app-that-was-fixed-by-a-crash.html