"Simon Marlow"
That sounds hard to program with - surely you want to stop the program in order to clean up? Otherwise the program is going to continue working, generating more exit handlers, and we might never get to exit.
Here is how I've done it in Kogut: An equivalent of Haskell's exitWith simply throws a predefined exception. When an unhandled exception reaches the toplevel, this exception is treated specially and is not printed with a stack trace. Exceptions caused by system signals are special too. There is a central list of registered exit handlers. On program exit each handler is run once. Handlers registered during this cleanup are run too. Any exceptions thrown from handlers are caught and ignored. This happens after printing a stack trace from an unhandled exception, just before shutting down the runtime and exiting. One of exit handlers cancels all other threads (except those which has been garbage collected) and waits until they finish. New threads started during this cleanup are canceled too. -- __("< Marcin Kowalczyk \__/ qrczak@knm.org.pl ^^ http://qrnik.knm.org.pl/~qrczak/