Hi Joachim,
You need to intercept the various events that may cause a console windows to be closed; this is done via the Windows API call SetConsoleCtrlHandler . https://stackoverflow.com/a/30843219/6944068 gives an overview
very informative, thanks!
I don't know how to register a Haskell function as a Windows callback, that will have to be answered by somebody else.
With your tips, I came across https://hackage.haskell.org/package/base-4.11.0.0/docs/GHC-ConsoleHandler.ht.... (The documentation doesn't work, but you can look at the source to see the gist of it). I think this may do what you describe. The documentation for this function says that
When the event is received, if the 'Handler' value is @Catch f@, then a new thread will be spawned by the system to execute @f e@, where @e@ is the 'ConsoleEvent' that was received.
I wonder if I can add a handler function that detects Control-C and Close events, and responds by throwing a userInterrupt exception to the main thread, and then sleeping forever. The main thread then sees an asynchronous exception, the bracket cleanup action fires (which is my goal here), main thread shuts down and the program stops. Will try to experiment with that later. Thanks again Peter