On 10 April 2006 22:19, John Meacham wrote:

On Fri, Apr 07, 2006 at 02:58:01PM +0100, Simon Marlow wrote:

...

According to your definition of exitWith above, I can't both raise an exception *and* exit in the same thread. If I register an onExit handler that throws an exception to the current thread, things go wrong if the current thread also calls exitWith. Also, you couldn't call exitWith while holding an MVar, if the handlers need access to the same MVar.

hrm? nothing goes wrong. it is the same as calling 'throw' in the current thread.

Your code for exitWith: exitWith status = do takeMVar exitMVar -- winner takes all let handleLoop = do hs <- swapMVar handlerMVar [] sequence_ hs if null hs then return () else handleLoop handleLoop exitWith_ status now If I have a handler registered that throws an exception to the current thread, what happens? handleLoop is aborted, the exception is propagated to the top level of the thread, where the top-level exception handler calls exitWith again, and promptly deadlocks because exitMVar is already empty. In the interests of keeping the discussion manageable, I'll deal with the rest of the points later. Cheers, Simon