On Fri, Aug 13, 2010 at 4:53 AM, Simon Marlow <marlo...@gmail.com> wrote: > Ah yes, that works too. But other similar versions don't, like this one: > > process :: String -> String > process _ = let x = x in x > > Hence why I added the "tail" in my version.
Without "-O", this version doesn't work, but with "-O" it does. Why? > > So what happens is this: > > - the recursive definition causes the main thread to block on itself > (known as a "black hole") > > - the program is deadlocked (no threads to run), so the runtime > invokes the GC to see if any threads are unreachable > > - the GC finds that > (a) the main thread is unreachable and blocked on a blackhole, so it > gets a NonTermination exception > (b) the Handle is unreachable, so its finalizer is started > > - the finalizer runs first, and closes the Handle > > - the main thread runs next, and the exception handler for writeFile > tries to close the Handle, which has already been finalized > > Really hClose shouldn't complain about a finalized handle, I'll see if I can > fix that. > > Cheers, > Simon > _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe
