> "Simon Marlow" <[EMAIL PROTECTED]> writes:
>
> > I think what's going on here is that the finalizer for
> stdout is running
> > before your finalizer, and since stdout has already been
> closed it can't
> > print out the message :-)
>
> How is is possible for stdout to be finalised before putStrLn has run?
> Surely the closure for the putStrLn action holds a reference
> to stdout,
> so stdout should remain live and not-GCed until after the putStrLn
> has completed?
You're right, this is a little strange. There are actually two reasons
for this behaviour:
- in GHC, references from a finalizer are treated as weak
references, that is, they don't keep anything alive. In our
paper on weak pointers I seem to recall there was a good reason
for this, but I'll need to go back and look it up again. I'm
beginning to think the decision seems a bit odd (after all, in
the next GC, the references become non-weak again, because the
finalizer is up and running).
- at the end of execution, GHC just runs all the outstanding
finalizers in any order. So stdout might get finalized before
another finalizer that refers to it. I suppose we might do
something better here: repeatedly GC and run finalizers until
there are none left, perhaps.
Cheers,
Simon
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