[Haskell-cafe] hugs segmentation fault

William Lee Irwin III wli at holomorphy.com
Fri Oct 29 14:00:27 EDT 2004

On Thu, Oct 28, 2004 at 05:51:18PM -0700, Fergus Henderson wrote:
> We ran into a related problem recently.  I think the problem may only
> show up on Windows, not on Linux.  The problem is that when a loop
> occurs, ghc's garbage collection detects that the standard I/O handles
> for stdin/stdout/stderr can no longer be referenced and finalizes them,
> *before* detecting the loop and throwing an exception.  Subsequent code
> may then attempt to use these already-finalized standard I/O handles.
> A possible work-around is to create stable pointers to those handles.
> But I'm not sure whether this is the same problem that you are
> experiencing.

I've seen a couple of oddities with the Windows Nov 2003 hugs build
some students have run into on EfNet #haskell but the users were all
too naive to get adequate descriptions out of.

The first of these had to do with qualified names, the second had to do
with some explicitly-typed top-level expressions. I don't have access
to Windows systems to try to reproduce these on my own. The "issues"
weren't crashes, they were merely behavior differing from ghci et al in
the former case and with the UNIX builds in the latter. I don't have
adequate specifics myself, so if someone could chase these down for me,
I'd be much obliged.

-- wli

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