[Haskell-cafe] Obscure weirdness

Ross Mellgren rmm-haskell at z.odi.ac
Sat Jun 20 13:54:41 EDT 2009

Really, without code or more than "it just disappears", it's just  
conjecture what's happening. Can you post the code, or even better yet  
a minimized case that reproduces it?


On Jun 20, 2009, at 1:34 PM, Andrew Coppin wrote:

> Alexander Dunlap wrote:
>> On Sat, Jun 20, 2009 at 8:29 AM, Andrew Coppin
>> <andrewcoppin at btinternet.com> wrote:
>>> OK, so here's an interesting problem...
>>> I've been coding away all day, but now my program is doing  
>>> something slightly weird. For a specific input, it summarily  
>>> terminates. The registered exception handler does not fire. There  
>>> is no output to stdout or stderr indicating what the problem is.  
>>> It just *stops* half way through the printout.
>>> Weirder: If I run it in GHCi, then GHCi itself terminates. (I  
>>> didn't think you could *do* that!)
>> I think you'll need to provide a bit more detail about what you're
>> doing in order for anyone to have anything to go off of. If you can
>> link to the source, that would help, or even give a summary of what
>> you're trying to do.
> The program takes some text, parses it as a lambda calculus  
> expression, and prints it out again. Except, somewhere during the  
> variable uniqueness pass, the program just halts. For no defined  
> reason.
> As you can see, nothing remotely unusual for a Haskell program to be  
> doing. And yet, the result is very unusual. (I.e., halting part-way  
> through some pure code without throwing an exception.)
> Given that it doesn't appear to be a known bug (presumably somebody  
> would have said something by now if it was...), I think I'm going to  
> try upgrading GHC anyway, just for arguments' sake, and see if that  
> fixes it.
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