Unreproducible bug

[Matthew Fluet]

> > And, these are occuring using the
> > SML/NJ version of MLton, not a self-compiled version.  I've gotten it a
> > couple of times on the regression suite, but when I rerun it on the same
> > file, there's no error.  
> 
> I find the irreproducibility very difficult to understand.  There is no
> randomness in MLton.  The only thing I can think of (and this is a huge stretch) 
> is some kind of state being kept in the filesystem.
> 
> Please send me any of the .sml files that are causing a problem.  I don't really
> have anything to go on.  I haven't seen these sorts of bugs since June, and they
> were always completely reproducible at the time.

The files that I've seen it occur on were:
regression/array.sml
regression/klife_eq.sml
and a self-compile.

The only other thing I can possibly think of might be that I was
(SML/NJ) recompiling MLton while the regressions were going.  I don't know
what NJ does if it's image file is rewritten while it's running -- I would
have assumed it loads it all in at invocation.  But I wouldn't have done
that on the self-compile, since I set that going before I left last night.