[MLton] Build problems on Mac OS X

[Matthew Fluet]

> Haven't played with MLton in a while.  I decided to try running it 
> under Mac OS X 10.3, and find that I can't get it to bootstrap:
>
> /Users/brent/Projects/mlton/build/lib/mlton-compile @MLton -- 
> /Users/brent/Projects/mlton/build/lib/world
> MLton bug: toplevel handler not installed.
> Please send a bug report to MLton@mlton.org.
> make[2]: *** [world-no-check] Error 2
> make[1]: *** [world] Error 2
> make: *** [all-no-docs] Error 2
> Chaz:~/Projects/mlton brent$
> 
> Any idea where to get started troubleshooting?

The MLton bug message indicates that an exception was raised by the Basis 
Library implementation before the toplevel handler was installed.  
I just checked in a minor modification to the Basis Library implementation 
to install an emergency exception handler at the earliest possible point.  
If you try to bootstrap again with this change, you should see a message 
like:

unhandled exception: ???
MLton bug: unhandled exception in Basis Library.
Please send a bug report to MLton@mlton.org.

where ??? hopefully will be filled in by something informative.  We can 
start troubleshooting from there.