[Haskell] modern language design, stone age tools

Fergus Henderson fjh007 at galois.com
Tue Jun 22 21:44:12 EDT 2004


Seeing as Haskell is apparently such a popular language these days,
I don't suppose a working debugger would be too much to ask for, would it?
Or even just a decent call stack trace when a program terminates with an exception?

In case you're wondering, yes I have already tried using Hat and Buddha.
But I'm trying to debug a real application, not a toy one, and neither Hat
nor Buddha support enough of Haskell.  Buddha doesn't even come close,
as far as I can tell, and Hat lacks support for library modules such as Data.Word.

I've also tried using ghc's profiling to get stack traces, but that doesn't
work very well either.  Firstly, the stack traces that you get only include
function names, not line numbers.  Secondly, the stack traces are often
incomplete, for reasons that I don't fully understand.  One likely cause is
tail call optimization.  (Is there any option to switch off tail call optimization?
I didn't see any such option in the ghc man page.)
Thirdly, profiling seems to be incompatible with the use of ghci; there
doesn't seem to be any easy way to build a workspace so that you can
get stack traces and use ghci in that workspace at the same time.
And ghc is slow enough (even on a 3.2GHz Pentium 4) that recompiling
the whole workspace is highly unpalettable.

There's a hell of a lot of languages out there that _do_ support decent
stack traces when an exception is thrown.  

What's the point of using a high-level functional language if it means
you're stuck with poor library support and/or stone-age tools?


Fergus J. Henderson                 |  "I have always known that the pursuit
Galois Connections, Inc.            |  of excellence is a lethal habit"
Phone: +1 503 626 6616              |     -- the last words of T. S. Garp.

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