I wrote such a debugger as part of my PhD work. It is called "hsdebug" and you can read the Haskell Workshop paper on it here:
http://www.cambridge.intel-research.net/~rennals/hw2003.pdf Unfortunately, HsDebug depends on Optimistic Evaluation, and it seems unlikely that Optimistic Evaluation will appear in a release version of GHC (too hard to maintain, and I've gone off to work for Intel Research). HsDebug is a GDB-style debugger which takes advantage of the fact that Optimistic Evaluation makes programs evaluate in a largely-strict evaluation order. It also uses a trick called "transient tail frames" to allow tail calls to be visible in stack traces. HsDebug can debug any GHC-compilable Haskell program, including GHC itself. -Rob > \begin{gripe} > > 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? > > \end{gripe} > > -- > 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. > _______________________________________________ > Haskell mailing list > [EMAIL PROTECTED] > http://www.haskell.org/mailman/listinfo/haskell > _______________________________________________ Haskell mailing list [EMAIL PROTECTED] http://www.haskell.org/mailman/listinfo/haskell
