On 23 June 2004 09:27, Robert Ennals wrote:

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.

We would be delighted if someone would take Robert's hsdebug and port it to the non-speculative version of the compiler. In fact, this is one of the items on the GHC Task list: http://sourceforge.net/pm/task.php?func=detailtask&project_task_id=98684 &group_id=8032&group_project_id=31802 It would make a great student project, or a summer hack for someone with lots of spare time... Cheers, Simon