parsergen debugging

Is there a way to watch / trace / step / debug a parser built by parsergen?

I need to manipulate some C programs.  I yanked a LALR C grammar from the net 
and have it almost running on a large test case, but the latest grammar bug 
has me baffled.  It would be nice to be able to trace the parser's actions to 
see what subtlety is causing me grief.

thanx
pt