Re: Debugging plans

[Neil Jerram]

>>>>> "Martin" == Martin Grabmueller <address@hidden> writes:

    >> From: Neil Jerram <address@hidden> Date: 28 Jun 2001
    >> 22:44:17 +0100
    >> 
    >> This allows for many kinds of breakpoint specification, for
    >> example [...]

    Martin> I like this very much.  It's schemey and looks like it's
    Martin> quite flexible.

Thanks!  I think Marius is also correct, that it's inefficient for
some simple breakpoints, but we can mix and match.

    >> (Perhaps it would be better if these procedures simply returned
    >> non-#f to indicate that their caller should then do
    >> (debug-stack stack); this way the procedures could be logically
    >> composed.)

    Martin> I'm not sure about it.  Maybe we should try out the
    Martin> #f/non-#f returning variants first, because it offers more
    Martin> flexibility.

Sorry, which way are you arguing for ??.  (I think you mean the
non-(#f/non-#f returning) variants.)

    >> Things like gdb's `tb +1' could be done by adding a hook
    >> procedure that automatically removed itself after being called
    >> once.  Does anyone know how to implement a hook procedure that
    >> can remove itself?

    Martin> First I thought about implementing the hook procedures
    Martin> like this [...]

    Martin> but then I noticed that `proc' above is not known, because
    Martin> it is any of the elements of the hook.  Hmmm.  It seems
    Martin> that the hook implementation is not the Right Thing for
    Martin> breakpoints.

Yes, perhaps we need something other than hooks.  But it seems like an
uncharacteristic (for Scheme) language limitation that it isn't
possible to construct a closure that includes a reference to itself.
Are we missing something?

    Martin> Another possibility would be that the breakpoint
    Martin> procedures do not remove themselves from the hook but
    Martin> rather disable themselves when they don't want to be
    Martin> called again.  This could be done with a simple flag
    Martin> variable.

Good idea.

    Martin> Don't know if all this helps, but you asked for it.

Yes :-) and I appreciate your input - thanks!

        Neil