RE: [FYI] tutorial for process record and reverse debugging

Jakob Engblom
2009-10-26T08:06:34Z

> > FWIW, early versions of UndoDB operated in "Marc-mode". We
> > changed it
> > because replay mode and record are quite different,
> > particularly w.r.t.
> > to the program's interaction with the outside world. "Silent"
> > transition
> > from replay to record mode could be quite confusing/surprising.
>
> In cases where the program does interact with the outside world,
> I agree that "auto-mode" could be confusing. In fact, "record mode"
> may not be the one we want in this case either. For instance, in
> some cases I may want to re-execute instructions that affect the outside
> world, even if I'm gone backwards. In this case I would want to use
> the recorded data to go backwards, but never to go forward (never use
> "replay mode").

Well, it actually can be made to work:

* Make sure the target is isolated, and that the debugger system can catch
anything going to the outside. This is trivial in a simulator or VM.

* When working with past time, don't send on things to the outside world. This
means reverse, replay, and going back again.

* When in progression forward, do connect to the outside world. The only problem
here are time-outs.

Obviously, my favorite solution is to just get around the entire problem by
including a sufficient component of the world inside the reversible system,
inside a system simulator.

Best regards,

/jakob

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Jakob Engblom, PhD, Technical Marketing Manager

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