Re: Using reverse execution

[Stan Shebs <shebs at apple dot com>]

Eli Zaretskii wrote:

> Anyway, I really don't understand why we need to discuss all this at
> such length.  Either there is a volunteer who is ready to do the job
> of adding this, or there isn't.  In the latter case, there's no sense
> arguing about the value of the feature; in the former case, will we
> really consider rejecting the patches that implement the feature
> because some of us are unsure how useful it will be?
I must not be getting my point across very well then. Apple is quite
interested in getting reverse execution going outside of the simulator
context, and I've been playing with some prototype machinery. However,
it's clear that a full-blown handles-every-situation implementation
will require a huge amount of kernel hacking in addition to the GDB
part. I don't want to get into a situation like that of tracepoints,
where the feature ultimately falls by the wayside because it's too
narrow in applicability and implementation.

So I'm not questioning the value of the feature, but trying to get a
sense of the user requirements. Undoing a single a=b+c is relatively
easy, and my prototype can do that now, but reversing through 15
minutes of iTunes usage is fiendishly hard, and would require a major
commitment by Apple involving multiple software groups. The level of
effort I'll be able to get depends on what we think the requirements
look like.

This is a rare opportunity to weigh in on a feature *before* it's
implemented; an unfamiliar situation I know :-) , but something
people ought to take advantage of rather than brush off. A lot of
past GDB projects would have come out better had there been open
discussion earlier in the process.

Stan