[RFC] reverse-step, reverse-next

[Stan Shebs]

Michael Snyder wrote:

> This isn't for submission, just for discussion.  This is something
> that Johan Rydberg (of Virtutech) and I have been working on.
>
> I'd like to hear what everybody thinks about this
> bit of infrun implementation for the reverse debugging
> that we discussed a few months ago.
>
Seems plausible to me. I've actually been experimenting with
a reverse execution prototype based on GDB managing all the
checkpoints, rather than pushing them down into the target as
Simics apparently does, and while GDB-managed checkpoints are
more powerful in some ways (random access to arbitrary states,
general undo), it's also looking rather more complicated.

> This part is enough to get step and next to work in reverse,
> based solely on the assumption that the backend (or someone)
> provides an interface "get_exec_direction ()", which returns
> forward or reverse.  It's also assumed that the backend will
> know which direction to go (leaving user-interface issues
> out of the picture).  One can imagine either a "set direction"
> interface, or a "reverse-step/reverse-continue".

Presumably there is a set_exec_direction, and both it and
get_exec_direction are target vector entries?

BTW, I have a little discussion of usage models for reverse
execution that I'm planning to post on Monday.

Stan