Re: GDB MI Reverse Commands added [2 of 3]

[Greg Law <glaw at undo-software dot com>]

Eli Zaretskii wrote:
> > Date: Fri, 28 Aug 2009 12:08:08 +0100
> > From: Greg Law <glaw@undo-software.com>
> > CC: Jakob Engblom <jakob@virtutech.com>, gdb-patches@sourceware.org
> >
> > Eli Zaretskii wrote:
> > > > From: "Jakob Engblom" <jakob@virtutech.com>
> > > > Cc: <gdb-patches@sourceware.org>
> > > > Date: Fri, 28 Aug 2009 12:05:29 +0200
> > > >
> > > > "Resumes the execution of the inferior program until a breakpoint is
> > > > encountered, or until the inferior exits. If the @samp{--reverse}
> > > > option is specified, resumes the reverse execution of the inferior
> > > > program until a breakpoint is encountered, or until the execution
> > > > reaches that start of the inferior. "
> > >           ^^^^
> > > You meant "the", I presume.
> > >
> > > Otherwise, this is fine, thanks.
> > Would it be more accurate to say "start of the record log"?
>
> I don't think so, because reverse debugging is not limited to record
> and replay.
>
> But I see what you mean.  Maybe this:
>
>   or until the execution reaches the point that is as close to the
>   inferior's start as @value{GDBN} can.  (This could be the start of
>   the inferior executable code or the start of the record log, for
>   example.)

Yes, that's ok.  But I'm struggling to think of a plausible way in which 
a target could provide reverse debugging without some kind of log.  Any 
stateful program will clobber its state as it runs, and so to go 
backwards you need to have a log somewhere that tells you what the state 
was before you clobbered it.  And it will not be possible to go 
backwards to a time before you started recording.

Or have I misunderstood you?

(Note: I'm more interested in the semantics of reverse debugging here 
rather than the exact wording in the manual :)

Greg
--
Greg Law, Undo Software                       http://undo-software.com/