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Date: Fri, 20 May 2005 21:11:00 -0000
From: Michael Snyder <msnyder@redhat.com>
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To: gdb@sources.redhat.com, Eli Zaretskii <eliz@is.elta.co.il>,
        Daniel Jacobowitz <drow@mvista.com>
Subject: Re: [discuss] Support for reverse-execution
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X-SW-Source: 2005-05/txt/msg00237.txt.bz2

In regards to the question "where does a reverse-step put you?"
(ie. at the beginning of a line, or somewhere in the line):

 > Sorry, I'm confused.  Isn't it right that if I'm stepping
 > backwards through code such as this:
 >
 >    i += 1;
 >    foo (i);
 >  =>i = 0;
 >
 > where "=>" shows the current source line, then typing `rnext'
 > once will get me to this:
 >
 >    i += 1;
 >  =>foo (i);
 >    i = 0;
 >
 > which means I'm now before the CALL insn that calls `foo'?

I agree with this interpretation.  If I am a user (and I am),
and I were to say:
     (gdb) step
     (gdb) reverse-step (or whatever)
I would expect to be back where I started, ie. at the
*beginning* of the original line.

Dan J. has said that we might need to reverse-stepi until
we've gone back one too many, and then do a forward step.
I agree.  In fact, I think it will be necessary to do
the following:

     (gdb) reverse-step
     # reverse-stepi once (or until we leave the *current* line)
     # now establish the step-range start and end (prev line)
     # reverse-stepi until we leave the prev line
     # stepi once to get back to the desired line.