Re: [reverse RFA] no singlestep-over-BP in reverse

Michael Snyder
2008-09-15T19:07:45Z

Daniel Jacobowitz wrote:
> On Mon, Sep 15, 2008 at 11:31:33AM -0700, Michael Snyder wrote:
>> When we're stopped at a breakpoint and we want to
>> continue in reverse, we're not actually going to
>> execute the instruction at the breakpoint -- we're
>> going to de-execute the previous instruction.
>>
>> Therefore there's no need to singlestep before
>> inserting breakpoints. In fact it would be a bad
>> idea to do so, because if there is a breakpoint at
>> the previous instruction, we WANT to hit it.
>>
>> Note that this patch is to be applied to the reverse branch.
>
> If there is a breakpoint on the previous instruction, will you hit it
> before or after de-executing that instruction?

Well, if trap insns are in place, that's what will be
executed (not the shadow insn).

> It seems like this
> logic should be somehow still necessary... but I can't put my finger
> on when.

Good point -- there is a test in the testsuite for consecutive
breakpoints. I'll try to reversify that.