Re: break of close loop

['Daniel Jacobowitz' <drow@false.org>]

On Fri, Nov 04, 2005 at 03:46:29PM -0000, Dave Korn wrote:
> 'Daniel Jacobowitz' wrote:
> > On Fri, Nov 04, 2005 at 04:18:57PM +0100, Simon Richter wrote:
> >> Hi,
> >> 
> >> Dave Korn wrote:
> >> 
> >>>  The stub is probably implemented by placing a temp breakpoint
> >>> immediately after the instruction to be tested, but has negelected the
> >>> fact that to handle jumps you may need to place the temp breakpoint
> >>> somewhere _other_ than immediately after the instruction,
> >> 
> >> The question at hand appears to be breakpoints placed on top of the
> >> instruction being stepped, as the instruction steps back to itself. This
> >> is especially common on architectures with a dedicated "decrement and
> >> jump if not zero" instruction.
> > 
> > If you have such instructions, and you don't have hardware single step,
> > then you need to be prepared to either wait for the instruction to
> > finish or else interrupt it.  I don't see the problem.
> 
>   No, I still think that's a buggy stub; I think that, given a djnz-style
> instruction, "stepi" should execute it precisely once (decrement the counter,
> keep PC the same if non-zero or advanced to next instruction if counter reg
> now == 0), and "nexti" should run it to completion, shouldn't they?  That's
> certainly how x86 debugging works natively.  The lack of hardware single-step
> is something the stub should transparently handle.

If you feel like defining it as buggy, go ahead.  In practice it may
not be practical to do this - there's a difference between buggy and
sub-ideal.

-- 
Daniel Jacobowitz
CodeSourcery, LLC