Turn software singlestep off?

Turn software singlestep off?

[Michael Snyder]

Got a kind of a basic question here...

Is there a way to tell gdb "don't use software
singlestep, even though you think the architecture
calls for it"?

I thought there used to be, but now I can't find it.

Re: Turn software singlestep off?

[Joel Brobecker]

> I thought there used to be, but now I can't find it.

I don't think there is such a switch either. I don't think it would
be very hard to implement, though... And it could actually be useful
on architectures such as Tru64 (I think) where we enable SW single step
because the kernel stepping doesn't work for threaded program. Such
a switch would probably give the user a chance to have better
performance when debugging a program that doesn't use threads...
It would be a pretty geeky switch, though, and I would be ready to
bet that the number of people knowing about it would remain very small.

-- 
Joel

Re: Turn software singlestep off?

[Michael Snyder]

On Mon, 2008-06-23 at 22:58 -0400, Joel Brobecker wrote:
> > I thought there used to be, but now I can't find it.
> 
> I don't think there is such a switch either. I don't think it would
> be very hard to implement, though... And it could actually be useful
> on architectures such as Tru64 (I think) where we enable SW single step
> because the kernel stepping doesn't work for threaded program. Such
> a switch would probably give the user a chance to have better
> performance when debugging a program that doesn't use threads...
> It would be a pretty geeky switch, though, and I would be ready to
> bet that the number of people knowing about it would remain very small.

Thanks.  Sounds about right.

There could be other contexts where it would be useful.
Imagine you're talking to a remote target, but you (gdb)
don't really know what it is.

It could be a simulator.  Or a record/replay type of thing.
Something that wouldn't have a problem with singlestep, 
even though the native architecture would.

However, here's my real reason for asking:  I'm trying
to implement reverse debugging for mips.  Reverse
debugging and software singlestep don't mix very well.
GDB would have to figure out where to put the singlestep
breakpoint.  Singlestepping thru a jump, you can do that
going forward, but not going backward!   ;-)

Re: Turn software singlestep off?

[Daniel Jacobowitz]

On Mon, Jun 23, 2008 at 07:49:56PM -0700, Michael Snyder wrote:
> Got a kind of a basic question here...
> 
> Is there a way to tell gdb "don't use software
> singlestep, even though you think the architecture
> calls for it"?
> 
> I thought there used to be, but now I can't find it.

No, there never has been one (at least not since I started working on
GDB).

-- 
Daniel Jacobowitz
CodeSourcery