RE: Remote Debugging with NEXT Command

["Abid, Hafiz" <Hafiz_Abid at mentor dot com>]

> -----Original Message-----
> From: gdb-owner@sourceware.org [mailto:gdb-owner@sourceware.org] On
> Behalf Of Ken Mandelberg
> Sent: 10 June 2014 22:21
> To: Paul_Koning@dell.com
> Cc: gdb@sourceware.org
> Subject: Re: Remote Debugging with NEXT Command
> 
> On 06/10/2014 05:12 PM, Paul_Koning@dell.com wrote:
> >
> > On Jun 10, 2014, at 5:02 PM, Ken Mandelberg <km@mathcs.emory.edu>
> wrote:
> >
> >> I'm doing remote gdb deugging to a stub implemented on the target over
> tcp. SI works and NEXT works well enough skipping over a function call.
> >>
> >> What can be very slow is NEXT from one C statement to the next.
> >>
> >> When NEXT skips over a function call it implements it by setting a
> breakpoint at the return address.
> >>
> >> When NEXT skips from one C statement to the next, it does it by doing
> >> repeated SI's. This forces the target to send back a bunch of state at each
> SI. This is slow and very slow if the C statement actually has a loop in it.
> >>
> >> Is there any way around this other than carefully avoiding NEXT in the
> worst cases and manually setting breakpoints/CONT?
> >
> > If your stub supports breakpoints, it will take less work for GDB to do the
> stepping.  Basic stepping involves placing break instructions and restoring
> the content, repeatedly.  That's a lot more round trips but it requires less
> stub magic.
> >
> > 	paul
> >
> >
> 
> Yes, the stub supports breakpoints. Thats why NEXT through a function call
> works so well. gdb is smart enough to ask the stub to set a breakpoint at the
> return address,
> 
> When gdb is just trying to get to the next statement in the current function
> with NEXT, it sends the stub a bunch of SI's, which is the problem since its so
> slow.
> 
> I can put more logic in the stub, but I can't change what gdb does, and gdb
> doesn't give the stub any indication that it is doing NEXT.
> 
Have you looked at the range stepping? It might be what you are looking for.
https://sourceware.org/gdb/onlinedocs/gdb/Continuing-and-Stepping.html#range-stepping

Regards,
Abid