Defer register reading from remote target until needed?

Defer register reading from remote target until needed?

[Orjan Friberg]

When single-stepping a remote target, after the stop reply paket is 
sent, GDB immediately sends a request for all registers.  Is there a way 
to defer sending this request until some register other than what was 
sent with the stop reply packet (pc, stack and frame pointer) is 
actually needed?

-- 
Orjan Friberg
Axis Communications

Re: Defer register reading from remote target until needed?

[Michael Snyder]

Orjan Friberg wrote:
> When single-stepping a remote target, after the stop reply paket is 
> sent, GDB immediately sends a request for all registers.  Is there a way 
> to defer sending this request until some register other than what was 
> sent with the stop reply packet (pc, stack and frame pointer) is 
> actually needed?

It's supposed to work that way already.  Either something's broken, or
some register other than the ones you named *is* needed.  The 'g' pkt
should only go out if gdb needs the value of a register that it doesn't
already have.

This can sometimes happen 'indirectly', eg. if you try to set a 
register, gdb may try to read it first.

Try setting a breakpoint in remote_fetch_registers, then go up
the stack and see what register gdb is trying to read.

Re: Defer register reading from remote target until needed?

[Orjan Friberg]

Michael Snyder wrote:
> 
> It's supposed to work that way already.  Either something's broken, or
> some register other than the ones you named *is* needed.  The 'g' pkt
> should only go out if gdb needs the value of a register that it doesn't
> already have.
> 
> This can sometimes happen 'indirectly', eg. if you try to set a 
> register, gdb may try to read it first.
> 
> Try setting a breakpoint in remote_fetch_registers, then go up
> the stack and see what register gdb is trying to read.

Ah; it's because we need the subroutine return pointer when unwinding 
the pc.  Thanks.


-- 
Orjan Friberg
Axis Communications