Re: Error running remote gdb

[Daniel Jacobowitz <drow at false dot org>]

On Thu, Aug 31, 2006 at 03:47:28PM -0700, Michael Snyder wrote:
> > Sending packet: $vCont?#49...Ack
> > Packet received: vCont;c;C;s;S
> > Packet vCont (verbose-resume) is supported
> > Sending packet: $vCont;c#a8...Ack
> > Packet received: T0501:7ffff850;40:3000ce98;
> 
> gdb asks the target to continue.  Target continues, 
> then informs gdb "I hit a breakpoint at 0x3000ce98".
> 
> This is the first breakpoint that gdb set, above.
> I'm pretty sure now that it's the thread event breakpoint.

More likely it's the shared library event breakpoint; we don't set the
thread breakpoints until after we've got a load event for libpthread.

> > Packet received: T0501:7ffffd30;40:10000560;thread:6098;
> > [Switching to thread 24728]

> > Sending packet: $m3000ce98,4#c9...Ack
> > Packet received: 9421fff0
> > Sending packet: $M3000ce98,4:7d821008#b1...Ack
> > Packet received: OK
> > Sending packet: $m10000560,4#59...Ack
> > Packet received: 48000181
> > Sending packet: $M10000560,4:7d821008#41...Ack
> > Packet received: OK
> > Sending packet: $vCont;s:6098;c#67...Ack
> 
> Finally, gdb restores the breakpoints and tells the target
> to continue.
> 
> > Packet received: T0501:7ffffd30;40:10000560;thread:6098;
> 
> Whereupon we immediately hit the breakpoint at main.
> This is where we went wrong.  This shouldn't have happened.

Actually, this looks fine.  But we're at 0x10000560; why are we
reinserting the breakpoint _at this address_ and then continuing?
Normally you leave the breakpoint out to step over it.

I can't think what could cause that.

> This is where I have to admit that I don't know the exact
> semantics of the vCont message.  Over to you, Daniel?

That's a "step only thread 6098, continue all other threads"
packet, in other words, it corresponds to a single step
other than over a breakpoint.  If we're stepping over a breakpoint we'd
have not had the trailing ;c.

-- 
Daniel Jacobowitz
CodeSourcery