gdb influencing app behaviour ?

gdb influencing app behaviour ?

[Danny Backx]

Hi,

I was trying to debug the interaction between RoadMap and gpsd's client
library recently. 

I believe I've found my problem, but I think gdb influenced application
behaviour in a way I'd like to understand.

The application uses some gtk call which presumably ends up using
select(2) to trigger a function when data can be read from a socket.

The application appears to behave differently when I set a breakpoint in
that function. (The application and the library were both trying to read
from the socket, by setting the breakpoint the other one would always
win the race.)

How can this be explained ? Am I wrong ?

This is on Ubuntu on a regular PC. http://sf.net/projects/roadmap and
http://gpsd.berlios.de .

	Danny
-- 
Danny Backx ; danny.backx - at - scarlet.be ; http://danny.backx.info

Re: gdb influencing app behaviour ?

[Andreas Schwab]

Danny Backx <danny.backx@scarlet.be> writes:

> The application appears to behave differently when I set a breakpoint in
> that function. (The application and the library were both trying to read
> from the socket, by setting the breakpoint the other one would always
> win the race.)
>
> How can this be explained ?

Any debugger will change the timing of the debuggee.

Andreas.

-- 
Andreas Schwab, schwab@redhat.com
GPG Key fingerprint = D4E8 DBE3 3813 BB5D FA84  5EC7 45C6 250E 6F00 984E
"And now for something completely different."

Re: gdb influencing app behaviour ?

[Danny Backx]

On di, 2011-03-15 at 10:09 +0100, Andreas Schwab wrote:
> Danny Backx <danny.backx@scarlet.be> writes:
> 
> > The application appears to behave differently when I set a breakpoint in
> > that function. (The application and the library were both trying to read
> > from the socket, by setting the breakpoint the other one would always
> > win the race.)
> >
> > How can this be explained ?
> 
> Any debugger will change the timing of the debuggee.

Yeah, I'm aware of that. I was trying to figure out whether this
scenario rings a bell for anyone here. Googling it turned up nothing.

	Danny
-- 
Danny Backx ; danny.backx - at - scarlet.be ; http://danny.backx.info