[zeromq-dev] Checking for errors on zmq_poll: is it correct?

[gonzalo diethelm]

A tiny nitpick: it is an ERROR to check errno (or zmq_error()) if the call did not return an error status.

-- 
Gonzalo Diethelm
DCV Chile

> -----Original Message-----
> From: zeromq-dev-bounces at lists.zeromq.org [mailto:zeromq-dev-
> bounces at lists.zeromq.org] On Behalf Of Chuck Remes
> Sent: Thursday, August 16, 2012 2:16 PM
> To: ZeroMQ development list
> Cc: erupter at libero.it
> Subject: Re: [zeromq-dev] Checking for errors on zmq_poll: is it correct?
> 
> Correct. No need to check zmq_error() unless zmq_poll() returns an error
> code.
> 
> cr
> 
> On Aug 16, 2012, at 12:11 PM, Michel Pelletier wrote:
> 
> > It looks like you are assigning zerr twice and not checking the return
> > from poll.  I don't think zmq_error() will return a sensible value
> > unless zmq_poll returns -1.
> >
> > -Michel
> >
> > On Thu, Aug 16, 2012 at 9:49 AM, erupter at libero.it <erupter at libero.it>
> wrote:
> >> Hello.
> >>
> >> I'm a newbie still playing around trying to grasp 0mq.
> >>
> >>
> >> I'm re-writing the first example with polling.
> >>
> >> So my REP has become
> >>
> >>
> >> zmq_pollitem_t local_zmq_sockets[1];
> >>
> >>
> >> int main (void)
> >> {
> >>    zmq_msg_t request;
> >>    void *context = zmq_init (1);
> >>    const char * chptr = 0;
> >>    int zerr = 0;
> >>    // Socket to talk to clients
> >>    void *responder = zmq_socket (context, ZMQ_REP);
> >>    zmq_bind (responder, "tcp://*:5555");
> >>    s_catch_signals ();
> >>    local_zmq_sockets[0].socket = responder;
> >>    local_zmq_sockets[0].events = ZMQ_POLLIN;
> >>
> >>    while (1) {
> >>        // Wait for next request from client
> >>
> >>
> >>        zerr = zmq_poll(local_zmq_sockets,1,5);
> >>        if (local_zmq_sockets[0].revents & ZMQ_POLLIN) {
> >>            zmq_msg_init (&request);
> >>            zmq_recv (responder, &request, 0);
> >>            zmq_msg_close(&request);
> >>        }
> >>        zerr = zmq_errno();
> >>        if (zerr != 0)
> >>        {       chptr = zmq_strerror(zerr);
> >>                printf ("\n%s\n", chptr);
> >>        }
> >>
> >>        zmq_msg_close (&request);
> >>        if (s_interrupted) {
> >>            printf ("\nSIGTERM interrupt received, killing server...\n");
> >>            break;
> >>        }
> >>        // Do some 'work'
> >>        sleep (1);
> >>
> >>        // Send reply back to client
> >>        zmq_msg_t reply;
> >>        zmq_msg_init_size (&reply, 5);
> >>        memcpy (zmq_msg_data (&reply), "Prova", 5);
> >>        zmq_send (responder, &reply, 0);
> >>        zmq_msg_close (&reply);
> >>    }
> >>    // We never get here but if we did, this would be how we end
> >>    zmq_close (responder);
> >>    zmq_term (context);
> >>    return 0;
> >> }
> >>
> >>
> >> Now the fact is that when it's sitting idly waiting for a REQ, the
> >> error number reported after the POLL call is always 11, and the
> >> associated string is
> >>
> >> "Resource temporarily unavailable"
> >>
> >>
> >> I don't get this: should I *not* check for errors after zmq_poll???
> >> I expected a 0 after a correct poll.
> >>
> >> Even when a message comes in, it still gives the same error code.
> >>
> >>
> >> Can anyone please explaing this behviour to me?
> >> Thanks
> >>
> >> Regards
> >>
> >> Claudio Carbone
> >>
> >>
> >>
> >>
> >> _______________________________________________
> >> zeromq-dev mailing list
> >> zeromq-dev at lists.zeromq.org
> >> http://lists.zeromq.org/mailman/listinfo/zeromq-dev
> >>
> > _______________________________________________
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> > zeromq-dev at lists.zeromq.org
> > http://lists.zeromq.org/mailman/listinfo/zeromq-dev
> 
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