[zeromq-dev] zmq_poll return value and C-CTRL interrupts

Stathis Gkotsis stathis.gkotsis at commsquare.com
Fri Feb 15 14:47:31 CET 2013


"Upon failure, zmq_poll() shall return -1 and set errno to one of the values defined below", so you should check errno.


From: zeromq-dev-bounces at lists.zeromq.org [mailto:zeromq-dev-bounces at lists.zeromq.org] On Behalf Of mycircuit
Sent: Friday, February 15, 2013 2:05 PM
To: zeromq-dev at lists.zeromq.org
Subject: [zeromq-dev] zmq_poll return value and C-CTRL interrupts

I am using zeromq 3.2.2 on linux ubuntu 12.04.
I am confused about the behavior of zmq_poll when getting a ctrl-c.

The guide says:
If your code is blocking in zmq_msg_recv()<http://api.zeromq.org/3-2:zmq_msg_recv>, zmq_poll()<http://api.zeromq.org/3-2:zmq_poll>, or zmq_msg_send()<http://api.zeromq.org/3-2:zmq_msg_send>, when a signal arrives, the call will return with EINTR.

EINTR is defined as 4 , but when I interrupt the zmq_poll , I get -1 as return value.
Am I missing something ?
The code is below. I get :

start poll
^Cfinished poll with -1
start poll
^Cfinished poll with -1
each time I press CTRL-C. I am not sending anything to this socket during this test.
Thanks for your thoughts.
#include "czmq.h"

static int s_interrupted = 0;
static void s_signal_handler (int signal_value)
    (void) signal_value;
    s_interrupted = 1;
    printf("handle interrupt \n");

static void s_catch_signals (void)
    struct sigaction action;
    action.sa_handler = s_signal_handler;
    action.sa_flags = 0;
    sigemptyset (&action.sa_mask);
    sigaction (SIGINT, &action, NULL);
    sigaction (SIGTERM, &action, NULL);

int main (void)
    char *interf = "*";
    int service = 5562;
    zctx_t *ctx = zctx_new ();
    assert (ctx);
    void *rep_skt = zsocket_new (ctx, ZMQ_REP);
    assert (rep_skt);
    int rc = zsocket_bind (rep_skt, "tcp://%s:%d", interf, service);
    assert (rc == service);

    zmq_pollitem_t items [] = {
        { rep_skt, 0, ZMQ_POLLIN, 0 }
    while (!s_interrupted) {
        printf("start poll \n");
        int rc = zmq_poll(items, 1, -1);
        printf("finished poll with %d \n", rc);
    zsocket_destroy (ctx, rep_skt);
    zctx_destroy (&ctx);
    return 0;
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