Problem: timers are called twice if they change the pollset

[sphaero]

Solution:

• first delete timers to delete then break
• move rc==-1 check to beginning of loop to prevent the loop from not breaking

Here's a small test program which reproduces the problem:

#include "czmq.h"

static
int timer_end(zloop_t *loop, int timer_id, void *args) {
    zloop_reader_end( loop, (zsock_t *)args);
    return -1;
}

int socket_event(zloop_t *loop, zsock_t *handle, void *args)
{
    zmsg_t *msg = zmsg_recv(handle);
    zsys_notice( "Main sockect event: %s", zmsg_popstr( msg ));
    zmsg_destroy(&msg);
    return -1;
}

int main (void) {
    zsys_init();

    zloop_t *loop = zloop_new ();
    assert (loop);
    zloop_set_verbose (loop, true);

    //add a socket
    zsock_t *pub = zsock_new_pair("inproc://bla");
    int rc = zloop_reader( loop, pub, socket_event, pub);
    assert(rc == 0);
    zloop_timer(loop, 1000, 1, timer_end, pub);
    zstr_send(pub, "Test");
    zloop_start(loop);
    zsys_notice("loop ended");
    zloop_destroy(&loop);
    zsock_destroy(&pub);
    return 0;
}

it outputs:

D: 19-02-09 13:02:10 zloop: register PAIR reader
D: 19-02-09 13:02:10 zloop: register timer id=1 delay=1000 times=1
D: 19-02-09 13:02:10 zloop polling for 1000 msec
D: 19-02-09 13:02:11 zloop: call timer handler id=1
D: 19-02-09 13:02:11 zloop: cancel PAIR reader
D: 19-02-09 13:02:11 zloop polling for 0 msec
D: 19-02-09 13:02:11 zloop: call timer handler id=1
D: 19-02-09 13:02:11 zloop: cancel PAIR reader
N: 19-02-09 13:02:11 loop ended

which clearly shows the timer handler being called twice while we registered it as only to be called once