Problem: zmq_poller_* uses ETIMEDOUT (instead of the usual EAGAIN) to indicate timeouts

Solution: replace ETIMEDOUT within socket_poller_t and all client code by EAGAIN

Fixes #2713

src/proxy.cpp

@@ -271,13 +271,13 @@ int zmq::proxy (
         //  If one of receiving end's queue is full ('ZMQ_POLLOUT' not available),
         //  'poller_wait' is pointed to 'poller_receive_blocked', 'poller_send_blocked' or 'poller_both_blocked'.
         rc = poller_wait->wait (events, 3, -1);
-        if (rc < 0 && errno == ETIMEDOUT)
+        if (rc < 0 && errno == EAGAIN)
             rc = 0;
         CHECK_RC_EXIT_ON_FAILURE ();
 
         //  Some of events waited for by 'poller_wait' have arrived, now poll for everything without blocking.
         rc = poller_all->wait (events, 3, 0);
-        if (rc < 0 && errno == ETIMEDOUT)
+        if (rc < 0 && errno == EAGAIN)
             rc = 0;
         CHECK_RC_EXIT_ON_FAILURE ();
 

src/socket_poller.cpp

@@ -415,7 +415,7 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
         // no event occured within the specified timeout. Otherwise the caller
         // needs to check the return value AND the event to avoid using the
         // nullified event data.
-        errno = ETIMEDOUT;
+        errno = EAGAIN;
         if (timeout_ == 0)
             return -1;
 #if defined ZMQ_HAVE_WINDOWS
@@ -550,7 +550,7 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
         if (now >= end)
             break;
     }
-    errno = ETIMEDOUT;
+    errno = EAGAIN;
     return -1;
 
 #elif defined ZMQ_POLL_BASED_ON_SELECT
@@ -560,7 +560,7 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
         // no event occured within the specified timeout. Otherwise the caller
         // needs to check the return value AND the event to avoid using the
         // nullified event data.
-        errno = ETIMEDOUT;
+        errno = EAGAIN;
         if (timeout_ == 0)
             return -1;
 #if defined ZMQ_HAVE_WINDOWS
@@ -711,7 +711,7 @@ int zmq::socket_poller_t::wait (zmq::socket_poller_t::event_t *events_, int n_ev
             break;
     }
 
-    errno = ETIMEDOUT;
+    errno = EAGAIN;
     return -1;
 
 #else

src/zmq.cpp

@@ -813,7 +813,7 @@ inline int zmq_poller_poll (zmq_pollitem_t *items_, int nitems_, long timeout_)
     rc = zmq_poller_wait_all (&poller, events, nitems_, timeout_);
     if (rc < 0) {
         delete [] events;
-        if (zmq_errno() == ETIMEDOUT) {
+        if (zmq_errno() == EAGAIN) {
             return 0;
         }
         return rc;

tests/test_poller.cpp

@@ -170,18 +170,16 @@ void test_wait_corner_cases (void *ctx)
     void *poller = zmq_poller_new ();
     assert (poller != NULL);
 
-    //  TODO zmq_poller_wait should return EAGAIN instead of ETIMEDOUT (like all other zmq functions)
-
     zmq_poller_event_t event;
     int rc = zmq_poller_wait(poller, &event, 0);
-    assert (rc == -1 && errno == ETIMEDOUT);
+    assert (rc == -1 && errno == EAGAIN);
 
     //  this can never return since no socket was registered, and should yield an error
     rc = zmq_poller_wait(poller, &event, -1);
     assert (rc == -1 && errno == EFAULT);
 
     rc = zmq_poller_wait_all (poller, &event, 0, 0);
-    assert (rc == -1 && errno == ETIMEDOUT);
+    assert (rc == -1 && errno == EAGAIN);
 
     //  this can never return since no socket was registered, and should yield an error
     rc = zmq_poller_wait_all (poller, &event, 0, -1);
@@ -238,7 +236,7 @@ int main (void)
     // waiting on poller with no registered sockets should report error
     rc = zmq_poller_wait (poller, &event, 0);
     assert (rc == -1);
-    assert (errno == ETIMEDOUT);
+    assert (errno == EAGAIN);
 
     // register sink
     rc = zmq_poller_add (poller, sink, sink, ZMQ_POLLIN);
@@ -260,7 +258,7 @@ int main (void)
     //  We expect timed out
     rc = zmq_poller_wait (poller, &event, 0);
     assert (rc == -1);
-    assert (errno == ETIMEDOUT);
+    assert (errno == EAGAIN);
 
     //  Stop polling sink
     rc = zmq_poller_remove (poller, sink);