zloop: ignore EINTR from poll if nonstop is enabled

If SIGINT signal arrives while poll is blocking, regardless of attached
signal handler it will cause the poll to return with errno EINTR.
Currently, this causes zloop to return from the event loop. For nonstop
mode to work as intended, we have to ignore EINTR in this case.

Added test cases that verify the functionality when catching an actual
SIGINT signal with and without nonstop mode. Tested in Linux and
Windows.

src/zloop.c

@@ -723,6 +723,10 @@ zloop_start (zloop_t *self)
         }
         rc = zmq_poll (self->pollset, (int) self->poll_size, s_tickless (self));
         if (rc == -1 || (zsys_interrupted && !self->nonstop)) {
+            if (errno == EINTR && self->nonstop) {
+                rc = 0;
+                continue;
+            }
             if (self->verbose) {
                 if (rc == -1)
                     zsys_debug ("zloop: interrupted: %s", strerror (errno));
@@ -915,6 +919,22 @@ s_timer_event5 (zloop_t *loop, int timer_id, void *arg)
     return 0;
 }
 
+static void
+s_raise_sigint_actor (zsock_t *pipe, void *args)
+{
+    zsock_signal (pipe, 0);
+    assert (zsys_interrupted == 0);
+    zsock_wait (pipe);
+    zclock_sleep (100);
+#if defined (__WINDOWS__)
+    assert (GenerateConsoleCtrlEvent (CTRL_C_EVENT, 0) != 0);
+#else
+    assert (kill (getpid(), SIGINT) == 0);
+#endif
+    zclock_sleep (100);
+    assert (zsys_interrupted != 0);
+}
+
 void
 zloop_test (bool verbose)
 {
@@ -976,6 +996,34 @@ zloop_test (bool verbose)
     assert (timer_event_called);
     zsys_interrupted = 0;
 
+    // Check that SIGINT terminates loop if nonstop is not set
+    zloop_destroy (&loop);
+    zactor_t *raise_sigint_actor = zactor_new (s_raise_sigint_actor, NULL);
+    assert (raise_sigint_actor);
+    loop = zloop_new ();
+    zloop_set_nonstop (loop, false);
+    timer_event_called = false;
+    zloop_timer (loop, 1000, 1, s_timer_event3, &timer_event_called);
+    zsock_signal (raise_sigint_actor, 0);
+    zloop_start (loop);
+    zactor_destroy (&raise_sigint_actor);
+    assert (!timer_event_called);
+    zsys_interrupted = 0;
+
+    // Check that SIGINT does not terminate the loop if nonstop is set
+    zloop_destroy (&loop);
+    raise_sigint_actor = zactor_new (s_raise_sigint_actor, NULL);
+    assert (raise_sigint_actor);
+    loop = zloop_new ();
+    zloop_set_nonstop (loop, true);
+    timer_event_called = false;
+    zloop_timer (loop, 500, 1, s_timer_event3, &timer_event_called);
+    zsock_signal (raise_sigint_actor, 0);
+    zloop_start (loop);
+    zactor_destroy (&raise_sigint_actor);
+    assert (timer_event_called);
+    zsys_interrupted = 0;
+
     //  Check if reader removed in timer is not called
     zloop_destroy (&loop);
     loop = zloop_new ();