core/dbus: modernize bus_foreach_bus

src/core/dbus.c

@@ -1113,31 +1113,29 @@ int bus_foreach_bus(
                 int (*send_message)(sd_bus *bus, void *userdata),
                 void *userdata) {
 
-        sd_bus *b;
-        int r, ret = 0;
+        int r = 0;
+
+        assert(m);
+        assert(send_message);
 
         /* Send to all direct buses, unconditionally */
+        sd_bus *b;
         SET_FOREACH(b, m->private_buses) {
 
                 /* Don't bother with enqueuing these messages to clients that haven't started yet */
                 if (sd_bus_is_ready(b) <= 0)
                         continue;
 
-                r = send_message(b, userdata);
-                if (r < 0)
-                        ret = r;
+                RET_GATHER(r, send_message(b, userdata));
         }
 
         /* Send to API bus, but only if somebody is subscribed */
         if (m->api_bus &&
             (sd_bus_track_count(m->subscribed) > 0 ||
-             sd_bus_track_count(subscribed2) > 0)) {
-                r = send_message(m->api_bus, userdata);
-                if (r < 0)
-                        ret = r;
-        }
+             sd_bus_track_count(subscribed2) > 0))
+                RET_GATHER(r, send_message(m->api_bus, userdata));
 
-        return ret;
+        return r;
 }
 
 void bus_track_serialize(sd_bus_track *t, FILE *f, const char *prefix) {