sd-event: make errors on EPOLL_CTL_DEL pseudo-fatal

If we call EPOLL_CTL_DEL, we *REALLY* expect the file-descriptor to be
present in that given epoll-set. We actually track such state via our
s->io.registered flag, so it better be true.

Make sure if that's not true, we treat it similar to assert_return() (ie.,
print a loud warning).

src/basic/macro.h

@@ -248,18 +248,19 @@ static inline unsigned long ALIGN_POWER2(unsigned long u) {
         REENABLE_WARNING
 #endif
 
+#define assert_log(expr) ((_likely_(expr))      \
+        ? (true)                                \
+        : (log_assert_failed_return(#expr, __FILE__, __LINE__, __PRETTY_FUNCTION__), false))
+
 #define assert_return(expr, r)                                          \
         do {                                                            \
-                if (_unlikely_(!(expr))) {                              \
-                        log_assert_failed_return(#expr, __FILE__, __LINE__, __PRETTY_FUNCTION__); \
+                if (!assert_log(expr))                                  \
                         return (r);                                     \
-                }                                                       \
         } while (false)
 
 #define assert_return_errno(expr, r, err)                               \
         do {                                                            \
-                if (_unlikely_(!(expr))) {                              \
-                        log_assert_failed_return(#expr, __FILE__, __LINE__, __PRETTY_FUNCTION__); \
+                if (!assert_log(expr)) {                                \
                         errno = err;                                    \
                         return (r);                                     \
                 }                                                       \

src/libsystemd/sd-event/sd-event.c

@@ -468,24 +468,22 @@ static bool event_pid_changed(sd_event *e) {
         return e->original_pid != getpid();
 }
 
-static int source_io_unregister(sd_event_source *s) {
+static void source_io_unregister(sd_event_source *s) {
         int r;
 
         assert(s);
         assert(s->type == SOURCE_IO);
 
         if (event_pid_changed(s->event))
-                return 0;
+                return;
 
         if (!s->io.registered)
-                return 0;
+                return;
 
         r = epoll_ctl(s->event->epoll_fd, EPOLL_CTL_DEL, s->io.fd, NULL);
-        if (r < 0)
-                return -errno;
+        assert_log(r >= 0);
 
         s->io.registered = false;
-        return 0;
 }
 
 static int source_io_register(
@@ -1457,10 +1455,7 @@ _public_ int sd_event_source_set_enabled(sd_event_source *s, int m) {
                 switch (s->type) {
 
                 case SOURCE_IO:
-                        r = source_io_unregister(s);
-                        if (r < 0)
-                                return r;
-
+                        source_io_unregister(s);
                         s->enabled = m;
                         break;