gobject: Change GObject notify semantics under static analysis

Coverity notices the `g_object_unref()` call in `g_object_notify()`, but
not the paired `g_object_ref()` call. It therefore incorrectly assumes
that every call to `g_object_notify()` frees the object. This causes a
lot (hundreds) of false positive reports about double-frees or
use-after-frees.

I can’t find a way to fix this using a model file, so the other options
are:
 * Manually mark every report as a false positive and keep updating them
   as the code changes over time. This would take a lot of maintainer
   effort.
 * Comment out the `g_object_ref()`/`g_object_unref()` calls when
   running static analysis (but not in a normal production build). This
   is ugly, but cheap and shouldn’t impact maintainability much.

So this commit implements option 2.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

gobject/gobject.c

@@ -1465,13 +1465,24 @@ g_object_notify_by_spec_internal (GObject    *object,
         }
       else
         {
+          /*
+           * Coverity doesn’t understand the paired ref/unref here and seems to
+           * ignore the ref, thus reports every call to g_object_notify() as
+           * causing a double-free. That’s incorrect, but I can’t get a model
+           * file to work for avoiding the false positives, so instead comment
+           * out the ref/unref when doing static analysis.
+           */
+#ifndef __COVERITY__
           g_object_ref (object);
+#endif
 
           /* not frozen, so just dispatch the notification directly */
           G_OBJECT_GET_CLASS (object)
               ->dispatch_properties_changed (object, 1, &pspec);
 
+#ifndef __COVERITY__
           g_object_unref (object);
+#endif
         }
     }
 }