gobject: Cleanup weak locations when the last one has been removed

As per the previous change, an object that had weak locations set may
need to lock again the weak locations mutex during qdata cleanup, but
we can avoid this when we know we're removing the last location, by
removing the qdata entry and freeing the data.

In case a new location is needed for the same object, new data will be
added.

However, by doing this the weak locations during dispose may be
invalidated once the weak locations lock is passed, so check again if
this is the case while removing them.

2 files changed, 22 insertions, 3 deletions

diff --git a/gobject/gobject.c b/gobject/gobject.c
index c558c1197..4f4a463ef 100644
--- a/gobject/gobject.c
+++ b/gobject/gobject.c
@@ -3536,10 +3536,11 @@ g_object_unref (gpointer _object)
             }
 
           /* We got the lock first, so the object will definitely die
-           * now. Clear out all the weak references.
+           * now. Clear out all the weak references, if they're still set.
            */
-          weak_locations_free_unlocked (weak_locations);
-          g_datalist_id_remove_no_notify (&object->qdata, quark_weak_locations);
+          weak_locations = g_datalist_id_remove_no_notify (&object->qdata,
+                                                           quark_weak_locations);
+          g_clear_pointer (&weak_locations, weak_locations_free_unlocked);
 
           g_rw_lock_writer_unlock (&weak_locations_lock);
         }
@@ -4731,6 +4732,12 @@ g_weak_ref_set (GWeakRef *weak_ref,
           g_assert (weak_locations != NULL);
 
           *weak_locations = g_slist_remove (*weak_locations, weak_ref);
+
+          if (!*weak_locations)
+            {
+              weak_locations_free_unlocked (weak_locations);
+              g_datalist_id_remove_no_notify (&old_object->qdata, quark_weak_locations);
+            }
         }
 
       /* Add the weak ref to the new object */
diff --git a/gobject/tests/reference.c b/gobject/tests/reference.c
index de49ff1fd..e84c66467 100644
--- a/gobject/tests/reference.c
+++ b/gobject/tests/reference.c
@@ -558,6 +558,18 @@ test_weak_ref (void)
 
   g_weak_ref_clear (&weak3);
 
+  /* unset dynamic_weak... */
+  g_weak_ref_set (dynamic_weak, NULL);
+  g_assert_null (g_weak_ref_get (dynamic_weak));
+
+  /* initializing a weak reference to an object that had before works */
+  g_weak_ref_set (dynamic_weak, obj2);
+  tmp = g_weak_ref_get (dynamic_weak);
+  g_assert_true (tmp == obj2);
+  g_assert_cmpint (obj2->ref_count, ==, 2);
+  g_object_unref (tmp);
+  g_assert_cmpint (obj2->ref_count, ==, 1);
+
   /* clear and free dynamic_weak... */
   g_weak_ref_clear (dynamic_weak);