Don't check reference count in QLinkedList<T>::free

This is a private function that was always* called after d->ref.deref()
returned false to free the linked list. Still, it needlessly verified
the reference count to be zero.

The check is thus replaced with a Q_ASSERT to check the invariant on
debug builds.

*This commit also fixes an issue where free would be called on a block
that hadn't been deref'ed, thus leaking the nodes. Since this was in an
exception handling block, and happens before any code has a chance to
reference the block the explicit deref is skipped in that case.

Change-Id: Ie73c174d0a1b84f297bf5531e45f829e66a46346
Reviewed-by: Robin Burchell <robin+qt@viroteck.net>
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Bradley T. Hughes <bradley.hughes@nokia.com>

1 files changed, 7 insertions, 7 deletions

diff --git a/src/corelib/tools/qlinkedlist.h b/src/corelib/tools/qlinkedlist.h
index 966b74ddfa..279eda673a 100644
--- a/src/corelib/tools/qlinkedlist.h
+++ b/src/corelib/tools/qlinkedlist.h
@@ -266,6 +266,7 @@ void QLinkedList<T>::detach_helper()
             copy = copy->n;
         } QT_CATCH(...) {
             copy->n = x.e;
+            Q_ASSERT(!x.d->ref.deref()); // Don't trigger assert in free
             free(x.d);
             QT_RETHROW;
         }
@@ -282,14 +283,13 @@ void QLinkedList<T>::free(QLinkedListData *x)
 {
     Node *y = reinterpret_cast<Node*>(x);
     Node *i = y->n;
-    if (x->ref == 0) {
-        while(i != y) {
-            Node *n = i;
-            i = i->n;
-            delete n;
-        }
-        delete x;
+    Q_ASSERT(x->ref.atomic.load() == 0);
+    while (i != y) {
+        Node *n = i;
+        i = i->n;
+        delete n;
     }
+    delete x;
 }
 
 template <typename T>