QCache: when overwriting, store the new cost instead of the delta

The delta was clearly intended to be used on the total (and still is)
but it also wound up getting stored in the cache, which wouldn't be a
big problem unless the object was removed, in which case we could
incidentally 'free up more space' than intended.

Change-Id: Ib2b0f072d30da6d16a93dce60e4c5f6080c109fc
Reviewed-by: Lars Knoll <lars.knoll@qt.io>
(cherry picked from commit d2e2d0d3a6249ccbc17ec92acb32fec9a0d71807)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

1 files changed, 2 insertions, 1 deletions

diff --git a/src/corelib/tools/qcache.h b/src/corelib/tools/qcache.h
index 41cf9abc46..8a341c8555 100644
--- a/src/corelib/tools/qcache.h
+++ b/src/corelib/tools/qcache.h
@@ -245,8 +245,9 @@ public:
         auto result = d.findOrInsert(key);
         Node *n = result.it.node();
         if (result.initialized) {
-            cost -= n->value.cost;
+            auto prevCost = n->value.cost;
             result.it.node()->emplace(object, cost);
+            cost -= prevCost;
             relink(key);
         } else {
             Node::createInPlace(n, key, object, cost);