Fix race condition in QQmlData::createPropertyCache

As noted in QJSEnginePrivate::cache, there can be a race  between
calling addRef on the QQmlPropertyCache and another thread derefing and
consequently deleting it. To avoid this, we introduce a doRef flag in
QQmlMetaTypeData::propertyCache, which tells it to ref the the cache.
This fixes the issue, as the QQmlMetaTypeDataPtr in propertyCache() acts
as a mutex.

Fixes: QTBUG-84692
Pick-to: 5.15
Change-Id: I962d28cfd22696aad89a660e41c55f63a8791b44
Reviewed-by: Ulf Hermann <ulf.hermann@qt.io>

1 files changed, 1 insertions, 1 deletions

diff --git a/src/qml/qml/qqmlmetatype_p.h b/src/qml/qml/qqmlmetatype_p.h
index 0ac86e7d20..08d79d2e5b 100644
--- a/src/qml/qml/qqmlmetatype_p.h
+++ b/src/qml/qml/qqmlmetatype_p.h
@@ -114,7 +114,7 @@ public:
     static QQmlType qmlType(const QUrl &unNormalizedUrl, bool includeNonFileImports = false);
 
     static QQmlPropertyCache *propertyCache(const QMetaObject *metaObject,
-                                            QTypeRevision version = QTypeRevision());
+                                            QTypeRevision version = QTypeRevision(), bool doRef = false);
     static QQmlPropertyCache *propertyCache(const QQmlType &type, QTypeRevision version);
 
     static void freeUnusedTypesAndCaches();