Fix crashes with closures created in QML components

When closures created inside QML components are called after the
surrounding component (and consequently QML context) has been destroyed,
we are in a somewhat limited environment. Initially we would just crash
as the calling QML context is not valid anymore. We can alleviate that
by introducing reference counting on the context and letting the QML
context wrapper keep a strong reference. This avoids the crashes and
also ensures that at least imports continue to be accessible within
these contexts (as the singleton test case demonstrates).

Task-number: QTBUG-61781
Change-Id: I893f171842d01b0863d95a02ea738adc2620e236
Reviewed-by: Lars Knoll <lars.knoll@qt.io>

1 files changed, 2 insertions, 11 deletions

diff --git a/src/qml/jsruntime/qv4qmlcontext_p.h b/src/qml/jsruntime/qv4qmlcontext_p.h
index 9aec7467da..9caeb75b8c 100644
--- a/src/qml/jsruntime/qv4qmlcontext_p.h
+++ b/src/qml/jsruntime/qv4qmlcontext_p.h
@@ -67,13 +67,12 @@ struct QmlContextWrapper;
 namespace Heap {
 
 struct QmlContextWrapper : Object {
-    void init(QQmlContextData *context, QObject *scopeObject, bool ownsContext = false);
+    void init(QQmlContextData *context, QObject *scopeObject);
     void destroy();
     bool readOnly;
-    bool ownsContext;
     bool isNullWrapper;
 
-    QQmlGuardedContextData *context;
+    QQmlContextDataRef *context;
     QQmlQPointer<QObject> scopeObject;
 };
 
@@ -90,10 +89,6 @@ struct Q_QML_EXPORT QmlContextWrapper : Object
     V4_OBJECT2(QmlContextWrapper, Object)
     V4_NEEDS_DESTROY
 
-    void takeContextOwnership() {
-        d()->ownsContext = true;
-    }
-
     inline QObject *getScopeObject() const { return d()->scopeObject; }
     inline QQmlContextData *getContext() const { return *d()->context; }
 
@@ -116,10 +111,6 @@ struct Q_QML_EXPORT QmlContext : public ExecutionContext
     QQmlContextData *qmlContext() const {
         return *d()->qml->context;
     }
-
-    void takeContextOwnership() {
-        d()->qml->ownsContext = true;
-    }
 };
 
 }