Fix issue with bindings to aliases that cannot yet be resolved

When an alias points to a child object which has not yet been
initialized, it's id won't have been registered yet, so setting up a
binding to it will result in a crash.

The fix is: when setting a binding target fails, and its target property
is an alias, queue them until all bindings have been set up, and try
again.

Task-number: QTBUG-57041
Change-Id: I4dc5a6d25c0a32fed9fd952c955e2006c76be45a
Reviewed-by: Simon Hausmann <simon.hausmann@qt.io>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/qml/qml/qqmlbinding_p.h b/src/qml/qml/qqmlbinding_p.h
index 19ec3f5d4f..b67b02975f 100644
--- a/src/qml/qml/qqmlbinding_p.h
+++ b/src/qml/qml/qqmlbinding_p.h
@@ -72,6 +72,8 @@ class Q_QML_PRIVATE_EXPORT QQmlBinding : public QQmlJavaScriptExpression,
 {
     friend class QQmlAbstractBinding;
 public:
+    typedef QExplicitlySharedDataPointer<QQmlBinding> Ptr;
+
     static QQmlBinding *create(const QQmlPropertyData *, const QQmlScriptString &, QObject *, QQmlContext *);
     static QQmlBinding *create(const QQmlPropertyData *, const QString &, QObject *, QQmlContextData *,
                                const QString &url = QString(), quint16 lineNumber = 0);
@@ -82,7 +84,7 @@ public:
     ~QQmlBinding() override;
 
     void setTarget(const QQmlProperty &);
-    void setTarget(QObject *, const QQmlPropertyData &, const QQmlPropertyData *valueType);
+    bool setTarget(QObject *, const QQmlPropertyData &, const QQmlPropertyData *valueType);
 
     void setNotifyOnValueChanged(bool);