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, 4 deletions

diff --git a/src/qml/qml/qqmltypeloader.cpp b/src/qml/qml/qqmltypeloader.cpp
index ce795be757..342e6c0725 100644
--- a/src/qml/qml/qqmltypeloader.cpp
+++ b/src/qml/qml/qqmltypeloader.cpp
@@ -2817,7 +2817,7 @@ QV4::ReturnedValue QQmlScriptData::scriptValueForContext(QQmlContextData *parent
         effectiveCtxt = 0;
 
     // Create the script context if required
-    QQmlContextData *ctxt = new QQmlContextData;
+    QQmlContextDataRef ctxt(new QQmlContextData);
     ctxt->isInternal = true;
     ctxt->isJSContext = true;
     if (shared)
@@ -2837,7 +2837,7 @@ QV4::ReturnedValue QQmlScriptData::scriptValueForContext(QQmlContextData *parent
     }
 
     if (effectiveCtxt) {
-        ctxt->setParent(effectiveCtxt, true);
+        ctxt->setParent(effectiveCtxt);
     } else {
         ctxt->engine = parentCtxt->engine; // Fix for QTBUG-21620
     }
@@ -2859,12 +2859,10 @@ QV4::ReturnedValue QQmlScriptData::scriptValueForContext(QQmlContextData *parent
     if (!m_program) {
         if (shared)
             m_loaded = true;
-        ctxt->destroy();
         return QV4::Encode::undefined();
     }
 
     QV4::Scoped<QV4::QmlContext> qmlContext(scope, QV4::QmlContext::create(v4->rootContext(), ctxt, 0));
-    qmlContext->takeContextOwnership();
 
     m_program->qmlContext.set(scope.engine, qmlContext);
     m_program->run();