Abort application if QJSEngine is constructed before QCoreApplication

QJSEngine requires a QCoreApplication instance in order to function
correctly, and 57f7fe3e enforces this further. However, currently an
application will simply crash because of accessing a non-existent
QCoreApplication instance.

This patch makes it clear to the user that they need to construct an
instance first.

Change-Id: Ieaef005ef03da250cc60457b4b1a4baa5db81215
Reviewed-by: Simon Hausmann <simon.hausmann@theqtcompany.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/src/qml/jsapi/qjsengine.cpp b/src/qml/jsapi/qjsengine.cpp
index 4241213c09..5bcc4600a2 100644
--- a/src/qml/jsapi/qjsengine.cpp
+++ b/src/qml/jsapi/qjsengine.cpp
@@ -247,6 +247,11 @@ Q_DECLARE_METATYPE(QList<int>)
 
 QT_BEGIN_NAMESPACE
 
+static void checkForApplicationInstance()
+{
+    if (!QCoreApplication::instance())
+        qFatal("QJSEngine: Must construct a QCoreApplication before a QJSEngine");
+}
 
 /*!
     Constructs a QJSEngine object.
@@ -258,6 +263,8 @@ QJSEngine::QJSEngine()
     : QObject(*new QJSEnginePrivate, 0)
     , d(new QV8Engine(this))
 {
+    checkForApplicationInstance();
+
     QJSEnginePrivate::addToDebugServer(this);
 }
 
@@ -272,6 +279,8 @@ QJSEngine::QJSEngine(QObject *parent)
     : QObject(*new QJSEnginePrivate, parent)
     , d(new QV8Engine(this))
 {
+    checkForApplicationInstance();
+
     QJSEnginePrivate::addToDebugServer(this);
 }
 
@@ -282,6 +291,7 @@ QJSEngine::QJSEngine(QJSEnginePrivate &dd, QObject *parent)
     : QObject(dd, parent)
     , d(new QV8Engine(this))
 {
+    checkForApplicationInstance();
 }
 
 /*!