Check dynamic slot function for nullness before evaluation

Previously, we didn't check whether the function object handle
associated with a dynamic slot's method index was null before
attempting to evaluate it, which could cause a crash in some
circumstances.  This change also adds better error reporting
during function compilation.

Task-number: QTBUG-24064
Task-number: QTBUG-24037
Task-number: QTBUG-23387
Change-Id: I3c5e35e8c16187870125736013a5935fcc5cb1f2
Reviewed-by: Aaron Kennedy <aaron.kennedy@nokia.com>

src/declarative/qml/qdeclarativeexpression.cpp

@@ -148,13 +148,33 @@ QDeclarativeExpressionPrivate::evalFunction(QDeclarativeContextData *ctxt, QObje
     // QtScript days
     v8::HandleScope handle_scope;
     v8::Context::Scope ctxtscope(ep->v8engine()->context());
-    
+
     v8::TryCatch tc;
     v8::Local<v8::Object> scopeobject = ep->v8engine()->qmlScope(ctxt, scope);
     v8::Local<v8::Script> script = ep->v8engine()->qmlModeCompile(code, filename, line);
-    if (tc.HasCaught()) return v8::Persistent<v8::Function>();
+    if (tc.HasCaught()) {
+        QDeclarativeError error;
+        error.setDescription(QLatin1String("Exception occurred during function compilation"));
+        error.setLine(line);
+        error.setUrl(QUrl::fromLocalFile(filename));
+        v8::Local<v8::Message> message = tc.Message();
+        if (!message.IsEmpty())
+            QDeclarativeExpressionPrivate::exceptionToError(message, error);
+        ep->warning(error);
+        return v8::Persistent<v8::Function>();
+    }
     v8::Local<v8::Value> result = script->Run(scopeobject);
-    if (tc.HasCaught()) return v8::Persistent<v8::Function>();
+    if (tc.HasCaught()) {
+        QDeclarativeError error;
+        error.setDescription(QLatin1String("Exception occurred during function evaluation"));
+        error.setLine(line);
+        error.setUrl(QUrl::fromLocalFile(filename));
+        v8::Local<v8::Message> message = tc.Message();
+        if (!message.IsEmpty())
+            QDeclarativeExpressionPrivate::exceptionToError(message, error);
+        ep->warning(error);
+        return v8::Persistent<v8::Function>();
+    }
     if (qmlscope) *qmlscope = qPersistentNew<v8::Object>(scopeobject);
     return qPersistentNew<v8::Function>(v8::Local<v8::Function>::Cast(result));
 }

src/declarative/qml/qdeclarativevmemetaobject.cpp

@@ -730,6 +730,17 @@ int QDeclarativeVMEMetaObject::metaCall(QMetaObject::Call c, int _id, void **a)
                 ep->referenceScarceResources(); // "hold" scarce resources in memory during evaluation.
 
                 v8::Handle<v8::Function> function = method(id);
+                if (function.IsEmpty()) {
+                    // The function was not compiled.  There are some exceptional cases which the
+                    // expression rewriter does not rewrite properly (e.g., \r-terminated lines
+                    // are not rewritten correctly but this bug is deemed out-of-scope to fix for
+                    // performance reasons; see QTBUG-24064) and thus compilation will have failed.
+                    QDeclarativeError e;
+                    e.setDescription(QString(QLatin1String("Exception occurred during compilation of function: %1")).arg(QMetaObject::method(_id).signature()));
+                    ep->warning(e);
+                    return -1; // The dynamic method with that id is not available.
+                }
+
                 QDeclarativeVMEMetaData::MethodData *data = metaData->methodData() + id;
 
                 v8::HandleScope handle_scope;

tests/auto/declarative/qdeclarativeecmascript/data/v8functionException.qml

@@ -0,0 +1,15 @@
+import QtQuick 2.0
+
+// This test uses a multi-line string which has \r-terminated
+// string fragments.  The expression rewriter deliberately doesn't
+// handle \r-terminated string fragments (see QTBUG-24064) and thus
+// this test ensures that we don't crash when the client attempts
+// to invoke a non-compiled dynamic slot.
+
+Item {
+    id: root
+
+    function dynamicSlot() {
+        var someString = "Hello,        this is a        multiline string";
+    }
+}

tests/auto/declarative/qdeclarativeecmascript/tst_qdeclarativeecmascript.cpp

@@ -196,6 +196,7 @@ private slots:
     void functionAssignmentfromJS_invalid();
     void eval();
     void function();
+    void functionException();
     void qtbug_10696();
     void qtbug_11606();
     void qtbug_11600();
@@ -5071,6 +5072,19 @@ void tst_qdeclarativeecmascript::function()
     delete o;
 }
 
+void tst_qdeclarativeecmascript::functionException()
+{
+    // QTBUG-24037 - shouldn't crash.
+    QString errstr = testFileUrl("v8functionException.qml").toString() + QLatin1String(":13: SyntaxError: Unexpected token ILLEGAL");
+    QTest::ignoreMessage(QtWarningMsg, qPrintable(errstr));
+    QTest::ignoreMessage(QtWarningMsg, "<Unknown File>: Exception occurred during compilation of function: dynamicSlot()");
+    QDeclarativeComponent component(&engine, testFileUrl("v8functionException.qml"));
+    QObject *o = component.create();
+    QVERIFY(o != 0);
+    QMetaObject::invokeMethod(o, "dynamicSlot");
+    delete o;
+}
+
 // Test the "Qt.include" method
 void tst_qdeclarativeecmascript::include()
 {