1 files changed, 26 insertions, 48 deletions

diff --git a/src/qml/jsruntime/qv4string.cpp b/src/qml/jsruntime/qv4string.cpp
index fc004a2ce0..8b5594b43b 100644
--- a/src/qml/jsruntime/qv4string.cpp
+++ b/src/qml/jsruntime/qv4string.cpp
@@ -1,48 +1,11 @@
-/****************************************************************************
-**
-** Copyright (C) 2016 The Qt Company Ltd.
-** Contact: https://www.qt.io/licensing/
-**
-** This file is part of the QtQml module of the Qt Toolkit.
-**
-** $QT_BEGIN_LICENSE:LGPL$
-** Commercial License Usage
-** Licensees holding valid commercial Qt licenses may use this file in
-** accordance with the commercial license agreement provided with the
-** Software or, alternatively, in accordance with the terms contained in
-** a written agreement between you and The Qt Company. For licensing terms
-** and conditions see https://www.qt.io/terms-conditions. For further
-** information use the contact form at https://www.qt.io/contact-us.
-**
-** GNU Lesser General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU Lesser
-** General Public License version 3 as published by the Free Software
-** Foundation and appearing in the file LICENSE.LGPL3 included in the
-** packaging of this file. Please review the following information to
-** ensure the GNU Lesser General Public License version 3 requirements
-** will be met: https://www.gnu.org/licenses/lgpl-3.0.html.
-**
-** GNU General Public License Usage
-** Alternatively, this file may be used under the terms of the GNU
-** General Public License version 2.0 or (at your option) the GNU General
-** Public license version 3 or any later version approved by the KDE Free
-** Qt Foundation. The licenses are as published by the Free Software
-** Foundation and appearing in the file LICENSE.GPL2 and LICENSE.GPL3
-** included in the packaging of this file. Please review the following
-** information to ensure the GNU General Public License requirements will
-** be met: https://www.gnu.org/licenses/gpl-2.0.html and
-** https://www.gnu.org/licenses/gpl-3.0.html.
-**
-** $QT_END_LICENSE$
-**
-****************************************************************************/
+// Copyright (C) 2016 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
 
 #include "qv4string_p.h"
 #include "qv4value_p.h"
 #include "qv4identifiertable_p.h"
 #include "qv4runtime_p.h"
-#include "qv4objectproto_p.h"
-#include "qv4stringobject_p.h"
+#include <QtQml/private/qv4mm_p.h>
 #include <QtCore/QHash>
 #include <QtCore/private/qnumeric_p.h>
 
@@ -207,23 +170,38 @@ bool Heap::String::startsWithUpper() const
 
 void Heap::String::append(const String *data, QChar *ch)
 {
-    std::vector<const String *> worklist;
+    // in-order visitation with explicit stack
+    // where leaf nodes are "real" strings that get appended to ch
+
+    enum StatusTag : bool { NotVisited, Visited };
+    using Pointer = QTaggedPointer<const String, StatusTag>;
+
+    std::vector<Pointer> worklist;
     worklist.reserve(32);
-    worklist.push_back(data);
+    worklist.push_back(Pointer(data));
 
     while (!worklist.empty()) {
-        const String *item = worklist.back();
-        worklist.pop_back();
+        Pointer item = worklist.back();
+        if (item.tag() == Visited) {
+            Q_ASSERT(item->subtype == StringType_AddedString);
+            const ComplexString *cs = static_cast<const ComplexString *>(item.data());
+            worklist.pop_back();
+            worklist.push_back(Pointer(cs->right));
+            continue;
+        }
 
         if (item->subtype == StringType_AddedString) {
-            const ComplexString *cs = static_cast<const ComplexString *>(item);
-            worklist.push_back(cs->right);
-            worklist.push_back(cs->left);
+            // we need to keep the node in the worklist, as we still need to handle "right"
+            worklist.back().setTag(Visited);
+            const ComplexString *cs = static_cast<const ComplexString *>(item.data());
+            worklist.push_back(Pointer(cs->left));
         } else if (item->subtype == StringType_SubString) {
-            const ComplexString *cs = static_cast<const ComplexString *>(item);
+            worklist.pop_back();
+            const ComplexString *cs = static_cast<const ComplexString *>(item.data());
             memcpy(ch, cs->left->toQString().constData() + cs->from, cs->len*sizeof(QChar));
             ch += cs->len;
         } else {
+            worklist.pop_back();
             memcpy(static_cast<void *>(ch), item->text().data(), item->text().size * sizeof(QChar));
             ch += item->text().size;
         }