moc: Don't link to inexistent parent staticMetaObject

Contrarily to Q_OBJECTs, Q_GADGETs are not guaranteed to
descend from a Q_GADGET. Here, we ensure that if the first
superclass is a Q_GADGET, then the derived class will be
treated as one. This allows gaps in the Q_GADGET hierarchy
while preventing from trying to link to the inexistent
staticMetaObject if there's no such ancestor.

Change-Id: If10fb952e23655102a425bb18fe8babaf447a47f
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>
Reviewed-by: Jędrzej Nowacki <jedrzej.nowacki@theqtcompany.com>

6 files changed, 113 insertions, 1 deletions

diff --git a/src/tools/moc/generator.cpp b/src/tools/moc/generator.cpp
index 2c41b17b68..f27c155da5 100644
--- a/src/tools/moc/generator.cpp
+++ b/src/tools/moc/generator.cpp
@@ -530,7 +530,7 @@ void Generator::generateCode()
 
     if (isQObject)
         fprintf(out, "    { Q_NULLPTR, ");
-    else if (cdef->superclassList.size())
+    else if (cdef->superclassList.size() && (!cdef->hasQGadget || knownGadgets.contains(purestSuperClass)))
         fprintf(out, "    { &%s::staticMetaObject, ", purestSuperClass.constData());
     else
         fprintf(out, "    { Q_NULLPTR, ");
diff --git a/src/tools/moc/moc.cpp b/src/tools/moc/moc.cpp
index 5506dc75c5..75349191d4 100644
--- a/src/tools/moc/moc.cpp
+++ b/src/tools/moc/moc.cpp
@@ -139,6 +139,12 @@ bool Moc::parseClassHead(ClassDef *def)
                 def->superclassList += qMakePair(type, access);
             }
         } while (test(COMMA));
+
+        if (knownGadgets.contains(def->superclassList.first().first)) {
+            // Q_GADGET subclasses are treated as Q_GADGETs
+            knownGadgets.insert(def->classname, def->qualified);
+            knownGadgets.insert(def->qualified, def->qualified);
+        }
     }
     if (!test(LBRACE))
         return false;
diff --git a/tests/auto/tools/moc/grand-parent-gadget-class.h b/tests/auto/tools/moc/grand-parent-gadget-class.h
new file mode 100644
index 0000000000..b589e55b27
--- /dev/null
+++ b/tests/auto/tools/moc/grand-parent-gadget-class.h
@@ -0,0 +1,48 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** 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 Digia. For licensing terms and
+** conditions see http://qt.digia.com/licensing. For further information
+** use the contact form at http://qt.digia.com/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 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights. These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef GRANDPARENTGADGETCLASS_H
+#define GRANDPARENTGADGETCLASS_H
+
+#include <QtCore/qobjectdefs.h>
+
+namespace GrandParentGadget {
+
+struct BaseGadget { Q_GADGET };
+struct Derived : BaseGadget {};
+struct DerivedGadget : Derived { Q_GADGET };
+
+}
+
+#endif // GRANDPARENTGADGETCLASS_H
+
diff --git a/tests/auto/tools/moc/moc.pro b/tests/auto/tools/moc/moc.pro
index cc8c2c671d..99e226c5f4 100644
--- a/tests/auto/tools/moc/moc.pro
+++ b/tests/auto/tools/moc/moc.pro
@@ -27,6 +27,7 @@ HEADERS += using-namespaces.h no-keywords.h task87883.h c-comments.h backslash-n
            single-quote-digit-separator-n3781.h \
            related-metaobjects-in-namespaces.h \
            qtbug-35657-gadget.h \
+           non-gadget-parent-class.h grand-parent-gadget-class.h \
            related-metaobjects-in-gadget.h \
            related-metaobjects-name-conflict.h
 
diff --git a/tests/auto/tools/moc/non-gadget-parent-class.h b/tests/auto/tools/moc/non-gadget-parent-class.h
new file mode 100644
index 0000000000..9e2158d170
--- /dev/null
+++ b/tests/auto/tools/moc/non-gadget-parent-class.h
@@ -0,0 +1,47 @@
+/****************************************************************************
+**
+** Copyright (C) 2015 Digia Plc and/or its subsidiary(-ies).
+** Contact: http://www.qt-project.org/legal
+**
+** This file is part of the test suite of the Qt Toolkit.
+**
+** $QT_BEGIN_LICENSE:LGPL21$
+** 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 Digia. For licensing terms and
+** conditions see http://qt.digia.com/licensing. For further information
+** use the contact form at http://qt.digia.com/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 2.1 or version 3 as published by the Free
+** Software Foundation and appearing in the file LICENSE.LGPLv21 and
+** LICENSE.LGPLv3 included in the packaging of this file. Please review the
+** following information to ensure the GNU Lesser General Public License
+** requirements will be met: https://www.gnu.org/licenses/lgpl.html and
+** http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
+**
+** In addition, as a special exception, Digia gives you certain additional
+** rights. These rights are described in the Digia Qt LGPL Exception
+** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
+**
+** $QT_END_LICENSE$
+**
+****************************************************************************/
+
+#ifndef NONGADGETPARENTCLASS_H
+#define NONGADGETPARENTCLASS_H
+
+#include <QtCore/qobjectdefs.h>
+
+namespace NonGadgetParent {
+
+struct Base {};
+struct Derived : Base { Q_GADGET };
+
+}
+
+#endif // NONGADGETPARENTCLASS_H
+
diff --git a/tests/auto/tools/moc/tst_moc.cpp b/tests/auto/tools/moc/tst_moc.cpp
index d67b3e011a..3117bcd09a 100644
--- a/tests/auto/tools/moc/tst_moc.cpp
+++ b/tests/auto/tools/moc/tst_moc.cpp
@@ -72,6 +72,9 @@
 #include "related-metaobjects-in-gadget.h"
 #include "related-metaobjects-name-conflict.h"
 
+#include "non-gadget-parent-class.h"
+#include "grand-parent-gadget-class.h"
+
 QT_USE_NAMESPACE
 
 template <bool b> struct QTBUG_31218 {};
@@ -574,6 +577,7 @@ private slots:
     void relatedMetaObjectsNameConflict();
     void strignLiteralsInMacroExtension();
     void veryLongStringData();
+    void gadgetHierarchy();
 
 signals:
     void sigWithUnsignedArg(unsigned foo);
@@ -3379,6 +3383,12 @@ void tst_Moc::veryLongStringData()
     QCOMPARE(strlen(mobj->classInfo(3).value()), static_cast<size_t>(1));
 }
 
+void tst_Moc::gadgetHierarchy()
+{
+    QCOMPARE(NonGadgetParent::Derived::staticMetaObject.superClass(), static_cast<const QMetaObject*>(Q_NULLPTR));
+    QCOMPARE(GrandParentGadget::DerivedGadget::staticMetaObject.superClass(), &GrandParentGadget::BaseGadget::staticMetaObject);
+}
+
 QTEST_MAIN(tst_Moc)
 
 // the generated code must compile with QT_NO_KEYWORDS