Add -Wweak-vtables to headersclean

This requires some fixes in several classes that are also included
in this patch.

The QTestEvent hierarchy is all-inline and changes layout depending on
QT_GUI_LIB and QT_WIDGETS_LIB, so we can't just export it. Suppress the
warning in that header for now. Created QTBUG-104486 to track a fix for
the real issue.

The QFutureInterface hierarchy is also all-inline, but templates, so
doesn't trigger, except the <void> specialization. Created
QTBUG-125115 to track a fix for the real issue.

Done-with: Marc Mutz <marc.mutz@qt.io>
Task-number: QTBUG-45582
Change-Id: I96b3e109aa989b70e0d4809b90bd53a369e50d55
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

cmake/QtHeadersClean.cmake

@@ -130,7 +130,8 @@ function(qt_internal_add_headersclean_target module_target module_headers)
         endif()
 
         if ("${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang|IntelLLVM")
-            list(APPEND hcleanFLAGS -Wshorten-64-to-32)
+            list(APPEND hcleanFLAGS -Wshorten-64-to-32
+                -Wweak-vtables)
         endif()
 
         separate_arguments(cxx_flags NATIVE_COMMAND ${CMAKE_CXX_FLAGS})

src/corelib/thread/qfutureinterface.h

@@ -465,6 +465,9 @@ std::vector<T> QFutureInterface<T>::takeResults()
 }
 #endif
 
+QT_WARNING_PUSH
+QT_WARNING_DISABLE_CLANG("-Wweak-vtables") // QTBUG-125115
+
 template <>
 class QFutureInterface<void> : public QFutureInterfaceBase
 {
@@ -495,6 +498,8 @@ public:
     }
 };
 
+QT_WARNING_POP // Clang -Wweak-vtables
+
 template<typename T>
 inline void swap(QFutureInterface<T> &a, QFutureInterface<T> &b) noexcept
 {

src/gui/accessible/qaccessiblebridge.cpp

@@ -33,6 +33,8 @@ QT_BEGIN_NAMESPACE
 
     Destroys the accessibility bridge object.
 */
+QAccessibleBridge::~QAccessibleBridge()
+    = default;
 
 /*!
     \fn void QAccessibleBridge::setRootObject(QAccessibleInterface *object)

src/gui/accessible/qaccessiblebridge.h

@@ -16,10 +16,10 @@ QT_BEGIN_NAMESPACE
 class QAccessibleInterface;
 class QAccessibleEvent;
 
-class QAccessibleBridge
+class Q_GUI_EXPORT QAccessibleBridge
 {
 public:
-    virtual ~QAccessibleBridge() {}
+    virtual ~QAccessibleBridge();
     virtual void setRootObject(QAccessibleInterface *) = 0;
     virtual void notifyAccessibilityUpdate(QAccessibleEvent *event) = 0;
 };

src/gui/text/qtextdocument.cpp

@@ -53,6 +53,9 @@ namespace {
     QTextDocument::ResourceProvider qt_defaultResourceProvider;
 };
 
+QAbstractUndoItem::~QAbstractUndoItem()
+    = default;
+
 /*!
     \fn bool Qt::mightBeRichText(QAnyStringView text)
 

src/gui/text/qtextdocument.h

@@ -45,15 +45,11 @@ namespace Qt
 class Q_GUI_EXPORT QAbstractUndoItem
 {
 public:
-    virtual ~QAbstractUndoItem() = 0;
+    virtual ~QAbstractUndoItem();
     virtual void undo() = 0;
     virtual void redo() = 0;
 };
 
-inline QAbstractUndoItem::~QAbstractUndoItem()
-{
-}
-
 class QTextDocumentPrivate;
 
 class Q_GUI_EXPORT QTextDocument : public QObject

src/printsupport/CMakeLists.txt

@@ -14,7 +14,7 @@ qt_internal_add_module(PrintSupport
         kernel/qplatformprintplugin.cpp kernel/qplatformprintplugin.h
         kernel/qprint.cpp kernel/qprint_p.h
         kernel/qprintdevice.cpp kernel/qprintdevice_p.h
-        kernel/qprintengine.h
+        kernel/qprintengine.cpp kernel/qprintengine.h
         kernel/qprintengine_pdf.cpp kernel/qprintengine_pdf_p.h
         kernel/qprinter.cpp kernel/qprinter.h kernel/qprinter_p.h
         kernel/qprinterinfo.cpp kernel/qprinterinfo.h kernel/qprinterinfo_p.h

src/printsupport/kernel/qprintengine.cpp

@@ -0,0 +1,15 @@
+// Copyright (C) 2024 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 <QtPrintSupport/qprintengine.h>
+
+QT_BEGIN_NAMESPACE
+
+#ifndef QT_NO_PRINTER
+
+QPrintEngine::~QPrintEngine()
+    = default;
+
+#endif // QT_NO_PRINTER
+
+QT_END_NAMESPACE

src/printsupport/kernel/qprintengine.h

@@ -19,7 +19,8 @@ QT_BEGIN_NAMESPACE
 class Q_PRINTSUPPORT_EXPORT QPrintEngine
 {
 public:
-    virtual ~QPrintEngine() {}
+    virtual ~QPrintEngine();
+
     enum PrintEnginePropertyKey {
         PPK_CollateCopies,
         PPK_ColorMode,

src/sql/kernel/qsqldatabase.cpp

@@ -239,6 +239,8 @@ void QSqlDatabasePrivate::disable()
 
     Destroys the SQL driver creator object.
 */
+QSqlDriverCreatorBase::~QSqlDriverCreatorBase()
+    = default;
 
 /*!
     \fn QSqlDriver *QSqlDriverCreatorBase::createObject() const

src/sql/kernel/qsqldatabase.h

@@ -23,7 +23,7 @@ class QThread;
 class Q_SQL_EXPORT QSqlDriverCreatorBase
 {
 public:
-    virtual ~QSqlDriverCreatorBase() {}
+    virtual ~QSqlDriverCreatorBase();
     virtual QSqlDriver *createObject() const = 0;
 };
 

src/testlib/qtestevent.h

@@ -28,6 +28,9 @@ QT_BEGIN_NAMESPACE
 # define QT_ONLY_WIDGETLIB_USES Q_DECL_UNUSED_MEMBER
 #endif
 
+QT_WARNING_PUSH
+QT_WARNING_DISABLE_CLANG("-Wweak-vtables") // QTBUG-1044486
+
 class QTestEvent
 {
 public:
@@ -36,13 +39,15 @@ public:
 #endif
     virtual QTestEvent *clone() const = 0;
 
-    virtual ~QTestEvent() {}
+    virtual ~QTestEvent() = default; // ### FIXME: weak vtable (QTBUG-104486)
 };
 
 #ifdef QT_GUI_LIB
 class QTestKeyEvent: public QTestEvent
 {
 public:
+    ~QTestKeyEvent() override = default; // ### FIXME: weak vtable (QTBUG-104486)
+
     inline QTestKeyEvent(QTest::KeyAction action, Qt::Key key, Qt::KeyboardModifiers modifiers, int delay)
         : _action(action), _delay(delay), _modifiers(modifiers), _ascii(0), _key(key) {}
     inline QTestKeyEvent(QTest::KeyAction action, char ascii, Qt::KeyboardModifiers modifiers, int delay)
@@ -71,6 +76,8 @@ protected:
 class QTestKeyClicksEvent: public QTestEvent
 {
 public:
+    ~QTestKeyClicksEvent() override = default; // ### FIXME: weak vtables (QTBUG-104486)
+
     inline QTestKeyClicksEvent(const QString &keys, Qt::KeyboardModifiers modifiers, int delay)
         : _keys(keys), _modifiers(modifiers), _delay(delay) {}
     inline QTestEvent *clone() const override { return new QTestKeyClicksEvent(*this); }
@@ -91,6 +98,8 @@ private:
 class QTestMouseEvent: public QTestEvent
 {
 public:
+    ~QTestMouseEvent() override = default; // ### FIXME: weak vtables (QTBUG-104486)
+
     inline QTestMouseEvent(QTest::MouseAction action, Qt::MouseButton button,
             Qt::KeyboardModifiers modifiers, QPoint position, int delay)
         : _action(action), _button(button), _modifiers(modifiers), _pos(position), _delay(delay) {}
@@ -117,6 +126,8 @@ class QTestDelayEvent: public QTestEvent
 {
 public:
     inline QTestDelayEvent(int msecs): _delay(msecs) {}
+    ~QTestDelayEvent() override = default; // ### FIXME: weak vtables (QTBUG-104486)
+
     inline QTestEvent *clone() const override { return new QTestDelayEvent(*this); }
 
 #ifdef QT_WIDGETS_LIB
@@ -190,6 +201,8 @@ public:
 
 #undef QT_ONLY_WIDGETLIB_USES
 
+QT_WARNING_POP // Clang -Wweak-vtables
+
 QT_END_NAMESPACE
 
 Q_DECLARE_METATYPE(QTestEventList)