QObjectPrivate: encode the version number in the constructor parameters

Instead of allowing the code to start and then possibly fail at runtime.

This isn't a 100% sure solution because it's a function call. With lazy
symbol binding on some OSes, the mistake won't be noticed until the
function call is attempted. However, most OSes now resolve *all* calls
at load time so they can mark the GOT (or equivalent) pages read-only,
meaning the loading of the library will fail.

qversiontagging_p.h is a more sure way in OSes / executable formats it
works on.

Change-Id: If7867a37256b7141001dfffd9bd299bb1bbd7c63
Reviewed-by: Marc Mutz <marc.mutz@qt.io>

src/corelib/kernel/qobject.cpp

@@ -158,11 +158,9 @@ QMetaObject *QObjectData::dynamicMetaObject() const
     return metaObject->toDynamicMetaObject(q_ptr);
 }
 
-QObjectPrivate::QObjectPrivate(int version)
+QObjectPrivate::QObjectPrivate(decltype(QObjectPrivateVersion))
     : threadData(nullptr), currentChildBeingDeleted(nullptr)
 {
-    checkForIncompatibleLibraryVersion(version);
-
     // QObjectData initialization
     q_ptr = nullptr;
     parent = nullptr;                           // no parent yet. It is set by setParent()

src/corelib/kernel/qobject_p.h

@@ -39,6 +39,19 @@ QT_BEGIN_NAMESPACE
 #define QT_ANONYMOUS_PRIVATE_PROPERTY(d, text) QT_ANNOTATE_CLASS2(qt_anonymous_private_property, d, text)
 #endif
 
+#define QT_CONCAT(B, M, m, u)   QT_CONCAT2(B, M, m, u)
+#define QT_CONCAT2(B, M, m, u)  B ## M ## _ ## m ## _ ## u
+#if defined(QT_BUILD_INTERNAL) && !QT_CONFIG(elf_private_full_version)
+// Don't check the version parameter in internal builds.
+// This allows incompatible versions to be loaded, possibly for testing.
+enum QObjectPrivateVersionEnum
+#else
+enum QT_CONCAT(QtPrivate_, QT_VERSION_MAJOR, QT_VERSION_MINOR, QT_VERSION_PATCH)
+#endif
+{ QObjectPrivateVersion = QT_VERSION };
+#undef QT_CONCAT
+#undef QT_CONCAT2
+
 class QVariant;
 class QThreadData;
 class QObjectConnectionListVector;
@@ -58,8 +71,6 @@ void Q_CORE_EXPORT qt_register_signal_spy_callbacks(QSignalSpyCallbackSet *callb
 
 extern Q_CORE_EXPORT QBasicAtomicPointer<QSignalSpyCallbackSet> qt_signal_spy_callback_set;
 
-enum { QObjectPrivateVersion = QT_VERSION };
-
 class Q_CORE_EXPORT QAbstractDeclarativeData
 {
 public:
@@ -130,14 +141,12 @@ public:
         linked list.
     */
 
-    QObjectPrivate(int version = QObjectPrivateVersion);
+    QObjectPrivate(decltype(QObjectPrivateVersion) version = QObjectPrivateVersion);
     virtual ~QObjectPrivate();
     void deleteChildren();
     // used to clear binding storage early in ~QObject
     void clearBindingStorage();
 
-    inline void checkForIncompatibleLibraryVersion(int version) const;
-
     void setParent_helper(QObject *);
     void moveToThread_helper();
     void setThreadData_helper(QThreadData *currentData, QThreadData *targetData, QBindingStatus *status);
@@ -216,28 +225,6 @@ public:
     QAtomicPointer<QtSharedPointer::ExternalRefCountData> sharedRefcount;
 };
 
-/*
-    Catch mixing of incompatible library versions.
-
-    Should be called from the constructor of every non-final subclass
-    of QObjectPrivate, to ensure we catch incompatibilities between
-    the intermediate base and subclasses thereof.
-*/
-inline void QObjectPrivate::checkForIncompatibleLibraryVersion(int version) const
-{
-#if defined(QT_BUILD_INTERNAL)
-    // Don't check the version parameter in internal builds.
-    // This allows incompatible versions to be loaded, possibly for testing.
-    Q_UNUSED(version);
-#else
-    if (Q_UNLIKELY(version != QObjectPrivateVersion)) {
-        qFatal("Cannot mix incompatible Qt library (%d.%d.%d) with this library (%d.%d.%d)",
-                (version >> 16) & 0xff, (version >> 8) & 0xff, version & 0xff,
-                (QObjectPrivateVersion >> 16) & 0xff, (QObjectPrivateVersion >> 8) & 0xff, QObjectPrivateVersion & 0xff);
-    }
-#endif
-}
-
 inline bool QObjectPrivate::isDeclarativeSignalConnected(uint signal_index) const
 {
     return !isDeletingChildren && declarativeData && QAbstractDeclarativeData::isSignalConnected

src/widgets/graphicsview/qgraphicsanchorlayout_p.cpp

@@ -25,7 +25,7 @@ using namespace Qt::StringLiterals;
 // we use a tighter limit for the variables range.
 const qreal g_offset = (sizeof(qreal) == sizeof(double)) ? QWIDGETSIZE_MAX : QWIDGETSIZE_MAX / 32;
 
-QGraphicsAnchorPrivate::QGraphicsAnchorPrivate(int version)
+QGraphicsAnchorPrivate::QGraphicsAnchorPrivate(decltype(QObjectPrivateVersion) version)
     : QObjectPrivate(version), layoutPrivate(nullptr), data(nullptr),
       sizePolicy(QSizePolicy::Fixed), preferredSize(0),
       hasSize(true)

src/widgets/graphicsview/qgraphicsanchorlayout_p.h

@@ -313,7 +313,7 @@ class QGraphicsAnchorPrivate : public QObjectPrivate
     Q_DECLARE_PUBLIC(QGraphicsAnchor)
 
 public:
-    explicit QGraphicsAnchorPrivate(int version = QObjectPrivateVersion);
+    explicit QGraphicsAnchorPrivate(decltype(QObjectPrivateVersion) = QObjectPrivateVersion);
     ~QGraphicsAnchorPrivate();
 
     void setSpacing(qreal value);

src/widgets/kernel/qwidget.cpp

@@ -103,7 +103,7 @@ static inline bool qRectIntersects(const QRect &r1, const QRect &r2)
 
 extern bool qt_sendSpontaneousEvent(QObject*, QEvent*); // qapplication.cpp
 
-QWidgetPrivate::QWidgetPrivate(int version)
+QWidgetPrivate::QWidgetPrivate(decltype(QObjectPrivateVersion) version)
     : QObjectPrivate(version)
       , focus_next(nullptr)
       , focus_prev(nullptr)
@@ -164,16 +164,6 @@ QWidgetPrivate::QWidgetPrivate(int version)
         return;
     }
 
-#ifdef QT_BUILD_INTERNAL
-    // Don't check the version parameter in internal builds.
-    // This allows incompatible versions to be loaded, possibly for testing.
-    Q_UNUSED(version);
-#else
-    if (Q_UNLIKELY(version != QObjectPrivateVersion))
-        qFatal("Cannot mix incompatible Qt library (version 0x%x) with this library (version 0x%x)",
-                version, QObjectPrivateVersion);
-#endif
-
     willBeWidget = true; // used in QObject's ctor
     memset(high_attributes, 0, sizeof(high_attributes));
 

src/widgets/kernel/qwidget_p.h

@@ -207,7 +207,7 @@ public:
     Q_ENUM(Direction)
 
     // Functions.
-    explicit QWidgetPrivate(int version = QObjectPrivateVersion);
+    explicit QWidgetPrivate(decltype(QObjectPrivateVersion) = QObjectPrivateVersion);
     ~QWidgetPrivate();
 
     static QWidgetPrivate *get(QWidget *w) { return w->d_func(); }