Q_OBJECT macro gives many inconsistent-override-warnings

[samueljackson92]

When compiling with clang the Q_OBJECT macro emits an inconsistent-override-warning. In a large project with many Q_OBJECTs this leads to a huge number of warnings which are unrelated to the project itself.

Below is a patch which should fix the issue. I've based the changes on a stripped down version of how this is solved in Qt5.

diff --git a/src/corelib/kernel/qobjectdefs.h b/src/corelib/kernel/qobjectdefs.h
index 0e0a3be..248ed91 100644
--- a/src/corelib/kernel/qobjectdefs.h
+++ b/src/corelib/kernel/qobjectdefs.h
@@ -153,16 +153,39 @@ inline void qYouForgotTheQ_OBJECT_Macro(T1, T2) {}
 #define Q_OBJECT_GETSTATICMETAOBJECT
 #endif

+#ifdef Q_CC_CLANG
+#  define Q_CC_CLANG_VERSION ((__clang_major__ * 100) + __clang_minor__)
+#  if Q_CC_CLANG_VERSION >= 306
+#    define QT_WARNING_PUSH                 _Pragma("clang diagnostic push")
+#    define QT_WARNING_POP                  _Pragma("clang diagnostic pop")
+#    define Q_OBJECT_NO_OVERRIDE_WARNING    _Pragma("clang diagnostic ignored \"-Winconsistent-missing-override\"")
+#  endif
+#elif defined(Q_CC_GNU) && !defined(Q_CC_INTEL)
+#  define Q_CC_GNU_VERSION          (__GNUC__ * 100 + __GNUC_MINOR__)
+#  if Q_CC_GNU_VERSION >= 501
+#    define QT_WARNING_PUSH                 _Pragma("GCC diagnostic push")
+#    define QT_WARNING_POP                  _Pragma("GCC diagnostic pop")
+#    define Q_OBJECT_NO_OVERRIDE_WARNING    _Pragma("GCC diagnostic ignored \"-Wsuggest-override\"")
+#  endif
+#else
+#  define QT_WARNING_PUSH
+#  define QT_WARNING_POP
+#  define Q_OBJECT_NO_OVERRIDE_WARNING
+#endif
+
 /* tmake ignore Q_OBJECT */
 #define Q_OBJECT \
 public: \
     Q_OBJECT_CHECK \
+    QT_WARNING_PUSH \
+    Q_OBJECT_NO_OVERRIDE_WARNING \
     static const QMetaObject staticMetaObject; \
     Q_OBJECT_GETSTATICMETAOBJECT \
     virtual const QMetaObject *metaObject() const; \
     virtual void *qt_metacast(const char *); \
-    QT_TR_FUNCTIONS \
     virtual int qt_metacall(QMetaObject::Call, int, void **); \
+    QT_WARNING_POP \
+    QT_TR_FUNCTIONS \
 private: \
     Q_DECL_HIDDEN static const QMetaObjectExtraData staticMetaObjectExtraData; \
     Q_DECL_HIDDEN static void qt_static_metacall(QObject *, QMetaObject::Call, int, void **);