Add copy(SlotObjUniquePtr), use it in QHostInfoResult & SlotObjSharedPtr

It's a free function, because a) it rhymes with move(ptr) and, of
course, SlotObjUniquePtr being a std::unique_ptr, b) we can't add
member functions to it (and no, inheriting from a type whose dtor is
neither protected nor virtual is nothing you will catch yours truly
doing).

Pick-to: 6.6 6.5
Change-Id: I2026126857a7bba204d683bad118e8a2c5cb2924
Reviewed-by: Ivan Solovev <ivan.solovev@qt.io>

src/corelib/kernel/qobjectdefs_impl.h

@@ -452,6 +452,12 @@ namespace QtPrivate {
 
     using SlotObjUniquePtr = std::unique_ptr<QSlotObjectBase,
                                              QSlotObjectBase::Deleter>;
+    inline SlotObjUniquePtr copy(const SlotObjUniquePtr &other) noexcept
+    {
+        if (other)
+            other->ref();
+        return SlotObjUniquePtr{other.get()};
+    }
 
     class SlotObjSharedPtr {
         SlotObjUniquePtr obj;
@@ -465,11 +471,7 @@ namespace QtPrivate {
             // (that's why (QSlotObjectBase*) ctor doesn't exisit: don't know whether that one _should_)
         }
         Q_NODISCARD_CTOR SlotObjSharedPtr(const SlotObjSharedPtr &other) noexcept
-            : obj(other.obj.get())
-        {
-            if (obj)
-                obj->ref();
-        }
+            : obj{copy(other.obj)} {}
         SlotObjSharedPtr &operator=(const SlotObjSharedPtr &other) noexcept
         { auto copy = other; swap(copy); return *this; }
 

src/network/kernel/qhostinfo_p.h

@@ -61,11 +61,9 @@ protected:
 
 private:
     QHostInfoResult(const QHostInfoResult *other)
-        : receiver(other->receiver), slotObj(other->slotObj.get()), // ugly, but copy the pointer...
+        : receiver(other->receiver), slotObj{copy(other->slotObj)},
           withContextObject(other->withContextObject)
     {
-        if (slotObj)
-            slotObj->ref(); // ... and ref it here
         // cleanup if the application terminates before results are delivered
         connect(QCoreApplication::instance(), &QCoreApplication::aboutToQuit,
                 this, &QObject::deleteLater);