QProperty: Use RefCounted as intended

You're not supposed to mess with the refcount directly. That's what the
addRef() and deref() methods are for.

Change-Id: I5cae946cef7ac72dd99b247ade95590d142c269e
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

src/corelib/kernel/qproperty.cpp

@@ -27,9 +27,9 @@ void QPropertyBindingPrivatePtr::reset(QtPrivate::RefCounted *ptr) noexcept
 {
     if (ptr != d) {
         if (ptr)
-            ptr->ref++;
+            ptr->addRef();
         auto *old = std::exchange(d, ptr);
-        if (old && (--old->ref == 0))
+        if (old && !old->deref())
             QPropertyBindingPrivate::destroyAndFreeMemory(static_cast<QPropertyBindingPrivate *>(d));
     }
 }
@@ -310,7 +310,7 @@ void QPropertyBindingPrivate::unlinkAndDeref()
 {
     clearDependencyObservers();
     propertyDataPtr = nullptr;
-    if (--ref == 0)
+    if (!deref())
         destroyAndFreeMemory(this);
 }
 

src/corelib/kernel/qpropertyprivate.h

@@ -36,9 +36,13 @@ namespace QtPrivate {
 // QPropertyBindingPrivatePtr operates on a RefCountingMixin solely so that we can inline
 // the constructor and copy constructor
 struct RefCounted {
+
+    int refCount() const { return ref; }
+    void addRef() { ++ref; }
+    bool deref() { return --ref != 0; }
+
+private:
     int ref = 0;
-    void addRef() {++ref;}
-    bool deref() {--ref; return ref;}
 };
 }
 
@@ -61,7 +65,7 @@ public:
     QPropertyBindingPrivatePtr() noexcept : d(nullptr) { }
     ~QPropertyBindingPrivatePtr()
     {
-        if (d && (--d->ref == 0))
+        if (d && !d->deref())
             destroyAndFreeMemory();
     }
     Q_CORE_EXPORT void destroyAndFreeMemory();