To disallow copying or assigning a class it\'s common practice to make the copy constructor and assignment operator private. Both Google and Qt have macros to make this eas
Qt version is backward compatible, while google's is not.
If you develop your library and deprecate the use of assignment before you completely remove it, in Qt it will most likely retain the signature it originally had. In this case older application will continue to run with new version of library (however, they won't compile with the newer version).
Google's macro doesn't have such a property.