If a class contains an unsized array, it cannot be used as the base class for another class. In addition, a class containing an unsized array cannot be used to declare any member except the last member of another class. A class containing an unsized array cannot have a direct or indirect virtual base class.
The sizeof operator, when applied to a class containing an unsized array, returns the amount of storage required for all members except the unsized array. Implementors of classes that contain unsized arrays should provide alternate methods for obtaining the correct size of the class.
You cannot declare arrays of objects that have unsized array components. Also, performing pointer arithmetic on pointers to such objects generates an error message.