This is not only about data member access. It also applies to adding methods on the base class that change the behavior of existing methods in already declared subclasses.
Take a cup of coffee and read this famous paper about the issue,
http://www.cas.mcmaster.ca/~emil/Publications_files/Mikhajlo...
This is not only about data member access. It also applies to adding methods on the base class that change the behavior of existing methods in already declared subclasses.
Take a cup of coffee and read this famous paper about the issue,
http://www.cas.mcmaster.ca/~emil/Publications_files/Mikhajlo...