Question

struct Foo {
char * DataPtr;
};

class ISomeInterface {
public:
    Foo GetFoo( ) const;
    Foo GetFoo( );
};

The Foo::DataPtr is a pointer to an internal buffer of the object behing ISomeInterface. Is there a way to make sure that the Foo::DataPtr returned by the const version of ISomeInterface::GetFoo is a const char * ?

Answer 1

You need a

struct ConstFoo {
   const char* DataPtr;
};

for this. The const in C++ is not transitive. (this is also why you have iterator and const_iterator.)