Could you explain 'type conversions (casts)' in class access control to me?

[fl]

Hi,

When I read access control to class member on web of MSDN, I am confused by
its last sentence:

'This protection is lost when explicit type conversions
(casts) are performed.'

Please see the pasted below. I do not know there is a cast in access control
yet. Could you explain it to me?


Thanks,




You can increase the integrity of software built with C++ by helping control
access to class member data and functions. Class members can be declared as
having private, protected, or public access, as shown in the following table:

......

Access control helps prevent you from using objects in ways they were not
intended to be used. This protection is lost when explicit type conversions
(casts) are performed.

[fl]

After I post my question, I guess that the original statement means the
specific access word before class derivation. It can change the access
level in the derived class. This can be called a cast?

class Foo
{
public:
Foo() { std::cout << "Foo's constructor" << std::endl; }
};
class Bar : public Foo
or
class Bar : protected Foo
or
class Bar : private Foo
{
public:
Bar() { std::cout << "Bar's constructor" << std::endl; }
};

[Paavo Helde]

fl <rxj...@gmail.com> wrote in
news:9a550a88-3242-4b99...@googlegroups.com:

Maybe they think something like:

class Bar {
private:
int i;
};

Bar a;
* (int*) &a = 42;

or

class Foo {
public:
int i;
};

class Bar: private Foo {};

Bar a;
((Foo*) &a)->i = 42;

If so, then the casts are not only violating the intended access rules,
but are also pretty fragile and unportable (as they assume a certain
memory layout).