An additional access check beyond those described earlier in
[class.access]
is applied when a non-static data member or non-static member function is a
protected member of its designating class (
[class.access.base])
and is not designated by a
splice-expression.
As described earlier, access to a protected member is granted because the
reference occurs in a friend or direct member of some class
C.Otherwise, if the access involves a (possibly implicit)
object expression (
[expr.prim.id.general],
[expr.ref]),
the class of the object expression shall be
C or a class derived from
C.[
Example 1:
class B {
protected:
int i;
static int j;
};
class D1 : public B {
};
class D2 : public B {
friend void fr(B*,D1*,D2*);
void mem(B*,D1*);
};
void fr(B* pb, D1* p1, D2* p2) {
pb->i = 1;
p1->i = 2;
p2->i = 3;
p2->B::i = 4;
int B::* pmi_B = &B::i;
int B::* pmi_B2 = &D2::i;
B::j = 5;
D2::j = 6;
}
void D2::mem(B* pb, D1* p1) {
pb->i = 1;
p1->i = 2;
i = 3;
B::i = 4;
int B::* pmi_B = &B::i;
int B::* pmi_B2 = &D2::i;
j = 5;
B::j = 6;
}
void g(B* pb, D1* p1, D2* p2) {
pb->i = 1;
p1->i = 2;
p2->i = 3;
}
—
end example]