This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 110b. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2023-01-15


175. Class name injection and base name access

Section: Clause 11  [class]     Status: CD1     Submitter: John Spicer     Date: 21 February 1999

[Moved to DR at 10/01 meeting.]

With class name injection, when a base class name is used in a derived class, the name found is the injected name in the base class, not the name of the class in the scope containing the base class. Consequently, if the base class name is not accessible (e.g., because is is in a private base class), the base class name cannot be used unless a qualified name is used to name the class in the class or namespace of which it is a member.

Without class name injection the following example is valid. With class name injection, A is inaccessible in class C.

    class A { };
    class B: private A { };
    class C: public B {
        A* p;    // error: A inaccessible
    };

At the least, the standard should be more explicit that this is, in fact, ill-formed.

(See paper J16/99-0010 = WG21 N1187.)

Proposed resolution (04/01):

Add to the end of 11.8.2 [class.access.spec] paragraph 3:

[Note: In a derived class, the lookup of a base class name will find the injected-class-name instead of the name of the base class in the scope in which it was declared. The injected-class-name might be less accessible than the name of the base class in the scope in which it was declared.] [Example:

    class A { };
    class B : private A { };
    class C : public B {
        A* p;    // error: injected-class-name A is inaccessible
        ::A* q;  // OK
    };

end example]