CWG Issue 239 (original) (raw)

This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 118e. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2025-11-05

239. Footnote 116 and Koenig lookup

Section: 12.2.2.2.2 [over.call.func]Status: CD1Submitter: Steve ClamageDate: 2 Aug 2000

[Moved to DR at 4/01 meeting.]

In describing non-member functions in an overload set, footnote 116 (12.2.2.2.2 [over.call.func]) says,

Because of the usual name hiding rules, these will be introduced by declarations or by _using-directive_s all found in the same block or all found at namespace scope.

At least in terms of the current state of the Standard, this is not correct: a block extern declaration does not prevent Koenig lookup from occurring. For example,

enum E { zero };
void f(E);
void g() {
    void f(int);
    f(zero);
}

In this example, the overload set will include declarations from both namespace and block scope.

(See also issue 12.)

Proposed resolution (04/01):

1. In 6.5.4 [basic.lookup.argdep] paragraph 2, change

   If the ordinary unqualified lookup of the name finds the declaration of a class member function, the associated namespaces and classes are not considered.
   to
   If the ordinary unqualified lookup of the name finds the declaration of a class member function, or a block-scope function declaration that is not a using-declaration, the associated namespaces and classes are not considered.
   and change the example to:
   namespace NS {
   class T { };
   void f(T);
   void g(T, int);
   }
   NS::T parm;
   void g(NS::T, float);
   int main() {
   f(parm); // OK: calls NS::f
   extern void g(NS::T, float);
   g(parm, 1); // OK: calls g(NS::T, float)
   }

2. In 12.2.2.2.2 [over.call.func] paragraph 3 from:

   If the name resolves to a non-member function declaration, that function and its overloaded declarations constitute the set of candidate functions.
   to
   If the name resolves to a set of non-member function declarations, that set of functions constitutes the set of candidate functions.
   Note that this text is also edited by issue 364. Also, remove the associated footnote 116.