CWG Issue 216 (original) (raw)

This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 117a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2025-04-13

216. Linkage of nameless class-scope enumeration types

Section: 6.6 [basic.link]Status: CD1Submitter: Daveed VandevoordeDate: 13 Mar 2000

[Moved to DR at 10/01 meeting.]

6.6 [basic.link] paragraph 4 says (among other things):

A name having namespace scope has external linkage if it is the name of

• [...]
• a named enumeration (9.8.1 [dcl.enum]), or an unnamed enumeration defined in a typedef declaration in which the enumeration has the typedef name for linkage purposes (9.2.4 [dcl.typedef])

That prohibits for example:

typedef enum { e1 } *PE;
void f(PE) {}  // Cannot declare a function (with linkage) using a
       // type with no linkage.

However, the same prohibition was not made for class scope types. Indeed, 6.6 [basic.link] paragraph 5 says:

In addition, a member function, static data member, class or enumeration of class scope has external linkage if the name of the class has external linkage.

That allows for:

struct S {
   typedef enum { e1 } *MPE;
   void mf(MPE) {}
};

My guess is that this is an unintentional consequence of 6.6 [basic.link] paragraph 5, but I would like confirmation on that.

Proposed resolution:

Change text in 6.6 [basic.link] paragraph 5 from:

In addition, a member function, static data member, class or enumeration of class scope has external linkage if the name of the class has external linkage.

to:

In addition, a member function, a static data member, a named class or enumeration of class scope, or an unnamed class or enumeration defined in a class-scope typedef declaration such that the class or enumeration has the typedef name for linkage purposes (9.2.4 [dcl.typedef]), has external linkage if the name of the class has external linkage.