This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 116a. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2024-12-19

132. Local types and linkage

Section: 6.6  [basic.link]     Status: NAD     Submitter: Daveed Vandevoorde     Date: 25 June 1999

6.6 [basic.link] paragraph 8 says,

A name with no linkage (notably, the name of a class or enumeration declared in a local scope (6.4.3 [basic.scope.block] )) shall not be used to declare an entity with linkage.
This wording does not, but should, prohibit use of an unnamed local type in the declaration of an entity with linkage. For example, 
    void f() {
        extern struct { } x;  // currently allowed
    }

Proposed resolution: Change the text in 6.6 [basic.link] paragraph 8 from:

A name with no linkage (notably, the name of a class or enumeration declared in a local scope (6.4.3 [basic.scope.block])) shall not be used to declare an entity with linkage.
to:
A name with no linkage (notably, the name of a class or enumeration declared in a local scope (6.4.3 [basic.scope.block])) or an unnamed type shall not be used to declare an entity with linkage.
In section 6.6 [basic.link] paragraph 8, add to the example, before the closing brace of function f:
extern struct {} x;    // ill-formed

Rationale (10/00): The proposed change would have introduced an incompatibility with the C language. For example, the global declaration

    static enum { A, B, C } abc;

represents an idiom that is used in C but would be prohibited under this resolution.