This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 114a. See for the official list.


1818. Visibility and inherited language linkage

Section: 9.11  []     Status: CD6     Submitter: Richard Smith     Date: 2013-12-04

[Accepted at the November, 2020 meeting as part of paper P1787R6 and moved to DR at the February, 2021 meeting.]

Does the language linkage of a block-scope declaration determine the language linkage of a subsequent declaration of the same name in a different scope? For example,

   extern "C" void f() {
     void g();    // Implicitly extern "C"
   void g() { }   // Also extern "C" or linkage mismatch?

In other contexts, inheritance of linkage requires that the earlier declaration be visible, as in 6.6 [] paragraph 6:

The name of a function declared in block scope and the name of a variable declared by a block scope extern declaration have linkage. If there is a visible declaration of an entity with linkage having the same name and type, ignoring entities declared outside the innermost enclosing namespace scope, the block scope declaration declares that same entity and receives the linkage of the previous declaration.

The specification for language linkage in 9.11 [] paragraph 5, however, makes no mention of visibility:

A function can be declared without a linkage specification after an explicit linkage specification has been seen; the linkage explicitly specified in the earlier declaration is not affected by such a function declaration.