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

2023-02-07


29. Linkage of locally declared functions

Section: 9.11  [dcl.link]     Status: CD1     Submitter: Mike Ball     Date: 19 Mar 1998

[Moved to DR at October 2002 meeting. This was incorrectly marked as having DR status between 4/01 and 4/02. It was overlooked when issue 4 was moved to DR at the 4/01 meeting; this one should have been moved as well, because it's resolved by the changes there.]

Consider the following:

    extern "C" void foo()
    {
        extern void bar();
        bar();
    }
Does "bar()" have "C" language linkage?

The ARM is explicit and says

A linkage-specification for a function also applies to functions and objects declared within it.
The DIS says
In a linkage-specification, the specified language linkage applies to the function types of all function declarators, function names, and variable names introduced by the declaration(s).
Is the body of a function definition part of the declaration?

From Mike Miller:

Yes: from 9.1 [dcl.pre] paragraph 1,

and 9.5 [dcl.fct.def] paragraph 1: At least that's how I'd read it.

From Dag Brück:

Consider the following where extern "C" has been moved to a separate declaration:

    extern "C" void foo();

    void foo() { extern void bar(); bar(); }
I think the ARM wording could possibly be interpreted such that bar() has "C" linkage in my example, but not the DIS wording.

As a side note, I have always wanted to think that placing extern "C" on a function definition or a separate declaration would produce identical programs.

Proposed Resolution (04/01):

See the proposed resolution for Core issue 4, which covers this case.

The ODR should also be checked to see whether it addresses name and type linkage.