Proposed resolution (approved by CWG 2022-11-11):

Insert after 6.3 [basic.def.odr] bullet 14.7 as follows:

• ...
• In each such definition, corresponding entities shall have the same language linkage.
• In each such definition, const objects with static or thread storage duration shall be constant-initialized if the object is constant-initialized in any such definition.
• ...

[Accepted as a DR at the November, 2022 meeting.]

Consider the following example:

  // tu1.cpp
  extern const int a = 1;
  inline auto f() {
    static const int b = a;
    struct A { auto operator()() { return &b; } } a;
    return a;
  }

  // tu2.cpp
  extern const int a;
  inline auto f() {
    static const int b = a;
    struct A { auto operator()() { return &b; } } a;
    return a;
  }
  int main() {
    return *decltype(f())()();
  }

Here, b may or may not have constant initialization. This example should be an ODR violation.

(Split off from issue 2123.)