This is an unofficial snapshot of the ISO/IEC JTC1 SC22 WG21 Core Issues List revision 120c. See http://www.open-std.org/jtc1/sc22/wg21/ for the official list.

2026-09-04

3228. Empty initializers vs. empty packs

(From submission #998.)

Consider:

  void foo(auto...x) {
    int y[]{x...};
  }
  void bar(auto...z) {
    int w(z...);
  }
  int main(){
    foo();
    bar();
  }

The rules around empty initializers are syntax-based and do not appear to address situations involving empty packs.

Proposed resolution (approved by CWG 2026-09-01):

1. Change in 9.5.1 [dcl.init.general] bullet 15.4 as follows:

   • ...
   • If the initializer is () of the form ( expression-list_opt ) and the expression-list is absent (after any pack expansion (13.7.4 [temp.variadic])), the object is value-initialized. [ Note: ... ]
   • ...

2. Change in 9.5.2 [dcl.init.aggr] paragraph 11 as follows:

   ... An array of unknown bound shall not be initialized with an empty a braced-init-list {} that has no elements. [ Footnote: ... ] ...