Rationale (November, 2018):

See also issue 1962, which asks that the type of __func__ be const char*. These two goals are incompatible, so EWG input is requested.

EWG 2022-11-11

This is tracked in github issue cplusplus/papers#1378.

Notes from the October, 2018 teleconference:

CWG agreed with the proposed change.

The definition of __func__ in 9.6.1 [dcl.fct.def.general] paragraph 8 is:

  static const char __func__[] = "function-name";

This prohibits its use in constant expressions, e.g.,

  int main () {
    // error: the value of __func__ is not usable in a constant expression
    constexpr char c = __func__[0];
  }