[Bug c++/86678] constexpr evaluation incorrectly diagnoses unevaluated call to non-constexpr function

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86678

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2018-07-26 00:00:00         |2018-8-14

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
constexpr bool always_true() { return true; }
int f() { return 1; }
constexpr int g() {
  if (always_true())
    return 0;
  return f();
}

ce.cc: In function 'constexpr int g()':
ce.cc:6:11: error: call to non-'constexpr' function 'int f()'
6 |   return f();
  |          ~^~

This makes it awkward to use the new __builtin_is_constant_evaluated().