[Bug c++/108223] New: GCC reject QNaN in constant expressions

[nikolasklauser at berlin dot de via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108223

            Bug ID: 108223
           Summary: GCC reject QNaN in constant expressions
           Product: gcc
           Version: 12.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: nikolasklauser at berlin dot de
  Target Milestone: ---

GCC rejects the following code with "error: '__builtin_fmax(+QNaN, +QNaN)' is
not a constant expression" even though it's perfectly defined behaviour.

test code (Godbolt: https://godbolt.org/z/1hfxM9PEW):

constexpr bool test() {
  auto val = __builtin_fmax(__builtin_nan(""), __builtin_nan(""));

  return true;
}

static_assert(test());