CHECK_CXX_SOURCE_COMPILES(
  "
  int main()
  {
    int i = 42;
    int j = 10;
    switch(i)
      {
      case 1:
        ++j;
        [[fallthrough]];
      case 2:
        ++j;
        [[fallthrough]];
      default:
        break;
      }
   }
   "
   DEAL_II_HAVE_CXX17_ATTRIBUTE_FALLTHROUGH
   )