Fix new clang warnings.

configure.ac

@@ -313,6 +313,16 @@ AC_CACHE_CHECK([whether __builtin_complex is available],
      [AS_VAR_SET([acx_cv_have_decl___builtin_complex],[yes])],
      [AS_VAR_SET([acx_cv_have_decl___builtin_complex],[no])])])
 ACX_CHECK_ASM_BSR
+AC_CACHE_CHECK([whether __builtin_unreachable is declared],
+  [acx_cv_have_decl___builtin_unreachable],
+  [AC_LINK_IFELSE([AC_LANG_PROGRAM(,[  int v;
+  scanf("%d", &v);
+  if (v < 0) __builtin_unreachable()])],
+     [AS_VAR_SET([acx_cv_have_decl___builtin_unreachable],[yes])],
+     [AS_VAR_SET([acx_cv_have_decl___builtin_unreachable],[no])])])
+AC_DEFINE_UNQUOTED([HAVE_DECL___BUILTIN_UNREACHABLE],
+  [`test "$acx_cv_have_decl___builtin_unreachable" = yes ; expr 1 - $?`],
+  [GCC style __builtin_unreachable is available])
 dnl ######################################################################
 dnl Test whether cfortran.h works correctly
 dnl ######################################################################

src/xt_ddt_create.c

@@ -729,6 +729,10 @@ static void xt_ddt_tree_elem_delete(struct xt_ddt_tree_elem *elem) {
   case MULTI_SUB:
     num_sub_elem = elem->displ_count;
     break;
+#  if HAVE_DECL___BUILTIN_UNREACHABLE && !__clang__
+  default:
+    __builtin_unreachable();
+#  endif
   }
   struct xt_ddt_tree_elem **sub_elems
     = (struct xt_ddt_tree_elem **)(elem->displs + elem->displ_count);
@@ -813,6 +817,10 @@ static void xt_ddt_tree_elem_get_data_sizes(
             sub_elems[i], prev_dtype, prev_data_idx, data);
       break;
     }
+#  if HAVE_DECL___BUILTIN_UNREACHABLE && !__clang__
+  default:
+    __builtin_unreachable();
+#  endif
   }
 }
 
@@ -878,6 +886,10 @@ static void xt_ddt_tree_elem_to_data(
             prev_dtype, prev_data_idx);
       break;
     }
+#  if HAVE_DECL___BUILTIN_UNREACHABLE && !__clang__
+  default:
+    __builtin_unreachable();
+#  endif
   }
 }
 

src/xt_idxlist_collection.c

@@ -195,6 +195,12 @@ xt_idxlist_collection_new(Xt_idxlist *idxlists, int num_idxlists) {
     case -1:
       ++nsort_dsc;
       break;
+    case 0:
+      break;
+#  if HAVE_DECL___BUILTIN_UNREACHABLE
+    default:
+      __builtin_unreachable();
+#  endif
     }
     for (int i = (int)first_non_empty_idxlist+1; i < num_idxlists; ++i) {
       int num_indices_of_list = xt_idxlist_get_num_indices(idxlists[i]);
@@ -215,6 +221,12 @@ xt_idxlist_collection_new(Xt_idxlist *idxlists, int num_idxlists) {
         case -1:
           ++nsort_dsc;
           break;
+        case 0:
+          break;
+#  if HAVE_DECL___BUILTIN_UNREACHABLE
+        default:
+          __builtin_unreachable();
+#  endif
         }
         num_indices += num_indices_of_list;
       }