re PR c++/85033 (internal compiler error: in fold_offsetof_1, at c-family/c-common.c:6269)

	PR c++/85033
	* semantics.c (finish_offsetof): Don't allow CONST_DECLs.

	* g++.dg/ext/builtin-offsetof2.C: New test.

From-SVN: r258801

gcc/cp/ChangeLog

+2018-03-23  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/85033
+	* semantics.c (finish_offsetof): Don't allow CONST_DECLs.
+
 2018-03-23  Alexandre Oliva <aoliva@redhat.com>
 
 	PR c++/71251

gcc/cp/semantics.c

@@ -4072,6 +4072,11 @@ finish_offsetof (tree object_ptr, tree expr, location_t loc)
 	}
       return error_mark_node;
     }
+  if (TREE_CODE (expr) == CONST_DECL)
+    {
+      error ("cannot apply %<offsetof%> to an enumerator %qD", expr);
+      return error_mark_node;
+    }
   if (REFERENCE_REF_P (expr))
     expr = TREE_OPERAND (expr, 0);
   if (!complete_type_or_else (TREE_TYPE (TREE_TYPE (object_ptr)), object_ptr))

gcc/testsuite/ChangeLog

+2018-03-23  Marek Polacek  <polacek@redhat.com>
+
+	PR c++/85033
+	* g++.dg/ext/builtin-offsetof2.C: New test.
+
 2018-03-23  Eric Botcazou  <ebotcazou@adacore.com>
 
 	PR debug/85020

gcc/testsuite/g++.dg/ext/builtin-offsetof2.C

+// PR c++/85033
+
+struct S {
+  enum { E };
+};
+
+int b = __builtin_offsetof(S, E); // { dg-error "cannot apply .offsetof. to an enumerator" }