metadata.type = attr_type;                \
    metadata.total_size = size_expr;          \
    break;

    SINGLE_CASE(kS, TF_ATTR_STRING, attr->s().length());
    SINGLE_CASE(kI, TF_ATTR_INT, -1);
    SINGLE_CASE(kF, TF_ATTR_FLOAT, -1);
    SINGLE_CASE(kB, TF_ATTR_BOOL, -1);
    SINGLE_CASE(kType, TF_ATTR_TYPE, -1);
    SINGLE_CASE(kShape, TF_ATTR_SHAPE,

    case tensorflow::AttrValue::kS: {
      const string& v = default_value.s();
      TFE_OpSetAttrString(op, attr_name, v.data(), v.size());
      break;
    }
    case tensorflow::AttrValue::kI:
      TFE_OpSetAttrInt(op, attr_name, static_cast<int64_t>(default_value.i()));
      break;
    case tensorflow::AttrValue::kF:
      TFE_OpSetAttrFloat(op, attr_name, default_value.f());
      break;