It seems we have to add an access_flag for each record component because we have to mark if the record component is a varargs or not.
So the format should be Record_attribute { u2 attribute_name_index; u4 attribute_length; u2 number_of_record_components; { u2 component_access_flags; u2 component_name_index; u2 component_descriptor_index; u2 attribute_count; attribute_info attributes[attributes_count]; } } with the component_access_flags allowing ACC_VARARGS. Rémi