rb_econv_add_converter 1805 transcode.c        return rb_econv_add_converter(ec, "", decorator_name, n);
rb_econv_add_converter 2919 transcode.c        ret = rb_econv_add_converter(a->ec, sname, dname, a->index);
rb_econv_add_converter 2957 transcode.c                ret = rb_econv_add_converter(ec, sname, dname, ec->num_trans);