/* md to be consisten you really should have this init here */
        if( attrib )  {
                BU_INIT_EXTERNAL(attrib);
                BU_CK_EXTERNAL(attrib);
                if( attrib->ext_nbytes > 0 )  {
                        a_width = db5_select_length_encoding(attrib->ext_nbytes)
                        need += attrib->ext_nbytes + db5_enc_len[a_width];
                } else {
                        attrib = NULL;
                        a_width = 0;
                }
        } else {
                a_width = 0;

That snippit is from db5_io.c line 519 i added the init.