DB_SYM_NULL       253 ddb/db_sym.c   	if (sym == DB_SYM_NULL)
DB_SYM_NULL       450 ddb/db_sym.c   	db_sym_t	ret = DB_SYM_NULL, sym;
DB_SYM_NULL       476 ddb/db_sym.c   	if (sym == DB_SYM_NULL) {