PyCodeObject *co = (PyCodeObject *)v;
        W_TYPE(TYPE_CODE, p);
        w_long(co->co_argcount, p);
        w_long(co->co_posonlyargcount, p);
        w_long(co->co_kwonlyargcount, p);
        w_long(co->co_nlocals, p);
        w_long(co->co_stacksize, p);
        w_long(co->co_flags, p);
        w_object(co->co_code, p);
        w_object(co->co_consts, p);
        w_object(co->co_names, p);
        w_object(co->co_varnames, p);
        w_object(co->co_freevars, p);
        w_object(co->co_cellvars, p);
        w_object(co->co_filename, p);
        w_object(co->co_name, p);
        w_long(co->co_firstlineno, p);
        w_object(co->co_lnotab, p);

#define TYPE_CODE               'c'
#define TYPE_TUPLE              '('
#define TYPE_REF                'r'
#define TYPE_NONE               'N'


#define W_TYPE(t, p) do { \
    w_byte((t) | flag, (p)); \
} while(0)

#define FLAG_REF                '\x80' /* with a type, add obj to index */

static int
w_ref(PyObject *v, char *flag, WFILE *p)
{
    _Py_hashtable_entry_t *entry;
    int w;

    if (p->version < 3 || p->hashtable == NULL)
        return 0; /* not writing object references */

    /* if it has only one reference, it definitely isn't shared */
    if (Py_REFCNT(v) == 1)
        return 0;

    entry = _Py_hashtable_get_entry(p->hashtable, v);
    if (entry != NULL) {
        /* write the reference index to the stream */
        w = (int)(uintptr_t)entry->value;
        /* we don't store "long" indices in the dict */
        assert(0 <= w && w <= 0x7fffffff);
        w_byte(TYPE_REF, p);
        w_long(w, p);
        return 1;
    } else {
        size_t s = p->hashtable->nentries;
        /* we don't support long indices */
        if (s >= 0x7fffffff) {
            PyErr_SetString(PyExc_ValueError, "too many objects");
            goto err;
        }
        w = (int)s;
        Py_INCREF(v);
        if (_Py_hashtable_set(p->hashtable, v, (void *)(uintptr_t)w) < 0) {
            Py_DECREF(v);
            goto err;
        }
        *flag |= FLAG_REF;
        return 0;
    }
err:
    p->error = WFERR_UNMARSHALLABLE;
    return 1;
}
#在这个函数中flag被定义为FLAG_REF('\x80')