python tp_ready函数分析

int
PyType_Ready(PyTypeObject *type)
{
    PyObject *dict, *bases;
    PyTypeObject *base;
    Py_ssize_t i, n;

    if (type->tp_flags & Py_TPFLAGS_READY) {
        assert(type->tp_dict != NULL);
        return 0;
    }
    assert((type->tp_flags & Py_TPFLAGS_READYING) == 0);

    type->tp_flags |= Py_TPFLAGS_READYING;

#ifdef Py_TRACE_REFS
    /* PyType_Ready is the closest thing we have to a choke point
     * for type objects, so is the best place I can think of to try
     * to get type objects into the doubly-linked list of all objects.
     * Still, not all type objects go thru PyType_Ready.
     */
    _Py_AddToAllObjects((PyObject *)type, 0);
#endif

    /* Initialize tp_base (defaults to BaseObject unless that's us) */
    base = type->tp_base;
    if (base == NULL && type != &PyBaseObject_Type) {
        base = type->tp_base = &PyBaseObject_Type;
        Py_INCREF(base);
    }

    /* Now the only way base can still be NULL is if type is
     * &PyBaseObject_Type.
     */

    /* Initialize the base class */
    if (base && base->tp_dict == NULL) {
        if (PyType_Ready(base) < 0)
            goto error;
    }

    /* Initialize ob_type if NULL.      This means extensions that want to be
       compilable separately on Windows can call PyType_Ready() instead of
       initializing the ob_type field of their type objects. */
    /* The test for base != NULL is really unnecessary, since base is only
       NULL when type is &PyBaseObject_Type, and we know its ob_type is
       not NULL (it's initialized to &PyType_Type).      But coverity doesn't
       know that. */
    if (Py_TYPE(type) == NULL && base != NULL)
        Py_TYPE(type) = Py_TYPE(base);

    /* Initialize tp_bases */
    bases = type->tp_bases;
    if (bases == NULL) {
        if (base == NULL)
            bases = PyTuple_New(0);
        else
            bases = PyTuple_Pack(1, base);
        if (bases == NULL)
            goto error;
        type->tp_bases = bases;
    }

    /* Initialize tp_dict */
    dict = type->tp_dict;
    if (dict == NULL) {
        dict = PyDict_New();
        if (dict == NULL)
            goto error;
        type->tp_dict = dict;
    }

    /* Add type-specific descriptors to tp_dict */
    if (add_operators(type) < 0)
        goto error;
    if (type->tp_methods != NULL) {
        if (add_methods(type, type->tp_methods) < 0)
            goto error;
    }
    if (type->tp_members != NULL) {
        if (add_members(type, type->tp_members) < 0)
            goto error;
    }
    if (type->tp_getset != NULL) {
        if (add_getset(type, type->tp_getset) < 0)
            goto error;
    }

    /* Calculate method resolution order */
    if (mro_internal(type) < 0) {
        goto error;
    }

    /* Inherit special flags from dominant base */
    if (type->tp_base != NULL)
        inherit_special(type, type->tp_base);

    /* Initialize tp_dict properly */
    bases = type->tp_mro;
    assert(bases != NULL);
    assert(PyTuple_Check(bases));
    n = PyTuple_GET_SIZE(bases);
    for (i = 1; i < n; i++) {
        PyObject *b = PyTuple_GET_ITEM(bases, i);
        if (PyType_Check(b))
            inherit_slots(type, (PyTypeObject *)b);
    }

    /* Sanity check for tp_free. */
    if (PyType_IS_GC(type) && (type->tp_flags & Py_TPFLAGS_BASETYPE) &&
        (type->tp_free == NULL || type->tp_free == PyObject_Del)) {
        /* This base class needs to call tp_free, but doesn't have
         * one, or its tp_free is for non-gc'ed objects.
         */
        PyErr_Format(PyExc_TypeError, "type '%.100s' participates in "
                     "gc and is a base type but has inappropriate "
                     "tp_free slot",
                     type->tp_name);
        goto error;
    }

    /* if the type dictionary doesn't contain a __doc__, set it from
       the tp_doc slot.
     */
    if (PyDict_GetItemString(type->tp_dict, "__doc__") == NULL) {
        if (type->tp_doc != NULL) {
            PyObject *doc = PyString_FromString(type->tp_doc);
            if (doc == NULL)
                goto error;
            PyDict_SetItemString(type->tp_dict, "__doc__", doc);
            Py_DECREF(doc);
        } else {
            PyDict_SetItemString(type->tp_dict,
                                 "__doc__", Py_None);
        }
    }

    /* Some more special stuff */
    base = type->tp_base;
    if (base != NULL) {
        if (type->tp_as_number == NULL)
            type->tp_as_number = base->tp_as_number;
        if (type->tp_as_sequence == NULL)
            type->tp_as_sequence = base->tp_as_sequence;
        if (type->tp_as_mapping == NULL)
            type->tp_as_mapping = base->tp_as_mapping;
        if (type->tp_as_buffer == NULL)
            type->tp_as_buffer = base->tp_as_buffer;
    }

    /* Link into each base class's list of subclasses */
    bases = type->tp_bases;
    n = PyTuple_GET_SIZE(bases);
    for (i = 0; i < n; i++) {
        PyObject *b = PyTuple_GET_ITEM(bases, i);
        if (PyType_Check(b) &&
            add_subclass((PyTypeObject *)b, type) < 0)
            goto error;
    }

    /* All done -- set the ready flag */
    assert(type->tp_dict != NULL);
    type->tp_flags =
        (type->tp_flags & ~Py_TPFLAGS_READYING) | Py_TPFLAGS_READY;
    return 0;

  error:
    type->tp_flags &= ~Py_TPFLAGS_READYING;
    return -1;
}