Objects/descrobject.c (part 4)

Source:

cpython 3.14 @ ab2d84fe1023/Objects/descrobject.c ↗

This annotation covers classmethod/staticmethod descriptor access and the slot wrapper mechanism that exposes C-level tp_* slots as Python methods. See objects_descrobject_detail through objects_descrobject3_detail for PyMethodDescr, PyGetSetDescr, and property.

Map

Lines	Symbol	Role
1-80	classmethod_get	__get__ for classmethod: bind to the class
81-160	staticmethod_get	__get__ for staticmethod: return the raw function
161-300	PyWrapperDescrObject	Wraps a C tp_* slot as a Python method
301-450	slot_tp_richcompare	Generated wrapper for __eq__, __lt__, etc.
451-600	wrapperdescr_call	Call a slot wrapper: call the C function via d_wrapped

Reading

classmethod.__get__

// CPython: Objects/descrobject.c:48 classmethod_get
static PyObject *
classmethod_get(PyObject *self, PyObject *obj, PyObject *type)
{
    /* classmethod bound to the class (or its metaclass) */
    PyClassMethodObject *cm = (PyClassMethodObject *)self;
    if (type == NULL) type = Py_TYPE(obj);
    if (Py_TYPE(cm->cm_callable)->tp_descr_get != NULL) {
        /* Inner callable is itself a descriptor (e.g. another classmethod) */
        return Py_TYPE(cm->cm_callable)->tp_descr_get(
            cm->cm_callable, type, (PyObject *)Py_TYPE(type));
    }
    return PyMethod_New(cm->cm_callable, type);
}

MyClass.my_classmethod returns a bound method where self is MyClass (the class object, not an instance).

staticmethod.__get__

// CPython: Objects/descrobject.c:100 staticmethod_get
static PyObject *
staticmethod_get(PyObject *self, PyObject *obj, PyObject *type)
{
    /* Returns the raw function — no binding */
    PyStaticMethodObject *sm = (PyStaticMethodObject *)self;
    if (Py_TYPE(sm->sm_callable)->tp_descr_get != NULL) {
        return Py_TYPE(sm->sm_callable)->tp_descr_get(
            sm->sm_callable, NULL, type);
    }
    return Py_NewRef(sm->sm_callable);
}

staticmethod is a descriptor only in that it implements __get__ (returns the function unmodified). It does not pass self or cls.

PyWrapperDescrObject

// CPython: Objects/descrobject.c:180 PyWrapperDescrObject
typedef struct {
    PyDescrObject d_common;
    PyWrapperBase *d_wrapped;  /* the C function pointer */
    int d_base;                /* offset into PyObject for the slot */
} PyWrapperDescrObject;

When Python calls int.__add__(1, 2), it calls wrapperdescr_call which extracts the tp_as_number->nb_add slot from int's type and calls it.

slot_tp_richcompare

// CPython: Objects/typeobject.c:7800 slot_tp_richcompare
/* This C function is installed as tp_richcompare for types that define
   __eq__, __lt__, etc. in Python.  It looks up the appropriate __*__
   method and calls it. */
static PyObject *
slot_tp_richcompare(PyObject *self, PyObject *other, int op)
{
    PyObject *stack[2] = {self, other};
    PyObject *meth = lookup_method(self, richcmp_methods[op]);
    if (meth == NULL) return Py_NewRef(Py_NotImplemented);
    return vectorcall_method(meth, stack, 2);
}

The richcmp_methods array maps Py_EQ → __eq__, Py_LT → __lt__, etc.

gopy notes

classmethod.__get__ is objects.ClassMethodGet in objects/method.go. staticmethod.__get__ is objects.StaticMethodGet. PyWrapperDescrObject is objects.WrapperDescr which stores a Go function value as d_wrapped. slot_tp_richcompare is generated in objects/type.go as a dispatch through the type's __eq__ / __lt__ methods.