Include/cpython/abstract.h

#ifndef Py_CPYTHON_ABSTRACTOBJECT_H
#  error "this header file must not be included directly"
#endif

/* === Vectorcall protocol (PEP 590) ============================= */

// PyVectorcall_NARGS() is exported as a function for the stable ABI.
// Here (when we are not using the stable ABI), the name is overridden to
// call a static inline function for best performance.
static inline Py_ssize_t
_PyVectorcall_NARGS(size_t n)
{
    return n & ~PY_VECTORCALL_ARGUMENTS_OFFSET;
}
#define PyVectorcall_NARGS(n) _PyVectorcall_NARGS(n)

PyAPI_FUNC(vectorcallfunc) PyVectorcall_Function(PyObject *callable);

/* Same as PyObject_Vectorcall except that keyword arguments are passed as
   dict, which may be NULL if there are no keyword arguments. */
PyAPI_FUNC(PyObject *) PyObject_VectorcallDict(
    PyObject *callable,
    PyObject *const *args,
    size_t nargsf,
    PyObject *kwargs);

PyAPI_FUNC(PyObject *) PyObject_CallOneArg(PyObject *func, PyObject *arg);

static inline PyObject *
PyObject_CallMethodNoArgs(PyObject *self, PyObject *name)
{
    size_t nargsf = 1 | PY_VECTORCALL_ARGUMENTS_OFFSET;
    return PyObject_VectorcallMethod(name, &self, nargsf, _Py_NULL);
}

static inline PyObject *
PyObject_CallMethodOneArg(PyObject *self, PyObject *name, PyObject *arg)
{
    PyObject *args[2] = {self, arg};
    size_t nargsf = 2 | PY_VECTORCALL_ARGUMENTS_OFFSET;
    assert(arg != NULL);
    return PyObject_VectorcallMethod(name, args, nargsf, _Py_NULL);
}

/* Guess the size of object 'o' using len(o) or o.__length_hint__().
   If neither of those return a non-negative value, then return the default
   value.  If one of the calls fails, this function returns -1. */
PyAPI_FUNC(Py_ssize_t) PyObject_LengthHint(PyObject *o, Py_ssize_t);

/* === Sequence protocol ================================================ */

/* Assume tp_as_sequence and sq_item exist and that 'i' does not
   need to be corrected for a negative index. */
#define PySequence_ITEM(o, i)\
    ( Py_TYPE(o)->tp_as_sequence->sq_item((o), (i)) )

/* === Mapping protocol ================================================= */

// Convert Python int to Py_ssize_t. Do nothing if the argument is None.
// Cannot be moved to the internal C API: used by Argument Clinic.
PyAPI_FUNC(int) _Py_convert_optional_to_ssize_t(PyObject *, void *);

// Same as PyNumber_Index but can return an instance of a subclass of int.
// Cannot be moved to the internal C API: used by Argument Clinic.
PyAPI_FUNC(PyObject *) _PyNumber_Index(PyObject *o);