bpo-41342: Convert int.__round__ to Argument Clinic (pythonGH-21549)

Author: serhiy-storchaka

Misc/NEWS.d/next/Core and Builtins/2020-07-19-15-40-52.bpo-41342.RRk_m_.rst

@@ -0,0 +1 @@
+:func:`round` with integer argument is now faster (9--60%).

Objects/clinic/longobject.c.h

@@ -5155,10 +5155,22 @@ _PyLong_DivmodNear(PyObject *a, PyObject *b)
     return NULL;
 }
 
+/*[clinic input]
+int.__round__
+
+    ndigits as o_ndigits: object = NULL
+    /
+
+Rounding an Integral returns itself.
+
+Rounding with an ndigits argument also returns an integer.
+[clinic start generated code]*/
+
 static PyObject *
-long_round(PyObject *self, PyObject *args)
+int___round___impl(PyObject *self, PyObject *o_ndigits)
+/*[clinic end generated code: output=954fda6b18875998 input=1614cf23ec9e18c3]*/
 {
-    PyObject *o_ndigits=NULL, *temp, *result, *ndigits;
+    PyObject *temp, *result, *ndigits;
 
     /* To round an integer m to the nearest 10**n (n positive), we make use of
      * the divmod_near operation, defined by:
@@ -5174,8 +5186,6 @@ long_round(PyObject *self, PyObject *args)
      *
      *   m - divmod_near(m, 10**n)[1].
      */
-    if (!PyArg_ParseTuple(args, "|O", &o_ndigits))
-        return NULL;
     if (o_ndigits == NULL)
         return long_long(self);
 
@@ -5536,9 +5546,7 @@ static PyMethodDef long_methods[] = {
      "Flooring an Integral returns itself."},
     {"__ceil__",        long_long_meth, METH_NOARGS,
      "Ceiling of an Integral returns itself."},
-    {"__round__",       (PyCFunction)long_round, METH_VARARGS,
-     "Rounding an Integral returns itself.\n"
-     "Rounding with an ndigits argument also returns an integer."},
+    INT___ROUND___METHODDEF
     INT___GETNEWARGS___METHODDEF
     INT___FORMAT___METHODDEF
     INT___SIZEOF___METHODDEF