Issue #1811: Improve accuracy and consistency of true division for integers.
diff --git a/Objects/intobject.c b/Objects/intobject.c
index b03ef70..8fe31bf 100644
--- a/Objects/intobject.c
+++ b/Objects/intobject.c
@@ -645,16 +645,35 @@
}
static PyObject *
-int_true_divide(PyObject *v, PyObject *w)
+int_true_divide(PyIntObject *x, PyIntObject *y)
{
+ long xi, yi;
/* If they aren't both ints, give someone else a chance. In
particular, this lets int/long get handled by longs, which
underflows to 0 gracefully if the long is too big to convert
to float. */
- if (PyInt_Check(v) && PyInt_Check(w))
- return PyFloat_Type.tp_as_number->nb_true_divide(v, w);
- Py_INCREF(Py_NotImplemented);
- return Py_NotImplemented;
+ CONVERT_TO_LONG(x, xi);
+ CONVERT_TO_LONG(y, yi);
+ if (yi == 0) {
+ PyErr_SetString(PyExc_ZeroDivisionError,
+ "division by zero");
+ return NULL;
+ }
+ if (xi == 0)
+ return PyFloat_FromDouble(yi < 0 ? -0.0 : 0.0);
+
+#define WIDTH_OF_ULONG (CHAR_BIT*SIZEOF_LONG)
+#if DBL_MANT_DIG < WIDTH_OF_ULONG
+ if ((xi >= 0 ? 0UL + xi : 0UL - xi) >> DBL_MANT_DIG ||
+ (yi >= 0 ? 0UL + yi : 0UL - yi) >> DBL_MANT_DIG)
+ /* Large x or y. Use long integer arithmetic. */
+ return PyLong_Type.tp_as_number->nb_true_divide(
+ (PyObject *)x, (PyObject *)y);
+ else
+#endif
+ /* Both ints can be exactly represented as doubles. Do a
+ floating-point division. */
+ return PyFloat_FromDouble((double)xi / (double)yi);
}
static PyObject *
@@ -1355,7 +1374,7 @@
0, /*nb_inplace_xor*/
0, /*nb_inplace_or*/
(binaryfunc)int_div, /* nb_floor_divide */
- int_true_divide, /* nb_true_divide */
+ (binaryfunc)int_true_divide, /* nb_true_divide */
0, /* nb_inplace_floor_divide */
0, /* nb_inplace_true_divide */
(unaryfunc)int_int, /* nb_index */