Stop duplicating code and handle slice indices consistently and correctly

wrt to ssize_t.

Include/sliceobject.h

@@ -30,6 +30,7 @@ PyAPI_DATA(PyTypeObject) PySlice_Type;
 
 PyAPI_FUNC(PyObject *) PySlice_New(PyObject* start, PyObject* stop,
                                   PyObject* step);
+PyAPI_FUNC(PyObject *) _PySlice_FromIndices(Py_ssize_t start, Py_ssize_t stop);
 PyAPI_FUNC(int) PySlice_GetIndices(PySliceObject *r, Py_ssize_t length,
                                   Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step);
 PyAPI_FUNC(int) PySlice_GetIndicesEx(PySliceObject *r, Py_ssize_t length,

Objects/abstract.c

@@ -1247,24 +1247,6 @@ PySequence_GetItem(PyObject *s, Py_ssize_t i)
 	return type_error("unindexable object");
 }
 
-static PyObject *
-sliceobj_from_ssizet_ssizet(Py_ssize_t i, Py_ssize_t j)
-{
-	PyObject *start, *end, *slice;
-	start = PyInt_FromSsize_t(i);
-	if (!start)
-		return NULL;
-	end = PyInt_FromSsize_t(j);
-	if (!end) {
-		Py_DECREF(start);
-		return NULL;
-	}
-	slice = PySlice_New(start, end, NULL);
-	Py_DECREF(start);
-	Py_DECREF(end);
-	return slice;
-}
-
 PyObject *
 PySequence_GetSlice(PyObject *s, Py_ssize_t i1, Py_ssize_t i2)
 {
@@ -1289,7 +1271,7 @@ PySequence_GetSlice(PyObject *s, Py_ssize_t i1, Py_ssize_t i2)
 		return m->sq_slice(s, i1, i2);
 	} else if ((mp = s->ob_type->tp_as_mapping) && mp->mp_subscript) {
 		PyObject *res;
-		PyObject *slice = sliceobj_from_ssizet_ssizet(i1, i2);
+		PyObject *slice = _PySlice_FromIndices(i1, i2);
 		if (!slice)
 			return NULL;
 		res = mp->mp_subscript(s, slice);
@@ -1381,7 +1363,7 @@ PySequence_SetSlice(PyObject *s, Py_ssize_t i1, Py_ssize_t i2, PyObject *o)
 		return m->sq_ass_slice(s, i1, i2, o);
 	} else if ((mp = s->ob_type->tp_as_mapping) && mp->mp_ass_subscript) {
 		int res;
-		PyObject *slice = sliceobj_from_ssizet_ssizet(i1, i2);
+		PyObject *slice = _PySlice_FromIndices(i1, i2);
 		if (!slice)
 			return -1;
 		res = mp->mp_ass_subscript(s, slice, o);

Objects/classobject.c

@@ -1127,27 +1127,6 @@ instance_item(PyInstanceObject *inst, Py_ssize_t i)
 	return res;
 }
 
-static PyObject *
-sliceobj_from_intint(Py_ssize_t i, Py_ssize_t j)
-{
-	PyObject *start, *end, *res;
-
-	start = PyInt_FromLong((long)i);
-	if (!start)
-		return NULL;
-
-	end = PyInt_FromLong((long)j);
-	if (!end) {
-		Py_DECREF(start);
-		return NULL;
-	}
-	res = PySlice_New(start, end, NULL);
-	Py_DECREF(start);
-	Py_DECREF(end);
-	return res;
-}
-
-
 static PyObject *
 instance_slice(PyInstanceObject *inst, Py_ssize_t i, Py_ssize_t j)
 {
@@ -1168,7 +1147,7 @@ instance_slice(PyInstanceObject *inst, Py_ssize_t i, Py_ssize_t j)
 		func = instance_getattr(inst, getitemstr);
 		if (func == NULL)
 			return NULL;
-		arg = Py_BuildValue("(N)", sliceobj_from_intint(i, j));
+		arg = Py_BuildValue("(N)", _PySlice_FromIndices(i, j));
 	} else
 		arg = Py_BuildValue("(nn)", i, j);
 
@@ -1239,7 +1218,7 @@ instance_ass_slice(PyInstanceObject *inst, Py_ssize_t i, Py_ssize_t j, PyObject
 				return -1;
 
 			arg = Py_BuildValue("(N)",
-					    sliceobj_from_intint(i, j));
+					    _PySlice_FromIndices(i, j));
 		} else
 			arg = Py_BuildValue("(nn)", i, j);
 	}
@@ -1260,7 +1239,7 @@ instance_ass_slice(PyInstanceObject *inst, Py_ssize_t i, Py_ssize_t j, PyObject
 				return -1;
 
 			arg = Py_BuildValue("(NO)",
-					    sliceobj_from_intint(i, j), value);
+					    _PySlice_FromIndices(i, j), value);
 		} else
 			arg = Py_BuildValue("(nnO)", i, j, value);
 	}

Objects/sliceobject.c

@@ -79,6 +79,25 @@ PySlice_New(PyObject *start, PyObject *stop, PyObject *step)
 	return (PyObject *) obj;
 }
 
+PyObject *
+_PySlice_FromIndices(Py_ssize_t istart, Py_ssize_t istop)
+{
+	PyObject *start, *end, *slice;
+	start = PyInt_FromSsize_t(istart);
+	if (!start)
+		return NULL;
+	end = PyInt_FromSsize_t(istop);
+	if (!end) {
+		Py_DECREF(start);
+		return NULL;
+	}
+
+	slice = PySlice_New(start, end, NULL);
+	Py_DECREF(start);
+	Py_DECREF(end);
+	return slice;
+}
+
 int
 PySlice_GetIndices(PySliceObject *r, Py_ssize_t length,
                    Py_ssize_t *start, Py_ssize_t *stop, Py_ssize_t *step)