* Specialize ins1() into app1() for appends. Saves several unnecessary

  steps and further improves the speed of list append.

* Add guards to the list iterator length method to handle corner cases.

diff --git a/Objects/listobject.c b/Objects/listobject.c
index 890c279dbd93ae460e5a245a7e7cf458c4f4b623..9368e897ccb8b8162da18f960a6ea32c1079c4f8 100644 (file)
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -180,6 +180,26 @@ PyList_Insert(PyObject *op, int where, PyObject *newitem)
        return ins1((PyListObject *)op, where, newitem);
 }
 
+static int
+app1(PyListObject *self, PyObject *v)
+{
+       int n = PyList_GET_SIZE(self);
+
+       assert (v != NULL);
+       if (n == INT_MAX) {
+               PyErr_SetString(PyExc_OverflowError,
+                       "cannot add more objects to list");
+               return -1;
+       }
+
+       if (list_resize(self, n+1) == -1)
+               return -1;
+
+       Py_INCREF(v);
+       PyList_SET_ITEM(self, n, v);
+       return 0;
+}
+
 int
 PyList_Append(PyObject *op, PyObject *newitem)
 {
@@ -187,8 +207,11 @@ PyList_Append(PyObject *op, PyObject *newitem)
                PyErr_BadInternalCall();
                return -1;
        }
-       return ins1((PyListObject *)op,
-               (int) ((PyListObject *)op)->ob_size, newitem);
+       if (newitem == NULL) {
+               PyErr_BadInternalCall();
+               return -1;
+       }
+       return app1((PyListObject *)op, newitem);
 }
 
 /* Methods */
@@ -726,7 +749,7 @@ listextend(PyListObject *self, PyObject *b)
                if (i < mn)
                        PyList_SET_ITEM(self, i, item); /* steals ref */
                else {
-                       int status = ins1(self, self->ob_size, item);
+                       int status = app1(self, item);
                        Py_DECREF(item);  /* append creates a new ref */
                        if (status < 0)
                                goto error;
@@ -2684,8 +2707,12 @@ listiter_next(listiterobject *it)
 static int
 listiter_len(listiterobject *it)
 {
-       if (it->it_seq)
-               return PyList_GET_SIZE(it->it_seq) - it->it_index;
+       int len;
+       if (it->it_seq) {
+               len = PyList_GET_SIZE(it->it_seq) - it->it_index;
+               if (len >= 0)
+                       return len;
+       }
        return 0;
 }
 
@@ -2799,7 +2826,10 @@ listreviter_next(listreviterobject *it)
 static int
 listreviter_len(listreviterobject *it)
 {
-       return it->it_index + 1;
+       int len = it->it_index + 1;
+       if (it->it_seq == NULL || PyList_GET_SIZE(it->it_seq) < len)
+               return 0;
+       return len;
 }
 
 static PySequenceMethods listreviter_as_sequence = {