Make StopIteration a sink state. This is done by clearing out the

object references (it_seq for seqiterobject, it_callable and
it_sentinel for calliterobject) when the end of the list is reached.

Also remove the next() methods -- one is supplied automatically by
PyType_Ready() because the tp_iternext slot is set.  That's a good
thing, because the implementation given here was buggy (it never
raised StopIteration).

diff --git a/Objects/iterobject.c b/Objects/iterobject.c
index ce1fe3dc89d969f3e44c1885e85bcda433243786..447edbac503d6e56cc6565b580936e53409bf1fb 100644 (file)
--- a/Objects/iterobject.c
+++ b/Objects/iterobject.c
@@ -5,7 +5,7 @@
 typedef struct {
        PyObject_HEAD
        long      it_index;
-       PyObject *it_seq;
+       PyObject *it_seq; /* Set to NULL when iterator is exhausted */
 } seqiterobject;
 
 PyObject *
@@ -26,31 +26,23 @@ PySeqIter_New(PyObject *seq)
        _PyObject_GC_TRACK(it);
        return (PyObject *)it;
 }
+
 static void
 iter_dealloc(seqiterobject *it)
 {
        _PyObject_GC_UNTRACK(it);
-       Py_DECREF(it->it_seq);
+       Py_XDECREF(it->it_seq);
        PyObject_GC_Del(it);
 }
 
 static int
 iter_traverse(seqiterobject *it, visitproc visit, void *arg)
 {
+       if (it->it_seq == NULL)
+               return 0;
        return visit(it->it_seq, arg);
 }
 
-static PyObject *
-iter_next(seqiterobject *it)
-{
-       PyObject *seq = it->it_seq;
-       PyObject *result = PySequence_GetItem(seq, it->it_index++);
-
-       if (result == NULL && PyErr_ExceptionMatches(PyExc_IndexError))
-               PyErr_SetObject(PyExc_StopIteration, Py_None);
-       return result;
-}
-
 static PyObject *
 iter_getiter(PyObject *it)
 {
@@ -67,6 +59,8 @@ iter_iternext(PyObject *iterator)
        assert(PySeqIter_Check(iterator));
        it = (seqiterobject *)iterator;
        seq = it->it_seq;
+       if (seq == NULL)
+               return NULL;
 
        if (PyTuple_CheckExact(seq)) {
                if (it->it_index < PyTuple_GET_SIZE(seq)) {
@@ -76,31 +70,27 @@ iter_iternext(PyObject *iterator)
                        Py_INCREF(item);
                        return item;
                }
+               Py_DECREF(seq);
+               it->it_seq = NULL;
                return NULL;
        }
        else {
-               PyObject *result = PySequence_ITEM(seq, it->it_index);
-               it->it_index++;
+               PyObject *result = PySequence_GetItem(seq, it->it_index);
                if (result != NULL) {
+                       it->it_index++;
                        return result;
                }
                if (PyErr_ExceptionMatches(PyExc_IndexError) ||
-                       PyErr_ExceptionMatches(PyExc_StopIteration)) {
+                   PyErr_ExceptionMatches(PyExc_StopIteration))
+               {
                        PyErr_Clear();
-                       return NULL;
-               }
-               else {
-                       return NULL;
+                       Py_DECREF(seq);
+                       it->it_seq = NULL;
                }
+               return NULL;
        }
 }
 
-static PyMethodDef iter_methods[] = {
-       {"next",        (PyCFunction)iter_next, METH_NOARGS,
-        "it.next() -- get the next value, or raise StopIteration"},
-       {NULL,          NULL}           /* sentinel */
-};
-
 PyTypeObject PySeqIter_Type = {
        PyObject_HEAD_INIT(&PyType_Type)
        0,                                      /* ob_size */
@@ -131,7 +121,7 @@ PyTypeObject PySeqIter_Type = {
        0,                                      /* tp_weaklistoffset */
        (getiterfunc)iter_getiter,              /* tp_iter */
        (iternextfunc)iter_iternext,            /* tp_iternext */
-       iter_methods,                           /* tp_methods */
+       0,                                      /* tp_methods */
        0,                                      /* tp_members */
        0,                                      /* tp_getset */
        0,                                      /* tp_base */
@@ -144,8 +134,8 @@ PyTypeObject PySeqIter_Type = {
 
 typedef struct {
        PyObject_HEAD
-       PyObject *it_callable;
-       PyObject *it_sentinel;
+       PyObject *it_callable; /* Set to NULL when iterator is exhausted */
+       PyObject *it_sentinel; /* Set to NULL when iterator is exhausted */
 } calliterobject;
 
 PyObject *
@@ -166,8 +156,8 @@ static void
 calliter_dealloc(calliterobject *it)
 {
        _PyObject_GC_UNTRACK(it);
-       Py_DECREF(it->it_callable);
-       Py_DECREF(it->it_sentinel);
+       Py_XDECREF(it->it_callable);
+       Py_XDECREF(it->it_sentinel);
        PyObject_GC_Del(it);
 }
 
@@ -175,47 +165,42 @@ static int
 calliter_traverse(calliterobject *it, visitproc visit, void *arg)
 {
        int err;
-       if ((err = visit(it->it_callable, arg)))
+       if (it->it_callable != NULL && (err = visit(it->it_callable, arg)))
                return err;
-       if ((err = visit(it->it_sentinel, arg)))
+       if (it->it_sentinel != NULL && (err = visit(it->it_sentinel, arg)))
                return err;
        return 0;
 }
 
-static PyObject *
-calliter_next(calliterobject *it, PyObject *args)
-{
-       PyObject *result = PyObject_CallObject(it->it_callable, NULL);
-       if (result != NULL) {
-               if (PyObject_RichCompareBool(result, it->it_sentinel, Py_EQ)) {
-                       PyErr_SetObject(PyExc_StopIteration, Py_None);
-                       Py_DECREF(result);
-                       result = NULL;
-               }
-       }
-       return result;
-}
-
-static PyMethodDef calliter_methods[] = {
-       {"next",        (PyCFunction)calliter_next,     METH_VARARGS,
-        "it.next() -- get the next value, or raise StopIteration"},
-       {NULL,          NULL}           /* sentinel */
-};
-
 static PyObject *
 calliter_iternext(calliterobject *it)
 {
-       PyObject *result = PyObject_CallObject(it->it_callable, NULL);
-       if (result != NULL) {
-               if (PyObject_RichCompareBool(result, it->it_sentinel, Py_EQ)) {
+       if (it->it_callable != NULL) {
+               PyObject *result = PyObject_CallObject(it->it_callable, NULL);
+               if (result != NULL) {
+                       int ok;
+                       ok = PyObject_RichCompareBool(result,
+                                                     it->it_sentinel,
+                                                     Py_EQ);
+                       if (ok == 0)
+                               return result; /* Common case, fast path */
                        Py_DECREF(result);
-                       result = NULL;
+                       if (ok > 0) {
+                               Py_DECREF(it->it_callable);
+                               it->it_callable = NULL;
+                               Py_DECREF(it->it_sentinel);
+                               it->it_sentinel = NULL;
+                       }
+               }
+               else if (PyErr_ExceptionMatches(PyExc_StopIteration)) {
+                       PyErr_Clear();
+                       Py_DECREF(it->it_callable);
+                       it->it_callable = NULL;
+                       Py_DECREF(it->it_sentinel);
+                       it->it_sentinel = NULL;
                }
        }
-       else if (PyErr_ExceptionMatches(PyExc_StopIteration)) {
-               PyErr_Clear();
-       }
-       return result;
+       return NULL;
 }
 
 PyTypeObject PyCallIter_Type = {
@@ -248,7 +233,7 @@ PyTypeObject PyCallIter_Type = {
        0,                                      /* tp_weaklistoffset */
        (getiterfunc)iter_getiter,              /* tp_iter */
        (iternextfunc)calliter_iternext,        /* tp_iternext */
-       calliter_methods,                       /* tp_methods */
+       0,                                      /* tp_methods */
        0,                                      /* tp_members */
        0,                                      /* tp_getset */
        0,                                      /* tp_base */