Address SF bug #442813. The sequence getitem wrappers should do

interpretation of negative indices, since neither the sq_*item slots
nor the slot_ wrappers do this.  (Slices are a different story, there
the size wrapping is done too early.)

diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index c49275bc792d7a1ca58871a381cd6cb6a56af622..f2e6f4d4c91b663658e09212cfee4b47ab4e34d5 100644 (file)
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1661,8 +1661,43 @@ static struct wrapperbase tab_imul_int[] = {
        {0}
 };
 
+static int
+getindex(PyObject *self, PyObject *arg)
+{
+       int i;
+
+       i = PyInt_AsLong(arg);
+       if (i == -1 && PyErr_Occurred())
+               return -1;
+       if (i < 0) {
+               PySequenceMethods *sq = self->ob_type->tp_as_sequence;
+               if (sq && sq->sq_length) {
+                       int n = (*sq->sq_length)(self);
+                       if (n < 0)
+                               return -1;
+                       i += n;
+               }
+       }
+       return i;
+}
+
+static PyObject *
+wrap_sq_item(PyObject *self, PyObject *args, void *wrapped)
+{
+       intargfunc func = (intargfunc)wrapped;
+       PyObject *arg;
+       int i;
+
+       if (!PyArg_ParseTuple(args, "O", &arg))
+               return NULL;
+       i = getindex(self, arg);
+       if (i == -1 && PyErr_Occurred())
+               return NULL;
+       return (*func)(self, i);
+}
+
 static struct wrapperbase tab_getitem_int[] = {
-       {"__getitem__", (wrapperfunc)wrap_intargfunc,
+       {"__getitem__", (wrapperfunc)wrap_sq_item,
         "x.__getitem__(i) <==> x[i]"},
        {0}
 };
@@ -1685,13 +1720,16 @@ static struct wrapperbase tab_getslice[] = {
 };
 
 static PyObject *
-wrap_intobjargproc(PyObject *self, PyObject *args, void *wrapped)
+wrap_sq_setitem(PyObject *self, PyObject *args, void *wrapped)
 {
        intobjargproc func = (intobjargproc)wrapped;
        int i, res;
-       PyObject *value;
+       PyObject *arg, *value;
 
-       if (!PyArg_ParseTuple(args, "iO", &i, &value))
+       if (!PyArg_ParseTuple(args, "OO", &arg, &value))
+               return NULL;
+       i = getindex(self, arg);
+       if (i == -1 && PyErr_Occurred())
                return NULL;
        res = (*func)(self, i, value);
        if (res == -1 && PyErr_Occurred())
@@ -1701,12 +1739,16 @@ wrap_intobjargproc(PyObject *self, PyObject *args, void *wrapped)
 }
 
 static PyObject *
-wrap_delitem_int(PyObject *self, PyObject *args, void *wrapped)
+wrap_sq_delitem(PyObject *self, PyObject *args, void *wrapped)
 {
        intobjargproc func = (intobjargproc)wrapped;
        int i, res;
+       PyObject *arg;
 
-       if (!PyArg_ParseTuple(args, "i", &i))
+       if (!PyArg_ParseTuple(args, "O", &arg))
+               return NULL;
+       i = getindex(self, arg);
+       if (i == -1 && PyErr_Occurred())
                return NULL;
        res = (*func)(self, i, NULL);
        if (res == -1 && PyErr_Occurred())
@@ -1716,9 +1758,9 @@ wrap_delitem_int(PyObject *self, PyObject *args, void *wrapped)
 }
 
 static struct wrapperbase tab_setitem_int[] = {
-       {"__setitem__", (wrapperfunc)wrap_intobjargproc,
+       {"__setitem__", (wrapperfunc)wrap_sq_setitem,
         "x.__setitem__(i, y) <==> x[i]=y"},
-       {"__delitem__", (wrapperfunc)wrap_delitem_int,
+       {"__delitem__", (wrapperfunc)wrap_sq_delitem,
         "x.__delitem__(y) <==> del x[y]"},
        {0}
 };