Index: Modules/posixmodule.c
===================================================================
--- Modules/posixmodule.c   (revision 88757)
+++ Modules/posixmodule.c   (working copy)
@@ -2336,7 +2336,136 @@
 }
 #endif /* MS_WINDOWS */

+typedef struct {
+  PyObject_HEAD
+  DIR * dirp;
+  PyObject *oname;
+  int arg_is_unicode;
+} xlistdir_Iter;

+static PyObject *
+posix_XListDirIter_iter(PyObject *self)
+{
+    Py_INCREF(self);
+    return self;
+}
+
+static void posix_XListDirIter_dealloc(PyObject *obj)
+{
+    xlistdir_Iter *self = (xlistdir_Iter *)obj;
+    if(self->dirp){
+        Py_BEGIN_ALLOW_THREADS
+        closedir(self->dirp);
+        Py_END_ALLOW_THREADS
+        self->dirp = NULL;
+    }
+    Py_XDECREF(self->oname);
+}
+
+PyObject* posix_XListDirIter_iternext(PyObject *obj)
+{
+    PyObject *v;
+    struct dirent* ep;
+    xlistdir_Iter *self = (xlistdir_Iter *)obj;
+    errno = 0;
+    for(;;) {
+        Py_BEGIN_ALLOW_THREADS
+        ep = readdir(self->dirp);
+        Py_END_ALLOW_THREADS
+        if (ep == NULL) {
+            if (errno == 0) {
+                break;
+            } else {
+                posix_error_with_allocated_filename(self->oname);
+                return NULL;
+            }
+        }
+        if (ep->d_name[0] == '.' &&
+            (NAMLEN(ep) == 1 ||
+             (ep->d_name[1] == '.' && NAMLEN(ep) == 2)))
+            continue;
+        if (self->arg_is_unicode)
+            v = PyUnicode_DecodeFSDefaultAndSize(ep->d_name, NAMLEN(ep));
+        else
+            v = PyBytes_FromStringAndSize(ep->d_name, NAMLEN(ep));
+        if (v == NULL) {
+            break;
+        }
+        return v;
+        }
+    return NULL;
+}
+
+static PyTypeObject posix_XListDirIterType =
+{
+    PyObject_HEAD_INIT(NULL)
+    "posix._XListDirIter",            /*tp_name*/
+    sizeof(xlistdir_Iter),       /*tp_basicsize*/
+    0,                         /*tp_itemsize*/
+    posix_XListDirIter_dealloc,   /*tp_dealloc*/
+    0,                         /*tp_print*/
+    0,                         /*tp_getattr*/
+    0,                         /*tp_setattr*/
+    0,                                /*tp_compare*/
+    0,                         /*tp_repr*/
+    0,                         /*tp_as_number*/
+    0,                         /*tp_as_sequence*/
+    0,                         /*tp_as_mapping*/
+    0,                         /*tp_hash */
+    0,                         /*tp_call*/
+    0,                         /*tp_str*/
+    0,                         /*tp_getattro*/
+    0,                         /*tp_setattro*/
+    0,                         /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT,
+    "Internal posix xlistdir iterator object.",           /* tp_doc */
+    0,                         /*tp_traverse*/
+    0,                          /*tp_clear*/
+    0,                         /*tp_richcompare*/
+    0,                         /*tp_weaklistoffset*/
+    posix_XListDirIter_iter,
+    posix_XListDirIter_iternext
+};
+
+static PyObject *
+posix_xlistdir(PyObject *self, PyObject *args)
+{
+    char *name;
+    PyObject *v;
+    xlistdir_Iter *iter;
+
+    iter = PyObject_New(xlistdir_Iter, &posix_XListDirIterType);
+    if (!iter) return NULL;
+    /* I'm not sure if it's strictly necessary. */
+      if (!PyObject_Init((PyObject *)iter, &posix_XListDirIterType)) {
+        Py_DECREF(iter);
+        return NULL;
+      }
+    iter->arg_is_unicode = 1;
+    iter->oname = NULL;
+
+    errno = 0;
+    /* v is never read, so it does not need to be initialized yet. */
+    if (!PyArg_ParseTuple(args, "|U:xlistdir", &v)) {
+        iter->arg_is_unicode = 0;
+        PyErr_Clear();
+    }
+    if (!PyArg_ParseTuple(args, "|O&:xlistdir", PyUnicode_FSConverter, &iter->oname))
+        return NULL;
+    if (iter->oname == NULL) { /* Default arg: "." */
+        iter->oname = PyBytes_FromString(".");
+    }
+    name = PyBytes_AsString(iter->oname);
+    Py_BEGIN_ALLOW_THREADS
+    iter->dirp = opendir(name);
+    Py_END_ALLOW_THREADS
+    if (iter->dirp == NULL) {
+        return posix_error_with_allocated_filename(iter->oname);
+    }
+    return (PyObject *)iter;
+}
+
+
 PyDoc_STRVAR(posix_listdir__doc__,
 "listdir([path]) -> list_of_strings\n\n\
 Return a list containing the names of the entries in the directory.\n\
@@ -8684,6 +8813,7 @@
     {"link",            posix_link, METH_VARARGS, posix_link__doc__},
 #endif /* HAVE_LINK */
     {"listdir",         posix_listdir, METH_VARARGS, posix_listdir__doc__},
+    {"xlistdir",   posix_xlistdir, METH_VARARGS, NULL},
 #ifdef HAVE_FDOPENDIR
     {"fdlistdir",       posix_fdlistdir, METH_VARARGS, posix_fdlistdir__doc__},
 #endif