1 files changed, 79 insertions, 0 deletions
diff --git a/Doc/ext/cycle-gc.c b/Doc/ext/cycle-gc.c
new file mode 100644
index 0000000..c3a0caa
--- /dev/null
+++ b/Doc/ext/cycle-gc.c
@@ -0,0 +1,79 @@
+#include "Python.h"
+
+typedef struct {
+    PyObject_HEAD
+    PyObject *container;
+} MyObject;
+
+static int
+my_traverse(MyObject *self, visitproc visit, void *arg)
+{
+    if (self->container != NULL)
+        return visit(self->container, arg);
+    else
+        return 0;
+}
+
+static int
+my_clear(MyObject *self)
+{
+    Py_XDECREF(self->container);
+    self->container = NULL;
+
+    return 0;
+}
+
+static void
+my_dealloc(MyObject *self)
+{
+    PyObject_GC_UnTrack((PyObject *) self);
+    Py_XDECREF(self->container);
+    PyObject_GC_Del(self);
+}
+
+static PyTypeObject
+MyObject_Type = {
+    PyObject_HEAD_INIT(NULL)
+    0,
+    "MyObject",
+    sizeof(MyObject),
+    0,
+    (destructor)my_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 | Py_TPFLAGS_HAVE_GC,
+    0,                          /* tp_doc */
+    (traverseproc)my_traverse,  /* tp_traverse */
+    (inquiry)my_clear,          /* tp_clear */
+    0,                          /* tp_richcompare */
+    0,                          /* tp_weaklistoffset */
+};
+
+/* This constructor should be made accessible from Python. */
+static PyObject *
+new_object(PyObject *unused, PyObject *args)
+{
+    PyObject *container = NULL;
+    MyObject *result = NULL;
+
+    if (PyArg_ParseTuple(args, "|O:new_object", &container)) {
+        result = PyObject_GC_New(MyObject, &MyObject_Type);
+        if (result != NULL) {
+            result->container = container;
+            PyObject_GC_Track(result);
+        }
+    }
+    return (PyObject *) result;
+}