Doc/ext/cycle-gc.c

   1 #include "Python.h"
   2
   3 typedef struct {
   4     PyObject_HEAD
   5     PyObject *container;
   6 } MyObject;
   7
   8 static int
   9 my_traverse(MyObject *self, visitproc visit, void *arg)
  10 {
  11     if (self->container != NULL)
  12         return visit(self->container, arg);
  13     else
  14         return 0;
  15 }
  16
  17 static int
  18 my_clear(MyObject *self)
  19 {
  20     Py_XDECREF(self->container);
  21     self->container = NULL;
  22
  23     return 0;
  24 }
  25
  26 static void
  27 my_dealloc(MyObject *self)
  28 {
  29     PyObject_GC_UnTrack((PyObject *) self);
  30     Py_XDECREF(self->container);
  31     PyObject_GC_Del(self);
  32 }
  33
  34 static PyTypeObject
  35 MyObject_Type = {
  36     PyObject_HEAD_INIT(NULL)
  37     0,
  38     "MyObject",
  39     sizeof(MyObject),
  40     0,
  41     (destructor)my_dealloc,     /* tp_dealloc */
  42     0,                          /* tp_print */
  43     0,                          /* tp_getattr */
  44     0,                          /* tp_setattr */
  45     0,                          /* tp_compare */
  46     0,                          /* tp_repr */
  47     0,                          /* tp_as_number */
  48     0,                          /* tp_as_sequence */
  49     0,                          /* tp_as_mapping */
  50     0,                          /* tp_hash */
  51     0,                          /* tp_call */
  52     0,                          /* tp_str */
  53     0,                          /* tp_getattro */
  54     0,                          /* tp_setattro */
  55     0,                          /* tp_as_buffer */
  56     Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,
  57     0,                          /* tp_doc */
  58     (traverseproc)my_traverse,  /* tp_traverse */
  59     (inquiry)my_clear,          /* tp_clear */
  60     0,                          /* tp_richcompare */
  61     0,                          /* tp_weaklistoffset */
  62 };
  63
  64 /* This constructor should be made accessible from Python. */
  65 static PyObject *
  66 new_object(PyObject *unused, PyObject *args)
  67 {
  68     PyObject *container = NULL;
  69     MyObject *result = NULL;
  70
  71     if (PyArg_ParseTuple(args, "|O:new_object", &container)) {
  72         result = PyObject_GC_New(MyObject, &MyObject_Type);
  73         if (result != NULL) {
  74             result->container = container;
  75             PyObject_GC_Track(result);
  76         }
  77     }
  78     return (PyObject *) result;
  79 }