* psycopg/connection_type.c:

* psycopg/cursor_type.c: add support for cyclic GC.

	* psycopg/python.h: add definitions for Py_CLEAR() and Py_VISIT()
	for compatibility with old versions of Python.

psycopg/connection_type.c

@@ -450,11 +450,11 @@ connection_dealloc(PyObject* obj)
     if (self->encoding) free(self->encoding);
     if (self->critical) free(self->critical);
 
-    Py_XDECREF(self->notice_list);
-    Py_XDECREF(self->notifies);
-    Py_XDECREF(self->async_cursor);
-    Py_XDECREF(self->string_types);
-    Py_XDECREF(self->binary_types);
+    Py_CLEAR(self->notice_list);
+    Py_CLEAR(self->notifies);
+    Py_CLEAR(self->async_cursor);
+    Py_CLEAR(self->string_types);
+    Py_CLEAR(self->binary_types);
 
     pthread_mutex_destroy(&(self->lock));
 
@@ -486,7 +486,7 @@ connection_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static void
 connection_del(PyObject* self)
 {
-    PyObject_Del(self);
+    PyObject_GC_Del(self);
 }
 
 static PyObject *
@@ -497,6 +497,18 @@ connection_repr(connectionObject *self)
         self, self->dsn, self->closed);
 }
 
+static int
+connection_traverse(connectionObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->async_cursor);
+    Py_VISIT(self->notice_list);
+    Py_VISIT(self->notice_filter);
+    Py_VISIT(self->notifies);
+    Py_VISIT(self->string_types);
+    Py_VISIT(self->binary_types);
+    return 0;
+}
+
 
 /* object type */
 
@@ -530,10 +542,10 @@ PyTypeObject connectionType = {
     0,          /*tp_setattro*/
     0,          /*tp_as_buffer*/
 
-    Py_TPFLAGS_DEFAULT|Py_TPFLAGS_BASETYPE, /*tp_flags*/
+    Py_TPFLAGS_DEFAULT|Py_TPFLAGS_BASETYPE|Py_TPFLAGS_HAVE_GC, /*tp_flags*/
     connectionType_doc, /*tp_doc*/
 
-    0,          /*tp_traverse*/
+    (traverseproc)connection_traverse, /*tp_traverse*/
     0,          /*tp_clear*/
 
     0,          /*tp_richcompare*/

psycopg/cursor_type.c

@@ -1634,15 +1634,15 @@ cursor_dealloc(PyObject* obj)
 
     if (self->name) PyMem_Free(self->name);
 
-    Py_XDECREF((PyObject*)self->conn);
-    Py_XDECREF(self->casts);
-    Py_XDECREF(self->description);
-    Py_XDECREF(self->pgstatus);
-    Py_XDECREF(self->tuple_factory);
-    Py_XDECREF(self->tzinfo_factory);
-    Py_XDECREF(self->query);
-    Py_XDECREF(self->string_types);
-    Py_XDECREF(self->binary_types);
+    Py_CLEAR(self->conn);
+    Py_CLEAR(self->casts);
+    Py_CLEAR(self->description);
+    Py_CLEAR(self->pgstatus);
+    Py_CLEAR(self->tuple_factory);
+    Py_CLEAR(self->tzinfo_factory);
+    Py_CLEAR(self->query);
+    Py_CLEAR(self->string_types);
+    Py_CLEAR(self->binary_types);
 
     IFCLEARPGRES(self->pgres);
 
@@ -1675,7 +1675,7 @@ cursor_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static void
 cursor_del(PyObject* self)
 {
-    PyObject_Del(self);
+    PyObject_GC_Del(self);
 }
 
 static PyObject *
@@ -1685,6 +1685,23 @@ cursor_repr(cursorObject *self)
         "<cursor object at %p; closed: %d>", self, self->closed);
 }
 
+static int
+cursor_traverse(cursorObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->conn);
+    Py_VISIT(self->description);
+    Py_VISIT(self->pgstatus);
+    Py_VISIT(self->casts);
+    Py_VISIT(self->caster);
+    Py_VISIT(self->copyfile);
+    Py_VISIT(self->tuple_factory);
+    Py_VISIT(self->tzinfo_factory);
+    Py_VISIT(self->query);
+    Py_VISIT(self->string_types);
+    Py_VISIT(self->binary_types);
+    return 0;
+}
+
 
 /* object type */
 
@@ -1714,10 +1731,11 @@ PyTypeObject cursorType = {
     0,          /*tp_setattro*/
     0,          /*tp_as_buffer*/
 
-    Py_TPFLAGS_DEFAULT|Py_TPFLAGS_BASETYPE|Py_TPFLAGS_HAVE_ITER, /*tp_flags*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_ITER |
+      Py_TPFLAGS_HAVE_GC, /*tp_flags*/
     cursorType_doc, /*tp_doc*/
 
-    0,          /*tp_traverse*/
+    (traverseproc)cursor_traverse, /*tp_traverse*/
     0,          /*tp_clear*/
 
     0,          /*tp_richcompare*/

psycopg/python.h

@@ -41,4 +41,27 @@
 #define freefunc destructor
 #endif
 
+/* Py_VISIT and Py_CLEAR introduced in Python 2.4 */
+#ifndef Py_VISIT
+#define Py_VISIT(op)                                    \
+        do {                                            \
+                if (op) {                               \
+                        int vret = visit((op), arg);    \
+                        if (vret)                       \
+                                return vret;            \
+                }                                       \
+        } while (0)
+#endif
+
+#ifndef Py_CLEAR
+#define Py_CLEAR(op)                            \
+        do {                                    \
+                if (op) {                       \
+                        PyObject *tmp = (PyObject *)(op);       \
+                        (op) = NULL;            \
+                        Py_DECREF(tmp);         \
+                }                               \
+        } while (0)
+#endif
+
 #endif /* !defined(PSYCOPG_PYTHON_H) */