Merge from jh

14 files changed, 274 insertions, 81 deletions

diff --git a/ChangeLog b/ChangeLog
index 1e2820a..cbeb111 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,56 @@
 	* psycopg/connection_type.c: merged get_backend_pid() method
 	by Casey Duncan.
 
+2008-07-23  James Henstridge  <james@jamesh.id.au>
+
+	* psycopg/lobject_type.c (lobject_setup): use
+	FORMAT_CODE_PY_SSIZE_T in Dprintf() call for 64-bit compatibility
+	when using Python 2.5 or later.
+	(lobject_dealloc): same here.
+
+2008-07-18  James Henstridge  <james@jamesh.id.au>
+
+	* psycopg/adapter_qstring.c (qstring_traverse): add cyclic GC
+	traversal for quoted string adapters.
+
+	* psycopg/adapter_pboolean.c (pboolean_traverse): add cyclic GC
+	traversal for boolean adapters.
+
+	* psycopg/adapter_mxdatetime.c (mxdatetime_traverse): add cyclic
+	GC traversal for mxdatetime adapters.
+
+	* psycopg/adapter_datetime.c (pydatetime_traverse): add cyclic GC
+	traversal for datetime adapters.
+
+2008-07-01  James Henstridge  <james@jamesh.id.au>
+
+	* psycopg/adapter_binary.c (binary_traverse): add cyclic GC
+	traversal for binary adapters.
+
+	* psycopg/adapter_asis.c (asis_traverse): add cyclic GC traversal
+	for AsIs adapters.
+
+	* psycopg/adapter_list.c (list_traverse): add cyclic GC traversal
+	for list adapters.
+
+2008-05-28  James Henstridge  <james@jamesh.id.au>
+
+	* psycopg/cursor_type.c (cursor_setup): incref before setting
+	attributes, to make things GC-safe.
+
+	* psycopg/cursor_int.c (curs_reset): make clearing of description
+	and casts attributes GC-safe.
+
+	* psycopg/typecast.c (typecast_traverse): implement cyclic GC
+	traversal for typecasters.
+
+	* psycopg/connection_type.c:
+	* psycopg/cursor_type.c: add support for cyclic GC traversal (no
+	support for clearing).
+
+	* psycopg/python.h: add definitions for Py_CLEAR() and Py_VISIT()
+	for compatibility with old versions of Python.
+
 2008-06-28  Federico Di Gregorio <fog@initd.org>
 
 	* setup.py: fixed problem with spaces in pg_config path.
diff --git a/psycopg/adapter_asis.c b/psycopg/adapter_asis.c
index 0e64eb5..2ad6ef5 100644
--- a/psycopg/adapter_asis.c
+++ b/psycopg/adapter_asis.c
@@ -96,8 +96,8 @@ asis_setup(asisObject *self, PyObject *obj)
         self, ((PyObject *)self)->ob_refcnt
       );
 
+    Py_INCREF(obj);
     self->wrapped = obj;
-    Py_INCREF(self->wrapped);
 
     Dprintf("asis_setup: good asis object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -106,12 +106,19 @@ asis_setup(asisObject *self, PyObject *obj)
     return 0;
 }
 
+static int
+asis_traverse(asisObject *self, visitproc visit, void *arg)
+{
+    Py_VISIT(self->wrapped);
+    return 0;
+}
+
 static void
 asis_dealloc(PyObject* obj)
 {
     asisObject *self = (asisObject *)obj;
 
-    Py_XDECREF(self->wrapped);
+    Py_CLEAR(self->wrapped);
 
     Dprintf("asis_dealloc: deleted asis object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -141,7 +148,7 @@ asis_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static void
 asis_del(PyObject* self)
 {
-    PyObject_Del(self);
+    PyObject_GC_Del(self);
 }
 
 static PyObject *
@@ -183,10 +190,10 @@ PyTypeObject asisType = {
     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*/
     asisType_doc, /*tp_doc*/
 
-    0,          /*tp_traverse*/
+    (traverseproc)asis_traverse, /*tp_traverse*/
     0,          /*tp_clear*/
 
     0,          /*tp_richcompare*/
diff --git a/psycopg/adapter_binary.c b/psycopg/adapter_binary.c
index 1fb9d40..306c9e5 100644
--- a/psycopg/adapter_binary.c
+++ b/psycopg/adapter_binary.c
@@ -257,8 +257,8 @@ binary_setup(binaryObject *self, PyObject *str)
 
     self->buffer = NULL;
     self->conn = NULL;
+    Py_INCREF(str);
     self->wrapped = str;
-    Py_INCREF(self->wrapped);
 
     Dprintf("binary_setup: good binary object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -266,14 +266,25 @@ binary_setup(binaryObject *self, PyObject *str)
     return 0;
 }
 
+static int
+binary_traverse(PyObject *obj, visitproc visit, void *arg)
+{
+    binaryObject *self = (binaryObject *)obj;
+
+    Py_VISIT(self->wrapped);
+    Py_VISIT(self->buffer);
+    Py_VISIT(self->conn);
+    return 0;
+}
+
 static void
 binary_dealloc(PyObject* obj)
 {
     binaryObject *self = (binaryObject *)obj;
 
-    Py_XDECREF(self->wrapped);
-    Py_XDECREF(self->buffer);
-    Py_XDECREF(self->conn);
+    Py_CLEAR(self->wrapped);
+    Py_CLEAR(self->buffer);
+    Py_CLEAR(self->conn);
 
     Dprintf("binary_dealloc: deleted binary object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -303,7 +314,7 @@ binary_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static void
 binary_del(PyObject* self)
 {
-    PyObject_Del(self);
+    PyObject_GC_Del(self);
 }
 
 static PyObject *
@@ -341,11 +352,11 @@ PyTypeObject binaryType = {
     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*/
 
     binaryType_doc, /*tp_doc*/
 
-    0,          /*tp_traverse*/
+    binary_traverse, /*tp_traverse*/
     0,          /*tp_clear*/
 
     0,          /*tp_richcompare*/
diff --git a/psycopg/adapter_datetime.c b/psycopg/adapter_datetime.c
index e9fcc1e..bf337ee 100644
--- a/psycopg/adapter_datetime.c
+++ b/psycopg/adapter_datetime.c
@@ -131,8 +131,8 @@ pydatetime_setup(pydatetimeObject *self, PyObject *obj, int type)
         self, ((PyObject *)self)->ob_refcnt);
 
     self->type = type;
+    Py_INCREF(obj);
     self->wrapped = obj;
-    Py_INCREF(self->wrapped);
 
     Dprintf("pydatetime_setup: good pydatetime object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -140,12 +140,21 @@ pydatetime_setup(pydatetimeObject *self, PyObject *obj, int type)
     return 0;
 }
 
+static int
+pydatetime_traverse(PyObject *obj, visitproc visit, void *arg)
+{
+    pydatetimeObject *self = (pydatetimeObject *)obj;
+
+    Py_VISIT(self->wrapped);
+    return 0;
+}
+
 static void
 pydatetime_dealloc(PyObject* obj)
 {
     pydatetimeObject *self = (pydatetimeObject *)obj;
 
-    Py_XDECREF(self->wrapped);
+    Py_CLEAR(self->wrapped);
 
     Dprintf("mpydatetime_dealloc: deleted pydatetime object at %p, "
             "refcnt = " FORMAT_CODE_PY_SSIZE_T, obj, obj->ob_refcnt);
@@ -174,7 +183,7 @@ pydatetime_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static void
 pydatetime_del(PyObject* self)
 {
-    PyObject_Del(self);
+    PyObject_GC_Del(self);
 }
 
 static PyObject *
@@ -213,11 +222,11 @@ PyTypeObject pydatetimeType = {
     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*/
 
     pydatetimeType_doc, /*tp_doc*/
 
-    0,          /*tp_traverse*/
+    pydatetime_traverse, /*tp_traverse*/
     0,          /*tp_clear*/
 
     0,          /*tp_richcompare*/
diff --git a/psycopg/adapter_list.c b/psycopg/adapter_list.c
index b6022bd..2d26c39 100644
--- a/psycopg/adapter_list.c
+++ b/psycopg/adapter_list.c
@@ -108,9 +108,9 @@ list_prepare(listObject *self, PyObject *args)
        reference to it; we'll need it during the recursive adapt() call (the
        encoding is here for a future expansion that will make .getquoted()
        work even without a connection to the backend. */
-    Py_XDECREF(self->connection);
+    Py_CLEAR(self->connection);
+    Py_INCREF(conn);
     self->connection = (PyObject*)conn;
-    Py_INCREF(self->connection);
 
     Py_INCREF(Py_None);
     return Py_None;
@@ -169,8 +169,8 @@ list_setup(listObject *self, PyObject *obj, const char *enc)
     if (enc) self->encoding = strdup(enc);
 
     self->connection = NULL;
+    Py_INCREF(obj);
     self->wrapped = obj;
-    Py_INCREF(self->wrapped);
 
     Dprintf("list_setup: good list object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -179,13 +179,23 @@ list_setup(listObject *self, PyObject *obj, const char *enc)
     return 0;
 }
 
+static int
+list_traverse(PyObject *obj, visitproc visit, void *arg)
+{
+    listObject *self = (listObject *)obj;
+
+    Py_VISIT(self->wrapped);
+    Py_VISIT(self->connection);
+    return 0;
+}
+
 static void
 list_dealloc(PyObject* obj)
 {
     listObject *self = (listObject *)obj;
 
-    Py_XDECREF(self->wrapped);
-    Py_XDECREF(self->connection);
+    Py_CLEAR(self->wrapped);
+    Py_CLEAR(self->connection);
     if (self->encoding) free(self->encoding);
 
     Dprintf("list_dealloc: deleted list object at %p, "
@@ -215,7 +225,7 @@ list_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static void
 list_del(PyObject* self)
 {
-    PyObject_Del(self);
+    PyObject_GC_Del(self);
 }
 
 static PyObject *
@@ -253,11 +263,11 @@ PyTypeObject listType = {
     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*/
 
     listType_doc, /*tp_doc*/
 
-    0,          /*tp_traverse*/
+    list_traverse, /*tp_traverse*/
     0,          /*tp_clear*/
 
     0,          /*tp_richcompare*/
diff --git a/psycopg/adapter_mxdatetime.c b/psycopg/adapter_mxdatetime.c
index 48ead92..92b2181 100644
--- a/psycopg/adapter_mxdatetime.c
+++ b/psycopg/adapter_mxdatetime.c
@@ -152,8 +152,8 @@ mxdatetime_setup(mxdatetimeObject *self, PyObject *obj, int type)
       );
 
     self->type = type;
+    Py_INCREF(obj);
     self->wrapped = obj;
-    Py_INCREF(self->wrapped);
 
     Dprintf("mxdatetime_setup: good mxdatetime object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -162,12 +162,21 @@ mxdatetime_setup(mxdatetimeObject *self, PyObject *obj, int type)
     return 0;
 }
 
+static int
+mxdatetime_traverse(PyObject *obj, visitproc visit, void *arg)
+{
+    mxdatetimeObject *self = (mxdatetimeObject *)obj;
+
+    Py_VISIT(self->wrapped);
+    return 0;
+}
+
 static void
 mxdatetime_dealloc(PyObject* obj)
 {
     mxdatetimeObject *self = (mxdatetimeObject *)obj;
 
-    Py_XDECREF(self->wrapped);
+    Py_CLEAR(self->wrapped);
 
     Dprintf("mxdatetime_dealloc: deleted mxdatetime object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -198,7 +207,7 @@ mxdatetime_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static void
 mxdatetime_del(PyObject* self)
 {
-    PyObject_Del(self);
+    PyObject_GC_Del(self);
 }
 
 static PyObject *
@@ -237,11 +246,11 @@ PyTypeObject mxdatetimeType = {
     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*/
 
     mxdatetimeType_doc, /*tp_doc*/
 
-    0,          /*tp_traverse*/
+    mxdatetime_traverse, /*tp_traverse*/
     0,          /*tp_clear*/
 
     0,          /*tp_richcompare*/
diff --git a/psycopg/adapter_pboolean.c b/psycopg/adapter_pboolean.c
index 05d1d04..1ce80dd 100644
--- a/psycopg/adapter_pboolean.c
+++ b/psycopg/adapter_pboolean.c
@@ -106,8 +106,8 @@ pboolean_setup(pbooleanObject *self, PyObject *obj)
         self, ((PyObject *)self)->ob_refcnt
       );
 
+    Py_INCREF(obj);
     self->wrapped = obj;
-    Py_INCREF(self->wrapped);
 
     Dprintf("pboolean_setup: good pboolean object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -116,12 +116,21 @@ pboolean_setup(pbooleanObject *self, PyObject *obj)
     return 0;
 }
 
+static int
+pboolean_traverse(PyObject *obj, visitproc visit, void *arg)
+{
+    pbooleanObject *self = (pbooleanObject *)obj;
+
+    Py_VISIT(self->wrapped);
+    return 0;
+}
+
 static void
 pboolean_dealloc(PyObject* obj)
 {
     pbooleanObject *self = (pbooleanObject *)obj;
 
-    Py_XDECREF(self->wrapped);
+    Py_CLEAR(self->wrapped);
 
     Dprintf("pboolean_dealloc: deleted pboolean object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -151,7 +160,7 @@ pboolean_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static void
 pboolean_del(PyObject* self)
 {
-    PyObject_Del(self);
+    PyObject_GC_Del(self);
 }
 
 static PyObject *
@@ -194,10 +203,10 @@ PyTypeObject pbooleanType = {
     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*/
     pbooleanType_doc, /*tp_doc*/
 
-    0,          /*tp_traverse*/
+    pboolean_traverse, /*tp_traverse*/
     0,          /*tp_clear*/
 
     0,          /*tp_richcompare*/
diff --git a/psycopg/adapter_qstring.c b/psycopg/adapter_qstring.c
index f469fe4..e1eb4e1 100644
--- a/psycopg/adapter_qstring.c
+++ b/psycopg/adapter_qstring.c
@@ -213,10 +213,10 @@ qstring_prepare(qstringObject *self, PyObject *args)
         Dprintf("qstring_prepare: set encoding to %s", conn->encoding);
     }
 
-    Py_XDECREF(self->conn);
+    Py_CLEAR(self->conn);
     if (conn) {
+        Py_INCREF(conn);
         self->conn = (PyObject*)conn;
-        Py_INCREF(self->conn);
     }
 
     Py_INCREF(Py_None);
@@ -277,8 +277,8 @@ qstring_setup(qstringObject *self, PyObject *str, const char *enc)
     /* FIXME: remove this orrible strdup */
     if (enc) self->encoding = strdup(enc);
 
+    Py_INCREF(str);
     self->wrapped = str;
-    Py_INCREF(self->wrapped);
 
     Dprintf("qstring_setup: good qstring object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -287,14 +287,25 @@ qstring_setup(qstringObject *self, PyObject *str, const char *enc)
     return 0;
 }
 
+static int
+qstring_traverse(PyObject *obj, visitproc visit, void *arg)
+{
+    qstringObject *self = (qstringObject *)obj;
+
+    Py_VISIT(self->wrapped);
+    Py_VISIT(self->buffer);
+    Py_VISIT(self->conn);
+    return 0;
+}
+
 static void
 qstring_dealloc(PyObject* obj)
 {
     qstringObject *self = (qstringObject *)obj;
 
-    Py_XDECREF(self->wrapped);
-    Py_XDECREF(self->buffer);
-    Py_XDECREF(self->conn);
+    Py_CLEAR(self->wrapped);
+    Py_CLEAR(self->buffer);
+    Py_CLEAR(self->conn);
 
     if (self->encoding) free(self->encoding);
 
@@ -327,7 +338,7 @@ qstring_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static void
 qstring_del(PyObject* self)
 {
-    PyObject_Del(self);
+    PyObject_GC_Del(self);
 }
 
 static PyObject *
@@ -366,11 +377,11 @@ PyTypeObject qstringType = {
     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*/
 
     qstringType_doc, /*tp_doc*/
 
-    0,          /*tp_traverse*/
+    qstring_traverse, /*tp_traverse*/
     0,          /*tp_clear*/
 
     0,          /*tp_richcompare*/
diff --git a/psycopg/connection_type.c b/psycopg/connection_type.c
index 35b116a..e03cf3d 100644
--- a/psycopg/connection_type.c
+++ b/psycopg/connection_type.c
@@ -465,11 +465,11 @@ 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));
 
@@ -501,7 +501,7 @@ connection_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 static void
 connection_del(PyObject* self)
 {
-    PyObject_Del(self);
+    PyObject_GC_Del(self);
 }
 
 static PyObject *
@@ -512,6 +512,18 @@ 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 */
 
@@ -545,10 +557,10 @@ 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*/
diff --git a/psycopg/cursor_int.c b/psycopg/cursor_int.c
index 483e2c4..9d3c861 100644
--- a/psycopg/cursor_int.c
+++ b/psycopg/cursor_int.c
@@ -34,15 +34,19 @@
 void
 curs_reset(cursorObject *self)
 {
+    PyObject *tmp;
+
     /* initialize some variables to default values */
     self->notuples = 1;
     self->rowcount = -1;
     self->row = 0;
 
-    Py_XDECREF(self->description);
+    tmp = self->description;
     Py_INCREF(Py_None);
     self->description = Py_None;
+    Py_XDECREF(tmp);
 
-    Py_XDECREF(self->casts);
+    tmp = self->casts;
     self->casts = NULL;
+    Py_XDECREF(tmp);
 }
diff --git a/psycopg/cursor_type.c b/psycopg/cursor_type.c
index 5b0cd02..8000816 100644
--- a/psycopg/cursor_type.c
+++ b/psycopg/cursor_type.c
@@ -1590,8 +1590,8 @@ cursor_setup(cursorObject *self, connectionObject *conn, const char *name)
             "argument 1 must be subclass of psycopg2._psycopg.connection");
         return 1;
     } */
+    Py_INCREF(conn);
     self->conn = conn;
-    Py_INCREF((PyObject*)self->conn);
 
     self->closed = 0;
     self->mark = conn->mark;
@@ -1607,6 +1607,7 @@ cursor_setup(cursorObject *self, connectionObject *conn, const char *name)
     self->string_types = NULL;
     self->binary_types = NULL;
 
+    Py_INCREF(Py_None);
     self->description = Py_None;
     Py_INCREF(Py_None);
     self->pgstatus = Py_None;
@@ -1614,11 +1615,10 @@ cursor_setup(cursorObject *self, connectionObject *conn, const char *name)
     self->tuple_factory = Py_None;
     Py_INCREF(Py_None);
     self->query = Py_None;
-    Py_INCREF(Py_None);
 
     /* default tzinfo factory */
+    Py_INCREF(pyPsycopgTzFixedOffsetTimezone);
     self->tzinfo_factory = pyPsycopgTzFixedOffsetTimezone;
-    Py_INCREF(self->tzinfo_factory);
 
     Dprintf("cursor_setup: good cursor object at %p, refcnt = "
         FORMAT_CODE_PY_SSIZE_T,
@@ -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((PyObject *)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*/
diff --git a/psycopg/lobject_type.c b/psycopg/lobject_type.c
index ca0a82b..c4386bf 100644
--- a/psycopg/lobject_type.c
+++ b/psycopg/lobject_type.c
@@ -282,8 +282,8 @@ lobject_setup(lobjectObject *self, connectionObject *conn,
     if (lobject_open(self, conn, oid, mode, new_oid, new_file) == -1)
         return -1;
 
-   Dprintf("lobject_setup: good lobject object at %p, refcnt = %d",
-       self, ((PyObject *)self)->ob_refcnt);
+   Dprintf("lobject_setup: good lobject object at %p, refcnt = "
+           FORMAT_CODE_PY_SSIZE_T, self, ((PyObject *)self)->ob_refcnt);
    Dprintf("lobject_setup:    oid = %d, fd = %d", self->oid, self->fd);
    return 0;
 }
@@ -297,8 +297,8 @@ lobject_dealloc(PyObject* obj)
         PyErr_Print();
     Py_XDECREF((PyObject*)self->conn);
 
-    Dprintf("lobject_dealloc: deleted lobject object at %p, refcnt = %d",
-            obj, obj->ob_refcnt);
+    Dprintf("lobject_dealloc: deleted lobject object at %p, refcnt = "
+            FORMAT_CODE_PY_SSIZE_T, obj, obj->ob_refcnt);
 
     obj->ob_type->tp_free(obj);
 }
diff --git a/psycopg/python.h b/psycopg/python.h
index 84bacaa..13d6ce7 100644
--- a/psycopg/python.h
+++ b/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) */
diff --git a/psycopg/typecast.c b/psycopg/typecast.c
index 86e2149..f786960 100644
--- a/psycopg/typecast.c
+++ b/psycopg/typecast.c
@@ -382,11 +382,28 @@ typecast_dealloc(PyObject *obj)
 {
     typecastObject *self = (typecastObject*)obj;
 
-    Py_XDECREF(self->values);
-    Py_XDECREF(self->name);
-    Py_XDECREF(self->pcast);
+    Py_CLEAR(self->values);
+    Py_CLEAR(self->name);
+    Py_CLEAR(self->pcast);
 
-    PyObject_Del(self);
+    obj->ob_type->tp_free(obj);
+}
+
+static int
+typecast_traverse(PyObject *obj, visitproc visit, void *arg)
+{
+    typecastObject *self = (typecastObject*)obj;
+
+    Py_VISIT(self->values);
+    Py_VISIT(self->name);
+    Py_VISIT(self->pcast);
+    return 0;
+}
+
+static void
+typecast_del(void *self)
+{
+    PyObject_GC_Del(self);
 }
 
 static PyObject *
@@ -427,10 +444,11 @@ PyTypeObject typecastType = {
     0,          /*tp_setattro*/
     0,          /*tp_as_buffer*/
 
-    Py_TPFLAGS_HAVE_RICHCOMPARE, /*tp_flags*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_RICHCOMPARE |
+      Py_TPFLAGS_HAVE_GC, /*tp_flags*/
     "psycopg type-casting object", /*tp_doc*/
 
-    0,          /*tp_traverse*/
+    typecast_traverse, /*tp_traverse*/
     0,          /*tp_clear*/
 
     typecast_richcompare, /*tp_richcompare*/
@@ -454,7 +472,7 @@ PyTypeObject typecastType = {
     0, /*tp_init*/
     0, /*tp_alloc  will be set to PyType_GenericAlloc in module init*/
     0, /*tp_new*/
-    0, /*tp_free  Low-level free-memory routine */
+    typecast_del, /*tp_free  Low-level free-memory routine */
     0,          /*tp_is_gc For PyObject_IS_GC */
     0,          /*tp_bases*/
     0,          /*tp_mro method resolution order */
@@ -468,7 +486,7 @@ typecast_new(PyObject *name, PyObject *values, PyObject *cast, PyObject *base)
 {
     typecastObject *obj;
 
-    obj = PyObject_NEW(typecastObject, &typecastType);
+    obj = PyObject_GC_New(typecastObject, &typecastType);
     if (obj == NULL) return NULL;
 
     Dprintf("typecast_new: new type at = %p, refcnt = " FORMAT_CODE_PY_SSIZE_T,
@@ -498,6 +516,8 @@ typecast_new(PyObject *name, PyObject *values, PyObject *cast, PyObject *base)
         obj->pcast = cast;
     }
 
+    PyObject_GC_Track(obj);
+
     Dprintf("typecast_new: typecast object created at %p", obj);
 
     return (PyObject *)obj;