SF patch #1200018: Restore GC support to set objects

Reverts 1.26 and 1.27.
And adds cycle testing.

3 files changed, 36 insertions, 7 deletions

diff --git a/Lib/test/test_set.py b/Lib/test/test_set.py
index 900d8e4..26e38ab 100644
--- a/Lib/test/test_set.py
+++ b/Lib/test/test_set.py
@@ -202,6 +202,16 @@ class TestJointOps(unittest.TestCase):
         self.assertNotEqual(id(t), id(newt))
         self.assertEqual(t.value + 1, newt.value)
 
+    def test_gc(self):
+        # Create a nest of cycles to exercise overall ref count check
+        class A:
+            pass
+        s = set(A() for i in xrange(1000))
+        for elem in s:
+            elem.cycle = s
+            elem.sub = elem
+            elem.set = set([elem])
+
 class TestSet(TestJointOps):
     thetype = set
 
diff --git a/Misc/NEWS b/Misc/NEWS
index 28b9c2a..b4e626f 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,8 @@ What's New in Python 2.4.2a
 Core and builtins
 -----------------
 
+- Fix garbage collection for set and frozenset objects.  SF patch #1200018.
+
 - It is now safe to call PyGILState_Release() before
   PyEval_InitThreads() (note that if there is reason to believe there
   are multiple threads around you still must call PyEval_InitThreads()
diff --git a/Objects/setobject.c b/Objects/setobject.c
index 8ef671e..f9448c9 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -114,12 +114,21 @@ frozenset_dict_wrapper(PyObject *d)
 static void
 set_dealloc(PySetObject *so)
 {
+	PyObject_GC_UnTrack(so);
 	if (so->weakreflist != NULL)
 		PyObject_ClearWeakRefs((PyObject *) so);
 	Py_XDECREF(so->data);
 	so->ob_type->tp_free(so);
 }
 
+static int
+set_traverse(PySetObject *so, visitproc visit, void *arg)
+{
+	if (so->data)
+		return visit(so->data, arg);
+	return 0;
+}
+
 static PyObject *
 set_iter(PySetObject *so)
 {
@@ -757,6 +766,14 @@ set_clear(PySetObject *so)
 
 PyDoc_STRVAR(clear_doc, "Remove all elements from this set.");
 
+static int
+set_tp_clear(PySetObject *so)
+{
+	PyDict_Clear(so->data);
+	so->hash = -1;
+	return 0;
+}
+
 static PyObject *
 set_add(PySetObject *so, PyObject *item)
 {
@@ -1007,11 +1024,11 @@ PyTypeObject PySet_Type = {
 	PyObject_GenericGetAttr,	/* tp_getattro */
 	0,				/* tp_setattro */
 	0,				/* tp_as_buffer */
-	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_CHECKTYPES |
+	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_CHECKTYPES |
 		Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_WEAKREFS,	/* tp_flags */
 	set_doc,			/* tp_doc */
-	0,				/* tp_traverse */
-	0,				/* tp_clear */
+	(traverseproc)set_traverse,	/* tp_traverse */
+	(inquiry)set_tp_clear,		/* tp_clear */
 	(richcmpfunc)set_richcompare,	/* tp_richcompare */
 	offsetof(PySetObject, weakreflist),	/* tp_weaklistoffset */
 	(getiterfunc)set_iter,		/* tp_iter */
@@ -1027,7 +1044,7 @@ PyTypeObject PySet_Type = {
 	(initproc)set_init,		/* tp_init */
 	PyType_GenericAlloc,		/* tp_alloc */
 	set_new,			/* tp_new */
-	PyObject_Del,			/* tp_free */
+	PyObject_GC_Del,		/* tp_free */
 };
 
 /* frozenset object ********************************************************/
@@ -1102,10 +1119,10 @@ PyTypeObject PyFrozenSet_Type = {
 	PyObject_GenericGetAttr,	/* tp_getattro */
 	0,				/* tp_setattro */
 	0,				/* tp_as_buffer */
-	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_CHECKTYPES |
+	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | Py_TPFLAGS_CHECKTYPES |
 		Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_WEAKREFS,	/* tp_flags */
 	frozenset_doc,			/* tp_doc */
-	0,				/* tp_traverse */
+	(traverseproc)set_traverse,	/* tp_traverse */
 	0,				/* tp_clear */
 	(richcmpfunc)set_richcompare,	/* tp_richcompare */
 	offsetof(PySetObject, weakreflist),	/* tp_weaklistoffset */
@@ -1122,5 +1139,5 @@ PyTypeObject PyFrozenSet_Type = {
 	0,				/* tp_init */
 	PyType_GenericAlloc,		/* tp_alloc */
 	frozenset_new,			/* tp_new */
-	PyObject_Del,			/* tp_free */
+	PyObject_GC_Del,		/* tp_free */
 };