Ignore the references to the dummy objects used as deleted keys

in dicts and sets when computing the total number of references.

Include/object.h

@@ -578,6 +578,9 @@ environment the global variable trick is not safe.)
 PyAPI_DATA(Py_ssize_t) _Py_RefTotal;
 PyAPI_FUNC(void) _Py_NegativeRefcount(const char *fname,
 					    int lineno, PyObject *op);
+PyAPI_FUNC(PyObject *) _PyDict_Dummy(void);
+PyAPI_FUNC(PyObject *) _PySet_Dummy(void);
+PyAPI_FUNC(Py_ssize_t) _Py_GetRefTotal(void);
 #define _Py_INC_REFTOTAL	_Py_RefTotal++
 #define _Py_DEC_REFTOTAL	_Py_RefTotal--
 #define _Py_REF_DEBUG_COMMA	,

Objects/dictobject.c

@@ -115,6 +115,14 @@ equally good collision statistics, needed less code & used less memory.
 /* Object used as dummy key to fill deleted entries */
 static PyObject *dummy = NULL; /* Initialized by first call to newdictobject() */
 
+#ifdef Py_REF_DEBUG
+PyObject *
+_PyDict_Dummy(void)
+{
+	return dummy;
+}
+#endif
+
 /* forward declarations */
 static dictentry *
 lookdict_string(dictobject *mp, PyObject *key, long hash);

Objects/object.c

@@ -5,7 +5,24 @@
 
 #ifdef Py_REF_DEBUG
 Py_ssize_t _Py_RefTotal;
-#endif
+
+Py_ssize_t
+_Py_GetRefTotal(void)
+{
+	PyObject *o;
+	Py_ssize_t total = _Py_RefTotal;
+        /* ignore the references to the dummy object of the dicts and sets
+           because they are not reliable and not useful (now that the
+           hash table code is well-tested) */
+	o = _PyDict_Dummy();
+	if (o != NULL)
+		total -= o->ob_refcnt;
+	o = _PySet_Dummy();
+	if (o != NULL)
+		total -= o->ob_refcnt;
+	return total;
+}
+#endif /* Py_REF_DEBUG */
 
 int Py_DivisionWarningFlag;
 

Objects/setobject.c

@@ -16,6 +16,14 @@
 /* Object used as dummy key to fill deleted entries */
 static PyObject *dummy = NULL; /* Initialized by first call to make_new_set() */
 
+#ifdef Py_REF_DEBUG
+PyObject *
+_PySet_Dummy(void)
+{
+	return dummy;
+}
+#endif
+
 #define INIT_NONZERO_SET_SLOTS(so) do {				\
 	(so)->table = (so)->smalltable;				\
 	(so)->mask = PySet_MINSIZE - 1;				\

Python/pythonrun.c

@@ -34,7 +34,7 @@
 #else /* Py_REF_DEBUG */
 #define PRINT_TOTAL_REFS() fprintf(stderr,				\
 				   "[%" PY_FORMAT_SIZE_T "d refs]\n",	\
-				   _Py_RefTotal)
+				   _Py_GetRefTotal())
 #endif
 
 extern char *Py_GetPath(void);

Python/sysmodule.c

@@ -604,10 +604,9 @@ sys_getrefcount(PyObject *self, PyObject *arg)
 static PyObject *
 sys_gettotalrefcount(PyObject *self)
 {
-	return PyInt_FromSsize_t(_Py_RefTotal);
+	return PyInt_FromSsize_t(_Py_GetRefTotal());
 }
-
-#endif /* Py_TRACE_REFS */
+#endif /* Py_REF_DEBUG */
 
 PyDoc_STRVAR(getrefcount_doc,
 "getrefcount(object) -> integer\n\