From 75ccea3777f77f001102493170490874166eb3b2 Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <python@rcn.com>
Date: Wed, 1 Sep 2004 07:02:44 +0000
Subject: [PATCH] SF patch #1020188:  Use Py_CLEAR where necessary to avoid
 crashes (Contributed by Dima Dorfman)

---
 Include/object.h          |  2 +-
 Modules/itertoolsmodule.c |  3 +--
 Objects/enumobject.c      |  5 +----
 Objects/genobject.c       |  3 +--
 Objects/iterobject.c      | 12 ++++--------
 5 files changed, 8 insertions(+), 17 deletions(-)

diff --git a/Include/object.h b/Include/object.h
index 5db4dac0610..258b0744968 100644
--- a/Include/object.h
+++ b/Include/object.h
@@ -623,7 +623,7 @@ PyAPI_FUNC(void) _Py_AddToAllObjects(PyObject *, int force);
 #define Py_CLEAR(op)				\
         do {                            	\
                 if (op) {			\
-                        PyObject *tmp = (op);	\
+                        PyObject *tmp = (PyObject *)(op);	\
                         (op) = NULL;		\
                         Py_DECREF(tmp);		\
                 }				\
diff --git a/Modules/itertoolsmodule.c b/Modules/itertoolsmodule.c
index 21659fbca2e..bf2c49311ff 100644
--- a/Modules/itertoolsmodule.c
+++ b/Modules/itertoolsmodule.c
@@ -250,8 +250,7 @@ _grouper_next(_grouperobject *igo)
 
 	r = gbo->currvalue;
 	gbo->currvalue = NULL;
-	Py_DECREF(gbo->currkey);
-	gbo->currkey = NULL;
+	Py_CLEAR(gbo->currkey);
 
 	return r;
 }
diff --git a/Objects/enumobject.c b/Objects/enumobject.c
index ebe7e7c10f2..aac88dbb012 100644
--- a/Objects/enumobject.c
+++ b/Objects/enumobject.c
@@ -230,10 +230,7 @@ reversed_next(reversedobject *ro)
 			PyErr_Clear();
 	}
 	ro->index = -1;
-	if (ro->seq != NULL) {
-		Py_DECREF(ro->seq);
-		ro->seq = NULL;
-	}
+	Py_CLEAR(ro->seq);
 	return NULL;
 }
 
diff --git a/Objects/genobject.c b/Objects/genobject.c
index 66a5106487a..174c6971373 100644
--- a/Objects/genobject.c
+++ b/Objects/genobject.c
@@ -51,8 +51,7 @@ gen_iternext(PyGenObject *gen)
 	 * may keep a chain of frames alive or it could create a reference
 	 * cycle. */
 	assert(f->f_back != NULL);
-	Py_DECREF(f->f_back);
-	f->f_back = NULL;
+	Py_CLEAR(f->f_back);
 
 	/* If the generator just returned (as opposed to yielding), signal
 	 * that the generator is exhausted. */
diff --git a/Objects/iterobject.c b/Objects/iterobject.c
index 25e4e11154a..b414cc2e9f4 100644
--- a/Objects/iterobject.c
+++ b/Objects/iterobject.c
@@ -192,18 +192,14 @@ calliter_iternext(calliterobject *it)
 				return result; /* Common case, fast path */
 			Py_DECREF(result);
 			if (ok > 0) {
-				Py_DECREF(it->it_callable);
-				it->it_callable = NULL;
-				Py_DECREF(it->it_sentinel);
-				it->it_sentinel = NULL;
+				Py_CLEAR(it->it_callable);
+				Py_CLEAR(it->it_sentinel);
 			}
 		}
 		else if (PyErr_ExceptionMatches(PyExc_StopIteration)) {
 			PyErr_Clear();
-			Py_DECREF(it->it_callable);
-			it->it_callable = NULL;
-			Py_DECREF(it->it_sentinel);
-			it->it_sentinel = NULL;
+			Py_CLEAR(it->it_callable);
+			Py_CLEAR(it->it_sentinel);
 		}
 	}
 	return NULL;