Crashers of the day: Py_CLEAR must be used when there is a chance that the

amaury.forgeotdarc · amaury.forgeotdarc · commit 7bdd036ef1fd · 2008-02-16T14:34:57.000Z
function can be called recursively. This was discussed in issue1020188. In python codebase, all occurrences of Py_[X]DECREF(xxx->yyy) are suspect, except when they appear in tp_new or tp_dealloc functions, or when the member cannot be of a user-defined class. Note that tp_init is not safe. I do have a (crashing) example for every changed line. Is it worth adding them to the test suite? Example: class SpecialStr(str): def __del__(self): s.close() import cStringIO s = cStringIO.StringIO(SpecialStr("text")) s.close() # Segfault git-svn-id: http://svn.python.org/projects/python/trunk@60860 6015fed2-1504-0410-9fe1-9d1591cc4771
diff --git a/Modules/_struct.c b/Modules/_struct.c
@@ -1471,7 +1471,7 @@ s_init(PyObject *self, PyObject *args, PyObject *kwds)
 		return -1;
 
 	Py_INCREF(o_format);
-	Py_XDECREF(soself->s_format);
+	Py_CLEAR(soself->s_format);
 	soself->s_format = o_format;
 
 	ret = prepare_s(soself);
diff --git a/Modules/cStringIO.c b/Modules/cStringIO.c
@@ -575,8 +575,7 @@ newOobject(int  size) {
 
 static PyObject *
 I_close(Iobject *self, PyObject *unused) {
-        Py_XDECREF(self->pbuf);
-        self->pbuf = NULL;
+        Py_CLEAR(self->pbuf);
         self->buf = NULL;
 
         self->pos = self->string_size = 0;
