Issue #20437: Fixed 22 potential bugs when deleting objects references.

Misc/NEWS

@@ -10,6 +10,8 @@ Release date: 2014-02-09
 Core and Builtins
 -----------------
 
+- Issue #20437: Fixed 22 potential bugs when deleting objects references.
+
 - Issue #20500: Displaying an exception at interpreter shutdown no longer
   risks triggering an assertion failure in PyObject_Str.
 

Modules/_ctypes/_ctypes.c

@@ -159,10 +159,8 @@ _DictRemover_call(PyObject *myself, PyObject *args, PyObject *kw)
         if (-1 == PyDict_DelItem(self->dict, self->key))
             /* XXX Error context */
             PyErr_WriteUnraisable(Py_None);
-        Py_DECREF(self->key);
+        Py_CLEAR(self->key);
-        self->key = NULL;
+        Py_CLEAR(self->dict);
-        Py_DECREF(self->dict);
-        self->dict = NULL;
     }
     Py_INCREF(Py_None);
     return Py_None;
@@ -2934,10 +2932,8 @@ static int
 PyCFuncPtr_set_restype(PyCFuncPtrObject *self, PyObject *ob)
 {
     if (ob == NULL) {
-        Py_XDECREF(self->restype);
+        Py_CLEAR(self->restype);
-        self->restype = NULL;
+        Py_CLEAR(self->checker);
-        Py_XDECREF(self->checker);
-        self->checker = NULL;
         return 0;
     }
     if (ob != Py_None && !PyType_stgdict(ob) && !PyCallable_Check(ob)) {
@@ -2980,10 +2976,8 @@ PyCFuncPtr_set_argtypes(PyCFuncPtrObject *self, PyObject *ob)
     PyObject *converters;
 
     if (ob == NULL || ob == Py_None) {
-        Py_XDECREF(self->converters);
+        Py_CLEAR(self->converters);
-        self->converters = NULL;
+        Py_CLEAR(self->argtypes);
-        Py_XDECREF(self->argtypes);
-        self->argtypes = NULL;
     } else {
         converters = converters_from_argtypes(ob);
         if (!converters)

Modules/_sqlite/cursor.c

@@ -229,8 +229,7 @@ int pysqlite_build_row_cast_map(pysqlite_Cursor* self)
             if (converter != Py_None) {
                 Py_DECREF(converter);
             }
-            Py_XDECREF(self->row_cast_map);
+            Py_CLEAR(self->row_cast_map);
-            self->row_cast_map = NULL;
 
             return -1;
         }
@@ -447,8 +446,7 @@ PyObject* _pysqlite_query_execute(pysqlite_Cursor* self, int multiple, PyObject*
     self->locked = 1;
     self->reset = 0;
 
-    Py_XDECREF(self->next_row);
+    Py_CLEAR(self->next_row);
-    self->next_row = NULL;
 
     if (multiple) {
         /* executemany() */
@@ -864,8 +862,7 @@ PyObject* pysqlite_cursor_iternext(pysqlite_Cursor *self)
     if (!self->next_row) {
          if (self->statement) {
             (void)pysqlite_statement_reset(self->statement);
-            Py_DECREF(self->statement);
+            Py_CLEAR(self->statement);
-            self->statement = NULL;
         }
         return NULL;
     }

Modules/posixmodule.c

@@ -780,8 +780,7 @@ typedef struct {
 static void
 path_cleanup(path_t *path) {
     if (path->cleanup) {
-        Py_DECREF(path->cleanup);
+        Py_CLEAR(path->cleanup);
-        path->cleanup = NULL;
     }
 }
 

Modules/pyexpat.c

@@ -317,8 +317,7 @@ call_with_frame(PyCodeObject *c, PyObject* func, PyObject* args,
     }
     else {
         if (trace_frame(tstate, f, PyTrace_RETURN, res) < 0) {
-            Py_XDECREF(res);
+            Py_CLEAR(res);
-            res = NULL;
         }
     }
 #else

Modules/readline.c

@@ -281,8 +281,7 @@ set_hook(const char *funcname, PyObject **hook_var, PyObject *args)
     if (!PyArg_ParseTuple(args, buf, &function))
         return NULL;
     if (function == Py_None) {
-        Py_XDECREF(*hook_var);
+        Py_CLEAR(*hook_var);
-        *hook_var = NULL;
     }
     else if (PyCallable_Check(function)) {
         PyObject *tmp = *hook_var;
@@ -885,7 +884,7 @@ on_completion_display_matches_hook(char **matches,
         (r != Py_None && PyLong_AsLong(r) == -1 && PyErr_Occurred())) {
         goto error;
     }
-    Py_XDECREF(r); r=NULL;
+    Py_CLEAR(r);
 
     if (0) {
     error:

Modules/selectmodule.c

@@ -66,8 +66,7 @@ reap_obj(pylist fd2obj[FD_SETSIZE + 1])
 {
     int i;
     for (i = 0; i < FD_SETSIZE + 1 && fd2obj[i].sentinel >= 0; i++) {
-        Py_XDECREF(fd2obj[i].obj);
+        Py_CLEAR(fd2obj[i].obj);
-        fd2obj[i].obj = NULL;
     }
     fd2obj[0].sentinel = -1;
 }

Modules/signalmodule.c

@@ -1305,12 +1305,9 @@ finisignal(void)
         Py_XDECREF(func);
     }
 
-    Py_XDECREF(IntHandler);
+    Py_CLEAR(IntHandler);
-    IntHandler = NULL;
+    Py_CLEAR(DefaultHandler);
-    Py_XDECREF(DefaultHandler);
+    Py_CLEAR(IgnoreHandler);
-    DefaultHandler = NULL;
-    Py_XDECREF(IgnoreHandler);
-    IgnoreHandler = NULL;
 }
 
 

Modules/syslogmodule.c

@@ -197,8 +197,7 @@ syslog_closelog(PyObject *self, PyObject *unused)
 {
     if (S_log_open) {
         closelog();
-        Py_XDECREF(S_ident_o);
+        Py_CLEAR(S_ident_o);
-        S_ident_o = NULL;
         S_log_open = 0;
     }
     Py_INCREF(Py_None);

Modules/zlibmodule.c

@@ -463,8 +463,7 @@ zlib_compressobj_impl(PyModuleDef *module, int level, int method, int wbits, int
     }
 
  error:
-    Py_XDECREF(self);
+    Py_CLEAR(self);
-    self = NULL;
  success:
     return (PyObject*)self;
 }

Objects/tupleobject.c

@@ -879,8 +879,7 @@ _PyTuple_Resize(PyObject **pv, Py_ssize_t newsize)
     _Py_ForgetReference((PyObject *) v);
     /* DECREF items deleted by shrinkage */
     for (i = newsize; i < oldsize; i++) {
-        Py_XDECREF(v->ob_item[i]);
+        Py_CLEAR(v->ob_item[i]);
-        v->ob_item[i] = NULL;
     }
     sv = PyObject_GC_Resize(PyTupleObject, v, newsize);
     if (sv == NULL) {
@@ -926,8 +925,7 @@ PyTuple_Fini(void)
 #if PyTuple_MAXSAVESIZE > 0
     /* empty tuples are used all over the place and applications may
      * rely on the fact that an empty tuple is a singleton. */
-    Py_XDECREF(free_list[0]);
+    Py_CLEAR(free_list[0]);
-    free_list[0] = NULL;
 
     (void)PyTuple_ClearFreeList();
 #endif

Objects/unicodeobject.c

@@ -1902,8 +1902,7 @@ _PyUnicode_ClearStaticStrings()
 {
     _Py_Identifier *tmp, *s = static_strings;
     while (s) {
-        Py_DECREF(s->object);
+        Py_CLEAR(s->object);
-        s->object = NULL;
         tmp = s->next;
         s->next = NULL;
         s = tmp;
@@ -4005,8 +4004,7 @@ make_decode_exception(PyObject **exceptionObject,
     return;
 
 onError:
-    Py_DECREF(*exceptionObject);
+    Py_CLEAR(*exceptionObject);
-    *exceptionObject = NULL;
 }
 
 #ifdef HAVE_MBCS
@@ -6366,8 +6364,7 @@ make_encode_exception(PyObject **exceptionObject,
             goto onError;
         return;
       onError:
-        Py_DECREF(*exceptionObject);
+        Py_CLEAR(*exceptionObject);
-        *exceptionObject = NULL;
     }
 }
 
@@ -8410,8 +8407,7 @@ make_translate_exception(PyObject **exceptionObject,
             goto onError;
         return;
       onError:
-        Py_DECREF(*exceptionObject);
+        Py_CLEAR(*exceptionObject);
-        *exceptionObject = NULL;
     }
 }
 
@@ -13502,8 +13498,7 @@ _PyUnicodeWriter_Finish(_PyUnicodeWriter *writer)
         PyObject *newbuffer;
         newbuffer = resize_compact(writer->buffer, writer->pos);
         if (newbuffer == NULL) {
-            Py_DECREF(writer->buffer);
+            Py_CLEAR(writer->buffer);
-            writer->buffer = NULL;
             return NULL;
         }
         writer->buffer = newbuffer;

Python/ceval.c

@@ -3189,8 +3189,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
                 if (call_trace(tstate->c_tracefunc, tstate->c_traceobj,
                                tstate, f,
                                PyTrace_RETURN, retval)) {
-                    Py_XDECREF(retval);
+                    Py_CLEAR(retval);
-                    retval = NULL;
                     why = WHY_EXCEPTION;
                 }
             }
@@ -3209,8 +3208,7 @@ PyEval_EvalFrameEx(PyFrameObject *f, int throwflag)
             else if (call_trace(tstate->c_profilefunc, tstate->c_profileobj,
                                 tstate, f,
                                 PyTrace_RETURN, retval)) {
-                Py_XDECREF(retval);
+                Py_CLEAR(retval);
-                retval = NULL;
                 /* why = WHY_EXCEPTION; */
             }
         }
@@ -3568,8 +3566,7 @@ PyEval_EvalCodeEx(PyObject *_co, PyObject *globals, PyObject *locals,
     if (co->co_flags & CO_GENERATOR) {
         /* Don't need to keep the reference to f_back, it will be set
          * when the generator is resumed. */
-        Py_XDECREF(f->f_back);
+        Py_CLEAR(f->f_back);
-        f->f_back = NULL;
 
         PCALL(PCALL_GENERATOR);
 

Python/import.c

@@ -349,8 +349,7 @@ _imp_release_lock_impl(PyModuleDef *module)
 void
 _PyImport_Fini(void)
 {
-    Py_XDECREF(extensions);
+    Py_CLEAR(extensions);
-    extensions = NULL;
 #ifdef WITH_THREAD
     if (import_lock != NULL) {
         PyThread_free_lock(import_lock);
@@ -598,8 +597,7 @@ _PyImport_FixupExtensionObject(PyObject *mod, PyObject *name,
             /* Somebody already imported the module,
                likely under a different name.
                XXX this should really not happen. */
-            Py_DECREF(def->m_base.m_copy);
+            Py_CLEAR(def->m_base.m_copy);
-            def->m_base.m_copy = NULL;
         }
         dict = PyModule_GetDict(mod);
         if (dict == NULL)

Python/sysmodule.c

@@ -430,8 +430,7 @@ trace_trampoline(PyObject *self, PyFrameObject *frame,
     result = call_trampoline(callback, frame, what, arg);
     if (result == NULL) {
         PyEval_SetTrace(NULL, NULL);
-        Py_XDECREF(frame->f_trace);
+        Py_CLEAR(frame->f_trace);
-        frame->f_trace = NULL;
         return -1;
     }
     if (result != Py_None) {