Issue #20440: Massive replacing unsafe attribute setting code with special

macro Py_SETREF.

Objects/bytesobject.c

@@ -3520,8 +3520,7 @@ PyBytes_Concat(PyObject **pv, PyObject *w)
         /* Multiple references, need to create new object */
         PyObject *v;
         v = bytes_concat(*pv, w);
-        Py_DECREF(*pv);
-        *pv = v;
+        Py_SETREF(*pv, v);
     }
 }
 

Objects/descrobject.c

@@ -1509,8 +1509,7 @@ property_init(PyObject *self, PyObject *args, PyObject *kwds)
         PyObject *get_doc = _PyObject_GetAttrId(get, &PyId___doc__);
         if (get_doc) {
             if (Py_TYPE(self) == &PyProperty_Type) {
-                Py_XDECREF(prop->prop_doc);
-                prop->prop_doc = get_doc;
+                Py_SETREF(prop->prop_doc, get_doc);
             }
             else {
                 /* If this is a property subclass, put __doc__

Objects/exceptions.c

@@ -236,8 +236,7 @@ BaseException_set_tb(PyBaseExceptionObject *self, PyObject *tb)
     }
 
     Py_XINCREF(tb);
-    Py_XDECREF(self->traceback);
-    self->traceback = tb;
+    Py_SETREF(self->traceback, tb);
     return 0;
 }
 

Objects/frameobject.c

@@ -857,8 +857,7 @@ dict_to_map(PyObject *map, Py_ssize_t nmap, PyObject *dict, PyObject **values,
             }
         } else if (values[j] != value) {
             Py_XINCREF(value);
-            Py_XDECREF(values[j]);
-            values[j] = value;
+            Py_SETREF(values[j], value);
         }
         Py_XDECREF(value);
     }

Objects/funcobject.c

@@ -127,8 +127,7 @@ PyFunction_SetDefaults(PyObject *op, PyObject *defaults)
         PyErr_SetString(PyExc_SystemError, "non-tuple default args");
         return -1;
     }
-    Py_XDECREF(((PyFunctionObject *) op) -> func_defaults);
-    ((PyFunctionObject *) op) -> func_defaults = defaults;
+    Py_SETREF(((PyFunctionObject *)op)->func_defaults, defaults);
     return 0;
 }
 
@@ -159,8 +158,7 @@ PyFunction_SetKwDefaults(PyObject *op, PyObject *defaults)
                         "non-dict keyword only default args");
         return -1;
     }
-    Py_XDECREF(((PyFunctionObject *)op) -> func_kwdefaults);
-    ((PyFunctionObject *) op) -> func_kwdefaults = defaults;
+    Py_SETREF(((PyFunctionObject *)op)->func_kwdefaults, defaults);
     return 0;
 }
 
@@ -192,8 +190,7 @@ PyFunction_SetClosure(PyObject *op, PyObject *closure)
                      closure->ob_type->tp_name);
         return -1;
     }
-    Py_XDECREF(((PyFunctionObject *) op) -> func_closure);
-    ((PyFunctionObject *) op) -> func_closure = closure;
+    Py_SETREF(((PyFunctionObject *)op)->func_closure, closure);
     return 0;
 }
 
@@ -224,8 +221,7 @@ PyFunction_SetAnnotations(PyObject *op, PyObject *annotations)
                         "non-dict annotations");
         return -1;
     }
-    Py_XDECREF(((PyFunctionObject *)op) -> func_annotations);
-    ((PyFunctionObject *) op) -> func_annotations = annotations;
+    Py_SETREF(((PyFunctionObject *)op)->func_annotations, annotations);
     return 0;
 }
 
@@ -531,8 +527,7 @@ func_new(PyTypeObject* type, PyObject* args, PyObject* kw)
 
     if (name != Py_None) {
         Py_INCREF(name);
-        Py_DECREF(newfunc->func_name);
-        newfunc->func_name = name;
+        Py_SETREF(newfunc->func_name, name);
     }
     if (defaults != Py_None) {
         Py_INCREF(defaults);

Objects/moduleobject.c

@@ -69,8 +69,7 @@ module_init_dict(PyModuleObject *mod, PyObject *md_dict,
         return -1;
     if (PyUnicode_CheckExact(name)) {
         Py_INCREF(name);
-        Py_XDECREF(mod->md_name);
-        mod->md_name = name;
+        Py_SETREF(mod->md_name, name);
     }
 
     return 0;

Objects/rangeobject.c

@@ -1066,8 +1066,7 @@ longrangeiter_next(longrangeiterobject *r)
     result = PyNumber_Add(r->start, product);
     Py_DECREF(product);
     if (result) {
-        Py_DECREF(r->index);
-        r->index = new_index;
+        Py_SETREF(r->index, new_index);
     }
     else {
         Py_DECREF(new_index);

Objects/typeobject.c

@@ -315,9 +315,8 @@ assign_version_tag(PyTypeObject *type)
            are borrowed reference */
         for (i = 0; i < (1 << MCACHE_SIZE_EXP); i++) {
             method_cache[i].value = NULL;
-            Py_XDECREF(method_cache[i].name);
-            method_cache[i].name = Py_None;
             Py_INCREF(Py_None);
+            Py_SETREF(method_cache[i].name, Py_None);
         }
         /* mark all version tags as invalid */
         PyType_Modified(&PyBaseObject_Type);
@@ -462,8 +461,7 @@ type_set_qualname(PyTypeObject *type, PyObject *value, void *context)
 
     et = (PyHeapTypeObject*)type;
     Py_INCREF(value);
-    Py_DECREF(et->ht_qualname);
-    et->ht_qualname = value;
+    Py_SETREF(et->ht_qualname, value);
     return 0;
 }
 
@@ -2910,8 +2908,7 @@ _PyType_Lookup(PyTypeObject *type, PyObject *name)
         else
             method_cache_misses++;
 #endif
-        Py_DECREF(method_cache[h].name);
-        method_cache[h].name = name;
+        Py_SETREF(method_cache[h].name, name);
     }
     return res;
 }

Objects/unicodeobject.c

@@ -1665,8 +1665,7 @@ unicode_resize(PyObject **p_unicode, Py_ssize_t length)
         _Py_INCREF_UNICODE_EMPTY();
         if (!unicode_empty)
             return -1;
-        Py_DECREF(*p_unicode);
-        *p_unicode = unicode_empty;
+        Py_SETREF(*p_unicode, unicode_empty);
         return 0;
     }
 
@@ -1674,8 +1673,7 @@ unicode_resize(PyObject **p_unicode, Py_ssize_t length)
         PyObject *copy = resize_copy(unicode, length);
         if (copy == NULL)
             return -1;
-        Py_DECREF(*p_unicode);
-        *p_unicode = copy;
+        Py_SETREF(*p_unicode, copy);
         return 0;
     }
 
@@ -13322,8 +13320,7 @@ _PyUnicodeWriter_PrepareInternal(_PyUnicodeWriter *writer,
             return -1;
         _PyUnicode_FastCopyCharacters(newbuffer, 0,
                                       writer->buffer, 0, writer->pos);
-        Py_DECREF(writer->buffer);
-        writer->buffer = newbuffer;
+        Py_SETREF(writer->buffer, newbuffer);
     }
     _PyUnicodeWriter_Update(writer);
     return 0;
@@ -15009,8 +15006,7 @@ PyUnicode_InternInPlace(PyObject **p)
 
     if (t) {
         Py_INCREF(t);
-        Py_DECREF(*p);
-        *p = t;
+        Py_SETREF(*p, t);
         return;
     }