Issue python#20440: More use of Py_SETREF.

This patch is manually crafted and contains changes that couldn't be handled
automatically.

Author: serhiy-storchaka

Modules/_ctypes/_ctypes.c

@@ -2983,10 +2983,9 @@ PyCFuncPtr_set_restype(PyCFuncPtrObject *self, PyObject *ob)
                         "restype must be a type, a callable, or None");
         return -1;
     }
-    Py_XDECREF(self->checker);
     Py_INCREF(ob);
     Py_SETREF(self->restype, ob);
-    self->checker = PyObject_GetAttrString(ob, "_check_retval_");
+    Py_SETREF(self->checker, PyObject_GetAttrString(ob, "_check_retval_"));
     if (self->checker == NULL)
         PyErr_Clear();
     return 0;

Modules/_elementtree.c

@@ -965,9 +965,8 @@ element_setstate_from_attributes(ElementObject *self,
         return NULL;
     }
 
-    Py_CLEAR(self->tag);
-    self->tag = tag;
-    Py_INCREF(self->tag);
+    Py_INCREF(tag);
+    Py_SETREF(self->tag, tag);
 
     _clear_joined_ptr(&self->text);
     self->text = text ? JOIN_SET(text, PyList_CheckExact(text)) : Py_None;
@@ -1010,9 +1009,8 @@ element_setstate_from_attributes(ElementObject *self,
 
     /* Stash attrib. */
     if (attrib) {
-        Py_CLEAR(self->extra->attrib);
-        self->extra->attrib = attrib;
         Py_INCREF(attrib);
+        Py_SETREF(self->extra->attrib, attrib);
     }
 
     Py_RETURN_NONE;
@@ -1961,8 +1959,7 @@ element_tag_setter(ElementObject *self, PyObject *value, void *closure)
 {
     _VALIDATE_ATTR_VALUE(value);
     Py_INCREF(value);
-    Py_DECREF(self->tag);
-    self->tag = value;
+    Py_SETREF(self->tag, value);
     return 0;
 }
 
@@ -1995,8 +1992,7 @@ element_attrib_setter(ElementObject *self, PyObject *value, void *closure)
             return -1;
     }
     Py_INCREF(value);
-    Py_DECREF(self->extra->attrib);
-    self->extra->attrib = value;
+    Py_SETREF(self->extra->attrib, value);
     return 0;
 }
 
@@ -2533,13 +2529,10 @@ treebuilder_handle_start(TreeBuilderObject* self, PyObject* tag,
     }
     self->index++;
 
-    Py_DECREF(this);
     Py_INCREF(node);
-    self->this = node;
-
-    Py_DECREF(self->last);
+    Py_SETREF(self->this, node);
     Py_INCREF(node);
-    self->last = node;
+    Py_SETREF(self->last, node);
 
     if (treebuilder_append_event(self, self->start_event_obj, node) < 0)
         goto error;
@@ -2612,15 +2605,12 @@ treebuilder_handle_end(TreeBuilderObject* self, PyObject* tag)
         return NULL;
     }
 
-    self->index--;
-
-    item = PyList_GET_ITEM(self->stack, self->index);
-    Py_INCREF(item);
-
-    Py_DECREF(self->last);
-
+    item = self->last;
     self->last = self->this;
-    self->this = item;
+    self->index--;
+    self->this = PyList_GET_ITEM(self->stack, self->index);
+    Py_INCREF(self->this);
+    Py_DECREF(item);
 
     if (treebuilder_append_event(self, self->end_event_obj, self->last) < 0)
         return NULL;

Modules/_sqlite/cursor.c

@@ -524,10 +524,10 @@ PyObject* _pysqlite_query_execute(pysqlite_Cursor* self, int multiple, PyObject*
 
     if (self->statement) {
         (void)pysqlite_statement_reset(self->statement);
-        Py_DECREF(self->statement);
     }
 
-    self->statement = (pysqlite_Statement*)pysqlite_cache_get(self->connection->statement_cache, func_args);
+    Py_SETREF(self->statement,
+              (pysqlite_Statement *)pysqlite_cache_get(self->connection->statement_cache, func_args));
     Py_DECREF(func_args);
 
     if (!self->statement) {

Modules/zlibmodule.c

@@ -961,14 +961,11 @@ zlib_Compress_copy_impl(compobject *self)
         goto error;
     }
     Py_INCREF(self->unused_data);
+    Py_SETREF(retval->unused_data, self->unused_data);
     Py_INCREF(self->unconsumed_tail);
+    Py_SETREF(retval->unconsumed_tail, self->unconsumed_tail);
     Py_XINCREF(self->zdict);
-    Py_XDECREF(retval->unused_data);
-    Py_XDECREF(retval->unconsumed_tail);
-    Py_XDECREF(retval->zdict);
-    retval->unused_data = self->unused_data;
-    retval->unconsumed_tail = self->unconsumed_tail;
-    retval->zdict = self->zdict;
+    Py_SETREF(retval->zdict, self->zdict);
     retval->eof = self->eof;
 
     /* Mark it as being initialized */
@@ -1020,14 +1017,11 @@ zlib_Decompress_copy_impl(compobject *self)
     }
 
     Py_INCREF(self->unused_data);
+    Py_SETREF(retval->unused_data, self->unused_data);
     Py_INCREF(self->unconsumed_tail);
+    Py_SETREF(retval->unconsumed_tail, self->unconsumed_tail);
     Py_XINCREF(self->zdict);
-    Py_XDECREF(retval->unused_data);
-    Py_XDECREF(retval->unconsumed_tail);
-    Py_XDECREF(retval->zdict);
-    retval->unused_data = self->unused_data;
-    retval->unconsumed_tail = self->unconsumed_tail;
-    retval->zdict = self->zdict;
+    Py_SETREF(retval->zdict, self->zdict);
     retval->eof = self->eof;
 
     /* Mark it as being initialized */

Objects/exceptions.c

@@ -561,12 +561,14 @@ SystemExit_init(PySystemExitObject *self, PyObject *args, PyObject *kwds)
 
     if (size == 0)
         return 0;
-    Py_CLEAR(self->code);
-    if (size == 1)
-        self->code = PyTuple_GET_ITEM(args, 0);
-    else /* size > 1 */
-        self->code = args;
-    Py_INCREF(self->code);
+    if (size == 1) {
+        Py_INCREF(PyTuple_GET_ITEM(args, 0));
+        Py_SETREF(self->code, PyTuple_GET_ITEM(args, 0));
+    }
+    else { /* size > 1 */
+        Py_INCREF(args);
+        Py_SETREF(self->code, args);
+    }
     return 0;
 }
 
@@ -625,9 +627,8 @@ ImportError_init(PyImportErrorObject *self, PyObject *args, PyObject *kwds)
 #define GET_KWD(kwd) { \
     kwd = PyDict_GetItemString(kwds, #kwd); \
     if (kwd) { \
-        Py_CLEAR(self->kwd); \
-        self->kwd = kwd;   \
-        Py_INCREF(self->kwd);\
+        Py_INCREF(kwd); \
+        Py_SETREF(self->kwd, kwd); \
         if (PyDict_DelItemString(kwds, #kwd)) \
             return -1; \
     } \

Objects/unicodeobject.c

@@ -14443,8 +14443,8 @@ unicode_format_arg_parse(struct unicode_formatter_t *ctx,
         if (key == NULL)
             return -1;
         if (ctx->args_owned) {
-            Py_DECREF(ctx->args);
             ctx->args_owned = 0;
+            Py_DECREF(ctx->args);
         }
         ctx->args = PyObject_GetItem(ctx->dict, key);
         Py_DECREF(key);

Python/ast.c

@@ -4496,8 +4496,7 @@ fstring_find_literal_and_expr(PyObject *str, Py_ssize_t *ofs, int recurse_lvl,
     return 0;
 
 error:
-    Py_XDECREF(*literal);
-    *literal = NULL;
+    Py_CLEAR(*literal);
     return -1;
 }
 
@@ -4692,11 +4691,8 @@ FstringParser_ConcatAndDel(FstringParser *state, PyObject *str)
         state->last_str = str;
     } else {
         /* Concatenate this with the previous string. */
-        PyObject *temp = PyUnicode_Concat(state->last_str, str);
-        Py_DECREF(state->last_str);
-        Py_DECREF(str);
-        state->last_str = temp;
-        if (!temp)
+        PyUnicode_AppendAndDel(&state->last_str, str);
+        if (!state->last_str)
             return -1;
     }
     FstringParser_check_invariants(state);

Python/errors.c

@@ -315,14 +315,11 @@ PyErr_NormalizeException(PyObject **exc, PyObject **val, PyObject **tb)
     tstate = PyThreadState_GET();
     if (++tstate->recursion_depth > Py_GetRecursionLimit()) {
         --tstate->recursion_depth;
-        /* throw away the old exception... */
-        Py_DECREF(*exc);
-        Py_DECREF(*val);
-        /* ... and use the recursion error instead */
-        *exc = PyExc_RecursionError;
-        *val = PyExc_RecursionErrorInst;
-        Py_INCREF(*exc);
-        Py_INCREF(*val);
+        /* throw away the old exception and use the recursion error instead */
+        Py_INCREF(PyExc_RecursionError);
+        Py_SETREF(*exc, PyExc_RecursionError);
+        Py_INCREF(PyExc_RecursionErrorInst);
+        Py_SETREF(*val, PyExc_RecursionErrorInst);
         /* just keeping the old traceback */
         return;
     }