gh-99537: Use Py_SETREF() function in C code (#99656)

Fix potential race condition in code patterns:

* Replace "Py_DECREF(var); var = new;" with "Py_SETREF(var, new);"
* Replace "Py_XDECREF(var); var = new;" with "Py_XSETREF(var, new);"
* Replace "Py_CLEAR(var); var = new;" with "Py_XSETREF(var, new);"

Other changes:

* Replace "old = var; var = new; Py_DECREF(var)"
  with "Py_SETREF(var, new);"
* Replace "old = var; var = new; Py_XDECREF(var)"
  with "Py_XSETREF(var, new);"
* And remove the "old" variable.

1 files changed, 1 insertions, 2 deletions

diff --git a/Modules/_sqlite/cursor.c b/Modules/_sqlite/cursor.c
index 7844b6e..a4e22bb 100644
--- a/Modules/_sqlite/cursor.c
+++ b/Modules/_sqlite/cursor.c
@@ -1123,8 +1123,7 @@ pysqlite_cursor_iternext(pysqlite_Cursor *self)
         PyObject *factory = self->row_factory;
         PyObject *args[] = { (PyObject *)self, row, };
         PyObject *new_row = PyObject_Vectorcall(factory, args, 2, NULL);
-        Py_DECREF(row);
-        row = new_row;
+        Py_SETREF(row, new_row);
     }
     return row;
 }