gh-111654: remove redundant decref in LOAD_FROM_DICT_OR_DEREF (#111655)

Author: aisk

Lib/test/test_exceptions.py

@@ -1844,6 +1844,13 @@ def f():
         self.assertIn("nonsense", err.getvalue())
         self.assertIn("ZeroDivisionError", err.getvalue())
 
+    def test_gh_111654(self):
+        def f():
+            class TestClass:
+                TestClass
+
+        self.assertRaises(NameError, f)
+
     # Note: name suggestion tests live in `test_traceback`.
 
 

Misc/NEWS.d/next/Core and Builtins/2023-11-03-01-04-55.gh-issue-111654.scUhDO.rst

@@ -0,0 +1,2 @@
+Fix runtime crash when some error happens in opcode
+``LOAD_FROM_DICT_OR_DEREF``.

Python/bytecodes.c

@@ -1535,10 +1535,8 @@ dummy_func(
             assert(oparg >= 0 && oparg < _PyFrame_GetCode(frame)->co_nlocalsplus);
             name = PyTuple_GET_ITEM(_PyFrame_GetCode(frame)->co_localsplusnames, oparg);
             if (PyMapping_GetOptionalItem(class_dict, name, &value) < 0) {
-                Py_DECREF(class_dict);
                 GOTO_ERROR(error);
             }
-            Py_DECREF(class_dict);
             if (!value) {
                 PyObject *cell = GETLOCAL(oparg);
                 value = PyCell_GET(cell);
@@ -1548,6 +1546,7 @@ dummy_func(
                 }
                 Py_INCREF(value);
             }
+            Py_DECREF(class_dict);
         }
 
         inst(LOAD_DEREF, ( -- value)) {