[3.12] gh-111654: remove redundant decref in LOAD_FROM_DICT_OR_DEREF (GH-111655) (#111674)

(cherry picked from commit 3a1b09e)

Co-authored-by: AN Long <[email protected]>

Author: JelleZijlstra

Lib/test/test_exceptions.py

@@ -1824,6 +1824,13 @@ 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

@@ -1425,21 +1425,18 @@ dummy_func(
                     Py_INCREF(value);
                 }
                 else if (_PyErr_Occurred(tstate)) {
-                    Py_DECREF(class_dict);
                     goto error;
                 }
             }
             else {
                 value = PyObject_GetItem(class_dict, name);
                 if (value == NULL) {
                     if (!_PyErr_ExceptionMatches(tstate, PyExc_KeyError)) {
-                        Py_DECREF(class_dict);
                         goto error;
                     }
                     _PyErr_Clear(tstate);
                 }
             }
-            Py_DECREF(class_dict);
             if (!value) {
                 PyObject *cell = GETLOCAL(oparg);
                 value = PyCell_GET(cell);
@@ -1449,6 +1446,7 @@ dummy_func(
                 }
                 Py_INCREF(value);
             }
+            Py_DECREF(class_dict);
         }
 
         inst(LOAD_DEREF, ( -- value)) {