gh-154817: Fix OrderedDict.pop() crash with inconsistent equality

Author: BHUVANSH855

Lib/test/test_ordered_dict.py

@@ -281,6 +281,28 @@ def __missing__(self, key):
         with self.assertRaises(KeyError):
             m.pop('a')
 
+    def test_pop_inconsistent_eq(self):
+        class K:
+            def __init__(self):
+                self.calls = 0
+
+            def __hash__(self):
+                return 12345
+
+            # Behave inconsistently across repeated equality checks.
+            def __eq__(self, other):
+                self.calls += 1
+                return self.calls == 1
+
+        k1 = K()
+        k2 = K()
+
+        od = self.OrderedDict()
+        od[k1] = "value"
+
+        with self.assertRaises(KeyError):
+            od.pop(k2)
+
     def test_equality(self):
         OrderedDict = self.OrderedDict
         pairs = [('c', 1), ('b', 2), ('a', 3), ('d', 4), ('e', 5), ('f', 6)]

Objects/odictobject.c

@@ -1095,7 +1095,12 @@ _odict_popkey_hash(PyObject *od, PyObject *key, PyObject *failobj,
         /* Now delete the value from the dict. */
         if (_PyDict_Pop_KnownHash((PyDictObject *)od, key, hash,
                                   &value) == 0) {
-            value = Py_NewRef(failobj);
+            if (failobj) {
+                value = Py_NewRef(failobj);
+            }
+            else {
+                PyErr_SetObject(PyExc_KeyError, key);
+            }
         }
     }
     else if (value == NULL && !PyErr_Occurred()) {