python
diff --git a/‎Include/cpython/dictobject.h‎
Lines changed: 0 additions & 3 deletions b/‎Include/cpython/dictobject.h‎
Lines changed: 0 additions & 3 deletions
diff --git a/‎Include/cpython/object.h‎
Lines changed: 4 additions & 0 deletions b/‎Include/cpython/object.h‎
Lines changed: 4 additions & 0 deletions
diff --git a/‎Include/internal/pycore_object.h‎
Lines changed: 34 additions & 9 deletions b/‎Include/internal/pycore_object.h‎
Lines changed: 34 additions & 9 deletions
diff --git a/‎Misc/NEWS.d/next/Core and Builtins/2022-07-26-12-59-03.gh-issue-95245.GHWczn.rst‎
Lines changed: 2 additions & 0 deletions b/‎Misc/NEWS.d/next/Core and Builtins/2022-07-26-12-59-03.gh-issue-95245.GHWczn.rst‎
Lines changed: 2 additions & 0 deletions
diff --git a/‎Objects/dictobject.c‎
Lines changed: 90 additions & 71 deletions b/‎Objects/dictobject.c‎
Lines changed: 90 additions & 71 deletions
@@ -83,6 +83,3 @@ typedef struct {
 
 PyAPI_FUNC(PyObject *) _PyDictView_New(PyObject *, PyTypeObject *);
 PyAPI_FUNC(PyObject *) _PyDictView_Intersect(PyObject* self, PyObject *other);
-
-PyAPI_FUNC(int) _PyObject_VisitManagedDict(PyObject *self, visitproc visit, void *arg);
-PyAPI_FUNC(void) _PyObject_ClearManagedDict(PyObject *self);
@@ -510,3 +510,7 @@ Py_DEPRECATED(3.11) typedef int UsingDeprecatedTrashcanMacro;
 #define Py_TRASHCAN_SAFE_END(op) \
         Py_TRASHCAN_END; \
     } while(0);
+
+
+PyAPI_FUNC(int) _PyObject_VisitManagedDict(PyObject *obj, visitproc visit, void *arg);
+PyAPI_FUNC(void) _PyObject_ClearManagedDict(PyObject *obj);
@@ -274,24 +274,49 @@ extern int _PyObject_StoreInstanceAttribute(PyObject *obj, PyDictValues *values,
 PyObject * _PyObject_GetInstanceAttribute(PyObject *obj, PyDictValues *values,
                                         PyObject *name);
 
-static inline PyDictValues **_PyObject_ValuesPointer(PyObject *obj)
+typedef union {
+    PyObject *dict;
+    /* Use a char* to generate a warning if directly assigning a PyDictValues */
+    char *values;
+} PyDictOrValues;
+
+static inline PyDictOrValues *
+_PyObject_DictOrValuesPointer(PyObject *obj)
 {
     assert(Py_TYPE(obj)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
-    return ((PyDictValues **)obj)-4;
+    return ((PyDictOrValues *)obj)-3;
 }
 
-static inline PyObject **_PyObject_ManagedDictPointer(PyObject *obj)
+static inline int
+_PyDictOrValues_IsValues(PyDictOrValues dorv)
 {
-    assert(Py_TYPE(obj)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
-    return ((PyObject **)obj)-3;
+    return ((uintptr_t)dorv.values) & 1;
+}
+
+static inline PyDictValues *
+_PyDictOrValues_GetValues(PyDictOrValues dorv)
+{
+    assert(_PyDictOrValues_IsValues(dorv));
+    return (PyDictValues *)(dorv.values + 1);
+}
+
+static inline PyObject *
+_PyDictOrValues_GetDict(PyDictOrValues dorv)
+{
+    assert(!_PyDictOrValues_IsValues(dorv));
+    return dorv.dict;
+}
+
+static inline void
+_PyDictOrValues_SetValues(PyDictOrValues *ptr, PyDictValues *values)
+{
+    ptr->values = ((char *)values) - 1;
 }
 
 #define MANAGED_DICT_OFFSET (((int)sizeof(PyObject *))*-3)
 
-extern PyObject ** _PyObject_DictPointer(PyObject *);
-extern int _PyObject_VisitInstanceAttributes(PyObject *self, visitproc visit, void *arg);
-extern void _PyObject_ClearInstanceAttributes(PyObject *self);
-extern void _PyObject_FreeInstanceAttributes(PyObject *self);
+extern PyObject ** _PyObject_ComputedDictPointer(PyObject *);
+extern void _PyObject_FreeInstanceAttributes(PyObject *obj);
 extern int _PyObject_IsInstanceDictEmpty(PyObject *);
 extern PyObject* _PyType_GetSubclasses(PyTypeObject *);
 
 
@@ -0,0 +1,2 @@
+Merge managed dict and values pointer into a single tagged pointer to save
+one word in the pre-header.
@@ -5368,7 +5368,7 @@ init_inline_values(PyObject *obj, PyTypeObject *tp)
     for (int i = 0; i < size; i++) {
         values->values[i] = NULL;
     }
-    *_PyObject_ValuesPointer(obj) = values;
+    _PyDictOrValues_SetValues(_PyObject_DictOrValuesPointer(obj), values);
     return 0;
 }
 
@@ -5394,7 +5394,7 @@ _PyObject_InitializeDict(PyObject *obj)
     if (dict == NULL) {
         return -1;
     }
-    PyObject **dictptr = _PyObject_DictPointer(obj);
+    PyObject **dictptr = _PyObject_ComputedDictPointer(obj);
     *dictptr = dict;
     return 0;
 }
@@ -5422,7 +5422,6 @@ make_dict_from_instance_attributes(PyDictKeysObject *keys, PyDictValues *values)
 PyObject *
 _PyObject_MakeDictFromInstanceAttributes(PyObject *obj, PyDictValues *values)
 {
-    assert(Py_TYPE(obj)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
     PyDictKeysObject *keys = CACHED_KEYS(Py_TYPE(obj));
     OBJECT_STAT_INC(dict_materialized_on_request);
     return make_dict_from_instance_attributes(keys, values);
@@ -5458,8 +5457,7 @@ _PyObject_StoreInstanceAttribute(PyObject *obj, PyDictValues *values,
         if (dict == NULL) {
             return -1;
         }
-        *_PyObject_ValuesPointer(obj) = NULL;
-        *_PyObject_ManagedDictPointer(obj) = dict;
+        _PyObject_DictOrValuesPointer(obj)->dict = dict;
         if (value == NULL) {
             return PyDict_DelItem(dict, name);
         }
@@ -5488,6 +5486,37 @@ _PyObject_StoreInstanceAttribute(PyObject *obj, PyDictValues *values,
     return 0;
 }
 
+/* Sanity check for managed dicts */
+#if 0
+#define CHECK(val) assert(val); if (!(val)) { return 0; }
+
+int
+_PyObject_ManagedDictValidityCheck(PyObject *obj)
+{
+    PyTypeObject *tp = Py_TYPE(obj);
+    CHECK(tp->tp_flags & Py_TPFLAGS_MANAGED_DICT);
+    PyDictOrValues *dorv_ptr = _PyObject_DictOrValuesPointer(obj);
+    if (_PyDictOrValues_IsValues(*dorv_ptr)) {
+        PyDictValues *values = _PyDictOrValues_GetValues(*dorv_ptr);
+        int size = ((uint8_t *)values)[-2];
+        int count = 0;
+        PyDictKeysObject *keys = CACHED_KEYS(tp);
+        for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
+            if (values->values[i] != NULL) {
+                count++;
+            }
+        }
+        CHECK(size == count);
+    }
+    else {
+        if (dorv_ptr->dict != NULL) {
+            CHECK(PyDict_Check(dorv_ptr->dict));
+        }
+    }
+    return 1;
+}
+#endif
+
 PyObject *
 _PyObject_GetInstanceAttribute(PyObject *obj, PyDictValues *values,
                               PyObject *name)
@@ -5511,105 +5540,94 @@ _PyObject_IsInstanceDictEmpty(PyObject *obj)
     if (tp->tp_dictoffset == 0) {
         return 1;
     }
-    PyObject **dictptr;
+    PyObject *dict;
     if (tp->tp_flags & Py_TPFLAGS_MANAGED_DICT) {
-        PyDictValues *values = *_PyObject_ValuesPointer(obj);
-        if (values) {
+        PyDictOrValues dorv = *_PyObject_DictOrValuesPointer(obj);
+        if (_PyDictOrValues_IsValues(dorv)) {
             PyDictKeysObject *keys = CACHED_KEYS(tp);
             for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
-                if (values->values[i] != NULL) {
+                if (_PyDictOrValues_GetValues(dorv)->values[i] != NULL) {
                     return 0;
                 }
             }
             return 1;
         }
-        dictptr = _PyObject_ManagedDictPointer(obj);
+        dict = _PyDictOrValues_GetDict(dorv);
     }
     else {
-       dictptr = _PyObject_DictPointer(obj);
+        PyObject **dictptr = _PyObject_ComputedDictPointer(obj);
+        dict = *dictptr;
     }
-    PyObject *dict = *dictptr;
     if (dict == NULL) {
         return 1;
     }
     return ((PyDictObject *)dict)->ma_used == 0;
 }
 
-
-int
-_PyObject_VisitInstanceAttributes(PyObject *self, visitproc visit, void *arg)
-{
-    PyTypeObject *tp = Py_TYPE(self);
-    assert(Py_TYPE(self)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
-    PyDictValues **values_ptr = _PyObject_ValuesPointer(self);
-    if (*values_ptr == NULL) {
-        return 0;
-    }
-    PyDictKeysObject *keys = CACHED_KEYS(tp);
-    for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
-        Py_VISIT((*values_ptr)->values[i]);
-    }
-    return 0;
-}
-
-void
-_PyObject_ClearInstanceAttributes(PyObject *self)
-{
-    PyTypeObject *tp = Py_TYPE(self);
-    assert(Py_TYPE(self)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
-    PyDictValues **values_ptr = _PyObject_ValuesPointer(self);
-    if (*values_ptr == NULL) {
-        return;
-    }
-    PyDictKeysObject *keys = CACHED_KEYS(tp);
-    for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
-        Py_CLEAR((*values_ptr)->values[i]);
-    }
-}
-
 void
 _PyObject_FreeInstanceAttributes(PyObject *self)
 {
     PyTypeObject *tp = Py_TYPE(self);
     assert(Py_TYPE(self)->tp_flags & Py_TPFLAGS_MANAGED_DICT);
-    PyDictValues **values_ptr = _PyObject_ValuesPointer(self);
-    if (*values_ptr == NULL) {
+    PyDictOrValues dorv = *_PyObject_DictOrValuesPointer(self);
+    if (!_PyDictOrValues_IsValues(dorv)) {
         return;
     }
+    PyDictValues *values = _PyDictOrValues_GetValues(dorv);
     PyDictKeysObject *keys = CACHED_KEYS(tp);
     for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
-        Py_XDECREF((*values_ptr)->values[i]);
+        Py_XDECREF(values->values[i]);
     }
-    free_values(*values_ptr);
+    free_values(values);
 }
 
 int
-_PyObject_VisitManagedDict(PyObject *self, visitproc visit, void *arg)
+_PyObject_VisitManagedDict(PyObject *obj, visitproc visit, void *arg)
 {
-    PyTypeObject *tp = Py_TYPE(self);
+    PyTypeObject *tp = Py_TYPE(obj);
     if((tp->tp_flags & Py_TPFLAGS_MANAGED_DICT) == 0) {
         return 0;
     }
     assert(tp->tp_dictoffset);
-    int err = _PyObject_VisitInstanceAttributes(self, visit, arg);
-    if (err) {
-        return err;
+    PyDictOrValues dorv = *_PyObject_DictOrValuesPointer(obj);
+    if (_PyDictOrValues_IsValues(dorv)) {
+        PyDictValues *values = _PyDictOrValues_GetValues(dorv);
+        PyDictKeysObject *keys = CACHED_KEYS(tp);
+        for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
+            Py_VISIT(values->values[i]);
+        }
+    }
+    else {
+        PyObject *dict = _PyDictOrValues_GetDict(dorv);
+        Py_VISIT(dict);
     }
-    Py_VISIT(*_PyObject_ManagedDictPointer(self));
     return 0;
 }
 
-
 void
-_PyObject_ClearManagedDict(PyObject *self)
+_PyObject_ClearManagedDict(PyObject *obj)
 {
-    PyTypeObject *tp = Py_TYPE(self);
+    PyTypeObject *tp = Py_TYPE(obj);
     if((tp->tp_flags & Py_TPFLAGS_MANAGED_DICT) == 0) {
         return;
     }
-    _PyObject_FreeInstanceAttributes(self);
-    *_PyObject_ValuesPointer(self) = NULL;
-    Py_CLEAR(*_PyObject_ManagedDictPointer(self));
+    PyDictOrValues *dorv_ptr = _PyObject_DictOrValuesPointer(obj);
+    if (_PyDictOrValues_IsValues(*dorv_ptr)) {
+        PyDictValues *values = _PyDictOrValues_GetValues(*dorv_ptr);
+        PyDictKeysObject *keys = CACHED_KEYS(tp);
+        for (Py_ssize_t i = 0; i < keys->dk_nentries; i++) {
+            Py_CLEAR(values->values[i]);
+        }
+        dorv_ptr->dict = NULL;
+        free_values(values);
+    }
+    else {
+        PyObject *dict = dorv_ptr->dict;
+        if (dict) {
+            dorv_ptr->dict = NULL;
+            Py_DECREF(dict);
+        }
+    }
 }
 
 PyObject *
@@ -5618,25 +5636,26 @@ PyObject_GenericGetDict(PyObject *obj, void *context)
     PyObject *dict;
     PyTypeObject *tp = Py_TYPE(obj);
     if (_PyType_HasFeature(tp, Py_TPFLAGS_MANAGED_DICT)) {
-        PyDictValues **values_ptr = _PyObject_ValuesPointer(obj);
-        PyObject **dictptr = _PyObject_ManagedDictPointer(obj);
-        if (*values_ptr) {
-            assert(*dictptr == NULL);
+        PyDictOrValues *dorv_ptr = _PyObject_DictOrValuesPointer(obj);
+        if (_PyDictOrValues_IsValues(*dorv_ptr)) {
+            PyDictValues *values = _PyDictOrValues_GetValues(*dorv_ptr);
             OBJECT_STAT_INC(dict_materialized_on_request);
-            *dictptr = dict = make_dict_from_instance_attributes(CACHED_KEYS(tp), *values_ptr);
+            dict = make_dict_from_instance_attributes(CACHED_KEYS(tp), values);
             if (dict != NULL) {
-                *values_ptr = NULL;
+                dorv_ptr->dict = dict;
             }
         }
-        else if (*dictptr == NULL) {
-            *dictptr = dict = PyDict_New();
-        }
         else {
-            dict = *dictptr;
+            dict = _PyDictOrValues_GetDict(*dorv_ptr);
+            if (dict == NULL) {
+                dictkeys_incref(CACHED_KEYS(tp));
+                dict = new_dict_with_shared_keys(CACHED_KEYS(tp));
+                dorv_ptr->dict = dict;
+            }
         }
     }
     else {
-        PyObject **dictptr = _PyObject_DictPointer(obj);
+        PyObject **dictptr = _PyObject_ComputedDictPointer(obj);
         if (dictptr == NULL) {
             PyErr_SetString(PyExc_AttributeError,
                             "This object has no __dict__");
Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+Merge managed dict and values pointer into a single tagged pointer to save`
	`2`	`+one word in the pre-header.`