bpo-44821: Eagerly assign __dict__ for new objects. (GH-27589)

2 files changed, 37 insertions, 4 deletions

diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 5fb9d01..5ad630f 100644
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -4866,19 +4866,44 @@ _PyDict_NewKeysForClass(void)
 
 #define CACHED_KEYS(tp) (((PyHeapTypeObject*)tp)->ht_cached_keys)
 
+int
+_PyObject_InitializeDict(PyObject *obj)
+{
+    PyObject **dictptr = _PyObject_GetDictPtr(obj);
+    if (dictptr == NULL) {
+        return 0;
+    }
+    assert(*dictptr == NULL);
+    PyTypeObject *tp = Py_TYPE(obj);
+    PyObject *dict;
+    if (_PyType_HasFeature(tp, Py_TPFLAGS_HEAPTYPE) && CACHED_KEYS(tp)) {
+        dictkeys_incref(CACHED_KEYS(tp));
+        dict = new_dict_with_shared_keys(CACHED_KEYS(tp));
+    }
+    else {
+        dict = PyDict_New();
+    }
+    if (dict == NULL) {
+        return -1;
+    }
+    *dictptr = dict;
+    return 0;
+}
+
+
 PyObject *
 PyObject_GenericGetDict(PyObject *obj, void *context)
 {
-    PyObject *dict, **dictptr = _PyObject_GetDictPtr(obj);
+    PyObject **dictptr = _PyObject_GetDictPtr(obj);
     if (dictptr == NULL) {
         PyErr_SetString(PyExc_AttributeError,
                         "This object has no __dict__");
         return NULL;
     }
-    dict = *dictptr;
+    PyObject *dict = *dictptr;
     if (dict == NULL) {
         PyTypeObject *tp = Py_TYPE(obj);
-        if ((tp->tp_flags & Py_TPFLAGS_HEAPTYPE) && CACHED_KEYS(tp)) {
+        if (_PyType_HasFeature(tp, Py_TPFLAGS_HEAPTYPE) && CACHED_KEYS(tp)) {
             dictkeys_incref(CACHED_KEYS(tp));
             *dictptr = dict = new_dict_with_shared_keys(CACHED_KEYS(tp));
         }
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index 2240f78..7ae50c4 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -4505,7 +4505,15 @@ object_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
         Py_DECREF(joined);
         return NULL;
     }
-    return type->tp_alloc(type, 0);
+    PyObject *obj = type->tp_alloc(type, 0);
+    if (obj == NULL) {
+        return NULL;
+    }
+    if (_PyObject_InitializeDict(obj)) {
+        Py_DECREF(obj);
+        return NULL;
+    }
+    return obj;
 }
 
 static void