Make sure that instance dicts are GC tracked when necessary.

Author: markshannon

Objects/dictobject.c

@@ -4969,10 +4969,19 @@ make_dict_from_instance_attributes(PyDictKeysObject *keys, PyDictValues *values)
 {
     dictkeys_incref(keys);
     Py_ssize_t used = 0;
+    Py_ssize_t track = 0;
     for (Py_ssize_t i = 0; i < shared_keys_usable_size(keys); i++) {
-        used += values->values[i] != NULL;
+        PyObject *val = values->values[i];
+        if (val != NULL) {
+            used += 1;
+            track += _PyObject_GC_MAY_BE_TRACKED(val);
+        }
+    }
+    PyObject *res = new_dict(keys, values, used, 0);
+    if (track && res) {
+        _PyObject_GC_TRACK(res);
     }
-    return new_dict(keys, values, used, 0);
+    return res;
 }
 
 PyObject *
@@ -5025,7 +5034,6 @@ _PyObject_StoreInstanceAttribute(PyObject *obj, PyDictValues *values,
     return 0;
 }
 
-
 PyObject *
 _PyObject_GetInstanceAttribute(PyObject *obj, PyDictValues *values,
                               PyObject *name)
@@ -5072,8 +5080,9 @@ int
 _PyObject_VisitInstanceAttributes(PyObject *self, visitproc visit, void *arg)
 {
     PyTypeObject *tp = Py_TYPE(self);
+    assert(tp->tp_inline_values_offset);
     PyDictValues **values_ptr = _PyObject_ValuesPointer(self);
-    if (values_ptr == NULL || *values_ptr == NULL) {
+    if (*values_ptr == NULL) {
         return 0;
     }
     PyDictKeysObject *keys = CACHED_KEYS(tp);
@@ -5087,8 +5096,9 @@ void
 _PyObject_ClearInstanceAttributes(PyObject *self)
 {
     PyTypeObject *tp = Py_TYPE(self);
+    assert(tp->tp_inline_values_offset);
     PyDictValues **values_ptr = _PyObject_ValuesPointer(self);
-    if (values_ptr == NULL || *values_ptr == NULL) {
+    if (*values_ptr == NULL) {
         return;
     }
     PyDictKeysObject *keys = CACHED_KEYS(tp);
@@ -5101,8 +5111,9 @@ void
 _PyObject_FreeInstanceAttributes(PyObject *self)
 {
     PyTypeObject *tp = Py_TYPE(self);
+    assert(tp->tp_inline_values_offset);
     PyDictValues **values_ptr = _PyObject_ValuesPointer(self);
-    if (values_ptr == NULL || *values_ptr == NULL) {
+    if (*values_ptr == NULL) {
         return;
     }
     PyDictKeysObject *keys = CACHED_KEYS(tp);

Objects/object.c

@@ -1100,7 +1100,7 @@ _PyObject_GetDictPtr(PyObject *obj)
         return NULL;
     }
     if (*dict_ptr != NULL) {
-        return (PyObject **)dict_ptr;
+        return dict_ptr;
     }
     PyDictValues **values_ptr = _PyObject_ValuesPointer(obj);
     if (values_ptr == NULL || *values_ptr == NULL) {
@@ -1111,6 +1111,8 @@ _PyObject_GetDictPtr(PyObject *obj)
         PyErr_Clear();
         return NULL;
     }
+    assert(*dict_ptr == NULL);
+    assert(*values_ptr != NULL);
     *values_ptr = NULL;
     *dict_ptr = dict;
     return dict_ptr;

Objects/typeobject.c

@@ -1232,7 +1232,8 @@ subtype_traverse(PyObject *self, visitproc visit, void *arg)
         assert(base);
     }
 
-    if (type->tp_inline_values_offset != base->tp_inline_values_offset) {
+    if (type->tp_inline_values_offset) {
+        assert(type->tp_dictoffset);
         int err = _PyObject_VisitInstanceAttributes(self, visit, arg);
         if (err) {
             return err;
@@ -1300,7 +1301,7 @@ subtype_clear(PyObject *self)
 
     /* Clear the instance dict (if any), to break cycles involving only
        __dict__ slots (as in the case 'self.__dict__ is self'). */
-    if (type->tp_inline_values_offset != base->tp_inline_values_offset) {
+    if (type->tp_inline_values_offset) {
         _PyObject_ClearInstanceAttributes(self);
     }
     if (type->tp_dictoffset != base->tp_dictoffset) {
@@ -1444,7 +1445,7 @@ subtype_dealloc(PyObject *self)
     }
 
     /* If we added a dict, DECREF it, or free inline values. */
-    if (type->tp_inline_values_offset != base->tp_inline_values_offset) {
+    if (type->tp_inline_values_offset) {
         _PyObject_FreeInstanceAttributes(self);
     }
     if (type->tp_dictoffset && !base->tp_dictoffset) {
@@ -4940,17 +4941,14 @@ _PyObject_GetState(PyObject *obj, int required)
                          Py_TYPE(obj)->tp_name);
             return NULL;
         }
-
-        {
-            if (_PyObject_DictEmpty(obj)) {
-                state = Py_None;
-                Py_INCREF(state);
-            }
-            else {
-                state = PyObject_GenericGetDict(obj, NULL);
-                if (state == NULL) {
-                   return NULL;
-                }
+        if (_PyObject_DictEmpty(obj)) {
+            state = Py_None;
+            Py_INCREF(state);
+        }
+        else {
+            state = PyObject_GenericGetDict(obj, NULL);
+            if (state == NULL) {
+                return NULL;
             }
         }