Restore dubious "optimization".

serhiy-storchaka · Jul 25, 2024 · 1c2aa22 · 1c2aa22
1 parent 8d22183
commit 1c2aa22
Showing 1 changed file with 37 additions and 20 deletions.
diff --git a/Modules/_pickle.c b/Modules/_pickle.c
@@ -1829,22 +1829,27 @@ get_dotted_path(PyObject *obj, PyObject *name)
 }
 
 static PyObject *
-get_deep_attribute(PyObject *obj, PyObject *names)
+get_deep_attribute(PyObject *obj, PyObject *names, PyObject **pparent)
 {
     Py_ssize_t i, n;
+    PyObject *parent = NULL;
 
     assert(PyList_CheckExact(names));
     Py_INCREF(obj);
     n = PyList_GET_SIZE(names);
     for (i = 0; i < n; i++) {
         PyObject *name = PyList_GET_ITEM(names, i);
-        PyObject *parent = obj;
+        Py_XSETREF(parent, obj);
         (void)PyObject_GetOptionalAttr(parent, name, &obj);
-        Py_DECREF(parent);
         if (obj == NULL) {
+            Py_DECREF(parent);
             return NULL;
         }
     }
+    if (pparent != NULL)
+        *pparent = parent;
+    else
+        Py_XDECREF(parent);
     return obj;
 }
 
@@ -1858,7 +1863,7 @@ getattribute(PyObject *obj, PyObject *name, int allow_qualname)
         dotted_path = get_dotted_path(obj, name);
         if (dotted_path == NULL)
             return NULL;
-        attr = get_deep_attribute(obj, dotted_path);
+        attr = get_deep_attribute(obj, dotted_path, NULL);
         Py_DECREF(dotted_path);
     }
     else {
@@ -1883,7 +1888,7 @@ _checkmodule(PyObject *module_name, PyObject *module,
         return -1;
     }
 
-    PyObject *candidate = get_deep_attribute(module, dotted_path);
+    PyObject *candidate = get_deep_attribute(module, dotted_path, NULL);
     if (candidate == NULL) {
         return -1;
     }
@@ -3585,6 +3590,7 @@ save_global(PickleState *st, PicklerObject *self, PyObject *obj,
     PyObject *global_name = NULL;
     PyObject *module_name = NULL;
     PyObject *module = NULL;
+    PyObject *parent = NULL;
     PyObject *dotted_path = NULL;
     PyObject *cls;
     int status = 0;
@@ -3626,7 +3632,7 @@ save_global(PickleState *st, PicklerObject *self, PyObject *obj,
                      obj, module_name);
         goto error;
     }
-    cls = get_deep_attribute(module, dotted_path);
+    cls = get_deep_attribute(module, dotted_path, &parent);
     if (cls == NULL) {
         PyErr_Format(st->PicklingError,
                      "Can't pickle %R: attribute lookup %S on %S failed",
@@ -3713,6 +3719,12 @@ save_global(PickleState *st, PicklerObject *self, PyObject *obj,
     }
     else {
   gen_global:
+        if (parent == module) {
+            Py_SETREF(global_name,
+                Py_NewRef(PyList_GET_ITEM(dotted_path,
+                                          PyList_GET_SIZE(dotted_path) - 1)));
+            Py_CLEAR(dotted_path);
+        }
         if (self->proto >= 4) {
             const char stack_global_op = STACK_GLOBAL;
 
@@ -3735,14 +3747,16 @@ save_global(PickleState *st, PicklerObject *self, PyObject *obj,
             const char tupletwo_op = (self->proto < 2) ? TUPLE : TUPLE2;
             const char reduce_op = REDUCE;
             Py_ssize_t i;
-            if (PyList_GET_SIZE(dotted_path) > 1) {
-                Py_SETREF(global_name, Py_NewRef(PyList_GET_ITEM(dotted_path, 0)));
-            }
-            for (i = 1; i < PyList_GET_SIZE(dotted_path); i++) {
-                if (save(st, self, st->getattr, 0) < 0 ||
-                    (self->proto < 2 && _Pickler_Write(self, &mark_op, 1) < 0))
-                {
-                    goto error;
+            if (dotted_path) {
+                if (PyList_GET_SIZE(dotted_path) > 1) {
+                    Py_SETREF(global_name, Py_NewRef(PyList_GET_ITEM(dotted_path, 0)));
+                }
+                for (i = 1; i < PyList_GET_SIZE(dotted_path); i++) {
+                    if (save(st, self, st->getattr, 0) < 0 ||
+                        (self->proto < 2 && _Pickler_Write(self, &mark_op, 1) < 0))
+                    {
+                        goto error;
+                    }
                 }
             }
 
@@ -3808,12 +3822,14 @@ save_global(PickleState *st, PicklerObject *self, PyObject *obj,
             if (_Pickler_Write(self, "\n", 1) < 0)
                 goto error;
 
-            for (i = 1; i < PyList_GET_SIZE(dotted_path); i++) {
-                if (save(st, self, PyList_GET_ITEM(dotted_path, i), 0) < 0 ||
-                    _Pickler_Write(self, &tupletwo_op, 1) < 0 ||
-                    _Pickler_Write(self, &reduce_op, 1) < 0)
-                {
-                    goto error;
+            if (dotted_path) {
+                for (i = 1; i < PyList_GET_SIZE(dotted_path); i++) {
+                    if (save(st, self, PyList_GET_ITEM(dotted_path, i), 0) < 0 ||
+                        _Pickler_Write(self, &tupletwo_op, 1) < 0 ||
+                        _Pickler_Write(self, &reduce_op, 1) < 0)
+                    {
+                        goto error;
+                    }
                 }
             }
         }
@@ -3829,6 +3845,7 @@ save_global(PickleState *st, PicklerObject *self, PyObject *obj,
     Py_XDECREF(module_name);
     Py_XDECREF(global_name);
     Py_XDECREF(module);
+    Py_XDECREF(parent);
     Py_XDECREF(dotted_path);
 
     return status;