Issue #22676: Make the pickling of global objects which don't have a __module__ attribute less slow.

Misc/NEWS

@@ -181,6 +181,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #22676: Make the pickling of global objects which don't have a
+  __module__ attribute less slow.
+
 - Issue #18853: Fixed ResourceWarning in shlex.__nain__.
 
 - Issue #9351: Defaults set with set_defaults on an argparse subparser

Modules/_pickle.c

@@ -1535,18 +1535,18 @@ memo_put(PicklerObject *self, PyObject *obj)
 }
 
 static PyObject *
-getattribute(PyObject *obj, PyObject *name, int allow_qualname) {
-    PyObject *dotted_path;
-    Py_ssize_t i;
+get_dotted_path(PyObject *obj, PyObject *name, int allow_qualname) {
     _Py_static_string(PyId_dot, ".");
     _Py_static_string(PyId_locals, "<locals>");
+    PyObject *dotted_path;
+    Py_ssize_t i, n;
 
     dotted_path = PyUnicode_Split(name, _PyUnicode_FromId(&PyId_dot), -1);
-    if (dotted_path == NULL) {
+    if (dotted_path == NULL)
         return NULL;
-    }
-    assert(Py_SIZE(dotted_path) >= 1);
-    if (!allow_qualname && Py_SIZE(dotted_path) > 1) {
+    n = PyList_GET_SIZE(dotted_path);
+    assert(n >= 1);
+    if (!allow_qualname && n > 1) {
         PyErr_Format(PyExc_AttributeError,
                      "Can't get qualified attribute %R on %R;"
                      "use protocols >= 4 to enable support",
@@ -1554,10 +1554,8 @@ getattribute(PyObject *obj, PyObject *name, int allow_qualname) {
         Py_DECREF(dotted_path);
         return NULL;
     }
-    Py_INCREF(obj);
-    for (i = 0; i < Py_SIZE(dotted_path); i++) {
+    for (i = 0; i < n; i++) {
         PyObject *subpath = PyList_GET_ITEM(dotted_path, i);
-        PyObject *tmp;
         PyObject *result = PyUnicode_RichCompare(
             subpath, _PyUnicode_FromId(&PyId_locals), Py_EQ);
         int is_equal = (result == Py_True);
@@ -1567,37 +1565,69 @@ getattribute(PyObject *obj, PyObject *name, int allow_qualname) {
             PyErr_Format(PyExc_AttributeError,
                          "Can't get local attribute %R on %R", name, obj);
             Py_DECREF(dotted_path);
-            Py_DECREF(obj);
             return NULL;
         }
-        tmp = PyObject_GetAttr(obj, subpath);
+    }
+    return dotted_path;
+}
+
+static PyObject *
+get_deep_attribute(PyObject *obj, PyObject *names)
+{
+    Py_ssize_t i, n;
+
+    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 *tmp;
+        tmp = PyObject_GetAttr(obj, name);
         Py_DECREF(obj);
-        if (tmp == NULL) {
-            if (PyErr_ExceptionMatches(PyExc_AttributeError)) {
-                PyErr_Clear();
-                PyErr_Format(PyExc_AttributeError,
-                             "Can't get attribute %R on %R", name, obj);
-            }
-            Py_DECREF(dotted_path);
+        if (tmp == NULL)
             return NULL;
-        }
         obj = tmp;
     }
-    Py_DECREF(dotted_path);
     return obj;
 }
 
+static void
+reformat_attribute_error(PyObject *obj, PyObject *name)
+{
+    if (PyErr_ExceptionMatches(PyExc_AttributeError)) {
+        PyErr_Clear();
+        PyErr_Format(PyExc_AttributeError,
+                     "Can't get attribute %R on %R", name, obj);
+    }
+}
+
+
+static PyObject *
+getattribute(PyObject *obj, PyObject *name, int allow_qualname)
+{
+    PyObject *dotted_path, *attr;
+
+    dotted_path = get_dotted_path(obj, name, allow_qualname);
+    if (dotted_path == NULL)
+        return NULL;
+    attr = get_deep_attribute(obj, dotted_path);
+    Py_DECREF(dotted_path);
+    if (attr == NULL)
+        reformat_attribute_error(obj, name);
+    return attr;
+}
+
 static PyObject *
 whichmodule(PyObject *global, PyObject *global_name, int allow_qualname)
 {
     PyObject *module_name;
     PyObject *modules_dict;
     PyObject *module;
-    PyObject *obj;
-    Py_ssize_t i, j;
+    Py_ssize_t i;
     _Py_IDENTIFIER(__module__);
     _Py_IDENTIFIER(modules);
     _Py_IDENTIFIER(__main__);
+    PyObject *dotted_path;
 
     module_name = _PyObject_GetAttrId(global, &PyId___module__);
 
@@ -1616,43 +1646,49 @@ whichmodule(PyObject *global, PyObject *global_name, int allow_qualname)
     }
     assert(module_name == NULL);
 
+    /* Fallback on walking sys.modules */
     modules_dict = _PySys_GetObjectId(&PyId_modules);
     if (modules_dict == NULL) {
         PyErr_SetString(PyExc_RuntimeError, "unable to get sys.modules");
         return NULL;
     }
 
+    dotted_path = get_dotted_path(module, global_name, allow_qualname);
+    if (dotted_path == NULL)
+        return NULL;
+
     i = 0;
-    while ((j = PyDict_Next(modules_dict, &i, &module_name, &module))) {
-        PyObject *result = PyUnicode_RichCompare(
-            module_name, _PyUnicode_FromId(&PyId___main__), Py_EQ);
-        int is_equal = (result == Py_True);
-        assert(PyBool_Check(result));
-        Py_DECREF(result);
-        if (is_equal)
+    while (PyDict_Next(modules_dict, &i, &module_name, &module)) {
+        PyObject *candidate;
+        if (PyUnicode_Check(module_name) &&
+            !PyUnicode_CompareWithASCIIString(module_name, "__main__"))
             continue;
         if (module == Py_None)
             continue;
 
-        obj = getattribute(module, global_name, allow_qualname);
-        if (obj == NULL) {
-            if (!PyErr_ExceptionMatches(PyExc_AttributeError))
+        candidate = get_deep_attribute(module, dotted_path);
+        if (candidate == NULL) {
+            if (!PyErr_ExceptionMatches(PyExc_AttributeError)) {
+                Py_DECREF(dotted_path);
                 return NULL;
+            }
             PyErr_Clear();
             continue;
         }
 
-        if (obj == global) {
-            Py_DECREF(obj);
+        if (candidate == global) {
             Py_INCREF(module_name);
+            Py_DECREF(dotted_path);
+            Py_DECREF(candidate);
             return module_name;
         }
-        Py_DECREF(obj);
+        Py_DECREF(candidate);
     }
 
     /* If no module is found, use __main__. */
     module_name = _PyUnicode_FromId(&PyId___main__);
     Py_INCREF(module_name);
+    Py_DECREF(dotted_path);
     return module_name;
 }