Clarifying code rearrangement and comments by David Abrahams. I've

got to admit that I haven't reviewed this carefully, but it looks okay
from 30,000 views, and doesn't break anything.  (SF patch 536407.)

diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index a3fefe66410d842aaf0db5e5ca5678c8f354b83d..c369ff793453a553634be7c3864881b63195d040 100644 (file)
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -1236,8 +1236,8 @@ static PyObject *
 type_getattro(PyTypeObject *type, PyObject *name)
 {
        PyTypeObject *metatype = type->ob_type;
-       PyObject *descr, *res;
-       descrgetfunc f;
+       PyObject *meta_attribute, *attribute;
+       descrgetfunc meta_get;
 
        /* Initialize this type (we'll assume the metatype is initialized) */
        if (type->tp_dict == NULL) {
@@ -1245,40 +1245,58 @@ type_getattro(PyTypeObject *type, PyObject *name)
                        return NULL;
        }
 
-       /* Get a descriptor from the metatype */
-       descr = _PyType_Lookup(metatype, name);
-       f = NULL;
-       if (descr != NULL) {
-               f = descr->ob_type->tp_descr_get;
-               if (f != NULL && PyDescr_IsData(descr))
-                       return f(descr,
-                                (PyObject *)type, (PyObject *)metatype);
+       /* No readable descriptor found yet */
+       meta_get = NULL;
+               
+       /* Look for the attribute in the metatype */
+       meta_attribute = _PyType_Lookup(metatype, name);
+
+       if (meta_attribute != NULL) {
+               meta_get = meta_attribute->ob_type->tp_descr_get;
+                               
+               if (meta_get != NULL && PyDescr_IsData(meta_attribute)) {
+                       /* Data descriptors implement tp_descr_set to intercept
+                        * writes. Assume the attribute is not overridden in
+                        * type's tp_dict (and bases): call the descriptor now.
+                        */
+                       return meta_get(meta_attribute, (PyObject *)type,
+                                       (PyObject *)metatype);
+               }
        }
 
-       /* Look in tp_dict of this type and its bases */
-       res = _PyType_Lookup(type, name);
-       if (res != NULL) {
-               f = res->ob_type->tp_descr_get;
-               if (f != NULL)
-                       return f(res, (PyObject *)NULL, (PyObject *)type);
-               Py_INCREF(res);
-               return res;
+       /* No data descriptor found on metatype. Look in tp_dict of this
+        * type and its bases */
+       attribute = _PyType_Lookup(type, name);
+       if (attribute != NULL) {
+               /* Implement descriptor functionality, if any */
+               descrgetfunc local_get = attribute->ob_type->tp_descr_get;
+               if (local_get != NULL) {
+                       /* NULL 2nd argument indicates the descriptor was
+                        * found on the target object itself (or a base)  */
+                       return local_get(attribute, (PyObject *)NULL,
+                                        (PyObject *)type);
+               }
+               
+               Py_INCREF(attribute);
+               return attribute;
        }
 
-       /* Use the descriptor from the metatype */
-       if (f != NULL) {
-               res = f(descr, (PyObject *)type, (PyObject *)metatype);
-               return res;
-       }
-       if (descr != NULL) {
-               Py_INCREF(descr);
-               return descr;
+       /* No attribute found in local __dict__ (or bases): use the
+        * descriptor from the metatype, if any */
+       if (meta_get != NULL)
+               return meta_get(meta_attribute, (PyObject *)type,
+                               (PyObject *)metatype);
+
+       /* If an ordinary attribute was found on the metatype, return it now */
+       if (meta_attribute != NULL) {
+               Py_INCREF(meta_attribute);
+               return meta_attribute;
        }
 
        /* Give up */
        PyErr_Format(PyExc_AttributeError,
-                    "type object '%.50s' has no attribute '%.400s'",
-                    type->tp_name, PyString_AS_STRING(name));
+                        "type object '%.50s' has no attribute '%.400s'",
+                        type->tp_name, PyString_AS_STRING(name));
        return NULL;
 }