Issue #4701: implicitly call PyType_Ready from PyObject_Hash

Lib/test/test_hash.py

@@ -111,9 +111,32 @@ class HashInheritanceTestCase(unittest.TestCase):
             self.assertFalse(isinstance(obj, Hashable), repr(obj))
 
 
+# Issue #4701: Check that some builtin types are correctly hashable
+#  (This test only used to fail in Python 3.0, but has been included
+#   in 2.x along with the lazy call to PyType_Ready in PyObject_Hash)
+class DefaultIterSeq(object):
+    seq = range(10)
+    def __len__(self):
+        return len(self.seq)
+    def __getitem__(self, index):
+        return self.seq[index]
+
+class HashBuiltinsTestCase(unittest.TestCase):
+    hashes_to_check = [xrange(10),
+                       enumerate(xrange(10)),
+                       iter(DefaultIterSeq()),
+                       iter(lambda: 0, 0),
+                      ]
+
+    def test_hashes(self):
+        _default_hash = object.__hash__
+        for obj in self.hashes_to_check:
+            self.assertEqual(hash(obj), _default_hash(obj))
+
 def test_main():
     test_support.run_unittest(HashEqualityTestCase,
-                              HashInheritanceTestCase)
+                              HashInheritanceTestCase,
+                              HashBuiltinsTestCase)
 
 
 if __name__ == "__main__":

Misc/NEWS

@@ -12,6 +12,9 @@ What's New in Python 2.7 alpha 1
 Core and Builtins
 -----------------
 
+- Issue #4701: PyObject_Hash now implicitly calls PyType_Ready on types
+  where the tp_hash and tp_dict slots are both NULL.
+
 - Issue #4764: With io.open, IOError.filename is set when trying to open a
   directory on POSIX systems.
 

Modules/_testcapimodule.c

@@ -173,6 +173,106 @@ test_dict_iteration(PyObject* self)
 }
 
 
+/* Issue #4701: Check that PyObject_Hash implicitly calls
+ *   PyType_Ready if it hasn't already been called
+ */
+static PyTypeObject _HashInheritanceTester_Type = {
+	PyObject_HEAD_INIT(&PyType_Type)
+	0,			/* Number of items for varobject */
+	"hashinheritancetester",	/* Name of this type */
+	sizeof(PyObject),	/* Basic object size */
+	0,			/* Item size for varobject */
+	(destructor)PyObject_Del, /* tp_dealloc */
+	0,			/* tp_print */
+	0,			/* tp_getattr */
+	0,			/* tp_setattr */
+	0,			/* tp_compare */
+	0,			/* tp_repr */
+	0,			/* tp_as_number */
+	0,			/* tp_as_sequence */
+	0,			/* tp_as_mapping */
+	0,			/* tp_hash */
+	0,			/* tp_call */
+	0,			/* tp_str */
+	PyObject_GenericGetAttr,  /* tp_getattro */
+	0,			/* tp_setattro */
+	0,			/* tp_as_buffer */
+	Py_TPFLAGS_DEFAULT,	/* tp_flags */
+	0,			/* tp_doc */
+	0,			/* tp_traverse */
+	0,			/* tp_clear */
+	0,			/* tp_richcompare */
+	0,			/* tp_weaklistoffset */
+	0,			/* tp_iter */
+	0,			/* tp_iternext */
+	0,			/* tp_methods */
+	0,			/* tp_members */
+	0,			/* tp_getset */
+	0,			/* tp_base */
+	0,			/* tp_dict */
+	0,			/* tp_descr_get */
+	0,			/* tp_descr_set */
+	0,			/* tp_dictoffset */
+	0,			/* tp_init */
+	0,			/* tp_alloc */
+	PyType_GenericNew,		/* tp_new */
+};
+
+static PyObject*
+test_lazy_hash_inheritance(PyObject* self)
+{
+	PyTypeObject *type;
+	PyObject *obj;
+	long hash;
+
+	type = &_HashInheritanceTester_Type;
+	obj = PyObject_New(PyObject, type);
+	if (obj == NULL) {
+		PyErr_Clear();
+		PyErr_SetString(
+			TestError,
+			"test_lazy_hash_inheritance: failed to create object");
+		return NULL;
+	}
+
+	if (type->tp_dict != NULL) {
+		PyErr_SetString(
+			TestError,
+			"test_lazy_hash_inheritance: type initialised too soon");
+		Py_DECREF(obj);
+		return NULL;
+	}
+
+	hash = PyObject_Hash(obj);
+	if ((hash == -1) && PyErr_Occurred()) {
+		PyErr_Clear();
+		PyErr_SetString(
+			TestError,
+			"test_lazy_hash_inheritance: could not hash object");
+		Py_DECREF(obj);
+		return NULL;
+	}
+
+	if (type->tp_dict == NULL) {
+		PyErr_SetString(
+			TestError,
+			"test_lazy_hash_inheritance: type not initialised by hash()");
+		Py_DECREF(obj);
+		return NULL;
+	}
+
+	if (type->tp_hash != PyType_Type.tp_hash) {
+		PyErr_SetString(
+			TestError,
+			"test_lazy_hash_inheritance: unexpected hash function");
+		Py_DECREF(obj);
+		return NULL;
+	}
+
+	Py_RETURN_NONE;
+}
+
+
 /* Tests of PyLong_{As, From}{Unsigned,}Long(), and (#ifdef HAVE_LONG_LONG)
    PyLong_{As, From}{Unsigned,}LongLong().
 
@@ -805,6 +905,7 @@ static PyMethodDef TestMethods[] = {
 	{"test_config",		(PyCFunction)test_config,	 METH_NOARGS},
 	{"test_list_api",	(PyCFunction)test_list_api,	 METH_NOARGS},
 	{"test_dict_iteration",	(PyCFunction)test_dict_iteration,METH_NOARGS},
+	{"test_lazy_hash_inheritance",	(PyCFunction)test_lazy_hash_inheritance,METH_NOARGS},
 	{"test_long_api",	(PyCFunction)test_long_api,	 METH_NOARGS},
 	{"test_long_numbits",	(PyCFunction)test_long_numbits,	 METH_NOARGS},
 	{"test_k_code",		(PyCFunction)test_k_code,	 METH_NOARGS},

Objects/object.c

@@ -1100,6 +1100,17 @@ PyObject_Hash(PyObject *v)
 	PyTypeObject *tp = v->ob_type;
 	if (tp->tp_hash != NULL)
 		return (*tp->tp_hash)(v);
+	/* To keep to the general practice that inheriting
+	 * solely from object in C code should work without
+	 * an explicit call to PyType_Ready, we implicitly call
+	 * PyType_Ready here and then check the tp_hash slot again
+	 */
+	if (tp->tp_dict == NULL) {
+		if (PyType_Ready(tp) < 0)
+			return -1;
+		if (tp->tp_hash != NULL)
+			return (*tp->tp_hash)(v);
+	}
 	if (tp->tp_compare == NULL && RICHCOMPARE(tp) == NULL) {
 		return _Py_HashPointer(v); /* Use address as hash value */
 	}