#2538: bytes objects can only provide read-only buffers

Lib/test/test_bytes.py

@@ -453,6 +453,11 @@ def test_ord(self):
 class BytesTest(BaseBytesTest):
     type2test = bytes
 
+    def test_buffer_is_readonly(self):
+        with open(sys.stdin.fileno(), "rb", buffering=0) as f:
+            self.assertRaises(TypeError, f.readinto, b"")
+
+
 class ByteArrayTest(BaseBytesTest):
     type2test = bytearray
 

Lib/test/test_socket.py

@@ -1112,7 +1112,7 @@ def __init__(self, methodName='runTest'):
         SocketConnectedTest.__init__(self, methodName=methodName)
 
     def testRecvInto(self):
-        buf = b" "*1024
+        buf = bytearray(1024)
         nbytes = self.cli_conn.recv_into(buf)
         self.assertEqual(nbytes, len(MSG))
         msg = buf[:len(MSG)]
@@ -1123,7 +1123,7 @@ def _testRecvInto(self):
         self.serv_conn.send(buf)
 
     def testRecvFromInto(self):
-        buf = b" "*1024
+        buf = bytearray(1024)
         nbytes, addr = self.cli_conn.recvfrom_into(buf)
         self.assertEqual(nbytes, len(MSG))
         msg = buf[:len(MSG)]

Objects/bytesobject.c

@@ -965,7 +965,7 @@ static int
 string_buffer_getbuffer(PyBytesObject *self, Py_buffer *view, int flags)
 {
 	return PyBuffer_FillInfo(view, (void *)self->ob_sval, Py_SIZE(self),
-				 0, flags);
+				 1, flags);
 }
 
 static PySequenceMethods string_as_sequence = {

Objects/memoryobject.c

@@ -56,7 +56,7 @@ PyMemoryView_FromObject(PyObject *base)
         if (mview == NULL) return NULL;
 
         mview->base = NULL;
-        if (PyObject_GetBuffer(base, &(mview->view), PyBUF_FULL) < 0) {
+        if (PyObject_GetBuffer(base, &(mview->view), PyBUF_FULL_RO) < 0) {
                 Py_DECREF(mview);
                 return NULL;
         }