title: ctypes showing incorrect byte size
body: <pre><code>import ctypes
  from ctypes import *
  import sys
  
  
  
  class A(Structure):
      _fields_ = [("a",c_uint64),
          ("b",c_uint64),
          ("c",c_uint64),
          ("d",c_uint64),
          ("e",c_uint64),
          ("f",c_uint64),
          ("g",c_uint64),
          ("h",c_uint64),
          ("i",c_uint64),
          ("j",c_uint64),
          ("k",c_uint64),
          ("l",c_uint64),
          ("m",c_uint64),
          ("n",c_uint64),
          ("o",c_uint64),
          ("p",c_uint64),
          ("q",c_uint64),
          ("r",c_uint64*16),
          ("s",c_uint64*16),
          ("t",c_uint64*16),
          ("u",c_uint64*16),
          ("v",c_uint64*16),
          ("w",c_uint64),
          ("x",c_uint64),
          ("y",c_uint64),
          ("z",c_uint64)
          ]
  
  class B(Structure):
      _fields_ = [("a1",c_uint64),
                  ("b1",c_uint64),
                  ("c1",c_uint64)
             ]
  
  class C(Structure):
      _fields_ = [("a2",c_uint64*32),
                  ("b2",c_uint64*32),
                  ("c2",c_uint64)
                 ]
  
  
  class U_union(Union):
      _fields_ = [("a3", A),
          ("b3",B),
          ("c3",C),
          ("d3",c_uint32),
          ("e3",c_uint32)
          ]
  
  
  class ether_header(Structure):
     _fields_ = [("ether_dhost", c_uint8*6),
             ("ether_shost", c_uint8*6),
             ("ether_type", c_uint16)
            ]
  
  class D(Structure):
      _fields_ = [ ("ether",ether_header),
           ("a4", c_uint8),
                   ("b4", c_uint8),
                   ("c4", c_uint8),
                   ("d4", c_uint8),
                   ("e4", c_uint16),
                   ("f4",U_union),
          ]
  
  
  class Send:
      def __init__(self,a):
          file=D()
          print sizeof(file)
  
  if __name__== "__main__":
      Send("hello")
  </code></pre>
  
  <p>I have to send 830  byte structure.Here dual padding(2bytes at each) is taking place.
  This is my sample code,ETHER_HEAD structure is 14 bytes,FILE_HEAD without ether_head structure member is 816 bytes and with ether_head member as 832 bytes.How come 2 bytes got added ?
  And i am trying other scenerio like to send only 830 bytes like concatenating 2 structures seperately ,but if i create two object reference for two classes and making + operator in between the objets it showing cannot concat the objects error .how can i simulate it ?</p>