removing undefined as many as possible.

Network/Socket/ByteString/Lazy/Posix.hs

@@ -38,7 +38,7 @@ send s lbs = do
             | k < maxNumBytes = unsafeUseAsCStringLen c $ \(ptr, len) -> do
                 poke q $ IOVec (castPtr ptr) (fromIntegral len)
                 loop cs
-                     (q `plusPtr` sizeOf (undefined :: IOVec))
+                     (q `plusPtr` sizeOf (IOVec nullPtr 0))
                      (k + fromIntegral len)
                      (niovs + 1)
             | otherwise = f niovs

Network/Socket/Info.hsc

@@ -110,7 +110,7 @@ data AddrInfo = AddrInfo {
 
 instance Storable AddrInfo where
     sizeOf    _ = #const sizeof(struct addrinfo)
-    alignment _ = alignment (undefined :: CInt)
+    alignment _ = alignment (0 :: CInt)
 
     peek p = do
         ai_flags <- (#peek struct addrinfo, ai_flags) p
@@ -181,9 +181,7 @@ niFlagMapping = [(NI_DGRAM, #const NI_DGRAM),
                  (NI_NUMERICHOST, #const NI_NUMERICHOST),
                  (NI_NUMERICSERV, #const NI_NUMERICSERV)]
 
--- | Default hints for address lookup with 'getAddrInfo'.  The values
--- of the 'addrAddress' and 'addrCanonName' fields are 'undefined',
--- and are never inspected by 'getAddrInfo'.
+-- | Default hints for address lookup with 'getAddrInfo'.
 --
 -- >>> addrFlags defaultHints
 -- []
@@ -200,29 +198,10 @@ defaultHints = AddrInfo {
   , addrFamily     = AF_UNSPEC
   , addrSocketType = NoSocketType
   , addrProtocol   = defaultProtocol
-  , addrAddress    = undefined
-  , addrCanonName  = undefined
+  , addrAddress    = SockAddrInet 0 0
+  , addrCanonName  = Nothing
   }
 
--- | Shows the fields of 'defaultHints', without inspecting the by-default undefined fields 'addrAddress' and 'addrCanonName'.
-showDefaultHints :: AddrInfo -> String
-showDefaultHints AddrInfo{..} = concat [
-    "AddrInfo {"
-  , "addrFlags = "
-  , show addrFlags
-  , ", addrFamily = "
-  , show addrFamily
-  , ", addrSocketType = "
-  , show addrSocketType
-  , ", addrProtocol = "
-  , show addrProtocol
-  , ", addrAddress = "
-  , "<assumed to be undefined>"
-  , ", addrCanonName = "
-  , "<assumed to be undefined>"
-  , "}"
-  ]
-
 -----------------------------------------------------------------------------
 -- | Resolve a host or service name to one or more addresses.
 -- The 'AddrInfo' values that this function returns contain 'SockAddr'
@@ -294,7 +273,7 @@ getAddrInfo hints node service = alloc getaddrinfo
                         err
     message = concat [
         "Network.Socket.getAddrInfo (called with preferred socket type/protocol: "
-      , maybe (show hints) showDefaultHints hints
+      , maybe "Nothing" show hints
       , ", host name: "
       , show node
       , ", service name: "

Network/Socket/Options.hsc

@@ -285,8 +285,8 @@ pattern CustomSockOpt xy <- ((\(SockOpt x y) -> (x, y)) -> xy)
 data StructLinger = StructLinger CInt CInt
 
 instance Storable StructLinger where
-    sizeOf _ = (#const sizeof(struct linger))
-    alignment _ = alignment (undefined :: CInt)
+    sizeOf    _ = (#const sizeof(struct linger))
+    alignment _ = alignment (0 :: CInt)
 
     peek p = do
         onoff  <- (#peek struct linger, l_onoff) p

Network/Socket/Posix/Cmsg.hsc

@@ -169,8 +169,8 @@ instance ControlMessage IPv4PktInfo where
 
 instance Storable IPv4PktInfo where
 #if defined (IP_PKTINFO)
-    sizeOf _ = (#size struct in_pktinfo)
-    alignment _ = alignment (undefined :: CInt)
+    sizeOf    _ = (#size struct in_pktinfo)
+    alignment _ = alignment (0 :: CInt)
     poke p (IPv4PktInfo n sa ha) = do
         (#poke struct in_pktinfo, ipi_ifindex)  p (fromIntegral n :: CInt)
         (#poke struct in_pktinfo, ipi_spec_dst) p sa
@@ -181,7 +181,7 @@ instance Storable IPv4PktInfo where
         ha <- (#peek struct in_pktinfo, ipi_addr)     p
         return $ IPv4PktInfo n sa ha
 #else
-    sizeOf _ = 0
+    sizeOf    _ = 0
     alignment _ = 1
     poke _ _ = error "Unsupported control message type"
     peek _   = error "Unsupported control message type"
@@ -200,8 +200,8 @@ instance ControlMessage IPv6PktInfo where
 
 instance Storable IPv6PktInfo where
 #if defined (IPV6_PKTINFO)
-    sizeOf _ = (#size struct in6_pktinfo)
-    alignment _ = alignment (undefined :: CInt)
+    sizeOf    _ = (#size struct in6_pktinfo)
+    alignment _ = alignment (0 :: CInt)
     poke p (IPv6PktInfo n ha6) = do
         (#poke struct in6_pktinfo, ipi6_ifindex) p (fromIntegral n :: CInt)
         (#poke struct in6_pktinfo, ipi6_addr)    p (In6Addr ha6)
@@ -210,7 +210,7 @@ instance Storable IPv6PktInfo where
         n :: CInt   <- (#peek struct in6_pktinfo, ipi6_ifindex) p
         return $ IPv6PktInfo (fromIntegral n) ha6
 #else
-    sizeOf _ = 0
+    sizeOf    _ = 0
     alignment _ = 1
     poke _ _ = error "Unsupported control message type"
     peek _   = error "Unsupported control message type"

Network/Socket/Posix/CmsgHdr.hsc

@@ -28,8 +28,8 @@ data CmsgHdr = CmsgHdr {
   } deriving (Eq, Show)
 
 instance Storable CmsgHdr where
-  sizeOf _    = (#size struct cmsghdr)
-  alignment _ = alignment (undefined :: CInt)
+  sizeOf    _ = (#size struct cmsghdr)
+  alignment _ = alignment (0 :: CInt)
 
   peek p = do
     len <- (#peek struct cmsghdr, cmsg_len)   p

Network/Socket/Posix/IOVec.hsc

@@ -19,8 +19,8 @@ data IOVec = IOVec
     }
 
 instance Storable IOVec where
-  sizeOf _    = (#const sizeof(struct iovec))
-  alignment _ = alignment (undefined :: CInt)
+  sizeOf    _ = (#const sizeof(struct iovec))
+  alignment _ = alignment (0 :: CInt)
 
   peek p = do
     base <- (#peek struct iovec, iov_base) p

Network/Socket/Posix/MsgHdr.hsc

@@ -24,8 +24,8 @@ data MsgHdr sa = MsgHdr
     }
 
 instance Storable (MsgHdr sa) where
-  sizeOf _    = (#const sizeof(struct msghdr))
-  alignment _ = alignment (undefined :: CInt)
+  sizeOf    _ = (#const sizeof(struct msghdr))
+  alignment _ = alignment (0 :: CInt)
 
   peek p = do
     name       <- (#peek struct msghdr, msg_name)       p

Network/Socket/Types.hsc

@@ -910,8 +910,8 @@ foreign import CALLCONV unsafe "ntohl" ntohl :: Word32 -> Word32
 {-# DEPRECATED ntohl "Use getAddrInfo instead" #-}
 
 instance Storable PortNumber where
-   sizeOf    _ = sizeOf    (undefined :: Word16)
-   alignment _ = alignment (undefined :: Word16)
+   sizeOf    _ = sizeOf    (0 :: Word16)
+   alignment _ = alignment (0 :: Word16)
    poke p (PortNum po) = poke (castPtr p) (htons po)
    peek p = PortNum . ntohs <$> peek (castPtr p)
 
@@ -1221,7 +1221,7 @@ newtype In6Addr = In6Addr HostAddress6
 #endif
 
 instance Storable In6Addr where
-    sizeOf _    = #const sizeof(struct in6_addr)
+    sizeOf    _ = #const sizeof(struct in6_addr)
     alignment _ = #alignment struct in6_addr
 
     peek p = do

Network/Socket/Unix.hsc

@@ -81,8 +81,8 @@ getPeerCred s = do
 
 newtype PeerCred = PeerCred (CUInt, CUInt, CUInt)
 instance Storable PeerCred where
-    sizeOf _ = (#const sizeof(struct ucred))
-    alignment _ = alignment (undefined :: CInt)
+    sizeOf    _ = (#const sizeof(struct ucred))
+    alignment _ = alignment (0 :: CInt)
     poke _ _ = return ()
     peek p = do
         pid <- (#peek struct ucred, pid) p

Network/Socket/Win32/Cmsg.hsc

@@ -147,7 +147,7 @@ instance ControlMessage IPv4PktInfo where
     controlMessageId = CmsgIdIPv4PktInfo
 
 instance Storable IPv4PktInfo where
-    sizeOf      = const #{size IN_PKTINFO}
+    sizeOf    _ = #{size IN_PKTINFO}
     alignment _ = #alignment IN_PKTINFO
     poke p (IPv4PktInfo n ha) = do
         (#poke IN_PKTINFO, ipi_ifindex)  p (fromIntegral n :: CInt)
@@ -169,7 +169,7 @@ instance ControlMessage IPv6PktInfo where
     controlMessageId = CmsgIdIPv6PktInfo
 
 instance Storable IPv6PktInfo where
-    sizeOf      = const #{size IN6_PKTINFO}
+    sizeOf    _ = #{size IN6_PKTINFO}
     alignment _ = #alignment IN6_PKTINFO
     poke p (IPv6PktInfo n ha6) = do
         (#poke IN6_PKTINFO, ipi6_ifindex) p (fromIntegral n :: CInt)

Network/Socket/Win32/CmsgHdr.hsc

@@ -25,7 +25,7 @@ data CmsgHdr = CmsgHdr {
   } deriving (Eq, Show)
 
 instance Storable CmsgHdr where
-  sizeOf      = const #{size WSACMSGHDR}
+  sizeOf    _ = #{size WSACMSGHDR}
   alignment _ = #alignment WSACMSGHDR
 
   peek p = do

Network/Socket/Win32/MsgHdr.hsc

@@ -28,7 +28,7 @@ data MsgHdr sa = MsgHdr
     } deriving Show
 
 instance Storable (MsgHdr sa) where
-  sizeOf      = const #{size WSAMSG}
+  sizeOf    _ = #{size WSAMSG}
   alignment _ = #alignment WSAMSG
 
   peek p = do

Network/Socket/Win32/WSABuf.hsc

@@ -20,7 +20,7 @@ data WSABuf = WSABuf
     }
 
 instance Storable WSABuf where
-  sizeOf      = const #{size WSABUF}
+  sizeOf    _ = #{size WSABUF}
   alignment _ = #alignment WSABUF
 
   peek p = do