Make `-Wall` clean and drop `-fno-warn-unused-imports`

CPP conditional code sections have been carefully taken into account
while performing this warning cleanup. Most `OPTIONS_GHC` declarations
could be dropped (now only a lonely `{-# OPTIONS_GHC -fno-cse #-}`
remains in `Posix.Signals`).

Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>

System/Posix/Directory.hsc

 {-# LANGUAGE NondecreasingIndentation #-}
-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif

System/Posix/Directory/ByteString.hsc

 {-# LANGUAGE NondecreasingIndentation #-}
-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif

System/Posix/Directory/Common.hsc

-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif
@@ -32,8 +31,6 @@ module System.Posix.Directory.Common (
        changeWorkingDirectoryFd,
   ) where
 
-import System.IO.Error
-import System.Posix.Error
 import System.Posix.Types
 import Foreign
 import Foreign.C

System/Posix/Files.hsc

-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif
@@ -95,12 +94,9 @@ module System.Posix.Files (
 import Foreign
 import Foreign.C
 
-import System.Posix.Error
 import System.Posix.Types
-import System.Posix.Internals
 import System.Posix.Files.Common
-
-import System.Posix.Internals (withFilePath, peekFilePath)
+import System.Posix.Internals
 
 import Data.Time.Clock.POSIX
 

System/Posix/Files/Common.hsc

-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif
@@ -81,17 +80,22 @@ module System.Posix.Files.Common (
 #endif
   ) where
 
-import System.Posix.Error
 import System.Posix.Types
 import System.IO.Unsafe
 import Data.Bits
+#if defined(HAVE_STRUCT_STAT_ST_CTIM) || \
+    defined(HAVE_STRUCT_STAT_ST_MTIM) || \
+    defined(HAVE_STRUCT_STAT_ST_ATIM)
 import Data.Int
-import Data.Time.Clock.POSIX
 import Data.Ratio
+#endif
+import Data.Time.Clock.POSIX
 import System.Posix.Internals
 import Foreign.C
 import Foreign.ForeignPtr
-import Foreign.Marshal
+#if defined(HAVE_FUTIMES) || defined(HAVE_FUTIMENS)
+import Foreign.Marshal (withArray)
+#endif
 import Foreign.Ptr
 import Foreign.Storable
 

System/Posix/IO.hsc

-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif

System/Posix/IO/ByteString.hsc

-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif
@@ -68,17 +67,9 @@ module System.Posix.IO.ByteString (
 
 import System.Posix.Types
 import System.Posix.IO.Common
-import Foreign.C hiding (
-     throwErrnoPath,
-     throwErrnoPathIf,
-     throwErrnoPathIf_,
-     throwErrnoPathIfNull,
-     throwErrnoPathIfMinus1,
-     throwErrnoPathIfMinus1_ )
 
 import System.Posix.ByteString.FilePath
 
-
 -- |Open and optionally create this file.  See 'System.Posix.Files'
 -- for information on how to use the 'FileMode' type.
 openFd :: RawFilePath

System/Posix/IO/Common.hsc

 {-# LANGUAGE NondecreasingIndentation, RecordWildCards #-}
-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif
@@ -63,15 +62,12 @@ module System.Posix.IO.Common (
 import System.IO
 import System.IO.Error
 import System.Posix.Types
-import System.Posix.Error
 import qualified System.Posix.Internals as Base
 
 import Foreign
 import Foreign.C
-import Data.Bits
 
 #ifdef __GLASGOW_HASKELL__
-import GHC.IO.Handle
 import GHC.IO.Handle.Internals
 import GHC.IO.Handle.Types
 import qualified GHC.IO.FD as FD

System/Posix/Resource.hsc

-{-# OPTIONS_GHC -w #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif
--- The above warning supression flag is a temporary kludge.
--- While working on this module you are encouraged to remove it and fix
--- any warnings in the module. See
---     http://hackage.haskell.org/trac/ghc/wiki/WorkingConventions#Warnings
--- for details
 -----------------------------------------------------------------------------
 -- |
 -- Module      :  System.Posix.Resource
@@ -70,7 +64,7 @@ foreign import ccall unsafe "HsUnix.h __hscore_setrlimit"
 getResourceLimit :: Resource -> IO ResourceLimits
 getResourceLimit res = do
   allocaBytes (#const sizeof(struct rlimit)) $ \p_rlimit -> do
-    throwErrnoIfMinus1 "getResourceLimit" $
+    throwErrnoIfMinus1_ "getResourceLimit" $
       c_getrlimit (packResource res) p_rlimit
     soft <- (#peek struct rlimit, rlim_cur) p_rlimit
     hard <- (#peek struct rlimit, rlim_max) p_rlimit
@@ -84,7 +78,7 @@ setResourceLimit res ResourceLimits{softLimit=soft,hardLimit=hard} = do
   allocaBytes (#const sizeof(struct rlimit)) $ \p_rlimit -> do
     (#poke struct rlimit, rlim_cur) p_rlimit (packRLimit soft True)
     (#poke struct rlimit, rlim_max) p_rlimit (packRLimit hard False)
-    throwErrnoIfMinus1 "setResourceLimit" $
+    throwErrnoIfMinus1_ "setResourceLimit" $
 	c_setrlimit (packResource res) p_rlimit
     return ()
 
@@ -101,16 +95,20 @@ packResource ResourceTotalMemory   = (#const RLIMIT_AS)
 
 unpackRLimit :: CRLim -> ResourceLimit
 unpackRLimit (#const RLIM_INFINITY)  = ResourceLimitInfinity
-#ifdef RLIM_SAVED_MAX
+#if defined(RLIM_SAVED_MAX) && (RLIM_SAVED_MAX != RLIM_INFINITY)
 unpackRLimit (#const RLIM_SAVED_MAX) = ResourceLimitUnknown
+#endif
+#if defined(RLIM_SAVED_CUR) && (RLIM_SAVED_CUR != RLIM_INFINITY)
 unpackRLimit (#const RLIM_SAVED_CUR) = ResourceLimitUnknown
 #endif
 unpackRLimit other = ResourceLimit (fromIntegral other)
 
 packRLimit :: ResourceLimit -> Bool -> CRLim
 packRLimit ResourceLimitInfinity _     = (#const RLIM_INFINITY)
-#ifdef RLIM_SAVED_MAX
+#ifdef RLIM_SAVED_CUR
 packRLimit ResourceLimitUnknown  True  = (#const RLIM_SAVED_CUR)
+#endif
+#ifdef RLIM_SAVED_MAX
 packRLimit ResourceLimitUnknown  False = (#const RLIM_SAVED_MAX)
 #endif
 packRLimit (ResourceLimit other) _     = fromIntegral other

System/Posix/SharedMem.hsc

-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif
@@ -27,9 +26,12 @@ module System.Posix.SharedMem
 #include "HsUnix.h"
 
 import System.Posix.Types
-import System.Posix.Error
+#if defined(HAVE_SHM_OPEN) || defined(HAVE_SHM_UNLINK)
 import Foreign.C
+#endif
+#ifdef HAVE_SHM_OPEN
 import Data.Bits
+#endif
 
 data ShmOpenFlags = ShmOpenFlags 
     { shmReadWrite :: Bool,

System/Posix/Terminal.hsc

-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif
@@ -76,9 +75,11 @@ import Foreign
 import Foreign.C
 import System.Posix.Terminal.Common
 import System.Posix.Types
+#ifndef HAVE_OPENPTY
 import System.Posix.IO
+#endif
 
-import System.Posix.Internals (withFilePath, peekFilePath)
+import System.Posix.Internals (peekFilePath)
 
 -- | @getTerminalName fd@ calls @ttyname@ to obtain a name associated
 --   with the terminal for @Fd@ @fd@. If @fd@ is associated

System/Posix/Terminal/ByteString.hsc

-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif
@@ -75,8 +74,10 @@ module System.Posix.Terminal.ByteString (
 import Foreign
 import System.Posix.Types
 import System.Posix.Terminal.Common
-import System.Posix.IO.ByteString
-import Data.ByteString.Char8 as B
+#ifndef HAVE_OPENPTY
+import System.Posix.IO.ByteString (defaultFileFlags, openFd, noctty, OpenMode(ReadWrite))
+import Data.ByteString.Char8 as B ( pack, )
+#endif
 
 import Foreign.C hiding (
      throwErrnoPath,
@@ -185,9 +186,9 @@ foreign import ccall unsafe "__hsunix_unlockpt"
   c_unlockpt :: CInt -> IO CInt
 #else
 c_grantpt :: CInt -> IO CInt
-c_grantpt _ = return (fromIntegral 0)
+c_grantpt _ = return (fromIntegral (0::Int))
 
 c_unlockpt :: CInt -> IO CInt
-c_unlockpt _ = return (fromIntegral 0)
+c_unlockpt _ = return (fromIntegral (0::Int))
 #endif /* HAVE_PTSNAME */
 #endif /* !HAVE_OPENPTY */

System/Posix/Terminal/Common.hsc

-{-# OPTIONS_GHC -fno-warn-unused-imports #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif
@@ -69,22 +68,13 @@ module System.Posix.Terminal.Common (
 
 import Data.Bits
 import Data.Char
-import Foreign.C.Error ( errnoToIOError, throwErrnoIfMinus1,
-                         throwErrnoIfMinus1_, throwErrnoIfNull )
-#ifndef HAVE_PTSNAME
-import Foreign.C.Error ( eNOSYS )
-#endif
-import Foreign.C.String ( CString, peekCString, withCString )
+import Foreign.C.Error ( throwErrnoIfMinus1, throwErrnoIfMinus1_ )
 import Foreign.C.Types
 import Foreign.ForeignPtr ( ForeignPtr, withForeignPtr, mallocForeignPtrBytes )
-import Foreign.Marshal.Alloc ( alloca )
 import Foreign.Marshal.Utils ( copyBytes )
-import Foreign.Ptr ( Ptr, nullPtr, plusPtr )
+import Foreign.Ptr ( Ptr, plusPtr )
 import Foreign.Storable ( Storable(..) )
-import System.IO.Error ( ioError )
 import System.IO.Unsafe ( unsafePerformIO )
-import System.Posix.IO ( OpenFileFlags(..), OpenMode(..), defaultFileFlags,
-                         openFd )
 import System.Posix.Types
 
 -- -----------------------------------------------------------------------------

System/Posix/Unistd.hsc

 {-# LANGUAGE NondecreasingIndentation #-}
-{-# OPTIONS_GHC -fno-warn-unused-imports -fno-warn-unused-binds #-}
 #ifdef __GLASGOW_HASKELL__
 {-# LANGUAGE Trustworthy #-}
 #endif
@@ -56,7 +55,6 @@ import Foreign.C.Error
 import Foreign.C.String ( peekCString )
 import Foreign.C.Types
 import Foreign
-import System.Posix.Types
 import System.Posix.Internals
 
 -- -----------------------------------------------------------------------------

unix.cabal

@@ -117,6 +117,8 @@ library
         System.Posix.Process.Common
         System.Posix.Terminal.Common
 
+    ghc-options: -Wall
+
     include-dirs: 	include
     includes:       HsUnix.h execvpe.h
     install-includes: