Add --host-os and --host-arch command-line options and "ios" os

ios-and-host-arch-host-os-options.patch

diff --git a/Cabal/Distribution/Simple/Bench.hs b/Cabal/Distribution/Simple/Bench.hs
index f34c888..4f1d30f 100644
--- a/Cabal/Distribution/Simple/Bench.hs
+++ b/Cabal/Distribution/Simple/Bench.hs
@@ -54,7 +54,8 @@ import Distribution.Simple.InstallDirs
     , substPathTemplate , toPathTemplate, PathTemplate )
 import qualified Distribution.Simple.LocalBuildInfo as LBI
     ( LocalBuildInfo(..) )
-import Distribution.Simple.Setup ( BenchmarkFlags(..), fromFlag )
+import Distribution.Simple.Setup
+    ( BenchmarkFlags(..), fromFlag, configHostPlatform )
 import Distribution.Simple.UserHooks ( Args )
 import Distribution.Simple.Utils ( die, notice, rawSystemExitCode )
 import Distribution.Text
@@ -152,5 +153,6 @@ benchOption pkg_descr lbi bm template =
     fromPathTemplate $ substPathTemplate env template
   where
     env = initialPathTemplateEnv
-          (PD.package pkg_descr) (compilerId $ LBI.compiler lbi) ++
+          (PD.package pkg_descr) (compilerId $ LBI.compiler lbi)
+          (configHostPlatform (LBI.configFlags lbi)) ++
           [(BenchmarkNameVar, toPathTemplate $ PD.benchmarkName bm)]
diff --git a/Cabal/Distribution/Simple/Command.hs b/Cabal/Distribution/Simple/Command.hs
index f908ac0..bc7b7f8 100644
--- a/Cabal/Distribution/Simple/Command.hs
+++ b/Cabal/Distribution/Simple/Command.hs
@@ -79,7 +79,7 @@ module Distribution.Simple.Command (
 
 -- ** OptDescr 'smart' constructors
   MkOptDescr,
-  reqArg, reqArg', optArg, optArg', noArg,
+  reqArg, reqArg', textReqArg, optArg, optArg', noArg,
   boolOpt, boolOpt', choiceOpt, choiceOptFromEnum
 
   ) where
@@ -91,7 +91,7 @@ import Data.Maybe
 import Data.Monoid
 import qualified Distribution.GetOpt as GetOpt
 import Distribution.Text
-         ( Text(disp, parse) )
+         ( Text(disp, parse), simpleParse, display )
 import Distribution.ParseUtils
 import Distribution.ReadE
 import Distribution.Simple.Utils (die, intercalate)
@@ -176,6 +176,14 @@ reqArg' :: Monoid b => ArgPlaceHolder -> (String -> b) -> (b -> [String])
 reqArg' ad mkflag showflag =
     reqArg ad (succeedReadE mkflag) showflag
 
+textReqArg :: (Monoid b, Text b) => ArgPlaceHolder -> MkOptDescr (a -> b) (b -> a -> a) a
+textReqArg ad = reqArg ad parseIt formatIt
+  where
+    parseIt = ReadE $ \txt -> case simpleParse txt of
+        Just a  -> Right a
+        Nothing -> Left $ "Can't parse "++ad
+    formatIt = (:[]) . display
+
 -- | (String -> a) variant of "optArg"
 optArg' :: Monoid b => ArgPlaceHolder -> (Maybe String -> b) -> (b -> [Maybe String])
                     -> MkOptDescr (a -> b) (b -> a -> a) a
diff --git a/Cabal/Distribution/Simple/Configure.hs b/Cabal/Distribution/Simple/Configure.hs
index 9c3c07f..bb91225 100644
--- a/Cabal/Distribution/Simple/Configure.hs
+++ b/Cabal/Distribution/Simple/Configure.hs
@@ -99,7 +99,8 @@ import Distribution.Simple.Program
     , requireProgram, requireProgramVersion
     , pkgConfigProgram, gccProgram, rawSystemProgramStdoutConf )
 import Distribution.Simple.Setup
-    ( ConfigFlags(..), CopyDest(..), fromFlag, fromFlagOrDefault, flagToMaybe )
+    ( ConfigFlags(..), CopyDest(..), fromFlag, fromFlagOrDefault, flagToMaybe
+    , configHostPlatform )
 import Distribution.Simple.InstallDirs
     ( InstallDirs(..), defaultInstallDirs, combineInstallDirs )
 import Distribution.Simple.LocalBuildInfo
@@ -114,7 +115,7 @@ import Distribution.Simple.Utils
     , withFileContents, writeFileAtomic
     , withTempFile )
 import Distribution.System
-    ( OS(..), buildOS, Arch(..), buildArch, buildPlatform )
+    ( OS(..), buildOS, Arch(..), Platform(..) )
 import Distribution.Version
          ( Version(..), anyVersion, orLaterVersion, withinRange, isAnyVersion )
 import Distribution.Verbosity
@@ -343,7 +344,7 @@ configure (pkg_descr0, pbi) cfg
                 case finalizePackageDescription
                        (configConfigurationsFlags cfg)
                        dependencySatisfiable
-                       Distribution.System.buildPlatform
+                       (configHostPlatform cfg)
                        (compilerId comp)
                        (configConstraints cfg)
                        pkg_descr0''
@@ -1027,7 +1028,7 @@ checkForeignDeps pkg lbi verbosity = do
         hcDefines comp =
           case compilerFlavor comp of
             GHC  ->
-                let ghcOS = case buildOS of
+                let ghcOS = case configHostOS (configFlags lbi) of
                             Linux     -> ["linux"]
                             Windows   -> ["mingw32"]
                             OSX       -> ["darwin"]
@@ -1039,8 +1040,9 @@ checkForeignDeps pkg lbi verbosity = do
                             HPUX      -> ["hpux"]
                             IRIX      -> ["irix"]
                             HaLVM     -> []
+                            IOS       -> ["ios"]
                             OtherOS _ -> []
-                    ghcArch = case buildArch of
+                    ghcArch = case configHostArch (configFlags lbi) of
                               I386        -> ["i386"]
                               X86_64      -> ["x86_64"]
                               PPC         -> ["powerpc"]
diff --git a/Cabal/Distribution/Simple/Haddock.hs b/Cabal/Distribution/Simple/Haddock.hs
index 3e45ea4..7f48832 100644
--- a/Cabal/Distribution/Simple/Haddock.hs
+++ b/Cabal/Distribution/Simple/Haddock.hs
@@ -70,7 +70,7 @@ import Distribution.Simple.PreProcess (ppCpp', ppUnlit
                                       , preprocessComponent)
 import Distribution.Simple.Setup
         ( defaultHscolourFlags, Flag(..), toFlag, flagToMaybe, flagToList, fromFlag
-        , HaddockFlags(..), HscolourFlags(..) )
+        , HaddockFlags(..), HscolourFlags(..), configHostPlatform )
 import Distribution.Simple.Build (initialBuildSteps)
 import Distribution.Simple.InstallDirs (InstallDirs(..), PathTemplateEnv, PathTemplate,
                                         PathTemplateVariable(..),
@@ -525,6 +525,7 @@ haddockPackageFlags lbi clbi htmlTemplate = do
 haddockTemplateEnv :: LocalBuildInfo -> PackageIdentifier -> PathTemplateEnv
 haddockTemplateEnv lbi pkg_id = (PrefixVar, prefix (installDirTemplates lbi))
                                 : initialPathTemplateEnv pkg_id (compilerId (compiler lbi))
+                                  (configHostPlatform (configFlags lbi))
 
 -- --------------------------------------------------------------------------
 -- hscolour support
diff --git a/Cabal/Distribution/Simple/InstallDirs.hs b/Cabal/Distribution/Simple/InstallDirs.hs
index b847523..a0c827b 100644
--- a/Cabal/Distribution/Simple/InstallDirs.hs
+++ b/Cabal/Distribution/Simple/InstallDirs.hs
@@ -84,7 +84,7 @@ import System.FilePath (dropDrive)
 import Distribution.Package
          ( PackageIdentifier, packageName, packageVersion )
 import Distribution.System
-         ( OS(..), buildOS, Platform(..), buildPlatform )
+         ( OS(..), buildOS, Platform(..) )
 import Distribution.Compiler
          ( CompilerId, CompilerFlavor(..) )
 import Distribution.Text
@@ -310,10 +310,10 @@ substituteInstallDirTemplates env dirs = dirs'
 -- | Convert from abstract install directories to actual absolute ones by
 -- substituting for all the variables in the abstract paths, to get real
 -- absolute path.
-absoluteInstallDirs :: PackageIdentifier -> CompilerId -> CopyDest
+absoluteInstallDirs :: PackageIdentifier -> CompilerId -> CopyDest -> Platform
                     -> InstallDirs PathTemplate
                     -> InstallDirs FilePath
-absoluteInstallDirs pkgId compilerId copydest dirs =
+absoluteInstallDirs pkgId compilerId copydest platform dirs =
     (case copydest of
        CopyTo destdir -> fmap ((destdir </>) . dropDrive)
        _              -> id)
@@ -321,7 +321,7 @@ absoluteInstallDirs pkgId compilerId copydest dirs =
   . fmap fromPathTemplate
   $ substituteInstallDirTemplates env dirs
   where
-    env = initialPathTemplateEnv pkgId compilerId
+    env = initialPathTemplateEnv pkgId compilerId platform
 
 
 -- |The location prefix for the /copy/ command.
@@ -336,10 +336,10 @@ data CopyDest
 -- prevents us from making a relocatable package (also known as a \"prefix
 -- independent\" package).
 --
-prefixRelativeInstallDirs :: PackageIdentifier -> CompilerId
+prefixRelativeInstallDirs :: PackageIdentifier -> CompilerId -> Platform
                           -> InstallDirTemplates
                           -> InstallDirs (Maybe FilePath)
-prefixRelativeInstallDirs pkgId compilerId dirs =
+prefixRelativeInstallDirs pkgId compilerId platform dirs =
     fmap relative
   . appendSubdirs combinePathTemplate
   $ -- substitute the path template into each other, except that we map
@@ -349,7 +349,7 @@ prefixRelativeInstallDirs pkgId compilerId dirs =
       prefix = PathTemplate [Variable PrefixVar]
     }
   where
-    env = initialPathTemplateEnv pkgId compilerId
+    env = initialPathTemplateEnv pkgId compilerId platform
 
     -- If it starts with $prefix then it's relative and produce the relative
     -- path by stripping off $prefix/ or $prefix
@@ -421,12 +421,11 @@ substPathTemplate environment (PathTemplate template) =
                   Nothing                        -> [component]
 
 -- | The initial environment has all the static stuff but no paths
-initialPathTemplateEnv :: PackageIdentifier -> CompilerId -> PathTemplateEnv
-initialPathTemplateEnv pkgId compilerId =
+initialPathTemplateEnv :: PackageIdentifier -> CompilerId -> Platform -> PathTemplateEnv
+initialPathTemplateEnv pkgId compilerId platform =
      packageTemplateEnv  pkgId
   ++ compilerTemplateEnv compilerId
-  ++ platformTemplateEnv buildPlatform -- platform should be param if we want
-                                       -- to do cross-platform configuation
+  ++ platformTemplateEnv platform
 
 packageTemplateEnv :: PackageIdentifier -> PathTemplateEnv
 packageTemplateEnv pkgId =
diff --git a/Cabal/Distribution/Simple/LocalBuildInfo.hs b/Cabal/Distribution/Simple/LocalBuildInfo.hs
index b757a89..0965fda 100644
--- a/Cabal/Distribution/Simple/LocalBuildInfo.hs
+++ b/Cabal/Distribution/Simple/LocalBuildInfo.hs
@@ -86,7 +86,7 @@ import Distribution.Simple.PackageIndex
 import Distribution.Simple.Utils
          ( die )
 import Distribution.Simple.Setup
-         ( ConfigFlags )
+         ( ConfigFlags, configHostPlatform )
 import Distribution.Text
          ( display )
 
@@ -317,6 +317,7 @@ absoluteInstallDirs pkg lbi copydest =
     (packageId pkg)
     (compilerId (compiler lbi))
     copydest
+    (configHostPlatform (configFlags lbi))
     (installDirTemplates lbi)
 
 -- |See 'InstallDirs.prefixRelativeInstallDirs'
@@ -326,6 +327,7 @@ prefixRelativeInstallDirs pkg_descr lbi =
   InstallDirs.prefixRelativeInstallDirs
     (packageId pkg_descr)
     (compilerId (compiler lbi))
+    (configHostPlatform (configFlags lbi))
     (installDirTemplates lbi)
 
 substPathTemplate :: PackageId -> LocalBuildInfo
@@ -335,3 +337,4 @@ substPathTemplate pkgid lbi = fromPathTemplate
     where env = initialPathTemplateEnv
                    pkgid
                    (compilerId (compiler lbi))
+                   (configHostPlatform (configFlags lbi))
diff --git a/Cabal/Distribution/Simple/Setup.hs b/Cabal/Distribution/Simple/Setup.hs
index b450d78..d3445d6 100644
--- a/Cabal/Distribution/Simple/Setup.hs
+++ b/Cabal/Distribution/Simple/Setup.hs
@@ -75,7 +75,7 @@ module Distribution.Simple.Setup (
   BenchmarkFlags(..), emptyBenchmarkFlags, defaultBenchmarkFlags, benchmarkCommand,
   CopyDest(..),
   configureArgs, configureOptions, configureCCompiler, configureLinker,
-  buildOptions, installDirsOptions,
+  buildOptions, installDirsOptions, configHostPlatform,
 
   defaultDistPref,
 
@@ -112,6 +112,7 @@ import Distribution.Simple.Program (Program(..), ProgramConfiguration,
 import Distribution.Simple.InstallDirs
          ( InstallDirs(..), CopyDest(..),
            PathTemplate, toPathTemplate, fromPathTemplate )
+import Distribution.System (OS, Arch, buildOS, buildArch, Platform(..))
 import Distribution.Verbosity
 
 import Data.List   ( sort )
@@ -294,7 +295,9 @@ data ConfigFlags = ConfigFlags {
     configConfigurationsFlags :: FlagAssignment,
     configTests :: Flag Bool,     -- ^Enable test suite compilation
     configBenchmarks :: Flag Bool,     -- ^Enable benchmark compilation
-    configLibCoverage :: Flag Bool    -- ^ Enable test suite program coverage
+    configLibCoverage :: Flag Bool,   -- ^ Enable test suite program coverage
+    configHostOS        :: OS,
+    configHostArch      :: Arch
   }
   deriving (Read,Show)
 
@@ -482,6 +485,14 @@ configureOptions showOrParseArgs =
          "dependency checking and compilation for benchmarks listed in the package description file."
          configBenchmarks (\v flags -> flags { configBenchmarks = v })
          (boolOpt [] [])
+      ,option "" ["host-os"]
+         "specify host OS, i.e. OS to cross-compile to"
+         configHostOS (\v flags -> flags { configHostOS = v })
+         (textReqArg "HOST_OS")
+      ,option "" ["host-arch"]
+         "specify host Arch, i.e. CPU to cross-compile to"
+         configHostArch (\v flags -> flags { configHostArch = v })
+         (textReqArg "HOST_ARCH")
       ]
   where
     readFlagList :: String -> FlagAssignment
@@ -606,7 +617,9 @@ instance Monoid ConfigFlags where
     configConfigurationsFlags = mempty,
     configTests   = mempty,
     configLibCoverage = mempty,
-    configBenchmarks    = mempty
+    configBenchmarks    = mempty,
+    configHostOS        = buildOS,
+    configHostArch      = buildArch
   }
   mappend a b =  ConfigFlags {
     configPrograms      = configPrograms b,
@@ -639,7 +652,9 @@ instance Monoid ConfigFlags where
     configConfigurationsFlags = combine configConfigurationsFlags,
     configTests = combine configTests,
     configLibCoverage = combine configLibCoverage,
-    configBenchmarks    = combine configBenchmarks
+    configBenchmarks    = combine configBenchmarks,
+    configHostOS        = combine configHostOS,
+    configHostArch      = combine configHostArch
   }
     where combine field = field a `mappend` field b
 
@@ -1644,6 +1659,9 @@ splitArgs  = space []
     word [] s = s
     word w  s = reverse w : s
 
+configHostPlatform :: ConfigFlags -> Platform
+configHostPlatform cfg = Platform (configHostArch cfg) (configHostOS cfg)
+
 -- The test cases kinda have to be rewritten from the ground up... :/
 --hunitTests :: [Test]
 --hunitTests =
diff --git a/Cabal/Distribution/Simple/Test.hs b/Cabal/Distribution/Simple/Test.hs
index 990b3a5..c9e2ea3 100644
--- a/Cabal/Distribution/Simple/Test.hs
+++ b/Cabal/Distribution/Simple/Test.hs
@@ -70,7 +70,8 @@ import Distribution.Simple.InstallDirs
     , substPathTemplate , toPathTemplate, PathTemplate )
 import qualified Distribution.Simple.LocalBuildInfo as LBI
     ( LocalBuildInfo(..) )
-import Distribution.Simple.Setup ( TestFlags(..), TestShowDetails(..), fromFlag )
+import Distribution.Simple.Setup
+    ( TestFlags(..), TestShowDetails(..), fromFlag, configHostPlatform )
 import Distribution.Simple.Utils ( die, notice, rawSystemIOWithEnv )
 import Distribution.TestSuite
     ( OptionDescr(..), Options, Progress(..), Result(..), TestInstance(..)
@@ -430,6 +431,7 @@ testSuiteLogPath template pkg_descr lbi testLog =
     where
         env = initialPathTemplateEnv
                 (PD.package pkg_descr) (compilerId $ LBI.compiler lbi)
+                (configHostPlatform (LBI.configFlags lbi))
                 ++  [ (TestSuiteNameVar, toPathTemplate $ testSuiteName testLog)
                     , (TestSuiteResultVar, result)
                     ]
@@ -446,7 +448,8 @@ testOption pkg_descr lbi suite template =
     fromPathTemplate $ substPathTemplate env template
   where
     env = initialPathTemplateEnv
-          (PD.package pkg_descr) (compilerId $ LBI.compiler lbi) ++
+          (PD.package pkg_descr) (compilerId $ LBI.compiler lbi)
+          (configHostPlatform (LBI.configFlags lbi)) ++
           [(TestSuiteNameVar, toPathTemplate $ PD.testName suite)]
 
 packageLogPath :: PathTemplate
@@ -458,6 +461,7 @@ packageLogPath template pkg_descr lbi =
     where
         env = initialPathTemplateEnv
                 (PD.package pkg_descr) (compilerId $ LBI.compiler lbi)
+                (configHostPlatform (LBI.configFlags lbi))
 
 -- | The filename of the source file for the stub executable associated with a
 -- library 'TestSuite'.
diff --git a/Cabal/Distribution/System.hs b/Cabal/Distribution/System.hs
index 02d5da7..c2fd1f4 100644
--- a/Cabal/Distribution/System.hs
+++ b/Cabal/Distribution/System.hs
@@ -31,6 +31,7 @@ import qualified System.Info (os, arch)
 import qualified Data.Char as Char (toLower, isAlphaNum)
 
 import Data.Maybe (fromMaybe)
+import Data.Monoid (Monoid(..))
 import Distribution.Text (Text(..), display)
 import qualified Distribution.Compat.ReadP as Parse
 import qualified Text.PrettyPrint as Disp
@@ -63,6 +64,7 @@ data OS = Linux | Windows | OSX        -- teir 1 desktop OSs
         | FreeBSD | OpenBSD | NetBSD   -- other free unix OSs
         | Solaris | AIX | HPUX | IRIX  -- ageing Unix OSs
         | HaLVM                        -- bare metal / VMs / hypervisors
+        | IOS                          -- mobile OSes
         | OtherOS String
   deriving (Eq, Ord, Show, Read)
 
@@ -75,12 +77,13 @@ knownOSs :: [OS]
 knownOSs = [Linux, Windows, OSX
            ,FreeBSD, OpenBSD, NetBSD
            ,Solaris, AIX, HPUX, IRIX
-           ,HaLVM]
+           ,HaLVM, IOS]
 
 osAliases :: ClassificationStrictness -> OS -> [String]
 osAliases Permissive Windows = ["mingw32", "cygwin32"]
 osAliases Compat     Windows = ["mingw32", "win32"]
 osAliases _          OSX     = ["darwin"]
+osAliases _          IOS     = ["ios"]
 osAliases Permissive FreeBSD = ["kfreebsdgnu"]
 osAliases Permissive Solaris = ["solaris2"]
 osAliases _          _       = []
@@ -91,6 +94,11 @@ instance Text OS where
 
   parse = fmap (classifyOS Compat) ident
 
+instance Monoid OS where
+  mempty = buildOS
+  a `mappend` b = if a == buildOS then b else
+                  if b == buildOS then a else a
+
 classifyOS :: ClassificationStrictness -> String -> OS
 classifyOS strictness s =
   fromMaybe (OtherOS s) $ lookup (lowercase s) osMap
@@ -137,6 +145,11 @@ instance Text Arch where
 
   parse = fmap (classifyArch Strict) ident
 
+instance Monoid Arch where
+  mempty = buildArch
+  a `mappend` b = if a == buildArch then b else
+                  if b == buildArch then a else a
+
 classifyArch :: ClassificationStrictness -> String -> Arch
 classifyArch strictness s =
   fromMaybe (OtherArch s) $ lookup (lowercase s) archMap