Distribution/Simple/InstallDirs.hs

    {-# LANGUAGE CPP #-}
    {-# LANGUAGE DeriveFunctor #-}
    {-# LANGUAGE DeriveGeneric #-}
    {-# LANGUAGE FlexibleContexts #-}
    {-# LANGUAGE RankNTypes #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Simple.InstallDirs
    -- Copyright   :  Isaac Jones 2003-2004
    -- License     :  BSD3
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- This manages everything to do with where files get installed (though does
    -- not get involved with actually doing any installation). It provides an
    -- 'InstallDirs' type which is a set of directories for where to install
    -- things. It also handles the fact that we use templates in these install
    -- dirs. For example most install dirs are relative to some @$prefix@ and by
    -- changing the prefix all other dirs still end up changed appropriately. So it
    -- provides a 'PathTemplate' type and functions for substituting for these
    -- templates.

    module Distribution.Simple.InstallDirs (
            InstallDirs(..),
            InstallDirTemplates,
            defaultInstallDirs,
            defaultInstallDirs',
            combineInstallDirs,
            absoluteInstallDirs,
            CopyDest(..),
            prefixRelativeInstallDirs,
            substituteInstallDirTemplates,

            PathTemplate,
            PathTemplateVariable(..),
            PathTemplateEnv,
            toPathTemplate,
            fromPathTemplate,
            combinePathTemplate,
            substPathTemplate,
            initialPathTemplateEnv,
            platformTemplateEnv,
            compilerTemplateEnv,
            packageTemplateEnv,
            abiTemplateEnv,
            installDirsTemplateEnv,
      ) where

    import Prelude ()
    import Distribution.Compat.Prelude

    import Distribution.Package
    import Distribution.System
    import Distribution.Compiler
    import Distribution.Text

    import System.Directory (getAppUserDataDirectory)
    import System.FilePath ((</>), isPathSeparator, pathSeparator)
    import System.FilePath (dropDrive)

    #ifdef mingw32_HOST_OS
    import qualified Prelude
    import Foreign
    import Foreign.C
    #endif

    -- ---------------------------------------------------------------------------
    -- Installation directories

    -- | The directories where we will install files for packages.
    --
    -- We have several different directories for different types of files since
    -- many systems have conventions whereby different types of files in a package
    -- are installed in different directories. This is particularly the case on
    -- Unix style systems.
    --
    data InstallDirs dir = InstallDirs {
            prefix       :: dir,
            bindir       :: dir,
            libdir       :: dir,
            libsubdir    :: dir,
            dynlibdir    :: dir,
            flibdir      :: dir, -- ^ foreign libraries
            libexecdir   :: dir,
            libexecsubdir:: dir,
            includedir   :: dir,
            datadir      :: dir,
            datasubdir   :: dir,
            docdir       :: dir,
            mandir       :: dir,
            htmldir      :: dir,
            haddockdir   :: dir,
            sysconfdir   :: dir
        } deriving (Eq, Read, Show, Functor, Generic)

    instance Binary dir => Binary (InstallDirs dir)

    instance (Semigroup dir, Monoid dir) => Monoid (InstallDirs dir) where
      mempty = gmempty
      mappend = (<>)

    instance Semigroup dir => Semigroup (InstallDirs dir) where
      (<>) = gmappend

    combineInstallDirs :: (a -> b -> c)
                       -> InstallDirs a
                       -> InstallDirs b
                       -> InstallDirs c
    combineInstallDirs combine a b = InstallDirs {
        prefix       = prefix a     `combine` prefix b,
        bindir       = bindir a     `combine` bindir b,
        libdir       = libdir a     `combine` libdir b,
        libsubdir    = libsubdir a  `combine` libsubdir b,
        dynlibdir    = dynlibdir a  `combine` dynlibdir b,
        flibdir      = flibdir a    `combine` flibdir b,
        libexecdir   = libexecdir a `combine` libexecdir b,
        libexecsubdir= libexecsubdir a `combine` libexecsubdir b,
        includedir   = includedir a `combine` includedir b,
        datadir      = datadir a    `combine` datadir b,
        datasubdir   = datasubdir a `combine` datasubdir b,
        docdir       = docdir a     `combine` docdir b,
        mandir       = mandir a     `combine` mandir b,
        htmldir      = htmldir a    `combine` htmldir b,
        haddockdir   = haddockdir a `combine` haddockdir b,
        sysconfdir   = sysconfdir a `combine` sysconfdir b
      }

    appendSubdirs :: (a -> a -> a) -> InstallDirs a -> InstallDirs a
    appendSubdirs append dirs = dirs {
        libdir     = libdir dirs `append` libsubdir dirs,
        libexecdir = libexecdir dirs `append` libexecsubdir dirs,
        datadir    = datadir dirs `append` datasubdir dirs,
        libsubdir  = error "internal error InstallDirs.libsubdir",
        libexecsubdir = error "internal error InstallDirs.libexecsubdir",
        datasubdir = error "internal error InstallDirs.datasubdir"
      }

    -- | The installation directories in terms of 'PathTemplate's that contain
    -- variables.
    --
    -- The defaults for most of the directories are relative to each other, in
    -- particular they are all relative to a single prefix. This makes it
    -- convenient for the user to override the default installation directory
    -- by only having to specify --prefix=... rather than overriding each
    -- individually. This is done by allowing $-style variables in the dirs.
    -- These are expanded by textual substitution (see 'substPathTemplate').
    --
    -- A few of these installation directories are split into two components, the
    -- dir and subdir. The full installation path is formed by combining the two
    -- together with @\/@. The reason for this is compatibility with other Unix
    -- build systems which also support @--libdir@ and @--datadir@. We would like
    -- users to be able to configure @--libdir=\/usr\/lib64@ for example but
    -- because by default we want to support installing multiple versions of
    -- packages and building the same package for multiple compilers we append the
    -- libsubdir to get: @\/usr\/lib64\/$libname\/$compiler@.
    --
    -- An additional complication is the need to support relocatable packages on
    -- systems which support such things, like Windows.
    --
    type InstallDirTemplates = InstallDirs PathTemplate

    -- ---------------------------------------------------------------------------
    -- Default installation directories

    defaultInstallDirs :: CompilerFlavor -> Bool -> Bool -> IO InstallDirTemplates
    defaultInstallDirs = defaultInstallDirs' False

    defaultInstallDirs' :: Bool {- use external internal deps -}
                        -> CompilerFlavor -> Bool -> Bool -> IO InstallDirTemplates
    defaultInstallDirs' True comp userInstall hasLibs = do
      dflt <- defaultInstallDirs' False comp userInstall hasLibs
      -- Be a bit more hermetic about per-component installs
      return dflt { datasubdir = toPathTemplate $ "$abi" </> "$libname",
                    docdir     = toPathTemplate $ "$datadir" </> "doc" </> "$abi" </> "$libname"
                  }
    defaultInstallDirs' False comp userInstall _hasLibs = do
      installPrefix <-
          if userInstall
          then getAppUserDataDirectory "cabal"
          else case buildOS of
               Windows -> do windowsProgramFilesDir <- getWindowsProgramFilesDir
                             return (windowsProgramFilesDir </> "Haskell")
               _       -> return "/usr/local"
      installLibDir <-
          case buildOS of
          Windows -> return "$prefix"
          _       -> case comp of
                     LHC | userInstall -> getAppUserDataDirectory "lhc"
                     _                 -> return ("$prefix" </> "lib")
      return $ fmap toPathTemplate $ InstallDirs {
          prefix       = installPrefix,
          bindir       = "$prefix" </> "bin",
          libdir       = installLibDir,
          libsubdir    = case comp of
               JHC    -> "$compiler"
               LHC    -> "$compiler"
               UHC    -> "$pkgid"
               _other -> "$abi" </> "$libname",
          dynlibdir    = "$libdir" </> case comp of
               JHC    -> "$compiler"
               LHC    -> "$compiler"
               UHC    -> "$pkgid"
               _other -> "$abi",
          libexecsubdir= "$abi" </> "$pkgid",
          flibdir      = "$libdir",
          libexecdir   = case buildOS of
            Windows   -> "$prefix" </> "$libname"
            _other    -> "$prefix" </> "libexec",
          includedir   = "$libdir" </> "$libsubdir" </> "include",
          datadir      = case buildOS of
            Windows   -> "$prefix"
            _other    -> "$prefix" </> "share",
          datasubdir   = "$abi" </> "$pkgid",
          docdir       = "$datadir" </> "doc" </> "$abi" </> "$pkgid",
          mandir       = "$datadir" </> "man",
          htmldir      = "$docdir"  </> "html",
          haddockdir   = "$htmldir",
          sysconfdir   = "$prefix" </> "etc"
      }

    -- ---------------------------------------------------------------------------
    -- Converting directories, absolute or prefix-relative

    -- | Substitute the install dir templates into each other.
    --
    -- To prevent cyclic substitutions, only some variables are allowed in
    -- particular dir templates. If out of scope vars are present, they are not
    -- substituted for. Checking for any remaining unsubstituted vars can be done
    -- as a subsequent operation.
    --
    -- The reason it is done this way is so that in 'prefixRelativeInstallDirs' we
    -- can replace 'prefix' with the 'PrefixVar' and get resulting
    -- 'PathTemplate's that still have the 'PrefixVar' in them. Doing this makes it
    -- each to check which paths are relative to the $prefix.
    --
    substituteInstallDirTemplates :: PathTemplateEnv
                                  -> InstallDirTemplates -> InstallDirTemplates
    substituteInstallDirTemplates env dirs = dirs'
      where
        dirs' = InstallDirs {
          -- So this specifies exactly which vars are allowed in each template
          prefix     = subst prefix     [],
          bindir     = subst bindir     [prefixVar],
          libdir     = subst libdir     [prefixVar, bindirVar],
          libsubdir  = subst libsubdir  [],
          dynlibdir  = subst dynlibdir  [prefixVar, bindirVar, libdirVar],
          flibdir    = subst flibdir    [prefixVar, bindirVar, libdirVar],
          libexecdir = subst libexecdir prefixBinLibVars,
          libexecsubdir = subst libexecsubdir [],
          includedir = subst includedir prefixBinLibVars,
          datadir    = subst datadir    prefixBinLibVars,
          datasubdir = subst datasubdir [],
          docdir     = subst docdir     prefixBinLibDataVars,
          mandir     = subst mandir     (prefixBinLibDataVars ++ [docdirVar]),
          htmldir    = subst htmldir    (prefixBinLibDataVars ++ [docdirVar]),
          haddockdir = subst haddockdir (prefixBinLibDataVars ++
                                          [docdirVar, htmldirVar]),
          sysconfdir = subst sysconfdir prefixBinLibVars
        }
        subst dir env' = substPathTemplate (env'++env) (dir dirs)

        prefixVar        = (PrefixVar,     prefix     dirs')
        bindirVar        = (BindirVar,     bindir     dirs')
        libdirVar        = (LibdirVar,     libdir     dirs')
        libsubdirVar     = (LibsubdirVar,  libsubdir  dirs')
        datadirVar       = (DatadirVar,    datadir    dirs')
        datasubdirVar    = (DatasubdirVar, datasubdir dirs')
        docdirVar        = (DocdirVar,     docdir     dirs')
        htmldirVar       = (HtmldirVar,    htmldir    dirs')
        prefixBinLibVars = [prefixVar, bindirVar, libdirVar, libsubdirVar]
        prefixBinLibDataVars = prefixBinLibVars ++ [datadirVar, datasubdirVar]

    -- | 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
                        -> UnitId
                        -> CompilerInfo
                        -> CopyDest
                        -> Platform
                        -> InstallDirs PathTemplate
                        -> InstallDirs FilePath
    absoluteInstallDirs pkgId libname compilerId copydest platform dirs =
        (case copydest of
           CopyTo destdir -> fmap ((destdir </>) . dropDrive)
           _              -> id)
      . appendSubdirs (</>)
      . fmap fromPathTemplate
      $ substituteInstallDirTemplates env dirs
      where
        env = initialPathTemplateEnv pkgId libname compilerId platform

    -- |The location prefix for the /copy/ command.
    data CopyDest
      = NoCopyDest
      | CopyTo FilePath
      deriving (Eq, Show)

    -- | Check which of the paths are relative to the installation $prefix.
    --
    -- If any of the paths are not relative, ie they are absolute paths, then it
    -- prevents us from making a relocatable package (also known as a \"prefix
    -- independent\" package).
    --
    prefixRelativeInstallDirs :: PackageIdentifier
                              -> UnitId
                              -> CompilerInfo
                              -> Platform
                              -> InstallDirTemplates
                              -> InstallDirs (Maybe FilePath)
    prefixRelativeInstallDirs pkgId libname compilerId platform dirs =
        fmap relative
      . appendSubdirs combinePathTemplate
      $ -- substitute the path template into each other, except that we map
        -- \$prefix back to $prefix. We're trying to end up with templates that
        -- mention no vars except $prefix.
        substituteInstallDirTemplates env dirs {
          prefix = PathTemplate [Variable PrefixVar]
        }
      where
        env = initialPathTemplateEnv pkgId libname compilerId platform

        -- If it starts with $prefix then it's relative and produce the relative
        -- path by stripping off $prefix/ or $prefix
        relative dir = case dir of
          PathTemplate cs -> fmap (fromPathTemplate . PathTemplate) (relative' cs)
        relative' (Variable PrefixVar : Ordinary (s:rest) : rest')
                          | isPathSeparator s = Just (Ordinary rest : rest')
        relative' (Variable PrefixVar : rest) = Just rest
        relative' _                           = Nothing

    -- ---------------------------------------------------------------------------
    -- Path templates

    -- | An abstract path, possibly containing variables that need to be
    -- substituted for to get a real 'FilePath'.
    --
    newtype PathTemplate = PathTemplate [PathComponent]
      deriving (Eq, Ord, Generic)

    instance Binary PathTemplate

    data PathComponent =
           Ordinary FilePath
         | Variable PathTemplateVariable
         deriving (Eq, Ord, Generic)

    instance Binary PathComponent

    data PathTemplateVariable =
           PrefixVar     -- ^ The @$prefix@ path variable
         | BindirVar     -- ^ The @$bindir@ path variable
         | LibdirVar     -- ^ The @$libdir@ path variable
         | LibsubdirVar  -- ^ The @$libsubdir@ path variable
         | DynlibdirVar  -- ^ The @$dynlibdir@ path variable
         | DatadirVar    -- ^ The @$datadir@ path variable
         | DatasubdirVar -- ^ The @$datasubdir@ path variable
         | DocdirVar     -- ^ The @$docdir@ path variable
         | HtmldirVar    -- ^ The @$htmldir@ path variable
         | PkgNameVar    -- ^ The @$pkg@ package name path variable
         | PkgVerVar     -- ^ The @$version@ package version path variable
         | PkgIdVar      -- ^ The @$pkgid@ package Id path variable, eg @foo-1.0@
         | LibNameVar    -- ^ The @$libname@ path variable
         | CompilerVar   -- ^ The compiler name and version, eg @ghc-6.6.1@
         | OSVar         -- ^ The operating system name, eg @windows@ or @linux@
         | ArchVar       -- ^ The CPU architecture name, eg @i386@ or @x86_64@
         | AbiVar        -- ^ The Compiler's ABI identifier, $arch-$os-$compiler-$abitag
         | AbiTagVar     -- ^ The optional ABI tag for the compiler
         | ExecutableNameVar -- ^ The executable name; used in shell wrappers
         | TestSuiteNameVar   -- ^ The name of the test suite being run
         | TestSuiteResultVar -- ^ The result of the test suite being run, eg
                              -- @pass@, @fail@, or @error@.
         | BenchmarkNameVar   -- ^ The name of the benchmark being run
      deriving (Eq, Ord, Generic)

    instance Binary PathTemplateVariable

    type PathTemplateEnv = [(PathTemplateVariable, PathTemplate)]

    -- | Convert a 'FilePath' to a 'PathTemplate' including any template vars.
    --
    toPathTemplate :: FilePath -> PathTemplate
    toPathTemplate = PathTemplate . read -- TODO: eradicateNoParse

    -- | Convert back to a path, any remaining vars are included
    --
    fromPathTemplate :: PathTemplate -> FilePath
    fromPathTemplate (PathTemplate template) = show template

    combinePathTemplate :: PathTemplate -> PathTemplate -> PathTemplate
    combinePathTemplate (PathTemplate t1) (PathTemplate t2) =
      PathTemplate (t1 ++ [Ordinary [pathSeparator]] ++ t2)

    substPathTemplate :: PathTemplateEnv -> PathTemplate -> PathTemplate
    substPathTemplate environment (PathTemplate template) =
        PathTemplate (concatMap subst template)

        where subst component@(Ordinary _) = [component]
              subst component@(Variable variable) =
                  case lookup variable environment of
                      Just (PathTemplate components) -> components
                      Nothing                        -> [component]

    -- | The initial environment has all the static stuff but no paths
    initialPathTemplateEnv :: PackageIdentifier
                           -> UnitId
                           -> CompilerInfo
                           -> Platform
                           -> PathTemplateEnv
    initialPathTemplateEnv pkgId libname compiler platform =
         packageTemplateEnv  pkgId libname
      ++ compilerTemplateEnv compiler
      ++ platformTemplateEnv platform
      ++ abiTemplateEnv compiler platform

    packageTemplateEnv :: PackageIdentifier -> UnitId -> PathTemplateEnv
    packageTemplateEnv pkgId uid =
      [(PkgNameVar,  PathTemplate [Ordinary $ display (packageName pkgId)])
      ,(PkgVerVar,   PathTemplate [Ordinary $ display (packageVersion pkgId)])
      -- Invariant: uid is actually a HashedUnitId.  Hard to enforce because
      -- it's an API change.
      ,(LibNameVar,  PathTemplate [Ordinary $ display uid])
      ,(PkgIdVar,    PathTemplate [Ordinary $ display pkgId])
      ]

    compilerTemplateEnv :: CompilerInfo -> PathTemplateEnv
    compilerTemplateEnv compiler =
      [(CompilerVar, PathTemplate [Ordinary $ display (compilerInfoId compiler)])
      ]

    platformTemplateEnv :: Platform -> PathTemplateEnv
    platformTemplateEnv (Platform arch os) =
      [(OSVar,       PathTemplate [Ordinary $ display os])
      ,(ArchVar,     PathTemplate [Ordinary $ display arch])
      ]

    abiTemplateEnv :: CompilerInfo -> Platform -> PathTemplateEnv
    abiTemplateEnv compiler (Platform arch os) =
      [(AbiVar,      PathTemplate [Ordinary $ display arch ++ '-':display os ++
                                              '-':display (compilerInfoId compiler) ++
                                              case compilerInfoAbiTag compiler of
                                                NoAbiTag   -> ""
                                                AbiTag tag -> '-':tag])
      ,(AbiTagVar,   PathTemplate [Ordinary $ abiTagString (compilerInfoAbiTag compiler)])
      ]

    installDirsTemplateEnv :: InstallDirs PathTemplate -> PathTemplateEnv
    installDirsTemplateEnv dirs =
      [(PrefixVar,     prefix     dirs)
      ,(BindirVar,     bindir     dirs)
      ,(LibdirVar,     libdir     dirs)
      ,(LibsubdirVar,  libsubdir  dirs)
      ,(DynlibdirVar,  dynlibdir  dirs)
      ,(DatadirVar,    datadir    dirs)
      ,(DatasubdirVar, datasubdir dirs)
      ,(DocdirVar,     docdir     dirs)
      ,(HtmldirVar,    htmldir    dirs)
      ]

    -- ---------------------------------------------------------------------------
    -- Parsing and showing path templates:

    -- The textual format is that of an ordinary Haskell String, eg
    -- "$prefix/bin"
    -- and this gets parsed to the internal representation as a sequence of path
    -- spans which are either strings or variables, eg:
    -- PathTemplate [Variable PrefixVar, Ordinary "/bin" ]

    instance Show PathTemplateVariable where
      show PrefixVar     = "prefix"
      show LibNameVar    = "libname"
      show BindirVar     = "bindir"
      show LibdirVar     = "libdir"
      show LibsubdirVar  = "libsubdir"
      show DynlibdirVar  = "dynlibdir"
      show DatadirVar    = "datadir"
      show DatasubdirVar = "datasubdir"
      show DocdirVar     = "docdir"
      show HtmldirVar    = "htmldir"
      show PkgNameVar    = "pkg"
      show PkgVerVar     = "version"
      show PkgIdVar      = "pkgid"
      show CompilerVar   = "compiler"
      show OSVar         = "os"
      show ArchVar       = "arch"
      show AbiTagVar     = "abitag"
      show AbiVar        = "abi"
      show ExecutableNameVar = "executablename"
      show TestSuiteNameVar   = "test-suite"
      show TestSuiteResultVar = "result"
      show BenchmarkNameVar   = "benchmark"

    instance Read PathTemplateVariable where
      readsPrec _ s =
        take 1
        [ (var, drop (length varStr) s)
        | (varStr, var) <- vars
        , varStr `isPrefixOf` s ]
        -- NB: order matters! Longer strings first
        where vars = [("prefix",     PrefixVar)
                     ,("bindir",     BindirVar)
                     ,("libdir",     LibdirVar)
                     ,("libsubdir",  LibsubdirVar)
                     ,("dynlibdir",  DynlibdirVar)
                     ,("datadir",    DatadirVar)
                     ,("datasubdir", DatasubdirVar)
                     ,("docdir",     DocdirVar)
                     ,("htmldir",    HtmldirVar)
                     ,("pkgid",      PkgIdVar)
                     ,("libname",    LibNameVar)
                     ,("pkgkey",     LibNameVar) -- backwards compatibility
                     ,("pkg",        PkgNameVar)
                     ,("version",    PkgVerVar)
                     ,("compiler",   CompilerVar)
                     ,("os",         OSVar)
                     ,("arch",       ArchVar)
                     ,("abitag",     AbiTagVar)
                     ,("abi",        AbiVar)
                     ,("executablename", ExecutableNameVar)
                     ,("test-suite", TestSuiteNameVar)
                     ,("result", TestSuiteResultVar)
                     ,("benchmark", BenchmarkNameVar)]

    instance Show PathComponent where
      show (Ordinary path) = path
      show (Variable var)  = '$':show var
      showList = foldr (\x -> (shows x .)) id

    instance Read PathComponent where
      -- for some reason we collapse multiple $ symbols here
      readsPrec _ = lex0
        where lex0 [] = []
              lex0 ('$':'$':s') = lex0 ('$':s')
              lex0 ('$':s') = case [ (Variable var, s'')
                                   | (var, s'') <- reads s' ] of
                                [] -> lex1 "$" s'
                                ok -> ok
              lex0 s' = lex1 [] s'
              lex1 ""  ""      = []
              lex1 acc ""      = [(Ordinary (reverse acc), "")]
              lex1 acc ('$':'$':s) = lex1 acc ('$':s)
              lex1 acc ('$':s) = [(Ordinary (reverse acc), '$':s)]
              lex1 acc (c:s)   = lex1 (c:acc) s
      readList [] = [([],"")]
      readList s  = [ (component:components, s'')
                    | (component, s') <- reads s
                    , (components, s'') <- readList s' ]

    instance Show PathTemplate where
      show (PathTemplate template) = show (show template)

    instance Read PathTemplate where
      readsPrec p s = [ (PathTemplate template, s')
                      | (path, s')     <- readsPrec p s
                      , (template, "") <- reads path ]

    -- ---------------------------------------------------------------------------
    -- Internal utilities

    getWindowsProgramFilesDir :: NoCallStackIO FilePath
    getWindowsProgramFilesDir = do
    #ifdef mingw32_HOST_OS
      m <- shGetFolderPath csidl_PROGRAM_FILES
    #else
      let m = Nothing
    #endif
      return (fromMaybe "C:\\Program Files" m)

    #ifdef mingw32_HOST_OS
    shGetFolderPath :: CInt -> NoCallStackIO (Maybe FilePath)
    shGetFolderPath n =
      allocaArray long_path_size $ \pPath -> do
         r <- c_SHGetFolderPath nullPtr n nullPtr 0 pPath
         if (r /= 0)
            then return Nothing
            else do s <- peekCWString pPath; return (Just s)
      where
        long_path_size      = 1024 -- MAX_PATH is 260, this should be plenty

    csidl_PROGRAM_FILES :: CInt
    csidl_PROGRAM_FILES = 0x0026
    -- csidl_PROGRAM_FILES_COMMON :: CInt
    -- csidl_PROGRAM_FILES_COMMON = 0x002b

    #ifdef x86_64_HOST_ARCH
    #define CALLCONV ccall
    #else
    #define CALLCONV stdcall
    #endif

    foreign import CALLCONV unsafe "shlobj.h SHGetFolderPathW"
                c_SHGetFolderPath :: Ptr ()
                                  -> CInt
                                  -> Ptr ()
                                  -> CInt
                                  -> CWString
                                  -> Prelude.IO CInt
    #endif