Distribution/Simple/GHC.hs

    {-# LANGUAGE FlexibleContexts #-}
    {-# LANGUAGE MultiWayIf #-}
    {-# LANGUAGE RankNTypes #-}
    {-# LANGUAGE TupleSections #-}
    {-# LANGUAGE CPP #-}

    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Simple.GHC
    -- Copyright   :  Isaac Jones 2003-2007
    -- License     :  BSD3
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- This is a fairly large module. It contains most of the GHC-specific code for
    -- configuring, building and installing packages. It also exports a function
    -- for finding out what packages are already installed. Configuring involves
    -- finding the @ghc@ and @ghc-pkg@ programs, finding what language extensions
    -- this version of ghc supports and returning a 'Compiler' value.
    --
    -- 'getInstalledPackages' involves calling the @ghc-pkg@ program to find out
    -- what packages are installed.
    --
    -- Building is somewhat complex as there is quite a bit of information to take
    -- into account. We have to build libs and programs, possibly for profiling and
    -- shared libs. We have to support building libraries that will be usable by
    -- GHCi and also ghc's @-split-objs@ feature. We have to compile any C files
    -- using ghc. Linking, especially for @split-objs@ is remarkably complex,
    -- partly because there tend to be 1,000's of @.o@ files and this can often be
    -- more than we can pass to the @ld@ or @ar@ programs in one go.
    --
    -- Installing for libs and exes involves finding the right files and copying
    -- them to the right places. One of the more tricky things about this module is
    -- remembering the layout of files in the build directory (which is not
    -- explicitly documented) and thus what search dirs are used for various kinds
    -- of files.

    module Distribution.Simple.GHC (
            getGhcInfo,
            configure,
            getInstalledPackages,
            getInstalledPackagesMonitorFiles,
            getPackageDBContents,
            buildLib, buildFLib, buildExe,
            replLib, replFLib, replExe,
            startInterpreter,
            installLib, installFLib, installExe,
            libAbiHash,
            hcPkgInfo,
            registerPackage,
            componentGhcOptions,
            componentCcGhcOptions,
            getLibDir,
            isDynamic,
            getGlobalPackageDB,
            pkgRoot,
            -- * Constructing and deconstructing GHC environment files
            Internal.GhcEnvironmentFileEntry(..),
            Internal.simpleGhcEnvironmentFile,
            Internal.renderGhcEnvironmentFile,
            Internal.writeGhcEnvironmentFile,
            Internal.ghcPlatformAndVersionString,
            readGhcEnvironmentFile,
            parseGhcEnvironmentFile,
            ParseErrorExc(..),
            -- * Version-specific implementation quirks
            getImplInfo,
            GhcImplInfo(..)
     ) where

    import Prelude ()
    import Distribution.Compat.Prelude

    import qualified Distribution.Simple.GHC.Internal as Internal
    import Distribution.Simple.GHC.ImplInfo
    import Distribution.Simple.GHC.EnvironmentParser
    import Distribution.PackageDescription.Utils (cabalBug)
    import Distribution.PackageDescription as PD
    import Distribution.InstalledPackageInfo (InstalledPackageInfo)
    import qualified Distribution.InstalledPackageInfo as InstalledPackageInfo
    import Distribution.Simple.PackageIndex (InstalledPackageIndex)
    import qualified Distribution.Simple.PackageIndex as PackageIndex
    import Distribution.Simple.LocalBuildInfo
    import Distribution.Types.ComponentLocalBuildInfo
    import qualified Distribution.Simple.Hpc as Hpc
    import Distribution.Simple.BuildPaths
    import Distribution.Simple.Utils
    import Distribution.Package
    import qualified Distribution.ModuleName as ModuleName
    import Distribution.ModuleName (ModuleName)
    import Distribution.Simple.Program
    import Distribution.Simple.Program.Builtin (runghcProgram)
    import qualified Distribution.Simple.Program.HcPkg as HcPkg
    import qualified Distribution.Simple.Program.Ar    as Ar
    import qualified Distribution.Simple.Program.Ld    as Ld
    import qualified Distribution.Simple.Program.Strip as Strip
    import Distribution.Simple.Program.GHC
    import Distribution.Simple.Setup
    import qualified Distribution.Simple.Setup as Cabal
    import Distribution.Simple.Compiler hiding (Flag)
    import Distribution.Version
    import Distribution.System
    import Distribution.Verbosity
    import Distribution.Pretty
    import Distribution.Types.ForeignLib
    import Distribution.Types.ForeignLibType
    import Distribution.Types.ForeignLibOption
    import Distribution.Types.UnqualComponentName
    import Distribution.Utils.NubList
    import Language.Haskell.Extension

    import Control.Monad (msum, forM_)
    import Data.Char (isLower)
    import qualified Data.Map as Map
    import System.Directory
             ( doesFileExist, getAppUserDataDirectory, createDirectoryIfMissing
             , canonicalizePath, removeFile, renameFile, getDirectoryContents )
    import System.FilePath          ( (</>), (<.>), takeExtension
                                    , takeDirectory, replaceExtension
                                    ,isRelative )
    import qualified System.Info
    #ifndef mingw32_HOST_OS
    import System.Posix (createSymbolicLink)
    #endif /* mingw32_HOST_OS */

    -- -----------------------------------------------------------------------------
    -- Configuring

    configure :: Verbosity -> Maybe FilePath -> Maybe FilePath
              -> ProgramDb
              -> IO (Compiler, Maybe Platform, ProgramDb)
    configure verbosity hcPath hcPkgPath conf0 = do

      (ghcProg, ghcVersion, progdb1) <-
        requireProgramVersion verbosity ghcProgram
          (orLaterVersion (mkVersion [7,0,1]))
          (userMaybeSpecifyPath "ghc" hcPath conf0)
      let implInfo = ghcVersionImplInfo ghcVersion

      -- Cabal currently supports ghc >= 7.0.1 && < 8.12
      unless (ghcVersion < mkVersion [8,12]) $
        warn verbosity $
             "Unknown/unsupported 'ghc' version detected "
          ++ "(Cabal " ++ prettyShow cabalVersion ++ " supports 'ghc' version < 8.12): "
          ++ programPath ghcProg ++ " is version " ++ prettyShow ghcVersion

      -- This is slightly tricky, we have to configure ghc first, then we use the
      -- location of ghc to help find ghc-pkg in the case that the user did not
      -- specify the location of ghc-pkg directly:
      (ghcPkgProg, ghcPkgVersion, progdb2) <-
        requireProgramVersion verbosity ghcPkgProgram {
          programFindLocation = guessGhcPkgFromGhcPath ghcProg
        }
        anyVersion (userMaybeSpecifyPath "ghc-pkg" hcPkgPath progdb1)

      when (ghcVersion /= ghcPkgVersion) $ die' verbosity $
           "Version mismatch between ghc and ghc-pkg: "
        ++ programPath ghcProg ++ " is version " ++ prettyShow ghcVersion ++ " "
        ++ programPath ghcPkgProg ++ " is version " ++ prettyShow ghcPkgVersion

      -- Likewise we try to find the matching hsc2hs and haddock programs.
      let hsc2hsProgram' = hsc2hsProgram {
                               programFindLocation = guessHsc2hsFromGhcPath ghcProg
                           }
          haddockProgram' = haddockProgram {
                               programFindLocation = guessHaddockFromGhcPath ghcProg
                           }
          hpcProgram' = hpcProgram {
                            programFindLocation = guessHpcFromGhcPath ghcProg
                        }
          runghcProgram' = runghcProgram {
                            programFindLocation = guessRunghcFromGhcPath ghcProg
                        }
          progdb3 = addKnownProgram haddockProgram' $
                  addKnownProgram hsc2hsProgram' $
                  addKnownProgram hpcProgram' $
                  addKnownProgram runghcProgram' progdb2

      languages  <- Internal.getLanguages verbosity implInfo ghcProg
      extensions0 <- Internal.getExtensions verbosity implInfo ghcProg

      ghcInfo <- Internal.getGhcInfo verbosity implInfo ghcProg
      let ghcInfoMap = Map.fromList ghcInfo
          extensions = -- workaround https://ghc.haskell.org/ticket/11214
                       filterExt JavaScriptFFI $
                       -- see 'filterExtTH' comment below
                       filterExtTH $ extensions0

          -- starting with GHC 8.0, `TemplateHaskell` will be omitted from
          -- `--supported-extensions` when it's not available.
          -- for older GHCs we can use the "Have interpreter" property to
          -- filter out `TemplateHaskell`
          filterExtTH | ghcVersion < mkVersion [8]
                       , Just "NO" <- Map.lookup "Have interpreter" ghcInfoMap
                       = filterExt TemplateHaskell
                      | otherwise = id

          filterExt ext = filter ((/= EnableExtension ext) . fst)

      let comp = Compiler {
            compilerId         = CompilerId GHC ghcVersion,
            compilerAbiTag     = NoAbiTag,
            compilerCompat     = [],
            compilerLanguages  = languages,
            compilerExtensions = extensions,
            compilerProperties = ghcInfoMap
          }
          compPlatform = Internal.targetPlatform ghcInfo
          -- configure gcc and ld
          progdb4 = Internal.configureToolchain implInfo ghcProg ghcInfoMap progdb3
      return (comp, compPlatform, progdb4)

    -- | Given something like /usr/local/bin/ghc-6.6.1(.exe) we try and find
    -- the corresponding tool; e.g. if the tool is ghc-pkg, we try looking
    -- for a versioned or unversioned ghc-pkg in the same dir, that is:
    --
    -- > /usr/local/bin/ghc-pkg-ghc-6.6.1(.exe)
    -- > /usr/local/bin/ghc-pkg-6.6.1(.exe)
    -- > /usr/local/bin/ghc-pkg(.exe)
    --
    guessToolFromGhcPath :: Program -> ConfiguredProgram
                         -> Verbosity -> ProgramSearchPath
                         -> IO (Maybe (FilePath, [FilePath]))
    guessToolFromGhcPath tool ghcProg verbosity searchpath
      = do let toolname          = programName tool
               given_path        = programPath ghcProg
               given_dir         = takeDirectory given_path
           real_path <- canonicalizePath given_path
           let real_dir           = takeDirectory real_path
               versionSuffix path = takeVersionSuffix (dropExeExtension path)
               given_suf = versionSuffix given_path
               real_suf  = versionSuffix real_path
               guessNormal       dir = dir </> toolname <.> exeExtension buildPlatform
               guessGhcVersioned dir suf = dir </> (toolname ++ "-ghc" ++ suf)
                                               <.> exeExtension buildPlatform
               guessVersioned    dir suf = dir </> (toolname ++ suf)
                                               <.> exeExtension buildPlatform
               mkGuesses dir suf | null suf  = [guessNormal dir]
                                 | otherwise = [guessGhcVersioned dir suf,
                                                guessVersioned dir suf,
                                                guessNormal dir]
               guesses = mkGuesses given_dir given_suf ++
                                if real_path == given_path
                                    then []
                                    else mkGuesses real_dir real_suf
           info verbosity $ "looking for tool " ++ toolname
             ++ " near compiler in " ++ given_dir
           debug verbosity $ "candidate locations: " ++ show guesses
           exists <- traverse doesFileExist guesses
           case [ file | (file, True) <- zip guesses exists ] of
                       -- If we can't find it near ghc, fall back to the usual
                       -- method.
             []     -> programFindLocation tool verbosity searchpath
             (fp:_) -> do info verbosity $ "found " ++ toolname ++ " in " ++ fp
                          let lookedAt = map fst
                                       . takeWhile (\(_file, exist) -> not exist)
                                       $ zip guesses exists
                          return (Just (fp, lookedAt))

      where takeVersionSuffix :: FilePath -> String
            takeVersionSuffix = takeWhileEndLE isSuffixChar

            isSuffixChar :: Char -> Bool
            isSuffixChar c = isDigit c || c == '.' || c == '-'

    -- | Given something like /usr/local/bin/ghc-6.6.1(.exe) we try and find a
    -- corresponding ghc-pkg, we try looking for both a versioned and unversioned
    -- ghc-pkg in the same dir, that is:
    --
    -- > /usr/local/bin/ghc-pkg-ghc-6.6.1(.exe)
    -- > /usr/local/bin/ghc-pkg-6.6.1(.exe)
    -- > /usr/local/bin/ghc-pkg(.exe)
    --
    guessGhcPkgFromGhcPath :: ConfiguredProgram
                           -> Verbosity -> ProgramSearchPath
                           -> IO (Maybe (FilePath, [FilePath]))
    guessGhcPkgFromGhcPath = guessToolFromGhcPath ghcPkgProgram

    -- | Given something like /usr/local/bin/ghc-6.6.1(.exe) we try and find a
    -- corresponding hsc2hs, we try looking for both a versioned and unversioned
    -- hsc2hs in the same dir, that is:
    --
    -- > /usr/local/bin/hsc2hs-ghc-6.6.1(.exe)
    -- > /usr/local/bin/hsc2hs-6.6.1(.exe)
    -- > /usr/local/bin/hsc2hs(.exe)
    --
    guessHsc2hsFromGhcPath :: ConfiguredProgram
                           -> Verbosity -> ProgramSearchPath
                           -> IO (Maybe (FilePath, [FilePath]))
    guessHsc2hsFromGhcPath = guessToolFromGhcPath hsc2hsProgram

    -- | Given something like /usr/local/bin/ghc-6.6.1(.exe) we try and find a
    -- corresponding haddock, we try looking for both a versioned and unversioned
    -- haddock in the same dir, that is:
    --
    -- > /usr/local/bin/haddock-ghc-6.6.1(.exe)
    -- > /usr/local/bin/haddock-6.6.1(.exe)
    -- > /usr/local/bin/haddock(.exe)
    --
    guessHaddockFromGhcPath :: ConfiguredProgram
                           -> Verbosity -> ProgramSearchPath
                           -> IO (Maybe (FilePath, [FilePath]))
    guessHaddockFromGhcPath = guessToolFromGhcPath haddockProgram

    guessHpcFromGhcPath :: ConfiguredProgram
                           -> Verbosity -> ProgramSearchPath
                           -> IO (Maybe (FilePath, [FilePath]))
    guessHpcFromGhcPath = guessToolFromGhcPath hpcProgram

    guessRunghcFromGhcPath :: ConfiguredProgram
                           -> Verbosity -> ProgramSearchPath
                           -> IO (Maybe (FilePath, [FilePath]))
    guessRunghcFromGhcPath = guessToolFromGhcPath runghcProgram

    getGhcInfo :: Verbosity -> ConfiguredProgram -> IO [(String, String)]
    getGhcInfo verbosity ghcProg = Internal.getGhcInfo verbosity implInfo ghcProg
      where
        version = fromMaybe (error "GHC.getGhcInfo: no ghc version") $ programVersion ghcProg
        implInfo = ghcVersionImplInfo version

    -- | Given a single package DB, return all installed packages.
    getPackageDBContents :: Verbosity -> PackageDB -> ProgramDb
                            -> IO InstalledPackageIndex
    getPackageDBContents verbosity packagedb progdb = do
      pkgss <- getInstalledPackages' verbosity [packagedb] progdb
      toPackageIndex verbosity pkgss progdb

    -- | Given a package DB stack, return all installed packages.
    getInstalledPackages :: Verbosity -> Compiler -> PackageDBStack
                         -> ProgramDb
                         -> IO InstalledPackageIndex
    getInstalledPackages verbosity comp packagedbs progdb = do
      checkPackageDbEnvVar verbosity
      checkPackageDbStack verbosity comp packagedbs
      pkgss <- getInstalledPackages' verbosity packagedbs progdb
      index <- toPackageIndex verbosity pkgss progdb
      return $! hackRtsPackage index

      where
        hackRtsPackage index =
          case PackageIndex.lookupPackageName index (mkPackageName "rts") of
            [(_,[rts])]
               -> PackageIndex.insert (removeMingwIncludeDir rts) index
            _  -> index -- No (or multiple) ghc rts package is registered!!
                        -- Feh, whatever, the ghc test suite does some crazy stuff.

    -- | Given a list of @(PackageDB, InstalledPackageInfo)@ pairs, produce a
    -- @PackageIndex@. Helper function used by 'getPackageDBContents' and
    -- 'getInstalledPackages'.
    toPackageIndex :: Verbosity
                   -> [(PackageDB, [InstalledPackageInfo])]
                   -> ProgramDb
                   -> IO InstalledPackageIndex
    toPackageIndex verbosity pkgss progdb = do
      -- On Windows, various fields have $topdir/foo rather than full
      -- paths. We need to substitute the right value in so that when
      -- we, for example, call gcc, we have proper paths to give it.
      topDir <- getLibDir' verbosity ghcProg
      let indices = [ PackageIndex.fromList (map (Internal.substTopDir topDir) pkgs)
                    | (_, pkgs) <- pkgss ]
      return $! mconcat indices

      where
        ghcProg = fromMaybe (error "GHC.toPackageIndex: no ghc program") $ lookupProgram ghcProgram progdb

    getLibDir :: Verbosity -> LocalBuildInfo -> IO FilePath
    getLibDir verbosity lbi =
        dropWhileEndLE isSpace `fmap`
         getDbProgramOutput verbosity ghcProgram
         (withPrograms lbi) ["--print-libdir"]

    getLibDir' :: Verbosity -> ConfiguredProgram -> IO FilePath
    getLibDir' verbosity ghcProg =
        dropWhileEndLE isSpace `fmap`
         getProgramOutput verbosity ghcProg ["--print-libdir"]

    -- | Return the 'FilePath' to the global GHC package database.
    getGlobalPackageDB :: Verbosity -> ConfiguredProgram -> IO FilePath
    getGlobalPackageDB verbosity ghcProg =
        dropWhileEndLE isSpace `fmap`
         getProgramOutput verbosity ghcProg ["--print-global-package-db"]

    -- | Return the 'FilePath' to the per-user GHC package database.
    getUserPackageDB
      :: Verbosity -> ConfiguredProgram -> Platform -> NoCallStackIO FilePath
    getUserPackageDB _verbosity ghcProg platform = do
        -- It's rather annoying that we have to reconstruct this, because ghc
        -- hides this information from us otherwise. But for certain use cases
        -- like change monitoring it really can't remain hidden.
        appdir <- getAppUserDataDirectory "ghc"
        return (appdir </> platformAndVersion </> packageConfFileName)
      where
        platformAndVersion = Internal.ghcPlatformAndVersionString
                               platform ghcVersion
        packageConfFileName = "package.conf.d"
        ghcVersion = fromMaybe (error "GHC.getUserPackageDB: no ghc version") $ programVersion ghcProg

    checkPackageDbEnvVar :: Verbosity -> IO ()
    checkPackageDbEnvVar verbosity =
        Internal.checkPackageDbEnvVar verbosity "GHC" "GHC_PACKAGE_PATH"

    checkPackageDbStack :: Verbosity -> Compiler -> PackageDBStack -> IO ()
    checkPackageDbStack verbosity comp =
        if flagPackageConf implInfo
          then checkPackageDbStackPre76 verbosity
          else checkPackageDbStackPost76 verbosity
      where implInfo = ghcVersionImplInfo (compilerVersion comp)

    checkPackageDbStackPost76 :: Verbosity -> PackageDBStack -> IO ()
    checkPackageDbStackPost76 _ (GlobalPackageDB:rest)
      | GlobalPackageDB `notElem` rest = return ()
    checkPackageDbStackPost76 verbosity rest
      | GlobalPackageDB `elem` rest =
      die' verbosity $ "If the global package db is specified, it must be "
         ++ "specified first and cannot be specified multiple times"
    checkPackageDbStackPost76 _ _ = return ()

    checkPackageDbStackPre76 :: Verbosity -> PackageDBStack -> IO ()
    checkPackageDbStackPre76 _ (GlobalPackageDB:rest)
      | GlobalPackageDB `notElem` rest = return ()
    checkPackageDbStackPre76 verbosity rest
      | GlobalPackageDB `notElem` rest =
      die' verbosity $
            "With current ghc versions the global package db is always used "
         ++ "and must be listed first. This ghc limitation is lifted in GHC 7.6,"
         ++ "see http://ghc.haskell.org/trac/ghc/ticket/5977"
    checkPackageDbStackPre76 verbosity _ =
      die' verbosity $ "If the global package db is specified, it must be "
         ++ "specified first and cannot be specified multiple times"

    -- GHC < 6.10 put "$topdir/include/mingw" in rts's installDirs. This
    -- breaks when you want to use a different gcc, so we need to filter
    -- it out.
    removeMingwIncludeDir :: InstalledPackageInfo -> InstalledPackageInfo
    removeMingwIncludeDir pkg =
        let ids = InstalledPackageInfo.includeDirs pkg
            ids' = filter (not . ("mingw" `isSuffixOf`)) ids
        in pkg { InstalledPackageInfo.includeDirs = ids' }

    -- | Get the packages from specific PackageDBs, not cumulative.
    --
    getInstalledPackages' :: Verbosity -> [PackageDB] -> ProgramDb
                         -> IO [(PackageDB, [InstalledPackageInfo])]
    getInstalledPackages' verbosity packagedbs progdb =
      sequenceA
        [ do pkgs <- HcPkg.dump (hcPkgInfo progdb) verbosity packagedb
             return (packagedb, pkgs)
        | packagedb <- packagedbs ]

    getInstalledPackagesMonitorFiles :: Verbosity -> Platform
                                     -> ProgramDb
                                     -> [PackageDB]
                                     -> IO [FilePath]
    getInstalledPackagesMonitorFiles verbosity platform progdb =
        traverse getPackageDBPath
      where
        getPackageDBPath :: PackageDB -> IO FilePath
        getPackageDBPath GlobalPackageDB =
          selectMonitorFile =<< getGlobalPackageDB verbosity ghcProg

        getPackageDBPath UserPackageDB =
          selectMonitorFile =<< getUserPackageDB verbosity ghcProg platform

        getPackageDBPath (SpecificPackageDB path) = selectMonitorFile path

        -- GHC has old style file dbs, and new style directory dbs.
        -- Note that for dir style dbs, we only need to monitor the cache file, not
        -- the whole directory. The ghc program itself only reads the cache file
        -- so it's safe to only monitor this one file.
        selectMonitorFile path = do
          isFileStyle <- doesFileExist path
          if isFileStyle then return path
                         else return (path </> "package.cache")

        ghcProg = fromMaybe (error "GHC.toPackageIndex: no ghc program") $ lookupProgram ghcProgram progdb

    -- -----------------------------------------------------------------------------
    -- Building a library

    buildLib :: Verbosity          -> Cabal.Flag (Maybe Int)
             -> PackageDescription -> LocalBuildInfo
             -> Library            -> ComponentLocalBuildInfo -> IO ()
    buildLib = buildOrReplLib Nothing

    replLib :: [String]                -> Verbosity
            -> Cabal.Flag (Maybe Int)  -> PackageDescription
            -> LocalBuildInfo          -> Library
            -> ComponentLocalBuildInfo -> IO ()
    replLib = buildOrReplLib . Just

    buildOrReplLib :: Maybe [String] -> Verbosity
                   -> Cabal.Flag (Maybe Int) -> PackageDescription
                   -> LocalBuildInfo -> Library
                   -> ComponentLocalBuildInfo -> IO ()
    buildOrReplLib mReplFlags verbosity numJobs pkg_descr lbi lib clbi = do
      let uid = componentUnitId clbi
          libTargetDir = componentBuildDir lbi clbi
          whenVanillaLib forceVanilla =
            when (forceVanilla || withVanillaLib lbi)
          whenProfLib = when (withProfLib lbi)
          whenSharedLib forceShared =
            when (forceShared || withSharedLib lbi)
          whenStaticLib forceStatic =
            when (forceStatic || withStaticLib lbi)
          whenGHCiLib = when (withGHCiLib lbi)
          forRepl = maybe False (const True) mReplFlags
          whenReplLib = when forRepl
          replFlags = fromMaybe mempty mReplFlags
          comp = compiler lbi
          ghcVersion = compilerVersion comp
          implInfo  = getImplInfo comp
          platform@(Platform _hostArch hostOS) = hostPlatform lbi
          has_code = not (componentIsIndefinite clbi)

      (ghcProg, _) <- requireProgram verbosity ghcProgram (withPrograms lbi)
      let runGhcProg = runGHC verbosity ghcProg comp platform

      let libBi = libBuildInfo lib

      let isGhcDynamic        = isDynamic comp
          dynamicTooSupported = supportsDynamicToo comp
          doingTH = usesTemplateHaskellOrQQ libBi
          forceVanillaLib = doingTH && not isGhcDynamic
          forceSharedLib  = doingTH &&     isGhcDynamic
          -- TH always needs default libs, even when building for profiling

      -- Determine if program coverage should be enabled and if so, what
      -- '-hpcdir' should be.
      let isCoverageEnabled = libCoverage lbi
          -- TODO: Historically HPC files have been put into a directory which
          -- has the package name.  I'm going to avoid changing this for
          -- now, but it would probably be better for this to be the
          -- component ID instead...
          pkg_name = prettyShow (PD.package pkg_descr)
          distPref = fromFlag $ configDistPref $ configFlags lbi
          hpcdir way
            | forRepl = mempty  -- HPC is not supported in ghci
            | isCoverageEnabled = toFlag $ Hpc.mixDir distPref way pkg_name
            | otherwise = mempty

      createDirectoryIfMissingVerbose verbosity True libTargetDir
      -- TODO: do we need to put hs-boot files into place for mutually recursive
      -- modules?
      let cLikeFiles  = fromNubListR $ mconcat
                          [ toNubListR (cSources   libBi)
                          , toNubListR (cxxSources libBi)
                          , toNubListR (cmmSources libBi)
                          , toNubListR (asmSources libBi)
                          ]
          cObjs       = map (`replaceExtension` objExtension) cLikeFiles
          baseOpts    = componentGhcOptions verbosity lbi libBi clbi libTargetDir
          vanillaOpts = baseOpts `mappend` mempty {
                          ghcOptMode         = toFlag GhcModeMake,
                          ghcOptNumJobs      = numJobs,
                          ghcOptInputModules = toNubListR $ allLibModules lib clbi,
                          ghcOptHPCDir       = hpcdir Hpc.Vanilla
                        }

          profOpts    = vanillaOpts `mappend` mempty {
                          ghcOptProfilingMode = toFlag True,
                          ghcOptProfilingAuto = Internal.profDetailLevelFlag True
                                                  (withProfLibDetail lbi),
                          ghcOptHiSuffix      = toFlag "p_hi",
                          ghcOptObjSuffix     = toFlag "p_o",
                          ghcOptExtra         = hcProfOptions GHC libBi,
                          ghcOptHPCDir        = hpcdir Hpc.Prof
                        }

          sharedOpts  = vanillaOpts `mappend` mempty {
                          ghcOptDynLinkMode = toFlag GhcDynamicOnly,
                          ghcOptFPic        = toFlag True,
                          ghcOptHiSuffix    = toFlag "dyn_hi",
                          ghcOptObjSuffix   = toFlag "dyn_o",
                          ghcOptExtra       = hcSharedOptions GHC libBi,
                          ghcOptHPCDir      = hpcdir Hpc.Dyn
                        }
          linkerOpts = mempty {
                          ghcOptLinkOptions       = PD.ldOptions libBi
                                                    ++ [ "-static"
                                                       | withFullyStaticExe lbi ]
                                                    -- Pass extra `ld-options` given
                                                    -- through to GHC's linker.
                                                    ++ maybe [] programOverrideArgs
                                                         (lookupProgram ldProgram (withPrograms lbi)),
                          ghcOptLinkLibs          = extraLibs libBi,
                          ghcOptLinkLibPath       = toNubListR $ extraLibDirs libBi,
                          ghcOptLinkFrameworks    = toNubListR $ PD.frameworks libBi,
                          ghcOptLinkFrameworkDirs = toNubListR $
                                                    PD.extraFrameworkDirs libBi,
                          ghcOptInputFiles     = toNubListR
                                                 [libTargetDir </> x | x <- cObjs]
                       }
          replOpts    = vanillaOpts {
                          ghcOptExtra        = Internal.filterGhciFlags
                                               (ghcOptExtra vanillaOpts)
                                               <> replFlags,
                          ghcOptNumJobs      = mempty
                        }
                        `mappend` linkerOpts
                        `mappend` mempty {
                          ghcOptMode         = toFlag GhcModeInteractive,
                          ghcOptOptimisation = toFlag GhcNoOptimisation
                        }

          vanillaSharedOpts = vanillaOpts `mappend` mempty {
                          ghcOptDynLinkMode  = toFlag GhcStaticAndDynamic,
                          ghcOptDynHiSuffix  = toFlag "dyn_hi",
                          ghcOptDynObjSuffix = toFlag "dyn_o",
                          ghcOptHPCDir       = hpcdir Hpc.Dyn
                        }

      unless (forRepl || null (allLibModules lib clbi)) $
        do let vanilla = whenVanillaLib forceVanillaLib (runGhcProg vanillaOpts)
               shared  = whenSharedLib  forceSharedLib  (runGhcProg sharedOpts)
               useDynToo = dynamicTooSupported &&
                           (forceVanillaLib || withVanillaLib lbi) &&
                           (forceSharedLib  || withSharedLib  lbi) &&
                           null (hcSharedOptions GHC libBi)
           if not has_code
            then vanilla
            else
             if useDynToo
              then do
                  runGhcProg vanillaSharedOpts
                  case (hpcdir Hpc.Dyn, hpcdir Hpc.Vanilla) of
                    (Cabal.Flag dynDir, Cabal.Flag vanillaDir) ->
                        -- When the vanilla and shared library builds are done
                        -- in one pass, only one set of HPC module interfaces
                        -- are generated. This set should suffice for both
                        -- static and dynamically linked executables. We copy
                        -- the modules interfaces so they are available under
                        -- both ways.
                        copyDirectoryRecursive verbosity dynDir vanillaDir
                    _ -> return ()
              else if isGhcDynamic
                then do shared;  vanilla
                else do vanilla; shared
           whenProfLib (runGhcProg profOpts)

      -- Build any C++ sources separately.
      unless (not has_code || null (cxxSources libBi)) $ do
        info verbosity "Building C++ Sources..."
        sequence_
          [ do let baseCxxOpts    = Internal.componentCxxGhcOptions verbosity implInfo
                                    lbi libBi clbi libTargetDir filename
                   vanillaCxxOpts = if isGhcDynamic
                                    then baseCxxOpts { ghcOptFPic = toFlag True }
                                    else baseCxxOpts
                   profCxxOpts    = vanillaCxxOpts `mappend` mempty {
                                      ghcOptProfilingMode = toFlag True,
                                      ghcOptObjSuffix     = toFlag "p_o"
                                    }
                   sharedCxxOpts  = vanillaCxxOpts `mappend` mempty {
                                     ghcOptFPic        = toFlag True,
                                     ghcOptDynLinkMode = toFlag GhcDynamicOnly,
                                     ghcOptObjSuffix   = toFlag "dyn_o"
                                   }
                   odir           = fromFlag (ghcOptObjDir vanillaCxxOpts)
               createDirectoryIfMissingVerbose verbosity True odir
               let runGhcProgIfNeeded cxxOpts = do
                     needsRecomp <- checkNeedsRecompilation filename cxxOpts
                     when needsRecomp $ runGhcProg cxxOpts
               runGhcProgIfNeeded vanillaCxxOpts
               unless forRepl $
                 whenSharedLib forceSharedLib (runGhcProgIfNeeded sharedCxxOpts)
               unless forRepl $ whenProfLib   (runGhcProgIfNeeded   profCxxOpts)
          | filename <- cxxSources libBi]

      -- build any C sources
      unless (not has_code || null (cSources libBi)) $ do
        info verbosity "Building C Sources..."
        sequence_
          [ do let baseCcOpts    = Internal.componentCcGhcOptions verbosity implInfo
                                   lbi libBi clbi libTargetDir filename
                   vanillaCcOpts = if isGhcDynamic
                                   -- Dynamic GHC requires C sources to be built
                                   -- with -fPIC for REPL to work. See #2207.
                                   then baseCcOpts { ghcOptFPic = toFlag True }
                                   else baseCcOpts
                   profCcOpts    = vanillaCcOpts `mappend` mempty {
                                     ghcOptProfilingMode = toFlag True,
                                     ghcOptObjSuffix     = toFlag "p_o"
                                   }
                   sharedCcOpts  = vanillaCcOpts `mappend` mempty {
                                     ghcOptFPic        = toFlag True,
                                     ghcOptDynLinkMode = toFlag GhcDynamicOnly,
                                     ghcOptObjSuffix   = toFlag "dyn_o"
                                   }
                   odir          = fromFlag (ghcOptObjDir vanillaCcOpts)
               createDirectoryIfMissingVerbose verbosity True odir
               let runGhcProgIfNeeded ccOpts = do
                     needsRecomp <- checkNeedsRecompilation filename ccOpts
                     when needsRecomp $ runGhcProg ccOpts
               runGhcProgIfNeeded vanillaCcOpts
               unless forRepl $
                 whenSharedLib forceSharedLib (runGhcProgIfNeeded sharedCcOpts)
               unless forRepl $ whenProfLib (runGhcProgIfNeeded profCcOpts)
          | filename <- cSources libBi]

      -- build any ASM sources
      unless (not has_code || null (asmSources libBi)) $ do
        info verbosity "Building Assembler Sources..."
        sequence_
          [ do let baseAsmOpts    = Internal.componentAsmGhcOptions verbosity implInfo
                                    lbi libBi clbi libTargetDir filename
                   vanillaAsmOpts = if isGhcDynamic
                                    -- Dynamic GHC requires objects to be built
                                    -- with -fPIC for REPL to work. See #2207.
                                    then baseAsmOpts { ghcOptFPic = toFlag True }
                                    else baseAsmOpts
                   profAsmOpts    = vanillaAsmOpts `mappend` mempty {
                                     ghcOptProfilingMode = toFlag True,
                                     ghcOptObjSuffix     = toFlag "p_o"
                                   }
                   sharedAsmOpts  = vanillaAsmOpts `mappend` mempty {
                                     ghcOptFPic        = toFlag True,
                                     ghcOptDynLinkMode = toFlag GhcDynamicOnly,
                                     ghcOptObjSuffix   = toFlag "dyn_o"
                                   }
                   odir           = fromFlag (ghcOptObjDir vanillaAsmOpts)
               createDirectoryIfMissingVerbose verbosity True odir
               let runGhcProgIfNeeded asmOpts = do
                     needsRecomp <- checkNeedsRecompilation filename asmOpts
                     when needsRecomp $ runGhcProg asmOpts
               runGhcProgIfNeeded vanillaAsmOpts
               unless forRepl $
                 whenSharedLib forceSharedLib (runGhcProgIfNeeded sharedAsmOpts)
               unless forRepl $ whenProfLib (runGhcProgIfNeeded profAsmOpts)
          | filename <- asmSources libBi]

      -- build any Cmm sources
      unless (not has_code || null (cmmSources libBi)) $ do
        info verbosity "Building C-- Sources..."
        sequence_
          [ do let baseCmmOpts    = Internal.componentCmmGhcOptions verbosity implInfo
                                    lbi libBi clbi libTargetDir filename
                   vanillaCmmOpts = if isGhcDynamic
                                    -- Dynamic GHC requires C sources to be built
                                    -- with -fPIC for REPL to work. See #2207.
                                    then baseCmmOpts { ghcOptFPic = toFlag True }
                                    else baseCmmOpts
                   profCmmOpts    = vanillaCmmOpts `mappend` mempty {
                                     ghcOptProfilingMode = toFlag True,
                                     ghcOptObjSuffix     = toFlag "p_o"
                                   }
                   sharedCmmOpts  = vanillaCmmOpts `mappend` mempty {
                                     ghcOptFPic        = toFlag True,
                                     ghcOptDynLinkMode = toFlag GhcDynamicOnly,
                                     ghcOptObjSuffix   = toFlag "dyn_o"
                                   }
                   odir          = fromFlag (ghcOptObjDir vanillaCmmOpts)
               createDirectoryIfMissingVerbose verbosity True odir
               let runGhcProgIfNeeded cmmOpts = do
                     needsRecomp <- checkNeedsRecompilation filename cmmOpts
                     when needsRecomp $ runGhcProg cmmOpts
               runGhcProgIfNeeded vanillaCmmOpts
               unless forRepl $
                 whenSharedLib forceSharedLib (runGhcProgIfNeeded sharedCmmOpts)
               unless forRepl $ whenProfLib (runGhcProgIfNeeded profCmmOpts)
          | filename <- cmmSources libBi]

      -- TODO: problem here is we need the .c files built first, so we can load them
      -- with ghci, but .c files can depend on .h files generated by ghc by ffi
      -- exports.
      whenReplLib $ do
        when (null (allLibModules lib clbi)) $ warn verbosity "No exposed modules"
        runGhcProg replOpts

      -- link:
      when has_code . unless forRepl $ do
        info verbosity "Linking..."
        let cProfObjs            = map (`replaceExtension` ("p_" ++ objExtension))
                                   (cSources libBi ++ cxxSources libBi)
            cSharedObjs          = map (`replaceExtension` ("dyn_" ++ objExtension))
                                   (cSources libBi ++ cxxSources libBi)
            compiler_id          = compilerId (compiler lbi)
            vanillaLibFilePath   = libTargetDir </> mkLibName uid
            profileLibFilePath   = libTargetDir </> mkProfLibName uid
            sharedLibFilePath    = libTargetDir </>
                                   mkSharedLibName (hostPlatform lbi) compiler_id uid
            staticLibFilePath    = libTargetDir </>
                                   mkStaticLibName (hostPlatform lbi) compiler_id uid
            ghciLibFilePath      = libTargetDir </> Internal.mkGHCiLibName uid
            ghciProfLibFilePath  = libTargetDir </> Internal.mkGHCiProfLibName uid
            libInstallPath       = libdir $
                                   absoluteComponentInstallDirs
                                   pkg_descr lbi uid NoCopyDest
            sharedLibInstallPath = libInstallPath </>
                                   mkSharedLibName (hostPlatform lbi) compiler_id uid

        stubObjs <- catMaybes <$> sequenceA
          [ findFileWithExtension [objExtension] [libTargetDir]
              (ModuleName.toFilePath x ++"_stub")
          | ghcVersion < mkVersion [7,2] -- ghc-7.2+ does not make _stub.o files
          , x <- allLibModules lib clbi ]
        stubProfObjs <- catMaybes <$> sequenceA
          [ findFileWithExtension ["p_" ++ objExtension] [libTargetDir]
              (ModuleName.toFilePath x ++"_stub")
          | ghcVersion < mkVersion [7,2] -- ghc-7.2+ does not make _stub.o files
          , x <- allLibModules lib clbi ]
        stubSharedObjs <- catMaybes <$> sequenceA
          [ findFileWithExtension ["dyn_" ++ objExtension] [libTargetDir]
              (ModuleName.toFilePath x ++"_stub")
          | ghcVersion < mkVersion [7,2] -- ghc-7.2+ does not make _stub.o files
          , x <- allLibModules lib clbi ]

        hObjs     <- Internal.getHaskellObjects implInfo lib lbi clbi
                          libTargetDir objExtension True
        hProfObjs <-
          if withProfLib lbi
                  then Internal.getHaskellObjects implInfo lib lbi clbi
                          libTargetDir ("p_" ++ objExtension) True
                  else return []
        hSharedObjs <-
          if withSharedLib lbi
                  then Internal.getHaskellObjects implInfo lib lbi clbi
                          libTargetDir ("dyn_" ++ objExtension) False
                  else return []

        unless (null hObjs && null cObjs && null stubObjs) $ do
          rpaths <- getRPaths lbi clbi

          let staticObjectFiles =
                     hObjs
                  ++ map (libTargetDir </>) cObjs
                  ++ stubObjs
              profObjectFiles =
                     hProfObjs
                  ++ map (libTargetDir </>) cProfObjs
                  ++ stubProfObjs
              dynamicObjectFiles =
                     hSharedObjs
                  ++ map (libTargetDir </>) cSharedObjs
                  ++ stubSharedObjs
              -- After the relocation lib is created we invoke ghc -shared
              -- with the dependencies spelled out as -package arguments
              -- and ghc invokes the linker with the proper library paths
              ghcSharedLinkArgs =
                  mempty {
                    ghcOptShared             = toFlag True,
                    ghcOptDynLinkMode        = toFlag GhcDynamicOnly,
                    ghcOptInputFiles         = toNubListR dynamicObjectFiles,
                    ghcOptOutputFile         = toFlag sharedLibFilePath,
                    ghcOptExtra              = hcSharedOptions GHC libBi,
                    -- For dynamic libs, Mac OS/X needs to know the install location
                    -- at build time. This only applies to GHC < 7.8 - see the
                    -- discussion in #1660.
                    ghcOptDylibName          = if hostOS == OSX
                                                  && ghcVersion < mkVersion [7,8]
                                                then toFlag sharedLibInstallPath
                                                else mempty,
                    ghcOptHideAllPackages    = toFlag True,
                    ghcOptNoAutoLinkPackages = toFlag True,
                    ghcOptPackageDBs         = withPackageDB lbi,
                    ghcOptThisUnitId = case clbi of
                        LibComponentLocalBuildInfo { componentCompatPackageKey = pk }
                          -> toFlag pk
                        _ -> mempty,
                    ghcOptThisComponentId = case clbi of
                        LibComponentLocalBuildInfo
                          { componentInstantiatedWith = insts } ->
                            if null insts
                                then mempty
                                else toFlag (componentComponentId clbi)
                        _ -> mempty,
                    ghcOptInstantiatedWith = case clbi of
                        LibComponentLocalBuildInfo
                          { componentInstantiatedWith = insts }
                          -> insts
                        _ -> [],
                    ghcOptPackages           = toNubListR $
                                               Internal.mkGhcOptPackages clbi ,
                    ghcOptLinkLibs           = extraLibs libBi,
                    ghcOptLinkLibPath        = toNubListR $ extraLibDirs libBi,
                    ghcOptLinkFrameworks     = toNubListR $ PD.frameworks libBi,
                    ghcOptLinkFrameworkDirs  =
                      toNubListR $ PD.extraFrameworkDirs libBi,
                    ghcOptRPaths             = rpaths
                  }
              ghcStaticLinkArgs =
                  mempty {
                    ghcOptStaticLib          = toFlag True,
                    ghcOptInputFiles         = toNubListR staticObjectFiles,
                    ghcOptOutputFile         = toFlag staticLibFilePath,
                    ghcOptExtra              = hcStaticOptions GHC libBi,
                    ghcOptHideAllPackages    = toFlag True,
                    ghcOptNoAutoLinkPackages = toFlag True,
                    ghcOptPackageDBs         = withPackageDB lbi,
                    ghcOptThisUnitId = case clbi of
                        LibComponentLocalBuildInfo { componentCompatPackageKey = pk }
                          -> toFlag pk
                        _ -> mempty,
                    ghcOptThisComponentId = case clbi of
                        LibComponentLocalBuildInfo
                          { componentInstantiatedWith = insts } ->
                            if null insts
                                then mempty
                                else toFlag (componentComponentId clbi)
                        _ -> mempty,
                    ghcOptInstantiatedWith = case clbi of
                        LibComponentLocalBuildInfo
                          { componentInstantiatedWith = insts }
                          -> insts
                        _ -> [],
                    ghcOptPackages           = toNubListR $
                                               Internal.mkGhcOptPackages clbi ,
                    ghcOptLinkLibs           = extraLibs libBi,
                    ghcOptLinkLibPath        = toNubListR $ extraLibDirs libBi
                  }

          info verbosity (show (ghcOptPackages ghcSharedLinkArgs))

          whenVanillaLib False $ do
            Ar.createArLibArchive verbosity lbi vanillaLibFilePath staticObjectFiles
            whenGHCiLib $ do
              (ldProg, _) <- requireProgram verbosity ldProgram (withPrograms lbi)
              Ld.combineObjectFiles verbosity lbi ldProg
                ghciLibFilePath staticObjectFiles

          whenProfLib $ do
            Ar.createArLibArchive verbosity lbi profileLibFilePath profObjectFiles
            whenGHCiLib $ do
              (ldProg, _) <- requireProgram verbosity ldProgram (withPrograms lbi)
              Ld.combineObjectFiles verbosity lbi ldProg
                ghciProfLibFilePath profObjectFiles

          whenSharedLib False $
            runGhcProg ghcSharedLinkArgs

          whenStaticLib False $
            runGhcProg ghcStaticLinkArgs

    -- | Start a REPL without loading any source files.
    startInterpreter :: Verbosity -> ProgramDb -> Compiler -> Platform
                     -> PackageDBStack -> IO ()
    startInterpreter verbosity progdb comp platform packageDBs = do
      let replOpts = mempty {
            ghcOptMode       = toFlag GhcModeInteractive,
            ghcOptPackageDBs = packageDBs
            }
      checkPackageDbStack verbosity comp packageDBs
      (ghcProg, _) <- requireProgram verbosity ghcProgram progdb
      runGHC verbosity ghcProg comp platform replOpts

    -- -----------------------------------------------------------------------------
    -- Building an executable or foreign library

    -- | Build a foreign library
    buildFLib
      :: Verbosity          -> Cabal.Flag (Maybe Int)
      -> PackageDescription -> LocalBuildInfo
      -> ForeignLib         -> ComponentLocalBuildInfo -> IO ()
    buildFLib v njobs pkg lbi = gbuild v njobs pkg lbi . GBuildFLib

    replFLib
      :: [String]                -> Verbosity
      -> Cabal.Flag (Maybe Int)  -> PackageDescription
      -> LocalBuildInfo          -> ForeignLib
      -> ComponentLocalBuildInfo -> IO ()
    replFLib replFlags  v njobs pkg lbi =
      gbuild v njobs pkg lbi . GReplFLib replFlags

    -- | Build an executable with GHC.
    --
    buildExe
      :: Verbosity          -> Cabal.Flag (Maybe Int)
      -> PackageDescription -> LocalBuildInfo
      -> Executable         -> ComponentLocalBuildInfo -> IO ()
    buildExe v njobs pkg lbi = gbuild v njobs pkg lbi . GBuildExe

    replExe
      :: [String]                -> Verbosity
      -> Cabal.Flag (Maybe Int)  -> PackageDescription
      -> LocalBuildInfo          -> Executable
      -> ComponentLocalBuildInfo -> IO ()
    replExe replFlags v njobs pkg lbi =
      gbuild v njobs pkg lbi . GReplExe replFlags

    -- | Building an executable, starting the REPL, and building foreign
    -- libraries are all very similar and implemented in 'gbuild'. The
    -- 'GBuildMode' distinguishes between the various kinds of operation.
    data GBuildMode =
        GBuildExe  Executable
      | GReplExe   [String] Executable
      | GBuildFLib ForeignLib
      | GReplFLib  [String] ForeignLib

    gbuildInfo :: GBuildMode -> BuildInfo
    gbuildInfo (GBuildExe  exe)  = buildInfo exe
    gbuildInfo (GReplExe   _ exe)  = buildInfo exe
    gbuildInfo (GBuildFLib flib) = foreignLibBuildInfo flib
    gbuildInfo (GReplFLib  _ flib) = foreignLibBuildInfo flib

    gbuildName :: GBuildMode -> String
    gbuildName (GBuildExe  exe)  = unUnqualComponentName $ exeName exe
    gbuildName (GReplExe   _ exe)  = unUnqualComponentName $ exeName exe
    gbuildName (GBuildFLib flib) = unUnqualComponentName $ foreignLibName flib
    gbuildName (GReplFLib  _ flib) = unUnqualComponentName $ foreignLibName flib

    gbuildTargetName :: LocalBuildInfo -> GBuildMode -> String
    gbuildTargetName lbi (GBuildExe  exe)  = exeTargetName (hostPlatform lbi) exe
    gbuildTargetName lbi (GReplExe   _ exe)  = exeTargetName (hostPlatform lbi) exe
    gbuildTargetName lbi (GBuildFLib flib) = flibTargetName lbi flib
    gbuildTargetName lbi (GReplFLib  _ flib) = flibTargetName lbi flib

    exeTargetName :: Platform -> Executable -> String
    exeTargetName platform exe = unUnqualComponentName (exeName exe) `withExt` exeExtension platform

    -- | Target name for a foreign library (the actual file name)
    --
    -- We do not use mkLibName and co here because the naming for foreign libraries
    -- is slightly different (we don't use "_p" or compiler version suffices, and we
    -- don't want the "lib" prefix on Windows).
    --
    -- TODO: We do use `dllExtension` and co here, but really that's wrong: they
    -- use the OS used to build cabal to determine which extension to use, rather
    -- than the target OS (but this is wrong elsewhere in Cabal as well).
    flibTargetName :: LocalBuildInfo -> ForeignLib -> String
    flibTargetName lbi flib =
        case (os, foreignLibType flib) of
          (Windows, ForeignLibNativeShared) -> nm <.> "dll"
          (Windows, ForeignLibNativeStatic) -> nm <.> "lib"
          (Linux,   ForeignLibNativeShared) -> "lib" ++ nm <.> versionedExt
          (_other,  ForeignLibNativeShared) ->
            "lib" ++ nm <.> dllExtension (hostPlatform lbi)
          (_other,  ForeignLibNativeStatic) ->
            "lib" ++ nm <.> staticLibExtension (hostPlatform lbi)
          (_any,    ForeignLibTypeUnknown)  -> cabalBug "unknown foreign lib type"
      where
        nm :: String
        nm = unUnqualComponentName $ foreignLibName flib

        os :: OS
        os = let (Platform _ os') = hostPlatform lbi
             in os'

        -- If a foreign lib foo has lib-version-info 5:1:2 or
        -- lib-version-linux 3.2.1, it should be built as libfoo.so.3.2.1
        -- Libtool's version-info data is translated into library versions in a
        -- nontrivial way: so refer to libtool documentation.
        versionedExt :: String
        versionedExt =
          let nums = foreignLibVersion flib os
          in foldl (<.>) "so" (map show nums)

    -- | Name for the library when building.
    --
    -- If the `lib-version-info` field or the `lib-version-linux` field of
    -- a foreign library target is set, we need to incorporate that
    -- version into the SONAME field.
    --
    -- If a foreign library foo has lib-version-info 5:1:2, it should be
    -- built as libfoo.so.3.2.1.  We want it to get soname libfoo.so.3.
    -- However, GHC does not allow overriding soname by setting linker
    -- options, as it sets a soname of its own (namely the output
    -- filename), after the user-supplied linker options.  Hence, we have
    -- to compile the library with the soname as its filename.  We rename
    -- the compiled binary afterwards.
    --
    -- This method allows to adjust the name of the library at build time
    -- such that the correct soname can be set.
    flibBuildName :: LocalBuildInfo -> ForeignLib -> String
    flibBuildName lbi flib
      -- On linux, if a foreign-library has version data, the first digit is used
      -- to produce the SONAME.
      | (os, foreignLibType flib) ==
        (Linux, ForeignLibNativeShared)
      = let nums = foreignLibVersion flib os
        in "lib" ++ nm <.> foldl (<.>) "so" (map show (take 1 nums))
      | otherwise = flibTargetName lbi flib
      where
        os :: OS
        os = let (Platform _ os') = hostPlatform lbi
             in os'

        nm :: String
        nm = unUnqualComponentName $ foreignLibName flib

    gbuildIsRepl :: GBuildMode -> Bool
    gbuildIsRepl (GBuildExe  _) = False
    gbuildIsRepl (GReplExe _ _) = True
    gbuildIsRepl (GBuildFLib _) = False
    gbuildIsRepl (GReplFLib _ _) = True

    gbuildNeedDynamic :: LocalBuildInfo -> GBuildMode -> Bool
    gbuildNeedDynamic lbi bm =
        case bm of
          GBuildExe  _    -> withDynExe lbi
          GReplExe   _ _  -> withDynExe lbi
          GBuildFLib flib -> withDynFLib flib
          GReplFLib  _ flib -> withDynFLib flib
      where
        withDynFLib flib =
          case foreignLibType flib of
            ForeignLibNativeShared ->
              ForeignLibStandalone `notElem` foreignLibOptions flib
            ForeignLibNativeStatic ->
              False
            ForeignLibTypeUnknown  ->
              cabalBug "unknown foreign lib type"

    gbuildModDefFiles :: GBuildMode -> [FilePath]
    gbuildModDefFiles (GBuildExe _)     = []
    gbuildModDefFiles (GReplExe  _ _)     = []
    gbuildModDefFiles (GBuildFLib flib) = foreignLibModDefFile flib
    gbuildModDefFiles (GReplFLib _ flib) = foreignLibModDefFile flib

    -- | "Main" module name when overridden by @ghc-options: -main-is ...@
    -- or 'Nothing' if no @-main-is@ flag could be found.
    --
    -- In case of 'Nothing', 'Distribution.ModuleName.main' can be assumed.
    exeMainModuleName :: Executable -> Maybe ModuleName
    exeMainModuleName Executable{buildInfo = bnfo} =
        -- GHC honors the last occurrence of a module name updated via -main-is
        --
        -- Moreover, -main-is when parsed left-to-right can update either
        -- the "Main" module name, or the "main" function name, or both,
        -- see also 'decodeMainIsArg'.
        msum $ reverse $ map decodeMainIsArg $ findIsMainArgs ghcopts
      where
        ghcopts = hcOptions GHC bnfo

        findIsMainArgs [] = []
        findIsMainArgs ("-main-is":arg:rest) = arg : findIsMainArgs rest
        findIsMainArgs (_:rest) = findIsMainArgs rest

    -- | Decode argument to '-main-is'
    --
    -- Returns 'Nothing' if argument set only the function name.
    --
    -- This code has been stolen/refactored from GHC's DynFlags.setMainIs
    -- function. The logic here is deliberately imperfect as it is
    -- intended to be bug-compatible with GHC's parser. See discussion in
    -- https://github.com/haskell/cabal/pull/4539#discussion_r118981753.
    decodeMainIsArg :: String -> Maybe ModuleName
    decodeMainIsArg arg
      | headOf main_fn isLower
                            -- The arg looked like "Foo.Bar.baz"
      = Just (ModuleName.fromString main_mod)
      | headOf arg isUpper  -- The arg looked like "Foo" or "Foo.Bar"
      = Just (ModuleName.fromString arg)
      | otherwise           -- The arg looked like "baz"
      = Nothing
      where
        headOf :: String -> (Char -> Bool) -> Bool
        headOf str pred' = any pred' (safeHead str)

        (main_mod, main_fn) = splitLongestPrefix arg (== '.')

        splitLongestPrefix :: String -> (Char -> Bool) -> (String,String)
        splitLongestPrefix str pred'
          | null r_pre = (str,           [])
          | otherwise  = (reverse (safeTail r_pre), reverse r_suf)
                               -- 'safeTail' drops the char satisfying 'pred'
          where (r_suf, r_pre) = break pred' (reverse str)

    -- | A collection of:
    --    * C input files
    --    * C++ input files
    --    * GHC input files
    --    * GHC input modules
    --
    -- Used to correctly build and link sources.
    data BuildSources = BuildSources {
            cSourcesFiles      :: [FilePath],
            cxxSourceFiles     :: [FilePath],
            inputSourceFiles   :: [FilePath],
            inputSourceModules :: [ModuleName]
        }

    -- | Locate and return the 'BuildSources' required to build and link.
    gbuildSources :: Verbosity
                  -> Version -- ^ specVersion
                  -> FilePath
                  -> GBuildMode
                  -> IO BuildSources
    gbuildSources verbosity specVer tmpDir bm =
        case bm of
          GBuildExe  exe  -> exeSources exe
          GReplExe   _ exe  -> exeSources exe
          GBuildFLib flib -> return $ flibSources flib
          GReplFLib  _ flib -> return $ flibSources flib
      where
        exeSources :: Executable -> IO BuildSources
        exeSources exe@Executable{buildInfo = bnfo, modulePath = modPath} = do
          main <- findFileEx verbosity (tmpDir : hsSourceDirs bnfo) modPath
          let mainModName = fromMaybe ModuleName.main $ exeMainModuleName exe
              otherModNames = exeModules exe

          if isHaskell main
            then
              if specVer < mkVersion [2] && (mainModName `elem` otherModNames)
              then do
                 -- The cabal manual clearly states that `other-modules` is
                 -- intended for non-main modules.  However, there's at least one
                 -- important package on Hackage (happy-1.19.5) which
                 -- violates this. We workaround this here so that we don't
                 -- invoke GHC with e.g.  'ghc --make Main src/Main.hs' which
                 -- would result in GHC complaining about duplicate Main
                 -- modules.
                 --
                 -- Finally, we only enable this workaround for
                 -- specVersion < 2, as 'cabal-version:>=2.0' cabal files
                 -- have no excuse anymore to keep doing it wrong... ;-)
                 warn verbosity $ "Enabling workaround for Main module '"
                                ++ prettyShow mainModName
                                ++ "' listed in 'other-modules' illegally!"

                 return BuildSources {
                            cSourcesFiles      = cSources bnfo,
                            cxxSourceFiles     = cxxSources bnfo,
                            inputSourceFiles   = [main],
                            inputSourceModules = filter (/= mainModName) $
                                                 exeModules exe
                        }

              else return BuildSources {
                              cSourcesFiles      = cSources bnfo,
                              cxxSourceFiles     = cxxSources bnfo,
                              inputSourceFiles   = [main],
                              inputSourceModules = exeModules exe
                          }
            else let (csf, cxxsf)
                       | isCxx main = (       cSources bnfo, main : cxxSources bnfo)
                       -- if main is not a Haskell source
                       -- and main is not a C++ source
                       -- then we assume that it is a C source
                       | otherwise  = (main : cSources bnfo,        cxxSources bnfo)

                 in  return BuildSources {
                                cSourcesFiles      = csf,
                                cxxSourceFiles     = cxxsf,
                                inputSourceFiles   = [],
                                inputSourceModules = exeModules exe
                            }

        flibSources :: ForeignLib -> BuildSources
        flibSources flib@ForeignLib{foreignLibBuildInfo = bnfo} =
            BuildSources {
                cSourcesFiles      = cSources bnfo,
                cxxSourceFiles     = cxxSources bnfo,
                inputSourceFiles   = [],
                inputSourceModules = foreignLibModules flib
            }

        isHaskell :: FilePath -> Bool
        isHaskell fp = elem (takeExtension fp) [".hs", ".lhs"]

        isCxx :: FilePath -> Bool
        isCxx fp = elem (takeExtension fp) [".cpp", ".cxx", ".c++"]

    -- | Generic build function. See comment for 'GBuildMode'.
    gbuild :: Verbosity          -> Cabal.Flag (Maybe Int)
           -> PackageDescription -> LocalBuildInfo
           -> GBuildMode         -> ComponentLocalBuildInfo -> IO ()
    gbuild verbosity numJobs pkg_descr lbi bm clbi = do
      (ghcProg, _) <- requireProgram verbosity ghcProgram (withPrograms lbi)
      let replFlags = case bm of
              GReplExe flags _  -> flags
              GReplFLib flags _ -> flags
              GBuildExe{}       -> mempty
              GBuildFLib{}      -> mempty
          comp       = compiler lbi
          platform   = hostPlatform lbi
          implInfo   = getImplInfo comp
          runGhcProg = runGHC verbosity ghcProg comp platform

      let (bnfo, threaded) = case bm of
            GBuildFLib _ -> popThreadedFlag (gbuildInfo bm)
            _            -> (gbuildInfo bm, False)

      -- the name that GHC really uses (e.g., with .exe on Windows for executables)
      let targetName = gbuildTargetName lbi bm
      let targetDir  = buildDir lbi </> (gbuildName bm)
      let tmpDir     = targetDir    </> (gbuildName bm ++ "-tmp")
      createDirectoryIfMissingVerbose verbosity True targetDir
      createDirectoryIfMissingVerbose verbosity True tmpDir

      -- TODO: do we need to put hs-boot files into place for mutually recursive
      -- modules?  FIX: what about exeName.hi-boot?

      -- Determine if program coverage should be enabled and if so, what
      -- '-hpcdir' should be.
      let isCoverageEnabled = exeCoverage lbi
          distPref = fromFlag $ configDistPref $ configFlags lbi
          hpcdir way
            | gbuildIsRepl bm   = mempty  -- HPC is not supported in ghci
            | isCoverageEnabled = toFlag $ Hpc.mixDir distPref way (gbuildName bm)
            | otherwise         = mempty

      rpaths <- getRPaths lbi clbi
      buildSources <- gbuildSources verbosity (specVersion pkg_descr) tmpDir bm

      let cSrcs               = cSourcesFiles buildSources
          cxxSrcs             = cxxSourceFiles buildSources
          inputFiles          = inputSourceFiles buildSources
          inputModules        = inputSourceModules buildSources
          isGhcDynamic        = isDynamic comp
          dynamicTooSupported = supportsDynamicToo comp
          cObjs               = map (`replaceExtension` objExtension) cSrcs
          cxxObjs             = map (`replaceExtension` objExtension) cxxSrcs
          needDynamic         = gbuildNeedDynamic lbi bm
          needProfiling       = withProfExe lbi

      -- build executables
          baseOpts   = (componentGhcOptions verbosity lbi bnfo clbi tmpDir)
                        `mappend` mempty {
                          ghcOptMode         = toFlag GhcModeMake,
                          ghcOptInputFiles   = toNubListR inputFiles,
                          ghcOptInputModules = toNubListR inputModules
                        }
          staticOpts = baseOpts `mappend` mempty {
                          ghcOptDynLinkMode    = toFlag GhcStaticOnly,
                          ghcOptHPCDir         = hpcdir Hpc.Vanilla
                       }
          profOpts   = baseOpts `mappend` mempty {
                          ghcOptProfilingMode  = toFlag True,
                          ghcOptProfilingAuto  = Internal.profDetailLevelFlag False
                                                 (withProfExeDetail lbi),
                          ghcOptHiSuffix       = toFlag "p_hi",
                          ghcOptObjSuffix      = toFlag "p_o",
                          ghcOptExtra          = hcProfOptions GHC bnfo,
                          ghcOptHPCDir         = hpcdir Hpc.Prof
                        }
          dynOpts    = baseOpts `mappend` mempty {
                          ghcOptDynLinkMode    = toFlag GhcDynamicOnly,
                          -- TODO: Does it hurt to set -fPIC for executables?
                          ghcOptFPic           = toFlag True,
                          ghcOptHiSuffix       = toFlag "dyn_hi",
                          ghcOptObjSuffix      = toFlag "dyn_o",
                          ghcOptExtra          = hcSharedOptions GHC bnfo,
                          ghcOptHPCDir         = hpcdir Hpc.Dyn
                        }
          dynTooOpts = staticOpts `mappend` mempty {
                          ghcOptDynLinkMode    = toFlag GhcStaticAndDynamic,
                          ghcOptDynHiSuffix    = toFlag "dyn_hi",
                          ghcOptDynObjSuffix   = toFlag "dyn_o",
                          ghcOptHPCDir         = hpcdir Hpc.Dyn
                        }
          linkerOpts = mempty {
                          ghcOptLinkOptions       = PD.ldOptions bnfo
                                                    ++ [ "-static"
                                                       | withFullyStaticExe lbi ]
                                                    -- Pass extra `ld-options` given
                                                    -- through to GHC's linker.
                                                    ++ maybe [] programOverrideArgs
                                                         (lookupProgram ldProgram (withPrograms lbi)),
                          ghcOptLinkLibs          = extraLibs bnfo,
                          ghcOptLinkLibPath       = toNubListR $ extraLibDirs bnfo,
                          ghcOptLinkFrameworks    = toNubListR $
                                                    PD.frameworks bnfo,
                          ghcOptLinkFrameworkDirs = toNubListR $
                                                    PD.extraFrameworkDirs bnfo,
                          ghcOptInputFiles     = toNubListR
                                                 [tmpDir </> x | x <- cObjs ++ cxxObjs]
                        }
          dynLinkerOpts = mempty {
                          ghcOptRPaths         = rpaths
                       }
          replOpts   = baseOpts {
                        ghcOptExtra            = Internal.filterGhciFlags
                                                 (ghcOptExtra baseOpts)
                                                 <> replFlags
                       }
                       -- For a normal compile we do separate invocations of ghc for
                       -- compiling as for linking. But for repl we have to do just
                       -- the one invocation, so that one has to include all the
                       -- linker stuff too, like -l flags and any .o files from C
                       -- files etc.
                       `mappend` linkerOpts
                       `mappend` mempty {
                          ghcOptMode         = toFlag GhcModeInteractive,
                          ghcOptOptimisation = toFlag GhcNoOptimisation
                         }
          commonOpts  | needProfiling = profOpts
                      | needDynamic   = dynOpts
                      | otherwise     = staticOpts
          compileOpts | useDynToo = dynTooOpts
                      | otherwise = commonOpts
          withStaticExe = not needProfiling && not needDynamic

          -- For building exe's that use TH with -prof or -dynamic we actually have
          -- to build twice, once without -prof/-dynamic and then again with
          -- -prof/-dynamic. This is because the code that TH needs to run at
          -- compile time needs to be the vanilla ABI so it can be loaded up and run
          -- by the compiler.
          -- With dynamic-by-default GHC the TH object files loaded at compile-time
          -- need to be .dyn_o instead of .o.
          doingTH = usesTemplateHaskellOrQQ bnfo
          -- Should we use -dynamic-too instead of compiling twice?
          useDynToo = dynamicTooSupported && isGhcDynamic
                      && doingTH && withStaticExe
                      && null (hcSharedOptions GHC bnfo)
          compileTHOpts | isGhcDynamic = dynOpts
                        | otherwise    = staticOpts
          compileForTH
            | gbuildIsRepl bm = False
            | useDynToo       = False
            | isGhcDynamic    = doingTH && (needProfiling || withStaticExe)
            | otherwise       = doingTH && (needProfiling || needDynamic)

       -- Build static/dynamic object files for TH, if needed.
      when compileForTH $
        runGhcProg compileTHOpts { ghcOptNoLink  = toFlag True
                                 , ghcOptNumJobs = numJobs }

      -- Do not try to build anything if there are no input files.
      -- This can happen if the cabal file ends up with only cSrcs
      -- but no Haskell modules.
      unless ((null inputFiles && null inputModules)
              || gbuildIsRepl bm) $
        runGhcProg compileOpts { ghcOptNoLink  = toFlag True
                               , ghcOptNumJobs = numJobs }

      -- build any C++ sources
      unless (null cxxSrcs) $ do
       info verbosity "Building C++ Sources..."
       sequence_
         [ do let baseCxxOpts    = Internal.componentCxxGhcOptions verbosity implInfo
                                   lbi bnfo clbi tmpDir filename
                  vanillaCxxOpts = if isGhcDynamic
                                    -- Dynamic GHC requires C++ sources to be built
                                    -- with -fPIC for REPL to work. See #2207.
                                   then baseCxxOpts { ghcOptFPic = toFlag True }
                                   else baseCxxOpts
                  profCxxOpts    = vanillaCxxOpts `mappend` mempty {
                                     ghcOptProfilingMode = toFlag True
                                   }
                  sharedCxxOpts  = vanillaCxxOpts `mappend` mempty {
                                     ghcOptFPic        = toFlag True,
                                     ghcOptDynLinkMode = toFlag GhcDynamicOnly
                                   }
                  opts | needProfiling = profCxxOpts
                       | needDynamic   = sharedCxxOpts
                       | otherwise     = vanillaCxxOpts
                  -- TODO: Placing all Haskell, C, & C++ objects in a single directory
                  --       Has the potential for file collisions. In general we would
                  --       consider this a user error. However, we should strive to
                  --       add a warning if this occurs.
                  odir = fromFlag (ghcOptObjDir opts)
              createDirectoryIfMissingVerbose verbosity True odir
              needsRecomp <- checkNeedsRecompilation filename opts
              when needsRecomp $
                runGhcProg opts
         | filename <- cxxSrcs ]

      -- build any C sources
      unless (null cSrcs) $ do
       info verbosity "Building C Sources..."
       sequence_
         [ do let baseCcOpts    = Internal.componentCcGhcOptions verbosity implInfo
                                  lbi bnfo clbi tmpDir filename
                  vanillaCcOpts = if isGhcDynamic
                                  -- Dynamic GHC requires C sources to be built
                                  -- with -fPIC for REPL to work. See #2207.
                                  then baseCcOpts { ghcOptFPic = toFlag True }
                                  else baseCcOpts
                  profCcOpts    = vanillaCcOpts `mappend` mempty {
                                    ghcOptProfilingMode = toFlag True
                                  }
                  sharedCcOpts  = vanillaCcOpts `mappend` mempty {
                                    ghcOptFPic        = toFlag True,
                                    ghcOptDynLinkMode = toFlag GhcDynamicOnly
                                  }
                  opts | needProfiling = profCcOpts
                       | needDynamic   = sharedCcOpts
                       | otherwise     = vanillaCcOpts
                  odir = fromFlag (ghcOptObjDir opts)
              createDirectoryIfMissingVerbose verbosity True odir
              needsRecomp <- checkNeedsRecompilation filename opts
              when needsRecomp $
                runGhcProg opts
         | filename <- cSrcs ]

      -- TODO: problem here is we need the .c files built first, so we can load them
      -- with ghci, but .c files can depend on .h files generated by ghc by ffi
      -- exports.
      case bm of
        GReplExe  _ _ -> runGhcProg replOpts
        GReplFLib _ _ -> runGhcProg replOpts
        GBuildExe _ -> do
          let linkOpts = commonOpts
                       `mappend` linkerOpts
                       `mappend` mempty {
                          ghcOptLinkNoHsMain = toFlag (null inputFiles)
                         }
                       `mappend` (if withDynExe lbi then dynLinkerOpts else mempty)

          info verbosity "Linking..."
          -- Work around old GHCs not relinking in this
          -- situation, see #3294
          let target = targetDir </> targetName
          when (compilerVersion comp < mkVersion [7,7]) $ do
            e <- doesFileExist target
            when e (removeFile target)
          runGhcProg linkOpts { ghcOptOutputFile = toFlag target }
        GBuildFLib flib -> do
          let rtsInfo  = extractRtsInfo lbi
              rtsOptLinkLibs = [
                  if needDynamic
                      then if threaded
                                then dynRtsThreadedLib (rtsDynamicInfo rtsInfo)
                                else dynRtsVanillaLib (rtsDynamicInfo rtsInfo)
                      else if threaded
                               then statRtsThreadedLib (rtsStaticInfo rtsInfo)
                               else statRtsVanillaLib (rtsStaticInfo rtsInfo)
                  ]
              linkOpts = case foreignLibType flib of
                ForeignLibNativeShared ->
                            commonOpts
                  `mappend` linkerOpts
                  `mappend` dynLinkerOpts
                  `mappend` mempty {
                     ghcOptLinkNoHsMain    = toFlag True,
                     ghcOptShared          = toFlag True,
                     ghcOptLinkLibs        = rtsOptLinkLibs,
                     ghcOptLinkLibPath     = toNubListR $ rtsLibPaths rtsInfo,
                     ghcOptFPic            = toFlag True,
                     ghcOptLinkModDefFiles = toNubListR $ gbuildModDefFiles bm
                    }
                  -- See Note [RPATH]
                  `mappend` ifNeedsRPathWorkaround lbi mempty {
                      ghcOptLinkOptions = ["-Wl,--no-as-needed"]
                    , ghcOptLinkLibs    = ["ffi"]
                    }
                ForeignLibNativeStatic ->
                  -- this should be caught by buildFLib
                  -- (and if we do implement this, we probably don't even want to call
                  -- ghc here, but rather Ar.createArLibArchive or something)
                  cabalBug "static libraries not yet implemented"
                ForeignLibTypeUnknown ->
                  cabalBug "unknown foreign lib type"
          -- We build under a (potentially) different filename to set a
          -- soname on supported platforms.  See also the note for
          -- @flibBuildName@.
          info verbosity "Linking..."
          let buildName = flibBuildName lbi flib
          runGhcProg linkOpts { ghcOptOutputFile = toFlag (targetDir </> buildName) }
          renameFile (targetDir </> buildName) (targetDir </> targetName)

    {-
    Note [RPATH]
    ~~~~~~~~~~~~

    Suppose that the dynamic library depends on `base`, but not (directly) on
    `integer-gmp` (which, however, is a dependency of `base`). We will link the
    library as

        gcc ... -lHSbase-4.7.0.2-ghc7.8.4 -lHSinteger-gmp-0.5.1.0-ghc7.8.4 ...

    However, on systems (like Ubuntu) where the linker gets called with `-as-needed`
    by default, the linker will notice that `integer-gmp` isn't actually a direct
    dependency and hence omit the link.

    Then when we attempt to link a C program against this dynamic library, the
    _static_ linker will attempt to verify that all symbols can be resolved.  The
    dynamic library itself does not require any symbols from `integer-gmp`, but
    `base` does. In order to verify that the symbols used by `base` can be
    resolved, the static linker needs to be able to _find_ integer-gmp.

    Finding the `base` dependency is simple, because the dynamic elf header
    (`readelf -d`) for the library that we have created looks something like

        (NEEDED) Shared library: [libHSbase-4.7.0.2-ghc7.8.4.so]
        (RPATH)  Library rpath: [/path/to/base-4.7.0.2:...]

    However, when it comes to resolving the dependency on `integer-gmp`, it needs
    to look at the dynamic header for `base`. On modern ghc (7.8 and higher) this
    looks something like

        (NEEDED) Shared library: [libHSinteger-gmp-0.5.1.0-ghc7.8.4.so]
        (RPATH)  Library rpath: [$ORIGIN/../integer-gmp-0.5.1.0:...]

    This specifies the location of `integer-gmp` _in terms of_ the location of base
    (using the `$ORIGIN`) variable. But here's the crux: when the static linker
    attempts to verify that all symbols can be resolved, [**IT DOES NOT RESOLVE
    `$ORIGIN`**](http://stackoverflow.com/questions/6323603/ld-using-rpath-origin-inside-a-shared-library-recursive).
    As a consequence, it will not be able to resolve the symbols and report the
    missing symbols as errors, _even though the dynamic linker **would** be able to
    resolve these symbols_. We can tell the static linker not to report these
    errors by using `--unresolved-symbols=ignore-all` and all will be fine when we
    run the program ([(indeed, this is what the gold linker
    does)](https://sourceware.org/ml/binutils/2013-05/msg00038.html), but it makes
    the resulting library more difficult to use.

    Instead what we can do is make sure that the generated dynamic library has
    explicit top-level dependencies on these libraries. This means that the static
    linker knows where to find them, and when we have transitive dependencies on
    the same libraries the linker will only load them once, so we avoid needing to
    look at the `RPATH` of our dependencies. We can do this by passing
    `--no-as-needed` to the linker, so that it doesn't omit any libraries.

    Note that on older ghc (7.6 and before) the Haskell libraries don't have an
    RPATH set at all, which makes it even more important that we make these
    top-level dependencies.

    Finally, we have to explicitly link against `libffi` for the same reason. For
    newer ghc this _happens_ to be unnecessary on many systems because `libffi` is
    a library which is not specific to GHC, and when the static linker verifies
    that all symbols can be resolved it will find the `libffi` that is globally
    installed (completely independent from ghc). Of course, this may well be the
    _wrong_ version of `libffi`, but it's quite possible that symbol resolution
    happens to work. This is of course the wrong approach, which is why we link
    explicitly against `libffi` so that we will find the _right_ version of
    `libffi`.
    -}

    -- | Do we need the RPATH workaround?
    --
    -- See Note [RPATH].
    ifNeedsRPathWorkaround :: Monoid a => LocalBuildInfo -> a -> a
    ifNeedsRPathWorkaround lbi a =
      case hostPlatform lbi of
        Platform _ Linux -> a
        _otherwise       -> mempty

    data DynamicRtsInfo = DynamicRtsInfo {
        dynRtsVanillaLib          :: FilePath
      , dynRtsThreadedLib         :: FilePath
      , dynRtsDebugLib            :: FilePath
      , dynRtsEventlogLib         :: FilePath
      , dynRtsThreadedDebugLib    :: FilePath
      , dynRtsThreadedEventlogLib :: FilePath
      }

    data StaticRtsInfo = StaticRtsInfo {
        statRtsVanillaLib           :: FilePath
      , statRtsThreadedLib          :: FilePath
      , statRtsDebugLib             :: FilePath
      , statRtsEventlogLib          :: FilePath
      , statRtsThreadedDebugLib     :: FilePath
      , statRtsThreadedEventlogLib  :: FilePath
      , statRtsProfilingLib         :: FilePath
      , statRtsThreadedProfilingLib :: FilePath
      }

    data RtsInfo = RtsInfo {
        rtsDynamicInfo :: DynamicRtsInfo
      , rtsStaticInfo  :: StaticRtsInfo
      , rtsLibPaths    :: [FilePath]
      }

    -- | Extract (and compute) information about the RTS library
    --
    -- TODO: This hardcodes the name as @HSrts-ghc<version>@. I don't know if we can
    -- find this information somewhere. We can lookup the 'hsLibraries' field of
    -- 'InstalledPackageInfo' but it will tell us @["HSrts", "Cffi"]@, which
    -- doesn't really help.
    extractRtsInfo :: LocalBuildInfo -> RtsInfo
    extractRtsInfo lbi =
        case PackageIndex.lookupPackageName
             (installedPkgs lbi) (mkPackageName "rts") of
          [(_, [rts])] -> aux rts
          _otherwise   -> error "No (or multiple) ghc rts package is registered"
      where
        aux :: InstalledPackageInfo -> RtsInfo
        aux rts = RtsInfo {
            rtsDynamicInfo = DynamicRtsInfo {
                dynRtsVanillaLib          = withGhcVersion "HSrts"
              , dynRtsThreadedLib         = withGhcVersion "HSrts_thr"
              , dynRtsDebugLib            = withGhcVersion "HSrts_debug"
              , dynRtsEventlogLib         = withGhcVersion "HSrts_l"
              , dynRtsThreadedDebugLib    = withGhcVersion "HSrts_thr_debug"
              , dynRtsThreadedEventlogLib = withGhcVersion "HSrts_thr_l"
              }
          , rtsStaticInfo = StaticRtsInfo {
                statRtsVanillaLib           = "HSrts"
              , statRtsThreadedLib          = "HSrts_thr"
              , statRtsDebugLib             = "HSrts_debug"
              , statRtsEventlogLib          = "HSrts_l"
              , statRtsThreadedDebugLib     = "HSrts_thr_debug"
              , statRtsThreadedEventlogLib  = "HSrts_thr_l"
              , statRtsProfilingLib         = "HSrts_p"
              , statRtsThreadedProfilingLib = "HSrts_thr_p"
              }
          , rtsLibPaths   = InstalledPackageInfo.libraryDirs rts
          }
        withGhcVersion = (++ ("-ghc" ++ prettyShow (compilerVersion (compiler lbi))))

    -- | Returns True if the modification date of the given source file is newer than
    -- the object file we last compiled for it, or if no object file exists yet.
    checkNeedsRecompilation :: FilePath -> GhcOptions -> NoCallStackIO Bool
    checkNeedsRecompilation filename opts = filename `moreRecentFile` oname
        where oname = getObjectFileName filename opts

    -- | Finds the object file name of the given source file
    getObjectFileName :: FilePath -> GhcOptions -> FilePath
    getObjectFileName filename opts = oname
        where odir  = fromFlag (ghcOptObjDir opts)
              oext  = fromFlagOrDefault "o" (ghcOptObjSuffix opts)
              oname = odir </> replaceExtension filename oext

    -- | Calculate the RPATHs for the component we are building.
    --
    -- Calculates relative RPATHs when 'relocatable' is set.
    getRPaths :: LocalBuildInfo
              -> ComponentLocalBuildInfo -- ^ Component we are building
              -> NoCallStackIO (NubListR FilePath)
    getRPaths lbi clbi | supportRPaths hostOS = do
        libraryPaths <- depLibraryPaths False (relocatable lbi) lbi clbi
        let hostPref = case hostOS of
                         OSX -> "@loader_path"
                         _   -> "$ORIGIN"
            relPath p = if isRelative p then hostPref </> p else p
            rpaths    = toNubListR (map relPath libraryPaths)
        return rpaths
      where
        (Platform _ hostOS) = hostPlatform lbi
        compid              = compilerId . compiler $ lbi

        -- The list of RPath-supported operating systems below reflects the
        -- platforms on which Cabal's RPATH handling is tested. It does _NOT_
        -- reflect whether the OS supports RPATH.

        -- E.g. when this comment was written, the *BSD operating systems were
        -- untested with regards to Cabal RPATH handling, and were hence set to
        -- 'False', while those operating systems themselves do support RPATH.
        supportRPaths Linux   = True
        supportRPaths Windows     = False
        supportRPaths OSX     = True
        supportRPaths FreeBSD =
          case compid of
            CompilerId GHC ver | ver >= mkVersion [7,10,2] -> True
            _                                              -> False
        supportRPaths OpenBSD = False
        supportRPaths NetBSD  = False
        supportRPaths DragonFly   = False
        supportRPaths Solaris     = False
        supportRPaths AIX         = False
        supportRPaths HPUX        = False
        supportRPaths IRIX        = False
        supportRPaths HaLVM       = False
        supportRPaths IOS         = False
        supportRPaths Android     = False
        supportRPaths Ghcjs       = False
        supportRPaths Hurd        = False
        supportRPaths (OtherOS _) = False
        -- Do _not_ add a default case so that we get a warning here when a new OS
        -- is added.

    getRPaths _ _ = return mempty

    -- | Remove the "-threaded" flag when building a foreign library, as it has no
    --   effect when used with "-shared". Returns the updated 'BuildInfo', along
    --   with whether or not the flag was present, so we can use it to link against
    --   the appropriate RTS on our own.
    popThreadedFlag :: BuildInfo -> (BuildInfo, Bool)
    popThreadedFlag bi =
      ( bi { options = filterHcOptions (/= "-threaded") (options bi) }
      , hasThreaded (options bi))

      where
        filterHcOptions :: (String -> Bool)
                        -> PerCompilerFlavor [String]
                        -> PerCompilerFlavor [String]
        filterHcOptions p (PerCompilerFlavor ghc ghcjs) =
            PerCompilerFlavor (filter p ghc) ghcjs

        hasThreaded :: PerCompilerFlavor [String] -> Bool
        hasThreaded (PerCompilerFlavor ghc _) = elem "-threaded" ghc

    -- | Extracts a String representing a hash of the ABI of a built
    -- library.  It can fail if the library has not yet been built.
    --
    libAbiHash :: Verbosity -> PackageDescription -> LocalBuildInfo
               -> Library -> ComponentLocalBuildInfo -> IO String
    libAbiHash verbosity _pkg_descr lbi lib clbi = do
      let
          libBi = libBuildInfo lib
          comp        = compiler lbi
          platform    = hostPlatform lbi
          vanillaArgs0 =
            (componentGhcOptions verbosity lbi libBi clbi (componentBuildDir lbi clbi))
            `mappend` mempty {
              ghcOptMode         = toFlag GhcModeAbiHash,
              ghcOptInputModules = toNubListR $ exposedModules lib
            }
          vanillaArgs =
              -- Package DBs unnecessary, and break ghc-cabal. See #3633
              -- BUT, put at least the global database so that 7.4 doesn't
              -- break.
              vanillaArgs0 { ghcOptPackageDBs = [GlobalPackageDB]
                           , ghcOptPackages = mempty }
          sharedArgs = vanillaArgs `mappend` mempty {
                           ghcOptDynLinkMode = toFlag GhcDynamicOnly,
                           ghcOptFPic        = toFlag True,
                           ghcOptHiSuffix    = toFlag "dyn_hi",
                           ghcOptObjSuffix   = toFlag "dyn_o",
                           ghcOptExtra       = hcSharedOptions GHC libBi
                       }
          profArgs   = vanillaArgs `mappend` mempty {
                         ghcOptProfilingMode = toFlag True,
                         ghcOptProfilingAuto = Internal.profDetailLevelFlag True
                                                 (withProfLibDetail lbi),
                         ghcOptHiSuffix      = toFlag "p_hi",
                         ghcOptObjSuffix     = toFlag "p_o",
                         ghcOptExtra         = hcProfOptions GHC libBi
                       }
          ghcArgs
            | withVanillaLib lbi = vanillaArgs
            | withSharedLib lbi = sharedArgs
            | withProfLib lbi = profArgs
            | otherwise = error "libAbiHash: Can't find an enabled library way"

      (ghcProg, _) <- requireProgram verbosity ghcProgram (withPrograms lbi)
      hash <- getProgramInvocationOutput verbosity
              (ghcInvocation ghcProg comp platform ghcArgs)
      return (takeWhile (not . isSpace) hash)

    componentGhcOptions :: Verbosity -> LocalBuildInfo
                        -> BuildInfo -> ComponentLocalBuildInfo -> FilePath
                        -> GhcOptions
    componentGhcOptions verbosity lbi =
      Internal.componentGhcOptions verbosity implInfo lbi
      where
        comp     = compiler lbi
        implInfo = getImplInfo comp

    componentCcGhcOptions :: Verbosity -> LocalBuildInfo
                          -> BuildInfo -> ComponentLocalBuildInfo
                          -> FilePath -> FilePath
                          -> GhcOptions
    componentCcGhcOptions verbosity lbi =
        Internal.componentCcGhcOptions verbosity implInfo lbi
      where
        comp     = compiler lbi
        implInfo = getImplInfo comp

    -- -----------------------------------------------------------------------------
    -- Installing

    -- |Install executables for GHC.
    installExe :: Verbosity
               -> LocalBuildInfo
               -> FilePath -- ^Where to copy the files to
               -> FilePath  -- ^Build location
               -> (FilePath, FilePath)  -- ^Executable (prefix,suffix)
               -> PackageDescription
               -> Executable
               -> IO ()
    installExe verbosity lbi binDir buildPref
      (progprefix, progsuffix) _pkg exe = do
      createDirectoryIfMissingVerbose verbosity True binDir
      let exeName' = unUnqualComponentName $ exeName exe
          exeFileName = exeTargetName (hostPlatform lbi) exe
          fixedExeBaseName = progprefix ++ exeName' ++ progsuffix
          installBinary dest = do
              installExecutableFile verbosity
                (buildPref </> exeName' </> exeFileName)
                (dest <.> exeExtension (hostPlatform lbi))
              when (stripExes lbi) $
                Strip.stripExe verbosity (hostPlatform lbi) (withPrograms lbi)
                               (dest <.> exeExtension (hostPlatform lbi))
      installBinary (binDir </> fixedExeBaseName)

    -- |Install foreign library for GHC.
    installFLib :: Verbosity
                -> LocalBuildInfo
                -> FilePath  -- ^install location
                -> FilePath  -- ^Build location
                -> PackageDescription
                -> ForeignLib
                -> IO ()
    installFLib verbosity lbi targetDir builtDir _pkg flib =
        install (foreignLibIsShared flib)
                builtDir
                targetDir
                (flibTargetName lbi flib)
      where
        install isShared srcDir dstDir name = do
          let src = srcDir </> name
              dst = dstDir </> name
          createDirectoryIfMissingVerbose verbosity True targetDir
          -- TODO: Should we strip? (stripLibs lbi)
          if isShared
            then installExecutableFile verbosity src dst
            else installOrdinaryFile   verbosity src dst
          -- Now install appropriate symlinks if library is versioned
          let (Platform _ os) = hostPlatform lbi
          when (not (null (foreignLibVersion flib os))) $ do
              when (os /= Linux) $ die' verbosity
                -- It should be impossible to get here.
                "Can't install foreign-library symlink on non-Linux OS"
    #ifndef mingw32_HOST_OS
              -- 'createSymbolicLink file1 file2' creates a symbolic link
              -- named 'file2' which points to the file 'file1'.
              -- Note that we do want a symlink to 'name' rather than
              -- 'dst', because the symlink will be relative to the
              -- directory it's created in.
              -- Finally, we first create the symlinks in a temporary
              -- directory and then rename to simulate 'ln --force'.
              withTempDirectory verbosity dstDir nm $ \tmpDir -> do
                  let link1 = flibBuildName lbi flib
                      link2 = "lib" ++ nm <.> "so"
                  createSymbolicLink name (tmpDir </> link1)
                  renameFile (tmpDir </> link1) (dstDir </> link1)
                  createSymbolicLink name (tmpDir </> link2)
                  renameFile (tmpDir </> link2) (dstDir </> link2)
            where
              nm :: String
              nm = unUnqualComponentName $ foreignLibName flib
    #endif /* mingw32_HOST_OS */

    -- |Install for ghc, .hi, .a and, if --with-ghci given, .o
    installLib    :: Verbosity
                  -> LocalBuildInfo
                  -> FilePath  -- ^install location
                  -> FilePath  -- ^install location for dynamic libraries
                  -> FilePath  -- ^Build location
                  -> PackageDescription
                  -> Library
                  -> ComponentLocalBuildInfo
                  -> IO ()
    installLib verbosity lbi targetDir dynlibTargetDir _builtDir pkg lib clbi = do
      -- copy .hi files over:
      whenVanilla $ copyModuleFiles "hi"
      whenProf    $ copyModuleFiles "p_hi"
      whenShared  $ copyModuleFiles "dyn_hi"

      -- copy the built library files over:
      whenHasCode $ do
        whenVanilla $ do
          sequence_ [ installOrdinary
                        builtDir
                        targetDir
                        (mkGenericStaticLibName (l ++ f))
                    | l <- getHSLibraryName
                           (componentUnitId clbi):(extraBundledLibs (libBuildInfo lib))
                    , f <- "":extraLibFlavours (libBuildInfo lib)
                    ]
          whenGHCi $ installOrdinary builtDir targetDir ghciLibName
        whenProf $ do
          installOrdinary builtDir targetDir profileLibName
          whenGHCi $ installOrdinary builtDir targetDir ghciProfLibName
        whenShared $ if
          -- The behavior for "extra-bundled-libraries" changed in version 2.5.0.
          -- See ghc issue #15837 and Cabal PR #5855.
          | specVersion pkg < mkVersion [2,5] -> do
            sequence_ [ installShared builtDir dynlibTargetDir
                  (mkGenericSharedLibName platform compiler_id (l ++ f))
              | l <- getHSLibraryName uid : extraBundledLibs (libBuildInfo lib)
              , f <- "":extraDynLibFlavours (libBuildInfo lib)
              ]
          | otherwise -> do
            sequence_ [ installShared
                            builtDir
                            dynlibTargetDir
                            (mkGenericSharedLibName
                              platform
                              compiler_id
                              (getHSLibraryName uid ++ f))
                      | f <- "":extraDynLibFlavours (libBuildInfo lib)
                      ]
            sequence_ [ do
                        files <- getDirectoryContents builtDir
                        let l' = mkGenericSharedBundledLibName
                                  platform
                                  compiler_id
                                  l
                        forM_ files $ \ file ->
                          when (l' `isPrefixOf` file) $ do
                            isFile <- doesFileExist (builtDir </> file)
                            when isFile $ do
                              installShared
                                builtDir
                                dynlibTargetDir
                                file
                      | l <- extraBundledLibs (libBuildInfo lib)
                      ]

      where
        builtDir = componentBuildDir lbi clbi

        install isShared srcDir dstDir name = do
          let src = srcDir </> name
              dst = dstDir </> name

          createDirectoryIfMissingVerbose verbosity True dstDir

          if isShared
            then installExecutableFile verbosity src dst
            else installOrdinaryFile   verbosity src dst

          when (stripLibs lbi) $ Strip.stripLib verbosity
                                 platform (withPrograms lbi) dst

        installOrdinary = install False
        installShared   = install True

        copyModuleFiles ext =
          findModuleFilesEx verbosity [builtDir] [ext] (allLibModules lib clbi)
          >>= installOrdinaryFiles verbosity targetDir

        compiler_id = compilerId (compiler lbi)
        platform = hostPlatform lbi
        uid = componentUnitId clbi
        profileLibName = mkProfLibName          uid
        ghciLibName    = Internal.mkGHCiLibName uid
        ghciProfLibName = Internal.mkGHCiProfLibName uid

        hasLib    = not $ null (allLibModules lib clbi)
                       && null (cSources (libBuildInfo lib))
                       && null (cxxSources (libBuildInfo lib))
                       && null (cmmSources (libBuildInfo lib))
                       && null (asmSources (libBuildInfo lib))
        has_code = not (componentIsIndefinite clbi)
        whenHasCode = when has_code
        whenVanilla = when (hasLib && withVanillaLib lbi)
        whenProf    = when (hasLib && withProfLib    lbi && has_code)
        whenGHCi    = when (hasLib && withGHCiLib    lbi && has_code)
        whenShared  = when (hasLib && withSharedLib  lbi && has_code)

    -- -----------------------------------------------------------------------------
    -- Registering

    hcPkgInfo :: ProgramDb -> HcPkg.HcPkgInfo
    hcPkgInfo progdb = HcPkg.HcPkgInfo
      { HcPkg.hcPkgProgram         = ghcPkgProg
      , HcPkg.noPkgDbStack         = v < [6,9]
      , HcPkg.noVerboseFlag        = v < [6,11]
      , HcPkg.flagPackageConf      = v < [7,5]
      , HcPkg.supportsDirDbs       = v >= [6,8]
      , HcPkg.requiresDirDbs       = v >= [7,10]
      , HcPkg.nativeMultiInstance  = v >= [7,10]
      , HcPkg.recacheMultiInstance = v >= [6,12]
      , HcPkg.suppressFilesCheck   = v >= [6,6]
      }
      where
        v          = versionNumbers ver
        ghcPkgProg = fromMaybe (error "GHC.hcPkgInfo: no ghc program") $ lookupProgram ghcPkgProgram progdb
        ver        = fromMaybe (error "GHC.hcPkgInfo: no ghc version") $ programVersion ghcPkgProg

    registerPackage
      :: Verbosity
      -> ProgramDb
      -> PackageDBStack
      -> InstalledPackageInfo
      -> HcPkg.RegisterOptions
      -> IO ()
    registerPackage verbosity progdb packageDbs installedPkgInfo registerOptions =
        HcPkg.register (hcPkgInfo progdb) verbosity packageDbs
                       installedPkgInfo registerOptions

    pkgRoot :: Verbosity -> LocalBuildInfo -> PackageDB -> IO FilePath
    pkgRoot verbosity lbi = pkgRoot'
       where
        pkgRoot' GlobalPackageDB =
          let ghcProg = fromMaybe (error "GHC.pkgRoot: no ghc program") $ lookupProgram ghcProgram (withPrograms lbi)
          in  fmap takeDirectory (getGlobalPackageDB verbosity ghcProg)
        pkgRoot' UserPackageDB = do
          appDir <- getAppUserDataDirectory "ghc"
          let ver      = compilerVersion (compiler lbi)
              subdir   = System.Info.arch ++ '-':System.Info.os
                         ++ '-':prettyShow ver
              rootDir  = appDir </> subdir
          -- We must create the root directory for the user package database if it
          -- does not yet exists. Otherwise '${pkgroot}' will resolve to a
          -- directory at the time of 'ghc-pkg register', and registration will
          -- fail.
          createDirectoryIfMissing True rootDir
          return rootDir
        pkgRoot' (SpecificPackageDB fp) = return (takeDirectory fp)

    -- -----------------------------------------------------------------------------
    -- Utils

    isDynamic :: Compiler -> Bool
    isDynamic = Internal.ghcLookupProperty "GHC Dynamic"

    supportsDynamicToo :: Compiler -> Bool
    supportsDynamicToo = Internal.ghcLookupProperty "Support dynamic-too"

    withExt :: FilePath -> String -> FilePath
    withExt fp ext = fp <.> if takeExtension fp /= ('.':ext) then ext else ""