GHC.hs

-----------------------------------------------------------------------------
-- |
-- Module      :  Distribution.Simple.GHC
-- Copyright   :  Isaac Jones 2003-2007
--
-- 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.

{- Copyright (c) 2003-2005, Isaac Jones
All rights reserved.

Redistribution and use in source and binary forms, with or without
modiication, are permitted provided that the following conditions are
met:

    * Redistributions of source code must retain the above copyright
      notice, this list of conditions and the following disclaimer.

    * Redistributions in binary form must reproduce the above
      copyright notice, this list of conditions and the following
      disclaimer in the documentation and/or other materials provided
      with the distribution.

    * Neither the name of Isaac Jones nor the names of other
      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. -}

module Distribution.Simple.GHC (
        getGhcInfo,
        configure, getInstalledPackages, getPackageDBContents,
        buildLib, buildExe,
        replLib, replExe,
        installLib, installExe,
        libAbiHash,
        initPackageDB,
        invokeHcPkg,
        registerPackage,
        componentGhcOptions,
        ghcLibDir,
        ghcDynamic,
 ) where

import qualified Distribution.Simple.GHC.IPI641 as IPI641
import qualified Distribution.Simple.GHC.IPI642 as IPI642
import Distribution.PackageDescription as PD
         ( PackageDescription(..), BuildInfo(..), Executable(..)
         , Library(..), libModules, exeModules, hcOptions
         , usedExtensions, allExtensions )
import Distribution.InstalledPackageInfo
         ( InstalledPackageInfo )
import qualified Distribution.InstalledPackageInfo as InstalledPackageInfo
                                ( InstalledPackageInfo_(..) )
import Distribution.Simple.PackageIndex (PackageIndex)
import qualified Distribution.Simple.PackageIndex as PackageIndex
import Distribution.Simple.LocalBuildInfo
         ( LocalBuildInfo(..), ComponentLocalBuildInfo(..)
         , LibraryName(..), absoluteInstallDirs )
import Distribution.Simple.InstallDirs hiding ( absoluteInstallDirs )
import Distribution.Simple.BuildPaths
import Distribution.Simple.Utils
import Distribution.Package
         ( Package(..), PackageName(..) )
import qualified Distribution.ModuleName as ModuleName
import Distribution.Simple.Program
         ( Program(..), ConfiguredProgram(..), ProgramConfiguration
         , ProgramLocation(..), ProgramSearchPath, ProgramSearchPathEntry(..)
         , rawSystemProgram
         , rawSystemProgramStdout, rawSystemProgramStdoutConf
         , getProgramOutput, getProgramInvocationOutput, suppressOverrideArgs
         , requireProgramVersion, requireProgram
         , userMaybeSpecifyPath, programPath, lookupProgram, addKnownProgram
         , ghcProgram, ghcPkgProgram, hsc2hsProgram
         , arProgram, ranlibProgram, ldProgram
         , gccProgram, stripProgram )
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 Distribution.Simple.Program.GHC
import Distribution.Simple.Setup
         ( toFlag, fromFlag, fromFlagOrDefault )
import qualified Distribution.Simple.Setup as Cabal
        ( Flag )
import Distribution.Simple.Compiler
         ( CompilerFlavor(..), CompilerId(..), Compiler(..), compilerVersion
         , OptimisationLevel(..), PackageDB(..), PackageDBStack
         , Flag )
import Distribution.Version
         ( Version(..), anyVersion, orLaterVersion )
import Distribution.System
         ( OS(..), buildOS )
import Distribution.Verbosity
import Distribution.Text
         ( display, simpleParse )
import Language.Haskell.Extension (Language(..), Extension(..)
                                  ,KnownExtension(..))

import Control.Monad            ( unless, when )
import Data.Char                ( isSpace )
import Data.List
import qualified Data.Map as M  ( Map, fromList, lookup )
import Data.Maybe               ( catMaybes, fromMaybe, maybeToList )
import Data.Monoid              ( Monoid(..) )
import System.Directory
         ( getDirectoryContents, doesFileExist, getTemporaryDirectory )
import System.FilePath          ( (</>), (<.>), takeExtension,
                                  takeDirectory, replaceExtension,
                                  splitExtension )
import System.IO (hClose, hPutStrLn)
import System.Environment (getEnv)
import Distribution.Compat.Exception (catchExit, catchIO)
import Distribution.System (Platform, platformFromTriple)


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

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

  (ghcProg, ghcVersion, conf1) <-
    requireProgramVersion verbosity ghcProgram
      (orLaterVersion (Version [6,4] []))
      (userMaybeSpecifyPath "ghc" hcPath conf0)

  -- 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, conf2) <-
    requireProgramVersion verbosity ghcPkgProgram {
      programFindLocation = guessGhcPkgFromGhcPath ghcProg
    }
    anyVersion (userMaybeSpecifyPath "ghc-pkg" hcPkgPath conf1)

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

  -- Likewise we try to find the matching hsc2hs program.
  let hsc2hsProgram' = hsc2hsProgram {
                           programFindLocation = guessHsc2hsFromGhcPath ghcProg
                       }
      conf3 = addKnownProgram hsc2hsProgram' conf2

  languages  <- getLanguages verbosity ghcProg
  extensions <- getExtensions verbosity ghcProg

  ghcInfo <- getGhcInfo verbosity ghcProg
  let ghcInfoMap = M.fromList ghcInfo

  let comp = Compiler {
        compilerId         = CompilerId GHC ghcVersion,
        compilerLanguages  = languages,
        compilerExtensions = extensions,
        compilerProperties = ghcInfoMap
      }
      compPlatform = targetPlatform ghcInfo
      conf4 = configureToolchain ghcProg ghcInfoMap conf3 -- configure gcc and ld
  return (comp, compPlatform, conf4)

targetPlatform :: [(String, String)] -> Maybe Platform
targetPlatform ghcInfo = platformFromTriple =<< lookup "Target platform" ghcInfo

-- | 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)
guessToolFromGhcPath tool ghcProg verbosity searchpath
  = do let toolname          = programName tool
           path              = programPath ghcProg
           dir               = takeDirectory path
           versionSuffix     = takeVersionSuffix (dropExeExtension path)
           guessNormal       = dir </> toolname <.> exeExtension
           guessGhcVersioned = dir </> (toolname ++ "-ghc" ++ versionSuffix)
                               <.> exeExtension
           guessVersioned    = dir </> (toolname ++ versionSuffix)
                               <.> exeExtension
           guesses | null versionSuffix = [guessNormal]
                   | otherwise          = [guessGhcVersioned,
                                           guessVersioned,
                                           guessNormal]
       info verbosity $ "looking for tool " ++ toolname
         ++ " near compiler in " ++ dir
       exists <- mapM 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
                      return (Just fp)

  where takeVersionSuffix :: FilePath -> String
        takeVersionSuffix = reverse . takeWhile (`elem ` "0123456789.-") .
                            reverse

        dropExeExtension :: FilePath -> FilePath
        dropExeExtension filepath =
          case splitExtension filepath of
            (filepath', extension) | extension == exeExtension -> filepath'
                                   | otherwise                 -> filepath

-- | 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)
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)
guessHsc2hsFromGhcPath = guessToolFromGhcPath hsc2hsProgram

-- | Adjust the way we find and configure gcc and ld
--
configureToolchain :: ConfiguredProgram -> M.Map String String
                                        -> ProgramConfiguration
                                        -> ProgramConfiguration
configureToolchain ghcProg ghcInfo =
    addKnownProgram gccProgram {
      programFindLocation = findProg gccProgram extraGccPath,
      programPostConf     = configureGcc
    }
  . addKnownProgram ldProgram {
      programFindLocation = findProg ldProgram extraLdPath,
      programPostConf     = configureLd
    }
  . addKnownProgram arProgram {
      programFindLocation = findProg arProgram extraArPath
    }
  . addKnownProgram stripProgram {
      programFindLocation = findProg stripProgram extraStripPath
    }
  where
    Just ghcVersion = programVersion ghcProg
    compilerDir = takeDirectory (programPath ghcProg)
    baseDir     = takeDirectory compilerDir
    mingwBinDir = baseDir </> "mingw" </> "bin"
    libDir      = baseDir </> "gcc-lib"
    includeDir  = baseDir </> "include" </> "mingw"
    isWindows   = case buildOS of Windows -> True; _ -> False
    binPrefix   = ""

    mkExtraPath :: Maybe FilePath -> FilePath -> [FilePath]
    mkExtraPath mbPath mingwPath | isWindows = mbDir ++ [mingwPath]
                                 | otherwise = mbDir
      where
        mbDir = maybeToList . fmap takeDirectory $ mbPath

    extraGccPath   = mkExtraPath mbGccLocation   windowsExtraGccDir
    extraLdPath    = mkExtraPath mbLdLocation    windowsExtraLdDir
    extraArPath    = mkExtraPath mbArLocation    windowsExtraArDir
    extraStripPath = mkExtraPath mbStripLocation windowsExtraStripDir

    -- on Windows finding and configuring ghc's gcc & binutils is a bit special
    windowsExtraGccDir
      | ghcVersion >= Version [6,12] [] = mingwBinDir </> binPrefix
      | otherwise                       = baseDir
    windowsExtraLdDir
      | ghcVersion >= Version [6,12] [] = mingwBinDir </> binPrefix
      | otherwise                       = libDir
    windowsExtraArDir
      | ghcVersion >= Version [6,12] [] = mingwBinDir </> binPrefix
      | otherwise                       = libDir
    windowsExtraStripDir
      | ghcVersion >= Version [6,12] [] = mingwBinDir </> binPrefix
      | otherwise                       = libDir

    findProg :: Program -> [FilePath]
             -> Verbosity -> ProgramSearchPath -> IO (Maybe FilePath)
    findProg prog extraPath v searchpath =
        programFindLocation prog v searchpath'
      where
        searchpath' = (map ProgramSearchPathDir extraPath) ++ searchpath

    -- Read tool locations from the 'ghc --info' output. Useful when
    -- cross-compiling.
    mbGccLocation   = M.lookup "C compiler command" ghcInfo
    mbLdLocation    = M.lookup "ld command" ghcInfo
    mbArLocation    = M.lookup "ar command" ghcInfo
    mbStripLocation = M.lookup "strip command" ghcInfo

    ccFlags        = getFlags "C compiler flags"
    gccLinkerFlags = getFlags "Gcc Linker flags"
    ldLinkerFlags  = getFlags "Ld Linker flags"

    getFlags key = case M.lookup key ghcInfo of
                   Nothing -> []
                   Just flags ->
                       case reads flags of
                       [(args, "")] -> args
                       _ -> [] -- XXX Should should be an error really

    configureGcc :: Verbosity -> ConfiguredProgram -> IO ConfiguredProgram
    configureGcc v gccProg = do
      gccProg' <- configureGcc' v gccProg
      return gccProg' {
        programDefaultArgs = programDefaultArgs gccProg'
                             ++ ccFlags ++ gccLinkerFlags
      }

    configureGcc' :: Verbosity -> ConfiguredProgram -> IO ConfiguredProgram
    configureGcc'
      | isWindows = \_ gccProg -> case programLocation gccProg of
          -- if it's found on system then it means we're using the result
          -- of programFindLocation above rather than a user-supplied path
          -- Pre GHC 6.12, that meant we should add these flags to tell
          -- ghc's gcc where it lives and thus where gcc can find its
          -- various files:
          FoundOnSystem {}
           | ghcVersion < Version [6,11] [] ->
               return gccProg { programDefaultArgs = ["-B" ++ libDir,
                                                      "-I" ++ includeDir] }
          _ -> return gccProg
      | otherwise = \_ gccProg -> return gccProg

    configureLd :: Verbosity -> ConfiguredProgram -> IO ConfiguredProgram
    configureLd v ldProg = do
      ldProg' <- configureLd' v ldProg
      return ldProg' {
        programDefaultArgs = programDefaultArgs ldProg' ++ ldLinkerFlags
      }

    -- we need to find out if ld supports the -x flag
    configureLd' :: Verbosity -> ConfiguredProgram -> IO ConfiguredProgram
    configureLd' verbosity ldProg = do
      tempDir <- getTemporaryDirectory
      ldx <- withTempFile tempDir ".c" $ \testcfile testchnd ->
             withTempFile tempDir ".o" $ \testofile testohnd -> do
               hPutStrLn testchnd "int foo() { return 0; }"
               hClose testchnd; hClose testohnd
               rawSystemProgram verbosity ghcProg ["-c", testcfile,
                                                   "-o", testofile]
               withTempFile tempDir ".o" $ \testofile' testohnd' ->
                 do
                   hClose testohnd'
                   _ <- rawSystemProgramStdout verbosity ldProg
                     ["-x", "-r", testofile, "-o", testofile']
                   return True
                 `catchIO`   (\_ -> return False)
                 `catchExit` (\_ -> return False)
      if ldx
        then return ldProg { programDefaultArgs = ["-x"] }
        else return ldProg

getLanguages :: Verbosity -> ConfiguredProgram -> IO [(Language, Flag)]
getLanguages _ ghcProg
  -- TODO: should be using --supported-languages rather than hard coding
  | ghcVersion >= Version [7] [] = return [(Haskell98,   "-XHaskell98")
                                          ,(Haskell2010, "-XHaskell2010")]
  | otherwise                    = return [(Haskell98,   "")]
  where
    Just ghcVersion = programVersion ghcProg

getGhcInfo :: Verbosity -> ConfiguredProgram -> IO [(String, String)]
getGhcInfo verbosity ghcProg =
    case programVersion ghcProg of
    Just ghcVersion
     | ghcVersion >= Version [6,7] [] ->
        do xs <- getProgramOutput verbosity (suppressOverrideArgs ghcProg)
                 ["--info"]
           case reads xs of
               [(i, ss)]
                | all isSpace ss ->
                   return i
               _ ->
                   die "Can't parse --info output of GHC"
    _ ->
        return []

getExtensions :: Verbosity -> ConfiguredProgram -> IO [(Extension, Flag)]
getExtensions verbosity ghcProg
  | ghcVersion >= Version [6,7] [] = do

    str <- getProgramOutput verbosity (suppressOverrideArgs ghcProg)
              ["--supported-languages"]
    let extStrs = if ghcVersion >= Version [7] []
                  then lines str
                  else -- Older GHCs only gave us either Foo or NoFoo,
                       -- so we have to work out the other one ourselves
                       [ extStr''
                       | extStr <- lines str
                       , let extStr' = case extStr of
                                       'N' : 'o' : xs -> xs
                                       _              -> "No" ++ extStr
                       , extStr'' <- [extStr, extStr']
                       ]
    let extensions0 = [ (ext, "-X" ++ display ext)
                      | Just ext <- map simpleParse extStrs ]
        extensions1 = if ghcVersion >= Version [6,8]  [] &&
                         ghcVersion <  Version [6,10] []
                      then -- ghc-6.8 introduced RecordPuns however it
                           -- should have been NamedFieldPuns. We now
                           -- encourage packages to use NamedFieldPuns
                           -- so for compatability we fake support for
                           -- it in ghc-6.8 by making it an alias for
                           -- the old RecordPuns extension.
                           (EnableExtension  NamedFieldPuns, "-XRecordPuns") :
                           (DisableExtension NamedFieldPuns, "-XNoRecordPuns") :
                           extensions0
                      else extensions0
        extensions2 = if ghcVersion <  Version [7,1] []
                      then -- ghc-7.2 split NondecreasingIndentation off
                           -- into a proper extension. Before that it
                           -- was always on.
                           (EnableExtension  NondecreasingIndentation, "") :
                           (DisableExtension NondecreasingIndentation, "") :
                           extensions1
                      else extensions1
    return extensions2

  | otherwise = return oldLanguageExtensions

  where
    Just ghcVersion = programVersion ghcProg

-- | For GHC 6.6.x and earlier, the mapping from supported extensions to flags
oldLanguageExtensions :: [(Extension, Flag)]
oldLanguageExtensions =
    let doFlag (f, (enable, disable)) = [(EnableExtension  f, enable),
                                         (DisableExtension f, disable)]
        fglasgowExts = ("-fglasgow-exts",
                        "") -- This is wrong, but we don't want to turn
                            -- all the extensions off when asked to just
                            -- turn one off
        fFlag flag = ("-f" ++ flag, "-fno-" ++ flag)
    in concatMap doFlag
    [(OverlappingInstances       , fFlag "allow-overlapping-instances")
    ,(TypeSynonymInstances       , fglasgowExts)
    ,(TemplateHaskell            , fFlag "th")
    ,(ForeignFunctionInterface   , fFlag "ffi")
    ,(MonomorphismRestriction    , fFlag "monomorphism-restriction")
    ,(MonoPatBinds               , fFlag "mono-pat-binds")
    ,(UndecidableInstances       , fFlag "allow-undecidable-instances")
    ,(IncoherentInstances        , fFlag "allow-incoherent-instances")
    ,(Arrows                     , fFlag "arrows")
    ,(Generics                   , fFlag "generics")
    ,(ImplicitPrelude            , fFlag "implicit-prelude")
    ,(ImplicitParams             , fFlag "implicit-params")
    ,(CPP                        , ("-cpp", ""{- Wrong -}))
    ,(BangPatterns               , fFlag "bang-patterns")
    ,(KindSignatures             , fglasgowExts)
    ,(RecursiveDo                , fglasgowExts)
    ,(ParallelListComp           , fglasgowExts)
    ,(MultiParamTypeClasses      , fglasgowExts)
    ,(FunctionalDependencies     , fglasgowExts)
    ,(Rank2Types                 , fglasgowExts)
    ,(RankNTypes                 , fglasgowExts)
    ,(PolymorphicComponents      , fglasgowExts)
    ,(ExistentialQuantification  , fglasgowExts)
    ,(ScopedTypeVariables        , fFlag "scoped-type-variables")
    ,(FlexibleContexts           , fglasgowExts)
    ,(FlexibleInstances          , fglasgowExts)
    ,(EmptyDataDecls             , fglasgowExts)
    ,(PatternGuards              , fglasgowExts)
    ,(GeneralizedNewtypeDeriving , fglasgowExts)
    ,(MagicHash                  , fglasgowExts)
    ,(UnicodeSyntax              , fglasgowExts)
    ,(PatternSignatures          , fglasgowExts)
    ,(UnliftedFFITypes           , fglasgowExts)
    ,(LiberalTypeSynonyms        , fglasgowExts)
    ,(TypeOperators              , fglasgowExts)
    ,(GADTs                      , fglasgowExts)
    ,(RelaxedPolyRec             , fglasgowExts)
    ,(ExtendedDefaultRules       , fFlag "extended-default-rules")
    ,(UnboxedTuples              , fglasgowExts)
    ,(DeriveDataTypeable         , fglasgowExts)
    ,(ConstrainedClassMethods    , fglasgowExts)
    ]
-- | Given a single package DB, return all installed packages.
getPackageDBContents :: Verbosity -> PackageDB -> ProgramConfiguration
                        -> IO PackageIndex
getPackageDBContents verbosity packagedb conf = do
  pkgss <- getInstalledPackages' verbosity [packagedb] conf
  toPackageIndex verbosity pkgss conf

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

  where
    hackRtsPackage index =
      case PackageIndex.lookupPackageName index (PackageName "rts") of
        [(_,[rts])]
           -> PackageIndex.insert (removeMingwIncludeDir rts) index
        _  -> index -- No (or multiple) ghc rts package is registered!!
                    -- Feh, whatever, the ghc testsuite 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])]
               -> ProgramConfiguration
               -> IO PackageIndex
toPackageIndex verbosity pkgss conf = 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 <- ghcLibDir' verbosity ghcProg
  let indices = [ PackageIndex.fromList (map (substTopDir topDir) pkgs)
                | (_, pkgs) <- pkgss ]
  return $! (mconcat indices)

  where
    Just ghcProg = lookupProgram ghcProgram conf

ghcLibDir :: Verbosity -> LocalBuildInfo -> IO FilePath
ghcLibDir verbosity lbi =
    (reverse . dropWhile isSpace . reverse) `fmap`
     rawSystemProgramStdoutConf verbosity ghcProgram
     (withPrograms lbi) ["--print-libdir"]

ghcLibDir' :: Verbosity -> ConfiguredProgram -> IO FilePath
ghcLibDir' verbosity ghcProg =
    (reverse . dropWhile isSpace . reverse) `fmap`
     rawSystemProgramStdout verbosity ghcProg ["--print-libdir"]

-- Cabal does not use the environment variable GHC_PACKAGE_PATH; let users
-- know that this is the case. See ticket #335. Simply ignoring it is not a
-- good idea, since then ghc and cabal are looking at different sets of
-- package dbs and chaos is likely to ensue.
checkPackageDbEnvVar :: IO ()
checkPackageDbEnvVar = do
    hasGPP <- (getEnv "GHC_PACKAGE_PATH" >> return True)
              `catchIO` (\_ -> return False)
    when hasGPP $
      die $ "Use of GHC's environment variable GHC_PACKAGE_PATH is "
         ++ "incompatible with Cabal. Use the flag --package-db to specify a "
         ++ "package database (it can be used multiple times)."

checkPackageDbStack :: PackageDBStack -> IO ()
checkPackageDbStack (GlobalPackageDB:rest)
  | GlobalPackageDB `notElem` rest = return ()
checkPackageDbStack rest
  | GlobalPackageDB `notElem` rest =
  die $ "With current ghc versions the global package db is always used "
     ++ "and must be listed first. This ghc limitation may be lifted in "
     ++ "future, see http://hackage.haskell.org/trac/ghc/ticket/5977"
checkPackageDbStack _ =
  die $ "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] -> ProgramConfiguration
                     -> IO [(PackageDB, [InstalledPackageInfo])]
getInstalledPackages' verbosity packagedbs conf
  | ghcVersion >= Version [6,9] [] =
  sequence
    [ do pkgs <- HcPkg.dump verbosity ghcPkgProg packagedb
         return (packagedb, pkgs)
    | packagedb <- packagedbs ]

  where
    Just ghcPkgProg = lookupProgram ghcPkgProgram conf
    Just ghcProg    = lookupProgram ghcProgram conf
    Just ghcVersion = programVersion ghcProg

getInstalledPackages' verbosity packagedbs conf = do
    str <- rawSystemProgramStdoutConf verbosity ghcPkgProgram conf ["list"]
    let pkgFiles = [ init line | line <- lines str, last line == ':' ]
        dbFile packagedb = case (packagedb, pkgFiles) of
          (GlobalPackageDB, global:_)      -> return $ Just global
          (UserPackageDB,  _global:user:_) -> return $ Just user
          (UserPackageDB,  _global:_)      -> return $ Nothing
          (SpecificPackageDB specific, _)  -> return $ Just specific
          _ -> die "cannot read ghc-pkg package listing"
    pkgFiles' <- mapM dbFile packagedbs
    sequence [ withFileContents file $ \content -> do
                  pkgs <- readPackages file content
                  return (db, pkgs)
             | (db , Just file) <- zip packagedbs pkgFiles' ]
  where
    -- Depending on the version of ghc we use a different type's Read
    -- instance to parse the package file and then convert.
    -- It's a bit yuck. But that's what we get for using Read/Show.
    readPackages
      | ghcVersion >= Version [6,4,2] []
      = \file content -> case reads content of
          [(pkgs, _)] -> return (map IPI642.toCurrent pkgs)
          _           -> failToRead file
      | otherwise
      = \file content -> case reads content of
          [(pkgs, _)] -> return (map IPI641.toCurrent pkgs)
          _           -> failToRead file
    Just ghcProg = lookupProgram ghcProgram conf
    Just ghcVersion = programVersion ghcProg
    failToRead file = die $ "cannot read ghc package database " ++ file

substTopDir :: FilePath -> InstalledPackageInfo -> InstalledPackageInfo
substTopDir topDir ipo
 = ipo {
       InstalledPackageInfo.importDirs
           = map f (InstalledPackageInfo.importDirs ipo),
       InstalledPackageInfo.libraryDirs
           = map f (InstalledPackageInfo.libraryDirs ipo),
       InstalledPackageInfo.includeDirs
           = map f (InstalledPackageInfo.includeDirs ipo),
       InstalledPackageInfo.frameworkDirs
           = map f (InstalledPackageInfo.frameworkDirs ipo),
       InstalledPackageInfo.haddockInterfaces
           = map f (InstalledPackageInfo.haddockInterfaces ipo),
       InstalledPackageInfo.haddockHTMLs
           = map f (InstalledPackageInfo.haddockHTMLs ipo)
   }
    where f ('$':'t':'o':'p':'d':'i':'r':rest) = topDir ++ rest
          f x = x

-- -----------------------------------------------------------------------------
-- Building

-- | Build a library with GHC.
--
buildLib, replLib :: Verbosity          -> Cabal.Flag (Maybe Int)
                  -> PackageDescription -> LocalBuildInfo
                  -> Library            -> ComponentLocalBuildInfo -> IO ()
buildLib = buildOrReplLib False
replLib  = buildOrReplLib True

buildOrReplLib :: Bool -> Verbosity  -> Cabal.Flag (Maybe Int)
               -> PackageDescription -> LocalBuildInfo
               -> Library            -> ComponentLocalBuildInfo -> IO ()
buildOrReplLib forRepl verbosity numJobsFlag pkg_descr lbi lib clbi = do
  libName <- case componentLibraries clbi of
             [libName] -> return libName
             [] -> die "No library name found when building library"
             _  -> die "Multiple library names found when building library"

  let libTargetDir = buildDir lbi
      numJobs = fromMaybe 1 $ fromFlagOrDefault Nothing numJobsFlag
      pkgid = packageId pkg_descr
      whenVanillaLib forceVanilla =
        when (not forRepl && (forceVanilla || withVanillaLib lbi))
      whenProfLib = when (not forRepl && withProfLib lbi)
      whenSharedLib forceShared =
        when (not forRepl &&  (forceShared || withSharedLib lbi))
      whenGHCiLib = when (not forRepl && withGHCiLib lbi && withVanillaLib lbi)
      ifReplLib = when forRepl
      comp = compiler lbi
      ghcVersion = compilerVersion comp

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

  libBi <- hackThreadedFlag verbosity
             comp (withProfLib lbi) (libBuildInfo lib)

  let isGhcDynamic        = ghcDynamic comp
      dynamicTooSupported = ghcSupportsDynamicToo comp
      doingTH = EnableExtension TemplateHaskell `elem` allExtensions libBi
      forceVanillaLib = doingTH && not isGhcDynamic
      forceSharedLib  = doingTH &&     isGhcDynamic
      -- TH always needs default libs, even when building for profiling

  createDirectoryIfMissingVerbose verbosity True libTargetDir
  -- TODO: do we need to put hs-boot files into place for mutually recursive
  -- modules?
  let cObjs       = map (`replaceExtension` objExtension) (cSources libBi)
      baseOpts    = componentGhcOptions verbosity lbi libBi clbi libTargetDir
      vanillaOpts = baseOpts `mappend` mempty {
                      ghcOptMode         = toFlag GhcModeMake,
                      ghcOptNumJobs      = toFlag numJobs,
                      ghcOptPackageName  = toFlag pkgid,
                      ghcOptInputModules = libModules lib
                    }

      profOpts    = vanillaOpts `mappend` mempty {
                      ghcOptProfilingMode = toFlag True,
                      ghcOptHiSuffix      = toFlag "p_hi",
                      ghcOptObjSuffix     = toFlag "p_o",
                      ghcOptExtra         = ghcProfOptions libBi
                    }

      sharedOpts  = vanillaOpts `mappend` mempty {
                      ghcOptDynLinkMode = toFlag GhcDynamicOnly,
                      ghcOptFPic        = toFlag True,
                      ghcOptHiSuffix    = toFlag "dyn_hi",
                      ghcOptObjSuffix   = toFlag "dyn_o",
                      ghcOptExtra       = ghcSharedOptions libBi
                    }
      linkerOpts = mempty {
                      ghcOptLinkOptions    = PD.ldOptions libBi,
                      ghcOptLinkLibs       = extraLibs libBi,
                      ghcOptLinkLibPath    = extraLibDirs libBi,
                      ghcOptLinkFrameworks = PD.frameworks libBi,
                      ghcOptInputFiles     = [libTargetDir </> x | x <- cObjs]
                   }
      replOpts    = vanillaOpts {
                      ghcOptExtra        = filterGhciFlags
                                           (ghcOptExtra vanillaOpts),
                      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"
                    }

  unless (null (libModules lib)) $
    do let vanilla = whenVanillaLib forceVanillaLib (runGhcProg vanillaOpts)
           shared  = whenSharedLib  forceSharedLib  (runGhcProg sharedOpts)
           useDynToo = dynamicTooSupported &&
                       (forceVanillaLib || withVanillaLib lbi) &&
                       (forceSharedLib  || withSharedLib  lbi) &&
                       null (ghcSharedOptions libBi)
       if useDynToo
           then runGhcProg vanillaSharedOpts
           else if isGhcDynamic then do shared;  vanilla
                                else do vanilla; shared
       whenProfLib (runGhcProg profOpts)

  -- build any C sources
  unless (null (cSources libBi)) $ do
     info verbosity "Building C Sources..."
     sequence_
       [ do let vanillaCcOpts = (componentCcGhcOptions verbosity lbi
                                    libBi clbi libTargetDir filename)
                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
            runGhcProg vanillaCcOpts
            whenSharedLib forceSharedLib (runGhcProg sharedCcOpts)
            whenProfLib (runGhcProg profCcOpts)
       | filename <- cSources 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.
  unless (null (libModules lib)) $
     ifReplLib (runGhcProg replOpts)


  -- link:
  info verbosity "Linking..."
  let cProfObjs   = map (`replaceExtension` ("p_" ++ objExtension))
                    (cSources libBi)
      cSharedObjs = map (`replaceExtension` ("dyn_" ++ objExtension))
                    (cSources libBi)
      cid = compilerId (compiler lbi)
      vanillaLibFilePath = libTargetDir </> mkLibName           libName
      profileLibFilePath = libTargetDir </> mkProfLibName       libName
      sharedLibFilePath  = libTargetDir </> mkSharedLibName cid libName
      ghciLibFilePath    = libTargetDir </> mkGHCiLibName       libName
      libInstallPath = libdir $ absoluteInstallDirs pkg_descr lbi NoCopyDest
      sharedLibInstallPath = libInstallPath </> mkSharedLibName cid libName

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

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

  unless (null hObjs && null cObjs && null stubObjs) $ do

    let staticObjectFiles =
               hObjs
            ++ map (libTargetDir </>) cObjs
            ++ stubObjs
        profObjectFiles =
               hProfObjs
            ++ map (libTargetDir </>) cProfObjs
            ++ stubProfObjs
        ghciObjFiles =
               hObjs
            ++ map (libTargetDir </>) cObjs
            ++ stubObjs
        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         = dynamicObjectFiles,
              ghcOptOutputFile         = toFlag sharedLibFilePath,
              -- For dynamic libs, Mac OS/X needs to know the install location
              -- at build time.
              ghcOptDylibName          = if buildOS == OSX
                                          then toFlag sharedLibInstallPath
                                          else mempty,
              ghcOptPackageName        = toFlag pkgid,
              ghcOptNoAutoLinkPackages = toFlag True,
              ghcOptPackageDBs         = withPackageDB lbi,
              ghcOptPackages           = componentPackageDeps clbi,
              ghcOptLinkLibs           = extraLibs libBi,
              ghcOptLinkLibPath        = extraLibDirs libBi
            }

    whenVanillaLib False $ do
      (arProg, _) <- requireProgram verbosity arProgram (withPrograms lbi)
      Ar.createArLibArchive verbosity arProg
        vanillaLibFilePath staticObjectFiles

    whenProfLib $ do
      (arProg, _) <- requireProgram verbosity arProgram (withPrograms lbi)
      Ar.createArLibArchive verbosity arProg
        profileLibFilePath profObjectFiles

    whenGHCiLib $ do
      (ldProg, _) <- requireProgram verbosity ldProgram (withPrograms lbi)
      Ld.combineObjectFiles verbosity ldProg
        ghciLibFilePath ghciObjFiles

    whenSharedLib False $
      runGhcProg ghcSharedLinkArgs


-- | Build an executable with GHC.
--
buildExe, replExe :: Verbosity          -> Cabal.Flag (Maybe Int)
                  -> PackageDescription -> LocalBuildInfo
                  -> Executable         -> ComponentLocalBuildInfo -> IO ()
buildExe = buildOrReplExe False
replExe  = buildOrReplExe True

buildOrReplExe :: Bool -> Verbosity  -> Cabal.Flag (Maybe Int)
               -> PackageDescription -> LocalBuildInfo
               -> Executable         -> ComponentLocalBuildInfo -> IO ()
buildOrReplExe forRepl verbosity numJobsFlag _pkg_descr lbi
  exe@Executable { exeName = exeName', modulePath = modPath } clbi = do

  (ghcProg, _) <- requireProgram verbosity ghcProgram (withPrograms lbi)
  let comp       = compiler lbi
      numJobs    = fromMaybe 1 $
                   fromFlagOrDefault Nothing numJobsFlag
      runGhcProg = runGHC verbosity ghcProg comp

  exeBi <- hackThreadedFlag verbosity
             comp (withProfExe lbi) (buildInfo exe)

  -- exeNameReal, the name that GHC really uses (with .exe on Windows)
  let exeNameReal = exeName' <.>
                    (if takeExtension exeName' /= ('.':exeExtension)
                       then exeExtension
                       else "")

  let targetDir = (buildDir lbi) </> exeName'
  let exeDir    = targetDir </> (exeName' ++ "-tmp")
  createDirectoryIfMissingVerbose verbosity True targetDir
  createDirectoryIfMissingVerbose verbosity True exeDir
  -- TODO: do we need to put hs-boot files into place for mutually recursive
  -- modules?  FIX: what about exeName.hi-boot?

  -- build executables

  srcMainFile         <- findFile (exeDir : hsSourceDirs exeBi) modPath
  let isGhcDynamic        = ghcDynamic comp
      dynamicTooSupported = ghcSupportsDynamicToo comp
      isHaskellMain = elem (takeExtension srcMainFile) [".hs", ".lhs"]
      cSrcs         = cSources exeBi ++ [srcMainFile | not isHaskellMain]
      cObjs         = map (`replaceExtension` objExtension) cSrcs
      baseOpts   = (componentGhcOptions verbosity lbi exeBi clbi exeDir)
                    `mappend` mempty {
                      ghcOptMode         = toFlag GhcModeMake,
                      ghcOptInputFiles   =
                        [ srcMainFile | isHaskellMain],
                      ghcOptInputModules =
                        [ m | not isHaskellMain, m <- exeModules exe]
                    }
      staticOpts = baseOpts `mappend` mempty {
                      ghcOptDynLinkMode    = toFlag GhcStaticOnly
                   }
      profOpts   = baseOpts `mappend` mempty {
                      ghcOptProfilingMode  = toFlag True,
                      ghcOptHiSuffix       = toFlag "p_hi",
                      ghcOptObjSuffix      = toFlag "p_o",
                      ghcOptExtra          = ghcProfOptions exeBi
                    }
      dynOpts    = baseOpts `mappend` mempty {
                      ghcOptDynLinkMode    = toFlag GhcDynamicOnly,
                      ghcOptHiSuffix       = toFlag "dyn_hi",
                      ghcOptObjSuffix      = toFlag "dyn_o",
                      ghcOptExtra          = ghcSharedOptions exeBi
                    }
      dynTooOpts = staticOpts `mappend` mempty {
                      ghcOptDynLinkMode    = toFlag GhcStaticAndDynamic,
                      ghcOptDynHiSuffix    = toFlag "dyn_hi",
                      ghcOptDynObjSuffix   = toFlag "dyn_o"
                    }
      linkerOpts = mempty {
                      ghcOptLinkOptions    = PD.ldOptions exeBi,
                      ghcOptLinkLibs       = extraLibs exeBi,
                      ghcOptLinkLibPath    = extraLibDirs exeBi,
                      ghcOptLinkFrameworks = PD.frameworks exeBi,
                      ghcOptInputFiles     = [exeDir </> x | x <- cObjs]
                   }
      replOpts   = baseOpts {
                      ghcOptExtra          = filterGhciFlags
                                             (ghcOptExtra baseOpts)
                   }
                   -- 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  | withProfExe