PreProcess.hs

{-# LANGUAGE DataKinds #-}
{-# LANGUAGE FlexibleContexts #-}
{-# LANGUAGE RankNTypes #-}

-----------------------------------------------------------------------------

-- |
-- Module      :  Distribution.Simple.PreProcess
-- Copyright   :  (c) 2003-2005, Isaac Jones, Malcolm Wallace
-- License     :  BSD3
--
-- Maintainer  :  cabal-devel@haskell.org
-- Portability :  portable
--
-- This module defines 'PPSuffixHandler', which is a combination of a file
-- extension and a function for configuring a 'PreProcessor'. It also defines
-- a bunch of known built-in preprocessors like @cpp@, @cpphs@, @c2hs@,
-- @hsc2hs@, @happy@, @alex@ etc and lists them in 'knownSuffixHandlers'.
-- On top of this it provides a function for actually preprocessing some sources
-- given a bunch of known suffix handlers.
-- This module is not as good as it could be, it could really do with a rewrite
-- to address some of the problems we have with pre-processors.
module Distribution.Simple.PreProcess
  ( preprocessComponent
  , preprocessExtras
  , preprocessFile
  , knownSuffixHandlers
  , ppSuffixes
  , PPSuffixHandler
  , Suffix (..)
  , builtinHaskellSuffixes
  , builtinHaskellBootSuffixes
  , PreProcessor (..)
  , mkSimplePreProcessor
  , runSimplePreProcessor
  , ppCpp
  , ppCpp'
  , ppC2hs
  , ppHsc2hs
  , ppHappy
  , ppAlex
  , ppUnlit
  , platformDefines
  , unsorted
  )
where

import Distribution.Compat.Prelude
import Distribution.Compat.Stack
import Prelude ()

import Distribution.Backpack.DescribeUnitId
import qualified Distribution.InstalledPackageInfo as Installed
import Distribution.ModuleName (ModuleName)
import Distribution.Package
import Distribution.PackageDescription as PD
import Distribution.Simple.BuildPaths
import Distribution.Simple.CCompiler
import Distribution.Simple.Compiler
import Distribution.Simple.Errors
import Distribution.Simple.LocalBuildInfo
import qualified Distribution.Simple.PackageIndex as PackageIndex
import Distribution.Simple.PreProcess.Types
import Distribution.Simple.PreProcess.Unlit
import Distribution.Simple.Program
import Distribution.Simple.Program.ResponseFile
import Distribution.Simple.Test.LibV09
import Distribution.Simple.Utils
import Distribution.System
import Distribution.Types.PackageName.Magic
import Distribution.Utils.Path
import Distribution.Verbosity
import Distribution.Version

import System.Directory (doesDirectoryExist, doesFileExist)
import System.FilePath
  ( normalise
  , replaceExtension
  , splitExtension
  , takeDirectory
  , takeExtensions
  )
import System.Info (arch, os)

-- | Just present the modules in the order given; this is the default and it is
-- appropriate for preprocessors which do not have any sort of dependencies
-- between modules.
unsorted
  :: Verbosity
  -> [path]
  -> [ModuleName]
  -> IO [ModuleName]
unsorted _ _ ms = pure ms

-- | Function to determine paths to possible extra C sources for a
-- preprocessor: just takes the path to the build directory and uses
-- this to search for C sources with names that match the
-- preprocessor's output name format.
type PreProcessorExtras =
  Maybe (SymbolicPath CWD (Dir Pkg))
  -> SymbolicPath Pkg (Dir Source)
  -> IO [RelativePath Source File]

mkSimplePreProcessor
  :: (FilePath -> FilePath -> Verbosity -> IO ())
  -> (FilePath, FilePath)
  -> (FilePath, FilePath)
  -> Verbosity
  -> IO ()
mkSimplePreProcessor
  simplePP
  (inBaseDir, inRelativeFile)
  (outBaseDir, outRelativeFile)
  verbosity = simplePP inFile outFile verbosity
    where
      inFile = normalise (inBaseDir </> inRelativeFile)
      outFile = normalise (outBaseDir </> outRelativeFile)

runSimplePreProcessor
  :: PreProcessor
  -> FilePath
  -> FilePath
  -> Verbosity
  -> IO ()
runSimplePreProcessor pp inFile outFile verbosity =
  runPreProcessor pp (".", inFile) (".", outFile) verbosity

-- | A preprocessor for turning non-Haskell files with the given 'Suffix'
-- (i.e. file extension) into plain Haskell source files.
type PPSuffixHandler =
  (Suffix, BuildInfo -> LocalBuildInfo -> ComponentLocalBuildInfo -> PreProcessor)

-- | Apply preprocessors to the sources from 'hsSourceDirs' for a given
-- component (lib, exe, or test suite).
--
-- XXX: This is terrible
preprocessComponent
  :: PackageDescription
  -> Component
  -> LocalBuildInfo
  -> ComponentLocalBuildInfo
  -> Bool
  -> Verbosity
  -> [PPSuffixHandler]
  -> IO ()
preprocessComponent pd comp lbi clbi isSrcDist verbosity handlers =
  -- Skip preprocessing for scripts since they should be regular Haskell files,
  -- but may have no or unknown extensions.
  when (package pd /= fakePackageId) $ do
    -- NB: never report instantiation here; we'll report it properly when
    -- building.
    setupMessage'
      verbosity
      "Preprocessing"
      (packageId pd)
      (componentLocalName clbi)
      (Nothing :: Maybe [(ModuleName, Module)])
    case comp of
      (CLib lib@Library{libBuildInfo = bi}) -> do
        let dirs =
              hsSourceDirs bi
                ++ [autogenComponentModulesDir lbi clbi, autogenPackageModulesDir lbi]
        let hndlrs = localHandlers bi
        mods <- orderingFromHandlers verbosity dirs hndlrs (allLibModules lib clbi)
        for_ (map moduleNameSymbolicPath mods) $
          pre dirs (componentBuildDir lbi clbi) hndlrs
      (CFLib flib@ForeignLib{foreignLibBuildInfo = bi}) -> do
        let flibDir = flibBuildDir lbi flib
            dirs =
              hsSourceDirs bi
                ++ [ autogenComponentModulesDir lbi clbi
                   , autogenPackageModulesDir lbi
                   ]
        let hndlrs = localHandlers bi
        mods <- orderingFromHandlers verbosity dirs hndlrs (foreignLibModules flib)
        for_ (map moduleNameSymbolicPath mods) $
          pre dirs flibDir hndlrs
      (CExe exe@Executable{buildInfo = bi}) -> do
        let exeDir = exeBuildDir lbi exe
            dirs =
              hsSourceDirs bi
                ++ [ autogenComponentModulesDir lbi clbi
                   , autogenPackageModulesDir lbi
                   ]
        let hndlrs = localHandlers bi
        mods <- orderingFromHandlers verbosity dirs hndlrs (otherModules bi)
        for_ (map moduleNameSymbolicPath mods) $
          pre dirs exeDir hndlrs
        pre (hsSourceDirs bi) exeDir (localHandlers bi) $
          dropExtensionsSymbolicPath (modulePath exe)
      CTest test@TestSuite{} -> do
        let testDir = testBuildDir lbi test
        case testInterface test of
          TestSuiteExeV10 _ f ->
            preProcessTest test f testDir
          TestSuiteLibV09 _ _ -> do
            writeSimpleTestStub test (i testDir)
            preProcessTest test (makeRelativePathEx $ stubFilePath test) testDir
          TestSuiteUnsupported tt ->
            dieWithException verbosity $ NoSupportForPreProcessingTest tt
      CBench bm@Benchmark{} -> do
        let benchDir = benchmarkBuildDir lbi bm
        case benchmarkInterface bm of
          BenchmarkExeV10 _ f ->
            preProcessBench bm f benchDir
          BenchmarkUnsupported tt ->
            dieWithException verbosity $ NoSupportForPreProcessingBenchmark tt
  where
    orderingFromHandlers v d hndlrs mods =
      foldM (\acc (_, pp) -> ppOrdering pp v d acc) mods hndlrs
    builtinCSuffixes = map Suffix cSourceExtensions
    builtinSuffixes = builtinHaskellSuffixes ++ builtinCSuffixes
    localHandlers bi = [(ext, h bi lbi clbi) | (ext, h) <- handlers]
    mbWorkDir = mbWorkDirLBI lbi
    i = interpretSymbolicPathLBI lbi -- See Note [Symbolic paths] in Distribution.Utils.Path
    pre dirs dir lhndlrs fp =
      preprocessFile mbWorkDir dirs dir isSrcDist fp verbosity builtinSuffixes lhndlrs True
    preProcessTest test =
      preProcessComponent
        (testBuildInfo test)
        (testModules test)
    preProcessBench bm =
      preProcessComponent
        (benchmarkBuildInfo bm)
        (benchmarkModules bm)

    preProcessComponent
      :: BuildInfo
      -> [ModuleName]
      -> RelativePath Source File
      -> SymbolicPath Pkg (Dir Build)
      -> IO ()
    preProcessComponent bi modules exePath outputDir = do
      let biHandlers = localHandlers bi
          sourceDirs =
            hsSourceDirs bi
              ++ [ autogenComponentModulesDir lbi clbi
                 , autogenPackageModulesDir lbi
                 ]
      sequence_
        [ preprocessFile
          mbWorkDir
          sourceDirs
          outputDir
          isSrcDist
          (moduleNameSymbolicPath modu)
          verbosity
          builtinSuffixes
          biHandlers
          False
        | modu <- modules
        ]
      -- Note we don't fail on missing in this case, because the main file
      -- may be generated later (i.e. by a test code generator)
      preprocessFile
        mbWorkDir
        (coerceSymbolicPath outputDir : hsSourceDirs bi)
        outputDir
        isSrcDist
        (dropExtensionsSymbolicPath exePath)
        verbosity
        builtinSuffixes
        biHandlers
        False

-- TODO: try to list all the modules that could not be found
--      not just the first one. It's annoying and slow due to the need
--      to reconfigure after editing the .cabal file each time.

-- | Find the first extension of the file that exists, and preprocess it
-- if required.
preprocessFile
  :: Maybe (SymbolicPath CWD (Dir Pkg))
  -- ^ package directory location
  -> [SymbolicPath Pkg (Dir Source)]
  -- ^ source directories
  -> SymbolicPath Pkg (Dir Build)
  -- ^ build directory
  -> Bool
  -- ^ preprocess for sdist
  -> RelativePath Source File
  -- ^ module file name
  -> Verbosity
  -- ^ verbosity
  -> [Suffix]
  -- ^ builtin suffixes
  -> [(Suffix, PreProcessor)]
  -- ^ possible preprocessors
  -> Bool
  -- ^ fail on missing file
  -> IO ()
preprocessFile mbWorkDir searchLoc buildLoc forSDist baseFile verbosity builtinSuffixes handlers failOnMissing = do
  -- look for files in the various source dirs with this module name
  -- and a file extension of a known preprocessor
  psrcFiles <- findFileCwdWithExtension' mbWorkDir (map fst handlers) searchLoc baseFile
  case psrcFiles of
    -- no preprocessor file exists, look for an ordinary source file
    -- just to make sure one actually exists at all for this module.

    -- Note [Dodgy build dirs for preprocessors]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    -- By looking in the target/output build dir too, we allow
    -- source files to appear magically in the target build dir without
    -- any corresponding "real" source file. This lets custom Setup.hs
    -- files generate source modules directly into the build dir without
    -- the rest of the build system being aware of it (somewhat dodgy)
    Nothing -> do
      bsrcFiles <- findFileCwdWithExtension mbWorkDir builtinSuffixes (buildAsSrcLoc : searchLoc) baseFile
      case (bsrcFiles, failOnMissing) of
        (Nothing, True) ->
          dieWithException verbosity $
            CantFindSourceForPreProcessFile $
              "can't find source for "
                ++ getSymbolicPath baseFile
                ++ " in "
                ++ intercalate ", " (map getSymbolicPath searchLoc)
        _ -> return ()
    -- found a pre-processable file in one of the source dirs
    Just (psrcLoc, psrcRelFile) -> do
      let (srcStem, ext) = splitExtension $ getSymbolicPath psrcRelFile
          psrcFile = psrcLoc </> psrcRelFile
          pp =
            fromMaybe
              (error "Distribution.Simple.PreProcess: Just expected")
              (lookup (Suffix $ safeTail ext) handlers)
      -- Preprocessing files for 'sdist' is different from preprocessing
      -- for 'build'.  When preprocessing for sdist we preprocess to
      -- avoid that the user has to have the preprocessors available.
      -- ATM, we don't have a way to specify which files are to be
      -- preprocessed and which not, so for sdist we only process
      -- platform independent files and put them into the 'buildLoc'
      -- (which we assume is set to the temp. directory that will become
      -- the tarball).
      -- TODO: eliminate sdist variant, just supply different handlers
      when (not forSDist || forSDist && platformIndependent pp) $ do
        -- look for existing pre-processed source file in the dest dir to
        -- see if we really have to re-run the preprocessor.
        ppsrcFiles <- findFileCwdWithExtension mbWorkDir builtinSuffixes [buildAsSrcLoc] baseFile
        recomp <- case ppsrcFiles of
          Nothing -> return True
          Just ppsrcFile ->
            i psrcFile `moreRecentFile` i ppsrcFile
        when recomp $ do
          let destDir = i buildLoc </> takeDirectory srcStem
          createDirectoryIfMissingVerbose verbosity True destDir
          runPreProcessorWithHsBootHack
            pp
            (psrcLoc, getSymbolicPath psrcRelFile)
            (buildLoc, srcStem <.> "hs")
  where
    i = interpretSymbolicPath mbWorkDir -- See Note [Symbolic paths] in Distribution.Utils.Path
    buildAsSrcLoc :: SymbolicPath Pkg (Dir Source)
    buildAsSrcLoc = coerceSymbolicPath buildLoc

    -- FIXME: This is a somewhat nasty hack. GHC requires that hs-boot files
    -- be in the same place as the hs files, so if we put the hs file in dist/
    -- then we need to copy the hs-boot file there too. This should probably be
    -- done another way. Possibly we should also be looking for .lhs-boot
    -- files, but I think that preprocessors only produce .hs files.
    runPreProcessorWithHsBootHack
      pp
      (inBaseDir, inRelativeFile)
      (outBaseDir, outRelativeFile) = do
        -- Preprocessors are expected to take into account the working
        -- directory, e.g. using runProgramCwd with a working directory
        -- computed with mbWorkDirLBI.
        -- Hence the use of 'getSymbolicPath' here.
        runPreProcessor
          pp
          (getSymbolicPath inBaseDir, inRelativeFile)
          (getSymbolicPath outBaseDir, outRelativeFile)
          verbosity

        -- Here we interact directly with the file system, so we must
        -- interpret symbolic paths with respect to the working directory.
        let
          inFile = normalise (i inBaseDir </> inRelativeFile)
          outFile = normalise (i outBaseDir </> outRelativeFile)
          inBoot = replaceExtension inFile "hs-boot"
          outBoot = replaceExtension outFile "hs-boot"
        exists <- doesFileExist inBoot
        when exists $ copyFileVerbose verbosity inBoot outBoot

-- ------------------------------------------------------------

-- * known preprocessors

-- ------------------------------------------------------------

-- This one is useful for preprocessors that can't handle literate source.
-- We also need a way to chain preprocessors.
ppUnlit :: PreProcessor
ppUnlit =
  PreProcessor
    { platformIndependent = True
    , ppOrdering = unsorted
    , runPreProcessor = mkSimplePreProcessor $ \inFile outFile verbosity ->
        withUTF8FileContents inFile $ \contents ->
          either (writeUTF8File outFile) (dieWithException verbosity) (unlit inFile contents)
    }

ppCpp :: BuildInfo -> LocalBuildInfo -> ComponentLocalBuildInfo -> PreProcessor
ppCpp = ppCpp' []

ppCpp' :: [String] -> BuildInfo -> LocalBuildInfo -> ComponentLocalBuildInfo -> PreProcessor
ppCpp' extraArgs bi lbi clbi =
  case compilerFlavor (compiler lbi) of
    GHC -> ppGhcCpp ghcProgram (const True) args bi lbi clbi
    GHCJS -> ppGhcCpp ghcjsProgram (const True) args bi lbi clbi
    _ -> ppCpphs args bi lbi clbi
  where
    cppArgs = getCppOptions bi lbi
    args = cppArgs ++ extraArgs

ppGhcCpp
  :: Program
  -> (Version -> Bool)
  -> [String]
  -> BuildInfo
  -> LocalBuildInfo
  -> ComponentLocalBuildInfo
  -> PreProcessor
ppGhcCpp program xHs extraArgs _bi lbi clbi =
  PreProcessor
    { platformIndependent = False
    , ppOrdering = unsorted
    , runPreProcessor = mkSimplePreProcessor $ \inFile outFile verbosity -> do
        (prog, version, _) <-
          requireProgramVersion
            verbosity
            program
            anyVersion
            (withPrograms lbi)
        runProgramCwd verbosity (mbWorkDirLBI lbi) prog $
          ["-E", "-cpp"]
            -- This is a bit of an ugly hack. We're going to
            -- unlit the file ourselves later on if appropriate,
            -- so we need GHC not to unlit it now or it'll get
            -- double-unlitted. In the future we might switch to
            -- using cpphs --unlit instead.
            ++ (if xHs version then ["-x", "hs"] else [])
            ++ ["-optP-include", "-optP" ++ u (autogenComponentModulesDir lbi clbi </> makeRelativePathEx cppHeaderName)]
            ++ ["-o", outFile, inFile]
            ++ extraArgs
    }
  where
    -- See Note [Symbolic paths] in Distribution.Utils.Path
    u :: SymbolicPath Pkg to -> FilePath
    u = interpretSymbolicPathCWD

ppCpphs :: [String] -> BuildInfo -> LocalBuildInfo -> ComponentLocalBuildInfo -> PreProcessor
ppCpphs extraArgs _bi lbi clbi =
  PreProcessor
    { platformIndependent = False
    , ppOrdering = unsorted
    , runPreProcessor = mkSimplePreProcessor $ \inFile outFile verbosity -> do
        (cpphsProg, cpphsVersion, _) <-
          requireProgramVersion
            verbosity
            cpphsProgram
            anyVersion
            (withPrograms lbi)
        runProgramCwd verbosity (mbWorkDirLBI lbi) cpphsProg $
          ("-O" ++ outFile)
            : inFile
            : "--noline"
            : "--strip"
            : ["--include=" ++ u (autogenComponentModulesDir lbi clbi </> makeRelativePathEx cppHeaderName) | cpphsVersion >= mkVersion [1, 6]]
            ++ extraArgs
    }
  where
    -- See Note [Symbolic paths] in Distribution.Utils.Path
    u :: SymbolicPath Pkg to -> FilePath
    u = interpretSymbolicPathCWD

ppHsc2hs :: BuildInfo -> LocalBuildInfo -> ComponentLocalBuildInfo -> PreProcessor
ppHsc2hs bi lbi clbi =
  PreProcessor
    { platformIndependent = False
    , ppOrdering = unsorted
    , runPreProcessor = mkSimplePreProcessor $ \inFile outFile verbosity -> do
        (gccProg, _) <- requireProgram verbosity gccProgram (withPrograms lbi)
        (hsc2hsProg, hsc2hsVersion, _) <-
          requireProgramVersion
            verbosity
            hsc2hsProgram
            anyVersion
            (withPrograms lbi)
        let runHsc2hs = runProgramCwd verbosity mbWorkDir hsc2hsProg
        -- See Trac #13896 and https://github.com/haskell/cabal/issues/3122.
        let isCross = hostPlatform lbi /= buildPlatform
            prependCrossFlags = if isCross then ("-x" :) else id
        let hsc2hsSupportsResponseFiles = hsc2hsVersion >= mkVersion [0, 68, 4]
            pureArgs = genPureArgs hsc2hsVersion gccProg inFile outFile
        if hsc2hsSupportsResponseFiles
          then
            withResponseFile
              verbosity
              defaultTempFileOptions
              "hsc2hs-response.txt"
              Nothing
              pureArgs
              ( \responseFileName ->
                  runHsc2hs (prependCrossFlags ["@" ++ responseFileName])
              )
          else runHsc2hs (prependCrossFlags pureArgs)
    }
  where
    -- See Note [Symbolic paths] in Distribution.Utils.Path
    u :: SymbolicPathX allowAbs Pkg to -> FilePath
    u = interpretSymbolicPathCWD
    mbWorkDir = mbWorkDirLBI lbi

    -- Returns a list of command line arguments that can either be passed
    -- directly, or via a response file.
    genPureArgs :: Version -> ConfiguredProgram -> String -> String -> [String]
    genPureArgs hsc2hsVersion gccProg inFile outFile =
      cflags
        ++ ldflags
        ++ preccldFlags
        ++ hsc2hsOptions bi
        ++ postccldFlags
        ++ ["-o", outFile, inFile]
      where
        ldflags =
          map ("--lflag=" ++) $
            ordNub $
              concat
                [ programDefaultArgs gccProg ++ programOverrideArgs gccProg
                , osxFrameworkDirs
                , [ arg
                  | isOSX
                  , opt <- map getSymbolicPath (PD.frameworks bi) ++ concatMap Installed.frameworks pkgs
                  , arg <- ["-framework", opt]
                  ]
                , -- Note that on ELF systems, wherever we use -L, we must also use -R
                  -- because presumably that -L dir is not on the normal path for the
                  -- system's dynamic linker. This is needed because hsc2hs works by
                  -- compiling a C program and then running it.

                  -- Options from the current package:
                  [ "-L" ++ u opt
                  | opt <-
                      if withFullyStaticExe lbi
                        then PD.extraLibDirsStatic bi
                        else PD.extraLibDirs bi
                  ]
                , [ "-Wl,-R," ++ u opt
                  | isELF
                  , opt <-
                      if withFullyStaticExe lbi
                        then PD.extraLibDirsStatic bi
                        else PD.extraLibDirs bi
                  ]
                , ["-l" ++ opt | opt <- PD.extraLibs bi]
                , PD.ldOptions bi
                , -- Options from dependent packages
                  [ opt
                  | pkg <- pkgs
                  , opt <-
                      ["-L" ++ opt | opt <- Installed.libraryDirs pkg]
                        ++ [ "-Wl,-R," ++ opt | isELF, opt <- Installed.libraryDirs pkg
                           ]
                        ++ [ "-l" ++ opt
                           | opt <-
                              if withFullyStaticExe lbi
                                then Installed.extraLibrariesStatic pkg
                                else Installed.extraLibraries pkg
                           ]
                        ++ Installed.ldOptions pkg
                  ]
                ]

        cflags =
          map ("--cflag=" ++) $
            ordNub $
              concat
                [ programDefaultArgs gccProg ++ programOverrideArgs gccProg
                , osxFrameworkDirs
                , platformDefines lbi
                , -- Options from the current package:
                  ["-I" ++ u dir | dir <- PD.includeDirs bi]
                , [ "-I" ++ u (buildDir lbi </> unsafeCoerceSymbolicPath relDir)
                  | relDir <- mapMaybe symbolicPathRelative_maybe $ PD.includeDirs bi
                  ]
                , -- hsc2hs uses the C ABI
                  -- We assume that there are only C sources
                  -- and C++ functions are exported via a C
                  -- interface and wrapped in a C source file.
                  -- Therefore we do not supply C++ flags
                  -- because there will not be C++ sources.
                  --
                  -- DO NOT add PD.cxxOptions unless this changes!
                  PD.ccOptions bi ++ PD.cppOptions bi
                ,
                  [ "-I" ++ u (autogenComponentModulesDir lbi clbi)
                  , "-I" ++ u (autogenPackageModulesDir lbi)
                  , "-include"
                  , u $ autogenComponentModulesDir lbi clbi </> makeRelativePathEx cppHeaderName
                  ]
                , -- Options from dependent packages
                  [ opt
                  | pkg <- pkgs
                  , opt <-
                      ["-I" ++ opt | opt <- Installed.includeDirs pkg]
                        ++ Installed.ccOptions pkg
                  ]
                ]

        osxFrameworkDirs =
          [ "-F" ++ opt
          | isOSX
          , opt <- ordNub (concatMap Installed.frameworkDirs pkgs)
          ]

        -- hsc2hs flag parsing was wrong
        -- (see -- https://github.com/haskell/hsc2hs/issues/35)
        -- so we need to put -- --cc/--ld *after* hsc2hsOptions,
        -- for older hsc2hs (pre 0.68.8) so that they can be overridden.
        ccldFlags =
          [ "--cc=" ++ programPath gccProg
          , "--ld=" ++ programPath gccProg
          ]

        (preccldFlags, postccldFlags)
          | hsc2hsVersion >= mkVersion [0, 68, 8] = (ccldFlags, [])
          | otherwise = ([], ccldFlags)

    hacked_index = packageHacks (installedPkgs lbi)
    -- Look only at the dependencies of the current component
    -- being built!  This relies on 'installedPkgs' maintaining
    -- 'InstalledPackageInfo' for internal deps too; see #2971.
    pkgs = PackageIndex.topologicalOrder $
      case PackageIndex.dependencyClosure
        hacked_index
        (map fst (componentPackageDeps clbi)) of
        Left index' -> index'
        Right inf ->
          error ("ppHsc2hs: broken closure: " ++ show inf)
    isOSX = case buildOS of OSX -> True; _ -> False
    isELF = case buildOS of OSX -> False; Windows -> False; AIX -> False; _ -> True
    packageHacks = case compilerFlavor (compiler lbi) of
      GHC -> hackRtsPackage
      GHCJS -> hackRtsPackage
      _ -> id
    -- We don't link in the actual Haskell libraries of our dependencies, so
    -- the -u flags in the ldOptions of the rts package mean linking fails on
    -- OS X (its ld is a tad stricter than gnu ld). Thus we remove the
    -- ldOptions for GHC's rts package:
    hackRtsPackage index =
      case PackageIndex.lookupPackageName index (mkPackageName "rts") of
        [(_, [rts])] ->
          PackageIndex.insert rts{Installed.ldOptions = []} index
        _ -> error "No (or multiple) ghc rts package is registered!!"

ppHsc2hsExtras :: PreProcessorExtras
ppHsc2hsExtras mbWorkDir buildBaseDir = do
  fs <- getDirectoryContentsRecursive $ interpretSymbolicPath mbWorkDir buildBaseDir
  let hscCFiles = filter ("_hsc.c" `isSuffixOf`) fs
  return $ map makeRelativePathEx hscCFiles

ppC2hs :: BuildInfo -> LocalBuildInfo -> ComponentLocalBuildInfo -> PreProcessor
ppC2hs bi lbi clbi =
  PreProcessor
    { platformIndependent = False
    , ppOrdering = unsorted
    , runPreProcessor =
        \(inBaseDir, inRelativeFile)
         (outBaseDir, outRelativeFile)
         verbosity -> do
            (c2hsProg, _, _) <-
              requireProgramVersion
                verbosity
                c2hsProgram
                (orLaterVersion (mkVersion [0, 15]))
                (withPrograms lbi)
            (gccProg, _) <- requireProgram verbosity gccProgram (withPrograms lbi)
            runProgramCwd verbosity mbWorkDir c2hsProg $
              -- Options from the current package:
              ["--cpp=" ++ programPath gccProg, "--cppopts=-E"]
                ++ ["--cppopts=" ++ opt | opt <- getCppOptions bi lbi]
                ++ ["--cppopts=-include" ++ u (autogenComponentModulesDir lbi clbi </> makeRelativePathEx cppHeaderName)]
                ++ ["--include=" ++ outBaseDir]
                -- Options from dependent packages
                ++ [ "--cppopts=" ++ opt
                   | pkg <- pkgs
                   , opt <-
                      ["-I" ++ opt | opt <- Installed.includeDirs pkg]
                        ++ [ opt | opt@('-' : c : _) <- Installed.ccOptions pkg,
                           -- c2hs uses the C ABI
                           -- We assume that there are only C sources
                           -- and C++ functions are exported via a C
                           -- interface and wrapped in a C source file.
                           -- Therefore we do not supply C++ flags
                           -- because there will not be C++ sources.
                           --
                           --
                           -- DO NOT add Installed.cxxOptions unless this changes!
                           c `elem` "DIU"
                           ]
                   ]
                -- TODO: install .chi files for packages, so we can --include
                -- those dirs here, for the dependencies

                -- input and output files
                ++ [ "--output-dir=" ++ outBaseDir
                   , "--output=" ++ outRelativeFile
                   , inBaseDir </> inRelativeFile
                   ]
    }
  where
    pkgs = PackageIndex.topologicalOrder (installedPkgs lbi)
    mbWorkDir = mbWorkDirLBI lbi
    -- See Note [Symbolic paths] in Distribution.Utils.Path
    u :: SymbolicPath Pkg to -> FilePath
    u = interpretSymbolicPathCWD

ppC2hsExtras :: PreProcessorExtras
ppC2hsExtras mbWorkDir buildBaseDir = do
  fs <- getDirectoryContentsRecursive $ interpretSymbolicPath mbWorkDir buildBaseDir
  return $
    map makeRelativePathEx $
      filter (\p -> takeExtensions p == ".chs.c") fs

-- TODO: perhaps use this with hsc2hs too
-- TODO: remove cc-options from cpphs for cabal-version: >= 1.10
-- TODO: Refactor and add separate getCppOptionsForHs, getCppOptionsForCxx, & getCppOptionsForC
--      instead of combining all these cases in a single function. This blind combination can
--      potentially lead to compilation inconsistencies.
getCppOptions :: BuildInfo -> LocalBuildInfo -> [String]
getCppOptions bi lbi =
  platformDefines lbi
    ++ cppOptions bi
    ++ ["-I" ++ getSymbolicPath dir | dir <- PD.includeDirs bi]
    ++ [opt | opt@('-' : c : _) <- PD.ccOptions bi ++ PD.cxxOptions bi, c `elem` "DIU"]

platformDefines :: LocalBuildInfo -> [String]
platformDefines lbi =
  case compilerFlavor comp of
    GHC ->
      ["-D__GLASGOW_HASKELL__=" ++ versionInt version]
        ++ ["-D" ++ os ++ "_BUILD_OS=1"]
        ++ ["-D" ++ arch ++ "_BUILD_ARCH=1"]
        ++ map (\os' -> "-D" ++ os' ++ "_HOST_OS=1") osStr
        ++ map (\arch' -> "-D" ++ arch' ++ "_HOST_ARCH=1") archStr
    GHCJS ->
      compatGlasgowHaskell
        ++ ["-D__GHCJS__=" ++ versionInt version]
        ++ ["-D" ++ os ++ "_BUILD_OS=1"]
        ++ ["-D" ++ arch ++ "_BUILD_ARCH=1"]
        ++ map (\os' -> "-D" ++ os' ++ "_HOST_OS=1") osStr
        ++ map (\arch' -> "-D" ++ arch' ++ "_HOST_ARCH=1") archStr
    _ -> []
  where
    comp = compiler lbi
    Platform hostArch hostOS = hostPlatform lbi
    version = compilerVersion comp
    compatGlasgowHaskell =
      maybe
        []
        (\v -> ["-D__GLASGOW_HASKELL__=" ++ versionInt v])
        (compilerCompatVersion GHC comp)
    -- TODO: move this into the compiler abstraction
    -- FIXME: this forces GHC's crazy 4.8.2 -> 408 convention on all
    -- the other compilers. Check if that's really what they want.
    versionInt :: Version -> String
    versionInt v = case versionNumbers v of
      [] -> "1"
      [n] -> show n
      n1 : n2 : _ ->
        -- 6.8.x -> 608
        -- 6.10.x -> 610
        let s1 = show n1
            s2 = show n2
            middle = case s2 of
              _ : _ : _ -> ""
              _ -> "0"
         in s1 ++ middle ++ s2

    osStr = case hostOS of
      Linux -> ["linux"]
      Windows -> ["mingw32"]
      OSX -> ["darwin"]
      FreeBSD -> ["freebsd"]
      OpenBSD -> ["openbsd"]
      NetBSD -> ["netbsd"]
      DragonFly -> ["dragonfly"]
      Solaris -> ["solaris2"]
      AIX -> ["aix"]
      HPUX -> ["hpux"]
      IRIX -> ["irix"]
      HaLVM -> []
      IOS -> ["ios"]
      Android -> ["android"]
      Ghcjs -> ["ghcjs"]
      Wasi -> ["wasi"]
      Hurd -> ["gnu"]
      Haiku -> ["haiku"]
      OtherOS _ -> []
    archStr = case hostArch of
      I386 -> ["i386"]
      X86_64 -> ["x86_64"]
      PPC -> ["powerpc"]
      PPC64 -> ["powerpc64"]
      PPC64LE -> ["powerpc64le"]
      Sparc -> ["sparc"]
      Sparc64 -> ["sparc64"]
      Arm -> ["arm"]
      AArch64 -> ["aarch64"]
      Mips -> ["mips"]
      SH -> []
      IA64 -> ["ia64"]
      S390 -> ["s390"]
      S390X -> ["s390x"]
      Alpha -> ["alpha"]
      Hppa -> ["hppa"]
      Rs6000 -> ["rs6000"]
      M68k -> ["m68k"]
      Vax -> ["vax"]
      RISCV64 -> ["riscv64"]
      LoongArch64 -> ["loongarch64"]
      JavaScript -> ["javascript"]
      Wasm32 -> ["wasm32"]
      OtherArch _ -> []

ppHappy :: BuildInfo -> LocalBuildInfo -> ComponentLocalBuildInfo -> PreProcessor
ppHappy _ lbi _ = pp{platformIndependent = True}
  where
    pp = standardPP lbi happyProgram (hcFlags hc)
    hc = compilerFlavor (compiler lbi)
    hcFlags GHC = ["-agc"]
    hcFlags GHCJS = ["-agc"]
    hcFlags _ = []

ppAlex :: BuildInfo -> LocalBuildInfo -> ComponentLocalBuildInfo -> PreProcessor
ppAlex _ lbi _ = pp{platformIndependent = True}
  where
    pp = standardPP lbi alexProgram (hcFlags hc)
    hc = compilerFlavor (compiler lbi)
    hcFlags GHC = ["-g"]
    hcFlags GHCJS = ["-g"]
    hcFlags _ = []

standardPP :: LocalBuildInfo -> Program -> [String] -> PreProcessor
standardPP lbi prog args =
  PreProcessor
    { platformIndependent = False
    , ppOrdering = unsorted
    , runPreProcessor = mkSimplePreProcessor $ \inFile outFile verbosity ->
        runDbProgramCwd
          verbosity
          (mbWorkDirLBI lbi)
          prog
          (withPrograms lbi)
          (args ++ ["-o", outFile, inFile])
    }

-- | Convenience function; get the suffixes of these preprocessors.
ppSuffixes :: [PPSuffixHandler] -> [Suffix]
ppSuffixes = map fst

-- | Standard preprocessors: c2hs, hsc2hs, happy, alex and cpphs.
knownSuffixHandlers :: [PPSuffixHandler]
knownSuffixHandlers =
  [ (Suffix "chs", ppC2hs)
  , (Suffix "hsc", ppHsc2hs)
  , (Suffix "x", ppAlex)
  , (Suffix "y", ppHappy)
  , (Suffix "ly", ppHappy)
  , (Suffix "cpphs", ppCpp)
  ]

-- | Standard preprocessors with possible extra C sources: c2hs, hsc2hs.
knownExtrasHandlers :: [PreProcessorExtras]
knownExtrasHandlers = [ppC2hsExtras, ppHsc2hsExtras]

-- | Find any extra C sources generated by preprocessing that need to
-- be added to the component (addresses issue #238).
preprocessExtras
  :: Verbosity
  -> Component
  -> LocalBuildInfo
  -> IO [SymbolicPath Pkg File]
preprocessExtras verbosity comp lbi = case comp of
  CLib _ -> pp $ buildDir lbi
  (CExe exe@Executable{}) -> pp $ exeBuildDir lbi exe
  (CFLib flib@ForeignLib{}) -> pp $ flibBuildDir lbi flib
  CTest test ->
    case testInterface test of
      TestSuiteUnsupported tt ->
        dieWithException verbosity $ NoSupportPreProcessingTestExtras tt
      _ -> pp $ testBuildDir lbi test
  CBench bm ->
    case benchmarkInterface bm of
      BenchmarkUnsupported tt ->
        dieWithException verbosity $ NoSupportPreProcessingBenchmarkExtras tt
      _ -> pp $ benchmarkBuildDir lbi bm
  where
    pp :: SymbolicPath Pkg (Dir Build) -> IO [SymbolicPath Pkg File]
    pp builddir = do
      -- Use the build dir as a source dir.
      let dir :: SymbolicPath Pkg (Dir Source)
          dir = coerceSymbolicPath builddir
          mbWorkDir = mbWorkDirLBI lbi
      b <- doesDirectoryExist (interpretSymbolicPathLBI lbi dir)
      if b
        then do
          xs <- for knownExtrasHandlers $ withLexicalCallStack $ \f -> f mbWorkDir dir
          let not_subs =
                map (dir </>) $
                  filter (not_sub . getSymbolicPath) $
                    concat xs
          return not_subs
        else pure []
    -- TODO: This is a terrible hack to work around #3545 while we don't
    -- reorganize the directory layout.  Basically, for the main
    -- library, we might accidentally pick up autogenerated sources for
    -- our subcomponents, because they are all stored as subdirectories
    -- in dist/build.  This is a cheap and cheerful check to prevent
    -- this from happening.  It is not particularly correct; for example
    -- if a user has a test suite named foobar and puts their C file in
    -- foobar/foo.c, this test will incorrectly exclude it.  But I
    -- didn't want to break BC...
    not_sub p = and [not (pre `isPrefixOf` p) | pre <- component_dirs]
    component_dirs = component_names (localPkgDescr lbi)
    -- TODO: libify me
    component_names pkg_descr =
      fmap unUnqualComponentName $
        mapMaybe (libraryNameString . libName) (subLibraries pkg_descr)
          ++ map exeName (executables pkg_descr)
          ++ map testName (testSuites pkg_descr)
          ++ map benchmarkName (benchmarks pkg_descr)