----------------------------------------------------------------------------- -- -- (c) The University of Glasgow 2001-2003 -- -- Access to system tools: gcc, cp, rm etc -- ----------------------------------------------------------------------------- \begin{code}

    module SysTools (
            -- Initialisation
            initSysTools,

            -- Interface to system tools
            runUnlit, runCpp, runCc, -- [Option] -> IO ()
            runPp,                   -- [Option] -> IO ()
            runMangle, runSplit,     -- [Option] -> IO ()
            runAs, runLink,          -- [Option] -> IO ()
            runMkDLL,
            runWindres,
            runLlvmOpt,
            runLlvmLlc,

            touch,                  -- String -> String -> IO ()
            copy,
            copyWithHeader,
            getExtraViaCOpts,

            -- Temporary-file management
            setTmpDir,
            newTempName,
            cleanTempDirs, cleanTempFiles, cleanTempFilesExcept,
            addFilesToClean,

            Option(..)

     ) where

    #include "HsVersions.h"

    import DriverPhases
    import Config
    import Outputable
    import ErrUtils
    import Panic
    import Util
    import DynFlags

    import Exception
    import Data.IORef
    import Control.Monad
    import System.Exit
    import System.Environment
    import System.FilePath
    import System.IO
    import System.IO.Error as IO
    import System.Directory
    import Data.Char
    import Data.List
    import qualified Data.Map as Map

    #ifndef mingw32_HOST_OS
    import qualified System.Posix.Internals
    #else /* Must be Win32 */
    import Foreign
    import Foreign.C.String
    #endif

    import System.Process   ( runInteractiveProcess, getProcessExitCode )
    import Control.Concurrent
    import FastString
    import SrcLoc           ( SrcLoc, mkSrcLoc, noSrcSpan, mkSrcSpan )

\end{code} How GHC finds its files ~~~~~~~~~~~~~~~~~~~~~~~ [Note topdir] GHC needs various support files (library packages, RTS etc), plus various auxiliary programs (cp, gcc, etc). It starts by finding topdir, the root of GHC's support files On Unix: - ghc always has a shell wrapper that passes a -B option On Windows: - ghc never has a shell wrapper. - we can find the location of the ghc binary, which is $topdir/bin/<something>.exe where <something> may be "ghc", "ghc-stage2", or similar - we strip off the "bin/<something>.exe" to leave $topdir. from topdir we can find package.conf, ghc-asm, etc. SysTools.initSysProgs figures out exactly where all the auxiliary programs are, and initialises mutable variables to make it easy to call them. To to this, it makes use of definitions in Config.hs, which is a Haskell file containing variables whose value is figured out by the build system. Config.hs contains two sorts of things cGCC, The *names* of the programs cCPP e.g. cGCC = gcc cUNLIT cCPP = gcc -E etc They do *not* include paths cUNLIT_DIR The *path* to the directory containing unlit, split etc cSPLIT_DIR *relative* to the root of the build tree, for use when running *in-place* in a build tree (only) --------------------------------------------- NOTES for an ALTERNATIVE scheme (i.e *not* what is currently implemented): Another hair-brained scheme for simplifying the current tool location nightmare in GHC: Simon originally suggested using another configuration file along the lines of GCC's specs file - which is fine except that it means adding code to read yet another configuration file. What I didn't notice is that the current package.conf is general enough to do this: Package {name = "tools", import_dirs = [], source_dirs = [], library_dirs = [], hs_libraries = [], extra_libraries = [], include_dirs = [], c_includes = [], package_deps = [], extra_ghc_opts = ["-pgmc/usr/bin/gcc","-pgml${topdir}/bin/unlit", ... etc.], extra_cc_opts = [], extra_ld_opts = []} Which would have the advantage that we get to collect together in one place the path-specific package stuff with the path-specific tool stuff. End of NOTES --------------------------------------------- %************************************************************************ %* * \subsection{Initialisation} %* * %************************************************************************ \begin{code}

    initSysTools :: Maybe String    -- Maybe TopDir path (without the '-B' prefix)

                 -> DynFlags
                 -> IO DynFlags     -- Set all the mutable variables above, holding
                                    --      (a) the system programs
                                    --      (b) the package-config file
                                    --      (c) the GHC usage message

    initSysTools mbMinusB dflags0
      = do  { top_dir <- findTopDir mbMinusB
                    -- see [Note topdir]
                    -- NB: top_dir is assumed to be in standard Unix
                    -- format, '/' separated

            ; let installed :: FilePath -> FilePath
                  installed file = top_dir </> file
                  installed_mingw_bin file = top_dir </> ".." </> "mingw" </> "bin" </> file
                  installed_perl_bin file = top_dir </> ".." </> "perl" </> file

            ; let pkgconfig_path = installed "package.conf.d"
                  ghc_usage_msg_path  = installed "ghc-usage.txt"
                  ghci_usage_msg_path = installed "ghci-usage.txt"

                    -- For all systems, unlit, split, mangle are GHC utilities
                    -- architecture-specific stuff is done when building Config.hs
                  unlit_path = installed cGHC_UNLIT_PGM

                    -- split and mangle are Perl scripts
                  split_script  = installed cGHC_SPLIT_PGM
                  mangle_script = installed cGHC_MANGLER_PGM

                  windres_path  = installed_mingw_bin "windres"

            ; tmpdir <- getTemporaryDirectory
            ; let dflags1 = setTmpDir tmpdir dflags0

            -- On Windows, mingw is distributed with GHC,
            --      so we look in TopDir/../mingw/bin
            ; let
                  gcc_prog
                    | isWindowsHost = installed_mingw_bin "gcc"
                    | otherwise     = cGCC
                  perl_path
                    | isWindowsHost = installed_perl_bin cGHC_PERL
                    | otherwise     = cGHC_PERL
                  -- 'touch' is a GHC util for Windows
                  touch_path
                    | isWindowsHost = installed cGHC_TOUCHY_PGM
                    | otherwise     = "touch"
                  -- On Win32 we don't want to rely on #!/bin/perl, so we prepend
                  -- a call to Perl to get the invocation of split and mangle.
                  -- On Unix, scripts are invoked using the '#!' method.  Binary
                  -- installations of GHC on Unix place the correct line on the
                  -- front of the script at installation time, so we don't want
                  -- to wire-in our knowledge of $(PERL) on the host system here.
                  (split_prog,  split_args)
                    | isWindowsHost = (perl_path,    [Option split_script])
                    | otherwise     = (split_script, [])
                  (mangle_prog, mangle_args)
                    | isWindowsHost = (perl_path,   [Option mangle_script])
                    | otherwise     = (mangle_script, [])
                  (mkdll_prog, mkdll_args)
                    | not isWindowsHost
                        = panic "Can't build DLLs on a non-Win32 system"
                    | otherwise =
                        (installed_mingw_bin cMKDLL, [])

            -- cpp is derived from gcc on all platforms
            -- HACK, see setPgmP below. We keep 'words' here to remember to fix
            -- Config.hs one day.
            ; let cpp_path  = (gcc_prog,
                               (Option "-E"):(map Option (words cRAWCPP_FLAGS)))

            -- Other things being equal, as and ld are simply gcc
            ; let   as_prog  = gcc_prog
                    ld_prog  = gcc_prog

            -- figure out llvm location. (TODO: Acutally implement).
            ; let lc_prog = "llc"
                  lo_prog = "opt"

            ; return dflags1{
                            ghcUsagePath = ghc_usage_msg_path,
                            ghciUsagePath = ghci_usage_msg_path,
                            topDir  = top_dir,
                            systemPackageConfig = pkgconfig_path,
                            pgm_L   = unlit_path,
                            pgm_P   = cpp_path,
                            pgm_F   = "",
                            pgm_c   = (gcc_prog,[]),
                            pgm_m   = (mangle_prog,mangle_args),
                            pgm_s   = (split_prog,split_args),
                            pgm_a   = (as_prog,[]),
                            pgm_l   = (ld_prog,[]),
                            pgm_dll = (mkdll_prog,mkdll_args),
                            pgm_T   = touch_path,
                            pgm_sysman = top_dir ++ "/ghc/rts/parallel/SysMan",
                            pgm_windres = windres_path,
                            pgm_lo  = (lo_prog,[]),
                            pgm_lc  = (lc_prog,[])
                            -- Hans: this isn't right in general, but you can
                            -- elaborate it in the same way as the others
                    }
            }

\end{code} \begin{code}

    -- returns a Unix-format path (relying on getBaseDir to do so too)
    findTopDir :: Maybe String -- Maybe TopDir path (without the '-B' prefix).
               -> IO String    -- TopDir (in Unix format '/' separated)
    findTopDir (Just minusb) = return (normalise minusb)
    findTopDir Nothing
        = do -- Get directory of executable
             maybe_exec_dir <- getBaseDir
             case maybe_exec_dir of
                 -- "Just" on Windows, "Nothing" on unix
                 Nothing  -> ghcError (InstallationError "missing -B<dir> option")
                 Just dir -> return dir

\end{code} %************************************************************************ %* * \subsection{Running an external program} %* * %************************************************************************ \begin{code}

    runUnlit :: DynFlags -> [Option] -> IO ()
    runUnlit dflags args = do
      let p = pgm_L dflags
      runSomething dflags "Literate pre-processor" p args

    runCpp :: DynFlags -> [Option] -> IO ()
    runCpp dflags args =   do
      let (p,args0) = pgm_P dflags
          args1 = args0 ++ args
          args2 = if dopt Opt_WarnIsError dflags
                  then Option "-Werror" : args1
                  else                    args1
      mb_env <- getGccEnv args2
      runSomethingFiltered dflags id  "C pre-processor" p args2 mb_env

    runPp :: DynFlags -> [Option] -> IO ()
    runPp dflags args =   do
      let p = pgm_F dflags
      runSomething dflags "Haskell pre-processor" p args

    runCc :: DynFlags -> [Option] -> IO ()
    runCc dflags args =   do
      let (p,args0) = pgm_c dflags
          args1 = args0 ++ args
      mb_env <- getGccEnv args1
      runSomethingFiltered dflags cc_filter "C Compiler" p args1 mb_env
     where
      -- discard some harmless warnings from gcc that we can't turn off
      cc_filter = unlines . doFilter . lines

      {-
      gcc gives warnings in chunks like so:
          In file included from /foo/bar/baz.h:11,
                           from /foo/bar/baz2.h:22,
                           from wibble.c:33:
          /foo/flibble:14: global register variable ...
          /foo/flibble:15: warning: call-clobbered r...
      We break it up into its chunks, remove any call-clobbered register
      warnings from each chunk, and then delete any chunks that we have
      emptied of warnings.
      -}
      doFilter = unChunkWarnings . filterWarnings . chunkWarnings []
      -- We can't assume that the output will start with an "In file inc..."
      -- line, so we start off expecting a list of warnings rather than a
      -- location stack.
      chunkWarnings :: [String] -- The location stack to use for the next
                                -- list of warnings
                    -> [String] -- The remaining lines to look at
                    -> [([String], [String])]
      chunkWarnings loc_stack [] = [(loc_stack, [])]
      chunkWarnings loc_stack xs
          = case break loc_stack_start xs of
            (warnings, lss:xs') ->
                case span loc_start_continuation xs' of
                (lsc, xs'') ->
                    (loc_stack, warnings) : chunkWarnings (lss : lsc) xs''
            _ -> [(loc_stack, xs)]

      filterWarnings :: [([String], [String])] -> [([String], [String])]
      filterWarnings [] = []
      -- If the warnings are already empty then we are probably doing
      -- something wrong, so don't delete anything
      filterWarnings ((xs, []) : zs) = (xs, []) : filterWarnings zs
      filterWarnings ((xs, ys) : zs) = case filter wantedWarning ys of
                                           [] -> filterWarnings zs
                                           ys' -> (xs, ys') : filterWarnings zs

      unChunkWarnings :: [([String], [String])] -> [String]
      unChunkWarnings [] = []
      unChunkWarnings ((xs, ys) : zs) = xs ++ ys ++ unChunkWarnings zs

      loc_stack_start        s = "In file included from " `isPrefixOf` s
      loc_start_continuation s = "                 from " `isPrefixOf` s
      wantedWarning w
       | "warning: call-clobbered register used" `isContainedIn` w = False
       | otherwise = True

    isContainedIn :: String -> String -> Bool
    xs `isContainedIn` ys = any (xs `isPrefixOf`) (tails ys)

    -- If the -B<dir> option is set, add <dir> to PATH.  This works around
    -- a bug in gcc on Windows Vista where it can't find its auxiliary
    -- binaries (see bug #1110).
    getGccEnv :: [Option] -> IO (Maybe [(String,String)])
    getGccEnv opts =
      if null b_dirs
         then return Nothing
         else do env <- getEnvironment
                 return (Just (map mangle_path env))
     where
      (b_dirs, _) = partitionWith get_b_opt opts

      get_b_opt (Option ('-':'B':dir)) = Left dir
      get_b_opt other = Right other

      mangle_path (path,paths) | map toUpper path == "PATH"
            = (path, '\"' : head b_dirs ++ "\";" ++ paths)
      mangle_path other = other

    runMangle :: DynFlags -> [Option] -> IO ()
    runMangle dflags args = do
      let (p,args0) = pgm_m dflags
      runSomething dflags "Mangler" p (args0++args)

    runSplit :: DynFlags -> [Option] -> IO ()
    runSplit dflags args = do
      let (p,args0) = pgm_s dflags
      runSomething dflags "Splitter" p (args0++args)

    runAs :: DynFlags -> [Option] -> IO ()
    runAs dflags args = do
      let (p,args0) = pgm_a dflags
          args1 = args0 ++ args
      mb_env <- getGccEnv args1
      runSomethingFiltered dflags id "Assembler" p args1 mb_env

    runLlvmOpt :: DynFlags -> [Option] -> IO ()
    runLlvmOpt dflags args = do
      let (p,args0) = pgm_lo dflags
      runSomething dflags "LLVM Optimiser" p (args0++args)

    runLlvmLlc :: DynFlags -> [Option] -> IO ()
    runLlvmLlc dflags args = do
      let (p,args0) = pgm_lc dflags
      runSomething dflags "LLVM Compiler" p (args0++args)

    runLink :: DynFlags -> [Option] -> IO ()
    runLink dflags args = do
      let (p,args0) = pgm_l dflags
          args1 = args0 ++ args
      mb_env <- getGccEnv args1
      runSomethingFiltered dflags id "Linker" p args1 mb_env

    runMkDLL :: DynFlags -> [Option] -> IO ()
    runMkDLL dflags args = do
      let (p,args0) = pgm_dll dflags
          args1 = args0 ++ args
      mb_env <- getGccEnv (args0++args)
      runSomethingFiltered dflags id "Make DLL" p args1 mb_env

    runWindres :: DynFlags -> [Option] -> IO ()
    runWindres dflags args = do
      let (gcc, gcc_args) = pgm_c dflags
          windres = pgm_windres dflags
          quote x = "\"" ++ x ++ "\""
          args' = -- If windres.exe and gcc.exe are in a directory containing
                  -- spaces then windres fails to run gcc. We therefore need
                  -- to tell it what command to use...
                  Option ("--preprocessor=" ++
                          unwords (map quote (gcc :
                                              map showOpt gcc_args ++
                                              ["-E", "-xc", "-DRC_INVOKED"])))
                  -- ...but if we do that then if windres calls popen then
                  -- it can't understand the quoting, so we have to use
                  -- --use-temp-file so that it interprets it correctly.
                  -- See #1828.
                : Option "--use-temp-file"
                : args
      mb_env <- getGccEnv gcc_args
      runSomethingFiltered dflags id "Windres" windres args' mb_env

    touch :: DynFlags -> String -> String -> IO ()
    touch dflags purpose arg =
      runSomething dflags purpose (pgm_T dflags) [FileOption "" arg]

    copy :: DynFlags -> String -> FilePath -> FilePath -> IO ()
    copy dflags purpose from to = copyWithHeader dflags purpose Nothing from to

    copyWithHeader :: DynFlags -> String -> Maybe String -> FilePath -> FilePath
                   -> IO ()
    copyWithHeader dflags purpose maybe_header from to = do
      showPass dflags purpose

      hout <- openBinaryFile to   WriteMode
      hin  <- openBinaryFile from ReadMode
      ls <- hGetContents hin -- inefficient, but it'll do for now. ToDo: speed up
      maybe (return ()) (hPutStr hout) maybe_header
      hPutStr hout ls
      hClose hout
      hClose hin

    getExtraViaCOpts :: DynFlags -> IO [String]
    getExtraViaCOpts dflags = do
      f <- readFile (topDir dflags </> "extra-gcc-opts")
      return (words f)

\end{code} %************************************************************************ %* * \subsection{Managing temporary files %* * %************************************************************************ \begin{code}

    cleanTempDirs :: DynFlags -> IO ()
    cleanTempDirs dflags
       = unless (dopt Opt_KeepTmpFiles dflags)
       $ do let ref = dirsToClean dflags
            ds <- readIORef ref
            removeTmpDirs dflags (Map.elems ds)
            writeIORef ref Map.empty

    cleanTempFiles :: DynFlags -> IO ()
    cleanTempFiles dflags
       = unless (dopt Opt_KeepTmpFiles dflags)
       $ do let ref = filesToClean dflags
            fs <- readIORef ref
            removeTmpFiles dflags fs
            writeIORef ref []

    cleanTempFilesExcept :: DynFlags -> [FilePath] -> IO ()
    cleanTempFilesExcept dflags dont_delete
       = unless (dopt Opt_KeepTmpFiles dflags)
       $ do let ref = filesToClean dflags
            files <- readIORef ref
            let (to_keep, to_delete) = partition (`elem` dont_delete) files
            removeTmpFiles dflags to_delete
            writeIORef ref to_keep

    -- find a temporary name that doesn't already exist.
    newTempName :: DynFlags -> Suffix -> IO FilePath
    newTempName dflags extn
      = do d <- getTempDir dflags
           x <- getProcessID
           findTempName (d </> "ghc" ++ show x ++ "_") 0
      where
        findTempName :: FilePath -> Integer -> IO FilePath
        findTempName prefix x
          = do let filename = (prefix ++ show x) <.> extn
               b  <- doesFileExist filename
               if b then findTempName prefix (x+1)
                    else do -- clean it up later
                            consIORef (filesToClean dflags) filename
                            return filename

    -- return our temporary directory within tmp_dir, creating one if we
    -- don't have one yet
    getTempDir :: DynFlags -> IO FilePath
    getTempDir dflags@(DynFlags{tmpDir=tmp_dir})
      = do let ref = dirsToClean dflags
           mapping <- readIORef ref
           case Map.lookup tmp_dir mapping of
               Nothing ->
                   do x <- getProcessID
                      let prefix = tmp_dir </> "ghc" ++ show x ++ "_"
                      let
                          mkTempDir :: Integer -> IO FilePath
                          mkTempDir x
                           = let dirname = prefix ++ show x
                             in do createDirectory dirname
                                   let mapping' = Map.insert tmp_dir dirname mapping
                                   writeIORef ref mapping'
                                   debugTraceMsg dflags 2 (ptext (sLit "Created temporary directory:") <+> text dirname)
                                   return dirname
                                `IO.catch` \e ->
                                        if isAlreadyExistsError e
                                        then mkTempDir (x+1)
                                        else ioError e
                      mkTempDir 0
               Just d -> return d

    addFilesToClean :: DynFlags -> [FilePath] -> IO ()
    -- May include wildcards [used by DriverPipeline.run_phase SplitMangle]
    addFilesToClean dflags files = mapM_ (consIORef (filesToClean dflags)) files

    removeTmpDirs :: DynFlags -> [FilePath] -> IO ()
    removeTmpDirs dflags ds
      = traceCmd dflags "Deleting temp dirs"
                 ("Deleting: " ++ unwords ds)
                 (mapM_ (removeWith dflags removeDirectory) ds)

    removeTmpFiles :: DynFlags -> [FilePath] -> IO ()
    removeTmpFiles dflags fs
      = warnNon $
        traceCmd dflags "Deleting temp files"
                 ("Deleting: " ++ unwords deletees)
                 (mapM_ (removeWith dflags removeFile) deletees)
      where
         -- Flat out refuse to delete files that are likely to be source input
         -- files (is there a worse bug than having a compiler delete your source
         -- files?)
         --
         -- Deleting source files is a sign of a bug elsewhere, so prominently flag
         -- the condition.
        warnNon act
         | null non_deletees = act
         | otherwise         = do
            putMsg dflags (text "WARNING - NOT deleting source files:" <+> hsep (map text non_deletees))
            act

        (non_deletees, deletees) = partition isHaskellUserSrcFilename fs

    removeWith :: DynFlags -> (FilePath -> IO ()) -> FilePath -> IO ()
    removeWith dflags remover f = remover f `IO.catch`
      (\e ->
       let msg = if isDoesNotExistError e
                 then ptext (sLit "Warning: deleting non-existent") <+> text f
                 else ptext (sLit "Warning: exception raised when deleting")
                                                <+> text f <> colon
                   $$ text (show e)
       in debugTraceMsg dflags 2 msg
      )

    -----------------------------------------------------------------------------
    -- Running an external program

    runSomething :: DynFlags
                 -> String          -- For -v message
                 -> String          -- Command name (possibly a full path)
                                    --      assumed already dos-ified
                 -> [Option]        -- Arguments
                                    --      runSomething will dos-ify them
                 -> IO ()

    runSomething dflags phase_name pgm args =
      runSomethingFiltered dflags id phase_name pgm args Nothing

    runSomethingFiltered
      :: DynFlags -> (String->String) -> String -> String -> [Option]
      -> Maybe [(String,String)] -> IO ()

    runSomethingFiltered dflags filter_fn phase_name pgm args mb_env = do
      let real_args = filter notNull (map showOpt args)
      traceCmd dflags phase_name (unwords (pgm:real_args)) $ do
      (exit_code, doesn'tExist) <-
         IO.catch (do
             rc <- builderMainLoop dflags filter_fn pgm real_args mb_env
             case rc of
               ExitSuccess{} -> return (rc, False)
               ExitFailure n
                 -- rawSystem returns (ExitFailure 127) if the exec failed for any
                 -- reason (eg. the program doesn't exist).  This is the only clue
                 -- we have, but we need to report something to the user because in
                 -- the case of a missing program there will otherwise be no output
                 -- at all.
                | n == 127  -> return (rc, True)
                | otherwise -> return (rc, False))
                    -- Should 'rawSystem' generate an IO exception indicating that
                    -- 'pgm' couldn't be run rather than a funky return code, catch
                    -- this here (the win32 version does this, but it doesn't hurt
                    -- to test for this in general.)
                  (\ err ->
                    if IO.isDoesNotExistError err
                     then return (ExitFailure 1, True)
                     else IO.ioError err)
      case (doesn'tExist, exit_code) of
         (True, _)        -> ghcError (InstallationError ("could not execute: " ++ pgm))
         (_, ExitSuccess) -> return ()
         _                -> ghcError (PhaseFailed phase_name exit_code)

    builderMainLoop :: DynFlags -> (String -> String) -> FilePath
                    -> [String] -> Maybe [(String, String)]
                    -> IO ExitCode
    builderMainLoop dflags filter_fn pgm real_args mb_env = do
      chan <- newChan
      (hStdIn, hStdOut, hStdErr, hProcess) <- runInteractiveProcess pgm real_args Nothing mb_env

      -- and run a loop piping the output from the compiler to the log_action in DynFlags
      hSetBuffering hStdOut LineBuffering
      hSetBuffering hStdErr LineBuffering
      _ <- forkIO (readerProc chan hStdOut filter_fn)
      _ <- forkIO (readerProc chan hStdErr filter_fn)
      -- we don't want to finish until 2 streams have been completed
      -- (stdout and stderr)
      -- nor until 1 exit code has been retrieved.
      rc <- loop chan hProcess (2::Integer) (1::Integer) ExitSuccess
      -- after that, we're done here.
      hClose hStdIn
      hClose hStdOut
      hClose hStdErr
      return rc
      where
        -- status starts at zero, and increments each time either
        -- a reader process gets EOF, or the build proc exits.  We wait
        -- for all of these to happen (status==3).
        -- ToDo: we should really have a contingency plan in case any of
        -- the threads dies, such as a timeout.
        loop _    _        0 0 exitcode = return exitcode
        loop chan hProcess t p exitcode = do
          mb_code <- if p > 0
                       then getProcessExitCode hProcess
                       else return Nothing
          case mb_code of
            Just code -> loop chan hProcess t (p-1) code
            Nothing
              | t > 0 -> do
                  msg <- readChan chan
                  case msg of
                    BuildMsg msg -> do
                      log_action dflags SevInfo noSrcSpan defaultUserStyle msg
                      loop chan hProcess t p exitcode
                    BuildError loc msg -> do
                      log_action dflags SevError (mkSrcSpan loc loc) defaultUserStyle msg
                      loop chan hProcess t p exitcode
                    EOF ->
                      loop chan hProcess (t-1) p exitcode
              | otherwise -> loop chan hProcess t p exitcode

    readerProc :: Chan BuildMessage -> Handle -> (String -> String) -> IO ()
    readerProc chan hdl filter_fn =
        (do str <- hGetContents hdl
            loop (linesPlatform (filter_fn str)) Nothing)
        `finally`
           writeChan chan EOF
            -- ToDo: check errors more carefully
            -- ToDo: in the future, the filter should be implemented as
            -- a stream transformer.
        where
            loop []     Nothing    = return ()
            loop []     (Just err) = writeChan chan err
            loop (l:ls) in_err     =
                    case in_err of
                      Just err@(BuildError srcLoc msg)
                        | leading_whitespace l -> do
                            loop ls (Just (BuildError srcLoc (msg $$ text l)))
                        | otherwise -> do
                            writeChan chan err
                            checkError l ls
                      Nothing -> do
                            checkError l ls
                      _ -> panic "readerProc/loop"

            checkError l ls
               = case parseError l of
                    Nothing -> do
                        writeChan chan (BuildMsg (text l))
                        loop ls Nothing
                    Just (file, lineNum, colNum, msg) -> do
                        let srcLoc = mkSrcLoc (mkFastString file) lineNum colNum
                        loop ls (Just (BuildError srcLoc (text msg)))

            leading_whitespace []    = False
            leading_whitespace (x:_) = isSpace x

    parseError :: String -> Maybe (String, Int, Int, String)
    parseError s0 = case breakColon s0 of
                    Just (filename, s1) ->
                        case breakIntColon s1 of
                        Just (lineNum, s2) ->
                            case breakIntColon s2 of
                            Just (columnNum, s3) ->
                                Just (filename, lineNum, columnNum, s3)
                            Nothing ->
                                Just (filename, lineNum, 0, s2)
                        Nothing -> Nothing
                    Nothing -> Nothing

    breakColon :: String -> Maybe (String, String)
    breakColon xs = case break (':' ==) xs of
                        (ys, _:zs) -> Just (ys, zs)
                        _ -> Nothing

    breakIntColon :: String -> Maybe (Int, String)
    breakIntColon xs = case break (':' ==) xs of
                           (ys, _:zs)
                            | not (null ys) && all isAscii ys && all isDigit ys ->
                               Just (read ys, zs)
                           _ -> Nothing

    data BuildMessage
      = BuildMsg   !SDoc
      | BuildError !SrcLoc !SDoc
      | EOF

    traceCmd :: DynFlags -> String -> String -> IO () -> IO ()
    -- a) trace the command (at two levels of verbosity)
    -- b) don't do it at all if dry-run is set
    traceCmd dflags phase_name cmd_line action
     = do   { let verb = verbosity dflags
            ; showPass dflags phase_name
            ; debugTraceMsg dflags 3 (text cmd_line)
            ; hFlush stderr

               -- Test for -n flag
            ; unless (dopt Opt_DryRun dflags) $ do {

               -- And run it!
            ; action `IO.catch` handle_exn verb
            }}
      where
        handle_exn _verb exn = do { debugTraceMsg dflags 2 (char '\n')
                                  ; debugTraceMsg dflags 2 (ptext (sLit "Failed:") <+> text cmd_line <+> text (show exn))
                                  ; ghcError (PhaseFailed phase_name (ExitFailure 1)) }

\end{code} %************************************************************************ %* * \subsection{Support code} %* * %************************************************************************ \begin{code}

    -----------------------------------------------------------------------------
    -- Define       getBaseDir     :: IO (Maybe String)

    getBaseDir :: IO (Maybe String)
    #if defined(mingw32_HOST_OS)
    -- Assuming we are running ghc, accessed by path  $(stuff)/bin/ghc.exe,
    -- return the path $(stuff)/lib.
    getBaseDir = do let len = (2048::Int) -- plenty, PATH_MAX is 512 under Win32.
                    buf <- mallocArray len
                    ret <- getModuleFileName nullPtr buf len
                    if ret == 0 then free buf >> return Nothing
                                else do s <- peekCString buf
                                        free buf
                                        return (Just (rootDir s))
      where
        rootDir s = case splitFileName $ normalise s of
                    (d, ghc_exe)
                     | lower ghc_exe `elem` ["ghc.exe",
                                             "ghc-stage1.exe",
                                             "ghc-stage2.exe",
                                             "ghc-stage3.exe"] ->
                        case splitFileName $ takeDirectory d of
                        -- ghc is in $topdir/bin/ghc.exe
                        (d', bin) | lower bin == "bin" -> takeDirectory d' </> "lib"
                        _ -> fail
                    _ -> fail
            where fail = panic ("can't decompose ghc.exe path: " ++ show s)
                  lower = map toLower

    foreign import stdcall unsafe "GetModuleFileNameA"
      getModuleFileName :: Ptr () -> CString -> Int -> IO Int32
    #else
    getBaseDir = return Nothing
    #endif

    #ifdef mingw32_HOST_OS
    foreign import ccall unsafe "_getpid" getProcessID :: IO Int -- relies on Int == Int32 on Windows
    #else
    getProcessID :: IO Int
    getProcessID = System.Posix.Internals.c_getpid >>= return . fromIntegral
    #endif

    -- Divvy up text stream into lines, taking platform dependent
    -- line termination into account.
    linesPlatform :: String -> [String]
    #if !defined(mingw32_HOST_OS)
    linesPlatform ls = lines ls
    #else
    linesPlatform "" = []
    linesPlatform xs =
      case lineBreak xs of
        (as,xs1) -> as : linesPlatform xs1
      where
       lineBreak "" = ("","")
       lineBreak ('\r':'\n':xs) = ([],xs)
       lineBreak ('\n':xs) = ([],xs)
       lineBreak (x:xs) = let (as,bs) = lineBreak xs in (x:as,bs)

    #endif

\end{code}