    -----------------------------------------------------------------------------
    -- |
    -- Module      :  Distribution.Simple.Program.Ld
    -- Copyright   :  Duncan Coutts 2009
    --
    -- Maintainer  :  cabal-devel@haskell.org
    -- Portability :  portable
    --
    -- This module provides an library interface to the @ld@ linker program.

    module Distribution.Simple.Program.Ld (
        combineObjectFiles,
      ) where

    import Distribution.Simple.Program.Types
             ( ConfiguredProgram(..) )
    import Distribution.Simple.Program.Run
             ( programInvocation, multiStageProgramInvocation
             , runProgramInvocation )
    import Distribution.Verbosity
             ( Verbosity )

    import System.Directory
             ( renameFile )
    import System.FilePath
             ( (<.>) )

    -- | Call @ld -r@ to link a bunch of object files together.
    --
    combineObjectFiles :: Verbosity -> ConfiguredProgram
                       -> FilePath -> [FilePath] -> IO ()
    combineObjectFiles verbosity ld target files =

      -- Unlike "ar", the "ld" tool is not designed to be used with xargs. That is,
      -- if we have more object files than fit on a single command line then we
      -- have a slight problem. What we have to do is link files in batches into
      -- a temp object file and then include that one in the next batch.

      let simpleArgs  = ["-r", "-o", target]

          initialArgs = ["-r", "-o", target]
          middleArgs  = ["-r", "-o", target, tmpfile]
          finalArgs   = middleArgs

          simple      = programInvocation ld simpleArgs
          initial     = programInvocation ld initialArgs
          middle      = programInvocation ld middleArgs
          final       = programInvocation ld finalArgs

          invocations = multiStageProgramInvocation
                          simple (initial, middle, final) files

       in run invocations

      where
        tmpfile        = target <.> "tmp" -- perhaps should use a proper temp file

        run []         = return ()
        run [inv]      = runProgramInvocation verbosity inv
        run (inv:invs) = do runProgramInvocation verbosity inv
                            renameFile target tmpfile
                            run invs