content: {-# LANGUAGE RecordWildCards #-}
  
  -- | This module manages storing the various GHC option flags in a modules
  -- interface file as part of the recompilation checking infrastructure.
  module Eta.Iface.FlagChecker (
          fingerprintDynFlags
      ) where
  
  import Eta.Utils.Binary
  import Eta.Iface.BinIface ()
  import Eta.Main.DynFlags
  import Eta.Main.HscTypes
  import Eta.BasicTypes.Module
  import Eta.BasicTypes.Name
  import Eta.Utils.Fingerprint
  import Eta.Iface.BinFingerprint
  -- import Eta.Utils.Outputable
  import qualified Eta.Utils.EnumSet as EnumSet
  import System.FilePath (normalise)
  
  -- | Produce a fingerprint of a @DynFlags@ value. We only base
  -- the finger print on important fields in @DynFlags@ so that
  -- the recompilation checker can use this fingerprint.
  fingerprintDynFlags :: DynFlags -> Module
                      -> (BinHandle -> Name -> IO ())
                      -> IO Fingerprint
  
  fingerprintDynFlags dflags@DynFlags{..} this_mod nameio =
      let mainis   = if mainModIs == this_mod then Just mainFunIs else Nothing
                        -- see #5878
          -- pkgopts  = (thisPackage dflags, sort $ packageFlags dflags)
          safeHs   = setSafeMode safeHaskell
          -- oflags   = sort $ filter filterOFlags $ flags dflags
  
          -- *all* the extension flags and the language
          lang = (fmap fromEnum language,
                  map fromEnum $ EnumSet.toList extensionFlags)
  
          -- -I, -D and -U flags affect CPP
          cpp = (map normalise includePaths, opt_P dflags ++ picPOpts dflags)
              -- normalise: eliminate spurious differences due to "./foo" vs "foo"
  
          -- Note [path flags and recompilation]
          paths = [ hcSuf ]
  
          -- -fprof-auto etc.
          prof = if gopt Opt_SccProfilingOn dflags then fromEnum profAuto else 0
  
      in -- pprTrace "flags" (ppr (mainis, safeHs, lang, cpp, paths)) $
         computeFingerprint nameio (mainis, safeHs, lang, cpp, paths, prof)
  
  
  {- Note [path flags and recompilation]
  
  There are several flags that we deliberately omit from the
  recompilation check; here we explain why.
  
  -osuf, -odir, -hisuf, -hidir
    If GHC decides that it does not need to recompile, then
    it must have found an up-to-date .hi file and .o file.
    There is no point recording these flags - the user must
    have passed the correct ones.  Indeed, the user may
    have compiled the source file in one-shot mode using
    -o to specify the .o file, and then loaded it in GHCi
    using -odir.
  
  -stubdir
    We omit this one because it is automatically set by -outputdir, and
    we don't want changes in -outputdir to automatically trigger
    recompilation.  This could be wrong, but only in very rare cases.
  
  -i (importPaths)
    For the same reason as -osuf etc. above: if GHC decides not to
    recompile, then it must have already checked all the .hi files on
    which the current module depends, so it must have found them
    successfully.  It is occasionally useful to be able to cd to a
    different directory and use -i flags to enable GHC to find the .hi
    files; we don't want this to force recompilation.
  
  The only path-related flag left is -hcsuf.
  -}
  