Adding TODOs regarding more robust build proceedures [skip ci]

Cabal/Distribution/Simple/GHC.hs

@@ -1352,6 +1352,10 @@ gbuild verbosity numJobs pkg_descr lbi bm clbi = do
               opts | needProfiling = profCxxOpts
                    | needDynamic   = sharedCxxOpts
                    | otherwise     = vanillaCxxOpts
+              -- TODO: Placing all Haskell, C, & C++ objects in a single directory
+              --       Has the potential for file collisions. In general we would
+              --       consider this a user error. However, we should strive to
+              --       add a warning if this occurs.
               odir = fromFlag (ghcOptObjDir opts)
           createDirectoryIfMissingVerbose verbosity True odir
           needsRecomp <- checkNeedsRecompilation filename opts

Cabal/Distribution/Simple/PreProcess.hs

@@ -538,6 +538,9 @@ ppC2hsExtras d = filter (\p -> takeExtensions p == ".chs.c") `fmap`
 
 --TODO: perhaps use this with hsc2hs too
 --TODO: remove cc-options from cpphs for cabal-version: >= 1.10
+--TODO: Refactor and add seperate 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