Always pass -hide-all-packages to ghc.

Makes error messages more obvious.

GHC/ParMake/Engine.hs

@@ -72,8 +72,9 @@ workerThread outHooks verbosity totNum ghcArgs wch cch
 
     runGHC :: [String] -> IO ExitCode
     runGHC args =
-      do debug outHooks verbosity $ show ("ghc":args)
-         runProcess outHooks Nothing "ghc" args
+      do let args' = "-hide-all-packages":args
+         debug outHooks verbosity $ show ("ghc":args')
+         runProcess outHooks Nothing "ghc" args'
 
     onSuccess :: ExitCode -> ControlMessage -> ControlMessage -> IO ()
     onSuccess exitCode msgSucc msgFail =

README

@@ -27,5 +27,7 @@ Known limitations:
 
       * Building libraries is not yet supported.
       * Build fails when -odir != -hidir.
+      * Unlike 'ghc --make', ghc-parmake can't figure out package dependencies automatically,
+        so you'll need to specify them by hand with the -package option.
       * -hisuf/-osuf are not supported (needed for building libs for profiling).
       * Tested only on Linux.

tests/Tests.hs

@@ -108,7 +108,7 @@ mkTestCase dirName numJobs =
      curDir <- getCurrentDirectory
      createDirectory oDir
      exitCode <- getExitCode (curDir </> makeProgram)
-                 [ "Main.hs", "-j", show numJobs
+                 [ "Main.hs", "-package", "base", "-j", show numJobs
                  , "-odir", oDirName, "-hidir", oDirName] testDir
      assertEqual "ghc-parmake invocation failed!" ExitSuccess exitCode
      removeDirectoryRecursive oDir