Add Werror to CC and HC (#309)

src/Settings/Builders/Cc.hs

@@ -8,7 +8,10 @@ ccBuilderArgs = builder Cc ? mconcat
     , argSettingList . ConfCcArgs =<< getStage
     , cIncludeArgs
 
-    , builder (Cc CompileC) ? mconcat [ arg "-c", arg =<< getInput
+    , builder (Cc CompileC) ? mconcat [ arg "-Werror"
+                                      -- mk/warning.mk:
+                                      --  SRC_CC_OPTS     += -Wall $(WERROR)
+                                      , arg "-c", arg =<< getInput
                                       , arg "-o", arg =<< getOutput ]
 
     , builder (Cc FindCDependencies) ? do

src/Settings/Default.hs

@@ -65,10 +65,24 @@ defaultArgs = mconcat
     , sourceArgs defaultSourceArgs
     , defaultPackageArgs ]
 
+-- | Default flags about Werror
+-- | mk/warnings.mk
+defaultErrorGhcFlags :: Args
+defaultErrorGhcFlags =
+  mconcat [ notStage0 ? arg "-Werror"
+          , (not <$> flag GccIsClang) ? mconcat [
+                (not <$> flag GccLt46) ? (not <$> windowsHost) ?
+                  arg "-Werror=unused-but-set-variable"
+              , (not <$> flag GccLt44) ? arg "-Wno-error=inline" ]
+          , flag GccIsClang ? arg "-Wno-unknown-pragmas" ]
+
 -- | Default source arguments, e.g. optimisation settings.
 defaultSourceArgs :: SourceArgs
 defaultSourceArgs = SourceArgs
-    { hsDefault  = mconcat [stage0 ? arg "-O", notStage0 ? arg "-O2", arg "-H32m"]
+    { hsDefault  = mconcat [ stage0 ? arg "-O"
+                           , notStage0 ? arg "-O2"
+                           , arg "-H32m"
+                           , defaultErrorGhcFlags ]
     , hsLibrary  = mempty
     , hsCompiler = mempty
     , hsGhc      = mempty }

src/Settings/Packages/GhcPrim.hs

@@ -10,4 +10,5 @@ ghcPrimPackageArgs = package ghcPrim ? mconcat
 
     , builder (Cc CompileC)    ?
       (not <$> flag GccLt44)   ?
+      (not <$> flag GccIsClang) ?
       input "//cbits/atomic.c" ? arg "-Wno-sync-nand" ]

src/Settings/Packages/Rts.hs

@@ -89,7 +89,9 @@ rtsPackageArgs = package rts ? do
             , inputs ["//Evac.c", "//Evac_thr.c"] ? arg "-funroll-loops"
 
             , inputs ["//Evac_thr.c", "//Scav_thr.c"] ?
-              append [ "-DPARALLEL_GC", "-Irts/sm" ] ]
+              append [ "-DPARALLEL_GC", "-Irts/sm" ]
+
+            , input "//StgCRun.c" ? windowsHost ? arg "-Wno-return-local-addr" ]
 
         , builder Ghc ? arg "-Irts"