Add --supported-languages support to dummy-ghc

We used to call the bootstrapping compiler to get its --supported-languages
but that doesn't work when it doesn't support all the extensions that we
need. In particular, compiling the new bytestring which needs NamedFieldPuns
broken when building with 6.8.2.
There's now a rather ugly sed script to extract the extensions from
DynFlags.hs.

diff --git a/utils/ghc-cabal/ghc.mk b/utils/ghc-cabal/ghc.mk
index 71232fb..b4b599d 100644 (file)
--- a/utils/ghc-cabal/ghc.mk
+++ b/utils/ghc-cabal/ghc.mk
@@ -51,10 +51,34 @@ $(GHC_CABAL_DIR)_dist-dummy-ghc_MODULES = dummy-ghc
 $(GHC_CABAL_DIR)_dist-dummy-ghc_PROG    = dummy-ghc$(exeext)
 
 # depend on project.mk, so we pick up the new version number if it changes.
-$(GHC_CABAL_DIR)/dist-dummy-ghc/build/dummy-ghc.hs : $(GHC_CABAL_DIR)/ghc.mk mk/project.mk | $$(dir $$@)/.
-       echo "import System.Environment; import System.Cmd; import System.Exit" >$@
-       echo "main :: IO ()" >>$@
-       echo "main = do args <- getArgs; if args == [\"--numeric-version\"] then putStrLn \"$(ProjectVersion)\" else do e <- rawSystem \"$(GHC_STAGE0)\" args; exitWith e" >>$@
+$(GHC_CABAL_DIR)/dist-dummy-ghc/build/dummy-ghc.hs : $(GHC_CABAL_DIR)/ghc.mk $(MKDIRHIER) mk/project.mk compiler/main/DynFlags.hs
+       "$(MKDIRHIER)" $(dir $@)
+       "$(RM)" $(RM_OPTS) $@
+       echo 'import System.Environment'                                  >> $@
+       echo 'import System.Cmd'                                          >> $@
+       echo 'import System.Exit'                                         >> $@
+       echo 'main :: IO ()'                                              >> $@
+       echo 'main = do args <- getArgs'                                  >> $@
+       echo '          case args of'                                     >> $@
+       echo '              ["--numeric-version"] ->'                     >> $@
+       echo '                  putStrLn "$(ProjectVersion)"'             >> $@
+       echo '              ["--supported-languages"] ->'                 >> $@
+       echo '                  mapM_ putStrLn extensions'                >> $@
+       echo '              _ ->'                                         >> $@
+       echo '                  do e <- rawSystem "$(GHC_STAGE0)" args'   >> $@
+       echo '                     exitWith e'                            >> $@
+# This unpleasant sed script grabs the lines between the
+#      xFlags ::
+# line and the
+#   ]
+# line of compiler/main/DynFlags.hs, and if they look like
+#   ( "PostfixOperators", ...
+# then it translates them into
+#   ["PostfixOperators"] ++
+       echo 'extensions :: [String]'                                     >> $@
+       echo 'extensions ='                                               >> $@
+       sed '/^xFlags/,/]/{/^  (/{s/^[^"]*"/  ["/; s/"[^"]*$$/"] ++/; p}}; d' compiler/main/DynFlags.hs >> $@
+       echo '  []'                                                       >> $@
 
 # We don't build dummy-ghc with Cabal, so we need to pass -package
 # flags manually