Make ambient MinGW support a proper settings

Get rid of `USE_INPLACE_MINGW_TOOLCHAIN` and use a settings file entry
instead.

The CPP setting was originally introduced in f065b6b012.

4 files changed, 39 insertions, 26 deletions

diff --git a/compiler/GHC/Driver/Session.hs b/compiler/GHC/Driver/Session.hs
index 2a4d5aae3c..ccf4d18f2f 100644
--- a/compiler/GHC/Driver/Session.hs
+++ b/compiler/GHC/Driver/Session.hs
@@ -4544,8 +4544,9 @@ compilerInfo dflags
     showBool False = "NO"
     platform  = targetPlatform dflags
     isWindows = platformOS platform == OSMinGW32
+    useInplaceMinGW = toolSettings_useInplaceMinGW $ toolSettings dflags
     expandDirectories :: FilePath -> Maybe FilePath -> String -> String
-    expandDirectories topd mtoold = expandToolDir mtoold . expandTopDir topd
+    expandDirectories topd mtoold = expandToolDir useInplaceMinGW mtoold . expandTopDir topd
 
 
 wordAlignment :: Platform -> Alignment
diff --git a/compiler/GHC/Settings.hs b/compiler/GHC/Settings.hs
index 73f3b97b54..679d0266fe 100644
--- a/compiler/GHC/Settings.hs
+++ b/compiler/GHC/Settings.hs
@@ -22,6 +22,7 @@ module GHC.Settings
   , sLdSupportsFilelist
   , sLdIsGnuLd
   , sGccSupportsNoPie
+  , sUseInplaceMinGW
   , sPgm_L
   , sPgm_P
   , sPgm_F
@@ -89,6 +90,7 @@ data ToolSettings = ToolSettings
   , toolSettings_ldSupportsFilelist      :: Bool
   , toolSettings_ldIsGnuLd               :: Bool
   , toolSettings_ccSupportsNoPie         :: Bool
+  , toolSettings_useInplaceMinGW         :: Bool
 
   -- commands for particular phases
   , toolSettings_pgm_L       :: String
@@ -190,6 +192,8 @@ sLdIsGnuLd :: Settings -> Bool
 sLdIsGnuLd = toolSettings_ldIsGnuLd . sToolSettings
 sGccSupportsNoPie :: Settings -> Bool
 sGccSupportsNoPie = toolSettings_ccSupportsNoPie . sToolSettings
+sUseInplaceMinGW :: Settings -> Bool
+sUseInplaceMinGW = toolSettings_useInplaceMinGW . sToolSettings
 
 sPgm_L :: Settings -> String
 sPgm_L = toolSettings_pgm_L . sToolSettings
diff --git a/compiler/GHC/Settings/IO.hs b/compiler/GHC/Settings/IO.hs
index 1e56d1c087..7d9be2f403 100644
--- a/compiler/GHC/Settings/IO.hs
+++ b/compiler/GHC/Settings/IO.hs
@@ -35,12 +35,6 @@ initSettings
   => String -- ^ TopDir path
   -> ExceptT SettingsError m Settings
 initSettings top_dir = do
-  -- see Note [topdir: How GHC finds its files]
-  -- NB: top_dir is assumed to be in standard Unix
-  -- format, '/' separated
-  mtool_dir <- liftIO $ findToolDir top_dir
-        -- see Note [tooldir: How GHC finds mingw on Windows]
-
   let installed :: FilePath -> FilePath
       installed file = top_dir </> file
       libexec :: FilePath -> FilePath
@@ -58,24 +52,31 @@ initSettings top_dir = do
     Nothing -> throwE $ SettingsError_BadData $
       "Can't parse " ++ show settingsFile
   let mySettings = Map.fromList settingsList
+      getBooleanSetting :: String -> ExceptT SettingsError m Bool
+      getBooleanSetting key = either pgmError pure $
+        getRawBooleanSetting settingsFile mySettings key
+
+  -- On Windows, by mingw is often distributed with GHC,
+  -- so we look in TopDir/../mingw/bin,
+  -- as well as TopDir/../../mingw/bin for hadrian.
+  -- But we might be disabled, in which we we don't do that.
+  useInplaceMinGW <- getBooleanSetting "Use inplace MinGW toolchain"
+
+  -- see Note [topdir: How GHC finds its files]
+  -- NB: top_dir is assumed to be in standard Unix
+  -- format, '/' separated
+  mtool_dir <- liftIO $ findToolDir useInplaceMinGW top_dir
+        -- see Note [tooldir: How GHC finds mingw on Windows]
+
   -- See Note [Settings file] for a little more about this file. We're
   -- just partially applying those functions and throwing 'Left's; they're
   -- written in a very portable style to keep ghc-boot light.
   let getSetting key = either pgmError pure $
         getRawFilePathSetting top_dir settingsFile mySettings key
       getToolSetting :: String -> ExceptT SettingsError m String
-      getToolSetting key = expandToolDir mtool_dir <$> getSetting key
-      getBooleanSetting :: String -> ExceptT SettingsError m Bool
-      getBooleanSetting key = either pgmError pure $
-        getRawBooleanSetting settingsFile mySettings key
+      getToolSetting key = expandToolDir useInplaceMinGW mtool_dir <$> getSetting key
   targetPlatformString <- getSetting "target platform string"
   myExtraGccViaCFlags <- getSetting "GCC extra via C opts"
-  -- On Windows, mingw is distributed with GHC,
-  -- so we look in TopDir/../mingw/bin,
-  -- as well as TopDir/../../mingw/bin for hadrian.
-  -- It would perhaps be nice to be able to override this
-  -- with the settings file, but it would be a little fiddly
-  -- to make that possible, so for now you can't.
   cc_prog <- getToolSetting "C compiler command"
   cc_args_str <- getSetting "C compiler flags"
   cxx_args_str <- getSetting "C++ compiler flags"
@@ -162,6 +163,7 @@ initSettings top_dir = do
       , toolSettings_ldSupportsFilelist      = ldSupportsFilelist
       , toolSettings_ldIsGnuLd               = ldIsGnuLd
       , toolSettings_ccSupportsNoPie         = gccSupportsNoPie
+      , toolSettings_useInplaceMinGW         = useInplaceMinGW
 
       , toolSettings_pgm_L   = unlit_path
       , toolSettings_pgm_P   = (cpp_prog, cpp_args)
diff --git a/compiler/GHC/SysTools/BaseDir.hs b/compiler/GHC/SysTools/BaseDir.hs
index 03169523c6..c0a1fa2cee 100644
--- a/compiler/GHC/SysTools/BaseDir.hs
+++ b/compiler/GHC/SysTools/BaseDir.hs
@@ -139,12 +139,16 @@ play nice with the system compiler instead.
 
 -- | Expand occurrences of the @$tooldir@ interpolation in a string
 -- on Windows, leave the string untouched otherwise.
-expandToolDir :: Maybe FilePath -> String -> String
-#if defined(mingw32_HOST_OS) && !defined(USE_INPLACE_MINGW_TOOLCHAIN)
-expandToolDir (Just tool_dir) s = expandPathVar "tooldir" tool_dir s
-expandToolDir Nothing         _ = panic "Could not determine $tooldir"
+expandToolDir
+  :: Bool -- ^ whether we are use the ambiant mingw toolchain
+  -> Maybe FilePath -- ^ tooldir
+  -> String -> String
+#if defined(mingw32_HOST_OS)
+expandToolDir False (Just tool_dir) s = expandPathVar "tooldir" tool_dir s
+expandToolDir False Nothing         _ = panic "Could not determine $tooldir"
+expandToolDir True  _               s = s
 #else
-expandToolDir _ s = s
+expandToolDir _ _ s = s
 #endif
 
 -- | Returns a Unix-format path pointing to TopDir.
@@ -180,10 +184,11 @@ tryFindTopDir Nothing
 -- tooldir can't be located, or returns @Just tooldirpath@.
 -- If the distro toolchain is being used we treat Windows the same as Linux
 findToolDir
-  :: FilePath -- ^ topdir
+  :: Bool -- ^ whether we are use the ambiant mingw toolchain
+  -> FilePath -- ^ topdir
   -> IO (Maybe FilePath)
-#if defined(mingw32_HOST_OS) && !defined(USE_INPLACE_MINGW_TOOLCHAIN)
-findToolDir top_dir = go 0 (top_dir </> "..") []
+#if defined(mingw32_HOST_OS)
+findToolDir False top_dir = go 0 (top_dir </> "..") []
   where maxDepth = 3
         go :: Int -> FilePath -> [FilePath] -> IO (Maybe FilePath)
         go k path tried
@@ -196,6 +201,7 @@ findToolDir top_dir = go 0 (top_dir </> "..") []
               if oneLevel
                 then return (Just path)
                 else go (k+1) (path </> "..") tried
+findToolDir True _ = return Nothing
 #else
-findToolDir _ = return Nothing
+findToolDir _ _ = return Nothing
 #endif