Document how to use GHCup's msys2 with stack, fixes #1040

Plus a tiny bit of copy editing.

.github/workflows/cross.yaml

@@ -21,8 +21,8 @@ jobs:
     name: Build linux binary
     runs-on: [self-hosted, Linux, X64, maerwald]
     env:
-      CABAL_VER: 3.10.1.0
-      JSON_VERSION: "0.0.7"
+      CABAL_VER: 3.10.3.0
+      JSON_VERSION: "0.0.8"
       AWS_SECRET_ACCESS_KEY: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
       AWS_ACCESS_KEY_ID: ${{ secrets.AWS_ACCESS_KEY_ID }}
       S3_HOST: ${{ secrets.S3_HOST }}
@@ -31,7 +31,7 @@ jobs:
       ARCH: 64
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           submodules: 'true'
 
@@ -50,7 +50,7 @@ jobs:
 
       - if: always()
         name: Upload artifact
-        uses: actions/upload-artifact@v3
+        uses: actions/upload-artifact@v4
         with:
           name: artifacts
           path: |
@@ -61,13 +61,13 @@ jobs:
     needs: "build"
     runs-on: [self-hosted, Linux, X64]
     container:
-      image: registry.gitlab.haskell.org/ghc/ci-images/x86_64-linux-deb10:8d0224e6b2a08157649651e69302380b2bd24e11
+      image: registry.gitlab.haskell.org/ghc/ci-images/x86_64-linux-deb12:a9297a370025101b479cfd4977f8f910814e03ab
       options: --user root
       env:
-        CABAL_VER: 3.6.2.0
+        CABAL_VER: 3.10.3.0
         BUILD_CONF_ARGS: "--enable-unregisterised"
         HADRIAN_FLAVOUR: ""
-        JSON_VERSION: "0.0.7"
+        JSON_VERSION: "0.0.8"
         GHC_VER: 8.10.6
         GHC_TARGET_VERSION: "8.10.7"
         ARCH: 64
@@ -77,11 +77,11 @@ jobs:
         WRAPPER: "run"
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           submodules: 'true'
 
-      - uses: actions/download-artifact@v3
+      - uses: actions/download-artifact@v4
         with:
           name: artifacts
           path: ./out
@@ -89,11 +89,18 @@ jobs:
       - name: Run test (64 bit linux)
         run: |
           sudo apt-get update -y
-          sudo apt-get install -y libnuma-dev zlib1g-dev libgmp-dev libgmp10 libssl-dev liblzma-dev libbz2-dev git wget lsb-release software-properties-common gnupg2 apt-transport-https gcc autoconf automake build-essential curl gzip
-          sudo apt-get install -y gcc-arm-linux-gnueabihf
+          sudo apt-get install -y libnuma-dev zlib1g-dev libgmp-dev libgmp10 libssl-dev liblzma-dev libbz2-dev git wget lsb-release software-properties-common gnupg2 apt-transport-https gcc autoconf automake build-essential curl gzip libstdc++-11-dev
+          sudo apt-get install -y gcc-arm-linux-gnueabihf g++-arm-linux-gnueabihf
           sudo dpkg --add-architecture armhf
           sudo apt-get update -y
-          sudo apt-get install -y libncurses-dev:armhf
+          sudo apt-get install -y libncurses-dev:armhf libstdc++-11-dev:armhf
+          # ld.bfd is broken on armv7: https://sourceware.org/bugzilla/show_bug.cgi?id=16177
+          update-alternatives --install "/usr/bin/x86_64-linux-gnu-ld" "ld" "/usr/bin/x86_64-linux-gnu-ld.gold" 20
+          update-alternatives --install "/usr/bin/x86_64-linux-gnu-ld" "ld" "/usr/bin/x86_64-linux-gnu-ld.bfd" 10
+          update-alternatives --set "ld" "/usr/bin/x86_64-linux-gnu-ld.gold"
+          update-alternatives --install "/usr/bin/arm-linux-gnueabihf-ld" "ld-arm" "/usr/bin/arm-linux-gnueabihf-ld.gold" 20
+          update-alternatives --install "/usr/bin/arm-linux-gnueabihf-ld" "ld-arm" "/usr/bin/arm-linux-gnueabihf-ld.bfd" 10
+          update-alternatives --set "ld-arm" "/usr/bin/arm-linux-gnueabihf-ld.gold"
           sh .github/scripts/cross.sh
 
   test-cross-js:
@@ -101,13 +108,13 @@ jobs:
     needs: "build"
     runs-on: [self-hosted, Linux, X64]
     container:
-      image: registry.gitlab.haskell.org/ghc/ci-images/x86_64-linux-deb10:8d0224e6b2a08157649651e69302380b2bd24e11
+      image: registry.gitlab.haskell.org/ghc/ci-images/x86_64-linux-deb12:a9297a370025101b479cfd4977f8f910814e03ab
       options: --user root
       env:
-        CABAL_VER: 3.6.2.0
+        CABAL_VER: 3.10.3.0
         BUILD_CONF_ARGS: ""
         HADRIAN_FLAVOUR: "default+native_bignum"
-        JSON_VERSION: "0.0.7"
+        JSON_VERSION: "0.0.8"
         GHC_VER: 9.6.2
         GHC_TARGET_VERSION: "9.6.2"
         ARCH: 64
@@ -117,11 +124,11 @@ jobs:
         WRAPPER: "emconfigure"
     steps:
       - name: Checkout code
-        uses: actions/checkout@v3
+        uses: actions/checkout@v4
         with:
           submodules: 'true'
 
-      - uses: actions/download-artifact@v3
+      - uses: actions/download-artifact@v4
         with:
           name: artifacts
           path: ./out

.github/workflows/release.yaml

@@ -126,6 +126,7 @@ jobs:
           AWS_SECRET_ACCESS_KEY: ${{ env.AWS_SECRET_ACCESS_KEY }}
           AWS_ACCESS_KEY_ID: ${{ env.AWS_ACCESS_KEY_ID }}
           S3_HOST: ${{ env.S3_HOST }}
+          LD: ld.gold
 
       - if: matrix.ARCH == 'ARM64'
         uses: docker://hasufell/arm64v8-debian-haskell:10
@@ -397,6 +398,7 @@ jobs:
           ARCH: ${{ matrix.ARCH }}
           GHC_VER: ${{ matrix.GHC_VER }}
           DISTRO: Ubuntu
+          LD: ld.gold
 
       - if: matrix.ARCH == 'ARM64'
         uses: docker://hasufell/arm64v8-debian-haskell:10

.github/workflows/stack.yaml

@@ -30,7 +30,6 @@ jobs:
         run: |
           env
           ghcup --version
-          ghcup config add-release-channel https://raw.githubusercontent.com/haskell/ghcup-metadata/master/ghcup-prereleases-0.0.8.yaml
-          ghcup run -i --stack latest-prerelease -- stack build
+          ghcup run -i --stack latest -- stack build
         shell: bash
 

app/ghcup/Main.hs

@@ -90,6 +90,7 @@ toSettings options = do
          gpgSetting  = fromMaybe (fromMaybe (Types.gpgSetting defaultSettings) uGPGSetting) optGpg
          platformOverride = optPlatform <|> (uPlatformOverride <|> Types.platformOverride defaultSettings)
          mirrors  = fromMaybe (Types.mirrors defaultSettings) uMirrors
+         defGHCConfOptions  = fromMaybe (Types.defGHCConfOptions defaultSettings) uDefGHCConfOptions
      in (Settings {..}, keyBindings)
 #if defined(INTERNAL_DOWNLOADER)
    defaultDownloader = Internal

data/config.yaml

@@ -128,3 +128,12 @@ mirrors:
     authority:
       host: "mirror.sjtu.edu.cn"
 
+# Arguments to pass to the configure script of the prebuilt bindist.
+#
+# Do not pass '--prefix' here.
+#
+# GHCup by default passes '--disable-ld-override', so if you want to enable
+# the vanilla way, which aggressively favors 'ld.gold' linker, add the following:
+def-ghc-conf-options:
+  - "--enable-ld-override"
+

docs/about.md

@@ -40,6 +40,80 @@ All you wanted to know about GHCup.
 * [haskell.org](https://www.haskell.org/haskell-org-committee/) via CI and infrastructure
 * [Haskell Foundation](https://haskell.foundation/affiliates/) via affiliation
 
+## Project ownership and hierarchy
+
+The project at the time of writing (2024-04-22) follows the model of
+[benevolent dictator for life](https://en.wikipedia.org/wiki/Benevolent_dictator_for_life), which is
+Julian Ospald at the moment.
+
+Ideally, the ownership should be shared across a core team of collaborators sharing the same vision and
+engagement in the future.
+
+I do not believe in people making decisions over projects they are barely involved in. Instead I believe
+in listening to end users needs very carefully and making decisions based on that. People who want a direct
+influence on the decision process have to both demonstrate they share the vision of GHCup and do the actual
+work.
+
+"Work" here doesn't have to be "writing code". There are many ways to be engaged in a project.
+
+### Transition plan in case of maintainer absence
+
+In case the current maintainer of GHCup (Julian Ospald) is unreachable for a prolonged period of time (3 months),
+the ownership of this project will be automatically transferred to the following individuals:
+
+- [Moritz Angerman](https://github.com/angerman)
+- [Andrew Lelechenko](https://github.com/Bodigrim)
+
+They will be tasked with finding new maintainers in whatever way they see fit (be it appointing themselves or asking HF for help).
+
+The appointed owners may choose to stay owners after the transition period (whether it's in a passive or active capacity) or
+fully transfer ownership to someone else or an organization.
+
+The community shall be informed about this process.
+
+If not otherwise specified by the newly appointed owners, the following principles shall apply to the *transition period*:
+
+#### During the transition period
+
+During the transition period, no other individual or organization is allowed to drive changes to
+[ghcup-hs](https://github.com/haskell/ghcup-hs) repository, unless they are explicitly allowed to do so by the appointed owners.
+
+The following people (in addition to the owners) shall have full write access to the
+[ghcup-metadata](https://github.com/haskell/ghcup-metadata) repository
+(all files) for the length of the transition period, unless otherwise specified by the appointed owners:
+
+- [Ben Gamari](https://github.com/bgamari)
+- [Hécate Moonlight](https://github.com/Kleidukos)
+- [Mike Pilgrem](https://github.com/mpilgrem)
+- [Jens Petersen](https://github.com/juhp)
+
+Contributions to the metadata are expected to follow a review process. If that turns out to be impractical due to lack of engagement, a wait
+time of 2 days before merging shall be followed anyway, except for the `-vanilla` files, which may be merged at any time.
+
+#### Access
+
+The GHCup website, various scripts and unofficial bindists are hosted on haskell.org infrastructure. Contact the
+[Haskell.org committee](https://www.haskell.org/haskell-org-committee/) for access.
+
+The backup owners should already have admin rights on the GHCup repositories, which are hosted on the
+[Github haskell namespace](https://github.com/haskell). In case of issues contact one of the
+organization admins for access, e.g.:
+
+- [Andrew Lelechenko](https://github.com/orgs/haskell/people/Bodigrim)
+- [gbaz](https://github.com/orgs/haskell/people/gbaz)
+- [Hécate Moonlight](https://github.com/Kleidukos)
+- [davean](https://github.com/orgs/haskell/people/davean)
+- [chessai](https://github.com/orgs/haskell/people/chessai)
+
+The owners should already have access to the [hackage package](https://hackage.haskell.org/package/ghcup/maintainers/).
+In case of issues contact the [hackage trustees](https://github.com/haskell-infra/hackage-trustees).
+
+#### Private runners
+
+Private runners maintained by Julian Ospald may cease to work. Moritz Angerman will have SSH access to the machines.
+However, no one will have access to the Hetzner account and billing information. As such, those runners will simply
+have to be replaced.
+
 ## How to help
 
 * if you want to contribute code or documentation, check out the [issue tracker](https://github.com/haskell/ghcup-hs/issues) and the [Development guide](./dev.md)

docs/guide.md

@@ -151,7 +151,7 @@ of metadata files to understand their purpose. These can be combined.
 For example, if you want access to both prerelease and cross bindists, you'd do:
 
 ```sh
-ghcup config add-release-channel https://raw.githubusercontent.com/haskell/ghcup-metadata/master/ghcup-prereleases-0.0.7.yaml
+ghcup config add-release-channel https://raw.githubusercontent.com/haskell/ghcup-metadata/master/ghcup-prereleases-0.0.8.yaml
 ghcup config add-release-channel https://raw.githubusercontent.com/haskell/ghcup-metadata/master/ghcup-cross-0.0.8.yaml
 ```
 
@@ -180,7 +180,7 @@ url-source:
 Also see [config.yaml](https://github.com/haskell/ghcup-hs/blob/master/data/config.yaml)
 for more options.
 
-You can also use an alternative metadata via one-shot cli option:
+You can also use an alternative metadata via the one-shot CLI option:
 
 ```sh
 ghcup --url-source=https://some-url/ghcup-0.0.8.yaml tui
@@ -207,7 +207,7 @@ Note that later versions of GHCup allow more sophisticated mirror support, see [
 1. [https://mirror.sjtu.edu.cn/docs/ghcup](https://mirror.sjtu.edu.cn/docs/ghcup)
 2. [https://mirrors.ustc.edu.cn/help/ghcup.html](https://mirrors.ustc.edu.cn/help/ghcup.html)
 
-### Git based metadata config
+### Git-based metadata config
 
 If you don't like the way ghcup updates its metadata with caching and fetching via curl, you can also do as follows:
 
@@ -322,8 +322,24 @@ Stack metadata doesn't have a concept of those and we don't try to be smart when
 
 ### Windows
 
-On windows, you may find the following config options useful too:
-`skip-msys`, `extra-path`, `extra-include-dirs`, `extra-lib-dirs`.
+#### Using GHCup's MSYS2 installation
+
+Stack usually maintains its own msys2 installation. However, you can instruct it to use GHCup's MSYS2 or any other. E.g. if you
+had GHCup install msys2 into `C:\ghcup\msys64\`, then you would add the following config to stack's `config.yaml`
+(you can find its location via `stack path --stack-root`):
+
+```yaml
+skip-msys: true
+extra-lib-dirs:
+- C:\ghcup\msys64\mingw64\lib
+- C:\ghcup\msys64\mingw64\bin
+extra-path:
+- C:\ghcup\msys64\mingw64\bin
+- C:\ghcup\msys64\usr\bin
+- C:\ghcup\msys64\usr\local\bin
+extra-include-dirs:
+- C:\ghcup\msys64\mingw64\include
+```
 
 Also check out: [https://docs.haskellstack.org/en/stable/yaml_configuration](https://docs.haskellstack.org/en/stable/yaml_configuration)
 
@@ -360,6 +376,28 @@ mirrors:
 
 The configuration depends on the host of the mirror and they have to provide the correct configuration.
 
+## Linkers
+
+The GHC bindist configure script by default doesn't honour the system `ld` that is set, but instead
+probes for `ld.lld`, `ld.gold` and only then `ld` in order, see
+[find_ld.m4](https://gitlab.haskell.org/ghc/ghc/-/blob/master/m4/find_ld.m4?ref_type=heads).
+
+This is controlled by the configure switch `--enable-ld-override`/`--disable-ld-override`, which is enabled by default in GHC.
+GHCup however [has decided](https://github.com/haskell/ghcup-hs/issues/1032) **to disable this switch by default**,
+for reasons of stability and simplicity.
+
+That means, when `--disable-ld-override` is passed, the linker is picked simply by:
+
+* checking if `LD` env var is set, then use whatever is specified
+* otherwise use `ld` binary in PATH (system/distro default)
+
+You can restore the GHC vanilla default by adding this to your `~/.ghcup/config.yaml`:
+
+```yaml
+def-ghc-conf-options:
+  - "--enable-ld-override"
+```
+
 # More on installation
 
 ## Customisation of the installation scripts

lib-opt/GHCup/OptParse/Config.hs

@@ -133,7 +133,8 @@ updateSettings usl usr =
        gpgSetting' = uGPGSetting usl <|> uGPGSetting usr
        platformOverride' = uPlatformOverride usl <|> uPlatformOverride usr
        mirrors' = uMirrors usl <|> uMirrors usr
-   in UserSettings cache' metaCache' metaMode' noVerify' verbose' keepDirs' downloader' (updateKeyBindings (uKeyBindings usl) (uKeyBindings usr)) urlSource' noNetwork' gpgSetting' platformOverride' mirrors'
+       defGHCconfOptions' = uDefGHCConfOptions usl <|> uDefGHCConfOptions usr
+   in UserSettings cache' metaCache' metaMode' noVerify' verbose' keepDirs' downloader' (updateKeyBindings (uKeyBindings usl) (uKeyBindings usr)) urlSource' noNetwork' gpgSetting' platformOverride' mirrors' defGHCconfOptions'
  where
   updateKeyBindings :: Maybe UserKeyBindings -> Maybe UserKeyBindings -> Maybe UserKeyBindings
   updateKeyBindings Nothing Nothing = Nothing

lib/GHCup/GHC.hs

@@ -439,39 +439,22 @@ installUnpackedGHC path inst tver forceInstall addConfArgs
       liftE $ mergeGHCFileTree path inst tver forceInstall
   | otherwise = do
       PlatformRequest {..} <- lift getPlatformReq
+      Settings {..} <- lift getSettings
 
-      let ldOverride
-           | _tvVersion tver >= [vver|8.2.2|]
-           , _rPlatform `elem` [Linux Alpine, Darwin]
-           = ["--disable-ld-override"]
-           | otherwise
-           = []
+      addConfArgs' <- sanitizefGHCconfOptions (T.unpack <$> addConfArgs)
+      defGHCConfOptions' <- sanitizefGHCconfOptions defGHCConfOptions
 
       lift $ logInfo "Installing GHC (this may take a while)"
-      env <- case _rPlatform of
-               -- https://github.com/haskell/ghcup-hs/issues/967
-               Linux Alpine
-                 -- lets not touch LD for cross targets
-                 | Nothing <- _tvTarget tver -> do
-                     cEnv <- liftIO getEnvironment
-                     spaths <- liftIO getSearchPath
-                     has_ld_bfd <- isJust <$> liftIO (searchPath spaths "ld.bfd")
-                     let ldSet = isJust $ lookup "LD" cEnv
-                     -- only set LD if ld.bfd exists in PATH and LD is not set
-                     -- already
-                     if has_ld_bfd && not ldSet
-                     then do
-                       lift $ logInfo "Detected alpine linux... setting LD=ld.bfd"
-                       pure $ Just (("LD", "ld.bfd") : cEnv)
-                     else pure Nothing
-               _ -> pure Nothing
       lEM $ execLogged "sh"
                        ("./configure" : ("--prefix=" <> fromInstallDir inst)
-                        : (maybe mempty (\x -> ["--target=" <> T.unpack x]) (_tvTarget tver) <> ldOverride <> (T.unpack <$> addConfArgs))
+                        : (maybe mempty (\x -> ["--target=" <> T.unpack x]) (_tvTarget tver)
+                          <> ldOverride (_tvVersion tver)
+                          <> defGHCConfOptions'
+                          <> addConfArgs')
                        )
                        (Just $ fromGHCupPath path)
                        "ghc-configure"
-                       env
+                       Nothing
       tmpInstallDest <- lift withGHCupTmpDir
       lEM $ make ["DESTDIR=" <> fromGHCupPath tmpInstallDest, "install"] (Just $ fromGHCupPath path)
       liftE $ catchWarn $ lEM @_ @'[ProcessError] $ darwinNotarization _rPlatform (fromGHCupPath tmpInstallDest)
@@ -479,6 +462,7 @@ installUnpackedGHC path inst tver forceInstall addConfArgs
       pure ()
 
 
+
 mergeGHCFileTree :: ( MonadReader env m
                     , HasPlatformReq env
                     , HasDirs env
@@ -1313,6 +1297,8 @@ compileGHC targetGhc crossTarget vps bstrap jobs mbuildConfig patches aargs buil
                 (_tvTarget tver)
       ++ ["--prefix=" <> ghcdir]
       ++ (if isWindows then ["--enable-tarballs-autodownload"] else [])
+      -- https://github.com/haskell/ghcup-hs/issues/1032
+      ++ ldOverride (_tvVersion tver)
       ++ fmap T.unpack aargs
       )
       (Just workdir)
@@ -1387,3 +1373,16 @@ postGHCInstall ver@GHCTargetVersion {..} = do
   forM_ v' $ \(mj, mi) -> lift (getGHCForPVP (PVP (fromIntegral mj :| [fromIntegral mi])) _tvTarget)
     >>= mapM_ (\v -> liftE $ setGHC v SetGHC_XY Nothing)
 
+
+ldOverride ::  Version -> [String]
+ldOverride ver
+  | ver >= [vver|8.2.2|]
+  = ["--disable-ld-override"]
+  | otherwise
+  = []
+
+sanitizefGHCconfOptions :: MonadFail m => [String] -> m [String]
+sanitizefGHCconfOptions args
+  | "--prefix" `elem` fmap (takeWhile (/= '=')) args = fail "Don't explicitly set --prefix ...aborting"
+  | otherwise = pure args
+

lib/GHCup/Prelude/Process/Windows.hs

@@ -150,7 +150,7 @@ executeOut' :: MonadIO m
             -> m CapturedProcess
 executeOut' path args chdir env' = do
   cp <- createProcessWithMingwPath ((proc path args){ cwd = chdir, env = env' })
-  (exit, out, err) <- liftIO $ readCreateProcessWithExitCodeBS cp ""
+  (exit, out, err) <- liftIO $ withRestorePath (env cp) $ readCreateProcessWithExitCodeBS cp ""
   pure $ CapturedProcess exit out err
 
 
@@ -166,20 +166,21 @@ execLogged :: ( MonadReader env m
            -> FilePath         -- ^ log filename (opened in append mode)
            -> Maybe [(String, String)] -- ^ optional environment
            -> m (Either ProcessError ())
-execLogged exe args chdir lfile env = do
+execLogged exe args chdir lfile env' = do
   Dirs {..} <- getDirs
   logDebug $ T.pack $ "Running " <> exe <> " with arguments " <> show args
   let stdoutLogfile = fromGHCupPath logsDir </> lfile <> ".stdout.log"
       stderrLogfile = fromGHCupPath logsDir </> lfile <> ".stderr.log"
   cp <- createProcessWithMingwPath ((proc exe args)
     { cwd = chdir
-    , env = env
+    , env = env'
     , std_in = CreatePipe
     , std_out = CreatePipe
     , std_err = CreatePipe
     })
   fmap (toProcessError exe args)
     $ liftIO
+    $ withRestorePath (env cp)
     $ withCreateProcess cp
     $ \_ mout merr ph ->
         case (mout, merr) of
@@ -213,16 +214,9 @@ exec :: MonadIO m
      -> Maybe FilePath   -- ^ optionally chdir into this
      -> Maybe [(String, String)] -- ^ optional environment
      -> m (Either ProcessError ())
-exec exe args chdir env = do
-  -- https://gitlab.haskell.org/haskell/ghcup-hs/-/issues/375
-  forM_ (Map.fromList <$> env) $ \cEnv -> do
-    let paths = ["PATH", "Path"]
-        curPaths = (\x -> maybe [] splitSearchPath (Map.lookup x cEnv)) =<< paths
-        newPath = intercalate [searchPathSeparator] curPaths
-    liftIO $ setEnv "PATH" ""
-    liftIO $ setEnv "Path" newPath
-  cp <- createProcessWithMingwPath ((proc exe args) { cwd = chdir, env = env })
-  exit_code <- liftIO $ withCreateProcess cp $ \_ _ _ p -> waitForProcess p
+exec exe args chdir env' = do
+  cp <- createProcessWithMingwPath ((proc exe args) { cwd = chdir, env = env' })
+  exit_code <- liftIO $ withRestorePath (env cp) $ withCreateProcess cp $ \_ _ _ p -> waitForProcess p
   pure $ toProcessError exe args exit_code
 
 -- | Like 'exec', except doesn't add msys2 stuff to PATH.
@@ -233,13 +227,6 @@ execNoMinGW :: MonadIO m
      -> Maybe [(String, String)] -- ^ optional environment
      -> m (Either ProcessError ())
 execNoMinGW exe args chdir env = do
-  -- https://gitlab.haskell.org/haskell/ghcup-hs/-/issues/375
-  forM_ (Map.fromList <$> env) $ \cEnv -> do
-    let paths = ["PATH", "Path"]
-        curPaths = (\x -> maybe [] splitSearchPath (Map.lookup x cEnv)) =<< paths
-        newPath = intercalate [searchPathSeparator] curPaths
-    liftIO $ setEnv "PATH" ""
-    liftIO $ setEnv "Path" newPath
   let cp = (proc exe args) { cwd = chdir, env = env }
   exit_code <- liftIO $ withCreateProcess cp $ \_ _ _ p -> waitForProcess p
   pure $ toProcessError exe args exit_code
@@ -270,7 +257,27 @@ createProcessWithMingwPath cp = do
       newPath = intercalate [searchPathSeparator] (mingWPaths ++ curPaths)
       envWithoutPath = foldr (\x y -> Map.delete x y) cEnv paths
       envWithNewPath = Map.insert "Path" newPath envWithoutPath
-  liftIO $ setEnv "Path" newPath
   pure $ cp { env = Just $ Map.toList envWithNewPath }
 
 
+withRestorePath :: MonadIO m => Maybe [(String, String)] -- ^ optional env we want to extract 'PATH' from
+                             -> m a                      -- ^ action to perform
+                             -> m a
+withRestorePath env action = do
+  -- https://gitlab.haskell.org/haskell/ghcup-hs/-/issues/375
+  oldPATH <- liftIO $ lookupEnv "PATH"
+  oldPath <- liftIO $ lookupEnv "Path"
+
+  forM_ (Map.fromList <$> env) $ \cEnv -> do
+    let paths = ["PATH", "Path"]
+        curPaths = (\x -> maybe [] splitSearchPath (Map.lookup x cEnv)) =<< paths
+        newPath = intercalate [searchPathSeparator] curPaths
+    liftIO $ setEnv "PATH" ""
+    liftIO $ setEnv "Path" newPath
+    liftIO $ print newPath
+
+  r <- action
+  liftIO $ maybe (unsetEnv "PATH") (setEnv "PATH") oldPATH
+  liftIO $ maybe (unsetEnv "Path") (setEnv "Path") oldPath
+  pure r
+

lib/GHCup/Types.hs

@@ -392,11 +392,12 @@ data UserSettings = UserSettings
   , uGPGSetting        :: Maybe GPGSetting
   , uPlatformOverride  :: Maybe PlatformRequest
   , uMirrors           :: Maybe DownloadMirrors
+  , uDefGHCConfOptions :: Maybe [String]
   }
   deriving (Show, GHC.Generic, Eq)
 
 defaultUserSettings :: UserSettings
-defaultUserSettings = UserSettings Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing
+defaultUserSettings = UserSettings Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing Nothing
 
 fromSettings :: Settings -> Maybe KeyBindings -> UserSettings
 fromSettings Settings{..} Nothing =
@@ -414,6 +415,7 @@ fromSettings Settings{..} Nothing =
     , uGPGSetting = Just gpgSetting
     , uPlatformOverride = platformOverride
     , uMirrors = Just mirrors
+    , uDefGHCConfOptions = Just defGHCConfOptions
   }
 fromSettings Settings{..} (Just KeyBindings{..}) =
   let ukb = UserKeyBindings
@@ -440,6 +442,7 @@ fromSettings Settings{..} (Just KeyBindings{..}) =
     , uGPGSetting = Just gpgSetting
     , uPlatformOverride = platformOverride
     , uMirrors = Just mirrors
+    , uDefGHCConfOptions = Just defGHCConfOptions
   }
 
 data UserKeyBindings = UserKeyBindings
@@ -525,6 +528,7 @@ data Settings = Settings
   , noColor           :: Bool -- this also exists in LoggerConfig
   , platformOverride  :: Maybe PlatformRequest
   , mirrors           :: DownloadMirrors
+  , defGHCConfOptions :: [String]
   }
   deriving (Show, GHC.Generic)
 
@@ -532,7 +536,7 @@ defaultMetaCache :: Integer
 defaultMetaCache = 300 -- 5 minutes
 
 defaultSettings :: Settings
-defaultSettings = Settings False defaultMetaCache Lax False Never Curl False GHCupURL False GPGNone False Nothing (DM mempty)
+defaultSettings = Settings False defaultMetaCache Lax False Never Curl False GHCupURL False GPGNone False Nothing (DM mempty) []
 
 instance NFData Settings