Change default msys2 environment to CLANG64

ChangeLog.md

@@ -8,6 +8,14 @@ Release notes:
 
 Major changes:
 
+* On 64-bit Windows, the default `msys-environment` configuration option is now
+  `CLANG64`, rather than `MINGW64` (which remains an option). The MSYS2 project
+  deprecated the latter environment on 15 March 2026. The GHC project has used
+  the former toolchain from GHC 9.4.1. No default is provided for 32-bit
+  Windows, rather than `MINGW32` (which remains an option). The MSYS2 project
+  ceased to actively support it on 17 May 2020. 32-bit Windows is not supported
+  by the GHC project from GHC 8.12.
+
 Behavior changes:
 
 Other enhancements:

doc/configure/yaml/non-project.md

@@ -946,7 +946,9 @@ modify-code-page: false
 
 Restrictions: Windows systems only.
 
-Default: `MINGW64` (64-bit Windows) or `MINGW32` (32-bit Windows)
+Default:
+([:octicons-tag-24: 3.11.1](https://github.com/commercialhaskell/stack/releases/tag/v3.11.1))
+`CLANG64` (64-bit Windows)
 
 The name of the MSYS2 environment (case-sensitive) used in the Stack
 environment. Valid environments are `CLANG32`, `CLANG64`, `CLANGARM64`,

doc/topics/GHC_from_source.md

@@ -167,25 +167,25 @@ Stack will build and install `happy` and `alex`, if not already on the PATH.
     ~~~pwsh
     stack exec -- pacman --sync --refresh
     # Synchronize MSYS2 package databases
-    stack exec -- pacman --sync mingw-w64-x86_64-python-pip
+    stack exec -- pacman --sync mingw-w64-clang-x86_64-python-pip
     # The PyPA recommended tool (pip) for installing Python packages. Also
     # installs Python as a dependency. GHC uses a Python script named `boot`.
-    # The package must be the one from the `mingw64` MSYS2 repository, as Python
+    # The package must be the one from the `clang64` MSYS2 repository, as Python
     # from the `msys` repository cannot interpret Windows file paths correctly.
-    stack exec -- pacman --sync mingw-w64-x86_64-autotools
+    stack exec -- pacman --sync mingw-w64-clang-x86_64-autotools
     # The GNU autotools build system, including `autoreconf`, `aclocal`
     # and `make`. GHC uses a sh script named `configure` which is itself created
     # from a file named `configure.ac`.
     stack exec -- pacman --sync patch
     # A utility to apply patch files to original sources.
-    stack exec -- pacman --sync texinfo
+    stack exec -- pacman --sync mingw-w64-clang-x86_64-texinfo
     # Utilities to work with and produce manuals, ASCII text, and on-line
     # documentation from a single source file, including `makeinfo`.
-    stack exec -- pacman --sync mingw-w64-x86_64-ca-certificates
+    stack exec -- pacman --sync mingw-w64-clang-x86_64-ca-certificates
     # Common CA (certificate authority) certificates.
-    stack exec -- pacman -sync mingw-w64-x86_64-python-sphinx
+    stack exec -- pacman -sync mingw-w64-clang-x86_64-python-sphinx
     # Sphinx is the Python documentation generator.
-    stack exec -- pacman -sync mingw-w64-x86_64-texlive-full
+    stack exec -- pacman -sync mingw-w64-clang-x86_64-texlive-full
     # The TeX Live distribution.
     ~~~
 

doc/topics/developing_on_windows.md

@@ -3,11 +3,11 @@
 # Developing on Windows #
 
 On Windows, Stack comes with an installation of [MSYS2](https://www.msys2.org/).
-An environment of MSYS2 (by default, `MINGW64` on 64-bit Windows or `MINGW32` on
-32-bit Windows) will be used by Stack to provide a Unix-like shell and
-environment for Stack. This may be necessary for installing some Haskell
-packages, such as those which use `configure` scripts, or if your project needs
-some additional tools during the build phase.
+An environment of MSYS2 (by default, `CLANG64` on 64-bit Windows) will be used
+by Stack to provide a Unix-like shell and environment for Stack. This may be
+necessary for installing some Haskell packages, such as those which use
+`configure` scripts, or if your project needs some additional tools during the
+build phase.
 
 No matter which terminal software you choose (Windows Terminal, Console Windows
 Host, Command Prompt, PowerShell, Git bash or any other) you can use this
@@ -26,22 +26,22 @@ example, help about the operation `--sync` (or `-S`) can be obtained with
 `stack exec -- pacman --sync --help` or, equivalently,
 `stack exec -- pacman -Sh`.
 
-Command `stack path --bin-path` to see the PATH in the Stack environment. If the
-relevant MSYS2 environment is `MINGW64`, on Windows, it includes the
-`\mingw64\bin`, `\usr\bin` and `\usr\local\bin` directories of the
-Stack-supplied MSYS2. (It includes the corresponding directory if the relevant
-MSYS2 environment is other than `MINGW64`.) If your executable depends on files
-(for example, dynamic-link libraries) in those directories and you want to run
-it outside of the Stack environment, you will need to ensure copies of those
-files are on the PATH.
+Command `stack path --bin-path` to see the PATH in the
+[Stack environment](stack_environment.md). If the relevant MSYS2 environment is
+`CLANG64`, on Windows, it includes the `\clang64\bin`, `\usr\local\bin` and
+`\usr\bin` directories of the Stack-supplied MSYS2. (It includes the
+corresponding directory if the relevant MSYS2 environment is other than
+`CLANG64`.) If your executable depends on files (for example, dynamic-link
+libraries) in those directories and you want to run it outside of the Stack
+environment, you will need to ensure copies of those files are on the PATH.
 
 Command `stack path --extra-include-dirs` and `stack path --extra-library-dirs`
 to see the extra directories searched for C header files or system libraries
-files in the Stack environment. If the relevant MSYS2 environment is `MINGW64`,
-on Windows, it includes the `\mingw64\include` (include) and the `\mingw64\lib`
-and `\mingw64\bin` directories (library) of the Stack-supplied MSYS2. (It
+files in the Stack environment. If the relevant MSYS2 environment is `CLANG64`,
+on Windows, it includes the `\clang64\include` (include) and the `\clang64\lib`
+and `\clang64\bin` directories (library) of the Stack-supplied MSYS2. (It
 includes the corresponding directories if the relevant MSYS2 environment is
-other than `MINGW64`.)
+other than `CLANG64`.)
 
 For further information about configuring the relevant MSYS2 environment, see
 Stack's [`msys-environment`](../configure/yaml/non-project.md#msys-environment)
@@ -72,7 +72,7 @@ common Haskell packages on Windows. Feel free to submit additional entries via a
 pull request.
 
 *   For [text-icu](https://hackage.haskell.org/package/text-icu) install
-    `mingw64/mingw-w64-x86_64-icu`.
+    `mingw-w64-clang-x86_64-icu`.
 
 *   For [zlib >= 0.7](https://hackage.haskell.org/package/zlib) the default
     Cabal flag `pkg-config` is `true` and requires executable `pkg-config` on
@@ -83,27 +83,3 @@ pull request.
         stack exec -- pacman -S pkgconf
 
     Alternatively, build with `--flag zlib:-pkg-config`.
-
-## CMake ##
-
-CMake has trouble finding other tools even if they are available on the PATH.
-Likely this is not a CMake problem but one of the environment not fully
-integrating. For example GHC comes with a copy of GCC which is not installed by
-MSYS2 itself. If you want to use this GCC you can provide a full path to it, or
-find it first with `System.Directory.findExecutable` if you want to launch GCC
-from a Haskell file such as `Setup.hs`.
-
-Experience tells that the `mingw-w64` versions of Make and CMake are most
-likely to work. Though there are other versions available through `pacman`, so
-have a look to see what works for you. Both tools can be installed with the
-commands:
-
-    stack exec -- pacman -S mingw-w64-x86_64-make
-    stack exec -- pacman -S mingw-w64-x86_64-cmake
-
-Even though Make and CMake are then both installed into the same environment,
-CMake still seems to have trouble to find Make. To help CMake find GCC and Make
-supply the following flags:
-
-    -DCMAKE_C_COMPILER=path
-    -DCMAKE_MAKE_PROGRAM=path

doc/tutorial/hello_world_example.md

@@ -324,7 +324,7 @@ environment.
 !!! info
 
     On Windows, the [Stack environment](../topics/stack_environment.md) includes
-    the `\mingw64\bin`, `\usr\bin` and `\usr\local\bin` directories of the
+    the `\clang64\bin`, `\usr\bin` and `\usr\local\bin` directories of the
     Stack-supplied MSYS2. If your executable depends on files (for example,
     dynamic-link libraries) in those directories and you want ro run it outside
     of the Stack environment, you will need to ensure copies of those files are

src/Stack/Config.hs

@@ -306,10 +306,6 @@ configFromConfigMonoid
         installMsys = fromFirst installGHC configMonoid.installMsys
         skipGHCCheck = fromFirstFalse configMonoid.skipGHCCheck
         skipMsys = fromFirstFalse configMonoid.skipMsys
-        defMsysEnvironment = case platform of
-          Platform I386 Windows -> Just MINGW32
-          Platform X86_64 Windows -> Just MINGW64
-          _ -> Nothing
         extraIncludeDirs = configMonoid.extraIncludeDirs
         extraLibDirs = configMonoid.extraLibDirs
         customPreprocessorExts = configMonoid.customPreprocessorExts
@@ -324,15 +320,19 @@ configFromConfigMonoid
         requireStackVersion = simplifyVersionRange
           configMonoid.requireStackVersion.intersectingVersionRange
         compilerCheck = fromFirst MatchMinor configMonoid.compilerCheck
-    msysEnvironment <- case defMsysEnvironment of
-      -- Ignore the configuration setting if there is no default for the
-      -- platform.
+        mMsysEnv = case platform of
+          Platform X86_64 Windows ->
+            -- Default CLANG64 on 64-bit Windows:
+            Just $ fromFirst CLANG64 configMonoid.msysEnvironment
+          Platform _ Windows ->
+            -- No default on unsupported 32-bit Windows:
+            getFirst configMonoid.msysEnvironment
+          _ -> Nothing
+    msysEnvironment <- case mMsysEnv of
       Nothing -> pure Nothing
-      Just defMsysEnv -> do
-        let msysEnv = fromFirst defMsysEnv configMonoid.msysEnvironment
-        if msysEnvArch msysEnv == arch
-          then pure $ Just msysEnv
-          else prettyThrowM $ BadMsysEnvironment msysEnv arch
+      Just msysEnv
+        | msysEnvArch msysEnv == arch -> pure $ Just msysEnv
+        | otherwise -> prettyThrowM $ BadMsysEnvironment msysEnv arch
     platformVariant <- liftIO $
       maybe PlatformVariantNone PlatformVariant <$> lookupEnv platformVariantEnvVar
     let build = buildOptsFromMonoid configMonoid.buildOpts

src/Stack/Types/MsysEnvironment.hs

@@ -26,13 +26,10 @@ import           Stack.Prelude
 data MsysEnvironment
   = CLANG32
   | CLANG64
+    -- ^ Stack's default on architecture x86_64.
   | CLANGARM64
   | MINGW32
-    -- ^ Stack's default on architecture i386, and applied if GHC version is
-    -- earlier than GHC 9.6.
   | MINGW64
-    -- ^ Stack's default on architecture x86_64, and applied if GHC version is
-    -- earlier than GHC 9.6.
   | UCRT64
   deriving (Eq, Ord, Show)