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Developing on Windows

On Windows, Stack comes with an installation of MSYS2. 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 environment too by executing all programs through stack exec -- <program_name>.

Executables and libraries can be installed with the MSYS2 package manager pacman. All tools can be found in the index to MSYS2 packages. A guide to package management with pacman is also available. pacman — like all other tools in the Stack environment — should be started with stack exec -- pacman. Help about pacman commands (operations) can be obtained by stack exec -- pacman --help. Help about a specific pacman operation can be obtained by using --help (or -h) with an operation. For 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 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 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 CLANG64.)

For further information about configuring the relevant MSYS2 environment, see Stack's msys-environment non-project specific configuration option documentation.

Updating the Stack-supplied MSYS2

The Stack-supplied MSYS2 can itself be updated with the Stack-supplied pacman. See the MSYS2 guide Updating MSYS2. If the Stack-supplied pacman has a version that is 5.0.1.6403 or greater (see stack exec -- pacman --version) then the command to update is simply:

stack exec -- pacman -Suy

This command may need to be run more than once, until everything is reported by pacman as 'up to date' and 'nothing to do'.

Setup.hs

Setup.hs is automatically run inside the Stack environment. So when you need to launch another tool you do not need to prefix the command with stack exec -- within the custom Setup.hs file.

Pacman packages to install for common Haskell packages

The following lists MSYS2 packages known to allow the installation of some common Haskell packages on Windows. Feel free to submit additional entries via a pull request.

  • For text-icu install mingw-w64-clang-x86_64-icu.

  • For zlib >= 0.7 the default Cabal flag pkg-config is true and requires executable pkg-config on the PATH. MSYS2 defaults to pkgconf as its pkg-config implementation. Installation:

    stack exec -- pacman -S pkgconf

    Alternatively, build with --flag zlib:-pkg-config.