3. How to use Cabal in Windows
This document describes how to use Cabal in a Windows system. See the Further reading section for some other references that might provide some more explanations. For a TL;DR, jump to the Complete configuration.
3.1. Install the Haskell environment
Haskell development on Windows makes use of the MSYS2 tools.
The recommended way of setting up a Haskell environment in Windows is by using GHCup. Follow the steps outlined in its webpage to install at least GHC and Cabal. GHCup will install its own MSYS2 system in your computer unless told not to do so: refer to its documentation for more information.
Note
Stack is another tool you can use to set up a Haskell environment on Windows. Stack can be installed on its own or via GHCup. See Stack’s webpage and/or GHCup’s section on Stack integration, in particular the Windows related subsection.
3.2. Ensure that Cabal can call the tools it needs
Cabal sometimes needs to call tools that do not come with Windows (such as
make
or even git
). The MSYS2 project makes many of them available on
Windows. The directories where those are located need to be made visible in the
PATH
when executing cabal
. For that, Cabal provides the
extra-prog-path
configuration option. Your global configuration should include this option:
extra-prog-path: <msys-dir>\<environment>\bin
<msys-dir>\usr\bin
Where <msys-dir>
points to the location of your MSYS2 installation. Refer to
GHCup’s documentation on the default location of this directory.
<environment>
has to be one of the environments of MSYS2, which for GHCup is
mingw64
. You can learn more about the different environments in the MSYS2
documentation.
Note
Unless told otherwise, the GHCup bootstrap script already adds these directories to extra-prog-path by default.
3.3. Ensure that Cabal can use system libraries
Third-party libraries can be installed using the pacman
package manager on
the MSYS2 installation. When installing a third party package its libraries and
header files will (usually) be placed in
<msys-dir>\<environment>\{lib,include}
respectively. These directories need
to be specified in the extra-lib-dirs
and extra-include-dirs
respectively. Your global configuration should
include these options:
extra-include-dirs: <msys-dir>\<environment>\include
extra-lib-dirs: <msys-dir>\<environment>\lib
Note
Unless told otherwise, the GHCup bootstrap script already adds these directories to extra-include-dirs and extra-lib-dirs by default.
Warning
Packages in the msys/
repo are not native Windows libraries and will
probably not work when one tries to link to them. Install the packages for
your selected environment, which for GHCup is mingw64/
. Refer to MSYS2’s
package management documentation for more information.
3.4. Ensure that Cabal can call Haskell tools
Haskell tools are located in two places:
<ghcup-dir>\bin
for standard Haskell tools such as GHC, Cabal, Haddock,hsc2hs
…The
installdir
that Cabal is configured with for user-installed Haskell tools.
For Cabal to be able to invoke these tools, those directories need to be made
visible in the PATH
. Your global configuration should
include these options:
installdir: <installdir>
extra-prog-path: ...
<ghcup-dir>\bin
<installdir>
Note
Unless told otherwise, the GHCup bootstrap script already adds these directories to extra-prog-path by default.
3.5. Complete configuration
The complete global configuration should finally look like this:
installdir: <installdir>
extra-include-dirs: <msys-dir>\<environment>\include
extra-lib-dirs: <msys-dir>\<environment>\lib
extra-prog-path: <ghcup-dir>\bin
<installdir>
<msys-dir>\<environment>\bin
<msys-dir>\usr\bin
Note
Unless told otherwise, the GHCup bootstrap script already sets this configuration file to the right values by default.
3.6. Further reading
MSYS2 homepage: https://www.msys2.org
MinGW-W64 homepage: https://www.mingw-w64.org/
Setting up Windows to build GHC: https://gitlab.haskell.org/ghc/ghc/-/wikis/building/preparation/windows
Some definitions and useful tools: https://gitlab.haskell.org/ghc/ghc/-/wikis/surviving-windows
3.6.1. Outdated links
These links are outdated but still useful to understand the overall picture:
GHC’s wiki about the Windows platform (outdated, GHC now uses MSYS2): https://gitlab.haskell.org/ghc/ghc/-/wikis/building/platforms/windows
The Windows toolchain (outdated, GHC now uses the
CLANG64
environment): https://gitlab.haskell.org/ghc/ghc/-/wikis/working-conventions/windows-toolchainHaskell Wiki on Windows (outdated, it talks about MSYS and old tools such as the Haskell platform): https://wiki.haskell.org/Windows