275 lines
10 KiB
Markdown
275 lines
10 KiB
Markdown
`ghcup` makes it easy to install specific versions of `ghc` on GNU/Linux,
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macOS (aka Darwin), FreeBSD and Windows and can also bootstrap a fresh Haskell developer environment from scratch.
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It follows the unix UNIX philosophy of [do one thing and do it well](https://en.wikipedia.org/wiki/Unix_philosophy#Do_One_Thing_and_Do_It_Well).
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Similar in scope to [rustup](https://github.com/rust-lang-nursery/rustup.rs), [pyenv](https://github.com/pyenv/pyenv) and [jenv](http://www.jenv.be).
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## Table of Contents
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* [Installation](#installation)
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* [Simple bootstrap](#simple-bootstrap)
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* [Manual install](#manual-install)
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* [Vim integration](#vim-integration)
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* [Usage](#usage)
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* [Configuration](#configuration)
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* [Manpages](#manpages)
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* [Shell-completion](#shell-completion)
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* [Cross support](#cross-support)
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* [XDG support](#xdg-support)
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* [Env variables](#env-variables)
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* [Installing custom bindists](#installing-custom-bindists)
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* [Design goals](#design-goals)
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* [How](#how)
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* [Known users](#known-users)
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* [Known problems](#known-problems)
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* [FAQ](#faq)
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## Installation
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### Simple bootstrap
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Follow the instructions at [https://www.haskell.org/ghcup/](https://www.haskell.org/ghcup/)
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### Manual install
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Download the binary for your platform at [https://downloads.haskell.org/~ghcup/](https://downloads.haskell.org/~ghcup/)
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and place it into your `PATH` anywhere.
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Then adjust your `PATH` in `~/.bashrc` (or similar, depending on your shell) like so:
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```sh
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export PATH="$HOME/.cabal/bin:$HOME/.ghcup/bin:$PATH"
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```
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### Vim integration
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See [ghcup.vim](https://github.com/hasufell/ghcup.vim).
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## Usage
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See `ghcup --help`.
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For the simple interactive TUI, run:
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```sh
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ghcup tui
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```
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For the full functionality via cli:
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```sh
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# list available ghc/cabal versions
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ghcup list
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# install the recommended GHC version
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ghcup install ghc
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# install a specific GHC version
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ghcup install ghc 8.2.2
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# set the currently "active" GHC version
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ghcup set ghc 8.4.4
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# install cabal-install
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ghcup install cabal
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# update ghcup itself
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ghcup upgrade
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```
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GHCup works very well with [`cabal-install`](https://hackage.haskell.org/package/cabal-install), which
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handles your haskell packages and can demand that [a specific version](https://cabal.readthedocs.io/en/latest/nix-local-build.html#cfg-flag---with-compiler) of `ghc` is available, which `ghcup` can do.
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### Configuration
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A configuration file can be put in `~/.ghcup/config.yaml`. The default config file
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explaining all possible configurations can be found in this repo: [config.yaml](./config.yaml).
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Partial configuration is fine. Command line options always override the config file settings.
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### Manpages
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For man pages to work you need [man-db](http://man-db.nongnu.org/) as your `man` provider, then issue `man ghc`. Manpages only work for the currently set ghc.
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`MANPATH` may be required to be unset.
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### Shell-completion
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Shell completions are in `shell-completions`.
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For bash: install `shell-completions/bash`
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as e.g. `/etc/bash_completion.d/ghcup` (depending on distro)
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and make sure your bashrc sources the startup script
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(`/usr/share/bash-completion/bash_completion` on some distros).
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### Cross support
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ghcup can compile and install a cross GHC for any target. However, this
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requires that the build host has a complete cross toolchain and various
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libraries installed for the target platform.
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Consult the GHC documentation on the [prerequisites](https://gitlab.haskell.org/ghc/ghc/-/wikis/building/cross-compiling#tools-to-install).
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For distributions with non-standard locations of cross toolchain and
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libraries, this may need some tweaking of `build.mk` or configure args.
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See `ghcup compile ghc --help` for further information.
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### XDG support
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To enable XDG style directories, set the environment variable `GHCUP_USE_XDG_DIRS` to anything.
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Then you can control the locations via XDG environment variables as such:
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* `XDG_DATA_HOME`: GHCs will be unpacked in `ghcup/ghc` subdir (default: `~/.local/share`)
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* `XDG_CACHE_HOME`: logs and download files will be stored in `ghcup` subdir (default: `~/.cache`)
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* `XDG_BIN_HOME`: binaries end up here (default: `~/.local/bin`)
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* `XDG_CONFIG_HOME`: the config file is stored in `ghcup` subdir as `config.yaml` (default: `~/.config`)
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**Note that `ghcup` makes some assumptions about structure of files in `XDG_BIN_HOME`. So if you have other tools
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installing e.g. stack/cabal/ghc into it, this will likely clash. In that case consider disabling XDG support.**
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### Env variables
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This is the complete list of env variables that change GHCup behavior:
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* `GHCUP_USE_XDG_DIRS`: see [XDG support](#xdg-support) above
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* `TMPDIR`: where ghcup does the work (unpacking, building, ...)
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* `GHCUP_INSTALL_BASE_PREFIX`: the base of ghcup (default: `$HOME`)
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* `GHCUP_CURL_OPTS`: additional options that can be passed to curl
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* `GHCUP_WGET_OPTS`: additional options that can be passed to wget
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* `GHCUP_SKIP_UPDATE_CHECK`: Skip the (possibly annoying) update check when you run a command
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* `CC`/`LD` etc.: full environment is passed to the build system when compiling GHC via GHCup
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### Installing custom bindists
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There are a couple of good use cases to install custom bindists:
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1. manually built bindists (e.g. with patches)
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- example: `ghcup install ghc -u 'file:///home/mearwald/tmp/ghc-eff-patches/ghc-8.10.2-x86_64-deb10-linux.tar.xz' 8.10.2-eff`
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2. GHC head CI bindists
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- example: `ghcup install ghc -u 'https://gitlab.haskell.org/api/v4/projects/1/jobs/artifacts/master/raw/ghc-x86_64-fedora27-linux.tar.xz?job=validate-x86_64-linux-fedora27' head`
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3. DWARF bindists
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- example: `ghcup install ghc -u 'https://downloads.haskell.org/~ghc/8.10.2/ghc-8.10.2-x86_64-deb10-linux-dwarf.tar.xz' 8.10.2-dwarf`
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Since the version parser is pretty lax, `8.10.2-eff` and `head` are both valid versions
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and produce the binaries `ghc-8.10.2-eff` and `ghc-head` respectively.
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GHCup always needs to know which version the bindist corresponds to (this is not automatically
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detected).
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## Design goals
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1. simplicity
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2. non-interactive
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3. portable (eh)
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4. do one thing and do it well (UNIX philosophy)
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### Non-goals
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1. invoking `sudo`, `apt-get` or *any* package manager
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2. handling system packages
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3. handling cabal projects
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4. being a stack alternative
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## How
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Installs a specified GHC version into `~/.ghcup/ghc/<ver>`, and places `ghc-<ver>` symlinks in `~/.ghcup/bin/`.
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Optionally, an unversioned `ghc` link can point to a default version of your choice.
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This uses precompiled GHC binaries that have been compiled on fedora/debian by [upstream GHC](https://www.haskell.org/ghc/download_ghc_8_6_1.html#binaries).
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Alternatively, you can also tell it to compile from source (note that this might fail due to missing requirements).
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In addition this script can also install `cabal-install`.
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## Known users
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* Github action [haskell/actions/setup](https://github.com/haskell/actions/tree/main/setup)
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* [vabal](https://github.com/Franciman/vabal)
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## Known problems
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### Custom ghc version names
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When installing ghc bindists with custom version names as outlined in
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[installing custom bindists](#installing-custom-bindists), then cabal might
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be unable to find the correct `ghc-pkg` (also see [#73](https://gitlab.haskell.org/haskell/ghcup-hs/-/issues/73))
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if you use `cabal build --with-compiler=ghc-foo`. Instead, point it to the full path, such as:
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`cabal build --with-compiler=$HOME/.ghcup/ghc/<version-name>/bin/ghc` or set that GHC version
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as the current one via: `ghcup set ghc <version-name>`.
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This problem doesn't exist for regularly installed GHC versions.
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### Limited distributions supported
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Currently only GNU/Linux distributions compatible with the [upstream GHC](https://www.haskell.org/ghc/download_ghc_8_6_1.html#binaries) binaries are supported.
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### Precompiled binaries
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Since this uses precompiled binaries you may run into
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several problems.
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#### Missing libtinfo (ncurses)
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You may run into problems with *ncurses* and **missing libtinfo**, in case
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your distribution doesn't use the legacy way of building
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ncurses and has no compatibility symlinks in place.
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Ask your distributor on how to solve this or
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try to compile from source via `ghcup compile <version>`.
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#### Libnuma required
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This was a [bug](https://ghc.haskell.org/trac/ghc/ticket/15688) in the build system of some GHC versions that lead to
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unconditionally enabled libnuma support. To mitigate this you might have to install the libnuma
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package of your distribution. See [here](https://gitlab.haskell.org/haskell/ghcup/issues/58) for a discussion.
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### Compilation
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Although this script can compile GHC for you, it's just a very thin
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wrapper around the build system. It makes no effort in trying
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to figure out whether you have the correct toolchain and
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the correct dependencies. Refer to [the official docs](https://ghc.haskell.org/trac/ghc/wiki/Building/Preparation/Linux)
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on how to prepare your environment for building GHC.
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### Stack support
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There may be a number of bugs when trying to make ghcup installed GHC versions work with stack,
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such as:
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- https://gitlab.haskell.org/haskell/ghcup-hs/-/issues/188
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Further, stack's upgrade procedure may break/confuse ghcup. There are a number of integration
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issues discussed here:
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- https://gitlab.haskell.org/haskell/ghcup-hs/-/issues/153
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### Windows support
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Windows support is in early stages. Since windows doesn't support symbolic links properly,
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ghcup uses a [shimgen wrapper](https://github.com/71/scoop-better-shimexe). It seems to work
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well, but there may be unknown issues with that approach.
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Windows 7 and Powershell 2.0 aren't well supported at the moment, also see:
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- https://gitlab.haskell.org/haskell/ghcup-hs/-/issues/140
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- https://gitlab.haskell.org/haskell/ghcup-hs/-/issues/197
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## FAQ
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1. Why reimplement stack?
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ghcup is not a reimplementation of stack. The only common part is automatic installation of GHC, but even that differs in scope and design.
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2. Why not support windows?
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We do.
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3. Why the haskell reimplementation?
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ghcup started as a portable posix shell script of maybe 50 LOC. GHC installation itself can be carried out in
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about ~3 lines of shell code (download, unpack , configure+make install). However, much convenient functionality
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has been added since, as well as ensuring that all operations are safe and correct. The shell script ended up with
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over 2k LOC, which was very hard to maintain.
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The main concern when switching from a portable shell script to haskell was platform/architecture support.
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However, ghcup now re-uses GHCs CI infrastructure and as such is perfectly in sync with all platforms that
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GHC supports.
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