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Merge pull request #23627 from alexeymuranov/haskell-doc-markdown

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doc: enable code syntax highlighting
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doc/languages-frameworks/haskell.md
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@ -11,18 +11,19 @@ date: 2015-06-01
Nixpkgs distributes build instructions for all Haskell packages registered on
[Hackage](http://hackage.haskell.org/), but strangely enough normal Nix package
lookups don't seem to discover any of them, except for the default version of ghc, cabal-install, and stack:
```
$ nix-env -i alex
error: selector ‘alex’ matches no derivations
$ nix-env -qa ghc
ghc-7.10.2
```
The Haskell package set is not registered in the top-level namespace because it
is *huge*. If all Haskell packages were visible to these commands, then
name-based search/install operations would be much slower than they are now. We
avoided that by keeping all Haskell-related packages in a separate attribute
set called `haskellPackages`, which the following command will list:
```
$ nix-env -f "<nixpkgs>" -qaP -A haskellPackages
haskellPackages.a50 a50-0.5
haskellPackages.abacate haskell-abacate-0.0.0.0
@ -32,11 +33,13 @@ set called `haskellPackages`, which the following command will list:
haskellPackages.Allure Allure-0.4.101.1
haskellPackages.alms alms-0.6.7
[... some 8000 entries omitted ...]
```
To install any of those packages into your profile, refer to them by their
attribute path (first column):
$ nix-env -f "<nixpkgs>" -iA haskellPackages.Allure ...
```shell
nix-env -f "<nixpkgs>" -iA haskellPackages.Allure ...
```
The attribute path of any Haskell packages corresponds to the name of that
particular package on Hackage: the package `cabal-install` has the attribute
@ -58,41 +61,45 @@ Attribute paths are deterministic inside of Nixpkgs, but the path necessary to
reach Nixpkgs varies from system to system. We dodged that problem by giving
`nix-env` an explicit `-f "<nixpkgs>"` parameter, but if you call `nix-env`
without that flag, then chances are the invocation fails:
```
$ nix-env -iA haskellPackages.cabal-install
error: attribute ‘haskellPackages’ in selection path
‘haskellPackages.cabal-install’ not found
```
On NixOS, for example, Nixpkgs does *not* exist in the top-level namespace by
default. To figure out the proper attribute path, it's easiest to query for the
path of a well-known Nixpkgs package, i.e.:
```
$ nix-env -qaP coreutils
nixos.coreutils coreutils-8.23
```
If your system responds like that (most NixOS installations will), then the
attribute path to `haskellPackages` is `nixos.haskellPackages`. Thus, if you
want to use `nix-env` without giving an explicit `-f` flag, then that's the way
to do it:
$ nix-env -qaP -A nixos.haskellPackages
$ nix-env -iA nixos.haskellPackages.cabal-install
```shell
nix-env -qaP -A nixos.haskellPackages
nix-env -iA nixos.haskellPackages.cabal-install
```
Our current default compiler is GHC 7.10.x and the `haskellPackages` set
contains packages built with that particular version. Nixpkgs contains the
latest major release of every GHC since 6.10.4, however, and there is a whole
family of package sets available that defines Hackage packages built with each
of those compilers, too:
$ nix-env -f "<nixpkgs>" -qaP -A haskell.packages.ghc6123
$ nix-env -f "<nixpkgs>" -qaP -A haskell.packages.ghc763
```shell
nix-env -f "<nixpkgs>" -qaP -A haskell.packages.ghc6123
nix-env -f "<nixpkgs>" -qaP -A haskell.packages.ghc763
```
The name `haskellPackages` is really just a synonym for
`haskell.packages.ghc7102`, because we prefer that package set internally and
recommend it to our users as their default choice, but ultimately you are free
to compile your Haskell packages with any GHC version you please. The following
command displays the complete list of available compilers:
```
$ nix-env -f "<nixpkgs>" -qaP -A haskell.compiler
haskell.compiler.ghc6104 ghc-6.10.4
haskell.compiler.ghc6123 ghc-6.12.3
@ -107,6 +114,7 @@ command displays the complete list of available compilers:
haskell.compiler.ghcjs ghcjs-0.1.0
haskell.compiler.jhc jhc-0.8.2
haskell.compiler.uhc uhc-1.1.9.0
```
We have no package sets for `jhc` or `uhc` yet, unfortunately, but for every
version of GHC listed above, there exists a package set based on that compiler.
@ -121,8 +129,9 @@ A simple development environment consists of a Haskell compiler and one or both
of the tools `cabal-install` and `stack`. We saw in section
[How to install Haskell packages] how you can install those programs into your
user profile:
$ nix-env -f "<nixpkgs>" -iA haskellPackages.ghc haskellPackages.cabal-install
```shell
nix-env -f "<nixpkgs>" -iA haskellPackages.ghc haskellPackages.cabal-install
```
Instead of the default package set `haskellPackages`, you can also use the more
precise name `haskell.compiler.ghc7102`, which has the advantage that it refers
@ -131,24 +140,25 @@ given time.
Once you've made those tools available in `$PATH`, it's possible to build
Hackage packages the same way people without access to Nix do it all the time:
$ cabal get lens-4.11 && cd lens-4.11
$ cabal install -j --dependencies-only
$ cabal configure
$ cabal build
```shell
cabal get lens-4.11 && cd lens-4.11
cabal install -j --dependencies-only
cabal configure
cabal build
```
If you enjoy working with Cabal sandboxes, then that's entirely possible too:
just execute the command
$ cabal sandbox init
```shell
cabal sandbox init
```
before installing the required dependencies.
The `nix-shell` utility makes it easy to switch to a different compiler
version; just enter the Nix shell environment with the command
$ nix-shell -p haskell.compiler.ghc784
```shell
nix-shell -p haskell.compiler.ghc784
```
to bring GHC 7.8.4 into `$PATH`. Alternatively, you can use Stack instead of
`nix-shell` directly to select compiler versions and other build tools
per-project. It uses `nix-shell` under the hood when Nix support is turned on.
@ -159,8 +169,9 @@ shell switches your build to use that compiler instead. If you're working on
a project that doesn't depend on any additional system libraries outside of GHC,
then it's even sufficient to just run the `cabal configure` command inside of
the shell:
$ nix-shell -p haskell.compiler.ghc784 --command "cabal configure"
```shell
nix-shell -p haskell.compiler.ghc784 --command "cabal configure"
```
Afterwards, all other commands like `cabal build` work just fine in any shell
environment, because the configure phase recorded the absolute paths to all
@ -187,16 +198,17 @@ packages, which determines the libraries known to that particular version of
GHC. For example, the Nix expression `ghcWithPackages (pkgs: [pkgs.mtl])`
generates a copy of GHC that has the `mtl` library registered in addition to
its normal core packages:
```
$ nix-shell -p "haskellPackages.ghcWithPackages (pkgs: [pkgs.mtl])"
[nix-shell:~]$ ghc-pkg list mtl
/nix/store/zy79...-ghc-7.10.2/lib/ghc-7.10.2/package.conf.d:
mtl-2.2.1
```
This function allows users to define their own development environment by means
of an override. After adding the following snippet to `~/.config/nixpkgs/config.nix`,
```nix
{
packageOverrides = super: let self = super.pkgs; in
{
@ -209,7 +221,7 @@ of an override. After adding the following snippet to `~/.config/nixpkgs/config.
]);
};
}
```
it's possible to install that compiler with `nix-env -f "<nixpkgs>" -iA
myHaskellEnv`. If you'd like to switch that development environment to a
different version of GHC, just replace the `ghc7102` bit in the previous
@ -221,7 +233,7 @@ file conflicts.)
The generated `ghc` program is a wrapper script that re-directs the real
GHC executable to use a new `lib` directory --- one that we specifically
constructed to contain all those packages the user requested:
```
$ cat $(type -p ghc)
#! /nix/store/xlxj...-bash-4.3-p33/bin/bash -e
export NIX_GHC=/nix/store/19sm...-ghc-7.10.2/bin/ghc
@ -229,6 +241,7 @@ constructed to contain all those packages the user requested:
export NIX_GHC_DOCDIR=/nix/store/19sm...-ghc-7.10.2/share/doc/ghc/html
export NIX_GHC_LIBDIR=/nix/store/19sm...-ghc-7.10.2/lib/ghc-7.10.2
exec /nix/store/j50p...-ghc-7.10.2/bin/ghc "-B$NIX_GHC_LIBDIR" "$@"
```
The variables `$NIX_GHC`, `$NIX_GHCPKG`, etc. point to the *new* store path
`ghcWithPackages` constructed specifically for this environment. The last line
@ -248,23 +261,25 @@ than trying to guess them at compile-time.
To make sure that mechanism works properly all the time, we recommend that you
set those variables to meaningful values in your shell environment, too, i.e.
by adding the following code to your `~/.bashrc`:
```bash
if type >/dev/null 2>&1 -p ghc; then
eval "$(egrep ^export "$(type -p ghc)")"
fi
```
If you are certain that you'll use only one GHC environment which is located in
your user profile, then you can use the following code, too, which has the
advantage that it doesn't contain any paths from the Nix store, i.e. those
settings always remain valid even if a `nix-env -u` operation updates the GHC
environment in your profile:
```bash
if [ -e ~/.nix-profile/bin/ghc ]; then
export NIX_GHC="$HOME/.nix-profile/bin/ghc"
export NIX_GHCPKG="$HOME/.nix-profile/bin/ghc-pkg"
export NIX_GHC_DOCDIR="$HOME/.nix-profile/share/doc/ghc/html"
export NIX_GHC_LIBDIR="$HOME/.nix-profile/lib/ghc-$($NIX_GHC --numeric-version)"
fi
```
### How to install a compiler with libraries, hoogle and documentation indexes
@ -280,7 +295,7 @@ uses all those things. A precise name for this thing would be
long and scary.
For example, installing the following environment
```nix
{
packageOverrides = super: let self = super.pkgs; in
{
@ -293,7 +308,7 @@ For example, installing the following environment
]);
};
}
```
allows one to browse module documentation index [not too dissimilar to
this](https://downloads.haskell.org/~ghc/latest/docs/html/libraries/index.html)
for all the specified packages and their dependencies by directing a browser of
@ -303,23 +318,24 @@ choice to `~/.nix-profiles/share/doc/hoogle/index.html` (or
After you've marveled enough at that try adding the following to your
`~/.ghc/ghci.conf`
```
:def hoogle \s -> return $ ":! hoogle search -cl --count=15 \"" ++ s ++ "\""
:def doc \s -> return $ ":! hoogle search -cl --info \"" ++ s ++ "\""
```
and test it by typing into `ghci`:
```
:hoogle a -> a
:doc a -> a
```
Be sure to note the links to `haddock` files in the output. With any modern and
properly configured terminal emulator you can just click those links to
navigate there.
Finally, you can run
```shell
hoogle server -p 8080
```
and navigate to http://localhost:8080/ for your own local
[Hoogle](https://www.haskell.org/hoogle/). Note, however, that Firefox and
possibly other browsers disallow navigation from `http:` to `file:` URIs for
@ -334,18 +350,20 @@ It has first-class support for Nix. Stack can optionally use Nix to
automatically select the right version of GHC and other build tools to build,
test and execute apps in an existing project downloaded from somewhere on the
Internet. Pass the `--nix` flag to any `stack` command to do so, e.g.
$ git clone --recursive http://github.com/yesodweb/wai
$ cd wai
$ stack --nix build
```shell
git clone --recursive http://github.com/yesodweb/wai
cd wai
stack --nix build
```
If you want `stack` to use Nix by default, you can add a `nix` section to the
`stack.yaml` file, as explained in the [Stack documentation][stack-nix-doc]. For
example:
```yaml
nix:
enable: true
packages: [pkgconfig zeromq zlib]
```
The example configuration snippet above tells Stack to create an ad hoc
environment for `nix-shell` as in the below section, in which the `pkgconfig`,
@ -356,10 +374,11 @@ Some projects have more sophisticated needs. For examples, some ad hoc
environments might need to expose Nixpkgs packages compiled in a certain way, or
with extra environment variables. In these cases, you'll need a `shell` field
instead of `packages`:
```yaml
nix:
enable: true
shell-file: shell.nix
```
For more on how to write a `shell.nix` file see the below section. You'll need
to express a derivation. Note that Nixpkgs ships with a convenience wrapper
@ -368,7 +387,7 @@ create this derivation in exactly the way Stack expects. All of the same inputs
as `mkDerivation` can be provided. For example, to build a Stack project that
including packages that link against a version of the R library compiled with
special options turned on:
```nix
with (import <nixpkgs> { });
let R = pkgs.R.override { enableStrictBarrier = true; };
@ -377,12 +396,13 @@ special options turned on:
name = "HaskellR";
buildInputs = [ R zeromq zlib ];
}
```
You can select a particular GHC version to compile with by setting the
`ghc` attribute as an argument to `buildStackProject`. Better yet, let
Stack choose what GHC version it wants based on the snapshot specified
in `stack.yaml` (only works with Stack >= 1.1.3):
```nix
{nixpkgs ? import <nixpkgs> { }, ghc ? nixpkgs.ghc}:
with nixpkgs;
@ -394,6 +414,7 @@ in `stack.yaml` (only works with Stack >= 1.1.3):
buildInputs = [ R zeromq zlib ];
inherit ghc;
}
```
[stack-nix-doc]: http://docs.haskellstack.org/en/stable/nix_integration.html
@ -401,12 +422,13 @@ in `stack.yaml` (only works with Stack >= 1.1.3):
The easiest way to create an ad hoc development environment is to run
`nix-shell` with the appropriate GHC environment given on the command-line:
```shell
nix-shell -p "haskellPackages.ghcWithPackages (pkgs: with pkgs; [mtl pandoc])"
```
For more sophisticated use-cases, however, it's more convenient to save the
desired configuration in a file called `shell.nix` that looks like this:
```nix
{ nixpkgs ? import <nixpkgs> {}, compiler ? "ghc7102" }:
let
inherit (nixpkgs) pkgs;
@ -419,6 +441,7 @@ desired configuration in a file called `shell.nix` that looks like this:
buildInputs = [ ghc ];
shellHook = "eval $(egrep ^export ${ghc}/bin/ghc)";
}
```
Now run `nix-shell` --- or even `nix-shell --pure` --- to enter a shell
environment that has the appropriate compiler in `$PATH`. If you use `--pure`,
@ -434,13 +457,14 @@ already! Every Haskell package has an `env` attribute that provides a shell
environment suitable for compiling that particular package. If you'd like to
hack the `lens` library, for example, then you just have to check out the
source code and enter the appropriate environment:
```
$ cabal get lens-4.11 && cd lens-4.11
Downloading lens-4.11...
Unpacking to lens-4.11/
$ nix-shell "<nixpkgs>" -A haskellPackages.lens.env
[nix-shell:/tmp/lens-4.11]$
```
At point, you can run `cabal configure`, `cabal build`, and all the other
development commands. Note that you need `cabal-install` installed in your
@ -459,18 +483,20 @@ convert those automatically into build instructions for Nix using the
For example, let's assume that you're working on a private project called
`foo`. To generate a Nix build expression for it, change into the project's
top-level directory and run the command:
$ cabal2nix . >foo.nix
```shell
cabal2nix . > foo.nix
```
Then write the following snippet into a file called `default.nix`:
```nix
{ nixpkgs ? import <nixpkgs> {}, compiler ? "ghc7102" }:
nixpkgs.pkgs.haskell.packages.${compiler}.callPackage ./foo.nix { }
```
Finally, store the following code in a file called `shell.nix`:
```nix
{ nixpkgs ? import <nixpkgs> {}, compiler ? "ghc7102" }:
(import ./default.nix { inherit nixpkgs compiler; }).env
```
At this point, you can run `nix-build` to have Nix compile your project and
install it into a Nix store path. The local directory will contain a symlink
@ -486,9 +512,9 @@ libraries your package might need.
If your package does not depend on any system-level libraries, then it's
sufficient to run
$ nix-shell --command "cabal configure"
```shell
nix-shell --command "cabal configure"
```
once to set up your build. `cabal-install` determines the absolute paths to all
resources required for the build and writes them into a config file in the
`dist/` directory. Once that's done, you can run `cabal build` and any other
@ -502,14 +528,15 @@ If you want to do some quick-and-dirty hacking and don't want to bother setting
up a `default.nix` and `shell.nix` file manually, then you can use the
`--shell` flag offered by `cabal2nix` to have it generate a stand-alone
`nix-shell` environment for you. With that feature, running
$ cabal2nix --shell . >shell.nix
$ nix-shell --command "cabal configure"
```shell
cabal2nix --shell . > shell.nix
nix-shell --command "cabal configure"
```
is usually enough to set up a build environment for any given Haskell package.
You can even use that generated file to run `nix-build`, too:
$ nix-build shell.nix
```shell
nix-build shell.nix
```
### How to build projects that depend on each other
@ -518,13 +545,13 @@ you'll have to register those packages in the Nixpkgs set to make them visible
for the dependency resolution performed by `callPackage`. First of all, change
into each of your projects top-level directories and generate a `default.nix`
file with `cabal2nix`:
$ cd ~/src/foo && cabal2nix . >default.nix
$ cd ~/src/bar && cabal2nix . >default.nix
```shell
cd ~/src/foo && cabal2nix . > default.nix
cd ~/src/bar && cabal2nix . > default.nix
```
Then edit your `~/.config/nixpkgs/config.nix` file to register those builds in the
default Haskell package set:
```nix
{
packageOverrides = super: let self = super.pkgs; in
{
@ -536,15 +563,16 @@ default Haskell package set:
};
};
}
```
Once that's accomplished, `nix-env -f "<nixpkgs>" -qA haskellPackages` will
show your packages like any other package from Hackage, and you can build them
$ nix-build "<nixpkgs>" -A haskellPackages.foo
```shell
nix-build "<nixpkgs>" -A haskellPackages.foo
```
or enter an interactive shell environment suitable for building them:
$ nix-shell "<nixpkgs>" -A haskellPackages.bar.env
```shell
nix-shell "<nixpkgs>" -A haskellPackages.bar.env
```
## Miscellaneous Topics
@ -555,7 +583,7 @@ to manipulate the package as much as you please. One useful application of this
feature is to replace the default `mkDerivation` function with one that enables
library profiling for all packages. To accomplish that, add configure the
following snippet in your `~/.config/nixpkgs/config.nix` file:
```nix
{
packageOverrides = super: let self = super.pkgs; in
{
@ -568,7 +596,7 @@ following snippet in your `~/.config/nixpkgs/config.nix` file:
};
};
}
```
Then, replace instances of `haskellPackages` in the `cabal2nix`-generated
`default.nix` or `shell.nix` files with `profiledHaskellPackages`.
@ -580,11 +608,11 @@ at the time of this writing. This is fine for users of GHC 7.10.x, but GHC
7.8.4 cannot compile that binary. Now, one way to solve that problem is to
register an older version of `ghc-events` in the 7.8.x-specific package set.
The first step is to generate Nix build instructions with `cabal2nix`:
$ cabal2nix cabal://ghc-events-0.4.3.0 >~/.nixpkgs/ghc-events-0.4.3.0.nix
```shell
cabal2nix cabal://ghc-events-0.4.3.0 > ~/.nixpkgs/ghc-events-0.4.3.0.nix
```
Then add the override in `~/.config/nixpkgs/config.nix`:
```nix
{
packageOverrides = super: let self = super.pkgs; in
{
@ -599,16 +627,20 @@ Then add the override in `~/.config/nixpkgs/config.nix`:
};
};
}
```
This code is a little crazy, no doubt, but it's necessary because the intuitive
version
```nix
{ # ...
haskell.packages.ghc784 = super.haskell.packages.ghc784.override {
overrides = self: super: {
ghc-events = self.callPackage ./ghc-events-0.4.3.0.nix {};
};
};
}
```
doesn't do what we want it to: that code replaces the `haskell` package set in
Nixpkgs with one that contains only one entry,`packages`, which contains only
one entry `ghc784`. This override loses the `haskell.compiler` set, and it
@ -618,16 +650,16 @@ iterating over each step in hierarchy.
Once it's accomplished, however, we can install a variant of `ghc-events`
that's compiled with GHC 7.8.4:
```shell
nix-env -f "<nixpkgs>" -iA haskell.packages.ghc784.ghc-events
```
Unfortunately, it turns out that this build fails again while executing the
test suite! Apparently, the release archive on Hackage is missing some data
files that the test suite requires, so we cannot run it. We accomplish that by
re-generating the Nix expression with the `--no-check` flag:
$ cabal2nix --no-check cabal://ghc-events-0.4.3.0 >~/.nixpkgs/ghc-events-0.4.3.0.nix
```shell
cabal2nix --no-check cabal://ghc-events-0.4.3.0 > ~/.nixpkgs/ghc-events-0.4.3.0.nix
```
Now the builds succeeds.
Of course, in the concrete example of `ghc-events` this whole exercise is not
@ -642,71 +674,77 @@ older version might be useful.
GHC and distributed build farms don't get along well:
https://ghc.haskell.org/trac/ghc/ticket/4012
- https://ghc.haskell.org/trac/ghc/ticket/4012
When you see an error like this one
```
package foo-0.7.1.0 is broken due to missing package
text-1.2.0.4-98506efb1b9ada233bb5c2b2db516d91
```
then you have to download and re-install `foo` and all its dependents from
scratch:
# nix-store -q --referrers /nix/store/*-haskell-text-1.2.0.4 \
```shell
nix-store -q --referrers /nix/store/*-haskell-text-1.2.0.4 \
| xargs -L 1 nix-store --repair-path
```
If you're using additional Hydra servers other than `hydra.nixos.org`, then it
might be necessary to purge the local caches that store data from those
machines to disable these binary channels for the duration of the previous
command, i.e. by running:
```shell
rm /nix/var/nix/binary-cache-v3.sqlite
rm /nix/var/nix/manifests/*
rm /nix/var/nix/channel-cache/*
```
### How to use the Haste Haskell-to-Javascript transpiler
Open a shell with `haste-compiler` and `haste-cabal-install` (you don't actually need
`node`, but it can be useful to test stuff):
$ nix-shell -p "haskellPackages.ghcWithPackages (self: with self; [haste-cabal-install haste-compiler])" -p nodejs
```shell
nix-shell \
-p "haskellPackages.ghcWithPackages (self: with self; [haste-cabal-install haste-compiler])" \
-p nodejs
```
You may not need the following step but if `haste-boot` fails to compile all the
packages it needs, this might do the trick
$ haste-cabal update
```shell
haste-cabal update
```
`haste-boot` builds a set of core libraries so that they can be used from Javascript
transpiled programs:
$ haste-boot
```shell
haste-boot
```
Transpile and run a "Hello world" program:
```
$ echo 'module Main where main = putStrLn "Hello world"' > hello-world.hs
$ hastec --onexec hello-world.hs
$ node hello-world.js
Hello world
```
### Builds on Darwin fail with `math.h` not found
Users of GHC on Darwin have occasionally reported that builds fail, because the
compiler complains about a missing include file:
```
fatal error: 'math.h' file not found
```
The issue has been discussed at length in [ticket
6390](https://github.com/NixOS/nixpkgs/issues/6390), and so far no good
solution has been proposed. As a work-around, users who run into this problem
can configure the environment variables
```shell
export NIX_CFLAGS_COMPILE="-idirafter /usr/include"
export NIX_CFLAGS_LINK="-L/usr/lib"
```
in their `~/.bashrc` file to avoid the compiler error.
### Builds using Stack complain about missing system libraries
```
-- While building package zlib-0.5.4.2 using:
runhaskell -package=Cabal-1.22.4.0 -clear-package-db [... lots of flags ...]
Process exited with code: ExitFailure 1
@ -722,11 +760,12 @@ in their `~/.bashrc` file to avoid the compiler error.
If the header file does exist, it may contain errors that are caught by the C
compiler at the preprocessing stage. In this case you can re-run configure
with the verbosity flag -v3 to see the error messages.
```
When you run the build inside of the nix-shell environment, the system
is configured to find libz.so without any special flags -- the compiler
is configured to find `libz.so` without any special flags -- the compiler
and linker "just know" how to find it. Consequently, Cabal won't record
any search paths for libz.so in the package description, which means
any search paths for `libz.so` in the package description, which means
that the package works fine inside of nix-shell, but once you leave the
shell the shared object can no longer be found. That issue is by no
means specific to Stack: you'll have that problem with any other
@ -735,39 +774,41 @@ environment.
You can remedy this issue in several ways. The easiest is to add a `nix` section
to the `stack.yaml` like the following:
```yaml
nix:
enable: true
packages: [ zlib ]
```
Stack's Nix support knows to add `${zlib.out}/lib` and `${zlib.dev}/include` as an
`--extra-lib-dirs` and `extra-include-dirs`, respectively. Alternatively, you
can achieve the same effect by hand. First of all, run
Stack's Nix support knows to add `${zlib.out}/lib` and `${zlib.dev}/include`
as an `--extra-lib-dirs` and `extra-include-dirs`, respectively.
Alternatively, you can achieve the same effect by hand. First of all, run
```
$ nix-build --no-out-link "<nixpkgs>" -A zlib
/nix/store/alsvwzkiw4b7ip38l4nlfjijdvg3fvzn-zlib-1.2.8
```
to find out the store path of the system's zlib library. Now, you can
1) add that path (plus a "/lib" suffix) to your $LD_LIBRARY_PATH
environment variable to make sure your system linker finds libz.so
1. add that path (plus a "/lib" suffix) to your `$LD_LIBRARY_PATH`
environment variable to make sure your system linker finds `libz.so`
automatically. It's no pretty solution, but it will work.
2) As a variant of (1), you can also install any number of system
2. As a variant of (1), you can also install any number of system
libraries into your user's profile (or some other profile) and point
$LD_LIBRARY_PATH to that profile instead, so that you don't have to
`$LD_LIBRARY_PATH` to that profile instead, so that you don't have to
list dozens of those store paths all over the place.
3) The solution I prefer is to call stack with an appropriate
3. The solution I prefer is to call stack with an appropriate
--extra-lib-dirs flag like so:
```shell
stack --extra-lib-dirs=/nix/store/alsvwzkiw4b7ip38l4nlfjijdvg3fvzn-zlib-1.2.8/lib build
```
$ stack --extra-lib-dirs=/nix/store/alsvwzkiw4b7ip38l4nlfjijdvg3fvzn-zlib-1.2.8/lib build
Typically, you'll need --extra-include-dirs as well. It's possible
to add those flag to the project's "stack.yaml" or your user's
global "~/.stack/global/stack.yaml" file so that you don't have to
specify them manually every time. But again, you're likely better off using
Stack's Nix support instead.
Typically, you'll need `--extra-include-dirs` as well. It's possible
to add those flag to the project's `stack.yaml` or your user's
global `~/.stack/global/stack.yaml` file so that you don't have to
specify them manually every time. But again, you're likely better off
using Stack's Nix support instead.
The same thing applies to `cabal configure`, of course, if you're
building with `cabal-install` instead of Stack.
@ -777,21 +818,22 @@ to find out the store path of the system's zlib library. Now, you can
There are two levels of static linking. The first option is to configure the
build with the Cabal flag `--disable-executable-dynamic`. In Nix expressions,
this can be achieved by setting the attribute:
```
enableSharedExecutables = false;
```
That gives you a binary with statically linked Haskell libraries and
dynamically linked system libraries.
To link both Haskell libraries and system libraries statically, the additional
flags `--ghc-option=-optl=-static --ghc-option=-optl=-pthread` need to be used.
In Nix, this is accomplished with:
```
configureFlags = [ "--ghc-option=-optl=-static" "--ghc-option=-optl=-pthread" ];
```
It's important to realize, however, that most system libraries in Nix are built
as shared libraries only, i.e. there is just no static library available that
Cabal could link!
It's important to realize, however, that most system libraries in Nix are
built as shared libraries only, i.e. there is just no static library
available that Cabal could link!
### Building GHC with integer-simple
@ -801,7 +843,7 @@ The implementation can be found in the
[integer-gmp](http://hackage.haskell.org/package/integer-gmp) package.
A potential problem with this is that GMP is licensed under the
[​GNU Lesser General Public License (LGPL)](http://www.gnu.org/copyleft/lesser.html),
[GNU Lesser General Public License (LGPL)](http://www.gnu.org/copyleft/lesser.html),
a kind of "copyleft" license. According to the terms of the LGPL, paragraph 5,
you may distribute a program that is designed to be compiled and dynamically
linked with the library under the terms of your choice (i.e., commercially) but
@ -814,7 +856,7 @@ The LGPL licensing for GMP is a problem for the overall licensing of binary
programs compiled with GHC because most distributions (and builds) of GHC use
static libraries. (Dynamic libraries are currently distributed only for OS X.)
The LGPL licensing situation may be worse: even though
​[The Glasgow Haskell Compiler License](https://www.haskell.org/ghc/license)
[The Glasgow Haskell Compiler License](https://www.haskell.org/ghc/license)
is essentially a "free software" license (BSD3), according to
paragraph 2 of the LGPL, GHC must be distributed under the terms of the LGPL!
@ -825,14 +867,14 @@ alternative implemention for Integer called
To get a GHC compiler build with `integer-simple` instead of `integer-gmp` use
the attribute: `haskell.compiler.integer-simple."${ghcVersion}"`.
For example:
```
$ nix-build -E '(import <nixpkgs> {}).haskell.compiler.integer-simple.ghc802'
...
$ result/bin/ghc-pkg list | grep integer
integer-simple-0.1.1.1
```
The following command displays the complete list of GHC compilers build with `integer-simple`:
```
$ nix-env -f "<nixpkgs>" -qaP -A haskell.compiler.integer-simple
haskell.compiler.integer-simple.ghc7102 ghc-7.10.2
haskell.compiler.integer-simple.ghc7103 ghc-7.10.3
@ -843,13 +885,14 @@ The following command displays the complete list of GHC compilers build with `in
haskell.compiler.integer-simple.ghc801 ghc-8.0.1
haskell.compiler.integer-simple.ghc802 ghc-8.0.2
haskell.compiler.integer-simple.ghcHEAD ghc-8.1.20170106
```
To get a package set supporting `integer-simple` use the attribute:
`haskell.packages.integer-simple."${ghcVersion}"`. For example
use the following to get the `scientific` package build with `integer-simple`:
$ nix-build -A haskell.packages.integer-simple.ghc802.scientific
```shell
nix-build -A haskell.packages.integer-simple.ghc802.scientific
```
## Other resources