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Configuration
=============

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.. highlight:: cabal

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Overview
--------

The global configuration file for ``cabal-install`` is
``~/.cabal/config``. If you do not have this file, ``cabal`` will create
it for you on the first call to ``cabal update``. Alternatively, you can
explicitly ask ``cabal`` to create it for you using

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.. code-block:: console

    $ cabal user-config update
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Most of the options in this configuration file are also available as
command line arguments, and the corresponding documentation can be used
to lookup their meaning. The created configuration file only specifies
values for a handful of options. Most options are left at their default
value, which it documents; for instance,

::

    -- executable-stripping: True

means that the configuration file currently does not specify a value for
the ``executable-stripping`` option (the line is commented out), and
that the default is ``True``; if you wanted to disable stripping of
executables by default, you would change this line to

::

    executable-stripping: False

You can also use ``cabal user-config update`` to migrate configuration
files created by older versions of ``cabal``.

Repository specification
------------------------

An important part of the configuration if the specification of the
repository. When ``cabal`` creates a default config file, it configures
the repository to be the central Hackage server:

::

    repository hackage.haskell.org
      url: http://hackage.haskell.org/

The name of the repository is given on the first line, and can be
anything; packages downloaded from this repository will be cached under
``~/.cabal/packages/hackage.haskell.org`` (or whatever name you specify;
you can change the prefix by changing the value of
``remote-repo-cache``). If you want, you can configure multiple
repositories, and ``cabal`` will combine them and be able to download
packages from any of them.

Using secure repositories
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^^^^^^^^^^^^^^^^^^^^^^^^^
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For repositories that support the TUF security infrastructure (this
includes Hackage), you can enable secure access to the repository by
specifying:

::

    repository hackage.haskell.org
      url: http://hackage.haskell.org/
      secure: True
      root-keys: <root-key-IDs>
      key-threshold: <key-threshold>

The ``<root-key-IDs>`` and ``<key-threshold>`` values are used for
bootstrapping. As part of the TUF infrastructure the repository will
contain a file ``root.json`` (for instance,
http://hackage.haskell.org/root.json) which the client needs to do
verification. However, how can ``cabal`` verify the ``root.json`` file
*itself*? This is known as bootstrapping: if you specify a list of root
key IDs and a corresponding threshold, ``cabal`` will verify that the
downloaded ``root.json`` file has been signed with at least
``<key-threshold>`` keys from your set of ``<root-key-IDs>``.

You can, but are not recommended to, omit these two fields. In that case
``cabal`` will download the ``root.json`` field and use it without
verification. Although this bootstrapping step is then unsafe, all
subsequent access is secure (provided that the downloaded ``root.json``
was not tempered with). Of course, adding ``root-keys`` and
``key-threshold`` to your repository specification only shifts the
problem, because now you somehow need to make sure that the key IDs you
received were the right ones. How that is done is however outside the
scope of ``cabal`` proper.

More information about the security infrastructure can be found at
https://github.com/well-typed/hackage-security.

Legacy repositories
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^^^^^^^^^^^^^^^^^^^
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Currently ``cabal`` supports two kinds of legacy repositories. The
first is specified using

::

    remote-repo: hackage.haskell.org:http://hackage.haskell.org/packages/archive

This is just syntactic sugar for

::

    repository hackage.haskell.org
      url: hackage.haskell.org:http://hackage.haskell.org/packages/archive

although, in (and only in) the specific case of Hackage, the URL
``http://hackage.haskell.org/packages/archive`` will be silently
translated to ``http://hackage.haskell.org/``.

The second kind of legacy repositories are so-called local
repositories:

::

    local-repo: my-local-repo:/path/to/local/repo

This can be used to access repositories on the local file system.
However, the layout of these local repositories is different from the
layout of remote repositories, and usage of these local repositories is
deprecated.

Secure local repositories
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^^^^^^^^^^^^^^^^^^^^^^^^^
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If you want to use repositories on your local file system, it is
recommended instead to use a *secure* local repository:

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::
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    repository my-local-repo
      url: file:/path/to/local/repo
      secure: True
      root-keys: <root-key-IDs>
      key-threshold: <key-threshold>

The layout of these secure local repos matches the layout of remote
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repositories exactly; the :hackage-pkg:`hackage-repo-tool`
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can be used to create and manage such repositories.

Building and installing packages
================================

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.. highlight:: console

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After you've unpacked a Cabal package, you can build it by moving into
the root directory of the package and running the ``cabal`` tool there:

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::

    $ cabal [command] [option...]
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The *command* argument selects a particular step in the build/install
process.

You can also get a summary of the command syntax with

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::

    $ cabal help
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Alternatively, you can also use the ``Setup.hs`` or ``Setup.lhs``
script:

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::

    $ runhaskell Setup.hs [command] [option...]
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For the summary of the command syntax, run:

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::

    $ cabal help
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or

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::

    $ runhaskell Setup.hs --help
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Building and installing a system package
----------------------------------------

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::
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    $ runhaskell Setup.hs configure --ghc
    $ runhaskell Setup.hs build
    $ runhaskell Setup.hs install
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The first line readies the system to build the tool using GHC; for
example, it checks that GHC exists on the system. The second line
performs the actual building, while the last both copies the build
results to some permanent place and registers the package with GHC.

Building and installing a user package
--------------------------------------

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::
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    $ runhaskell Setup.hs configure --user
    $ runhaskell Setup.hs build
    $ runhaskell Setup.hs install
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The package is installed under the user's home directory and is
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registered in the user's package database (:option:`setup configure --user`).
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Installing packages from Hackage
--------------------------------

The ``cabal`` tool also can download, configure, build and install a
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Hackage_ package and all of its
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dependencies in a single step. To do this, run:

::

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   $ cabal install [PACKAGE...]
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To browse the list of available packages, visit the
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Hackage_ web site.
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Developing with sandboxes
-------------------------

By default, any dependencies of the package are installed into the
global or user package databases (e.g. using
``cabal install --only-dependencies``). If you're building several
different packages that have incompatible dependencies, this can cause
the build to fail. One way to avoid this problem is to build each
package in an isolated environment ("sandbox"), with a sandbox-local
package database. Because sandboxes are per-project, inconsistent
dependencies can be simply disallowed.

For more on sandboxes, see also `this
article <http://coldwa.st/e/blog/2013-08-20-Cabal-sandbox.html>`__.

Sandboxes: basic usage
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^^^^^^^^^^^^^^^^^^^^^^
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To initialise a fresh sandbox in the current directory, run
``cabal sandbox init``. All subsequent commands (such as ``build`` and
``install``) from this point will use the sandbox.

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::
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    $ cd /path/to/my/haskell/library
    $ cabal sandbox init                   # Initialise the sandbox
    $ cabal install --only-dependencies    # Install dependencies into the sandbox
    $ cabal build                          # Build your package inside the sandbox

It can be useful to make a source package available for installation in
the sandbox - for example, if your package depends on a patched or an
unreleased version of a library. This can be done with the
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``cabal sandbox add-source`` command - think of it as "local Hackage_".
If an add-source dependency is later modified, it is reinstalled automatically.
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::
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    $ cabal sandbox add-source /my/patched/library # Add a new add-source dependency
    $ cabal install --dependencies-only            # Install it into the sandbox
    $ cabal build                                  # Build the local package
    $ $EDITOR /my/patched/library/Source.hs        # Modify the add-source dependency
    $ cabal build                                  # Modified dependency is automatically reinstalled

Normally, the sandbox settings (such as optimisation level) are
inherited from the main Cabal config file (``$HOME/cabal/config``).
Sometimes, though, you need to change some settings specifically for a
single sandbox. You can do this by creating a ``cabal.config`` file in
the same directory with your ``cabal.sandbox.config`` (which was created
by ``sandbox init``). This file has the same syntax as the main Cabal
config file.

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::
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    $ cat cabal.config
    documentation: True
    constraints: foo == 1.0, bar >= 2.0, baz
    $ cabal build                                  # Uses settings from the cabal.config file

When you have decided that you no longer want to build your package
inside a sandbox, just delete it:

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::
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    $ cabal sandbox delete                       # Built-in command
    $ rm -rf .cabal-sandbox cabal.sandbox.config # Alternative manual method

Sandboxes: advanced usage
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^^^^^^^^^^^^^^^^^^^^^^^^^
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The default behaviour of the ``add-source`` command is to track
modifications done to the added dependency and reinstall the sandbox
copy of the package when needed. Sometimes this is not desirable: in
these cases you can use ``add-source --snapshot``, which disables the
change tracking. In addition to ``add-source``, there are also
``list-sources`` and ``delete-source`` commands.

Sometimes one wants to share a single sandbox between multiple packages.
This can be easily done with the ``--sandbox`` option:

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::
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    $ mkdir -p /path/to/shared-sandbox
    $ cd /path/to/shared-sandbox
    $ cabal sandbox init --sandbox .
    $ cd /path/to/package-a
    $ cabal sandbox init --sandbox /path/to/shared-sandbox
    $ cd /path/to/package-b
    $ cabal sandbox init --sandbox /path/to/shared-sandbox

Note that ``cabal sandbox init --sandbox .`` puts all sandbox files into
the current directory. By default, ``cabal sandbox init`` initialises a
new sandbox in a newly-created subdirectory of the current working
directory (``./.cabal-sandbox``).

Using multiple different compiler versions simultaneously is also
supported, via the ``-w`` option:

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::
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    $ cabal sandbox init
    $ cabal install --only-dependencies -w /path/to/ghc-1 # Install dependencies for both compilers
    $ cabal install --only-dependencies -w /path/to/ghc-2
    $ cabal configure -w /path/to/ghc-1                   # Build with the first compiler
    $ cabal build
    $ cabal configure -w /path/to/ghc-2                   # Build with the second compiler
    $ cabal build

It can be occasionally useful to run the compiler-specific package
manager tool (e.g. ``ghc-pkg``) tool on the sandbox package DB directly
(for example, you may need to unregister some packages). The
``cabal sandbox hc-pkg`` command is a convenient wrapper that runs the
compiler-specific package manager tool with the arguments:

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::
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    $ cabal -v sandbox hc-pkg list
    Using a sandbox located at /path/to/.cabal-sandbox
    'ghc-pkg' '--global' '--no-user-package-conf'
        '--package-conf=/path/to/.cabal-sandbox/i386-linux-ghc-7.4.2-packages.conf.d'
        'list'
    [...]

The ``--require-sandbox`` option makes all sandbox-aware commands
(``install``/``build``/etc.) exit with error if there is no sandbox
present. This makes it harder to accidentally modify the user package
database. The option can be also turned on via the per-user
configuration file (``~/.cabal/config``) or the per-project one
(``$PROJECT_DIR/cabal.config``). The error can be squelched with
``--no-require-sandbox``.

The option ``--sandbox-config-file`` allows to specify the location of
the ``cabal.sandbox.config`` file (by default, ``cabal`` searches for it
in the current directory). This provides the same functionality as
shared sandboxes, but sometimes can be more convenient. Example:

::

    $ mkdir my/sandbox
    $ cd my/sandbox
    $ cabal sandbox init
    $ cd /path/to/my/project
    $ cabal --sandbox-config-file=/path/to/my/sandbox/cabal.sandbox.config install
    # Uses the sandbox located at /path/to/my/sandbox/.cabal-sandbox
    $ cd ~
    $ cabal --sandbox-config-file=/path/to/my/sandbox/cabal.sandbox.config install
    # Still uses the same sandbox

The sandbox config file can be also specified via the
``CABAL_SANDBOX_CONFIG`` environment variable.

Finally, the flag ``--ignore-sandbox`` lets you temporarily ignore an
existing sandbox:

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::
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    $ mkdir my/sandbox
    $ cd my/sandbox
    $ cabal sandbox init
    $ cabal --ignore-sandbox install text
    # Installs 'text' in the user package database ('~/.cabal').

Creating a binary package
-------------------------

When creating binary packages (e.g. for Red Hat or Debian) one needs to
create a tarball that can be sent to another system for unpacking in the
root directory:

::

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    $ runhaskell Setup.hs configure --prefix=/usr
    $ runhaskell Setup.hs build
    $ runhaskell Setup.hs copy --destdir=/tmp/mypkg
    $ tar -czf mypkg.tar.gz /tmp/mypkg/
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If the package contains a library, you need two additional steps:

::

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    $ runhaskell Setup.hs register --gen-script
    $ runhaskell Setup.hs unregister --gen-script
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This creates shell scripts ``register.sh`` and ``unregister.sh``, which
must also be sent to the target system. After unpacking there, the
package must be registered by running the ``register.sh`` script. The
``unregister.sh`` script would be used in the uninstall procedure of the
package. Similar steps may be used for creating binary packages for
Windows.

The following options are understood by all commands:

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.. program:: setup

.. option:: --help, -h or -?

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    List the available options for the command.
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.. option:: --verbose=n or -v n

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    Set the verbosity level (0-3). The normal level is 1; a missing *n*
    defaults to 2.

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    There is also an extended version of this command which can be
    used to fine-tune the verbosity of output.  It takes the
    form ``[silent|normal|verbose|debug]``\ *flags*, where *flags*
    is a list of ``+`` flags which toggle various aspects of
    output.  At the moment, only ``+callsite`` and ``+callstack``
    are supported, which respectively toggle call site and call
    stack printing (these are only supported if Cabal
    is built with a sufficiently recent GHC.)

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The various commands and the additional options they support are
described below. In the simple build infrastructure, any other options
will be reported as errors.

setup configure
---------------

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.. program:: setup configure

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Prepare to build the package. Typically, this step checks that the
target platform is capable of building the package, and discovers
platform-specific features that are needed during the build.

The user may also adjust the behaviour of later stages using the options
listed in the following subsections. In the simple build infrastructure,
the values supplied via these options are recorded in a private file
read by later stages.

If a user-supplied ``configure`` script is run (see the section on
`system-dependent
parameters <developing-packages.html#system-dependent-parameters>`__ or
on `complex
packages <developing-packages.html#more-complex-packages>`__), it is
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passed the :option:`--with-hc-pkg`, :option:`--prefix`, :option:`--bindir`,
:option:`--libdir`, :option:`--datadir`, :option:`--libexecdir` and
:option:`--sysconfdir` options. In addition the value of the
:option:`--with-compiler` option is passed in a :option:`--with-hc-pkg` option
and all options specified with :option:`--configure-option` are passed on.
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In Cabal 2.0, support for a single positional argument was added to
``setup configure`` This makes Cabal configure a the specific component
to be configured. Specified names can be qualified with ``lib:`` or
``exe:`` in case just a name is ambiguous (as would be the case for a
package named ``p`` which has a library and an executable named ``p``.)
This has the following effects:

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-  Subsequent invocations of ``cabal build``, ``register``, etc. operate only
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   on the configured component.

-  Cabal requires all "internal" dependencies (e.g., an executable
   depending on a library defined in the same package) must be found in
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   the set of databases via :option:`--package-db` (and related flags): these
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   dependencies are assumed to be up-to-date. A dependency can be
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   explicitly specified using :option:`--dependency` simply by giving the name
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   of the internal library; e.g., the dependency for an internal library
   named ``foo`` is given as
   ``--dependency=pkg-internal=pkg-1.0-internal-abcd``.

-  Only the dependencies needed for the requested component are
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   required. Similarly, when :option:`--exact-configuration` is specified,
   it's only necessary to specify :option:`--dependency` for the component.
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   (As mentioned previously, you *must* specify internal dependencies as
   well.)

-  Internal ``build-tools`` dependencies are expected to be in the
   ``PATH`` upon subsequent invocations of ``setup``.

Full details can be found in the `Componentized Cabal
proposal <https://github.com/ezyang/ghc-proposals/blob/master/proposals/0000-componentized-cabal.rst>`__.

Programs used for building
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^^^^^^^^^^^^^^^^^^^^^^^^^^
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The following options govern the programs used to process the source
files of a package:

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.. option:: --ghc or -g, --jhc, --lhc, --uhc

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    Specify which Haskell implementation to use to build the package. At
    most one of these flags may be given. If none is given, the
    implementation under which the setup script was compiled or
    interpreted is used.
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.. option:: --with-compiler=path or -w *path*

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    Specify the path to a particular compiler. If given, this must match
    the implementation selected above. The default is to search for the
    usual name of the selected implementation.

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    This flag also sets the default value of the :option:`--with-hc-pkg`
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    option to the package tool for this compiler. Check the output of
    ``setup configure -v`` to ensure that it finds the right package
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    tool (or use :option:`--with-hc-pkg` explicitly).

.. option:: --with-hc-pkg=path
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    Specify the path to the package tool, e.g. ``ghc-pkg``. The package
    tool must be compatible with the compiler specified by
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    :option:`--with-compiler`. If this option is omitted, the default value is
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    determined from the compiler selected.
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.. option:: --with-prog=path

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    Specify the path to the program *prog*. Any program known to Cabal
    can be used in place of *prog*. It can either be a fully path or the
    name of a program that can be found on the program search path. For
    example: ``--with-ghc=ghc-6.6.1`` or
    ``--with-cpphs=/usr/local/bin/cpphs``. The full list of accepted
    programs is not enumerated in this user guide. Rather, run
    ``cabal install --help`` to view the list.
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.. option:: --prog-options=options

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    Specify additional options to the program *prog*. Any program known
    to Cabal can be used in place of *prog*. For example:
    ``--alex-options="--template=mytemplatedir/"``. The *options* is
    split into program options based on spaces. Any options containing
    embedded spaced need to be quoted, for example
    ``--foo-options='--bar="C:\Program File\Bar"'``. As an alternative
    that takes only one option at a time but avoids the need to quote,
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    use :option:`--prog-option` instead.

.. option:: --prog-option=option

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    Specify a single additional option to the program *prog*. For
    passing an option that contain embedded spaces, such as a file name
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    with embedded spaces, using this rather than :option:`--prog-options`
    means you do not need an additional level of quoting. Of course if you
    are using a command shell you may still need to quote, for example
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    ``--foo-options="--bar=C:\Program File\Bar"``.

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All of the options passed with either :option:`--prog-options`
or :option:`--prog-option` are passed in the order they were
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specified on the configure command line.

Installation paths
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^^^^^^^^^^^^^^^^^^
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The following options govern the location of installed files from a
package:

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.. option:: --prefix=dir

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    The root of the installation. For example for a global install you
    might use ``/usr/local`` on a Unix system, or ``C:\Program Files``
    on a Windows system. The other installation paths are usually
    subdirectories of *prefix*, but they don't have to be.

    In the simple build system, *dir* may contain the following path
    variables: ``$pkgid``, ``$pkg``, ``$version``, ``$compiler``,
    ``$os``, ``$arch``, ``$abi``, ``$abitag``

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.. option:: --bindir=dir

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    Executables that the user might invoke are installed here.

    In the simple build system, *dir* may contain the following path
    variables: ``$prefix``, ``$pkgid``, ``$pkg``, ``$version``,
    ``$compiler``, ``$os``, ``$arch``, ``$abi``, \`$abitag

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.. option:: --libdir=dir

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    Object-code libraries are installed here.

    In the simple build system, *dir* may contain the following path
    variables: ``$prefix``, ``$bindir``, ``$pkgid``, ``$pkg``,
    ``$version``, ``$compiler``, ``$os``, ``$arch``, ``$abi``,
    ``$abitag``

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.. option:: --libexecdir=dir

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    Executables that are not expected to be invoked directly by the user
    are installed here.

    In the simple build system, *dir* may contain the following path
    variables: ``$prefix``, ``$bindir``, ``$libdir``, ``$libsubdir``,
    ``$pkgid``, ``$pkg``, ``$version``, ``$compiler``, ``$os``,
    ``$arch``, ``$abi``, ``$abitag``

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.. option:: --datadir=dir

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    Architecture-independent data files are installed here.

    In the simple build system, *dir* may contain the following path
    variables: ``$prefix``, ``$bindir``, ``$libdir``, ``$libsubdir``,
    ``$pkgid``, ``$pkg``, ``$version``, ``$compiler``, ``$os``,
    ``$arch``, ``$abi``, ``$abitag``

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.. option:: --sysconfdir=dir

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    Installation directory for the configuration files.

    In the simple build system, *dir* may contain the following path
    variables: ``$prefix``, ``$bindir``, ``$libdir``, ``$libsubdir``,
    ``$pkgid``, ``$pkg``, ``$version``, ``$compiler``, ``$os``,
    ``$arch``, ``$abi``, ``$abitag``

In addition the simple build system supports the following installation
path options:

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.. option:: --libsubdir=dir

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    A subdirectory of *libdir* in which libraries are actually
    installed. For example, in the simple build system on Unix, the
    default *libdir* is ``/usr/local/lib``, and *libsubdir* contains the
    package identifier and compiler, e.g. ``mypkg-0.2/ghc-6.4``, so
    libraries would be installed in
    ``/usr/local/lib/mypkg-0.2/ghc-6.4``.

    *dir* may contain the following path variables: ``$pkgid``,
    ``$pkg``, ``$version``, ``$compiler``, ``$os``, ``$arch``, ``$abi``,
    ``$abitag``

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.. option:: --datasubdir=dir

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    A subdirectory of *datadir* in which data files are actually
    installed.

    *dir* may contain the following path variables: ``$pkgid``,
    ``$pkg``, ``$version``, ``$compiler``, ``$os``, ``$arch``, ``$abi``,
    ``$abitag``

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.. option:: --docdir=dir

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    Documentation files are installed relative to this directory.

    *dir* may contain the following path variables: ``$prefix``,
    ``$bindir``, ``$libdir``, ``$libsubdir``, ``$datadir``,
    ``$datasubdir``, ``$pkgid``, ``$pkg``, ``$version``, ``$compiler``,
    ``$os``, ``$arch``, ``$abi``, ``$abitag``

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.. option:: --htmldir=dir

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    HTML documentation files are installed relative to this directory.

    *dir* may contain the following path variables: ``$prefix``,
    ``$bindir``, ``$libdir``, ``$libsubdir``, ``$datadir``,
    ``$datasubdir``, ``$docdir``, ``$pkgid``, ``$pkg``, ``$version``,
    ``$compiler``, ``$os``, ``$arch``, ``$abi``, ``$abitag``

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.. option:: --program-prefix=prefix

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    Prepend *prefix* to installed program names.

    *prefix* may contain the following path variables: ``$pkgid``,
    ``$pkg``, ``$version``, ``$compiler``, ``$os``, ``$arch``, ``$abi``,
    ``$abitag``

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.. option:: --program-suffix=suffix

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    Append *suffix* to installed program names. The most obvious use for
    this is to append the program's version number to make it possible
    to install several versions of a program at once:
    ``--program-suffix='$version'``.

    *suffix* may contain the following path variables: ``$pkgid``,
    ``$pkg``, ``$version``, ``$compiler``, ``$os``, ``$arch``, ``$abi``,
    ``$abitag``

Path variables in the simple build system
690
"""""""""""""""""""""""""""""""""""""""""
691 692 693 694 695 696 697 698 699

For the simple build system, there are a number of variables that can be
used when specifying installation paths. The defaults are also specified
in terms of these variables. A number of the variables are actually for
other paths, like ``$prefix``. This allows paths to be specified
relative to each other rather than as absolute paths, which is important
for building relocatable packages (see `prefix
independence <#prefix-independence>`__).

700
$prefix
701 702 703
    The path variable that stands for the root of the installation. For
    an installation to be relocatable, all other installation paths must
    be relative to the ``$prefix`` variable.
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$bindir
    The path variable that expands to the path given by the :option:`--bindir`
706
    configure option (or the default).
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$libdir
    As above but for :option:`--libdir`
$libsubdir
    As above but for :option:`--libsubdir`
$datadir
    As above but for :option:`--datadir`
$datasubdir
    As above but for :option:`--datasubdir`
$docdir
    As above but for :option:`--docdir`
$pkgid
718
    The name and version of the package, e.g. ``mypkg-0.2``
719
$pkg
720
    The name of the package, e.g. ``mypkg``
721
$version
722
    The version of the package, e.g. ``0.2``
723
$compiler
724
    The compiler being used to build the package, e.g. ``ghc-6.6.1``
725
$os
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    The operating system of the computer being used to build the
    package, e.g. ``linux``, ``windows``, ``osx``, ``freebsd`` or
    ``solaris``
729
$arch
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    The architecture of the computer being used to build the package,
    e.g. ``i386``, ``x86_64``, ``ppc`` or ``sparc``
732
$abitag
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    An optional tag that a compiler can use for telling incompatible
    ABI's on the same architecture apart. GHCJS encodes the underlying
    GHC version in the ABI tag.
736
$abi
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    A shortcut for getting a path that completely identifies the
    platform in terms of binary compatibility. Expands to the same value
    as ``$arch-$os-compiler-$abitag`` if the compiler uses an abi tag,
    ``$arch-$os-$compiler`` if it doesn't.

Paths in the simple build system
743
""""""""""""""""""""""""""""""""
744 745 746

For the simple build system, the following defaults apply:

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.. list-table:: Default installation paths

    * - Option
      - Windows Default
      - Unix Default
    * - :option:`--prefix` (global)
      - ``C:\Program Files\Haskell``
      - ``/usr/local``
    * - :option:`--prefix` (per-user)
      - ``C:\Documents And Settings\user\Application Data\cabal``
      - ``$HOME/.cabal``
    * - :option:`--bindir`
      - ``$prefix\bin``
      - ``$prefix/bin``
    * - :option:`--libdir`
      - ``$prefix``
      - ``$prefix/lib``
    * - :option:`--libsubdir` (others)
      - ``$pkgid\$compiler``
      - ``$pkgid/$compiler``
    * - :option:`--libexecdir`
      - ``$prefix\$pkgid``
      - ``$prefix/libexec``
    * - :option:`--datadir` (executable)
      - ``$prefix``
      - ``$prefix/share``
    * - :option:`--datadir` (library)
      - ``C:\Program Files\Haskell``
      - ``$prefix/share``
    * - :option:`--datasubdir`
      - ``$pkgid``
      - ``$pkgid``
    * - :option:`--docdir`
      - ``$prefix\doc\$pkgid``
      - ``$datadir/doc/$pkgid``
    * - :option:`--sysconfdir`
      - ``$prefix\etc``
      - ``$prefix/etc``
    * - :option:`--htmldir`
      - ``$docdir\html``
      - ``$docdir/html``
    * - :option:`--program-prefix`
      - (empty)
      - (empty)
    * - :option:`--program-suffix`
      - (empty)
      - (empty)
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Prefix-independence
796
"""""""""""""""""""
797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823

On Windows it is possible to obtain the pathname of the running program.
This means that we can construct an installable executable package that
is independent of its absolute install location. The executable can find
its auxiliary files by finding its own path and knowing the location of
the other files relative to ``$bindir``. Prefix-independence is
particularly useful: it means the user can choose the install location
(i.e. the value of ``$prefix``) at install-time, rather than having to
bake the path into the binary when it is built.

In order to achieve this, we require that for an executable on Windows,
all of ``$bindir``, ``$libdir``, ``$datadir`` and ``$libexecdir`` begin
with ``$prefix``. If this is not the case then the compiled executable
will have baked-in all absolute paths.

The application need do nothing special to achieve prefix-independence.
If it finds any files using ``getDataFileName`` and the `other functions
provided for the
purpose <developing-packages.html#accessing-data-files-from-package-code>`__,
the files will be accessed relative to the location of the current
executable.

A library cannot (currently) be prefix-independent, because it will be
linked into an executable whose file system location bears no relation
to the library package.

Controlling Flag Assignments
824
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
825 826 827 828 829

Flag assignments (see the `resolution of conditions and
flags <developing-packages.html#resolution-of-conditions-and-flags>`__)
can be controlled with the following command line options.

830 831
.. option:: -f flagname or -f -flagname

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    Force the specified flag to ``true`` or ``false`` (if preceded with
    a ``-``). Later specifications for the same flags will override
    earlier, i.e., specifying ``-fdebug -f-debug`` is equivalent to
    ``-f-debug``
836 837 838

.. option:: --flags=flagspecs

839 840 841 842 843 844 845 846
    Same as ``-f``, but allows specifying multiple flag assignments at
    once. The parameter is a space-separated list of flag names (to
    force a flag to ``true``), optionally preceded by a ``-`` (to force
    a flag to ``false``). For example,
    ``--flags="debug -feature1 feature2"`` is equivalent to
    ``-fdebug -f-feature1 -ffeature2``.

Building Test Suites
847
^^^^^^^^^^^^^^^^^^^^
848

849 850
.. option:: --enable-tests

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    Build the test suites defined in the package description file during
    the ``build`` stage. Check for dependencies required by the test
    suites. If the package is configured with this option, it will be
    possible to run the test suites with the ``test`` command after the
    package is built.
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.. option:: --disable-tests

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    (default) Do not build any test suites during the ``build`` stage.
    Do not check for dependencies required only by the test suites. It
    will not be possible to invoke the ``test`` command without
    reconfiguring the package.
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.. option:: --enable-coverage

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    Build libraries and executables (including test suites) with Haskell
    Program Coverage enabled. Running the test suites will automatically
    generate coverage reports with HPC.
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.. option:: --disable-coverage

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    (default) Do not enable Haskell Program Coverage.

Miscellaneous options
875
^^^^^^^^^^^^^^^^^^^^^
876

877 878
.. option:: --user

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    Does a per-user installation. This changes the `default installation
    prefix <#paths-in-the-simple-build-system>`__. It also allow
    dependencies to be satisfied by the user's package database, in
    addition to the global database. This also implies a default of
    ``--user`` for any subsequent ``install`` command, as packages
    registered in the global database should not depend on packages
    registered in a user's database.
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.. option:: --global

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    (default) Does a global installation. In this case package
    dependencies must be satisfied by the global package database. All
    packages in the user's package database will be ignored. Typically
    the final installation step will require administrative privileges.
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.. option:: --package-db=db

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    Allows package dependencies to be satisfied from this additional
    package database *db* in addition to the global package database.
    All packages in the user's package database will be ignored. The
    interpretation of *db* is implementation-specific. Typically it will
    be a file or directory. Not all implementations support arbitrary
    package databases.

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    This pushes an extra db onto the db stack. The :option:`--global` and
    :option:`--user` mode switches add the respective [Global] and [Global,
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    User] dbs to the initial stack. There is a compiler-implementation
    constraint that the global db must appear first in the stack, and if
    the user one appears at all, it must appear immediately after the
    global db.

    To reset the stack, use ``--package-db=clear``.

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.. option:: --ipid=ipid

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    Specifies the *installed package identifier* of the package to be
    built; this identifier is passed on to GHC and serves as the basis
    for linker symbols and the ``id`` field in a ``ghc-pkg``
    registration. When a package has multiple components, the actual
    component identifiers are derived off of this identifier (e.g., an
    internal library ``foo`` from package ``p-0.1-abcd`` will get the
    identifier ``p-0.1-abcd-foo``.
921 922 923

.. option:: --cid=cid

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    Specifies the *component identifier* of the component being built;
    this is only valid if you are configuring a single component.
926 927 928

.. option:: --default-user-config=file

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    Allows a "default" ``cabal.config`` freeze file to be passed in
    manually. This file will only be used if one does not exist in the
    project directory already. Typically, this can be set from the
    global cabal ``config`` file so as to provide a default set of
    partial constraints to be used by projects, providing a way for
    users to peg themselves to stable package collections.
935 936 937

.. option:: --enable-optimization[=n] or -O [n]

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    (default) Build with optimization flags (if available). This is
    appropriate for production use, taking more time to build faster
    libraries and programs.

    The optional *n* value is the optimisation level. Some compilers
    support multiple optimisation levels. The range is 0 to 2. Level 0
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    is equivalent to :option:`--disable-optimization`, level 1 is the
    default if no *n* parameter is given. Level 2 is higher optimisation
    if the compiler supports it. Level 2 is likely to lead to longer
    compile times and bigger generated code.

.. option:: --disable-optimization
950 951 952 953

    Build without optimization. This is suited for development: building
    will be quicker, but the resulting library or programs will be
    slower.
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.. option:: --enable-profiling

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    Build libraries and executables with profiling enabled (for
    compilers that support profiling as a separate mode). For this to
    work, all libraries used by this package must also have been built
    with profiling support. For libraries this involves building an
    additional instance of the library in addition to the normal
    non-profiling instance. For executables it changes the single
    executable to be built in profiling mode.

    This flag covers both libraries and executables, but can be
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    overridden by the :option:`--enable-library-profiling` flag.

    See also the :option:`--profiling-detail` flag below.
969

970
.. option:: --disable-profiling
971 972 973

    (default) Do not enable profiling in generated libraries and
    executables.
974 975 976 977

.. option:: --enable-library-profiling or -p

    As with :option:`--enable-profiling` above, but it applies only for
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    libraries. So this generates an additional profiling instance of the
    library in addition to the normal non-profiling instance.

981
    The :option:`--enable-profiling` flag controls the profiling mode for both
982
    libraries and executables, but if different modes are desired for
983
    libraries versus executables then use :option:`--enable-library-profiling`
984 985
    as well.

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.. option:: --disable-library-profiling

    (default) Do not generate an additional profiling version of the library.

.. option:: --profiling-detail[=level]

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    Some compilers that support profiling, notably GHC, can allocate
    costs to different parts of the program and there are different
    levels of granularity or detail with which this can be done. In
    particular for GHC this concept is called "cost centers", and GHC
    can automatically add cost centers, and can do so in different ways.

    This flag covers both libraries and executables, but can be
999
    overridden by the :option:`--library-profiling-detail` flag.
1000 1001 1002 1003

    Currently this setting is ignored for compilers other than GHC. The
    levels that cabal currently supports are:

1004
    default
1005 1006
        For GHC this uses ``exported-functions`` for libraries and
        ``toplevel-functions`` for executables.
1007
    none
1008
        No costs will be assigned to any code within this component.
1009
    exported-functions
1010 1011 1012
        Costs will be assigned at the granularity of all top level
        functions exported from each module. In GHC specifically, this
        is for non-inline functions.
1013
    toplevel-functions
1014 1015 1016 1017
        Costs will be assigned at the granularity of all top level
        functions in each module, whether they are exported from the
        module or not. In GHC specifically, this is for non-inline
        functions.
1018
    all-functions
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        Costs will be assigned at the granularity of all functions in
        each module, whether top level or local. In GHC specifically,
        this is for non-inline toplevel or where-bound functions or
        values.

    This flag is new in Cabal-1.24. Prior versions used the equivalent
    of ``none`` above.

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.. option:: --library-profiling-detail[=level]

    As with :option:`--profiling-detail` above, but it applies only for
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    libraries.

    The level for both libraries and executables is set by the
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    :option:`--profiling-detail` flag, but if different levels are desired
    for libraries versus executables then use
    :option:`--library-profiling-detail` as well.

.. option:: --enable-library-vanilla
1038 1039 1040

    (default) Build ordinary libraries (as opposed to profiling
    libraries). This is independent of the
1041
    :option:`--enable-library-profiling` option. If you enable both, you get
1042
    both.
1043 1044 1045

.. option:: --disable-library-vanilla

1046
    Do not build ordinary libraries. This is useful in conjunction with
1047
    :option:`--enable-library-profiling` to build only profiling libraries,
1048
    rather than profiling and ordinary libraries.
1049 1050 1051

.. option:: --enable-library-for-ghci

1052
    (default) Build libraries suitable for use with GHCi.
1053 1054 1055

.. option:: --disable-library-for-ghci

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    Not all platforms support GHCi and indeed on some platforms, trying
    to build GHCi libs fails. In such cases this flag can be used as a
    workaround.
1059 1060 1061

.. option:: --enable-split-objs

1062 1063 1064 1065 1066
    Use the GHC ``-split-objs`` feature when building the library. This
    reduces the final size of the executables that use the library by
    allowing them to link with only the bits that they use rather than
    the entire library. The downside is that building the library takes
    longer and uses considerably more memory.
1067 1068 1069

.. option:: --disable-split-objs

1070 1071 1072
    (default) Do not use the GHC ``-split-objs`` feature. This makes
    building the library quicker but the final executables that use the
    library will be larger.
1073 1074 1075

.. option:: --enable-executable-stripping

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    (default) When installing binary executable programs, run the
    ``strip`` program on the binary. This can considerably reduce the
    size of the executable binary file. It does this by removing
    debugging information and symbols. While such extra information is
    useful for debugging C programs with traditional debuggers it is
    rarely helpful for debugging binaries produced by Haskell compilers.

    Not all Haskell implementations generate native binaries. For such
    implementations this option has no effect.

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.. option:: --disable-executable-stripping

1088 1089 1090 1091 1092 1093
    Do not strip binary executables during installation. You might want
    to use this option if you need to debug a program using gdb, for
    example if you want to debug the C parts of a program containing
    both Haskell and C code. Another reason is if your are building a
    package for a system which has a policy of managing the stripping
    itself (such as some Linux distributions).
1094 1095 1096

.. option:: --enable-shared

1097 1098
    Build shared library. This implies a separate compiler run to
    generate position independent code as required on most platforms.
1099 1100 1101

.. option:: --disable-shared

1102
    (default) Do not build shared library.
1103 1104 1105

.. option:: --enable-executable-dynamic

1106
    Link executables dynamically. The executable's library dependencies
1107 1108 1109 1110 1111 1112 1113 1114 1115
    should be built as shared objects. This implies :option:`--enable-shared`
    unless :option:`--disable-shared` is explicitly specified.

.. option:: --disable-executable-dynamic

   (default) Link executables statically.

.. option:: --configure-option=str

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    An extra option to an external ``configure`` script, if one is used
    (see the section on `system-dependent
    parameters <developing-packages.html#system-dependent-parameters>`__).
    There can be several of these options.
1120 1121 1122

.. option:: --extra-include-dirs[=dir]

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    An extra directory to search for C header files. You can use this
    flag multiple times to get a list of directories.

    You might need to use this flag if you have standard system header
    files in a non-standard location that is not mentioned in the
    package's ``.cabal`` file. Using this option has the same affect as
    appending the directory *dir* to the ``include-dirs`` field in each
    library and executable in the package's ``.cabal`` file. The
    advantage of course is that you do not have to modify the package at
    all. These extra directories will be used while building the package
    and for libraries it is also saved in the package registration
    information and used when compiling modules that use the library.

1136 1137
.. option:: --extra-lib-dirs[=dir]

1138 1139
    An extra directory to search for system libraries files. You can use
    this flag multiple times to get a list of directories.
1140 1141 1142

.. option:: --extra-framework-dirs[=dir]

1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155
    An extra directory to search for frameworks (OS X only). You can use
    this flag multiple times to get a list of directories.

    You might need to use this flag if you have standard system
    libraries in a non-standard location that is not mentioned in the
    package's ``.cabal`` file. Using this option has the same affect as
    appending the directory *dir* to the ``extra-lib-dirs`` field in
    each library and executable in the package's ``.cabal`` file. The
    advantage of course is that you do not have to modify the package at
    all. These extra directories will be used while building the package
    and for libraries it is also saved in the package registration
    information and used when compiling modules that use the library.

1156 1157
.. option:: --dependency[=pkgname=ipid]

1158 1159 1160
    Specify that a particular dependency should used for a particular
    package name. In particular, it declares that any reference to
    *pkgname* in a ``build-depends`` should be resolved to *ipid*.
1161 1162 1163

.. option:: --exact-configuration

1164
    This changes Cabal to require every dependency be explicitly
1165
    specified using :option:`--dependency`, rather than use Cabal's (very
1166 1167
    simple) dependency solver. This is useful for programmatic use of
    Cabal's API, where you want to error if you didn't specify enough
1168 1169 1170 1171
    :option:`--dependency` flags.

.. option:: --allow-newer[=pkgs], --allow-older[=pkgs]

1172 1173 1174 1175
    Selectively relax upper or lower bounds in dependencies without
    editing the package description respectively.

    The following description focuses on upper bounds and the
1176 1177 1178
    :option:`--allow-newer` flag, but applies analogously to
    :option:`--allow-older` and lower bounds. :option:`--allow-newer`
    and :option:`--allow-older` can be used at the same time.
1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211

    If you want to install a package A that depends on B >= 1.0 && <
    2.0, but you have the version 2.0 of B installed, you can compile A
    against B 2.0 by using ``cabal install --allow-newer=B A``. This
    works for the whole package index: if A also depends on C that in
    turn depends on B < 2.0, C's dependency on B will be also relaxed.

    Example:

    ::

        $ cd foo
        $ cabal configure
        Resolving dependencies...
        cabal: Could not resolve dependencies:
        [...]
        $ cabal configure --allow-newer
        Resolving dependencies...
        Configuring foo...

    Additional examples:

    ::

        # Relax upper bounds in all dependencies.
        $ cabal install --allow-newer foo

        # Relax upper bounds only in dependencies on bar, baz and quux.
        $ cabal install --allow-newer=bar,baz,quux foo

        # Relax the upper bound on bar and force bar==2.1.
        $ cabal install --allow-newer=bar --constraint="bar==2.1" foo

1212
    It's also possible to limit the scope of :option:`--allow-newer` to single
1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229
    packages with the ``--allow-newer=scope:dep`` syntax. This means
    that the dependency on ``dep`` will be relaxed only for the package
    ``scope``.

    Example:

    ::

        # Relax upper bound in foo's dependency on base; also relax upper bound in
        # every package's dependency on lens.
        $ cabal install --allow-newer=foo:base,lens

        # Relax upper bounds in foo's dependency on base and bar's dependency
        # on time; also relax the upper bound in the dependency on lens specified by
        # any package.
        $ cabal install --allow-newer=foo:base,lens --allow-newer=bar:time

1230
    Finally, one can enable :option:`--allow-newer` permanently by setting
1231 1232 1233 1234
    ``allow-newer: True`` in the ``~/.cabal/config`` file. Enabling
    'allow-newer' selectively is also supported in the config file
    (``allow-newer: foo, bar, baz:base``).

1235 1236
.. option:: --constraint=constraint

1237 1238 1239 1240 1241 1242 1243 1244 1245 1246 1247 1248 1249
    Restrict solutions involving a package to a given version range. For
    example, ``cabal install --constraint="bar==2.1"`` will only
    consider install plans that do not use ``bar`` at all, or ``bar`` of
    version 2.1.

    As a special case, ``cabal install --constraint="bar -none"``
    prevents ``bar`` from being used at all (``-none`` abbreviates
    ``> 1 && < 1``); ``cabal install --constraint="bar installed"``
    prevents reinstallation of the ``bar`` package;
    ``cabal install --constraint="bar +foo -baz"`` specifies that the
    flag ``foo`` should be turned on and the ``baz`` flag should be
    turned off.

1250 1251
.. option:: --preference=preference

1252 1253 1254 1255 1256 1257 1258 1259 1260 1261 1262
    Specify a soft constraint on versions of a package. The solver will
    attempt to satisfy these preferences on a "best-effort" basis.

setup build
-----------

Perform any preprocessing or compilation needed to make this package
ready for installation.

This command takes the following options:

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.. program:: setup build

.. option:: --prog-options=options, --prog-option=option

1267 1268 1269 1270 1271 1272 1273 1274 1275 1276
    These are mostly the same as the `options configure
    step <#setup-configure>`__. Unlike the options specified at the
    configure step, any program options specified at the build step are
    not persistent but are used for that invocation only. They options
    specified at the build step are in addition not in replacement of
    any options specified at the configure step.

setup haddock
-------------

1277 1278
.. program:: setup haddock

1279 1280
Build the documentation for the package using Haddock_.
By default, only the documentation for the exposed modules is generated
1281
(but see the :option:`--executables` and :option:`--internal` flags below).
1282 1283 1284

This command takes the following options:

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.. option:: --hoogle

1287
    Generate a file ``dist/doc/html/``\ *pkgid*\ ``.txt``, which can be