nix-local-build.rst 62.9 KB
Newer Older
Leonid Onokhov's avatar
Leonid Onokhov committed
1
.. highlight:: console
2 3 4 5 6 7 8 9 10 11

Quickstart
==========

Suppose that you are in a directory containing a single Cabal package
which you wish to build. You can configure and build it using Nix-style
local builds with this command (configuring is not necessary):

::

Leonid Onokhov's avatar
Leonid Onokhov committed
12
    $ cabal new-build
13 14 15 16 17

To open a GHCi shell with this package, use this command:

::

Leonid Onokhov's avatar
Leonid Onokhov committed
18
    $ cabal new-repl
19 20 21 22 23 24 25 26 27 28 29 30

Developing multiple packages
----------------------------

Many Cabal projects involve multiple packages which need to be built
together. To build multiple Cabal packages, you need to first create a
``cabal.project`` file which declares where all the local package
directories live. For example, in the Cabal repository, there is a root
directory with a folder per package, e.g., the folders ``Cabal`` and
``cabal-install``. The ``cabal.project`` file specifies each folder as
part of the project:

Leonid Onokhov's avatar
Leonid Onokhov committed
31
.. code-block:: cabal
32 33 34 35 36 37 38 39 40 41 42 43 44 45 46

    packages: Cabal/
              cabal-install/

The expectation is that a ``cabal.project`` is checked into your source
control, to be used by all developers of a project. If you need to make
local changes, they can be placed in ``cabal.project.local`` (which
should not be checked in.)

Then, to build every component of every package, from the top-level
directory, run the command: (Warning: cabal-install-1.24 does NOT have
this behavior; you will need to upgrade to HEAD.)

::

Leonid Onokhov's avatar
Leonid Onokhov committed
47
    $ cabal new-build
48 49 50 51 52 53

To build a specific package, you can either run ``new-build`` from the
directory of the package in question:

::

Leonid Onokhov's avatar
Leonid Onokhov committed
54 55
    $ cd cabal-install
    $ cabal new-build
56 57 58 59 60 61

or you can pass the name of the package as an argument to
``cabal new-build`` (this works in any subdirectory of the project):

::

Leonid Onokhov's avatar
Leonid Onokhov committed
62
    $ cabal new-build cabal-install
63 64 65 66 67 68

You can also specify a specific component of the package to build. For
example, to build a test suite named ``package-tests``, use the command:

::

Leonid Onokhov's avatar
Leonid Onokhov committed
69
    $ cabal new-build package-tests
70 71 72 73 74 75 76 77 78

Targets can be qualified with package names. So to request
``package-tests`` *from* the ``Cabal`` package, use
``Cabal:package-tests``.

Unlike sandboxes, there is no need to setup a sandbox or ``add-source``
projects; just check in ``cabal.project`` to your repository and
``new-build`` will just work.

79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104
Cookbook
========

How can I profile my library/application?
-----------------------------------------

First, make sure you have HEAD; 1.24 is affected by :issue:`3790`,
which means that if any project which transitively depends on a
package which has a Custom setup built against Cabal 1.22 or earlier
will silently not work.

Create or edit your ``cabal.project.local``, adding the following
line::

    profiling: True

Now, ``cabal new-build`` will automatically build all libraries and
executables with profiling.  You can fine-tune the profiling settings
for each package using :cfg-field:`profiling-detail`::

    package p
        profiling-detail: toplevel-functions

Alternately, you can call ``cabal new-build --enable-profiling`` to
temporarily build with profiling.

105 106 107 108 109 110 111 112 113
How it works
============

Local versus external packages
------------------------------

One of the primary innovations of Nix-style local builds is the
distinction between local packages, which users edit and recompile and
must be built per-project, versus external packages, which can be cached
114
across projects. To be more precise:
115 116 117 118 119

1. A **local package** is one that is listed explicitly in the
   ``packages``, ``optional-packages`` or ``extra-packages`` field of a
   project. Usually, these refer to packages whose source code lives
   directly in a folder in your project (although, you can list an
120
   arbitrary Hackage package in ``extra-packages`` to force it to be
121 122 123 124 125 126 127 128
   treated as local).

Local packages, as well as the external packages (below) which depend on
them, are built **inplace**, meaning that they are always built
specifically for the project and are not installed globally. Inplace
packages are not cached and not given unique hashes, which makes them
suitable for packages which you want to edit and recompile.

129
2. An **external package** is any package which is not listed in the
130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305
   ``packages`` field. The source code for external packages is usually
   retrieved from Hackage.

When an external package does not depend on an inplace package, it can
be built and installed to a **global** store, which can be shared across
projects. These build products are identified by a hash that over all of
the inputs which would influence the compilation of a package (flags,
dependency selection, etc.). Just as in Nix, these hashes uniquely
identify the result of a build; if we compute this identifier and we
find that we already have this ID built, we can just use the already
built version.

The global package store is ``~/.cabal/store``; if you need to clear
your store for whatever reason (e.g., to reclaim disk space or because
the global store is corrupted), deleting this directory is safe
(``new-build`` will just rebuild everything it needs on its next
invocation).

This split motivates some of the UI choices for Nix-style local build
commands. For example, flags passed to ``cabal new-build`` are only
applied to *local* packages, so that adding a flag to
``cabal new-build`` doesn't necessitate a rebuild of *every* transitive
dependency in the global package store.

In cabal-install HEAD, Nix-style local builds also take advantage of a
new Cabal library feature, `per-component
builds <https://github.com/ezyang/ghc-proposals/blob/master/proposals/0000-componentized-cabal.rst>`__,
where each component of a package is configured and built separately.
This can massively speed up rebuilds of packages with lots of components
(e.g., a package that defines multiple executables), as only one
executable needs to be rebuilt. Packages that use Custom setup scripts
are not currently built on a per-component basis.

Where are my build products?
----------------------------

A major deficiency in the current implementation of new-build is that
there is no programmatic way to access the location of build products.
The location of the build products is intended to be an internal
implementation detail of new-build, but we also understand that many
unimplemented features (e.g., ``new-test``) can only be reasonably
worked around by accessing build products directly.

The location where build products can be found varies depending on the
version of cabal-install:

-  In cabal-install-1.24, the dist directory for a package ``p-0.1`` is
   stored in ``dist-newstyle/build/p-0.1``. For example, if you built an
   executable or test suite named ``pexe``, it would be located at
   ``dist-newstyle/build/p-0.1/build/pexe/pexe``.

-  In cabal-install HEAD, the dist directory for a package ``p-0.1``
   defining a library built with GHC 8.0.1 on 64-bit Linux is
   ``dist-newstyle/build/x86_64-linux/ghc-8.0.1/p-0.1``. When
   per-component builds are enabled (any non-Custom package), a
   subcomponent like an executable or test suite named ``pexe`` will be
   stored at
   ``dist-newstyle/build/x86_64-linux/ghc-8.0.1/p-0.1/c/pexe``; thus,
   the full path of the executable is
   ``dist-newstyle/build/x86_64-linux/ghc-8.0.1/p-0.1/c/pexe/build/pexe/pexe``
   (you can see why we want this to be an implementation detail!)

The paths are a bit longer in HEAD but the benefit is that you can
transparently have multiple builds with different versions of GHC. We
plan to add the ability to create aliases for certain build
configurations, and more convenient paths to access particularly useful
build products like executables.

Caching
-------

Nix-style local builds sport a robust caching system which help reduce
the time it takes to execute a rebuild cycle. While the details of how
``cabal-install`` does caching are an implementation detail and may
change in the future, knowing what gets cached is helpful for
understanding the performance characteristics of invocations to
``new-build``. The cached intermediate results are stored in
``dist-newstyle/cache``; this folder can be safely deleted to clear the
cache.

The following intermediate results are cached in the following files in
this folder (the most important two are first):

``solver-plan`` (binary)
    The result of calling the dependency solver, assuming that the
    Hackage index, local ``cabal.project`` file, and local ``cabal``
    files are unmodified. (Notably, we do NOT have to dependency solve
    again if new build products are stored in the global store; the
    invocation of the dependency solver is independent of what is
    already available in the store.)
``source-hashes`` (binary)
    The hashes of all local source files. When all local source files of
    a local package are unchanged, ``cabal new-build`` will skip
    invoking ``setup build`` entirely (saving us from a possibly
    expensive call to ``ghc --make``). The full list of source files
    participating in compilation are determined using
    ``setup sdist --list-sources`` (thus, if you do not list all your
    source files in a Cabal file, you may fail to recompile when you
    edit them.)
``config`` (same format as ``cabal.project``)
    The full project configuration, merged from ``cabal.project`` (and
    friends) as well as the command line arguments.
``compiler`` (binary)
    The configuration of the compiler being used to build the project.
``improved-plan`` (binary)
    Like ``solver-plan``, but with all non-inplace packages improved
    into pre-existing copies from the store.

Note that every package also has a local cache managed by the Cabal
build system, e.g., in ``$distdir/cache``.

There is another useful file in ``dist-newstyle/cache``, ``plan.json``,
which is a JSON serialization of the computed install plan. (TODO: docs)

Commands
========

We now give an in-depth description of all the commands, describing the
arguments and flags they accept.

cabal new-configure
-------------------

``cabal new-configure`` takes a set of arguments and writes a
``cabal.project.local`` file based on the flags passed to this command.
``cabal new-configure FLAGS; cabal new-build`` is roughly equivalent to
``cabal new-build FLAGS``, except that with ``new-configure`` the flags
are persisted to all subsequent calls to ``new-build``.

``cabal new-configure`` is intended to be a convenient way to write out
a ``cabal.project.local`` for simple configurations; e.g.,
``cabal new-configure -w ghc-7.8`` would ensure that all subsequent
builds with ``cabal new-build`` are performed with the compiler
``ghc-7.8``. For more complex configuration, we recommend writing the
``cabal.project.local`` file directly (or placing it in
``cabal.project``!)

``cabal new-configure`` inherits options from ``Cabal``. semantics:

-  Any flag accepted by ``./Setup configure``.

-  Any flag accepted by ``cabal configure`` beyond
   ``./Setup configure``, namely ``--cabal-lib-version``,
   ``--constraint``, ``--preference`` and ``--solver.``

-  Any flag accepted by ``cabal install`` beyond ``./Setup configure``.

-  Any flag accepted by ``./Setup haddock``.

The options of all of these flags apply only to *local* packages in a
project; this behavior is different than that of ``cabal install``,
which applies flags to every package that would be built. The motivation
for this is to avoid an innocuous addition to the flags of a package
resulting in a rebuild of every package in the store (which might need
to happen if a flag actually applied to every transitive dependency). To
apply options to an external package, use a ``package`` stanza in a
``cabal.project`` file.

cabal new-build
---------------

``cabal new-build`` takes a set of targets and builds them. It
automatically handles building and installing any dependencies of these
targets.

A target can take any of the following forms:

-  A package target: ``package``, which specifies that all enabled
   components of a package to be built. By default, test suites and
   benchmarks are *not* enabled, unless they are explicitly requested
   (e.g., via ``--enable-tests``.)

-  A component target: ``[package:][ctype:]component``, which specifies
   a specific component (e.g., a library, executable, test suite or
   benchmark) to be built.

Duncan Coutts's avatar
Duncan Coutts committed
306 307 308 309 310
-  All packages: ``all``, which specifies all packages within the project.

-  Components of a particular type: ``ctype``, ``package:ctype``, ``all:ctype``:
   which specifies all components of the given type.

311 312 313 314 315 316 317 318 319 320 321
In component targets, ``package:`` and ``ctype:`` (valid component types
are ``lib``, ``exe``, ``test`` and ``bench``) can be used to
disambiguate when multiple packages define the same component, or the
same component name is used in a package (e.g., a package ``foo``
defines both an executable and library named ``foo``). We always prefer
interpreting a target as a package name rather than as a component name.

Some example targets:

::

Leonid Onokhov's avatar
Leonid Onokhov committed
322 323
    $ cabal new-build lib:foo-pkg       # build the library named foo-pkg
    $ cabal new-build foo-pkg:foo-tests # build foo-tests in foo-pkg
324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352

(There is also syntax for specifying module and file targets, but it
doesn't currently do anything.)

Beyond a list of targets, ``cabal new-build`` accepts all the flags that
``cabal new-configure`` takes. Most of these flags are only taken into
consideration when building local packages; however, some flags may
cause extra store packages to be built (for example,
``--enable-profiling`` will automatically make sure profiling libraries
for all transitive dependencies are built and installed.)

cabal new-repl
--------------

``cabal new-repl TARGET`` loads all of the modules of the target into
GHCi as interpreted bytecode. It takes the same flags as
``cabal new-build``.

Currently, it is not supported to pass multiple targets to ``new-repl``
(``new-repl`` will just successively open a separate GHCi session for
each target.)

cabal new-freeze
----------------

``cabal new-freeze`` writes out a ``cabal.project.freeze`` file which
records all of the versions and flags which that are picked by the
solver under the current index and flags. A ``cabal.project.freeze``
file has the same syntax as ``cabal.project`` and looks something like
353
this:
354

Leonid Onokhov's avatar
Leonid Onokhov committed
355
.. highlight:: cabal
356

Leonid Onokhov's avatar
Leonid Onokhov committed
357
::
Leonid Onokhov's avatar
Leonid Onokhov committed
358

359 360 361 362
    constraints: HTTP ==4000.3.3,
                 HTTP +warp-tests -warn-as-error -network23 +network-uri -mtl1 -conduit10,
                 QuickCheck ==2.9.1,
                 QuickCheck +templatehaskell,
363 364
                 -- etc...

365 366 367 368 369 370 371 372 373 374 375 376

For end-user executables, it is recommended that you distribute the
``cabal.project.freeze`` file in your source repository so that all
users see a consistent set of dependencies. For libraries, this is not
recommended: users often need to build against different versions of
libraries than what you developed against.

Unsupported commands
--------------------

The following commands are not currently supported:

377
``cabal new-test`` (:issue:`3638`)
378 379
    Workaround: run the test executable directly (see `Where are my
    build products <#where-are-my-build-products>`__?)
380

381
``cabal new-bench`` (:issue:`3638`)
382 383
    Workaround: run the benchmark executable directly (see `Where are my
    build products <#where-are-my-build-products>`__?)
384

385
``cabal new-run`` (:issue:`3638`)
386 387
    Workaround: run the executable directly (see `Where are my build
    products <#where-are-my-build-products>`__?)
388

389 390 391 392
``cabal new-exec``
    Workaround: if you wanted to execute GHCi, consider using
    ``cabal new-repl`` instead. Otherwise, use ``-v`` to find the list
    of flags GHC is being invoked with and pass it manually.
393

394
``cabal new-haddock`` (:issue:`3535`)
395 396 397
    Workaround: run
    ``cabal act-as-setup -- haddock --builddir=dist-newstyle/build/pkg-0.1``
    (or execute the Custom setup script directly).
398

399
``cabal new-install`` (:issue:`3737`)
400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420
    Workaround: no good workaround at the moment. (But note that you no
    longer need to install libraries before building!)

Configuring builds with cabal.project
=====================================

``cabal.project`` files support a variety of options which configure the
details of your build. The general syntax of a ``cabal.project`` file is
similar to that of a Cabal file: there are a number of fields, some of
which live inside stanzas:

::

    packages: */*.cabal
    with-compiler: /opt/ghc/8.0.1/bin/ghc

    package cryptohash
      optimization: False

In general, the accepted field names coincide with the accepted command
line flags that ``cabal install`` and other commands take. For example,
421 422
``cabal new-configure --enable-profiling`` will write out a project
file with ``profiling: True``.
423 424 425 426 427 428 429 430 431 432 433 434

The full configuration of a project is determined by combining the
following sources (later entries override earlier ones):

1. ``~/.cabal/config`` (the user-wide global configuration)

2. ``cabal.project`` (the project configuratoin)

3. ``cabal.project.freeze`` (the output of ``cabal new-freeze``)

4. ``cabal.project.local`` (the output of ``cabal new-configure``)

435

436 437 438 439 440 441
Specifying the local packages
-----------------------------

The following top-level options specify what the local packages of a
project are:

442
.. cfg-field:: packages: package location list (space or comma separated)
Leonid Onokhov's avatar
Leonid Onokhov committed
443
    :synopsis: Project packages.
444 445

    :default: ``./*.cabal``
446

447 448 449 450 451
    Specifies the list of package locations which contain the local
    packages to be built by this project. Package locations can take the
    following forms:

    1. They can specify a Cabal file, or a directory containing a Cabal
452
       file, e.g., ``packages: Cabal cabal-install/cabal-install.cabal``.
453 454 455 456 457 458 459 460 461 462 463 464 465 466

    2. They can specify a glob-style wildcards, which must match one or
       more (a) directories containing a (single) Cabal file, (b) Cabal
       files (extension ``.cabal``), or (c) [STRIKEOUT:tarballs which
       contain Cabal packages (extension ``.tar.gz``)] (not implemented
       yet). For example, to match all Cabal files in all
       subdirectories, as well as the Cabal projects in the parent
       directories ``foo`` and ``bar``, use
       ``packages: */*.cabal ../{foo,bar}/``

    3. [STRIKEOUT:They can specify an ``http``, ``https`` or ``file``
       URL, representing the path to a remote tarball to be downloaded
       and built.] (not implemented yet)

467
    There is no command line variant of this field; see :issue:`3585`.
468

469
.. cfg-field:: optional-packages: package location list (space or comma-separated)
Leonid Onokhov's avatar
Leonid Onokhov committed
470
    :synopsis: Optional project packages.
471 472 473

    :default: ``./*/*.cabal``

Leonid Onokhov's avatar
Leonid Onokhov committed
474 475 476 477 478 479
    Like :cfg-field:`packages`, specifies a list of package locations
    containing local packages to be built. Unlike :cfg-field:`packages`,
    if we glob for a package, it is permissible for the glob to match against
    zero packages. The intended use-case for :cfg-field:`optional-packages`
    is to make it so that vendored packages can be automatically picked up if
    they are placed in a subdirectory, but not error if there aren't any.
480 481 482

    There is no command line variant of this field.

483
.. cfg-field:: extra-packages: package list with version bounds (comma separated)
Leonid Onokhov's avatar
Leonid Onokhov committed
484
    :synopsis: Adds external pacakges as local
485

486 487 488 489 490 491 492 493 494
    [STRIKEOUT:Specifies a list of external packages from Hackage which
    should be considered local packages.] (Not implemented)

    There is no command line variant of this field.

[STRIKEOUT:There is also a stanza ``source-repository-package`` for
specifying packages from an external version control.] (Not
implemented.)

495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510
All local packages are *vendored*, in the sense that if other packages
(including external ones from Hackage) depend on a package with the name
of a local package, the local package is preferentially used.  This
motivates the default settings::

    packages: ./*.cabal
    optional-packages: ./*/*.cabal

...any package can be vendored simply by making a checkout in the
top-level project directory, as might be seen in this hypothetical
directory layout::

    foo.cabal
    foo-helper/     # local package
    unix/           # vendored external package

511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526
All of these options support globs. ``cabal new-build`` has its own glob
format:

-  Anywhere in a path, as many times as you like, you can specify an
   asterisk ``*`` wildcard. E.g., ``*/*.cabal`` matches all ``.cabal``
   files in all immediate subdirectories. Like in glob(7), asterisks do
   not match hidden files unless there is an explicit period, e.g.,
   ``.*/foo.cabal`` will match ``.private/foo.cabal`` (but
   ``*/foo.cabal`` will not).

-  You can use braces to specify specific directories; e.g.,
   ``{vendor,pkgs}/*.cabal`` matches all Cabal files in the ``vendor``
   and ``pkgs`` subdirectories.

Formally, the format described by the following BNF:

527
.. code-block:: abnf
528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549

    FilePathGlob    ::= FilePathRoot FilePathGlobRel
    FilePathRoot    ::= {- empty -}        # relative to cabal.project
                      | "/"                # Unix root
                      | [a-zA-Z] ":" [/\\] # Windows root
                      | "~"                # home directory
    FilePathGlobRel ::= Glob "/"  FilePathGlobRel # Unix directory
                      | Glob "\\" FilePathGlobRel # Windows directory
                      | Glob         # file
                      | {- empty -}  # trailing slash
    Glob      ::= GlobPiece *
    GlobPiece ::= "*"            # wildcard
                | [^*{},/\\] *   # literal string
                | "\\" [*{},]    # escaped reserved character
                | "{" Glob "," ... "," Glob "}" # union (match any of these)

Global configuration options
----------------------------

The following top-level configuration options are not specific to any
package, and thus apply globally:

550 551
.. cfg-field:: verbose: nat
               --verbose=n, -vn
Leonid Onokhov's avatar
Leonid Onokhov committed
552
    :synopsis: Build verbosity level.
553 554 555

    :default: 1

556 557 558 559 560 561
    Control the verbosity of ``cabal`` commands, valid values are from 0
    to 3.

    The command line variant of this field is ``--verbose=2``; a short
    form ``-v2`` is also supported.

562 563
.. cfg-field:: jobs: nat or $ncpus
               --jobs=n, -jn, --jobs=$ncpus
Leonid Onokhov's avatar
Leonid Onokhov committed
564
    :synopsis: Number of builds running in parallel.
565 566 567

    :default: 1

568 569 570 571 572 573 574 575 576
    Run *nat* jobs simultaneously when building. If ``$ncpus`` is
    specified, run the number of jobs equal to the number of CPUs.
    Package building is often quite parallel, so turning on parallelism
    can speed up build times quite a bit!

    The command line variant of this field is ``--jobs=2``; a short form
    ``-j2`` is also supported; a bare ``--jobs`` or ``-j`` is equivalent
    to ``--jobs=$ncpus``.

577 578
.. cfg-field::  keep-going: boolean
                --keep-going
Leonid Onokhov's avatar
Leonid Onokhov committed
579
    :synopsis: Try to continue building on failure.
580 581 582

    :default: False

583 584 585 586 587
    If true, after a build failure, continue to build other unaffected
    packages.

    The command line variant of this field is ``--keep-going``.

588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613
.. option:: --builddir=DIR

    Specifies the name of the directory where build products for
    build will be stored; defaults to ``dist-newstyle``.  If a
    relative name is specified, this directory is resolved relative
    to the root of the project (i.e., where the ``cabal.project``
    file lives.)

    This option cannot be specified via a ``cabal.project`` file.

.. option:: --project-file=FILE

    Specifies the name of the project file used to specify the
    rest of the top-level configuration; defaults to ``cabal.project``.
    This name not only specifies the name of the main project file,
    but also the auxiliary project files ``cabal.project.freeze``
    and ``cabal.project.local``; for example, if you specify
    ``--project-file=my.project``, then the other files that will
    be probed are ``my.project.freeze`` and ``my.project.local``.

    If the specified project file is a relative path, we will
    look for the file relative to the current working directory,
    and then for the parent directory, until the project file is
    found or we have hit the top of the user's home directory.

    This option cannot be specified via a ``cabal.project`` file.
614

615 616 617 618 619
Solver configuration options
----------------------------

The following settings control the behavior of the dependency solver:

620
.. cfg-field:: constraints: constraints list (comma separated)
621
               --constraint="pkg >= 2.0"
Leonid Onokhov's avatar
Leonid Onokhov committed
622
    :synopsis: Extra dependencies constraints.
623

624 625 626 627
    Add extra constraints to the version bounds, flag settings,
    and other properties a solver can pick for a
    package. For example:
               
628 629 630 631 632 633 634 635 636 637
    ::

        constraints: bar == 2.1

    A package can be specified multiple times in ``constraints``, in
    which case the specified constraints are intersected. This is
    useful, since the syntax does not allow you to specify multiple
    constraints at once. For example, to specify both version bounds and
    flag assignments, you would write:

638 639 640
    ::

        constraints: bar == 2.1,
641
                     bar +foo -baz
642

643 644 645
    Valid constraints take the same form as for the `constraint
    command line option
    <installing-packages.html#cmdoption-setup-configure--constraint>`__.
646

647 648
.. cfg-field:: preferences: preference (comma separated)
               --preference="pkg >= 2.0"
Leonid Onokhov's avatar
Leonid Onokhov committed
649
    :synopsis: Prefered dependency versions.
650 651 652

    Like :cfg-field:`constraints`, but the solver will attempt to satisfy
    these preferences on a best-effort basis. The resulting install is locally
653 654 655 656 657 658 659 660
    optimal with respect to preferences; specifically, no single package
    could be replaced with a more preferred version that still satisfies
    the hard constraints.

    Operationally, preferences can cause the solver to attempt certain
    version choices of a package before others, which can improve
    dependency solver runtime.

661
    One way to use :cfg-field:`preferences` is to take a known working set of
662 663 664 665 666 667 668 669 670 671
    constraints (e.g., via ``cabal new-freeze``) and record them as
    preferences. In this case, the solver will first attempt to use this
    configuration, and if this violates hard constraints, it will try to
    find the minimal number of upgrades to satisfy the hard constraints
    again.

    The command line variant of this field is
    ``--preference="pkg >= 2.0"``; to specify multiple preferences, pass
    the flag multiple times.

672
.. cfg-field:: allow-newer: none, all or list of scoped package names (space or comma separated)
673
               --allow-newer, --allow-newer=[none,all,[scope:][^]pkg]
Leonid Onokhov's avatar
Leonid Onokhov committed
674
    :synopsis: Lift dependencies upper bound constaints.
675 676 677

    :default: ``none``

678
    Allow the solver to pick an newer version of some packages than
679 680
    would normally be permitted by than the :pkg-field:`build-depends` bounds
    of packages in the install plan. This option may be useful if the
681 682
    dependency solver cannot otherwise find a valid install plan.

683
    For example, to relax ``pkg``\ s :pkg-field:`build-depends` upper bound on
684 685 686 687 688 689
    ``dep-pkg``, write a scoped package name of the form:

    ::

        allow-newer: pkg:dep-pkg

690 691 692 693 694 695 696 697 698 699 700
    If the scope shall be limited to specific releases of ``pkg``, the
    extended form as in

    ::

        allow-newer: pkg-1.2.3:dep-pkg, pkg-1.1.2:dep-pkg

    can be used to limit the relaxation of dependencies on
    ``dep-pkg`` by the ``pkg-1.2.3`` and ``pkg-1.1.2`` releases only.

    The scoped syntax is recommended, as it is often only a single package
701 702 703 704
    whose upper bound is misbehaving. In this case, the upper bounds of
    other packages should still be respected; indeed, relaxing the bound
    can break some packages which test the selected version of packages.

705 706 707 708 709 710 711
    The syntax also allows to prefix the dependee package with a
    modifier symbol to modify the scope/semantic of the relaxation
    transformation in a additional ways. Currently only one modifier
    symbol is defined, i.e. ``^`` (i.e. caret) which causes the
    relaxation to be applied only to ``^>=`` operators and leave all other
    version operators untouched.

712 713 714 715 716 717 718 719
    However, in some situations (e.g., when attempting to build packages
    on a new version of GHC), it is useful to disregard *all*
    upper-bounds, with respect to a package or all packages. This can be
    done by specifying just a package name, or using the keyword ``all``
    to specify all packages:

    ::

Leonid Onokhov's avatar
Leonid Onokhov committed
720
        -- Disregard upper bounds involving the dependencies on
721 722 723
        -- packages bar, baz. For quux only, relax
        -- 'quux ^>= ...'-style constraints only.
        allow-newer: bar, baz, ^quux
724

Leonid Onokhov's avatar
Leonid Onokhov committed
725
        -- Disregard all upper bounds when dependency solving
726 727
        allow-newer: all

728 729 730 731 732 733 734 735 736 737

    For consistency, there is also the explicit wildcard scope syntax
    ``*`` (or its alphabetic synonym ``all``). Consequently, the first
    part of the example above is equivalent to the explicitly scoped
    variant:

    ::

        allow-newer: all:bar, *:baz, *:^quux

738 739 740
    :cfg-field:`allow-newer` is often used in conjunction with a constraint
    (in the cfg-field:`constraints` field) forcing the usage of a specific,
    newer version of a package.
741

742
    The command line variant of this field is e.g. ``--allow-newer=bar``. A
743 744
    bare ``--allow-newer`` is equivalent to ``--allow-newer=all``.

745
.. cfg-field:: allow-older: none, all, list of scoped package names (space or comma separated)
746
               --allow-older, --allow-older=[none,all,[scope:][^]pkg]
Leonid Onokhov's avatar
Leonid Onokhov committed
747
    :synopsis: Lift dependency lower bound constaints.
748 749 750 751 752

    :default: ``none``

    Like :cfg-field:`allow-newer`, but applied to lower bounds rather than
    upper bounds.
753 754 755 756

    The command line variant of this field is ``--allow-older=all``. A
    bare ``--allow-older`` is equivalent to ``--allow-older=all``.

757 758 759

.. cfg-field:: index-state: HEAD, unix-timestamp, ISO8601 UTC timestamp.
   :synopsis: Use source package index state as it existed at a previous time.
760
   :since: 2.0
761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779

   :default: ``HEAD``

   This allows to change the source package index state the solver uses
   to compute install-plans. This is particularly useful in
   combination with freeze-files in order to also freeze the state the
   package index was in at the time the install-plan was frozen.

   ::

      -- UNIX timestamp format example
      index-state: @1474739268

      -- ISO8601 UTC timestamp format example
      -- This format is used by 'cabal new-configure'
      -- for storing `--index-state` values.
      index-state: 2016-09-24T17:47:48Z


780 781 782 783 784 785 786 787 788 789 790 791 792
Package configuration options
-----------------------------

Package options affect the building of specific packages. There are two
ways a package option can be specified:

-  They can be specified at the top-level, in which case they apply only
   to **local package**, or

-  They can be specified inside a ``package`` stanza, in which case they
   apply to the build of the package, whether or not it is local or
   external.

793 794 795
For example, the following options specify that :cfg-field:`optimization`
should be turned off for all local packages, and that ``bytestring`` (possibly
an external dependency) should be built with ``-fno-state-hack``::
796 797 798 799 800 801

    optimization: False

    package bytestring
        ghc-options: -fno-state-hack

802 803 804 805
``ghc-options`` is not specifically described in this documentation,
but is one of many fields for configuring programs.  They take the form
``progname-options`` and ``progname-location``, and
can only be set inside package stanzas.  (TODO: They are not supported
806
at top-level, see :issue:`3579`.)
807

808 809 810 811 812 813 814 815 816 817
At the moment, there is no way to specify an option to apply to all
external packages or all inplace packages. Additionally, it is only
possible to specify these options on the command line for all local
packages (there is no per-package command line interface.)

Some flags were added by more recent versions of the Cabal library. This
means that they are NOT supported by packages which use Custom setup
scripts that require a version of the Cabal library older than when the
feature was added.

818 819
.. cfg-field:: flags: list of +flagname or -flagname (space separated)
               --flags="+foo -bar", -ffoo, -f-bar
Leonid Onokhov's avatar
Leonid Onokhov committed
820
    :synopsis: Enable or disable package flags.
821

822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841
    Force all flags specified as ``+flagname`` to be true, and all flags
    specified as ``-flagname`` to be false. For example, to enable the
    flag ``foo`` and disable ``bar``, set:

    ::

        flags: +foo -bar

    If there is no leading punctuation, it is assumed that the flag
    should be enabled; e.g., this is equivalent:

    ::

        flags: foo -bar

    Flags are *per-package*, so it doesn't make much sense to specify
    flags at the top-level, unless you happen to know that *all* of your
    local packages support the same named flags. If a flag is not
    supported by a package, it is ignored.

842
    See also the solver configuration field :cfg-field:`constraints`.
843 844 845 846 847 848 849 850 851 852

    The command line variant of this flag is ``--flags``. There is also
    a shortened form ``-ffoo -f-bar``.

    A common mistake is to say ``cabal new-build -fhans``, where
    ``hans`` is a flag for a transitive dependency that is not in the
    local package; in this case, the flag will be silently ignored. If
    ``haskell-tor`` is the package you want this flag to apply to, try
    ``--constraint="haskell-tor +hans"`` instead.

853 854
.. cfg-field:: with-compiler: executable
               --with-compiler=executable
Leonid Onokhov's avatar
Leonid Onokhov committed
855
    :synopsis: Path to compiler executable.
856

857
    Specify the path to a particular compiler to be used. If not an
858
    absolute path, it will be resolved according to the :envvar:`PATH`
859
    environment. The type of the compiler (GHC, GHCJS, etc) must be
860
    consistent with the setting of the :cfg-field:`compiler` field.
861 862 863 864 865

    The most common use of this option is to specify a different version
    of your compiler to be used; e.g., if you have ``ghc-7.8`` in your
    path, you can specify ``with-compiler: ghc-7.8`` to use it.

866 867
    This flag also sets the default value of :cfg-field:`with-hc-pkg`, using
    the heuristic that it is named ``ghc-pkg-7.8`` (if your executable name
868 869
    is suffixed with a version number), or is the executable named
    ``ghc-pkg`` in the same directory as the ``ghc`` directory. If this
870
    heuristic does not work, set :cfg-field:`with-hc-pkg` explicitly.
871 872 873 874 875 876

    For inplace packages, ``cabal new-build`` maintains a separate build
    directory for each version of GHC, so you can maintain multiple
    build trees for different versions of GHC without clobbering each
    other.

877
    At the moment, it's not possible to set :cfg-field:`with-compiler` on a
878 879 880 881 882 883 884
    per-package basis, but eventually we plan on relaxing this
    restriction. If this is something you need, give us a shout.

    The command line variant of this flag is
    ``--with-compiler=ghc-7.8``; there is also a short version
    ``-w ghc-7.8``.

885 886
.. cfg-field:: with-hc-pkg: executable
               --with-hc-pkg=executable
Leonid Onokhov's avatar
Leonid Onokhov committed
887
    :synopsis: Specifies package tool.
888

889 890
    Specify the path to the package tool, e.g., ``ghc-pkg``. This
    package tool must be compatible with the compiler specified by
891 892 893
    :cfg-field:`with-compiler` (generally speaking, it should be precisely
    the tool that was distributed with the compiler). If this option is
    omitted, the default value is determined from :cfg-field:`with-compiler`.
894 895 896 897

    The command line variant of this flag is
    ``--with-hc-pkg=ghc-pkg-7.8``.

898 899 900
.. cfg-field:: optimization: nat
               --enable-optimization
               --disable-optimization
Leonid Onokhov's avatar
Leonid Onokhov committed
901
    :synopsis: Build with optimization.
902 903 904

    :default: ``1``

905 906 907 908 909 910 911 912 913 914 915 916 917 918 919
    Build with optimization. This is appropriate for production use,
    taking more time to build faster libraries and programs.

    The optional *nat* value is the optimisation level. Some compilers
    support multiple optimisation levels. The range is 0 to 2. Level 0
    disables optimization, level 1 is the default. Level 2 is higher
    optimisation if the compiler supports it. Level 2 is likely to lead
    to longer compile times and bigger generated code. If you are not
    planning to run code, turning off optimization will lead to better
    build times and less code to be rebuilt when a module changes.

    We also accept ``True`` (equivalent to 1) and ``False`` (equivalent
    to 0).

    Note that as of GHC 8.0, GHC does not recompile when optimization
920
    levels change (see :ghc-ticket:`10923`), so if
921 922 923 924 925 926 927 928
    you change the optimization level for a local package you may need
    to blow away your old build products in order to rebuild with the
    new optimization level.

    The command line variant of this flag is ``-O2`` (with ``-O1``
    equivalent to ``-O``). There are also long-form variants
    ``--enable-optimization`` and ``--disable-optimization``.

929 930
.. cfg-field:: configure-options: args (space separated)
               --configure-option=arg
Leonid Onokhov's avatar
Leonid Onokhov committed
931
    :synopsis: Options to pass to configure script.
932

933 934 935 936 937 938 939 940 941
    A list of extra arguments to pass to the external ``./configure``
    script, if one is used. This is only useful for packages which have
    the ``Configure`` build type. See also the section on
    `system-dependent
    parameters <developing-packages.html#system-dependent-parameters>`__.

    The command line variant of this flag is ``--configure-option=arg``,
    which can be specified multiple times to pass multiple options.

942 943
.. cfg-field:: compiler: ghc, ghcjs, jhc, lhc, uhc or haskell-suite
               --compiler=compiler
Leonid Onokhov's avatar
Leonid Onokhov committed
944
    :synopsis: Compiler to build with.
945 946 947

    :default: ``ghc``

948 949 950 951 952 953
    Specify which compiler toolchain to be used. This is independent of
    ``with-compiler``, because the choice of toolchain affects Cabal's
    build logic.

    The command line variant of this flag is ``--compiler=ghc``.

954 955 956
.. cfg-field:: tests: boolean
               --enable-tests
               --disable-tests
Leonid Onokhov's avatar
Leonid Onokhov committed
957
    :synopsis: Build tests.
958 959 960

    :default: ``False``

961 962 963 964 965 966 967 968
    Force test suites to be enabled. For most users this should not be
    needed, as we always attempt to solve for test suite dependencies,
    even when this value is ``False``; furthermore, test suites are
    automatically enabled if they are requested as a built target.

    The command line variant of this flag is ``--enable-tests`` and
    ``--disable-tests``.

969 970 971
.. cfg-field:: benchmarks: boolean
               --enable-benchmarks
               --disable-benchmarks
Leonid Onokhov's avatar
Leonid Onokhov committed
972
    :synopsis: Build benchmarks.
973 974 975

    :default: ``False``

976 977 978 979 980 981 982 983
    Force benchmarks to be enabled. For most users this should not be
    needed, as we always attempt to solve for benchmark dependencies,
    even when this value is ``False``; furthermore, benchmarks are
    automatically enabled if they are requested as a built target.

    The command line variant of this flag is ``--enable-benchmarks`` and
    ``--disable-benchmarks``.

984 985
.. cfg-field:: extra-prog-path: paths (newline or comma separated)
               --extra-prog-path=PATH
Leonid Onokhov's avatar
Leonid Onokhov committed
986
    :synopsis: Add directories to program search path.
987 988
    :since: 1.18

989 990 991 992 993 994 995 996 997
    A list of directories to search for extra required programs. Most
    users should not need this, as programs like ``happy`` and ``alex``
    will automatically be installed and added to the path. This can be
    useful if a ``Custom`` setup script relies on an exotic extra
    program.

    The command line variant of this flag is ``--extra-prog-path=PATH``,
    which can be specified multiple times.

998 999
.. cfg-field:: run-tests: boolean
               --run-tests
Leonid Onokhov's avatar
Leonid Onokhov committed
1000
    :synopsis: Run package test suite upon installation.
1001 1002 1003

    :default: ``False``

1004 1005 1006 1007
    Run the package test suite upon installation. This is useful for
    saying "When this package is installed, check that the test suite
    passes, terminating the rest of the build if it is broken."

1008 1009 1010 1011 1012 1013 1014
    .. warning::

      One deficiency: the :cfg-field:`run-tests` setting of a package is NOT
      recorded as part of the hash, so if you install something without
      :cfg-field:`run-tests` and then turn on ``run-tests``, we won't
      subsequently test the package. If this is causing you problems, give
      us a shout.
1015 1016 1017 1018

    The command line variant of this flag is ``--run-tests``.

Object code options
1019
^^^^^^^^^^^^^^^^^^^
1020

1021 1022 1023
.. cfg-field:: debug-info: boolean
               --enable-debug-info
               --disable-debug-info
Leonid Onokhov's avatar
Leonid Onokhov committed
1024
    :synopsis: Build with debug info enabled.
1025 1026 1027 1028
    :since: 1.22

    :default: False

1029 1030
    If the compiler (e.g., GHC 7.10 and later) supports outputing OS
    native debug info (e.g., DWARF), setting ``debug-info: True`` will
1031 1032
    instruct it to do so. See the GHC wiki page on :ghc-wiki:`DWARF`
    for more information about this feature.
1033 1034 1035 1036 1037 1038 1039

    (This field also accepts numeric syntax, but as of GHC 8.0 this
    doesn't do anything.)

    The command line variant of this flag is ``--enable-debug-info`` and
    ``--disable-debug-info``.

1040 1041 1042
.. cfg-field:: split-objs: boolean
               --enable-split-objs
               --disable-split-objs
Leonid Onokhov's avatar
Leonid Onokhov committed
1043
    :synopsis: Use GHC split objects feature.
1044 1045 1046

    :default: False

1047 1048 1049 1050 1051 1052 1053 1054 1055
    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.

    The command line variant of this flag is ``--enable-split-objs`` and
    ``--disable-split-objs``.

1056 1057 1058
.. cfg-field:: executable-stripping: boolean
               --enable-executable-stripping
               --disable-executable-stripping
Leonid Onokhov's avatar
Leonid Onokhov committed
1059
    :synopsis: Strip installed programs.
1060 1061 1062

    :default: True

1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076
    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.

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

    (TODO: Check what happens if you combine this with ``debug-info``.)

    The command line variant of this flag is
    ``--enable-executable-stripping`` and
    ``--disable-executable-stripping``.

1077 1078 1079
.. cfg-field:: library-stripping: boolean
               --enable-library-stripping
               --disable-library-stripping
Leonid Onokhov's avatar
Leonid Onokhov committed
1080
    :synopsis: Strip installed libraries.
1081 1082
    :since: 1.19

1083 1084 1085 1086 1087 1088 1089 1090
    When installing binary libraries, run the ``strip`` program on the
    binary, saving space on the file system. See also
    ``executable-stripping``.

    The command line variant of this flag is
    ``--enable-library-stripping`` and ``--disable-library-stripping``.

Executable options
1091
^^^^^^^^^^^^^^^^^^
1092

1093 1094
.. cfg-field:: program-prefix: prefix
               --program-prefix=prefix
Leonid Onokhov's avatar
Leonid Onokhov committed
1095
    :synopsis: Prepend prefix to program names.
1096

1097 1098 1099 1100 1101 1102 1103 1104 1105 1106
    [STRIKEOUT:Prepend *prefix* to installed program names.] (Currently
    implemented in a silly and not useful way. If you need this to work
    give us a shout.)

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

    The command line variant of this flag is ``--program-prefix=foo-``.

1107 1108
.. cfg-field:: program-suffix: suffix
               --program-suffix=suffix
Leonid Onokhov's avatar
Leonid Onokhov committed
1109
    :synopsis: Append refix to program names.
1110

1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126
    [STRIKEOUT:Append *suffix* to installed program names.] (Currently
    implemented in a silly and not useful way. If you need this to work
    give us a shout.)

    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``

    The command line variant of this flag is
    ``--program-suffix='$version'``.

Dynamic linking options
1127
^^^^^^^^^^^^^^^^^^^^^^^
1128

1129 1130 1131
.. cfg-field:: shared: boolean
               --enable-shared
               --disable-shared
Leonid Onokhov's avatar
Leonid Onokhov committed
1132
    :synopsis: Build shared library.
1133 1134 1135

    :default: False

1136 1137 1138 1139 1140 1141
    Build shared library. This implies a separate compiler run to
    generate position independent code as required on most platforms.

    The command line variant of this flag is ``--enable-shared`` and
    ``--disable-shared``.

1142 1143 1144
.. cfg-field:: executable-dynamic: boolean
               --enable-executable-dynamic
               --disable-executable-dynamic
Leonid Onokhov's avatar
Leonid Onokhov committed
1145
    :synopsis: Link executables dynamically.
1146 1147 1148

    :default: False

1149 1150 1151 1152 1153 1154 1155 1156
    Link executables dynamically. The executable's library dependencies
    should be built as shared objects. This implies ``shared: True``
    unless ``shared: False`` is explicitly specified.

    The command line variant of this flag is
    ``--enable-executable-dynamic`` and
    ``--disable-executable-dynamic``.

1157 1158 1159
.. cfg-field:: library-for-ghci: boolean
               --enable-library-for-ghci
               --disable-library-for-ghci
Leonid Onokhov's avatar
Leonid Onokhov committed
1160
    :synopsis: Build libraries suitable for use with GHCi.
1161 1162 1163

    :default: True

1164 1165 1166 1167 1168 1169 1170 1171 1172 1173
    Build libraries suitable for use with GHCi. This involves an extra
    linking step after the build.

    Not all platforms support GHCi and indeed on some platforms, trying
    to build GHCi libs fails. In such cases, consider setting
    ``library-for-ghci: False``.

    The command line variant of this flag is
    ``--enable-library-for-ghci`` and ``--disable-library-for-ghci``.

1174 1175
.. cfg-field:: relocatable:
               --relocatable
Leonid Onokhov's avatar
Leonid Onokhov committed
1176
    :synopsis: Build relocatable package.
1177 1178 1179 1180
    :since: 1.21

    :default: False

1181 1182 1183 1184 1185 1186
    [STRIKEOUT:Build a package which is relocatable.] (TODO: It is not
    clear what this actually does, or if it works at all.)

    The command line variant of this flag is ``--relocatable``.

Foreign function interface options
1187
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1188

1189 1190
.. cfg-field:: extra-include-dirs: directories (comma or newline separated list)
               --extra-include-dirs=DIR
Leonid Onokhov's avatar
Leonid Onokhov committed
1191
    :synopsis: Adds C header search path.
1192

1193 1194 1195 1196 1197 1198
    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
1199
    appending the directory *dir* to the :pkg-field:`include-dirs` field in each
1200 1201 1202 1203 1204 1205 1206 1207 1208
    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.

    The command line variant of this flag is
    ``--extra-include-dirs=DIR``, which can be specified multiple times.

1209 1210
.. cfg-field:: extra-lib-dirs: directories (comma or newline separated list)
               --extra-lib-dirs=DIR
Leonid Onokhov's avatar
Leonid Onokhov committed
1211
    :synopsis: Adds library search directory.
1212

1213 1214 1215 1216 1217
    An extra directory to search for system libraries files.

    The command line variant of this flag is ``--extra-lib-dirs=DIR``,
    which can be specified multiple times.

1218 1219
.. cfg-field:: extra-framework-dirs: directories (comma or newline separated list)
               --extra-framework-dirs=DIR
Leonid Onokhov's avatar
Leonid Onokhov committed
1220
    :synopsis: Adds framework search directory (OS X only).
1221

1222 1223 1224 1225 1226
    An extra directory to search for frameworks (OS X only).

    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
1227
    appending the directory *dir* to the :cfg-field:`extra-lib-dirs` field in
1228 1229 1230 1231 1232 1233 1234 1235 1236 1237 1238
    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.

    The command line variant of this flag is
    ``--extra-framework-dirs=DIR``, which can be specified multiple
    times.

Profiling options
1239
^^^^^^^^^^^^^^^^^
1240

1241 1242 1243
.. cfg-field:: profiling: boolean
               --enable-profiling
               --disable-profiling
Leonid Onokhov's avatar
Leonid Onokhov committed
1244
    :synopsis: Enable profiling builds.
1245 1246 1247 1248
    :since: 1.21

    :default: False

1249 1250
    Build libraries and executables with profiling enabled (for
    compilers that support profiling as a separate mode). It is only
1251 1252
    necessary to specify :cfg-field:`profiling` for the specific package you
    want to profile; ``cabal new-build`` will ensure that all of its
1253 1254 1255
    transitive dependencies are built with profiling enabled.

    To enable profiling for only libraries or executables, see
1256
    :cfg-field:`library-profiling` and :cfg-field:`executable-profiling`.
1257 1258

    For useful profiling, it can be important to control precisely what
1259
    cost centers are allocated; see :cfg-field:`profiling-detail`.
1260 1261 1262 1263

    The command line variant of this flag is ``--enable-profiling`` and
    ``--disable-profiling``.

1264 1265
.. cfg-field:: profiling-detail: level
               --profiling-detail=level
Leonid Onokhov's avatar
Leonid Onokhov committed
1266
    :synopsis: Profiling detail level.
1267 1268
    :since: 1.23

1269 1270 1271