1 <?xml version="1.0" encoding="iso-8859-1"?>
6 <indexterm><primary>packages</primary></indexterm>
8 <para>A package is a library of Haskell modules known to the compiler. GHC
9 comes with several packages: see the accompanying
10 <ulink url="../libraries/index.html">library documentation</ulink>.</para>
12 <para>Using a package couldn't be simpler: if you're using
13 <option>--make</option> or GHCi, then most of the installed packages will be
14 automatically available to your program without any further options. The
15 exceptions to this rule are covered below in <xref
16 linkend="using-packages" />.</para>
18 <para>Building your own packages is also quite straightforward: we provide
19 the <ulink url="http://www.haskell.org/cabal/">Cabal</ulink> infrastructure which
20 automates the process of configuring, building, installing and distributing
21 a package. All you need to do is write a simple configuration file, put a
22 few files in the right places, and you have a package. See the
23 <ulink url="../Cabal/index.html">Cabal documentation</ulink>
24 for details, and also the Cabal libraries (<ulink url="../libraries/Cabal/Distribution.Simple.html">Distribution.Simple</ulink>,
27 <sect2 id="using-packages">
30 <indexterm><primary>packages</primary>
31 <secondary>using</secondary></indexterm>
33 <para>To see which packages are installed, use the
34 <literal>ghc-pkg</literal> command:</para>
38 /usr/lib/ghc-6.4/package.conf:
39 base-1.0, haskell98-1.0, template-haskell-1.0, mtl-1.0, unix-1.0,
40 Cabal-1.0, haskell-src-1.0, parsec-1.0, network-1.0,
41 QuickCheck-1.0, HUnit-1.1, fgl-1.0, X11-1.1, HGL-3.1, OpenGL-2.0,
42 GLUT-2.0, stm-1.0, readline-1.0, (lang-1.0), (concurrent-1.0),
43 (posix-1.0), (util-1.0), (data-1.0), (text-1.0), (net-1.0),
44 (hssource-1.0), rts-1.0
47 <para>Packages are either exposed or hidden. Only
48 modules from exposed packages may be imported by your Haskell code; if
49 you try to import a module from a hidden package, GHC will emit an error
52 <para>Each package has an exposed flag, which says whether it is exposed by
53 default or not. Packages hidden by default are listed in
54 parentheses (eg. <literal>(lang-1.0)</literal>) in the output from
55 <literal>ghc-pkg list</literal>. To expose a package which is hidden by
56 default, use the <option>-package</option>
57 flag (see below).</para>
59 <para>To see which modules are exposed by a package:</para>
62 $ ghc-pkg field network exposed-modules
63 exposed-modules: Network.BSD,
70 <para>In general, packages containing hierarchical modules are usually
71 exposed by default. However, it is possible for two packages to contain
72 the same module: in this case, only one of the packages can be
73 exposed. This might happen if you have two versions of the same package
74 installed, for example. The general rule is:</para>
76 <blockquote><para>There must be no overlaps in the modules provided by all
77 of the exposed packages, and the packages they depend on, and so
78 on.</para></blockquote>
80 <para>The GHC command line options that control packages are:</para>
85 <option>-package <replaceable>P</replaceable></option>
86 <indexterm><primary><option>-package</option></primary></indexterm>
89 <para>This option causes package <replaceable>P</replaceable> to be
90 exposed. The package <replaceable>P</replaceable> can be specified
91 in full with its version number
92 (e.g. <literal>network-1.0</literal>) or the version number can be
93 omitted if there is only one version of the package
96 <para>If there are multiple versions of <replaceable>P</replaceable>
97 installed, then all other versions will become hidden.</para>
99 <para>The <option>-package <replaceable>P</replaceable></option>
100 option also causes package <replaceable>P</replaceable> to be
101 linked into the resulting executable. In
102 <option>––make</option> mode and GHCi, the compiler
103 normally determines which packages are required by the current
104 Haskell modules, and links only those. In batch mode however, the
105 dependency information isn't available, and explicit
106 <option>-package</option> options must be given when linking.</para>
108 <para>For example, to link a program consisting of objects
109 <filename>Foo.o</filename> and <filename>Main.o</filename>, where
110 we made use of the <literal>network</literal> package, we need to
111 give GHC the <literal>-package</literal> flag thus:
113 <screen>$ ghc -o myprog Foo.o Main.o -package network</screen>
115 The same flag is necessary even if we compiled the modules from
116 source, because GHC still reckons it's in batch mode:
118 <screen>$ ghc -o myprog Foo.hs Main.hs -package network</screen>
120 In <literal>--make</literal> and <literal>--interactive</literal>
121 modes (<xref linkend="modes" />), however, GHC figures out the
122 packages required for linking without further assistance.</para>
124 <para>The one other time you might need to use
125 <option>-package</option> to force linking a package is when the
126 package does not contain any Haskell modules (it might contain a C
127 library only, for example). In that case, GHC
128 will never discover a dependency on it, so it has to be mentioned
134 <term><option>-hide-package</option> <replaceable>P</replaceable>
135 <indexterm><primary><option>-hide-package</option></primary>
138 <para>This option does the opposite of <option>-package</option>: it
139 causes the specified package to be <firstterm>hidden</firstterm>,
140 which means that none of its modules will be available for import
141 by Haskell <literal>import</literal> directives.</para>
143 <para>Note that the package might still end up being linked into the
144 final program, if it is a dependency (direct or indirect) of
145 another exposed package.</para>
150 <term><option>-ignore-package</option> <replaceable>P</replaceable>
151 <indexterm><primary><option>-ignore-package</option></primary>
154 <para>Causes the compiler to behave as if package
155 <replaceable>P</replaceable> is not installed at all. This is not
156 the same as <option>-hide-package</option>, because under
157 <option>-hide-package</option> the package might still be present
158 in the program if another package depends on it.</para>
160 <para><option>-ignore-package</option> <replaceable>P</replaceable>
161 not only causes package <replaceable>P</replaceable> to be removed,
162 but also everything that depends on <replaceable>P</replaceable>,
165 <para>Why do we need <option>-ignore-package</option>? Well, it is
166 particularly useful when you're actually compiling package
167 <replaceable>P</replaceable> itself. The compiler will refuse to
168 compile module <replaceable>M</replaceable> if
169 <replaceable>M</replaceable> is already part of a package. So we
170 might try <option>-hide-package</option>
171 <replaceable>P</replaceable>; but then if
172 <replaceable>P</replaceable> is a dependency of another package
173 <replaceable>P'</replaceable> we would have to
174 <option>-hide-package</option> <replaceable>P'</replaceable> too;
175 and the author of the code can't know in advance which packages are
176 installed on the system and hence which
177 <option>-hide-package</option> flags are required. So, we provide
178 <option>-ignore-package</option> which does the Right Thing.</para>
184 <sect2 id="package-databases">
185 <title>Package Databases</title>
187 <para>A package database is a file, normally called
188 <literal>package.conf</literal> which contains descriptions of installed
189 packages. GHC usually knows about two package databases:</para>
193 <para>The global package database, which comes with your GHC
197 <para>A package database private to each user. On Unix
199 <filename>$HOME/.ghc/<replaceable>arch</replaceable>-<replaceable>os</replaceable>-<replaceable>version</replaceable>/package.conf</filename>, and on
200 Windows it will be something like
201 <filename>C:\Documents And Settings\<replaceable>user</replaceable>\ghc</filename>.
202 The <literal>ghc-pkg</literal> tool knows where this file should be
203 located, and will create it if it doesn't exist (see <xref
204 linkend="package-management" />).</para>
208 <para>When GHC starts up, it reads the contents of these two package
209 databases, and builds up a list of the packages it knows about. You can
210 see GHC's package table by running GHC with the <option>-v</option>
213 <para>Package databases may overlap: for example, packages in the user
214 database will override those of the same name in the global
217 <para>You can control the loading of package databses using the following
223 <option>-package-conf <replaceable>file</replaceable></option>
224 <indexterm><primary><option>-package-conf</option></primary></indexterm>
227 <para>Read in the package configuration file
228 <replaceable>file</replaceable> in addition to the system
229 default file and the user's local file. Packages in additional
230 files read this way will override those in the global and user
236 <term><option>-no-user-package-conf</option>
237 <indexterm><primary><option>-no-user-package-conf</option></primary>
241 <para>Prevent loading of the user's local package database.</para>
246 <para>To create a new package database, just create
247 a new file and put the string
248 <quote><literal>[]</literal></quote> in it. Packages can be
249 added to the file using the
250 <literal>ghc-pkg</literal> tool, described in <xref
251 linkend="package-management"/>.</para>
254 <sect2 id="building-packages">
255 <title>Building a package from Haskell source</title>
256 <indexterm><primary>packages</primary>
257 <secondary>building</secondary></indexterm>
259 <para>We don't recommend building packages the hard way. Instead, use the
260 <ulink url="../Cabal/index.html">Cabal</ulink> infrastructure
261 if possible. If your package is particularly complicated or requires a
262 lot of configuration, then you might have to fall back to the low-level
263 mechanisms, so a few hints for those brave souls follow.</para>
267 <para>You need to build an "installed package info" file for
268 passing to <literal>ghc-pkg</literal> when installing your
269 package. The contents of this file are described in <xref
270 linkend="installed-pkg-info" />.</para>
274 <para>The Haskell code in a package may be built into one or
275 more archive libraries
276 (e.g. <filename>libHSfoo.a</filename>), or a single DLL on
277 Windows (e.g. <filename>HSfoo.dll</filename>). The
278 restriction to a single DLL on Windows is because the
279 package system is used to tell the compiler when it should
280 make an inter-DLL call rather than an intra-DLL call
281 (inter-DLL calls require an extra
282 indirection). <emphasis>Building packages as DLLs doesn't
283 work at the moment; see <xref linkend="win32-dlls-create"/>
284 for the gory details.</emphasis>
287 <para>Building a static library is done by using the
288 <literal>ar</literal> tool, like so:</para>
290 <screen>ar cqs libHSfoo.a A.o B.o C.o ...</screen>
292 <para>where <filename>A.o</filename>,
293 <filename>B.o</filename> and so on are the compiled Haskell
294 modules, and <filename>libHSfoo.a</filename> is the library
295 you wish to create. The syntax may differ slightly on your
296 system, so check the documentation if you run into
299 <para>Versions of the Haskell libraries for use with GHCi
300 may also be included: GHCi cannot load <literal>.a</literal>
301 files directly, instead it will look for an object file
302 called <filename>HSfoo.o</filename> and load that. On some
303 systems, the <literal>ghc-pkg</literal> tool can
304 automatically build the GHCi version of each library, see
305 <xref linkend="package-management"/>. To build these
306 libraries by hand from the <literal>.a</literal> archive, it
307 is possible to use GNU <command>ld</command> as
310 <screen>ld -r ––whole-archive -o HSfoo.o libHSfoo.a</screen>
313 <literal>––--whole-archive</literal> with
314 <literal>–all_load</literal> on MacOS X)</para>
316 <para>GHC does not maintain detailed cross-package
317 dependency information. It does remember which modules in
318 other packages the current module depends on, but not which
319 things within those imported things.</para>
323 <para>When compiling a Haskell module which is to be part of a new package
324 <replaceable>P</replaceable>, use
325 <option>-ignore-package</option> <replaceable>P</replaceable>.</para>
329 <para>It is worth noting that on Windows, when each package
330 is built as a DLL, since a reference to a DLL costs an extra
331 indirection, intra-package references are cheaper than
332 inter-package references. Of course, this applies to the
333 <filename>Main</filename> package as well.</para>
336 <sect2 id="package-management">
337 <title>Package management (the <literal>ghc-pkg</literal> command)</title>
338 <indexterm><primary>packages</primary>
339 <secondary>management</secondary></indexterm>
341 <para>The <literal>ghc-pkg</literal> tool allows packages to be
342 added or removed from a package database. By default,
343 the system-wide package database is used, but alternatively
344 the user's local package database or another specified
345 file can be used.</para>
347 <para>The <literal>ghc-pkg</literal> program may be run in the following
348 ways. Where a package name is required, the package can be named either
349 in full including the version number
350 (e.g. <literal>network-1.0</literal>), or without the version number if
351 that is unambiguous.</para>
355 <term><literal>ghc-pkg register <replaceable>file</replaceable></literal></term>
357 <para>Reads a package specification from
358 <replaceable>file</replaceable> (which may be “<literal>-</literal>”
359 to indicate standard input),
360 and adds it to the database of installed packages. The syntax of
361 <replaceable>file</replaceable> is given in <xref
362 linkend="installed-pkg-info" />.</para>
364 <para>The package specification must be a package that isn't already
370 <term><literal>ghc-pkg update <replaceable>file</replaceable></literal></term>
372 <para>The same as <literal>register</literal>, except that if a
373 package of the same name is already installed, it is
374 replaced by the new one.</para>
379 <term><literal>ghc-pkg unregister <replaceable>P</replaceable></literal></term>
381 <para>Remove the specified package from the database.</para>
386 <term><literal>ghc-pkg expose <replaceable>P</replaceable></literal></term>
388 <para>Sets the <literal>exposed</literal> flag for package
389 <replaceable>P</replaceable> to <literal>True</literal>.</para>
394 <term><literal>ghc-pkg hide <replaceable>P</replaceable></literal></term>
396 <para>Sets the <literal>exposed</literal> flag for package
397 <replaceable>P</replaceable> to <literal>False</literal>.</para>
402 <term><literal>ghc-pkg list</literal></term>
404 <para>This option displays the currently installed
405 packages, for each of the databases known to
406 <literal>ghc-pkg</literal>. That includes the global database, the
407 user's local database, and any further files
408 specified using the <option>-f</option> option on the command
411 <para>Hidden packages (those for which the <literal>exposed</literal>
412 flag is <literal>False</literal>) are shown in parentheses in the
413 list of packages.</para>
418 <term><literal>ghc-pkg describe <replaceable>P</replaceable></literal></term>
420 <para>Emit the full description of the specified package. The
421 description is in the form of an
422 <literal>InstalledPackageInfo</literal>, the same as the input file
423 format for <literal>ghc-pkg register</literal>. See <xref
424 linkend="installed-pkg-info" /> for details.</para>
429 <term><literal>ghc-pkg field <replaceable>P</replaceable> <replaceable>field</replaceable></literal></term>
431 <para>Show just a single field of the installed package description
432 for <literal>P</literal>.</para>
437 <para>Additionally, the following flags are accepted by
438 <literal>ghc-pkg</literal>:</para>
443 <option>––auto-ghci-libs</option><indexterm><primary><option>––user</option></primary>
447 <para>Automatically generate the GHCi
448 <filename>.o</filename> version of each
449 <filename>.a</filename> Haskell library, using GNU ld (if
450 that is available). Without this option,
451 <literal>ghc-pkg</literal> will warn if GHCi versions of
452 any Haskell libraries in the package don't exist.</para>
454 <para>GHCi <literal>.o</literal> libraries don't
455 necessarily have to live in the same directory as the
456 corresponding <literal>.a</literal> library. However,
457 this option will cause the GHCi library to be created in
458 the same directory as the <literal>.a</literal>
465 <option>-f</option> <replaceable>file</replaceable>
466 <indexterm><primary><option>-f</option></primary>
470 <option>-package-conf</option> <replaceable>file</replaceable>
471 <indexterm><primary><option>-package-conf</option></primary>
475 <para>Operate on the package database in
476 <replaceable>file</replaceable>.
477 This flag affects the <literal>register</literal>,
478 <literal>update</literal>, <literal>unregister</literal>,
479 <literal>expose</literal>, and <literal>hide</literal>
482 <para>When multiple <option>-f</option> options are given, or
483 <option>-f</option> is used in conjunction with
484 <option>--user</option> or <option>--global</option>, the last
485 one on the command-line takes precedence. When listing packages
486 with <literal>ghc-pkg list</literal>, the contents of all the
487 databases specified on the command-line are listed.</para>
493 <option>––force</option>
495 <option>––force</option>
496 </primary></indexterm>
499 <para>Causes <literal>ghc-pkg</literal> to ignore missing
500 dependencies, directories and libraries when registering a package,
501 and just go ahead and add it anyway. This might be useful if your
502 package installation system needs to add the package to
503 GHC before building and installing the files.</para>
509 <option>––global</option><indexterm><primary><option>––user</option></primary>
513 <para>Operate on the global package database (this is the default).
514 This flag affects the <literal>register</literal>,
515 <literal>update</literal>, <literal>unregister</literal>,
516 <literal>expose</literal>, and <literal>hide</literal>
523 <option>––help</option><indexterm><primary><option>––user</option></primary>
527 <option>-?</option><indexterm><primary><option>-?</option></primary>
531 <para>Outputs the command-line syntax.</para>
537 <option>––user</option><indexterm><primary><option>––user</option></primary>
541 <para>Operate on the current user's local package database.
542 This flag affects the <literal>register</literal>,
543 <literal>update</literal>, <literal>unregister</literal>,
544 <literal>expose</literal>, and <literal>hide</literal>
551 <option>-V</option><indexterm><primary><option>-V</option></primary>
555 <option>––version</option><indexterm><primary><option>––user</option></primary>
559 <para>Output the <literal>ghc-pkg</literal> version number.</para>
564 <para>When modifying the package database
565 <replaceable>file</replaceable>, a copy of the original file is
566 saved in <replaceable>file</replaceable><literal>.old</literal>,
567 so in an emergency you can always restore the old settings by
568 copying the old file back again.</para>
572 <sect2 id="installed-pkg-info">
574 <literal>InstalledPackageInfo</literal>: a package specification
577 <para>A package specification is a Haskell record; in particular, it is the
579 url="../libraries/Cabal/Distribution.InstalledPackageInfo#%tInstalledPackageInfo">InstalledPackageInfo</ulink> in the module Distribution.InstalledPackageInfo, which is part of the Cabal package distributed with GHC.</para>
581 <para>An <literal>InstalledPackageInfo</literal> has a human
582 readable/writable syntax. The functions
583 <literal>parseInstalledPackageInfo</literal> and
584 <literal>showInstalledPackageInfo</literal> read and write this syntax
585 respectively. Here's an example of the
586 <literal>InstalledPackageInfo</literal> for the <literal>unix</literal> package:</para>
589 $ ghc-pkg describe unix
594 maintainer: libraries@haskell.org
602 exposed-modules: System.Posix,
603 System.Posix.DynamicLinker.Module,
604 System.Posix.DynamicLinker.Prim,
605 System.Posix.Directory,
606 System.Posix.DynamicLinker,
611 System.Posix.Process,
612 System.Posix.Resource,
614 System.Posix.Terminal,
618 System.Posix.Signals.Exts
619 import-dirs: /usr/lib/ghc-6.4/libraries/unix
620 library-dirs: /usr/lib/ghc-6.4/libraries/unix
622 extra-libs: HSunix_cbits, dl
623 include-dirs: /usr/lib/ghc-6.4/libraries/unix/include
628 <para>The full <ulink url="../Cabal/index.html">Cabal documentation</ulink>
629 is still in preparation (at time of writing), so in the meantime
630 here is a brief description of the syntax of this file:</para>
632 <para>A package description consists of a number of field/value pairs. A
633 field starts with the field name in the left-hand column followed by a
634 “<literal>:</literal>”, and the value continues until the next line that begins in the
635 left-hand column, or the end of file.</para>
637 <para>The syntax of the value depends on the field. The various field
642 <term>freeform</term>
644 <para>Any arbitrary string, no interpretation or parsing is
651 <para>A sequence of non-space characters, or a sequence of arbitrary
652 characters surrounded by quotes <literal>"...."</literal>.</para>
656 <term>string list</term>
658 <para>A sequence of strings, separated by commas. The sequence may
664 <para>In addition, there are some fields with special syntax (e.g. package
665 names, version, dependencies).</para>
667 <para>The allowed fields, with their types, are:</para>
672 <literal>name</literal>
673 <indexterm><primary><literal>name</literal></primary><secondary>package specification</secondary></indexterm>
676 <para>The package's name (without the version).</para>
682 <literal>version</literal>
683 <indexterm><primary><literal>version</literal></primary><secondary>package specification</secondary></indexterm>
686 <para>The package's version, usually in the form
687 <literal>A.B</literal> (any number of components are allowed).</para>
693 <literal>license</literal>
694 <indexterm><primary><literal>auto</literal></primary><secondary>package specification</secondary></indexterm>
697 <para>(string) The type of license under which this package is distributed.
698 This field is a value of the <ulink
699 url="../libraries/Cabal/Distribution.License.html#t:License"><literal>License</literal></ulink> type.</para>
705 <literal>license-file</literal>
706 <indexterm><primary><literal>license-file</literal></primary><secondary>package specification</secondary></indexterm>
709 <para>(optional string) The name of a file giving detailed license
710 information for this package.</para>
716 <literal>copyright</literal>
717 <indexterm><primary><literal>copyright</literal></primary><secondary>package specification</secondary></indexterm>
720 <para>(optional freeform) The copyright string.</para>
726 <literal>maintainer</literal>
727 <indexterm><primary><literal>maintainer</literal></primary><secondary>package specification</secondary></indexterm>
730 <para>(optinoal freeform) The email address of the package's maintainer.</para>
736 <literal>stability</literal>
737 <indexterm><primary><literal>stability</literal></primary><secondary>package specification</secondary></indexterm>
740 <para>(optional freeform) A string describing the stability of the package
741 (eg. stable, provisional or experimental).</para>
747 <literal>homepage</literal>
748 <indexterm><primary><literal>homepage</literal></primary><secondary>package specification</secondary></indexterm>
751 <para>(optional freeform) URL of the package's home page.</para>
757 <literal>package-url</literal>
758 <indexterm><primary><literal>package-url</literal></primary><secondary>package specification</secondary></indexterm>
761 <para>(optional freeform) URL of a downloadable distribution for this
762 package. The distribution should be a Cabal package.</para>
768 <literal>description</literal>
769 <indexterm><primary><literal>description</literal></primary><secondary>package specification</secondary></indexterm>
772 <para>(optional freeform) Description of the package.</para>
778 <literal>category</literal>
779 <indexterm><primary><literal>category</literal></primary><secondary>package specification</secondary></indexterm>
782 <para>(optinoal freeform) Which category the package belongs to. This field
783 is for use in conjunction with a future centralised package
784 distribution framework, tentatively titled Hackage.</para>
790 <literal>author</literal>
791 <indexterm><primary><literal>author</literal></primary><secondary>package specification</secondary></indexterm>
794 <para>(optional freeform) Author of the package.</para>
800 <literal>exposed</literal>
801 <indexterm><primary><literal>exposed</literal></primary><secondary>package specification</secondary></indexterm>
804 <para>(bool) Whether the package is exposed or not.</para>
810 <literal>exposed-modules</literal>
811 <indexterm><primary><literal>exposed-modules</literal></primary><secondary>package specification</secondary></indexterm>
814 <para>(string list) modules exposed by this package.</para>
820 <literal>hidden-modules</literal>
821 <indexterm><primary><literal>hidden-modules</literal></primary><secondary>package specification</secondary></indexterm>
824 <para>(string list) modules provided by this package,
825 but not exposed to the programmer. These modules cannot be
826 imported, but they are still subject to the overlapping constraint:
827 no other package in the same program may provide a module of the
834 <literal>import-dirs</literal>
835 <indexterm><primary><literal>import-dirs</literal></primary><secondary>package specification</secondary></indexterm>
838 <para>(string list) A list of directories containing interface files
839 (<literal>.hi</literal> files) for this package.</para>
841 <para>If the package contains profiling libraries, then
842 the interface files for those library modules should have
843 the suffix <literal>.p_hi</literal>. So the package can
844 contain both normal and profiling versions of the same
845 library without conflict (see also
846 <literal>library_dirs</literal> below).</para>
852 <literal>library-dirs</literal>
853 <indexterm><primary><literal>library-dirs</literal></primary><secondary>package specification</secondary></indexterm>
856 <para>(string list) A list of directories containing libraries for this
863 <literal>hs-libraries</literal>
864 <indexterm><primary><literal>hs-libraries</literal></primary><secondary>package specification</secondary></indexterm>
867 <para>(string list) A list of libraries containing Haskell code for this
868 package, with the <literal>.a</literal> or
869 <literal>.dll</literal> suffix omitted. When packages are
870 built as libraries, the
871 <literal>lib</literal> prefix is also omitted.</para>
873 <para>For use with GHCi, each library should have an
874 object file too. The name of the object file does
875 <emphasis>not</emphasis> have a <literal>lib</literal>
876 prefix, and has the normal object suffix for your
879 <para>For example, if we specify a Haskell library as
880 <filename>HSfoo</filename> in the package spec, then the
881 various flavours of library that GHC actually uses will be
885 <term><filename>libHSfoo.a</filename></term>
887 <para>The name of the library on Unix and Windows
888 (mingw) systems. Note that we don't support
889 building dynamic libraries of Haskell code on Unix
894 <term><filename>HSfoo.dll</filename></term>
896 <para>The name of the dynamic library on Windows
897 systems (optional).</para>
901 <term><filename>HSfoo.o</filename></term>
902 <term><filename>HSfoo.obj</filename></term>
904 <para>The object version of the library used by
914 <literal>extra-libs</literal>
915 <indexterm><primary><literal>extra-libs</literal></primary><secondary>package specification</secondary></indexterm>
918 <para>(string list) A list of extra libraries for this package. The
919 difference between <literal>hs-libraries</literal> and
920 <literal>extra-libs</literal> is that
921 <literal>hs-libraries</literal> normally have several
922 versions, to support profiling, parallel and other build
923 options. The various versions are given different
924 suffixes to distinguish them, for example the profiling
925 version of the standard prelude library is named
926 <filename>libHSbase_p.a</filename>, with the
927 <literal>_p</literal> indicating that this is a profiling
928 version. The suffix is added automatically by GHC for
929 <literal>hs-libraries</literal> only, no suffix is added
931 <literal>extra-libs</literal>.</para>
933 <para>The libraries listed in
934 <literal>extra-libs</literal> may be any libraries
935 supported by your system's linker, including dynamic
936 libraries (<literal>.so</literal> on Unix,
937 <literal>.DLL</literal> on Windows).</para>
939 <para>Also, <literal>extra-libs</literal> are placed
940 on the linker command line after the
941 <literal>hs-libraries</literal> for the same package. If
942 your package has dependencies in the other direction (i.e.
943 <literal>extra-libs</literal> depends on
944 <literal>hs-libraries</literal>), and the libraries are
945 static, you might need to make two separate
952 <literal>include-dirs</literal>
953 <indexterm><primary><literal>include-dirs</literal></primary><secondary>package specification</secondary></indexterm>
956 <para>(string list) A list of directories containing C includes for this
963 <literal>includes</literal>
964 <indexterm><primary><literal>includes</literal></primary><secondary>package specification</secondary></indexterm>
967 <para>(string list) A list of files to include for via-C compilations
968 using this package. Typically the include file(s) will
969 contain function prototypes for any C functions used in
970 the package, in case they end up being called as a result
971 of Haskell functions from the package being
978 <literal>depends</literal>
979 <indexterm><primary><literal>depends</literal></primary><secondary>package specification</secondary></indexterm>
982 <para>(package name list) Packages on which this package depends. This field contains
983 packages with explicit versions are required, except that when
984 submitting a package to <literal>ghc-pkg register</literal>, the
985 versions will be filled in if they are unambiguous.</para>
991 <literal>extra-hugs-opts</literal>
992 <indexterm><primary><literal>extra-hugs-opts</literal></primary><secondary>package specification</secondary></indexterm>
995 <para>(string list) Options to pass to Hugs for this package.</para>
1001 <literal>extra-cc-opts</literal>
1002 <indexterm><primary><literal>extra-cc-opts</literal></primary><secondary>package specification</secondary></indexterm>
1005 <para>(string list) Extra arguments to be added to the gcc command line
1006 when this package is being used (only for via-C
1007 compilations).</para>
1013 <literal>extra-ld-opts</literal>
1014 <indexterm><primary><literal>extra-ld-opts</literal></primary><secondary>package specification</secondary></indexterm>
1017 <para>(string list) Extra arguments to be added to the
1018 <command>gcc</command> command line (for linking) when
1019 this package is being used.</para>
1025 <literal>framework-dirs</literal>
1026 <indexterm><primary><literal>framework-dirs</literal></primary><secondary>package specification</secondary></indexterm>
1029 <para>(string list) On Darwin/MacOS X, a list of directories containing
1030 frameworks for this package. This corresponds to the
1031 <option>-framework-path</option> option. It is ignored on all other
1038 <literal>extra-frameworks</literal>
1039 <indexterm><primary><literal>extra-frameworks</literal></primary><secondary>package specification</secondary></indexterm>
1042 <para>(string list) On Darwin/MacOS X, a list of frameworks to link to. This
1043 corresponds to the <option>-framework</option> option. Take a look
1044 at Apple's developer documentation to find out what frameworks
1045 actually are. This entry is ignored on all other platforms.</para>
1051 <literal>haddock-interfaces</literal>
1052 <indexterm><primary><literal>haddock-interfaces</literal></primary><secondary>package specification</secondary></indexterm>
1055 <para>(string list) A list of filenames containing <ulink
1056 url="http://www.haskell.org/haddock/">Haddock</ulink> interface
1057 files (<literal>.haddock</literal> files) for this package.</para>
1063 <literal>haddock-html</literal>
1064 <indexterm><primary><literal>haddock-html</literal></primary><secondary>package specification</secondary></indexterm>
1067 <para>(optional string) The directory containing the Haddock-generated HTML
1068 for this package.</para>
1073 <!-- This isn't true any more. I'm not sure if we still need it -SDM
1075 The <literal>ghc-pkg</literal> tool performs expansion of
1076 environment variables occurring in input package specifications.
1077 So, if the <literal>mypkg</literal> was added to the package
1078 database as follows:
1081 $ installdir=/usr/local/lib ghc-pkg -a < mypkg.pkg
1085 The occurrence of <literal>${installdir}</literal> is replaced
1086 with <literal>/usr/local/lib</literal> in the package data that
1087 is added for <literal>mypkg</literal>.
1091 This feature enables the distribution of package specification
1092 files that can be easily configured when installing.
1095 <para>For examples of more package specifications, take a look
1096 at the <literal>package.conf</literal> in your GHC
1097 installation.</para>
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