</VarListEntry>
<VarListEntry>
-<Term><Option>-package <lib></Option></Term>
-<ListItem>
-<Para>
-<IndexTerm><Primary>-package <lib> option</Primary></IndexTerm>
-If you are using a system-supplied non-Prelude library (e.g., the
-POSIX library), just use a <Option>-package posix</Option> option (for
-example). The right interface files should then be available. The
-accompanying HsLibs document lists the libraries available by this
-mechanism.
-</Para>
-</ListItem>
-</VarListEntry>
-
-<VarListEntry>
<Term><Option>-I<dir></Option></Term>
<ListItem>
<Para>
the details have changed quite a bit). <ULink URL="mailto:sansom@dcs.gla.ac.uk">Ask him</ULink> if you want a copy.
</Para>
-<Sect3 id="packages">
-<Title>Packages</Title>
-
-<Para>
-<IndexTerm><Primary>packages</Primary></IndexTerm>
-To simplify organisation and compilation, GHC keeps libraries in <Emphasis>packages</Emphasis>. Packages are also compiled into single libraries on Unix, and DLLs on Windows. The term ``package'' can be used pretty much synonymously with ``library'', except that an application also forms a package, the Main package.
-</Para>
-
-<ItemizedList>
-<ListItem>
-<Para>
-A package is a group of modules. It may span many directories, or many packages may exist in a single directory. Packages may not be mutually recursive.
-</Para>
-</ListItem>
-
-<ListItem>
-<Para>
-A package has a name (e.g. <Filename>std</Filename>)
-</Para>
-</ListItem>
-
-<ListItem>
-<Para>
-Each package is built into a single library (Unix; e.g. <Filename>libHSfoo.a</Filename>), or a single DLL (Windows; e.g. <Filename>HSfoo.dll</Filename>)
-</Para>
-</ListItem>
-
-<ListItem>
-<Para>
-The <Option>-package-name foo</Option> flag tells GHC that the module being compiled is destined for package <Filename>foo</Filename>. If this is omitted, the default package, <Filename>Main</Filename>, is assumed.
-</Para>
-</ListItem>
-
-<ListItem>
-<Para>
-The <Option>-package foo</Option> flag tells GHC to make available modules
-from package <Filename>foo</Filename>. It replaces <Option>-syslib foo</Option>, which is now deprecated.
-</Para>
-</ListItem>
-
-<ListItem>
-<Para>
-GHC does not maintain detailed cross-package dependency information.
-It does remember which modules in other packages the current module
-depends on, but not which things within those imported things.
-</Para>
-</ListItem>
-</ItemizedList>
-
-<Para>
-All of this tidies up the Prelude enormously. The Prelude and
-Standard Libraries are built into a single package called <Filename>std</Filename>. (This
-is a change; the library is now called <Filename>libHSstd.a</Filename> instead of <Filename>libHS.a</Filename>).
-</Para>
-
-<Para>
-It is worth noting that on Windows, because each package is built as a DLL, and a reference to a DLL costs an extra indirection, intra-package references are cheaper than inter-package references. Of course, this applies to the <Filename>Main</Filename> package as well. This is not normally the case on most Unices.
-</Para>
-
-</Sect3>
-
</Sect2>
</Sect1>
+ <sect1 id="packages">
+ <title>Packages</title>
+ <indexterm><primary>packages</primary></indexterm>
+
+ <para>Packages are collections of libraries, conveniently grouped
+ together as a single entity. The package system is flexible: a
+ package may consist of Haskell code, foreign language code (eg. C
+ libraries), or a mixture of the two. A package is a good way to
+ group together related Haskell modules, and is essential if you
+ intend to make the modules into a Windows DLL (see below).</para>
+
+ <para>Because packages can contain both Haskell and C libraries, they
+ are also a good way to provide convenient access to a Haskell
+ layer over a C library.</para>
+
+ <para>GHC comes with several packages (see <xref
+ linkend="book-hslibs">), and packages can be added/removed from an
+ existing GHC installation.</para>
+
+ <sect2 id="listing-packages">
+ <title>Listing the available packages</title>
+ <indexterm><primary>packages</primary>
+ <secondary>listing</secondary></indexterm>
+
+ <para>To see what packages are currently installed, use the
+ <literal>--list-packages</literal> option:</para>
+ <indexterm><primary><literal>--list-packages</literal></primary>
+ </indexterm>
+
+<screen>
+ $ ghc --list-packages
+ gmp, rts, std, lang, concurrent, data, net, posix, text, util
+</screen>
+
+ <para>Note that your GHC installation might have a slightly
+ different set of packages installed.</para>
+
+ <para>The <literal>gmp</literal> and <literal>rts</literal>
+ packages are always present, and represent the multi-precision
+ integer and runtime system libraries respectively. The
+ <literal>std</literal> package contains the Haskell prelude.
+ The rest of the packages are optional libraries.</para>
+
+ </sect2>
+
+ <sect2 id="using-packages">
+ <title>Using a package</title>
+ <indexterm><primary>packages</primary>
+ <secondary>using</secondary></indexterm>
+
+ <para>To use a package, add the <literal>-package</literal> flag
+ to the command line:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><option>-package <lib></option></term>
+ <indexterm><primary>-package <lib> option</primary></indexterm>
+ <listitem>
+ <para>This option brings into scope all the modules from
+ package <literal><lib></literal> (they still have to
+ be imported in your Haskell source, however). It also
+ causes the relevant libraries to be linked when linking is
+ being done.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>Some packages depend on other packages, for example the
+ <literal>text</literal> package makes use of some of the modules
+ in the <literal>lang</literal> package. The package system
+ takes care of all these dependencies, so that when you say
+ <literal>-package text</literal> on the command line, you
+ automatically get <literal>-package lang</literal> too.</para>
+ </sect2>
+
+ <sect2 id="building-packages">
+ <title>Building a package from Haskell source</title>
+ <indexterm><primary>packages</primary>
+ <secondary>building</secondary></indexterm>
+
+ <para>It takes some special considerations to build a new
+ package:</para>
+
+ <itemizedlist>
+ <listitem>
+ <para>A package may contain several Haskell modules. A
+ package may span many directories, or many packages may
+ exist in a single directory. Packages may not be mutually
+ recursive.</para>
+ </listitem>
+
+ <listitem>
+ <para>A package has a name
+ (e.g. <filename>std</filename>)</para>
+ </listitem>
+
+ <listitem>
+ <para>The Haskell code in a package may be built into one or
+ more Unix libraries (e.g. <Filename>libHSfoo.a</Filename>),
+ or a single DLL on Windows
+ (e.g. <Filename>HSfoo.dll</Filename>). The restriction to a
+ single DLL on Windows is that the package system is used to
+ tell the compiler when it should make an inter-DLL call
+ rather than an intra-DLL call (inter-DLL calls require an
+ extra indirection).</para>
+ </listitem>
+
+ <listitem>
+ <para>GHC does not maintain detailed cross-package
+ dependency information. It does remember which modules in
+ other packages the current module depends on, but not which
+ things within those imported things.</para>
+ </listitem>
+ </itemizedlist>
+
+ <para>To compile a module which is to be part of a new package,
+ use the <literal>-package-name</literal> option:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><option>-package-name <foo></option></term>
+ <indexterm><primary><literal>-package-name</literal></primary>
+ <secondary>option</secondary></indexterm>
+ <listitem>
+ <para>This option is added to the command line when
+ compiling a module that is destined to be part of package
+ <literal>foo</literal>. If this flag is omitted then the
+ default package <literal>Main</literal> is assumed.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>Failure to use the <literal>-package-name</literal> option
+ when compiling a package will result in disaster on Windows, but
+ is relatively harmless on Unix at the moment (it will just cause
+ a few extra dependencies in some interface files). However,
+ bear in mind that we might add support for Unix shared libraries
+ at some point in the future.</para>
+
+ <para>It is worth noting that on Windows, because each package
+ is built as a DLL, and a reference to a DLL costs an extra
+ indirection, intra-package references are cheaper than
+ inter-package references. Of course, this applies to the
+ <Filename>Main</Filename> package as well.</para>
+
+ </sect2>
+ <sect2 id="package-management">
+ <title>Package management</title>
+ <indexterm><primary>packages</primary>
+ <secondary>management</secondary></indexterm>
+
+ <para>GHC uses a package configuration file, called
+ <literal>packages.conf</literal>, which can be found in your GHC
+ install directory. This file isn't intended to be edited
+ directly, instead GHC provides options for adding & removing
+ packages:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><option>--add-package</option></term>
+ <indexterm><primary><literal>--add-package</literal></primary>
+ <secondary>option</secondary></indexterm>
+ <listitem>
+ <para>Reads a package specification (see below) on stdin,
+ and adds it to the database of installed packages. The
+ package specification must be a package that isn't already
+ installed.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><option>--delete-package <foo></option></term>
+ <indexterm><primary><literal>--delete-package</literal></primary>
+ <secondary>option</secondary></indexterm>
+ <listitem>
+ <para>Removes the specified package from the installed
+ configuration.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>In both cases, the old package configuration file is saved
+ in <literal>packages.conf.old</literal> in your GHC install
+ directory, so in an emergency you can always copy this file into
+ <literal>package.conf</literal> to restore the old
+ settings.</para>
+
+ <para>A package specification looks like this:</para>
+
+<screen>
+ ("mypkg",
+ "4.08",
+ Package
+ {
+ import_dirs = ["/usr/local/lib/imports/mypkg"],
+ library_dirs = ["/usr/local/lib"],
+ libraries = ["HSmypkg", "HSmypkg_cbits"],
+ include_dir = "",
+ c_include = "HsMyPkg.h",
+ package_deps = ["text", "data"],
+ extra_ghc_opts = "",
+ extra_cc_opts = "",
+ extra_ld_opts = "-lmy_clib"
+ }
+ )
+</screen>
+
+ <para>The first line is the name of the package, for use with
+ the <literal>-package</literal> flag and as listed in the
+ <literal>--list-packages</literal> list. The second line is the
+ version of GHC that was used to compile any Haskell code in this
+ package (GHC will refuse to add the package if its version
+ number differs from this one). The rest of the components of
+ the package speecification may be specified in any order, and
+ are:</para>
+
+ <variablelist>
+ <varlistentry>
+ <term><literal>import_dirs</literal></term>
+ <indexterm><primary><literal>import_dirs</literal></primary>
+ <secondary>package specification</secondary></indexterm>
+ <listitem>
+ <para>A list of directories containing interface files
+ (<literal>.hi</literal> files) for this package.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>library_dirs</literal></term>
+ <indexterm><primary><literal>library_dirs</literal></primary>
+ <secondary>package specification</secondary></indexterm>
+ <listitem>
+ <para>A list of directories containing libraries for this
+ package.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>libraries</literal></term>
+ <indexterm><primary><literal>libraries</literal></primary>
+ <secondary>package specification</secondary></indexterm>
+ <listitem>
+ <para>A list of libraries for this package, with the
+ <literal>.a</literal> or <literal>.dll</literal> suffix
+ omitted. On Unix, the <literal>lib</literal> prefix is
+ also omitted.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>include_dir</literal></term>
+ <indexterm><primary><literal>include_dir</literal></primary>
+ <secondary>package specification</secondary></indexterm>
+ <listitem>
+ <para>A directory containing C includes for this package
+ (may be the empty string).</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>c_include</literal></term>
+ <indexterm><primary><literal>c_include</literal></primary>
+ <secondary>package specification</secondary></indexterm>
+ <listitem>
+ <para>A file to include for via-C compilations using this
+ package. Typically this include file will contain
+ function prototypes for any C functions used in the
+ package, in case they end up being called as a result of
+ Haskell functions from the package being inlined.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>package_deps</literal></term>
+ <indexterm><primary><literal>package_deps</literal></primary>
+ <secondary>package specification</secondary></indexterm>
+ <listitem>
+ <para>A list of packages which this package depends
+ on.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>extra_ghc_opts</literal></term>
+ <indexterm><primary><literal>extra_ghc_opts</literal></primary>
+ <secondary>package specification</secondary></indexterm>
+ <listitem>
+ <para>Extra arguments to be added to the GHC command line
+ when this package is being used.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>extra_cc_opts</literal></term>
+ <indexterm><primary><literal>extra_cc_opts</literal></primary>
+ <secondary>package specification</secondary></indexterm>
+ <listitem>
+ <para>Extra arguments to be added to the gcc command line
+ when this package is being used (only for via-C
+ compilations).</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>extra_ld_opts</literal></term>
+ <indexterm><primary><literal>extra_ld_opts</literal></primary>
+ <secondary>package specification</secondary></indexterm>
+ <listitem>
+ <para>Extra arguments to be added to the gcc command line
+ (for linking) when this package is being used.</para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <para>For examples of more package specifications, take a look
+ at the <literal>package.conf</literal> in your GHC
+ installation.</para>
+ </sect2>
+ </sect1>
+
+
<Sect1 id="options-optimise">
<Title>Optimisation (code improvement)
</Title>
projects / ghc-hetmet.git / commitdiff