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<?xml version="1.0" encoding="UTF8"?>
<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.2//EN"
  "file:////usr/share/sgml/docbook/dtd/4.2/docbookx.dtd" [
    <!ENTITY C2hs 'C&#10132;Haskell'>
    <!ENTITY c2hs '<command>c2hs</command>'>
  ]>

<!-- C->Haskell documentation
 -->
<article>
<articleinfo>
  <title>The Binding Generator &C2hs;</title>
  <authorgroup>
    <author>
      <firstname>Manuel</firstname>
      <surname>Chakravarty</surname>
      <email>chak@cse.unsw.edu.au</email>
    </author>
<!--    <author>
      <firstname>Duncan</firstname>
      <surname>Coutts</surname>
      <email>duncan@haskell.org</email>
    </author>-->
  </authorgroup>
  <pubdate>November 2007</pubdate>
</articleinfo>
<abstract>
  <para>
  &C2hs; is an interface generator that simplifies the development of
  <ulink url="http://haskell.org">Haskell</ulink> bindings to C libraries.  The
  tool processes existing C header files that determine data layout and function
  signatures on the C side in conjunction with Haskell modules that specify
  Haskell-side type signatures and marshaling details.  Hooks embedded in the
  Haskell code signal access to C structures and functions -- they are expanded
  by the interfacing tool in dependence on information from the corresponding C
  header file.  Another noteworthy property is the lightweight nature of the
  approach.
  </para>
</abstract>

<para>
More background information is available in a research paper discussing
&C2hs;, which is at
<ulink url="http://www.cse.unsw.edu.au/~chak/papers/papers.html#c2hs"/>.
However, this paper does not cover the more recent advanced features such as
function hooks and conditional compilation.
</para>

<sect1 id="installation">
  <title>Installation</title>
  <para>
  It follows a brief discussion of the installation from source.  There is,
  however, a file <filename>INSTALL</filename> in the source distribution, which is
  more frequently updated and should be consulted in any case.
  </para>

  <sect2>
    <title>Where is the Source?</title>
    <para>
    The master site of &C2hs; is at
    <ulink url="http://www.cse.unsw.edu.au/~chak/haskell/c2hs/"/>.  It has all the
    latest information and sources.  Furthermore, it explains how to get access to
    the &C2hs; Darcs repository and has references to pre-compiled binaries.
    </para>
  </sect2>

  <sect2>
    <title>What Else Do I Need?</title>
    <para>
    You need a Haskell system supported by &C2hs;. Currently, this is only
    the <firstterm>Glasgow Haskell Compiler (GHC)</firstterm>, which you can obtain
    from <ulink url="http://haskell.org/ghc/"/>.  Furthermore, you need the Haskell
    package system Cabal. See the <filename>INSTALL</filename> file for details on
    supported versions.
    </para>

    <para>
    To build the documentation, you will also need the <firstterm>SGML
    Tools</firstterm>, which you find at your nearest sunsite or Linux mirror or at
    <ulink url="ftp://ftp.lip6.fr/pub/sgml-tools/"/>.  On an up-to-date Linux
    system, the tools are probably already installed.
    </para>
  </sect2>

  <sect2>
    <title>I Got Everything, and Now?</title>
    <para>
    The short answer is
<screen>
$ tar -xzf <replaceable>package</replaceable>.tar.gz      # unpack the sources
$ cd <replaceable>package</replaceable>                   # change to the toplevel directory
$ runghc Setup.hs configure    # configure the build system
$ runghc Setup.hs build        # build everything
[ Become root if necessary ]
$ runghc Setup.hs install      # install c2hs
</screen>
    </para>

    <para>
    In the <filename>INSTALL</filename> file, there are more details.
    </para>

    <para>
    Optionally, you can build the documentation by issuing <userinput>make
    doc</userinput> and install it with <userinput>make install-doc</userinput>.
    </para>
  </sect2>
</sect1>

<sect1 id="usage">
  <title>Usage of &C2hs;</title>
  <para>
  Let's have a brief look at how to call the tool and how to use the generated
  interfaces.
  </para>

  <sect2>
    <title>Usage of &c2hs;</title>
    <para>
    &C2hs; is implemented by the executable &c2hs;. The simplest form of usage
    is

<screen>
c2hs <replaceable>Lib</replaceable><literal>.chs</literal>
</screen>

    where <replaceable>Lib</replaceable><literal>.chs</literal> is the Haskell
    binding module defining the Haskell interface to a C library together with
    the required marshalling code. If &c2hs; is invoked in this manner, the
    binding module must contain a cpp <literal>#include</literal> directive to
    determine the C-side interface of the library. Alternatively, a C header
    file can be specified on the command line, as in

<screen>
c2hs <replaceable>lib</replaceable><literal>.h </literal><replaceable>Lib</replaceable><literal>.chs</literal>
</screen>

    However, the latter option is only preserved for backwards compatibility and
    not recommended.  If no errors occur, &c2hs; generates three files:
    <orderedlist>
      <listitem>
        <para>
        a pure Haskell module <replaceable>Lib</replaceable><literal>.hs</literal>,
        which implements the Haskell API of the library
        </para>
      </listitem>
      <listitem>
        <para>
         a C header file <replaceable>Lib</replaceable><literal>.h</literal>
         which some Haskell systems need to compile the generated Haskell code.
        </para>
      </listitem>
      <listitem>
        <para>
        a &c2hs; interface file
        <replaceable>Lib</replaceable><literal>.chi</literal> that is used by
        other binding modules that import
        <replaceable>Lib</replaceable><literal>.hs</literal> using an import
        hook (see <xref linkend="import"/>the section on import hooks for details).
        </para>
      </listitem>
    </orderedlist>
    </para>

    <para>
    The executable &c2hs; has a couple more options:
<screen>
Usage: c2hs [ option... ] [header-file] binding-file

  -C CPPOPTS   --cppopts=CPPOPTS    pass CPPOPTS to the C preprocessor
  -c CPP       --cpp=CPP            use executable CPP to invoke C preprocessor
  -d TYPE      --dump=TYPE          dump internal information (for debugging)
  -h, -?       --help               brief help (the present message)
  -i INCLUDE   --include=INCLUDE    include paths for .chi files
  -k           --keep               keep pre-processed C header
  -l           --copy-library       copy `C2HS' library module in
  -o FILE      --output=FILE        output result to FILE (should end in .hs)
  -p PLATFORM  --platform=PLATFORM  platform to use for cross compilation
  -t PATH      --output-dir=PATH    place generated files in PATH
  -v           --version            show version information
               --numeric-version    show version number

The header file must be a C header file matching the given binding file.
The dump TYPE can be
  trace   -- trace compiler phases
  genbind -- trace binding generation
  ctrav   -- trace C declaration traversal
  chs     -- dump the binding file (adds `.dump' to the name)
PLATFORM can be x86_64-linux, i686-linux, m68k-palmos
</screen>

    The most useful of these is probably <literal>--cppopts=</literal> (or
    <literal>-C</literal>).  If the C header file needs any special options
    (like <literal>-D</literal> or <literal>-I</literal>) to go through the C
    pre-processor, here is the place to pass them.  A call may look like this:

<screen>
c2hs --cppopts='-I/some/obscure/dir' --cppopts=-DEXTRA' <replaceable>Lib</replaceable>.chs
</screen>

    If you have more than one option that you want to pass to the pre-processor
    it is best to use multiple <literal>--cppopts=</literal> flags. That way
    there is no need to worry about quoting.
    </para>
    
    <para>
    Often, <replaceable>lib</replaceable><literal>.h</literal> will not be in
    the current directory, but in one of the header file directories. &c2hs;
    leaves locating the header file to the standard C preprocessor, which
    usually looks in two places for the header: first, in the standard include
    directory of the used system, this is usually <filename>/usr/include</filename> and
    <filename>/usr/local/include</filename>; and second, it will look in every directory
    that is mentioned in a <literal>-IDIR</literal> option passed to the
    pre-processor via <literal>--cppopts</literal>.
    </para>

    <para>
    If the compiled binding module contains import hooks, &C2hs; needs to
    find the <literal>.chi</literal> (&C2hs; interface files) produced while compiling
    the corresponding binding modules.  By default, they will be searched for in
    the current working directory.  If they are located elsewhere, the
    <literal>--include=<replaceable>INCLUDE</replaceable></literal> option has
    to be used to indicate the location, where
    <replaceable>INCLUDE</replaceable> is a colon-separated list of
    directories.  Multiple such options are admissible.  Paths specified later
    are searched first.
    </para>
  </sect2>
  
  <sect2>
    <title>Compilation of a Generated Haskell API</title>
    <para>
    &C2hs; comes with a marshalling library, called <literal>C2HS</literal>,
    which needs to be explicitly imported into Haskell binding modules.  The
    library contains functions that users might use explicitly, but also
    functions that &C2hs; will generate for some classes of bindings.  The
    library takes the form of a single Haskell module, which &c2hs; places in
    the same directory as the generated binding whenever it is given the
    <literal>--copy-library</literal> (or <literal>-l</literal>) option.
    </para>
  </sect2>
</sect1>

<sect1 id="implementing">
  <title>Implementation of Haskell Binding Modules</title>
  <para>
  A discussion of binding modules, the principles behind the tool, and a
  discussion of related work can be found in a research paper located at <ulink
  url="http://www.cse.unsw.edu.au/~chak/papers/papers.html#c2hs" />.  All
  features described in the paper, except <literal>enum define</literal> hooks
  are implemented in the tool, but since the publication of the paper, the tool
  has been extended further.  The library interface essentially consists of the
  new Haskell FFI Marshalling Library.  More details about this library are
  provided in the next section.
  </para>

  <para>
  The remainder of this section describes the hooks that are available in
  binding modules.
  </para>

  <sect2 id="import">
    <title>Import Hooks</title>
    <para>
<programlisting>
{#import [qualified] <replaceable>modid</replaceable>#}
</programlisting>

    Is translated into the same syntactic form in Haskell, which implies that
    it may be followed by an explicit import list.  Moreover, it implies that
    the module <replaceable>modid</replaceable> is also generated by &C2hs; and
    instructs the tool to read the file
    <replaceable>modid</replaceable><literal>.chi</literal>.
    </para>
    <para>
    If an explicit output file name is given (<literal>--output</literal>
    option), this name determines the basename for the <literal>.chi</literal>
    file of the currently translated module. 
    </para>
    <para>
    Currently, only pointer hooks generate information that is stored in a
    <literal>.chi</literal> file and needs to be incorporated into any client
    module that makes use of these pointer types.  It is, however, regarded as
    good style to use import hooks for any module generated by &C2hs;.
    </para>
    <note>
      <title>Restriction</title>
      <para>
      &C2hs; does not use qualified names.  This can be a problem, for example,
      if two pointer hooks are defined to have the same unqualified Haskell
      name in two different modules, which are then imported by a third module.
       To partially work around this problem, it is guaranteed that the
       declaration of the textually later import hook dominates.
      </para>
    </note>
  </sect2>

  <sect2>
  <title>Context Hooks</title>
    <para>
<programlisting>
{#context [lib = <replaceable>lib</replaceable>] [prefix = <replaceable>prefix</replaceable>]#}
</programlisting>

    Context hooks define a set of global configuration options.  Currently,
    there are two parameters which are both strings
    <itemizedlist>
      <listitem>
        <para>
        <replaceable>lib</replaceable> is a dynamic library that contains
        symbols needed by the present binding.
        </para>
      </listitem>
      <listitem>
        <para><replaceable>prefix</replaceable> is an identifier prefix that
        may be omitted in the lexemes of identifiers referring to C definitions
        in any binding hook.  The is useful as C libraries often use a prefix,
        such as <literal>gtk_</literal>, as a form of poor man's name spaces. 
        Any occurrence of underline characters between a prefix and the main
        part of an identifier must also be dropped.  Case is not relevant in a
        prefix.  In case of a conflict of the abbreviation with an explicitly
        defined identifier, the explicit definition takes preference.
        </para>
      </listitem>
    </itemizedlist>

    Both parameters are optional.  An example of a context hook is the
    following:
<programlisting>
{#context prefix = "gtk"#}
</programlisting>
    </para>
    <para>
    If a binding module contains a binding hook, it must be the first hook in
    the module.
    </para>
  </sect2>

  <sect2>
    <title>Type Hooks</title>
    <para>
<programlisting>
{#type <replaceable>ident</replaceable>#}
</programlisting>

    A type hooks maps a C type to a Haskell type.  As an example, consider

<programlisting>
type GInt = {#type gint#}
</programlisting>

    The type must be a defined type, primitive types, such as
    <literal>int</literal>, are not admissible.
    </para>
  </sect2>

  <sect2>
    <title>Sizeof Hooks</title>
    <para>
<programlisting>
{#sizeof <replaceable>ident</replaceable>#}
</programlisting>

    A sizeof hooks maps a C type to its size in bytes.  As an example, consider

<programlisting>
gIntSize :: Int
gIntSize  = {#sizeof gint#}
</programlisting>

    The type must be a defined type, primitive types, such as
    <literal>int</literal>, are not admissible.  The size of primitive types can
    always be obtained using <literal>Storable.sizeOf</literal>. 
    </para>
  </sect2>

  <sect2>
    <title>Enumeration Hooks</title>
    <para>
<programlisting>
{#enum <replaceable>cid</replaceable> [as <replaceable>hsid</replaceable>] {<replaceable>alias1</replaceable> , ... , <replaceable>aliasn</replaceable>}
  [with prefix = <replaceable>pref</replaceable>] [deriving (<replaceable>clid1</replaceable> , ... , <replaceable>clidn</replaceable>)]#}
</programlisting>

    Rewrite the C enumeration called <replaceable>cid</replaceable> into a
    Haskell data type declaration, which is made an instance of
    <literal>Enum</literal> such that the ordinals match those of the
    enumeration values in C.  This takes explicit enumeration values in the C
    definitions into account.  If <replaceable>hsid</replaceable> is given, this
    is the name of the Haskell data type.  The identifiers
    <replaceable>clid1</replaceable> to <replaceable>clidn</replaceable> are
    added to the deriving clause of the Haskell type.
    </para>

    <para>
    By default, the names of the C enumeration are used for the constructors in
    Haskell.  If <replaceable>alias1</replaceable> is
    <literal>underscoreToCase</literal>, the original C names are capitalised
    and the use of underscores is rewritten to caps.  If it is
    <literal>upcaseFirstLetter</literal> or
    <literal>downcaseFirstLetter</literal>, the first letter of the original C
    name changes case correspondingly.  It is also possible to combine
    <literal>underscoreToCase</literal> with one of
    <literal>upcaseFirstLetter</literal> or
    <literal>downcaseFirstLetter</literal>. Moreover,
    <replaceable>alias1</replaceable> to <replaceable>aliasn</replaceable> may
    be aliases of the form <replaceable>cid</replaceable> <literal>as</literal>
    <replaceable>hsid</replaceable>, which map individual C names to Haskell
    names.  Instead of the global prefix introduced by a context hook, a local
    prefix <replaceable>pref</replaceable> can optionally be specified.
    </para>

    <para>
    As an example, consider

<programlisting>
{#enum WindowType {underscoreToCase} deriving (Eq)#}
</programlisting>
 </para>

  </sect2>
    <sect2>
	    <title><literal>enum define</literal> hooks</title>
      <para>Many C libraries do not use enum types, but macro definitions to implement constants.	          
c2hs provides <literal>enum define</literal> hooks generate a haskell datatype from a collection of macro definitions.											
       </para>

<programlisting>
{#enum define <replaceable>hsid</replaceable> {<replaceable>alias1</replaceable> , ... , <replaceable>aliasn</replaceable>} [deriving (<replaceable>clid1</replaceable> , ... , <replaceable>clidn</replaceable>)]#}
</programlisting>
<para>
Create a haskell datatype <replaceable>hsid</replaceable>, with nullary constructors as given by the aliases <replaceable>alias1</replaceable> through <replaceable>aliasn</replaceable>. Each alias has to be of the form <replaceable>macrodef as hsid</replaceable>, where <replaceable>hsid</replaceable> is the name of the nullary haskell constructor, and <replaceable>macrodef</replaceable> the C macro which the haskell constructor should map to. The deriving part is handled as in ordinary <literal>enum</literal> hooks.
</para>
<para>
	Here's an example
<programlisting>
#define X 0
#define Y 1
</programlisting>	
<programlisting>
{#enum define Axis {X as Axis0, Y as Axis1} deriving (Eq,Ord) #}
</programlisting>	
</para>        
    </sect2>

  <sect2>
    <title>Call Hooks</title>
    <para>
<programlisting>
{#call [pure] [unsafe] <replaceable>cid</replaceable> [as (<replaceable>hsid</replaceable> | ^)]#}
</programlisting>

    A call hook rewrites to a call to the C function
    <replaceable>cid</replaceable> and also ensures that the appropriate foreign
    import declaration is generated.  The tags <literal>pure</literal> and
    <literal>unsafe</literal> specify that the external function is purely
    functional and cannot re-enter the Haskell runtime, respectively.  If
    <replaceable>hsid</replaceable> is present, it is used as the identifier for
    the foreign declaration, which otherwise defaults to the
    <replaceable>cid</replaceable>.  When instead of
    <replaceable>hsid</replaceable>, the symbol <literal>^</literal> is given,
    the <replaceable>cid</replaceable> after conversion from C's underscore
    notation to a capitalised identifier is used.
    </para>

    <para>
    As an example, consider

<programlisting>
sin :: Float -> Float
sin  = {#call pure sin as "_sin"#}
</programlisting>
    </para>
  </sect2>

  <sect2>
    <title>Function Hooks</title>
    <para>
<programlisting>
{#fun  [pure] [unsafe] <replaceable>cid</replaceable> [as (<replaceable>hsid</replaceable> | ^)]
[<replaceable>ctxt</replaceable> =>] { <replaceable>parm1</replaceable> , ... , <replaceable>parmn</replaceable> } -> <replaceable>parm</replaceable>
</programlisting>

    Function hooks are call hooks including parameter marshalling.  Thus, the
    components of a function hook up to and including the <literal>as</literal>
    alias are the same as for call hooks.  However, an <literal>as</literal>
    alias has a different meaning; it specifies the name of the generated
    Haskell function.  The remaining components use literals enclosed in
    backwards and foward single quotes (<literal>`</literal> and
    <literal>'</literal>) to denote Haskell code fragments (or more precisely,
    parts of the Haskell type signature for the bound function).  The first one
    is the phrase <replaceable>ctxt</replaceable> preceding
    <literal>=></literal>, which denotes the type context.  This is followed by
    zero or more type and marshalling specifications
    <replaceable>parm1</replaceable> to <replaceable>parmn</replaceable> for the
    function arguments and one <replaceable>parm</replaceable> for the function
    result.  Each such specification <replaceable>parm</replaceable> has the
    form

<programlisting>
[<replaceable>inmarsh</replaceable> [* | -]] <replaceable>hsty</replaceable>[&amp;] [<replaceable>outmarsh</replaceable> [*] [-]]
</programlisting>

    where <replaceable>hsty</replaceable> is a Haskell code fragment denoting a
    Haskell type.  The optional information to the left and right of this type
    determines the marshalling of the corresponding Haskell value to and from C;
    they are called the <firstterm>in</firstterm> and <firstterm>out</firstterm>
    marshaller, respectively.
    </para>

    <para>
    Each marshalling specification <replaceable>parm</replaceable> corresponds
    to one or two arguments of the C function, in the order in which they are
    given.  A marshalling specification in which the symbol
    <literal>&amp;</literal> follows the Haskell type corresponds to two C
    function arguments; otherwise, it corresponds only to one argument.  The
    <replaceable>parm</replaceable> following the left arrow
    <literal>-></literal> determines the marshalling of the result of the C
    function and may not contain the symbol <literal>&amp;</literal>.
    </para>

    <para>
    The <literal>*-</literal> output marshal specification is for monadic
    actions that must be executed but whose results are discarded. This is very
    useful for e.g. checking an error value and throwing an exception if needed.
    </para>

    <para>
    Both <replaceable>inmarsh</replaceable> and
    <replaceable>outmarsh</replaceable> are identifiers of Haskell marshalling
    functions.  By default they are assumed to be pure functions; if they have
    to be executed in the <literal>IO</literal> monad, the function name needs
    to be followed by a star symbol <literal>*</literal>.  Alternatively, the
    identifier may be followed by a minux sign <literal>-</literal>, in which
    case the Haskell type does <emphasis>not</emphasis> appear as an argument
    (in marshaller) or result (out marshaller) of the generated Haskell
    function.  In other words, the argument types of the Haskell function is
    determined by the set of all marshalling specifications where the in
    marshaller is not followed by a minus sign.  Conversely, the result tuple of
    the Haskell function is determined by the set of all marshalling
    specifications where the out marshaller is not followed by a minus sign. 
    The order of function arguments and components in the result tuple is the
    same as the order in which the marshalling specifications are given, with
    the exception that the value of the result marshaller is always the first
    component in the result tuple if it is included at all.
    </para>
    <para>
    For a set of commonly occuring Haskell and C type combinations,
    <emphasis>default marshallers</emphasis> are provided by &C2hs; if no
    explicit marshaller is given.   The out marshaller for function arguments
    is by default <literal>void-</literal>. The defaults for the in marshallers
    for function arguments are as follows: 

    <itemizedlist>
      <listitem>
        <para>
        <literal>Bool</literal> and integral C type (including chars):
        <literal>cFromBool</literal>
        </para>
      </listitem>
      <listitem>
        <para>
        Integral Haskell and integral C type: <literal>cIntConv</literal>
        </para>
      </listitem>
      <listitem>
        <para>
        Floating Haskell and floating C type: <literal>cFloatConv</literal>
        </para>
      </listitem>
      <listitem>
        <para>
        <literal>String</literal> and <literal>char*</literal>:
        <literal>withCString*</literal>
        </para>
      </listitem>
      <listitem>
        <para>
        <literal>String</literal> and <literal>char*</literal> with
        explicit length: <literal>withCStringLen*</literal>
        </para>
      </listitem>
      <listitem>
        <para>
        <replaceable>T</replaceable> and
        <replaceable>T</replaceable><literal>*</literal>:
        <literal>with*</literal>
        </para>
      </listitem>
      <listitem>
        <para>
        <replaceable>T</replaceable> and
        <replaceable>T</replaceable><literal>*</literal> where
        <replaceable>T</replaceable> is an integral type:
        <literal>withIntConv*</literal>
        </para>
      </listitem>
      <listitem>
        <para>
        <replaceable>T</replaceable> and
        <replaceable>T</replaceable><literal>*</literal> where
        <replaceable>T</replaceable> is a floating type:
        <literal>withFloatConv*</literal>
        </para>
      </listitem>
      <listitem>
        <para>
        <literal>Bool</literal> and
        <replaceable>T</replaceable><literal>*</literal> where
        <replaceable>T</replaceable> is an integral type:
        <literal>withFromBool*</literal>
        </para>
      </listitem>
    </itemizedlist>

    The defaults for the out marshaller of the result are the converse of the
    above; i.e., instead of the <literal>with</literal> functions, the
    corresponding <literal>peek</literal> functions are used.  Moreover, when
    the Haskell type is <literal>()</literal>, the default marshaller is
    <literal>void-</literal>.
    </para>

    <para>
    As an example, consider

<programlisting>
{#fun notebook_query_tab_label_packing as ^
  `(NotebookClass nb, WidgetClass cld)' => 
  {notebook `nb'                , 
   widget   `cld'               , 
   alloca-  `Bool'     peekBool*, 
   alloca-  `Bool'     peekBool*,
   alloca-  `PackType' peekEnum*} -> `()'#}
</programlisting>

    which results in the Haskell type signature

<programlisting>
notebookQueryTabLabelPacking :: (NotebookClass nb, WidgetClass cld)
			     => nb -> cld -> IO (Bool, Bool, PackType)
</programlisting>

    which binds the following C function:

<programlisting>
void gtk_notebook_query_tab_label_packing (GtkNotebook *notebook,
					   GtkWidget   *child,
					   gboolean    *expand,
					   gboolean    *fill,
					   GtkPackType *pack_type);
</programlisting>
    </para>
  </sect2>

  <sect2>
    <title>Get Hooks</title>
    <para>
<programlisting>
{#get <replaceable>apath</replaceable>#}
</programlisting>

    A get hook supports accessing a member value of a C structure.  The hook
    itself yields a function that, when given the address of a structure of the
    right type, performs the structure access.  The member that is to be
    extracted is specified by the access path <replaceable>apath</replaceable>. 
    Access paths are formed as follows (following a subset of the C expression
    syntax):

    <itemizedlist>
      <listitem>
        <para>
        The root of any access path is a simple identifier, which denotes either
        a type name or <literal>struct</literal> tag.
        </para>
      </listitem>
      <listitem>
        <para>
        An access path of the form
        <literal>*</literal><replaceable>apath</replaceable> denotes
        dereferencing of the pointer yielded by accessing the access path
        <replaceable>apath</replaceable>.
        </para>
      </listitem>
      <listitem>
        <para>
        An access path of the form
        <replaceable>apath</replaceable><literal>.</literal><replaceable>cid</replaceable>
        specifies that the value of the <literal>struct</literal> member called
        <replaceable>cid</replaceable> should be accessed. 
        </para>
      </listitem>
      <listitem>
        <para>Finally, an access path of the form       
        <replaceable>apath</replaceable><literal>-></literal><replaceable>cid</replaceable>,
        as in C, specifies a combination of dereferencing and member selection.
        </para>
      </listitem>
    </itemizedlist>

    For example, we may have

<programlisting>
visualGetType              :: Visual -> IO VisualType
visualGetType (Visual vis)  = liftM cToEnum $ {#get Visual->type#} vis
</programlisting>
    </para>
  </sect2>

  <sect2>
    <title>Set Hooks</title>
    <para>
<programlisting>
{#set <replaceable>apath</replaceable>#}
</programlisting>

    Set hooks are formed in the same way as get hooks, but yield a function that
    assigns a value to a member of a C structure.  These functions expect a
    pointer to the structure as the first and the value to be assigned as the
    second argument.  For example, we may have

<programlisting>
{#set sockaddr_in.sin_family#} addr_in (cFromEnum AF_NET)
</programlisting>
    </para>
  </sect2>

  <sect2>
    <title>Pointer Hooks</title>
    <para>
<programlisting>
{#pointer [*] <replaceable>cid</replaceable> [as <replaceable>hsid</replaceable>] [foreign | stable] [newtype | -&gt;
<replaceable>hsid2</replaceable>] [nocode]#}
</programlisting>

    A pointer hook facilitates the mapping of C to Haskell pointer types.  In
    particular, it enables the use of <literal>ForeignPtr</literal> and
    <literal>StablePtr</literal> types and defines type name translations for
    pointers to non-basic types.  In general, such a hook establishes an
    association between the C type <replaceable>cid</replaceable> or
    <literal>*</literal><replaceable>cid</replaceable> and the Haskell type
    <replaceable>hsid</replaceable>, where the latter defaults to
    <replaceable>cid</replaceable> if not explicitly given.  The identifier
    <replaceable>cid</replaceable> will usually be a type name, but in the case
    of <literal>*</literal><replaceable>cid</replaceable> may also be a struct,
    union, or enum tag.  If both a type name and a tag of the same name are
    available, the type name takes precedence.  Optionally, the Haskell
    representation of the pointer can be by a <literal>ForeignPtr</literal> or
    <literal>StablePtr</literal> instead of a plain <literal>Ptr</literal>.  If
    the <literal>newtype</literal> tag is given, the Haskell type
    <replaceable>hsid</replaceable> is defined as a <literal>newtype</literal>
    rather than a transparent type synonym.  In case of a
    <literal>newtype</literal>, the type argument to the Haskell pointer type
    will be <replaceable>hsid</replaceable>, which gives a cyclic definition,
    but the type argument is here really only used as a unique type tag. 
    Without <literal>newtype</literal>, the default type argument is
    <literal>()</literal>, but another type can be specified after the symbol
    <literal>-&gt;</literal>.
    </para>

    <para>
    For example, we may have

<programlisting>
{#pointer *GtkObject as Object newtype#}
</programlisting>

    This will generate a new type <literal>Object</literal> as follows:

<programlisting>
newtype Object = Object (Ptr Object)
</programlisting>

    which enables exporting <literal>Object</literal> as an abstract type and
    facilitates type checking at call sites of imported functions using the
    encapsulated pointer.  The latter is achieved by &C2hs; as follows.  The
    tool remembers the association of the C type <literal>*GtkObject</literal>
    with the Haskell type <literal>Object</literal>, and so, it generates for
    the C function

<programlisting>
void gtk_unref_object (GtkObject *obj);
</programlisting>

    the import declaration

<programlisting>
foreign import gtk_unref_object :: Object -> IO ()
</programlisting>

    This function can obviously only be applied to pointers of the right type,
    and thus, protects against the common mistake of confusing the order of
    pointer arguments in function calls.
    </para>

    <para>
    However, as the Haskell FFI does not permit to directly pass
    <literal>ForeignPtr</literal>s to function calls or return them, the tool
    will use the type <literal>Ptr HsName</literal> in this case, where
    <literal>HsName</literal> is the Haskell name of the type.  So, if we modify
    the above declaration to be

<programlisting>
{#pointer *GtkObject as Object foreign newtype#}
</programlisting>

    the type <literal>Ptr Object</literal> will be used instead of a plain
    <literal>Object</literal> in import declarations; i.e., the previous
    <literal>import</literal> declaration will become

<programlisting>
foreign import gtk_unref_object :: Ptr Object -> IO ()
</programlisting>

    To simplify the required marshalling code for such pointers,
    the tool automatically generates a function

<programlisting>
withObject :: Object -> (Ptr Object -> IO a) -> IO a
</programlisting>

    As an example that does not represent the pointer as an abstract type,
    consider the C type declaration:

<programlisting>
typedef struct {int x, y;} *point;
</programlisting>

    We can represent it in Haskell as

<programlisting>
data Point = Point {x :: Int, y :: Int}
{#pointer point as PointPtr -> Point#}
</programlisting>

    which will translate to

<programlisting>
data Point = Point {x :: Int, y :: Int}
type PointPtr = Ptr Point
</programlisting>

    and establish a type association between <literal>point</literal> and
    <literal>PointPtr</literal>.
    </para>

    <para>
    If the keyword <literal>nocode</literal> is added to the end of a pointer
    hook, &C2hs; will not emit a type declaration.  This is useful when a &C2hs;
    module wants to make use of an existing type declaration in a binding not
    generated by &C2hs; (i.e., where there are no <literal>.chi</literal>
    files).
    </para>

    <note>
      <title>Restriction</title>
      <para>
      The name <replaceable>cid</replaceable> cannot be a basic C type (such as
      <literal>int</literal>), it must be a defined name.
      </para>
    </note>
  </sect2>

  <sect2>
    <title>Class Hooks</title>
    <para>
<programlisting>
{#class [<replaceable>hsid1</replaceable> =>] <replaceable>hsid2</replaceable> <replaceable>hsid3</replaceable>#}
</programlisting>

    Class hooks facilitate the definition of a single inheritance class hierachy
    for external pointers including up and down cast functionality.  This is
    meant to be used in cases where the objects referred to by the external
    pointers are order in such a hierachy in the external API - such structures
    are encountered in C libraries that provide an object-oriented interface. 
    Each class hook rewrites to a class declaration and one or more instance
    declarations.
    </para>

    <para>
    All classes in a hierarchy, except the root, will have a superclass
    identified by <replaceable>hsid1</replaceable>.  The new class is given by
    <replaceable>hsid2</replaceable> and the corresponding external pointer is
    identified by <replaceable>hsid3</replaceable>.  Both the superclass and the
    pointer type must already have been defined by binding hooks that precede
    the class hook.
    </para>

    <para>
    The pointers in a hierachy must either all be foreign pointers or all be
    normal pointers.  Stable pointers are not allowed.  Both pointer defined as
    <literal>newtype</literal>s and those defined by type synonyms may be used
    in class declarations and they may be mixed.  In the case of synonyms,
    Haskell's usual restrictions regarding overlapping instance declarations
    apply.
    </para>

    <para>
    The newly defined class has two members whose names are derived from the
    type name <replaceable>hsid3</replaceable>.  The name of first member is
    derived from <replaceable>hsid3</replaceable> by converting the first
    character to lower case.  This function casts from any superclass to the
    current class.  The name of the second member is derived by prefixing
    <replaceable>hsid3</replaceable> with the <literal>from</literal>.  It casts
    from the current class to any superclass.  A class hook generates an
    instance for the pointer in the newly defined class as well as in all its
    superclasses.
    </para>

    <para>
    As an example, consider

<programlisting>
{#pointer *GtkObject newtype#}
{#class GtkObjectClass GtkObject#}

{#pointer *GtkWidget newtype#}
{#class GtkObjectClass => GtkWidgetClass GtkWidget#}
</programlisting>

    The second class hook generates an instance for <literal>GtkWidget</literal>
    for both the <literal>GtkWidgetClass</literal> as well as for the
    <literal>GtkObjectClass</literal>.
    </para>
  </sect2>

  <sect2 id="cpp">
    <title>CPP Directives and Inline C Code</title>
    <para>
    A Haskell binding module may include arbitrary C pre-processor directives
    using the standard C syntax.  The directives are used in two ways: Firstly,
    they are included in the C header file generated by &C2hs; in exactly
    the same order in which they appear in the binding module.  Secondly, all
    conditional directives are honoured by &C2hs; in that all Haskell
    binding code in alternatives that are discarded by the C pre-processor are
    also discarded by &C2hs;.  This latter feature is, for example, useful
    to maintain different bindings for multiple versions of the same C API in a
    single Haskell binding module.
    </para>

    <para>
    In addition to C pre-processor directives, vanilla C code can be maintained
    in a Haskell binding module by bracketing this C code with the pseudo
    directives <literal>#c</literal> and <literal>#endc</literal>.  Such inline
    C code is emitted into the C header generated by &C2hs; at exactly the same
    position relative to CPP directives as it occurs in the binding module. 
    Pre-processor directives may encompass the <literal>#include</literal>
    directive, which can be used instead of specifying a C header file as an
    argument to <literal>c2hs</literal>.  In particular, this enables the
    simultaneous use of multiple header files without the need to provide a
    custom header file that binds them together.  If a header file
    <replaceable>lib</replaceable><literal>.h</literal> is specified as an
    argument to <literal>c2hs</literal>, the tool will emit the directive 
    <literal>#include"</literal><replaceable>lib</replaceable><literal>.h"</literal>
    into the generated C header before any other CPP directive or inline C code.
    </para>

    <para>
    As an artificial example of these features consider the following code:

<programlisting>
#define VERSION 2

#if (VERSION == 1)
foo :: CInt -> CInt
foo = {#call pure fooC#}
#else
foo :: CInt -> CInt -> CInt
foo = {#call pure fooC#}
#endif

#c
int fooC (int, int);
#endc
</programlisting>

    One of two versions of the Haskell function <literal>foo</literal> (having
    different arities) is selected in dependence on the value of the CPP macro
    <literal>VERSION</literal>, which in this example is defined in the same
    file.  In realistic code, <literal>VERSION</literal> would be defined in
    the header file supplied with the C library that is made accessible from
    Haskell by a binding module.  The above code fragment also includes one
    line of inline C code that declares a C prototype for
    <literal>fooC</literal>.
    </para>

    <note>
      <title>Current limitation of the implementation</title>
      <para>
      Inline C code can currently not contain any code blocks; i.e., only
      declarations as typically found in header files may be included.
      </para>
    </note>
  </sect2>

  <sect2>
    <title>Grammar Rules</title>
    <para>
    The following grammar rules define the syntax of binding hooks:

<programlisting>
hook     -> `{#' inner `#}'
inner    -> `import' ['qualified'] ident
          | `context' ctxt
          | `type' ident
          | `sizeof' ident
          | `enum' idalias trans [`with' prefix] [deriving]
          | `call' [`pure'] [`unsafe'] idalias
          | `fun' [`pure'] [`unsafe'] idalias parms
          | `get' apath
          | `set' apath
          | `pointer' ['*'] idalias ptrkind
          | `class' [ident `=>'] ident ident

ctxt     -> [`lib' `=' string] [prefix]
idalias  -> ident [(`as' ident | `^')]
prefix   -> `prefix' `=' string
deriving -> `deriving' `(' ident_1 `,' ... `,' ident_n `)'
parms    -> [verbhs `=>'] `{' parm_1 `,' ... `,' parm_n `}' `->' parm
parm     -> [ident_1 [`*' | `-']] verbhs [`&amp;'] [ident_2 [`*'] [`-']]
apath    -> ident
          | `*' apath
          | apath `.' ident
          | apath `->' ident
trans    -> `{' alias_1 `,' ... `,' alias_n `}'
alias    -> `underscoreToCase' | `upcaseFirstLetter' | `downcaseFirstLetter'
          | ident `as' ident
ptrkind  -> [`foreign' | `stable'] ['newtype' | '->' ident]
</programlisting>

    Identifier <literal>ident</literal> follow the lexis of Haskell.  They may
    be enclosed in single quotes to disambiguate them from C->Haskell keywords.
    </para>
  </sect2>
</sect1>

<sect1 id="bugs">
  <title>Bug Reports and Suggestions</title>
  <para>
  There is a tracker for bugs and feature requests:
  <ulink url="http://hackage.haskell.org/trac/c2hs/" />.
  Alternatively if you prefer email please send your bug reports and
  suggestions to the C->Haskell List <email>c2hs@haskell.org</email>.
  </para>

  <para>
  A good bug report contains information on the used operating system and
  Haskell compiler as well as the version of &C2hs; that you have been using. 
  You can obtain the version information by running <literal>c2hs
  --version</literal>. If possible a concise example illustrating your problem
  would be appreciated.
  </para>
</sect1>

<sect1 id="copyright">
  <title>Copyright</title>
  <para>
  &C2hs; is Copyright (C) [1999..2005] Manuel M. T. Chakravarty
  </para>

  <sect2>
    <title>&C2hs; License</title>
    <para>
    <literallayout>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
    </literallayout>
    </para>
  </sect2>

  <sect2>
    <title>Documentation License</title>
    <para>
    <literallayout>
This manual is Copyright (c) [2000..2005] by Manuel M. T. Chakravarty. 
Permission is granted to copy, distribute and/or modify this document under
the terms of the GNU Free Documentation License, Version 1.1 or any later
version published by the Free Software Foundation; with no Invariant Sections,
with no Front-Cover Texts, and with the no Back-Cover Texts.  A copy of the
license is included in the section entitled "GNU Free Documentation License".
    </literallayout>
    </para>
  </sect2>

  <sect2>
    <title>Possible Licenses of Generated Code</title>
    <para>
    All code included into generated bindings is under a BSD-style
    license that does not place any restrictions on the license of the
    inteface produced with &C2hs; (ie, closed proprietary licenses are
    possible, too).  In other words, I do not care what you use &C2hs;
    for or to whom you are giving &C2hs; or any interfaces generated with
    &C2hs;, only if you modify or improve &C2hs; itself, you have to
    contribute your changes back to the community.  Nevertheless, I will of
    course be particularly delighted if you choose to make your work freely
    available.
    </para>
  </sect2>
</sect1>

<sect1 id="gfdl">
  <title>GNU Free Documentation License</title>
  <para>
  The GNU Free Documentation License is available at
  <ulink url="http://www.fsf.org/copyleft/fdl.html" />.
  </para>
</sect1>

<sect1 id="release-notes">
  <title>Release Notes</title>
  <para>
  Important changes (especially those affecting the semantics of the tool) are
  documented in the following.
  </para>

  <sect2>
    <title>Version 0.15.1 "Rainy Days"</title>
    <itemizedlist>
      <listitem>
        <para>
        New C parser that can parse all of C99 and GNU C
        </para>
      </listitem>
      <listitem>
        <para>
        Make c2hs integrate better with Cabal (1.2 and later)
        </para>
      </listitem> 
      <listitem><para>Adapted to GHC 6.8.</para></listitem>
      <listitem><para>Now requires Cabal 1.2.</para></listitem>
      <listitem><para>Lots and lots of old code removal</para></listitem>
      <listitem>
        <para>
        Several bug fixes and improvements from Udo Stenzel:
        <itemizedlist>
          <listitem>
            <para>allowing variadic functions in structures</para>
          </listitem>
          <listitem>
            <para>allowing call and fun hooks for FunPtrs in C structs</para>
          </listitem>
          <listitem>
            <para>embedded arrays size calculated correctly</para>
          </listitem>
        </itemizedlist>
        </para>
      </listitem>
    </itemizedlist>
  </sect2>

  <sect2>
    <title>Version 0.14.5 "Travelling Lightly"</title>
    <itemizedlist>
      <listitem>
        <para>
        Added <literal>nocode</literal> directive to pointer hooks
        </para>
      </listitem>
      <listitem>
        <para>
        Can use structs properly in pointer hooks now (contributed by Jelmer
        Vernooij)
      </para>
      </listitem>
      <listitem>
        <para>
        <literal>upcaseFirstLetter</literal> and
        <literal>downcaseFirstLetter</literal>
        </para>
      </listitem>
      <listitem>
        <para>Cross-compiling with <literal>--platform</literal> flag
        </para>
      </listitem>
      <listitem>
        <para>
        Gcc's <literal>asm</literal> construct is supported (contributed by
        Duncan Coutts)
        </para>
      </listitem>
      <listitem>
        <para>
        Hierarchical modules syntax in <literal>import</literal> hooks supported
        </para>
      </listitem> 
      <listitem>
        <para>
        No separately installed marshaling library anymore; as a result binary
        &C2hs; packages and installations are now independent of the targeted
        Haskell system
        </para>
      </listitem>
      <listitem>
        <para>
        New lexer and parser generated with Alex and Happy (contributed by
        Duncan Coutts)
        </para>
      </listitem>
      <listitem><para>Cabal build system</para></listitem>
    </itemizedlist>
  </sect2>

  <sect2>
    <title>Version 0.13.6 "Pressing Forward"</title>
    <itemizedlist>
      <listitem>
        <para>Works with GHC 6.4 and Cabal packages
        </para>
      </listitem>
      <listitem>
        <para>
        Strings may contain 8-bit characters (e.g., umlauts).
        </para>
      </listitem>
      <listitem>
        <para>
        Identifier may optionally be put in single quotes.  (This is useful if
        they would otherwise collide with a &C2hs; keyword.)
        </para>
      </listitem>
      <listitem>
        <para>
        Some smaller bug fixes
        </para>
      </listitem>
      <listitem>
        <para>
        C chars are treated as integral types for marshalling purposes.
        </para>
      </listitem>
      <listitem>
        <para>
        If there is no explicit output file specified, the generated header
        file is put in the same directory as the binding file; otherwise, it
        goes in the directory where the output file is put.  Moreover, the
        <literal>--output-dir</literal> option enables the specification of
        directory where all generated files are to be put.
        </para>
      </listitem>
      <listitem>
        <para>Foreign import declarations include the name of the header file
        generated by &C2hs; (ie, it needs neither be passed to the Haskell
        compiler at the command line nor in an OPTIONS pragma).
        </para>
      </listitem>
      <listitem>
        <para>
        We allow structs and unions with no declarations.
        </para>
      </listitem>
      <listitem>
        <para>Headers including function bodies are now parsed correctly.
        </para>
      </listitem>
      <listitem>
        <para>Duncan Coutts identified a space leak in the parser whose removal
        improved performance significantly.
        </para>
      </listitem>
    </itemizedlist>
  </sect2>

  <sect2>
    <title>Version 0.12.1 "Springtime"</title>
    <itemizedlist>
      <listitem><para>Removed support for deprecated <literal>C2HS</literal>
      interface and for old versions of the FFI libraries</para></listitem>
      <listitem><para>Improved line pragma generation</para></listitem>
      <listitem><para>Works with GHC 6.3</para></listitem>
      <listitem>
        <para>
        Builds on Mac OS X thanks to a patch by Sean Seefried
        </para>
      </listitem>
    </itemizedlist>
  </sect2>

  <sect2>
    <title>Version 0.11.5 "Powder Snow"</title>
    <itemizedlist>
      <listitem><para>Bug fixes</para></listitem>
      <listitem>
        <para>Constant expression can now contain enumerators</para>
      </listitem>
      <listitem>
        <para>
        <literal>header</literal> label removed from <literal>context</literal>
        hooks
        </para>
      </listitem>
      <listitem>
        <warning>
          <para>
          This version of <literal>c2hs</literal> may
          <emphasis>overwrite</emphasis> C header files in the current
          directory. More precisely, if a binding module with the name
          <literal>Foo.chs</literal> is processed, a header file with the name 
          <literal>Foo.h</literal> is generated and will
          <emphasis>overwrite</emphasis> any file of the same name in the
          current directory or the directory specified via the 
          <literal>-o</literal> option.
          </para>
        </warning>
      </listitem>
      <listitem>
        <para>
        Added support for CPP directives, including special treatment of
        conditions, and for inline C code; specification of a header file as an
        argument to <literal>c2hs</literal> is now option.
        </para>
      </listitem>
      <listitem>
        <para>
        GHC line pragmas are emitted into generated Haskell code
        </para>
      </listitem>
      <listitem>
        <para>
        Swap the order of reading the binding module and the C header (i.e., we
        now read the binding module first)
        </para>
      </listitem>
    </itemizedlist>
  </sect2>

  <sect2>
    <title>Version 0.10.17 "Altocumulus Stratiformis Perlucidus Undulatus"
    </title>
    <itemizedlist>
      <listitem>
        <para>Worked around a bug in GHC 5.04.1</para></listitem>
      <listitem>
        <para>Solaris-related fix</para></listitem>
      <listitem>
        <para>
        Marshalling support for bit masks represented as enumeration types
        </para>
      </listitem>
      <listitem>
        <para>Added <literal>fun</literal> hooks</para>
      </listitem>
      <listitem>
        <para>
        <literal>as</literal> aliases can use <literal>^</literal> convert the
        orignal identifier with underscore2case
        </para>
      </listitem>
      <listitem>
        <para>
        In call hooks, the attributes `fun' was replaced by `pure' (`fun' is
        will still be recognised for a while to ensure backwards compatibility,
        but it's use is deprecated)
        </para>
      </listitem>
      <listitem>
        <para>GHC's package system is now supported</para>
      </listitem>
      <listitem>
        <para>
        If two import hooks add a type mapping for a pointer hook with the same
        name, the textual later one dominates.
      </para>
      </listitem>
      <listitem>
        <para>Bug fixes</para>
      </listitem>
      <listitem>
        <para>
        Support for bitfields (they are correctly handled when computing struct
        offsets and they can be accessed using <literal>set</literal> and
        <literal>get</literal> hooks)
       </para>
      </listitem>
      <listitem>
        <para>
          Some more support for GNU C extensions ("alignof" and better support
        "__attribute__")
        </para>
      </listitem>
      <listitem>
        <para>Added <literal>class</literal> hooks</para>
      </listitem>
    </itemizedlist>
  </sect2>

  <sect2>
    <title>Version 0.9.9 "Blue Ginger"</title>
    <itemizedlist>
      <listitem><para>Bug fixes</para></listitem>
      <listitem>
        <para>
        Library names in <literal>foreign import</literal>s have been removed
        until the convention of the new FFI is implemented (they are currently
        <emphasis>silently</emphasis> omitted)
        </para>
      </listitem>
      <listitem>
        <para>
        Added <literal>sizeof</literal> hooks; sizeof of type names is now also
        supported in constant expressions
        </para>
      </listitem>
      <listitem>
        <para>
        Local prefix for <literal>enum</literal> hooks; courtesy of Armin Sander
        </para>
      </listitem>
      <listitem>
        <para>
        Added <literal>import</literal> hooks</para></listitem>
      <listitem>
        <para>
        The documentation includes a description of binding hooks
        </para>
      </listitem>
      <listitem>
        <para>
        Added <literal>pointer</literal> hooks, which were derived from code
        for a similar feature by Axel Simon; this includes proper treatment of
        parametrised pointers
        </para>
      </listitem>
      <listitem>
        <para>
        Integrated <literal>deriving</literal> option for
        <literal>enum</literal> hooks, which was contributed by Axel Simon
        </para>
      </listitem>
      <listitem><para>Adapted to GHC 5.0</para></listitem>
    </itemizedlist>
  </sect2>

  <sect2>
    <title>Version 0.8.2 "Gentle Moon"</title>
    <itemizedlist>
      <listitem>
        <para>
        Adaptation layer for legacy <literal>StablePtr</literal> interface
        </para>
      </listitem>
      <listitem>
        <para>
        Forgot to export <literal>FunPtr</literal> and associated functions
        from <literal>C2HS</literal>
        </para>
      </listitem>
      <listitem>
        <para>
        Forgot to export some names in <literal>C2HSDeprecated</literal>
        </para>
      </listitem>
      <listitem>
        <para>
        Added support for gcc's <literal>__builtin_va_list</literal>
        </para>
      </listitem>
    </itemizedlist>
  </sect2>

  <sect2>
    <title>Version 0.8.1 "Gentle Moon"</title>
    <itemizedlist>
      <listitem>
        <para>Library adapted to New FFI; the old interface can still be used
        by importing <literal>C2HSDeprecated</literal>
        </para>
      </listitem>
      <listitem>
        <para>
        FFI Library specification added to the documentation
        </para>
      </listitem>
    </itemizedlist>
  </sect2>

  <sect2>
    <title>Version 0.7.10 "Afterthought"</title>
    <itemizedlist>
      <listitem>
        <para>
          CygWin support; based on suggestions by Anibal Maffioletti Rodrigues
          de DEUS <email>anibaldedeus@email.com</email>
        </para>
      </listitem>
      <listitem>
        <para>
        <literal>IntConv</literal> instances for <literal>Int8</literal>,
        <literal>Word8</literal>, and <literal>Char</literal>
        </para>
      </listitem>
    </itemizedlist>
  </sect2>

  <sect2>
    <title>Version 0.7.9 "Afterthought"</title>
    <itemizedlist>
      <listitem>
        <para>
        Debugged the stripping of prefixes from enumerators; prefixes are now
        generally stripped, independent of whether they can be stripped from
        all enumerators of a given enumeration type
        </para>
      </listitem>
      <listitem>
        <para>Comma now correctly required after
        <literal>underscoreToCase</literal>.
        </para>
        <warning>
          <para>This breaks source compatibility with previous versions.
          </para>
        </warning>
      </listitem> 
    </itemizedlist>
  </sect2>

  <sect2>
    <title>Version 0.7.8</title>
    <itemizedlist>
      <listitem><para>Provisional support for GHC 4.08</para></listitem>
      <listitem><para>Corrected constant folding</para></listitem>
    </itemizedlist>
  </sect2>

  <sect2>
    <title>Version 0.7.7</title>
    <para>
    Ignores any occurrence of <literal>#pragma</literal>.
    </para>
  </sect2>

  <sect2>
    <title>Version 0.7.6</title>
    <para>
    Bug fixes and support for <literal>long long</literal>.
    </para>
  </sect2>

  <sect2>
    <title>Version 0.7.5</title>
    <para>
    This is mainly a bug fix release.  In particular, the space behaviour of
    &C2hs; has been significantly improved.
    </para>

    <para>
    IMPORTANT NOTE: From this release on, library names in
    <literal>lib</literal> tags in <literal>context</literal> hooks should
    <emphasis>not</emphasis> contain a suffix (i.e., omit
    <literal>.so</literal> etc).
    </para>
  </sect2>
</sect1>

</article>