This is mit-scheme-ffi.info, produced by makeinfo version 6.5 from
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This manual documents FFI 1.0.

   Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018,
2019 Massachusetts Institute of Technology

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     document under the terms of the GNU Free Documentation License,
     Version 1.2 or any later version published by the Free Software
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     section entitled "GNU Free Documentation License."
INFO-DIR-SECTION Programming Languages
START-INFO-DIR-ENTRY
* MIT/GNU Scheme FFI: (mit-scheme-ffi).
                                Foreign Function Interface
END-INFO-DIR-ENTRY


File: mit-scheme-ffi.info,  Node: Top,  Next: Introduction,  Prev: (dir),  Up: (dir)

FFI
***

This manual documents FFI 1.0.

   Copyright (C) 1986, 1987, 1988, 1989, 1990, 1991, 1992, 1993, 1994,
1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006,
2007, 2008, 2009, 2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017, 2018,
2019 Massachusetts Institute of Technology

     Permission is granted to copy, distribute and/or modify this
     document under the terms of the GNU Free Documentation License,
     Version 1.2 or any later version published by the Free Software
     Foundation; with no Invariant Sections, with no Front-Cover Texts
     and no Back-Cover Texts.  A copy of the license is included in the
     section entitled "GNU Free Documentation License."

* Menu:

* Introduction:: A synopsis and quick summary.
* C Declarations:: Declare C types and functions.
* Alien Data:: Manipulate C data.
* Alien Functions:: Generate callout trampolines and call them.
* Callbacks:: Generate callback trampolines and register handlers for them.
* Compiling and Linking:: Build and install the shim.
* Hello World:: A short example.
* GNU Free Documentation License::


File: mit-scheme-ffi.info,  Node: Introduction,  Next: C Declarations,  Prev: Top,  Up: Top

1 Introduction
**************

This FFI provides Scheme syntax for calling C functions and accessing C
data.  The functions and data structures are declared in a case
sensitive '.cdecl' file, which is used by a shim generator to produce
callout and callback trampoline functions.  The trampolines are compiled
and linked to the C toolkit, producing a shared object that Scheme can
dynamically load.

Synopsis
========

Examples of the new syntax:

     (C-include "prhello")

     (malloc (C-sizeof "GdkEvent"))
     => #[alien 42 0x081afc60]

     (C->= #@42 "GdkEvent any type" 14)

     (C-> #@42 "GdkEvent any type")
     => 14

     (C-enum "GdkEventType" 14)
     => |GDK_MAP|

     (C-enum "GDK_MAP")
     => 14

     (C-sizeof "GdkColor")
     => 12

     (C-offset "GdkColor blue")
     => 8

     (C-array-loc #@43 "GdkColor" (C-enum "GTK_STATE_NORMAL"))
     => #[alien 44 0x081afc60] ; New alien.

     (C-array-loc! #@43 "GdkColor" (C-enum "GTK_STATE_PRELIGHT"))
     => #[alien 43 0x081afc78] ; Modified alien.

     (C-call "gtk_window_new" retval args ...)
     => #!unspecific

     (C-callback "delete_event")
     => #[alien-function 44 Scm_delete_event]

     (C-callback (lambda (window event) ...))
     => 13                     ; A fixnum registration ID.

Summary
=======

A Scheme-like declaration of a toolkit's C functions, constants, and
data types is given in a case sensitive '.cdecl' file.  The C
declarations look like this:

     (extern (* GtkWidget)
             gtk_window_new
             (type GtkWindowType))

     (typedef GtkWindowType
              (enum
               (GTK_WINDOW_TOPLEVEL)
               (GTK_WINDOW_POPUP)))

   The *'c-generate'* procedure reads these declarations and writes
three files: 'library-types.bin' (a fasdump of the parsed declarations),
'library-const.c' (a C program that prints C constants and struct
offsets), and 'library-shim.c' (trampoline functions adapting Scheme
procedure application to C function call).  The '-const.c' program
generates a '-const.scm' file, which can be expanded into a '-const.bin'
file.

     (load-option 'FFI)
     (c-generate "prhello" "#include <gtk/gtk.h>")

   The '-types.bin' and '-const.bin' files together provide the
information needed to expand 'C-...' syntax, and are only needed at
syntax time.  The compiled '-shim.so' file is used at run time,
dynamically loaded into the Scheme machine.  *Note Compiling and
Linking::, which describes these files in more detail, and shows how
they might be built and installed.

     (C-include "prhello")

   The *'C-include'* syntax loads the '-types.bin' and '-const.bin'
files _at syntax time_.  It should appear at the top level of any file
containing 'C-...' syntax, or be expanded in the syntax environment of
such code.

   The *'C-call'* syntax arranges to invoke a callout trampoline.
Arguments to the trampoline can be integers, floats, strings (or
bytevectors) or aliens (non-heap pointers, to C data structures, *note
Alien Data::).  If a string argument might contain non-ASCII characters
(code points U+0080 and larger), it should be converted to a bytevector
e.g. by 'string->utf8', else an error could be signaled.

     (let ((alien (make-alien '|GtkWidget|)))
       (C-call "gtk_window_new" alien type)
       (if (alien-null? alien) (error "could not open new window"))
       alien)

   The *'C-callback'* syntax is used when registering a Scheme callback
trampoline.  The two forms of the syntax provide two arguments for the
registration function: the callback trampoline's address, and a "user
data" argument.  When the toolkit calls the trampoline, it must provide
the fixnum-sized user data as an argument.

     (C-call "g_signal_connect" window "delete_event"
             (C-callback "delete_event")     ; e.g. &Scm_delete_event
             (C-callback                     ; e.g. 314
               (lambda (window event)
                 (C-call "gtk_widget_destroy" window)
                 0)))

   The first use of 'C-callback' (above) expands into a callback
trampoline address -- an alien function.  The second use evaluates to a
fixnum, which is associated with the given Scheme procedure.

   The *'C->'* and *'C->='* syntaxes peek and poke values into alien
data structures.  They take an alien and a constant string specifying
the alien data type and the member to be accessed (if any).

     (C-> alien "GdkRectangle y")
     ==>
     (#[primitive c-peek-int] alien 4)

     (C->= alien "GdkRectangle width" 0)
     ==>
     (#[primitive c-poke-int] alien 8 0)

     (C-> alien "GdkEvent any type")
     ==>
     (#[primitive c-peek-int] alien 0)

     (C-> alien "gfloat")
     ==>
     (#[primitive c-peek-float] alien 0)

   A three argument form of the syntax provides an alien to receive a
peeked pointer.  This avoids consing a new alien.

     (C-> alien "GtkWidget style" alien)

   The above syntax is understood to say "The data at this 'alien'
address is a GtkWidget.  Load its 'style' member into 'alien'
(clobbering 'alien''s old address)."

   The *'C-enum'*, *'C-sizeof'* and *'C-offset'* syntaxes all transform
into integer constants.  The last two transform into a padded byte size
and a byte offset respectively.

     (C-enum "GTK_WINDOW_POPUP")
     ==>
     1

     (C-sizeof "GdkColor")
     ==>
     12

     (C-offset "GdkColor blue")
     ==>
     8

   The two element form of the 'C-enum' syntax can be used to find the
name of a constant given its runtime value.  It expects the name of an
enum type in a constant string.  If the runtime (second) argument is not
one of the constants declared by that type, the returned value is '#f'.

     (C-enum "GdkEventType" (C-> #@42 "GdkEvent any type"))
     => |GDK_MAP|

   The *'c-array-loc'* and *'c-array-loc!'* syntaxes compute the
locations of C array elements.  They can be used to advance a scan
pointer or locate an element by its index.  The examples in the synopsis
might expand as shown here.

     (C-array-loc #@43 "GdkColor" (C-enum "GTK_STATE_NORMAL"))
     ==>
     (alien-byte-increment #@43 (* (C-sizeof "GdkColor")
                                   (C-enum "GTK_STATE_NORMAL")))
     ==>
     (alien-byte-increment #@43 (* 12 0))
     => #@44

     (C-array-loc! #@43 "GdkColor" (C-enum "GTK_STATE_PRELIGHT"))
     ==>
     (alien-byte-increment! #@43 (* (C-sizeof "GdkColor")
                                    (C-enum "GTK_STATE_PRELIGHT")))
     ==>
     (alien-byte-increment! #@43 (* 12 2))
     => #@43

   A simple scan of characters in the wide string 'alien' might look
like this.

     (let ((len (C-> alien "toolkit_string_type int_member"))
           (scan (C-> alien "toolkit_string_type array_member")))
       (let loop ((n 0))
         (if (< n len)
             (let ((wchar (C-> scan "wchar")))
               (process wchar)
               (C-array-loc! scan "wchar" 1)
               (loop (1+ n))))))

   That is a quick look at the facilities.  The next section describes
the C declaration language, and the following sections examine the FFI's
syntax and runtime facilities in detail.  Final sections provide an
example program and show how its dynamically loaded shim is built.


File: mit-scheme-ffi.info,  Node: C Declarations,  Next: Alien Data,  Prev: Introduction,  Up: Top

2 C Declarations
****************

A shim between Scheme and a C toolkit is specified by a case sensitive
'.cdecl' file containing Scheme-like declarations of all relevant
toolkit types, constants, and functions.  Callback functions to be
passed to the toolkit are also specified here.

   Each top-level form in the C declaration file must look like one of
these:

     (include "filename")
     (typedef Name ANY)
     (struct Name (Member TYPE) ...)
     (union Name (Member TYPE) ...)
     (enum Name (Member) ...)
     (extern FUNCTION-TYPE Name (param1 ARG-TYPE) ...)
     (callback CALLBACK-TYPE Name (param1 CALLBACK-ARG-TYPE) ...)

   The 'include' expression includes another '.cdecl' file in the
current '.cdecl' file.  The string argument is interpreted relative to
the current file's directory.

   ANY can be a TYPE or the word 'void'.

   ARG-TYPE can be any TYPE _except_ anonymous structs and unions.

   FUNCTION-TYPE can be any ARG-TYPE or 'void'.

   CALLBACK-ARG-TYPE can be any TYPE _except_ struct and union types.

   CALLBACK-TYPE can be any CALLBACK-ARG-TYPE or 'void'.

   TYPE can look like any of these:

     Name
     BASICS
     (* ANY)
     (enum Name)
     (enum Name (Member) ...)
     (struct Name)
     (struct Name (Member TYPE) ...)
     (union Name)
     (union Name (Member TYPE) ...)

   NAME should be defined via a 'typedef' form somewhere in the
(included) file(s).  It does not have to be defined before it is
referenced.  It does not have to be defined _at all_ if it is only the
target of a pointer type.

   BASICS can be any of the words: 'char', 'uchar', 'short', 'ushort',
'int', 'uint', 'long', 'ulong', 'float', or 'double' (all lowercase).

   While the informal grammar above allows anonymous structs to be
member types, they are useless outside a named type declaration.  The
peek and poke ('C->' and 'C->=') syntaxes require a type name (e.g.
'"GdkEventAny"' or '"struct _GdkEventAny"') before any member names.

     (C-include "prhello")

   The *'C-include'* syntax takes a library name and loads the
corresponding '-types' and '-const' files at syntax time.  This makes
the C types and constants available to the other 'C-...' syntax
expanders.  The form binds 'c-includes' in the syntax environment unless
it is already defined there.  Thus a '(C-include "library")' form can be
placed at the top of every file with 'C-...' syntax, _or_ loaded into
the syntax-time environment of those files.


File: mit-scheme-ffi.info,  Node: Alien Data,  Next: Alien Functions,  Prev: C Declarations,  Up: Top

3 Alien Data
************

A C data structure is represented by an alien containing the data
structure's memory address.  "Peek" primitives are available to read
pointers and the basic C types (e.g.  ints, floats) at small (fixnum)
offsets from an alien's address.  They return to Scheme an alien
address, integer or flonum as appropriate.  "Poke" primitives do the
reverse, storing pointers, integers or floats at fixnum offsets from
alien addresses.  Other procedures on aliens are 'alien?',
'alien-null?', 'alien-null!', 'copy-alien', 'alien=?',
'alien-byte-increment', and 'c-peek-cstring'.  Refer to 'ffi.pkg' in The
Source for a complete list.

   The 'C->' and 'C->=' syntaxes apply the peek and poke primitives to
constant offsets.  They expect their first argument subform to be a
constant string -- space-separated words naming a C type and any member
to be accessed.  A member within a struct or union member is specified
by appending its name.  For example '"struct _GdkEvent any window"'
would specify a peek at the 'window' member of the 'any' member of the
'struct _GdkEvent' data at some alien address.  Note that the final
member's type must be a basic C type, pointer type, or enum type.
Otherwise, an error is signaled at syntax time.

     (C-> alien "struct _GdkEvent any window" window-alien)
     ==>
     (#[primitive c-peek-pointer] alien 0 window-alien)
     => #[alien 44 (* GdkWindow) 0x081afc60]

   Note that in the example above, the final member has a pointer type.
In this case an extra alien argument can be provided to receive the
peeked pointer.  Otherwise a new alien is created and returned.

Malloc
======

The 'malloc' procedure returns an alien that will automatically free the
malloced memory when it is garbage collected.  It can also be explicitly
freed with the 'free' procedure.  The alien address can be incremented
to scan the malloced memory, then freed (without returning it to the
original, malloced address).  A band restore marks all malloced aliens
as though they have been freed.

     (free (malloc '|GdkRectangle|))


File: mit-scheme-ffi.info,  Node: Alien Functions,  Next: Callbacks,  Prev: Alien Data,  Up: Top

4 Alien Functions
*****************

The 'C-call' syntax produces code that applies 'call-alien' to an alien
function structure -- a cache for the callout trampoline's entry
address.

     (C-call "gtk_button_new" (make-alien '(* |GtkWidget|)))
     ==>
     (call-alien '#[alien-function gtk_button_new] (make-alien ...))

   The alien function contains all the information needed to load the
callout trampoline on demand (i.e.  its name and library).  Once the
alien function has cached the entry address, 'call-alien' can invoke the
trampoline (via '#[primitive c-call]').  The trampoline gets its
arguments off the Scheme stack, converts them to C values, calls the C
function, conses a result, and returns it to Scheme.

   A function returning a pointer type is treated specially.  Its
trampoline expects an extra (first) argument.  If the argument is '#f',
the return value is ignored.  If the argument is an alien, the
function's return value clobbers the alien's address.  This makes it
easy to grab pointers to toolkit resources without dropping them, and to
avoid unnecessary consing of aliens.

   A function returning a struct or union type is treated similarly.
Its trampoline expects an extra (first) argument.  If the argument is
'#f', the return value is ignored.  If the argument is an alien, the
returned struct or union is copied to that address.

   Struct and union type parameters of a function are treated similarly.
The function's trampoline expects an alien argument for each such
parameter and copies the struct or union from the argument address into
a local variable.  Callbacks currently cannot receive struct or union
type arguments, though they _can_ receive pointer type arguments
(consing an alien for each).

   The 'alien-function' structures are fasdumpable.  The caching
mechanism invalidates the cache when a band is restored, or a fasdumped
object is fasloaded.  The alien function will lookup the trampoline
entry point again on demand.


File: mit-scheme-ffi.info,  Node: Callbacks,  Next: Compiling and Linking,  Prev: Alien Functions,  Up: Top

5 Callbacks
***********

A callback declaration must include a parameter named "ID". The ID
argument will be used to find the Scheme callback procedure.  It must be
the same "user data" value provided to the toolkit when the callback was
registered.  For example, a callback trampoline named 'Scm_delete_event'
might be declared like this:

     (callback gint
               delete_event
               (window (* GtkWidget))
               (event (* GdkEventAny))
               (ID gpointer))

   The callback might be registered with the toolkit like this:

     (C-call "g_signal_connect" window "delete_event"
             (C-callback "delete_event")     ; e.g. &Scm_delete_event
             (C-callback                     ; e.g. 314
               (lambda (window event)
                 (C-call "gtk_widget_destroy" window)
                 0)))

   The toolkit's registration function, 'g_signal_connect', would be
declared like this:

     (extern void
             g_signal_connect
             (object (* GtkObject))
             (name (* gchar))
             (CALLBACK GtkSignalFunc)
             (ID gpointer))

   This function should have parameters named 'CALLBACK' and 'ID'.  The
callout trampoline will convert the callback argument from a Scheme
alien function to an entry address.  The 'ID' argument will be converted
to a C integer and then cast to its declared type (in this example,
'gpointer').

   Note that the registered callback procedures are effectively pinned.
They cannot be garbage collected.  They are "on call" to handle
callbacks from the toolkit until they are explicitly de-registered.  A
band restore automatically de-registers all callbacks.

   Callback procedures are executed with thread preemption suspended.
Thus Scheme will not switch to another thread, especially not one
preempted in an earlier callback.  Such a thread could finish its
callback and return from the later callback, not to its original caller.

   Scheme will not preempt a callback, but if the callback calls
'suspend-thread' it will switch to a running thread.  If the callback
does IO (and blocks), suspends, yields, sleeps, or grabs (waits for) a
mutex, the runtime system will switch to another thread, possibly a
thread that blocked for IO during an earlier callback but is now
recently unblocked and determined to finish and return to the wrong
caller.  Thus callback procedures should be written as if they were
interrupt handlers.  They should be short and simple because they must
not wait.

   The 'outf-error' procedure is provided for debugging purposes.  It
writes one or more argument strings (and 'write's any non-strings) to
the Unix "stderr" channel, atomically, via a machine primitive,
bypassing the runtime's IO buffering and thread switching.  Thus trace
messages from multiple threads will appear on stderr intact,
uninterrupted.


File: mit-scheme-ffi.info,  Node: Compiling and Linking,  Next: Hello World,  Prev: Callbacks,  Up: Top

6 Compiling and Linking
***********************

The *'c-generate'* procedure takes a library name and an optional
preamble.  It reads the 'library.cdecl' file and writes two '.c' files.
The preamble is included at the top of both.  It typically contains
'#include' C pre-processor directives required by the C library, but
could include additional shim code.  Here is a short script that
generates a shim for the example "Hello, World!"  program.

     (load-option 'FFI)
     (c-generate "prhello" "#include <gtk/gtk.h>")

   This script will produce three files:

'prhello-shim.c'
     This file contains the trampoline functions -- one for each
     declared C extern or callback.  It includes the 'mit-scheme.h'
     header file, found in the 'AUXDIR' directory -- e.g.
     '/usr/local/lib/mit-scheme-i386/'.

'prhello-const.c'
     This file contains a C program that creates 'prhello-const.scm'.
     It is compiled and linked as normal for programs using the toolkit,
     and does not depend on the Scheme machine.  It does not actually
     call any toolkit functions.  It just collects information from the
     compiler about the declared C types and constants.

'prhello-types.bin'
     This file is a fasdumped 'c-includes' structure containing all of
     the types, constants and functions declared in the '.cdecl' file.

   The following Makefile rules describe the process of building and
installing a shim for the example "Hello, World!"  program.

     AUXDIR=/usr/local/lib/mit-scheme-i386
     
     install: build
     	install -m 644 prhello-types.bin $(AUXDIR)
     	install -m 644 prhello-const.bin $(AUXDIR)
     	install -m 644 prhello-shim.so $(AUXDIR)
     
     uninstall:
     	rm $(AUXDIR)/prhello-*
     
     clean:
     	rm prhello-const* prhello-types* prhello-shim* 
     
     build: prhello-shim.so prhello-types.bin prhello-const.bin
     
     prhello-shim.so: prhello-shim.o
     	$(CC) -shared -fPIC -o $@ $^ `pkg-config --libs gtk+-3.0`
     
     prhello-shim.o: prhello-shim.c
     	$(CC) -I$(AUXDIR) -Wall -fPIC `pkg-config --cflags gtk+-3.0` -o $@ -c $<
     
     prhello-shim.c prhello-const.c prhello-types.bin: prhello.cdecl
     	echo '(generate-shim "prhello" "#include <gtk/gtk.h>")' \
     	| mit-scheme --batch-mode
     
     prhello-const.bin: prhello-const.scm
     	echo '(sf "prhello-const")' | mit-scheme --batch-mode
     
     prhello-const.scm: prhello-const
     	./prhello-const
     
     prhello-const: prhello-const.o
     	$(CC) $(CFLAGS) -o $@ $^ $(LDFLAGS) `pkg-config --libs gtk+-3.0`
     
     prhello-const.o: prhello-const.c
     	$(CC) `pkg-config --cflags gtk+-3.0` $(CFLAGS) -o $@ -c $<

   The FFI also supports libraries created by GNU automake (libtool).
The source distribution includes several simple plugins.  Each uses a
portable Makefile.am to build and install its shared object.


File: mit-scheme-ffi.info,  Node: Hello World,  Next: GNU Free Documentation License,  Prev: Compiling and Linking,  Up: Top

7 Hello World
*************

This node includes the C declarations and Scheme code required to
implement Havoc Pennington's Hello World example from GGAD
(http://developer.gnome.org/doc/GGAD/).  For an extra, Schemely treat,
its 'delete_event' callback is a Scheme procedure closed over a binding
of 'counter' that is used to implement some impertinent behavior.
     #| -*-Scheme-*-
     
     This is Havoc Pennington's Hello World example from GGAD, in the raw
     FFI.  Note that no arrangements have been made to de-register the
     callbacks. |#
     
     (declare (usual-integrations))
     
     (C-include "prhello")
     
     (define (hello)
       (C-call "gtk_init" 0 null-alien)
       (let ((window (let ((alien (make-alien '|GtkWidget|)))
     		  (C-call "gtk_window_new" alien
     			  (C-enum "GTK_WINDOW_TOPLEVEL"))
     		  (if (alien-null? alien) (error "Could not create window."))
     		  alien))
     	(button (let ((alien (make-alien '|GtkWidget|)))
     		  (C-call "gtk_button_new" alien)
     		  (if (alien-null? alien) (error "Could not create button."))
     		  alien))
     	(label (let ((alien (make-alien '|GtkWidget|)))
     		 (C-call "gtk_label_new" alien "Hello, World!")
     		 (if (alien-null? alien) (error "Could not create label."))
     		 alien)))
         (C-call "gtk_container_add" button label)
         (C-call "gtk_container_add" window button)
         (C-call "gtk_window_set_title" window "Hello")
         (C-call "gtk_container_set_border_width" button 10)
         (let ((counter 0))
           (C-call "g_signal_connect" window "delete_event"
     	      (C-callback "delete_event")	;trampoline
     	      (C-callback			;callback ID
     	       (lambda (w e)
     		 (outf-error ";Delete me "(- 2 counter)" times.\n")
     		 (set! counter (1+ counter))
     		 ;; Three or more is the charm.
     		 (if (> counter 2)
     		     (begin
     		       (C-call "gtk_main_quit")
     		       0)
     		     1))))
           (C-call "g_signal_connect" button "clicked"
     	      (C-callback "clicked")	;trampoline
     	      (C-callback			;callback ID
     	       (lambda (w)
     		 (let ((gstring (make-alien '(* |gchar|))))
     		   (C-call "gtk_label_get_text" gstring label)
     		   (let ((text (c-peek-cstring gstring)))
     		     (C-call "gtk_label_set_text" label
     			     (list->string (reverse! (string->list text))))))
     		 unspecific))))
         (C-call "gtk_widget_show_all" window)
         (C-call "gtk_main")
         window))

   Here are the C declarations.
     #| -*-Scheme-*-
     
     C declarations for prhello.scm. |#
     
     (typedef gint int)
     (typedef guint uint)
     (typedef gchar char)
     (typedef gboolean gint)
     (typedef gpointer (* mumble))
     
     (extern void
     	gtk_init
     	(argc (* int))
     	(argv (* (* (* char)))))
     
     (extern (* GtkWidget)
     	gtk_window_new
     	(type GtkWindowType))
     
     (typedef GtkWindowType
     	 (enum
     	  (GTK_WINDOW_TOPLEVEL)
     	  (GTK_WINDOW_POPUP)))
     
     (extern (* GtkWidget)
     	gtk_button_new)
     
     (extern (* GtkWidget)
     	gtk_label_new
     	(str (* (const char))))
     
     (extern void
     	gtk_container_add
     	(container (* GtkContainer))
     	(widget    (* GtkWidget)))
     
     (extern void
     	gtk_window_set_title
     	(window (* GtkWindow))
     	(title  (* (const gchar))))
     
     (extern void
     	gtk_container_set_border_width
     	(container (* GtkContainer))
     	(border_width guint))
     
     (extern void
     	gtk_widget_show_all
     	(widget (* GtkWidget)))
     
     (extern void
     	g_signal_connect
     	(instance gpointer)
     	(name (* gchar))
     	(CALLBACK GCallback)
     	(ID gpointer))
     
     (typedef GCallback (* mumble))
     
     (callback gboolean
     	  delete_event
     	  (window (* GtkWidget))
     	  (event (* GdkEventAny))
     	  (ID gpointer))
     
     (callback void
     	  clicked
     	  (widget (* GtkWidget))
     	  (ID gpointer))
     
     (extern void
     	gtk_widget_destroy
     	(widget (* GtkWidget)))
     
     (extern (* (const gchar))
     	gtk_label_get_text
     	(label (* GtkLabel)))
     
     (extern void
     	gtk_label_set_text
     	(label (* GtkLabel))
     	(str (* (const char))))
     
     (extern void gtk_main)
     (extern void gtk_main_quit)


File: mit-scheme-ffi.info,  Node: GNU Free Documentation License,  Prev: Hello World,  Up: Top

Appendix A GNU Free Documentation License
*****************************************

                      Version 1.2, November 2002

     Copyright (C) 2000,2001,2002 Free Software Foundation, Inc.
     51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA

     Everyone is permitted to copy and distribute verbatim copies
     of this license document, but changing it is not allowed.

  0. PREAMBLE

     The purpose of this License is to make a manual, textbook, or other
     functional and useful document "free" in the sense of freedom: to
     assure everyone the effective freedom to copy and redistribute it,
     with or without modifying it, either commercially or
     noncommercially.  Secondarily, this License preserves for the
     author and publisher a way to get credit for their work, while not
     being considered responsible for modifications made by others.

     This License is a kind of "copyleft", which means that derivative
     works of the document must themselves be free in the same sense.
     It complements the GNU General Public License, which is a copyleft
     license designed for free software.

     We have designed this License in order to use it for manuals for
     free software, because free software needs free documentation: a
     free program should come with manuals providing the same freedoms
     that the software does.  But this License is not limited to
     software manuals; it can be used for any textual work, regardless
     of subject matter or whether it is published as a printed book.  We
     recommend this License principally for works whose purpose is
     instruction or reference.

  1. APPLICABILITY AND DEFINITIONS

     This License applies to any manual or other work, in any medium,
     that contains a notice placed by the copyright holder saying it can
     be distributed under the terms of this License.  Such a notice
     grants a world-wide, royalty-free license, unlimited in duration,
     to use that work under the conditions stated herein.  The
     "Document", below, refers to any such manual or work.  Any member
     of the public is a licensee, and is addressed as "you".  You accept
     the license if you copy, modify or distribute the work in a way
     requiring permission under copyright law.

     A "Modified Version" of the Document means any work containing the
     Document or a portion of it, either copied verbatim, or with
     modifications and/or translated into another language.

     A "Secondary Section" is a named appendix or a front-matter section
     of the Document that deals exclusively with the relationship of the
     publishers or authors of the Document to the Document's overall
     subject (or to related matters) and contains nothing that could
     fall directly within that overall subject.  (Thus, if the Document
     is in part a textbook of mathematics, a Secondary Section may not
     explain any mathematics.)  The relationship could be a matter of
     historical connection with the subject or with related matters, or
     of legal, commercial, philosophical, ethical or political position
     regarding them.

     The "Invariant Sections" are certain Secondary Sections whose
     titles are designated, as being those of Invariant Sections, in the
     notice that says that the Document is released under this License.
     If a section does not fit the above definition of Secondary then it
     is not allowed to be designated as Invariant.  The Document may
     contain zero Invariant Sections.  If the Document does not identify
     any Invariant Sections then there are none.

     The "Cover Texts" are certain short passages of text that are
     listed, as Front-Cover Texts or Back-Cover Texts, in the notice
     that says that the Document is released under this License.  A
     Front-Cover Text may be at most 5 words, and a Back-Cover Text may
     be at most 25 words.

     A "Transparent" copy of the Document means a machine-readable copy,
     represented in a format whose specification is available to the
     general public, that is suitable for revising the document
     straightforwardly with generic text editors or (for images composed
     of pixels) generic paint programs or (for drawings) some widely
     available drawing editor, and that is suitable for input to text
     formatters or for automatic translation to a variety of formats
     suitable for input to text formatters.  A copy made in an otherwise
     Transparent file format whose markup, or absence of markup, has
     been arranged to thwart or discourage subsequent modification by
     readers is not Transparent.  An image format is not Transparent if
     used for any substantial amount of text.  A copy that is not
     "Transparent" is called "Opaque".

     Examples of suitable formats for Transparent copies include plain
     ASCII without markup, Texinfo input format, LaTeX input format,
     SGML or XML using a publicly available DTD, and standard-conforming
     simple HTML, PostScript or PDF designed for human modification.
     Examples of transparent image formats include PNG, XCF and JPG.
     Opaque formats include proprietary formats that can be read and
     edited only by proprietary word processors, SGML or XML for which
     the DTD and/or processing tools are not generally available, and
     the machine-generated HTML, PostScript or PDF produced by some word
     processors for output purposes only.

     The "Title Page" means, for a printed book, the title page itself,
     plus such following pages as are needed to hold, legibly, the
     material this License requires to appear in the title page.  For
     works in formats which do not have any title page as such, "Title
     Page" means the text near the most prominent appearance of the
     work's title, preceding the beginning of the body of the text.

     A section "Entitled XYZ" means a named subunit of the Document
     whose title either is precisely XYZ or contains XYZ in parentheses
     following text that translates XYZ in another language.  (Here XYZ
     stands for a specific section name mentioned below, such as
     "Acknowledgements", "Dedications", "Endorsements", or "History".)
     To "Preserve the Title" of such a section when you modify the
     Document means that it remains a section "Entitled XYZ" according
     to this definition.

     The Document may include Warranty Disclaimers next to the notice
     which states that this License applies to the Document.  These
     Warranty Disclaimers are considered to be included by reference in
     this License, but only as regards disclaiming warranties: any other
     implication that these Warranty Disclaimers may have is void and
     has no effect on the meaning of this License.

  2. VERBATIM COPYING

     You may copy and distribute the Document in any medium, either
     commercially or noncommercially, provided that this License, the
     copyright notices, and the license notice saying this License
     applies to the Document are reproduced in all copies, and that you
     add no other conditions whatsoever to those of this License.  You
     may not use technical measures to obstruct or control the reading
     or further copying of the copies you make or distribute.  However,
     you may accept compensation in exchange for copies.  If you
     distribute a large enough number of copies you must also follow the
     conditions in section 3.

     You may also lend copies, under the same conditions stated above,
     and you may publicly display copies.

  3. COPYING IN QUANTITY

     If you publish printed copies (or copies in media that commonly
     have printed covers) of the Document, numbering more than 100, and
     the Document's license notice requires Cover Texts, you must
     enclose the copies in covers that carry, clearly and legibly, all
     these Cover Texts: Front-Cover Texts on the front cover, and
     Back-Cover Texts on the back cover.  Both covers must also clearly
     and legibly identify you as the publisher of these copies.  The
     front cover must present the full title with all words of the title
     equally prominent and visible.  You may add other material on the
     covers in addition.  Copying with changes limited to the covers, as
     long as they preserve the title of the Document and satisfy these
     conditions, can be treated as verbatim copying in other respects.

     If the required texts for either cover are too voluminous to fit
     legibly, you should put the first ones listed (as many as fit
     reasonably) on the actual cover, and continue the rest onto
     adjacent pages.

     If you publish or distribute Opaque copies of the Document
     numbering more than 100, you must either include a machine-readable
     Transparent copy along with each Opaque copy, or state in or with
     each Opaque copy a computer-network location from which the general
     network-using public has access to download using public-standard
     network protocols a complete Transparent copy of the Document, free
     of added material.  If you use the latter option, you must take
     reasonably prudent steps, when you begin distribution of Opaque
     copies in quantity, to ensure that this Transparent copy will
     remain thus accessible at the stated location until at least one
     year after the last time you distribute an Opaque copy (directly or
     through your agents or retailers) of that edition to the public.

     It is requested, but not required, that you contact the authors of
     the Document well before redistributing any large number of copies,
     to give them a chance to provide you with an updated version of the
     Document.

  4. MODIFICATIONS

     You may copy and distribute a Modified Version of the Document
     under the conditions of sections 2 and 3 above, provided that you
     release the Modified Version under precisely this License, with the
     Modified Version filling the role of the Document, thus licensing
     distribution and modification of the Modified Version to whoever
     possesses a copy of it.  In addition, you must do these things in
     the Modified Version:

       A. Use in the Title Page (and on the covers, if any) a title
          distinct from that of the Document, and from those of previous
          versions (which should, if there were any, be listed in the
          History section of the Document).  You may use the same title
          as a previous version if the original publisher of that
          version gives permission.

       B. List on the Title Page, as authors, one or more persons or
          entities responsible for authorship of the modifications in
          the Modified Version, together with at least five of the
          principal authors of the Document (all of its principal
          authors, if it has fewer than five), unless they release you
          from this requirement.

       C. State on the Title page the name of the publisher of the
          Modified Version, as the publisher.

       D. Preserve all the copyright notices of the Document.

       E. Add an appropriate copyright notice for your modifications
          adjacent to the other copyright notices.

       F. Include, immediately after the copyright notices, a license
          notice giving the public permission to use the Modified
          Version under the terms of this License, in the form shown in
          the Addendum below.

       G. Preserve in that license notice the full lists of Invariant
          Sections and required Cover Texts given in the Document's
          license notice.

       H. Include an unaltered copy of this License.

       I. Preserve the section Entitled "History", Preserve its Title,
          and add to it an item stating at least the title, year, new
          authors, and publisher of the Modified Version as given on the
          Title Page.  If there is no section Entitled "History" in the
          Document, create one stating the title, year, authors, and
          publisher of the Document as given on its Title Page, then add
          an item describing the Modified Version as stated in the
          previous sentence.

       J. Preserve the network location, if any, given in the Document
          for public access to a Transparent copy of the Document, and
          likewise the network locations given in the Document for
          previous versions it was based on.  These may be placed in the
          "History" section.  You may omit a network location for a work
          that was published at least four years before the Document
          itself, or if the original publisher of the version it refers
          to gives permission.

       K. For any section Entitled "Acknowledgements" or "Dedications",
          Preserve the Title of the section, and preserve in the section
          all the substance and tone of each of the contributor
          acknowledgements and/or dedications given therein.

       L. Preserve all the Invariant Sections of the Document, unaltered
          in their text and in their titles.  Section numbers or the
          equivalent are not considered part of the section titles.

       M. Delete any section Entitled "Endorsements".  Such a section
          may not be included in the Modified Version.

       N. Do not retitle any existing section to be Entitled
          "Endorsements" or to conflict in title with any Invariant
          Section.

       O. Preserve any Warranty Disclaimers.

     If the Modified Version includes new front-matter sections or
     appendices that qualify as Secondary Sections and contain no
     material copied from the Document, you may at your option designate
     some or all of these sections as invariant.  To do this, add their
     titles to the list of Invariant Sections in the Modified Version's
     license notice.  These titles must be distinct from any other
     section titles.

     You may add a section Entitled "Endorsements", provided it contains
     nothing but endorsements of your Modified Version by various
     parties--for example, statements of peer review or that the text
     has been approved by an organization as the authoritative
     definition of a standard.

     You may add a passage of up to five words as a Front-Cover Text,
     and a passage of up to 25 words as a Back-Cover Text, to the end of
     the list of Cover Texts in the Modified Version.  Only one passage
     of Front-Cover Text and one of Back-Cover Text may be added by (or
     through arrangements made by) any one entity.  If the Document
     already includes a cover text for the same cover, previously added
     by you or by arrangement made by the same entity you are acting on
     behalf of, you may not add another; but you may replace the old
     one, on explicit permission from the previous publisher that added
     the old one.

     The author(s) and publisher(s) of the Document do not by this
     License give permission to use their names for publicity for or to
     assert or imply endorsement of any Modified Version.

  5. COMBINING DOCUMENTS

     You may combine the Document with other documents released under
     this License, under the terms defined in section 4 above for
     modified versions, provided that you include in the combination all
     of the Invariant Sections of all of the original documents,
     unmodified, and list them all as Invariant Sections of your
     combined work in its license notice, and that you preserve all
     their Warranty Disclaimers.

     The combined work need only contain one copy of this License, and
     multiple identical Invariant Sections may be replaced with a single
     copy.  If there are multiple Invariant Sections with the same name
     but different contents, make the title of each such section unique
     by adding at the end of it, in parentheses, the name of the
     original author or publisher of that section if known, or else a
     unique number.  Make the same adjustment to the section titles in
     the list of Invariant Sections in the license notice of the
     combined work.

     In the combination, you must combine any sections Entitled
     "History" in the various original documents, forming one section
     Entitled "History"; likewise combine any sections Entitled
     "Acknowledgements", and any sections Entitled "Dedications".  You
     must delete all sections Entitled "Endorsements."

  6. COLLECTIONS OF DOCUMENTS

     You may make a collection consisting of the Document and other
     documents released under this License, and replace the individual
     copies of this License in the various documents with a single copy
     that is included in the collection, provided that you follow the
     rules of this License for verbatim copying of each of the documents
     in all other respects.

     You may extract a single document from such a collection, and
     distribute it individually under this License, provided you insert
     a copy of this License into the extracted document, and follow this
     License in all other respects regarding verbatim copying of that
     document.

  7. AGGREGATION WITH INDEPENDENT WORKS

     A compilation of the Document or its derivatives with other
     separate and independent documents or works, in or on a volume of a
     storage or distribution medium, is called an "aggregate" if the
     copyright resulting from the compilation is not used to limit the
     legal rights of the compilation's users beyond what the individual
     works permit.  When the Document is included an aggregate, this
     License does not apply to the other works in the aggregate which
     are not themselves derivative works of the Document.

     If the Cover Text requirement of section 3 is applicable to these
     copies of the Document, then if the Document is less than one half
     of the entire aggregate, the Document's Cover Texts may be placed
     on covers that bracket the Document within the aggregate, or the
     electronic equivalent of covers if the Document is in electronic
     form.  Otherwise they must appear on printed covers that bracket
     the whole aggregate.

  8. TRANSLATION

     Translation is considered a kind of modification, so you may
     distribute translations of the Document under the terms of section
     4.  Replacing Invariant Sections with translations requires special
     permission from their copyright holders, but you may include
     translations of some or all Invariant Sections in addition to the
     original versions of these Invariant Sections.  You may include a
     translation of this License, and all the license notices in the
     Document, and any Warrany Disclaimers, provided that you also
     include the original English version of this License and the
     original versions of those notices and disclaimers.  In case of a
     disagreement between the translation and the original version of
     this License or a notice or disclaimer, the original version will
     prevail.

     If a section in the Document is Entitled "Acknowledgements",
     "Dedications", or "History", the requirement (section 4) to
     Preserve its Title (section 1) will typically require changing the
     actual title.

  9. TERMINATION

     You may not copy, modify, sublicense, or distribute the Document
     except as expressly provided for under this License.  Any other
     attempt to copy, modify, sublicense or distribute the Document is
     void, and will automatically terminate your rights under this
     License.  However, parties who have received copies, or rights,
     from you under this License will not have their licenses terminated
     so long as such parties remain in full compliance.

  10. FUTURE REVISIONS OF THIS LICENSE

     The Free Software Foundation may publish new, revised versions of
     the GNU Free Documentation License from time to time.  Such new
     versions will be similar in spirit to the present version, but may
     differ in detail to address new problems or concerns.  See
     <http://www.gnu.org/copyleft/>.

     Each version of the License is given a distinguishing version
     number.  If the Document specifies that a particular numbered
     version of this License "or any later version" applies to it, you
     have the option of following the terms and conditions either of
     that specified version or of any later version that has been
     published (not as a draft) by the Free Software Foundation.  If the
     Document does not specify a version number of this License, you may
     choose any version ever published (not as a draft) by the Free
     Software Foundation.

A.1 ADDENDUM: How to use this License for your documents
========================================================

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and license
notices just after the title page:

       Copyright (C)  YEAR  YOUR NAME.
       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.2
       or any later version published by the Free Software Foundation;
       with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
       A copy of the license is included in the section entitled ``GNU
       Free Documentation License''.

   If you have Invariant Sections, Front-Cover Texts and Back-Cover
Texts, replace the "with...Texts."  line with this:

         with the Invariant Sections being LIST THEIR TITLES, with
         the Front-Cover Texts being LIST, and with the Back-Cover Texts
         being LIST.

   If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

   If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of free
software license, such as the GNU General Public License, to permit
their use in free software.


Tag Table:
Node: Top954
Node: Introduction2149
Node: C Declarations9441
Node: Alien Data12000
Node: Alien Functions14179
Node: Callbacks16258
Node: Compiling and Linking19240
Node: Hello World22221
Node: GNU Free Documentation License26734

End Tag Table
