doc/ref/libguile-linking.texi

   1 @c -*-texinfo-*-
   2 @c This is part of the GNU Guile Reference Manual.
   3 @c Copyright (C)  1996, 1997, 2000, 2001, 2002, 2003, 2004, 2005, 2010, 2011
   4 @c   Free Software Foundation, Inc.
   5 @c See the file guile.texi for copying conditions.
   6
   7 @node Linking Programs With Guile
   8 @section Linking Programs With Guile
   9
  10 This section covers the mechanics of linking your program with Guile
  11 on a typical POSIX system.
  12
  13 The header file @code{<libguile.h>} provides declarations for all of
  14 Guile's functions and constants.  You should @code{#include} it at the
  15 head of any C source file that uses identifiers described in this
  16 manual.  Once you've compiled your source files, you need to link them
  17 against the Guile object code library, @code{libguile}.
  18
  19 As noted in the previous section, @code{<libguile.h>} is not in the
  20 default search path for headers.  The following command lines give
  21 respectively the C compilation and link flags needed to build programs
  22 using Guile @value{EFFECTIVE-VERSION}:
  23
  24 @example
  25 pkg-config guile-@value{EFFECTIVE-VERSION} --cflags
  26 pkg-config guile-@value{EFFECTIVE-VERSION} --libs
  27 @end example
  28
  29 @menu
  30 * Guile Initialization Functions::  What to call first.
  31 * A Sample Guile Main Program::  Sources and makefiles.
  32 @end menu
  33
  34
  35 @node Guile Initialization Functions
  36 @subsection Guile Initialization Functions
  37
  38 To initialize Guile, you can use one of several functions.  The first,
  39 @code{scm_with_guile}, is the most portable way to initialize Guile.  It
  40 will initialize Guile when necessary and then call a function that you
  41 can specify.  Multiple threads can call @code{scm_with_guile}
  42 concurrently and it can also be called more than once in a given thread.
  43 The global state of Guile will survive from one call of
  44 @code{scm_with_guile} to the next.  Your function is called from within
  45 @code{scm_with_guile} since the garbage collector of Guile needs to know
  46 where the stack of each thread is.
  47
  48 A second function, @code{scm_init_guile}, initializes Guile for the
  49 current thread.  When it returns, you can use the Guile API in the
  50 current thread.  This function employs some non-portable magic to learn
  51 about stack bounds and might thus not be available on all platforms.
  52
  53 One common way to use Guile is to write a set of C functions which
  54 perform some useful task, make them callable from Scheme, and then link
  55 the program with Guile.  This yields a Scheme interpreter just like
  56 @code{guile}, but augmented with extra functions for some specific
  57 application --- a special-purpose scripting language.
  58
  59 In this situation, the application should probably process its
  60 command-line arguments in the same manner as the stock Guile
  61 interpreter.  To make that straightforward, Guile provides the
  62 @code{scm_boot_guile} and @code{scm_shell} function.
  63
  64 For more about these functions, see @ref{Initialization}.
  65
  66 @node A Sample Guile Main Program
  67 @subsection A Sample Guile Main Program
  68
  69 Here is @file{simple-guile.c}, source code for a @code{main} and an
  70 @code{inner_main} function that will produce a complete Guile
  71 interpreter.
  72
  73 @example
  74 /* simple-guile.c --- Start Guile from C.  */
  75
  76 #include <libguile.h>
  77
  78 static void
  79 inner_main (void *closure, int argc, char **argv)
  80 @{
  81   /* preparation */
  82   scm_shell (argc, argv);
  83   /* after exit */
  84 @}
  85
  86 int
  87 main (int argc, char **argv)
  88 @{
  89   scm_boot_guile (argc, argv, inner_main, 0);
  90   return 0; /* never reached, see inner_main */
  91 @}
  92 @end example
  93
  94 The @code{main} function calls @code{scm_boot_guile} to initialize
  95 Guile, passing it @code{inner_main}.  Once @code{scm_boot_guile} is
  96 ready, it invokes @code{inner_main}, which calls @code{scm_shell} to
  97 process the command-line arguments in the usual way.
  98
  99 @subsection Building the Example with Make
 100
 101 Here is a Makefile which you can use to compile the example program.  It
 102 uses @code{pkg-config} to learn about the necessary compiler and
 103 linker flags.
 104 @example
 105 # Use GCC, if you have it installed.
 106 CC=gcc
 107
 108 # Tell the C compiler where to find <libguile.h>
 109 CFLAGS=`pkg-config --cflags guile-@value{EFFECTIVE-VERSION}`
 110
 111 # Tell the linker what libraries to use and where to find them.
 112 LIBS=`pkg-config --libs guile-@value{EFFECTIVE-VERSION}`
 113
 114 simple-guile: simple-guile.o
 115         $@{CC@} simple-guile.o $@{LIBS@} -o simple-guile
 116
 117 simple-guile.o: simple-guile.c
 118         $@{CC@} -c $@{CFLAGS@} simple-guile.c
 119 @end example
 120
 121 @subsection Building the Example with Autoconf
 122
 123 If you are using the GNU Autoconf package to make your application more
 124 portable, Autoconf will settle many of the details in the Makefile
 125 automatically, making it much simpler and more portable; we recommend
 126 using Autoconf with Guile.  Here is a @file{configure.ac} file for
 127 @code{simple-guile} that uses the standard @code{PKG_CHECK_MODULES}
 128 macro to check for Guile.  Autoconf will process this file into a
 129 @code{configure} script.  We recommend invoking Autoconf via the
 130 @code{autoreconf} utility.
 131
 132 @example
 133 AC_INIT(simple-guile.c)
 134
 135 # Find a C compiler.
 136 AC_PROG_CC
 137
 138 # Check for Guile
 139 PKG_CHECK_MODULES([GUILE], [guile-@value{EFFECTIVE-VERSION}])
 140
 141 # Generate a Makefile, based on the results.
 142 AC_OUTPUT(Makefile)
 143 @end example
 144
 145 Run @code{autoreconf -vif} to generate @code{configure}.
 146
 147 Here is a @code{Makefile.in} template, from which the @code{configure}
 148 script produces a Makefile customized for the host system:
 149 @example
 150 # The configure script fills in these values.
 151 CC=@@CC@@
 152 CFLAGS=@@GUILE_CFLAGS@@
 153 LIBS=@@GUILE_LIBS@@
 154
 155 simple-guile: simple-guile.o
 156         $@{CC@} simple-guile.o $@{LIBS@} -o simple-guile
 157 simple-guile.o: simple-guile.c
 158         $@{CC@} -c $@{CFLAGS@} simple-guile.c
 159 @end example
 160
 161 The developer should use Autoconf to generate the @file{configure}
 162 script from the @file{configure.ac} template, and distribute
 163 @file{configure} with the application.  Here's how a user might go about
 164 building the application:
 165
 166 @example
 167 $ ls
 168 Makefile.in     configure*      configure.ac    simple-guile.c
 169 $ ./configure
 170 checking for gcc... ccache gcc
 171 checking whether the C compiler works... yes
 172 checking for C compiler default output file name... a.out
 173 checking for suffix of executables...
 174 checking whether we are cross compiling... no
 175 checking for suffix of object files... o
 176 checking whether we are using the GNU C compiler... yes
 177 checking whether ccache gcc accepts -g... yes
 178 checking for ccache gcc option to accept ISO C89... none needed
 179 checking for pkg-config... /usr/bin/pkg-config
 180 checking pkg-config is at least version 0.9.0... yes
 181 checking for GUILE... yes
 182 configure: creating ./config.status
 183 config.status: creating Makefile
 184 $ make
 185 [...]
 186 $ ./simple-guile
 187 guile> (+ 1 2 3)
 188 6
 189 guile> (getpwnam "jimb")
 190 #("jimb" "83Z7d75W2tyJQ" 4008 10 "Jim Blandy" "/u/jimb"
 191   "/usr/local/bin/bash")
 192 guile> (exit)
 193 $
 194 @end example
 195
 196
 197 @c Local Variables:
 198 @c TeX-master: "guile.texi"
 199 @c End: