A Sample Guile Main Program

Here is `simple-guile.c', source code for a main and an inner_main function that will produce a complete Guile interpreter.

/* simple-guile.c -- how to start up the Guile
   interpreter from C code.  */

/* Get declarations for all the scm_ functions.  */
#include <libguile.h>

static void
inner_main (void *closure, int argc, char **argv)
{
  /* module initializations would go here */
  scm_shell (argc, argv);
}

int
main (int argc, char **argv)
{
  scm_boot_guile (argc, argv, inner_main, 0);
  return 0; /* never reached */
}

The main function calls scm_boot_guile to initialize Guile, passing it inner_main. Once scm_boot_guile is ready, it invokes inner_main, which calls scm_shell to process the command-line arguments in the usual way.

Here is a Makefile which you can use to compile the above program.

# Use GCC, if you have it installed.
CC=gcc

# Tell the C compiler where to find <libguile.h> and -lguile.
CFLAGS=-I/usr/local/include -L/usr/local/lib

# Include -lqt and -lrx if they are present on your system.
LIBS=-lguile -lqt -lrx -lm

simple-guile: simple-guile.o
        ${CC} ${CFLAGS} simple-guile.o ${LIBS} -o simple-guile
simple-guile.o: simple-guile.c
        ${CC} -c ${CFLAGS} simple-guile.c

If you are using the GNU Autoconf package to make your application more portable, Autoconf will settle many of the details in the Makefile above automatically, making it much simpler and more portable; we recommend using Autoconf with Guile. Here is a `configure.in' file for simple-guile, which Autoconf can use as a template to generate a configure script:

AC_INIT(simple-guile.c)

# Find a C compiler.
AC_PROG_CC

# Check for libraries.
AC_CHECK_LIB(m, sin)
AC_CHECK_LIB(rx, regcomp)
AC_CHECK_LIB(qt, main)
AC_CHECK_LIB(guile, scm_boot_guile)

# Generate a Makefile, based on the results.
AC_OUTPUT(Makefile)

Here is a Makefile.in template, from which the configure script produces a Makefile customized for the host system:

# The configure script fills in these values.
CC=@CC@
CFLAGS=@CFLAGS@
LIBS=@LIBS@

simple-guile: simple-guile.o
        ${CC} ${CFLAGS} simple-guile.o ${LIBS} -o simple-guile
simple-guile.o: simple-guile.c
        ${CC} -c ${CFLAGS} simple-guile.c

The developer should use Autoconf to generate the `configure' script from the `configure.in' template, and distribute `configure' with the application. Here's how a user might go about building the application:

$ ls
Makefile.in     configure*      configure.in    simple-guile.c
$ ./configure
creating cache ./config.cache
checking for gcc... gcc
checking whether the C compiler (gcc  ) works... yes
checking whether the C compiler (gcc  ) is a cross-compiler... no
checking whether we are using GNU C... yes
checking whether gcc accepts -g... yes
checking for sin in -lm... yes
checking for regcomp in -lrx... yes
checking for main in -lqt... yes
checking for scm_boot_guile in -lguile... yes
updating cache ./config.cache
creating ./config.status
creating Makefile
$ make
gcc -c -g -O2 simple-guile.c
gcc -g -O2 simple-guile.o -lguile -lqt -lrx -lm  -o simple-guile
$ ./simple-guile
guile> (+ 1 2 3)
6
guile> (getpwnam "jimb")
#("jimb" "83Z7d75W2tyJQ" 4008 10 "Jim Blandy" "/u/jimb"
  "/usr/local/bin/bash")
guile> (exit)
$ 

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