/* Lisp interface to dynamic loading.
   Copyright (C) 1998  Joshua Rowe.
   Additional cleanup by Hrvoje Niksic.

This file is part of XEmacs.

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; see the file COPYING.  If not, write to
the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA.  */

/* Synched up with: Not in FSF. */

/* A shared object may have the following symbols defined:
      syms_of
      vars_of
      complex_vars_of
   They are called in that order.  Each takes and returns void
   arguments.

   All of this needs lots and LOTS of work.  Some things to work on:

   1) A good foreign interface.  We probably need to get rid of
   syms_of and similar junk, and define a more normal interfacing to
   the outside world, e.g. an init_emacs_module() function.  See below
   for more discussion about it.  Also, we need a modules/ directory
   with a few nice sample modules, a sample Makefile, etc. so people
   can start hacking.

   2) Compatibility concerns.  There are systems without dynamic
   libraries (Ultrix, to name one).  OK, scrap them, but not all
   systems out there use the exact dlopen() interface that this file
   uses.  Bill Perry said he had ready Makefiles for 14 or so systems
   to do this sort of things portably.  Check it out.  Or, use Gordon
   Matzigkeit's libtool.

   3) I'm getting coredumps very often -- practically every time I
   compile without USE_MINIMAL_TAGBITS, and even with it sometimes.  I
   wasn't able to resolve these.

   4) All of this is sooo simple-minded.  As it gets more complex,
   we'll have to look at how others have done similar things
   (e.g. Perl and Zsh 3.1), to avoid botching it up.  */

#include <config.h>
#include "lisp.h"
#include "emacsfns.h"
#include "buffer.h"

#include <stdio.h>
#include <dlfcn.h>
#include <errno.h>


DEFUN ("dl-open", Fdl_open, 1, 1, "FShared object: ", /*
Load LIBRARY as a shared object file.

After the LIBRARY is dynamically linked with the executable, the
following functions are called:

  syms_of(),		containing definitions of symbols and subr's;
  vars_of(),		containing definitions of variables;
  complex_vars_of(),	containing complex definitions of variables.

After this point, any lisp symbols defined in the shared object are
available for use.
*/
       (library))
{
  /* This function can GC */
  void *handle;
  char *file;
  void (*function)();

  CHECK_STRING (library);
  library = Fexpand_file_name (library, Qnil);

  file = XSTRING_DATA (library);
  /* #### Is this right? */
  GET_C_CHARPTR_EXT_FILENAME_DATA_ALLOCA (file, file);

  handle = dlopen (file, RTLD_LAZY);
  if (handle == NULL)
    {
      signal_error (Qerror,
		    list3 (build_translated_string ("Cannot load shared library"),
			   library, build_translated_string (dlerror ())));
    }

  /* #### This looks unnecessary here, because at this time one
     initialization function is fully sufficient.  However, I am not
     removing this support, since we may wish to add mechanisms for
     static linking, which would have invoke these function via normal
     paths.

     #### But then this is not sufficient, because one could as well
     honor specifier_vars_of_foo(), etc.  Maybe we should scrap it
     after all.

     #### What if one of the first two functions signal an error?
     Should we take care to execute the other two?  My fingers are
     getting itchy!  */

  function = dlsym (handle, "syms_of");
  if (function)
    (*function) ();

  function = dlsym (handle, "vars_of");
  if (function)
    (*function) ();

  function = dlsym (handle, "complex_vars_of");
  if (function)
    (*function) ();

  return Qnil;
}

void syms_of_dlopen ()
{
  DEFSUBR (Fdl_open);
}