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dlopen.c

/* loader-dlopen.c --  dynamic linking with dlopen/dlsym

   Copyright (C) 1998, 1999, 2000, 2004, 2006,
                 2007, 2008 Free Software Foundation, Inc.
   Written by Thomas Tanner, 1998

   NOTE: The canonical source of this file is maintained with the
   GNU Libtool package.  Report bugs to bug-libtool@gnu.org.

GNU Libltdl is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2 of the License, or (at your option) any later version.

As a special exception to the GNU Lesser General Public License,
if you distribute this file as part of a program or library that
is built using GNU Libtool, you may include this file under the
same distribution terms that you use for the rest of that program.

GNU Libltdl 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 Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with GNU Libltdl; see the file COPYING.LIB.  If not, a
copy can be downloaded from  http://www.gnu.org/licenses/lgpl.html,
or obtained by writing to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/

#include "lt__private.h"
#include "lt_dlloader.h"

/* Use the preprocessor to rename non-static symbols to avoid namespace
   collisions when the loader code is statically linked into libltdl.
   Use the "<module_name>_LTX_" prefix so that the symbol addresses can
   be fetched from the preloaded symbol list by lt_dlsym():  */
#define get_vtable      dlopen_LTX_get_vtable

LT_BEGIN_C_DECLS
LT_SCOPE lt_dlvtable *get_vtable (lt_user_data loader_data);
LT_END_C_DECLS


/* Boilerplate code to set up the vtable for hooking this loader into
   libltdl's loader list:  */
static int   vl_exit  (lt_user_data loader_data);
static lt_module vm_open  (lt_user_data loader_data, const char *filename,
                           lt_dladvise advise);
static int   vm_close (lt_user_data loader_data, lt_module module);
static void *      vm_sym   (lt_user_data loader_data, lt_module module,
                    const char *symbolname);

static lt_dlvtable *vtable = 0;

/* Return the vtable for this loader, only the name and sym_prefix
   attributes (plus the virtual function implementations, obviously)
   change between loaders.  */
lt_dlvtable *
get_vtable (lt_user_data loader_data)
{
  if (!vtable)
    {
      vtable = (lt_dlvtable *) lt__zalloc (sizeof *vtable);
    }

  if (vtable && !vtable->name)
    {
      vtable->name            = "lt_dlopen";
#if defined(DLSYM_USCORE)
      vtable->sym_prefix      = "_";
#endif
      vtable->module_open     = vm_open;
      vtable->module_close    = vm_close;
      vtable->find_sym        = vm_sym;
      vtable->dlloader_exit   = vl_exit;
      vtable->dlloader_data   = loader_data;
      vtable->priority        = LT_DLLOADER_PREPEND;
    }

  if (vtable && (vtable->dlloader_data != loader_data))
    {
      LT__SETERROR (INIT_LOADER);
      return 0;
    }

  return vtable;
}



/* --- IMPLEMENTATION --- */


#if defined(HAVE_DLFCN_H)
#  include <dlfcn.h>
#endif

#if defined(HAVE_SYS_DL_H)
#  include <sys/dl.h>
#endif


/* We may have to define LT_LAZY_OR_NOW in the command line if we
   find out it does not work in some platform. */
#if !defined(LT_LAZY_OR_NOW)
#  if defined(RTLD_LAZY)
#    define LT_LAZY_OR_NOW    RTLD_LAZY
#  else
#    if defined(DL_LAZY)
#      define LT_LAZY_OR_NOW  DL_LAZY
#    endif
#  endif /* !RTLD_LAZY */
#endif
#if !defined(LT_LAZY_OR_NOW)
#  if defined(RTLD_NOW)
#    define LT_LAZY_OR_NOW    RTLD_NOW
#  else
#    if defined(DL_NOW)
#      define LT_LAZY_OR_NOW  DL_NOW
#    endif
#  endif /* !RTLD_NOW */
#endif
#if !defined(LT_LAZY_OR_NOW)
#  define LT_LAZY_OR_NOW      0
#endif /* !LT_LAZY_OR_NOW */

/* We only support local and global symbols from modules for loaders
   that provide such a thing, otherwise the system default is used.  */
#if !defined(RTLD_GLOBAL)
#  if defined(DL_GLOBAL)
#    define RTLD_GLOBAL       DL_GLOBAL
#  endif
#endif /* !RTLD_GLOBAL */
#if !defined(RTLD_LOCAL)
#  if defined(DL_LOCAL)
#    define RTLD_LOCAL        DL_LOCAL
#  endif
#endif /* !RTLD_LOCAL */

#if defined(HAVE_DLERROR)
#  define DLERROR(arg)  dlerror ()
#else
#  define DLERROR(arg)  LT__STRERROR (arg)
#endif

#define DL__SETERROR(errorcode) \
      LT__SETERRORSTR (DLERROR (errorcode))


/* A function called through the vtable when this loader is no
   longer needed by the application.  */
static int
vl_exit (lt_user_data LT__UNUSED loader_data)
{
  vtable = NULL;
  return 0;
}


/* A function called through the vtable to open a module with this
   loader.  Returns an opaque representation of the newly opened
   module for processing with this loader's other vtable functions.  */
static lt_module
vm_open (lt_user_data LT__UNUSED loader_data, const char *filename,
         lt_dladvise advise)
{
  int       module_flags = LT_LAZY_OR_NOW;
  lt_module module;

  if (advise)
    {
#ifdef RTLD_GLOBAL
      /* If there is some means of asking for global symbol resolution,
         do so.  */
      if (advise->is_symglobal)
        module_flags |= RTLD_GLOBAL;
#else
      /* Otherwise, reset that bit so the caller can tell it wasn't
         acted on.  */
      advise->is_symglobal = 0;
#endif

/* And similarly for local only symbol resolution.  */
#ifdef RTLD_LOCAL
      if (advise->is_symlocal)
        module_flags |= RTLD_LOCAL;
#else
      advise->is_symlocal = 0;
#endif
    }

  module = dlopen (filename, module_flags);

  if (!module)
    {
      DL__SETERROR (CANNOT_OPEN);
    }

  return module;
}


/* A function called through the vtable when a particular module
   should be unloaded.  */
static int
vm_close (lt_user_data LT__UNUSED loader_data, lt_module module)
{
  int errors = 0;

  if (dlclose (module) != 0)
    {
      DL__SETERROR (CANNOT_CLOSE);
      ++errors;
    }

  return errors;
}


/* A function called through the vtable to get the address of
   a symbol loaded from a particular module.  */
static void *
vm_sym (lt_user_data LT__UNUSED loader_data, lt_module module, const char *name)
{
  void *address = dlsym (module, name);

  if (!address)
    {
      DL__SETERROR (SYMBOL_NOT_FOUND);
    }

  return address;
}

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