gmodule/gmodule-dl.c

   1 /* GMODULE - GLIB wrapper code for dynamic module loading
   2  * Copyright (C) 1998, 2000 Tim Janik
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2.1 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, see <http://www.gnu.org/licenses/>.
  16  */
  17
  18 /*
  19  * Modified by the GLib Team and others 1997-2000.  See the AUTHORS
  20  * file for a list of people on the GLib Team.  See the ChangeLog
  21  * files for a list of changes.  These files are distributed with
  22  * GLib at ftp://ftp.gtk.org/pub/gtk/.
  23  */
  24
  25 /*
  26  * MT safe
  27  */
  28 #include "config.h"
  29
  30 #include <dlfcn.h>
  31
  32 /* Perl includes <nlist.h> and <link.h> instead of <dlfcn.h> on some systmes? */
  33
  34
  35 /* dlerror() is not implemented on all systems
  36  */
  37 #ifndef G_MODULE_HAVE_DLERROR
  38 #  ifdef __NetBSD__
  39 #    define dlerror()   g_strerror (errno)
  40 #  else /* !__NetBSD__ */
  41 /* could we rely on errno's state here? */
  42 #    define dlerror()   "unknown dl-error"
  43 #  endif /* !__NetBSD__ */
  44 #endif  /* G_MODULE_HAVE_DLERROR */
  45
  46 /* some flags are missing on some systems, so we provide
  47  * harmless defaults.
  48  * The Perl sources say, RTLD_LAZY needs to be defined as (1),
  49  * at least for Solaris 1.
  50  *
  51  * Mandatory:
  52  * RTLD_LAZY   - resolve undefined symbols as code from the dynamic library
  53  *               is executed.
  54  * RTLD_NOW    - resolve all undefined symbols before dlopen returns, and fail
  55  *               if this cannot be done.
  56  * Optionally:
  57  * RTLD_GLOBAL - the external symbols defined in the library will be made
  58  *               available to subsequently loaded libraries.
  59  */
  60 #ifndef HAVE_RTLD_LAZY
  61 #define RTLD_LAZY       1
  62 #endif  /* RTLD_LAZY */
  63 #ifndef HAVE_RTLD_NOW
  64 #define RTLD_NOW        0
  65 #endif  /* RTLD_NOW */
  66 /* some systems (OSF1 V5.0) have broken RTLD_GLOBAL linkage */
  67 #ifdef G_MODULE_BROKEN_RTLD_GLOBAL
  68 #undef  RTLD_GLOBAL
  69 #undef  HAVE_RTLD_GLOBAL
  70 #endif /* G_MODULE_BROKEN_RTLD_GLOBAL */
  71 #ifndef HAVE_RTLD_GLOBAL
  72 #define RTLD_GLOBAL     0
  73 #endif  /* RTLD_GLOBAL */
  74
  75
  76 /* --- functions --- */
  77 static gchar*
  78 fetch_dlerror (gboolean replace_null)
  79 {
  80   gchar *msg = dlerror ();
  81
  82   /* make sure we always return an error message != NULL, if
  83    * expected to do so. */
  84
  85   if (!msg && replace_null)
  86     return "unknown dl-error";
  87
  88   return msg;
  89 }
  90
  91 static gpointer
  92 _g_module_open (const gchar *file_name,
  93                 gboolean     bind_lazy,
  94                 gboolean     bind_local)
  95 {
  96   gpointer handle;
  97
  98   handle = dlopen (file_name,
  99                    (bind_local ? 0 : RTLD_GLOBAL) | (bind_lazy ? RTLD_LAZY : RTLD_NOW));
 100   if (!handle)
 101     g_module_set_error (fetch_dlerror (TRUE));
 102
 103   return handle;
 104 }
 105
 106 static gpointer
 107 _g_module_self (void)
 108 {
 109   gpointer handle;
 110
 111   /* to query symbols from the program itself, special link options
 112    * are required on some systems.
 113    */
 114
 115   /* On Android 32 bit (i.e. not __LP64__), dlopen(NULL)
 116    * does not work reliable and generally no symbols are found
 117    * at all. RTLD_DEFAULT works though.
 118    * On Android 64 bit, dlopen(NULL) seems to work but dlsym(handle)
 119    * always returns 'undefined symbol'. Only if RTLD_DEFAULT or
 120    * NULL is given, dlsym returns an appropriate pointer.
 121    */
 122 #if defined(__BIONIC__)
 123   handle = RTLD_DEFAULT;
 124 #else
 125   handle = dlopen (NULL, RTLD_GLOBAL | RTLD_LAZY);
 126 #endif
 127   if (!handle)
 128     g_module_set_error (fetch_dlerror (TRUE));
 129
 130   return handle;
 131 }
 132
 133 static void
 134 _g_module_close (gpointer handle,
 135                  gboolean is_unref)
 136 {
 137   /* are there any systems out there that have dlopen()/dlclose()
 138    * without a reference count implementation?
 139    *
 140    * See above for the Android special case
 141    */
 142 #if defined(__BIONIC__)
 143   is_unref = (handle != RTLD_DEFAULT);
 144 #else
 145   is_unref |= 1;
 146 #endif
 147
 148   if (is_unref)
 149     {
 150       if (dlclose (handle) != 0)
 151         g_module_set_error (fetch_dlerror (TRUE));
 152     }
 153 }
 154
 155 static gpointer
 156 _g_module_symbol (gpointer     handle,
 157                   const gchar *symbol_name)
 158 {
 159   gpointer p;
 160   gchar *msg;
 161
 162   fetch_dlerror (FALSE);
 163   p = dlsym (handle, symbol_name);
 164   msg = fetch_dlerror (FALSE);
 165   if (msg)
 166     g_module_set_error (msg);
 167
 168   return p;
 169 }
 170
 171 static gchar*
 172 _g_module_build_path (const gchar *directory,
 173                       const gchar *module_name)
 174 {
 175   if (directory && *directory) {
 176     if (strncmp (module_name, "lib", 3) == 0)
 177       return g_strconcat (directory, "/", module_name, NULL);
 178     else
 179       return g_strconcat (directory, "/lib", module_name, "." G_MODULE_SUFFIX, NULL);
 180   } else if (strncmp (module_name, "lib", 3) == 0)
 181     return g_strdup (module_name);
 182   else
 183     return g_strconcat ("lib", module_name, "." G_MODULE_SUFFIX, NULL);
 184 }