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/* GMODULE - GLIB wrapper code for dynamic module loading
* Copyright (C) 1998, 2000 Tim Janik
*
* SPDX-License-Identifier: LGPL-2.1-or-later
*
* This library 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 2.1 of the License, or (at your option) any later version.
*
* This library 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 this library; if not, see <http://www.gnu.org/licenses/>.
*/
/*
* Modified by the GLib Team and others 1997-2000. See the AUTHORS
* file for a list of people on the GLib Team. See the ChangeLog
* files for a list of changes. These files are distributed with
* GLib at ftp://ftp.gtk.org/pub/gtk/.
*/
/*
* MT safe
*/
#include "config.h"
#include <dlfcn.h>
#include <glib.h>
/* Perl includes <nlist.h> and <link.h> instead of <dlfcn.h> on some systems? */
/* dlerror() is not implemented on all systems
*/
#ifndef G_MODULE_HAVE_DLERROR
# ifdef __NetBSD__
# define dlerror() g_strerror (errno)
# else /* !__NetBSD__ */
/* could we rely on errno's state here? */
# define dlerror() "unknown dl-error"
# endif /* !__NetBSD__ */
#endif /* G_MODULE_HAVE_DLERROR */
/* some flags are missing on some systems, so we provide
* harmless defaults.
* The Perl sources say, RTLD_LAZY needs to be defined as (1),
* at least for Solaris 1.
*
* Mandatory:
* RTLD_LAZY - resolve undefined symbols as code from the dynamic library
* is executed.
* RTLD_NOW - resolve all undefined symbols before dlopen returns, and fail
* if this cannot be done.
* Optionally:
* RTLD_GLOBAL - the external symbols defined in the library will be made
* available to subsequently loaded libraries.
*/
#ifndef HAVE_RTLD_LAZY
#define RTLD_LAZY 1
#endif /* RTLD_LAZY */
#ifndef HAVE_RTLD_NOW
#define RTLD_NOW 0
#endif /* RTLD_NOW */
/* some systems (OSF1 V5.0) have broken RTLD_GLOBAL linkage */
#ifdef G_MODULE_BROKEN_RTLD_GLOBAL
#undef RTLD_GLOBAL
#undef HAVE_RTLD_GLOBAL
#endif /* G_MODULE_BROKEN_RTLD_GLOBAL */
#ifndef HAVE_RTLD_GLOBAL
#define RTLD_GLOBAL 0
#endif /* RTLD_GLOBAL */
/* According to POSIX.1-2001, dlerror() is not necessarily thread-safe
* (see https://pubs.opengroup.org/onlinepubs/009695399/), and so must be
* called within the same locked section as the dlopen()/dlsym() call which
* may have caused an error.
*
* However, some libc implementations, such as glibc, implement dlerror() using
* thread-local storage, so are thread-safe. As of early 2021:
* - glibc is thread-safe: https://github.com/bminor/glibc/blob/HEAD/dlfcn/libc_dlerror_result.c
* - uclibc-ng is not thread-safe: https://cgit.uclibc-ng.org/cgi/cgit/uclibc-ng.git/tree/ldso/libdl/libdl.c?id=132decd2a043d0ccf799f42bf89f3ae0c11e95d5#n1075
* - Other libc implementations have not been checked, and no problems have
* been reported with them in 10 years, so default to assuming that they
* don’t need additional thread-safety from GLib
*/
#if defined(__UCLIBC__)
G_LOCK_DEFINE_STATIC (errors);
#else
#define DLERROR_IS_THREADSAFE 1
#endif
static void
lock_dlerror (void)
{
#ifndef DLERROR_IS_THREADSAFE
G_LOCK (errors);
#endif
}
static void
unlock_dlerror (void)
{
#ifndef DLERROR_IS_THREADSAFE
G_UNLOCK (errors);
#endif
}
/* This should be called with lock_dlerror() held */
static const gchar *
fetch_dlerror (gboolean replace_null)
{
const gchar *msg = dlerror ();
/* make sure we always return an error message != NULL, if
* expected to do so. */
if (!msg && replace_null)
return "unknown dl-error";
return msg;
}
static gpointer
_g_module_open (const gchar *file_name,
gboolean bind_lazy,
gboolean bind_local,
GError **error)
{
gpointer handle;
lock_dlerror ();
handle = dlopen (file_name,
(bind_local ? 0 : RTLD_GLOBAL) | (bind_lazy ? RTLD_LAZY : RTLD_NOW));
if (!handle)
{
const gchar *message = fetch_dlerror (TRUE);
g_module_set_error (message);
g_set_error_literal (error, G_MODULE_ERROR, G_MODULE_ERROR_FAILED, message);
}
unlock_dlerror ();
return handle;
}
static gpointer
_g_module_self (void)
{
gpointer handle;
/* to query symbols from the program itself, special link options
* are required on some systems.
*/
/* On Android 32 bit (i.e. not __LP64__), dlopen(NULL)
* does not work reliable and generally no symbols are found
* at all. RTLD_DEFAULT works though.
* On Android 64 bit, dlopen(NULL) seems to work but dlsym(handle)
* always returns 'undefined symbol'. Only if RTLD_DEFAULT or
* NULL is given, dlsym returns an appropriate pointer.
*/
lock_dlerror ();
#if defined(__BIONIC__) || defined(__NetBSD__)
handle = RTLD_DEFAULT;
#else
handle = dlopen (NULL, RTLD_GLOBAL | RTLD_LAZY);
#endif
if (!handle)
g_module_set_error (fetch_dlerror (TRUE));
unlock_dlerror ();
return handle;
}
static void
_g_module_close (gpointer handle)
{
#if defined(__BIONIC__) || defined(__NetBSD__)
if (handle != RTLD_DEFAULT)
#endif
{
lock_dlerror ();
if (dlclose (handle) != 0)
g_module_set_error (fetch_dlerror (TRUE));
unlock_dlerror ();
}
}
static gpointer
_g_module_symbol (gpointer handle,
const gchar *symbol_name)
{
gpointer p;
const gchar *msg;
lock_dlerror ();
fetch_dlerror (FALSE);
p = dlsym (handle, symbol_name);
msg = fetch_dlerror (FALSE);
if (msg)
g_module_set_error (msg);
unlock_dlerror ();
return p;
}
static gchar*
_g_module_build_path (const gchar *directory,
const gchar *module_name)
{
if (directory && *directory) {
if (strncmp (module_name, "lib", 3) == 0)
return g_strconcat (directory, "/", module_name, NULL);
else
return g_strconcat (directory, "/lib", module_name, "." G_MODULE_SUFFIX, NULL);
} else if (strncmp (module_name, "lib", 3) == 0)
return g_strdup (module_name);
else
return g_strconcat ("lib", module_name, "." G_MODULE_SUFFIX, NULL);
}
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