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diff --git a/libguile/extensions.c b/libguile/extensions.c
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+/* extensions.c - registering and loading extensions.
+
+ Copyright 2001,2006,2009-2011,2018
+ Free Software Foundation, Inc.
+
+ This file is part of Guile.
+
+ Guile 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 3 of the License, or
+ (at your option) any later version.
+
+ Guile 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 Guile. If not, see
+ <https://www.gnu.org/licenses/>. */
+
+#ifdef HAVE_CONFIG_H
+# include <config.h>
+#endif
+
+#include <string.h>
+
+#include "dynl.h"
+#include "dynwind.h"
+#include "gc.h"
+#include "gsubr.h"
+#include "strings.h"
+#include "threads.h"
+
+#include "extensions.h"
+
+
+typedef struct extension_t
+{
+ struct extension_t *next;
+ const char *lib;
+ const char *init;
+ void (*func)(void *);
+ void *data;
+} extension_t;
+
+static extension_t *registered_extensions = NULL;
+static scm_i_pthread_mutex_t ext_lock = SCM_I_PTHREAD_MUTEX_INITIALIZER;
+
+/* Register a LIB/INIT pair for use by `scm_load_extension'. LIB is
+ allowed to be NULL and then only INIT is used to identify the
+ registered entry. This is useful when you don't know the library
+ name (which isn't really relevant anyway in a completely linked
+ program) and you are sure that INIT is unique (which it must be for
+ static linking). Hmm, given this reasoning, what use is LIB
+ anyway?
+*/
+
+void
+scm_c_register_extension (const char *lib, const char *init,
+ void (*func) (void *), void *data)
+{
+ extension_t *ext = scm_malloc (sizeof(extension_t));
+ if (lib)
+ ext->lib = scm_strdup (lib);
+ else
+ ext->lib = NULL;
+ ext->init = scm_strdup (init);
+ ext->func = func;
+ ext->data = data;
+
+ scm_i_pthread_mutex_lock (&ext_lock);
+ ext->next = registered_extensions;
+ registered_extensions = ext;
+ scm_i_pthread_mutex_unlock (&ext_lock);
+}
+
+static void
+load_extension (SCM lib, SCM init)
+{
+ extension_t *head;
+
+ scm_i_pthread_mutex_lock (&ext_lock);
+ head = registered_extensions;
+ scm_i_pthread_mutex_unlock (&ext_lock);
+
+ /* Search the registry. */
+ if (head != NULL)
+ {
+ extension_t *ext;
+ char *clib, *cinit;
+ int found = 0;
+
+ scm_dynwind_begin (0);
+
+ clib = scm_to_locale_string (lib);
+ scm_dynwind_free (clib);
+ cinit = scm_to_locale_string (init);
+ scm_dynwind_free (cinit);
+
+ for (ext = head; ext; ext = ext->next)
+ if ((ext->lib == NULL || !strcmp (ext->lib, clib))
+ && !strcmp (ext->init, cinit))
+ {
+ ext->func (ext->data);
+ found = 1;
+ break;
+ }
+
+ scm_dynwind_end ();
+
+ if (found)
+ return;
+ }
+
+ /* Dynamically link the library. */
+#if HAVE_MODULES
+ scm_dynamic_call (init, scm_dynamic_link (lib));
+#else
+ scm_misc_error ("load-extension",
+ "extension ~S:~S not registered and dynamic-link disabled",
+ scm_list_2 (init, lib));
+#endif
+}
+
+void
+scm_c_load_extension (const char *lib, const char *init)
+{
+ load_extension (scm_from_locale_string (lib), scm_from_locale_string (init));
+}
+
+SCM_DEFINE (scm_load_extension, "load-extension", 2, 0, 0,
+ (SCM lib, SCM init),
+ "Load and initialize the extension designated by LIB and INIT.\n"
+ "When there is no pre-registered function for LIB/INIT, this is\n"
+ "equivalent to\n"
+ "\n"
+ "@lisp\n"
+ "(dynamic-call INIT (dynamic-link LIB))\n"
+ "@end lisp\n"
+ "\n"
+ "When there is a pre-registered function, that function is called\n"
+ "instead.\n"
+ "\n"
+ "Normally, there is no pre-registered function. This option exists\n"
+ "only for situations where dynamic linking is unavailable or unwanted.\n"
+ "In that case, you would statically link your program with the desired\n"
+ "library, and register its init function right after Guile has been\n"
+ "initialized.\n"
+ "\n"
+ "LIB should be a string denoting a shared library without any file type\n"
+ "suffix such as \".so\". The suffix is provided automatically. It\n"
+ "should also not contain any directory components. Libraries that\n"
+ "implement Guile Extensions should be put into the normal locations for\n"
+ "shared libraries. We recommend to use the naming convention\n"
+ "libguile-bla-blum for a extension related to a module `(bla blum)'.\n"
+ "\n"
+ "The normal way for a extension to be used is to write a small Scheme\n"
+ "file that defines a module, and to load the extension into this\n"
+ "module. When the module is auto-loaded, the extension is loaded as\n"
+ "well. For example,\n"
+ "\n"
+ "@lisp\n"
+ "(define-module (bla blum))\n"
+ "\n"
+ "(load-extension \"libguile-bla-blum\" \"bla_init_blum\")\n"
+ "@end lisp")
+#define FUNC_NAME s_scm_load_extension
+{
+ load_extension (lib, init);
+ return SCM_UNSPECIFIED;
+}
+#undef FUNC_NAME
+
+void
+scm_init_extensions ()
+{
+#include "extensions.x"
+}