Implement dynamic loading of GnuTLS on Windows.

* lisp/term/w32-win.el (dynamic-library-alist): Add `gnutls'.

* nt/INSTALL: Clarify GnuTLS support.

* src/callproc.c, src/emacs.c: Include lisp.h before src/w32.h, not after.

* src/gnutls.c (Qgnutls_dll): Define.
  (DEF_GNUTLS_FN, LOAD_GNUTLS_FN): New macros.
  (gnutls_*): Declare function pointers.
  (init_gnutls_functions): New function to initialize function pointers.
  (emacs_gnutls_handshake, Fgnutls_error_string, Fgnutls_deinit)
  (emacs_gnutls_global_init, Fgnutls_bye): Use function pointers.
  (emacs_gnutls_record_check_pending, emacs_gnutls_transport_set_errno):
  Wrappers for gnutls_record_check_pending and gnutls_transport_set_errno.
  (emacs_gnutls_write, emacs_gnutls_read)
  (emacs_gnutls_handle_error, Fgnutls_error_fatalp)
  (Fgnutls_available_p): New function.
  (Fgnutls_boot): Call Fgnutls_available_p.  Use function pointers.
  (syms_of_gnutls) <Qgnutls_dll>: Initialize and staticpro it.
  (syms_of_gnutls) <Sgnutls_available_p>: defsubr it.

* src/gnutls.h (GNUTLS_EMACS_ERROR_NOT_LOADED): New macro.
  (emacs_gnutls_write, emacs_gnutls_read): Mark as extern.
  (emacs_gnutls_record_check_pending, emacs_gnutls_transport_set_errno):
  Declare.

* src/w32.c (QCloaded_from, Vlibrary_cache): Define.
  (w32_delayed_load): Move from image.c.  When loading a library, record
  its filename in the :loaded-from property of the library id.
  (globals_of_w32) <QCloaded_from, Vlibrary_cache>:
  Initialize and staticpro them.
  (emacs_gnutls_pull, emacs_gnutls_push): Call emacs_gnutls_* functions.

* src/image.c: Include w32.h.
  (Vimage_type_cache): Delete.
  (syms_of_image) <Vimage_type_cache>: Don't initialize and staticpro it.
  (CACHE_IMAGE_TYPE, Finit_image_library): Use Vlibrary_cache instead.
  (w32_delayed_load): Move to w32.c.

* src/process.c: Include lisp.h before src/w32.h, not after.
  (wait_reading_process_output): Call emacs_gnutls_record_check_pending
  instead of gnutls_record_check_pending.

* src/w32.h (VlibraryCache, QCloaded_from, w32_delayed_load): Declare.

1 files changed, 270 insertions, 52 deletions

diff --git a/src/gnutls.c b/src/gnutls.c
index fd970910d24..7e821ccd41d 100644
--- a/src/gnutls.c
+++ b/src/gnutls.c
@@ -34,6 +34,7 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 static int
 emacs_gnutls_handle_error (gnutls_session_t, int err);
 
+static Lisp_Object Qgnutls_dll;
 static Lisp_Object Qgnutls_log_level;
 static Lisp_Object Qgnutls_code;
 static Lisp_Object Qgnutls_anon, Qgnutls_x509pki;
@@ -56,6 +57,181 @@ static Lisp_Object Qgnutls_bootprop_verify_hostname_error;
 /* Callback keys for `gnutls-boot'.  Unused currently.  */
 static Lisp_Object Qgnutls_bootprop_callbacks_verify;
 
+static void gnutls_log_function (int, const char *);
+static void gnutls_log_function2 (int, const char*, const char*);
+
+
+#ifdef WINDOWSNT
+
+/* Macro for defining functions that will be loaded from the GnuTLS DLL.  */
+#define DEF_GNUTLS_FN(rettype,func,args) rettype (FAR CDECL *fn_##func)args
+
+/* Macro for loading GnuTLS functions from the library.  */
+#define LOAD_GNUTLS_FN(lib,func) {					\
+    fn_##func = (void *) GetProcAddress (lib, #func);			\
+    if (!fn_##func) return 0;						\
+  }
+
+DEF_GNUTLS_FN (gnutls_alert_description_t, gnutls_alert_get,
+               (gnutls_session_t));
+DEF_GNUTLS_FN (const char *, gnutls_alert_get_name,
+               (gnutls_alert_description_t));
+DEF_GNUTLS_FN (int, gnutls_alert_send_appropriate, (gnutls_session_t, int));
+DEF_GNUTLS_FN (int, gnutls_anon_allocate_client_credentials,
+               (gnutls_anon_client_credentials_t *));
+DEF_GNUTLS_FN (void, gnutls_anon_free_client_credentials,
+               (gnutls_anon_client_credentials_t));
+DEF_GNUTLS_FN (int, gnutls_bye, (gnutls_session_t, gnutls_close_request_t));
+DEF_GNUTLS_FN (int, gnutls_certificate_allocate_credentials,
+               (gnutls_certificate_credentials_t *));
+DEF_GNUTLS_FN (void, gnutls_certificate_free_credentials,
+               (gnutls_certificate_credentials_t));
+DEF_GNUTLS_FN (const gnutls_datum_t *, gnutls_certificate_get_peers,
+               (gnutls_session_t, unsigned int *));
+DEF_GNUTLS_FN (void, gnutls_certificate_set_verify_flags,
+               (gnutls_certificate_credentials_t, unsigned int));
+DEF_GNUTLS_FN (int, gnutls_certificate_set_x509_crl_file,
+               (gnutls_certificate_credentials_t, const char *,
+                gnutls_x509_crt_fmt_t));
+DEF_GNUTLS_FN (int, gnutls_certificate_set_x509_key_file,
+               (gnutls_certificate_credentials_t, const char *, const char *,
+                gnutls_x509_crt_fmt_t));
+DEF_GNUTLS_FN (int, gnutls_certificate_set_x509_trust_file,
+               (gnutls_certificate_credentials_t, const char *,
+                gnutls_x509_crt_fmt_t));
+DEF_GNUTLS_FN (gnutls_certificate_type_t, gnutls_certificate_type_get,
+               (gnutls_session_t));
+DEF_GNUTLS_FN (int, gnutls_certificate_verify_peers2,
+               (gnutls_session_t, unsigned int *));
+DEF_GNUTLS_FN (int, gnutls_credentials_set,
+               (gnutls_session_t, gnutls_credentials_type_t, void *));
+DEF_GNUTLS_FN (void, gnutls_deinit, (gnutls_session_t));
+DEF_GNUTLS_FN (int, gnutls_error_is_fatal, (int));
+DEF_GNUTLS_FN (int, gnutls_global_init, (void));
+DEF_GNUTLS_FN (void, gnutls_global_set_log_function, (gnutls_log_func));
+DEF_GNUTLS_FN (void, gnutls_global_set_log_level, (int));
+DEF_GNUTLS_FN (int, gnutls_handshake, (gnutls_session_t));
+DEF_GNUTLS_FN (int, gnutls_init, (gnutls_session_t *, gnutls_connection_end_t));
+DEF_GNUTLS_FN (int, gnutls_priority_set_direct,
+               (gnutls_session_t, const char *, const char **));
+DEF_GNUTLS_FN (size_t, gnutls_record_check_pending, (gnutls_session_t));
+DEF_GNUTLS_FN (ssize_t, gnutls_record_recv, (gnutls_session_t, void *, size_t));
+DEF_GNUTLS_FN (ssize_t, gnutls_record_send,
+               (gnutls_session_t, const void *, size_t));
+DEF_GNUTLS_FN (const char *, gnutls_strerror, (int));
+DEF_GNUTLS_FN (void, gnutls_transport_set_errno, (gnutls_session_t, int));
+DEF_GNUTLS_FN (void, gnutls_transport_set_lowat, (gnutls_session_t, int));
+DEF_GNUTLS_FN (void, gnutls_transport_set_ptr2,
+               (gnutls_session_t, gnutls_transport_ptr_t,
+                gnutls_transport_ptr_t));
+DEF_GNUTLS_FN (void, gnutls_transport_set_pull_function,
+               (gnutls_session_t, gnutls_pull_func));
+DEF_GNUTLS_FN (void, gnutls_transport_set_push_function,
+               (gnutls_session_t, gnutls_push_func));
+DEF_GNUTLS_FN (int, gnutls_x509_crt_check_hostname,
+               (gnutls_x509_crt_t, const char *));
+DEF_GNUTLS_FN (void, gnutls_x509_crt_deinit, (gnutls_x509_crt_t));
+DEF_GNUTLS_FN (int, gnutls_x509_crt_import,
+               (gnutls_x509_crt_t, const gnutls_datum_t *,
+                gnutls_x509_crt_fmt_t));
+DEF_GNUTLS_FN (int, gnutls_x509_crt_init, (gnutls_x509_crt_t *));
+
+static int
+init_gnutls_functions (Lisp_Object libraries)
+{
+  HMODULE library;
+
+  if (!(library = w32_delayed_load (libraries, Qgnutls_dll)))
+    {
+      GNUTLS_LOG (1, 1, "GnuTLS library not found");
+      return 0;
+    }
+
+  LOAD_GNUTLS_FN (library, gnutls_alert_get);
+  LOAD_GNUTLS_FN (library, gnutls_alert_get_name);
+  LOAD_GNUTLS_FN (library, gnutls_alert_send_appropriate);
+  LOAD_GNUTLS_FN (library, gnutls_anon_allocate_client_credentials);
+  LOAD_GNUTLS_FN (library, gnutls_anon_free_client_credentials);
+  LOAD_GNUTLS_FN (library, gnutls_bye);
+  LOAD_GNUTLS_FN (library, gnutls_certificate_allocate_credentials);
+  LOAD_GNUTLS_FN (library, gnutls_certificate_free_credentials);
+  LOAD_GNUTLS_FN (library, gnutls_certificate_get_peers);
+  LOAD_GNUTLS_FN (library, gnutls_certificate_set_verify_flags);
+  LOAD_GNUTLS_FN (library, gnutls_certificate_set_x509_crl_file);
+  LOAD_GNUTLS_FN (library, gnutls_certificate_set_x509_key_file);
+  LOAD_GNUTLS_FN (library, gnutls_certificate_set_x509_trust_file);
+  LOAD_GNUTLS_FN (library, gnutls_certificate_type_get);
+  LOAD_GNUTLS_FN (library, gnutls_certificate_verify_peers2);
+  LOAD_GNUTLS_FN (library, gnutls_credentials_set);
+  LOAD_GNUTLS_FN (library, gnutls_deinit);
+  LOAD_GNUTLS_FN (library, gnutls_error_is_fatal);
+  LOAD_GNUTLS_FN (library, gnutls_global_init);
+  LOAD_GNUTLS_FN (library, gnutls_global_set_log_function);
+  LOAD_GNUTLS_FN (library, gnutls_global_set_log_level);
+  LOAD_GNUTLS_FN (library, gnutls_handshake);
+  LOAD_GNUTLS_FN (library, gnutls_init);
+  LOAD_GNUTLS_FN (library, gnutls_priority_set_direct);
+  LOAD_GNUTLS_FN (library, gnutls_record_check_pending);
+  LOAD_GNUTLS_FN (library, gnutls_record_recv);
+  LOAD_GNUTLS_FN (library, gnutls_record_send);
+  LOAD_GNUTLS_FN (library, gnutls_strerror);
+  LOAD_GNUTLS_FN (library, gnutls_transport_set_errno);
+  LOAD_GNUTLS_FN (library, gnutls_transport_set_lowat);
+  LOAD_GNUTLS_FN (library, gnutls_transport_set_ptr2);
+  LOAD_GNUTLS_FN (library, gnutls_transport_set_pull_function);
+  LOAD_GNUTLS_FN (library, gnutls_transport_set_push_function);
+  LOAD_GNUTLS_FN (library, gnutls_x509_crt_check_hostname);
+  LOAD_GNUTLS_FN (library, gnutls_x509_crt_deinit);
+  LOAD_GNUTLS_FN (library, gnutls_x509_crt_import);
+  LOAD_GNUTLS_FN (library, gnutls_x509_crt_init);
+
+  GNUTLS_LOG2 (1, 1, "GnuTLS library loaded:",
+               SDATA (Fget (Qgnutls_dll, QCloaded_from)));
+  return 1;
+}
+
+#else /* !WINDOWSNT */
+
+#define fn_gnutls_alert_get			gnutls_alert_get
+#define fn_gnutls_alert_get_name		gnutls_alert_get_name
+#define fn_gnutls_alert_send_appropriate	gnutls_alert_send_appropriate
+#define fn_gnutls_anon_allocate_client_credentials gnutls_anon_allocate_client_credentials
+#define fn_gnutls_anon_free_client_credentials	gnutls_anon_free_client_credentials
+#define fn_gnutls_bye				gnutls_bye
+#define fn_gnutls_certificate_allocate_credentials gnutls_certificate_allocate_credentials
+#define fn_gnutls_certificate_free_credentials	gnutls_certificate_free_credentials
+#define fn_gnutls_certificate_get_peers		gnutls_certificate_get_peers
+#define fn_gnutls_certificate_set_verify_flags	gnutls_certificate_set_verify_flags
+#define fn_gnutls_certificate_set_x509_crl_file	gnutls_certificate_set_x509_crl_file
+#define fn_gnutls_certificate_set_x509_trust_file gnutls_certificate_set_x509_trust_file
+#define fn_gnutls_certificate_type_get		gnutls_certificate_type_get
+#define fn_gnutls_certificate_verify_peers2	gnutls_certificate_verify_peers2
+#define fn_gnutls_credentials_set		gnutls_credentials_set
+#define fn_gnutls_deinit			gnutls_deinit
+#define fn_gnutls_error_is_fatal		gnutls_error_is_fatal
+#define fn_gnutls_global_init			gnutls_global_init
+#define fn_gnutls_global_set_log_function	gnutls_global_set_log_function
+#define fn_gnutls_global_set_log_level		gnutls_global_set_log_level
+#define fn_gnutls_handshake			gnutls_handshake
+#define fn_gnutls_init				gnutls_init
+#define fn_gnutls_priority_set_direct		gnutls_priority_set_direct
+#define fn_gnutls_record_check_pending		gnutls_record_check_pending
+#define fn_gnutls_record_recv			gnutls_record_recv
+#define fn_gnutls_record_send			gnutls_record_send
+#define fn_gnutls_strerror			gnutls_strerror
+#define fn_gnutls_transport_set_errno		gnutls_transport_set_errno
+#define fn_gnutls_transport_set_lowat		gnutls_transport_set_lowat
+#define fn_gnutls_transport_set_ptr2		gnutls_transport_set_ptr2
+#define fn_gnutls_transport_set_pull_function	gnutls_transport_set_pull_function
+#define fn_gnutls_transport_set_push_function	gnutls_transport_set_push_function
+#define fn_gnutls_x509_crt_check_hostname	gnutls_x509_crt_check_hostname
+#define fn_gnutls_x509_crt_deinit		gnutls_x509_crt_deinit
+#define fn_gnutls_x509_crt_import		gnutls_x509_crt_import
+#define fn_gnutls_x509_crt_init			gnutls_x509_crt_init
+
+#endif /* !WINDOWSNT */
+
+
 static void
 gnutls_log_function (int level, const char* string)
 {
@@ -83,11 +259,11 @@ emacs_gnutls_handshake (struct Lisp_Process *proc)
       /* On W32 we cannot transfer socket handles between different runtime
          libraries, so we tell GnuTLS to use our special push/pull
          functions.  */
-      gnutls_transport_set_ptr2 (state,
-                                 (gnutls_transport_ptr_t) proc,
-                                 (gnutls_transport_ptr_t) proc);
-      gnutls_transport_set_push_function (state, &emacs_gnutls_push);
-      gnutls_transport_set_pull_function (state, &emacs_gnutls_pull);
+      fn_gnutls_transport_set_ptr2 (state,
+                                    (gnutls_transport_ptr_t) proc,
+                                    (gnutls_transport_ptr_t) proc);
+      fn_gnutls_transport_set_push_function (state, &emacs_gnutls_push);
+      fn_gnutls_transport_set_pull_function (state, &emacs_gnutls_pull);
 
       /* For non blocking sockets or other custom made pull/push
          functions the gnutls_transport_set_lowat must be called, with
@@ -96,14 +272,14 @@ emacs_gnutls_handshake (struct Lisp_Process *proc)
          (Note: this is probably not strictly necessary as the lowat
           value is only used when no custom pull/push functions are
           set.)  */
-      gnutls_transport_set_lowat (state, 0);
+      fn_gnutls_transport_set_lowat (state, 0);
 #else
       /* This is how GnuTLS takes sockets: as file descriptors passed
          in.  For an Emacs process socket, infd and outfd are the
          same but we use this two-argument version for clarity.  */
-      gnutls_transport_set_ptr2 (state,
-        			 (gnutls_transport_ptr_t) (long) proc->infd,
-        			 (gnutls_transport_ptr_t) (long) proc->outfd);
+      fn_gnutls_transport_set_ptr2 (state,
+                                    (gnutls_transport_ptr_t) (long) proc->infd,
+                                    (gnutls_transport_ptr_t) (long) proc->outfd);
 #endif
 
       proc->gnutls_initstage = GNUTLS_STAGE_TRANSPORT_POINTERS_SET;
@@ -111,10 +287,10 @@ emacs_gnutls_handshake (struct Lisp_Process *proc)
 
   do
     {
-      ret = gnutls_handshake (state);
+      ret = fn_gnutls_handshake (state);
       emacs_gnutls_handle_error (state, ret);
     }
-  while (ret < 0 && gnutls_error_is_fatal (ret) == 0);
+  while (ret < 0 && fn_gnutls_error_is_fatal (ret) == 0);
 
   proc->gnutls_initstage = GNUTLS_STAGE_HANDSHAKE_TRIED;
 
@@ -125,11 +301,23 @@ emacs_gnutls_handshake (struct Lisp_Process *proc)
     }
   else
     {
-        gnutls_alert_send_appropriate (state, ret);
+      fn_gnutls_alert_send_appropriate (state, ret);
     }
   return ret;
 }
 
+int
+emacs_gnutls_record_check_pending (gnutls_session_t state)
+{
+  return fn_gnutls_record_check_pending (state);
+}
+
+void
+emacs_gnutls_transport_set_errno (gnutls_session_t state, int err)
+{
+  fn_gnutls_transport_set_errno (state, err);
+}
+
 EMACS_INT
 emacs_gnutls_write (int fildes, struct Lisp_Process *proc, const char *buf,
                     EMACS_INT nbyte)
@@ -152,7 +340,7 @@ emacs_gnutls_write (int fildes, struct Lisp_Process *proc, const char *buf,
 
   while (nbyte > 0)
     {
-      rtnval = gnutls_write (state, buf, nbyte);
+      rtnval = fn_gnutls_record_send (state, buf, nbyte);
 
       if (rtnval < 0)
         {
@@ -183,7 +371,7 @@ emacs_gnutls_read (int fildes, struct Lisp_Process *proc, char *buf,
       emacs_gnutls_handshake (proc);
       return -1;
     }
-  rtnval = gnutls_read (state, buf, nbyte);
+  rtnval = fn_gnutls_record_recv (state, buf, nbyte);
   if (rtnval >= 0)
     return rtnval;
   else if (emacs_gnutls_handle_error (state, rtnval) == 0)
@@ -215,11 +403,11 @@ emacs_gnutls_handle_error (gnutls_session_t session, int err)
 
   /* TODO: use gnutls-error-fatalp and gnutls-error-string.  */
 
-  str = gnutls_strerror (err);
+  str = fn_gnutls_strerror (err);
   if (!str)
     str = "unknown";
 
-  if (gnutls_error_is_fatal (err))
+  if (fn_gnutls_error_is_fatal (err))
     {
       ret = err;
       GNUTLS_LOG2 (0, max_log_level, "fatal error:", str);
@@ -234,9 +422,9 @@ emacs_gnutls_handle_error (gnutls_session_t session, int err)
   if (err == GNUTLS_E_WARNING_ALERT_RECEIVED
       || err == GNUTLS_E_FATAL_ALERT_RECEIVED)
     {
-      int alert = gnutls_alert_get (session);
+      int alert = fn_gnutls_alert_get (session);
       int level = (err == GNUTLS_E_FATAL_ALERT_RECEIVED) ? 0 : 1;
-      str = gnutls_alert_get_name (alert);
+      str = fn_gnutls_alert_get_name (alert);
       if (!str)
 	str = "unknown";
 
@@ -314,7 +502,7 @@ usage: (gnutls-error-fatalp ERROR)  */)
   if (!NUMBERP (err))
     error ("Not an error symbol or code");
 
-  if (0 == gnutls_error_is_fatal (XINT (err)))
+  if (0 == fn_gnutls_error_is_fatal (XINT (err)))
     return Qnil;
 
   return Qt;
@@ -346,7 +534,7 @@ usage: (gnutls-error-string ERROR)  */)
   if (!NUMBERP (err))
     return build_string ("Not an error symbol or code");
 
-  return build_string (gnutls_strerror (XINT (err)));
+  return build_string (fn_gnutls_strerror (XINT (err)));
 }
 
 DEFUN ("gnutls-deinit", Fgnutls_deinit, Sgnutls_deinit, 1, 1, 0,
@@ -361,13 +549,34 @@ See also `gnutls-init'.  */)
 
   if (GNUTLS_INITSTAGE (proc) >= GNUTLS_STAGE_INIT)
     {
-      gnutls_deinit (state);
+      fn_gnutls_deinit (state);
       GNUTLS_INITSTAGE (proc) = GNUTLS_STAGE_INIT - 1;
     }
 
   return Qt;
 }
 
+DEFUN ("gnutls-available-p", Fgnutls_available_p, Sgnutls_available_p, 0, 0, 0,
+       doc: /* Return t if GnuTLS is available in this instance of Emacs.  */)
+     (void)
+{
+#ifdef WINDOWSNT
+  Lisp_Object found = Fassq (Qgnutls_dll, Vlibrary_cache);
+  if (CONSP (found))
+    return XCDR (found);
+  else
+    {
+      Lisp_Object status;
+      status = init_gnutls_functions (Vdynamic_library_alist) ? Qt : Qnil;
+      Vlibrary_cache = Fcons (Fcons (Qgnutls_dll, status), Vlibrary_cache);
+      return status;
+    }
+#else
+  return Qt;
+#endif
+}
+
+
 /* Initializes global GnuTLS state to defaults.
 Call `gnutls-global-deinit' when GnuTLS usage is no longer needed.
 Returns zero on success.  */
@@ -377,8 +586,7 @@ emacs_gnutls_global_init (void)
   int ret = GNUTLS_E_SUCCESS;
 
   if (!gnutls_global_initialized)
-    ret = gnutls_global_init ();
-
+    ret = fn_gnutls_global_init ();
   gnutls_global_initialized = 1;
 
   return gnutls_make_error (ret);
@@ -488,6 +696,12 @@ one trustfile (usually a CA bundle).  */)
   CHECK_SYMBOL (type);
   CHECK_LIST (proplist);
 
+  if (NILP (Fgnutls_available_p ()))
+    {
+      error ("GnuTLS not available");
+      return gnutls_make_error (GNUTLS_EMACS_ERROR_NOT_LOADED);
+    }
+
   hostname              = Fplist_get (proplist, Qgnutls_bootprop_hostname);
   priority_string       = Fplist_get (proplist, Qgnutls_bootprop_priority);
   trustfiles            = Fplist_get (proplist, Qgnutls_bootprop_trustfiles);
@@ -509,8 +723,8 @@ one trustfile (usually a CA bundle).  */)
 
   if (NUMBERP (loglevel))
     {
-      gnutls_global_set_log_function (gnutls_log_function);
-      gnutls_global_set_log_level (XINT (loglevel));
+      fn_gnutls_global_set_log_function (gnutls_log_function);
+      fn_gnutls_global_set_log_level (XINT (loglevel));
       max_log_level = XINT (loglevel);
       XPROCESS (proc)->gnutls_log_level = max_log_level;
     }
@@ -529,13 +743,13 @@ one trustfile (usually a CA bundle).  */)
 	{
           GNUTLS_LOG (2, max_log_level, "deallocating x509 credentials");
           x509_cred = XPROCESS (proc)->gnutls_x509_cred;
-          gnutls_certificate_free_credentials (x509_cred);
+          fn_gnutls_certificate_free_credentials (x509_cred);
 	}
       else if (EQ (type, Qgnutls_anon))
 	{
           GNUTLS_LOG (2, max_log_level, "deallocating anon credentials");
           anon_cred = XPROCESS (proc)->gnutls_anon_cred;
-          gnutls_anon_free_client_credentials (anon_cred);
+          fn_gnutls_anon_free_client_credentials (anon_cred);
 	}
       else
 	{
@@ -558,7 +772,7 @@ one trustfile (usually a CA bundle).  */)
     {
       GNUTLS_LOG (2, max_log_level, "allocating x509 credentials");
       x509_cred = XPROCESS (proc)->gnutls_x509_cred;
-      if (gnutls_certificate_allocate_credentials (&x509_cred) < 0)
+      if (fn_gnutls_certificate_allocate_credentials (&x509_cred) < 0)
         memory_full ();
 
       if (NUMBERP (verify_flags))
@@ -576,13 +790,13 @@ one trustfile (usually a CA bundle).  */)
           /* The default is already GNUTLS_VERIFY_ALLOW_X509_V1_CA_CRT.  */
           GNUTLS_LOG (2, max_log_level, "ignoring invalid verify-flags");
         }
-      gnutls_certificate_set_verify_flags (x509_cred, gnutls_verify_flags);
+      fn_gnutls_certificate_set_verify_flags (x509_cred, gnutls_verify_flags);
     }
   else if (EQ (type, Qgnutls_anon))
     {
       GNUTLS_LOG (2, max_log_level, "allocating anon credentials");
       anon_cred = XPROCESS (proc)->gnutls_anon_cred;
-      if (gnutls_anon_allocate_client_credentials (&anon_cred) < 0)
+      if (fn_gnutls_anon_allocate_client_credentials (&anon_cred) < 0)
         memory_full ();
     }
   else
@@ -605,7 +819,7 @@ one trustfile (usually a CA bundle).  */)
             {
               GNUTLS_LOG2 (1, max_log_level, "setting the trustfile: ",
                            SSDATA (trustfile));
-              ret = gnutls_certificate_set_x509_trust_file
+              ret = fn_gnutls_certificate_set_x509_trust_file
                 (x509_cred,
                  SSDATA (trustfile),
                  file_format);
@@ -627,7 +841,7 @@ one trustfile (usually a CA bundle).  */)
             {
               GNUTLS_LOG2 (1, max_log_level, "setting the CRL file: ",
                            SSDATA (crlfile));
-              ret = gnutls_certificate_set_x509_crl_file
+              ret = fn_gnutls_certificate_set_x509_crl_file
                 (x509_cred,
                  SSDATA (crlfile),
                  file_format);
@@ -652,7 +866,7 @@ one trustfile (usually a CA bundle).  */)
                            SSDATA (keyfile));
               GNUTLS_LOG2 (1, max_log_level, "setting the client cert file: ",
                            SSDATA (certfile));
-              ret = gnutls_certificate_set_x509_key_file
+              ret = fn_gnutls_certificate_set_x509_key_file
                 (x509_cred,
                  SSDATA (certfile),
                  SSDATA (keyfile),
@@ -685,7 +899,7 @@ one trustfile (usually a CA bundle).  */)
 
   GNUTLS_LOG (1, max_log_level, "gnutls_init");
 
-  ret = gnutls_init (&state, GNUTLS_CLIENT);
+  ret = fn_gnutls_init (&state, GNUTLS_CLIENT);
 
   if (ret < GNUTLS_E_SUCCESS)
     return gnutls_make_error (ret);
@@ -708,9 +922,9 @@ one trustfile (usually a CA bundle).  */)
 
   GNUTLS_LOG (1, max_log_level, "setting the priority string");
 
-  ret = gnutls_priority_set_direct (state,
-				    priority_string_ptr,
-				    NULL);
+  ret = fn_gnutls_priority_set_direct (state,
+                                       priority_string_ptr,
+                                       NULL);
 
   if (ret < GNUTLS_E_SUCCESS)
     return gnutls_make_error (ret);
@@ -719,11 +933,11 @@ one trustfile (usually a CA bundle).  */)
 
   if (EQ (type, Qgnutls_x509pki))
     {
-      ret = gnutls_cred_set (state, GNUTLS_CRD_CERTIFICATE, x509_cred);
+      ret = fn_gnutls_credentials_set (state, GNUTLS_CRD_CERTIFICATE, x509_cred);
     }
   else if (EQ (type, Qgnutls_anon))
     {
-      ret = gnutls_cred_set (state, GNUTLS_CRD_ANON, anon_cred);
+      ret = fn_gnutls_credentials_set (state, GNUTLS_CRD_ANON, anon_cred);
     }
   else
     {
@@ -751,7 +965,7 @@ one trustfile (usually a CA bundle).  */)
      check of the certificate's hostname with
      gnutls_x509_crt_check_hostname() against :hostname.  */
 
-  ret = gnutls_certificate_verify_peers2 (state, &peer_verification);
+  ret = fn_gnutls_certificate_verify_peers2 (state, &peer_verification);
 
   if (ret < GNUTLS_E_SUCCESS)
     return gnutls_make_error (ret);
@@ -802,15 +1016,15 @@ one trustfile (usually a CA bundle).  */)
   /* Up to here the process is the same for X.509 certificates and
      OpenPGP keys.  From now on X.509 certificates are assumed.  This
      can be easily extended to work with openpgp keys as well.  */
-  if (gnutls_certificate_type_get (state) == GNUTLS_CRT_X509)
+  if (fn_gnutls_certificate_type_get (state) == GNUTLS_CRT_X509)
     {
-      ret = gnutls_x509_crt_init (&gnutls_verify_cert);
+      ret = fn_gnutls_x509_crt_init (&gnutls_verify_cert);
 
       if (ret < GNUTLS_E_SUCCESS)
         return gnutls_make_error (ret);
 
       gnutls_verify_cert_list =
-        gnutls_certificate_get_peers (state, &gnutls_verify_cert_list_size);
+        fn_gnutls_certificate_get_peers (state, &gnutls_verify_cert_list_size);
 
       if (NULL == gnutls_verify_cert_list)
         {
@@ -818,17 +1032,17 @@ one trustfile (usually a CA bundle).  */)
         }
 
       /* We only check the first certificate in the given chain.  */
-      ret = gnutls_x509_crt_import (gnutls_verify_cert,
-                                    &gnutls_verify_cert_list[0],
-                                    GNUTLS_X509_FMT_DER);
+      ret = fn_gnutls_x509_crt_import (gnutls_verify_cert,
+                                       &gnutls_verify_cert_list[0],
+                                       GNUTLS_X509_FMT_DER);
 
       if (ret < GNUTLS_E_SUCCESS)
         {
-          gnutls_x509_crt_deinit (gnutls_verify_cert);
+          fn_gnutls_x509_crt_deinit (gnutls_verify_cert);
           return gnutls_make_error (ret);
         }
 
-      if (!gnutls_x509_crt_check_hostname (gnutls_verify_cert, c_hostname))
+      if (!fn_gnutls_x509_crt_check_hostname (gnutls_verify_cert, c_hostname))
         {
           if (NILP (verify_hostname_error))
             {
@@ -837,13 +1051,13 @@ one trustfile (usually a CA bundle).  */)
             }
           else
             {
-              gnutls_x509_crt_deinit (gnutls_verify_cert);
+              fn_gnutls_x509_crt_deinit (gnutls_verify_cert);
               error ("The x509 certificate does not match \"%s\"",
                      c_hostname);
             }
         }
 
-      gnutls_x509_crt_deinit (gnutls_verify_cert);
+      fn_gnutls_x509_crt_deinit (gnutls_verify_cert);
     }
 
   return gnutls_make_error (ret);
@@ -872,8 +1086,8 @@ This function may also return `gnutls-e-again', or
 
   state = XPROCESS (proc)->gnutls_state;
 
-  ret = gnutls_bye (state,
-                    NILP (cont) ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
+  ret = fn_gnutls_bye (state,
+                       NILP (cont) ? GNUTLS_SHUT_RDWR : GNUTLS_SHUT_WR);
 
   return gnutls_make_error (ret);
 }
@@ -883,6 +1097,9 @@ syms_of_gnutls (void)
 {
   gnutls_global_initialized = 0;
 
+  Qgnutls_dll = intern_c_string ("gnutls");
+  staticpro (&Qgnutls_dll);
+
   Qgnutls_log_level = intern_c_string ("gnutls-log-level");
   staticpro (&Qgnutls_log_level);
 
@@ -956,6 +1173,7 @@ syms_of_gnutls (void)
   defsubr (&Sgnutls_boot);
   defsubr (&Sgnutls_deinit);
   defsubr (&Sgnutls_bye);
+  defsubr (&Sgnutls_available_p);
 }
 
 #endif /* HAVE_GNUTLS */