[glib-networking] gnutls: Fix a crash caused by loading and unloading the module

[Dan Winship <danw src gnome org>]

commit 187a710254b01ed8bd339f2a351de2adbe7c7765
Author: Dan Winship <danw gnome org>
Date:   Mon Nov 29 10:07:37 2010 -0500

    gnutls: Fix a crash caused by loading and unloading the module
    
    If gio-querymodules isn't run to update the cache then gio will need
    to load and unload the module at startup time. This was causing
    crashes in apps that used gcrypt elsewhere, because gcrypt was being
    initialized to use our module's mutex functions, which then no longer
    existed after unloading.
    
    Fix this in two different ways: first, force the module to remain
    resident after gtls_gnutls_init() has been called, and second, don't
    call gtls_gnutls_init() if we're just being called from
    g_io_modules_scan_all_in_directory().
    
    https://bugzilla.gnome.org/show_bug.cgi?id=636052

 tls/gnutls/gtlsbackend-gnutls.c |   22 +++++++++++++++++-----
 1 files changed, 17 insertions(+), 5 deletions(-)
---
diff --git a/tls/gnutls/gtlsbackend-gnutls.c b/tls/gnutls/gtlsbackend-gnutls.c
index fdf081c..9511ae8 100644
--- a/tls/gnutls/gtlsbackend-gnutls.c
+++ b/tls/gnutls/gtlsbackend-gnutls.c
@@ -34,13 +34,11 @@
 #include "gtlsclientconnection-gnutls.h"
 #include "gtlsserverconnection-gnutls.h"
 
-static void gtls_gnutls_init (void);
 static void g_tls_backend_gnutls_interface_init (GTlsBackendInterface *iface);
 
 G_DEFINE_DYNAMIC_TYPE_EXTENDED (GTlsBackendGnutls, g_tls_backend_gnutls, G_TYPE_OBJECT, 0,
 				G_IMPLEMENT_INTERFACE_DYNAMIC (G_TYPE_TLS_BACKEND,
-							       g_tls_backend_gnutls_interface_init);
-				gtls_gnutls_init ();)
+							       g_tls_backend_gnutls_interface_init);)
 
 #if defined(GCRY_THREAD_OPTION_PTHREAD_IMPL) && !defined(G_OS_WIN32)
 GCRY_THREAD_OPTION_PTHREAD_IMPL;
@@ -94,8 +92,8 @@ static struct gcry_thread_cbs gtls_gcry_threads_win32 = {		 \
 
 #endif
 
-static void
-gtls_gnutls_init (void)
+static gpointer
+gtls_gnutls_init (gpointer data)
 {
 #if defined(GCRY_THREAD_OPTION_PTHREAD_IMPL) && !defined(G_OS_WIN32)
   gcry_control (GCRYCTL_SET_THREAD_CBS, &gcry_threads_pthread);
@@ -103,11 +101,25 @@ gtls_gnutls_init (void)
   gcry_control (GCRYCTL_SET_THREAD_CBS, &gtls_gcry_threads_win32);
 #endif
   gnutls_global_init ();
+
+  /* Leak the module to keep it from being unloaded. */
+  g_type_plugin_use (g_type_get_plugin (G_TYPE_TLS_BACKEND_GNUTLS));
+  return NULL;
 }
 
+static GOnce gnutls_inited = G_ONCE_INIT;
+
 static void
 g_tls_backend_gnutls_init (GTlsBackendGnutls *backend)
 {
+  /* Once we call gtls_gnutls_init(), we can't allow the module to be
+   * unloaded, since that would break the pointers to the mutex
+   * functions we set for gcrypt. So we initialize it from here rather
+   * than at class init time so that it doesn't happen unless the app
+   * is actually using TLS (as opposed to just calling
+   * g_io_modules_scan_all_in_directory()).
+   */
+  g_once (&gnutls_inited, gtls_gnutls_init, NULL);
 }
 
 static void