Introduce our own shutdown callback mechanism.

Instead of adding stuff to `_shutdown()`, we can now register a shutdown
routine from the respective `init()` function of our modules.

This also has the advantage, that we're sure they're called in reverse
order from how the initialization happened.

I didn't simply use `atexit()` because POSIX says that the number of
possible callbacks is limited (min 32) and I was not sure whether
we will maybe extend this number at one point.

Signed-off-by: Steffen Jaeckel <s@jaeckel.eu>

src/omemo/omemo.c

@@ -116,10 +116,23 @@ static struct omemo_static_data
     GHashTable* fingerprint_ac;
 } omemo_static_data;
 
+static void
+_omemo_close(void)
+{
+    if (omemo_static_data.fingerprint_ac) {
+        g_hash_table_destroy(omemo_static_data.fingerprint_ac);
+        omemo_static_data.fingerprint_ac = NULL;
+    }
+    pthread_mutex_destroy(&omemo_static_data.lock);
+}
+
 void
 omemo_init(void)
 {
     log_info("[OMEMO] initialising");
+
+    prof_add_shutdown_routine(_omemo_close);
+
     if (omemo_crypto_init() != 0) {
         cons_show("Error initializing OMEMO crypto: gcry_check_version() failed");
     }
@@ -131,16 +144,6 @@ omemo_init(void)
     omemo_static_data.fingerprint_ac = g_hash_table_new_full(g_str_hash, g_str_equal, free, (GDestroyNotify)autocomplete_free);
 }
 
-void
-omemo_close(void)
-{
-    if (omemo_static_data.fingerprint_ac) {
-        g_hash_table_destroy(omemo_static_data.fingerprint_ac);
-        omemo_static_data.fingerprint_ac = NULL;
-    }
-    pthread_mutex_destroy(&omemo_static_data.lock);
-}
-
 void
 omemo_on_connect(ProfAccount* account)
 {

src/omemo/omemo.h

@@ -61,7 +61,6 @@ typedef struct omemo_key
 } omemo_key_t;
 
 void omemo_init(void);
-void omemo_close(void);
 void omemo_on_connect(ProfAccount* account);
 void omemo_on_disconnect(void);
 void omemo_generate_crypto_materials(ProfAccount* account);