lib: make glib initialization thread-safe

In principle this could be done without depending on C++11 features,
but these features should be available since gcc 4.8.1, and this
localized usage is easy to replace if it turns out to be problematic
for portability.

lib/Makefile.local

@@ -62,7 +62,8 @@ libnotmuch_cxx_srcs =		\
 	$(dir)/thread-fp.cc     \
 	$(dir)/features.cc	\
 	$(dir)/prefix.cc	\
-	$(dir)/open.cc
+	$(dir)/open.cc		\
+	$(dir)/init.cc
 
 libnotmuch_modules := $(libnotmuch_c_srcs:.c=.o) $(libnotmuch_cxx_srcs:.cc=.o)
 

lib/index.cc

@@ -148,8 +148,6 @@ notmuch_filter_discard_non_term_class_init (NotmuchFilterDiscardNonTermClass *kl
     GObjectClass *object_class = G_OBJECT_CLASS (klass);
     GMimeFilterClass *filter_class = GMIME_FILTER_CLASS (klass);
 
-    parent_class = (GMimeFilterClass *) g_type_class_ref (GMIME_TYPE_FILTER);
-
     object_class->finalize = notmuch_filter_discard_non_term_finalize;
 
     filter_class->copy = filter_copy;
@@ -240,14 +238,9 @@ filter_reset (GMimeFilter *gmime_filter)
  *
  * Returns: a new #NotmuchFilterDiscardNonTerm filter.
  **/
-static GMimeFilter *
-notmuch_filter_discard_non_term_new (GMimeContentType *content_type)
-{
-    static GType type = 0;
-    NotmuchFilterDiscardNonTerm *filter;
+static GType type = 0;
 
-    if (! type) {
-	static const GTypeInfo info = {
+static const GTypeInfo info = {
     .class_size = sizeof (NotmuchFilterDiscardNonTermClass),
     .base_init = NULL,
     .base_finalize = NULL,
@@ -258,11 +251,19 @@ notmuch_filter_discard_non_term_new (GMimeContentType *content_type)
     .n_preallocs = 0,
     .instance_init = NULL,
     .value_table = NULL,
-	};
+};
 
+void
+_notmuch_filter_init () {
     type = g_type_register_static (GMIME_TYPE_FILTER, "NotmuchFilterDiscardNonTerm", &info,
 				   (GTypeFlags) 0);
-    }
+    parent_class = (GMimeFilterClass *) g_type_class_ref (GMIME_TYPE_FILTER);
+}
+
+static GMimeFilter *
+notmuch_filter_discard_non_term_new (GMimeContentType *content_type)
+{
+    NotmuchFilterDiscardNonTerm *filter;
 
     filter = (NotmuchFilterDiscardNonTerm *) g_object_new (type, NULL);
     filter->content_type = content_type;

lib/init.cc

@@ -0,0 +1,21 @@
+#include "notmuch-private.h"
+
+#include <mutex>
+
+static void do_init ()
+{
+    /* Initialize the GLib type system and threads */
+#if ! GLIB_CHECK_VERSION (2, 35, 1)
+    g_type_init ();
+#endif
+
+    g_mime_init ();
+    _notmuch_filter_init ();
+}
+
+void
+_notmuch_init ()
+{
+    static std::once_flag initialized;
+    std::call_once (initialized, do_init);
+}

lib/message-file.c

@@ -141,7 +141,6 @@ _notmuch_message_file_parse (notmuch_message_file_t *message)
 {
     GMimeParser *parser;
     notmuch_status_t status = NOTMUCH_STATUS_SUCCESS;
-    static int initialized = 0;
     bool is_mbox;
 
     if (message->message)
@@ -149,10 +148,7 @@ _notmuch_message_file_parse (notmuch_message_file_t *message)
 
     is_mbox = _is_mbox (message->stream);
 
-    if (! initialized) {
-	g_mime_init ();
-	initialized = 1;
-    }
+    _notmuch_init ();
 
     message->headers = g_hash_table_new_full (strcase_hash, strcase_equal,
 					      free, g_free);

lib/notmuch-private.h

@@ -469,11 +469,18 @@ _notmuch_database_link_message_to_parents (notmuch_database_t *notmuch,
 					   const char **thread_id);
 /* index.cc */
 
+void
+_notmuch_filter_init ();
+
 notmuch_status_t
 _notmuch_message_index_file (notmuch_message_t *message,
 			     notmuch_indexopts_t *indexopts,
 			     notmuch_message_file_t *message_file);
 
+/* init.cc */
+void
+_notmuch_init ();
+
 /* messages.c */
 
 typedef struct _notmuch_message_node {

lib/open.cc

@@ -307,24 +307,6 @@ _set_database_path (notmuch_database_t *notmuch,
     _notmuch_config_cache (notmuch, NOTMUCH_CONFIG_DATABASE_PATH, path);
 }
 
-static void
-_init_libs ()
-{
-
-    static int initialized = 0;
-
-    /* Initialize the GLib type system and threads */
-#if ! GLIB_CHECK_VERSION (2, 35, 1)
-    g_type_init ();
-#endif
-
-    /* Initialize gmime */
-    if (! initialized) {
-	g_mime_init ();
-	initialized = 1;
-    }
-}
-
 static void
 _load_database_state (notmuch_database_t *notmuch)
 {
@@ -498,7 +480,7 @@ notmuch_database_open_with_config (const char *database_path,
     GKeyFile *key_file = NULL;
     bool split = false;
 
-    _init_libs ();
+    _notmuch_init ();
 
     notmuch = _alloc_notmuch ();
     if (! notmuch) {
@@ -595,7 +577,7 @@ notmuch_database_create_with_config (const char *database_path,
     int err;
     bool split = false;
 
-    _init_libs ();
+    _notmuch_init ();
 
     notmuch = _alloc_notmuch ();
     if (! notmuch) {
@@ -791,7 +773,7 @@ notmuch_database_load_config (const char *database_path,
     GKeyFile *key_file = NULL;
     bool split = false;
 
-    _init_libs ();
+    _notmuch_init ();
 
     notmuch = _alloc_notmuch ();
     if (! notmuch) {