[glib: 1/2] gtimezone: Tidy up UTC timezone creation

[Emmanuele Bassi <ebassi src gnome org>]

commit a8ef5fdf8a5847848ecf1006ff03b8e54713d4df
Author: Philip Withnall <withnall endlessm com>
Date:   Fri Oct 25 18:32:48 2019 +0100

    gtimezone: Tidy up UTC timezone creation
    
    Move the separate function inline using g_once_init_{enter,leave}(),
    rather than g_once().
    
    This marginally improves performance, taking 0.39s to create 10000000
    UTC timezones, rather than 0.43s previously. (Who cares?)
    
    Follow-up to !1105.
    
    Signed-off-by: Philip Withnall <withnall endlessm com>

 glib/gtimezone.c | 17 ++++++++---------
 1 file changed, 8 insertions(+), 9 deletions(-)
---
diff --git a/glib/gtimezone.c b/glib/gtimezone.c
index 0155a5841..5a835dea9 100644
--- a/glib/gtimezone.c
+++ b/glib/gtimezone.c
@@ -1676,20 +1676,19 @@ g_time_zone_new (const gchar *identifier)
  *
  * Since: 2.26
  **/
-static gpointer
-g_time_zone_utc_init (gpointer data)
-{
-  return g_time_zone_new ("UTC");
-}
-
 GTimeZone *
 g_time_zone_new_utc (void)
 {
-  static GOnce utc_once = G_ONCE_INIT;
+  static GTimeZone *utc = NULL;
+  static gsize initialised;
 
-  g_once (&utc_once, g_time_zone_utc_init, NULL);
+  if (g_once_init_enter (&initialised))
+    {
+      utc = g_time_zone_new ("UTC");
+      g_once_init_leave (&initialised, TRUE);
+    }
 
-  return g_time_zone_ref ((GTimeZone *)utc_once.retval);
+  return g_time_zone_ref (utc);
 }
 
 /**