[glib: 9/10] gthread: Use atomic pointer exchange to check value set on g_init_leave

[Philip Withnall <pwithnall src gnome org>]

commit 00f3f0d407da0cdfceed3342a51147e725ab3cf7
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Tue Jun 21 05:02:30 2022 +0200

    gthread: Use atomic pointer exchange to check value set on g_init_leave

 glib/gthread.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)
---
diff --git a/glib/gthread.c b/glib/gthread.c
index 0b03e64082..bc9b1c2b37 100644
--- a/glib/gthread.c
+++ b/glib/gthread.c
@@ -741,11 +741,13 @@ void
                      gsize          result)
 {
   gsize *value_location = (gsize *) location;
+  gsize old_value;
 
-  g_return_if_fail (g_atomic_pointer_get (value_location) == 0);
   g_return_if_fail (result != 0);
 
-  g_atomic_pointer_set (value_location, result);
+  old_value = (gsize) g_atomic_pointer_exchange (value_location, result);
+  g_return_if_fail (old_value == 0);
+
   g_mutex_lock (&g_once_mutex);
   g_return_if_fail (g_once_init_list != NULL);
   g_once_init_list = g_slist_remove (g_once_init_list, (void*) value_location);