[libgnome-keyring] Double check operation references

[Stefan Walter <stefw src gnome org>]

commit 767a3a755c10081694c19b62bbcd76d440e27673
Author: Stef Walter <stefw gnome org>
Date:   Tue Jan 31 13:47:47 2012 +0100

    Double check operation references
    
     * Print a warning if an invalid operation is referenced

 library/gkr-operation.c |   15 ++++++++++++++-
 1 files changed, 14 insertions(+), 1 deletions(-)
---
diff --git a/library/gkr-operation.c b/library/gkr-operation.c
index fc3ecc9..9e04cc1 100644
--- a/library/gkr-operation.c
+++ b/library/gkr-operation.c
@@ -96,8 +96,21 @@ gkr_operation_init (void)
 GkrOperation*
 gkr_operation_ref (GkrOperation *op)
 {
+	gint old;
+
 	g_assert (op);
-	g_atomic_int_inc (&op->refs);
+
+#if GLIB_CHECK_VERSION (2,30,0)
+	old = g_atomic_int_add (&op->refs, 1);
+#else
+	old = g_atomic_int_exchange_and_add (&op->refs, 1);
+#endif
+
+	if (old <= 0) {
+		g_warning ("invalid or unreferenced gnome-keyring operation in use");
+		return NULL;
+	}
+
 	return op;
 }