[gtk+] Fixed: If can’t add child, don’t add to child info

[Daniel Boles <dboles src gnome org>]

commit be5a7b2db2d8f4c8efa18f4ad2764a64163948d9
Author: Daniel Boles <dboles src gnome org>
Date:   Thu Oct 12 14:05:09 2017 +0100

    Fixed: If can’t add child, don’t add to child info
    
    If the call to set_parent() failed, we were still adding the child to
    the internal list of children, despite that it was not really added.
    That meant we could later try to do invalid stuff with that non-child.
    
    Fix that by asserting and giving up if the child that the user is
    attempting to add is already parented.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=701296

 gtk/gtkfixed.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/gtk/gtkfixed.c b/gtk/gtkfixed.c
index bdb8e95..355929e 100644
--- a/gtk/gtkfixed.c
+++ b/gtk/gtkfixed.c
@@ -235,6 +235,7 @@ gtk_fixed_put (GtkFixed  *fixed,
 
   g_return_if_fail (GTK_IS_FIXED (fixed));
   g_return_if_fail (GTK_IS_WIDGET (widget));
+  g_return_if_fail (_gtk_widget_get_parent (widget) == NULL);
 
   priv = fixed->priv;