g_settings_get: check validity of format string

Allow only format strings that copy all values (i.e, don't contain '&'),
as the returned pointers might become invalid in some rare cases.

Since this is technically an API break, this patch only prints a
critical when a faulty format string is detected, but still fetches the
values.

https://bugzilla.gnome.org/show_bug.cgi?id=719979

1 files changed, 7 insertions, 0 deletions

diff --git a/gio/gsettings.c b/gio/gsettings.c
index e0407deac..62a170801 100644
--- a/gio/gsettings.c
+++ b/gio/gsettings.c
@@ -1528,6 +1528,13 @@ g_settings_get (GSettings   *settings,
 
   value = g_settings_get_value (settings, key);
 
+  if (!g_variant_check_format_string (value, format, TRUE))
+    {
+      g_critical ("%s: invalid format string for key '%s' from schema '%s'. "
+                  "This call will probably stop working with a future version of glib.",
+                  G_STRFUNC, key, g_settings_schema_get_id (settings->priv->schema));
+    }
+
   va_start (ap, format);
   g_variant_get_va (value, format, NULL, &ap);
   va_end (ap);