g_variant_get_child_value: Add a precondition on length

Ensure callers get a warning if they pass a bad length.

Split into a separate commit and changed to order index before
n_children by Colin Walters <walters@verbum.org>

diff --git a/glib/gvariant-core.c b/glib/gvariant-core.c
index 6b27266..d2bd576 100644 (file)
--- a/glib/gvariant-core.c
+++ b/glib/gvariant-core.c
@@ -848,6 +848,8 @@ GVariant *
 g_variant_get_child_value (GVariant *value,
                            gsize     index_)
 {
+  g_return_val_if_fail (index_ < g_variant_n_children (value), NULL);
+
   if (~g_atomic_int_get (&value->state) & STATE_SERIALISED)
     {
       g_variant_lock (value);