This function ought to handle null T.
Tested x86_64-pc-linux-gnu, applying to trunk.
commit 5ce73161422bffd51252e639ad2da79df31438ee
Author: Jason Merrill <ja...@redhat.com>
Date: Tue Mar 5 12:38:34 2013 -0500
* search.c (lookup_base): Handle NULL_TREE.
diff --git a/gcc/cp/search.c b/gcc/cp/search.c
index 4cc02ba..54a5e4a 100644
--- a/gcc/cp/search.c
+++ b/gcc/cp/search.c
@@ -188,6 +188,14 @@ lookup_base (tree t, tree base, base_access access,
tree t_binfo;
base_kind bk;
+ /* "Nothing" is definitely not derived from Base. */
+ if (t == NULL_TREE)
+ {
+ if (kind_ptr)
+ *kind_ptr = bk_not_base;
+ return NULL_TREE;
+ }
+
if (t == error_mark_node || base == error_mark_node)
{
if (kind_ptr)
