http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59250
--- Comment #1 from Marek Polacek <mpolacek at gcc dot gnu.org> --- Yeah, I bet this hunk --- gcc/ubsan.c.jj 2013-11-22 01:40:03.000000000 +0100 +++ gcc/ubsan.c 2013-11-22 10:05:29.491725405 +0100 @@ -227,8 +227,8 @@ ubsan_source_location (location_t loc) xloc = expand_location (loc); /* Fill in the values from LOC. */ - size_t len = strlen (xloc.file); - tree str = build_string (len + 1, xloc.file); + size_t len = xloc.file ? strlen (xloc.file) : 0; + tree str = build_string (len + 1, xloc.file ? xloc.file : ""); TREE_TYPE (str) = build_array_type (char_type_node, build_index_type (size_int (len))); TREE_READONLY (str) = 1; @@ -642,7 +642,7 @@ ubsan_pass (void) { struct walk_stmt_info wi; gimple stmt = gsi_stmt (gsi); - if (is_gimple_debug (stmt)) + if (is_gimple_debug (stmt) || gimple_clobber_p (stmt)) { gsi_next (&gsi); continue; from Jakub's recent patch (http://gcc.gnu.org/ml/gcc-patches/2013-11/msg02831.html) will fix it.