gcc-6.3.patch

--- a/gcc/ubsan.c	2018-01-18 18:28:07.995225900 -0500
+++ b/gcc/ubsan.c	2018-01-18 20:40:40.029522900 -0500
@@ -1471,7 +1471,7 @@
 
   expanded_location xloc = expand_location (loc);
   if (xloc.file == NULL || strncmp (xloc.file, "\1", 2) == 0
-      || xloc.file == '\0' || xloc.file[0] == '\xff'
+      || xloc.file[0] == '\0' || xloc.file[0] == '\xff'
       || xloc.file[1] == '\xff')
     return false;