To be a little clearer: Since tok->filename is used as a flag in other
places, I'm not sure where to set it without breaking other things.
This is the location of the segfault and the following would "fix" it
(using a placeholder for the name):


Index: Parser/tokenizer.c
===================================================================
--- Parser/tokenizer.c  (revision 83019)
+++ Parser/tokenizer.c  (working copy)
@@ -582,6 +582,8 @@
     if (badchar) {
         /* Need to add 1 to the line number, since this line
            has not been counted, yet.  */
+        if (tok->filename == NULL)
+            tok->filename = "<file>";
         PyErr_Format(PyExc_SyntaxError,
             "Non-UTF-8 code starting with '\\x%.2x' "
             "in file %.200s on line %i, "