What can I do?

Consider this program:
int fn(int a)
{

         if (a == 6 || a == 7 || a == 4 || a == 67 || a == 78 &&
         a == 6 || a == 7 || a == 4 || a == 67 || a == 78 &&
         a == 6 || a == 7 || a == 4 || a == 67 || a == 78 &&
         a == 6 || a == 7 || a == 4 || a == 67 || a == 78 &&

	(4955 lines exactly the same as above elided)

         a == 6 || a == 7 || a == 4 || a == 67 || a == 78 &&
         a == 6 || a == 7 || a == 4 || a == 67 || a == 78 )
                 return 1;
         return 0;
}

This program makes the lcc compiler crash with stack overflow.
The evaluation of this SINGLE statement is recursive, each clause
calls recursively the expr3() function in expr.c.

What can I do here?

Fixing this would have to change drastically the design of the
compiler. In the other hand leaving this as is would leave a
compiler that can crash in some circumstances.

Is this legal C?

This program was generated by a customer, not
written by hand of course.

Is there a limit that the standard for this? In the limits section
(5.2.4.1) the standard does NOT mention this kind of limit, at
least as far as I can see (PLEASE correct me, I would be happy to be
wrong! :-) )

jacob