Thanks.  How about the attached simpler patch instead?  Since grep 
always uses glibc-compatible regex (and supplies its own substitute when 
the system lacks one), and since all known glibc-compatible 
implementations fail, it should be safe to assume that grep will fail on 
the new test.  We can worry about dealing with test successes later, 
when the bug gets fixed (and presumably grep's substitute regex 
implementation will get fixed too).