bug#16481: dfa.c and Rational Range Interpretation

[Paul Eggert]

Paolo Bonzini wrote:
> The correct course of action for grep is to defer range interpretation
> to regex, because otherwise you can get mismatches between regexes with
> backreferences and those without.

It depends on what one means by "correct".  POSIX doesn't say what to do 
in this situation, so it's OK as far as POSIX is concerned for grep to 
use RRI in the typical case (i.e., without backreferences), and for grep 
to use some other interpretation in the rare cases when backreferences 
are used.

The documentation for 'grep' attempts to address this issue, perhaps not 
as clearly as it could.  Maybe the installation instructions should talk 
about it as well, and suggest --with-included-regex for people who care 
about this sort of thing.