bug#16586: bug#17245: GREP BUG: grep -P and binary files

[Paul Eggert]

Jim Meyering wrote:
> anyone using grep -P to search data that is even a tiny bit
> inconsistent with their UTF-8 locale will now get an exit status of
> 2 rather than the matches they used to get.

Yes, I don't like that either, but <http://bugs.exim.org/1468> says 
libpcre intends to have undefined behavior here.  If so, it wouldn't 
help to wait until the next libprce release, which may well have a 
serious bug of this form in a different area, a bug that's not easy to 
test for.

Perhaps somebody should modify grep -P to discard input lines containing 
non-UTF-8 data instead of presenting them to libprce.  That way, it 
would be safe for grep -P to use PCRE_NO_UTF8_CHECK.  Although grep -P 
should report an error and exit with status 2 if it discards input due 
to encoding errors, it can also report matches in lines that do not 
contain encoding errors, so that users can see both the error messages 
and the matches.