UTF-16 surrogate pair handling in grep -i option

[Corinna Vinschen]

Hi,

two days ago we got a report on the Cygwin mailing list that under some
circumstances grep on Cygwin SEGVed.  I tracked this down to grep's -i
option, which calls the function mbtolower.  This function works fine on
systems with UCS-2 or UCS-4 wchar_t's, but it doesn't handle UTF-16
surrogates on UTF-16 wchar_t systems.  It does especially not handle
the case where wcrtomb returns 0, which is what causes the SEGV.

The below patch fixes this at least for Cygwin.  Actually, I don't
know any other OS which uses UTF-16 and provides this set of functions,
so I assume that this solution is very system-specific, unless another
Newlib based OS uses UTF-16 wchar_t as well.

I hope the patch is ok to go into mainline.  I added a lot of comment
to explain what happens.  Feel free to ask any question.

Please keep me CCed, I'm not subscribed to bugs-grep.


Thanks,
Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat

0001-src-searchutils.c-mbtolower-Handle-UTF-16-surrogate-.patch
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