Is this correct behaviour for 'rev'?

[Mark Geisert]

Replying to myself, I continue...

On 10/22/2024 10:33 PM, Mark Geisert via Cygwin wrote:
> On 10/22/2024 8:00 PM, Backwoods BC via Cygwin wrote:
>> It appears that 'rev' is choking on any character \x80 or higher, but
>> is OK with those \x1f or smaller. It doesn't give an error or ignore
>> it, it just stops.
>>
>> I don't have access to a Linux box so I can't see if this happens
>> there and nothing in the documentation suggests that this is the
>> correct functionality.
>>
>> Test case:
>> printf 'no non-ASCII characters\nhex 01 >\x01< here\nhex 80 >\x80<
>> here\nLine 4\n'|rev|rev
>>
>> This is for "rev from util-linux 2.33.1"
>>
>> I don't have the current version of 'rev' on my system due to not
>> having updated in a while. I accidentally screwed up my installation
>> and have been reluctant to wipe it and start over.
>>
>> So, is this the expected behaviour for the current version of 'rev'
>> under Cygwin and/or Linux?
> 
> The current Cygwin util-linux 2.39.3-2 rev behaves in the same, broken 
> way.  It looks like line-ending char(s) are not being handled correctly. 
>   Don't know yet if it's rev itself or fgetws() being used by rev that's 
> busted.  I'll investigate further.  Thanks for the report!

This is a locale issue.  In the default Cygwin locale, rev mishandles 
the \x80 byte and instead of stopping with an error message it enters an 
infinite loop.  I'll probably report this upstream instead of working 
out a local fix.

There is a work-around: change to the "C" locale just to run rev.
     LC_ALL=C rev zzz
where zzz is a file containing your four lines.  You can also run your 
original testcase with "rev" replaced by "LC_ALL=C rev" in both places.
HTH,

..mark

P.S. ASCII runs from \x00 to \x7F, so your \x80 is non-ASCII FWIW ;-)