Re: [PATCH] Workaround for strange cmp bug

From: Junio C Hamano <junkio@cox.net>
Date: Aug 9, 2006, 10:50 UTC
Message-ID: <7v3bc65gk0.fsf@assigned-by-dhcp.cox.net>
In-Reply-To: <Pine.LNX.4.63.0608091221550.1800@wbgn013.biozentrum.uni-wuerzburg.de>

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

Show 15 quoted lines

> The cmp(1) (cmp (GNU diffutils) 2.8.7) distributed with openSUSE 10.1 has
> a subtle "shortcoming":
>
> 	$ echo a > a
> 	$ echo b > b
> 	$ cmp a b && echo nonono
> 	a b differ: char 1, line 1
> 	$ cmp a b >/dev/null && echo nonono
> 	nonono
> 	$ cmp -s a b >/dev/null && echo nonono
>
> So, if cmp should _not_ be quiet, _and_ the output is redirected to
> /dev/null, it has a bogus exit value. Our test suite redirects to
> /dev/null, which triggers that bug. (Obviously, the tests pass when
> running with '-v', which made that a real bugger to debug.)

While I sympathize unfortunate users who are stuck with such a broken implementation of an important basic tool, such a rewrite unnecessarily makes debugging of both test scripts _and_ real breakage harder.

It actually is very useful, in the chain of &&, to see that these steps in our tests output something when they shouldn't when the tests are run under -v; you may have noticed that the tests written by me have seemingly useless "echo happy" (which always returns true) and such, and they are there for a reason.

Please get the distribution fixed.