linux-kernel - Re: [PATCH] Makefiles: Disable unused-variable warning

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Date:	Sun, 08 Jan 2012 16:01:17 +0100
From:	Michal Marek <mmarek@...e.cz>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	"Kirill A. Shutemov" <kirill@...temov.name>, linux-mm@...ck.org,
	cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
	containers@...ts.linux-foundation.org,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Balbir Singh <bsingharora@...il.com>,
	Johannes Weiner <hannes@...xchg.org>,
	linux-kbuild@...r.kernel.org
Subject: Re: [PATCH] Makefiles: Disable unused-variable warning

Dne 27.12.2011 14:57, Michal Hocko napsal(a):
> Anyway, I am wondering why unused-but-set-variable is disabled while
> unused-variable is enabled.

unused-but-set-variable was disabled, because it was a new warning in
gcc 4.6 and produced too much noise relatively to its severity. A make
W=1 build of x86_64_defconfig gives:
$ grep -c 'Wunused-but-set-variable' log
77
$ grep -c 'Wunused-variable' log
0

More exotic configuration will probably result in a couple of unused
variable warnings, but that IMO no reason to disable them globally.

> Shouldn't we just disable it as well rather
> than workaround this in the code? The warning is just pure noise in this
> case.

If it's noise in a particular case, there is always the option to add

CFLAGS_memcontrol.o := $(call cc-disable-warning, unused-variable)

to the respective Makefile.

Michal
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