linux-kernel - Re: lib/test_kasan_module.c:25:6: warning: variable 'unused' set but not used

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Message-Id: <20210405122908.a478d97cdc9495638e61b566@linux-foundation.org>
Date:   Mon, 5 Apr 2021 12:29:08 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     kernel test robot <lkp@...el.com>
Cc:     Andrey Konovalov <andreyknvl@...gle.com>, kbuild-all@...ts.01.org,
        linux-kernel@...r.kernel.org, Marco Elver <elver@...gle.com>,
        Alexander Potapenko <glider@...gle.com>,
        Linux Memory Management List <linux-mm@...ck.org>
Subject: Re: lib/test_kasan_module.c:25:6: warning: variable 'unused' set
 but not used

On Mon, 5 Apr 2021 02:16:25 +0800 kernel test robot <lkp@...el.com> wrote:

> Hi Andrey,
> 
> First bad commit (maybe != root cause):
> 
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   2023a53bdf41b7646b1d384b6816af06309f73a5
> commit: 5d92bdffd2d53f98de683229c0ad7d028703fdba kasan: rename CONFIG_TEST_KASAN_MODULE
> date:   6 weeks ago
> config: arm-randconfig-r024-20210404 (attached as .config)
> compiler: arm-linux-gnueabi-gcc (GCC) 9.3.0
> reproduce (this is a W=1 build):
>         wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
>         chmod +x ~/bin/make.cross
>         # https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=5d92bdffd2d53f98de683229c0ad7d028703fdba
>         git remote add linus https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
>         git fetch --no-tags linus master
>         git checkout 5d92bdffd2d53f98de683229c0ad7d028703fdba
>         # save the attached .config to linux build tree
>         COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-9.3.0 make.cross ARCH=arm 
> 
> If you fix the issue, kindly add following tag as appropriate
> Reported-by: kernel test robot <lkp@...el.com>
> 
> All warnings (new ones prefixed by >>):
> 
>    lib/test_kasan_module.c: In function 'copy_user_test':
> >> lib/test_kasan_module.c:25:6: warning: variable 'unused' set but not used [-Wunused-but-set-variable]
>       25 |  int unused;
>          |      ^~~~~~

Fair enough ;)

--- a/lib/test_kasan_module.c~a
+++ a/lib/test_kasan_module.c
@@ -22,7 +22,7 @@ static noinline void __init copy_user_te
 	char *kmem;
 	char __user *usermem;
 	size_t size = 10;
-	int unused;
+	int __maybe_unused unused;
 
 	kmem = kmalloc(size, GFP_KERNEL);
 	if (!kmem)
_

I guess we could test the copy_*_user return values are as expected,
but that isn't the point?