linux-kernel - Re: [PATCH] Enable '-Werror' by default for all kernel builds

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Date:   Mon, 6 Sep 2021 16:06:04 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Guenter Roeck <linux@...ck-us.net>,
        "David S. Miller" <davem@...emloft.net>,
        Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Christian Koenig <christian.koenig@....com>,
        Huang Rui <ray.huang@....com>
Cc:     Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-sparc <sparclinux@...r.kernel.org>
Subject: Re: [PATCH] Enable '-Werror' by default for all kernel builds

[ Adding some subsystem maintainers ]

On Mon, Sep 6, 2021 at 10:06 AM Guenter Roeck <linux@...ck-us.net> wrote:
>
> > But hopefully most cases are just "people haven't cared enough" and
> > easily fixed.
>
> We'll see. For my testbed I disabled the new configuration flag
> for the time being because its primary focus is boot tests, and
> there won't be any boot tests if images fail to build.

Sure, reasonable.

I've checked a few of the build errors by doing the appropriate cross
compiles, and it doesn't seem bad - but it does seem like we have a
number of really pointless long-standing warnings that should have
been fixed long ago.

For example, looking at sparc64, there are several build errors due to
those warnings now being fatal:

 - drivers/gpu/drm/ttm/ttm_pool.c:386

   This is a type mismatch error. It looks like __fls() on sparc64
returns 'int'. And the ttm_pool.c code assumes it returns 'unsigned
long'.

   Oddly enough, the very line after that line does "min_t(unsigned
int" to get the types in line.

   So  the immediate reason is "sparc64 is different". But the deeper
reason seems to be that ttm_pool.c has odd type assumptions. But that
warning should have been fixed long ago, either way.

   Christian/Huang? I get the feeling that both lines in that file
should use the min_t(). Hmm?

 - drivers/input/joystick/analog.c:160

   #warning Precise timer not defined for this architecture.

   Unfortunate. I suspect that warning just has to be removed. It has
never caused anything to be fixed, it's old to the point of predating
the git history. Dmitry?

 - at least a couple of stringop-overread errors. Attached is a
possible for for one of them.

The stringop overread is odd, because another one of them is

   fs/qnx4/dir.c: In function ‘qnx4_readdir’:
   fs/qnx4/dir.c:51:32: error: ‘strnlen’ specified bound 48 exceeds
source size 16 [-Werror=stringop-overread]
      51 |                         size = strnlen(de->di_fname, size);
         |                                ^~~~~~~~~~~~~~~~~~~~~~~~~~~

but I'm not seeing why that one happens on sparc64, but not on arm64
or x86-64. There doesn't seem to be anything architecture-specific
anywhere in that area.

Funky.

Davem - attached patch compiles cleanly for me, but I'm not sure it's
necessarily the right thing to do, and I didn't check the code
generation. Maybe it screws up. Can somebody test on sparc64 and
perhaps think about it more than I did?

               Linus

View attachment "patch.diff" of type "text/x-patch" (741 bytes)