Re: drivers/platform/surface/surface3_power.c:243:2: warning: 'snprintf' will always be truncated; specified size is 10, but format string expands to at least 12

[Andy Shevchenko]

On Wed, Jan 29, 2025 at 10:09 AM kernel test robot <lkp@xxxxxxxxx> wrote:
>
> tree:   https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master
> head:   05dbaf8dd8bf537d4b4eb3115ab42a5fb40ff1f5
> commit: 85f7582cd484dbf491b6d9bb2af6ef1467a024d2 platform/surface: Move Surface 3 Power OpRegion driver to platform/surface
> date:   4 years, 3 months ago
> config: x86_64-randconfig-071-20241231 (https://download.01.org/0day-ci/archive/20250129/202501291646.VtwF98qd-lkp@xxxxxxxxx/config)
> compiler: clang version 19.1.3 (https://github.com/llvm/llvm-project ab51eccf88f5321e7c60591c5546b254b6afab99)
> reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20250129/202501291646.VtwF98qd-lkp@xxxxxxxxx/reproduce)
>
> If you fix the issue in a separate patch/commit (i.e. not just a new version of
> the same patch/commit), kindly add following tags
> | Reported-by: kernel test robot <lkp@xxxxxxxxx>
> | Closes: https://lore.kernel.org/oe-kbuild-all/202501291646.VtwF98qd-lkp@xxxxxxxxx/
>
> All warnings (new ones prefixed by >>):
>
> >> drivers/platform/surface/surface3_power.c:243:2: warning: 'snprintf' will always be truncated; specified size is 10, but format string expands to at least 12 [-Wformat-truncation-non-kprintf]
>      243 |         snprintf(bix->serial, ARRAY_SIZE(bix->serial), "%3pE%6pE", buf + 7, buf);

3 + 'E' + 6 + 'E' + NUL, that's how the compiler thinks about this
formatting string...

>          |         ^
>    1 warning generated.

I do not know how to properly address this because it's false positive
due to the compiler not being aware of pointer extensions used in
Linux kernel. The w/a is to increase the buffer if we can, but is it
practical? OTOH, this warning will be translated to a compilation
error in case of default WERROR settings on `make W=1` builds which is
also annoying to people what want have that clean.

-- 
With Best Regards,
Andy Shevchenko