Re: [PATCH v6 2/3] x86/cpu: Check if feature string is non-zero

[Maciej Wieczor-Retman]

I'll replace the sizeof(buf) with 16 for the next version.

-- 
Kind regards
Maciej Wieczór-Retman

On 2026-02-21 at 00:19:59 +0800, kernel test robot wrote:
>Hi Maciej,
>
>kernel test robot noticed the following build warnings:
>
>[auto build test WARNING on tip/x86/core]
>[also build test WARNING on tip/smp/core v6.19]
>[cannot apply to peterz-queue/sched/core linus/master next-20260219]
>[If your patch is applied to the wrong git tree, kindly drop us a note.
>And when submitting patch, we suggest to use '--base' as documented in
>https://git-scm.com/docs/git-format-patch#_base_tree_information]
>
>url:    https://github.com/intel-lab-lkp/linux/commits/Maciej-Wieczor-Retman/x86-cpu-Clear-feature-bits-disabled-at-compile-time/20260220-204916
>base:   tip/x86/core
>patch link:    https://lore.kernel.org/r/bc0eebc8310acfae28a73e3780a67d721c739b89.1771590895.git.m.wieczorretman%40pm.me
>patch subject: [PATCH v6 2/3] x86/cpu: Check if feature string is non-zero
>config: x86_64-randconfig-003-20260220 (https://download.01.org/0day-ci/archive/20260221/202602210027.MJpPrtwD-lkp@xxxxxxxxx/config)
>compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
>reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20260221/202602210027.MJpPrtwD-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/202602210027.MJpPrtwD-lkp@xxxxxxxxx/
>
>All warnings (new ones prefixed by >>):
>
>   arch/x86/kernel/cpu/common.c: In function 'x86_cap_name':
>>> arch/x86/kernel/cpu/common.c:1987:29: warning: argument to 'sizeof' in 'snprintf' call is the same expression as the destination; did you mean to provide an explicit length? [-Wsizeof-pointer-memaccess]
>    1987 |         snprintf(buf, sizeof(buf), "%u:%u", word, bit & 31);
>         |                             ^
>>> arch/x86/kernel/cpu/common.c:1987:37: warning: '%u' directive output may be truncated writing between 1 and 9 bytes into a region of size 8 [-Wformat-truncation=]
>    1987 |         snprintf(buf, sizeof(buf), "%u:%u", word, bit & 31);
>         |                                     ^~
>   arch/x86/kernel/cpu/common.c:1987:36: note: directive argument in the range [0, 134217727]
>    1987 |         snprintf(buf, sizeof(buf), "%u:%u", word, bit & 31);
>         |                                    ^~~~~~~
>   arch/x86/kernel/cpu/common.c:1987:36: note: directive argument in the range [0, 31]
>   arch/x86/kernel/cpu/common.c:1987:9: note: 'snprintf' output between 4 and 13 bytes into a destination of size 8
>    1987 |         snprintf(buf, sizeof(buf), "%u:%u", word, bit & 31);
>         |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
>vim +1987 arch/x86/kernel/cpu/common.c
>
>  1973
>  1974	const char *x86_cap_name(unsigned int bit, char *buf)
>  1975	{
>  1976		unsigned int word = bit >> 5;
>  1977		const char *name = NULL;
>  1978
>  1979		if (likely(word < NCAPINTS))
>  1980			name = x86_cap_flags[bit];
>  1981		else if (likely(word < NCAPINTS + NBUGINTS))
>  1982			name = x86_bug_flags[bit - 32 * NCAPINTS];
>  1983
>  1984		if (name)
>  1985			return name;
>  1986
>> 1987		snprintf(buf, sizeof(buf), "%u:%u", word, bit & 31);
>  1988		return buf;
>  1989	}
>  1990
>
>--
>0-DAY CI Kernel Test Service
>https://github.com/intel/lkp-tests/wiki