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

[kernel test robot <lkp@intel.com>]

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@intel.com/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@intel.com/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@intel.com>
| Closes: https://lore.kernel.org/oe-kbuild-all/202602210027.MJpPrtwD-lkp@intel.com/

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	

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