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Date: Tue, 27 Feb 2024 09:34:25 +0800
From: kernel test robot <lkp@intel.com>
To: David Laight <David.Laight@aculab.com>,
	"'linux-kernel@vger.kernel.org'" <linux-kernel@vger.kernel.org>,
	'Linus Torvalds' <torvalds@linux-foundation.org>,
	'Netdev' <netdev@vger.kernel.org>,
	"'dri-devel@lists.freedesktop.org'" <dri-devel@lists.freedesktop.org>
Cc: oe-kbuild-all@lists.linux.dev, 'Jens Axboe' <axboe@kernel.dk>,
	"'Matthew Wilcox (Oracle)'" <willy@infradead.org>,
	'Christoph Hellwig' <hch@infradead.org>,
	"'linux-btrfs@vger.kernel.org'" <linux-btrfs@vger.kernel.org>,
	'Andrew Morton' <akpm@linux-foundation.org>,
	Linux Memory Management List <linux-mm@kvack.org>,
	'Andy Shevchenko' <andriy.shevchenko@linux.intel.com>,
	"'David S . Miller'" <davem@davemloft.net>,
	'Dan Carpenter' <dan.carpenter@linaro.org>,
	'Jani Nikula' <jani.nikula@linux.intel.com>
Subject: Re: [PATCH next v2 03/11] minmax: Simplify signedness check
Message-ID: <202402270937.9kmO5PFt-lkp@intel.com>
References: <8657dd5c2264456f8a005520a3b90e2b@AcuMS.aculab.com>
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In-Reply-To: <8657dd5c2264456f8a005520a3b90e2b@AcuMS.aculab.com>

Hi David,

kernel test robot noticed the following build warnings:

[auto build test WARNING on drm-misc/drm-misc-next]
[also build test WARNING on linux/master mkl-can-next/testing kdave/for-next akpm-mm/mm-nonmm-unstable axboe-block/for-next linus/master v6.8-rc6 next-20240226]
[cannot apply to next-20240223 dtor-input/next dtor-input/for-linus horms-ipvs/master]
[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/David-Laight/minmax-Put-all-the-clamp-definitions-together/20240226-005902
base:   git://anongit.freedesktop.org/drm/drm-misc drm-misc-next
patch link:    https://lore.kernel.org/r/8657dd5c2264456f8a005520a3b90e2b%40AcuMS.aculab.com
patch subject: [PATCH next v2 03/11] minmax: Simplify signedness check
config: alpha-defconfig (https://download.01.org/0day-ci/archive/20240227/202402270937.9kmO5PFt-lkp@intel.com/config)
compiler: alpha-linux-gcc (GCC) 13.2.0
reproduce (this is a W=1 build): (https://download.01.org/0day-ci/archive/20240227/202402270937.9kmO5PFt-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/202402270937.9kmO5PFt-lkp@intel.com/

All warnings (new ones prefixed by >>):

   In file included from include/linux/kernel.h:28,
                    from include/linux/cpumask.h:10,
                    from include/linux/smp.h:13,
                    from include/linux/lockdep.h:14,
                    from include/linux/spinlock.h:63,
                    from include/linux/swait.h:7,
                    from include/linux/completion.h:12,
                    from include/linux/crypto.h:15,
                    from include/crypto/aead.h:13,
                    from include/crypto/internal/aead.h:11,
                    from crypto/skcipher.c:12:
   crypto/skcipher.c: In function 'skcipher_get_spot':
>> include/linux/minmax.h:31:70: warning: ordered comparison of pointer with integer zero [-Wextra]
      31 |         (is_unsigned_type(typeof(x)) || (__is_constexpr(x) ? (x) + 0 >= 0 : 0))
         |                                                                      ^~
   include/linux/minmax.h:39:11: note: in expansion of macro '__is_ok_unsigned'
      39 |          (__is_ok_unsigned(x) && __is_ok_unsigned(y)))
         |           ^~~~~~~~~~~~~~~~
   include/linux/minmax.h:49:24: note: in expansion of macro '__types_ok'
      49 |         _Static_assert(__types_ok(x, y),                        \
         |                        ^~~~~~~~~~
   include/linux/minmax.h:56:17: note: in expansion of macro '__cmp_once'
      56 |                 __cmp_once(op, x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y)))
         |                 ^~~~~~~~~~
   include/linux/minmax.h:70:25: note: in expansion of macro '__careful_cmp'
      70 | #define max(x, y)       __careful_cmp(max, x, y)
         |                         ^~~~~~~~~~~~~
   crypto/skcipher.c:83:16: note: in expansion of macro 'max'
      83 |         return max(start, end_page);
         |                ^~~
>> include/linux/minmax.h:31:70: warning: ordered comparison of pointer with integer zero [-Wextra]
      31 |         (is_unsigned_type(typeof(x)) || (__is_constexpr(x) ? (x) + 0 >= 0 : 0))
         |                                                                      ^~
   include/linux/minmax.h:39:34: note: in expansion of macro '__is_ok_unsigned'
      39 |          (__is_ok_unsigned(x) && __is_ok_unsigned(y)))
         |                                  ^~~~~~~~~~~~~~~~
   include/linux/minmax.h:49:24: note: in expansion of macro '__types_ok'
      49 |         _Static_assert(__types_ok(x, y),                        \
         |                        ^~~~~~~~~~
   include/linux/minmax.h:56:17: note: in expansion of macro '__cmp_once'
      56 |                 __cmp_once(op, x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y)))
         |                 ^~~~~~~~~~
   include/linux/minmax.h:70:25: note: in expansion of macro '__careful_cmp'
      70 | #define max(x, y)       __careful_cmp(max, x, y)
         |                         ^~~~~~~~~~~~~
   crypto/skcipher.c:83:16: note: in expansion of macro 'max'
      83 |         return max(start, end_page);
         |                ^~~


vim +31 include/linux/minmax.h

     9	
    10	/*
    11	 * min()/max()/clamp() macros must accomplish several things:
    12	 *
    13	 * - Avoid multiple evaluations of the arguments (so side-effects like
    14	 *   "x++" happen only once) when non-constant.
    15	 * - Retain result as a constant expressions when called with only
    16	 *   constant expressions (to avoid tripping VLA warnings in stack
    17	 *   allocation usage).
    18	 * - Perform signed v unsigned type-checking (to generate compile
    19	 *   errors instead of nasty runtime surprises).
    20	 * - Unsigned char/short are always promoted to signed int and can be
    21	 *   compared against signed or unsigned arguments.
    22	 * - Unsigned arguments can be compared against non-negative signed constants.
    23	 * - Comparison of a signed argument against an unsigned constant fails
    24	 *   even if the constant is below __INT_MAX__ and could be cast to int.
    25	 */
    26	#define __typecheck(x, y) \
    27		(!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
    28	
    29	/* Allow unsigned compares against non-negative signed constants. */
    30	#define __is_ok_unsigned(x) \
  > 31		(is_unsigned_type(typeof(x)) || (__is_constexpr(x) ? (x) + 0 >= 0 : 0))
    32	

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