Re: [PATCH next v2 03/11] minmax: Simplify signedness check

kernel test robot
2024-02-27T01:35:06Z

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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