netdev - Re: [PATCH net-next v2 5/6] net: mpls: bump maximum number of labels

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Date:   Fri, 31 Mar 2017 10:43:01 +0800
From:   kbuild test robot <lkp@...el.com>
To:     David Ahern <dsa@...ulusnetworks.com>
Cc:     kbuild-all@...org, netdev@...r.kernel.org,
        roopa@...ulusnetworks.com, rshearma@...cade.com,
        ebiederm@...ssion.com, David Ahern <dsa@...ulusnetworks.com>
Subject: Re: [PATCH net-next v2 5/6] net: mpls: bump maximum number of labels

Hi David,

[auto build test WARNING on net-next/master]

url:    https://github.com/0day-ci/linux/commits/David-Ahern/net-mpls-Allow-users-to-configure-more-labels-per-route/20170331-080314
config: x86_64-randconfig-ne0-03310806 (attached as .config)
compiler: gcc-6 (Debian 6.2.0-3) 6.2.0 20160901
reproduce:
        # save the attached .config to linux build tree
        make ARCH=x86_64 

Note: it may well be a FALSE warning. FWIW you are at least aware of it now.
http://gcc.gnu.org/wiki/Better_Uninitialized_Warnings

All warnings (new ones prefixed by >>):

   In file included from include/linux/skbuff.h:17:0,
                    from net/mpls/af_mpls.c:2:
   net/mpls/af_mpls.c: In function 'mpls_rtm_newroute':
>> include/linux/kernel.h:766:21: warning: 'n_labels' may be used uninitialized in this function [-Wmaybe-uninitialized]
     max1 > max2 ? max1 : max2; })
                        ^
   net/mpls/af_mpls.c:774:6: note: 'n_labels' was declared here
      u8 n_labels;
         ^~~~~~~~
--
   In file included from include/linux/skbuff.h:17:0,
                    from net//mpls/af_mpls.c:2:
   net//mpls/af_mpls.c: In function 'mpls_rtm_newroute':
>> include/linux/kernel.h:766:21: warning: 'n_labels' may be used uninitialized in this function [-Wmaybe-uninitialized]
     max1 > max2 ? max1 : max2; })
                        ^
   net//mpls/af_mpls.c:774:6: note: 'n_labels' was declared here
      u8 n_labels;
         ^~~~~~~~

vim +/n_labels +766 include/linux/kernel.h

^1da177e Linus Torvalds     2005-04-16  750   * "unnecessary" pointer comparison.
^1da177e Linus Torvalds     2005-04-16  751   */
589a9785 Johannes Berg      2016-10-07  752  #define __min(t1, t2, min1, min2, x, y) ({		\
589a9785 Johannes Berg      2016-10-07  753  	t1 min1 = (x);					\
589a9785 Johannes Berg      2016-10-07  754  	t2 min2 = (y);					\
589a9785 Johannes Berg      2016-10-07  755  	(void) (&min1 == &min2);			\
589a9785 Johannes Berg      2016-10-07  756  	min1 < min2 ? min1 : min2; })
589a9785 Johannes Berg      2016-10-07  757  #define min(x, y)					\
589a9785 Johannes Berg      2016-10-07  758  	__min(typeof(x), typeof(y),			\
589a9785 Johannes Berg      2016-10-07  759  	      __UNIQUE_ID(min1_), __UNIQUE_ID(min2_),	\
589a9785 Johannes Berg      2016-10-07  760  	      x, y)
589a9785 Johannes Berg      2016-10-07  761  
589a9785 Johannes Berg      2016-10-07  762  #define __max(t1, t2, max1, max2, x, y) ({		\
589a9785 Johannes Berg      2016-10-07  763  	t1 max1 = (x);					\
589a9785 Johannes Berg      2016-10-07  764  	t2 max2 = (y);					\
589a9785 Johannes Berg      2016-10-07  765  	(void) (&max1 == &max2);			\
589a9785 Johannes Berg      2016-10-07 @766  	max1 > max2 ? max1 : max2; })
589a9785 Johannes Berg      2016-10-07  767  #define max(x, y)					\
589a9785 Johannes Berg      2016-10-07  768  	__max(typeof(x), typeof(y),			\
589a9785 Johannes Berg      2016-10-07  769  	      __UNIQUE_ID(max1_), __UNIQUE_ID(max2_),	\
589a9785 Johannes Berg      2016-10-07  770  	      x, y)
bdf4bbaa Harvey Harrison    2008-04-30  771  
2e1d06e1 Michal Nazarewicz  2014-10-09  772  #define min3(x, y, z) min((typeof(x))min(x, y), z)
2e1d06e1 Michal Nazarewicz  2014-10-09  773  #define max3(x, y, z) max((typeof(x))max(x, y), z)
f27c85c5 Hagen Paul Pfeifer 2010-10-26  774  

:::::: The code at line 766 was first introduced by commit
:::::: 589a9785ee3a7cb85f1dedc3dad1c9754c691880 min/max: remove sparse warnings when they're nested

:::::: TO: Johannes Berg <johannes.berg@...el.com>
:::::: CC: Linus Torvalds <torvalds@...ux-foundation.org>

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0-DAY kernel test infrastructure                Open Source Technology Center
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