Re: [PATCH] tracing: Error if a trace event has an array for a __field()

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

Hi Steven,

Thank you for the patch! Yet something to improve:

[auto build test ERROR on linus/master]
[also build test ERROR on v6.3-rc1]
[cannot apply to next-20230310]
[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/Steven-Rostedt/tracing-Error-if-a-trace-event-has-an-array-for-a-__field/20230310-111456
patch link:    https://lore.kernel.org/r/20230309221302.642e82d9%40gandalf.local.home
patch subject: [PATCH] tracing: Error if a trace event has an array for a __field()
config: x86_64-randconfig-a006 (https://download.01.org/0day-ci/archive/20230310/202303101645.28bnQoH2-lkp@intel.com/config)
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/4828e98216144ead91bbb26298aae865dac9f837
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Steven-Rostedt/tracing-Error-if-a-trace-event-has-an-array-for-a-__field/20230310-111456
        git checkout 4828e98216144ead91bbb26298aae865dac9f837
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=x86_64 olddefconfig
        make W=1 O=build_dir ARCH=x86_64 SHELL=/bin/bash kernel/rcu/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>
| Link: https://lore.kernel.org/oe-kbuild-all/202303101645.28bnQoH2-lkp@intel.com/

All errors (new ones prefixed by >>):

   In file included from include/trace/define_trace.h:102,
                    from include/trace/events/rcu.h:839,
                    from kernel/rcu/rcu.h:13,
                    from kernel/rcu/update.c:49:
   include/trace/events/rcu.h: In function 'trace_event_get_offsets_rcu_torture_read':
>> include/trace/stages/stage5_get_offsets.h:23:53: error: expected ')' before '*' token
      23 |         { (void)sizeof(struct _test_no_array_##item *); }
         |                       ~                             ^
   include/trace/trace_events.h:263:9: note: in definition of macro 'DECLARE_EVENT_CLASS'
     263 |         tstruct;                                                        \
         |         ^~~~~~~
   include/trace/trace_events.h:43:30: note: in expansion of macro 'PARAMS'
      43 |                              PARAMS(tstruct),                  \
         |                              ^~~~~~
   include/trace/events/rcu.h:11:25: note: in expansion of macro 'TRACE_EVENT'
      11 | #define TRACE_EVENT_RCU TRACE_EVENT
         |                         ^~~~~~~~~~~
   include/trace/events/rcu.h:770:9: note: in expansion of macro 'TP_STRUCT__entry'
     770 |         TP_STRUCT__entry(
         |         ^~~~~~~~~~~~~~~~
   include/trace/events/rcu.h:771:17: note: in expansion of macro '__field'
     771 |                 __field(char, rcutorturename[RCUTORTURENAME_LEN])
         |                 ^~~~~~~
>> include/trace/events/rcu.h:771:45: error: array type has incomplete element type 'struct _test_no_array_rcutorturename'
     771 |                 __field(char, rcutorturename[RCUTORTURENAME_LEN])
         |                                             ^
   include/trace/trace_events.h:263:9: note: in definition of macro 'DECLARE_EVENT_CLASS'
     263 |         tstruct;                                                        \
         |         ^~~~~~~
   include/trace/trace_events.h:43:30: note: in expansion of macro 'PARAMS'
      43 |                              PARAMS(tstruct),                  \
         |                              ^~~~~~
   include/trace/events/rcu.h:11:25: note: in expansion of macro 'TRACE_EVENT'
      11 | #define TRACE_EVENT_RCU TRACE_EVENT
         |                         ^~~~~~~~~~~
   include/trace/events/rcu.h:770:9: note: in expansion of macro 'TP_STRUCT__entry'
     770 |         TP_STRUCT__entry(
         |         ^~~~~~~~~~~~~~~~
   include/trace/events/rcu.h:771:17: note: in expansion of macro '__field'
     771 |                 __field(char, rcutorturename[RCUTORTURENAME_LEN])
         |                 ^~~~~~~


vim +23 include/trace/stages/stage5_get_offsets.h

    11	
    12	/*
    13	 * Fields should never declare an array: i.e. __field(int, arr[5])
    14	 * If they do, it will cause issues in parsing and possibly corrupt the
    15	 * events. To prevent that from happening, test the sizeof() a fictitious
    16	 * type called "struct _test_no_array_##item" which will fail if "item"
    17	 * contains array elements (like "arr[5]").
    18	 *
    19	 * If you hit this, use __array(int, arr, 5) instead.
    20	 */
    21	#undef __field
    22	#define __field(type, item)					\
  > 23		{ (void)sizeof(struct _test_no_array_##item *); }
    24	

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