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Date:   Wed, 13 Sep 2023 11:20:07 +0100
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Subject: Re: [PATCH 5/7] perf pmu: Move pmu__find_core_pmu() to pmus.c
To:     Arnaldo Carvalho de Melo <acme@kernel.org>
Cc:     linux-perf-users@vger.kernel.org, irogers@google.com,
        John Garry <john.g.garry@oracle.com>,
        Will Deacon <will@kernel.org>,
        Mike Leach <mike.leach@linaro.org>,
        Leo Yan <leo.yan@linaro.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>,
        Mark Rutland <mark.rutland@arm.com>,
        Alexander Shishkin <alexander.shishkin@linux.intel.com>,
        Jiri Olsa <jolsa@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Kan Liang <kan.liang@linux.intel.com>,
        Jing Zhang <renyu.zj@linux.alibaba.com>,
        Haixin Yu <yuhaixin.yhx@linux.alibaba.com>,
        Kajol Jain <kjain@linux.ibm.com>,
        Ravi Bangoria <ravi.bangoria@amd.com>,
        Yang Jihong <yangjihong1@huawei.com>,
        Eduard Zingerman <eddyz87@gmail.com>,
        Chen Zhongjin <chenzhongjin@huawei.com>,
        Miguel Ojeda <ojeda@kernel.org>,
        Liam Howlett <liam.howlett@oracle.com>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org
References: <20230831151632.124985-1-james.clark@arm.com>
 <20230831151632.124985-6-james.clark@arm.com> <ZQC7da2AM9ih8RMz@kernel.org>
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From:   James Clark <james.clark@arm.com>
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On 12/09/2023 20:26, Arnaldo Carvalho de Melo wrote:
> Em Thu, Aug 31, 2023 at 04:16:16PM +0100, James Clark escreveu:
>> pmu__find_core_pmu() more logically belongs in pmus.c because it
>> iterates over all PMUs, so move it to pmus.c
>>
>> At the same time rename it to perf_pmus__find_core_pmu() to match the
>> naming convention in this file.
>>
>> Signed-off-by: James Clark <james.clark@arm.com>
> 
> So, this one is hitting this:
> 
>   CC      /tmp/build/perf-tools-next/util/expr.o
> In file included from /var/home/acme/git/perf-tools-next/tools/include/linux/list.h:7,
>                  from util/pmus.c:2:
> In function ‘perf_pmus__scan_core’,
>     inlined from ‘perf_pmus__find_core_pmu’ at util/pmus.c:601:16:
> /var/home/acme/git/perf-tools-next/tools/include/linux/kernel.h:36:45: error: array subscript 0 is outside array bounds of ‘struct list_head[1]’ [-Werror=array-bounds]
>    36 |         const typeof(((type *)0)->member) * __mptr = (ptr);     \
>       |                                             ^~~~~~
> /var/home/acme/git/perf-tools-next/tools/include/linux/list.h:352:9: note: in expansion of macro ‘container_of’
>   352 |         container_of(ptr, type, member)
>       |         ^~~~~~~~~~~~
> /var/home/acme/git/perf-tools-next/tools/include/linux/list.h:404:9: note: in expansion of macro ‘list_entry’
>   404 |         list_entry((pos)->member.next, typeof(*(pos)), member)
>       |         ^~~~~~~~~~
> /var/home/acme/git/perf-tools-next/tools/include/linux/list.h:494:20: note: in expansion of macro ‘list_next_entry’
>   494 |         for (pos = list_next_entry(pos, member);                        \
>       |                    ^~~~~~~~~~~~~~~
> util/pmus.c:274:9: note: in expansion of macro ‘list_for_each_entry_continue’
>   274 |         list_for_each_entry_continue(pmu, &core_pmus, list)
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
> util/pmus.c: In function ‘perf_pmus__find_core_pmu’:
> util/pmus.c:35:18: note: at offset -128 into object ‘core_pmus’ of size 16
>    35 | static LIST_HEAD(core_pmus);
>       |                  ^~~~~~~~~
> /var/home/acme/git/perf-tools-next/tools/include/linux/list.h:23:26: note: in definition of macro ‘LIST_HEAD’
>    23 |         struct list_head name = LIST_HEAD_INIT(name)
>       |                          ^~~~
> cc1: all warnings being treated as errors
> make[4]: *** [/var/home/acme/git/perf-tools-next/tools/build/Makefile.build:97: /tmp/build/perf-tools-next/util/pmus.o] Error 1
> make[4]: *** Waiting for unfinished jobs....
>   LD      /tmp/build/perf-tools-next/ui/browsers/perf-in.o
> 
> 
> So I applied up to 4/7
> 
> Please continue from what will be in tmp.perf-tools-next in some
> jiffies.
> 
> - Arnaldo

I wasn't able to reproduce this on x86 or Arm, with either Clang or GCC.

That was with this patch applied onto 999b81b907e on tmp.perf-tools-next
and a pretty normal "make WERROR=1" command.

It seems like the 0 here is just to get the type rather than access
anything, if that's the 0 that the "array subscript 0" error is about,
so something seems a bit strange:

> /var/home/acme/git/perf-tools-next/tools/include/linux/kernel.h:36:45:
error: array subscript 0 is outside array bounds of ‘struct
list_head[1]’ [-Werror=array-bounds]
>    36 |         const typeof(((type *)0)->member) * __mptr = (ptr);     \