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From:   Ian Rogers <irogers@google.com>
Date:   Tue, 14 Mar 2023 13:01:16 -0700
Message-ID: <CAP-5=fXURWoZu2j6Y8xQy23i7=DfgThq3WC1RkGFBx-4moQKYQ@mail.gmail.com>
Subject: Re: next: zip.c:35:8: error: packed attribute causes inefficient
 alignment for 'magic' [-Werror=attributes]
To:     Andrii Nakryiko <andrii.nakryiko@gmail.com>
Cc:     Naresh Kamboju <naresh.kamboju@linaro.org>,
        Jiri Olsa <jolsa@kernel.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        Namhyung Kim <namhyung@kernel.org>,
        =?UTF-8?Q?Daniel_M=C3=BCller?= <deso@posteo.net>,
        open list <linux-kernel@vger.kernel.org>,
        bpf <bpf@vger.kernel.org>, lkft-triage@lists.linaro.org,
        Linux-Next Mailing List <linux-next@vger.kernel.org>,
        Andrii Nakryiko <andrii@kernel.org>,
        Alexei Starovoitov <ast@kernel.org>,
        Daniel Borkmann <daniel@iogearbox.net>,
        Song Liu <song@kernel.org>, Yonghong Song <yhs@fb.com>,
        KP Singh <kpsingh@kernel.org>,
        Anders Roxell <anders.roxell@linaro.org>
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On Tue, Mar 14, 2023 at 11:52=E2=80=AFAM Andrii Nakryiko
<andrii.nakryiko@gmail.com> wrote:
>
> On Mon, Mar 13, 2023 at 11:38=E2=80=AFPM Naresh Kamboju
> <naresh.kamboju@linaro.org> wrote:
> >
> > perf builds failing from Linux next-20230307..next-20230314 but pass on
> > Linux mainline v6.3-rc2.
> >
> > Reported-by: Linux Kernel Functional Testing <lkft@linaro.org>
>
> Thanks for the report, but I'm not sure what's wrong here. We added
> __attribute__((packed)) attribute intentionally and want to keep it
> this way. It seems like perf itself is using packed structs (e.g.,
> struct debug_line_header in util/genelf_debug.c), so I'm wondering why
> that code doesn't cause any problems.
>
> Any hints from perf folks?

We use a #pragma to disable the warnings in at least one place:
https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/tree/tools/l=
ib/perf/include/perf/event.h?h=3Dperf-tools#n194

Thanks,
Ian

> >
> > Build log:
> > ---
> > libbpf/staticobjs/zip.o
> > zip.c:35:8: error: packed attribute causes inefficient alignment for
> > 'magic' [-Werror=3Dattributes]
> >    35 |  __u32 magic;
> >       |        ^~~~~
> > zip.c:40:8: error: packed attribute causes inefficient alignment for
> > 'this_disk' [-Werror=3Dattributes]
> >    40 |  __u16 this_disk;
> >       |        ^~~~~~~~~
> > zip.c:45:8: error: packed attribute causes inefficient alignment for
> > 'cd_disk' [-Werror=3Dattributes]
> >    45 |  __u16 cd_disk;
> >       |        ^~~~~~~
> > zip.c:50:8: error: packed attribute causes inefficient alignment for
> > 'cd_records' [-Werror=3Dattributes]
> >    50 |  __u16 cd_records;
> >       |        ^~~~~~~~~~
> > zip.c:55:8: error: packed attribute causes inefficient alignment for
> > 'cd_records_total' [-Werror=3Dattributes]
> >    55 |  __u16 cd_records_total;
> >       |        ^~~~~~~~~~~~~~~~
> > zip.c:58:8: error: packed attribute causes inefficient alignment for
> > 'cd_size' [-Werror=3Dattributes]
> >    58 |  __u32 cd_size;
> >       |        ^~~~~~~
> > zip.c:63:8: error: packed attribute causes inefficient alignment for
> > 'cd_offset' [-Werror=3Dattributes]
> >    63 |  __u32 cd_offset;
> >       |        ^~~~~~~~~
> > zip.c:66:8: error: packed attribute causes inefficient alignment for
> > 'comment_length' [-Werror=3Dattributes]
> >    66 |  __u16 comment_length;
> >       |        ^~~~~~~~~~~~~~
> > zip.c:79:8: error: packed attribute causes inefficient alignment for
> > 'magic' [-Werror=3Dattributes]
> >    79 |  __u32 magic;
> >       |        ^~~~~
> > zip.c:80:8: error: packed attribute causes inefficient alignment for
> > 'version' [-Werror=3Dattributes]
> >    80 |  __u16 version;
> >       |        ^~~~~~~
> > zip.c:82:8: error: packed attribute causes inefficient alignment for
> > 'min_version' [-Werror=3Dattributes]
> >    82 |  __u16 min_version;
> >       |        ^~~~~~~~~~~
> > zip.c:83:8: error: packed attribute causes inefficient alignment for
> > 'flags' [-Werror=3Dattributes]
> >    83 |  __u16 flags;
> >       |        ^~~~~
> > zip.c:84:8: error: packed attribute causes inefficient alignment for
> > 'compression' [-Werror=3Dattributes]
> >    84 |  __u16 compression;
> >       |        ^~~~~~~~~~~
> > zip.c:85:8: error: packed attribute causes inefficient alignment for
> > 'last_modified_time' [-Werror=3Dattributes]
> >    85 |  __u16 last_modified_time;
> >       |        ^~~~~~~~~~~~~~~~~~
> > zip.c:86:8: error: packed attribute causes inefficient alignment for
> > 'last_modified_date' [-Werror=3Dattributes]
> >    86 |  __u16 last_modified_date;
> >       |        ^~~~~~~~~~~~~~~~~~
> > zip.c:87:8: error: packed attribute causes inefficient alignment for
> > 'crc' [-Werror=3Dattributes]
> >    87 |  __u32 crc;
> >       |        ^~~
> > zip.c:88:8: error: packed attribute causes inefficient alignment for
> > 'compressed_size' [-Werror=3Dattributes]
> >    88 |  __u32 compressed_size;
> >       |        ^~~~~~~~~~~~~~~
> > zip.c:89:8: error: packed attribute causes inefficient alignment for
> > 'uncompressed_size' [-Werror=3Dattributes]
> >    89 |  __u32 uncompressed_size;
> >       |        ^~~~~~~~~~~~~~~~~
> > zip.c:90:8: error: packed attribute causes inefficient alignment for
> > 'file_name_length' [-Werror=3Dattributes]
> >    90 |  __u16 file_name_length;
> >       |        ^~~~~~~~~~~~~~~~
> > zip.c:91:8: error: packed attribute causes inefficient alignment for
> > 'extra_field_length' [-Werror=3Dattributes]
> >    91 |  __u16 extra_field_length;
> >       |        ^~~~~~~~~~~~~~~~~~
> > zip.c:92:8: error: packed attribute causes inefficient alignment for
> > 'file_comment_length' [-Werror=3Dattributes]
> >    92 |  __u16 file_comment_length;
> >       |        ^~~~~~~~~~~~~~~~~~~
> > zip.c:94:8: error: packed attribute causes inefficient alignment for
> > 'disk' [-Werror=3Dattributes]
> >    94 |  __u16 disk;
> >       |        ^~~~
> > zip.c:95:8: error: packed attribute causes inefficient alignment for
> > 'internal_attributes' [-Werror=3Dattributes]
> >    95 |  __u16 internal_attributes;
> >       |        ^~~~~~~~~~~~~~~~~~~
> > zip.c:108:8: error: packed attribute causes inefficient alignment for
> > 'magic' [-Werror=3Dattributes]
> >   108 |  __u32 magic;
> >       |        ^~~~~
> > zip.c:110:8: error: packed attribute causes inefficient alignment for
> > 'min_version' [-Werror=3Dattributes]
> >   110 |  __u16 min_version;
> >       |        ^~~~~~~~~~~
> > zip.c:111:8: error: packed attribute causes inefficient alignment for
> > 'flags' [-Werror=3Dattributes]
> >   111 |  __u16 flags;
> >       |        ^~~~~
> > zip.c:112:8: error: packed attribute causes inefficient alignment for
> > 'compression' [-Werror=3Dattributes]
> >   112 |  __u16 compression;
> >       |        ^~~~~~~~~~~
> > zip.c:113:8: error: packed attribute causes inefficient alignment for
> > 'last_modified_time' [-Werror=3Dattributes]
> >   113 |  __u16 last_modified_time;
> >       |        ^~~~~~~~~~~~~~~~~~
> > zip.c:114:8: error: packed attribute causes inefficient alignment for
> > 'last_modified_date' [-Werror=3Dattributes]
> >   114 |  __u16 last_modified_date;
> >       |        ^~~~~~~~~~~~~~~~~~
> > zip.c:118:8: error: packed attribute causes inefficient alignment for
> > 'file_name_length' [-Werror=3Dattributes]
> >   118 |  __u16 file_name_length;
> >       |        ^~~~~~~~~~~~~~~~
> > zip.c:119:8: error: packed attribute causes inefficient alignment for
> > 'extra_field_length' [-Werror=3Dattributes]
> >   119 |  __u16 extra_field_length;
> >       |        ^~~~~~~~~~~~~~~~~~
> > cc1: all warnings being treated as errors
> >
> > Build links,
> > https://storage.tuxsuite.com/public/linaro/lkft/builds/2MfXEyvgh4ba9y3r=
kt6KPf6sUMR/
> >
> >
> > History link,
> > https://qa-reports.linaro.org/lkft/linux-next-master/build/next-2023031=
4/testrun/15564056/suite/build/test/gcc-10-lkftconfig-perf/history/
> >
> >
> > --
> > Linaro LKFT
> > https://lkft.linaro.org