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From:   Ian Rogers <irogers@google.com>
Date:   Wed, 21 Jun 2023 00:05:34 -0700
Message-ID: <CAP-5=fWOji8vCQfO-y4HnmFk2k+F70BtGHTjCg6XyORNfYNcww@mail.gmail.com>
Subject: Re: [PATCH] tools lib subcmd: Show parent options in help
To:     Namhyung Kim <namhyung@kernel.org>
Cc:     Arnaldo Carvalho de Melo <acme@kernel.org>,
        Jiri Olsa <jolsa@kernel.org>,
        Adrian Hunter <adrian.hunter@intel.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>,
        linux-perf-users@vger.kernel.org
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On Thu, May 25, 2023 at 3:09=E2=80=AFPM Namhyung Kim <namhyung@kernel.org> =
wrote:
>
> I've just realized that help message in a subcommand didn't show one
> in the parent command.  Since the option parser understands the parent,
> display code should do the same.  For example, `perf ftrace latency -h`
> should show options in the `perf ftrace` command too.
>
> Before:
>
>   $ perf ftrace latency -h
>
>    Usage: perf ftrace [<options>] [<command>]
>       or: perf ftrace [<options>] -- [<command>] [<options>]
>       or: perf ftrace {trace|latency} [<options>] [<command>]
>       or: perf ftrace {trace|latency} [<options>] -- [<command>] [<option=
s>]
>
>       -b, --use-bpf         Use BPF to measure function latency
>       -n, --use-nsec        Use nano-second histogram
>       -T, --trace-funcs <func>
>                             Show latency of given function
>
> After:
>
>   $ perf ftrace latency -h
>
>    Usage: perf ftrace [<options>] [<command>]
>       or: perf ftrace [<options>] -- [<command>] [<options>]
>       or: perf ftrace {trace|latency} [<options>] [<command>]
>       or: perf ftrace {trace|latency} [<options>] -- [<command>] [<option=
s>]
>
>       -a, --all-cpus        System-wide collection from all CPUs
>       -b, --use-bpf         Use BPF to measure function latency
>       -C, --cpu <cpu>       List of cpus to monitor
>       -n, --use-nsec        Use nano-second histogram
>       -p, --pid <pid>       Trace on existing process id
>       -T, --trace-funcs <func>
>                             Show latency of given function
>       -v, --verbose         Be more verbose
>           --tid <tid>       Trace on existing thread id (exclusive to --p=
id)
>
> Signed-off-by: Namhyung Kim <namhyung@kernel.org>
> ---
>  tools/lib/subcmd/parse-options.c | 26 ++++++++++++++++++--------
>  1 file changed, 18 insertions(+), 8 deletions(-)
>
> diff --git a/tools/lib/subcmd/parse-options.c b/tools/lib/subcmd/parse-op=
tions.c
> index 9fa75943f2ed..41de97671c72 100644
> --- a/tools/lib/subcmd/parse-options.c
> +++ b/tools/lib/subcmd/parse-options.c
> @@ -806,18 +806,28 @@ static int option__cmp(const void *va, const void *=
vb)
>
>  static struct option *options__order(const struct option *opts)
>  {
> -       int nr_opts =3D 0, nr_group =3D 0, len;
> -       const struct option *o =3D opts;
> -       struct option *opt, *ordered, *group;
> +       int nr_opts =3D 0, nr_group =3D 0, nr_parent =3D 0, len;
> +       const struct option *o, *p =3D opts;
> +       struct option *opt, *ordered =3D NULL, *group;
>
> -       for (o =3D opts; o->type !=3D OPTION_END; o++)
> +retry:

Why use "goto retry" and not compute the size with the parent upfront?

> +       for (o =3D p; o->type !=3D OPTION_END; o++)
>                 ++nr_opts;
>
> -       len =3D sizeof(*o) * (nr_opts + 1);
> -       ordered =3D malloc(len);
> -       if (!ordered)
> +       len =3D sizeof(*o) * (nr_opts + !o->parent);

It'd be nice to comment on why the "!o->parent" here.

Thanks,
Ian

> +       group =3D realloc(ordered, len);
> +       if (!group)
>                 goto out;
> -       memcpy(ordered, opts, len);
> +       ordered =3D group;
> +       memcpy(&ordered[nr_parent], p, sizeof(*o) * (nr_opts - nr_parent)=
);
> +
> +       if (o->parent) {
> +               p =3D o->parent;
> +               nr_parent =3D nr_opts;
> +               goto retry;
> +       }
> +       /* copy the last OPTION_END */
> +       memcpy(&ordered[nr_opts], o, sizeof(*o));
>
>         /* sort each option group individually */
>         for (opt =3D group =3D ordered; opt->type !=3D OPTION_END; opt++)=
 {
> --
> 2.41.0.rc0.172.g3f132b7071-goog
>