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From:   Ian Rogers <irogers@google.com>
Date:   Thu, 22 Jun 2023 17:56:30 -0700
Message-ID: <CAP-5=fXPpWgs6JXpQgvwrWmAFCVFwP3a_dq95YwnYuUbo+GQaA@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, Jun 22, 2023 at 3:28=E2=80=AFPM Namhyung Kim <namhyung@kernel.org> =
wrote:
>
> On Wed, Jun 21, 2023 at 12:05=E2=80=AFAM Ian Rogers <irogers@google.com> =
wrote:
> >
> > On Thu, May 25, 2023 at 3:09=E2=80=AFPM Namhyung Kim <namhyung@kernel.o=
rg> 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 paren=
t,
> > > 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>] [<op=
tions>]
> > >
> > >       -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>] [<op=
tions>]
> > >
> > >       -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=
 --pid)
> > >
> > > 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/pars=
e-options.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 vo=
id *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?
>
> No specific reason, just followed the same pattern as in
> parse_{short,long}_opt(). :)

:-) Could those loops not be:

for (; options; options =3D options->parent) {
...
}

rather than using a goto?

> >
> > > +       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.
>
> What about this?
>
> /* It needs a terminating NULL entry when there's no parent */

Perhaps:
the length is given by the number of options plus a null terminator
for the last loop iteration.

It may be cleaner to just compute this after nr_opts settles. perhaps
something along the lines of:

for (p =3D .. ; p; p =3D p->parent)
   for (o =3D p; o->type !=3D OPTION_END; o++)
                 ++nr_opts;
len =3D sizeof(*o) * (nr_opts + 1); /* +1 for terminator */

Thanks,
Ian

> Thanks,
> Namhyung
>
>
> >
> > 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_par=
ent));
> > > +
> > > +       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; op=
t++) {
> > > --
> > > 2.41.0.rc0.172.g3f132b7071-goog
> > >