linux-kernel - Re: [PATCH] tools lib subcmd: Show parent options in help

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Date:   Thu, 22 Jun 2023 15:28:31 -0700
From:   Namhyung Kim <namhyung@...nel.org>
To:     Ian Rogers <irogers@...gle.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-perf-users@...r.kernel.org
Subject: Re: [PATCH] tools lib subcmd: Show parent options in help

On Wed, Jun 21, 2023 at 12:05 AM Ian Rogers <irogers@...gle.com> wrote:
>
> On Thu, May 25, 2023 at 3:09 PM Namhyung Kim <namhyung@...nel.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>] [<options>]
> >
> >       -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>] [<options>]
> >
> >       -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@...nel.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-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 void *vb)
> >
> >  static struct option *options__order(const struct option *opts)
> >  {
> > -       int nr_opts = 0, nr_group = 0, len;
> > -       const struct option *o = opts;
> > -       struct option *opt, *ordered, *group;
> > +       int nr_opts = 0, nr_group = 0, nr_parent = 0, len;
> > +       const struct option *o, *p = opts;
> > +       struct option *opt, *ordered = NULL, *group;
> >
> > -       for (o = opts; o->type != 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(). :)

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

Thanks,
Namhyung


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