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

From: Ian Rogers
Date: Thu Jun 22 2023 - 20:56:53 EST


On Thu, Jun 22, 2023 at 3:28 PM Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
>
> On Wed, Jun 21, 2023 at 12:05 AM Ian Rogers <irogers@xxxxxxxxxx> wrote:
> >
> > On Thu, May 25, 2023 at 3:09 PM Namhyung Kim <namhyung@xxxxxxxxxx> 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@xxxxxxxxxx>
> > > ---
> > > 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(). :)

:-) Could those loops not be:

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

rather than using a goto?

> >
> > > + 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 */

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

Thanks,
Ian

> 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
> > >