netdev - Re: [PATCH bpf-next] tools: bpftool: do not pass json_wtr to emit_obj_refs

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Message-ID: <CACdoK4JtoehffN73A-q77JCOPc6O4hK9zMG1XSai2TdM7NCtYw@mail.gmail.com>
Date:   Tue, 23 Jun 2020 22:25:07 +0100
From:   Quentin Monnet <quentin@...valent.com>
To:     Andrii Nakryiko <andrii.nakryiko@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andriin@...com>, bpf <bpf@...r.kernel.org>,
        Networking <netdev@...r.kernel.org>
Subject: Re: [PATCH bpf-next] tools: bpftool: do not pass json_wtr to emit_obj_refs_json()

On Tue, 23 Jun 2020 at 19:27, Andrii Nakryiko <andrii.nakryiko@...il.com> wrote:
>
> On Tue, Jun 23, 2020 at 8:54 AM Quentin Monnet <quentin@...valent.com> wrote:
> >
> > Building bpftool yields the following complaint:
> >
> >     pids.c: In function ‘emit_obj_refs_json’:
> >     pids.c:175:80: warning: declaration of ‘json_wtr’ shadows a global declaration [-Wshadow]
> >       175 | void emit_obj_refs_json(struct obj_refs_table *table, __u32 id, json_writer_t *json_wtr)
> >           |                                                                 ~~~~~~~~~~~~~~~^~~~~~~~
> >     In file included from pids.c:11:
> >     main.h:141:23: note: shadowed declaration is here
> >       141 | extern json_writer_t *json_wtr;
> >           |                       ^~~~~~~~
> >
> > json_wtr being exposed in main.h (included in pids.c) as an extern, it
> > is directly available and there is no need to pass it through the
> > function. Let's simply use the global variable.
>
> I don't think it's a good approach to assume that emit_obj_refs_json
> is always going to be using a global json writer. I think this shadow
> warning is bogus in this case, honestly. But if it bothers you, let's
> just rename json_wtr into whatever other name of argument you prefer.

I didn't mind using the global JSON writer, but I'm not strictly opposed to
passing a writer down to emit_obj_refs_json() either, so ok. I'll
still respin to
rename the variable, it will be clearer that the function does not rely on the
global writer.

Thanks for the feedback.
Quentin