netdev - Re: [PATCH] bpftool: Fix generated code in codegen

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Date:   Mon, 28 Mar 2022 20:50:39 +0200
From:   Jiri Olsa <olsajiri@...il.com>
To:     Yonghong Song <yhs@...com>
Cc:     Jiri Olsa <jolsa@...nel.org>, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Delyan Kratunov <delyank@...com>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        netdev@...r.kernel.org, bpf@...r.kernel.org,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...omium.org>
Subject: Re: [PATCH] bpftool: Fix generated code in codegen_asserts

On Mon, Mar 28, 2022 at 08:41:18AM -0700, Yonghong Song wrote:
> 
> 
> On 3/28/22 1:37 AM, Jiri Olsa wrote:
> > Arnaldo reported perf compilation fail with:
> > 
> >    $ make -k BUILD_BPF_SKEL=1 CORESIGHT=1 PYTHON=python3
> >    ...
> >    In file included from util/bpf_counter.c:28:
> >    /tmp/build/perf//util/bpf_skel/bperf_leader.skel.h: In function ‘bperf_leader_bpf__assert’:
> >    /tmp/build/perf//util/bpf_skel/bperf_leader.skel.h:351:51: error: unused parameter ‘s’ [-Werror=unused-parameter]
> >      351 | bperf_leader_bpf__assert(struct bperf_leader_bpf *s)
> >          |                          ~~~~~~~~~~~~~~~~~~~~~~~~~^
> >    cc1: all warnings being treated as errors
> > 
> > If there's nothing to generate in the new assert function,
> > we will get unused 's' warn/error, adding 'unused' attribute to it.
> 
> If there is nothing to generate, should we avoid generating
> the assert function itself?

good point, will check

jirka

> 
> > 
> > Cc: Delyan Kratunov <delyank@...com>
> > Reported-by: Arnaldo Carvalho de Melo <acme@...hat.com>
> > Fixes: 08d4dba6ae77 ("bpftool: Bpf skeletons assert type sizes")
> > Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> > ---
> >   tools/bpf/bpftool/gen.c | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c
> > index 7ba7ff55d2ea..91af2850b505 100644
> > --- a/tools/bpf/bpftool/gen.c
> > +++ b/tools/bpf/bpftool/gen.c
> > @@ -477,7 +477,7 @@ static void codegen_asserts(struct bpf_object *obj, const char *obj_name)
> >   	codegen("\
> >   		\n\
> >   		__attribute__((unused)) static void			    \n\
> > -		%1$s__assert(struct %1$s *s)				    \n\
> > +		%1$s__assert(struct %1$s *s __attribute__((unused)))	    \n\
> >   		{							    \n\
> >   		#ifdef __cplusplus					    \n\
> >   		#define _Static_assert static_assert			    \n\