Re: [PATCH] libbpf: fix returnvar.cocci warnings

From: Andrii Nakryiko
Date: Thu Apr 28 2022 - 12:23:13 EST


On Wed, Apr 27, 2022 at 9:07 AM Alexei Starovoitov
<alexei.starovoitov@xxxxxxxxx> wrote:
>
> On Wed, Apr 27, 2022 at 1:04 AM kernel test robot <lkp@xxxxxxxxx> wrote:
> >
> > From: kernel test robot <lkp@xxxxxxxxx>
> >
> > tools/lib/bpf/relo_core.c:1064:8-11: Unneeded variable: "len". Return "0" on line 1086
> >
> >
> > Remove unneeded variable used to store return value.
> >
> > Generated by: scripts/coccinelle/misc/returnvar.cocci
> >
> > Fixes: b58af63aab11 ("libbpf: Refactor CO-RE relo human description formatting routine")
> > CC: Andrii Nakryiko <andrii@xxxxxxxxxx>
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > Signed-off-by: kernel test robot <lkp@xxxxxxxxx>
> > ---
> >
> > tree: https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> > head: f02ac5c95dfd45d2f50ecc68d79177de326c668c
> > commit: b58af63aab11e4ae00fe96de9505759cfdde8ee9 [6746/7265] libbpf: Refactor CO-RE relo human description formatting routine
> > :::::: branch date: 2 hours ago
> > :::::: commit date: 9 hours ago
> >
> > tools/lib/bpf/relo_core.c | 10 +++++-----
> > 1 file changed, 5 insertions(+), 5 deletions(-)
> >
> > --- a/tools/lib/bpf/relo_core.c
> > +++ b/tools/lib/bpf/relo_core.c
> > @@ -1061,7 +1061,7 @@ static int bpf_core_format_spec(char *bu
> > const struct btf_enum *e;
> > const char *s;
> > __u32 type_id;
> > - int i, len = 0;
> > + int i;
> >
> > #define append_buf(fmt, args...) \
> > ({ \
> > @@ -1083,7 +1083,7 @@ static int bpf_core_format_spec(char *bu
> > type_id, btf_kind_str(t), str_is_empty(s) ? "<anon>" : s);
> >
> > if (core_relo_is_type_based(spec->relo_kind))
> > - return len;
> > + return 0;
>
> cocci is wrong.
> It missed append_buf() macro.

Should be irrelevant once [0] lands. It makes use of that return value directly.

[0] https://patchwork.kernel.org/project/netdevbpf/patch/20220428041523.4089853-2-andrii@xxxxxxxxxx/

>
> Please fix cocci so we don't have to manually deal with
> broken patches like this one.