linux-kernel - Re: [PATCH v2 23/23] bpf: selftests: PSI struct ops test

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Message-ID: <CAADnVQLcmJ3X7X6oW_v0KgQCPtgjmYNtgfqXqH5tFrQ+Q+5v+A@mail.gmail.com>
Date: Tue, 28 Oct 2025 10:30:50 -0700
From: Alexei Starovoitov <alexei.starovoitov@...il.com>
To: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: bot+bpf-ci@...nel.org, Andrew Morton <akpm@...ux-foundation.org>, 
	LKML <linux-kernel@...r.kernel.org>, Alexei Starovoitov <ast@...nel.org>, 
	Suren Baghdasaryan <surenb@...gle.com>, Michal Hocko <mhocko@...nel.org>, 
	Shakeel Butt <shakeel.butt@...ux.dev>, Johannes Weiner <hannes@...xchg.org>, 
	Andrii Nakryiko <andrii@...nel.org>, inwardvessel <inwardvessel@...il.com>, 
	linux-mm <linux-mm@...ck.org>, 
	"open list:CONTROL GROUP (CGROUP)" <cgroups@...r.kernel.org>, bpf <bpf@...r.kernel.org>, 
	Martin KaFai Lau <martin.lau@...nel.org>, Song Liu <song@...nel.org>, 
	Kumar Kartikeya Dwivedi <memxor@...il.com>, Tejun Heo <tj@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Eduard <eddyz87@...il.com>, Yonghong Song <yonghong.song@...ux.dev>, Chris Mason <clm@...a.com>, 
	Ihor Solodrai <ihor.solodrai@...ux.dev>
Subject: Re: [PATCH v2 23/23] bpf: selftests: PSI struct ops test

On Tue, Oct 28, 2025 at 10:13 AM Roman Gushchin
<roman.gushchin@...ux.dev> wrote:
> >> +
> >> +/* cgroup which will be deleted */
> >> +u64 deleted_cgroup_id;
> >> +
> >> +/* cgroup which will be created */
> >> +u64 new_cgroup_id;
> >> +
> >> +/* cgroup which was deleted */
> >> +u64 deleted_cgroup_id;
> >>    ^^^^^^^^^^^^^^^^^^
> >
> > Is deleted_cgroup_id intentionally declared twice here? This appears
> > to be a duplicate global variable declaration - the same variable is
> > declared at line 13 with comment "cgroup which will be deleted" and
> > again at line 19 with comment "cgroup which was deleted".
>
> Correct, fixed.

wow. TIL.

I didn't know that C allows such double variable definition
outside of function bodies.
Even with -Wall gcc/clang don't warn about it.