linux-kernel - Re: [RFC v2 1/4] cleanup: Fix discarded const warning when defining guards

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Date: Fri, 26 Jan 2024 16:46:08 +0200
From: Amir Goldstein <amir73il@...il.com>
To: Vinicius Costa Gomes <vinicius.gomes@...el.com>
Cc: brauner@...nel.org, hu1.chen@...el.com, miklos@...redi.hu, 
	malini.bhandaru@...el.com, tim.c.chen@...el.com, mikko.ylinen@...el.com, 
	lizhen.you@...el.com, linux-unionfs@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [RFC v2 1/4] cleanup: Fix discarded const warning when defining guards

On Fri, Jan 26, 2024 at 1:57 AM Vinicius Costa Gomes
<vinicius.gomes@...el.com> wrote:
>
> When defining guards for const types the void* return implicitly
> discards the const modifier. Be explicit about it.
>
> Compiler warning (gcc 13.2.1):
>
> ./include/linux/cleanup.h:154:18: warning: return discards ‘const’ qualifier from pointer target type [-Wdiscarded-qualifiers]
>   154 |         { return *_T; }
>       |                  ^~~
> ./include/linux/cred.h:193:1: note: in expansion of macro ‘DEFINE_GUARD’
>   193 | DEFINE_GUARD(cred, const struct cred *, _T = override_creds_light(_T),
>       | ^~~~~~~~~~~~
>

I did not look closely, but can't you use DEFINE_LOCK_GUARD_1()?

Thanks,
Amir.