linux-kernel - Re: [PATCH] audit: avoid -Wempty-body warning

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Message-ID: <20210322143344.GN3141668@madcap2.tricolour.ca>
Date:   Mon, 22 Mar 2021 10:33:44 -0400
From:   Richard Guy Briggs <rgb@...hat.com>
To:     Arnd Bergmann <arnd@...nel.org>
Cc:     Paul Moore <paul@...l-moore.com>, Eric Paris <eparis@...hat.com>,
        Arnd Bergmann <arnd@...db.de>,
        Jules Irenge <jbi.octave@...il.com>, linux-audit@...hat.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] audit: avoid -Wempty-body warning

On 2021-03-22 12:45, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> gcc warns about an empty statement when audit_remove_mark is defined to
> nothing:
> 
> kernel/auditfilter.c: In function 'audit_data_to_entry':
> kernel/auditfilter.c:609:51: error: suggest braces around empty body in an 'if' statement [-Werror=empty-body]
>   609 |                 audit_remove_mark(entry->rule.exe); /* that's the template one */
>       |                                                   ^
> 
> Change the macros to use the usual "do { } while (0)" instead, and change a
> few more that were (void)0, for consistency.

So what about audit_put_watch() and audit_get_watch() which are set to
{}?   (And all of include/linux/audit.h that uses the latter...)  Does
this only matter if they are the only action called in an if or loop?

> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
>  kernel/audit.h | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/kernel/audit.h b/kernel/audit.h
> index 3b9c0945225a..c39c5f3b8422 100644
> --- a/kernel/audit.h
> +++ b/kernel/audit.h
> @@ -302,8 +302,8 @@ extern struct list_head *audit_killed_trees(void);
>  
>  #define audit_alloc_mark(k, p, l) (ERR_PTR(-EINVAL))
>  #define audit_mark_path(m) ""
> -#define audit_remove_mark(m)
> -#define audit_remove_mark_rule(k)
> +#define audit_remove_mark(m) do { } while (0)
> +#define audit_remove_mark_rule(k) do { } while (0)
>  #define audit_mark_compare(m, i, d) 0
>  #define audit_exe_compare(t, m) (-EINVAL)
>  #define audit_dupe_exe(n, o) (-EINVAL)
> @@ -311,8 +311,8 @@ extern struct list_head *audit_killed_trees(void);
>  #define audit_remove_tree_rule(rule) BUG()
>  #define audit_add_tree_rule(rule) -EINVAL
>  #define audit_make_tree(rule, str, op) -EINVAL
> -#define audit_trim_trees() (void)0
> -#define audit_put_tree(tree) (void)0
> +#define audit_trim_trees() do { } while (0)
> +#define audit_put_tree(tree) do { } while (0)
>  #define audit_tag_tree(old, new) -EINVAL
>  #define audit_tree_path(rule) ""	/* never called */
>  #define audit_kill_trees(context) BUG()
> -- 
> 2.29.2
> 

- RGB

--
Richard Guy Briggs <rgb@...hat.com>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635