linux-kernel - Re: [PATCH] sctp: chunk.c: correct format string for size

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Date:   Thu, 28 Feb 2019 10:55:34 -0300
From:   Marcelo Ricardo Leitner <marcelo.leitner@...il.com>
To:     Matthias Maennich <maennich@...gle.com>
Cc:     Vlad Yasevich <vyasevich@...il.com>,
        Neil Horman <nhorman@...driver.com>,
        "David S. Miller" <davem@...emloft.net>,
        linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sctp: chunk.c: correct format string for size_t in printk

On Thu, Feb 28, 2019 at 11:36:52AM +0000, Matthias Maennich wrote:
> According to Documentation/core-api/printk-formats.rst, size_t should be
> printed with %zu, rather than %Zu.
> 
> In addition, using %Zu triggers a warning on clang (-Wformat-extra-args):
> 
> net/sctp/chunk.c:196:25: warning: data argument not used by format string [-Wformat-extra-args]
>                                     __func__, asoc, max_data);
>                                     ~~~~~~~~~~~~~~~~^~~~~~~~~
> ./include/linux/printk.h:440:49: note: expanded from macro 'pr_warn_ratelimited'
>         printk_ratelimited(KERN_WARNING pr_fmt(fmt), ##__VA_ARGS__)
>         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~
> ./include/linux/printk.h:424:17: note: expanded from macro 'printk_ratelimited'
>                 printk(fmt, ##__VA_ARGS__);                             \
>                        ~~~    ^
> 
> Fixes: 5b5e0928f742 ("lib/vsprintf.c: remove %Z support")
> Link: https://github.com/ClangBuiltLinux/linux/issues/378
> Signed-off-by: Matthias Maennich <maennich@...gle.com>

Acked-by: Marcelo Ricardo Leitner <marcelo.leitner@...il.com>

> ---
>  net/sctp/chunk.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/sctp/chunk.c b/net/sctp/chunk.c
> index 64bef313d436..5cb7c1ff97e9 100644
> --- a/net/sctp/chunk.c
> +++ b/net/sctp/chunk.c
> @@ -192,7 +192,7 @@ struct sctp_datamsg *sctp_datamsg_from_user(struct sctp_association *asoc,
>  	if (unlikely(!max_data)) {
>  		max_data = sctp_min_frag_point(sctp_sk(asoc->base.sk),
>  					       sctp_datachk_len(&asoc->stream));
> -		pr_warn_ratelimited("%s: asoc:%p frag_point is zero, forcing max_data to default minimum (%Zu)",
> +		pr_warn_ratelimited("%s: asoc:%p frag_point is zero, forcing max_data to default minimum (%zu)",
>  				    __func__, asoc, max_data);
>  	}
>  
> -- 
> 2.21.0.rc2.261.ga7da99ff1b-goog
>