linux-kernel - Re: [PROBLEM linux-next] /kernel/bpf/btf.c:7581:9: error: function ‘btf_snprintf_show’ might be a candidate for ‘gnu_printf’ format attribute [-Werror=suggest-attribute=format]

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Message-ID: <da7aa81e-493b-452e-bf0d-5bbdda04cf8d@oracle.com>
Date: Thu, 11 Jul 2024 19:26:09 +0100
From: Alan Maguire <alan.maguire@...cle.com>
To: Mirsad Todorovac <mtodorovac69@...il.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Cc: Martin KaFai Lau <martin.lau@...ux.dev>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
        Yonghong Song <yonghong.song@...ux.dev>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        bpf@...r.kernel.org
Subject: Re: [PROBLEM linux-next] /kernel/bpf/btf.c:7581:9: error: function ‘btf_snprintf_show’ might be a candidate for ‘gnu_printf’ format attribute [-Werror=suggest-attribute=format]

On 10/07/2024 19:14, Mirsad Todorovac wrote:
> Dear all,
> 
> On the linux-next vanilla next-20240709 tree, I have attempted the seed KCONFIG_SEED=0xEE7AB52F
> which was known from before to trigger various errors in compile and build process.
> 
> Though this might seem as contributing to channel noise, Linux refuses to build this config,
> treating warnings as errors, using this build line:
> 
> $ time nice make W=1 -k -j 36 |& tee ../err-next-20230709-01a.log; date
> 
> As I know that the Chief Penguin doesn't like warnings, but I am also aware that there are plenty
> left, there seems to be more tedious work ahead to make the compilers happy.
> 
> The compiler output is:
> 
> ./kernel/bpf/btf.c: In function ‘btf_seq_show’:
> ./kernel/bpf/btf.c:7544:29: error: function ‘btf_seq_show’ might be a candidate for ‘gnu_printf’ format attribute [-Werror=suggest-attribute=format]
>  7544 |         seq_vprintf((struct seq_file *)show->target, fmt, args);
>       |                             ^~~~~~~~
> ./kernel/bpf/btf.c: In function ‘btf_snprintf_show’:
> ./kernel/bpf/btf.c:7581:9: error: function ‘btf_snprintf_show’ might be a candidate for ‘gnu_printf’ format attribute [-Werror=suggest-attribute=format]
>  7581 |         len = vsnprintf(show->target, ssnprintf->len_left, fmt, args);
>       |         ^~~
> 
> This doesn't seem alarming, but it prevents build with this config.
>

Thanks for the report! [1] should hopefully resolve this.

[1]
https://lore.kernel.org/bpf/20240711182321.963667-1-alan.maguire@oracle.com/

Alan