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Subject: Re: [PATCH bpf-next] selftests/bpf: Fix strncpy() fortify warning
To:     Rong Tao <rtoax@foxmail.com>, david.laight@aculab.com
Cc:     andrii.nakryiko@gmail.com, andrii@kernel.org, ast@kernel.org,
        bpf@vger.kernel.org, haoluo@google.com, john.fastabend@gmail.com,
        jolsa@kernel.org, kpsingh@kernel.org, linux-kernel@vger.kernel.org,
        linux-kselftest@vger.kernel.org, martin.lau@linux.dev,
        mykolal@fb.com, rongtao@cestc.cn, sdf@google.com, shuah@kernel.org,
        song@kernel.org, yhs@fb.com
References: <70ddf02157bc418cbc38230c87a7b228@AcuMS.aculab.com>
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From:   Daniel Borkmann <daniel@iogearbox.net>
Message-ID: <fc8634e8-6efd-9911-cab4-07ad6ba4ad33@iogearbox.net>
Date:   Tue, 1 Nov 2022 14:56:23 +0100
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On 11/1/22 1:21 PM, Rong Tao wrote:
> From: Rong Tao <rongtao@cestc.cn>
> 
> move libbpf_strlcpy() to bpf_util.h, and replace strncpy() with
> libbpf_strlcpy(), fix compile warning.
> 
> Compile samples/bpf, warning:
> $ cd samples/bpf
> $ make
> ...
> cgroup_helpers.c: In function ‘__enable_controllers’:
> cgroup_helpers.c:80:17: warning: ‘strncpy’ specified bound 4097 equals destination size [-Wstringop-truncation]
>     80 |                 strncpy(enable, controllers, sizeof(enable));
>        |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 

BPF CI now throws a new warning after your patch:

https://github.com/kernel-patches/bpf/actions/runs/3369416153/jobs/5589052613

   [...]
   xsk.c:536:2: error: call to undeclared function 'libbpf_strlcpy'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
           libbpf_strlcpy(ifr.ifr_name, ctx->ifname, IFNAMSIZ);
           ^
   xsk.c:755:2: error: call to undeclared function 'libbpf_strlcpy'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
           libbpf_strlcpy(ctx->ifname, ifname, IFNAMSIZ);
           ^
   xsk.c:942:2: error: call to undeclared function 'libbpf_strlcpy'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
           libbpf_strlcpy(ctx->ifname, ifname, IFNAMSIZ);
           ^
   3 errors generated.
   make: *** [Makefile:166: /tmp/work/bpf/bpf/tools/testing/selftests/bpf/xsk.o] Error 1
   make: *** Waiting for unfinished jobs....