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([2600:1700:6cf8:1240:769d:e8e1:4c99:3e97]) by smtp.gmail.com with ESMTPSA id 15-20020aca090f000000b003c3ede3ac23sm1586964oij.2.2024.04.01.10.59.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 01 Apr 2024 10:59:56 -0700 (PDT) Message-ID: Date: Mon, 1 Apr 2024 10:59:55 -0700 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next] bpftool: use __typeof__() instead of typeof() in BPF skeleton To: Andrii Nakryiko , bpf@vger.kernel.org, ast@kernel.org, daniel@iogearbox.net, martin.lau@kernel.org Cc: kernel-team@meta.com References: <20240401170713.2081368-1-andrii@kernel.org> Content-Language: en-US From: Kui-Feng Lee In-Reply-To: <20240401170713.2081368-1-andrii@kernel.org> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 4/1/24 10:07, Andrii Nakryiko wrote: > When generated BPF skeleton header is included in C++ code base, some > compiler setups will emit warning about using language extensions due to > typeof() usage, resulting in something like: > > error: extension used [-Werror,-Wlanguage-extension-token] > obj->struct_ops.empty_tcp_ca = (typeof(obj->struct_ops.empty_tcp_ca)) > ^ > > It looks like __typeof__() is a preferred way to do typeof() with better > C++ compatibility behavior, so switch to that. With __typeof__() we get > no such warning. > > Fixes: c2a0257c1edf ("bpftool: Cast pointers for shadow types explicitly.") > Fixes: 00389c58ffe9 ("bpftool: Add support for subskeletons") > Signed-off-by: Andrii Nakryiko > --- > tools/bpf/bpftool/gen.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/tools/bpf/bpftool/gen.c b/tools/bpf/bpftool/gen.c > index 786268f1a483..b3979ddc0189 100644 > --- a/tools/bpf/bpftool/gen.c > +++ b/tools/bpf/bpftool/gen.c > @@ -386,7 +386,7 @@ static int codegen_subskel_datasecs(struct bpf_object *obj, const char *obj_name > */ > needs_typeof = btf_is_array(var) || btf_is_ptr_to_func_proto(btf, var); > if (needs_typeof) > - printf("typeof("); > + printf("__typeof__("); > > err = btf_dump__emit_type_decl(d, var_type_id, &opts); > if (err) > @@ -1131,7 +1131,7 @@ static void gen_st_ops_shadow_init(struct btf *btf, struct bpf_object *obj) > continue; > codegen("\ > \n\ > - obj->struct_ops.%1$s = (typeof(obj->struct_ops.%1$s))\n\ > + obj->struct_ops.%1$s = (__typeof__(obj->struct_ops.%1$s))\n\ > bpf_map__initial_value(obj->maps.%1$s, NULL);\n\ > \n\ > ", ident); LGTM! Acked-by: Kui-Feng Lee Thanks!