Commit 2a24e248 authored by Andrii Nakryiko's avatar Andrii Nakryiko Committed by Daniel Borkmann
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bpftool: Use __typeof__() instead of typeof() in BPF skeleton 



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: c2a0257c ("bpftool: Cast pointers for shadow types explicitly.")
Fixes: 00389c58 ("bpftool: Add support for subskeletons")
Signed-off-by: default avatarAndrii Nakryiko <andrii@kernel.org>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarKui-Feng Lee <thinker.li@gmail.com>
Acked-by: default avatarQuentin Monnet <qmo@kernel.org>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20240401170713.2081368-1-andrii@kernel.org
parent 965c6167

tools/bpf/bpftool/gen.c

+2 −2
Original line number Diff line number Diff line
@@ -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);