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Date:   Sun, 19 Jul 2020 23:17:41 -0700
From:   Ian Rogers <>
To:     Alexei Starovoitov <>,
        Daniel Borkmann <>,
        Martin KaFai Lau <>,
        Song Liu <>, Yonghong Song <>,
        Andrii Nakryiko <>,
        John Fastabend <>,
        KP Singh <>,,,
Cc:     Stanislav Fomichev <>,
        Ian Rogers <>
Subject: [PATCH v2] libbpf bpf_helpers: Use __builtin_offsetof for offsetof

The non-builtin route for offsetof has a dependency on size_t from
stdlib.h/stdint.h that is undeclared and may break targets.
The offsetof macro in bpf_helpers may disable the same macro in other
headers that have a #ifdef offsetof guard. Rather than add additional
dependencies improve the offsetof macro declared here to use the
builtin that is available since llvm 3.7 (the first with a BPF backend).

Signed-off-by: Ian Rogers <>
 tools/lib/bpf/bpf_helpers.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h
index a510d8ed716f..bc14db706b88 100644
--- a/tools/lib/bpf/bpf_helpers.h
+++ b/tools/lib/bpf/bpf_helpers.h
@@ -40,7 +40,7 @@
  * Helper macro to manipulate data structures
 #ifndef offsetof
-#define offsetof(TYPE, MEMBER)  ((size_t)&((TYPE *)0)->MEMBER)
+#define offsetof(TYPE, MEMBER)  __builtin_offsetof(TYPE, MEMBER)
 #ifndef container_of
 #define container_of(ptr, type, member)				\

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