On 7/17/20 12:23 AM, Ian Rogers wrote:
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 if available. Signed-off-by: Ian Rogers <irogers@xxxxxxxxxx>
Thanks. I didn't pay attention to __builtin_offsetof() and clearly it is preferred. Ack the change with a nit below. Acked-by: Yonghong Song <yhs@xxxxxx>
--- tools/lib/bpf/bpf_helpers.h | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/tools/lib/bpf/bpf_helpers.h b/tools/lib/bpf/bpf_helpers.h index a510d8ed716f..ed2ac74fc515 100644 --- a/tools/lib/bpf/bpf_helpers.h +++ b/tools/lib/bpf/bpf_helpers.h @@ -40,8 +40,12 @@ * Helper macro to manipulate data structures */ #ifndef offsetof +#if __has_builtin(__builtin_offsetof) +#define offsetof(TYPE, MEMBER) __builtin_offsetof(TYPE, MEMBER)
The __builtin_offsetof is actually available at least since llvm 3.7, so it is safe to use it always.
+#else #define offsetof(TYPE, MEMBER) ((size_t)&((TYPE *)0)->MEMBER) #endif +#endif #ifndef container_of #define container_of(ptr, type, member) \ ({ \