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 <irog...@google.com>
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 <y...@fb.com>
---
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) \
({ \
