linux-kernel - [PATCH] tracing: Use alignof__(struct {type b;}) instead of offsetof()

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Date:   Tue, 2 Aug 2022 15:44:12 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     Ingo Molnar <mingo@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        David Laight <David.Laight@...LAB.COM>
Subject: [PATCH] tracing: Use alignof__(struct {type b;}) instead of
 offsetof()

From: "Steven Rostedt (Google)" <rostedt@...dmis.org>

Simplify:

  #define ALIGN_STRUCTFIELD(type) ((int)(offsetof(struct {char a; type b;}, b)))

with

  #define  ALIGN_STRUCTFIELD(type) __alignof__(struct {type b;})

Which works just the same.

Link: https://lore.kernel.org/all/a7d202457150472588df0bd3b7334b3f@AcuMS.aculab.com/

Suggested-by: David Laight <David.Laight@...LAB.COM>
Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>
---
 include/trace/stages/stage4_event_fields.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/trace/stages/stage4_event_fields.h b/include/trace/stages/stage4_event_fields.h
index 80d34f396555..a8fb25f39a99 100644
--- a/include/trace/stages/stage4_event_fields.h
+++ b/include/trace/stages/stage4_event_fields.h
@@ -2,7 +2,7 @@
 
 /* Stage 4 definitions for creating trace events */
 
-#define ALIGN_STRUCTFIELD(type) ((int)(offsetof(struct {char a; type b;}, b)))
+#define ALIGN_STRUCTFIELD(type) ((int)(__alignof__(struct {type b;})))
 
 #undef __field_ext
 #define __field_ext(_type, _item, _filter_type) {			\
-- 
2.35.1