linux-kernel - [PATCH v2 2/3] kernel.h: hide __is

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Message-Id: <20181109093534.15121-2-johannes@sipsolutions.net>
Date:   Fri,  9 Nov 2018 10:35:33 +0100
From:   Johannes Berg <johannes@...solutions.net>
To:     linux-kernel@...r.kernel.org, akpm@...ux-foundation.org
Cc:     Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH v2 2/3] kernel.h: hide __is_constexpr() from sparse

From: Johannes Berg <johannes.berg@...el.com>

__is_constexpr() is a work of art, understandable only to the most
respected wizards of C. Even sparse doesn't seem to belong to that
group and warns that there's an "expression using sizeof(void)".

Just hide the definition from sparse and pretend it's always true.

Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
 include/linux/kernel.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index d6aac75b51ba..d4d2233f95c9 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -844,6 +844,7 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
 #define __typecheck(x, y) \
 		(!!(sizeof((typeof(x) *)1 == (typeof(y) *)1)))
 
+#ifndef __CHECKER__
 /*
  * This returns a constant expression while determining if an argument is
  * a constant expression, most importantly without evaluating the argument.
@@ -851,6 +852,13 @@ static inline void ftrace_dump(enum ftrace_dump_mode oops_dump_mode) { }
  */
 #define __is_constexpr(x) \
 	(sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
+#else
+/*
+ * We don't really care about the check when running sparse and the
+ * above expression causes a warning due to sizeof(void).
+ */
+#define __is_constexpr(x) 1
+#endif
 
 #define __no_side_effects(x, y) \
 		(__is_constexpr(x) && __is_constexpr(y))
-- 
2.17.2