linux-kernel - [PATCH] typecheck.h: Force a compilation error if typecheck(type,x) fails

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Message-Id: <20220203143557.218112-1-abbotti@mev.co.uk>
Date:   Thu,  3 Feb 2022 14:35:57 +0000
From:   Ian Abbott <abbotti@....co.uk>
To:     linux-kernel@...r.kernel.org
Cc:     Ian Abbott <abbotti@....co.uk>
Subject: [PATCH] typecheck.h: Force a compilation error if typecheck(type,x) fails

Calling the `typecheck(type,x)` macro emits a compiler warning if the
type of `x` is incompatible with type `type`.  Change it to force a
compilation error instead.

Signed-off-by: Ian Abbott <abbotti@....co.uk>
---
 include/linux/typecheck.h | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/include/linux/typecheck.h b/include/linux/typecheck.h
index 46b15e2aaefb..c9125304f6ba 100644
--- a/include/linux/typecheck.h
+++ b/include/linux/typecheck.h
@@ -2,14 +2,15 @@
 #ifndef TYPECHECK_H_INCLUDED
 #define TYPECHECK_H_INCLUDED
 
+#include <linux/compiler_types.h>
+#include <linux/build_bug.h>
+
 /*
  * Check at compile time that something is of a particular type.
  * Always evaluates to 1 so you may use it easily in comparisons.
  */
 #define typecheck(type,x) \
-({	type __dummy; \
-	typeof(x) __dummy2; \
-	(void)(&__dummy == &__dummy2); \
+({	BUILD_BUG_ON(!__same_type(type, (x))); \
 	1; \
 })
 
-- 
2.34.1