linux-kernel - [PATCH next] compiler.h: Move __is

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Message-ID: <6d2b584e26544ee6a0810e494352d432@AcuMS.aculab.com>
Date:   Mon, 2 Oct 2023 14:34:05 +0000
From:   David Laight <David.Laight@...LAB.COM>
To:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "'linux@...musvillemoes.dk'" <linux@...musvillemoes.dk>,
        'Steven Rostedt' <rostedt@...dmis.org>,
        "keescook@...omium.org" <keescook@...omium.org>,
        "'bvanassche@....org'" <bvanassche@....org>,
        "torvalds@...ux-foundation.org" <torvalds@...ux-foundation.org>,
        Nathan Chancellor <nathan@...nel.org>,
        "Nick Desaulniers" <ndesaulniers@...gle.com>,
        Arnd Bergmann <arnd@...db.de>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: [PATCH next] compiler.h: Move __is_constexpr() to compiler.h.

Prior to f747e6667ebb2 __is_constexpr() was in its only user minmax.h.
That commit moved it to const.h - but that file just defined ULL(x) and
  UL(x) so that constants can be defined for .S and .c files.
So apart from the word 'const' it wasn't really a good location.
Instead move the definition to compiler.h just before the similar
  is_signed_type() and is_unsigned_type().
(Which were moved there by dcf8e5633e2e6)
This may not be a good long-term home, but the three definitions
  belong together.

Signed-off-by: David Laight <david.laight@...lab.com>
---
This makes it possible to use __is_constexpr() inside is_signed_type()
so that the result is constant integer expression for pointer types.
In particular (void *)1 isn't constant enough.

 include/linux/compiler.h    | 8 ++++++++
 include/linux/const.h       | 8 --------
 tools/include/linux/const.h | 8 --------
 3 files changed, 8 insertions(+), 16 deletions(-)

diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index d7779a18b24f..2efec9bfcc40 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -230,6 +230,14 @@ static inline void *offset_to_ptr(const int *off)
 /* &a[0] degrades to a pointer: a different type from an array */
 #define __must_be_array(a)	BUILD_BUG_ON_ZERO(__same_type((a), &(a)[0]))
 
+/*
+ * This returns a constant expression while determining if an argument is
+ * a constant expression, most importantly without evaluating the argument.
+ * Glory to Martin Uecker <Martin.Uecker@....uni-goettingen.de>
+ */
+#define __is_constexpr(x) \
+	(sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
+
 /*
  * Whether 'type' is a signed type or an unsigned type. Supports scalar types,
  * bool and also pointer types.
diff --git a/include/linux/const.h b/include/linux/const.h
index 435ddd72d2c4..81b8aae5a855 100644
--- a/include/linux/const.h
+++ b/include/linux/const.h
@@ -3,12 +3,4 @@
 
 #include <vdso/const.h>
 
-/*
- * This returns a constant expression while determining if an argument is
- * a constant expression, most importantly without evaluating the argument.
- * Glory to Martin Uecker <Martin.Uecker@....uni-goettingen.de>
- */
-#define __is_constexpr(x) \
-	(sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
-
 #endif /* _LINUX_CONST_H */
diff --git a/tools/include/linux/const.h b/tools/include/linux/const.h
index 435ddd72d2c4..81b8aae5a855 100644
--- a/tools/include/linux/const.h
+++ b/tools/include/linux/const.h
@@ -3,12 +3,4 @@
 
 #include <vdso/const.h>
 
-/*
- * This returns a constant expression while determining if an argument is
- * a constant expression, most importantly without evaluating the argument.
- * Glory to Martin Uecker <Martin.Uecker@....uni-goettingen.de>
- */
-#define __is_constexpr(x) \
-	(sizeof(int) == sizeof(*(8 ? ((void *)((long)(x) * 0l)) : (int *)8)))
-
 #endif /* _LINUX_CONST_H */
-- 
2.17.1

-
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