linux-kernel - [PATCH v2] minmax: substitute local variables using __UNIQUE

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Date: Thu, 15 Feb 2024 18:58:15 +0000
From: Yueh-Shun Li <shamrocklee@...teo.net>
To: Andrew Morton <akpm@...ux-foundation.org>,
	Mark Brown <broonie@...nel.org>,
	Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Yueh-Shun Li <shamrocklee@...teo.net>,
	Herve Codina <herve.codina@...tlin.com>,
	Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] minmax: substitute local variables using __UNIQUE_ID()

Substitute identifier names of local variables used in macro
definitions inside minmax.h with those generated by __UNIQUE_ID(prefix)
to eliminate passible naming collisions.

Identifier names like __x, __y and __tmp are everywhere inside the
kernel source. This patch ensures that macros provided by minmax.h
will work even when identifiers of these names appear in the expanded
input arguments.

Signed-off-by: Yueh-Shun Li <shamrocklee@...teo.net>
---
 include/linux/minmax.h | 41 ++++++++++++++++++++++++++++-------------
 1 file changed, 28 insertions(+), 13 deletions(-)

diff --git a/include/linux/minmax.h b/include/linux/minmax.h
index 2ec559284a9f..df7e45106c3a 100644
--- a/include/linux/minmax.h
+++ b/include/linux/minmax.h
@@ -129,10 +129,14 @@
  * @x: value1
  * @y: value2
  */
-#define min_not_zero(x, y) ({			\
-	typeof(x) __x = (x);			\
-	typeof(y) __y = (y);			\
-	__x == 0 ? __y : ((__y == 0) ? __x : min(__x, __y)); })
+#define min_not_zero(x, y)						\
+	__min_not_zero_impl(x, y, __UNIQUE_ID(__x), __UNIQUE_ID(__y))
+#define __min_not_zero_impl(x, y, __x, __y)				\
+	({								\
+		typeof(x) __x = (x);					\
+		typeof(y) __y = (y);					\
+		__x == 0 ? __y : ((__y == 0) ? __x : min(__x, __y));	\
+	})
 
 /**
  * clamp - return a value clamped to a given range with strict typechecking
@@ -185,13 +189,19 @@
  * typeof() keeps the const qualifier. Use __unqual_scalar_typeof() in order
  * to discard the const qualifier for the __element variable.
  */
-#define __minmax_array(op, array, len) ({				\
-	typeof(&(array)[0]) __array = (array);				\
-	typeof(len) __len = (len);					\
-	__unqual_scalar_typeof(__array[0]) __element = __array[--__len];\
-	while (__len--)							\
-		__element = op(__element, __array[__len]);		\
-	__element; })
+#define __minmax_array(op, array, len)					\
+	__minmax_array_impl(op, array, len, __UNIQUE_ID(__array),	\
+			    __UNIQUE_ID(__len), __UNIQUE_ID(__element))
+#define __minmax_array_impl(op, array, len, __array, __len, __element)	\
+	({								\
+		typeof(&(array)[0]) __array = (array);			\
+		typeof(len) __len = (len);				\
+		__unqual_scalar_typeof(__array[0])			\
+			__element = __array[--__len];			\
+		while (__len--)						\
+			__element = op(__element, __array[__len]);	\
+		__element;						\
+	})
 
 /**
  * min_array - return minimum of values present in an array
@@ -267,7 +277,12 @@ static inline bool in_range32(u32 val, u32 start, u32 len)
  * @a: first value
  * @b: second value
  */
-#define swap(a, b) \
-	do { typeof(a) __tmp = (a); (a) = (b); (b) = __tmp; } while (0)
+#define swap(a, b) __swap_impl(a, b, __UNIQUE_ID(__tmp))
+#define __swap_impl(a, b, __tmp)			\
+	do {						\
+		typeof(a) __tmp = (a);			\
+		(a) = (b);				\
+		(b) = __tmp;				\
+	} while (0)
 
 #endif	/* _LINUX_MINMAX_H */
-- 
2.42.0