[PATCH] minmax: substitute local variables using __UNIQUE_ID()

From: Yueh-Shun Li
Date: Thu Feb 15 2024 - 11:14:23 EST


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@xxxxxxxxxx>
---
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..70b740b76f73 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