From: Mark Charlebois <charlebm@xxxxxxxxx>
This code makes a compile time type check that is optimized away. Clang
complains that it generates an unused function:
linux/kernel/panic.c:471:1: warning: unused function '__check_panic'
[-Wunused-function]
core_param(panic, panic_timeout, int, 0644);
^
linux/moduleparam.h:283:2: note: expanded from macro
'core_param'
param_check_##type(name, &(var)); \
^
<scratch space>:87:1: note: expanded from here
param_check_int
^
linux/moduleparam.h:369:34: note: expanded from macro
'param_check_int'
#define param_check_int(name, p) __param_check(name, p, int)
^
linux/moduleparam.h:349:22: note: expanded from macro
'__param_check'
static inline type *__check_##name(void) { return(p); }
^
<scratch space>:88:1: note: expanded from here
__check_panic
GCC won't complain for a static inline function but would if it was just
a static function.
Adding the unused attribute to the function declaration removes the warning.
Per request from Rusty Russell it is marked as __always_unused as the code
is meant to be optimized away.
This code works for both GCC and clang.
Signed-off-by: Mark Charlebois <charlebm@xxxxxxxxx>
Signed-off-by: Behan Webster <behanw@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
(cherry picked from commit 0283f9a529c81e64bafea80d6d3e056d1c3f656d)
Signed-off-by: Chang Rebecca Swee Fun <rebecca.swee.fun.chang@xxxxxxxxx>
---
include/linux/moduleparam.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/linux/moduleparam.h b/include/linux/moduleparam.h
index c3eb102..175f699 100644
--- a/include/linux/moduleparam.h
+++ b/include/linux/moduleparam.h
@@ -346,7 +346,7 @@ static inline void destroy_params(const struct kernel_param *params,
/* The macros to do compile-time type checking stolen from Jakub
Jelinek, who IIRC came up with this idea for the 2.4 module init code. */
#define __param_check(name, p, type) \
- static inline type *__check_##name(void) { return(p); }
+ static inline type __always_unused *__check_##name(void) { return(p); }
extern struct kernel_param_ops param_ops_byte;
extern int param_set_byte(const char *val, const struct kernel_param *kp);
--
1.7.9.5
--
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