The function like macro __is_nonneg() casts its argument to (long long)
in an attempt to silence -Wtype-limits warnings on unsigned values.
But this workaround is incomplete as proven here:
$ cat foo.c
#include <linux/minmax.h>
int foo(unsigned int a)
{
return __is_nonneg(a);
}
$ make CFLAGS_KERNEL="-Wtype-limits" foo.o
CALL scripts/checksyscalls.sh
DESCEND objtool
INSTALL libsubcmd_headers
CC foo.o
foo.c: In function 'foo':
./include/linux/minmax.h:68:57: warning: comparison is always true due to
limited range of data type [-Wtype-limits]
68 | #define __is_nonneg(ux) statically_true((long long)(ux) >= 0)
| ^~
./include/linux/compiler.h:350:50: note: in definition of macro
'statically_true'
350 | #define statically_true(x) (__builtin_constant_p(x) && (x))
| ^
foo.c:5:16: note: in expansion of macro '__is_nonneg'
5 | return __is_nonneg(a);
| ^~~~~~~~~~~
./include/linux/minmax.h:68:57: warning: comparison is always true due to
limited range of data type [-Wtype-limits]
68 | #define __is_nonneg(ux) statically_true((long long)(ux) >= 0)
| ^~
./include/linux/compiler.h:350:57: note: in definition of macro
'statically_true'
350 | #define statically_true(x) (__builtin_constant_p(x) && (x))
| ^
foo.c:5:16: note: in expansion of macro '__is_nonneg'
5 | return __is_nonneg(a);
| ^~~~~~~~~~~
And because -Wtype-limits is now globally disabled, such a workaround
now becomes useless. Remove the __is_nonneg()'s cast and its related
comment.
Signed-off-by: Vincent Mailhol <[email protected]>
---
Changelog:
v1 -> v2: new patch
---
include/linux/minmax.h | 5 +----
1 file changed, 1 insertion(+), 4 deletions(-)
diff --git a/include/linux/minmax.h b/include/linux/minmax.h
index a0158db54a04..3e2e3e539ba1 100644
--- a/include/linux/minmax.h
+++ b/include/linux/minmax.h
@@ -52,9 +52,6 @@
/*
* Check whether a signed value is always non-negative.
*
- * A cast is needed to avoid any warnings from values that aren't signed
- * integer types (in which case the result doesn't matter).
- *
* On 64-bit any integer or pointer type can safely be cast to 'long long'.
* But on 32-bit we need to avoid warnings about casting pointers to integers
* of different sizes without truncating 64-bit values so 'long' or 'long long'
@@ -65,7 +62,7 @@
* but they are handled by the !is_signed_type() case).
*/
#if __SIZEOF_POINTER__ == __SIZEOF_LONG_LONG__
-#define __is_nonneg(ux) statically_true((long long)(ux) >= 0)
+#define __is_nonneg(ux) statically_true((ux) >= 0)
#else
#define __is_nonneg(ux) statically_true( \
(typeof(__builtin_choose_expr(sizeof(ux) > 4, 1LL, 1L)))(ux) >= 0)
--
2.51.2
