Messages in this thread |  | | Date | Thu, 9 Jun 2022 13:31:40 -0700 | From | Nathan Chancellor <> | Subject | Re: [PATCH v3] include/uapi/linux/swab.h: move explicit cast outside ternary |
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On Wed, Jun 08, 2022 at 03:35:39PM -0700, Justin Stitt wrote: > From: Justin Stitt <jstitt007@gmail.com> > > A cast inside __builtin_constant_p doesn't do anything since it should > evaluate as constant at compile time irrespective of this cast. Instead, > I moved this cast outside the ternary to ensure the return type is as > expected. > > Additionally, if __HAVE_BUILTIN_BSWAP16__ was not defined then __swab16 > is actually returning an `int` not a `u16` due to integer promotion. > > As Al Viro notes: > You *can't* get smaller-than-int out of ? :, same as you can't get it > out of addition, etc. > > This also fixes some clang -Wformat warnings involving default > argument promotion. > > Link: https://github.com/ClangBuiltLinux/linux/issues/378 > Suggested-by: Al Viro <viro@zeniv.linux.org.uk> > Suggested-by: Nathan Chancellor <nathan@kernel.org> > Suggested-by: Nick Desaulniers <ndesaulniers@google.com> > Signed-off-by: Justin Stitt <jstitt007@gmail.com>
Thanks for the patch and sticking with it through all the review!
Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> --- > diff from v2 -> v3: > * re-insert respective (u16, u32, u64) cast to __builtin_bswap as per > Nick's suggestion > * added note from Al Viro > > include/uapi/linux/swab.h | 6 +++--- > 1 file changed, 3 insertions(+), 3 deletions(-) > > diff --git a/include/uapi/linux/swab.h b/include/uapi/linux/swab.h > index 7272f85d6d6a..0723a9cce747 100644 > --- a/include/uapi/linux/swab.h > +++ b/include/uapi/linux/swab.h > @@ -102,7 +102,7 @@ static inline __attribute_const__ __u32 __fswahb32(__u32 val) > #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x)) > #else > #define __swab16(x) \ > - (__builtin_constant_p((__u16)(x)) ? \ > + (__u16)(__builtin_constant_p(x) ? \ > ___constant_swab16(x) : \ > __fswab16(x)) > #endif > @@ -115,7 +115,7 @@ static inline __attribute_const__ __u32 __fswahb32(__u32 val) > #define __swab32(x) (__u32)__builtin_bswap32((__u32)(x)) > #else > #define __swab32(x) \ > - (__builtin_constant_p((__u32)(x)) ? \ > + (__u32)(__builtin_constant_p(x) ? \ > ___constant_swab32(x) : \ > __fswab32(x)) > #endif > @@ -128,7 +128,7 @@ static inline __attribute_const__ __u32 __fswahb32(__u32 val) > #define __swab64(x) (__u64)__builtin_bswap64((__u64)(x)) > #else > #define __swab64(x) \ > - (__builtin_constant_p((__u64)(x)) ? \ > + (__u64)(__builtin_constant_p(x) ? \ > ___constant_swab64(x) : \ > __fswab64(x)) > #endif > -- > 2.36.1.476.g0c4daa206d-goog > >
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