Messages in this thread | | | Date | Thu, 9 Jun 2022 14:08:06 -0700 | From | Andrew Morton <> | Subject | Re: + include-uapi-linux-swabh-move-explicit-cast-outside-ternary.patch added to mm-nonmm-unstable branch |
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On Thu, 9 Jun 2022 14:01:17 -0700 Nick Desaulniers <ndesaulniers@google.com> wrote:
> On Thu, Jun 9, 2022 at 1:42 PM Alexey Dobriyan <adobriyan@gmail.com> wrote: > > > > On Thu, Jun 09, 2022 at 10:29:33AM -0700, Andrew Morton wrote: > > > 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. > > > > > --- a/include/uapi/linux/swab.h~include-uapi-linux-swabh-move-explicit-cast-outside-ternary > > > +++ a/include/uapi/linux/swab.h > > > @@ -102,7 +102,7 @@ static inline __attribute_const__ __u32 > > > #define __swab16(x) (__u16)__builtin_bswap16((__u16)(x)) > > > #else > > > #define __swab16(x) \ > > > - (__builtin_constant_p((__u16)(x)) ? \ > > > + (__u16)(__builtin_constant_p(x) ? \ > > > > This cast is necessary. > > > > > ___constant_swab16(x) : \ > > > __fswab16(x)) > > > #endif > > > @@ -115,7 +115,7 @@ static inline __attribute_const__ __u32 > > > #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 > > > #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)) > > > > These two aren't? typeof(c ? u32 : u32) is u32. > > Correct. > > Neither are the casts on the return values of the calls to > __builtin_bswap* in the cases where __HAVE_BUILTIN_BSWAP*__ are > defined. If you want to send a patch on top of Justin's/on top of > mm-nonmm-unstable, I'll ack it. Or Andrew, you can drop v3 and Justin > can send a v4 with Alexey's suggestions?
I figured we'd leave it as-is for simple symmetry.
If we're going to have one implementation different from the others then it would be good to have a code comment explaining why.
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