On Tue, 2019-08-06 at 21:27 +0200, Rikard Falkeborn wrote: > On Wed, Aug 07, 2019 at 12:19:36AM +0900, Masahiro Yamada wrote: > > How about this? > > #define GENMASK_INPUT_CHECK(high, low) \ > > BUILD_BUG_ON_ZERO(__builtin_choose_expr( \ > > __builtin_constant_p((low) > (high)), (low) > (high), 0)) > Thanks for the feedback, your version looks much cleaner than mine. I > *think* I had a reason for using __is_constexpr() instead of > __builtin_constant_p but I'll try a full rebuild to see if something > comes up.
Perhaps a statement expression so high and low aren't possibly evaluated multiple times? #define GENMASK_INPUT_CHECK(high, low) \ ({ \ typeof(high) _high = high; \ typeof(low) _low = low; \ BUILD_BUG_ON_ZERO(__builtin_constant_p(_low > _high, \ _low > _high, \ 0)) \ })