From: Vincent Mailhol > Sent: 18 November 2024 03:22 > > On Mon. 18 nov. 2024 à 07:58, Linus Torvalds > <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote: > > The "0*!(x)" is admittedly kind of ugly, and might be prettier as > > "0&&(x)". Same number of characters, but technically one op less and > > not mixing booleans and integer ops. > > I did a tree wide replacement of __is_constexpr() with is_const() and > did an allyesconfig build test. It yields a -Wint-in-bool-context > warning in GCC for both the "0*!(x)" and the "0&&(x)" each time the > expression contains non-boolean operators, for example: * or <<. > > I reproduced it in godbolt here: > > https://godbolt.org/z/5Wcbvanq3 Applies to pretty much all the variants. Needs to be (x) == 0 (or (x) != 0) rather than !(x) Fortunately comparison operators (and ?:) are all valid in constant integer expressions. Oh, one advantage of statically_const() is that you can give it a 'local' variable that contains the value. So this works: #define check_lo_ho(lo, hi) do { \ __auto_type _lo = lo; \ __auto_type _hi = hi; \ BUILD_BUG_ON_MSG(_lo > _hi, "inverted bounds"); \ } while (0) I'm trying to finalise a patch for min() and max(). David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
