On Fri, Jul 02, 2021 at 08:17:47PM IST, David Laight wrote: > From: Kumar Kartikeya Dwivedi > > Sent: 02 July 2021 12:18 > > > > cpumap needs to set, clear, and test the lowest bit in skb pointer in > > various places. To make these checks less noisy, add pointer friendly > > bitop macros that also do some typechecking to sanitize the argument. > > Would this work? > #define BIT_OP(val, op) ((typeof (val))((unsigned long)(val) op)) > > Should let you do: > ptr = BIT_OP(ptr, | 1); > ptr = BIT_OP(ptr, & ~1); > if (BIT_OPT(ptr, & 1)) > ... > > See https://godbolt.org/z/E57aGK4js > This certainly works, but my preference for keeping it this way was reusing the existing infrastructure (which also has KASAN/KCSAN instrumentation) and avoids UB while shifting. Ofcourse for this particular case, anything works, but if putting this in bitops, I thought we should keep it as simple wrappers over __set_bit/__clear_bit/test_bit. Also, I compared codegen for both, and it looks pretty much the same to me... See https://godbolt.org/z/s9cjEnYKj Let me know if I'm missing something. > David > > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK > Registration No: 1397386 (Wales) -- Kartikeya
