> From: dev [mailto:dev-boun...@dpdk.org] On Behalf Of Tyler Retzlaff > Sent: Friday, March 12, 2021 7:40 PM > > On Fri, Mar 12, 2021 at 10:36:15AM -0800, Tyler Retzlaff wrote: > > On Fri, Mar 12, 2021 at 05:37:41PM +0000, Bruce Richardson wrote: > > > On Fri, Mar 12, 2021 at 09:05:58AM -0800, Tyler Retzlaff wrote: > > > > > Not sure i agree. It's a very common pattern and is widely used and > > > > > understood. I mean, if anything, seeing `~0` would have me stop and > > > > > think as i've literally never seen such code before. > > > > > > > > it produces warnings under some compilers. in some enterprises we are > > > > required to fix certain classes of warnings (not suppress them from > the > > > > command line) as a function of security policies. > > > > > > > > as an alternative would you be more willing to accept something like > the > > > > following? ``(unsigned long long)-1LL'' if you don't like ``~0ULL'' > it > > > > would make explicit what the compiler is already doing. > > > > > > > > the issue is the application of the sign to what is clearly something > not > > > > signed; it get's flagged. so the cast is an explicit expression of > intent > > > > that will not generate the warnings. > > > > > > > > appreciate you're help in finding a solution even if it isn't the > > > > proposed solution. > > > > > > > What about using ULLONG_MAX and similar defines from limits.h?
The type of the variable being manipulated is not unsigned long long, but uint64_t, which theoretically is not the same. Long long can be more than 64 bit, although all current implementations use 64 bit for long long. So -1ULL was wrong from the start, and ~0ULL is similarly incorrect. The correct value would be UINT64_MAX from stdint.h. > > > > i think this would be okay even in circumstances where the code is > > building masks so long as in practice it results in "all bits being > > set". i'm not aware of a XXX_MAX where max isn't all bits set.. is > > there? > > just a qualification to my previous. > > specifically for the UXXX_MAX (unsigned) preprocessor definitions, we > aren't talking about signed here (or at least i wasn't).
