On 06/15/15 11:09, Eric Blake wrote: > On 06/15/2015 07:53 AM, Don Slutz wrote: >> On 06/12/15 18:38, Eric Blake wrote: > >>>> >>>> + /* Only support 1 address */ >>>> + if (addr) { >>>> + return ~0U; >>>> + } >>> >>> Different answer on 32-bit platforms (there, ~0U is 0xffffffff, which >>> then 0-extends to uint64_t rather than your desired result of >>> 0xffffffffffffffffULL). >>> >> >> This is not true: > > Oh, I was confusing ~0UL (where sign extension on 32- vs 64-bit matters) > and ~0U (which you used). > >> >>> Why can't you just 'return -1;'? >>> >> >> I/O instructions on x86 are limited to 32bits max. Also when EAX is >> changed via inl, the high 32bits are 0. So the correct result is ~0U >> not -1. > > Still, it might be better to write an explicit 0xffffffff or even have a > named constant, rather than making people reason about whether ~0U > promotes into a 64-bit value with only 32 bits set. >
Ok, Will switch to 0xffffffff. -Don Slutz