On Tue, Aug 26, 2014 at 9:58 AM, Bruce Evans <b...@optusnet.com.au> wrote:
> > That would be a further obfuscation. The *INT<n>C() macros expand to > integer constant expressions of the specified type suitable for use > in #if preprocessing directives. (It is otherwise difficult to > detemine the correct suffix, to add to the constant to give it the > specified type). There are no preprocessing directives here, so a > simple cast works. The cast could also be applied to the other > operand but it is easier to read when applied to the constant. > I thought that in C99, all integers in preprocessor evaluation were treated as if they were [u]intmax_t (6.10.1.4 in the n1256.pdf I have here). I was only just skimming that part yesterday for unrelated reasons, though, so maybe I'm missing the bigger picture. > The expression could also be written without a cast and without using > UINT64_C(), by using a 'ULL' suffix instead of 'LL'. That would still > use the long long abomination, and be different obfuscation -- the > type of the constant doesn't really matter, but we need to promote > to the type of 'frac', that is, uint64_t. 'ULL' works because long > longs are at least 64 bits (and I think unsigned long longs are also > 2's complemention, so their type is larger than uint64_t. Two's complement semantics are guaranteed for the fixed width types such as int64_t, but I'm not sure how that comes into play for unsigned types? -Ben _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
