Date: Wed, 03 Jul 2013 11:23:00 +0300 From: Andriy Gapon <avg@FreeBSD.org> To: Bruce Evans <brde@optusnet.com.au> Cc: attilio@FreeBSD.org, svn-src-head@FreeBSD.org, svn-src-all@FreeBSD.org, src-committers@FreeBSD.org Subject: Re: should_yield problem [Was: svn commit: r251322 - head/sys/kern] Message-ID: <51D3DF64.8040500@FreeBSD.org> In-Reply-To: <20130703134115.C1064@besplex.bde.org> References: <201306031736.r53Hain5093431@svn.freebsd.org> <51D30463.50608@FreeBSD.org> <CAJ-FndD5tCxe-L8V73MFtk_4xr0Wq3MHasKY4O_tcA3uYouKAw@mail.gmail.com> <51D30CE8.7030803@FreeBSD.org> <CAJ-FndATxzTwCkZGXw4jD_8O4KbnHbsjk4DwHwbp%2B0gd3VGTCQ@mail.gmail.com> <51D31724.6090807@FreeBSD.org> <20130703134115.C1064@besplex.bde.org>
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on 03/07/2013 07:40 Bruce Evans said the following: > On Tue, 2 Jul 2013, Andriy Gapon wrote: >> distance = (signed)( i1 - i2 ) > > With 2's complement and benign overflow, this is no different from > 'distance = i1 - i2'. Given the particular context I'd say that there is a difference. > But signed counters are not wanted here. A > negative distance, or equivalently with 32-bit unsigned ints, an unsigned > difference of >= 0x80000000 means overflow or an initialization error. > Your bug is an initialization error. Right. But I'd rather produce a positive (unsigned) number than a negative number when such an error happens (and is detectable). Again, I am speaking about the concrete context. -- Andriy Gapon
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