On Tue, Aug 29, 2017 at 8:30 AM, John Baldwin <j...@freebsd.org> wrote:
> On Monday, August 28, 2017 04:40:49 PM Maxim Sobolev wrote: > > John, well, this depends on how you look at it. The padding element size > is > > "int", which when you account for the alignment has the nice property on > > both 32 and 64-bit arches that no matter what kind of element you add > > (char, short, int or void *), you only need to bring down MDNPAD by 1 to > > keep the structure size the same. > > That's only true once. Add a second pointer and this trick won't work > again > on 64-bit platforms. It only worked this time by accident because there > was > unaccounted-for padding at the end of the structure, not on purpose. In > other places in the tree where ABI is more carefully maintained we use > explicit spare pointers or spare longs instead (e.g. padding in > kinfo_proc). > Yes, as someone that's lived through the 'All the World's a VAX' wars and the 'All the world's 32-bit' wars or even the more ancient 16-bit -> 32-bit wars, there's a reason we have uintptr_t and why it may not be an int... Warner _______________________________________________ svn-src-head@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
