Re: CVS commit: src/sys/kern

[Alexander Nasonov <alnsn%yandex.ru@localhost>]

Joerg Sonnenberger wrote:
> On Tue, Jan 31, 2012 at 07:32:52PM +0000, Alexander Nasonov wrote:
> > #define sizeof_fam(s, m, n) (sizeof(s) + sizeof(((s *)NULL)->m[0]) * (n))
> 
> That's still not necessarily optimal, depending on the padding rules of
> the platform. You want to do offsetof(s, m[0]) + n * sizeof((s*)NULL->m[0]).

I'm aware of this but I was merely following examples from the standard.

More specifically I was following DR 282 (flexible array members &
struct padding) which was incorporated into TC2.

http://std.dkuug.dk/jtc1/sc22/wg14/www/docs/dr_282.htm

I can add a comment about padding to sizeof_fam. If there is no padding,
my and your expression should return same values.

Alex