* Andy Lutomirski <l...@amacapital.net> wrote:
> > So I might be missing something, but what generic uses does it
> > have, beyond structures that have some rare size related
> > weirdness, such as alignment attributes? In 99% of the cases:
> >
> > sizeof(struct) == offsetofend(struct, last_member)
> >
> > right?
>
> struct foo {
> u64 a;
> char b;
> };
>
> sizeof(struct foo) will be 16, but offsetofend(struct foo, b) will be
> 9 on most platforms, right?
I knew I missed something obvious :-)
Let me attempt to get it right:
When the next byte after the last member of a structure is not aligned
to the largest alignment requirement of any structure member, then the
structure grows (is padded) and offsetofend() < sizeof().
'packed' or 'aligned' attributes will modify the largest alignment
requirement value so they are a common but not only mechanism for this
to be the case.
Thanks,
Ingo
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