Fabian Hugelshofer wrote:
> Patrick McHardy wrote:
>> Fabian Hugelshofer wrote:
>>> Aligns buffers to maximum alignment of architecture to make the cast of
>>> char pointers to struct pointers more portable.
>>>
>>> Signed-off-by: Fabian Hugelshofer <hugelshofer2006@gmx.ch>
>>
>> They all seem fine to me, but a union might make it look
>> a bit nicer :)
> 
> In libnfnetlink the union does not make sense, because multiple casts
> are done from the same buffer at different locations.
> 
> For libnetfilter-(conntrack|log) the union would be possible:
> 
> Original (aligned):
> << code begin >>
> char buf[...] __attribute__ ((aligned));
> struct nlmsghdr *nmh = (struct nlmsghdr *) buf;
> 
> nfnl_fill_hdr(h->nfnlssh, nmh, 0, pf, queuenum, ...);
> << code end >>
> 
> Union style:
> << code begin >>
> union {
>     char buf[...];
>     struct nlmsghdr nmh;
> } u;
> 
> nfnl_fill_hdr(h->nfnlssh, &u.nmh, 0, pf, queuenum, ...);
> << code end >>
> 
> I can rewrite it like this, if desired...

Please, use union wherever it is possible. BTW, it seems to me that the
conntrack-tools may suffer from the same portability problem. The
(supposed) fix, which is attached, is ugly but union does not help since
the size of struct nf_conntrack is not known. I do not find a way to do
this cleanly without removing the use of the stack for temporary object
allocation.

-- 
"Los honestos son inadaptados sociales" -- Les Luthiers