"M. Warner Losh" <i...@bsdimp.com> writes:
> Dag-Erling Smørgrav <d...@des.no> writes:
> > "M. Warner Losh" <i...@bsdimp.com> writes:
> > > /*
> > > * Macros to cast a struct sockaddr, or parts thereof.
> > > * On architectures with strict alignment requirements, the compiler
> > > * can bogusly warn about alignment problems since its static analysis
> > > * is insufficient for it to know that with the APIs used, there
> > > * really is no alignment issue.
> > > */
> > That's a bit harsh on the compiler, don't you think? It never pays to
> > hurt the compiler's feelings :)
>
> /*
> * Macros to cast a struct sockaddr, or parts thereof. struct
> * sockaddr's alginment is loose to later be cast to a sockaddr_in or
> * sockaddr_in6. On architectures with strict alignment requirements,
> * this leads to compiler warnings because the compiler doesn't know
> * the ABI guarantees proper alignment.
> */
That sounds more like what I had in mind (my point being that the
compiler is *right* to not make any such assumptions unless we say it's
safe to do so)
> But this leads me to think that the right fix might be:
>
> /*
> * Structure used by kernel to store most
> * addresses.
> */
> struct sockaddr {
> unsigned char sa_len; /* total length */
> sa_family_t sa_family; /* address family */
> char sa_data[14]; /* actually longer; address value */
> } __aligned(4);
>
> since that's what the ABI defines....
Yes, unfortunately that's not portable. I like the way it's done in
sockaddr_storage, but we can't do that here except possibly using
anonymous unions, which aren't portable either.
> > > Why 16 and 4 here? What's so magical about them?
> > 4 = bytes in a uint32_t, 16 = bytes in an ipv6 address.
> Isn't that better served by 'sizeof(uint32_t)' and
> 'sizeof(ipv6_addr_t)'?
Probably...
DES
--
Dag-Erling Smørgrav - d...@des.no
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