Le vendredi 20 janvier 2023, 20:38:32 UTC Alejandro Colomar a écrit :
> Hi Bastien,
>
> On 1/20/23 21:32, Bastien Roucariès wrote:
> [...]
>
> >> diff --git a/bits/socket.h b/bits/socket.h
> >> index aac8c49b00..c0c23b4e84 100644
> >> --- a/bits/socket.h
> >> +++ b/bits/socket.h
> >> @@ -168,9 +168,14 @@ struct sockaddr
> >>
> >> struct sockaddr_storage
> >> {
> >> - __SOCKADDR_COMMON (ss_); /* Address family, etc. */
> >> - char __ss_padding[_SS_PADSIZE];
> >> - __ss_aligntype __ss_align; /* Force desired alignment. */
> > no this is not correct you break ABI by reducing size
> >> + union
> >> + {
> >> + __SOCKADDR_COMMON (ss_); /* Address family, etc. */
> >> + struct sockaddr sa;
> >> + struct sockaddr_in sin;
> >> + struct sockaddr_in6 sin6;
> >> + struct sockaddr_un sun;
> >> + };
> >> };
> >
> > Correct one structure is
> >
> > struct __private_sock_storage {
> > __SOCKADDR_COMMON (ssprivate_); /* Address family, etc. */
> > char __ss_padding[_SS_PADSIZE];
> > __ss_aligntype __ss_align; /* Force desired alignment. */
> > }
>
> What is this structure for? I expect that it's for declaring a wide-enough and
> correctly aligned type, but the union containing all the other types already
> guarantees a size as wide as any other sockaddr_* and with the widest alignment.
>
> Also, any member that is necessary for superalignment or padding could be added
> at the end of sockaddr_storage, after the anon union; you don't need the extra
> struct, I guess.
No we need it, max of structure is struct sockaddr_un sun and is size of 108.
sizeof(sockaddr_storage) is 128...
Did you see the line of the kernel source I send you ? kernel expect size of 109 for un aka we should pad by a nul byte...
I think it is safer in a first step, to keep the old structure... Maybe later simplify
Did you also see
https://github.com/bminor/glibc/blob/master/socket/sys/socket.h#L63
Bastien
>
> Right?
>
> >
> > struct sockaddr_storage
> > {
> > union
> > {
> > __SOCKADDR_COMMON (ss_); /* Address family, etc. */
> > struct sockaddr sa;
> > struct sockaddr_in sin;
> > struct sockaddr_in6 sin6;
> > struct sockaddr_un sun;
> > struct __private_sock_storage _private;
> > };
> > };
> >
> > May it could be dropped later using align construct for modern C and padding
> >
>
> Cheers,
>
> Alex
>
> > Bastien
> >>
> >>
> >>
> >
>
> --
> <http://www.alejandro-colomar.es/>
>
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