On Mon, 2019-07-29 at 10:39 +0000, David Laight wrote:
> From: Qian Cai
> > Sent: 26 July 2019 21:58
> >
> > There are a lot of those warnings with GCC8+ 64bit,
> >
>
> ...
> > Fix them by aligning the structures and fields to 8 bytes instead.
>
> ...
> > struct sctp_setpeerprim {
> > sctp_assoc_t sspp_assoc_id;
> > - struct sockaddr_storage sspp_addr;
> > -} __attribute__((packed, aligned(4)));
> > + struct sockaddr_storage sspp_addr __attribute__((aligned(8)));
> > +} __attribute__((packed, aligned(8)));
>
> What happens to this one if you change both to aligned(4) ?
> Much the same way as:
> struct {
> int a;
> long b __attribute__((aligned(4));
> };
> is only 12 bytes on (most) 64bit systems.
No, that won't work. It because that,
#define sockaddr_storage __kernel_sockaddr_storage
struct __kernel_sockaddr_storage {
...
} __attribute__ ((aligned(_K_SS_ALIGNSIZE)))
#define _K_SS_ALIGNSIZE (__alignof__ (struct sockaddr *))
A pointer is 8-byte on 64-bit systems. If changed "struct
__kernel_sockaddr_storage" to use,
__attribute__ ((aligned((4)))
it then silence the warnings.
