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Re: [Libvir] [PATCH] to run on IA64



Hi, Mark

Thank you for your suggestion.
I just compiled it sucessfuly.
It should be work.
I will do test it tomorrow.

Thanks
Atsushi SAKAI

Mark McLoughlin <markmc redhat com> wrote:

> Hi,
> 	Thanks for that ...
> 
> On Tue, 2007-02-20 at 13:51 +0900, Atsushi SAKAI wrote:
> 
> > > > -    ((struct sockaddr_in *)&ifr.ifr_addr)->sin_family = AF_INET;
> > > > -    ((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr   = inaddr;
> > > > +    ((struct sockaddr_in *)((void *)&ifr.ifr_addr))->sin_family = AF_INET;
> > > > +    ((struct sockaddr_in *)((void *)&ifr.ifr_addr))->sin_addr   = inaddr; 
> 
> > bridge.c: In function 'brSetInetAddr':
> > bridge.c:344: warning: cast increases required alignment of target type
> > bridge.c:345: warning: cast increases required alignment of target type
> > bridge.c: In function 'brGetInetAddr':
> > bridge.c:381: warning: cast increases required alignment of target type
> 
> 	Okay, my understanding of this is that:
> 
>   - The warning is caused by -Wcast-align
> 
>   - Our problem is that we're casting between pointers to struct 
>     sockaddr and struct sockaddr_in, which look like
> 
>       struct sockaddr
>       {
>          unsigned short int sa_family;
>       };
> 
>       struct sockaddr_in
>       {
>          unsigned short int sin_family;
>          uint16_t sin_port;
>          struct { uint32_t s_addr } sin_addr;
>       };
> 
>   - Because of the uint32_t, struct sockaddr_in is required to be 
>     aligned to a 4 byte boundary, whereas on ia64 struct sockaddr is 
>     only required to be aligned to a 2 byte boundary
> 
>   - If we look at in the context of struct ifreq, though:
> 
>       struct ifreq
>       {
>           ....
>           union {
>               struct sockaddr ifru_addr;
>               ....
>               void *ifru_data;
>           } ifr_ifru;
>       };
>       #define ifr_addr ifr_ifru.ifru_addr
>       #define ifr_data ifr_ifru.ifru_data
> 
>     we see that because of the void pointer in the union, the struct 
>     sockaddr is actually guaranteed to be aligned to 8 bytes and so the 
>     warning can be ignored.
> 
>   - I'd prefer to avoid the void pointer cast as someone could come 
>     along and wonder whether the cast is hiding a genuine problem.
> 
>   - So, I think I'll go ahead and do it this way instead:
> 
> -    ((struct sockaddr_in *)&ifr.ifr_addr)->sin_family = AF_INET;
> -    ((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr   = inaddr;
> +    ((struct sockaddr_in *)&ifr.ifr_data)->sin_family = AF_INET;
> +    ((struct sockaddr_in *)&ifr.ifr_data)->sin_addr   = inaddr; 
> 
> Cheers,
> Mark.
> 



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