[libvirt] [PATCH] Fix cast errors with clang

[Eric Blake]

On 10/18/2014 10:41 AM, Roman Bogorodskiy wrote:
> Build with clang fails with:
> 
>   CC       util/libvirt_util_la-virsocketaddr.lo
> util/virsocketaddr.c:904:17: error: cast from 'struct sockaddr *' to
> 'struct sockaddr_in *' increases required alignment from 1 to 4
> [-Werror,-Wcast-align]
>         inet4 = (struct sockaddr_in*) res->ai_addr;
>                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> util/virsocketaddr.c:909:17: error: cast from 'struct sockaddr *' to
> 'struct sockaddr_in6 *' increases required alignment from 1 to 4
> [-Werror,-Wcast-align]
>         inet6 = (struct sockaddr_in6*) res->ai_addr;
>                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 2 errors generated.
> 
> Fix by introducing a union of the appropriate sturcts.

s/sturcts/structs/

> ---
>  src/util/virsocketaddr.c | 17 ++++++++++-------
>  1 file changed, 10 insertions(+), 7 deletions(-)
> 
> diff --git a/src/util/virsocketaddr.c b/src/util/virsocketaddr.c
> index 5f54e68..162108c 100644
> --- a/src/util/virsocketaddr.c
> +++ b/src/util/virsocketaddr.c
> @@ -892,22 +892,25 @@ virSocketAddrIsNumericLocalhost(const char *addr)
>  {
>      struct addrinfo *res;
>      struct in_addr tmp = { .s_addr = htonl(INADDR_LOOPBACK) };
> -    struct sockaddr_in *inet4;
> -    struct sockaddr_in6 *inet6;
> +    union {
> +        struct sockaddr *addr;
> +        struct sockaddr_in *inet4;
> +        struct sockaddr_in6 *inet6;
> +    } sa;

Close, but not quite.  The POSIX solution for this is the
sockaddr_storage type, in <sys/socket.h>.  You shouldn't need to create
your own union, but instead reuse sockaddr_storage.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org

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