[Spice-devel] [PATCH v2] remove a warning building a test

[Uri Lublin]

On 05/17/2016 07:43 PM, Frediano Ziglio wrote:
>>
>> On Tue, May 17, 2016 at 04:44:04PM +0100, Frediano Ziglio wrote:
>>> With my compile switches (which are mostly derived from RedHat spec
>>> file) I'm getting this warning:
>>>
>>> stream-test.c: In function 'sock_fd_read':
>>> stream-test.c:66:43: warning: dereferencing type-punned pointer will
>>> break strict-aliasing rules [-Wstrict-aliasing]
>>>              *fd = *((int *) CMSG_DATA(cmsg));
>>>                                            ^
>>>
>>> memcpy could decrease performance but as this is a test it's not
>>> an issue.
>>
>> Can you avoid the warning with an additional (void *) cast?
>> *fd = *((int *) (void *) CMSG_DATA(cmsg))); ?
>>
>> Christophe
>>
>
> Mumble...
>
>
> diff --git a/server/tests/stream-test.c b/server/tests/stream-test.c
> index 6317796..623a394 100644
> --- a/server/tests/stream-test.c
> +++ b/server/tests/stream-test.c
> @@ -63,7 +63,7 @@ sock_fd_read(int sock, void *buf, ssize_t bufsize, int *fd)
>                  exit(1);
>              }
>
> -            *fd = *((int *) CMSG_DATA(cmsg));
> +            memcpy(fd, CMSG_DATA(cmsg), sizeof(*fd));
>          } else
>              *fd = -1;
>      } else {
>
>
> memcpy but without the additional variable.


In man cmsg examples I see they use a pointer:
int *pi = (int*) CMSG_DATA(cmsg);
*fd = *pi;

(But also they use memcpy to copy several fds)

Uri