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

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