diff -r cea42629ddf5 Modules/socketmodule.c
--- a/Modules/socketmodule.c	Fri Dec 13 11:43:10 2013 -0500
+++ b/Modules/socketmodule.c	Fri Dec 13 11:53:27 2013 -0500
@@ -1917,9 +1917,16 @@
     static const size_t cmsg_len_end = (offsetof(struct cmsghdr, cmsg_len) +
                                         sizeof(cmsgh->cmsg_len));
 
-    /* Note that POSIX allows msg_controllen to be of signed type. */
-    if (cmsgh == NULL || msg->msg_control == NULL || msg->msg_controllen < 0)
+    if (cmsgh == NULL || msg->msg_control == NULL)
         return 0;
+    /* Note that POSIX allows msg_controllen to be of a signed type. This is a
+       problem under OS X as it's unsigned there. Turn off the compiler warning
+       in that instance using pragmas. */
+    #pragma clang diagnostic push
+    #pragma clang diagnostic ignored "-Wtautological-compare"
+    if (msg->msg_controllen < 0)
+        return 0;
+    #pragma clang diagnostic pop
     if (space < cmsg_len_end)
         space = cmsg_len_end;
     cmsg_offset = (char *)cmsgh - (char *)msg->msg_control;