_CMSG_HDR_ALIGN
hdr.msg_control = (void *)_CMSG_HDR_ALIGN(cinmsg);
(_CMSG_HDR_ALIGN(cinmsg) - (uintptr_t)cinmsg);
hdr.msg_control = (void *)_CMSG_HDR_ALIGN(coutmsg);
((((uintptr_t)_CMSG_HDR_ALIGN((char *)(c) + \
((struct cmsghdr *)_CMSG_HDR_ALIGN((char *)(c) + \
((unsigned int)_CMSG_HDR_ALIGN(sizeof (struct cmsghdr) + (l)))
((((uintptr_t)_CMSG_HDR_ALIGN((char *)(c) + \
((struct cmsghdr *)_CMSG_HDR_ALIGN((char *)(c) + \
((unsigned int)_CMSG_HDR_ALIGN(sizeof (struct cmsghdr) + (l)))