SHMSEG_WANTED
wanted = (shmseg->shm_perm.mode & SHMSEG_WANTED);
shmseg->shm_perm.mode |= SHMSEG_WANTED;
shmseg->shm_perm.mode = (shmseg->shm_perm.mode & SHMSEG_WANTED) |
if (shmseg->shm_perm.mode & SHMSEG_WANTED) {
shmseg->shm_perm.mode &= ~SHMSEG_WANTED;