gistfile1.cpp

static int trinst_xid_swap(void)
{
    uid_t ruid, euid;
    gid_t rgid, egid;

    // Interchange the real and effective user/group IDs
    ruid = getuid();
    euid = geteuid();
    if (setreuid(euid, ruid) != 0)
        return -errno;
    rgid = getgid();
    egid = getegid();
    if (setregid(egid, rgid) != 0)
        return -errno;
    return 0;
}