Mine

    if (*ldminfo.session == '\0') {
        if(!access("/etc/X11/xinit/Xsession", X_OK)) {
            /* Fedora, RHEL, CentOS, etc. */
            scopy(ldminfo.session, "/etc/X11/xinit/Xsession");
        }
        else if(!access("/etc/X11/xdm/Xsession", X_OK)) {
            scopy(ldminfo.session, "/etc/X11/xdm/Xsession");
        }
        else {
            /* Debian, Ubuntu */
            scopy(ldminfo.session, "/etc/X11/Xsession");
        }
    }