SCM_SYS_FDSET    2578 src/syslib.c     fdset = SCM_SYS_FDSET(fdset_scm);
SCM_SYS_FDSET    2608 src/syslib.c     fdset = SCM_SYS_FDSET(fdset_scm);
SCM_SYS_FDSET    2647 src/syslib.c     fdset = SCM_SYS_FDSET(fdset_scm);
SCM_SYS_FDSET    1323 src/system.c       return SCM_SYS_FDSET(fds);