Mark setitimer as unimplemented, obsolete

src/header/sys_time/mod.rs

@@ -114,6 +114,7 @@ pub unsafe extern "C" fn setitimer(
     value: *const itimerval,
     ovalue: *mut itimerval,
 ) -> c_int {
+    // TODO setitimer is unimplemented on Redox
     Sys::setitimer(which, &*value, ovalue.as_mut())
         .map(|()| 0)
         .or_minus_one_errno()

src/header/unistd/mod.rs

@@ -96,6 +96,7 @@ pub unsafe extern "C" fn access(path: *const c_char, mode: c_int) -> c_int {
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/alarm.html>.
 #[no_mangle]
 pub extern "C" fn alarm(seconds: c_uint) -> c_uint {
+    // TODO setitimer is unimplemented on Redox and obsolete
     let mut timer = sys_time::itimerval {
         it_value: sys_time::timeval {
             tv_sec: seconds as time_t,
@@ -1032,6 +1033,7 @@ pub extern "C" fn ttyname_r(fildes: c_int, name: *mut c_char, namesize: size_t)
 #[deprecated]
 #[no_mangle]
 pub extern "C" fn ualarm(usecs: useconds_t, interval: useconds_t) -> useconds_t {
+    // TODO setitimer is unimplemented on Redox and obsolete
     let mut timer = sys_time::itimerval {
         it_value: sys_time::timeval {
             tv_sec: 0,

src/platform/redox/signal.rs

@@ -90,6 +90,10 @@ impl PalSignal for Sys {
     }
 
     fn setitimer(which: c_int, _new: &itimerval, old: Option<&mut itimerval>) -> Result<()> {
+        // TODO: setitimer is no longer part of POSIX and should not be implemented in Redox
+        // Change the platform-independent implementation to use POSIX timers.
+        // For Redox, the timer should probably use "/scheme/time"
+        unimplemented!();
         let _path = match which {
             ITIMER_REAL => "/scheme/itimer/1",
             _ => return Err(Errno(EINVAL)),