Use a consistent error mechanism for timeout overflow. (#1422)

Make `select` and `kqueue::kevent` fail with `Errno::INVAL` when
converting a timeout value overflows, for consistency with the other
polling APIs.

Author: sunfishcode

src/backend/libc/event/syscalls.rs

@@ -229,7 +229,7 @@ pub(crate) unsafe fn select(
         Some(timeout) => {
             // Convert from `Timespec` to `c::timeval`.
             timeout_data = c::timeval {
-                tv_sec: timeout.tv_sec.try_into().map_err(|_| io::Errno::OVERFLOW)?,
+                tv_sec: timeout.tv_sec.try_into().map_err(|_| io::Errno::INVAL)?,
                 tv_usec: ((timeout.tv_nsec + 999) / 1000) as _,
             };
             &timeout_data
@@ -306,7 +306,7 @@ pub(crate) unsafe fn select(
         Some(timeout) => {
             // Convert from `Timespec` to `c::timeval`.
             timeout_data = c::timeval {
-                tv_sec: timeout.tv_sec.try_into().map_err(|_| io::Errno::OVERFLOW)?,
+                tv_sec: timeout.tv_sec.try_into().map_err(|_| io::Errno::INVAL)?,
                 tv_usec: ((timeout.tv_nsec + 999) / 1000) as _,
             };
             &timeout_data

src/event/kqueue.rs

@@ -398,6 +398,9 @@ pub fn kqueue() -> io::Result<OwnedFd> {
 /// `kevent(kqueue, changelist, eventlist, timeout)`—Wait for events on a
 /// `kqueue`.
 ///
+/// If an unsupported timeout is passed, this function fails with
+/// [`io::Errno::INVAL`].
+///
 /// # Safety
 ///
 /// The file descriptors referred to by the `Event` structs must be valid for
@@ -421,10 +424,13 @@ pub unsafe fn kevent<Fd: AsFd, Buf: Buffer<Event>>(
     mut eventlist: Buf,
     timeout: Option<Duration>,
 ) -> io::Result<Buf::Output> {
-    let timeout = timeout.map(|timeout| backend::c::timespec {
-        tv_sec: timeout.as_secs() as _,
-        tv_nsec: timeout.subsec_nanos() as _,
-    });
+    let timeout = match timeout {
+        Some(timeout) => Some(backend::c::timespec {
+            tv_sec: timeout.as_secs().try_into().map_err(|_| io::Errno::INVAL)?,
+            tv_nsec: timeout.subsec_nanos() as _,
+        }),
+        None => None,
+    };
 
     // Populate the event list with events.
     let len = syscalls::kevent(

src/event/port.rs

@@ -123,6 +123,9 @@ pub unsafe fn dissociate_fd<Fd: AsFd, RawFd: AsRawFd>(port: Fd, object: RawFd) -
 
 /// `port_get(port, timeout)`—Gets an event from a port.
 ///
+/// If an unsupported timeout is passed, this function fails with
+/// [`io::Errno::INVAL`].
+///
 /// # References
 ///  - [OpenSolaris]
 ///  - [illumos]
@@ -141,6 +144,9 @@ pub fn get<Fd: AsFd>(port: Fd, timeout: Option<&Timespec>) -> io::Result<Event>
 ///
 /// To query the number of events without retrieving any, use [`getn_query`].
 ///
+/// If an unsupported timeout is passed, this function fails with
+/// [`io::Errno::INVAL`].
+///
 /// # References
 ///  - [OpenSolaris]
 ///  - [illumos]

src/event/select.rs

@@ -69,6 +69,9 @@ pub struct FdSetElement(pub(crate) usize);
 /// `readfds`, `writefds`, `exceptfds` must point to arrays of `FdSetElement`
 /// containing at least `nfds.div_ceil(size_of::<FdSetElement>())` elements.
 ///
+/// If an unsupported timeout is passed, this function fails with
+/// [`io::Errno::INVAL`].
+///
 /// This `select` wrapper differs from POSIX in that `nfds` is not limited to
 /// `FD_SETSIZE`. Instead of using the fixed-sized `fd_set` type, this function
 /// takes raw pointers to arrays of `fd_set_num_elements(max_fd + 1, num_fds)`,