Return Errno::INVAL when converting a Timespec to i32.

src/backend/libc/event/syscalls.rs

@@ -191,7 +191,7 @@ pub(crate) fn poll(fds: &mut [PollFd<'_>], timeout: Option<&Timespec>) -> io::Re
                         millis.checked_add((i64::from(timeout.tv_nsec) + 999_999) / 1_000_000)
                     })
                     .and_then(|millis| c::c_int::try_from(millis).ok())
-                    .ok_or(io::Errno::OVERFLOW)?
+                    .ok_or(io::Errno::INVAL)?
             }
         };
         ret_c_int(unsafe { c::poll(fds.as_mut_ptr().cast(), nfds, timeout) })

src/backend/libc/event/windows_syscalls.rs

@@ -2,15 +2,32 @@
 
 use crate::backend::c;
 use crate::backend::conv::ret_c_int;
-use crate::event::{FdSetElement, PollFd};
+use crate::event::{FdSetElement, PollFd, Timespec};
 use crate::io;
 
-pub(crate) fn poll(fds: &mut [PollFd<'_>], timeout: c::c_int) -> io::Result<usize> {
+pub(crate) fn poll(fds: &mut [PollFd<'_>], timeout: Option<&Timespec>) -> io::Result<usize> {
     let nfds = fds
         .len()
         .try_into()
         .map_err(|_convert_err| io::Errno::INVAL)?;
 
+    let timeout = match timeout {
+        None => -1,
+        Some(timeout) => {
+            // Convert from `Timespec` to `c_int` milliseconds.
+            let secs = timeout.tv_sec;
+            if secs < 0 {
+                return Err(io::Errno::INVAL);
+            }
+            secs.checked_mul(1000)
+                .and_then(|millis| {
+                    millis.checked_add((i64::from(timeout.tv_nsec) + 999_999) / 1_000_000)
+                })
+                .and_then(|millis| c::c_int::try_from(millis).ok())
+                .ok_or(io::Errno::INVAL)?
+        }
+    };
+
     ret_c_int(unsafe { c::poll(fds.as_mut_ptr().cast(), nfds, timeout) })
         .map(|nready| nready as usize)
 }

src/event/poll.rs

@@ -6,10 +6,8 @@ pub use backend::event::poll_fd::{PollFd, PollFlags};
 /// `poll(self.fds, timeout)`—Wait for events on lists of file descriptors.
 ///
 /// Some platforms (those that don't support `ppoll`) don't support timeouts
-/// greater than `c_int::MAX` milliseconds, and some (those that aren't fully
-/// y2038-ready) don't support timeouts with a seconds value greater than
-/// `i32::MAX`; if an unsupported timeout is passed, this function fails with
-/// [`io::Errno::OVERFLOW`].
+/// greater than `c_int::MAX` milliseconds; if an unsupported timeout is
+/// passed, this function fails with [`io::Errno::INVAL`].
 ///
 /// On macOS, `poll` doesn't work on fds for /dev/tty or /dev/null, however
 /// [`select`] is available and does work on these fds.