Add rustc_nonnull_optimization_guaranteed to Owned/Borrowed Fd/Socket

library/std/src/os/fd/owned.rs

@@ -32,6 +32,7 @@ use crate::sys_common::{AsInner, FromInner, IntoInner};
 // 32-bit c_int. Below is -2, in two's complement, but that only works out
 // because c_int is 32 bits.
 #[rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FE)]
+#[rustc_nonnull_optimization_guaranteed]
 #[unstable(feature = "io_safety", issue = "87074")]
 pub struct BorrowedFd<'fd> {
  fd: RawFd,
@@ -52,6 +53,7 @@ pub struct BorrowedFd<'fd> {
 // 32-bit c_int. Below is -2, in two's complement, but that only works out
 // because c_int is 32 bits.
 #[rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FE)]
+#[rustc_nonnull_optimization_guaranteed]
 #[unstable(feature = "io_safety", issue = "87074")]
 pub struct OwnedFd {
  fd: RawFd,

library/std/src/os/fd/tests.rs

@@ -32,3 +32,22 @@ fn test_fd() {
  assert_eq!(stdin_as_file.as_fd().as_raw_fd(), raw_fd);
  assert_eq!(Into::<OwnedFd>::into(stdin_as_file).into_raw_fd(), raw_fd);
 }
+
+#[cfg(any(unix, target_os = "wasi"))]
+#[test]
+fn test_niche_optimizations() {
+ use crate::mem::size_of;
+ #[cfg(unix)]
+ use crate::os::unix::io::{BorrowedFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
+ #[cfg(target_os = "wasi")]
+ use crate::os::wasi::io::{BorrowedFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
+
+ assert_eq!(size_of::<Option<OwnedFd>>(), size_of::<RawFd>());
+ assert_eq!(size_of::<Option<BorrowedFd<'static>>>(), size_of::<RawFd>());
+ unsafe {
+ assert_eq!(OwnedFd::from_raw_fd(RawFd::MIN).into_raw_fd(), RawFd::MIN);
+ assert_eq!(OwnedFd::from_raw_fd(RawFd::MAX).into_raw_fd(), RawFd::MAX);
+ assert_eq!(Some(OwnedFd::from_raw_fd(RawFd::MIN)).unwrap().into_raw_fd(), RawFd::MIN);
+ assert_eq!(Some(OwnedFd::from_raw_fd(RawFd::MAX)).unwrap().into_raw_fd(), RawFd::MAX);
+ }
+}

library/std/src/os/windows/io/mod.rs

@@ -54,3 +54,6 @@ pub use handle::*;
 pub use raw::*;
 #[unstable(feature = "io_safety", issue = "87074")]
 pub use socket::*;
+
+#[cfg(test)]
+mod tests;

library/std/src/os/windows/io/socket.rs

@@ -34,6 +34,7 @@ use crate::sys::cvt;
  target_pointer_width = "64",
  rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FF_FF_FF_FF_FE)
 )]
+#[rustc_nonnull_optimization_guaranteed]
 #[unstable(feature = "io_safety", issue = "87074")]
 pub struct BorrowedSocket<'socket> {
  socket: RawSocket,
@@ -56,6 +57,7 @@ pub struct BorrowedSocket<'socket> {
  target_pointer_width = "64",
  rustc_layout_scalar_valid_range_end(0xFF_FF_FF_FF_FF_FF_FF_FE)
 )]
+#[rustc_nonnull_optimization_guaranteed]
 #[unstable(feature = "io_safety", issue = "87074")]
 pub struct OwnedSocket {
  socket: RawSocket,

library/std/src/os/windows/io/tests.rs

@@ -0,0 +1,21 @@
+#[test]
+fn test_niche_optimizations_socket() {
+ use crate::mem::size_of;
+ use crate::os::windows::io::{
+ BorrowedSocket, FromRawSocket, IntoRawSocket, OwnedSocket, RawSocket,
+ };
+
+ assert_eq!(size_of::<Option<OwnedSocket>>(), size_of::<RawSocket>());
+ assert_eq!(size_of::<Option<BorrowedSocket<'static>>>(), size_of::<RawSocket>(),);
+ unsafe {
+ #[cfg(target_pointer_width = "32")]
+ let (min, max) = (i32::MIN as u32, i32::MAX as u32);
+ #[cfg(target_pointer_width = "64")]
+ let (min, max) = (i64::MIN as u64, i64::MAX as u64);
+
+ assert_eq!(OwnedSocket::from_raw_socket(min).into_raw_socket(), min);
+ assert_eq!(OwnedSocket::from_raw_socket(max).into_raw_socket(), max);
+ assert_eq!(Some(OwnedSocket::from_raw_socket(min)).unwrap().into_raw_socket(), min);
+ assert_eq!(Some(OwnedSocket::from_raw_socket(max)).unwrap().into_raw_socket(), max);
+ }
+}