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-rw-r--r--library/std/src/fs/tests.rs4
-rw-r--r--library/std/src/io/error.rs3
-rw-r--r--library/std/src/io/mod.rs2
-rw-r--r--library/std/src/keyword_docs.rs102
-rw-r--r--library/std/src/lib.rs9
-rw-r--r--library/std/src/net/mod.rs21
-rw-r--r--library/std/src/net/socket_addr.rs41
-rw-r--r--library/std/src/net/tcp.rs4
-rw-r--r--library/std/src/net/tcp/tests.rs2
-rw-r--r--library/std/src/net/udp.rs4
-rw-r--r--library/std/src/net/udp/tests.rs1
-rw-r--r--library/std/src/num/f128.rs26
-rw-r--r--library/std/src/num/f16.rs26
-rw-r--r--library/std/src/num/f32.rs60
-rw-r--r--library/std/src/num/f64.rs32
-rw-r--r--library/std/src/os/cygwin/mod.rs1
-rw-r--r--library/std/src/os/cygwin/net.rs17
-rw-r--r--library/std/src/os/darwin/mod.rs2
-rw-r--r--library/std/src/os/darwin/objc.rs13
-rw-r--r--library/std/src/os/mod.rs2
-rw-r--r--library/std/src/os/net/linux_ext/mod.rs4
-rw-r--r--library/std/src/os/net/mod.rs2
-rw-r--r--library/std/src/os/unix/net/addr.rs8
-rw-r--r--library/std/src/os/unix/net/ancillary.rs31
-rw-r--r--library/std/src/os/unix/net/datagram.rs52
-rw-r--r--library/std/src/os/unix/net/mod.rs6
-rw-r--r--library/std/src/os/unix/net/stream.rs26
-rw-r--r--library/std/src/os/unix/net/tests.rs27
-rw-r--r--library/std/src/os/unix/process.rs2
-rw-r--r--library/std/src/panicking.rs26
-rw-r--r--library/std/src/path.rs8
-rw-r--r--library/std/src/process.rs29
-rw-r--r--library/std/src/process/tests.rs102
-rw-r--r--library/std/src/rt.rs6
-rw-r--r--library/std/src/sync/barrier.rs4
-rw-r--r--library/std/src/sync/nonpoison/condvar.rs9
-rw-r--r--library/std/src/sync/nonpoison/mutex.rs2
-rw-r--r--library/std/src/sync/nonpoison/rwlock.rs2
-rw-r--r--library/std/src/sync/poison/condvar.rs9
-rw-r--r--library/std/src/sync/poison/mutex.rs2
-rw-r--r--library/std/src/sync/poison/rwlock.rs2
-rw-r--r--library/std/src/sync/reentrant_lock.rs2
-rw-r--r--library/std/src/sys/args/zkvm.rs103
-rw-r--r--library/std/src/sys/env_consts.rs2
-rw-r--r--library/std/src/sys/fs/unix.rs186
-rw-r--r--library/std/src/sys/fs/wasi.rs9
-rw-r--r--library/std/src/sys/mod.rs2
-rw-r--r--library/std/src/sys/net/connection/mod.rs57
-rw-r--r--library/std/src/sys/net/connection/sgx.rs110
-rw-r--r--library/std/src/sys/net/connection/socket/hermit.rs3
-rw-r--r--library/std/src/sys/net/connection/socket/mod.rs (renamed from library/std/src/sys/net/connection/socket.rs)166
-rw-r--r--library/std/src/sys/net/connection/socket/tests.rs2
-rw-r--r--library/std/src/sys/net/connection/socket/unix.rs12
-rw-r--r--library/std/src/sys/net/connection/uefi/mod.rs49
-rw-r--r--library/std/src/sys/net/connection/unsupported.rs32
-rw-r--r--library/std/src/sys/net/connection/wasip1.rs32
-rw-r--r--library/std/src/sys/net/connection/xous/dns.rs45
-rw-r--r--library/std/src/sys/net/connection/xous/mod.rs2
-rw-r--r--library/std/src/sys/net/connection/xous/tcplistener.rs26
-rw-r--r--library/std/src/sys/net/connection/xous/tcpstream.rs9
-rw-r--r--library/std/src/sys/net/connection/xous/udp.rs81
-rw-r--r--library/std/src/sys/net/mod.rs48
-rw-r--r--library/std/src/sys/pal/hermit/mod.rs1
-rw-r--r--library/std/src/sys/pal/hermit/os.rs2
-rw-r--r--library/std/src/sys/pal/hermit/time.rs32
-rw-r--r--library/std/src/sys/pal/sgx/abi/mod.rs2
-rw-r--r--library/std/src/sys/pal/sgx/mod.rs1
-rw-r--r--library/std/src/sys/pal/sgx/time.rs15
-rw-r--r--library/std/src/sys/pal/solid/mod.rs4
-rw-r--r--library/std/src/sys/pal/solid/time.rs9
-rw-r--r--library/std/src/sys/pal/teeos/mod.rs1
-rw-r--r--library/std/src/sys/pal/trusty/mod.rs2
-rw-r--r--library/std/src/sys/pal/uefi/helpers.rs4
-rw-r--r--library/std/src/sys/pal/uefi/mod.rs1
-rw-r--r--library/std/src/sys/pal/uefi/thread.rs66
-rw-r--r--library/std/src/sys/pal/uefi/time.rs27
-rw-r--r--library/std/src/sys/pal/unix/mod.rs3
-rw-r--r--library/std/src/sys/pal/unix/time.rs30
-rw-r--r--library/std/src/sys/pal/unix/weak.rs130
-rw-r--r--library/std/src/sys/pal/unix/weak/tests.rs32
-rw-r--r--library/std/src/sys/pal/unsupported/mod.rs1
-rw-r--r--library/std/src/sys/pal/unsupported/time.rs15
-rw-r--r--library/std/src/sys/pal/wasip1/mod.rs1
-rw-r--r--library/std/src/sys/pal/wasip1/thread.rs214
-rw-r--r--library/std/src/sys/pal/wasip1/time.rs25
-rw-r--r--library/std/src/sys/pal/wasip2/mod.rs1
-rw-r--r--library/std/src/sys/pal/wasip2/thread.rs73
-rw-r--r--library/std/src/sys/pal/wasip2/time.rs27
-rw-r--r--library/std/src/sys/pal/wasm/atomics/thread.rs75
-rw-r--r--library/std/src/sys/pal/wasm/mod.rs15
-rw-r--r--library/std/src/sys/pal/windows/mod.rs5
-rw-r--r--library/std/src/sys/pal/windows/time.rs32
-rw-r--r--library/std/src/sys/pal/xous/mod.rs1
-rw-r--r--library/std/src/sys/pal/xous/time.rs15
-rw-r--r--library/std/src/sys/pal/zkvm/mod.rs2
-rw-r--r--library/std/src/sys/platform_version/darwin/core_foundation.rs180
-rw-r--r--library/std/src/sys/platform_version/darwin/mod.rs351
-rw-r--r--library/std/src/sys/platform_version/darwin/public_extern.rs156
-rw-r--r--library/std/src/sys/platform_version/darwin/tests.rs379
-rw-r--r--library/std/src/sys/platform_version/mod.rs13
-rw-r--r--library/std/src/sys/process/mod.rs2
-rw-r--r--library/std/src/sys/process/uefi.rs9
-rw-r--r--library/std/src/sys/process/unix/common.rs9
-rw-r--r--library/std/src/sys/process/unix/fuchsia.rs1
-rw-r--r--library/std/src/sys/process/unix/mod.rs2
-rw-r--r--library/std/src/sys/process/unix/unix.rs1
-rw-r--r--library/std/src/sys/process/unix/unix/tests.rs1
-rw-r--r--library/std/src/sys/process/unix/unsupported.rs1
-rw-r--r--library/std/src/sys/process/unix/vxworks.rs4
-rw-r--r--library/std/src/sys/process/unsupported.rs9
-rw-r--r--library/std/src/sys/process/windows.rs7
-rw-r--r--library/std/src/sys/stdio/mod.rs10
-rw-r--r--library/std/src/sys/stdio/wasip1.rs (renamed from library/std/src/sys/stdio/wasi.rs)0
-rw-r--r--library/std/src/sys/stdio/wasip2.rs120
-rw-r--r--library/std/src/sys/sync/once/queue.rs4
-rw-r--r--library/std/src/sys/thread/hermit.rs (renamed from library/std/src/sys/pal/hermit/thread.rs)66
-rw-r--r--library/std/src/sys/thread/mod.rs152
-rw-r--r--library/std/src/sys/thread/sgx.rs (renamed from library/std/src/sys/pal/sgx/thread.rs)49
-rw-r--r--library/std/src/sys/thread/solid.rs (renamed from library/std/src/sys/pal/itron/thread.rs)42
-rw-r--r--library/std/src/sys/thread/teeos.rs (renamed from library/std/src/sys/pal/teeos/thread.rs)71
-rw-r--r--library/std/src/sys/thread/uefi.rs25
-rw-r--r--library/std/src/sys/thread/unix.rs (renamed from library/std/src/sys/pal/unix/thread.rs)667
-rw-r--r--library/std/src/sys/thread/unsupported.rs (renamed from library/std/src/sys/pal/unsupported/thread.rs)39
-rw-r--r--library/std/src/sys/thread/wasip1.rs185
-rw-r--r--library/std/src/sys/thread/wasip2.rs32
-rw-r--r--library/std/src/sys/thread/wasm.rs23
-rw-r--r--library/std/src/sys/thread/windows.rs (renamed from library/std/src/sys/pal/windows/thread.rs)112
-rw-r--r--library/std/src/sys/thread/xous.rs (renamed from library/std/src/sys/pal/xous/thread.rs)54
-rw-r--r--library/std/src/thread/local.rs2
-rw-r--r--library/std/src/thread/mod.rs75
-rw-r--r--library/std/src/thread/tests.rs4
-rw-r--r--library/std/src/time.rs30
132 files changed, 3364 insertions, 2096 deletions
diff --git a/library/std/src/fs/tests.rs b/library/std/src/fs/tests.rs
index f4431cedd18..f8dfb0d6334 100644
--- a/library/std/src/fs/tests.rs
+++ b/library/std/src/fs/tests.rs
@@ -226,6 +226,7 @@ fn file_test_io_seek_and_write() {
     target_os = "freebsd",
     target_os = "linux",
     target_os = "netbsd",
+    target_os = "solaris",
     target_vendor = "apple",
 ))]
 fn file_lock_multiple_shared() {
@@ -249,6 +250,7 @@ fn file_lock_multiple_shared() {
     target_os = "freebsd",
     target_os = "linux",
     target_os = "netbsd",
+    target_os = "solaris",
     target_vendor = "apple",
 ))]
 fn file_lock_blocking() {
@@ -273,6 +275,7 @@ fn file_lock_blocking() {
     target_os = "freebsd",
     target_os = "linux",
     target_os = "netbsd",
+    target_os = "solaris",
     target_vendor = "apple",
 ))]
 fn file_lock_drop() {
@@ -294,6 +297,7 @@ fn file_lock_drop() {
     target_os = "freebsd",
     target_os = "linux",
     target_os = "netbsd",
+    target_os = "solaris",
     target_vendor = "apple",
 ))]
 fn file_lock_dup() {
diff --git a/library/std/src/io/error.rs b/library/std/src/io/error.rs
index 57a980d6acd..21e82d43a80 100644
--- a/library/std/src/io/error.rs
+++ b/library/std/src/io/error.rs
@@ -95,6 +95,9 @@ impl Error {
 
     pub(crate) const ZERO_TIMEOUT: Self =
         const_error!(ErrorKind::InvalidInput, "cannot set a 0 duration timeout");
+
+    pub(crate) const NO_ADDRESSES: Self =
+        const_error!(ErrorKind::InvalidInput, "could not resolve to any addresses");
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index ff0e29e04c2..a45edd08e8c 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -1081,7 +1081,7 @@ pub trait Read {
         default_read_buf_exact(self, cursor)
     }
 
-    /// Creates a "by reference" adaptor for this instance of `Read`.
+    /// Creates a "by reference" adapter for this instance of `Read`.
     ///
     /// The returned adapter also implements `Read` and will simply borrow this
     /// current reader.
diff --git a/library/std/src/keyword_docs.rs b/library/std/src/keyword_docs.rs
index 1c55824ab90..7ff4af8ede8 100644
--- a/library/std/src/keyword_docs.rs
+++ b/library/std/src/keyword_docs.rs
@@ -1257,6 +1257,108 @@ mod ref_keyword {}
 /// [`async`]: ../std/keyword.async.html
 mod return_keyword {}
 
+#[doc(keyword = "become")]
+//
+/// Perform a tail-call of a function.
+///
+/// <div class="warning">
+///
+/// `feature(explicit_tail_calls)` is currently incomplete and may not work properly.
+/// </div>
+///
+/// When tail calling a function, instead of its stack frame being added to the
+/// stack, the stack frame of the caller is directly replaced with the callee's.
+/// This means that as long as a loop in a call graph only uses tail calls, the
+/// stack growth will be bounded.
+///
+/// This is useful for writing functional-style code (since it prevents recursion
+/// from exhausting resources) or for code optimization (since a tail call
+/// *might* be cheaper than a normal call, tail calls can be used in a similar
+/// manner to computed goto).
+///
+/// Example of using `become` to implement functional-style `fold`:
+/// ```
+/// #![feature(explicit_tail_calls)]
+/// #![expect(incomplete_features)]
+///
+/// fn fold<T: Copy, S>(slice: &[T], init: S, f: impl Fn(S, T) -> S) -> S {
+///     match slice {
+///         // without `become`, on big inputs this could easily overflow the
+///         // stack. using a tail call guarantees that the stack will not grow unboundedly
+///         [first, rest @ ..] => become fold(rest, f(init, *first), f),
+///         [] => init,
+///     }
+/// }
+/// ```
+///
+/// Compilers can already perform "tail call optimization" -- they can replace normal
+/// calls with tail calls, although there are no guarantees that this will be done.
+/// However, to perform TCO, the call needs to be the last thing that happens
+/// in the functions and be returned from it. This requirement is often broken
+/// by drop code for locals, which is run after computing the return expression:
+///
+/// ```
+/// fn example() {
+///     let string = "meow".to_owned();
+///     println!("{string}");
+///     return help(); // this is *not* the last thing that happens in `example`...
+/// }
+///
+/// // ... because it is desugared to this:
+/// fn example_desugared() {
+///     let string = "meow".to_owned();
+///     println!("{string}");
+///     let tmp = help();
+///     drop(string);
+///     return tmp;
+/// }
+///
+/// fn help() {}
+/// ```
+///
+/// For this reason, `become` also changes the drop order, such that locals are
+/// dropped *before* evaluating the call.
+///
+/// In order to guarantee that the compiler can perform a tail call, `become`
+/// currently has these requirements:
+/// 1. callee and caller must have the same ABI, arguments, and return type
+/// 2. callee and caller must not have varargs
+/// 3. caller must not be marked with `#[track_caller]`
+///    - callee is allowed to be marked with `#[track_caller]` as otherwise
+///      adding `#[track_caller]` would be a breaking change. if callee is
+///      marked with `#[track_caller]` a tail call is not guaranteed.
+/// 4. callee and caller cannot be a closure
+///    (unless it's coerced to a function pointer)
+///
+/// It is possible to tail-call a function pointer:
+/// ```
+/// #![feature(explicit_tail_calls)]
+/// #![expect(incomplete_features)]
+///
+/// #[derive(Copy, Clone)]
+/// enum Inst { Inc, Dec }
+///
+/// fn dispatch(stream: &[Inst], state: u32) -> u32 {
+///     const TABLE: &[fn(&[Inst], u32) -> u32] = &[increment, decrement];
+///     match stream {
+///         [inst, rest @ ..] => become TABLE[*inst as usize](rest, state),
+///         [] => state,
+///     }
+/// }
+///
+/// fn increment(stream: &[Inst], state: u32) -> u32 {
+///     become dispatch(stream, state + 1)
+/// }
+///
+/// fn decrement(stream: &[Inst], state: u32) -> u32 {
+///     become dispatch(stream, state - 1)
+/// }
+///
+/// let program = &[Inst::Inc, Inst::Inc, Inst::Dec, Inst::Inc];
+/// assert_eq!(dispatch(program, 0), 2);
+/// ```
+mod become_keyword {}
+
 #[doc(keyword = "self")]
 //
 /// The receiver of a method, or the current module.
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 99b380c4793..45abd6bca8a 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -284,7 +284,6 @@
 #![feature(core_float_math)]
 #![feature(decl_macro)]
 #![feature(deprecated_suggestion)]
-#![feature(derive_const)]
 #![feature(doc_cfg)]
 #![feature(doc_cfg_hide)]
 #![feature(doc_masked)]
@@ -332,11 +331,7 @@
 #![feature(cfg_select)]
 #![feature(char_internals)]
 #![feature(clone_to_uninit)]
-#![feature(const_cmp)]
 #![feature(const_convert)]
-#![feature(const_ops)]
-#![feature(const_option_ops)]
-#![feature(const_try)]
 #![feature(core_intrinsics)]
 #![feature(core_io_borrowed_buf)]
 #![feature(drop_guard)]
@@ -350,10 +345,12 @@
 #![feature(float_gamma)]
 #![feature(float_minimum_maximum)]
 #![feature(fmt_internals)]
+#![feature(fn_ptr_trait)]
 #![feature(generic_atomic)]
 #![feature(hasher_prefixfree_extras)]
 #![feature(hashmap_internals)]
 #![feature(hint_must_use)]
+#![feature(int_from_ascii)]
 #![feature(ip)]
 #![feature(lazy_get)]
 #![feature(maybe_uninit_slice)]
@@ -369,6 +366,7 @@
 #![feature(slice_internals)]
 #![feature(slice_ptr_get)]
 #![feature(slice_range)]
+#![feature(slice_split_once)]
 #![feature(std_internals)]
 #![feature(str_internals)]
 #![feature(sync_unsafe_cell)]
@@ -383,7 +381,6 @@
 #![feature(allocator_api)]
 #![feature(get_mut_unchecked)]
 #![feature(map_try_insert)]
-#![feature(new_zeroed_alloc)]
 #![feature(slice_concat_trait)]
 #![feature(thin_box)]
 #![feature(try_reserve_kind)]
diff --git a/library/std/src/net/mod.rs b/library/std/src/net/mod.rs
index ddd3b68dd2d..40f1a93e39d 100644
--- a/library/std/src/net/mod.rs
+++ b/library/std/src/net/mod.rs
@@ -34,7 +34,6 @@ pub use self::tcp::IntoIncoming;
 pub use self::tcp::{Incoming, TcpListener, TcpStream};
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use self::udp::UdpSocket;
-use crate::io::{self, ErrorKind};
 
 mod ip_addr;
 mod socket_addr;
@@ -67,23 +66,3 @@ pub enum Shutdown {
     #[stable(feature = "rust1", since = "1.0.0")]
     Both,
 }
-
-fn each_addr<A: ToSocketAddrs, F, T>(addr: A, mut f: F) -> io::Result<T>
-where
-    F: FnMut(io::Result<&SocketAddr>) -> io::Result<T>,
-{
-    let addrs = match addr.to_socket_addrs() {
-        Ok(addrs) => addrs,
-        Err(e) => return f(Err(e)),
-    };
-    let mut last_err = None;
-    for addr in addrs {
-        match f(Ok(&addr)) {
-            Ok(l) => return Ok(l),
-            Err(e) => last_err = Some(e),
-        }
-    }
-    Err(last_err.unwrap_or_else(|| {
-        io::const_error!(ErrorKind::InvalidInput, "could not resolve to any addresses")
-    }))
-}
diff --git a/library/std/src/net/socket_addr.rs b/library/std/src/net/socket_addr.rs
index 41e623e79ce..5b56dd3f744 100644
--- a/library/std/src/net/socket_addr.rs
+++ b/library/std/src/net/socket_addr.rs
@@ -6,7 +6,6 @@ mod tests;
 pub use core::net::{SocketAddr, SocketAddrV4, SocketAddrV6};
 
 use crate::net::{IpAddr, Ipv4Addr, Ipv6Addr};
-use crate::sys::net::LookupHost;
 use crate::{io, iter, option, slice, vec};
 
 /// A trait for objects which can be converted or resolved to one or more
@@ -188,15 +187,9 @@ impl ToSocketAddrs for (Ipv6Addr, u16) {
     }
 }
 
-fn resolve_socket_addr(lh: LookupHost) -> io::Result<vec::IntoIter<SocketAddr>> {
-    let p = lh.port();
-    let v: Vec<_> = lh
-        .map(|mut a| {
-            a.set_port(p);
-            a
-        })
-        .collect();
-    Ok(v.into_iter())
+fn lookup_host(host: &str, port: u16) -> io::Result<vec::IntoIter<SocketAddr>> {
+    let addrs = crate::sys::net::lookup_host(host, port)?;
+    Ok(Vec::from_iter(addrs).into_iter())
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -205,17 +198,14 @@ impl ToSocketAddrs for (&str, u16) {
     fn to_socket_addrs(&self) -> io::Result<vec::IntoIter<SocketAddr>> {
         let (host, port) = *self;
 
-        // try to parse the host as a regular IP address first
-        if let Ok(addr) = host.parse::<Ipv4Addr>() {
-            let addr = SocketAddrV4::new(addr, port);
-            return Ok(vec![SocketAddr::V4(addr)].into_iter());
-        }
-        if let Ok(addr) = host.parse::<Ipv6Addr>() {
-            let addr = SocketAddrV6::new(addr, port, 0, 0);
-            return Ok(vec![SocketAddr::V6(addr)].into_iter());
+        // Try to parse the host as a regular IP address first
+        if let Ok(addr) = host.parse::<IpAddr>() {
+            let addr = SocketAddr::new(addr, port);
+            return Ok(vec![addr].into_iter());
         }
 
-        resolve_socket_addr((host, port).try_into()?)
+        // Otherwise, make the system look it up.
+        lookup_host(host, port)
     }
 }
 
@@ -232,12 +222,21 @@ impl ToSocketAddrs for (String, u16) {
 impl ToSocketAddrs for str {
     type Iter = vec::IntoIter<SocketAddr>;
     fn to_socket_addrs(&self) -> io::Result<vec::IntoIter<SocketAddr>> {
-        // try to parse as a regular SocketAddr first
+        // Try to parse as a regular SocketAddr first
         if let Ok(addr) = self.parse() {
             return Ok(vec![addr].into_iter());
         }
 
-        resolve_socket_addr(self.try_into()?)
+        // Otherwise, split the string by ':' and convert the second part to u16...
+        let Some((host, port_str)) = self.rsplit_once(':') else {
+            return Err(io::const_error!(io::ErrorKind::InvalidInput, "invalid socket address"));
+        };
+        let Ok(port) = port_str.parse::<u16>() else {
+            return Err(io::const_error!(io::ErrorKind::InvalidInput, "invalid port value"));
+        };
+
+        // ... and make the system look up the host.
+        lookup_host(host, port)
     }
 }
 
diff --git a/library/std/src/net/tcp.rs b/library/std/src/net/tcp.rs
index 10685b49319..ae50f531a71 100644
--- a/library/std/src/net/tcp.rs
+++ b/library/std/src/net/tcp.rs
@@ -167,7 +167,7 @@ impl TcpStream {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn connect<A: ToSocketAddrs>(addr: A) -> io::Result<TcpStream> {
-        super::each_addr(addr, net_imp::TcpStream::connect).map(TcpStream)
+        net_imp::TcpStream::connect(addr).map(TcpStream)
     }
 
     /// Opens a TCP connection to a remote host with a timeout.
@@ -782,7 +782,7 @@ impl TcpListener {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<TcpListener> {
-        super::each_addr(addr, net_imp::TcpListener::bind).map(TcpListener)
+        net_imp::TcpListener::bind(addr).map(TcpListener)
     }
 
     /// Returns the local socket address of this listener.
diff --git a/library/std/src/net/tcp/tests.rs b/library/std/src/net/tcp/tests.rs
index 03003037b29..7c7ef7b2f70 100644
--- a/library/std/src/net/tcp/tests.rs
+++ b/library/std/src/net/tcp/tests.rs
@@ -1,5 +1,5 @@
 use crate::io::prelude::*;
-use crate::io::{BorrowedBuf, IoSlice, IoSliceMut};
+use crate::io::{BorrowedBuf, ErrorKind, IoSlice, IoSliceMut};
 use crate::mem::MaybeUninit;
 use crate::net::test::{next_test_ip4, next_test_ip6};
 use crate::net::*;
diff --git a/library/std/src/net/udp.rs b/library/std/src/net/udp.rs
index a97b3299774..72e292e3d15 100644
--- a/library/std/src/net/udp.rs
+++ b/library/std/src/net/udp.rs
@@ -120,7 +120,7 @@ impl UdpSocket {
     /// [`Ipv4Addr::UNSPECIFIED`] or [`Ipv6Addr::UNSPECIFIED`].
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<UdpSocket> {
-        super::each_addr(addr, net_imp::UdpSocket::bind).map(UdpSocket)
+        net_imp::UdpSocket::bind(addr).map(UdpSocket)
     }
 
     /// Receives a single datagram message on the socket. On success, returns the number
@@ -677,7 +677,7 @@ impl UdpSocket {
     /// on the platform.
     #[stable(feature = "net2_mutators", since = "1.9.0")]
     pub fn connect<A: ToSocketAddrs>(&self, addr: A) -> io::Result<()> {
-        super::each_addr(addr, |addr| self.0.connect(addr))
+        self.0.connect(addr)
     }
 
     /// Sends data on the socket to the remote address to which it is connected.
diff --git a/library/std/src/net/udp/tests.rs b/library/std/src/net/udp/tests.rs
index 91da3135f97..0638b36c54f 100644
--- a/library/std/src/net/udp/tests.rs
+++ b/library/std/src/net/udp/tests.rs
@@ -1,3 +1,4 @@
+use crate::io::ErrorKind;
 use crate::net::test::{compare_ignore_zoneid, next_test_ip4, next_test_ip6};
 use crate::net::*;
 use crate::sync::mpsc::channel;
diff --git a/library/std/src/num/f128.rs b/library/std/src/num/f128.rs
index 64e604e35f7..5d206c4b7da 100644
--- a/library/std/src/num/f128.rs
+++ b/library/std/src/num/f128.rs
@@ -44,7 +44,7 @@ impl f128 {
     #[unstable(feature = "f128", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn powf(self, n: f128) -> f128 {
-        unsafe { intrinsics::powf128(self, n) }
+        intrinsics::powf128(self, n)
     }
 
     /// Returns `e^(self)`, (the exponential function).
@@ -76,7 +76,7 @@ impl f128 {
     #[unstable(feature = "f128", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn exp(self) -> f128 {
-        unsafe { intrinsics::expf128(self) }
+        intrinsics::expf128(self)
     }
 
     /// Returns `2^(self)`.
@@ -106,7 +106,7 @@ impl f128 {
     #[unstable(feature = "f128", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn exp2(self) -> f128 {
-        unsafe { intrinsics::exp2f128(self) }
+        intrinsics::exp2f128(self)
     }
 
     /// Returns the natural logarithm of the number.
@@ -151,7 +151,7 @@ impl f128 {
     #[unstable(feature = "f128", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn ln(self) -> f128 {
-        unsafe { intrinsics::logf128(self) }
+        intrinsics::logf128(self)
     }
 
     /// Returns the logarithm of the number with respect to an arbitrary base.
@@ -241,7 +241,7 @@ impl f128 {
     #[unstable(feature = "f128", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn log2(self) -> f128 {
-        unsafe { intrinsics::log2f128(self) }
+        intrinsics::log2f128(self)
     }
 
     /// Returns the base 10 logarithm of the number.
@@ -284,7 +284,7 @@ impl f128 {
     #[unstable(feature = "f128", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn log10(self) -> f128 {
-        unsafe { intrinsics::log10f128(self) }
+        intrinsics::log10f128(self)
     }
 
     /// Returns the cube root of a number.
@@ -385,7 +385,7 @@ impl f128 {
     #[unstable(feature = "f128", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn sin(self) -> f128 {
-        unsafe { intrinsics::sinf128(self) }
+        intrinsics::sinf128(self)
     }
 
     /// Computes the cosine of a number (in radians).
@@ -414,7 +414,7 @@ impl f128 {
     #[unstable(feature = "f128", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn cos(self) -> f128 {
-        unsafe { intrinsics::cosf128(self) }
+        intrinsics::cosf128(self)
     }
 
     /// Computes the tangent of a number (in radians).
@@ -467,10 +467,10 @@ impl f128 {
     /// # #[cfg(not(miri))]
     /// # #[cfg(target_has_reliable_f128_math)] {
     ///
-    /// let f = std::f128::consts::FRAC_PI_2;
+    /// let f = std::f128::consts::FRAC_PI_4;
     ///
     /// // asin(sin(pi/2))
-    /// let abs_difference = (f.sin().asin() - std::f128::consts::FRAC_PI_2).abs();
+    /// let abs_difference = (f.sin().asin() - f).abs();
     ///
     /// assert!(abs_difference <= f128::EPSILON);
     /// # }
@@ -912,10 +912,10 @@ impl f128 {
     /// # #[cfg(not(miri))]
     /// # #[cfg(target_has_reliable_f128_math)] {
     ///
-    /// let e = std::f128::consts::E;
-    /// let f = e.tanh().atanh();
+    /// let x = std::f128::consts::FRAC_PI_6;
+    /// let f = x.tanh().atanh();
     ///
-    /// let abs_difference = (f - e).abs();
+    /// let abs_difference = (f - x).abs();
     ///
     /// assert!(abs_difference <= 1e-5);
     /// # }
diff --git a/library/std/src/num/f16.rs b/library/std/src/num/f16.rs
index 7bdefb05858..2565ef0f9f2 100644
--- a/library/std/src/num/f16.rs
+++ b/library/std/src/num/f16.rs
@@ -44,7 +44,7 @@ impl f16 {
     #[unstable(feature = "f16", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn powf(self, n: f16) -> f16 {
-        unsafe { intrinsics::powf16(self, n) }
+        intrinsics::powf16(self, n)
     }
 
     /// Returns `e^(self)`, (the exponential function).
@@ -76,7 +76,7 @@ impl f16 {
     #[unstable(feature = "f16", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn exp(self) -> f16 {
-        unsafe { intrinsics::expf16(self) }
+        intrinsics::expf16(self)
     }
 
     /// Returns `2^(self)`.
@@ -106,7 +106,7 @@ impl f16 {
     #[unstable(feature = "f16", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn exp2(self) -> f16 {
-        unsafe { intrinsics::exp2f16(self) }
+        intrinsics::exp2f16(self)
     }
 
     /// Returns the natural logarithm of the number.
@@ -151,7 +151,7 @@ impl f16 {
     #[unstable(feature = "f16", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn ln(self) -> f16 {
-        unsafe { intrinsics::logf16(self) }
+        intrinsics::logf16(self)
     }
 
     /// Returns the logarithm of the number with respect to an arbitrary base.
@@ -241,7 +241,7 @@ impl f16 {
     #[unstable(feature = "f16", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn log2(self) -> f16 {
-        unsafe { intrinsics::log2f16(self) }
+        intrinsics::log2f16(self)
     }
 
     /// Returns the base 10 logarithm of the number.
@@ -284,7 +284,7 @@ impl f16 {
     #[unstable(feature = "f16", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn log10(self) -> f16 {
-        unsafe { intrinsics::log10f16(self) }
+        intrinsics::log10f16(self)
     }
 
     /// Compute the distance between the origin and a point (`x`, `y`) on the
@@ -350,7 +350,7 @@ impl f16 {
     #[unstable(feature = "f16", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn sin(self) -> f16 {
-        unsafe { intrinsics::sinf16(self) }
+        intrinsics::sinf16(self)
     }
 
     /// Computes the cosine of a number (in radians).
@@ -379,7 +379,7 @@ impl f16 {
     #[unstable(feature = "f16", issue = "116909")]
     #[must_use = "method returns a new number and does not mutate the original value"]
     pub fn cos(self) -> f16 {
-        unsafe { intrinsics::cosf16(self) }
+        intrinsics::cosf16(self)
     }
 
     /// Computes the tangent of a number (in radians).
@@ -432,10 +432,10 @@ impl f16 {
     /// # #[cfg(not(miri))]
     /// # #[cfg(target_has_reliable_f16_math)] {
     ///
-    /// let f = std::f16::consts::FRAC_PI_2;
+    /// let f = std::f16::consts::FRAC_PI_4;
     ///
     /// // asin(sin(pi/2))
-    /// let abs_difference = (f.sin().asin() - std::f16::consts::FRAC_PI_2).abs();
+    /// let abs_difference = (f.sin().asin() - f).abs();
     ///
     /// assert!(abs_difference <= f16::EPSILON);
     /// # }
@@ -877,10 +877,10 @@ impl f16 {
     /// # #[cfg(not(miri))]
     /// # #[cfg(target_has_reliable_f16_math)] {
     ///
-    /// let e = std::f16::consts::E;
-    /// let f = e.tanh().atanh();
+    /// let x = std::f16::consts::FRAC_PI_6;
+    /// let f = x.tanh().atanh();
     ///
-    /// let abs_difference = (f - e).abs();
+    /// let abs_difference = (f - x).abs();
     ///
     /// assert!(abs_difference <= 0.01);
     /// # }
diff --git a/library/std/src/num/f32.rs b/library/std/src/num/f32.rs
index 5dee68ad909..ac1d889cc37 100644
--- a/library/std/src/num/f32.rs
+++ b/library/std/src/num/f32.rs
@@ -338,7 +338,7 @@ impl f32 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn powf(self, n: f32) -> f32 {
-        unsafe { intrinsics::powf32(self, n) }
+        intrinsics::powf32(self, n)
     }
 
     /// Returns the square root of a number.
@@ -395,7 +395,7 @@ impl f32 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn exp(self) -> f32 {
-        unsafe { intrinsics::expf32(self) }
+        intrinsics::expf32(self)
     }
 
     /// Returns `2^(self)`.
@@ -420,7 +420,7 @@ impl f32 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn exp2(self) -> f32 {
-        unsafe { intrinsics::exp2f32(self) }
+        intrinsics::exp2f32(self)
     }
 
     /// Returns the natural logarithm of the number.
@@ -455,7 +455,7 @@ impl f32 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn ln(self) -> f32 {
-        unsafe { intrinsics::logf32(self) }
+        intrinsics::logf32(self)
     }
 
     /// Returns the logarithm of the number with respect to an arbitrary base.
@@ -525,7 +525,7 @@ impl f32 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn log2(self) -> f32 {
-        unsafe { intrinsics::log2f32(self) }
+        intrinsics::log2f32(self)
     }
 
     /// Returns the base 10 logarithm of the number.
@@ -558,7 +558,7 @@ impl f32 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn log10(self) -> f32 {
-        unsafe { intrinsics::log10f32(self) }
+        intrinsics::log10f32(self)
     }
 
     /// The positive difference of two numbers.
@@ -582,8 +582,8 @@ impl f32 {
     /// let abs_difference_x = (x.abs_sub(1.0) - 2.0).abs();
     /// let abs_difference_y = (y.abs_sub(1.0) - 0.0).abs();
     ///
-    /// assert!(abs_difference_x <= f32::EPSILON);
-    /// assert!(abs_difference_y <= f32::EPSILON);
+    /// assert!(abs_difference_x <= 1e-6);
+    /// assert!(abs_difference_y <= 1e-6);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
@@ -621,7 +621,7 @@ impl f32 {
     /// // x^(1/3) - 2 == 0
     /// let abs_difference = (x.cbrt() - 2.0).abs();
     ///
-    /// assert!(abs_difference <= f32::EPSILON);
+    /// assert!(abs_difference <= 1e-6);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
@@ -652,7 +652,7 @@ impl f32 {
     /// // sqrt(x^2 + y^2)
     /// let abs_difference = (x.hypot(y) - (x.powi(2) + y.powi(2)).sqrt()).abs();
     ///
-    /// assert!(abs_difference <= 1e-6);
+    /// assert!(abs_difference <= 1e-5);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
@@ -683,7 +683,7 @@ impl f32 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn sin(self) -> f32 {
-        unsafe { intrinsics::sinf32(self) }
+        intrinsics::sinf32(self)
     }
 
     /// Computes the cosine of a number (in radians).
@@ -707,7 +707,7 @@ impl f32 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn cos(self) -> f32 {
-        unsafe { intrinsics::cosf32(self) }
+        intrinsics::cosf32(self)
     }
 
     /// Computes the tangent of a number (in radians).
@@ -725,7 +725,7 @@ impl f32 {
     /// let x = std::f32::consts::FRAC_PI_4;
     /// let abs_difference = (x.tan() - 1.0).abs();
     ///
-    /// assert!(abs_difference <= f32::EPSILON);
+    /// assert!(abs_difference <= 1e-6);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
@@ -749,12 +749,12 @@ impl f32 {
     /// # Examples
     ///
     /// ```
-    /// let f = std::f32::consts::FRAC_PI_2;
+    /// let f = std::f32::consts::FRAC_PI_4;
     ///
     /// // asin(sin(pi/2))
-    /// let abs_difference = (f.sin().asin() - std::f32::consts::FRAC_PI_2).abs();
+    /// let abs_difference = (f.sin().asin() - f).abs();
     ///
-    /// assert!(abs_difference <= 1e-3);
+    /// assert!(abs_difference <= 1e-6);
     /// ```
     #[doc(alias = "arcsin")]
     #[rustc_allow_incoherent_impl]
@@ -813,7 +813,7 @@ impl f32 {
     /// // atan(tan(1))
     /// let abs_difference = (f.tan().atan() - 1.0).abs();
     ///
-    /// assert!(abs_difference <= f32::EPSILON);
+    /// assert!(abs_difference <= 1e-6);
     /// ```
     #[doc(alias = "arctan")]
     #[rustc_allow_incoherent_impl]
@@ -854,8 +854,8 @@ impl f32 {
     /// let abs_difference_1 = (y1.atan2(x1) - (-std::f32::consts::FRAC_PI_4)).abs();
     /// let abs_difference_2 = (y2.atan2(x2) - (3.0 * std::f32::consts::FRAC_PI_4)).abs();
     ///
-    /// assert!(abs_difference_1 <= f32::EPSILON);
-    /// assert!(abs_difference_2 <= f32::EPSILON);
+    /// assert!(abs_difference_1 <= 1e-5);
+    /// assert!(abs_difference_2 <= 1e-5);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
@@ -884,8 +884,8 @@ impl f32 {
     /// let abs_difference_0 = (f.0 - x.sin()).abs();
     /// let abs_difference_1 = (f.1 - x.cos()).abs();
     ///
-    /// assert!(abs_difference_0 <= 1e-6);
-    /// assert!(abs_difference_1 <= 1e-6);
+    /// assert!(abs_difference_0 <= 1e-4);
+    /// assert!(abs_difference_1 <= 1e-4);
     /// ```
     #[doc(alias = "sincos")]
     #[rustc_allow_incoherent_impl]
@@ -982,7 +982,7 @@ impl f32 {
     /// let g = ((e * e) - 1.0) / (2.0 * e);
     /// let abs_difference = (f - g).abs();
     ///
-    /// assert!(abs_difference <= f32::EPSILON);
+    /// assert!(abs_difference <= 1e-6);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
@@ -1012,7 +1012,7 @@ impl f32 {
     /// let abs_difference = (f - g).abs();
     ///
     /// // Same result
-    /// assert!(abs_difference <= f32::EPSILON);
+    /// assert!(abs_difference <= 1e-6);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
@@ -1042,7 +1042,7 @@ impl f32 {
     /// let g = (1.0 - e.powi(-2)) / (1.0 + e.powi(-2));
     /// let abs_difference = (f - g).abs();
     ///
-    /// assert!(abs_difference <= f32::EPSILON);
+    /// assert!(abs_difference <= 1e-6);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
@@ -1067,7 +1067,7 @@ impl f32 {
     ///
     /// let abs_difference = (f - x).abs();
     ///
-    /// assert!(abs_difference <= 1e-7);
+    /// assert!(abs_difference <= 1e-6);
     /// ```
     #[doc(alias = "arcsinh")]
     #[rustc_allow_incoherent_impl]
@@ -1120,10 +1120,10 @@ impl f32 {
     /// # Examples
     ///
     /// ```
-    /// let e = std::f32::consts::E;
-    /// let f = e.tanh().atanh();
+    /// let x = std::f32::consts::FRAC_PI_6;
+    /// let f = x.tanh().atanh();
     ///
-    /// let abs_difference = (f - e).abs();
+    /// let abs_difference = (f - x).abs();
     ///
     /// assert!(abs_difference <= 1e-5);
     /// ```
@@ -1153,7 +1153,7 @@ impl f32 {
     ///
     /// let abs_difference = (x.gamma() - 24.0).abs();
     ///
-    /// assert!(abs_difference <= f32::EPSILON);
+    /// assert!(abs_difference <= 1e-5);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
@@ -1248,7 +1248,7 @@ impl f32 {
     /// let one = x.erf() + x.erfc();
     /// let abs_difference = (one - 1.0).abs();
     ///
-    /// assert!(abs_difference <= f32::EPSILON);
+    /// assert!(abs_difference <= 1e-6);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
diff --git a/library/std/src/num/f64.rs b/library/std/src/num/f64.rs
index 3ec80f68bdb..55c8593a0c0 100644
--- a/library/std/src/num/f64.rs
+++ b/library/std/src/num/f64.rs
@@ -338,7 +338,7 @@ impl f64 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn powf(self, n: f64) -> f64 {
-        unsafe { intrinsics::powf64(self, n) }
+        intrinsics::powf64(self, n)
     }
 
     /// Returns the square root of a number.
@@ -395,7 +395,7 @@ impl f64 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn exp(self) -> f64 {
-        unsafe { intrinsics::expf64(self) }
+        intrinsics::expf64(self)
     }
 
     /// Returns `2^(self)`.
@@ -420,7 +420,7 @@ impl f64 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn exp2(self) -> f64 {
-        unsafe { intrinsics::exp2f64(self) }
+        intrinsics::exp2f64(self)
     }
 
     /// Returns the natural logarithm of the number.
@@ -455,7 +455,7 @@ impl f64 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn ln(self) -> f64 {
-        unsafe { intrinsics::logf64(self) }
+        intrinsics::logf64(self)
     }
 
     /// Returns the logarithm of the number with respect to an arbitrary base.
@@ -525,7 +525,7 @@ impl f64 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn log2(self) -> f64 {
-        unsafe { intrinsics::log2f64(self) }
+        intrinsics::log2f64(self)
     }
 
     /// Returns the base 10 logarithm of the number.
@@ -558,7 +558,7 @@ impl f64 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn log10(self) -> f64 {
-        unsafe { intrinsics::log10f64(self) }
+        intrinsics::log10f64(self)
     }
 
     /// The positive difference of two numbers.
@@ -683,7 +683,7 @@ impl f64 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn sin(self) -> f64 {
-        unsafe { intrinsics::sinf64(self) }
+        intrinsics::sinf64(self)
     }
 
     /// Computes the cosine of a number (in radians).
@@ -707,7 +707,7 @@ impl f64 {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn cos(self) -> f64 {
-        unsafe { intrinsics::cosf64(self) }
+        intrinsics::cosf64(self)
     }
 
     /// Computes the tangent of a number (in radians).
@@ -749,12 +749,12 @@ impl f64 {
     /// # Examples
     ///
     /// ```
-    /// let f = std::f64::consts::FRAC_PI_2;
+    /// let f = std::f64::consts::FRAC_PI_4;
     ///
     /// // asin(sin(pi/2))
-    /// let abs_difference = (f.sin().asin() - std::f64::consts::FRAC_PI_2).abs();
+    /// let abs_difference = (f.sin().asin() - f).abs();
     ///
-    /// assert!(abs_difference < 1e-7);
+    /// assert!(abs_difference < 1e-14);
     /// ```
     #[doc(alias = "arcsin")]
     #[rustc_allow_incoherent_impl]
@@ -1120,10 +1120,10 @@ impl f64 {
     /// # Examples
     ///
     /// ```
-    /// let e = std::f64::consts::E;
-    /// let f = e.tanh().atanh();
+    /// let x = std::f64::consts::FRAC_PI_6;
+    /// let f = x.tanh().atanh();
     ///
-    /// let abs_difference = (f - e).abs();
+    /// let abs_difference = (f - x).abs();
     ///
     /// assert!(abs_difference < 1.0e-10);
     /// ```
@@ -1153,7 +1153,7 @@ impl f64 {
     ///
     /// let abs_difference = (x.gamma() - 24.0).abs();
     ///
-    /// assert!(abs_difference <= f64::EPSILON);
+    /// assert!(abs_difference <= 1e-10);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
@@ -1248,7 +1248,7 @@ impl f64 {
     /// let one = x.erf() + x.erfc();
     /// let abs_difference = (one - 1.0).abs();
     ///
-    /// assert!(abs_difference <= f64::EPSILON);
+    /// assert!(abs_difference <= 1e-10);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
diff --git a/library/std/src/os/cygwin/mod.rs b/library/std/src/os/cygwin/mod.rs
index 7f6d6a645c8..a295a07caac 100644
--- a/library/std/src/os/cygwin/mod.rs
+++ b/library/std/src/os/cygwin/mod.rs
@@ -1,4 +1,5 @@
 //! Cygwin-specific definitions
 #![stable(feature = "raw_ext", since = "1.1.0")]
 pub mod fs;
+pub mod net;
 pub(crate) mod raw;
diff --git a/library/std/src/os/cygwin/net.rs b/library/std/src/os/cygwin/net.rs
new file mode 100644
index 00000000000..0cccddb85d0
--- /dev/null
+++ b/library/std/src/os/cygwin/net.rs
@@ -0,0 +1,17 @@
+//! Cygwin-specific networking functionality.
+//!
+//! There are some limitations of Unix domain sockets on Cygwin:
+//! * The syscalls `accept` and `connect` need
+//! [handshake](https://inbox.sourceware.org/cygwin/Z_UERXFI1g-1v3p2@calimero.vinschen.de/T/#t).
+//! * Cannot bind to abstract addr.
+//! * Unbounded unix socket has an abstract local addr.
+//! * Doesn't support recvmsg with control data.
+
+#![stable(feature = "unix_socket_abstract", since = "1.70.0")]
+
+#[stable(feature = "unix_socket_abstract", since = "1.70.0")]
+pub use crate::os::net::linux_ext::addr::SocketAddrExt;
+#[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
+pub use crate::os::net::linux_ext::socket::UnixSocketExt;
+#[stable(feature = "tcp_quickack", since = "1.89.0")]
+pub use crate::os::net::linux_ext::tcp::TcpStreamExt;
diff --git a/library/std/src/os/darwin/mod.rs b/library/std/src/os/darwin/mod.rs
index 3b1bd974fa3..ff184f477fb 100644
--- a/library/std/src/os/darwin/mod.rs
+++ b/library/std/src/os/darwin/mod.rs
@@ -17,6 +17,8 @@
 #![doc(cfg(target_vendor = "apple"))]
 
 pub mod fs;
+pub mod objc;
+
 // deprecated, but used for public reexport under `std::os::unix::raw`, as
 // well as `std::os::macos`/`std::os::ios`, because those modules precede the
 // decision to remove these.
diff --git a/library/std/src/os/darwin/objc.rs b/library/std/src/os/darwin/objc.rs
new file mode 100644
index 00000000000..a4b31fee7c5
--- /dev/null
+++ b/library/std/src/os/darwin/objc.rs
@@ -0,0 +1,13 @@
+//! Defines types and macros for Objective-C interoperability.
+//!
+//! This module re-exports all the items in [`core::os::darwin::objc`].
+//!
+//! [`core::os::darwin::objc`]: ../../../../core/os/darwin/objc/index.html "mod core::os::darwin::objc"
+
+#![unstable(feature = "darwin_objc", issue = "145496")]
+
+// We can't generate an intra-doc link for this automatically since `core::os::darwin` isn't
+// compiled into `core` on every platform even though it's documented on every platform.
+// We just link to it directly in the module documentation above instead.
+#[cfg(not(doc))]
+pub use core::os::darwin::objc::*;
diff --git a/library/std/src/os/mod.rs b/library/std/src/os/mod.rs
index ab7734a7952..96d9bfae8ca 100644
--- a/library/std/src/os/mod.rs
+++ b/library/std/src/os/mod.rs
@@ -185,5 +185,5 @@ pub mod xous;
 #[cfg(any(unix, target_os = "hermit", target_os = "trusty", target_os = "wasi", doc))]
 pub mod fd;
 
-#[cfg(any(target_os = "linux", target_os = "android", doc))]
+#[cfg(any(target_os = "linux", target_os = "android", target_os = "cygwin", doc))]
 mod net;
diff --git a/library/std/src/os/net/linux_ext/mod.rs b/library/std/src/os/net/linux_ext/mod.rs
index 3c9afe35479..f3f3fdd258c 100644
--- a/library/std/src/os/net/linux_ext/mod.rs
+++ b/library/std/src/os/net/linux_ext/mod.rs
@@ -1,6 +1,6 @@
-//! Linux and Android-specific networking functionality.
+//! Linux, Android and Cygwin-specific networking functionality.
 
-#![doc(cfg(any(target_os = "linux", target_os = "android")))]
+#![doc(cfg(any(target_os = "linux", target_os = "android", target_os = "cygwin")))]
 
 #[stable(feature = "unix_socket_abstract", since = "1.70.0")]
 pub(crate) mod addr;
diff --git a/library/std/src/os/net/mod.rs b/library/std/src/os/net/mod.rs
index b7046dd7c59..47e69b3a260 100644
--- a/library/std/src/os/net/mod.rs
+++ b/library/std/src/os/net/mod.rs
@@ -9,5 +9,5 @@
         all(target_vendor = "fortanix", target_env = "sgx")
     )
 )))]
-#[cfg(any(target_os = "linux", target_os = "android", doc))]
+#[cfg(any(target_os = "linux", target_os = "android", target_os = "cygwin", doc))]
 pub(super) mod linux_ext;
diff --git a/library/std/src/os/unix/net/addr.rs b/library/std/src/os/unix/net/addr.rs
index fd6fe72dd24..25b95014e08 100644
--- a/library/std/src/os/unix/net/addr.rs
+++ b/library/std/src/os/unix/net/addr.rs
@@ -1,6 +1,6 @@
 use crate::bstr::ByteStr;
 use crate::ffi::OsStr;
-#[cfg(any(doc, target_os = "android", target_os = "linux"))]
+#[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
 use crate::os::net::linux_ext;
 use crate::os::unix::ffi::OsStrExt;
 use crate::path::Path;
@@ -241,7 +241,7 @@ impl SocketAddr {
 
         // macOS seems to return a len of 16 and a zeroed sun_path for unnamed addresses
         if len == 0
-            || (cfg!(not(any(target_os = "linux", target_os = "android")))
+            || (cfg!(not(any(target_os = "linux", target_os = "android", target_os = "cygwin")))
                 && self.addr.sun_path[0] == 0)
         {
             AddressKind::Unnamed
@@ -256,8 +256,8 @@ impl SocketAddr {
 #[stable(feature = "unix_socket_abstract", since = "1.70.0")]
 impl Sealed for SocketAddr {}
 
-#[doc(cfg(any(target_os = "android", target_os = "linux")))]
-#[cfg(any(doc, target_os = "android", target_os = "linux"))]
+#[doc(cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin")))]
+#[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
 #[stable(feature = "unix_socket_abstract", since = "1.70.0")]
 impl linux_ext::addr::SocketAddrExt for SocketAddr {
     fn as_abstract_name(&self) -> Option<&[u8]> {
diff --git a/library/std/src/os/unix/net/ancillary.rs b/library/std/src/os/unix/net/ancillary.rs
index 36967fc3f98..d0984bdfb99 100644
--- a/library/std/src/os/unix/net/ancillary.rs
+++ b/library/std/src/os/unix/net/ancillary.rs
@@ -16,7 +16,8 @@ use crate::sys::net::Socket;
     not(target_os = "linux"),
     not(target_os = "android"),
     not(target_os = "netbsd"),
-    not(target_os = "freebsd")
+    not(target_os = "freebsd"),
+    not(target_os = "cygwin"),
 ))]
 #[allow(non_camel_case_types)]
 mod libc {
@@ -195,14 +196,15 @@ impl<'a, T> Iterator for AncillaryDataIter<'a, T> {
     not(target_os = "android"),
     not(target_os = "linux"),
     not(target_os = "netbsd"),
-    not(target_os = "freebsd")
+    not(target_os = "freebsd"),
+    not(target_os = "cygwin"),
 ))]
 #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
 #[derive(Clone)]
 pub struct SocketCred(());
 
 /// Unix credential.
-#[cfg(any(target_os = "android", target_os = "linux",))]
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
 #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
 #[derive(Clone)]
 pub struct SocketCred(libc::ucred);
@@ -217,8 +219,8 @@ pub struct SocketCred(libc::sockcred);
 #[derive(Clone)]
 pub struct SocketCred(libc::sockcred2);
 
-#[doc(cfg(any(target_os = "android", target_os = "linux")))]
-#[cfg(any(target_os = "android", target_os = "linux"))]
+#[doc(cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin")))]
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
 impl SocketCred {
     /// Creates a Unix credential struct.
     ///
@@ -407,7 +409,8 @@ impl<'a> Iterator for ScmRights<'a> {
     not(target_os = "android"),
     not(target_os = "linux"),
     not(target_os = "netbsd"),
-    not(target_os = "freebsd")
+    not(target_os = "freebsd"),
+    not(target_os = "cygwin"),
 ))]
 #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
 pub struct ScmCredentials<'a>(AncillaryDataIter<'a, ()>);
@@ -415,7 +418,7 @@ pub struct ScmCredentials<'a>(AncillaryDataIter<'a, ()>);
 /// This control message contains unix credentials.
 ///
 /// The level is equal to `SOL_SOCKET` and the type is equal to `SCM_CREDENTIALS` or `SCM_CREDS`.
-#[cfg(any(target_os = "android", target_os = "linux",))]
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
 #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
 pub struct ScmCredentials<'a>(AncillaryDataIter<'a, libc::ucred>);
 
@@ -432,7 +435,8 @@ pub struct ScmCredentials<'a>(AncillaryDataIter<'a, libc::sockcred>);
     target_os = "android",
     target_os = "linux",
     target_os = "netbsd",
-    target_os = "freebsd"
+    target_os = "freebsd",
+    target_os = "cygwin",
 ))]
 #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
 impl<'a> Iterator for ScmCredentials<'a> {
@@ -460,7 +464,8 @@ pub enum AncillaryData<'a> {
         target_os = "android",
         target_os = "linux",
         target_os = "netbsd",
-        target_os = "freebsd"
+        target_os = "freebsd",
+        target_os = "cygwin",
     ))]
     ScmCredentials(ScmCredentials<'a>),
 }
@@ -489,7 +494,8 @@ impl<'a> AncillaryData<'a> {
         target_os = "android",
         target_os = "linux",
         target_os = "netbsd",
-        target_os = "freebsd"
+        target_os = "freebsd",
+        target_os = "cygwin",
     ))]
     unsafe fn as_credentials(data: &'a [u8]) -> Self {
         let ancillary_data_iter = AncillaryDataIter::new(data);
@@ -507,7 +513,7 @@ impl<'a> AncillaryData<'a> {
             match (*cmsg).cmsg_level {
                 libc::SOL_SOCKET => match (*cmsg).cmsg_type {
                     libc::SCM_RIGHTS => Ok(AncillaryData::as_rights(data)),
-                    #[cfg(any(target_os = "android", target_os = "linux",))]
+                    #[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
                     libc::SCM_CREDENTIALS => Ok(AncillaryData::as_credentials(data)),
                     #[cfg(target_os = "freebsd")]
                     libc::SCM_CREDS2 => Ok(AncillaryData::as_credentials(data)),
@@ -729,7 +735,8 @@ impl<'a> SocketAncillary<'a> {
         target_os = "android",
         target_os = "linux",
         target_os = "netbsd",
-        target_os = "freebsd"
+        target_os = "freebsd",
+        target_os = "cygwin",
     ))]
     #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
     pub fn add_creds(&mut self, creds: &[SocketCred]) -> bool {
diff --git a/library/std/src/os/unix/net/datagram.rs b/library/std/src/os/unix/net/datagram.rs
index 7735637c840..469bfbb0d83 100644
--- a/library/std/src/os/unix/net/datagram.rs
+++ b/library/std/src/os/unix/net/datagram.rs
@@ -14,9 +14,9 @@
 use libc::MSG_NOSIGNAL;
 
 use super::{SocketAddr, sockaddr_un};
-#[cfg(any(doc, target_os = "android", target_os = "linux"))]
+#[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
 use super::{SocketAncillary, recv_vectored_with_ancillary_from, send_vectored_with_ancillary_to};
-#[cfg(any(doc, target_os = "android", target_os = "linux"))]
+#[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
 use crate::io::{IoSlice, IoSliceMut};
 use crate::net::Shutdown;
 use crate::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
@@ -397,8 +397,14 @@ impl UnixDatagram {
     ///
     /// # Examples
     ///
-    #[cfg_attr(any(target_os = "android", target_os = "linux"), doc = "```no_run")]
-    #[cfg_attr(not(any(target_os = "android", target_os = "linux")), doc = "```ignore")]
+    #[cfg_attr(
+        any(target_os = "android", target_os = "linux", target_os = "cygwin"),
+        doc = "```no_run"
+    )]
+    #[cfg_attr(
+        not(any(target_os = "android", target_os = "linux", target_os = "cygwin")),
+        doc = "```ignore"
+    )]
     /// #![feature(unix_socket_ancillary_data)]
     /// use std::os::unix::net::{UnixDatagram, SocketAncillary, AncillaryData};
     /// use std::io::IoSliceMut;
@@ -428,7 +434,7 @@ impl UnixDatagram {
     ///     Ok(())
     /// }
     /// ```
-    #[cfg(any(doc, target_os = "android", target_os = "linux"))]
+    #[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
     #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
     pub fn recv_vectored_with_ancillary_from(
         &self,
@@ -447,8 +453,14 @@ impl UnixDatagram {
     ///
     /// # Examples
     ///
-    #[cfg_attr(any(target_os = "android", target_os = "linux"), doc = "```no_run")]
-    #[cfg_attr(not(any(target_os = "android", target_os = "linux")), doc = "```ignore")]
+    #[cfg_attr(
+        any(target_os = "android", target_os = "linux", target_os = "cygwin"),
+        doc = "```no_run"
+    )]
+    #[cfg_attr(
+        not(any(target_os = "android", target_os = "linux", target_os = "cygwin")),
+        doc = "```ignore"
+    )]
     /// #![feature(unix_socket_ancillary_data)]
     /// use std::os::unix::net::{UnixDatagram, SocketAncillary, AncillaryData};
     /// use std::io::IoSliceMut;
@@ -478,7 +490,7 @@ impl UnixDatagram {
     ///     Ok(())
     /// }
     /// ```
-    #[cfg(any(doc, target_os = "android", target_os = "linux"))]
+    #[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
     #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
     pub fn recv_vectored_with_ancillary(
         &self,
@@ -588,8 +600,14 @@ impl UnixDatagram {
     ///
     /// # Examples
     ///
-    #[cfg_attr(any(target_os = "android", target_os = "linux"), doc = "```no_run")]
-    #[cfg_attr(not(any(target_os = "android", target_os = "linux")), doc = "```ignore")]
+    #[cfg_attr(
+        any(target_os = "android", target_os = "linux", target_os = "cygwin"),
+        doc = "```no_run"
+    )]
+    #[cfg_attr(
+        not(any(target_os = "android", target_os = "linux", target_os = "cygwin")),
+        doc = "```ignore"
+    )]
     /// #![feature(unix_socket_ancillary_data)]
     /// use std::os::unix::net::{UnixDatagram, SocketAncillary};
     /// use std::io::IoSlice;
@@ -613,7 +631,7 @@ impl UnixDatagram {
     ///     Ok(())
     /// }
     /// ```
-    #[cfg(any(doc, target_os = "android", target_os = "linux"))]
+    #[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
     #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
     pub fn send_vectored_with_ancillary_to<P: AsRef<Path>>(
         &self,
@@ -630,8 +648,14 @@ impl UnixDatagram {
     ///
     /// # Examples
     ///
-    #[cfg_attr(any(target_os = "android", target_os = "linux"), doc = "```no_run")]
-    #[cfg_attr(not(any(target_os = "android", target_os = "linux")), doc = "```ignore")]
+    #[cfg_attr(
+        any(target_os = "android", target_os = "linux", target_os = "cygwin"),
+        doc = "```no_run"
+    )]
+    #[cfg_attr(
+        not(any(target_os = "android", target_os = "linux", target_os = "cygwin")),
+        doc = "```ignore"
+    )]
     /// #![feature(unix_socket_ancillary_data)]
     /// use std::os::unix::net::{UnixDatagram, SocketAncillary};
     /// use std::io::IoSlice;
@@ -655,7 +679,7 @@ impl UnixDatagram {
     ///     Ok(())
     /// }
     /// ```
-    #[cfg(any(doc, target_os = "android", target_os = "linux"))]
+    #[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
     #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
     pub fn send_vectored_with_ancillary(
         &self,
diff --git a/library/std/src/os/unix/net/mod.rs b/library/std/src/os/unix/net/mod.rs
index 6cd62303a53..94523d7d1e4 100644
--- a/library/std/src/os/unix/net/mod.rs
+++ b/library/std/src/os/unix/net/mod.rs
@@ -4,8 +4,8 @@
 #![stable(feature = "unix_socket", since = "1.10.0")]
 
 mod addr;
-#[doc(cfg(any(target_os = "android", target_os = "linux")))]
-#[cfg(any(doc, target_os = "android", target_os = "linux"))]
+#[doc(cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin")))]
+#[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
 mod ancillary;
 mod datagram;
 mod listener;
@@ -27,7 +27,7 @@ mod ucred;
 
 #[stable(feature = "unix_socket", since = "1.10.0")]
 pub use self::addr::*;
-#[cfg(any(doc, target_os = "android", target_os = "linux"))]
+#[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
 #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
 pub use self::ancillary::*;
 #[stable(feature = "unix_socket", since = "1.10.0")]
diff --git a/library/std/src/os/unix/net/stream.rs b/library/std/src/os/unix/net/stream.rs
index 768fa77a5f8..ea4171a7d28 100644
--- a/library/std/src/os/unix/net/stream.rs
+++ b/library/std/src/os/unix/net/stream.rs
@@ -16,7 +16,7 @@ cfg_select! {
 }
 
 use super::{SocketAddr, sockaddr_un};
-#[cfg(any(doc, target_os = "android", target_os = "linux"))]
+#[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
 use super::{SocketAncillary, recv_vectored_with_ancillary_from, send_vectored_with_ancillary_to};
 #[cfg(any(
     target_os = "android",
@@ -508,8 +508,14 @@ impl UnixStream {
     ///
     /// # Examples
     ///
-    #[cfg_attr(any(target_os = "android", target_os = "linux"), doc = "```no_run")]
-    #[cfg_attr(not(any(target_os = "android", target_os = "linux")), doc = "```ignore")]
+    #[cfg_attr(
+        any(target_os = "android", target_os = "linux", target_os = "cygwin"),
+        doc = "```no_run"
+    )]
+    #[cfg_attr(
+        not(any(target_os = "android", target_os = "linux", target_os = "cygwin")),
+        doc = "```ignore"
+    )]
     /// #![feature(unix_socket_ancillary_data)]
     /// use std::os::unix::net::{UnixStream, SocketAncillary, AncillaryData};
     /// use std::io::IoSliceMut;
@@ -539,7 +545,7 @@ impl UnixStream {
     ///     Ok(())
     /// }
     /// ```
-    #[cfg(any(doc, target_os = "android", target_os = "linux"))]
+    #[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
     #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
     pub fn recv_vectored_with_ancillary(
         &self,
@@ -557,8 +563,14 @@ impl UnixStream {
     ///
     /// # Examples
     ///
-    #[cfg_attr(any(target_os = "android", target_os = "linux"), doc = "```no_run")]
-    #[cfg_attr(not(any(target_os = "android", target_os = "linux")), doc = "```ignore")]
+    #[cfg_attr(
+        any(target_os = "android", target_os = "linux", target_os = "cygwin"),
+        doc = "```no_run"
+    )]
+    #[cfg_attr(
+        not(any(target_os = "android", target_os = "linux", target_os = "cygwin")),
+        doc = "```ignore"
+    )]
     /// #![feature(unix_socket_ancillary_data)]
     /// use std::os::unix::net::{UnixStream, SocketAncillary};
     /// use std::io::IoSlice;
@@ -582,7 +594,7 @@ impl UnixStream {
     ///     Ok(())
     /// }
     /// ```
-    #[cfg(any(doc, target_os = "android", target_os = "linux"))]
+    #[cfg(any(doc, target_os = "android", target_os = "linux", target_os = "cygwin"))]
     #[unstable(feature = "unix_socket_ancillary_data", issue = "76915")]
     pub fn send_vectored_with_ancillary(
         &self,
diff --git a/library/std/src/os/unix/net/tests.rs b/library/std/src/os/unix/net/tests.rs
index 9a88687b1df..4666b5e3c6c 100644
--- a/library/std/src/os/unix/net/tests.rs
+++ b/library/std/src/os/unix/net/tests.rs
@@ -3,6 +3,8 @@ use crate::io::prelude::*;
 use crate::io::{self, ErrorKind, IoSlice, IoSliceMut};
 #[cfg(target_os = "android")]
 use crate::os::android::net::{SocketAddrExt, UnixSocketExt};
+#[cfg(target_os = "cygwin")]
+use crate::os::cygwin::net::{SocketAddrExt, UnixSocketExt};
 #[cfg(target_os = "linux")]
 use crate::os::linux::net::{SocketAddrExt, UnixSocketExt};
 #[cfg(any(target_os = "android", target_os = "linux"))]
@@ -170,6 +172,7 @@ fn long_path() {
 #[test]
 #[cfg(not(target_os = "nto"))]
 #[cfg_attr(target_os = "android", ignore)] // Android SELinux rules prevent creating Unix sockets
+#[cfg_attr(target_os = "cygwin", ignore)] // Cygwin connect needs handshake
 fn timeouts() {
     let dir = tmpdir();
     let socket_path = dir.path().join("sock");
@@ -198,6 +201,7 @@ fn timeouts() {
 
 #[test]
 #[cfg_attr(target_os = "android", ignore)] // Android SELinux rules prevent creating Unix sockets
+#[cfg_attr(target_os = "cygwin", ignore)] // Cygwin connect needs handshake
 fn test_read_timeout() {
     let dir = tmpdir();
     let socket_path = dir.path().join("sock");
@@ -218,6 +222,7 @@ fn test_read_timeout() {
 
 #[test]
 #[cfg_attr(target_os = "android", ignore)] // Android SELinux rules prevent creating Unix sockets
+#[cfg_attr(target_os = "cygwin", ignore)] // Cygwin connect needs handshake
 fn test_read_with_timeout() {
     let dir = tmpdir();
     let socket_path = dir.path().join("sock");
@@ -246,6 +251,7 @@ fn test_read_with_timeout() {
 // when passed zero Durations
 #[test]
 #[cfg_attr(target_os = "android", ignore)] // Android SELinux rules prevent creating Unix sockets
+#[cfg_attr(target_os = "cygwin", ignore)] // Cygwin connect needs handshake
 fn test_unix_stream_timeout_zero_duration() {
     let dir = tmpdir();
     let socket_path = dir.path().join("sock");
@@ -283,6 +289,7 @@ fn test_unix_datagram() {
 
 #[test]
 #[cfg_attr(target_os = "android", ignore)] // Android SELinux rules prevent creating Unix sockets
+#[cfg_attr(target_os = "cygwin", ignore)] // Cygwin autobinds an address
 fn test_unnamed_unix_datagram() {
     let dir = tmpdir();
     let path1 = dir.path().join("sock1");
@@ -326,6 +333,7 @@ fn test_unix_datagram_connect_to_recv_addr() {
 
 #[test]
 #[cfg_attr(target_os = "android", ignore)] // Android SELinux rules prevent creating Unix sockets
+#[cfg_attr(target_os = "cygwin", ignore)] // Cygwin autobinds an address
 fn test_connect_unix_datagram() {
     let dir = tmpdir();
     let path1 = dir.path().join("sock1");
@@ -425,8 +433,9 @@ fn abstract_namespace_not_allowed_connect() {
     assert!(UnixStream::connect("\0asdf").is_err());
 }
 
-#[cfg(any(target_os = "android", target_os = "linux"))]
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
 #[test]
+#[cfg_attr(target_os = "cygwin", ignore)] // Cygwin cannot bind to abstract addr
 fn test_abstract_stream_connect() {
     let msg1 = b"hello";
     let msg2 = b"world";
@@ -456,8 +465,9 @@ fn test_abstract_stream_connect() {
     thread.join().unwrap();
 }
 
-#[cfg(any(target_os = "android", target_os = "linux"))]
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
 #[test]
+#[cfg_attr(target_os = "cygwin", ignore)] // Cygwin cannot bind to abstract addr
 fn test_abstract_stream_iter() {
     let addr = or_panic!(SocketAddr::from_abstract_name(b"hidden"));
     let listener = or_panic!(UnixListener::bind_addr(&addr));
@@ -478,8 +488,9 @@ fn test_abstract_stream_iter() {
     thread.join().unwrap();
 }
 
-#[cfg(any(target_os = "android", target_os = "linux"))]
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
 #[test]
+#[cfg_attr(target_os = "cygwin", ignore)] // Cygwin cannot bind to abstract addr
 fn test_abstract_datagram_bind_send_to_addr() {
     let addr1 = or_panic!(SocketAddr::from_abstract_name(b"ns1"));
     let sock1 = or_panic!(UnixDatagram::bind_addr(&addr1));
@@ -499,8 +510,9 @@ fn test_abstract_datagram_bind_send_to_addr() {
     assert_eq!(addr.as_abstract_name().unwrap(), b"ns1");
 }
 
-#[cfg(any(target_os = "android", target_os = "linux"))]
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
 #[test]
+#[cfg_attr(target_os = "cygwin", ignore)] // Cygwin cannot bind to abstract addr
 fn test_abstract_datagram_connect_addr() {
     let addr1 = or_panic!(SocketAddr::from_abstract_name(b"ns3"));
     let bsock1 = or_panic!(UnixDatagram::bind_addr(&addr1));
@@ -524,7 +536,7 @@ fn test_abstract_datagram_connect_addr() {
     or_panic!(bsock2.recv_from(&mut buf));
 }
 
-#[cfg(any(target_os = "android", target_os = "linux"))]
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
 #[test]
 fn test_abstract_name_too_long() {
     match SocketAddr::from_abstract_name(
@@ -538,7 +550,7 @@ fn test_abstract_name_too_long() {
     }
 }
 
-#[cfg(any(target_os = "android", target_os = "linux"))]
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
 #[test]
 fn test_abstract_no_pathname_and_not_unnamed() {
     let name = b"local";
@@ -669,9 +681,10 @@ fn test_send_vectored_fds_unix_stream() {
     }
 }
 
-#[cfg(any(target_os = "android", target_os = "linux"))]
+#[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
 #[test]
 #[cfg_attr(target_os = "android", ignore)] // Android SELinux rules prevent creating Unix sockets
+#[cfg_attr(target_os = "cygwin", ignore)] // Cygwin recvmsg doesn't support Unix sockets
 fn test_send_vectored_with_ancillary_to_unix_datagram() {
     fn getpid() -> libc::pid_t {
         unsafe { libc::getpid() }
diff --git a/library/std/src/os/unix/process.rs b/library/std/src/os/unix/process.rs
index 09429af06e3..5b7b5a8ea80 100644
--- a/library/std/src/os/unix/process.rs
+++ b/library/std/src/os/unix/process.rs
@@ -406,8 +406,10 @@ pub trait ChildExt: Sealed {
     /// use libc::SIGTERM;
     ///
     /// fn main() -> io::Result<()> {
+    ///     # if cfg!(not(all(target_vendor = "apple", not(target_os = "macos")))) {
     ///     let child = Command::new("cat").stdin(Stdio::piped()).spawn()?;
     ///     child.send_signal(SIGTERM)?;
+    ///     # }
     ///     Ok(())
     /// }
     /// ```
diff --git a/library/std/src/panicking.rs b/library/std/src/panicking.rs
index 8b7282c51d1..b7be869c4eb 100644
--- a/library/std/src/panicking.rs
+++ b/library/std/src/panicking.rs
@@ -331,7 +331,7 @@ fn default_hook(info: &PanicHookInfo<'_>) {
 
 #[cfg(not(test))]
 #[doc(hidden)]
-#[cfg(feature = "panic_immediate_abort")]
+#[cfg(panic = "immediate-abort")]
 #[unstable(feature = "update_panic_count", issue = "none")]
 pub mod panic_count {
     /// A reason for forcing an immediate abort on panic.
@@ -371,7 +371,7 @@ pub mod panic_count {
 
 #[cfg(not(test))]
 #[doc(hidden)]
-#[cfg(not(feature = "panic_immediate_abort"))]
+#[cfg(not(panic = "immediate-abort"))]
 #[unstable(feature = "update_panic_count", issue = "none")]
 pub mod panic_count {
     use crate::cell::Cell;
@@ -499,13 +499,13 @@ pub mod panic_count {
 pub use realstd::rt::panic_count;
 
 /// Invoke a closure, capturing the cause of an unwinding panic if one occurs.
-#[cfg(feature = "panic_immediate_abort")]
+#[cfg(panic = "immediate-abort")]
 pub unsafe fn catch_unwind<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>> {
     Ok(f())
 }
 
 /// Invoke a closure, capturing the cause of an unwinding panic if one occurs.
-#[cfg(not(feature = "panic_immediate_abort"))]
+#[cfg(not(panic = "immediate-abort"))]
 pub unsafe fn catch_unwind<R, F: FnOnce() -> R>(f: F) -> Result<R, Box<dyn Any + Send>> {
     union Data<F, R> {
         f: ManuallyDrop<F>,
@@ -720,14 +720,14 @@ pub fn panic_handler(info: &core::panic::PanicInfo<'_>) -> ! {
 #[unstable(feature = "libstd_sys_internals", reason = "used by the panic! macro", issue = "none")]
 #[cfg_attr(not(any(test, doctest)), lang = "begin_panic")]
 // lang item for CTFE panic support
-// never inline unless panic_immediate_abort to avoid code
+// never inline unless panic=immediate-abort to avoid code
 // bloat at the call sites as much as possible
-#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never), cold, optimize(size))]
-#[cfg_attr(feature = "panic_immediate_abort", inline)]
+#[cfg_attr(not(panic = "immediate-abort"), inline(never), cold, optimize(size))]
+#[cfg_attr(panic = "immediate-abort", inline)]
 #[track_caller]
 #[rustc_do_not_const_check] // hooked by const-eval
 pub const fn begin_panic<M: Any + Send>(msg: M) -> ! {
-    if cfg!(feature = "panic_immediate_abort") {
+    if cfg!(panic = "immediate-abort") {
         intrinsics::abort()
     }
 
@@ -861,7 +861,7 @@ fn panic_with_hook(
 
 /// This is the entry point for `resume_unwind`.
 /// It just forwards the payload to the panic runtime.
-#[cfg_attr(feature = "panic_immediate_abort", inline)]
+#[cfg_attr(panic = "immediate-abort", inline)]
 pub fn resume_unwind(payload: Box<dyn Any + Send>) -> ! {
     panic_count::increase(false);
 
@@ -890,16 +890,14 @@ pub fn resume_unwind(payload: Box<dyn Any + Send>) -> ! {
 /// on which to slap yer breakpoints.
 #[inline(never)]
 #[cfg_attr(not(test), rustc_std_internal_symbol)]
-#[cfg(not(feature = "panic_immediate_abort"))]
+#[cfg(not(panic = "immediate-abort"))]
 fn rust_panic(msg: &mut dyn PanicPayload) -> ! {
     let code = unsafe { __rust_start_panic(msg) };
     rtabort!("failed to initiate panic, error {code}")
 }
 
 #[cfg_attr(not(test), rustc_std_internal_symbol)]
-#[cfg(feature = "panic_immediate_abort")]
+#[cfg(panic = "immediate-abort")]
 fn rust_panic(_: &mut dyn PanicPayload) -> ! {
-    unsafe {
-        crate::intrinsics::abort();
-    }
+    crate::intrinsics::abort();
 }
diff --git a/library/std/src/path.rs b/library/std/src/path.rs
index 19663e4a9df..70ba502d684 100644
--- a/library/std/src/path.rs
+++ b/library/std/src/path.rs
@@ -3037,6 +3037,14 @@ impl Path {
     ///
     /// This is an alias to [`fs::canonicalize`].
     ///
+    /// # Errors
+    ///
+    /// This method will return an error in the following situations, but is not
+    /// limited to just these cases:
+    ///
+    /// * `path` does not exist.
+    /// * A non-final component in path is not a directory.
+    ///
     /// # Examples
     ///
     /// ```no_run
diff --git a/library/std/src/process.rs b/library/std/src/process.rs
index 48265de90c4..5c0ac526a36 100644
--- a/library/std/src/process.rs
+++ b/library/std/src/process.rs
@@ -268,8 +268,8 @@ impl AsInner<imp::Process> for Child {
     }
 }
 
-impl FromInner<(imp::Process, imp::StdioPipes)> for Child {
-    fn from_inner((handle, io): (imp::Process, imp::StdioPipes)) -> Child {
+impl FromInner<(imp::Process, StdioPipes)> for Child {
+    fn from_inner((handle, io): (imp::Process, StdioPipes)) -> Child {
         Child {
             handle,
             stdin: io.stdin.map(ChildStdin::from_inner),
@@ -296,6 +296,15 @@ impl fmt::Debug for Child {
     }
 }
 
+/// The pipes connected to a spawned process.
+///
+/// Used to pass pipe handles between this module and [`imp`].
+pub(crate) struct StdioPipes {
+    pub stdin: Option<AnonPipe>,
+    pub stdout: Option<AnonPipe>,
+    pub stderr: Option<AnonPipe>,
+}
+
 /// A handle to a child process's standard input (stdin).
 ///
 /// This struct is used in the [`stdin`] field on [`Child`].
@@ -532,6 +541,7 @@ impl fmt::Debug for ChildStderr {
 /// to be changed (for example, by adding arguments) prior to spawning:
 ///
 /// ```
+/// # if cfg!(not(all(target_vendor = "apple", not(target_os = "macos")))) {
 /// use std::process::Command;
 ///
 /// let output = if cfg!(target_os = "windows") {
@@ -548,6 +558,7 @@ impl fmt::Debug for ChildStderr {
 /// };
 ///
 /// let hello = output.stdout;
+/// # }
 /// ```
 ///
 /// `Command` can be reused to spawn multiple processes. The builder methods
@@ -1348,7 +1359,7 @@ impl Output {
     ///
     /// ```
     /// #![feature(exit_status_error)]
-    /// # #[cfg(all(unix, not(target_os = "android")))] {
+    /// # #[cfg(all(unix, not(target_os = "android"), not(all(target_vendor = "apple", not(target_os = "macos")))))] {
     /// use std::process::Command;
     /// assert!(Command::new("false").output().unwrap().exit_ok().is_err());
     /// # }
@@ -1695,7 +1706,7 @@ impl From<io::Stdout> for Stdio {
     /// # Ok(())
     /// # }
     /// #
-    /// # if cfg!(all(unix, not(target_os = "android"))) {
+    /// # if cfg!(all(unix, not(target_os = "android"), not(all(target_vendor = "apple", not(target_os = "macos"))))) {
     /// #     test().unwrap();
     /// # }
     /// ```
@@ -1724,7 +1735,7 @@ impl From<io::Stderr> for Stdio {
     /// # Ok(())
     /// # }
     /// #
-    /// # if cfg!(all(unix, not(target_os = "android"))) {
+    /// # if cfg!(all(unix, not(target_os = "android"), not(all(target_vendor = "apple", not(target_os = "macos"))))) {
     /// #     test().unwrap();
     /// # }
     /// ```
@@ -1800,7 +1811,7 @@ impl ExitStatus {
     ///
     /// ```
     /// #![feature(exit_status_error)]
-    /// # if cfg!(unix) {
+    /// # if cfg!(all(unix, not(all(target_vendor = "apple", not(target_os = "macos"))))) {
     /// use std::process::Command;
     ///
     /// let status = Command::new("ls")
@@ -1907,7 +1918,7 @@ impl crate::sealed::Sealed for ExitStatusError {}
 ///
 /// ```
 /// #![feature(exit_status_error)]
-/// # if cfg!(all(unix, not(target_os = "android"))) {
+/// # if cfg!(all(unix, not(target_os = "android"), not(all(target_vendor = "apple", not(target_os = "macos"))))) {
 /// use std::process::{Command, ExitStatusError};
 ///
 /// fn run(cmd: &str) -> Result<(), ExitStatusError> {
@@ -1950,7 +1961,7 @@ impl ExitStatusError {
     ///
     /// ```
     /// #![feature(exit_status_error)]
-    /// # #[cfg(all(unix, not(target_os = "android")))] {
+    /// # #[cfg(all(unix, not(target_os = "android"), not(all(target_vendor = "apple", not(target_os = "macos")))))] {
     /// use std::process::Command;
     ///
     /// let bad = Command::new("false").status().unwrap().exit_ok().unwrap_err();
@@ -1975,7 +1986,7 @@ impl ExitStatusError {
     /// ```
     /// #![feature(exit_status_error)]
     ///
-    /// # if cfg!(all(unix, not(target_os = "android"))) {
+    /// # if cfg!(all(unix, not(target_os = "android"), not(all(target_vendor = "apple", not(target_os = "macos"))))) {
     /// use std::num::NonZero;
     /// use std::process::Command;
     ///
diff --git a/library/std/src/process/tests.rs b/library/std/src/process/tests.rs
index 5879914ca20..12c5130defe 100644
--- a/library/std/src/process/tests.rs
+++ b/library/std/src/process/tests.rs
@@ -5,7 +5,15 @@ use crate::mem::MaybeUninit;
 use crate::str;
 
 fn known_command() -> Command {
-    if cfg!(windows) { Command::new("help") } else { Command::new("echo") }
+    if cfg!(windows) {
+        Command::new("help")
+    } else if cfg!(all(target_vendor = "apple", not(target_os = "macos"))) {
+        // iOS/tvOS/watchOS/visionOS have a very limited set of commandline
+        // binaries available.
+        Command::new("log")
+    } else {
+        Command::new("echo")
+    }
 }
 
 #[cfg(target_os = "android")]
@@ -19,7 +27,10 @@ fn shell_cmd() -> Command {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn smoke() {
     let p = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "exit 0"]).spawn()
@@ -41,7 +52,10 @@ fn smoke_failure() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn exit_reported_right() {
     let p = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "exit 1"]).spawn()
@@ -56,7 +70,10 @@ fn exit_reported_right() {
 
 #[test]
 #[cfg(unix)]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn signal_reported_right() {
     use crate::os::unix::process::ExitStatusExt;
 
@@ -80,7 +97,10 @@ pub fn run_output(mut cmd: Command) -> String {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn stdout_works() {
     if cfg!(target_os = "windows") {
         let mut cmd = Command::new("cmd");
@@ -94,7 +114,11 @@ fn stdout_works() {
 }
 
 #[test]
-#[cfg_attr(any(windows, target_os = "vxworks"), ignore)]
+#[cfg_attr(windows, ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn set_current_dir_works() {
     // On many Unix platforms this will use the posix_spawn path.
     let mut cmd = shell_cmd();
@@ -116,7 +140,11 @@ fn set_current_dir_works() {
 }
 
 #[test]
-#[cfg_attr(any(windows, target_os = "vxworks"), ignore)]
+#[cfg_attr(windows, ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn stdin_works() {
     let mut p = shell_cmd()
         .arg("-c")
@@ -134,7 +162,10 @@ fn stdin_works() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn child_stdout_read_buf() {
     let mut cmd = if cfg!(target_os = "windows") {
         let mut cmd = Command::new("cmd");
@@ -165,7 +196,10 @@ fn child_stdout_read_buf() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_process_status() {
     let mut status = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "exit 1"]).status().unwrap()
@@ -191,7 +225,10 @@ fn test_process_output_fail_to_start() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_process_output_output() {
     let Output { status, stdout, stderr } = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "echo hello"]).output().unwrap()
@@ -206,7 +243,10 @@ fn test_process_output_output() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_process_output_error() {
     let Output { status, stdout, stderr } = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "mkdir ."]).output().unwrap()
@@ -221,7 +261,10 @@ fn test_process_output_error() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_finish_once() {
     let mut prog = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "exit 1"]).spawn().unwrap()
@@ -232,7 +275,10 @@ fn test_finish_once() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_finish_twice() {
     let mut prog = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "exit 1"]).spawn().unwrap()
@@ -244,7 +290,10 @@ fn test_finish_twice() {
 }
 
 #[test]
-#[cfg_attr(any(target_os = "vxworks"), ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_wait_with_output_once() {
     let prog = if cfg!(target_os = "windows") {
         Command::new("cmd").args(&["/C", "echo hello"]).stdout(Stdio::piped()).spawn().unwrap()
@@ -279,7 +328,10 @@ pub fn env_cmd() -> Command {
 }
 
 #[test]
-#[cfg_attr(target_os = "vxworks", ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_override_env() {
     use crate::env;
 
@@ -302,7 +354,10 @@ fn test_override_env() {
 }
 
 #[test]
-#[cfg_attr(target_os = "vxworks", ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_add_to_env() {
     let result = env_cmd().env("RUN_TEST_NEW_ENV", "123").output().unwrap();
     let output = String::from_utf8_lossy(&result.stdout).to_string();
@@ -314,7 +369,10 @@ fn test_add_to_env() {
 }
 
 #[test]
-#[cfg_attr(target_os = "vxworks", ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no shell available"
+)]
 fn test_capture_env_at_spawn() {
     use crate::env;
 
@@ -378,7 +436,10 @@ fn test_interior_nul_in_current_dir_is_error() {
 
 // Regression tests for #30862.
 #[test]
-#[cfg_attr(target_os = "vxworks", ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no `env` cmd available"
+)]
 fn test_interior_nul_in_env_key_is_error() {
     match env_cmd().env("has-some-\0\0s-inside", "value").spawn() {
         Err(e) => assert_eq!(e.kind(), ErrorKind::InvalidInput),
@@ -387,7 +448,10 @@ fn test_interior_nul_in_env_key_is_error() {
 }
 
 #[test]
-#[cfg_attr(target_os = "vxworks", ignore)]
+#[cfg_attr(
+    any(target_os = "vxworks", all(target_vendor = "apple", not(target_os = "macos"))),
+    ignore = "no `env` cmd available"
+)]
 fn test_interior_nul_in_env_value_is_error() {
     match env_cmd().env("key", "has-some-\0\0s-inside").spawn() {
         Err(e) => assert_eq!(e.kind(), ErrorKind::InvalidInput),
diff --git a/library/std/src/rt.rs b/library/std/src/rt.rs
index b3f3b301e3d..2717b7b469c 100644
--- a/library/std/src/rt.rs
+++ b/library/std/src/rt.rs
@@ -39,11 +39,11 @@ fn __rust_abort() {
 // - nothing (so this macro is a no-op)
 macro_rules! rtprintpanic {
     ($($t:tt)*) => {
-        #[cfg(not(feature = "panic_immediate_abort"))]
+        #[cfg(not(panic = "immediate-abort"))]
         if let Some(mut out) = crate::sys::stdio::panic_output() {
             let _ = crate::io::Write::write_fmt(&mut out, format_args!($($t)*));
         }
-        #[cfg(feature = "panic_immediate_abort")]
+        #[cfg(panic = "immediate-abort")]
         {
             let _ = format_args!($($t)*);
         }
@@ -161,7 +161,7 @@ fn lang_start_internal(
     // mechanism itself.
     //
     // There are a couple of instances where unwinding can begin. First is inside of the
-    // `rt::init`, `rt::cleanup` and similar functions controlled by bstd. In those instances a
+    // `rt::init`, `rt::cleanup` and similar functions controlled by std. In those instances a
     // panic is a std implementation bug. A quite likely one too, as there isn't any way to
     // prevent std from accidentally introducing a panic to these functions. Another is from
     // user code from `main` or, more nefariously, as described in e.g. issue #86030.
diff --git a/library/std/src/sync/barrier.rs b/library/std/src/sync/barrier.rs
index 712ce03f90b..8988126bd90 100644
--- a/library/std/src/sync/barrier.rs
+++ b/library/std/src/sync/barrier.rs
@@ -1,4 +1,5 @@
 use crate::fmt;
+use crate::panic::RefUnwindSafe;
 use crate::sync::nonpoison::{Condvar, Mutex};
 
 /// A barrier enables multiple threads to synchronize the beginning
@@ -31,6 +32,9 @@ pub struct Barrier {
     num_threads: usize,
 }
 
+#[stable(feature = "unwind_safe_lock_refs", since = "1.12.0")]
+impl RefUnwindSafe for Barrier {}
+
 // The inner state of a double barrier
 struct BarrierState {
     count: usize,
diff --git a/library/std/src/sync/nonpoison/condvar.rs b/library/std/src/sync/nonpoison/condvar.rs
index 49afdd87818..994fc6816a0 100644
--- a/library/std/src/sync/nonpoison/condvar.rs
+++ b/library/std/src/sync/nonpoison/condvar.rs
@@ -198,11 +198,10 @@ impl Condvar {
     /// the system time. This function is susceptible to spurious wakeups.
     /// Condition variables normally have a boolean predicate associated with
     /// them, and the predicate must always be checked each time this function
-    /// returns to protect against spurious wakeups. Additionally, it is
-    /// typically desirable for the timeout to not exceed some duration in
-    /// spite of spurious wakes, thus the sleep-duration is decremented by the
-    /// amount slept. Alternatively, use the `wait_timeout_while` method
-    /// to wait with a timeout while a predicate is true.
+    /// returns to protect against spurious wakeups.  Furthermore, since the timeout
+    /// is given relative to the moment this function is called, it needs to be adjusted
+    /// when this function is called in a loop. The [`wait_timeout_while`] method
+    /// lets you wait with a timeout while a predicate is true, taking care of all these concerns.
     ///
     /// The returned [`WaitTimeoutResult`] value indicates if the timeout is
     /// known to have elapsed.
diff --git a/library/std/src/sync/nonpoison/mutex.rs b/library/std/src/sync/nonpoison/mutex.rs
index 07430ce3a13..eeecf5d7107 100644
--- a/library/std/src/sync/nonpoison/mutex.rs
+++ b/library/std/src/sync/nonpoison/mutex.rs
@@ -373,7 +373,7 @@ impl<T: ?Sized> Mutex<T> {
     /// or written through after the mutex is dropped.
     #[unstable(feature = "mutex_data_ptr", issue = "140368")]
     // #[unstable(feature = "nonpoison_mutex", issue = "134645")]
-    pub fn data_ptr(&self) -> *mut T {
+    pub const fn data_ptr(&self) -> *mut T {
         self.data.get()
     }
 }
diff --git a/library/std/src/sync/nonpoison/rwlock.rs b/library/std/src/sync/nonpoison/rwlock.rs
index eb0aef99cc1..b2f26edc083 100644
--- a/library/std/src/sync/nonpoison/rwlock.rs
+++ b/library/std/src/sync/nonpoison/rwlock.rs
@@ -495,7 +495,7 @@ impl<T: ?Sized> RwLock<T> {
     /// or written through after the lock is dropped.
     #[unstable(feature = "rwlock_data_ptr", issue = "140368")]
     // #[unstable(feature = "nonpoison_rwlock", issue = "134645")]
-    pub fn data_ptr(&self) -> *mut T {
+    pub const fn data_ptr(&self) -> *mut T {
         self.data.get()
     }
 }
diff --git a/library/std/src/sync/poison/condvar.rs b/library/std/src/sync/poison/condvar.rs
index 5dc2b510f3a..de625a6cc5f 100644
--- a/library/std/src/sync/poison/condvar.rs
+++ b/library/std/src/sync/poison/condvar.rs
@@ -269,11 +269,10 @@ impl Condvar {
     /// the system time. This function is susceptible to spurious wakeups.
     /// Condition variables normally have a boolean predicate associated with
     /// them, and the predicate must always be checked each time this function
-    /// returns to protect against spurious wakeups. Additionally, it is
-    /// typically desirable for the timeout to not exceed some duration in
-    /// spite of spurious wakes, thus the sleep-duration is decremented by the
-    /// amount slept. Alternatively, use the `wait_timeout_while` method
-    /// to wait with a timeout while a predicate is true.
+    /// returns to protect against spurious wakeups. Furthermore, since the timeout
+    /// is given relative to the moment this function is called, it needs to be adjusted
+    /// when this function is called in a loop. The [`wait_timeout_while`] method
+    /// lets you wait with a timeout while a predicate is true, taking care of all these concerns.
     ///
     /// The returned [`WaitTimeoutResult`] value indicates if the timeout is
     /// known to have elapsed.
diff --git a/library/std/src/sync/poison/mutex.rs b/library/std/src/sync/poison/mutex.rs
index 7e9d920d92f..6fdb4f6799e 100644
--- a/library/std/src/sync/poison/mutex.rs
+++ b/library/std/src/sync/poison/mutex.rs
@@ -668,7 +668,7 @@ impl<T: ?Sized> Mutex<T> {
     /// are properly synchronized to avoid data races, and that it is not read
     /// or written through after the mutex is dropped.
     #[unstable(feature = "mutex_data_ptr", issue = "140368")]
-    pub fn data_ptr(&self) -> *mut T {
+    pub const fn data_ptr(&self) -> *mut T {
         self.data.get()
     }
 }
diff --git a/library/std/src/sync/poison/rwlock.rs b/library/std/src/sync/poison/rwlock.rs
index 0a463f3f9c7..e3a72c73bf4 100644
--- a/library/std/src/sync/poison/rwlock.rs
+++ b/library/std/src/sync/poison/rwlock.rs
@@ -667,7 +667,7 @@ impl<T: ?Sized> RwLock<T> {
     /// are properly synchronized to avoid data races, and that it is not read
     /// or written through after the lock is dropped.
     #[unstable(feature = "rwlock_data_ptr", issue = "140368")]
-    pub fn data_ptr(&self) -> *mut T {
+    pub const fn data_ptr(&self) -> *mut T {
         self.data.get()
     }
 }
diff --git a/library/std/src/sync/reentrant_lock.rs b/library/std/src/sync/reentrant_lock.rs
index 4140718560c..f560b616dd9 100644
--- a/library/std/src/sync/reentrant_lock.rs
+++ b/library/std/src/sync/reentrant_lock.rs
@@ -355,7 +355,7 @@ impl<T: ?Sized> ReentrantLock<T> {
     /// properly synchronized to avoid data races, and that it is not read
     /// through after the lock is dropped.
     #[unstable(feature = "reentrant_lock_data_ptr", issue = "140368")]
-    pub fn data_ptr(&self) -> *const T {
+    pub const fn data_ptr(&self) -> *const T {
         &raw const self.data
     }
 
diff --git a/library/std/src/sys/args/zkvm.rs b/library/std/src/sys/args/zkvm.rs
index 194ba7159d4..d26bf1eaff9 100644
--- a/library/std/src/sys/args/zkvm.rs
+++ b/library/std/src/sys/args/zkvm.rs
@@ -1,25 +1,20 @@
-use crate::ffi::OsString;
-use crate::fmt;
-use crate::sys::os_str;
+use crate::ffi::{OsStr, OsString};
+use crate::num::NonZero;
+use crate::sync::OnceLock;
 use crate::sys::pal::{WORD_SIZE, abi};
-use crate::sys_common::FromInner;
-
-pub struct Args {
-    i_forward: usize,
-    i_back: usize,
-    count: usize,
-}
+use crate::{fmt, ptr, slice};
 
 pub fn args() -> Args {
-    let count = unsafe { abi::sys_argc() };
-    Args { i_forward: 0, i_back: 0, count }
+    Args { iter: ARGS.get_or_init(|| get_args()).iter() }
 }
 
-impl Args {
-    /// Use sys_argv to get the arg at the requested index. Does not check that i is less than argc
-    /// and will not return if the index is out of bounds.
-    fn argv(i: usize) -> OsString {
-        let arg_len = unsafe { abi::sys_argv(crate::ptr::null_mut(), 0, i) };
+fn get_args() -> Vec<&'static OsStr> {
+    let argc = unsafe { abi::sys_argc() };
+    let mut args = Vec::with_capacity(argc);
+
+    for i in 0..argc {
+        // Get the size of the argument then the data.
+        let arg_len = unsafe { abi::sys_argv(ptr::null_mut(), 0, i) };
 
         let arg_len_words = (arg_len + WORD_SIZE - 1) / WORD_SIZE;
         let words = unsafe { abi::sys_alloc_words(arg_len_words) };
@@ -27,20 +22,24 @@ impl Args {
         let arg_len2 = unsafe { abi::sys_argv(words, arg_len_words, i) };
         debug_assert_eq!(arg_len, arg_len2);
 
-        // Convert to OsString.
-        //
-        // FIXME: We can probably get rid of the extra copy here if we
-        // reimplement "os_str" instead of just using the generic unix
-        // "os_str".
-        let arg_bytes: &[u8] =
-            unsafe { crate::slice::from_raw_parts(words.cast() as *const u8, arg_len) };
-        OsString::from_inner(os_str::Buf { inner: arg_bytes.to_vec() })
+        let arg_bytes = unsafe { slice::from_raw_parts(words.cast(), arg_len) };
+        args.push(unsafe { OsStr::from_encoded_bytes_unchecked(arg_bytes) });
     }
+    args
 }
 
+static ARGS: OnceLock<Vec<&'static OsStr>> = OnceLock::new();
+
+pub struct Args {
+    iter: slice::Iter<'static, &'static OsStr>,
+}
+
+impl !Send for Args {}
+impl !Sync for Args {}
+
 impl fmt::Debug for Args {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.debug_list().finish()
+        self.iter.as_slice().fmt(f)
     }
 }
 
@@ -48,34 +47,48 @@ impl Iterator for Args {
     type Item = OsString;
 
     fn next(&mut self) -> Option<OsString> {
-        if self.i_forward >= self.count - self.i_back {
-            None
-        } else {
-            let arg = Self::argv(self.i_forward);
-            self.i_forward += 1;
-            Some(arg)
-        }
+        self.iter.next().map(|arg| arg.to_os_string())
     }
 
+    #[inline]
     fn size_hint(&self) -> (usize, Option<usize>) {
-        (self.count, Some(self.count))
+        self.iter.size_hint()
     }
-}
 
-impl ExactSizeIterator for Args {
-    fn len(&self) -> usize {
-        self.count
+    #[inline]
+    fn count(self) -> usize {
+        self.iter.len()
+    }
+
+    fn last(self) -> Option<OsString> {
+        self.iter.last().map(|arg| arg.to_os_string())
+    }
+
+    #[inline]
+    fn advance_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
+        self.iter.advance_by(n)
     }
 }
 
 impl DoubleEndedIterator for Args {
     fn next_back(&mut self) -> Option<OsString> {
-        if self.i_back >= self.count - self.i_forward {
-            None
-        } else {
-            let arg = Self::argv(self.count - 1 - self.i_back);
-            self.i_back += 1;
-            Some(arg)
-        }
+        self.iter.next_back().map(|arg| arg.to_os_string())
+    }
+
+    #[inline]
+    fn advance_back_by(&mut self, n: usize) -> Result<(), NonZero<usize>> {
+        self.iter.advance_back_by(n)
+    }
+}
+
+impl ExactSizeIterator for Args {
+    #[inline]
+    fn len(&self) -> usize {
+        self.iter.len()
+    }
+
+    #[inline]
+    fn is_empty(&self) -> bool {
+        self.iter.is_empty()
     }
 }
diff --git a/library/std/src/sys/env_consts.rs b/library/std/src/sys/env_consts.rs
index 9683fd47cf9..711ba0a5f8a 100644
--- a/library/std/src/sys/env_consts.rs
+++ b/library/std/src/sys/env_consts.rs
@@ -2,7 +2,7 @@
 
 // Replaces the #[else] gate with #[cfg(not(any(…)))] of all the other gates.
 // This ensures that they must be mutually exclusive and do not have precedence
-// like cfg_if!.
+// like cfg_select!.
 macro cfg_unordered(
     $(#[cfg($cfg:meta)] $os:item)*
     #[else] $fallback:item
diff --git a/library/std/src/sys/fs/unix.rs b/library/std/src/sys/fs/unix.rs
index 3b525406223..33a1e7ff5e4 100644
--- a/library/std/src/sys/fs/unix.rs
+++ b/library/std/src/sys/fs/unix.rs
@@ -21,29 +21,31 @@ use libc::fstatat as fstatat64;
 #[cfg(any(all(target_os = "linux", not(target_env = "musl")), target_os = "hurd"))]
 use libc::fstatat64;
 #[cfg(any(
+    target_os = "aix",
     target_os = "android",
-    target_os = "solaris",
+    target_os = "freebsd",
     target_os = "fuchsia",
-    target_os = "redox",
     target_os = "illumos",
-    target_os = "aix",
     target_os = "nto",
+    target_os = "redox",
+    target_os = "solaris",
     target_os = "vita",
     all(target_os = "linux", target_env = "musl"),
 ))]
 use libc::readdir as readdir64;
 #[cfg(not(any(
+    target_os = "aix",
     target_os = "android",
-    target_os = "linux",
-    target_os = "solaris",
+    target_os = "freebsd",
+    target_os = "fuchsia",
+    target_os = "hurd",
     target_os = "illumos",
     target_os = "l4re",
-    target_os = "fuchsia",
-    target_os = "redox",
-    target_os = "aix",
+    target_os = "linux",
     target_os = "nto",
+    target_os = "redox",
+    target_os = "solaris",
     target_os = "vita",
-    target_os = "hurd",
 )))]
 use libc::readdir_r as readdir64_r;
 #[cfg(any(all(target_os = "linux", not(target_env = "musl")), target_os = "hurd"))]
@@ -271,16 +273,17 @@ unsafe impl Send for Dir {}
 unsafe impl Sync for Dir {}
 
 #[cfg(any(
+    target_os = "aix",
     target_os = "android",
-    target_os = "linux",
-    target_os = "solaris",
-    target_os = "illumos",
+    target_os = "freebsd",
     target_os = "fuchsia",
-    target_os = "redox",
-    target_os = "aix",
+    target_os = "hurd",
+    target_os = "illumos",
+    target_os = "linux",
     target_os = "nto",
+    target_os = "redox",
+    target_os = "solaris",
     target_os = "vita",
-    target_os = "hurd",
 ))]
 pub struct DirEntry {
     dir: Arc<InnerReadDir>,
@@ -295,16 +298,17 @@ pub struct DirEntry {
 // we're not using the immediate `d_name` on these targets. Keeping this as an
 // `entry` field in `DirEntry` helps reduce the `cfg` boilerplate elsewhere.
 #[cfg(any(
+    target_os = "aix",
     target_os = "android",
-    target_os = "linux",
-    target_os = "solaris",
-    target_os = "illumos",
+    target_os = "freebsd",
     target_os = "fuchsia",
-    target_os = "redox",
-    target_os = "aix",
+    target_os = "hurd",
+    target_os = "illumos",
+    target_os = "linux",
     target_os = "nto",
+    target_os = "redox",
+    target_os = "solaris",
     target_os = "vita",
-    target_os = "hurd",
 ))]
 struct dirent64_min {
     d_ino: u64,
@@ -319,16 +323,17 @@ struct dirent64_min {
 }
 
 #[cfg(not(any(
+    target_os = "aix",
     target_os = "android",
-    target_os = "linux",
-    target_os = "solaris",
-    target_os = "illumos",
+    target_os = "freebsd",
     target_os = "fuchsia",
-    target_os = "redox",
-    target_os = "aix",
+    target_os = "hurd",
+    target_os = "illumos",
+    target_os = "linux",
     target_os = "nto",
+    target_os = "redox",
+    target_os = "solaris",
     target_os = "vita",
-    target_os = "hurd",
 )))]
 pub struct DirEntry {
     dir: Arc<InnerReadDir>,
@@ -698,16 +703,17 @@ impl Iterator for ReadDir {
     type Item = io::Result<DirEntry>;
 
     #[cfg(any(
+        target_os = "aix",
         target_os = "android",
-        target_os = "linux",
-        target_os = "solaris",
+        target_os = "freebsd",
         target_os = "fuchsia",
-        target_os = "redox",
+        target_os = "hurd",
         target_os = "illumos",
-        target_os = "aix",
+        target_os = "linux",
         target_os = "nto",
+        target_os = "redox",
+        target_os = "solaris",
         target_os = "vita",
-        target_os = "hurd",
     ))]
     fn next(&mut self) -> Option<io::Result<DirEntry>> {
         use crate::sys::os::{errno, set_errno};
@@ -768,6 +774,9 @@ impl Iterator for ReadDir {
                 // only access those bytes.
                 #[cfg(not(target_os = "vita"))]
                 let entry = dirent64_min {
+                    #[cfg(target_os = "freebsd")]
+                    d_ino: (*entry_ptr).d_fileno,
+                    #[cfg(not(target_os = "freebsd"))]
                     d_ino: (*entry_ptr).d_ino as u64,
                     #[cfg(not(any(
                         target_os = "solaris",
@@ -791,16 +800,17 @@ impl Iterator for ReadDir {
     }
 
     #[cfg(not(any(
+        target_os = "aix",
         target_os = "android",
-        target_os = "linux",
-        target_os = "solaris",
+        target_os = "freebsd",
         target_os = "fuchsia",
-        target_os = "redox",
+        target_os = "hurd",
         target_os = "illumos",
-        target_os = "aix",
+        target_os = "linux",
         target_os = "nto",
+        target_os = "redox",
+        target_os = "solaris",
         target_os = "vita",
-        target_os = "hurd",
     )))]
     fn next(&mut self) -> Option<io::Result<DirEntry>> {
         if self.end_of_stream {
@@ -970,36 +980,32 @@ impl DirEntry {
     }
 
     #[cfg(any(
-        target_os = "linux",
+        target_os = "aix",
+        target_os = "android",
         target_os = "cygwin",
         target_os = "emscripten",
-        target_os = "android",
-        target_os = "solaris",
-        target_os = "illumos",
-        target_os = "haiku",
-        target_os = "l4re",
-        target_os = "fuchsia",
-        target_os = "redox",
-        target_os = "vxworks",
         target_os = "espidf",
+        target_os = "freebsd",
+        target_os = "fuchsia",
+        target_os = "haiku",
         target_os = "horizon",
-        target_os = "vita",
-        target_os = "aix",
-        target_os = "nto",
         target_os = "hurd",
+        target_os = "illumos",
+        target_os = "l4re",
+        target_os = "linux",
+        target_os = "nto",
+        target_os = "redox",
         target_os = "rtems",
+        target_os = "solaris",
+        target_os = "vita",
+        target_os = "vxworks",
         target_vendor = "apple",
     ))]
     pub fn ino(&self) -> u64 {
         self.entry.d_ino as u64
     }
 
-    #[cfg(any(
-        target_os = "freebsd",
-        target_os = "openbsd",
-        target_os = "netbsd",
-        target_os = "dragonfly"
-    ))]
+    #[cfg(any(target_os = "openbsd", target_os = "netbsd", target_os = "dragonfly"))]
     pub fn ino(&self) -> u64 {
         self.entry.d_fileno as u64
     }
@@ -1014,7 +1020,6 @@ impl DirEntry {
     #[cfg(any(
         target_os = "netbsd",
         target_os = "openbsd",
-        target_os = "freebsd",
         target_os = "dragonfly",
         target_vendor = "apple",
     ))]
@@ -1030,7 +1035,6 @@ impl DirEntry {
     #[cfg(not(any(
         target_os = "netbsd",
         target_os = "openbsd",
-        target_os = "freebsd",
         target_os = "dragonfly",
         target_vendor = "apple",
     )))]
@@ -1040,6 +1044,7 @@ impl DirEntry {
 
     #[cfg(not(any(
         target_os = "android",
+        target_os = "freebsd",
         target_os = "linux",
         target_os = "solaris",
         target_os = "illumos",
@@ -1055,6 +1060,7 @@ impl DirEntry {
     }
     #[cfg(any(
         target_os = "android",
+        target_os = "freebsd",
         target_os = "linux",
         target_os = "solaris",
         target_os = "illumos",
@@ -1293,6 +1299,15 @@ impl File {
         return Ok(());
     }
 
+    #[cfg(target_os = "solaris")]
+    pub fn lock(&self) -> io::Result<()> {
+        let mut flock: libc::flock = unsafe { mem::zeroed() };
+        flock.l_type = libc::F_WRLCK as libc::c_short;
+        flock.l_whence = libc::SEEK_SET as libc::c_short;
+        cvt(unsafe { libc::fcntl(self.as_raw_fd(), libc::F_SETLKW, &flock) })?;
+        Ok(())
+    }
+
     #[cfg(not(any(
         target_os = "freebsd",
         target_os = "fuchsia",
@@ -1300,6 +1315,7 @@ impl File {
         target_os = "netbsd",
         target_os = "openbsd",
         target_os = "cygwin",
+        target_os = "solaris",
         target_vendor = "apple",
     )))]
     pub fn lock(&self) -> io::Result<()> {
@@ -1320,6 +1336,15 @@ impl File {
         return Ok(());
     }
 
+    #[cfg(target_os = "solaris")]
+    pub fn lock_shared(&self) -> io::Result<()> {
+        let mut flock: libc::flock = unsafe { mem::zeroed() };
+        flock.l_type = libc::F_RDLCK as libc::c_short;
+        flock.l_whence = libc::SEEK_SET as libc::c_short;
+        cvt(unsafe { libc::fcntl(self.as_raw_fd(), libc::F_SETLKW, &flock) })?;
+        Ok(())
+    }
+
     #[cfg(not(any(
         target_os = "freebsd",
         target_os = "fuchsia",
@@ -1327,6 +1352,7 @@ impl File {
         target_os = "netbsd",
         target_os = "openbsd",
         target_os = "cygwin",
+        target_os = "solaris",
         target_vendor = "apple",
     )))]
     pub fn lock_shared(&self) -> io::Result<()> {
@@ -1355,6 +1381,23 @@ impl File {
         }
     }
 
+    #[cfg(target_os = "solaris")]
+    pub fn try_lock(&self) -> Result<(), TryLockError> {
+        let mut flock: libc::flock = unsafe { mem::zeroed() };
+        flock.l_type = libc::F_WRLCK as libc::c_short;
+        flock.l_whence = libc::SEEK_SET as libc::c_short;
+        let result = cvt(unsafe { libc::fcntl(self.as_raw_fd(), libc::F_SETLK, &flock) });
+        if let Err(err) = result {
+            if err.kind() == io::ErrorKind::WouldBlock {
+                Err(TryLockError::WouldBlock)
+            } else {
+                Err(TryLockError::Error(err))
+            }
+        } else {
+            Ok(())
+        }
+    }
+
     #[cfg(not(any(
         target_os = "freebsd",
         target_os = "fuchsia",
@@ -1362,6 +1405,7 @@ impl File {
         target_os = "netbsd",
         target_os = "openbsd",
         target_os = "cygwin",
+        target_os = "solaris",
         target_vendor = "apple",
     )))]
     pub fn try_lock(&self) -> Result<(), TryLockError> {
@@ -1393,6 +1437,23 @@ impl File {
         }
     }
 
+    #[cfg(target_os = "solaris")]
+    pub fn try_lock_shared(&self) -> Result<(), TryLockError> {
+        let mut flock: libc::flock = unsafe { mem::zeroed() };
+        flock.l_type = libc::F_RDLCK as libc::c_short;
+        flock.l_whence = libc::SEEK_SET as libc::c_short;
+        let result = cvt(unsafe { libc::fcntl(self.as_raw_fd(), libc::F_SETLK, &flock) });
+        if let Err(err) = result {
+            if err.kind() == io::ErrorKind::WouldBlock {
+                Err(TryLockError::WouldBlock)
+            } else {
+                Err(TryLockError::Error(err))
+            }
+        } else {
+            Ok(())
+        }
+    }
+
     #[cfg(not(any(
         target_os = "freebsd",
         target_os = "fuchsia",
@@ -1400,6 +1461,7 @@ impl File {
         target_os = "netbsd",
         target_os = "openbsd",
         target_os = "cygwin",
+        target_os = "solaris",
         target_vendor = "apple",
     )))]
     pub fn try_lock_shared(&self) -> Result<(), TryLockError> {
@@ -1423,6 +1485,15 @@ impl File {
         return Ok(());
     }
 
+    #[cfg(target_os = "solaris")]
+    pub fn unlock(&self) -> io::Result<()> {
+        let mut flock: libc::flock = unsafe { mem::zeroed() };
+        flock.l_type = libc::F_UNLCK as libc::c_short;
+        flock.l_whence = libc::SEEK_SET as libc::c_short;
+        cvt(unsafe { libc::fcntl(self.as_raw_fd(), libc::F_SETLKW, &flock) })?;
+        Ok(())
+    }
+
     #[cfg(not(any(
         target_os = "freebsd",
         target_os = "fuchsia",
@@ -1430,6 +1501,7 @@ impl File {
         target_os = "netbsd",
         target_os = "openbsd",
         target_os = "cygwin",
+        target_os = "solaris",
         target_vendor = "apple",
     )))]
     pub fn unlock(&self) -> io::Result<()> {
diff --git a/library/std/src/sys/fs/wasi.rs b/library/std/src/sys/fs/wasi.rs
index b65d86de12a..0b65b9cb389 100644
--- a/library/std/src/sys/fs/wasi.rs
+++ b/library/std/src/sys/fs/wasi.rs
@@ -848,7 +848,14 @@ fn remove_dir_all_recursive(parent: &WasiFd, path: &Path) -> io::Result<()> {
 
     // Iterate over all the entries in this directory, and travel recursively if
     // necessary
-    for entry in ReadDir::new(fd, dummy_root) {
+    //
+    // Note that all directory entries for this directory are read first before
+    // any removal is done. This works around the fact that the WASIp1 API for
+    // reading directories is not well-designed for handling mutations between
+    // invocations of reading a directory. By reading all the entries at once
+    // this ensures that, at least without concurrent modifications, it should
+    // be possible to delete everything.
+    for entry in ReadDir::new(fd, dummy_root).collect::<Vec<_>>() {
         let entry = entry?;
         let path = crate::str::from_utf8(&entry.name).map_err(|_| {
             io::const_error!(io::ErrorKind::Uncategorized, "invalid utf-8 file name found")
diff --git a/library/std/src/sys/mod.rs b/library/std/src/sys/mod.rs
index 6324c1a232a..2dbdc8a4e02 100644
--- a/library/std/src/sys/mod.rs
+++ b/library/std/src/sys/mod.rs
@@ -26,10 +26,12 @@ pub mod io;
 pub mod net;
 pub mod os_str;
 pub mod path;
+pub mod platform_version;
 pub mod process;
 pub mod random;
 pub mod stdio;
 pub mod sync;
+pub mod thread;
 pub mod thread_local;
 
 // FIXME(117276): remove this, move feature implementations into individual
diff --git a/library/std/src/sys/net/connection/mod.rs b/library/std/src/sys/net/connection/mod.rs
new file mode 100644
index 00000000000..7f9636a8ccf
--- /dev/null
+++ b/library/std/src/sys/net/connection/mod.rs
@@ -0,0 +1,57 @@
+cfg_select! {
+    any(
+        all(target_family = "unix", not(target_os = "l4re")),
+        target_os = "windows",
+        target_os = "hermit",
+        all(target_os = "wasi", target_env = "p2"),
+        target_os = "solid_asp3",
+    ) => {
+        mod socket;
+        pub use socket::*;
+    }
+    all(target_vendor = "fortanix", target_env = "sgx") => {
+        mod sgx;
+        pub use sgx::*;
+    }
+    all(target_os = "wasi", target_env = "p1") => {
+        mod wasip1;
+        pub use wasip1::*;
+    }
+    target_os = "xous" => {
+        mod xous;
+        pub use xous::*;
+    }
+    target_os = "uefi" => {
+        mod uefi;
+        pub use uefi::*;
+    }
+    _ => {
+        mod unsupported;
+        pub use unsupported::*;
+    }
+}
+
+#[cfg_attr(
+    // Make sure that this is used on some platforms at least.
+    not(any(target_os = "linux", target_os = "windows")),
+    allow(dead_code)
+)]
+fn each_addr<A: crate::net::ToSocketAddrs, F, T>(addr: A, mut f: F) -> crate::io::Result<T>
+where
+    F: FnMut(&crate::net::SocketAddr) -> crate::io::Result<T>,
+{
+    use crate::io::Error;
+
+    let mut last_err = None;
+    for addr in addr.to_socket_addrs()? {
+        match f(&addr) {
+            Ok(l) => return Ok(l),
+            Err(e) => last_err = Some(e),
+        }
+    }
+
+    match last_err {
+        Some(err) => Err(err),
+        None => Err(Error::NO_ADDRESSES),
+    }
+}
diff --git a/library/std/src/sys/net/connection/sgx.rs b/library/std/src/sys/net/connection/sgx.rs
index 2389fd1bcb6..8c9c17d3f17 100644
--- a/library/std/src/sys/net/connection/sgx.rs
+++ b/library/std/src/sys/net/connection/sgx.rs
@@ -1,3 +1,5 @@
+use crate::error;
+use crate::fmt::{self, Write};
 use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
 use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr, ToSocketAddrs};
 use crate::sync::Arc;
@@ -5,7 +7,6 @@ use crate::sys::abi::usercalls;
 use crate::sys::fd::FileDesc;
 use crate::sys::{AsInner, FromInner, IntoInner, TryIntoInner, sgx_ineffective, unsupported};
 use crate::time::Duration;
-use crate::{error, fmt};
 
 const DEFAULT_FAKE_TTL: u32 = 64;
 
@@ -63,18 +64,52 @@ impl fmt::Debug for TcpStream {
     }
 }
 
-fn io_err_to_addr(result: io::Result<&SocketAddr>) -> io::Result<String> {
-    match result {
-        Ok(saddr) => Ok(saddr.to_string()),
-        // need to downcast twice because io::Error::into_inner doesn't return the original
-        // value if the conversion fails
-        Err(e) => {
-            if e.get_ref().and_then(|e| e.downcast_ref::<NonIpSockAddr>()).is_some() {
-                Ok(e.into_inner().unwrap().downcast::<NonIpSockAddr>().unwrap().host)
-            } else {
-                Err(e)
+/// Converts each address in `addr` into a hostname.
+///
+/// SGX doesn't support DNS resolution but rather accepts hostnames in
+/// the same place as socket addresses. So, to make e.g.
+/// ```rust
+/// TcpStream::connect("example.com:80")`
+/// ```
+/// work, the DNS lookup returns a special error (`NonIpSockAddr`) instead,
+/// which contains the hostname being looked up. When `.to_socket_addrs()`
+/// fails, we inspect the error and try recover the hostname from it. If that
+/// succeeds, we thus continue with the hostname.
+///
+/// This is a terrible hack and leads to buggy code. For instance, when users
+/// use the result of `.to_socket_addrs()` in their own `ToSocketAddrs`
+/// implementation to select from a list of possible URLs, the only URL used
+/// will be that of the last item tried.
+// FIXME: This is a terrible, terrible hack. Fixing this requires Fortanix to
+// add a method for resolving addresses.
+fn each_addr<A: ToSocketAddrs, F, T>(addr: A, mut f: F) -> io::Result<T>
+where
+    F: FnMut(&str) -> io::Result<T>,
+{
+    match addr.to_socket_addrs() {
+        Ok(addrs) => {
+            let mut last_err = None;
+            let mut encoded = String::new();
+            for addr in addrs {
+                // Format the IP address as a string, reusing the buffer.
+                encoded.clear();
+                write!(encoded, "{}", &addr).unwrap();
+
+                match f(&encoded) {
+                    Ok(val) => return Ok(val),
+                    Err(err) => last_err = Some(err),
+                }
+            }
+
+            match last_err {
+                Some(err) => Err(err),
+                None => Err(io::Error::NO_ADDRESSES),
             }
         }
+        Err(err) => match err.get_ref().and_then(|e| e.downcast_ref::<NonIpSockAddr>()) {
+            Some(NonIpSockAddr { host }) => f(host),
+            None => Err(err),
+        },
     }
 }
 
@@ -86,17 +121,18 @@ fn addr_to_sockaddr(addr: Option<&str>) -> io::Result<SocketAddr> {
 }
 
 impl TcpStream {
-    pub fn connect(addr: io::Result<&SocketAddr>) -> io::Result<TcpStream> {
-        let addr = io_err_to_addr(addr)?;
-        let (fd, local_addr, peer_addr) = usercalls::connect_stream(&addr)?;
-        Ok(TcpStream { inner: Socket::new(fd, local_addr), peer_addr: Some(peer_addr) })
+    pub fn connect<A: ToSocketAddrs>(addr: A) -> io::Result<TcpStream> {
+        each_addr(addr, |addr| {
+            let (fd, local_addr, peer_addr) = usercalls::connect_stream(addr)?;
+            Ok(TcpStream { inner: Socket::new(fd, local_addr), peer_addr: Some(peer_addr) })
+        })
     }
 
     pub fn connect_timeout(addr: &SocketAddr, dur: Duration) -> io::Result<TcpStream> {
         if dur == Duration::default() {
             return Err(io::Error::ZERO_TIMEOUT);
         }
-        Self::connect(Ok(addr)) // FIXME: ignoring timeout
+        Self::connect(addr) // FIXME: ignoring timeout
     }
 
     pub fn set_read_timeout(&self, dur: Option<Duration>) -> io::Result<()> {
@@ -247,10 +283,11 @@ impl fmt::Debug for TcpListener {
 }
 
 impl TcpListener {
-    pub fn bind(addr: io::Result<&SocketAddr>) -> io::Result<TcpListener> {
-        let addr = io_err_to_addr(addr)?;
-        let (fd, local_addr) = usercalls::bind_stream(&addr)?;
-        Ok(TcpListener { inner: Socket::new(fd, local_addr) })
+    pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<TcpListener> {
+        each_addr(addr, |addr| {
+            let (fd, local_addr) = usercalls::bind_stream(addr)?;
+            Ok(TcpListener { inner: Socket::new(fd, local_addr) })
+        })
     }
 
     pub fn socket_addr(&self) -> io::Result<SocketAddr> {
@@ -316,7 +353,7 @@ impl FromInner<Socket> for TcpListener {
 pub struct UdpSocket(!);
 
 impl UdpSocket {
-    pub fn bind(_: io::Result<&SocketAddr>) -> io::Result<UdpSocket> {
+    pub fn bind<A: ToSocketAddrs>(_: A) -> io::Result<UdpSocket> {
         unsupported()
     }
 
@@ -436,7 +473,7 @@ impl UdpSocket {
         self.0
     }
 
-    pub fn connect(&self, _: io::Result<&SocketAddr>) -> io::Result<()> {
+    pub fn connect<A: ToSocketAddrs>(&self, _: A) -> io::Result<()> {
         self.0
     }
 }
@@ -462,16 +499,6 @@ impl fmt::Display for NonIpSockAddr {
 
 pub struct LookupHost(!);
 
-impl LookupHost {
-    fn new(host: String) -> io::Result<LookupHost> {
-        Err(io::Error::new(io::ErrorKind::Uncategorized, NonIpSockAddr { host }))
-    }
-
-    pub fn port(&self) -> u16 {
-        self.0
-    }
-}
-
 impl Iterator for LookupHost {
     type Item = SocketAddr;
     fn next(&mut self) -> Option<SocketAddr> {
@@ -479,18 +506,9 @@ impl Iterator for LookupHost {
     }
 }
 
-impl TryFrom<&str> for LookupHost {
-    type Error = io::Error;
-
-    fn try_from(v: &str) -> io::Result<LookupHost> {
-        LookupHost::new(v.to_owned())
-    }
-}
-
-impl<'a> TryFrom<(&'a str, u16)> for LookupHost {
-    type Error = io::Error;
-
-    fn try_from((host, port): (&'a str, u16)) -> io::Result<LookupHost> {
-        LookupHost::new(format!("{host}:{port}"))
-    }
+pub fn lookup_host(host: &str, port: u16) -> io::Result<LookupHost> {
+    Err(io::Error::new(
+        io::ErrorKind::Uncategorized,
+        NonIpSockAddr { host: format!("{host}:{port}") },
+    ))
 }
diff --git a/library/std/src/sys/net/connection/socket/hermit.rs b/library/std/src/sys/net/connection/socket/hermit.rs
index f49821657d9..5200eaa5786 100644
--- a/library/std/src/sys/net/connection/socket/hermit.rs
+++ b/library/std/src/sys/net/connection/socket/hermit.rs
@@ -304,7 +304,8 @@ impl Socket {
     }
 
     pub fn take_error(&self) -> io::Result<Option<io::Error>> {
-        unimplemented!()
+        let raw: c_int = getsockopt(self, libc::SOL_SOCKET, libc::SO_ERROR)?;
+        if raw == 0 { Ok(None) } else { Ok(Some(io::Error::from_raw_os_error(raw as i32))) }
     }
 
     // This is used by sys_common code to abstract over Windows and Unix.
diff --git a/library/std/src/sys/net/connection/socket.rs b/library/std/src/sys/net/connection/socket/mod.rs
index aa83ed65d4c..1dd06e97bba 100644
--- a/library/std/src/sys/net/connection/socket.rs
+++ b/library/std/src/sys/net/connection/socket/mod.rs
@@ -3,8 +3,11 @@ mod tests;
 
 use crate::ffi::{c_int, c_void};
 use crate::io::{self, BorrowedCursor, ErrorKind, IoSlice, IoSliceMut};
-use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr, SocketAddrV4, SocketAddrV6};
+use crate::net::{
+    Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr, SocketAddrV4, SocketAddrV6, ToSocketAddrs,
+};
 use crate::sys::common::small_c_string::run_with_cstr;
+use crate::sys::net::connection::each_addr;
 use crate::sys_common::{AsInner, FromInner};
 use crate::time::Duration;
 use crate::{cmp, fmt, mem, ptr};
@@ -255,7 +258,7 @@ fn to_ipv6mr_interface(value: u32) -> crate::ffi::c_uint {
 }
 
 ////////////////////////////////////////////////////////////////////////////////
-// get_host_addresses
+// lookup_host
 ////////////////////////////////////////////////////////////////////////////////
 
 pub struct LookupHost {
@@ -264,12 +267,6 @@ pub struct LookupHost {
     port: u16,
 }
 
-impl LookupHost {
-    pub fn port(&self) -> u16 {
-        self.port
-    }
-}
-
 impl Iterator for LookupHost {
     type Item = SocketAddr;
     fn next(&mut self) -> Option<SocketAddr> {
@@ -278,7 +275,10 @@ impl Iterator for LookupHost {
                 let cur = self.cur.as_ref()?;
                 self.cur = cur.ai_next;
                 match socket_addr_from_c(cur.ai_addr.cast(), cur.ai_addrlen as usize) {
-                    Ok(addr) => return Some(addr),
+                    Ok(mut addr) => {
+                        addr.set_port(self.port);
+                        return Some(addr);
+                    }
                     Err(_) => continue,
                 }
             }
@@ -295,42 +295,17 @@ impl Drop for LookupHost {
     }
 }
 
-impl TryFrom<&str> for LookupHost {
-    type Error = io::Error;
-
-    fn try_from(s: &str) -> io::Result<LookupHost> {
-        macro_rules! try_opt {
-            ($e:expr, $msg:expr) => {
-                match $e {
-                    Some(r) => r,
-                    None => return Err(io::const_error!(io::ErrorKind::InvalidInput, $msg)),
-                }
-            };
+pub fn lookup_host(host: &str, port: u16) -> io::Result<LookupHost> {
+    init();
+    run_with_cstr(host.as_bytes(), &|c_host| {
+        let mut hints: c::addrinfo = unsafe { mem::zeroed() };
+        hints.ai_socktype = c::SOCK_STREAM;
+        let mut res = ptr::null_mut();
+        unsafe {
+            cvt_gai(c::getaddrinfo(c_host.as_ptr(), ptr::null(), &hints, &mut res))
+                .map(|_| LookupHost { original: res, cur: res, port })
         }
-
-        // split the string by ':' and convert the second part to u16
-        let (host, port_str) = try_opt!(s.rsplit_once(':'), "invalid socket address");
-        let port: u16 = try_opt!(port_str.parse().ok(), "invalid port value");
-        (host, port).try_into()
-    }
-}
-
-impl<'a> TryFrom<(&'a str, u16)> for LookupHost {
-    type Error = io::Error;
-
-    fn try_from((host, port): (&'a str, u16)) -> io::Result<LookupHost> {
-        init();
-
-        run_with_cstr(host.as_bytes(), &|c_host| {
-            let mut hints: c::addrinfo = unsafe { mem::zeroed() };
-            hints.ai_socktype = c::SOCK_STREAM;
-            let mut res = ptr::null_mut();
-            unsafe {
-                cvt_gai(c::getaddrinfo(c_host.as_ptr(), ptr::null(), &hints, &mut res))
-                    .map(|_| LookupHost { original: res, cur: res, port })
-            }
-        })
-    }
+    })
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -342,14 +317,15 @@ pub struct TcpStream {
 }
 
 impl TcpStream {
-    pub fn connect(addr: io::Result<&SocketAddr>) -> io::Result<TcpStream> {
-        let addr = addr?;
-
+    pub fn connect<A: ToSocketAddrs>(addr: A) -> io::Result<TcpStream> {
         init();
+        return each_addr(addr, inner);
 
-        let sock = Socket::new(addr, c::SOCK_STREAM)?;
-        sock.connect(addr)?;
-        Ok(TcpStream { inner: sock })
+        fn inner(addr: &SocketAddr) -> io::Result<TcpStream> {
+            let sock = Socket::new(addr, c::SOCK_STREAM)?;
+            sock.connect(addr)?;
+            Ok(TcpStream { inner: sock })
+        }
     }
 
     pub fn connect_timeout(addr: &SocketAddr, timeout: Duration) -> io::Result<TcpStream> {
@@ -512,48 +488,45 @@ pub struct TcpListener {
 }
 
 impl TcpListener {
-    pub fn bind(addr: io::Result<&SocketAddr>) -> io::Result<TcpListener> {
-        let addr = addr?;
-
+    pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<TcpListener> {
         init();
-
-        let sock = Socket::new(addr, c::SOCK_STREAM)?;
-
-        // On platforms with Berkeley-derived sockets, this allows to quickly
-        // rebind a socket, without needing to wait for the OS to clean up the
-        // previous one.
-        //
-        // On Windows, this allows rebinding sockets which are actively in use,
-        // which allows “socket hijacking”, so we explicitly don't set it here.
-        // https://docs.microsoft.com/en-us/windows/win32/winsock/using-so-reuseaddr-and-so-exclusiveaddruse
-        #[cfg(not(windows))]
-        setsockopt(&sock, c::SOL_SOCKET, c::SO_REUSEADDR, 1 as c_int)?;
-
-        // Bind our new socket
-        let (addr, len) = socket_addr_to_c(addr);
-        cvt(unsafe { c::bind(sock.as_raw(), addr.as_ptr(), len as _) })?;
-
-        cfg_select! {
-            target_os = "horizon" => {
+        return each_addr(addr, inner);
+
+        fn inner(addr: &SocketAddr) -> io::Result<TcpListener> {
+            let sock = Socket::new(addr, c::SOCK_STREAM)?;
+
+            // On platforms with Berkeley-derived sockets, this allows to quickly
+            // rebind a socket, without needing to wait for the OS to clean up the
+            // previous one.
+            //
+            // On Windows, this allows rebinding sockets which are actively in use,
+            // which allows “socket hijacking”, so we explicitly don't set it here.
+            // https://docs.microsoft.com/en-us/windows/win32/winsock/using-so-reuseaddr-and-so-exclusiveaddruse
+            #[cfg(not(windows))]
+            setsockopt(&sock, c::SOL_SOCKET, c::SO_REUSEADDR, 1 as c_int)?;
+
+            // Bind our new socket
+            let (addr, len) = socket_addr_to_c(addr);
+            cvt(unsafe { c::bind(sock.as_raw(), addr.as_ptr(), len as _) })?;
+
+            let backlog = if cfg!(target_os = "horizon") {
                 // The 3DS doesn't support a big connection backlog. Sometimes
                 // it allows up to about 37, but other times it doesn't even
                 // accept 32. There may be a global limitation causing this.
-                let backlog = 20;
-            }
-            target_os = "haiku" => {
+                20
+            } else if cfg!(target_os = "haiku") {
                 // Haiku does not support a queue length > 32
                 // https://github.com/haiku/haiku/blob/979a0bc487864675517fb2fab28f87dc8bf43041/headers/posix/sys/socket.h#L81
-                let backlog = 32;
-            }
-            _ => {
+                32
+            } else {
                 // The default for all other platforms
-                let backlog = 128;
-            }
-        }
+                128
+            };
 
-        // Start listening
-        cvt(unsafe { c::listen(sock.as_raw(), backlog) })?;
-        Ok(TcpListener { inner: sock })
+            // Start listening
+            cvt(unsafe { c::listen(sock.as_raw(), backlog) })?;
+            Ok(TcpListener { inner: sock })
+        }
     }
 
     #[inline]
@@ -639,15 +612,16 @@ pub struct UdpSocket {
 }
 
 impl UdpSocket {
-    pub fn bind(addr: io::Result<&SocketAddr>) -> io::Result<UdpSocket> {
-        let addr = addr?;
-
+    pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<UdpSocket> {
         init();
+        return each_addr(addr, inner);
 
-        let sock = Socket::new(addr, c::SOCK_DGRAM)?;
-        let (addr, len) = socket_addr_to_c(addr);
-        cvt(unsafe { c::bind(sock.as_raw(), addr.as_ptr(), len as _) })?;
-        Ok(UdpSocket { inner: sock })
+        fn inner(addr: &SocketAddr) -> io::Result<UdpSocket> {
+            let sock = Socket::new(addr, c::SOCK_DGRAM)?;
+            let (addr, len) = socket_addr_to_c(addr);
+            cvt(unsafe { c::bind(sock.as_raw(), addr.as_ptr(), len as _) })?;
+            Ok(UdpSocket { inner: sock })
+        }
     }
 
     #[inline]
@@ -822,9 +796,13 @@ impl UdpSocket {
         Ok(ret as usize)
     }
 
-    pub fn connect(&self, addr: io::Result<&SocketAddr>) -> io::Result<()> {
-        let (addr, len) = socket_addr_to_c(addr?);
-        cvt_r(|| unsafe { c::connect(self.inner.as_raw(), addr.as_ptr(), len) }).map(drop)
+    pub fn connect<A: ToSocketAddrs>(&self, addr: A) -> io::Result<()> {
+        return each_addr(addr, |addr| inner(self, addr));
+
+        fn inner(this: &UdpSocket, addr: &SocketAddr) -> io::Result<()> {
+            let (addr, len) = socket_addr_to_c(addr);
+            cvt_r(|| unsafe { c::connect(this.inner.as_raw(), addr.as_ptr(), len) }).map(drop)
+        }
     }
 }
 
diff --git a/library/std/src/sys/net/connection/socket/tests.rs b/library/std/src/sys/net/connection/socket/tests.rs
index fc236b8027b..049355afca7 100644
--- a/library/std/src/sys/net/connection/socket/tests.rs
+++ b/library/std/src/sys/net/connection/socket/tests.rs
@@ -4,7 +4,7 @@ use crate::collections::HashMap;
 #[test]
 fn no_lookup_host_duplicates() {
     let mut addrs = HashMap::new();
-    let lh = match LookupHost::try_from(("localhost", 0)) {
+    let lh = match lookup_host("localhost", 0) {
         Ok(lh) => lh,
         Err(e) => panic!("couldn't resolve `localhost`: {e}"),
     };
diff --git a/library/std/src/sys/net/connection/socket/unix.rs b/library/std/src/sys/net/connection/socket/unix.rs
index 8b5970d1494..8216f8d2fd5 100644
--- a/library/std/src/sys/net/connection/socket/unix.rs
+++ b/library/std/src/sys/net/connection/socket/unix.rs
@@ -361,7 +361,7 @@ impl Socket {
         self.recv_from_with_flags(buf, 0)
     }
 
-    #[cfg(any(target_os = "android", target_os = "linux"))]
+    #[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
     pub fn recv_msg(&self, msg: &mut libc::msghdr) -> io::Result<usize> {
         let n = cvt(unsafe { libc::recvmsg(self.as_raw_fd(), msg, libc::MSG_CMSG_CLOEXEC) })?;
         Ok(n as usize)
@@ -384,7 +384,7 @@ impl Socket {
         self.0.is_write_vectored()
     }
 
-    #[cfg(any(target_os = "android", target_os = "linux"))]
+    #[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
     pub fn send_msg(&self, msg: &mut libc::msghdr) -> io::Result<usize> {
         let n = cvt(unsafe { libc::sendmsg(self.as_raw_fd(), msg, 0) })?;
         Ok(n as usize)
@@ -472,12 +472,12 @@ impl Socket {
         Ok(raw != 0)
     }
 
-    #[cfg(any(target_os = "android", target_os = "linux",))]
+    #[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
     pub fn set_quickack(&self, quickack: bool) -> io::Result<()> {
         setsockopt(self, libc::IPPROTO_TCP, libc::TCP_QUICKACK, quickack as c_int)
     }
 
-    #[cfg(any(target_os = "android", target_os = "linux",))]
+    #[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
     pub fn quickack(&self) -> io::Result<bool> {
         let raw: c_int = getsockopt(self, libc::IPPROTO_TCP, libc::TCP_QUICKACK)?;
         Ok(raw != 0)
@@ -541,12 +541,12 @@ impl Socket {
         Ok(raw != 0)
     }
 
-    #[cfg(any(target_os = "android", target_os = "linux",))]
+    #[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
     pub fn set_passcred(&self, passcred: bool) -> io::Result<()> {
         setsockopt(self, libc::SOL_SOCKET, libc::SO_PASSCRED, passcred as libc::c_int)
     }
 
-    #[cfg(any(target_os = "android", target_os = "linux",))]
+    #[cfg(any(target_os = "android", target_os = "linux", target_os = "cygwin"))]
     pub fn passcred(&self) -> io::Result<bool> {
         let passcred: libc::c_int = getsockopt(self, libc::SOL_SOCKET, libc::SO_PASSCRED)?;
         Ok(passcred != 0)
diff --git a/library/std/src/sys/net/connection/uefi/mod.rs b/library/std/src/sys/net/connection/uefi/mod.rs
index 16e3487a174..004f6d413a1 100644
--- a/library/std/src/sys/net/connection/uefi/mod.rs
+++ b/library/std/src/sys/net/connection/uefi/mod.rs
@@ -1,6 +1,7 @@
+use super::each_addr;
 use crate::fmt;
 use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
-use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr};
+use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr, ToSocketAddrs};
 use crate::sync::{Arc, Mutex};
 use crate::sys::unsupported;
 use crate::time::Duration;
@@ -15,13 +16,17 @@ pub struct TcpStream {
 }
 
 impl TcpStream {
-    pub fn connect(addr: io::Result<&SocketAddr>) -> io::Result<TcpStream> {
-        let inner = tcp::Tcp::connect(addr?, None)?;
-        Ok(Self {
-            inner,
-            read_timeout: Arc::new(Mutex::new(None)),
-            write_timeout: Arc::new(Mutex::new(None)),
-        })
+    pub fn connect<A: ToSocketAddrs>(addr: A) -> io::Result<TcpStream> {
+        return each_addr(addr, inner);
+
+        fn inner(addr: &SocketAddr) -> io::Result<TcpStream> {
+            let inner = tcp::Tcp::connect(addr, None)?;
+            Ok(TcpStream {
+                inner,
+                read_timeout: Arc::new(Mutex::new(None)),
+                write_timeout: Arc::new(Mutex::new(None)),
+            })
+        }
     }
 
     pub fn connect_timeout(addr: &SocketAddr, timeout: Duration) -> io::Result<TcpStream> {
@@ -145,7 +150,7 @@ pub struct TcpListener {
 }
 
 impl TcpListener {
-    pub fn bind(_: io::Result<&SocketAddr>) -> io::Result<TcpListener> {
+    pub fn bind<A: ToSocketAddrs>(_: A) -> io::Result<TcpListener> {
         unsupported()
     }
 
@@ -195,7 +200,7 @@ impl fmt::Debug for TcpListener {
 pub struct UdpSocket(!);
 
 impl UdpSocket {
-    pub fn bind(_: io::Result<&SocketAddr>) -> io::Result<UdpSocket> {
+    pub fn bind<A: ToSocketAddrs>(_: A) -> io::Result<UdpSocket> {
         unsupported()
     }
 
@@ -315,7 +320,7 @@ impl UdpSocket {
         self.0
     }
 
-    pub fn connect(&self, _: io::Result<&SocketAddr>) -> io::Result<()> {
+    pub fn connect<A: ToSocketAddrs>(&self, _: A) -> io::Result<()> {
         self.0
     }
 }
@@ -328,12 +333,6 @@ impl fmt::Debug for UdpSocket {
 
 pub struct LookupHost(!);
 
-impl LookupHost {
-    pub fn port(&self) -> u16 {
-        self.0
-    }
-}
-
 impl Iterator for LookupHost {
     type Item = SocketAddr;
     fn next(&mut self) -> Option<SocketAddr> {
@@ -341,18 +340,6 @@ impl Iterator for LookupHost {
     }
 }
 
-impl TryFrom<&str> for LookupHost {
-    type Error = io::Error;
-
-    fn try_from(_v: &str) -> io::Result<LookupHost> {
-        unsupported()
-    }
-}
-
-impl<'a> TryFrom<(&'a str, u16)> for LookupHost {
-    type Error = io::Error;
-
-    fn try_from(_v: (&'a str, u16)) -> io::Result<LookupHost> {
-        unsupported()
-    }
+pub fn lookup_host(_host: &str, _port: u16) -> io::Result<LookupHost> {
+    unsupported()
 }
diff --git a/library/std/src/sys/net/connection/unsupported.rs b/library/std/src/sys/net/connection/unsupported.rs
index da217439626..fb18e8dec55 100644
--- a/library/std/src/sys/net/connection/unsupported.rs
+++ b/library/std/src/sys/net/connection/unsupported.rs
@@ -1,13 +1,13 @@
 use crate::fmt;
 use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
-use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr};
+use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr, ToSocketAddrs};
 use crate::sys::unsupported;
 use crate::time::Duration;
 
 pub struct TcpStream(!);
 
 impl TcpStream {
-    pub fn connect(_: io::Result<&SocketAddr>) -> io::Result<TcpStream> {
+    pub fn connect<A: ToSocketAddrs>(_: A) -> io::Result<TcpStream> {
         unsupported()
     }
 
@@ -121,7 +121,7 @@ impl fmt::Debug for TcpStream {
 pub struct TcpListener(!);
 
 impl TcpListener {
-    pub fn bind(_: io::Result<&SocketAddr>) -> io::Result<TcpListener> {
+    pub fn bind<A: ToSocketAddrs>(_: A) -> io::Result<TcpListener> {
         unsupported()
     }
 
@@ -171,7 +171,7 @@ impl fmt::Debug for TcpListener {
 pub struct UdpSocket(!);
 
 impl UdpSocket {
-    pub fn bind(_: io::Result<&SocketAddr>) -> io::Result<UdpSocket> {
+    pub fn bind<A: ToSocketAddrs>(_: A) -> io::Result<UdpSocket> {
         unsupported()
     }
 
@@ -291,7 +291,7 @@ impl UdpSocket {
         self.0
     }
 
-    pub fn connect(&self, _: io::Result<&SocketAddr>) -> io::Result<()> {
+    pub fn connect<A: ToSocketAddrs>(&self, _: A) -> io::Result<()> {
         self.0
     }
 }
@@ -304,12 +304,6 @@ impl fmt::Debug for UdpSocket {
 
 pub struct LookupHost(!);
 
-impl LookupHost {
-    pub fn port(&self) -> u16 {
-        self.0
-    }
-}
-
 impl Iterator for LookupHost {
     type Item = SocketAddr;
     fn next(&mut self) -> Option<SocketAddr> {
@@ -317,18 +311,6 @@ impl Iterator for LookupHost {
     }
 }
 
-impl TryFrom<&str> for LookupHost {
-    type Error = io::Error;
-
-    fn try_from(_v: &str) -> io::Result<LookupHost> {
-        unsupported()
-    }
-}
-
-impl<'a> TryFrom<(&'a str, u16)> for LookupHost {
-    type Error = io::Error;
-
-    fn try_from(_v: (&'a str, u16)) -> io::Result<LookupHost> {
-        unsupported()
-    }
+pub fn lookup_host(_host: &str, _port: u16) -> io::Result<LookupHost> {
+    unsupported()
 }
diff --git a/library/std/src/sys/net/connection/wasip1.rs b/library/std/src/sys/net/connection/wasip1.rs
index 951dc65e5b4..048dafdcd7f 100644
--- a/library/std/src/sys/net/connection/wasip1.rs
+++ b/library/std/src/sys/net/connection/wasip1.rs
@@ -2,7 +2,7 @@
 
 use crate::fmt;
 use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
-use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr};
+use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr, ToSocketAddrs};
 use crate::os::wasi::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, RawFd};
 use crate::sys::fd::WasiFd;
 use crate::sys::{err2io, unsupported};
@@ -60,7 +60,7 @@ impl FromRawFd for Socket {
 }
 
 impl TcpStream {
-    pub fn connect(_: io::Result<&SocketAddr>) -> io::Result<TcpStream> {
+    pub fn connect<A: ToSocketAddrs>(_: A) -> io::Result<TcpStream> {
         unsupported()
     }
 
@@ -212,7 +212,7 @@ pub struct TcpListener {
 }
 
 impl TcpListener {
-    pub fn bind(_: io::Result<&SocketAddr>) -> io::Result<TcpListener> {
+    pub fn bind<A: ToSocketAddrs>(_: A) -> io::Result<TcpListener> {
         unsupported()
     }
 
@@ -316,7 +316,7 @@ pub struct UdpSocket {
 }
 
 impl UdpSocket {
-    pub fn bind(_: io::Result<&SocketAddr>) -> io::Result<UdpSocket> {
+    pub fn bind<A: ToSocketAddrs>(_: A) -> io::Result<UdpSocket> {
         unsupported()
     }
 
@@ -436,7 +436,7 @@ impl UdpSocket {
         unsupported()
     }
 
-    pub fn connect(&self, _: io::Result<&SocketAddr>) -> io::Result<()> {
+    pub fn connect<A: ToSocketAddrs>(&self, _: A) -> io::Result<()> {
         unsupported()
     }
 
@@ -477,12 +477,6 @@ impl fmt::Debug for UdpSocket {
 
 pub struct LookupHost(!);
 
-impl LookupHost {
-    pub fn port(&self) -> u16 {
-        self.0
-    }
-}
-
 impl Iterator for LookupHost {
     type Item = SocketAddr;
     fn next(&mut self) -> Option<SocketAddr> {
@@ -490,18 +484,6 @@ impl Iterator for LookupHost {
     }
 }
 
-impl<'a> TryFrom<&'a str> for LookupHost {
-    type Error = io::Error;
-
-    fn try_from(_v: &'a str) -> io::Result<LookupHost> {
-        unsupported()
-    }
-}
-
-impl<'a> TryFrom<(&'a str, u16)> for LookupHost {
-    type Error = io::Error;
-
-    fn try_from(_v: (&'a str, u16)) -> io::Result<LookupHost> {
-        unsupported()
-    }
+pub fn lookup_host(_host: &str, _port: u16) -> io::Result<LookupHost> {
+    unsupported()
 }
diff --git a/library/std/src/sys/net/connection/xous/dns.rs b/library/std/src/sys/net/connection/xous/dns.rs
index bb29d211fad..b139376f597 100644
--- a/library/std/src/sys/net/connection/xous/dns.rs
+++ b/library/std/src/sys/net/connection/xous/dns.rs
@@ -1,15 +1,8 @@
-use core::convert::{TryFrom, TryInto};
-
 use crate::io;
 use crate::net::{Ipv4Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
 use crate::os::xous::ffi::lend_mut;
 use crate::os::xous::services::{DnsLendMut, dns_server};
 
-pub struct DnsError {
-    #[allow(dead_code)]
-    pub code: u8,
-}
-
 #[repr(C, align(4096))]
 struct LookupHostQuery([u8; 4096]);
 
@@ -20,12 +13,6 @@ pub struct LookupHost {
     count: usize,
 }
 
-impl LookupHost {
-    pub fn port(&self) -> u16 {
-        self.port
-    }
-}
-
 impl Iterator for LookupHost {
     type Item = SocketAddr;
     fn next(&mut self) -> Option<SocketAddr> {
@@ -72,7 +59,7 @@ impl Iterator for LookupHost {
     }
 }
 
-pub fn lookup(query: &str, port: u16) -> Result<LookupHost, DnsError> {
+pub fn lookup_host(query: &str, port: u16) -> io::Result<LookupHost> {
     let mut result = LookupHost { data: LookupHostQuery([0u8; 4096]), offset: 0, count: 0, port };
 
     // Copy the query into the message that gets sent to the DNS server
@@ -89,7 +76,7 @@ pub fn lookup(query: &str, port: u16) -> Result<LookupHost, DnsError> {
     )
     .unwrap();
     if result.data.0[0] != 0 {
-        return Err(DnsError { code: result.data.0[1] });
+        return Err(io::const_error!(io::ErrorKind::InvalidInput, "DNS failure"));
     }
     assert_eq!(result.offset, 0);
     result.count = result.data.0[1] as usize;
@@ -98,31 +85,3 @@ pub fn lookup(query: &str, port: u16) -> Result<LookupHost, DnsError> {
     result.offset = 2;
     Ok(result)
 }
-
-impl TryFrom<&str> for LookupHost {
-    type Error = io::Error;
-
-    fn try_from(s: &str) -> io::Result<LookupHost> {
-        macro_rules! try_opt {
-            ($e:expr, $msg:expr) => {
-                match $e {
-                    Some(r) => r,
-                    None => return Err(io::const_error!(io::ErrorKind::InvalidInput, &$msg)),
-                }
-            };
-        }
-
-        // split the string by ':' and convert the second part to u16
-        let (host, port_str) = try_opt!(s.rsplit_once(':'), "invalid socket address");
-        let port: u16 = try_opt!(port_str.parse().ok(), "invalid port value");
-        (host, port).try_into()
-    }
-}
-
-impl TryFrom<(&str, u16)> for LookupHost {
-    type Error = io::Error;
-
-    fn try_from(v: (&str, u16)) -> io::Result<LookupHost> {
-        lookup(v.0, v.1).map_err(|_e| io::const_error!(io::ErrorKind::InvalidInput, "DNS failure"))
-    }
-}
diff --git a/library/std/src/sys/net/connection/xous/mod.rs b/library/std/src/sys/net/connection/xous/mod.rs
index e44a375b9e3..0f77be5c3fa 100644
--- a/library/std/src/sys/net/connection/xous/mod.rs
+++ b/library/std/src/sys/net/connection/xous/mod.rs
@@ -45,4 +45,4 @@ pub struct GetAddress {
     raw: [u8; 4096],
 }
 
-pub use dns::LookupHost;
+pub use dns::lookup_host;
diff --git a/library/std/src/sys/net/connection/xous/tcplistener.rs b/library/std/src/sys/net/connection/xous/tcplistener.rs
index bdf1fcd9302..8818ef2ca9a 100644
--- a/library/std/src/sys/net/connection/xous/tcplistener.rs
+++ b/library/std/src/sys/net/connection/xous/tcplistener.rs
@@ -2,9 +2,10 @@ use core::convert::TryInto;
 use core::sync::atomic::{Atomic, AtomicBool, AtomicU16, AtomicUsize, Ordering};
 
 use super::*;
-use crate::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};
+use crate::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, ToSocketAddrs};
 use crate::os::xous::services;
 use crate::sync::Arc;
+use crate::sys::net::connection::each_addr;
 use crate::{fmt, io};
 
 macro_rules! unimpl {
@@ -25,16 +26,19 @@ pub struct TcpListener {
 }
 
 impl TcpListener {
-    pub fn bind(socketaddr: io::Result<&SocketAddr>) -> io::Result<TcpListener> {
-        let mut addr = *socketaddr?;
-
-        let fd = TcpListener::bind_inner(&mut addr)?;
-        return Ok(TcpListener {
-            fd: Arc::new(AtomicU16::new(fd)),
-            local: addr,
-            handle_count: Arc::new(AtomicUsize::new(1)),
-            nonblocking: Arc::new(AtomicBool::new(false)),
-        });
+    pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<TcpListener> {
+        return each_addr(addr, inner);
+
+        fn inner(addr: &SocketAddr) -> io::Result<TcpListener> {
+            let mut addr = *addr;
+            let fd = TcpListener::bind_inner(&mut addr)?;
+            Ok(TcpListener {
+                fd: Arc::new(AtomicU16::new(fd)),
+                local: addr,
+                handle_count: Arc::new(AtomicUsize::new(1)),
+                nonblocking: Arc::new(AtomicBool::new(false)),
+            })
+        }
     }
 
     /// This returns the raw fd of a Listener, so that it can also be used by the
diff --git a/library/std/src/sys/net/connection/xous/tcpstream.rs b/library/std/src/sys/net/connection/xous/tcpstream.rs
index 54524767452..4df75453d1f 100644
--- a/library/std/src/sys/net/connection/xous/tcpstream.rs
+++ b/library/std/src/sys/net/connection/xous/tcpstream.rs
@@ -3,9 +3,12 @@ use core::sync::atomic::{Atomic, AtomicBool, AtomicU32, AtomicUsize, Ordering};
 use super::*;
 use crate::fmt;
 use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
-use crate::net::{IpAddr, Ipv4Addr, Shutdown, SocketAddr, SocketAddrV4, SocketAddrV6};
+use crate::net::{
+    IpAddr, Ipv4Addr, Shutdown, SocketAddr, SocketAddrV4, SocketAddrV6, ToSocketAddrs,
+};
 use crate::os::xous::services;
 use crate::sync::Arc;
+use crate::sys::net::connection::each_addr;
 use crate::time::Duration;
 
 macro_rules! unimpl {
@@ -79,8 +82,8 @@ impl TcpStream {
         }
     }
 
-    pub fn connect(socketaddr: io::Result<&SocketAddr>) -> io::Result<TcpStream> {
-        Self::connect_timeout(socketaddr?, Duration::ZERO)
+    pub fn connect<A: ToSocketAddrs>(addr: A) -> io::Result<TcpStream> {
+        each_addr(addr, |addr| Self::connect_timeout(addr, Duration::ZERO))
     }
 
     pub fn connect_timeout(addr: &SocketAddr, duration: Duration) -> io::Result<TcpStream> {
diff --git a/library/std/src/sys/net/connection/xous/udp.rs b/library/std/src/sys/net/connection/xous/udp.rs
index 2127d3267ed..ce54ea3b79e 100644
--- a/library/std/src/sys/net/connection/xous/udp.rs
+++ b/library/std/src/sys/net/connection/xous/udp.rs
@@ -3,9 +3,10 @@ use core::sync::atomic::{Atomic, AtomicUsize, Ordering};
 
 use super::*;
 use crate::cell::Cell;
-use crate::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};
+use crate::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, ToSocketAddrs};
 use crate::os::xous::services;
 use crate::sync::Arc;
+use crate::sys::net::connection::each_addr;
 use crate::time::Duration;
 use crate::{fmt, io};
 
@@ -32,40 +33,45 @@ pub struct UdpSocket {
 }
 
 impl UdpSocket {
-    pub fn bind(socketaddr: io::Result<&SocketAddr>) -> io::Result<UdpSocket> {
-        let addr = socketaddr?;
-        // Construct the request
-        let mut connect_request = ConnectRequest { raw: [0u8; 4096] };
-
-        // Serialize the StdUdpBind structure. This is done "manually" because we don't want to
-        // make an auto-serdes (like bincode or rkyv) crate a dependency of Xous.
-        let port_bytes = addr.port().to_le_bytes();
-        connect_request.raw[0] = port_bytes[0];
-        connect_request.raw[1] = port_bytes[1];
-        match addr.ip() {
-            IpAddr::V4(addr) => {
-                connect_request.raw[2] = 4;
-                for (dest, src) in connect_request.raw[3..].iter_mut().zip(addr.octets()) {
-                    *dest = src;
+    pub fn bind<A: ToSocketAddrs>(addr: A) -> io::Result<UdpSocket> {
+        return each_addr(addr, inner);
+
+        fn inner(addr: &SocketAddr) -> io::Result<UdpSocket> {
+            // Construct the request
+            let mut connect_request = ConnectRequest { raw: [0u8; 4096] };
+
+            // Serialize the StdUdpBind structure. This is done "manually" because we don't want to
+            // make an auto-serdes (like bincode or rkyv) crate a dependency of Xous.
+            let port_bytes = addr.port().to_le_bytes();
+            connect_request.raw[0] = port_bytes[0];
+            connect_request.raw[1] = port_bytes[1];
+            match addr.ip() {
+                IpAddr::V4(addr) => {
+                    connect_request.raw[2] = 4;
+                    for (dest, src) in connect_request.raw[3..].iter_mut().zip(addr.octets()) {
+                        *dest = src;
+                    }
                 }
-            }
-            IpAddr::V6(addr) => {
-                connect_request.raw[2] = 6;
-                for (dest, src) in connect_request.raw[3..].iter_mut().zip(addr.octets()) {
-                    *dest = src;
+                IpAddr::V6(addr) => {
+                    connect_request.raw[2] = 6;
+                    for (dest, src) in connect_request.raw[3..].iter_mut().zip(addr.octets()) {
+                        *dest = src;
+                    }
                 }
             }
-        }
 
-        let response = crate::os::xous::ffi::lend_mut(
-            services::net_server(),
-            services::NetLendMut::StdUdpBind.into(),
-            &mut connect_request.raw,
-            0,
-            4096,
-        );
+            let response = crate::os::xous::ffi::lend_mut(
+                services::net_server(),
+                services::NetLendMut::StdUdpBind.into(),
+                &mut connect_request.raw,
+                0,
+                4096,
+            );
+
+            let Ok((_, valid)) = response else {
+                return Err(io::const_error!(io::ErrorKind::InvalidInput, "invalid response"));
+            };
 
-        if let Ok((_, valid)) = response {
             // The first four bytes should be zero upon success, and will be nonzero
             // for an error.
             let response = connect_request.raw;
@@ -87,8 +93,9 @@ impl UdpSocket {
                     ));
                 }
             }
+
             let fd = response[1] as u16;
-            return Ok(UdpSocket {
+            Ok(UdpSocket {
                 fd,
                 local: *addr,
                 remote: Cell::new(None),
@@ -96,9 +103,8 @@ impl UdpSocket {
                 write_timeout: Cell::new(0),
                 handle_count: Arc::new(AtomicUsize::new(1)),
                 nonblocking: Cell::new(false),
-            });
+            })
         }
-        Err(io::const_error!(io::ErrorKind::InvalidInput, "invalid response"))
     }
 
     pub fn peer_addr(&self) -> io::Result<SocketAddr> {
@@ -198,10 +204,11 @@ impl UdpSocket {
         self.peek_from(buf).map(|(len, _addr)| len)
     }
 
-    pub fn connect(&self, maybe_addr: io::Result<&SocketAddr>) -> io::Result<()> {
-        let addr = maybe_addr?;
-        self.remote.set(Some(*addr));
-        Ok(())
+    pub fn connect<A: ToSocketAddrs>(&self, addr: A) -> io::Result<()> {
+        each_addr(addr, |addr| {
+            self.remote.set(Some(*addr));
+            Ok(())
+        })
     }
 
     pub fn send(&self, buf: &[u8]) -> io::Result<usize> {
diff --git a/library/std/src/sys/net/mod.rs b/library/std/src/sys/net/mod.rs
index 5df1fe138ab..dffc4ea7f81 100644
--- a/library/std/src/sys/net/mod.rs
+++ b/library/std/src/sys/net/mod.rs
@@ -1,46 +1,4 @@
-cfg_select! {
-    any(
-        all(target_family = "unix", not(target_os = "l4re")),
-        target_os = "windows",
-        target_os = "hermit",
-        all(target_os = "wasi", target_env = "p2"),
-        target_os = "solid_asp3",
-    ) => {
-        mod connection {
-            mod socket;
-            pub use socket::*;
-        }
-    }
-    all(target_vendor = "fortanix", target_env = "sgx") => {
-        mod connection {
-            mod sgx;
-            pub use sgx::*;
-        }
-    }
-    all(target_os = "wasi", target_env = "p1") => {
-        mod connection {
-            mod wasip1;
-            pub use wasip1::*;
-        }
-    }
-    target_os = "xous" => {
-        mod connection {
-            mod xous;
-            pub use xous::*;
-        }
-    }
-    target_os = "uefi" => {
-        mod connection {
-            mod uefi;
-            pub use uefi::*;
-        }
-    }
-    _ => {
-        mod connection {
-            mod unsupported;
-            pub use unsupported::*;
-        }
-    }
-}
-
+/// This module contains the implementations of `TcpStream`, `TcpListener` and
+/// `UdpSocket` as well as related functionality like DNS resolving.
+mod connection;
 pub use connection::*;
diff --git a/library/std/src/sys/pal/hermit/mod.rs b/library/std/src/sys/pal/hermit/mod.rs
index fb8d69b7375..3ddf6e5acb0 100644
--- a/library/std/src/sys/pal/hermit/mod.rs
+++ b/library/std/src/sys/pal/hermit/mod.rs
@@ -25,7 +25,6 @@ pub mod futex;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-pub mod thread;
 pub mod time;
 
 pub fn unsupported<T>() -> crate::io::Result<T> {
diff --git a/library/std/src/sys/pal/hermit/os.rs b/library/std/src/sys/pal/hermit/os.rs
index 0fe713a503b..9681964ed9b 100644
--- a/library/std/src/sys/pal/hermit/os.rs
+++ b/library/std/src/sys/pal/hermit/os.rs
@@ -3,7 +3,7 @@ use crate::ffi::{OsStr, OsString};
 use crate::marker::PhantomData;
 use crate::path::{self, PathBuf};
 use crate::sys::unsupported;
-use crate::{fmt, io, str};
+use crate::{fmt, io};
 
 pub fn errno() -> i32 {
     unsafe { hermit_abi::get_errno() }
diff --git a/library/std/src/sys/pal/hermit/time.rs b/library/std/src/sys/pal/hermit/time.rs
index 89a427ab88b..f76a5f96c87 100644
--- a/library/std/src/sys/pal/hermit/time.rs
+++ b/library/std/src/sys/pal/hermit/time.rs
@@ -25,15 +25,8 @@ impl Timespec {
         Timespec { t: timespec { tv_sec, tv_nsec } }
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    const fn sub_timespec(&self, other: &Timespec) -> Result<Duration, Duration> {
-        // FIXME: const PartialOrd
-        let mut cmp = self.t.tv_sec - other.t.tv_sec;
-        if cmp == 0 {
-            cmp = self.t.tv_nsec as i64 - other.t.tv_nsec as i64;
-        }
-
-        if cmp >= 0 {
+    fn sub_timespec(&self, other: &Timespec) -> Result<Duration, Duration> {
+        if self >= other {
             Ok(if self.t.tv_nsec >= other.t.tv_nsec {
                 Duration::new(
                     (self.t.tv_sec - other.t.tv_sec) as u64,
@@ -53,22 +46,20 @@ impl Timespec {
         }
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    const fn checked_add_duration(&self, other: &Duration) -> Option<Timespec> {
+    fn checked_add_duration(&self, other: &Duration) -> Option<Timespec> {
         let mut secs = self.t.tv_sec.checked_add_unsigned(other.as_secs())?;
 
         // Nano calculations can't overflow because nanos are <1B which fit
         // in a u32.
-        let mut nsec = other.subsec_nanos() + self.t.tv_nsec as u32;
-        if nsec >= NSEC_PER_SEC as u32 {
-            nsec -= NSEC_PER_SEC as u32;
+        let mut nsec = other.subsec_nanos() + u32::try_from(self.t.tv_nsec).unwrap();
+        if nsec >= NSEC_PER_SEC.try_into().unwrap() {
+            nsec -= u32::try_from(NSEC_PER_SEC).unwrap();
             secs = secs.checked_add(1)?;
         }
         Some(Timespec { t: timespec { tv_sec: secs, tv_nsec: nsec as _ } })
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    const fn checked_sub_duration(&self, other: &Duration) -> Option<Timespec> {
+    fn checked_sub_duration(&self, other: &Duration) -> Option<Timespec> {
         let mut secs = self.t.tv_sec.checked_sub_unsigned(other.as_secs())?;
 
         // Similar to above, nanos can't overflow.
@@ -222,18 +213,15 @@ impl SystemTime {
         SystemTime(time)
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
         self.0.sub_timespec(&other.0)
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_add_duration(other)?))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_sub_duration(other)?))
     }
 }
diff --git a/library/std/src/sys/pal/sgx/abi/mod.rs b/library/std/src/sys/pal/sgx/abi/mod.rs
index 57247cffad3..b8c4d7740c4 100644
--- a/library/std/src/sys/pal/sgx/abi/mod.rs
+++ b/library/std/src/sys/pal/sgx/abi/mod.rs
@@ -67,7 +67,7 @@ extern "C" fn entry(p1: u64, p2: u64, p3: u64, secondary: bool, p4: u64, p5: u64
     let tls_guard = unsafe { tls.activate() };
 
     if secondary {
-        let join_notifier = super::thread::Thread::entry();
+        let join_notifier = crate::sys::thread::Thread::entry();
         drop(tls_guard);
         drop(join_notifier);
 
diff --git a/library/std/src/sys/pal/sgx/mod.rs b/library/std/src/sys/pal/sgx/mod.rs
index 4a297b6823f..9a33873af58 100644
--- a/library/std/src/sys/pal/sgx/mod.rs
+++ b/library/std/src/sys/pal/sgx/mod.rs
@@ -13,7 +13,6 @@ mod libunwind_integration;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-pub mod thread;
 pub mod thread_parking;
 pub mod time;
 pub mod waitqueue;
diff --git a/library/std/src/sys/pal/sgx/time.rs b/library/std/src/sys/pal/sgx/time.rs
index 603dae952ab..db4cf2804bf 100644
--- a/library/std/src/sys/pal/sgx/time.rs
+++ b/library/std/src/sys/pal/sgx/time.rs
@@ -32,22 +32,15 @@ impl SystemTime {
         SystemTime(usercalls::insecure_time())
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
-        // FIXME: ok_or_else with const closures
-        match self.0.checked_sub(other.0) {
-            Some(duration) => Ok(duration),
-            None => Err(other.0 - self.0),
-        }
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+        self.0.checked_sub(other.0).ok_or_else(|| other.0 - self.0)
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_add(*other)?))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_sub(*other)?))
     }
 }
diff --git a/library/std/src/sys/pal/solid/mod.rs b/library/std/src/sys/pal/solid/mod.rs
index 0011cf256df..9ca6dc58118 100644
--- a/library/std/src/sys/pal/solid/mod.rs
+++ b/library/std/src/sys/pal/solid/mod.rs
@@ -10,10 +10,8 @@ pub mod itron {
     pub mod error;
     pub mod spin;
     pub mod task;
-    pub mod thread;
     pub mod thread_parking;
     pub mod time;
-    use super::unsupported;
 }
 
 // `error` is `pub(crate)` so that it can be accessed by `itron/error.rs` as
@@ -22,7 +20,7 @@ pub(crate) mod error;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-pub use self::itron::{thread, thread_parking};
+pub use self::itron::thread_parking;
 pub mod time;
 
 // SAFETY: must be called only once during runtime initialization.
diff --git a/library/std/src/sys/pal/solid/time.rs b/library/std/src/sys/pal/solid/time.rs
index e35e60df1a0..c39d715c6a6 100644
--- a/library/std/src/sys/pal/solid/time.rs
+++ b/library/std/src/sys/pal/solid/time.rs
@@ -39,8 +39,7 @@ impl SystemTime {
         Self(t)
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
         if self.0 >= other.0 {
             Ok(Duration::from_secs((self.0 as u64).wrapping_sub(other.0 as u64)))
         } else {
@@ -48,13 +47,11 @@ impl SystemTime {
         }
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_add_unsigned(other.as_secs())?))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_sub_unsigned(other.as_secs())?))
     }
 }
diff --git a/library/std/src/sys/pal/teeos/mod.rs b/library/std/src/sys/pal/teeos/mod.rs
index c7b17777258..dd0155265da 100644
--- a/library/std/src/sys/pal/teeos/mod.rs
+++ b/library/std/src/sys/pal/teeos/mod.rs
@@ -9,7 +9,6 @@
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-pub mod thread;
 #[allow(non_upper_case_globals)]
 #[path = "../unix/time.rs"]
 pub mod time;
diff --git a/library/std/src/sys/pal/trusty/mod.rs b/library/std/src/sys/pal/trusty/mod.rs
index 275f6062463..cf0c098f8a2 100644
--- a/library/std/src/sys/pal/trusty/mod.rs
+++ b/library/std/src/sys/pal/trusty/mod.rs
@@ -7,8 +7,6 @@ mod common;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-#[path = "../unsupported/thread.rs"]
-pub mod thread;
 #[path = "../unsupported/time.rs"]
 pub mod time;
 
diff --git a/library/std/src/sys/pal/uefi/helpers.rs b/library/std/src/sys/pal/uefi/helpers.rs
index b50574de937..c0d69c3e002 100644
--- a/library/std/src/sys/pal/uefi/helpers.rs
+++ b/library/std/src/sys/pal/uefi/helpers.rs
@@ -92,6 +92,9 @@ pub(crate) fn locate_handles(mut guid: Guid) -> io::Result<Vec<NonNull<crate::ff
 ///
 /// Queries a handle to determine if it supports a specified protocol. If the protocol is
 /// supported by the handle, it opens the protocol on behalf of the calling agent.
+///
+/// The protocol is opened with the attribute GET_PROTOCOL, which means the caller is not required
+/// to close the protocol interface with `EFI_BOOT_SERVICES.CloseProtocol()`
 pub(crate) fn open_protocol<T>(
     handle: NonNull<crate::ffi::c_void>,
     mut protocol_guid: Guid,
@@ -473,6 +476,7 @@ impl<'a> crate::fmt::Debug for DevicePathNode<'a> {
     }
 }
 
+/// Protocols installed by Rust side on a handle.
 pub(crate) struct OwnedProtocol<T> {
     guid: r_efi::efi::Guid,
     handle: NonNull<crate::ffi::c_void>,
diff --git a/library/std/src/sys/pal/uefi/mod.rs b/library/std/src/sys/pal/uefi/mod.rs
index 8911a2ee519..ebd311db1e1 100644
--- a/library/std/src/sys/pal/uefi/mod.rs
+++ b/library/std/src/sys/pal/uefi/mod.rs
@@ -17,7 +17,6 @@ pub mod helpers;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-pub mod thread;
 pub mod time;
 
 #[cfg(test)]
diff --git a/library/std/src/sys/pal/uefi/thread.rs b/library/std/src/sys/pal/uefi/thread.rs
deleted file mode 100644
index 47a48008c76..00000000000
--- a/library/std/src/sys/pal/uefi/thread.rs
+++ /dev/null
@@ -1,66 +0,0 @@
-use super::unsupported;
-use crate::ffi::CStr;
-use crate::io;
-use crate::num::NonZero;
-use crate::ptr::NonNull;
-use crate::time::{Duration, Instant};
-
-pub struct Thread(!);
-
-pub const DEFAULT_MIN_STACK_SIZE: usize = 64 * 1024;
-
-impl Thread {
-    // unsafe: see thread::Builder::spawn_unchecked for safety requirements
-    pub unsafe fn new(
-        _stack: usize,
-        _name: Option<&str>,
-        _p: Box<dyn FnOnce()>,
-    ) -> io::Result<Thread> {
-        unsupported()
-    }
-
-    pub fn yield_now() {
-        // do nothing
-    }
-
-    pub fn set_name(_name: &CStr) {
-        // nope
-    }
-
-    pub fn sleep(dur: Duration) {
-        let boot_services: NonNull<r_efi::efi::BootServices> =
-            crate::os::uefi::env::boot_services().expect("can't sleep").cast();
-        let mut dur_ms = dur.as_micros();
-        // ceil up to the nearest microsecond
-        if dur.subsec_nanos() % 1000 > 0 {
-            dur_ms += 1;
-        }
-
-        while dur_ms > 0 {
-            let ms = crate::cmp::min(dur_ms, usize::MAX as u128);
-            let _ = unsafe { ((*boot_services.as_ptr()).stall)(ms as usize) };
-            dur_ms -= ms;
-        }
-    }
-
-    pub fn sleep_until(deadline: Instant) {
-        let now = Instant::now();
-
-        if let Some(delay) = deadline.checked_duration_since(now) {
-            Self::sleep(delay);
-        }
-    }
-
-    pub fn join(self) {
-        self.0
-    }
-}
-
-pub(crate) fn current_os_id() -> Option<u64> {
-    None
-}
-
-pub fn available_parallelism() -> io::Result<NonZero<usize>> {
-    // UEFI is single threaded
-    Ok(NonZero::new(1).unwrap())
-}
diff --git a/library/std/src/sys/pal/uefi/time.rs b/library/std/src/sys/pal/uefi/time.rs
index 36ce3f7ef96..c6636626fd5 100644
--- a/library/std/src/sys/pal/uefi/time.rs
+++ b/library/std/src/sys/pal/uefi/time.rs
@@ -80,32 +80,19 @@ impl SystemTime {
             .unwrap_or_else(|| panic!("time not implemented on this platform"))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
-        // FIXME: ok_or_else with const closures
-        match self.0.checked_sub(other.0) {
-            Some(duration) => Ok(duration),
-            None => Err(other.0 - self.0),
-        }
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+        self.0.checked_sub(other.0).ok_or_else(|| other.0 - self.0)
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
-        let temp = self.0.checked_add(*other)?;
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+        let temp = Self(self.0.checked_add(*other)?);
 
         // Check if can be represented in UEFI
-        // FIXME: const PartialOrd
-        let mut cmp = temp.as_secs() - MAX_UEFI_TIME.0.as_secs();
-        if cmp == 0 {
-            cmp = temp.subsec_nanos() as u64 - MAX_UEFI_TIME.0.subsec_nanos() as u64;
-        }
-
-        if cmp <= 0 { Some(SystemTime(temp)) } else { None }
+        if temp <= MAX_UEFI_TIME { Some(temp) } else { None }
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
-        Some(SystemTime(self.0.checked_sub(*other)?))
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+        self.0.checked_sub(*other).map(Self)
     }
 }
 
diff --git a/library/std/src/sys/pal/unix/mod.rs b/library/std/src/sys/pal/unix/mod.rs
index ac5c823a1bf..dd1059fe04a 100644
--- a/library/std/src/sys/pal/unix/mod.rs
+++ b/library/std/src/sys/pal/unix/mod.rs
@@ -17,7 +17,6 @@ pub mod os;
 pub mod pipe;
 pub mod stack_overflow;
 pub mod sync;
-pub mod thread;
 pub mod thread_parking;
 pub mod time;
 
@@ -55,7 +54,7 @@ pub unsafe fn init(argc: isize, argv: *const *const u8, sigpipe: u8) {
     // thread-id for the main thread and so renaming the main thread will rename the
     // process and we only want to enable this on platforms we've tested.
     if cfg!(target_vendor = "apple") {
-        thread::Thread::set_name(&c"main");
+        crate::sys::thread::set_name(c"main");
     }
 
     unsafe fn sanitize_standard_fds() {
diff --git a/library/std/src/sys/pal/unix/time.rs b/library/std/src/sys/pal/unix/time.rs
index 328fe0bc960..bd7f74fea6a 100644
--- a/library/std/src/sys/pal/unix/time.rs
+++ b/library/std/src/sys/pal/unix/time.rs
@@ -38,18 +38,15 @@ impl SystemTime {
         SystemTime { t: Timespec::now(libc::CLOCK_REALTIME) }
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
         self.t.sub_timespec(&other.t)
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime { t: self.t.checked_add_duration(other)? })
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime { t: self.t.checked_sub_duration(other)? })
     }
 }
@@ -136,15 +133,8 @@ impl Timespec {
         Timespec::new(t.tv_sec as i64, t.tv_nsec as i64).unwrap()
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn sub_timespec(&self, other: &Timespec) -> Result<Duration, Duration> {
-        // FIXME: const PartialOrd
-        let mut cmp = self.tv_sec - other.tv_sec;
-        if cmp == 0 {
-            cmp = self.tv_nsec.as_inner() as i64 - other.tv_nsec.as_inner() as i64;
-        }
-
-        if cmp >= 0 {
+    pub fn sub_timespec(&self, other: &Timespec) -> Result<Duration, Duration> {
+        if self >= other {
             // NOTE(eddyb) two aspects of this `if`-`else` are required for LLVM
             // to optimize it into a branchless form (see also #75545):
             //
@@ -179,8 +169,7 @@ impl Timespec {
         }
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add_duration(&self, other: &Duration) -> Option<Timespec> {
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<Timespec> {
         let mut secs = self.tv_sec.checked_add_unsigned(other.as_secs())?;
 
         // Nano calculations can't overflow because nanos are <1B which fit
@@ -190,11 +179,10 @@ impl Timespec {
             nsec -= NSEC_PER_SEC as u32;
             secs = secs.checked_add(1)?;
         }
-        Some(unsafe { Timespec::new_unchecked(secs, nsec as i64) })
+        Some(unsafe { Timespec::new_unchecked(secs, nsec.into()) })
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<Timespec> {
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<Timespec> {
         let mut secs = self.tv_sec.checked_sub_unsigned(other.as_secs())?;
 
         // Similar to above, nanos can't overflow.
@@ -203,7 +191,7 @@ impl Timespec {
             nsec += NSEC_PER_SEC as i32;
             secs = secs.checked_sub(1)?;
         }
-        Some(unsafe { Timespec::new_unchecked(secs, nsec as i64) })
+        Some(unsafe { Timespec::new_unchecked(secs, nsec.into()) })
     }
 
     #[allow(dead_code)]
diff --git a/library/std/src/sys/pal/unix/weak.rs b/library/std/src/sys/pal/unix/weak.rs
index c8cf75b876c..a3b980a3f3d 100644
--- a/library/std/src/sys/pal/unix/weak.rs
+++ b/library/std/src/sys/pal/unix/weak.rs
@@ -22,11 +22,24 @@
 #![allow(dead_code, unused_macros)]
 #![forbid(unsafe_op_in_unsafe_fn)]
 
-use crate::ffi::CStr;
-use crate::marker::PhantomData;
-use crate::sync::atomic::{self, Atomic, AtomicPtr, Ordering};
+use crate::ffi::{CStr, c_char, c_void};
+use crate::marker::{FnPtr, PhantomData};
+use crate::sync::atomic::{Atomic, AtomicPtr, Ordering};
 use crate::{mem, ptr};
 
+// We currently only test `dlsym!`, but that doesn't work on all platforms, so
+// we gate the tests to only the platforms where it is actually used.
+//
+// FIXME(joboet): add more tests, reorganise the whole module and get rid of
+//                `#[allow(dead_code, unused_macros)]`.
+#[cfg(any(
+    target_vendor = "apple",
+    all(target_os = "linux", target_env = "gnu"),
+    target_os = "freebsd",
+))]
+#[cfg(test)]
+mod tests;
+
 // We can use true weak linkage on ELF targets.
 #[cfg(all(unix, not(target_vendor = "apple")))]
 pub(crate) macro weak {
@@ -64,7 +77,7 @@ impl<F: Copy> ExternWeak<F> {
 
 pub(crate) macro dlsym {
     (fn $name:ident($($param:ident : $t:ty),* $(,)?) -> $ret:ty;) => (
-         dlsym!(
+        dlsym!(
             #[link_name = stringify!($name)]
             fn $name($($param : $t),*) -> $ret;
         );
@@ -73,21 +86,39 @@ pub(crate) macro dlsym {
         #[link_name = $sym:expr]
         fn $name:ident($($param:ident : $t:ty),* $(,)?) -> $ret:ty;
     ) => (
-        static DLSYM: DlsymWeak<unsafe extern "C" fn($($t),*) -> $ret> =
-            DlsymWeak::new(concat!($sym, '\0'));
+        static DLSYM: DlsymWeak<unsafe extern "C" fn($($t),*) -> $ret> = {
+            let Ok(name) = CStr::from_bytes_with_nul(concat!($sym, '\0').as_bytes()) else {
+                panic!("symbol name may not contain NUL")
+            };
+
+            // SAFETY: Whoever calls the function pointer returned by `get()`
+            // is responsible for ensuring that the signature is correct. Just
+            // like with extern blocks, this is syntactically enforced by making
+            // the function pointer be unsafe.
+            unsafe { DlsymWeak::new(name) }
+        };
+
         let $name = &DLSYM;
     )
 }
+
 pub(crate) struct DlsymWeak<F> {
-    name: &'static str,
+    /// A pointer to the nul-terminated name of the symbol.
+    // Use a pointer instead of `&'static CStr` to save space.
+    name: *const c_char,
     func: Atomic<*mut libc::c_void>,
     _marker: PhantomData<F>,
 }
 
-impl<F> DlsymWeak<F> {
-    pub(crate) const fn new(name: &'static str) -> Self {
+impl<F: FnPtr> DlsymWeak<F> {
+    /// # Safety
+    ///
+    /// If the signature of `F` does not match the signature of the symbol (if
+    /// it exists), calling the function pointer returned by `get()` is
+    /// undefined behaviour.
+    pub(crate) const unsafe fn new(name: &'static CStr) -> Self {
         DlsymWeak {
-            name,
+            name: name.as_ptr(),
             func: AtomicPtr::new(ptr::without_provenance_mut(1)),
             _marker: PhantomData,
         }
@@ -95,62 +126,59 @@ impl<F> DlsymWeak<F> {
 
     #[inline]
     pub(crate) fn get(&self) -> Option<F> {
-        unsafe {
-            // Relaxed is fine here because we fence before reading through the
-            // pointer (see the comment below).
-            match self.func.load(Ordering::Relaxed) {
-                func if func.addr() == 1 => self.initialize(),
-                func if func.is_null() => None,
-                func => {
-                    let func = mem::transmute_copy::<*mut libc::c_void, F>(&func);
-                    // The caller is presumably going to read through this value
-                    // (by calling the function we've dlsymed). This means we'd
-                    // need to have loaded it with at least C11's consume
-                    // ordering in order to be guaranteed that the data we read
-                    // from the pointer isn't from before the pointer was
-                    // stored. Rust has no equivalent to memory_order_consume,
-                    // so we use an acquire fence (sorry, ARM).
-                    //
-                    // Now, in practice this likely isn't needed even on CPUs
-                    // where relaxed and consume mean different things. The
-                    // symbols we're loading are probably present (or not) at
-                    // init, and even if they aren't the runtime dynamic loader
-                    // is extremely likely have sufficient barriers internally
-                    // (possibly implicitly, for example the ones provided by
-                    // invoking `mprotect`).
-                    //
-                    // That said, none of that's *guaranteed*, and so we fence.
-                    atomic::fence(Ordering::Acquire);
-                    Some(func)
-                }
-            }
+        // The caller is presumably going to read through this value
+        // (by calling the function we've dlsymed). This means we'd
+        // need to have loaded it with at least C11's consume
+        // ordering in order to be guaranteed that the data we read
+        // from the pointer isn't from before the pointer was
+        // stored. Rust has no equivalent to memory_order_consume,
+        // so we use an acquire load (sorry, ARM).
+        //
+        // Now, in practice this likely isn't needed even on CPUs
+        // where relaxed and consume mean different things. The
+        // symbols we're loading are probably present (or not) at
+        // init, and even if they aren't the runtime dynamic loader
+        // is extremely likely have sufficient barriers internally
+        // (possibly implicitly, for example the ones provided by
+        // invoking `mprotect`).
+        //
+        // That said, none of that's *guaranteed*, so we use acquire.
+        match self.func.load(Ordering::Acquire) {
+            func if func.addr() == 1 => self.initialize(),
+            func if func.is_null() => None,
+            // SAFETY:
+            // `func` is not null and `F` implements `FnPtr`, thus this
+            // transmutation is well-defined. It is the responsibility of the
+            // creator of this `DlsymWeak` to ensure that calling the resulting
+            // function pointer does not result in undefined behaviour (though
+            // the `dlsym!` macro delegates this responsibility to the caller
+            // of the function by using `unsafe` function pointers).
+            // FIXME: use `transmute` once it stops complaining about generics.
+            func => Some(unsafe { mem::transmute_copy::<*mut c_void, F>(&func) }),
         }
     }
 
     // Cold because it should only happen during first-time initialization.
     #[cold]
-    unsafe fn initialize(&self) -> Option<F> {
-        assert_eq!(size_of::<F>(), size_of::<*mut libc::c_void>());
-
-        let val = unsafe { fetch(self.name) };
-        // This synchronizes with the acquire fence in `get`.
+    fn initialize(&self) -> Option<F> {
+        // SAFETY: `self.name` was created from a `&'static CStr` and is
+        // therefore a valid C string pointer.
+        let val = unsafe { libc::dlsym(libc::RTLD_DEFAULT, self.name) };
+        // This synchronizes with the acquire load in `get`.
         self.func.store(val, Ordering::Release);
 
         if val.is_null() {
             None
         } else {
+            // SAFETY: see the comment in `get`.
+            // FIXME: use `transmute` once it stops complaining about generics.
             Some(unsafe { mem::transmute_copy::<*mut libc::c_void, F>(&val) })
         }
     }
 }
 
-unsafe fn fetch(name: &str) -> *mut libc::c_void {
-    let name = match CStr::from_bytes_with_nul(name.as_bytes()) {
-        Ok(cstr) => cstr,
-        Err(..) => return ptr::null_mut(),
-    };
-    unsafe { libc::dlsym(libc::RTLD_DEFAULT, name.as_ptr()) }
-}
+unsafe impl<F> Send for DlsymWeak<F> {}
+unsafe impl<F> Sync for DlsymWeak<F> {}
 
 #[cfg(not(any(target_os = "linux", target_os = "android")))]
 pub(crate) macro syscall {
diff --git a/library/std/src/sys/pal/unix/weak/tests.rs b/library/std/src/sys/pal/unix/weak/tests.rs
new file mode 100644
index 00000000000..d807ba64e35
--- /dev/null
+++ b/library/std/src/sys/pal/unix/weak/tests.rs
@@ -0,0 +1,32 @@
+use super::*;
+
+#[test]
+fn dlsym_existing() {
+    const TEST_STRING: &'static CStr = c"Ferris!";
+
+    // Try to find a symbol that definitely exists.
+    dlsym! {
+        fn strlen(cs: *const c_char) -> usize;
+    }
+
+    dlsym! {
+        #[link_name = "strlen"]
+        fn custom_name(cs: *const c_char) -> usize;
+    }
+
+    let strlen = strlen.get().unwrap();
+    assert_eq!(unsafe { strlen(TEST_STRING.as_ptr()) }, TEST_STRING.count_bytes());
+
+    let custom_name = custom_name.get().unwrap();
+    assert_eq!(unsafe { custom_name(TEST_STRING.as_ptr()) }, TEST_STRING.count_bytes());
+}
+
+#[test]
+fn dlsym_missing() {
+    // Try to find a symbol that definitely does not exist.
+    dlsym! {
+        fn test_symbol_that_does_not_exist() -> i32;
+    }
+
+    assert!(test_symbol_that_does_not_exist.get().is_none());
+}
diff --git a/library/std/src/sys/pal/unsupported/mod.rs b/library/std/src/sys/pal/unsupported/mod.rs
index 5e3295b1331..e64bbc7c616 100644
--- a/library/std/src/sys/pal/unsupported/mod.rs
+++ b/library/std/src/sys/pal/unsupported/mod.rs
@@ -2,7 +2,6 @@
 
 pub mod os;
 pub mod pipe;
-pub mod thread;
 pub mod time;
 
 mod common;
diff --git a/library/std/src/sys/pal/unsupported/time.rs b/library/std/src/sys/pal/unsupported/time.rs
index 0c387917044..6d67b538a96 100644
--- a/library/std/src/sys/pal/unsupported/time.rs
+++ b/library/std/src/sys/pal/unsupported/time.rs
@@ -31,22 +31,15 @@ impl SystemTime {
         panic!("time not implemented on this platform")
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
-        // FIXME: ok_or_else with const closures
-        match self.0.checked_sub(other.0) {
-            Some(duration) => Ok(duration),
-            None => Err(other.0 - self.0),
-        }
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+        self.0.checked_sub(other.0).ok_or_else(|| other.0 - self.0)
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_add(*other)?))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_sub(*other)?))
     }
 }
diff --git a/library/std/src/sys/pal/wasip1/mod.rs b/library/std/src/sys/pal/wasip1/mod.rs
index 61dd1c3f98b..ae5da3c1f77 100644
--- a/library/std/src/sys/pal/wasip1/mod.rs
+++ b/library/std/src/sys/pal/wasip1/mod.rs
@@ -20,7 +20,6 @@ pub mod futex;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-pub mod thread;
 pub mod time;
 
 #[path = "../unsupported/common.rs"]
diff --git a/library/std/src/sys/pal/wasip1/thread.rs b/library/std/src/sys/pal/wasip1/thread.rs
deleted file mode 100644
index e062b49bd7a..00000000000
--- a/library/std/src/sys/pal/wasip1/thread.rs
+++ /dev/null
@@ -1,214 +0,0 @@
-#![forbid(unsafe_op_in_unsafe_fn)]
-
-use crate::ffi::CStr;
-use crate::num::NonZero;
-use crate::time::{Duration, Instant};
-use crate::{io, mem};
-
-cfg_select! {
-    target_feature = "atomics" => {
-        use crate::cmp;
-        use crate::ptr;
-        use crate::sys::os;
-        // Add a few symbols not in upstream `libc` just yet.
-        mod libc {
-            pub use crate::ffi;
-            pub use libc::*;
-
-            // defined in wasi-libc
-            // https://github.com/WebAssembly/wasi-libc/blob/a6f871343313220b76009827ed0153586361c0d5/libc-top-half/musl/include/alltypes.h.in#L108
-            #[repr(C)]
-            union pthread_attr_union {
-                __i: [ffi::c_int; if size_of::<ffi::c_long>() == 8 { 14 } else { 9 }],
-                __vi: [ffi::c_int; if size_of::<ffi::c_long>() == 8 { 14 } else { 9 }],
-                __s: [ffi::c_ulong; if size_of::<ffi::c_long>() == 8 { 7 } else { 9 }],
-            }
-
-            #[repr(C)]
-            pub struct pthread_attr_t {
-                __u: pthread_attr_union,
-            }
-
-            #[allow(non_camel_case_types)]
-            pub type pthread_t = *mut ffi::c_void;
-
-            pub const _SC_NPROCESSORS_ONLN: ffi::c_int = 84;
-
-            unsafe extern "C" {
-                pub fn pthread_create(
-                    native: *mut pthread_t,
-                    attr: *const pthread_attr_t,
-                    f: extern "C" fn(*mut ffi::c_void) -> *mut ffi::c_void,
-                    value: *mut ffi::c_void,
-                ) -> ffi::c_int;
-                pub fn pthread_join(native: pthread_t, value: *mut *mut ffi::c_void) -> ffi::c_int;
-                pub fn pthread_attr_init(attrp: *mut pthread_attr_t) -> ffi::c_int;
-                pub fn pthread_attr_setstacksize(
-                    attr: *mut pthread_attr_t,
-                    stack_size: libc::size_t,
-                ) -> ffi::c_int;
-                pub fn pthread_attr_destroy(attr: *mut pthread_attr_t) -> ffi::c_int;
-                pub fn pthread_detach(thread: pthread_t) -> ffi::c_int;
-            }
-        }
-
-        pub struct Thread {
-            id: libc::pthread_t,
-        }
-
-        impl Drop for Thread {
-            fn drop(&mut self) {
-                let ret = unsafe { libc::pthread_detach(self.id) };
-                debug_assert_eq!(ret, 0);
-            }
-        }
-    }
-    _ => {
-        pub struct Thread(!);
-    }
-}
-
-pub const DEFAULT_MIN_STACK_SIZE: usize = 1024 * 1024;
-
-impl Thread {
-    // unsafe: see thread::Builder::spawn_unchecked for safety requirements
-    cfg_select! {
-        target_feature = "atomics" => {
-            pub unsafe fn new(stack: usize, _name: Option<&str>, p: Box<dyn FnOnce()>) -> io::Result<Thread> {
-                let p = Box::into_raw(Box::new(p));
-                let mut native: libc::pthread_t = unsafe { mem::zeroed() };
-                let mut attr: libc::pthread_attr_t = unsafe { mem::zeroed() };
-                assert_eq!(unsafe { libc::pthread_attr_init(&mut attr) }, 0);
-
-                let stack_size = cmp::max(stack, DEFAULT_MIN_STACK_SIZE);
-
-                match unsafe { libc::pthread_attr_setstacksize(&mut attr, stack_size) } {
-                    0 => {}
-                    n => {
-                        assert_eq!(n, libc::EINVAL);
-                        // EINVAL means |stack_size| is either too small or not a
-                        // multiple of the system page size. Because it's definitely
-                        // >= PTHREAD_STACK_MIN, it must be an alignment issue.
-                        // Round up to the nearest page and try again.
-                        let page_size = os::page_size();
-                        let stack_size =
-                            (stack_size + page_size - 1) & (-(page_size as isize - 1) as usize - 1);
-                        assert_eq!(unsafe { libc::pthread_attr_setstacksize(&mut attr, stack_size) }, 0);
-                    }
-                };
-
-                let ret = unsafe { libc::pthread_create(&mut native, &attr, thread_start, p as *mut _) };
-                // Note: if the thread creation fails and this assert fails, then p will
-                // be leaked. However, an alternative design could cause double-free
-                // which is clearly worse.
-                assert_eq!(unsafe {libc::pthread_attr_destroy(&mut attr) }, 0);
-
-                return if ret != 0 {
-                    // The thread failed to start and as a result p was not consumed. Therefore, it is
-                    // safe to reconstruct the box so that it gets deallocated.
-                    unsafe { drop(Box::from_raw(p)); }
-                    Err(io::Error::from_raw_os_error(ret))
-                } else {
-                    Ok(Thread { id: native })
-                };
-
-                extern "C" fn thread_start(main: *mut libc::c_void) -> *mut libc::c_void {
-                    unsafe {
-                        // Finally, let's run some code.
-                        Box::from_raw(main as *mut Box<dyn FnOnce()>)();
-                    }
-                    ptr::null_mut()
-                }
-            }
-        }
-        _ => {
-            pub unsafe fn new(_stack: usize, _name: Option<&str>, _p: Box<dyn FnOnce()>) -> io::Result<Thread> {
-                crate::sys::unsupported()
-            }
-        }
-    }
-
-    pub fn yield_now() {
-        let ret = unsafe { wasi::sched_yield() };
-        debug_assert_eq!(ret, Ok(()));
-    }
-
-    pub fn set_name(_name: &CStr) {
-        // nope
-    }
-
-    pub fn sleep(dur: Duration) {
-        let mut nanos = dur.as_nanos();
-        while nanos > 0 {
-            const USERDATA: wasi::Userdata = 0x0123_45678;
-
-            let clock = wasi::SubscriptionClock {
-                id: wasi::CLOCKID_MONOTONIC,
-                timeout: u64::try_from(nanos).unwrap_or(u64::MAX),
-                precision: 0,
-                flags: 0,
-            };
-            nanos -= u128::from(clock.timeout);
-
-            let in_ = wasi::Subscription {
-                userdata: USERDATA,
-                u: wasi::SubscriptionU { tag: 0, u: wasi::SubscriptionUU { clock } },
-            };
-            unsafe {
-                let mut event: wasi::Event = mem::zeroed();
-                let res = wasi::poll_oneoff(&in_, &mut event, 1);
-                match (res, event) {
-                    (
-                        Ok(1),
-                        wasi::Event {
-                            userdata: USERDATA,
-                            error: wasi::ERRNO_SUCCESS,
-                            type_: wasi::EVENTTYPE_CLOCK,
-                            ..
-                        },
-                    ) => {}
-                    _ => panic!("thread::sleep(): unexpected result of poll_oneoff"),
-                }
-            }
-        }
-    }
-
-    pub fn sleep_until(deadline: Instant) {
-        let now = Instant::now();
-
-        if let Some(delay) = deadline.checked_duration_since(now) {
-            Self::sleep(delay);
-        }
-    }
-
-    pub fn join(self) {
-        cfg_select! {
-            target_feature = "atomics" => {
-                let id = mem::ManuallyDrop::new(self).id;
-                let ret = unsafe { libc::pthread_join(id, ptr::null_mut()) };
-                if ret != 0 {
-                    rtabort!("failed to join thread: {}", io::Error::from_raw_os_error(ret));
-                }
-            }
-            _ => {
-                self.0
-            }
-        }
-    }
-}
-
-pub(crate) fn current_os_id() -> Option<u64> {
-    None
-}
-
-pub fn available_parallelism() -> io::Result<NonZero<usize>> {
-    cfg_select! {
-        target_feature = "atomics" => {
-            match unsafe { libc::sysconf(libc::_SC_NPROCESSORS_ONLN) } {
-                -1 => Err(io::Error::last_os_error()),
-                cpus => NonZero::new(cpus as usize).ok_or(io::Error::UNKNOWN_THREAD_COUNT),
-            }
-        }
-        _ => crate::sys::unsupported(),
-    }
-}
diff --git a/library/std/src/sys/pal/wasip1/time.rs b/library/std/src/sys/pal/wasip1/time.rs
index 892661b312b..0d8d0b59ac1 100644
--- a/library/std/src/sys/pal/wasip1/time.rs
+++ b/library/std/src/sys/pal/wasip1/time.rs
@@ -43,34 +43,23 @@ impl SystemTime {
         SystemTime(current_time(wasi::CLOCKID_REALTIME))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn from_wasi_timestamp(ts: wasi::Timestamp) -> SystemTime {
+    pub fn from_wasi_timestamp(ts: wasi::Timestamp) -> SystemTime {
         SystemTime(Duration::from_nanos(ts))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn to_wasi_timestamp(&self) -> Option<wasi::Timestamp> {
-        // FIXME: const TryInto
-        let ns = self.0.as_nanos();
-        if ns <= u64::MAX as u128 { Some(ns as u64) } else { None }
+    pub fn to_wasi_timestamp(&self) -> Option<wasi::Timestamp> {
+        self.0.as_nanos().try_into().ok()
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
-        // FIXME: ok_or_else with const closures
-        match self.0.checked_sub(other.0) {
-            Some(duration) => Ok(duration),
-            None => Err(other.0 - self.0),
-        }
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+        self.0.checked_sub(other.0).ok_or_else(|| other.0 - self.0)
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_add(*other)?))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_sub(*other)?))
     }
 }
diff --git a/library/std/src/sys/pal/wasip2/mod.rs b/library/std/src/sys/pal/wasip2/mod.rs
index 5f3fb6d6ddf..c1d89da2677 100644
--- a/library/std/src/sys/pal/wasip2/mod.rs
+++ b/library/std/src/sys/pal/wasip2/mod.rs
@@ -14,7 +14,6 @@ pub mod futex;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-pub mod thread;
 pub mod time;
 
 #[path = "../unsupported/common.rs"]
diff --git a/library/std/src/sys/pal/wasip2/thread.rs b/library/std/src/sys/pal/wasip2/thread.rs
deleted file mode 100644
index ad52918f15a..00000000000
--- a/library/std/src/sys/pal/wasip2/thread.rs
+++ /dev/null
@@ -1,73 +0,0 @@
-use crate::ffi::CStr;
-use crate::io;
-use crate::num::NonZero;
-use crate::time::{Duration, Instant};
-
-pub struct Thread(!);
-
-pub const DEFAULT_MIN_STACK_SIZE: usize = 1024 * 1024;
-
-impl Thread {
-    pub unsafe fn new(
-        _stack: usize,
-        _name: Option<&str>,
-        _p: Box<dyn FnOnce()>,
-    ) -> io::Result<Thread> {
-        // Note that unlike WASIp1 even if the wasm `atomics` feature is enabled
-        // there is no support for threads, not even experimentally, not even in
-        // wasi-libc. Thus this is unconditionally unsupported.
-        crate::sys::unsupported()
-    }
-
-    pub fn yield_now() {
-        // no API for this in WASIp2, but there's also no threads, so that's
-        // sort of expected.
-    }
-
-    pub fn set_name(_name: &CStr) {
-        // nope
-    }
-
-    pub fn sleep(dur: Duration) {
-        // Sleep in increments of `u64::MAX` nanoseconds until the `dur` is
-        // entirely drained.
-        let mut remaining = dur.as_nanos();
-        while remaining > 0 {
-            let amt = u64::try_from(remaining).unwrap_or(u64::MAX);
-            wasip2::clocks::monotonic_clock::subscribe_duration(amt).block();
-            remaining -= u128::from(amt);
-        }
-    }
-
-    pub fn sleep_until(deadline: Instant) {
-        match u64::try_from(deadline.into_inner().as_duration().as_nanos()) {
-            // If the point in time we're sleeping to fits within a 64-bit
-            // number of nanoseconds then directly use `subscribe_instant`.
-            Ok(deadline) => {
-                wasip2::clocks::monotonic_clock::subscribe_instant(deadline).block();
-            }
-            // ... otherwise we're sleeping for 500+ years relative to the
-            // "start" of what the system is using as a clock so speed/accuracy
-            // is not so much of a concern. Use `sleep` instead.
-            Err(_) => {
-                let now = Instant::now();
-
-                if let Some(delay) = deadline.checked_duration_since(now) {
-                    Self::sleep(delay);
-                }
-            }
-        }
-    }
-
-    pub fn join(self) {
-        self.0
-    }
-}
-
-pub(crate) fn current_os_id() -> Option<u64> {
-    None
-}
-
-pub fn available_parallelism() -> io::Result<NonZero<usize>> {
-    crate::sys::unsupported()
-}
diff --git a/library/std/src/sys/pal/wasip2/time.rs b/library/std/src/sys/pal/wasip2/time.rs
index f1f6839774b..43489183994 100644
--- a/library/std/src/sys/pal/wasip2/time.rs
+++ b/library/std/src/sys/pal/wasip2/time.rs
@@ -25,7 +25,7 @@ impl Instant {
         Some(Instant(self.0.checked_sub(*other)?))
     }
 
-    pub(super) fn as_duration(&self) -> &Duration {
+    pub(crate) fn as_duration(&self) -> &Duration {
         &self.0
     }
 }
@@ -36,34 +36,23 @@ impl SystemTime {
         SystemTime(Duration::new(now.seconds, now.nanoseconds))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn from_wasi_timestamp(ts: wasi::Timestamp) -> SystemTime {
+    pub fn from_wasi_timestamp(ts: wasi::Timestamp) -> SystemTime {
         SystemTime(Duration::from_nanos(ts))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn to_wasi_timestamp(&self) -> Option<wasi::Timestamp> {
-        // FIXME: const TryInto
-        let ns = self.0.as_nanos();
-        if ns <= u64::MAX as u128 { Some(ns as u64) } else { None }
+    pub fn to_wasi_timestamp(&self) -> Option<wasi::Timestamp> {
+        self.0.as_nanos().try_into().ok()
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
-        // FIXME: ok_or_else with const closures
-        match self.0.checked_sub(other.0) {
-            Some(duration) => Ok(duration),
-            None => Err(other.0 - self.0),
-        }
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+        self.0.checked_sub(other.0).ok_or_else(|| other.0 - self.0)
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_add(*other)?))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_sub(*other)?))
     }
 }
diff --git a/library/std/src/sys/pal/wasm/atomics/thread.rs b/library/std/src/sys/pal/wasm/atomics/thread.rs
deleted file mode 100644
index 42a7dbdf8b8..00000000000
--- a/library/std/src/sys/pal/wasm/atomics/thread.rs
+++ /dev/null
@@ -1,75 +0,0 @@
-use crate::ffi::CStr;
-use crate::io;
-use crate::num::NonZero;
-use crate::sys::unsupported;
-use crate::time::{Duration, Instant};
-
-pub struct Thread(!);
-
-pub const DEFAULT_MIN_STACK_SIZE: usize = 1024 * 1024;
-
-impl Thread {
-    // unsafe: see thread::Builder::spawn_unchecked for safety requirements
-    pub unsafe fn new(
-        _stack: usize,
-        _name: Option<&str>,
-        _p: Box<dyn FnOnce()>,
-    ) -> io::Result<Thread> {
-        unsupported()
-    }
-
-    pub fn yield_now() {}
-
-    pub fn set_name(_name: &CStr) {}
-
-    pub fn sleep(dur: Duration) {
-        #[cfg(target_arch = "wasm32")]
-        use core::arch::wasm32 as wasm;
-        #[cfg(target_arch = "wasm64")]
-        use core::arch::wasm64 as wasm;
-
-        use crate::cmp;
-
-        // Use an atomic wait to block the current thread artificially with a
-        // timeout listed. Note that we should never be notified (return value
-        // of 0) or our comparison should never fail (return value of 1) so we
-        // should always only resume execution through a timeout (return value
-        // 2).
-        let mut nanos = dur.as_nanos();
-        while nanos > 0 {
-            let amt = cmp::min(i64::MAX as u128, nanos);
-            let mut x = 0;
-            let val = unsafe { wasm::memory_atomic_wait32(&mut x, 0, amt as i64) };
-            debug_assert_eq!(val, 2);
-            nanos -= amt;
-        }
-    }
-
-    pub fn sleep_until(deadline: Instant) {
-        let now = Instant::now();
-
-        if let Some(delay) = deadline.checked_duration_since(now) {
-            Self::sleep(delay);
-        }
-    }
-
-    pub fn join(self) {}
-}
-
-pub(crate) fn current_os_id() -> Option<u64> {
-    None
-}
-
-pub fn available_parallelism() -> io::Result<NonZero<usize>> {
-    unsupported()
-}
-
-pub mod guard {
-    pub type Guard = !;
-    pub unsafe fn current() -> Option<Guard> {
-        None
-    }
-    pub unsafe fn init() -> Option<Guard> {
-        None
-    }
-}
diff --git a/library/std/src/sys/pal/wasm/mod.rs b/library/std/src/sys/pal/wasm/mod.rs
index 346c9ff88c9..a20cd0e9ac7 100644
--- a/library/std/src/sys/pal/wasm/mod.rs
+++ b/library/std/src/sys/pal/wasm/mod.rs
@@ -23,18 +23,9 @@ pub mod pipe;
 #[path = "../unsupported/time.rs"]
 pub mod time;
 
-cfg_select! {
-    target_feature = "atomics" => {
-        #[path = "atomics/futex.rs"]
-        pub mod futex;
-        #[path = "atomics/thread.rs"]
-        pub mod thread;
-    }
-    _ => {
-        #[path = "../unsupported/thread.rs"]
-        pub mod thread;
-    }
-}
+#[cfg(target_feature = "atomics")]
+#[path = "atomics/futex.rs"]
+pub mod futex;
 
 #[path = "../unsupported/common.rs"]
 #[deny(unsafe_op_in_unsafe_fn)]
diff --git a/library/std/src/sys/pal/windows/mod.rs b/library/std/src/sys/pal/windows/mod.rs
index 3b6a86cbc8f..3357946b8f7 100644
--- a/library/std/src/sys/pal/windows/mod.rs
+++ b/library/std/src/sys/pal/windows/mod.rs
@@ -20,7 +20,6 @@ pub mod futex;
 pub mod handle;
 pub mod os;
 pub mod pipe;
-pub mod thread;
 pub mod time;
 cfg_select! {
     not(target_vendor = "uwp") => {
@@ -48,9 +47,9 @@ pub unsafe fn init(_argc: isize, _argv: *const *const u8, _sigpipe: u8) {
     unsafe {
         stack_overflow::init();
 
-        // Normally, `thread::spawn` will call `Thread::set_name` but since this thread already
+        // Normally, `thread::spawn` will call `set_name` but since this thread already
         // exists, we have to call it ourselves.
-        thread::Thread::set_name_wide(wide_str!("main"));
+        crate::sys::thread::set_name_wide(wide_str!("main"));
     }
 }
 
diff --git a/library/std/src/sys/pal/windows/time.rs b/library/std/src/sys/pal/windows/time.rs
index a948c07e0a3..0d31b80e56a 100644
--- a/library/std/src/sys/pal/windows/time.rs
+++ b/library/std/src/sys/pal/windows/time.rs
@@ -72,8 +72,7 @@ impl SystemTime {
         }
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    const fn from_intervals(intervals: i64) -> SystemTime {
+    fn from_intervals(intervals: i64) -> SystemTime {
         SystemTime {
             t: c::FILETIME {
                 dwLowDateTime: intervals as u32,
@@ -82,13 +81,11 @@ impl SystemTime {
         }
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    const fn intervals(&self) -> i64 {
+    fn intervals(&self) -> i64 {
         (self.t.dwLowDateTime as i64) | ((self.t.dwHighDateTime as i64) << 32)
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
         let me = self.intervals();
         let other = other.intervals();
         if me >= other {
@@ -98,14 +95,12 @@ impl SystemTime {
         }
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
         let intervals = self.intervals().checked_add(checked_dur2intervals(other)?)?;
         Some(SystemTime::from_intervals(intervals))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
         let intervals = self.intervals().checked_sub(checked_dur2intervals(other)?)?;
         Some(SystemTime::from_intervals(intervals))
     }
@@ -155,18 +150,15 @@ impl Hash for SystemTime {
     }
 }
 
-#[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-const fn checked_dur2intervals(dur: &Duration) -> Option<i64> {
-    // FIXME: const TryInto
-    let secs = dur
-        .as_secs()
+fn checked_dur2intervals(dur: &Duration) -> Option<i64> {
+    dur.as_secs()
         .checked_mul(INTERVALS_PER_SEC)?
-        .checked_add(dur.subsec_nanos() as u64 / 100)?;
-    if secs <= i64::MAX as u64 { Some(secs.cast_signed()) } else { None }
+        .checked_add(dur.subsec_nanos() as u64 / 100)?
+        .try_into()
+        .ok()
 }
 
-#[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-const fn intervals2dur(intervals: u64) -> Duration {
+fn intervals2dur(intervals: u64) -> Duration {
     Duration::new(intervals / INTERVALS_PER_SEC, ((intervals % INTERVALS_PER_SEC) * 100) as u32)
 }
 
@@ -232,7 +224,7 @@ mod perf_counter {
 }
 
 /// A timer you can wait on.
-pub(super) struct WaitableTimer {
+pub(crate) struct WaitableTimer {
     handle: c::HANDLE,
 }
 impl WaitableTimer {
diff --git a/library/std/src/sys/pal/xous/mod.rs b/library/std/src/sys/pal/xous/mod.rs
index 042c4ff862f..e673157e0eb 100644
--- a/library/std/src/sys/pal/xous/mod.rs
+++ b/library/std/src/sys/pal/xous/mod.rs
@@ -5,7 +5,6 @@ use crate::os::xous::ffi::exit;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-pub mod thread;
 pub mod time;
 
 #[path = "../unsupported/common.rs"]
diff --git a/library/std/src/sys/pal/xous/time.rs b/library/std/src/sys/pal/xous/time.rs
index d737416436e..ae8be81c0b7 100644
--- a/library/std/src/sys/pal/xous/time.rs
+++ b/library/std/src/sys/pal/xous/time.rs
@@ -43,22 +43,15 @@ impl SystemTime {
         SystemTime { 0: Duration::from_millis((upper as u64) << 32 | lower as u64) }
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
-        // FIXME: ok_or_else with const closures
-        match self.0.checked_sub(other.0) {
-            Some(duration) => Ok(duration),
-            None => Err(other.0 - self.0),
-        }
+    pub fn sub_time(&self, other: &SystemTime) -> Result<Duration, Duration> {
+        self.0.checked_sub(other.0).ok_or_else(|| other.0 - self.0)
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_add_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_add(*other)?))
     }
 
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
+    pub fn checked_sub_duration(&self, other: &Duration) -> Option<SystemTime> {
         Some(SystemTime(self.0.checked_sub(*other)?))
     }
 }
diff --git a/library/std/src/sys/pal/zkvm/mod.rs b/library/std/src/sys/pal/zkvm/mod.rs
index e1efa240685..9069c8d12fa 100644
--- a/library/std/src/sys/pal/zkvm/mod.rs
+++ b/library/std/src/sys/pal/zkvm/mod.rs
@@ -14,8 +14,6 @@ pub mod abi;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
-#[path = "../unsupported/thread.rs"]
-pub mod thread;
 #[path = "../unsupported/time.rs"]
 pub mod time;
 
diff --git a/library/std/src/sys/platform_version/darwin/core_foundation.rs b/library/std/src/sys/platform_version/darwin/core_foundation.rs
new file mode 100644
index 00000000000..1e0d15fcf66
--- /dev/null
+++ b/library/std/src/sys/platform_version/darwin/core_foundation.rs
@@ -0,0 +1,180 @@
+//! Minimal utilities for interfacing with a dynamically loaded CoreFoundation.
+#![allow(non_snake_case, non_upper_case_globals)]
+use super::root_relative;
+use crate::ffi::{CStr, c_char, c_void};
+use crate::ptr::null_mut;
+use crate::sys::common::small_c_string::run_path_with_cstr;
+
+// MacTypes.h
+pub(super) type Boolean = u8;
+// CoreFoundation/CFBase.h
+pub(super) type CFTypeID = usize;
+pub(super) type CFOptionFlags = usize;
+pub(super) type CFIndex = isize;
+pub(super) type CFTypeRef = *mut c_void;
+pub(super) type CFAllocatorRef = CFTypeRef;
+pub(super) const kCFAllocatorDefault: CFAllocatorRef = null_mut();
+// CoreFoundation/CFError.h
+pub(super) type CFErrorRef = CFTypeRef;
+// CoreFoundation/CFData.h
+pub(super) type CFDataRef = CFTypeRef;
+// CoreFoundation/CFPropertyList.h
+pub(super) const kCFPropertyListImmutable: CFOptionFlags = 0;
+pub(super) type CFPropertyListFormat = CFIndex;
+pub(super) type CFPropertyListRef = CFTypeRef;
+// CoreFoundation/CFString.h
+pub(super) type CFStringRef = CFTypeRef;
+pub(super) type CFStringEncoding = u32;
+pub(super) const kCFStringEncodingUTF8: CFStringEncoding = 0x08000100;
+// CoreFoundation/CFDictionary.h
+pub(super) type CFDictionaryRef = CFTypeRef;
+
+/// An open handle to the dynamically loaded CoreFoundation framework.
+///
+/// This is `dlopen`ed, and later `dlclose`d. This is done to try to avoid
+/// "leaking" the CoreFoundation symbols to the rest of the user's binary if
+/// they decided to not link CoreFoundation themselves.
+///
+/// It is also faster to look up symbols directly via this handle than with
+/// `RTLD_DEFAULT`.
+pub(super) struct CFHandle(*mut c_void);
+
+macro_rules! dlsym_fn {
+    (
+        unsafe fn $name:ident($($param:ident: $param_ty:ty),* $(,)?) $(-> $ret:ty)?;
+    ) => {
+        pub(super) unsafe fn $name(&self, $($param: $param_ty),*) $(-> $ret)? {
+            let ptr = unsafe {
+                libc::dlsym(
+                    self.0,
+                    concat!(stringify!($name), '\0').as_bytes().as_ptr().cast(),
+                )
+            };
+            if ptr.is_null() {
+                let err = unsafe { CStr::from_ptr(libc::dlerror()) };
+                panic!("could not find function {}: {err:?}", stringify!($name));
+            }
+
+            // SAFETY: Just checked that the symbol isn't NULL, and macro invoker verifies that
+            // the signature is correct.
+            let fnptr = unsafe {
+                crate::mem::transmute::<
+                    *mut c_void,
+                    unsafe extern "C" fn($($param_ty),*) $(-> $ret)?,
+                >(ptr)
+            };
+
+            // SAFETY: Upheld by caller.
+            unsafe { fnptr($($param),*) }
+        }
+    };
+}
+
+impl CFHandle {
+    /// Link to the CoreFoundation dylib, and look up symbols from that.
+    pub(super) fn new() -> Self {
+        // We explicitly use non-versioned path here, to allow this to work on older iOS devices.
+        let cf_path =
+            root_relative("/System/Library/Frameworks/CoreFoundation.framework/CoreFoundation");
+
+        let handle = run_path_with_cstr(&cf_path, &|path| unsafe {
+            Ok(libc::dlopen(path.as_ptr(), libc::RTLD_LAZY | libc::RTLD_LOCAL))
+        })
+        .expect("failed allocating string");
+
+        if handle.is_null() {
+            let err = unsafe { CStr::from_ptr(libc::dlerror()) };
+            panic!("could not open CoreFoundation.framework: {err:?}");
+        }
+
+        Self(handle)
+    }
+
+    pub(super) fn kCFAllocatorNull(&self) -> CFAllocatorRef {
+        // Available: in all CF versions.
+        let static_ptr = unsafe { libc::dlsym(self.0, c"kCFAllocatorNull".as_ptr()) };
+        if static_ptr.is_null() {
+            let err = unsafe { CStr::from_ptr(libc::dlerror()) };
+            panic!("could not find kCFAllocatorNull: {err:?}");
+        }
+        unsafe { *static_ptr.cast() }
+    }
+
+    // CoreFoundation/CFBase.h
+    dlsym_fn!(
+        // Available: in all CF versions.
+        unsafe fn CFRelease(cf: CFTypeRef);
+    );
+    dlsym_fn!(
+        // Available: in all CF versions.
+        unsafe fn CFGetTypeID(cf: CFTypeRef) -> CFTypeID;
+    );
+
+    // CoreFoundation/CFData.h
+    dlsym_fn!(
+        // Available: in all CF versions.
+        unsafe fn CFDataCreateWithBytesNoCopy(
+            allocator: CFAllocatorRef,
+            bytes: *const u8,
+            length: CFIndex,
+            bytes_deallocator: CFAllocatorRef,
+        ) -> CFDataRef;
+    );
+
+    // CoreFoundation/CFPropertyList.h
+    dlsym_fn!(
+        // Available: since macOS 10.6.
+        unsafe fn CFPropertyListCreateWithData(
+            allocator: CFAllocatorRef,
+            data: CFDataRef,
+            options: CFOptionFlags,
+            format: *mut CFPropertyListFormat,
+            error: *mut CFErrorRef,
+        ) -> CFPropertyListRef;
+    );
+
+    // CoreFoundation/CFString.h
+    dlsym_fn!(
+        // Available: in all CF versions.
+        unsafe fn CFStringGetTypeID() -> CFTypeID;
+    );
+    dlsym_fn!(
+        // Available: in all CF versions.
+        unsafe fn CFStringCreateWithCStringNoCopy(
+            alloc: CFAllocatorRef,
+            c_str: *const c_char,
+            encoding: CFStringEncoding,
+            contents_deallocator: CFAllocatorRef,
+        ) -> CFStringRef;
+    );
+    dlsym_fn!(
+        // Available: in all CF versions.
+        unsafe fn CFStringGetCString(
+            the_string: CFStringRef,
+            buffer: *mut c_char,
+            buffer_size: CFIndex,
+            encoding: CFStringEncoding,
+        ) -> Boolean;
+    );
+
+    // CoreFoundation/CFDictionary.h
+    dlsym_fn!(
+        // Available: in all CF versions.
+        unsafe fn CFDictionaryGetTypeID() -> CFTypeID;
+    );
+    dlsym_fn!(
+        // Available: in all CF versions.
+        unsafe fn CFDictionaryGetValue(
+            the_dict: CFDictionaryRef,
+            key: *const c_void,
+        ) -> *const c_void;
+    );
+}
+
+impl Drop for CFHandle {
+    fn drop(&mut self) {
+        // Ignore errors when closing. This is also what `libloading` does:
+        // https://docs.rs/libloading/0.8.6/src/libloading/os/unix/mod.rs.html#374
+        let _ = unsafe { libc::dlclose(self.0) };
+    }
+}
diff --git a/library/std/src/sys/platform_version/darwin/mod.rs b/library/std/src/sys/platform_version/darwin/mod.rs
new file mode 100644
index 00000000000..06b97fcdef4
--- /dev/null
+++ b/library/std/src/sys/platform_version/darwin/mod.rs
@@ -0,0 +1,351 @@
+use self::core_foundation::{
+    CFDictionaryRef, CFHandle, CFIndex, CFStringRef, CFTypeRef, kCFAllocatorDefault,
+    kCFPropertyListImmutable, kCFStringEncodingUTF8,
+};
+use crate::borrow::Cow;
+use crate::bstr::ByteStr;
+use crate::ffi::{CStr, c_char};
+use crate::num::{NonZero, ParseIntError};
+use crate::path::{Path, PathBuf};
+use crate::ptr::null_mut;
+use crate::sync::atomic::{AtomicU32, Ordering};
+use crate::{env, fs};
+
+mod core_foundation;
+mod public_extern;
+#[cfg(test)]
+mod tests;
+
+/// The version of the operating system.
+///
+/// We use a packed u32 here to allow for fast comparisons and to match Mach-O's `LC_BUILD_VERSION`.
+type OSVersion = u32;
+
+/// Combine parts of a version into an [`OSVersion`].
+///
+/// The size of the parts are inherently limited by Mach-O's `LC_BUILD_VERSION`.
+#[inline]
+const fn pack_os_version(major: u16, minor: u8, patch: u8) -> OSVersion {
+    let (major, minor, patch) = (major as u32, minor as u32, patch as u32);
+    (major << 16) | (minor << 8) | patch
+}
+
+/// [`pack_os_version`], but takes `i32` and saturates.
+///
+/// Instead of using e.g. `major as u16`, which truncates.
+#[inline]
+fn pack_i32_os_version(major: i32, minor: i32, patch: i32) -> OSVersion {
+    let major: u16 = major.try_into().unwrap_or(u16::MAX);
+    let minor: u8 = minor.try_into().unwrap_or(u8::MAX);
+    let patch: u8 = patch.try_into().unwrap_or(u8::MAX);
+    pack_os_version(major, minor, patch)
+}
+
+/// Get the current OS version, packed according to [`pack_os_version`].
+///
+/// # Semantics
+///
+/// The reported version on macOS might be 10.16 if the SDK version of the binary is less than 11.0.
+/// This is a workaround that Apple implemented to handle applications that assumed that macOS
+/// versions would always start with "10", see:
+/// <https://github.com/apple-oss-distributions/xnu/blob/xnu-11215.81.4/libsyscall/wrappers/system-version-compat.c>
+///
+/// It _is_ possible to get the real version regardless of the SDK version of the binary, this is
+/// what Zig does:
+/// <https://github.com/ziglang/zig/blob/0.13.0/lib/std/zig/system/darwin/macos.zig>
+///
+/// We choose to not do that, and instead follow Apple's behaviour here, and return 10.16 when
+/// compiled with an older SDK; the user should instead upgrade their tooling.
+///
+/// NOTE: `rustc` currently doesn't set the right SDK version when linking with ld64, so this will
+/// have the wrong behaviour with `-Clinker=ld` on x86_64. But that's a `rustc` bug:
+/// <https://github.com/rust-lang/rust/issues/129432>
+#[inline]
+fn current_version() -> OSVersion {
+    // Cache the lookup for performance.
+    //
+    // 0.0.0 is never going to be a valid version ("vtool" reports "n/a" on 0 versions), so we use
+    // that as our sentinel value.
+    static CURRENT_VERSION: AtomicU32 = AtomicU32::new(0);
+
+    // We use relaxed atomics instead of e.g. a `Once`, it doesn't matter if multiple threads end up
+    // racing to read or write the version, `lookup_version` should be idempotent and always return
+    // the same value.
+    //
+    // `compiler-rt` uses `dispatch_once`, but that's overkill for the reasons above.
+    let version = CURRENT_VERSION.load(Ordering::Relaxed);
+    if version == 0 {
+        let version = lookup_version().get();
+        CURRENT_VERSION.store(version, Ordering::Relaxed);
+        version
+    } else {
+        version
+    }
+}
+
+/// Look up the os version.
+///
+/// # Aborts
+///
+/// Aborts if reading or parsing the version fails (or if the system was out of memory).
+///
+/// We deliberately choose to abort, as having this silently return an invalid OS version would be
+/// impossible for a user to debug.
+// The lookup is costly and should be on the cold path because of the cache in `current_version`.
+#[cold]
+// Micro-optimization: We use `extern "C"` to abort on panic, allowing `current_version` (inlined)
+// to be free of unwind handling. Aborting is required for `__isPlatformVersionAtLeast` anyhow.
+extern "C" fn lookup_version() -> NonZero<OSVersion> {
+    // Try to read from `sysctl` first (faster), but if that fails, fall back to reading the
+    // property list (this is roughly what `_availability_version_check` does internally).
+    let version = version_from_sysctl().unwrap_or_else(version_from_plist);
+
+    // Use `NonZero` to try to make it clearer to the optimizer that this will never return 0.
+    NonZero::new(version).expect("version cannot be 0.0.0")
+}
+
+/// Read the version from `kern.osproductversion` or `kern.iossupportversion`.
+///
+/// This is faster than `version_from_plist`, since it doesn't need to invoke `dlsym`.
+fn version_from_sysctl() -> Option<OSVersion> {
+    // This won't work in the simulator, as `kern.osproductversion` returns the host macOS version,
+    // and `kern.iossupportversion` returns the host macOS' iOSSupportVersion (while you can run
+    // simulators with many different iOS versions).
+    if cfg!(target_abi = "sim") {
+        // Fall back to `version_from_plist` on these targets.
+        return None;
+    }
+
+    let sysctl_version = |name: &CStr| {
+        let mut buf: [u8; 32] = [0; 32];
+        let mut size = buf.len();
+        let ptr = buf.as_mut_ptr().cast();
+        let ret = unsafe { libc::sysctlbyname(name.as_ptr(), ptr, &mut size, null_mut(), 0) };
+        if ret != 0 {
+            // This sysctl is not available.
+            return None;
+        }
+        let buf = &buf[..(size - 1)];
+
+        if buf.is_empty() {
+            // The buffer may be empty when using `kern.iossupportversion` on an actual iOS device,
+            // or on visionOS when running under "Designed for iPad".
+            //
+            // In that case, fall back to `kern.osproductversion`.
+            return None;
+        }
+
+        Some(parse_os_version(buf).unwrap_or_else(|err| {
+            panic!("failed parsing version from sysctl ({}): {err}", ByteStr::new(buf))
+        }))
+    };
+
+    // When `target_os = "ios"`, we may be in many different states:
+    // - Native iOS device.
+    // - iOS Simulator.
+    // - Mac Catalyst.
+    // - Mac + "Designed for iPad".
+    // - Native visionOS device + "Designed for iPad".
+    // - visionOS simulator + "Designed for iPad".
+    //
+    // Of these, only native, Mac Catalyst and simulators can be differentiated at compile-time
+    // (with `target_abi = ""`, `target_abi = "macabi"` and `target_abi = "sim"` respectively).
+    //
+    // That is, "Designed for iPad" will act as iOS at compile-time, but the `ProductVersion` will
+    // still be the host macOS or visionOS version.
+    //
+    // Furthermore, we can't even reliably differentiate between these at runtime, since
+    // `dyld_get_active_platform` isn't publicly available.
+    //
+    // Fortunately, we won't need to know any of that; we can simply attempt to get the
+    // `iOSSupportVersion` (which may be set on native iOS too, but then it will be set to the host
+    // iOS version), and if that fails, fall back to the `ProductVersion`.
+    if cfg!(target_os = "ios") {
+        // https://github.com/apple-oss-distributions/xnu/blob/xnu-11215.81.4/bsd/kern/kern_sysctl.c#L2077-L2100
+        if let Some(ios_support_version) = sysctl_version(c"kern.iossupportversion") {
+            return Some(ios_support_version);
+        }
+
+        // On Mac Catalyst, if we failed looking up `iOSSupportVersion`, we don't want to
+        // accidentally fall back to `ProductVersion`.
+        if cfg!(target_abi = "macabi") {
+            return None;
+        }
+    }
+
+    // Introduced in macOS 10.13.4.
+    // https://github.com/apple-oss-distributions/xnu/blob/xnu-11215.81.4/bsd/kern/kern_sysctl.c#L2015-L2051
+    sysctl_version(c"kern.osproductversion")
+}
+
+/// Look up the current OS version(s) from `/System/Library/CoreServices/SystemVersion.plist`.
+///
+/// More specifically, from the `ProductVersion` and `iOSSupportVersion` keys, and from
+/// `$IPHONE_SIMULATOR_ROOT/System/Library/CoreServices/SystemVersion.plist` on the simulator.
+///
+/// This file was introduced in macOS 10.3, which is well below the minimum supported version by
+/// `rustc`, which is (at the time of writing) macOS 10.12.
+///
+/// # Implementation
+///
+/// We do roughly the same thing in here as `compiler-rt`, and dynamically look up CoreFoundation
+/// utilities for parsing PLists (to avoid having to re-implement that in here, as pulling in a full
+/// PList parser into `std` seems costly).
+///
+/// If this is found to be undesirable, we _could_ possibly hack it by parsing the PList manually
+/// (it seems to use the plain-text "xml1" encoding/format in all versions), but that seems brittle.
+fn version_from_plist() -> OSVersion {
+    // Read `SystemVersion.plist`. Always present on Apple platforms, reading it cannot fail.
+    let path = root_relative("/System/Library/CoreServices/SystemVersion.plist");
+    let plist_buffer = fs::read(&path).unwrap_or_else(|e| panic!("failed reading {path:?}: {e}"));
+    let cf_handle = CFHandle::new();
+    parse_version_from_plist(&cf_handle, &plist_buffer)
+}
+
+/// Parse OS version from the given PList.
+///
+/// Split out from [`version_from_plist`] to allow for testing.
+fn parse_version_from_plist(cf_handle: &CFHandle, plist_buffer: &[u8]) -> OSVersion {
+    let plist_data = unsafe {
+        cf_handle.CFDataCreateWithBytesNoCopy(
+            kCFAllocatorDefault,
+            plist_buffer.as_ptr(),
+            plist_buffer.len() as CFIndex,
+            cf_handle.kCFAllocatorNull(),
+        )
+    };
+    assert!(!plist_data.is_null(), "failed creating CFData");
+    let _plist_data_release = Deferred(|| unsafe { cf_handle.CFRelease(plist_data) });
+
+    let plist = unsafe {
+        cf_handle.CFPropertyListCreateWithData(
+            kCFAllocatorDefault,
+            plist_data,
+            kCFPropertyListImmutable,
+            null_mut(), // Don't care about the format of the PList.
+            null_mut(), // Don't care about the error data.
+        )
+    };
+    assert!(!plist.is_null(), "failed reading PList in SystemVersion.plist");
+    let _plist_release = Deferred(|| unsafe { cf_handle.CFRelease(plist) });
+
+    assert_eq!(
+        unsafe { cf_handle.CFGetTypeID(plist) },
+        unsafe { cf_handle.CFDictionaryGetTypeID() },
+        "SystemVersion.plist did not contain a dictionary at the top level"
+    );
+    let plist: CFDictionaryRef = plist.cast();
+
+    // Same logic as in `version_from_sysctl`.
+    if cfg!(target_os = "ios") {
+        if let Some(ios_support_version) =
+            unsafe { string_version_key(cf_handle, plist, c"iOSSupportVersion") }
+        {
+            return ios_support_version;
+        }
+
+        // Force Mac Catalyst to use iOSSupportVersion (do not fall back to ProductVersion).
+        if cfg!(target_abi = "macabi") {
+            panic!("expected iOSSupportVersion in SystemVersion.plist");
+        }
+    }
+
+    // On all other platforms, we can find the OS version by simply looking at `ProductVersion`.
+    unsafe { string_version_key(cf_handle, plist, c"ProductVersion") }
+        .expect("expected ProductVersion in SystemVersion.plist")
+}
+
+/// Look up a string key in a CFDictionary, and convert it to an [`OSVersion`].
+unsafe fn string_version_key(
+    cf_handle: &CFHandle,
+    plist: CFDictionaryRef,
+    lookup_key: &CStr,
+) -> Option<OSVersion> {
+    let cf_lookup_key = unsafe {
+        cf_handle.CFStringCreateWithCStringNoCopy(
+            kCFAllocatorDefault,
+            lookup_key.as_ptr(),
+            kCFStringEncodingUTF8,
+            cf_handle.kCFAllocatorNull(),
+        )
+    };
+    assert!(!cf_lookup_key.is_null(), "failed creating CFString");
+    let _lookup_key_release = Deferred(|| unsafe { cf_handle.CFRelease(cf_lookup_key) });
+
+    let value: CFTypeRef =
+        unsafe { cf_handle.CFDictionaryGetValue(plist, cf_lookup_key) }.cast_mut();
+    // `CFDictionaryGetValue` is a "getter", so we should not release,
+    // the value is held alive internally by the CFDictionary, see:
+    // https://developer.apple.com/library/archive/documentation/Cocoa/Conceptual/MemoryMgmt/Articles/mmPractical.html#//apple_ref/doc/uid/TP40004447-SW12
+    if value.is_null() {
+        return None;
+    }
+
+    assert_eq!(
+        unsafe { cf_handle.CFGetTypeID(value) },
+        unsafe { cf_handle.CFStringGetTypeID() },
+        "key in SystemVersion.plist must be a string"
+    );
+    let value: CFStringRef = value.cast();
+
+    let mut version_str = [0u8; 32];
+    let ret = unsafe {
+        cf_handle.CFStringGetCString(
+            value,
+            version_str.as_mut_ptr().cast::<c_char>(),
+            version_str.len() as CFIndex,
+            kCFStringEncodingUTF8,
+        )
+    };
+    assert_ne!(ret, 0, "failed getting string from CFString");
+
+    let version_str =
+        CStr::from_bytes_until_nul(&version_str).expect("failed converting CFString to CStr");
+
+    Some(parse_os_version(version_str.to_bytes()).unwrap_or_else(|err| {
+        panic!(
+            "failed parsing version from PList ({}): {err}",
+            ByteStr::new(version_str.to_bytes())
+        )
+    }))
+}
+
+/// Parse an OS version from a bytestring like b"10.1" or b"14.3.7".
+fn parse_os_version(version: &[u8]) -> Result<OSVersion, ParseIntError> {
+    if let Some((major, minor)) = version.split_once(|&b| b == b'.') {
+        let major = u16::from_ascii(major)?;
+        if let Some((minor, patch)) = minor.split_once(|&b| b == b'.') {
+            let minor = u8::from_ascii(minor)?;
+            let patch = u8::from_ascii(patch)?;
+            Ok(pack_os_version(major, minor, patch))
+        } else {
+            let minor = u8::from_ascii(minor)?;
+            Ok(pack_os_version(major, minor, 0))
+        }
+    } else {
+        let major = u16::from_ascii(version)?;
+        Ok(pack_os_version(major, 0, 0))
+    }
+}
+
+/// Get a path relative to the root directory in which all files for the current env are located.
+fn root_relative(path: &str) -> Cow<'_, Path> {
+    if cfg!(target_abi = "sim") {
+        let mut root = PathBuf::from(env::var_os("IPHONE_SIMULATOR_ROOT").expect(
+            "environment variable `IPHONE_SIMULATOR_ROOT` must be set when executing under simulator",
+        ));
+        // Convert absolute path to relative path, to make the `.push` work as expected.
+        root.push(Path::new(path).strip_prefix("/").unwrap());
+        root.into()
+    } else {
+        Path::new(path).into()
+    }
+}
+
+struct Deferred<F: FnMut()>(F);
+
+impl<F: FnMut()> Drop for Deferred<F> {
+    fn drop(&mut self) {
+        (self.0)();
+    }
+}
diff --git a/library/std/src/sys/platform_version/darwin/public_extern.rs b/library/std/src/sys/platform_version/darwin/public_extern.rs
new file mode 100644
index 00000000000..c0848d94798
--- /dev/null
+++ b/library/std/src/sys/platform_version/darwin/public_extern.rs
@@ -0,0 +1,156 @@
+//! # Runtime version checking ABI for other compilers.
+//!
+//! The symbols in this file are useful for us to expose to allow linking code written in the
+//! following languages when using their version checking functionality:
+//! - Clang's `__builtin_available` macro.
+//! - Objective-C's `@available`.
+//! - Swift's `#available`,
+//!
+//! Without Rust exposing these symbols, the user would encounter a linker error when linking to
+//! C/Objective-C/Swift libraries using these features.
+//!
+//! The presence of these symbols is mostly considered a quality-of-implementation detail, and
+//! should not be relied upon to be available. The intended effect is that linking with code built
+//! with Clang's `__builtin_available` (or similar) will continue to work. For example, we may
+//! decide to remove `__isOSVersionAtLeast` if support for Clang 11 (Xcode 11) is dropped.
+//!
+//! ## Background
+//!
+//! The original discussion of this feature can be found at:
+//! - <https://lists.llvm.org/pipermail/cfe-dev/2016-July/049851.html>
+//! - <https://reviews.llvm.org/D27827>
+//! - <https://reviews.llvm.org/D30136>
+//!
+//! And the upstream implementation of these can be found in `compiler-rt`:
+//! <https://github.com/llvm/llvm-project/blob/llvmorg-20.1.0/compiler-rt/lib/builtins/os_version_check.c>
+//!
+//! Ideally, these symbols should probably have been a part of Apple's `libSystem.dylib`, both
+//! because their implementation is quite complex, using allocation, environment variables, file
+//! access and dynamic library loading (and emitting all of this into every binary).
+//!
+//! The reason why Apple chose to not do that originally is lost to the sands of time, but a good
+//! reason would be that implementing it as part of `compiler-rt` allowed them to back-deploy this
+//! to older OSes immediately.
+//!
+//! In Rust's case, while we may provide a feature similar to `@available` in the future, we will
+//! probably do so as a macro exposed by `std` (and not as a compiler builtin). So implementing this
+//! in `std` makes sense, since then we can implement it using `std` utilities, and we can avoid
+//! having `compiler-builtins` depend on `libSystem.dylib`.
+//!
+//! This does mean that users that attempt to link C/Objective-C/Swift code _and_ use `#![no_std]`
+//! in all their crates may get a linker error because these symbols are missing. Using `no_std` is
+//! quite uncommon on Apple systems though, so it's probably fine to not support this use-case.
+//!
+//! The workaround would be to link `libclang_rt.osx.a` or otherwise use Clang's `compiler-rt`.
+//!
+//! See also discussion in <https://github.com/rust-lang/compiler-builtins/pull/794>.
+//!
+//! ## Implementation details
+//!
+//! NOTE: Since macOS 10.15, `libSystem.dylib` _has_ actually provided the undocumented
+//! `_availability_version_check` via `libxpc` for doing the version lookup (zippered, which is why
+//! it requires a platform parameter to differentiate between macOS and Mac Catalyst), though its
+//! usage may be a bit dangerous, see:
+//! - <https://reviews.llvm.org/D150397>
+//! - <https://github.com/llvm/llvm-project/issues/64227>
+//!
+//! Besides, we'd need to implement the version lookup via PList to support older versions anyhow,
+//! so we might as well use that everywhere (since it can also be optimized more after inlining).
+
+#![allow(non_snake_case)]
+
+use super::{current_version, pack_i32_os_version};
+
+/// Whether the current platform's OS version is higher than or equal to the given version.
+///
+/// The first argument is the _base_ Mach-O platform (i.e. `PLATFORM_MACOS`, `PLATFORM_IOS`, etc.,
+/// but not `PLATFORM_IOSSIMULATOR` or `PLATFORM_MACCATALYST`) of the invoking binary.
+///
+/// Arguments are specified statically by Clang. Inlining with LTO should allow the versions to be
+/// combined into a single `u32`, which should make comparisons faster, and should make the
+/// `BASE_TARGET_PLATFORM` check a no-op.
+//
+// SAFETY: The signature is the same as what Clang expects, and we export weakly to allow linking
+// both this and `libclang_rt.*.a`, similar to how `compiler-builtins` does it:
+// https://github.com/rust-lang/compiler-builtins/blob/0.1.113/src/macros.rs#L494
+//
+// NOTE: This symbol has a workaround in the compiler's symbol mangling to avoid mangling it, while
+// still not exposing it from non-cdylib (like `#[no_mangle]` would).
+#[rustc_std_internal_symbol]
+// NOTE: Making this a weak symbol might not be entirely the right solution for this, `compiler_rt`
+// doesn't do that, it instead makes the symbol have "hidden" visibility. But since this is placed
+// in `libstd`, which might be used as a dylib, we cannot do the same here.
+#[linkage = "weak"]
+// extern "C" is correct, Clang assumes the function cannot unwind:
+// https://github.com/llvm/llvm-project/blob/llvmorg-20.1.0/clang/lib/CodeGen/CGObjC.cpp#L3980
+//
+// If an error happens in this, we instead abort the process.
+pub(super) extern "C" fn __isPlatformVersionAtLeast(
+    platform: i32,
+    major: i32,
+    minor: i32,
+    subminor: i32,
+) -> i32 {
+    let version = pack_i32_os_version(major, minor, subminor);
+
+    // Mac Catalyst is a technology that allows macOS to run in a different "mode" that closely
+    // resembles iOS (and has iOS libraries like UIKit available).
+    //
+    // (Apple has added a "Designed for iPad" mode later on that allows running iOS apps
+    // natively, but we don't need to think too much about those, since they link to
+    // iOS-specific system binaries as well).
+    //
+    // To support Mac Catalyst, Apple added the concept of a "zippered" binary, which is a single
+    // binary that can be run on both macOS and Mac Catalyst (has two `LC_BUILD_VERSION` Mach-O
+    // commands, one set to `PLATFORM_MACOS` and one to `PLATFORM_MACCATALYST`).
+    //
+    // Most system libraries are zippered, which allows re-use across macOS and Mac Catalyst.
+    // This includes the `libclang_rt.osx.a` shipped with Xcode! This means that `compiler-rt`
+    // can't statically know whether it's compiled for macOS or Mac Catalyst, and thus this new
+    // API (which replaces `__isOSVersionAtLeast`) is needed.
+    //
+    // In short:
+    //      normal  binary calls  normal  compiler-rt --> `__isOSVersionAtLeast` was enough
+    //      normal  binary calls zippered compiler-rt --> `__isPlatformVersionAtLeast` required
+    //     zippered binary calls zippered compiler-rt --> `__isPlatformOrVariantPlatformVersionAtLeast` called
+
+    // FIXME(madsmtm): `rustc` doesn't support zippered binaries yet, see rust-lang/rust#131216.
+    // But once it does, we need the pre-compiled `std` shipped with rustup to be zippered, and thus
+    // we also need to handle the `platform` difference here:
+    //
+    // if cfg!(target_os = "macos") && platform == 2 /* PLATFORM_IOS */ && cfg!(zippered) {
+    //     return (version.to_u32() <= current_ios_version()) as i32;
+    // }
+    //
+    // `__isPlatformOrVariantPlatformVersionAtLeast` would also need to be implemented.
+
+    // The base Mach-O platform for the current target.
+    const BASE_TARGET_PLATFORM: i32 = if cfg!(target_os = "macos") {
+        1 // PLATFORM_MACOS
+    } else if cfg!(target_os = "ios") {
+        2 // PLATFORM_IOS
+    } else if cfg!(target_os = "tvos") {
+        3 // PLATFORM_TVOS
+    } else if cfg!(target_os = "watchos") {
+        4 // PLATFORM_WATCHOS
+    } else if cfg!(target_os = "visionos") {
+        11 // PLATFORM_VISIONOS
+    } else {
+        0 // PLATFORM_UNKNOWN
+    };
+    debug_assert_eq!(
+        platform, BASE_TARGET_PLATFORM,
+        "invalid platform provided to __isPlatformVersionAtLeast",
+    );
+
+    (version <= current_version()) as i32
+}
+
+/// Old entry point for availability. Used when compiling with older Clang versions.
+// SAFETY: Same as for `__isPlatformVersionAtLeast`.
+#[rustc_std_internal_symbol]
+#[linkage = "weak"]
+pub(super) extern "C" fn __isOSVersionAtLeast(major: i32, minor: i32, subminor: i32) -> i32 {
+    let version = pack_i32_os_version(major, minor, subminor);
+    (version <= current_version()) as i32
+}
diff --git a/library/std/src/sys/platform_version/darwin/tests.rs b/library/std/src/sys/platform_version/darwin/tests.rs
new file mode 100644
index 00000000000..17b2cc18ec0
--- /dev/null
+++ b/library/std/src/sys/platform_version/darwin/tests.rs
@@ -0,0 +1,379 @@
+use super::public_extern::*;
+use super::*;
+use crate::process::Command;
+
+#[test]
+fn test_general_available() {
+    // Lowest version always available.
+    assert_eq!(__isOSVersionAtLeast(0, 0, 0), 1);
+    // This high version never available.
+    assert_eq!(__isOSVersionAtLeast(9999, 99, 99), 0);
+}
+
+#[test]
+fn test_saturating() {
+    // Higher version than supported by OSVersion -> make sure we saturate.
+    assert_eq!(__isOSVersionAtLeast(0x10000, 0, 0), 0);
+}
+
+#[test]
+#[cfg_attr(not(target_os = "macos"), ignore = "`sw_vers` is only available on host macOS")]
+fn compare_against_sw_vers() {
+    let sw_vers = Command::new("sw_vers").arg("-productVersion").output().unwrap().stdout;
+    let sw_vers = String::from_utf8(sw_vers).unwrap();
+    let mut sw_vers = sw_vers.trim().split('.');
+
+    let major: i32 = sw_vers.next().unwrap().parse().unwrap();
+    let minor: i32 = sw_vers.next().unwrap_or("0").parse().unwrap();
+    let subminor: i32 = sw_vers.next().unwrap_or("0").parse().unwrap();
+    assert_eq!(sw_vers.count(), 0);
+
+    // Test directly against the lookup
+    assert_eq!(lookup_version().get(), pack_os_version(major as _, minor as _, subminor as _));
+
+    // Current version is available
+    assert_eq!(__isOSVersionAtLeast(major, minor, subminor), 1);
+
+    // One lower is available
+    assert_eq!(__isOSVersionAtLeast(major, minor, (subminor as u32).saturating_sub(1) as i32), 1);
+    assert_eq!(__isOSVersionAtLeast(major, (minor as u32).saturating_sub(1) as i32, subminor), 1);
+    assert_eq!(__isOSVersionAtLeast((major as u32).saturating_sub(1) as i32, minor, subminor), 1);
+
+    // One higher isn't available
+    assert_eq!(__isOSVersionAtLeast(major, minor, subminor + 1), 0);
+    assert_eq!(__isOSVersionAtLeast(major, minor + 1, subminor), 0);
+    assert_eq!(__isOSVersionAtLeast(major + 1, minor, subminor), 0);
+}
+
+#[test]
+fn sysctl_same_as_in_plist() {
+    if let Some(version) = version_from_sysctl() {
+        assert_eq!(version, version_from_plist());
+    }
+}
+
+#[test]
+fn lookup_idempotent() {
+    let version = lookup_version();
+    for _ in 0..10 {
+        assert_eq!(version, lookup_version());
+    }
+}
+
+/// Test parsing a bunch of different PLists found in the wild, to ensure that
+/// if we decide to parse it without CoreFoundation in the future, that it
+/// would continue to work, even on older platforms.
+#[test]
+fn parse_plist() {
+    #[track_caller]
+    fn check(
+        (major, minor, patch): (u16, u8, u8),
+        ios_version: Option<(u16, u8, u8)>,
+        plist: &str,
+    ) {
+        let expected = if cfg!(target_os = "ios") {
+            if let Some((ios_major, ios_minor, ios_patch)) = ios_version {
+                pack_os_version(ios_major, ios_minor, ios_patch)
+            } else if cfg!(target_abi = "macabi") {
+                // Skip checking iOS version on Mac Catalyst.
+                return;
+            } else {
+                // iOS version will be parsed from ProductVersion
+                pack_os_version(major, minor, patch)
+            }
+        } else {
+            pack_os_version(major, minor, patch)
+        };
+        let cf_handle = CFHandle::new();
+        assert_eq!(expected, parse_version_from_plist(&cf_handle, plist.as_bytes()));
+    }
+
+    // macOS 10.3.0
+    let plist = r#"<?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0">
+        <dict>
+            <key>ProductBuildVersion</key>
+            <string>7B85</string>
+            <key>ProductCopyright</key>
+            <string>Apple Computer, Inc. 1983-2003</string>
+            <key>ProductName</key>
+            <string>Mac OS X</string>
+            <key>ProductUserVisibleVersion</key>
+            <string>10.3</string>
+            <key>ProductVersion</key>
+            <string>10.3</string>
+        </dict>
+        </plist>
+    "#;
+    check((10, 3, 0), None, plist);
+
+    // macOS 10.7.5
+    let plist = r#"<?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0">
+        <dict>
+            <key>ProductBuildVersion</key>
+            <string>11G63</string>
+            <key>ProductCopyright</key>
+            <string>1983-2012 Apple Inc.</string>
+            <key>ProductName</key>
+            <string>Mac OS X</string>
+            <key>ProductUserVisibleVersion</key>
+            <string>10.7.5</string>
+            <key>ProductVersion</key>
+            <string>10.7.5</string>
+        </dict>
+        </plist>
+    "#;
+    check((10, 7, 5), None, plist);
+
+    // macOS 14.7.4
+    let plist = r#"<?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0">
+        <dict>
+            <key>BuildID</key>
+            <string>6A558D8A-E2EA-11EF-A1D3-6222CAA672A8</string>
+            <key>ProductBuildVersion</key>
+            <string>23H420</string>
+            <key>ProductCopyright</key>
+            <string>1983-2025 Apple Inc.</string>
+            <key>ProductName</key>
+            <string>macOS</string>
+            <key>ProductUserVisibleVersion</key>
+            <string>14.7.4</string>
+            <key>ProductVersion</key>
+            <string>14.7.4</string>
+            <key>iOSSupportVersion</key>
+            <string>17.7</string>
+        </dict>
+        </plist>
+    "#;
+    check((14, 7, 4), Some((17, 7, 0)), plist);
+
+    // SystemVersionCompat.plist on macOS 14.7.4
+    let plist = r#"<?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0">
+        <dict>
+            <key>BuildID</key>
+            <string>6A558D8A-E2EA-11EF-A1D3-6222CAA672A8</string>
+            <key>ProductBuildVersion</key>
+            <string>23H420</string>
+            <key>ProductCopyright</key>
+            <string>1983-2025 Apple Inc.</string>
+            <key>ProductName</key>
+            <string>Mac OS X</string>
+            <key>ProductUserVisibleVersion</key>
+            <string>10.16</string>
+            <key>ProductVersion</key>
+            <string>10.16</string>
+            <key>iOSSupportVersion</key>
+            <string>17.7</string>
+        </dict>
+        </plist>
+    "#;
+    check((10, 16, 0), Some((17, 7, 0)), plist);
+
+    // macOS 15.4 Beta 24E5238a
+    let plist = r#"<?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0">
+        <dict>
+            <key>BuildID</key>
+            <string>67A50F62-00DA-11F0-BDB6-F99BB8310D2A</string>
+            <key>ProductBuildVersion</key>
+            <string>24E5238a</string>
+            <key>ProductCopyright</key>
+            <string>1983-2025 Apple Inc.</string>
+            <key>ProductName</key>
+            <string>macOS</string>
+            <key>ProductUserVisibleVersion</key>
+            <string>15.4</string>
+            <key>ProductVersion</key>
+            <string>15.4</string>
+            <key>iOSSupportVersion</key>
+            <string>18.4</string>
+        </dict>
+        </plist>
+    "#;
+    check((15, 4, 0), Some((18, 4, 0)), plist);
+
+    // iOS Simulator 17.5
+    let plist = r#"<?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0">
+        <dict>
+            <key>BuildID</key>
+            <string>210B8A2C-09C3-11EF-9DB8-273A64AEFA1C</string>
+            <key>ProductBuildVersion</key>
+            <string>21F79</string>
+            <key>ProductCopyright</key>
+            <string>1983-2024 Apple Inc.</string>
+            <key>ProductName</key>
+            <string>iPhone OS</string>
+            <key>ProductVersion</key>
+            <string>17.5</string>
+        </dict>
+        </plist>
+    "#;
+    check((17, 5, 0), None, plist);
+
+    // visionOS Simulator 2.3
+    let plist = r#"<?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0">
+        <dict>
+            <key>BuildID</key>
+            <string>57CEFDE6-D079-11EF-837C-8B8C7961D0AC</string>
+            <key>ProductBuildVersion</key>
+            <string>22N895</string>
+            <key>ProductCopyright</key>
+            <string>1983-2025 Apple Inc.</string>
+            <key>ProductName</key>
+            <string>xrOS</string>
+            <key>ProductVersion</key>
+            <string>2.3</string>
+            <key>SystemImageID</key>
+            <string>D332C7F1-08DF-4DD9-8122-94EF39A1FB92</string>
+            <key>iOSSupportVersion</key>
+            <string>18.3</string>
+        </dict>
+        </plist>
+    "#;
+    check((2, 3, 0), Some((18, 3, 0)), plist);
+
+    // tvOS Simulator 18.2
+    let plist = r#"<?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0">
+        <dict>
+            <key>BuildID</key>
+            <string>617587B0-B059-11EF-BE70-4380EDE44645</string>
+            <key>ProductBuildVersion</key>
+            <string>22K154</string>
+            <key>ProductCopyright</key>
+            <string>1983-2024 Apple Inc.</string>
+            <key>ProductName</key>
+            <string>Apple TVOS</string>
+            <key>ProductVersion</key>
+            <string>18.2</string>
+            <key>SystemImageID</key>
+            <string>8BB5A425-33F0-4821-9F93-40E7ED92F4E0</string>
+        </dict>
+        </plist>
+    "#;
+    check((18, 2, 0), None, plist);
+
+    // watchOS Simulator 11.2
+    let plist = r#"<?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0">
+        <dict>
+            <key>BuildID</key>
+            <string>BAAE2D54-B122-11EF-BF78-C6C6836B724A</string>
+            <key>ProductBuildVersion</key>
+            <string>22S99</string>
+            <key>ProductCopyright</key>
+            <string>1983-2024 Apple Inc.</string>
+            <key>ProductName</key>
+            <string>Watch OS</string>
+            <key>ProductVersion</key>
+            <string>11.2</string>
+            <key>SystemImageID</key>
+            <string>79F773E2-2041-43B4-98EE-FAE52402AE95</string>
+        </dict>
+        </plist>
+    "#;
+    check((11, 2, 0), None, plist);
+
+    // iOS 9.3.6
+    let plist = r#"<?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0">
+        <dict>
+            <key>ProductBuildVersion</key>
+            <string>13G37</string>
+            <key>ProductCopyright</key>
+            <string>1983-2019 Apple Inc.</string>
+            <key>ProductName</key>
+            <string>iPhone OS</string>
+            <key>ProductVersion</key>
+            <string>9.3.6</string>
+        </dict>
+        </plist>
+    "#;
+    check((9, 3, 6), None, plist);
+}
+
+#[test]
+#[should_panic = "SystemVersion.plist did not contain a dictionary at the top level"]
+fn invalid_plist() {
+    let cf_handle = CFHandle::new();
+    let _ = parse_version_from_plist(&cf_handle, b"INVALID");
+}
+
+#[test]
+#[cfg_attr(
+    target_abi = "macabi",
+    should_panic = "expected iOSSupportVersion in SystemVersion.plist"
+)]
+#[cfg_attr(
+    not(target_abi = "macabi"),
+    should_panic = "expected ProductVersion in SystemVersion.plist"
+)]
+fn empty_plist() {
+    let plist = r#"<?xml version="1.0" encoding="UTF-8"?>
+        <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
+        <plist version="1.0">
+        <dict>
+        </dict>
+        </plist>
+    "#;
+    let cf_handle = CFHandle::new();
+    let _ = parse_version_from_plist(&cf_handle, plist.as_bytes());
+}
+
+#[test]
+fn parse_version() {
+    #[track_caller]
+    fn check(major: u16, minor: u8, patch: u8, version: &str) {
+        assert_eq!(
+            pack_os_version(major, minor, patch),
+            parse_os_version(version.as_bytes()).unwrap()
+        )
+    }
+
+    check(0, 0, 0, "0");
+    check(0, 0, 0, "0.0.0");
+    check(1, 0, 0, "1");
+    check(1, 2, 0, "1.2");
+    check(1, 2, 3, "1.2.3");
+    check(9999, 99, 99, "9999.99.99");
+
+    // Check leading zeroes
+    check(10, 0, 0, "010");
+    check(10, 20, 0, "010.020");
+    check(10, 20, 30, "010.020.030");
+    check(10000, 100, 100, "000010000.00100.00100");
+
+    // Too many parts
+    assert!(parse_os_version(b"1.2.3.4").is_err());
+
+    // Empty
+    assert!(parse_os_version(b"").is_err());
+
+    // Invalid digit
+    assert!(parse_os_version(b"A.B").is_err());
+
+    // Missing digits
+    assert!(parse_os_version(b".").is_err());
+    assert!(parse_os_version(b".1").is_err());
+    assert!(parse_os_version(b"1.").is_err());
+
+    // Too large
+    assert!(parse_os_version(b"100000").is_err());
+    assert!(parse_os_version(b"1.1000").is_err());
+    assert!(parse_os_version(b"1.1.1000").is_err());
+}
diff --git a/library/std/src/sys/platform_version/mod.rs b/library/std/src/sys/platform_version/mod.rs
new file mode 100644
index 00000000000..88896c97ea3
--- /dev/null
+++ b/library/std/src/sys/platform_version/mod.rs
@@ -0,0 +1,13 @@
+//! Runtime lookup of operating system / platform version.
+//!
+//! Related to [RFC 3750](https://github.com/rust-lang/rfcs/pull/3750), which
+//! does version detection at compile-time.
+//!
+//! See also the `os_info` crate.
+
+#[cfg(target_vendor = "apple")]
+mod darwin;
+
+// In the future, we could expand this module with:
+// - `RtlGetVersion` on Windows.
+// - `__system_property_get` on Android.
diff --git a/library/std/src/sys/process/mod.rs b/library/std/src/sys/process/mod.rs
index 9ef5496e57a..a1ed0cd2cdd 100644
--- a/library/std/src/sys/process/mod.rs
+++ b/library/std/src/sys/process/mod.rs
@@ -24,7 +24,7 @@ mod env;
 
 pub use env::CommandEnvs;
 pub use imp::{
-    Command, CommandArgs, EnvKey, ExitCode, ExitStatus, ExitStatusError, Process, Stdio, StdioPipes,
+    Command, CommandArgs, EnvKey, ExitCode, ExitStatus, ExitStatusError, Process, Stdio,
 };
 
 #[cfg(any(
diff --git a/library/std/src/sys/process/uefi.rs b/library/std/src/sys/process/uefi.rs
index 4864c586988..11c8b682bb9 100644
--- a/library/std/src/sys/process/uefi.rs
+++ b/library/std/src/sys/process/uefi.rs
@@ -6,6 +6,7 @@ pub use crate::ffi::OsString as EnvKey;
 use crate::ffi::{OsStr, OsString};
 use crate::num::{NonZero, NonZeroI32};
 use crate::path::Path;
+use crate::process::StdioPipes;
 use crate::sys::fs::File;
 use crate::sys::pal::helpers;
 use crate::sys::pal::os::error_string;
@@ -27,14 +28,6 @@ pub struct Command {
     env: CommandEnv,
 }
 
-// passed back to std::process with the pipes connected to the child, if any
-// were requested
-pub struct StdioPipes {
-    pub stdin: Option<AnonPipe>,
-    pub stdout: Option<AnonPipe>,
-    pub stderr: Option<AnonPipe>,
-}
-
 #[derive(Copy, Clone, Debug)]
 pub enum Stdio {
     Inherit,
diff --git a/library/std/src/sys/process/unix/common.rs b/library/std/src/sys/process/unix/common.rs
index ea45b08e90a..1d5909e99ba 100644
--- a/library/std/src/sys/process/unix/common.rs
+++ b/library/std/src/sys/process/unix/common.rs
@@ -9,6 +9,7 @@ use crate::collections::BTreeMap;
 use crate::ffi::{CStr, CString, OsStr, OsString};
 use crate::os::unix::prelude::*;
 use crate::path::Path;
+use crate::process::StdioPipes;
 use crate::sys::fd::FileDesc;
 use crate::sys::fs::File;
 #[cfg(not(target_os = "fuchsia"))]
@@ -104,14 +105,6 @@ pub struct Command {
     setsid: bool,
 }
 
-// passed back to std::process with the pipes connected to the child, if any
-// were requested
-pub struct StdioPipes {
-    pub stdin: Option<AnonPipe>,
-    pub stdout: Option<AnonPipe>,
-    pub stderr: Option<AnonPipe>,
-}
-
 // passed to do_exec() with configuration of what the child stdio should look
 // like
 #[cfg_attr(target_os = "vita", allow(dead_code))]
diff --git a/library/std/src/sys/process/unix/fuchsia.rs b/library/std/src/sys/process/unix/fuchsia.rs
index d71be510b6a..3fae5ec1468 100644
--- a/library/std/src/sys/process/unix/fuchsia.rs
+++ b/library/std/src/sys/process/unix/fuchsia.rs
@@ -2,6 +2,7 @@ use libc::{c_int, size_t};
 
 use super::common::*;
 use crate::num::NonZero;
+use crate::process::StdioPipes;
 use crate::sys::pal::fuchsia::*;
 use crate::{fmt, io, mem, ptr};
 
diff --git a/library/std/src/sys/process/unix/mod.rs b/library/std/src/sys/process/unix/mod.rs
index b4cf060fba9..cda1bf74f1c 100644
--- a/library/std/src/sys/process/unix/mod.rs
+++ b/library/std/src/sys/process/unix/mod.rs
@@ -23,5 +23,5 @@ cfg_select! {
 
 pub use imp::{ExitStatus, ExitStatusError, Process};
 
-pub use self::common::{Command, CommandArgs, ExitCode, Stdio, StdioPipes};
+pub use self::common::{Command, CommandArgs, ExitCode, Stdio};
 pub use crate::ffi::OsString as EnvKey;
diff --git a/library/std/src/sys/process/unix/unix.rs b/library/std/src/sys/process/unix/unix.rs
index 11d48878727..7d944f2f7ee 100644
--- a/library/std/src/sys/process/unix/unix.rs
+++ b/library/std/src/sys/process/unix/unix.rs
@@ -13,6 +13,7 @@ use libc::{gid_t, uid_t};
 use super::common::*;
 use crate::io::{self, Error, ErrorKind};
 use crate::num::NonZero;
+use crate::process::StdioPipes;
 use crate::sys::cvt;
 #[cfg(target_os = "linux")]
 use crate::sys::pal::linux::pidfd::PidFd;
diff --git a/library/std/src/sys/process/unix/unix/tests.rs b/library/std/src/sys/process/unix/unix/tests.rs
index f4d6ac6b4e3..663ba61f966 100644
--- a/library/std/src/sys/process/unix/unix/tests.rs
+++ b/library/std/src/sys/process/unix/unix/tests.rs
@@ -51,6 +51,7 @@ fn exitstatus_display_tests() {
 
 #[test]
 #[cfg_attr(target_os = "emscripten", ignore)]
+#[cfg_attr(any(target_os = "tvos", target_os = "watchos"), ignore = "fork is prohibited")]
 fn test_command_fork_no_unwind() {
     let got = catch_unwind(|| {
         let mut c = Command::new("echo");
diff --git a/library/std/src/sys/process/unix/unsupported.rs b/library/std/src/sys/process/unix/unsupported.rs
index 87403cd50f8..9bda394f246 100644
--- a/library/std/src/sys/process/unix/unsupported.rs
+++ b/library/std/src/sys/process/unix/unsupported.rs
@@ -3,6 +3,7 @@ use libc::{c_int, pid_t};
 use super::common::*;
 use crate::io;
 use crate::num::NonZero;
+use crate::process::StdioPipes;
 use crate::sys::pal::unsupported::*;
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/library/std/src/sys/process/unix/vxworks.rs b/library/std/src/sys/process/unix/vxworks.rs
index 2275cbb946a..346ca6d74c9 100644
--- a/library/std/src/sys/process/unix/vxworks.rs
+++ b/library/std/src/sys/process/unix/vxworks.rs
@@ -4,8 +4,8 @@ use libc::{self, RTP_ID, c_char, c_int};
 use super::common::*;
 use crate::io::{self, ErrorKind};
 use crate::num::NonZero;
-use crate::sys::cvt;
-use crate::sys::pal::thread;
+use crate::process::StdioPipes;
+use crate::sys::{cvt, thread};
 use crate::{fmt, sys};
 
 ////////////////////////////////////////////////////////////////////////////////
diff --git a/library/std/src/sys/process/unsupported.rs b/library/std/src/sys/process/unsupported.rs
index 469922c78ac..636465b68e5 100644
--- a/library/std/src/sys/process/unsupported.rs
+++ b/library/std/src/sys/process/unsupported.rs
@@ -3,6 +3,7 @@ pub use crate::ffi::OsString as EnvKey;
 use crate::ffi::{OsStr, OsString};
 use crate::num::NonZero;
 use crate::path::Path;
+use crate::process::StdioPipes;
 use crate::sys::fs::File;
 use crate::sys::pipe::AnonPipe;
 use crate::sys::unsupported;
@@ -23,14 +24,6 @@ pub struct Command {
     stderr: Option<Stdio>,
 }
 
-// passed back to std::process with the pipes connected to the child, if any
-// were requested
-pub struct StdioPipes {
-    pub stdin: Option<AnonPipe>,
-    pub stdout: Option<AnonPipe>,
-    pub stderr: Option<AnonPipe>,
-}
-
 #[derive(Debug)]
 pub enum Stdio {
     Inherit,
diff --git a/library/std/src/sys/process/windows.rs b/library/std/src/sys/process/windows.rs
index f9e15b82475..1f2001bdc20 100644
--- a/library/std/src/sys/process/windows.rs
+++ b/library/std/src/sys/process/windows.rs
@@ -15,6 +15,7 @@ use crate::os::windows::ffi::{OsStrExt, OsStringExt};
 use crate::os::windows::io::{AsHandle, AsRawHandle, BorrowedHandle, FromRawHandle, IntoRawHandle};
 use crate::os::windows::process::ProcThreadAttributeList;
 use crate::path::{Path, PathBuf};
+use crate::process::StdioPipes;
 use crate::sync::Mutex;
 use crate::sys::args::{self, Arg};
 use crate::sys::c::{self, EXIT_FAILURE, EXIT_SUCCESS};
@@ -169,12 +170,6 @@ pub enum Stdio {
     Handle(Handle),
 }
 
-pub struct StdioPipes {
-    pub stdin: Option<AnonPipe>,
-    pub stdout: Option<AnonPipe>,
-    pub stderr: Option<AnonPipe>,
-}
-
 impl Command {
     pub fn new(program: &OsStr) -> Command {
         Command {
diff --git a/library/std/src/sys/stdio/mod.rs b/library/std/src/sys/stdio/mod.rs
index 314f226f07b..7436e4d9de4 100644
--- a/library/std/src/sys/stdio/mod.rs
+++ b/library/std/src/sys/stdio/mod.rs
@@ -29,9 +29,13 @@ cfg_select! {
         mod uefi;
         pub use uefi::*;
     }
-    target_os = "wasi" => {
-        mod wasi;
-        pub use wasi::*;
+    all(target_os = "wasi", target_env = "p1") => {
+        mod wasip1;
+        pub use wasip1::*;
+    }
+    all(target_os = "wasi", target_env = "p2") => {
+        mod wasip2;
+        pub use wasip2::*;
     }
     target_os = "xous" => {
         mod xous;
diff --git a/library/std/src/sys/stdio/wasi.rs b/library/std/src/sys/stdio/wasip1.rs
index b70efd026f9..b70efd026f9 100644
--- a/library/std/src/sys/stdio/wasi.rs
+++ b/library/std/src/sys/stdio/wasip1.rs
diff --git a/library/std/src/sys/stdio/wasip2.rs b/library/std/src/sys/stdio/wasip2.rs
new file mode 100644
index 00000000000..1fcb49a083d
--- /dev/null
+++ b/library/std/src/sys/stdio/wasip2.rs
@@ -0,0 +1,120 @@
+use wasip2::cli;
+use wasip2::io::streams::{Error, InputStream, OutputStream, StreamError};
+
+use crate::io::{self, BorrowedBuf, BorrowedCursor};
+
+pub struct Stdin(Option<InputStream>);
+pub struct Stdout(Option<OutputStream>);
+pub struct Stderr(Option<OutputStream>);
+
+fn error_to_io(err: Error) -> io::Error {
+    // There exists a function in `wasi:filesystem` to optionally acquire an
+    // error code from an error, but the streams in use in this module are
+    // exclusively used with stdio meaning that a filesystem error is not
+    // possible here.
+    //
+    // In lieu of an error code, which WASIp2 does not specify, this instead
+    // carries along the `to_debug_string` implementation that the host
+    // supplies. If this becomes too expensive in the future this could also
+    // become `io::Error::from_raw_os_error(libc::EIO)` or similar.
+    io::Error::new(io::ErrorKind::Other, err.to_debug_string())
+}
+
+impl Stdin {
+    pub const fn new() -> Stdin {
+        Stdin(None)
+    }
+
+    fn stream(&mut self) -> &InputStream {
+        self.0.get_or_insert_with(cli::stdin::get_stdin)
+    }
+}
+
+impl io::Read for Stdin {
+    fn read(&mut self, data: &mut [u8]) -> io::Result<usize> {
+        let mut buf = BorrowedBuf::from(data);
+        self.read_buf(buf.unfilled())?;
+        Ok(buf.len())
+    }
+
+    fn read_buf(&mut self, mut buf: BorrowedCursor<'_>) -> io::Result<()> {
+        match self.stream().blocking_read(u64::try_from(buf.capacity()).unwrap()) {
+            Ok(result) => {
+                buf.append(&result);
+                Ok(())
+            }
+            Err(StreamError::Closed) => Ok(()),
+            Err(StreamError::LastOperationFailed(e)) => Err(error_to_io(e)),
+        }
+    }
+}
+
+impl Stdout {
+    pub const fn new() -> Stdout {
+        Stdout(None)
+    }
+
+    fn stream(&mut self) -> &OutputStream {
+        self.0.get_or_insert_with(cli::stdout::get_stdout)
+    }
+}
+
+fn write(stream: &OutputStream, buf: &[u8]) -> io::Result<usize> {
+    // WASIp2's `blocking_write_and_flush` function is defined as accepting no
+    // more than 4096 bytes. Larger writes can be issued by manually using
+    // `check_write`, `write`, and `blocking_flush`, but for now just go ahead
+    // and use `blocking_write_and_flush` and report a short write and let a
+    // higher level loop over the result.
+    const MAX: usize = 4096;
+    let buf = &buf[..buf.len().min(MAX)];
+    match stream.blocking_write_and_flush(buf) {
+        Ok(()) => Ok(buf.len()),
+        Err(StreamError::Closed) => Ok(0),
+        Err(StreamError::LastOperationFailed(e)) => Err(error_to_io(e)),
+    }
+}
+
+impl io::Write for Stdout {
+    fn write(&mut self, data: &[u8]) -> io::Result<usize> {
+        write(self.stream(), data)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        // Note that `OutputStream` has a `flush` function but for stdio all
+        // writes are accompanied with a flush which means that this flush
+        // doesn't need to do anything.
+        Ok(())
+    }
+}
+
+impl Stderr {
+    pub const fn new() -> Stderr {
+        Stderr(None)
+    }
+
+    fn stream(&mut self) -> &OutputStream {
+        self.0.get_or_insert_with(cli::stderr::get_stderr)
+    }
+}
+
+impl io::Write for Stderr {
+    fn write(&mut self, data: &[u8]) -> io::Result<usize> {
+        write(self.stream(), data)
+    }
+
+    fn flush(&mut self) -> io::Result<()> {
+        // See `Stdout::flush` for why this is a noop.
+        Ok(())
+    }
+}
+
+pub const STDIN_BUF_SIZE: usize = crate::sys::io::DEFAULT_BUF_SIZE;
+
+pub fn is_ebadf(_err: &io::Error) -> bool {
+    // WASIp2 stdio streams are always available so ebadf never shows up.
+    false
+}
+
+pub fn panic_output() -> Option<impl io::Write> {
+    Some(Stderr::new())
+}
diff --git a/library/std/src/sys/sync/once/queue.rs b/library/std/src/sys/sync/once/queue.rs
index 49e15d65f25..17d99cdb385 100644
--- a/library/std/src/sys/sync/once/queue.rs
+++ b/library/std/src/sys/sync/once/queue.rs
@@ -276,7 +276,9 @@ fn wait(
             // If the managing thread happens to signal and unpark us before we
             // can park ourselves, the result could be this thread never gets
             // unparked. Luckily `park` comes with the guarantee that if it got
-            // an `unpark` just before on an unparked thread it does not park.
+            // an `unpark` just before on an unparked thread it does not park. Crucially, we know
+            // the `unpark` must have happened between the `compare_exchange_weak` above and here,
+            // and there's no other `park` in that code that could steal our token.
             // SAFETY: we retrieved this handle on the current thread above.
             unsafe { node.thread.park() }
         }
diff --git a/library/std/src/sys/pal/hermit/thread.rs b/library/std/src/sys/thread/hermit.rs
index cc4734b6819..4d9f3b114c2 100644
--- a/library/std/src/sys/pal/hermit/thread.rs
+++ b/library/std/src/sys/thread/hermit.rs
@@ -1,10 +1,5 @@
-#![allow(dead_code)]
-
-use super::hermit_abi;
-use crate::ffi::CStr;
-use crate::mem::ManuallyDrop;
 use crate::num::NonZero;
-use crate::time::{Duration, Instant};
+use crate::time::Duration;
 use crate::{io, ptr};
 
 pub type Tid = hermit_abi::Tid;
@@ -68,57 +63,30 @@ impl Thread {
         }
     }
 
-    #[inline]
-    pub fn yield_now() {
-        unsafe {
-            hermit_abi::yield_now();
-        }
-    }
-
-    #[inline]
-    pub fn set_name(_name: &CStr) {
-        // nope
-    }
-
-    #[inline]
-    pub fn sleep(dur: Duration) {
-        let micros = dur.as_micros() + if dur.subsec_nanos() % 1_000 > 0 { 1 } else { 0 };
-        let micros = u64::try_from(micros).unwrap_or(u64::MAX);
-
-        unsafe {
-            hermit_abi::usleep(micros);
-        }
-    }
-
-    pub fn sleep_until(deadline: Instant) {
-        let now = Instant::now();
-
-        if let Some(delay) = deadline.checked_duration_since(now) {
-            Self::sleep(delay);
-        }
-    }
-
     pub fn join(self) {
         unsafe {
             let _ = hermit_abi::join(self.tid);
         }
     }
+}
 
-    #[inline]
-    pub fn id(&self) -> Tid {
-        self.tid
-    }
-
-    #[inline]
-    pub fn into_id(self) -> Tid {
-        ManuallyDrop::new(self).tid
-    }
+pub fn available_parallelism() -> io::Result<NonZero<usize>> {
+    unsafe { Ok(NonZero::new_unchecked(hermit_abi::available_parallelism())) }
 }
 
-pub(crate) fn current_os_id() -> Option<u64> {
-    None
+#[inline]
+pub fn sleep(dur: Duration) {
+    let micros = dur.as_micros() + if dur.subsec_nanos() % 1_000 > 0 { 1 } else { 0 };
+    let micros = u64::try_from(micros).unwrap_or(u64::MAX);
+
+    unsafe {
+        hermit_abi::usleep(micros);
+    }
 }
 
-pub fn available_parallelism() -> io::Result<NonZero<usize>> {
-    unsafe { Ok(NonZero::new_unchecked(hermit_abi::available_parallelism())) }
+#[inline]
+pub fn yield_now() {
+    unsafe {
+        hermit_abi::yield_now();
+    }
 }
diff --git a/library/std/src/sys/thread/mod.rs b/library/std/src/sys/thread/mod.rs
new file mode 100644
index 00000000000..6bb7fc1a20e
--- /dev/null
+++ b/library/std/src/sys/thread/mod.rs
@@ -0,0 +1,152 @@
+cfg_select! {
+    target_os = "hermit" => {
+        mod hermit;
+        pub use hermit::{Thread, available_parallelism, sleep, yield_now, DEFAULT_MIN_STACK_SIZE};
+        #[expect(dead_code)]
+        mod unsupported;
+        pub use unsupported::{current_os_id, set_name};
+    }
+    all(target_vendor = "fortanix", target_env = "sgx") => {
+        mod sgx;
+        pub use sgx::{Thread, current_os_id, sleep, yield_now, DEFAULT_MIN_STACK_SIZE};
+
+        // SGX should protect in-enclave data from outside attackers, so there
+        // must not be any data leakage to the OS, particularly no 1-1 mapping
+        // between SGX thread names and OS thread names. Hence `set_name` is
+        // intentionally a no-op.
+        //
+        // Note that the internally visible SGX thread name is already provided
+        // by the platform-agnostic Rust thread code. This can be observed in
+        // the [`std::thread::tests::test_named_thread`] test, which succeeds
+        // as-is with the SGX target.
+        #[expect(dead_code)]
+        mod unsupported;
+        pub use unsupported::{available_parallelism, set_name};
+    }
+    target_os = "solid_asp3" => {
+        mod solid;
+        pub use solid::{Thread, sleep, yield_now, DEFAULT_MIN_STACK_SIZE};
+        #[expect(dead_code)]
+        mod unsupported;
+        pub use unsupported::{available_parallelism, current_os_id, set_name};
+    }
+    target_os = "teeos" => {
+        mod teeos;
+        pub use teeos::{Thread, sleep, yield_now, DEFAULT_MIN_STACK_SIZE};
+        #[expect(dead_code)]
+        mod unsupported;
+        pub use unsupported::{available_parallelism, current_os_id, set_name};
+    }
+    target_os = "uefi" => {
+        mod uefi;
+        pub use uefi::{available_parallelism, sleep};
+        #[expect(dead_code)]
+        mod unsupported;
+        pub use unsupported::{Thread, current_os_id, set_name, yield_now, DEFAULT_MIN_STACK_SIZE};
+    }
+    target_family = "unix" => {
+        mod unix;
+        pub use unix::{Thread, available_parallelism, current_os_id, sleep, yield_now, DEFAULT_MIN_STACK_SIZE};
+        #[cfg(not(any(
+            target_env = "newlib",
+            target_os = "l4re",
+            target_os = "emscripten",
+            target_os = "redox",
+            target_os = "hurd",
+            target_os = "aix",
+        )))]
+        pub use unix::set_name;
+        #[cfg(any(
+            target_os = "freebsd",
+            target_os = "netbsd",
+            target_os = "linux",
+            target_os = "android",
+            target_os = "solaris",
+            target_os = "illumos",
+            target_os = "dragonfly",
+            target_os = "hurd",
+            target_os = "fuchsia",
+            target_os = "vxworks",
+        ))]
+        pub use unix::sleep_until;
+        #[expect(dead_code)]
+        mod unsupported;
+        #[cfg(any(
+            target_env = "newlib",
+            target_os = "l4re",
+            target_os = "emscripten",
+            target_os = "redox",
+            target_os = "hurd",
+            target_os = "aix",
+        ))]
+        pub use unsupported::set_name;
+    }
+    all(target_os = "wasi", target_env = "p1") => {
+        mod wasip1;
+        pub use wasip1::{DEFAULT_MIN_STACK_SIZE, sleep, yield_now};
+        #[cfg(target_feature = "atomics")]
+        pub use wasip1::{Thread, available_parallelism};
+        #[expect(dead_code)]
+        mod unsupported;
+        pub use unsupported::{current_os_id, set_name};
+        #[cfg(not(target_feature = "atomics"))]
+        pub use unsupported::{Thread, available_parallelism};
+    }
+    all(target_os = "wasi", target_env = "p2") => {
+        mod wasip2;
+        pub use wasip2::{sleep, sleep_until};
+        #[expect(dead_code)]
+        mod unsupported;
+        // Note that unlike WASIp1 even if the wasm `atomics` feature is enabled
+        // there is no support for threads, not even experimentally, not even in
+        // wasi-libc. Thus this is unconditionally unsupported.
+        pub use unsupported::{Thread, available_parallelism, current_os_id, set_name, yield_now, DEFAULT_MIN_STACK_SIZE};
+    }
+    all(target_family = "wasm", target_feature = "atomics") => {
+        mod wasm;
+        pub use wasm::sleep;
+
+        #[expect(dead_code)]
+        mod unsupported;
+        pub use unsupported::{Thread, available_parallelism, current_os_id, set_name, yield_now, DEFAULT_MIN_STACK_SIZE};
+    }
+    target_os = "windows" => {
+        mod windows;
+        pub use windows::{Thread, available_parallelism, current_os_id, set_name, set_name_wide, sleep, yield_now, DEFAULT_MIN_STACK_SIZE};
+    }
+    target_os = "xous" => {
+        mod xous;
+        pub use xous::{Thread, available_parallelism, sleep, yield_now, DEFAULT_MIN_STACK_SIZE};
+
+        #[expect(dead_code)]
+        mod unsupported;
+        pub use unsupported::{current_os_id, set_name};
+    }
+    _ => {
+        mod unsupported;
+        pub use unsupported::{Thread, available_parallelism, current_os_id, set_name, sleep, yield_now, DEFAULT_MIN_STACK_SIZE};
+    }
+}
+
+#[cfg(not(any(
+    target_os = "freebsd",
+    target_os = "netbsd",
+    target_os = "linux",
+    target_os = "android",
+    target_os = "solaris",
+    target_os = "illumos",
+    target_os = "dragonfly",
+    target_os = "hurd",
+    target_os = "fuchsia",
+    target_os = "vxworks",
+    all(target_os = "wasi", target_env = "p2"),
+)))]
+pub fn sleep_until(deadline: crate::time::Instant) {
+    use crate::time::Instant;
+
+    let now = Instant::now();
+
+    if let Some(delay) = deadline.checked_duration_since(now) {
+        sleep(delay);
+    }
+}
diff --git a/library/std/src/sys/pal/sgx/thread.rs b/library/std/src/sys/thread/sgx.rs
index 1f613badcd7..f20ef7d86b9 100644
--- a/library/std/src/sys/pal/sgx/thread.rs
+++ b/library/std/src/sys/thread/sgx.rs
@@ -1,11 +1,8 @@
 #![cfg_attr(test, allow(dead_code))] // why is this necessary?
 
-use super::abi::{thread, usercalls};
-use super::unsupported;
-use crate::ffi::CStr;
 use crate::io;
-use crate::num::NonZero;
-use crate::time::{Duration, Instant};
+use crate::sys::pal::abi::{thread, usercalls};
+use crate::time::Duration;
 
 pub struct Thread(task_queue::JoinHandle);
 
@@ -108,51 +105,27 @@ impl Thread {
         Ok(Thread(handle))
     }
 
-    pub(super) fn entry() -> JoinNotifier {
+    pub(crate) fn entry() -> JoinNotifier {
         let mut pending_tasks = task_queue::lock();
         let task = rtunwrap!(Some, pending_tasks.pop());
         drop(pending_tasks); // make sure to not hold the task queue lock longer than necessary
         task.run()
     }
 
-    pub fn yield_now() {
-        let wait_error = rtunwrap!(Err, usercalls::wait(0, usercalls::raw::WAIT_NO));
-        rtassert!(wait_error.kind() == io::ErrorKind::WouldBlock);
-    }
-
-    /// SGX should protect in-enclave data from the outside (attacker),
-    /// so there should be no data leakage to the OS,
-    /// and therefore also no 1-1 mapping between SGX thread names and OS thread names.
-    ///
-    /// This is why the method is intentionally No-Op.
-    pub fn set_name(_name: &CStr) {
-        // Note that the internally visible SGX thread name is already provided
-        // by the platform-agnostic (target-agnostic) Rust thread code.
-        // This can be observed in the [`std::thread::tests::test_named_thread`] test,
-        // which succeeds as-is with the SGX target.
-    }
-
-    pub fn sleep(dur: Duration) {
-        usercalls::wait_timeout(0, dur, || true);
-    }
-
-    pub fn sleep_until(deadline: Instant) {
-        let now = Instant::now();
-
-        if let Some(delay) = deadline.checked_duration_since(now) {
-            Self::sleep(delay);
-        }
-    }
-
     pub fn join(self) {
         self.0.wait();
     }
 }
 
-pub(crate) fn current_os_id() -> Option<u64> {
+pub fn current_os_id() -> Option<u64> {
     Some(thread::current().addr().get() as u64)
 }
 
-pub fn available_parallelism() -> io::Result<NonZero<usize>> {
-    unsupported()
+pub fn sleep(dur: Duration) {
+    usercalls::wait_timeout(0, dur, || true);
+}
+
+pub fn yield_now() {
+    let wait_error = rtunwrap!(Err, usercalls::wait(0, usercalls::raw::WAIT_NO));
+    rtassert!(wait_error.kind() == io::ErrorKind::WouldBlock);
 }
diff --git a/library/std/src/sys/pal/itron/thread.rs b/library/std/src/sys/thread/solid.rs
index 4e14cb3cbca..46a84faa802 100644
--- a/library/std/src/sys/pal/itron/thread.rs
+++ b/library/std/src/sys/thread/solid.rs
@@ -1,16 +1,14 @@
 //! Thread implementation backed by μITRON tasks. Assumes `acre_tsk` and
 //! `exd_tsk` are available.
 
-use super::error::{ItronError, expect_success, expect_success_aborting};
-use super::time::dur2reltims;
-use super::{abi, task};
 use crate::cell::UnsafeCell;
-use crate::ffi::CStr;
 use crate::mem::ManuallyDrop;
-use crate::num::NonZero;
 use crate::ptr::NonNull;
 use crate::sync::atomic::{Atomic, AtomicUsize, Ordering};
-use crate::time::{Duration, Instant};
+use crate::sys::pal::itron::error::{ItronError, expect_success, expect_success_aborting};
+use crate::sys::pal::itron::time::dur2reltims;
+use crate::sys::pal::itron::{abi, task};
+use crate::time::Duration;
 use crate::{hint, io};
 
 pub struct Thread {
@@ -195,28 +193,6 @@ impl Thread {
         Ok(Self { p_inner, task: new_task })
     }
 
-    pub fn yield_now() {
-        expect_success(unsafe { abi::rot_rdq(abi::TPRI_SELF) }, &"rot_rdq");
-    }
-
-    pub fn set_name(_name: &CStr) {
-        // nope
-    }
-
-    pub fn sleep(dur: Duration) {
-        for timeout in dur2reltims(dur) {
-            expect_success(unsafe { abi::dly_tsk(timeout) }, &"dly_tsk");
-        }
-    }
-
-    pub fn sleep_until(deadline: Instant) {
-        let now = Instant::now();
-
-        if let Some(delay) = deadline.checked_duration_since(now) {
-            Self::sleep(delay);
-        }
-    }
-
     pub fn join(self) {
         // Safety: `ThreadInner` is alive at this point
         let inner = unsafe { self.p_inner.as_ref() };
@@ -361,10 +337,12 @@ unsafe fn terminate_and_delete_current_task() -> ! {
     unsafe { crate::hint::unreachable_unchecked() };
 }
 
-pub(crate) fn current_os_id() -> Option<u64> {
-    None
+pub fn yield_now() {
+    expect_success(unsafe { abi::rot_rdq(abi::TPRI_SELF) }, &"rot_rdq");
 }
 
-pub fn available_parallelism() -> io::Result<NonZero<usize>> {
-    super::unsupported()
+pub fn sleep(dur: Duration) {
+    for timeout in dur2reltims(dur) {
+        expect_success(unsafe { abi::dly_tsk(timeout) }, &"dly_tsk");
+    }
 }
diff --git a/library/std/src/sys/pal/teeos/thread.rs b/library/std/src/sys/thread/teeos.rs
index 1812d11e692..cad100395c9 100644
--- a/library/std/src/sys/pal/teeos/thread.rs
+++ b/library/std/src/sys/thread/teeos.rs
@@ -1,12 +1,18 @@
-use crate::ffi::CStr;
 use crate::mem::{self, ManuallyDrop};
-use crate::num::NonZero;
 use crate::sys::os;
-use crate::time::{Duration, Instant};
+use crate::time::Duration;
 use crate::{cmp, io, ptr};
 
 pub const DEFAULT_MIN_STACK_SIZE: usize = 8 * 1024;
 
+unsafe extern "C" {
+    safe fn TEE_Wait(timeout: u32) -> u32;
+}
+
+fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
+    libc::PTHREAD_STACK_MIN.try_into().expect("Infallible")
+}
+
 pub struct Thread {
     id: libc::pthread_t,
 }
@@ -16,10 +22,6 @@ pub struct Thread {
 unsafe impl Send for Thread {}
 unsafe impl Sync for Thread {}
 
-unsafe extern "C" {
-    pub fn TEE_Wait(timeout: u32) -> u32;
-}
-
 impl Thread {
     // unsafe: see thread::Builder::spawn_unchecked for safety requirements
     pub unsafe fn new(
@@ -74,7 +76,7 @@ impl Thread {
         } else {
             // The new thread will start running earliest after the next yield.
             // We add a yield here, so that the user does not have to.
-            Thread::yield_now();
+            yield_now();
             Ok(Thread { id: native })
         };
 
@@ -91,36 +93,6 @@ impl Thread {
         }
     }
 
-    pub fn yield_now() {
-        let ret = unsafe { libc::sched_yield() };
-        debug_assert_eq!(ret, 0);
-    }
-
-    /// This does not do anything on teeos
-    pub fn set_name(_name: &CStr) {
-        // Both pthread_setname_np and prctl are not available to the TA,
-        // so we can't implement this currently. If the need arises please
-        // contact the teeos rustzone team.
-    }
-
-    /// only main thread could wait for sometime in teeos
-    pub fn sleep(dur: Duration) {
-        let sleep_millis = dur.as_millis();
-        let final_sleep: u32 =
-            if sleep_millis >= u32::MAX as u128 { u32::MAX } else { sleep_millis as u32 };
-        unsafe {
-            let _ = TEE_Wait(final_sleep);
-        }
-    }
-
-    pub fn sleep_until(deadline: Instant) {
-        let now = Instant::now();
-
-        if let Some(delay) = deadline.checked_duration_since(now) {
-            Self::sleep(delay);
-        }
-    }
-
     /// must join, because no pthread_detach supported
     pub fn join(self) {
         let id = self.into_id();
@@ -128,10 +100,6 @@ impl Thread {
         assert!(ret == 0, "failed to join thread: {}", io::Error::from_raw_os_error(ret));
     }
 
-    pub fn id(&self) -> libc::pthread_t {
-        self.id
-    }
-
     pub fn into_id(self) -> libc::pthread_t {
         ManuallyDrop::new(self).id
     }
@@ -144,16 +112,15 @@ impl Drop for Thread {
     }
 }
 
-pub(crate) fn current_os_id() -> Option<u64> {
-    None
-}
-
-// Note: Both `sched_getaffinity` and `sysconf` are available but not functional on
-// teeos, so this function always returns an Error!
-pub fn available_parallelism() -> io::Result<NonZero<usize>> {
-    Err(io::Error::UNKNOWN_THREAD_COUNT)
+pub fn yield_now() {
+    let ret = unsafe { libc::sched_yield() };
+    debug_assert_eq!(ret, 0);
 }
 
-fn min_stack_size(_: *const libc::pthread_attr_t) -> usize {
-    libc::PTHREAD_STACK_MIN.try_into().expect("Infallible")
+/// only main thread could wait for sometime in teeos
+pub fn sleep(dur: Duration) {
+    let sleep_millis = dur.as_millis();
+    let final_sleep: u32 =
+        if sleep_millis >= u32::MAX as u128 { u32::MAX } else { sleep_millis as u32 };
+    TEE_Wait(final_sleep);
 }
diff --git a/library/std/src/sys/thread/uefi.rs b/library/std/src/sys/thread/uefi.rs
new file mode 100644
index 00000000000..94f67d7ace2
--- /dev/null
+++ b/library/std/src/sys/thread/uefi.rs
@@ -0,0 +1,25 @@
+use crate::io;
+use crate::num::NonZero;
+use crate::ptr::NonNull;
+use crate::time::Duration;
+
+pub fn available_parallelism() -> io::Result<NonZero<usize>> {
+    // UEFI is single threaded
+    Ok(NonZero::new(1).unwrap())
+}
+
+pub fn sleep(dur: Duration) {
+    let boot_services: NonNull<r_efi::efi::BootServices> =
+        crate::os::uefi::env::boot_services().expect("can't sleep").cast();
+    let mut dur_ms = dur.as_micros();
+    // ceil up to the nearest microsecond
+    if dur.subsec_nanos() % 1000 > 0 {
+        dur_ms += 1;
+    }
+
+    while dur_ms > 0 {
+        let ms = crate::cmp::min(dur_ms, usize::MAX as u128);
+        let _ = unsafe { ((*boot_services.as_ptr()).stall)(ms as usize) };
+        dur_ms -= ms;
+    }
+}
diff --git a/library/std/src/sys/pal/unix/thread.rs b/library/std/src/sys/thread/unix.rs
index 3389b8c0c8a..2d2c4f90212 100644
--- a/library/std/src/sys/pal/unix/thread.rs
+++ b/library/std/src/sys/thread/unix.rs
@@ -1,3 +1,11 @@
+#[cfg(not(any(
+    target_env = "newlib",
+    target_os = "l4re",
+    target_os = "emscripten",
+    target_os = "redox",
+    target_os = "hurd",
+    target_os = "aix",
+)))]
 use crate::ffi::CStr;
 use crate::mem::{self, ManuallyDrop};
 use crate::num::NonZero;
@@ -6,7 +14,7 @@ use crate::sys::weak::dlsym;
 #[cfg(any(target_os = "solaris", target_os = "illumos", target_os = "nto",))]
 use crate::sys::weak::weak;
 use crate::sys::{os, stack_overflow};
-use crate::time::{Duration, Instant};
+use crate::time::Duration;
 use crate::{cmp, io, ptr};
 #[cfg(not(any(
     target_os = "l4re",
@@ -121,273 +129,6 @@ impl Thread {
         }
     }
 
-    pub fn yield_now() {
-        let ret = unsafe { libc::sched_yield() };
-        debug_assert_eq!(ret, 0);
-    }
-
-    #[cfg(target_os = "android")]
-    pub fn set_name(name: &CStr) {
-        const PR_SET_NAME: libc::c_int = 15;
-        unsafe {
-            let res = libc::prctl(
-                PR_SET_NAME,
-                name.as_ptr(),
-                0 as libc::c_ulong,
-                0 as libc::c_ulong,
-                0 as libc::c_ulong,
-            );
-            // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
-            debug_assert_eq!(res, 0);
-        }
-    }
-
-    #[cfg(any(
-        target_os = "linux",
-        target_os = "freebsd",
-        target_os = "dragonfly",
-        target_os = "nuttx",
-        target_os = "cygwin"
-    ))]
-    pub fn set_name(name: &CStr) {
-        unsafe {
-            cfg_select! {
-                any(target_os = "linux", target_os = "cygwin") => {
-                    // Linux and Cygwin limits the allowed length of the name.
-                    const TASK_COMM_LEN: usize = 16;
-                    let name = truncate_cstr::<{ TASK_COMM_LEN }>(name);
-                }
-                _ => {
-                    // FreeBSD, DragonFly BSD and NuttX do not enforce length limits.
-                }
-            };
-            // Available since glibc 2.12, musl 1.1.16, and uClibc 1.0.20 for Linux,
-            // FreeBSD 12.2 and 13.0, and DragonFly BSD 6.0.
-            let res = libc::pthread_setname_np(libc::pthread_self(), name.as_ptr());
-            // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
-            debug_assert_eq!(res, 0);
-        }
-    }
-
-    #[cfg(target_os = "openbsd")]
-    pub fn set_name(name: &CStr) {
-        unsafe {
-            libc::pthread_set_name_np(libc::pthread_self(), name.as_ptr());
-        }
-    }
-
-    #[cfg(target_vendor = "apple")]
-    pub fn set_name(name: &CStr) {
-        unsafe {
-            let name = truncate_cstr::<{ libc::MAXTHREADNAMESIZE }>(name);
-            let res = libc::pthread_setname_np(name.as_ptr());
-            // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
-            debug_assert_eq!(res, 0);
-        }
-    }
-
-    #[cfg(target_os = "netbsd")]
-    pub fn set_name(name: &CStr) {
-        unsafe {
-            let res = libc::pthread_setname_np(
-                libc::pthread_self(),
-                c"%s".as_ptr(),
-                name.as_ptr() as *mut libc::c_void,
-            );
-            debug_assert_eq!(res, 0);
-        }
-    }
-
-    #[cfg(any(target_os = "solaris", target_os = "illumos", target_os = "nto"))]
-    pub fn set_name(name: &CStr) {
-        weak!(
-            fn pthread_setname_np(
-                thread: libc::pthread_t,
-                name: *const libc::c_char,
-            ) -> libc::c_int;
-        );
-
-        if let Some(f) = pthread_setname_np.get() {
-            #[cfg(target_os = "nto")]
-            const THREAD_NAME_MAX: usize = libc::_NTO_THREAD_NAME_MAX as usize;
-            #[cfg(any(target_os = "solaris", target_os = "illumos"))]
-            const THREAD_NAME_MAX: usize = 32;
-
-            let name = truncate_cstr::<{ THREAD_NAME_MAX }>(name);
-            let res = unsafe { f(libc::pthread_self(), name.as_ptr()) };
-            debug_assert_eq!(res, 0);
-        }
-    }
-
-    #[cfg(target_os = "fuchsia")]
-    pub fn set_name(name: &CStr) {
-        use super::fuchsia::*;
-        unsafe {
-            zx_object_set_property(
-                zx_thread_self(),
-                ZX_PROP_NAME,
-                name.as_ptr() as *const libc::c_void,
-                name.to_bytes().len(),
-            );
-        }
-    }
-
-    #[cfg(target_os = "haiku")]
-    pub fn set_name(name: &CStr) {
-        unsafe {
-            let thread_self = libc::find_thread(ptr::null_mut());
-            let res = libc::rename_thread(thread_self, name.as_ptr());
-            // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
-            debug_assert_eq!(res, libc::B_OK);
-        }
-    }
-
-    #[cfg(target_os = "vxworks")]
-    pub fn set_name(name: &CStr) {
-        let mut name = truncate_cstr::<{ (libc::VX_TASK_RENAME_LENGTH - 1) as usize }>(name);
-        let res = unsafe { libc::taskNameSet(libc::taskIdSelf(), name.as_mut_ptr()) };
-        debug_assert_eq!(res, libc::OK);
-    }
-
-    #[cfg(any(
-        target_env = "newlib",
-        target_os = "l4re",
-        target_os = "emscripten",
-        target_os = "redox",
-        target_os = "hurd",
-        target_os = "aix",
-    ))]
-    pub fn set_name(_name: &CStr) {
-        // Newlib and Emscripten have no way to set a thread name.
-    }
-
-    #[cfg(not(target_os = "espidf"))]
-    pub fn sleep(dur: Duration) {
-        let mut secs = dur.as_secs();
-        let mut nsecs = dur.subsec_nanos() as _;
-
-        // If we're awoken with a signal then the return value will be -1 and
-        // nanosleep will fill in `ts` with the remaining time.
-        unsafe {
-            while secs > 0 || nsecs > 0 {
-                let mut ts = libc::timespec {
-                    tv_sec: cmp::min(libc::time_t::MAX as u64, secs) as libc::time_t,
-                    tv_nsec: nsecs,
-                };
-                secs -= ts.tv_sec as u64;
-                let ts_ptr = &raw mut ts;
-                if libc::nanosleep(ts_ptr, ts_ptr) == -1 {
-                    assert_eq!(os::errno(), libc::EINTR);
-                    secs += ts.tv_sec as u64;
-                    nsecs = ts.tv_nsec;
-                } else {
-                    nsecs = 0;
-                }
-            }
-        }
-    }
-
-    #[cfg(target_os = "espidf")]
-    pub fn sleep(dur: Duration) {
-        // ESP-IDF does not have `nanosleep`, so we use `usleep` instead.
-        // As per the documentation of `usleep`, it is expected to support
-        // sleep times as big as at least up to 1 second.
-        //
-        // ESP-IDF does support almost up to `u32::MAX`, but due to a potential integer overflow in its
-        // `usleep` implementation
-        // (https://github.com/espressif/esp-idf/blob/d7ca8b94c852052e3bc33292287ef4dd62c9eeb1/components/newlib/time.c#L210),
-        // we limit the sleep time to the maximum one that would not cause the underlying `usleep` implementation to overflow
-        // (`portTICK_PERIOD_MS` can be anything between 1 to 1000, and is 10 by default).
-        const MAX_MICROS: u32 = u32::MAX - 1_000_000 - 1;
-
-        // Add any nanoseconds smaller than a microsecond as an extra microsecond
-        // so as to comply with the `std::thread::sleep` contract which mandates
-        // implementations to sleep for _at least_ the provided `dur`.
-        // We can't overflow `micros` as it is a `u128`, while `Duration` is a pair of
-        // (`u64` secs, `u32` nanos), where the nanos are strictly smaller than 1 second
-        // (i.e. < 1_000_000_000)
-        let mut micros = dur.as_micros() + if dur.subsec_nanos() % 1_000 > 0 { 1 } else { 0 };
-
-        while micros > 0 {
-            let st = if micros > MAX_MICROS as u128 { MAX_MICROS } else { micros as u32 };
-            unsafe {
-                libc::usleep(st);
-            }
-
-            micros -= st as u128;
-        }
-    }
-
-    // Any unix that has clock_nanosleep
-    // If this list changes update the MIRI chock_nanosleep shim
-    #[cfg(any(
-        target_os = "freebsd",
-        target_os = "netbsd",
-        target_os = "linux",
-        target_os = "android",
-        target_os = "solaris",
-        target_os = "illumos",
-        target_os = "dragonfly",
-        target_os = "hurd",
-        target_os = "fuchsia",
-        target_os = "vxworks",
-    ))]
-    pub fn sleep_until(deadline: Instant) {
-        let Some(ts) = deadline.into_inner().into_timespec().to_timespec() else {
-            // The deadline is further in the future then can be passed to
-            // clock_nanosleep. We have to use Self::sleep instead. This might
-            // happen on 32 bit platforms, especially closer to 2038.
-            let now = Instant::now();
-            if let Some(delay) = deadline.checked_duration_since(now) {
-                Self::sleep(delay);
-            }
-            return;
-        };
-
-        unsafe {
-            // When we get interrupted (res = EINTR) call clock_nanosleep again
-            loop {
-                let res = libc::clock_nanosleep(
-                    super::time::Instant::CLOCK_ID,
-                    libc::TIMER_ABSTIME,
-                    &ts,
-                    core::ptr::null_mut(), // not required with TIMER_ABSTIME
-                );
-
-                if res == 0 {
-                    break;
-                } else {
-                    assert_eq!(
-                        res,
-                        libc::EINTR,
-                        "timespec is in range,
-                         clockid is valid and kernel should support it"
-                    );
-                }
-            }
-        }
-    }
-
-    // Any unix that does not have clock_nanosleep
-    #[cfg(not(any(
-        target_os = "freebsd",
-        target_os = "netbsd",
-        target_os = "linux",
-        target_os = "android",
-        target_os = "solaris",
-        target_os = "illumos",
-        target_os = "dragonfly",
-        target_os = "hurd",
-        target_os = "fuchsia",
-        target_os = "vxworks",
-    )))]
-    pub fn sleep_until(deadline: Instant) {
-        let now = Instant::now();
-        if let Some(delay) = deadline.checked_duration_since(now) {
-            Self::sleep(delay);
-        }
-    }
-
     pub fn join(self) {
         let id = self.into_id();
         let ret = unsafe { libc::pthread_join(id, ptr::null_mut()) };
@@ -410,84 +151,6 @@ impl Drop for Thread {
     }
 }
 
-pub(crate) fn current_os_id() -> Option<u64> {
-    // Most Unix platforms have a way to query an integer ID of the current thread, all with
-    // slightly different spellings.
-    //
-    // The OS thread ID is used rather than `pthread_self` so as to match what will be displayed
-    // for process inspection (debuggers, trace, `top`, etc.).
-    cfg_select! {
-        // Most platforms have a function returning a `pid_t` or int, which is an `i32`.
-        any(target_os = "android", target_os = "linux") => {
-            use crate::sys::weak::syscall;
-
-            // `libc::gettid` is only available on glibc 2.30+, but the syscall is available
-            // since Linux 2.4.11.
-            syscall!(fn gettid() -> libc::pid_t;);
-
-            // SAFETY: FFI call with no preconditions.
-            let id: libc::pid_t = unsafe { gettid() };
-            Some(id as u64)
-        }
-        target_os = "nto" => {
-            // SAFETY: FFI call with no preconditions.
-            let id: libc::pid_t = unsafe { libc::gettid() };
-            Some(id as u64)
-        }
-        target_os = "openbsd" => {
-            // SAFETY: FFI call with no preconditions.
-            let id: libc::pid_t = unsafe { libc::getthrid() };
-            Some(id as u64)
-        }
-        target_os = "freebsd" => {
-            // SAFETY: FFI call with no preconditions.
-            let id: libc::c_int = unsafe { libc::pthread_getthreadid_np() };
-            Some(id as u64)
-        }
-        target_os = "netbsd" => {
-            // SAFETY: FFI call with no preconditions.
-            let id: libc::lwpid_t = unsafe { libc::_lwp_self() };
-            Some(id as u64)
-        }
-        any(target_os = "illumos", target_os = "solaris") => {
-            // On Illumos and Solaris, the `pthread_t` is the same as the OS thread ID.
-            // SAFETY: FFI call with no preconditions.
-            let id: libc::pthread_t = unsafe { libc::pthread_self() };
-            Some(id as u64)
-        }
-        target_vendor = "apple" => {
-            // Apple allows querying arbitrary thread IDs, `thread=NULL` queries the current thread.
-            let mut id = 0u64;
-            // SAFETY: `thread_id` is a valid pointer, no other preconditions.
-            let status: libc::c_int = unsafe { libc::pthread_threadid_np(0, &mut id) };
-            if status == 0 {
-                Some(id)
-            } else {
-                None
-            }
-        }
-        // Other platforms don't have an OS thread ID or don't have a way to access it.
-        _ => None,
-    }
-}
-
-#[cfg(any(
-    target_os = "linux",
-    target_os = "nto",
-    target_os = "solaris",
-    target_os = "illumos",
-    target_os = "vxworks",
-    target_os = "cygwin",
-    target_vendor = "apple",
-))]
-fn truncate_cstr<const MAX_WITH_NUL: usize>(cstr: &CStr) -> [libc::c_char; MAX_WITH_NUL] {
-    let mut result = [0; MAX_WITH_NUL];
-    for (src, dst) in cstr.to_bytes().iter().zip(&mut result[..MAX_WITH_NUL - 1]) {
-        *dst = *src as libc::c_char;
-    }
-    result
-}
-
 pub fn available_parallelism() -> io::Result<NonZero<usize>> {
     cfg_select! {
         any(
@@ -668,6 +331,318 @@ pub fn available_parallelism() -> io::Result<NonZero<usize>> {
     }
 }
 
+pub fn current_os_id() -> Option<u64> {
+    // Most Unix platforms have a way to query an integer ID of the current thread, all with
+    // slightly different spellings.
+    //
+    // The OS thread ID is used rather than `pthread_self` so as to match what will be displayed
+    // for process inspection (debuggers, trace, `top`, etc.).
+    cfg_select! {
+        // Most platforms have a function returning a `pid_t` or int, which is an `i32`.
+        any(target_os = "android", target_os = "linux") => {
+            use crate::sys::pal::weak::syscall;
+
+            // `libc::gettid` is only available on glibc 2.30+, but the syscall is available
+            // since Linux 2.4.11.
+            syscall!(fn gettid() -> libc::pid_t;);
+
+            // SAFETY: FFI call with no preconditions.
+            let id: libc::pid_t = unsafe { gettid() };
+            Some(id as u64)
+        }
+        target_os = "nto" => {
+            // SAFETY: FFI call with no preconditions.
+            let id: libc::pid_t = unsafe { libc::gettid() };
+            Some(id as u64)
+        }
+        target_os = "openbsd" => {
+            // SAFETY: FFI call with no preconditions.
+            let id: libc::pid_t = unsafe { libc::getthrid() };
+            Some(id as u64)
+        }
+        target_os = "freebsd" => {
+            // SAFETY: FFI call with no preconditions.
+            let id: libc::c_int = unsafe { libc::pthread_getthreadid_np() };
+            Some(id as u64)
+        }
+        target_os = "netbsd" => {
+            // SAFETY: FFI call with no preconditions.
+            let id: libc::lwpid_t = unsafe { libc::_lwp_self() };
+            Some(id as u64)
+        }
+        any(target_os = "illumos", target_os = "solaris") => {
+            // On Illumos and Solaris, the `pthread_t` is the same as the OS thread ID.
+            // SAFETY: FFI call with no preconditions.
+            let id: libc::pthread_t = unsafe { libc::pthread_self() };
+            Some(id as u64)
+        }
+        target_vendor = "apple" => {
+            // Apple allows querying arbitrary thread IDs, `thread=NULL` queries the current thread.
+            let mut id = 0u64;
+            // SAFETY: `thread_id` is a valid pointer, no other preconditions.
+            let status: libc::c_int = unsafe { libc::pthread_threadid_np(0, &mut id) };
+            if status == 0 {
+                Some(id)
+            } else {
+                None
+            }
+        }
+        // Other platforms don't have an OS thread ID or don't have a way to access it.
+        _ => None,
+    }
+}
+
+#[cfg(any(
+    target_os = "linux",
+    target_os = "nto",
+    target_os = "solaris",
+    target_os = "illumos",
+    target_os = "vxworks",
+    target_os = "cygwin",
+    target_vendor = "apple",
+))]
+fn truncate_cstr<const MAX_WITH_NUL: usize>(cstr: &CStr) -> [libc::c_char; MAX_WITH_NUL] {
+    let mut result = [0; MAX_WITH_NUL];
+    for (src, dst) in cstr.to_bytes().iter().zip(&mut result[..MAX_WITH_NUL - 1]) {
+        *dst = *src as libc::c_char;
+    }
+    result
+}
+
+#[cfg(target_os = "android")]
+pub fn set_name(name: &CStr) {
+    const PR_SET_NAME: libc::c_int = 15;
+    unsafe {
+        let res = libc::prctl(
+            PR_SET_NAME,
+            name.as_ptr(),
+            0 as libc::c_ulong,
+            0 as libc::c_ulong,
+            0 as libc::c_ulong,
+        );
+        // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
+        debug_assert_eq!(res, 0);
+    }
+}
+
+#[cfg(any(
+    target_os = "linux",
+    target_os = "freebsd",
+    target_os = "dragonfly",
+    target_os = "nuttx",
+    target_os = "cygwin"
+))]
+pub fn set_name(name: &CStr) {
+    unsafe {
+        cfg_select! {
+            any(target_os = "linux", target_os = "cygwin") => {
+                // Linux and Cygwin limits the allowed length of the name.
+                const TASK_COMM_LEN: usize = 16;
+                let name = truncate_cstr::<{ TASK_COMM_LEN }>(name);
+            }
+            _ => {
+                // FreeBSD, DragonFly BSD and NuttX do not enforce length limits.
+            }
+        };
+        // Available since glibc 2.12, musl 1.1.16, and uClibc 1.0.20 for Linux,
+        // FreeBSD 12.2 and 13.0, and DragonFly BSD 6.0.
+        let res = libc::pthread_setname_np(libc::pthread_self(), name.as_ptr());
+        // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
+        debug_assert_eq!(res, 0);
+    }
+}
+
+#[cfg(target_os = "openbsd")]
+pub fn set_name(name: &CStr) {
+    unsafe {
+        libc::pthread_set_name_np(libc::pthread_self(), name.as_ptr());
+    }
+}
+
+#[cfg(target_vendor = "apple")]
+pub fn set_name(name: &CStr) {
+    unsafe {
+        let name = truncate_cstr::<{ libc::MAXTHREADNAMESIZE }>(name);
+        let res = libc::pthread_setname_np(name.as_ptr());
+        // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
+        debug_assert_eq!(res, 0);
+    }
+}
+
+#[cfg(target_os = "netbsd")]
+pub fn set_name(name: &CStr) {
+    unsafe {
+        let res = libc::pthread_setname_np(
+            libc::pthread_self(),
+            c"%s".as_ptr(),
+            name.as_ptr() as *mut libc::c_void,
+        );
+        debug_assert_eq!(res, 0);
+    }
+}
+
+#[cfg(any(target_os = "solaris", target_os = "illumos", target_os = "nto"))]
+pub fn set_name(name: &CStr) {
+    weak!(
+        fn pthread_setname_np(thread: libc::pthread_t, name: *const libc::c_char) -> libc::c_int;
+    );
+
+    if let Some(f) = pthread_setname_np.get() {
+        #[cfg(target_os = "nto")]
+        const THREAD_NAME_MAX: usize = libc::_NTO_THREAD_NAME_MAX as usize;
+        #[cfg(any(target_os = "solaris", target_os = "illumos"))]
+        const THREAD_NAME_MAX: usize = 32;
+
+        let name = truncate_cstr::<{ THREAD_NAME_MAX }>(name);
+        let res = unsafe { f(libc::pthread_self(), name.as_ptr()) };
+        debug_assert_eq!(res, 0);
+    }
+}
+
+#[cfg(target_os = "fuchsia")]
+pub fn set_name(name: &CStr) {
+    use crate::sys::pal::fuchsia::*;
+    unsafe {
+        zx_object_set_property(
+            zx_thread_self(),
+            ZX_PROP_NAME,
+            name.as_ptr() as *const libc::c_void,
+            name.to_bytes().len(),
+        );
+    }
+}
+
+#[cfg(target_os = "haiku")]
+pub fn set_name(name: &CStr) {
+    unsafe {
+        let thread_self = libc::find_thread(ptr::null_mut());
+        let res = libc::rename_thread(thread_self, name.as_ptr());
+        // We have no good way of propagating errors here, but in debug-builds let's check that this actually worked.
+        debug_assert_eq!(res, libc::B_OK);
+    }
+}
+
+#[cfg(target_os = "vxworks")]
+pub fn set_name(name: &CStr) {
+    let mut name = truncate_cstr::<{ (libc::VX_TASK_RENAME_LENGTH - 1) as usize }>(name);
+    let res = unsafe { libc::taskNameSet(libc::taskIdSelf(), name.as_mut_ptr()) };
+    debug_assert_eq!(res, libc::OK);
+}
+
+#[cfg(not(target_os = "espidf"))]
+pub fn sleep(dur: Duration) {
+    let mut secs = dur.as_secs();
+    let mut nsecs = dur.subsec_nanos() as _;
+
+    // If we're awoken with a signal then the return value will be -1 and
+    // nanosleep will fill in `ts` with the remaining time.
+    unsafe {
+        while secs > 0 || nsecs > 0 {
+            let mut ts = libc::timespec {
+                tv_sec: cmp::min(libc::time_t::MAX as u64, secs) as libc::time_t,
+                tv_nsec: nsecs,
+            };
+            secs -= ts.tv_sec as u64;
+            let ts_ptr = &raw mut ts;
+            if libc::nanosleep(ts_ptr, ts_ptr) == -1 {
+                assert_eq!(os::errno(), libc::EINTR);
+                secs += ts.tv_sec as u64;
+                nsecs = ts.tv_nsec;
+            } else {
+                nsecs = 0;
+            }
+        }
+    }
+}
+
+#[cfg(target_os = "espidf")]
+pub fn sleep(dur: Duration) {
+    // ESP-IDF does not have `nanosleep`, so we use `usleep` instead.
+    // As per the documentation of `usleep`, it is expected to support
+    // sleep times as big as at least up to 1 second.
+    //
+    // ESP-IDF does support almost up to `u32::MAX`, but due to a potential integer overflow in its
+    // `usleep` implementation
+    // (https://github.com/espressif/esp-idf/blob/d7ca8b94c852052e3bc33292287ef4dd62c9eeb1/components/newlib/time.c#L210),
+    // we limit the sleep time to the maximum one that would not cause the underlying `usleep` implementation to overflow
+    // (`portTICK_PERIOD_MS` can be anything between 1 to 1000, and is 10 by default).
+    const MAX_MICROS: u32 = u32::MAX - 1_000_000 - 1;
+
+    // Add any nanoseconds smaller than a microsecond as an extra microsecond
+    // so as to comply with the `std::thread::sleep` contract which mandates
+    // implementations to sleep for _at least_ the provided `dur`.
+    // We can't overflow `micros` as it is a `u128`, while `Duration` is a pair of
+    // (`u64` secs, `u32` nanos), where the nanos are strictly smaller than 1 second
+    // (i.e. < 1_000_000_000)
+    let mut micros = dur.as_micros() + if dur.subsec_nanos() % 1_000 > 0 { 1 } else { 0 };
+
+    while micros > 0 {
+        let st = if micros > MAX_MICROS as u128 { MAX_MICROS } else { micros as u32 };
+        unsafe {
+            libc::usleep(st);
+        }
+
+        micros -= st as u128;
+    }
+}
+
+// Any unix that has clock_nanosleep
+// If this list changes update the MIRI chock_nanosleep shim
+#[cfg(any(
+    target_os = "freebsd",
+    target_os = "netbsd",
+    target_os = "linux",
+    target_os = "android",
+    target_os = "solaris",
+    target_os = "illumos",
+    target_os = "dragonfly",
+    target_os = "hurd",
+    target_os = "fuchsia",
+    target_os = "vxworks",
+))]
+pub fn sleep_until(deadline: crate::time::Instant) {
+    use crate::time::Instant;
+
+    let Some(ts) = deadline.into_inner().into_timespec().to_timespec() else {
+        // The deadline is further in the future then can be passed to
+        // clock_nanosleep. We have to use Self::sleep instead. This might
+        // happen on 32 bit platforms, especially closer to 2038.
+        let now = Instant::now();
+        if let Some(delay) = deadline.checked_duration_since(now) {
+            sleep(delay);
+        }
+        return;
+    };
+
+    unsafe {
+        // When we get interrupted (res = EINTR) call clock_nanosleep again
+        loop {
+            let res = libc::clock_nanosleep(
+                crate::sys::time::Instant::CLOCK_ID,
+                libc::TIMER_ABSTIME,
+                &ts,
+                core::ptr::null_mut(), // not required with TIMER_ABSTIME
+            );
+
+            if res == 0 {
+                break;
+            } else {
+                assert_eq!(
+                    res,
+                    libc::EINTR,
+                    "timespec is in range,
+                         clockid is valid and kernel should support it"
+                );
+            }
+        }
+    }
+}
+
+pub fn yield_now() {
+    let ret = unsafe { libc::sched_yield() };
+    debug_assert_eq!(ret, 0);
+}
+
 #[cfg(any(target_os = "android", target_os = "linux"))]
 mod cgroups {
     //! Currently not covered
diff --git a/library/std/src/sys/pal/unsupported/thread.rs b/library/std/src/sys/thread/unsupported.rs
index 34d9b5ec70c..a5001efa3b4 100644
--- a/library/std/src/sys/pal/unsupported/thread.rs
+++ b/library/std/src/sys/thread/unsupported.rs
@@ -1,8 +1,7 @@
-use super::unsupported;
 use crate::ffi::CStr;
 use crate::io;
 use crate::num::NonZero;
-use crate::time::{Duration, Instant};
+use crate::time::Duration;
 
 pub struct Thread(!);
 
@@ -15,23 +14,7 @@ impl Thread {
         _name: Option<&str>,
         _p: Box<dyn FnOnce()>,
     ) -> io::Result<Thread> {
-        unsupported()
-    }
-
-    pub fn yield_now() {
-        // do nothing
-    }
-
-    pub fn set_name(_name: &CStr) {
-        // nope
-    }
-
-    pub fn sleep(_dur: Duration) {
-        panic!("can't sleep");
-    }
-
-    pub fn sleep_until(_deadline: Instant) {
-        panic!("can't sleep");
+        Err(io::Error::UNSUPPORTED_PLATFORM)
     }
 
     pub fn join(self) {
@@ -39,10 +22,22 @@ impl Thread {
     }
 }
 
-pub(crate) fn current_os_id() -> Option<u64> {
+pub fn available_parallelism() -> io::Result<NonZero<usize>> {
+    Err(io::Error::UNKNOWN_THREAD_COUNT)
+}
+
+pub fn current_os_id() -> Option<u64> {
     None
 }
 
-pub fn available_parallelism() -> io::Result<NonZero<usize>> {
-    unsupported()
+pub fn yield_now() {
+    // do nothing
+}
+
+pub fn set_name(_name: &CStr) {
+    // nope
+}
+
+pub fn sleep(_dur: Duration) {
+    panic!("can't sleep");
 }
diff --git a/library/std/src/sys/thread/wasip1.rs b/library/std/src/sys/thread/wasip1.rs
new file mode 100644
index 00000000000..83001fad49c
--- /dev/null
+++ b/library/std/src/sys/thread/wasip1.rs
@@ -0,0 +1,185 @@
+#![forbid(unsafe_op_in_unsafe_fn)]
+
+#[cfg(target_feature = "atomics")]
+use crate::io;
+use crate::mem;
+#[cfg(target_feature = "atomics")]
+use crate::num::NonZero;
+#[cfg(target_feature = "atomics")]
+use crate::sys::os;
+use crate::time::Duration;
+#[cfg(target_feature = "atomics")]
+use crate::{cmp, ptr};
+
+// Add a few symbols not in upstream `libc` just yet.
+#[cfg(target_feature = "atomics")]
+mod libc {
+    pub use libc::*;
+
+    pub use crate::ffi;
+
+    // defined in wasi-libc
+    // https://github.com/WebAssembly/wasi-libc/blob/a6f871343313220b76009827ed0153586361c0d5/libc-top-half/musl/include/alltypes.h.in#L108
+    #[repr(C)]
+    union pthread_attr_union {
+        __i: [ffi::c_int; if size_of::<ffi::c_long>() == 8 { 14 } else { 9 }],
+        __vi: [ffi::c_int; if size_of::<ffi::c_long>() == 8 { 14 } else { 9 }],
+        __s: [ffi::c_ulong; if size_of::<ffi::c_long>() == 8 { 7 } else { 9 }],
+    }
+
+    #[repr(C)]
+    pub struct pthread_attr_t {
+        __u: pthread_attr_union,
+    }
+
+    #[allow(non_camel_case_types)]
+    pub type pthread_t = *mut ffi::c_void;
+
+    pub const _SC_NPROCESSORS_ONLN: ffi::c_int = 84;
+
+    unsafe extern "C" {
+        pub fn pthread_create(
+            native: *mut pthread_t,
+            attr: *const pthread_attr_t,
+            f: extern "C" fn(*mut ffi::c_void) -> *mut ffi::c_void,
+            value: *mut ffi::c_void,
+        ) -> ffi::c_int;
+        pub fn pthread_join(native: pthread_t, value: *mut *mut ffi::c_void) -> ffi::c_int;
+        pub fn pthread_attr_init(attrp: *mut pthread_attr_t) -> ffi::c_int;
+        pub fn pthread_attr_setstacksize(
+            attr: *mut pthread_attr_t,
+            stack_size: libc::size_t,
+        ) -> ffi::c_int;
+        pub fn pthread_attr_destroy(attr: *mut pthread_attr_t) -> ffi::c_int;
+        pub fn pthread_detach(thread: pthread_t) -> ffi::c_int;
+    }
+}
+
+#[cfg(target_feature = "atomics")]
+pub struct Thread {
+    id: libc::pthread_t,
+}
+
+#[cfg(target_feature = "atomics")]
+impl Drop for Thread {
+    fn drop(&mut self) {
+        let ret = unsafe { libc::pthread_detach(self.id) };
+        debug_assert_eq!(ret, 0);
+    }
+}
+
+pub const DEFAULT_MIN_STACK_SIZE: usize = 1024 * 1024;
+
+#[cfg(target_feature = "atomics")]
+impl Thread {
+    // unsafe: see thread::Builder::spawn_unchecked for safety requirements
+    pub unsafe fn new(
+        stack: usize,
+        _name: Option<&str>,
+        p: Box<dyn FnOnce()>,
+    ) -> io::Result<Thread> {
+        let p = Box::into_raw(Box::new(p));
+        let mut native: libc::pthread_t = unsafe { mem::zeroed() };
+        let mut attr: libc::pthread_attr_t = unsafe { mem::zeroed() };
+        assert_eq!(unsafe { libc::pthread_attr_init(&mut attr) }, 0);
+
+        let stack_size = cmp::max(stack, DEFAULT_MIN_STACK_SIZE);
+
+        match unsafe { libc::pthread_attr_setstacksize(&mut attr, stack_size) } {
+            0 => {}
+            n => {
+                assert_eq!(n, libc::EINVAL);
+                // EINVAL means |stack_size| is either too small or not a
+                // multiple of the system page size. Because it's definitely
+                // >= PTHREAD_STACK_MIN, it must be an alignment issue.
+                // Round up to the nearest page and try again.
+                let page_size = os::page_size();
+                let stack_size =
+                    (stack_size + page_size - 1) & (-(page_size as isize - 1) as usize - 1);
+                assert_eq!(unsafe { libc::pthread_attr_setstacksize(&mut attr, stack_size) }, 0);
+            }
+        };
+
+        let ret = unsafe { libc::pthread_create(&mut native, &attr, thread_start, p as *mut _) };
+        // Note: if the thread creation fails and this assert fails, then p will
+        // be leaked. However, an alternative design could cause double-free
+        // which is clearly worse.
+        assert_eq!(unsafe { libc::pthread_attr_destroy(&mut attr) }, 0);
+
+        return if ret != 0 {
+            // The thread failed to start and as a result p was not consumed. Therefore, it is
+            // safe to reconstruct the box so that it gets deallocated.
+            unsafe {
+                drop(Box::from_raw(p));
+            }
+            Err(io::Error::from_raw_os_error(ret))
+        } else {
+            Ok(Thread { id: native })
+        };
+
+        extern "C" fn thread_start(main: *mut libc::c_void) -> *mut libc::c_void {
+            unsafe {
+                // Finally, let's run some code.
+                Box::from_raw(main as *mut Box<dyn FnOnce()>)();
+            }
+            ptr::null_mut()
+        }
+    }
+
+    pub fn join(self) {
+        let id = mem::ManuallyDrop::new(self).id;
+        let ret = unsafe { libc::pthread_join(id, ptr::null_mut()) };
+        if ret != 0 {
+            rtabort!("failed to join thread: {}", io::Error::from_raw_os_error(ret));
+        }
+    }
+}
+
+#[cfg(target_feature = "atomics")]
+pub fn available_parallelism() -> io::Result<NonZero<usize>> {
+    match unsafe { libc::sysconf(libc::_SC_NPROCESSORS_ONLN) } {
+        -1 => Err(io::Error::last_os_error()),
+        cpus => NonZero::new(cpus as usize).ok_or(io::Error::UNKNOWN_THREAD_COUNT),
+    }
+}
+
+pub fn yield_now() {
+    let ret = unsafe { wasi::sched_yield() };
+    debug_assert_eq!(ret, Ok(()));
+}
+
+pub fn sleep(dur: Duration) {
+    let mut nanos = dur.as_nanos();
+    while nanos > 0 {
+        const USERDATA: wasi::Userdata = 0x0123_45678;
+
+        let clock = wasi::SubscriptionClock {
+            id: wasi::CLOCKID_MONOTONIC,
+            timeout: u64::try_from(nanos).unwrap_or(u64::MAX),
+            precision: 0,
+            flags: 0,
+        };
+        nanos -= u128::from(clock.timeout);
+
+        let in_ = wasi::Subscription {
+            userdata: USERDATA,
+            u: wasi::SubscriptionU { tag: 0, u: wasi::SubscriptionUU { clock } },
+        };
+        unsafe {
+            let mut event: wasi::Event = mem::zeroed();
+            let res = wasi::poll_oneoff(&in_, &mut event, 1);
+            match (res, event) {
+                (
+                    Ok(1),
+                    wasi::Event {
+                        userdata: USERDATA,
+                        error: wasi::ERRNO_SUCCESS,
+                        type_: wasi::EVENTTYPE_CLOCK,
+                        ..
+                    },
+                ) => {}
+                _ => panic!("thread::sleep(): unexpected result of poll_oneoff"),
+            }
+        }
+    }
+}
diff --git a/library/std/src/sys/thread/wasip2.rs b/library/std/src/sys/thread/wasip2.rs
new file mode 100644
index 00000000000..420cad2a5e4
--- /dev/null
+++ b/library/std/src/sys/thread/wasip2.rs
@@ -0,0 +1,32 @@
+use crate::time::{Duration, Instant};
+
+pub fn sleep(dur: Duration) {
+    // Sleep in increments of `u64::MAX` nanoseconds until the `dur` is
+    // entirely drained.
+    let mut remaining = dur.as_nanos();
+    while remaining > 0 {
+        let amt = u64::try_from(remaining).unwrap_or(u64::MAX);
+        wasip2::clocks::monotonic_clock::subscribe_duration(amt).block();
+        remaining -= u128::from(amt);
+    }
+}
+
+pub fn sleep_until(deadline: Instant) {
+    match u64::try_from(deadline.into_inner().as_duration().as_nanos()) {
+        // If the point in time we're sleeping to fits within a 64-bit
+        // number of nanoseconds then directly use `subscribe_instant`.
+        Ok(deadline) => {
+            wasip2::clocks::monotonic_clock::subscribe_instant(deadline).block();
+        }
+        // ... otherwise we're sleeping for 500+ years relative to the
+        // "start" of what the system is using as a clock so speed/accuracy
+        // is not so much of a concern. Use `sleep` instead.
+        Err(_) => {
+            let now = Instant::now();
+
+            if let Some(delay) = deadline.checked_duration_since(now) {
+                sleep(delay);
+            }
+        }
+    }
+}
diff --git a/library/std/src/sys/thread/wasm.rs b/library/std/src/sys/thread/wasm.rs
new file mode 100644
index 00000000000..e843bc992ba
--- /dev/null
+++ b/library/std/src/sys/thread/wasm.rs
@@ -0,0 +1,23 @@
+use crate::cmp;
+use crate::time::Duration;
+
+pub fn sleep(dur: Duration) {
+    #[cfg(target_arch = "wasm32")]
+    use core::arch::wasm32 as wasm;
+    #[cfg(target_arch = "wasm64")]
+    use core::arch::wasm64 as wasm;
+
+    // Use an atomic wait to block the current thread artificially with a
+    // timeout listed. Note that we should never be notified (return value
+    // of 0) or our comparison should never fail (return value of 1) so we
+    // should always only resume execution through a timeout (return value
+    // 2).
+    let mut nanos = dur.as_nanos();
+    while nanos > 0 {
+        let amt = cmp::min(i64::MAX as u128, nanos);
+        let mut x = 0;
+        let val = unsafe { wasm::memory_atomic_wait32(&mut x, 0, amt as i64) };
+        debug_assert_eq!(val, 2);
+        nanos -= amt;
+    }
+}
diff --git a/library/std/src/sys/pal/windows/thread.rs b/library/std/src/sys/thread/windows.rs
index b0e38220a2d..a5640c51c4a 100644
--- a/library/std/src/sys/pal/windows/thread.rs
+++ b/library/std/src/sys/thread/windows.rs
@@ -1,14 +1,14 @@
 use core::ffi::c_void;
 
-use super::time::WaitableTimer;
-use super::to_u16s;
 use crate::ffi::CStr;
 use crate::num::NonZero;
 use crate::os::windows::io::{AsRawHandle, HandleOrNull};
 use crate::sys::handle::Handle;
+use crate::sys::pal::time::WaitableTimer;
+use crate::sys::pal::{dur2timeout, to_u16s};
 use crate::sys::{c, stack_overflow};
 use crate::sys_common::FromInner;
-use crate::time::{Duration, Instant};
+use crate::time::Duration;
 use crate::{io, ptr};
 
 pub const DEFAULT_MIN_STACK_SIZE: usize = 2 * 1024 * 1024;
@@ -62,24 +62,6 @@ impl Thread {
         }
     }
 
-    pub fn set_name(name: &CStr) {
-        if let Ok(utf8) = name.to_str() {
-            if let Ok(utf16) = to_u16s(utf8) {
-                unsafe {
-                    // SAFETY: the vec returned by `to_u16s` ends with a zero value
-                    Self::set_name_wide(&utf16)
-                }
-            };
-        };
-    }
-
-    /// # Safety
-    ///
-    /// `name` must end with a zero value
-    pub unsafe fn set_name_wide(name: &[u16]) {
-        unsafe { c::SetThreadDescription(c::GetCurrentThread(), name.as_ptr()) };
-    }
-
     pub fn join(self) {
         let rc = unsafe { c::WaitForSingleObject(self.handle.as_raw_handle(), c::INFINITE) };
         if rc == c::WAIT_FAILED {
@@ -87,37 +69,6 @@ impl Thread {
         }
     }
 
-    pub fn yield_now() {
-        // This function will return 0 if there are no other threads to execute,
-        // but this also means that the yield was useless so this isn't really a
-        // case that needs to be worried about.
-        unsafe {
-            c::SwitchToThread();
-        }
-    }
-
-    pub fn sleep(dur: Duration) {
-        fn high_precision_sleep(dur: Duration) -> Result<(), ()> {
-            let timer = WaitableTimer::high_resolution()?;
-            timer.set(dur)?;
-            timer.wait()
-        }
-        // Attempt to use high-precision sleep (Windows 10, version 1803+).
-        // On error fallback to the standard `Sleep` function.
-        // Also preserves the zero duration behavior of `Sleep`.
-        if dur.is_zero() || high_precision_sleep(dur).is_err() {
-            unsafe { c::Sleep(super::dur2timeout(dur)) }
-        }
-    }
-
-    pub fn sleep_until(deadline: Instant) {
-        let now = Instant::now();
-
-        if let Some(delay) = deadline.checked_duration_since(now) {
-            Self::sleep(delay);
-        }
-    }
-
     pub fn handle(&self) -> &Handle {
         &self.handle
     }
@@ -127,14 +78,6 @@ impl Thread {
     }
 }
 
-pub(crate) fn current_os_id() -> Option<u64> {
-    // SAFETY: FFI call with no preconditions.
-    let id: u32 = unsafe { c::GetCurrentThreadId() };
-
-    // A return value of 0 indicates failed lookup.
-    if id == 0 { None } else { Some(id.into()) }
-}
-
 pub fn available_parallelism() -> io::Result<NonZero<usize>> {
     let res = unsafe {
         let mut sysinfo: c::SYSTEM_INFO = crate::mem::zeroed();
@@ -146,3 +89,52 @@ pub fn available_parallelism() -> io::Result<NonZero<usize>> {
         cpus => Ok(unsafe { NonZero::new_unchecked(cpus) }),
     }
 }
+
+pub fn current_os_id() -> Option<u64> {
+    // SAFETY: FFI call with no preconditions.
+    let id: u32 = unsafe { c::GetCurrentThreadId() };
+
+    // A return value of 0 indicates failed lookup.
+    if id == 0 { None } else { Some(id.into()) }
+}
+
+pub fn set_name(name: &CStr) {
+    if let Ok(utf8) = name.to_str() {
+        if let Ok(utf16) = to_u16s(utf8) {
+            unsafe {
+                // SAFETY: the vec returned by `to_u16s` ends with a zero value
+                set_name_wide(&utf16)
+            }
+        };
+    };
+}
+
+/// # Safety
+///
+/// `name` must end with a zero value
+pub unsafe fn set_name_wide(name: &[u16]) {
+    unsafe { c::SetThreadDescription(c::GetCurrentThread(), name.as_ptr()) };
+}
+
+pub fn sleep(dur: Duration) {
+    fn high_precision_sleep(dur: Duration) -> Result<(), ()> {
+        let timer = WaitableTimer::high_resolution()?;
+        timer.set(dur)?;
+        timer.wait()
+    }
+    // Attempt to use high-precision sleep (Windows 10, version 1803+).
+    // On error fallback to the standard `Sleep` function.
+    // Also preserves the zero duration behavior of `Sleep`.
+    if dur.is_zero() || high_precision_sleep(dur).is_err() {
+        unsafe { c::Sleep(dur2timeout(dur)) }
+    }
+}
+
+pub fn yield_now() {
+    // This function will return 0 if there are no other threads to execute,
+    // but this also means that the yield was useless so this isn't really a
+    // case that needs to be worried about.
+    unsafe {
+        c::SwitchToThread();
+    }
+}
diff --git a/library/std/src/sys/pal/xous/thread.rs b/library/std/src/sys/thread/xous.rs
index 92803c94c6e..133e15a0928 100644
--- a/library/std/src/sys/pal/xous/thread.rs
+++ b/library/std/src/sys/thread/xous.rs
@@ -1,6 +1,5 @@
 use core::arch::asm;
 
-use crate::ffi::CStr;
 use crate::io;
 use crate::num::NonZero;
 use crate::os::xous::ffi::{
@@ -8,7 +7,7 @@ use crate::os::xous::ffi::{
     map_memory, update_memory_flags,
 };
 use crate::os::xous::services::{TicktimerScalar, ticktimer_server};
-use crate::time::{Duration, Instant};
+use crate::time::Duration;
 
 pub struct Thread {
     tid: ThreadId,
@@ -110,46 +109,29 @@ impl Thread {
         Ok(Thread { tid })
     }
 
-    pub fn yield_now() {
-        do_yield();
-    }
-
-    pub fn set_name(_name: &CStr) {
-        // nope
-    }
-
-    pub fn sleep(dur: Duration) {
-        // Because the sleep server works on units of `usized milliseconds`, split
-        // the messages up into these chunks. This means we may run into issues
-        // if you try to sleep a thread for more than 49 days on a 32-bit system.
-        let mut millis = dur.as_millis();
-        while millis > 0 {
-            let sleep_duration =
-                if millis > (usize::MAX as _) { usize::MAX } else { millis as usize };
-            blocking_scalar(ticktimer_server(), TicktimerScalar::SleepMs(sleep_duration).into())
-                .expect("failed to send message to ticktimer server");
-            millis -= sleep_duration as u128;
-        }
-    }
-
-    pub fn sleep_until(deadline: Instant) {
-        let now = Instant::now();
-
-        if let Some(delay) = deadline.checked_duration_since(now) {
-            Self::sleep(delay);
-        }
-    }
-
     pub fn join(self) {
         join_thread(self.tid).unwrap();
     }
 }
 
-pub(crate) fn current_os_id() -> Option<u64> {
-    None
-}
-
 pub fn available_parallelism() -> io::Result<NonZero<usize>> {
     // We're unicore right now.
     Ok(unsafe { NonZero::new_unchecked(1) })
 }
+
+pub fn yield_now() {
+    do_yield();
+}
+
+pub fn sleep(dur: Duration) {
+    // Because the sleep server works on units of `usized milliseconds`, split
+    // the messages up into these chunks. This means we may run into issues
+    // if you try to sleep a thread for more than 49 days on a 32-bit system.
+    let mut millis = dur.as_millis();
+    while millis > 0 {
+        let sleep_duration = if millis > (usize::MAX as _) { usize::MAX } else { millis as usize };
+        blocking_scalar(ticktimer_server(), TicktimerScalar::SleepMs(sleep_duration).into())
+            .expect("failed to send message to ticktimer server");
+        millis -= sleep_duration as u128;
+    }
+}
diff --git a/library/std/src/thread/local.rs b/library/std/src/thread/local.rs
index 797feeb2bbb..0a6f2e5d508 100644
--- a/library/std/src/thread/local.rs
+++ b/library/std/src/thread/local.rs
@@ -230,7 +230,7 @@ impl fmt::Display for AccessError {
 impl Error for AccessError {}
 
 // This ensures the panicking code is outlined from `with` for `LocalKey`.
-#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
+#[cfg_attr(not(panic = "immediate-abort"), inline(never))]
 #[track_caller]
 #[cold]
 fn panic_access_error(err: AccessError) -> ! {
diff --git a/library/std/src/thread/mod.rs b/library/std/src/thread/mod.rs
index b6059c28cec..4d09b2b4e9d 100644
--- a/library/std/src/thread/mod.rs
+++ b/library/std/src/thread/mod.rs
@@ -550,7 +550,7 @@ impl Builder {
             }
 
             if let Some(name) = their_thread.cname() {
-                imp::Thread::set_name(name);
+                imp::set_name(name);
             }
 
             let f = f.into_inner();
@@ -763,7 +763,7 @@ where
 /// [`Mutex`]: crate::sync::Mutex
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn yield_now() {
-    imp::Thread::yield_now()
+    imp::yield_now()
 }
 
 /// Determines whether the current thread is unwinding because of panic.
@@ -884,7 +884,7 @@ pub fn sleep_ms(ms: u32) {
 /// ```
 #[stable(feature = "thread_sleep", since = "1.4.0")]
 pub fn sleep(dur: Duration) {
-    imp::Thread::sleep(dur)
+    imp::sleep(dur)
 }
 
 /// Puts the current thread to sleep until the specified deadline has passed.
@@ -983,7 +983,7 @@ pub fn sleep(dur: Duration) {
 /// ```
 #[unstable(feature = "thread_sleep_until", issue = "113752")]
 pub fn sleep_until(deadline: Instant) {
-    imp::Thread::sleep_until(deadline)
+    imp::sleep_until(deadline)
 }
 
 /// Used to ensure that `park` and `park_timeout` do not unwind, as that can
@@ -1021,13 +1021,23 @@ impl Drop for PanicGuard {
 ///   specifying a maximum time to block the thread for.
 ///
 /// * The [`unpark`] method on a [`Thread`] atomically makes the token available
-///   if it wasn't already. Because the token is initially absent, [`unpark`]
-///   followed by [`park`] will result in the second call returning immediately.
-///
-/// The API is typically used by acquiring a handle to the current thread,
-/// placing that handle in a shared data structure so that other threads can
-/// find it, and then `park`ing in a loop. When some desired condition is met, another
-/// thread calls [`unpark`] on the handle.
+///   if it wasn't already. Because the token can be held by a thread even if it is currently not
+///   parked, [`unpark`] followed by [`park`] will result in the second call returning immediately.
+///   However, note that to rely on this guarantee, you need to make sure that your `unpark` happens
+///   after all `park` that may be done by other data structures!
+///
+/// The API is typically used by acquiring a handle to the current thread, placing that handle in a
+/// shared data structure so that other threads can find it, and then `park`ing in a loop. When some
+/// desired condition is met, another thread calls [`unpark`] on the handle. The last bullet point
+/// above guarantees that even if the `unpark` occurs before the thread is finished `park`ing, it
+/// will be woken up properly.
+///
+/// Note that the coordination via the shared data structure is crucial: If you `unpark` a thread
+/// without first establishing that it is about to be `park`ing within your code, that `unpark` may
+/// get consumed by a *different* `park` in the same thread, leading to a deadlock. This also means
+/// you must not call unknown code between setting up for parking and calling `park`; for instance,
+/// if you invoke `println!`, that may itself call `park` and thus consume your `unpark` and cause a
+/// deadlock.
 ///
 /// The motivation for this design is twofold:
 ///
@@ -1058,21 +1068,24 @@ impl Drop for PanicGuard {
 ///
 /// ```
 /// use std::thread;
-/// use std::sync::{Arc, atomic::{Ordering, AtomicBool}};
+/// use std::sync::atomic::{Ordering, AtomicBool};
 /// use std::time::Duration;
 ///
-/// let flag = Arc::new(AtomicBool::new(false));
-/// let flag2 = Arc::clone(&flag);
+/// static QUEUED: AtomicBool = AtomicBool::new(false);
+/// static FLAG: AtomicBool = AtomicBool::new(false);
 ///
 /// let parked_thread = thread::spawn(move || {
+///     println!("Thread spawned");
+///     // Signal that we are going to `park`. Between this store and our `park`, there may
+///     // be no other `park`, or else that `park` could consume our `unpark` token!
+///     QUEUED.store(true, Ordering::Release);
 ///     // We want to wait until the flag is set. We *could* just spin, but using
 ///     // park/unpark is more efficient.
-///     while !flag2.load(Ordering::Relaxed) {
-///         println!("Parking thread");
+///     while !FLAG.load(Ordering::Acquire) {
+///         // We can *not* use `println!` here since that could use thread parking internally.
 ///         thread::park();
 ///         // We *could* get here spuriously, i.e., way before the 10ms below are over!
 ///         // But that is no problem, we are in a loop until the flag is set anyway.
-///         println!("Thread unparked");
 ///     }
 ///     println!("Flag received");
 /// });
@@ -1080,11 +1093,22 @@ impl Drop for PanicGuard {
 /// // Let some time pass for the thread to be spawned.
 /// thread::sleep(Duration::from_millis(10));
 ///
+/// // Ensure the thread is about to park.
+/// // This is crucial! It guarantees that the `unpark` below is not consumed
+/// // by some other code in the parked thread (e.g. inside `println!`).
+/// while !QUEUED.load(Ordering::Acquire) {
+///     // Spinning is of course inefficient; in practice, this would more likely be
+///     // a dequeue where we have no work to do if there's nobody queued.
+///     std::hint::spin_loop();
+/// }
+///
 /// // Set the flag, and let the thread wake up.
-/// // There is no race condition here, if `unpark`
+/// // There is no race condition here: if `unpark`
 /// // happens first, `park` will return immediately.
+/// // There is also no other `park` that could consume this token,
+/// // since we waited until the other thread got queued.
 /// // Hence there is no risk of a deadlock.
-/// flag.store(true, Ordering::Relaxed);
+/// FLAG.store(true, Ordering::Release);
 /// println!("Unpark the thread");
 /// parked_thread.thread().unpark();
 ///
@@ -1494,10 +1518,14 @@ impl Thread {
     /// ```
     /// use std::thread;
     /// use std::time::Duration;
+    /// use std::sync::atomic::{AtomicBool, Ordering};
+    ///
+    /// static QUEUED: AtomicBool = AtomicBool::new(false);
     ///
     /// let parked_thread = thread::Builder::new()
     ///     .spawn(|| {
     ///         println!("Parking thread");
+    ///         QUEUED.store(true, Ordering::Release);
     ///         thread::park();
     ///         println!("Thread unparked");
     ///     })
@@ -1506,6 +1534,15 @@ impl Thread {
     /// // Let some time pass for the thread to be spawned.
     /// thread::sleep(Duration::from_millis(10));
     ///
+    /// // Wait until the other thread is queued.
+    /// // This is crucial! It guarantees that the `unpark` below is not consumed
+    /// // by some other code in the parked thread (e.g. inside `println!`).
+    /// while !QUEUED.load(Ordering::Acquire) {
+    ///     // Spinning is of course inefficient; in practice, this would more likely be
+    ///     // a dequeue where we have no work to do if there's nobody queued.
+    ///     std::hint::spin_loop();
+    /// }
+    ///
     /// println!("Unpark the thread");
     /// parked_thread.thread().unpark();
     ///
diff --git a/library/std/src/thread/tests.rs b/library/std/src/thread/tests.rs
index ae889f1e778..2117f5f93ce 100644
--- a/library/std/src/thread/tests.rs
+++ b/library/std/src/thread/tests.rs
@@ -287,6 +287,8 @@ fn test_park_unpark_called_other_thread() {
     for _ in 0..10 {
         let th = thread::current();
 
+        // Here we rely on `thread::spawn` (specifically the part that runs after spawning
+        // the thread) to not consume the parking token.
         let _guard = thread::spawn(move || {
             super::sleep(Duration::from_millis(50));
             th.unpark();
@@ -316,6 +318,8 @@ fn test_park_timeout_unpark_called_other_thread() {
     for _ in 0..10 {
         let th = thread::current();
 
+        // Here we rely on `thread::spawn` (specifically the part that runs after spawning
+        // the thread) to not consume the parking token.
         let _guard = thread::spawn(move || {
             super::sleep(Duration::from_millis(50));
             th.unpark();
diff --git a/library/std/src/time.rs b/library/std/src/time.rs
index 84fbb4c2fe4..31187adb6fe 100644
--- a/library/std/src/time.rs
+++ b/library/std/src/time.rs
@@ -551,13 +551,8 @@ impl SystemTime {
     /// println!("{difference:?}");
     /// ```
     #[stable(feature = "time2", since = "1.8.0")]
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn duration_since(&self, earlier: SystemTime) -> Result<Duration, SystemTimeError> {
-        // FIXME: map_err in const
-        match self.0.sub_time(&earlier.0) {
-            Ok(time) => Ok(time),
-            Err(err) => Err(SystemTimeError(err)),
-        }
+    pub fn duration_since(&self, earlier: SystemTime) -> Result<Duration, SystemTimeError> {
+        self.0.sub_time(&earlier.0).map_err(SystemTimeError)
     }
 
     /// Returns the difference from this system time to the
@@ -594,8 +589,7 @@ impl SystemTime {
     /// `SystemTime` (which means it's inside the bounds of the underlying data structure), `None`
     /// otherwise.
     #[stable(feature = "time_checked_add", since = "1.34.0")]
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_add(&self, duration: Duration) -> Option<SystemTime> {
+    pub fn checked_add(&self, duration: Duration) -> Option<SystemTime> {
         self.0.checked_add_duration(&duration).map(SystemTime)
     }
 
@@ -603,15 +597,13 @@ impl SystemTime {
     /// `SystemTime` (which means it's inside the bounds of the underlying data structure), `None`
     /// otherwise.
     #[stable(feature = "time_checked_add", since = "1.34.0")]
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn checked_sub(&self, duration: Duration) -> Option<SystemTime> {
+    pub fn checked_sub(&self, duration: Duration) -> Option<SystemTime> {
         self.0.checked_sub_duration(&duration).map(SystemTime)
     }
 }
 
 #[stable(feature = "time2", since = "1.8.0")]
-#[rustc_const_unstable(feature = "const_ops", issue = "143802")]
-impl const Add<Duration> for SystemTime {
+impl Add<Duration> for SystemTime {
     type Output = SystemTime;
 
     /// # Panics
@@ -624,16 +616,14 @@ impl const Add<Duration> for SystemTime {
 }
 
 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
-#[rustc_const_unstable(feature = "const_ops", issue = "143802")]
-impl const AddAssign<Duration> for SystemTime {
+impl AddAssign<Duration> for SystemTime {
     fn add_assign(&mut self, other: Duration) {
         *self = *self + other;
     }
 }
 
 #[stable(feature = "time2", since = "1.8.0")]
-#[rustc_const_unstable(feature = "const_ops", issue = "143802")]
-impl const Sub<Duration> for SystemTime {
+impl Sub<Duration> for SystemTime {
     type Output = SystemTime;
 
     fn sub(self, dur: Duration) -> SystemTime {
@@ -642,8 +632,7 @@ impl const Sub<Duration> for SystemTime {
 }
 
 #[stable(feature = "time_augmented_assignment", since = "1.9.0")]
-#[rustc_const_unstable(feature = "const_ops", issue = "143802")]
-impl const SubAssign<Duration> for SystemTime {
+impl SubAssign<Duration> for SystemTime {
     fn sub_assign(&mut self, other: Duration) {
         *self = *self - other;
     }
@@ -710,8 +699,7 @@ impl SystemTimeError {
     /// ```
     #[must_use]
     #[stable(feature = "time2", since = "1.8.0")]
-    #[rustc_const_unstable(feature = "const_system_time", issue = "144517")]
-    pub const fn duration(&self) -> Duration {
+    pub fn duration(&self) -> Duration {
         self.0
     }
 }