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-rw-r--r--library/std/Cargo.toml18
-rw-r--r--library/std/benches/lib.rs2
-rw-r--r--library/std/benches/path.rs114
-rw-r--r--library/std/benches/time.rs47
-rw-r--r--library/std/src/bstr.rs4
-rw-r--r--library/std/src/collections/hash/map.rs44
-rw-r--r--library/std/src/collections/hash/set.rs4
-rw-r--r--library/std/src/env.rs11
-rw-r--r--library/std/src/env/tests.rs120
-rw-r--r--library/std/src/error.rs3
-rw-r--r--library/std/src/f128.rs21
-rw-r--r--library/std/src/f16.rs21
-rw-r--r--library/std/src/f32.rs10
-rw-r--r--library/std/src/f64.rs10
-rw-r--r--library/std/src/ffi/os_str.rs4
-rw-r--r--library/std/src/fs.rs62
-rw-r--r--library/std/src/fs/tests.rs4
-rw-r--r--library/std/src/io/copy/tests.rs1
-rw-r--r--library/std/src/io/cursor.rs4
-rw-r--r--library/std/src/io/mod.rs254
-rw-r--r--library/std/src/io/pipe.rs260
-rw-r--r--library/std/src/io/pipe/tests.rs18
-rw-r--r--library/std/src/io/stdio/tests.rs7
-rw-r--r--library/std/src/io/tests.rs19
-rw-r--r--library/std/src/keyword_docs.rs9
-rw-r--r--library/std/src/lib.rs31
-rw-r--r--library/std/src/macros.rs15
-rw-r--r--library/std/src/net/socket_addr.rs3
-rw-r--r--library/std/src/net/tcp.rs3
-rw-r--r--library/std/src/net/test.rs33
-rw-r--r--library/std/src/net/udp.rs3
-rw-r--r--library/std/src/num.rs28
-rw-r--r--library/std/src/os/fd/net.rs4
-rw-r--r--library/std/src/os/fd/raw.rs5
-rw-r--r--library/std/src/os/hermit/io/net.rs2
-rw-r--r--library/std/src/os/solid/io.rs4
-rw-r--r--library/std/src/os/unix/fs/tests.rs4
-rw-r--r--library/std/src/os/unix/net/tests.rs2
-rw-r--r--library/std/src/os/wasi/io/fd.rs9
-rw-r--r--library/std/src/os/wasi/io/mod.rs4
-rw-r--r--library/std/src/os/wasi/io/raw.rs20
-rw-r--r--library/std/src/os/wasi/io/tests.rs (renamed from library/std/src/os/wasi/io/fd/tests.rs)0
-rw-r--r--library/std/src/os/windows/io/raw.rs8
-rw-r--r--library/std/src/os/windows/process.rs8
-rw-r--r--library/std/src/os/xous/ffi/definitions.rs66
-rw-r--r--library/std/src/panic.rs3
-rw-r--r--library/std/src/path.rs3
-rw-r--r--library/std/src/prelude/mod.rs10
-rw-r--r--library/std/src/process.rs12
-rw-r--r--library/std/src/process/tests.rs143
-rw-r--r--library/std/src/rt.rs5
-rw-r--r--library/std/src/sync/barrier.rs3
-rw-r--r--library/std/src/sync/lazy_lock.rs3
-rw-r--r--library/std/src/sync/mpmc/mod.rs16
-rw-r--r--library/std/src/sync/mpsc.rs (renamed from library/std/src/sync/mpsc/mod.rs)13
-rw-r--r--library/std/src/sync/once_lock.rs72
-rw-r--r--library/std/src/sync/poison/condvar.rs3
-rw-r--r--library/std/src/sync/poison/mutex.rs35
-rw-r--r--library/std/src/sync/poison/once.rs9
-rw-r--r--library/std/src/sync/poison/rwlock.rs3
-rw-r--r--library/std/src/sync/reentrant_lock.rs8
-rw-r--r--library/std/src/sys/alloc/wasm.rs4
-rw-r--r--library/std/src/sys/io/io_slice/iovec.rs (renamed from library/std/src/sys/pal/hermit/io.rs)14
-rw-r--r--library/std/src/sys/io/io_slice/unsupported.rs (renamed from library/std/src/sys/pal/unsupported/io.rs)4
-rw-r--r--library/std/src/sys/io/io_slice/wasi.rs (renamed from library/std/src/sys/pal/wasi/io.rs)8
-rw-r--r--library/std/src/sys/io/io_slice/windows.rs (renamed from library/std/src/sys/pal/solid/io.rs)38
-rw-r--r--library/std/src/sys/io/is_terminal/hermit.rs6
-rw-r--r--library/std/src/sys/io/is_terminal/isatty.rs6
-rw-r--r--library/std/src/sys/io/is_terminal/unsupported.rs3
-rw-r--r--library/std/src/sys/io/is_terminal/windows.rs (renamed from library/std/src/sys/pal/windows/io.rs)84
-rw-r--r--library/std/src/sys/io/mod.rs44
-rw-r--r--library/std/src/sys/mod.rs2
-rw-r--r--library/std/src/sys/net/connection/sgx.rs (renamed from library/std/src/sys/pal/sgx/net.rs)2
-rw-r--r--library/std/src/sys/net/connection/socket.rs (renamed from library/std/src/sys_common/net.rs)30
-rw-r--r--library/std/src/sys/net/connection/socket/hermit.rs (renamed from library/std/src/sys/pal/hermit/net.rs)13
-rw-r--r--library/std/src/sys/net/connection/socket/solid.rs (renamed from library/std/src/sys/pal/solid/net.rs)24
-rw-r--r--library/std/src/sys/net/connection/socket/tests.rs (renamed from library/std/src/sys_common/net/tests.rs)0
-rw-r--r--library/std/src/sys/net/connection/socket/unix.rs (renamed from library/std/src/sys/pal/unix/net.rs)10
-rw-r--r--library/std/src/sys/net/connection/socket/wasip2.rs (renamed from library/std/src/sys/pal/wasip2/net.rs)2
-rw-r--r--library/std/src/sys/net/connection/socket/windows.rs (renamed from library/std/src/sys/pal/windows/net.rs)21
-rw-r--r--library/std/src/sys/net/connection/uefi/mod.rs (renamed from library/std/src/sys/pal/unsupported/net.rs)0
-rw-r--r--library/std/src/sys/net/connection/unsupported.rs (renamed from library/std/src/sys/pal/teeos/net.rs)4
-rw-r--r--library/std/src/sys/net/connection/wasip1.rs (renamed from library/std/src/sys/pal/wasi/net.rs)5
-rw-r--r--library/std/src/sys/net/connection/xous/dns.rs (renamed from library/std/src/sys/pal/xous/net/dns.rs)0
-rw-r--r--library/std/src/sys/net/connection/xous/mod.rs (renamed from library/std/src/sys/pal/xous/net/mod.rs)0
-rw-r--r--library/std/src/sys/net/connection/xous/tcplistener.rs (renamed from library/std/src/sys/pal/xous/net/tcplistener.rs)0
-rw-r--r--library/std/src/sys/net/connection/xous/tcpstream.rs (renamed from library/std/src/sys/pal/xous/net/tcpstream.rs)0
-rw-r--r--library/std/src/sys/net/connection/xous/udp.rs (renamed from library/std/src/sys/pal/xous/net/udp.rs)0
-rw-r--r--library/std/src/sys/net/mod.rs41
-rw-r--r--library/std/src/sys/pal/hermit/mod.rs2
-rw-r--r--library/std/src/sys/pal/itron/time/tests.rs30
-rw-r--r--library/std/src/sys/pal/sgx/mod.rs3
-rw-r--r--library/std/src/sys/pal/sgx/stdio.rs2
-rw-r--r--library/std/src/sys/pal/solid/error.rs3
-rw-r--r--library/std/src/sys/pal/solid/mod.rs4
-rw-r--r--library/std/src/sys/pal/teeos/mod.rs3
-rw-r--r--library/std/src/sys/pal/uefi/helpers.rs50
-rw-r--r--library/std/src/sys/pal/uefi/mod.rs4
-rw-r--r--library/std/src/sys/pal/uefi/process.rs72
-rw-r--r--library/std/src/sys/pal/unix/fs.rs32
-rw-r--r--library/std/src/sys/pal/unix/io.rs87
-rw-r--r--library/std/src/sys/pal/unix/kernel_copy/tests.rs2
-rw-r--r--library/std/src/sys/pal/unix/l4re.rs564
-rw-r--r--library/std/src/sys/pal/unix/mod.rs7
-rw-r--r--library/std/src/sys/pal/unix/process/process_unix.rs13
-rw-r--r--library/std/src/sys/pal/unix/stdio.rs2
-rw-r--r--library/std/src/sys/pal/unix/thread.rs11
-rw-r--r--library/std/src/sys/pal/unsupported/mod.rs2
-rw-r--r--library/std/src/sys/pal/wasi/mod.rs8
-rw-r--r--library/std/src/sys/pal/wasi/stdio.rs2
-rw-r--r--library/std/src/sys/pal/wasip2/mod.rs3
-rw-r--r--library/std/src/sys/pal/wasm/mod.rs6
-rw-r--r--library/std/src/sys/pal/windows/args/tests.rs8
-rw-r--r--library/std/src/sys/pal/windows/fs.rs29
-rw-r--r--library/std/src/sys/pal/windows/mod.rs4
-rw-r--r--library/std/src/sys/pal/windows/process/tests.rs2
-rw-r--r--library/std/src/sys/pal/xous/mod.rs3
-rw-r--r--library/std/src/sys/pal/zkvm/mod.rs4
-rw-r--r--library/std/src/sys/pal/zkvm/stdio.rs2
-rw-r--r--library/std/src/sys/path/mod.rs8
-rw-r--r--library/std/src/sys/path/uefi.rs105
-rw-r--r--library/std/src/sys_common/io.rs49
-rw-r--r--library/std/src/sys_common/mod.rs15
-rw-r--r--library/std/src/sys_common/wtf8/tests.rs111
-rw-r--r--library/std/src/test_helpers.rs65
-rw-r--r--library/std/src/thread/local.rs30
-rw-r--r--library/std/src/time.rs3
-rw-r--r--library/std/tests/common/mod.rs2
-rw-r--r--library/std/tests/env.rs218
-rw-r--r--library/std/tests/env_modify.rs166
-rw-r--r--library/std/tests/error.rs (renamed from library/std/src/error/tests.rs)10
-rw-r--r--library/std/tests/floats/f128.rs (renamed from library/std/src/f128/tests.rs)10
-rw-r--r--library/std/tests/floats/f16.rs (renamed from library/std/src/f16/tests.rs)7
-rw-r--r--library/std/tests/floats/f32.rs (renamed from library/std/src/f32/tests.rs)8
-rw-r--r--library/std/tests/floats/f64.rs (renamed from library/std/src/f64/tests.rs)10
-rw-r--r--library/std/tests/floats/lib.rs42
-rw-r--r--library/std/tests/istr.rs4
-rw-r--r--library/std/tests/num.rs (renamed from library/std/src/num/tests.rs)6
-rw-r--r--library/std/tests/panic.rs (renamed from library/std/src/panic/tests.rs)8
-rw-r--r--library/std/tests/path.rs (renamed from library/std/src/path/tests.rs)149
-rw-r--r--library/std/tests/pipe_subprocess.rs2
-rw-r--r--library/std/tests/process_spawning.rs3
-rw-r--r--library/std/tests/seq-compare.rs22
-rw-r--r--library/std/tests/sync/barrier.rs (renamed from library/std/src/sync/barrier/tests.rs)6
-rw-r--r--library/std/tests/sync/condvar.rs (renamed from library/std/src/sync/poison/condvar/tests.rs)10
-rw-r--r--library/std/tests/sync/lazy_lock.rs (renamed from library/std/src/sync/lazy_lock/tests.rs)12
-rw-r--r--library/std/tests/sync/lib.rs31
-rw-r--r--library/std/tests/sync/mpmc.rs (renamed from library/std/src/sync/mpmc/tests.rs)5
-rw-r--r--library/std/tests/sync/mpsc.rs (renamed from library/std/src/sync/mpsc/tests.rs)5
-rw-r--r--library/std/tests/sync/mpsc_sync.rs (renamed from library/std/src/sync/mpsc/sync_tests.rs)9
-rw-r--r--library/std/tests/sync/mutex.rs (renamed from library/std/src/sync/poison/mutex/tests.rs)14
-rw-r--r--library/std/tests/sync/once.rs (renamed from library/std/src/sync/poison/once/tests.rs)12
-rw-r--r--library/std/tests/sync/once_lock.rs (renamed from library/std/src/sync/once_lock/tests.rs)22
-rw-r--r--library/std/tests/sync/reentrant_lock.rs (renamed from library/std/src/sync/reentrant_lock/tests.rs)7
-rw-r--r--library/std/tests/sync/rwlock.rs (renamed from library/std/src/sync/poison/rwlock/tests.rs)22
-rw-r--r--library/std/tests/thread_local/dynamic_tests.rs (renamed from library/std/src/thread/local/dynamic_tests.rs)6
-rw-r--r--library/std/tests/thread_local/lib.rs4
-rw-r--r--library/std/tests/thread_local/tests.rs (renamed from library/std/src/thread/local/tests.rs)10
-rw-r--r--library/std/tests/time.rs (renamed from library/std/src/time/tests.rs)55
-rw-r--r--library/std/tests/win_delete_self.rs8
160 files changed, 1886 insertions, 2398 deletions
diff --git a/library/std/Cargo.toml b/library/std/Cargo.toml
index da58d7c13bd..aa391a4b317 100644
--- a/library/std/Cargo.toml
+++ b/library/std/Cargo.toml
@@ -7,6 +7,7 @@ license = "MIT OR Apache-2.0"
 repository = "https://github.com/rust-lang/rust.git"
 description = "The Rust Standard Library"
 edition = "2021"
+autobenches = false
 
 [lib]
 crate-type = ["dylib", "rlib"]
@@ -17,7 +18,7 @@ cfg-if = { version = "1.0", features = ['rustc-dep-of-std'] }
 panic_unwind = { path = "../panic_unwind", optional = true }
 panic_abort = { path = "../panic_abort" }
 core = { path = "../core", public = true }
-compiler_builtins = { version = "=0.1.143" }
+compiler_builtins = { version = "=0.1.145" }
 unwind = { path = "../unwind" }
 hashbrown = { version = "0.15", default-features = false, features = [
     'rustc-dep-of-std',
@@ -130,6 +131,18 @@ name = "pipe-subprocess"
 path = "tests/pipe_subprocess.rs"
 harness = false
 
+[[test]]
+name = "sync"
+path = "tests/sync/lib.rs"
+
+[[test]]
+name = "floats"
+path = "tests/floats/lib.rs"
+
+[[test]]
+name = "thread_local"
+path = "tests/thread_local/lib.rs"
+
 [[bench]]
 name = "stdbenches"
 path = "benches/lib.rs"
@@ -139,7 +152,8 @@ test = true
 level = "warn"
 check-cfg = [
     'cfg(bootstrap)',
-    'cfg(target_arch, values("xtensa"))',
+    'cfg(target_arch, values("xtensa", "aarch64-unknown-nto-qnx710_iosock", "x86_64-pc-nto-qnx710_iosock", "x86_64-pc-nto-qnx800","aarch64-unknown-nto-qnx800"))',
+    'cfg(target_env, values("nto71_iosock", "nto80"))',
     # std use #[path] imports to portable-simd `std_float` crate
     # and to the `backtrace` crate which messes-up with Cargo list
     # of declared features, we therefor expect any feature cfg
diff --git a/library/std/benches/lib.rs b/library/std/benches/lib.rs
index 1b21c230a0b..e749d9c0f79 100644
--- a/library/std/benches/lib.rs
+++ b/library/std/benches/lib.rs
@@ -5,3 +5,5 @@
 extern crate test;
 
 mod hash;
+mod path;
+mod time;
diff --git a/library/std/benches/path.rs b/library/std/benches/path.rs
new file mode 100644
index 00000000000..094c00894a8
--- /dev/null
+++ b/library/std/benches/path.rs
@@ -0,0 +1,114 @@
+use core::hint::black_box;
+use std::collections::{BTreeSet, HashSet};
+use std::hash::{DefaultHasher, Hash, Hasher};
+use std::path::*;
+
+#[bench]
+#[cfg_attr(miri, ignore)] // Miri isn't fast...
+fn bench_path_cmp_fast_path_buf_sort(b: &mut test::Bencher) {
+    let prefix = "my/home";
+    let mut paths: Vec<_> =
+        (0..1000).map(|num| PathBuf::from(prefix).join(format!("file {num}.rs"))).collect();
+
+    paths.sort();
+
+    b.iter(|| {
+        black_box(paths.as_mut_slice()).sort_unstable();
+    });
+}
+
+#[bench]
+#[cfg_attr(miri, ignore)] // Miri isn't fast...
+fn bench_path_cmp_fast_path_long(b: &mut test::Bencher) {
+    let prefix = "/my/home/is/my/castle/and/my/castle/has/a/rusty/workbench/";
+    let paths: Vec<_> =
+        (0..1000).map(|num| PathBuf::from(prefix).join(format!("file {num}.rs"))).collect();
+
+    let mut set = BTreeSet::new();
+
+    paths.iter().for_each(|p| {
+        set.insert(p.as_path());
+    });
+
+    b.iter(|| {
+        set.remove(paths[500].as_path());
+        set.insert(paths[500].as_path());
+    });
+}
+
+#[bench]
+#[cfg_attr(miri, ignore)] // Miri isn't fast...
+fn bench_path_cmp_fast_path_short(b: &mut test::Bencher) {
+    let prefix = "my/home";
+    let paths: Vec<_> =
+        (0..1000).map(|num| PathBuf::from(prefix).join(format!("file {num}.rs"))).collect();
+
+    let mut set = BTreeSet::new();
+
+    paths.iter().for_each(|p| {
+        set.insert(p.as_path());
+    });
+
+    b.iter(|| {
+        set.remove(paths[500].as_path());
+        set.insert(paths[500].as_path());
+    });
+}
+
+#[bench]
+#[cfg_attr(miri, ignore)] // Miri isn't fast...
+fn bench_path_hashset(b: &mut test::Bencher) {
+    let prefix = "/my/home/is/my/castle/and/my/castle/has/a/rusty/workbench/";
+    let paths: Vec<_> =
+        (0..1000).map(|num| PathBuf::from(prefix).join(format!("file {num}.rs"))).collect();
+
+    let mut set = HashSet::new();
+
+    paths.iter().for_each(|p| {
+        set.insert(p.as_path());
+    });
+
+    b.iter(|| {
+        set.remove(paths[500].as_path());
+        set.insert(black_box(paths[500].as_path()))
+    });
+}
+
+#[bench]
+#[cfg_attr(miri, ignore)] // Miri isn't fast...
+fn bench_path_hashset_miss(b: &mut test::Bencher) {
+    let prefix = "/my/home/is/my/castle/and/my/castle/has/a/rusty/workbench/";
+    let paths: Vec<_> =
+        (0..1000).map(|num| PathBuf::from(prefix).join(format!("file {num}.rs"))).collect();
+
+    let mut set = HashSet::new();
+
+    paths.iter().for_each(|p| {
+        set.insert(p.as_path());
+    });
+
+    let probe = PathBuf::from(prefix).join("other");
+
+    b.iter(|| set.remove(black_box(probe.as_path())));
+}
+
+#[bench]
+fn bench_hash_path_short(b: &mut test::Bencher) {
+    let mut hasher = DefaultHasher::new();
+    let path = Path::new("explorer.exe");
+
+    b.iter(|| black_box(path).hash(&mut hasher));
+
+    black_box(hasher.finish());
+}
+
+#[bench]
+fn bench_hash_path_long(b: &mut test::Bencher) {
+    let mut hasher = DefaultHasher::new();
+    let path =
+        Path::new("/aaaaa/aaaaaa/./../aaaaaaaa/bbbbbbbbbbbbb/ccccccccccc/ddddddddd/eeeeeee.fff");
+
+    b.iter(|| black_box(path).hash(&mut hasher));
+
+    black_box(hasher.finish());
+}
diff --git a/library/std/benches/time.rs b/library/std/benches/time.rs
new file mode 100644
index 00000000000..552481cad92
--- /dev/null
+++ b/library/std/benches/time.rs
@@ -0,0 +1,47 @@
+use std::time::Instant;
+
+#[cfg(not(target_arch = "wasm32"))]
+use test::{Bencher, black_box};
+
+macro_rules! bench_instant_threaded {
+    ($bench_name:ident, $thread_count:expr) => {
+        #[bench]
+        #[cfg(not(target_arch = "wasm32"))]
+        fn $bench_name(b: &mut Bencher) -> std::thread::Result<()> {
+            use std::sync::Arc;
+            use std::sync::atomic::{AtomicBool, Ordering};
+
+            let running = Arc::new(AtomicBool::new(true));
+
+            let threads: Vec<_> = (0..$thread_count)
+                .map(|_| {
+                    let flag = Arc::clone(&running);
+                    std::thread::spawn(move || {
+                        while flag.load(Ordering::Relaxed) {
+                            black_box(Instant::now());
+                        }
+                    })
+                })
+                .collect();
+
+            b.iter(|| {
+                let a = Instant::now();
+                let b = Instant::now();
+                assert!(b >= a);
+            });
+
+            running.store(false, Ordering::Relaxed);
+
+            for t in threads {
+                t.join()?;
+            }
+            Ok(())
+        }
+    };
+}
+
+bench_instant_threaded!(instant_contention_01_threads, 0);
+bench_instant_threaded!(instant_contention_02_threads, 1);
+bench_instant_threaded!(instant_contention_04_threads, 3);
+bench_instant_threaded!(instant_contention_08_threads, 7);
+bench_instant_threaded!(instant_contention_16_threads, 15);
diff --git a/library/std/src/bstr.rs b/library/std/src/bstr.rs
new file mode 100644
index 00000000000..dd491771628
--- /dev/null
+++ b/library/std/src/bstr.rs
@@ -0,0 +1,4 @@
+//! The `ByteStr` and `ByteString` types and trait implementations.
+
+#[unstable(feature = "bstr", issue = "134915")]
+pub use alloc::bstr::{ByteStr, ByteString};
diff --git a/library/std/src/collections/hash/map.rs b/library/std/src/collections/hash/map.rs
index d2342d8fd51..6a0ff3a29e0 100644
--- a/library/std/src/collections/hash/map.rs
+++ b/library/std/src/collections/hash/map.rs
@@ -282,7 +282,7 @@ impl<K, V, S> HashMap<K, V, S> {
     /// manually using this function can expose a DoS attack vector.
     ///
     /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
-    /// the HashMap to be useful, see its documentation for details.
+    /// the `HashMap` to be useful, see its documentation for details.
     ///
     /// # Examples
     ///
@@ -314,7 +314,7 @@ impl<K, V, S> HashMap<K, V, S> {
     /// manually using this function can expose a DoS attack vector.
     ///
     /// The `hasher` passed should implement the [`BuildHasher`] trait for
-    /// the HashMap to be useful, see its documentation for details.
+    /// the `HashMap` to be useful, see its documentation for details.
     ///
     /// # Examples
     ///
@@ -969,7 +969,6 @@ where
     /// # Examples
     ///
     /// ```
-    /// #![feature(map_many_mut)]
     /// use std::collections::HashMap;
     ///
     /// let mut libraries = HashMap::new();
@@ -979,13 +978,13 @@ where
     /// libraries.insert("Library of Congress".to_string(), 1800);
     ///
     /// // Get Athenæum and Bodleian Library
-    /// let [Some(a), Some(b)] = libraries.get_many_mut([
+    /// let [Some(a), Some(b)] = libraries.get_disjoint_mut([
     ///     "Athenæum",
     ///     "Bodleian Library",
     /// ]) else { panic!() };
     ///
     /// // Assert values of Athenæum and Library of Congress
-    /// let got = libraries.get_many_mut([
+    /// let got = libraries.get_disjoint_mut([
     ///     "Athenæum",
     ///     "Library of Congress",
     /// ]);
@@ -998,7 +997,7 @@ where
     /// );
     ///
     /// // Missing keys result in None
-    /// let got = libraries.get_many_mut([
+    /// let got = libraries.get_disjoint_mut([
     ///     "Athenæum",
     ///     "New York Public Library",
     /// ]);
@@ -1012,21 +1011,24 @@ where
     /// ```
     ///
     /// ```should_panic
-    /// #![feature(map_many_mut)]
     /// use std::collections::HashMap;
     ///
     /// let mut libraries = HashMap::new();
     /// libraries.insert("Athenæum".to_string(), 1807);
     ///
     /// // Duplicate keys panic!
-    /// let got = libraries.get_many_mut([
+    /// let got = libraries.get_disjoint_mut([
     ///     "Athenæum",
     ///     "Athenæum",
     /// ]);
     /// ```
     #[inline]
-    #[unstable(feature = "map_many_mut", issue = "97601")]
-    pub fn get_many_mut<Q: ?Sized, const N: usize>(&mut self, ks: [&Q; N]) -> [Option<&'_ mut V>; N]
+    #[doc(alias = "get_many_mut")]
+    #[stable(feature = "map_many_mut", since = "CURRENT_RUSTC_VERSION")]
+    pub fn get_disjoint_mut<Q: ?Sized, const N: usize>(
+        &mut self,
+        ks: [&Q; N],
+    ) -> [Option<&'_ mut V>; N]
     where
         K: Borrow<Q>,
         Q: Hash + Eq,
@@ -1040,7 +1042,7 @@ where
     /// Returns an array of length `N` with the results of each query. `None` will be used if
     /// the key is missing.
     ///
-    /// For a safe alternative see [`get_many_mut`](`HashMap::get_many_mut`).
+    /// For a safe alternative see [`get_disjoint_mut`](`HashMap::get_disjoint_mut`).
     ///
     /// # Safety
     ///
@@ -1052,7 +1054,6 @@ where
     /// # Examples
     ///
     /// ```
-    /// #![feature(map_many_mut)]
     /// use std::collections::HashMap;
     ///
     /// let mut libraries = HashMap::new();
@@ -1062,13 +1063,13 @@ where
     /// libraries.insert("Library of Congress".to_string(), 1800);
     ///
     /// // SAFETY: The keys do not overlap.
-    /// let [Some(a), Some(b)] = (unsafe { libraries.get_many_unchecked_mut([
+    /// let [Some(a), Some(b)] = (unsafe { libraries.get_disjoint_unchecked_mut([
     ///     "Athenæum",
     ///     "Bodleian Library",
     /// ]) }) else { panic!() };
     ///
     /// // SAFETY: The keys do not overlap.
-    /// let got = unsafe { libraries.get_many_unchecked_mut([
+    /// let got = unsafe { libraries.get_disjoint_unchecked_mut([
     ///     "Athenæum",
     ///     "Library of Congress",
     /// ]) };
@@ -1081,7 +1082,7 @@ where
     /// );
     ///
     /// // SAFETY: The keys do not overlap.
-    /// let got = unsafe { libraries.get_many_unchecked_mut([
+    /// let got = unsafe { libraries.get_disjoint_unchecked_mut([
     ///     "Athenæum",
     ///     "New York Public Library",
     /// ]) };
@@ -1089,8 +1090,9 @@ where
     /// assert_eq!(got, [Some(&mut 1807), None]);
     /// ```
     #[inline]
-    #[unstable(feature = "map_many_mut", issue = "97601")]
-    pub unsafe fn get_many_unchecked_mut<Q: ?Sized, const N: usize>(
+    #[doc(alias = "get_many_unchecked_mut")]
+    #[stable(feature = "map_many_mut", since = "CURRENT_RUSTC_VERSION")]
+    pub unsafe fn get_disjoint_unchecked_mut<Q: ?Sized, const N: usize>(
         &mut self,
         ks: [&Q; N],
     ) -> [Option<&'_ mut V>; N]
@@ -1281,7 +1283,7 @@ impl<K, V, S> HashMap<K, V, S>
 where
     S: BuildHasher,
 {
-    /// Creates a raw entry builder for the HashMap.
+    /// Creates a raw entry builder for the `HashMap`.
     ///
     /// Raw entries provide the lowest level of control for searching and
     /// manipulating a map. They must be manually initialized with a hash and
@@ -1296,13 +1298,13 @@ where
     /// * Using custom comparison logic without newtype wrappers
     ///
     /// Because raw entries provide much more low-level control, it's much easier
-    /// to put the HashMap into an inconsistent state which, while memory-safe,
+    /// to put the `HashMap` into an inconsistent state which, while memory-safe,
     /// will cause the map to produce seemingly random results. Higher-level and
     /// more foolproof APIs like `entry` should be preferred when possible.
     ///
     /// In particular, the hash used to initialize the raw entry must still be
     /// consistent with the hash of the key that is ultimately stored in the entry.
-    /// This is because implementations of HashMap may need to recompute hashes
+    /// This is because implementations of `HashMap` may need to recompute hashes
     /// when resizing, at which point only the keys are available.
     ///
     /// Raw entries give mutable access to the keys. This must not be used
@@ -1318,7 +1320,7 @@ where
         RawEntryBuilderMut { map: self }
     }
 
-    /// Creates a raw immutable entry builder for the HashMap.
+    /// Creates a raw immutable entry builder for the `HashMap`.
     ///
     /// Raw entries provide the lowest level of control for searching and
     /// manipulating a map. They must be manually initialized with a hash and
diff --git a/library/std/src/collections/hash/set.rs b/library/std/src/collections/hash/set.rs
index bbb6ca23521..c265d42d06a 100644
--- a/library/std/src/collections/hash/set.rs
+++ b/library/std/src/collections/hash/set.rs
@@ -374,7 +374,7 @@ impl<T, S> HashSet<T, S> {
     /// manually using this function can expose a DoS attack vector.
     ///
     /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
-    /// the HashMap to be useful, see its documentation for details.
+    /// the `HashSet` to be useful, see its documentation for details.
     ///
     /// # Examples
     ///
@@ -406,7 +406,7 @@ impl<T, S> HashSet<T, S> {
     /// manually using this function can expose a DoS attack vector.
     ///
     /// The `hash_builder` passed should implement the [`BuildHasher`] trait for
-    /// the HashMap to be useful, see its documentation for details.
+    /// the `HashSet` to be useful, see its documentation for details.
     ///
     /// # Examples
     ///
diff --git a/library/std/src/env.rs b/library/std/src/env.rs
index 11a29cdae62..c665dfd3624 100644
--- a/library/std/src/env.rs
+++ b/library/std/src/env.rs
@@ -10,9 +10,6 @@
 
 #![stable(feature = "env", since = "1.0.0")]
 
-#[cfg(test)]
-mod tests;
-
 use crate::error::Error;
 use crate::ffi::{OsStr, OsString};
 use crate::path::{Path, PathBuf};
@@ -336,7 +333,10 @@ impl Error for VarError {
 ///  - [Austin Group Bugzilla](https://austingroupbugs.net/view.php?id=188)
 ///  - [GNU C library Bugzilla](https://sourceware.org/bugzilla/show_bug.cgi?id=15607#c2)
 ///
+/// To pass an environment variable to a child process, you can instead use [`Command::env`].
+///
 /// [`std::net::ToSocketAddrs`]: crate::net::ToSocketAddrs
+/// [`Command::env`]: crate::process::Command::env
 ///
 /// # Panics
 ///
@@ -396,7 +396,12 @@ pub unsafe fn set_var<K: AsRef<OsStr>, V: AsRef<OsStr>>(key: K, value: V) {
 ///  - [Austin Group Bugzilla](https://austingroupbugs.net/view.php?id=188)
 ///  - [GNU C library Bugzilla](https://sourceware.org/bugzilla/show_bug.cgi?id=15607#c2)
 ///
+/// To prevent a child process from inheriting an environment variable, you can
+/// instead use [`Command::env_remove`] or [`Command::env_clear`].
+///
 /// [`std::net::ToSocketAddrs`]: crate::net::ToSocketAddrs
+/// [`Command::env_remove`]: crate::process::Command::env_remove
+/// [`Command::env_clear`]: crate::process::Command::env_clear
 ///
 /// # Panics
 ///
diff --git a/library/std/src/env/tests.rs b/library/std/src/env/tests.rs
deleted file mode 100644
index d0217261068..00000000000
--- a/library/std/src/env/tests.rs
+++ /dev/null
@@ -1,120 +0,0 @@
-use super::*;
-
-#[test]
-#[cfg_attr(any(target_os = "emscripten", target_os = "wasi", target_env = "sgx"), ignore)]
-fn test_self_exe_path() {
-    let path = current_exe();
-    assert!(path.is_ok());
-    let path = path.unwrap();
-
-    // Hard to test this function
-    assert!(path.is_absolute());
-}
-
-#[test]
-fn test() {
-    assert!((!Path::new("test-path").is_absolute()));
-
-    #[cfg(not(target_env = "sgx"))]
-    current_dir().unwrap();
-}
-
-#[test]
-#[cfg(windows)]
-fn split_paths_windows() {
-    use crate::path::PathBuf;
-
-    fn check_parse(unparsed: &str, parsed: &[&str]) -> bool {
-        split_paths(unparsed).collect::<Vec<_>>()
-            == parsed.iter().map(|s| PathBuf::from(*s)).collect::<Vec<_>>()
-    }
-
-    assert!(check_parse("", &mut [""]));
-    assert!(check_parse(r#""""#, &mut [""]));
-    assert!(check_parse(";;", &mut ["", "", ""]));
-    assert!(check_parse(r"c:\", &mut [r"c:\"]));
-    assert!(check_parse(r"c:\;", &mut [r"c:\", ""]));
-    assert!(check_parse(r"c:\;c:\Program Files\", &mut [r"c:\", r"c:\Program Files\"]));
-    assert!(check_parse(r#"c:\;c:\"foo"\"#, &mut [r"c:\", r"c:\foo\"]));
-    assert!(check_parse(r#"c:\;c:\"foo;bar"\;c:\baz"#, &mut [r"c:\", r"c:\foo;bar\", r"c:\baz"]));
-}
-
-#[test]
-#[cfg(unix)]
-fn split_paths_unix() {
-    use crate::path::PathBuf;
-
-    fn check_parse(unparsed: &str, parsed: &[&str]) -> bool {
-        split_paths(unparsed).collect::<Vec<_>>()
-            == parsed.iter().map(|s| PathBuf::from(*s)).collect::<Vec<_>>()
-    }
-
-    assert!(check_parse("", &mut [""]));
-    assert!(check_parse("::", &mut ["", "", ""]));
-    assert!(check_parse("/", &mut ["/"]));
-    assert!(check_parse("/:", &mut ["/", ""]));
-    assert!(check_parse("/:/usr/local", &mut ["/", "/usr/local"]));
-}
-
-#[test]
-#[cfg(unix)]
-fn join_paths_unix() {
-    use crate::ffi::OsStr;
-
-    fn test_eq(input: &[&str], output: &str) -> bool {
-        &*join_paths(input.iter().cloned()).unwrap() == OsStr::new(output)
-    }
-
-    assert!(test_eq(&[], ""));
-    assert!(test_eq(&["/bin", "/usr/bin", "/usr/local/bin"], "/bin:/usr/bin:/usr/local/bin"));
-    assert!(test_eq(&["", "/bin", "", "", "/usr/bin", ""], ":/bin:::/usr/bin:"));
-    assert!(join_paths(["/te:st"].iter().cloned()).is_err());
-}
-
-#[test]
-#[cfg(windows)]
-fn join_paths_windows() {
-    use crate::ffi::OsStr;
-
-    fn test_eq(input: &[&str], output: &str) -> bool {
-        &*join_paths(input.iter().cloned()).unwrap() == OsStr::new(output)
-    }
-
-    assert!(test_eq(&[], ""));
-    assert!(test_eq(&[r"c:\windows", r"c:\"], r"c:\windows;c:\"));
-    assert!(test_eq(&["", r"c:\windows", "", "", r"c:\", ""], r";c:\windows;;;c:\;"));
-    assert!(test_eq(&[r"c:\te;st", r"c:\"], r#""c:\te;st";c:\"#));
-    assert!(join_paths([r#"c:\te"st"#].iter().cloned()).is_err());
-}
-
-#[test]
-fn args_debug() {
-    assert_eq!(
-        format!("Args {{ inner: {:?} }}", args().collect::<Vec<_>>()),
-        format!("{:?}", args())
-    );
-}
-
-#[test]
-fn args_os_debug() {
-    assert_eq!(
-        format!("ArgsOs {{ inner: {:?} }}", args_os().collect::<Vec<_>>()),
-        format!("{:?}", args_os())
-    );
-}
-
-#[test]
-fn vars_debug() {
-    assert_eq!(
-        format!("Vars {{ inner: {:?} }}", vars().collect::<Vec<_>>()),
-        format!("{:?}", vars())
-    );
-}
-
-#[test]
-fn vars_os_debug() {
-    assert_eq!(
-        format!("VarsOs {{ inner: {:?} }}", vars_os().collect::<Vec<_>>()),
-        format!("{:?}", vars_os())
-    );
-}
diff --git a/library/std/src/error.rs b/library/std/src/error.rs
index b3e63aaf1c5..def5f984c88 100644
--- a/library/std/src/error.rs
+++ b/library/std/src/error.rs
@@ -1,9 +1,6 @@
 #![doc = include_str!("../../core/src/error.md")]
 #![stable(feature = "rust1", since = "1.0.0")]
 
-#[cfg(test)]
-mod tests;
-
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::error::Error;
 #[unstable(feature = "error_generic_member_access", issue = "99301")]
diff --git a/library/std/src/f128.rs b/library/std/src/f128.rs
index 4f37e18a8cd..89612fa7475 100644
--- a/library/std/src/f128.rs
+++ b/library/std/src/f128.rs
@@ -4,9 +4,6 @@
 //!
 //! Mathematically significant numbers are provided in the `consts` sub-module.
 
-#[cfg(test)]
-mod tests;
-
 #[unstable(feature = "f128", issue = "116909")]
 pub use core::f128::consts;
 
@@ -324,6 +321,20 @@ impl f128 {
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform,
     /// Rust version, and can even differ within the same execution from one invocation to the next.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(f128)]
+    /// # #[cfg(reliable_f128_math)] {
+    ///
+    /// let x = 2.0_f128;
+    /// let abs_difference = (x.powi(2) - (x * x)).abs();
+    /// assert!(abs_difference <= f128::EPSILON);
+    ///
+    /// assert_eq!(f128::powi(f128::NAN, 0), 1.0);
+    /// # }
+    /// ```
     #[inline]
     #[rustc_allow_incoherent_impl]
     #[unstable(feature = "f128", issue = "116909")]
@@ -347,8 +358,10 @@ impl f128 {
     ///
     /// let x = 2.0_f128;
     /// let abs_difference = (x.powf(2.0) - (x * x)).abs();
-    ///
     /// assert!(abs_difference <= f128::EPSILON);
+    ///
+    /// assert_eq!(f128::powf(1.0, f128::NAN), 1.0);
+    /// assert_eq!(f128::powf(f128::NAN, 0.0), 1.0);
     /// # }
     /// ```
     #[inline]
diff --git a/library/std/src/f16.rs b/library/std/src/f16.rs
index 42cd6e3fe2a..cc523c93b4d 100644
--- a/library/std/src/f16.rs
+++ b/library/std/src/f16.rs
@@ -4,9 +4,6 @@
 //!
 //! Mathematically significant numbers are provided in the `consts` sub-module.
 
-#[cfg(test)]
-mod tests;
-
 #[unstable(feature = "f16", issue = "116909")]
 pub use core::f16::consts;
 
@@ -324,6 +321,20 @@ impl f16 {
     ///
     /// The precision of this function is non-deterministic. This means it varies by platform,
     /// Rust version, and can even differ within the same execution from one invocation to the next.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(f16)]
+    /// # #[cfg(reliable_f16_math)] {
+    ///
+    /// let x = 2.0_f16;
+    /// let abs_difference = (x.powi(2) - (x * x)).abs();
+    /// assert!(abs_difference <= f16::EPSILON);
+    ///
+    /// assert_eq!(f16::powi(f16::NAN, 0), 1.0);
+    /// # }
+    /// ```
     #[inline]
     #[rustc_allow_incoherent_impl]
     #[unstable(feature = "f16", issue = "116909")]
@@ -347,8 +358,10 @@ impl f16 {
     ///
     /// let x = 2.0_f16;
     /// let abs_difference = (x.powf(2.0) - (x * x)).abs();
-    ///
     /// assert!(abs_difference <= f16::EPSILON);
+    ///
+    /// assert_eq!(f16::powf(1.0, f16::NAN), 1.0);
+    /// assert_eq!(f16::powf(f16::NAN, 0.0), 1.0);
     /// # }
     /// ```
     #[inline]
diff --git a/library/std/src/f32.rs b/library/std/src/f32.rs
index 438d77b1626..260c499b7f4 100644
--- a/library/std/src/f32.rs
+++ b/library/std/src/f32.rs
@@ -12,9 +12,6 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 #![allow(missing_docs)]
 
-#[cfg(test)]
-mod tests;
-
 #[stable(feature = "rust1", since = "1.0.0")]
 #[allow(deprecated, deprecated_in_future)]
 pub use core::f32::{
@@ -306,8 +303,9 @@ impl f32 {
     /// ```
     /// let x = 2.0_f32;
     /// let abs_difference = (x.powi(2) - (x * x)).abs();
-    ///
     /// assert!(abs_difference <= f32::EPSILON);
+    ///
+    /// assert_eq!(f32::powi(f32::NAN, 0), 1.0);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
@@ -329,8 +327,10 @@ impl f32 {
     /// ```
     /// let x = 2.0_f32;
     /// let abs_difference = (x.powf(2.0) - (x * x)).abs();
-    ///
     /// assert!(abs_difference <= f32::EPSILON);
+    ///
+    /// assert_eq!(f32::powf(1.0, f32::NAN), 1.0);
+    /// assert_eq!(f32::powf(f32::NAN, 0.0), 1.0);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
diff --git a/library/std/src/f64.rs b/library/std/src/f64.rs
index 9bb4bfbab2a..7af646f8cfd 100644
--- a/library/std/src/f64.rs
+++ b/library/std/src/f64.rs
@@ -12,9 +12,6 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 #![allow(missing_docs)]
 
-#[cfg(test)]
-mod tests;
-
 #[stable(feature = "rust1", since = "1.0.0")]
 #[allow(deprecated, deprecated_in_future)]
 pub use core::f64::{
@@ -306,8 +303,9 @@ impl f64 {
     /// ```
     /// let x = 2.0_f64;
     /// let abs_difference = (x.powi(2) - (x * x)).abs();
+    /// assert!(abs_difference <= f64::EPSILON);
     ///
-    /// assert!(abs_difference < 1e-10);
+    /// assert_eq!(f64::powi(f64::NAN, 0), 1.0);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
@@ -329,8 +327,10 @@ impl f64 {
     /// ```
     /// let x = 2.0_f64;
     /// let abs_difference = (x.powf(2.0) - (x * x)).abs();
+    /// assert!(abs_difference <= f64::EPSILON);
     ///
-    /// assert!(abs_difference < 1e-10);
+    /// assert_eq!(f64::powf(1.0, f64::NAN), 1.0);
+    /// assert_eq!(f64::powf(f64::NAN, 0.0), 1.0);
     /// ```
     #[rustc_allow_incoherent_impl]
     #[must_use = "method returns a new number and does not mutate the original value"]
diff --git a/library/std/src/ffi/os_str.rs b/library/std/src/ffi/os_str.rs
index 7fb57d41043..c4c8dbccd7a 100644
--- a/library/std/src/ffi/os_str.rs
+++ b/library/std/src/ffi/os_str.rs
@@ -203,8 +203,8 @@ impl OsString {
         self
     }
 
-    /// Converts the `OsString` into a byte slice.  To convert the byte slice back into an
-    /// `OsString`, use the [`OsStr::from_encoded_bytes_unchecked`] function.
+    /// Converts the `OsString` into a byte vector.  To convert the byte vector back into an
+    /// `OsString`, use the [`OsString::from_encoded_bytes_unchecked`] function.
     ///
     /// The byte encoding is an unspecified, platform-specific, self-synchronizing superset of UTF-8.
     /// By being a self-synchronizing superset of UTF-8, this encoding is also a superset of 7-bit
diff --git a/library/std/src/fs.rs b/library/std/src/fs.rs
index 9b752ed1443..0871a9e22d3 100644
--- a/library/std/src/fs.rs
+++ b/library/std/src/fs.rs
@@ -629,9 +629,9 @@ impl File {
     /// This acquires an exclusive advisory lock; no other file handle to this file may acquire
     /// another lock.
     ///
-    /// If this file handle, or a clone of it, already holds an advisory lock the exact behavior is
-    /// unspecified and platform dependent, including the possibility that it will deadlock.
-    /// However, if this method returns, then an exclusive lock is held.
+    /// If this file handle/descriptor, or a clone of it, already holds an advisory lock the exact
+    /// behavior is unspecified and platform dependent, including the possibility that it will
+    /// deadlock. However, if this method returns, then an exclusive lock is held.
     ///
     /// If the file not open for writing, it is unspecified whether this function returns an error.
     ///
@@ -639,6 +639,9 @@ impl File {
     /// [`try_lock_shared`], and [`unlock`]. Its interactions with other methods, such as [`read`]
     /// and [`write`] are platform specific, and it may or may not cause non-lockholders to block.
     ///
+    /// The lock will be released when this file (along with any other file descriptors/handles
+    /// duplicated or inherited from it) is closed, or if the [`unlock`] method is called.
+    ///
     /// # Platform-specific behavior
     ///
     /// This function currently corresponds to the `flock` function on Unix with the `LOCK_EX` flag,
@@ -671,19 +674,22 @@ impl File {
         self.inner.lock()
     }
 
-    /// Acquire a shared advisory lock on the file. Blocks until the lock can be acquired.
+    /// Acquire a shared (non-exclusive) advisory lock on the file. Blocks until the lock can be acquired.
     ///
     /// This acquires a shared advisory lock; more than one file handle may hold a shared lock, but
-    /// none may hold an exclusive lock.
+    /// none may hold an exclusive lock at the same time.
     ///
-    /// If this file handle, or a clone of it, already holds an advisory lock, the exact behavior is
-    /// unspecified and platform dependent, including the possibility that it will deadlock.
-    /// However, if this method returns, then a shared lock is held.
+    /// If this file handle/descriptor, or a clone of it, already holds an advisory lock, the exact
+    /// behavior is unspecified and platform dependent, including the possibility that it will
+    /// deadlock. However, if this method returns, then a shared lock is held.
     ///
     /// Note, this is an advisory lock meant to interact with [`lock`], [`try_lock`],
     /// [`try_lock_shared`], and [`unlock`]. Its interactions with other methods, such as [`read`]
     /// and [`write`] are platform specific, and it may or may not cause non-lockholders to block.
     ///
+    /// The lock will be released when this file (along with any other file descriptors/handles
+    /// duplicated or inherited from it) is closed, or if the [`unlock`] method is called.
+    ///
     /// # Platform-specific behavior
     ///
     /// This function currently corresponds to the `flock` function on Unix with the `LOCK_SH` flag,
@@ -716,14 +722,18 @@ impl File {
         self.inner.lock_shared()
     }
 
-    /// Acquire an exclusive advisory lock on the file. Returns `Ok(false)` if the file is locked.
+    /// Try to acquire an exclusive advisory lock on the file.
+    ///
+    /// Returns `Ok(false)` if a different lock is already held on this file (via another
+    /// handle/descriptor).
     ///
     /// This acquires an exclusive advisory lock; no other file handle to this file may acquire
     /// another lock.
     ///
-    /// If this file handle, or a clone of it, already holds an advisory lock, the exact behavior is
-    /// unspecified and platform dependent, including the possibility that it will deadlock.
-    /// However, if this method returns, then an exclusive lock is held.
+    /// If this file handle/descriptor, or a clone of it, already holds an advisory lock, the exact
+    /// behavior is unspecified and platform dependent, including the possibility that it will
+    /// deadlock. However, if this method returns `Ok(true)`, then it has acquired an exclusive
+    /// lock.
     ///
     /// If the file not open for writing, it is unspecified whether this function returns an error.
     ///
@@ -731,6 +741,9 @@ impl File {
     /// [`try_lock_shared`], and [`unlock`]. Its interactions with other methods, such as [`read`]
     /// and [`write`] are platform specific, and it may or may not cause non-lockholders to block.
     ///
+    /// The lock will be released when this file (along with any other file descriptors/handles
+    /// duplicated or inherited from it) is closed, or if the [`unlock`] method is called.
+    ///
     /// # Platform-specific behavior
     ///
     /// This function currently corresponds to the `flock` function on Unix with the `LOCK_EX` and
@@ -764,20 +777,25 @@ impl File {
         self.inner.try_lock()
     }
 
-    /// Acquire a shared advisory lock on the file.
-    /// Returns `Ok(false)` if the file is exclusively locked.
+    /// Try to acquire a shared (non-exclusive) advisory lock on the file.
+    ///
+    /// Returns `Ok(false)` if an exclusive lock is already held on this file (via another
+    /// handle/descriptor).
     ///
     /// This acquires a shared advisory lock; more than one file handle may hold a shared lock, but
-    /// none may hold an exclusive lock.
+    /// none may hold an exclusive lock at the same time.
     ///
     /// If this file handle, or a clone of it, already holds an advisory lock, the exact behavior is
     /// unspecified and platform dependent, including the possibility that it will deadlock.
-    /// However, if this method returns, then a shared lock is held.
+    /// However, if this method returns `Ok(true)`, then it has acquired a shared lock.
     ///
     /// Note, this is an advisory lock meant to interact with [`lock`], [`try_lock`],
     /// [`try_lock`], and [`unlock`]. Its interactions with other methods, such as [`read`]
     /// and [`write`] are platform specific, and it may or may not cause non-lockholders to block.
     ///
+    /// The lock will be released when this file (along with any other file descriptors/handles
+    /// duplicated or inherited from it) is closed, or if the [`unlock`] method is called.
+    ///
     /// # Platform-specific behavior
     ///
     /// This function currently corresponds to the `flock` function on Unix with the `LOCK_SH` and
@@ -813,7 +831,12 @@ impl File {
 
     /// Release all locks on the file.
     ///
-    /// All remaining locks are released when the file handle, and all clones of it, are dropped.
+    /// All locks are released when the file (along with any other file descriptors/handles
+    /// duplicated or inherited from it) is closed. This method allows releasing locks without
+    /// closing the file.
+    ///
+    /// If no lock is currently held via this file descriptor/handle, this method may return an
+    /// error, or may return successfully without taking any action.
     ///
     /// # Platform-specific behavior
     ///
@@ -2284,8 +2307,8 @@ impl AsInner<fs_imp::DirEntry> for DirEntry {
 ///
 /// # Platform-specific behavior
 ///
-/// This function currently corresponds to the `unlink` function on Unix
-/// and the `DeleteFile` function on Windows.
+/// This function currently corresponds to the `unlink` function on Unix.
+/// On Windows, `DeleteFile` is used or `CreateFileW` and `SetInformationByHandle` for readonly files.
 /// Note that, this [may change in the future][changes].
 ///
 /// [changes]: io#platform-specific-behavior
@@ -2529,6 +2552,7 @@ pub fn copy<P: AsRef<Path>, Q: AsRef<Path>>(from: P, to: Q) -> io::Result<u64> {
 /// limited to just these cases:
 ///
 /// * The `original` path is not a file or doesn't exist.
+/// * The 'link' path already exists.
 ///
 /// # Examples
 ///
diff --git a/library/std/src/fs/tests.rs b/library/std/src/fs/tests.rs
index 28f16da1ed8..8e307f57cf9 100644
--- a/library/std/src/fs/tests.rs
+++ b/library/std/src/fs/tests.rs
@@ -14,7 +14,7 @@ use crate::os::unix::fs::symlink as junction_point;
 use crate::os::windows::fs::{OpenOptionsExt, junction_point, symlink_dir, symlink_file};
 use crate::path::Path;
 use crate::sync::Arc;
-use crate::sys_common::io::test::{TempDir, tmpdir};
+use crate::test_helpers::{TempDir, tmpdir};
 use crate::time::{Duration, Instant, SystemTime};
 use crate::{env, str, thread};
 
@@ -1384,7 +1384,7 @@ fn file_try_clone() {
 }
 
 #[test]
-#[cfg(not(windows))]
+#[cfg(not(target_vendor = "win7"))]
 fn unlink_readonly() {
     let tmpdir = tmpdir();
     let path = tmpdir.join("file");
diff --git a/library/std/src/io/copy/tests.rs b/library/std/src/io/copy/tests.rs
index 2e0eb6cdce6..25b1ece2745 100644
--- a/library/std/src/io/copy/tests.rs
+++ b/library/std/src/io/copy/tests.rs
@@ -126,6 +126,7 @@ mod io_benches {
     use crate::io::prelude::*;
 
     #[bench]
+    #[cfg_attr(target_os = "emscripten", ignore)] // no /dev
     fn bench_copy_buf_reader(b: &mut Bencher) {
         let mut file_in = File::open("/dev/zero").expect("opening /dev/zero failed");
         // use dyn to avoid specializations unrelated to readbuf
diff --git a/library/std/src/io/cursor.rs b/library/std/src/io/cursor.rs
index b2ffeb0f95d..606099c8bc6 100644
--- a/library/std/src/io/cursor.rs
+++ b/library/std/src/io/cursor.rs
@@ -153,7 +153,7 @@ impl<T> Cursor<T> {
     /// let reference = buff.get_mut();
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_mut_cursor", issue = "130801")]
+    #[rustc_const_stable(feature = "const_mut_cursor", since = "CURRENT_RUSTC_VERSION")]
     pub const fn get_mut(&mut self) -> &mut T {
         &mut self.inner
     }
@@ -201,7 +201,7 @@ impl<T> Cursor<T> {
     /// assert_eq!(buff.position(), 4);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
-    #[rustc_const_unstable(feature = "const_mut_cursor", issue = "130801")]
+    #[rustc_const_stable(feature = "const_mut_cursor", since = "CURRENT_RUSTC_VERSION")]
     pub const fn set_position(&mut self, pos: u64) {
         self.pos = pos;
     }
diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index 231c8712ebd..0ffad2c27a4 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -310,6 +310,8 @@ pub use self::error::RawOsError;
 pub use self::error::SimpleMessage;
 #[unstable(feature = "io_const_error", issue = "133448")]
 pub use self::error::const_error;
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+pub use self::pipe::{PipeReader, PipeWriter, pipe};
 #[stable(feature = "is_terminal", since = "1.70.0")]
 pub use self::stdio::IsTerminal;
 pub(crate) use self::stdio::attempt_print_to_stderr;
@@ -330,7 +332,6 @@ pub use self::{
 };
 use crate::mem::take;
 use crate::ops::{Deref, DerefMut};
-use crate::sys::anonymous_pipe::{AnonPipe, pipe as pipe_inner};
 use crate::{cmp, fmt, slice, str, sys};
 
 mod buffered;
@@ -338,11 +339,12 @@ pub(crate) mod copy;
 mod cursor;
 mod error;
 mod impls;
+mod pipe;
 pub mod prelude;
 mod stdio;
 mod util;
 
-const DEFAULT_BUF_SIZE: usize = crate::sys_common::io::DEFAULT_BUF_SIZE;
+const DEFAULT_BUF_SIZE: usize = crate::sys::io::DEFAULT_BUF_SIZE;
 
 pub(crate) use stdio::cleanup;
 
@@ -3251,251 +3253,3 @@ impl<B: BufRead> Iterator for Lines<B> {
         }
     }
 }
-
-/// Create anonymous pipe that is close-on-exec and blocking.
-///
-/// # Behavior
-///
-/// A pipe is a synchronous, unidirectional data channel between two or more processes, like an
-/// interprocess [`mpsc`](crate::sync::mpsc) provided by the OS. In particular:
-///
-/// * A read on a [`PipeReader`] blocks until the pipe is non-empty.
-/// * A write on a [`PipeWriter`] blocks when the pipe is full.
-/// * When all copies of a [`PipeWriter`] are closed, a read on the corresponding [`PipeReader`]
-///   returns EOF.
-/// * [`PipeReader`] can be shared, but only one process will consume the data in the pipe.
-///
-/// # Capacity
-///
-/// Pipe capacity is platform dependent. To quote the Linux [man page]:
-///
-/// > Different implementations have different limits for the pipe capacity. Applications should
-/// > not rely on a particular capacity: an application should be designed so that a reading process
-/// > consumes data as soon as it is available, so that a writing process does not remain blocked.
-///
-/// # Examples
-///
-/// ```no_run
-/// #![feature(anonymous_pipe)]
-/// # #[cfg(miri)] fn main() {}
-/// # #[cfg(not(miri))]
-/// # fn main() -> std::io::Result<()> {
-/// # use std::process::Command;
-/// # use std::io::{Read, Write};
-/// let (ping_rx, mut ping_tx) = std::io::pipe()?;
-/// let (mut pong_rx, pong_tx) = std::io::pipe()?;
-///
-/// // Spawn a process that echoes its input.
-/// let mut echo_server = Command::new("cat").stdin(ping_rx).stdout(pong_tx).spawn()?;
-///
-/// ping_tx.write_all(b"hello")?;
-/// // Close to unblock echo_server's reader.
-/// drop(ping_tx);
-///
-/// let mut buf = String::new();
-/// // Block until echo_server's writer is closed.
-/// pong_rx.read_to_string(&mut buf)?;
-/// assert_eq!(&buf, "hello");
-///
-/// echo_server.wait()?;
-/// # Ok(())
-/// # }
-/// ```
-/// [pipe]: https://man7.org/linux/man-pages/man2/pipe.2.html
-/// [CreatePipe]: https://learn.microsoft.com/en-us/windows/win32/api/namedpipeapi/nf-namedpipeapi-createpipe
-/// [man page]: https://man7.org/linux/man-pages/man7/pipe.7.html
-#[unstable(feature = "anonymous_pipe", issue = "127154")]
-#[inline]
-pub fn pipe() -> Result<(PipeReader, PipeWriter)> {
-    pipe_inner().map(|(reader, writer)| (PipeReader(reader), PipeWriter(writer)))
-}
-
-/// Read end of the anonymous pipe.
-#[unstable(feature = "anonymous_pipe", issue = "127154")]
-#[derive(Debug)]
-pub struct PipeReader(pub(crate) AnonPipe);
-
-/// Write end of the anonymous pipe.
-#[unstable(feature = "anonymous_pipe", issue = "127154")]
-#[derive(Debug)]
-pub struct PipeWriter(pub(crate) AnonPipe);
-
-impl PipeReader {
-    /// Create a new [`PipeReader`] instance that shares the same underlying file description.
-    ///
-    /// # Examples
-    ///
-    /// ```no_run
-    /// #![feature(anonymous_pipe)]
-    /// # #[cfg(miri)] fn main() {}
-    /// # #[cfg(not(miri))]
-    /// # fn main() -> std::io::Result<()> {
-    /// # use std::fs;
-    /// # use std::io::Write;
-    /// # use std::process::Command;
-    /// const NUM_SLOT: u8 = 2;
-    /// const NUM_PROC: u8 = 5;
-    /// const OUTPUT: &str = "work.txt";
-    ///
-    /// let mut jobs = vec![];
-    /// let (reader, mut writer) = std::io::pipe()?;
-    ///
-    /// // Write NUM_SLOT characters the pipe.
-    /// writer.write_all(&[b'|'; NUM_SLOT as usize])?;
-    ///
-    /// // Spawn several processes that read a character from the pipe, do some work, then
-    /// // write back to the pipe. When the pipe is empty, the processes block, so only
-    /// // NUM_SLOT processes can be working at any given time.
-    /// for _ in 0..NUM_PROC {
-    ///     jobs.push(
-    ///         Command::new("bash")
-    ///             .args(["-c",
-    ///                 &format!(
-    ///                      "read -n 1\n\
-    ///                       echo -n 'x' >> '{OUTPUT}'\n\
-    ///                       echo -n '|'",
-    ///                 ),
-    ///             ])
-    ///             .stdin(reader.try_clone()?)
-    ///             .stdout(writer.try_clone()?)
-    ///             .spawn()?,
-    ///     );
-    /// }
-    ///
-    /// // Wait for all jobs to finish.
-    /// for mut job in jobs {
-    ///     job.wait()?;
-    /// }
-    ///
-    /// // Check our work and clean up.
-    /// let xs = fs::read_to_string(OUTPUT)?;
-    /// fs::remove_file(OUTPUT)?;
-    /// assert_eq!(xs, "x".repeat(NUM_PROC.into()));
-    /// # Ok(())
-    /// # }
-    /// ```
-    #[unstable(feature = "anonymous_pipe", issue = "127154")]
-    pub fn try_clone(&self) -> Result<Self> {
-        self.0.try_clone().map(Self)
-    }
-}
-
-impl PipeWriter {
-    /// Create a new [`PipeWriter`] instance that shares the same underlying file description.
-    ///
-    /// # Examples
-    ///
-    /// ```no_run
-    /// #![feature(anonymous_pipe)]
-    /// # #[cfg(miri)] fn main() {}
-    /// # #[cfg(not(miri))]
-    /// # fn main() -> std::io::Result<()> {
-    /// # use std::process::Command;
-    /// # use std::io::Read;
-    /// let (mut reader, writer) = std::io::pipe()?;
-    ///
-    /// // Spawn a process that writes to stdout and stderr.
-    /// let mut peer = Command::new("bash")
-    ///     .args([
-    ///         "-c",
-    ///         "echo -n foo\n\
-    ///          echo -n bar >&2"
-    ///     ])
-    ///     .stdout(writer.try_clone()?)
-    ///     .stderr(writer)
-    ///     .spawn()?;
-    ///
-    /// // Read and check the result.
-    /// let mut msg = String::new();
-    /// reader.read_to_string(&mut msg)?;
-    /// assert_eq!(&msg, "foobar");
-    ///
-    /// peer.wait()?;
-    /// # Ok(())
-    /// # }
-    /// ```
-    #[unstable(feature = "anonymous_pipe", issue = "127154")]
-    pub fn try_clone(&self) -> Result<Self> {
-        self.0.try_clone().map(Self)
-    }
-}
-
-#[unstable(feature = "anonymous_pipe", issue = "127154")]
-impl Read for &PipeReader {
-    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
-        self.0.read(buf)
-    }
-    fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize> {
-        self.0.read_vectored(bufs)
-    }
-    #[inline]
-    fn is_read_vectored(&self) -> bool {
-        self.0.is_read_vectored()
-    }
-    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> {
-        self.0.read_to_end(buf)
-    }
-    fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<()> {
-        self.0.read_buf(buf)
-    }
-}
-
-#[unstable(feature = "anonymous_pipe", issue = "127154")]
-impl Read for PipeReader {
-    fn read(&mut self, buf: &mut [u8]) -> Result<usize> {
-        self.0.read(buf)
-    }
-    fn read_vectored(&mut self, bufs: &mut [IoSliceMut<'_>]) -> Result<usize> {
-        self.0.read_vectored(bufs)
-    }
-    #[inline]
-    fn is_read_vectored(&self) -> bool {
-        self.0.is_read_vectored()
-    }
-    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<usize> {
-        self.0.read_to_end(buf)
-    }
-    fn read_buf(&mut self, buf: BorrowedCursor<'_>) -> Result<()> {
-        self.0.read_buf(buf)
-    }
-}
-
-#[unstable(feature = "anonymous_pipe", issue = "127154")]
-impl Write for &PipeWriter {
-    fn write(&mut self, buf: &[u8]) -> Result<usize> {
-        self.0.write(buf)
-    }
-    #[inline]
-    fn flush(&mut self) -> Result<()> {
-        Ok(())
-    }
-
-    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize> {
-        self.0.write_vectored(bufs)
-    }
-
-    #[inline]
-    fn is_write_vectored(&self) -> bool {
-        self.0.is_write_vectored()
-    }
-}
-
-#[unstable(feature = "anonymous_pipe", issue = "127154")]
-impl Write for PipeWriter {
-    fn write(&mut self, buf: &[u8]) -> Result<usize> {
-        self.0.write(buf)
-    }
-    #[inline]
-    fn flush(&mut self) -> Result<()> {
-        Ok(())
-    }
-
-    fn write_vectored(&mut self, bufs: &[IoSlice<'_>]) -> Result<usize> {
-        self.0.write_vectored(bufs)
-    }
-
-    #[inline]
-    fn is_write_vectored(&self) -> bool {
-        self.0.is_write_vectored()
-    }
-}
diff --git a/library/std/src/io/pipe.rs b/library/std/src/io/pipe.rs
new file mode 100644
index 00000000000..266c7bc9638
--- /dev/null
+++ b/library/std/src/io/pipe.rs
@@ -0,0 +1,260 @@
+use crate::io;
+use crate::sys::anonymous_pipe::{AnonPipe, pipe as pipe_inner};
+
+/// Create an anonymous pipe.
+///
+/// # Behavior
+///
+/// A pipe is a one-way data channel provided by the OS, which works across processes. A pipe is
+/// typically used to communicate between two or more separate processes, as there are better,
+/// faster ways to communicate within a single process.
+///
+/// In particular:
+///
+/// * A read on a [`PipeReader`] blocks until the pipe is non-empty.
+/// * A write on a [`PipeWriter`] blocks when the pipe is full.
+/// * When all copies of a [`PipeWriter`] are closed, a read on the corresponding [`PipeReader`]
+///   returns EOF.
+/// * [`PipeWriter`] can be shared, and multiple processes or threads can write to it at once, but
+///   writes (above a target-specific threshold) may have their data interleaved.
+/// * [`PipeReader`] can be shared, and multiple processes or threads can read it at once. Any
+///   given byte will only get consumed by one reader. There are no guarantees about data
+///   interleaving.
+/// * Portable applications cannot assume any atomicity of messages larger than a single byte.
+///
+/// # Platform-specific behavior
+///
+/// This function currently corresponds to the `pipe` function on Unix and the
+/// `CreatePipe` function on Windows.
+///
+/// Note that this [may change in the future][changes].
+///
+/// # Capacity
+///
+/// Pipe capacity is platform dependent. To quote the Linux [man page]:
+///
+/// > Different implementations have different limits for the pipe capacity. Applications should
+/// > not rely on a particular capacity: an application should be designed so that a reading process
+/// > consumes data as soon as it is available, so that a writing process does not remain blocked.
+///
+/// # Examples
+///
+/// ```no_run
+/// #![feature(anonymous_pipe)]
+/// # #[cfg(miri)] fn main() {}
+/// # #[cfg(not(miri))]
+/// # fn main() -> std::io::Result<()> {
+/// use std::process::Command;
+/// use std::io::{pipe, Read, Write};
+/// let (ping_rx, mut ping_tx) = pipe()?;
+/// let (mut pong_rx, pong_tx) = pipe()?;
+///
+/// // Spawn a process that echoes its input.
+/// let mut echo_server = Command::new("cat").stdin(ping_rx).stdout(pong_tx).spawn()?;
+///
+/// ping_tx.write_all(b"hello")?;
+/// // Close to unblock echo_server's reader.
+/// drop(ping_tx);
+///
+/// let mut buf = String::new();
+/// // Block until echo_server's writer is closed.
+/// pong_rx.read_to_string(&mut buf)?;
+/// assert_eq!(&buf, "hello");
+///
+/// echo_server.wait()?;
+/// # Ok(())
+/// # }
+/// ```
+/// [changes]: io#platform-specific-behavior
+/// [man page]: https://man7.org/linux/man-pages/man7/pipe.7.html
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+#[inline]
+pub fn pipe() -> io::Result<(PipeReader, PipeWriter)> {
+    pipe_inner().map(|(reader, writer)| (PipeReader(reader), PipeWriter(writer)))
+}
+
+/// Read end of an anonymous pipe.
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+#[derive(Debug)]
+pub struct PipeReader(pub(crate) AnonPipe);
+
+/// Write end of an anonymous pipe.
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+#[derive(Debug)]
+pub struct PipeWriter(pub(crate) AnonPipe);
+
+impl PipeReader {
+    /// Create a new [`PipeReader`] instance that shares the same underlying file description.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// #![feature(anonymous_pipe)]
+    /// # #[cfg(miri)] fn main() {}
+    /// # #[cfg(not(miri))]
+    /// # fn main() -> std::io::Result<()> {
+    /// use std::fs;
+    /// use std::io::{pipe, Write};
+    /// use std::process::Command;
+    /// const NUM_SLOT: u8 = 2;
+    /// const NUM_PROC: u8 = 5;
+    /// const OUTPUT: &str = "work.txt";
+    ///
+    /// let mut jobs = vec![];
+    /// let (reader, mut writer) = pipe()?;
+    ///
+    /// // Write NUM_SLOT characters the pipe.
+    /// writer.write_all(&[b'|'; NUM_SLOT as usize])?;
+    ///
+    /// // Spawn several processes that read a character from the pipe, do some work, then
+    /// // write back to the pipe. When the pipe is empty, the processes block, so only
+    /// // NUM_SLOT processes can be working at any given time.
+    /// for _ in 0..NUM_PROC {
+    ///     jobs.push(
+    ///         Command::new("bash")
+    ///             .args(["-c",
+    ///                 &format!(
+    ///                      "read -n 1\n\
+    ///                       echo -n 'x' >> '{OUTPUT}'\n\
+    ///                       echo -n '|'",
+    ///                 ),
+    ///             ])
+    ///             .stdin(reader.try_clone()?)
+    ///             .stdout(writer.try_clone()?)
+    ///             .spawn()?,
+    ///     );
+    /// }
+    ///
+    /// // Wait for all jobs to finish.
+    /// for mut job in jobs {
+    ///     job.wait()?;
+    /// }
+    ///
+    /// // Check our work and clean up.
+    /// let xs = fs::read_to_string(OUTPUT)?;
+    /// fs::remove_file(OUTPUT)?;
+    /// assert_eq!(xs, "x".repeat(NUM_PROC.into()));
+    /// # Ok(())
+    /// # }
+    /// ```
+    #[unstable(feature = "anonymous_pipe", issue = "127154")]
+    pub fn try_clone(&self) -> io::Result<Self> {
+        self.0.try_clone().map(Self)
+    }
+}
+
+impl PipeWriter {
+    /// Create a new [`PipeWriter`] instance that shares the same underlying file description.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// #![feature(anonymous_pipe)]
+    /// # #[cfg(miri)] fn main() {}
+    /// # #[cfg(not(miri))]
+    /// # fn main() -> std::io::Result<()> {
+    /// use std::process::Command;
+    /// use std::io::{pipe, Read};
+    /// let (mut reader, writer) = pipe()?;
+    ///
+    /// // Spawn a process that writes to stdout and stderr.
+    /// let mut peer = Command::new("bash")
+    ///     .args([
+    ///         "-c",
+    ///         "echo -n foo\n\
+    ///          echo -n bar >&2"
+    ///     ])
+    ///     .stdout(writer.try_clone()?)
+    ///     .stderr(writer)
+    ///     .spawn()?;
+    ///
+    /// // Read and check the result.
+    /// let mut msg = String::new();
+    /// reader.read_to_string(&mut msg)?;
+    /// assert_eq!(&msg, "foobar");
+    ///
+    /// peer.wait()?;
+    /// # Ok(())
+    /// # }
+    /// ```
+    #[unstable(feature = "anonymous_pipe", issue = "127154")]
+    pub fn try_clone(&self) -> io::Result<Self> {
+        self.0.try_clone().map(Self)
+    }
+}
+
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl io::Read for &PipeReader {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        self.0.read(buf)
+    }
+    fn read_vectored(&mut self, bufs: &mut [io::IoSliceMut<'_>]) -> io::Result<usize> {
+        self.0.read_vectored(bufs)
+    }
+    #[inline]
+    fn is_read_vectored(&self) -> bool {
+        self.0.is_read_vectored()
+    }
+    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
+        self.0.read_to_end(buf)
+    }
+    fn read_buf(&mut self, buf: io::BorrowedCursor<'_>) -> io::Result<()> {
+        self.0.read_buf(buf)
+    }
+}
+
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl io::Read for PipeReader {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        self.0.read(buf)
+    }
+    fn read_vectored(&mut self, bufs: &mut [io::IoSliceMut<'_>]) -> io::Result<usize> {
+        self.0.read_vectored(bufs)
+    }
+    #[inline]
+    fn is_read_vectored(&self) -> bool {
+        self.0.is_read_vectored()
+    }
+    fn read_to_end(&mut self, buf: &mut Vec<u8>) -> io::Result<usize> {
+        self.0.read_to_end(buf)
+    }
+    fn read_buf(&mut self, buf: io::BorrowedCursor<'_>) -> io::Result<()> {
+        self.0.read_buf(buf)
+    }
+}
+
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl io::Write for &PipeWriter {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.0.write(buf)
+    }
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+    fn write_vectored(&mut self, bufs: &[io::IoSlice<'_>]) -> io::Result<usize> {
+        self.0.write_vectored(bufs)
+    }
+    #[inline]
+    fn is_write_vectored(&self) -> bool {
+        self.0.is_write_vectored()
+    }
+}
+
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+impl io::Write for PipeWriter {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.0.write(buf)
+    }
+    #[inline]
+    fn flush(&mut self) -> io::Result<()> {
+        Ok(())
+    }
+    fn write_vectored(&mut self, bufs: &[io::IoSlice<'_>]) -> io::Result<usize> {
+        self.0.write_vectored(bufs)
+    }
+    #[inline]
+    fn is_write_vectored(&self) -> bool {
+        self.0.is_write_vectored()
+    }
+}
diff --git a/library/std/src/io/pipe/tests.rs b/library/std/src/io/pipe/tests.rs
new file mode 100644
index 00000000000..f113b157459
--- /dev/null
+++ b/library/std/src/io/pipe/tests.rs
@@ -0,0 +1,18 @@
+use crate::io::{Read, Write, pipe};
+
+#[test]
+#[cfg(all(any(unix, windows), not(miri)))]
+fn pipe_creation_clone_and_rw() {
+    let (rx, tx) = pipe().unwrap();
+
+    tx.try_clone().unwrap().write_all(b"12345").unwrap();
+    drop(tx);
+
+    let mut rx2 = rx.try_clone().unwrap();
+    drop(rx);
+
+    let mut s = String::new();
+    rx2.read_to_string(&mut s).unwrap();
+    drop(rx2);
+    assert_eq!(s, "12345");
+}
diff --git a/library/std/src/io/stdio/tests.rs b/library/std/src/io/stdio/tests.rs
index bf8f3a5adfb..e68d8c29fbc 100644
--- a/library/std/src/io/stdio/tests.rs
+++ b/library/std/src/io/stdio/tests.rs
@@ -159,7 +159,8 @@ where
     assert_eq!(rx2.recv().unwrap(), Release2); // release th2
     th2.join().unwrap();
     th1.join().unwrap();
-    assert_eq!(*log.lock().unwrap(), [
-        Start1, Acquire1, Start2, Release1, Acquire2, Release2, Acquire1, Release1
-    ]);
+    assert_eq!(
+        *log.lock().unwrap(),
+        [Start1, Acquire1, Start2, Release1, Acquire2, Release2, Acquire1, Release1]
+    );
 }
diff --git a/library/std/src/io/tests.rs b/library/std/src/io/tests.rs
index 85098b3bb18..f64f034cce7 100644
--- a/library/std/src/io/tests.rs
+++ b/library/std/src/io/tests.rs
@@ -7,7 +7,6 @@ use crate::mem::MaybeUninit;
 use crate::ops::Deref;
 
 #[test]
-#[cfg_attr(target_os = "emscripten", ignore)]
 fn read_until() {
     let mut buf = Cursor::new(&b"12"[..]);
     let mut v = Vec::new();
@@ -359,7 +358,6 @@ fn chain_zero_length_read_is_not_eof() {
 }
 
 #[bench]
-#[cfg_attr(target_os = "emscripten", ignore)]
 #[cfg_attr(miri, ignore)] // Miri isn't fast...
 fn bench_read_to_end(b: &mut test::Bencher) {
     b.iter(|| {
@@ -823,20 +821,3 @@ fn try_oom_error() {
     let io_err = io::Error::from(reserve_err);
     assert_eq!(io::ErrorKind::OutOfMemory, io_err.kind());
 }
-
-#[test]
-#[cfg(all(windows, unix, not(miri)))]
-fn pipe_creation_clone_and_rw() {
-    let (rx, tx) = std::io::pipe().unwrap();
-
-    tx.try_clone().unwrap().write_all(b"12345").unwrap();
-    drop(tx);
-
-    let mut rx2 = rx.try_clone().unwrap();
-    drop(rx);
-
-    let mut s = String::new();
-    rx2.read_to_string(&mut s).unwrap();
-    drop(rx2);
-    assert_eq!(s, "12345");
-}
diff --git a/library/std/src/keyword_docs.rs b/library/std/src/keyword_docs.rs
index 0c526eafdf3..1d26bf37f4d 100644
--- a/library/std/src/keyword_docs.rs
+++ b/library/std/src/keyword_docs.rs
@@ -2387,13 +2387,12 @@ mod async_keyword {}
 /// [`async`]: ../std/keyword.async.html
 mod await_keyword {}
 
-// FIXME(dyn_compat_renaming): Update URL and link text.
 #[doc(keyword = "dyn")]
 //
 /// `dyn` is a prefix of a [trait object]'s type.
 ///
 /// The `dyn` keyword is used to highlight that calls to methods on the associated `Trait`
-/// are [dynamically dispatched]. To use the trait this way, it must be 'dyn-compatible'[^1].
+/// are [dynamically dispatched]. To use the trait this way, it must be *dyn compatible*[^1].
 ///
 /// Unlike generic parameters or `impl Trait`, the compiler does not know the concrete type that
 /// is being passed. That is, the type has been [erased].
@@ -2406,7 +2405,7 @@ mod await_keyword {}
 /// the function pointer and then that function pointer is called.
 ///
 /// See the Reference for more information on [trait objects][ref-trait-obj]
-/// and [object safety][ref-obj-safety].
+/// and [dyn compatibility][ref-dyn-compat].
 ///
 /// ## Trade-offs
 ///
@@ -2419,9 +2418,9 @@ mod await_keyword {}
 /// [trait object]: ../book/ch17-02-trait-objects.html
 /// [dynamically dispatched]: https://en.wikipedia.org/wiki/Dynamic_dispatch
 /// [ref-trait-obj]: ../reference/types/trait-object.html
-/// [ref-obj-safety]: ../reference/items/traits.html#object-safety
+/// [ref-dyn-compat]: ../reference/items/traits.html#dyn-compatibility
 /// [erased]: https://en.wikipedia.org/wiki/Type_erasure
-/// [^1]: Formerly known as 'object safe'.
+/// [^1]: Formerly known as *object safe*.
 mod dyn_keyword {}
 
 #[doc(keyword = "union")]
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 39f234e4ba6..954a4182fbd 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -320,6 +320,8 @@
 // Library features (core):
 // tidy-alphabetical-start
 #![feature(array_chunks)]
+#![feature(bstr)]
+#![feature(bstr_internals)]
 #![feature(c_str_module)]
 #![feature(char_internals)]
 #![feature(clone_to_uninit)]
@@ -528,6 +530,8 @@ pub use core::option;
 pub use core::pin;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::ptr;
+#[unstable(feature = "new_range_api", issue = "125687")]
+pub use core::range;
 #[stable(feature = "rust1", since = "1.0.0")]
 pub use core::result;
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -581,6 +585,8 @@ pub mod f64;
 pub mod thread;
 pub mod ascii;
 pub mod backtrace;
+#[unstable(feature = "bstr", issue = "134915")]
+pub mod bstr;
 pub mod collections;
 pub mod env;
 pub mod error;
@@ -733,27 +739,4 @@ mod sealed {
 
 #[cfg(test)]
 #[allow(dead_code)] // Not used in all configurations.
-pub(crate) mod test_helpers {
-    /// Test-only replacement for `rand::thread_rng()`, which is unusable for
-    /// us, as we want to allow running stdlib tests on tier-3 targets which may
-    /// not have `getrandom` support.
-    ///
-    /// Does a bit of a song and dance to ensure that the seed is different on
-    /// each call (as some tests sadly rely on this), but doesn't try that hard.
-    ///
-    /// This is duplicated in the `core`, `alloc` test suites (as well as
-    /// `std`'s integration tests), but figuring out a mechanism to share these
-    /// seems far more painful than copy-pasting a 7 line function a couple
-    /// times, given that even under a perma-unstable feature, I don't think we
-    /// want to expose types from `rand` from `std`.
-    #[track_caller]
-    pub(crate) fn test_rng() -> rand_xorshift::XorShiftRng {
-        use core::hash::{BuildHasher, Hash, Hasher};
-        let mut hasher = crate::hash::RandomState::new().build_hasher();
-        core::panic::Location::caller().hash(&mut hasher);
-        let hc64 = hasher.finish();
-        let seed_vec = hc64.to_le_bytes().into_iter().chain(0u8..8).collect::<Vec<u8>>();
-        let seed: [u8; 16] = seed_vec.as_slice().try_into().unwrap();
-        rand::SeedableRng::from_seed(seed)
-    }
-}
+pub(crate) mod test_helpers;
diff --git a/library/std/src/macros.rs b/library/std/src/macros.rs
index 1b0d7f3dbf2..e0f9f0bb5ce 100644
--- a/library/std/src/macros.rs
+++ b/library/std/src/macros.rs
@@ -372,18 +372,3 @@ macro_rules! dbg {
         ($($crate::dbg!($val)),+,)
     };
 }
-
-/// Verify that floats are within a tolerance of each other, 1.0e-6 by default.
-#[cfg(test)]
-macro_rules! assert_approx_eq {
-    ($a:expr, $b:expr) => {{ assert_approx_eq!($a, $b, 1.0e-6) }};
-    ($a:expr, $b:expr, $lim:expr) => {{
-        let (a, b) = (&$a, &$b);
-        let diff = (*a - *b).abs();
-        assert!(
-            diff < $lim,
-            "{a:?} is not approximately equal to {b:?} (threshold {lim:?}, difference {diff:?})",
-            lim = $lim
-        );
-    }};
-}
diff --git a/library/std/src/net/socket_addr.rs b/library/std/src/net/socket_addr.rs
index ba9c948a2e9..e8355cc31d7 100644
--- a/library/std/src/net/socket_addr.rs
+++ b/library/std/src/net/socket_addr.rs
@@ -6,8 +6,7 @@ mod tests;
 pub use core::net::{SocketAddr, SocketAddrV4, SocketAddrV6};
 
 use crate::net::{IpAddr, Ipv4Addr, Ipv6Addr};
-use crate::sys::net::netc as c;
-use crate::sys_common::net::LookupHost;
+use crate::sys::net::{LookupHost, netc as c};
 use crate::sys_common::{FromInner, IntoInner};
 use crate::{io, iter, mem, option, slice, vec};
 
diff --git a/library/std/src/net/tcp.rs b/library/std/src/net/tcp.rs
index 67a0f7e439d..9b68f872955 100644
--- a/library/std/src/net/tcp.rs
+++ b/library/std/src/net/tcp.rs
@@ -15,7 +15,8 @@ use crate::io::prelude::*;
 use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
 use crate::iter::FusedIterator;
 use crate::net::{Shutdown, SocketAddr, ToSocketAddrs};
-use crate::sys_common::{AsInner, FromInner, IntoInner, net as net_imp};
+use crate::sys::net as net_imp;
+use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::time::Duration;
 
 /// A TCP stream between a local and a remote socket.
diff --git a/library/std/src/net/test.rs b/library/std/src/net/test.rs
index d318d457f35..a5c3983cd89 100644
--- a/library/std/src/net/test.rs
+++ b/library/std/src/net/test.rs
@@ -5,14 +5,15 @@ use crate::net::{Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6, ToS
 use crate::sync::atomic::{AtomicUsize, Ordering};
 
 static PORT: AtomicUsize = AtomicUsize::new(0);
+const BASE_PORT: u16 = 19600;
 
 pub fn next_test_ip4() -> SocketAddr {
-    let port = PORT.fetch_add(1, Ordering::Relaxed) as u16 + base_port();
+    let port = PORT.fetch_add(1, Ordering::Relaxed) as u16 + BASE_PORT;
     SocketAddr::V4(SocketAddrV4::new(Ipv4Addr::new(127, 0, 0, 1), port))
 }
 
 pub fn next_test_ip6() -> SocketAddr {
-    let port = PORT.fetch_add(1, Ordering::Relaxed) as u16 + base_port();
+    let port = PORT.fetch_add(1, Ordering::Relaxed) as u16 + BASE_PORT;
     SocketAddr::V6(SocketAddrV6::new(Ipv6Addr::new(0, 0, 0, 0, 0, 0, 0, 1), port, 0, 0))
 }
 
@@ -30,31 +31,3 @@ pub fn tsa<A: ToSocketAddrs>(a: A) -> Result<Vec<SocketAddr>, String> {
         Err(e) => Err(e.to_string()),
     }
 }
-
-// The bots run multiple builds at the same time, and these builds
-// all want to use ports. This function figures out which workspace
-// it is running in and assigns a port range based on it.
-fn base_port() -> u16 {
-    let cwd = if cfg!(target_env = "sgx") {
-        String::from("sgx")
-    } else {
-        env::current_dir().unwrap().into_os_string().into_string().unwrap()
-    };
-    let dirs = [
-        "32-opt",
-        "32-nopt",
-        "musl-64-opt",
-        "cross-opt",
-        "64-opt",
-        "64-nopt",
-        "64-opt-vg",
-        "64-debug-opt",
-        "all-opt",
-        "snap3",
-        "dist",
-        "sgx",
-    ];
-    dirs.iter().enumerate().find(|&(_, dir)| cwd.contains(dir)).map(|p| p.0).unwrap_or(0) as u16
-        * 1000
-        + 19600
-}
diff --git a/library/std/src/net/udp.rs b/library/std/src/net/udp.rs
index 674c5fb7d6e..3eb798ad34a 100644
--- a/library/std/src/net/udp.rs
+++ b/library/std/src/net/udp.rs
@@ -12,7 +12,8 @@ mod tests;
 use crate::fmt;
 use crate::io::{self, ErrorKind};
 use crate::net::{Ipv4Addr, Ipv6Addr, SocketAddr, ToSocketAddrs};
-use crate::sys_common::{AsInner, FromInner, IntoInner, net as net_imp};
+use crate::sys::net as net_imp;
+use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::time::Duration;
 
 /// A UDP socket.
diff --git a/library/std/src/num.rs b/library/std/src/num.rs
index d2f679e7dde..ffb8789c906 100644
--- a/library/std/src/num.rs
+++ b/library/std/src/num.rs
@@ -6,9 +6,6 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 #![allow(missing_docs)]
 
-#[cfg(test)]
-mod tests;
-
 #[stable(feature = "int_error_matching", since = "1.55.0")]
 pub use core::num::IntErrorKind;
 #[stable(feature = "generic_nonzero", since = "1.79.0")]
@@ -29,28 +26,3 @@ pub use core::num::{FpCategory, ParseFloatError, ParseIntError, TryFromIntError}
 pub use core::num::{NonZeroI8, NonZeroI16, NonZeroI32, NonZeroI64, NonZeroI128, NonZeroIsize};
 #[stable(feature = "nonzero", since = "1.28.0")]
 pub use core::num::{NonZeroU8, NonZeroU16, NonZeroU32, NonZeroU64, NonZeroU128, NonZeroUsize};
-
-#[cfg(test)]
-use crate::fmt;
-#[cfg(test)]
-use crate::ops::{Add, Div, Mul, Rem, Sub};
-
-/// Helper function for testing numeric operations
-#[cfg(test)]
-pub fn test_num<T>(ten: T, two: T)
-where
-    T: PartialEq
-        + Add<Output = T>
-        + Sub<Output = T>
-        + Mul<Output = T>
-        + Div<Output = T>
-        + Rem<Output = T>
-        + fmt::Debug
-        + Copy,
-{
-    assert_eq!(ten.add(two), ten + two);
-    assert_eq!(ten.sub(two), ten - two);
-    assert_eq!(ten.mul(two), ten * two);
-    assert_eq!(ten.div(two), ten / two);
-    assert_eq!(ten.rem(two), ten % two);
-}
diff --git a/library/std/src/os/fd/net.rs b/library/std/src/os/fd/net.rs
index 843f45f7f5f..34479ca0e19 100644
--- a/library/std/src/os/fd/net.rs
+++ b/library/std/src/os/fd/net.rs
@@ -1,6 +1,6 @@
 use crate::os::fd::owned::OwnedFd;
 use crate::os::fd::raw::{AsRawFd, FromRawFd, IntoRawFd, RawFd};
-use crate::sys_common::{self, AsInner, FromInner, IntoInner};
+use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::{net, sys};
 
 macro_rules! impl_as_raw_fd {
@@ -24,7 +24,7 @@ macro_rules! impl_from_raw_fd {
             unsafe fn from_raw_fd(fd: RawFd) -> net::$t {
                 unsafe {
                     let socket = sys::net::Socket::from_inner(FromInner::from_inner(OwnedFd::from_raw_fd(fd)));
-                    net::$t::from_inner(sys_common::net::$t::from_inner(socket))
+                    net::$t::from_inner(sys::net::$t::from_inner(socket))
                 }
             }
         }
diff --git a/library/std/src/os/fd/raw.rs b/library/std/src/os/fd/raw.rs
index 22f5528248a..03dff94350d 100644
--- a/library/std/src/os/fd/raw.rs
+++ b/library/std/src/os/fd/raw.rs
@@ -19,11 +19,9 @@ use crate::sys_common::{AsInner, IntoInner};
 use crate::{fs, io};
 
 /// Raw file descriptors.
-#[rustc_allowed_through_unstable_modules]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg(not(target_os = "hermit"))]
 pub type RawFd = raw::c_int;
-#[rustc_allowed_through_unstable_modules]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg(target_os = "hermit")]
 pub type RawFd = i32;
@@ -33,7 +31,6 @@ pub type RawFd = i32;
 /// This is only available on unix and WASI platforms and must be imported in
 /// order to call the method. Windows platforms have a corresponding
 /// `AsRawHandle` and `AsRawSocket` set of traits.
-#[rustc_allowed_through_unstable_modules]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub trait AsRawFd {
     /// Extracts the raw file descriptor.
@@ -67,7 +64,6 @@ pub trait AsRawFd {
 
 /// A trait to express the ability to construct an object from a raw file
 /// descriptor.
-#[rustc_allowed_through_unstable_modules]
 #[stable(feature = "from_raw_os", since = "1.1.0")]
 pub trait FromRawFd {
     /// Constructs a new instance of `Self` from the given raw file
@@ -112,7 +108,6 @@ pub trait FromRawFd {
 
 /// A trait to express the ability to consume an object and acquire ownership of
 /// its raw file descriptor.
-#[rustc_allowed_through_unstable_modules]
 #[stable(feature = "into_raw_os", since = "1.4.0")]
 pub trait IntoRawFd {
     /// Consumes this object, returning the raw underlying file descriptor.
diff --git a/library/std/src/os/hermit/io/net.rs b/library/std/src/os/hermit/io/net.rs
index 7a774345b23..233bc885fc7 100644
--- a/library/std/src/os/hermit/io/net.rs
+++ b/library/std/src/os/hermit/io/net.rs
@@ -23,7 +23,7 @@ macro_rules! impl_from_raw_fd {
             unsafe fn from_raw_fd(fd: RawFd) -> net::$t {
                 unsafe {
                     let socket = sys::net::Socket::from_inner(FromInner::from_inner(OwnedFd::from_raw_fd(fd)));
-                    net::$t::from_inner(sys_common::net::$t::from_inner(socket))
+                    net::$t::from_inner(sys::net::$t::from_inner(socket))
                 }
             }
         }
diff --git a/library/std/src/os/solid/io.rs b/library/std/src/os/solid/io.rs
index b8601b533fe..b8c3440542d 100644
--- a/library/std/src/os/solid/io.rs
+++ b/library/std/src/os/solid/io.rs
@@ -48,7 +48,7 @@
 
 use crate::marker::PhantomData;
 use crate::mem::ManuallyDrop;
-use crate::sys_common::{self, AsInner, FromInner, IntoInner};
+use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::{fmt, net, sys};
 
 /// Raw file descriptors.
@@ -387,7 +387,7 @@ macro_rules! impl_from_raw_fd {
             #[inline]
             unsafe fn from_raw_fd(fd: RawFd) -> net::$t {
                 let socket = unsafe { sys::net::Socket::from_raw_fd(fd) };
-                net::$t::from_inner(sys_common::net::$t::from_inner(socket))
+                net::$t::from_inner(sys::net::$t::from_inner(socket))
             }
         }
     )*};
diff --git a/library/std/src/os/unix/fs/tests.rs b/library/std/src/os/unix/fs/tests.rs
index 67f607bd468..db9621c8c20 100644
--- a/library/std/src/os/unix/fs/tests.rs
+++ b/library/std/src/os/unix/fs/tests.rs
@@ -3,7 +3,7 @@ use super::*;
 #[test]
 fn read_vectored_at() {
     let msg = b"preadv is working!";
-    let dir = crate::sys_common::io::test::tmpdir();
+    let dir = crate::test_helpers::tmpdir();
 
     let filename = dir.join("preadv.txt");
     {
@@ -31,7 +31,7 @@ fn read_vectored_at() {
 #[test]
 fn write_vectored_at() {
     let msg = b"pwritev is not working!";
-    let dir = crate::sys_common::io::test::tmpdir();
+    let dir = crate::test_helpers::tmpdir();
 
     let filename = dir.join("preadv.txt");
     {
diff --git a/library/std/src/os/unix/net/tests.rs b/library/std/src/os/unix/net/tests.rs
index 21e2176185d..0398a535eb5 100644
--- a/library/std/src/os/unix/net/tests.rs
+++ b/library/std/src/os/unix/net/tests.rs
@@ -7,7 +7,7 @@ use crate::os::android::net::{SocketAddrExt, UnixSocketExt};
 use crate::os::linux::net::{SocketAddrExt, UnixSocketExt};
 #[cfg(any(target_os = "android", target_os = "linux"))]
 use crate::os::unix::io::AsRawFd;
-use crate::sys_common::io::test::tmpdir;
+use crate::test_helpers::tmpdir;
 use crate::thread;
 use crate::time::Duration;
 
diff --git a/library/std/src/os/wasi/io/fd.rs b/library/std/src/os/wasi/io/fd.rs
deleted file mode 100644
index 930aca887e3..00000000000
--- a/library/std/src/os/wasi/io/fd.rs
+++ /dev/null
@@ -1,9 +0,0 @@
-//! Owned and borrowed file descriptors.
-
-#![unstable(feature = "wasi_ext", issue = "71213")]
-
-// Tests for this module
-#[cfg(test)]
-mod tests;
-
-pub use crate::os::fd::owned::*;
diff --git a/library/std/src/os/wasi/io/mod.rs b/library/std/src/os/wasi/io/mod.rs
index 4e123a1eec8..5f9a735db08 100644
--- a/library/std/src/os/wasi/io/mod.rs
+++ b/library/std/src/os/wasi/io/mod.rs
@@ -4,3 +4,7 @@
 
 #[stable(feature = "io_safety_wasi", since = "1.65.0")]
 pub use crate::os::fd::*;
+
+// Tests for this module
+#[cfg(test)]
+mod tests;
diff --git a/library/std/src/os/wasi/io/raw.rs b/library/std/src/os/wasi/io/raw.rs
deleted file mode 100644
index da3b36adad4..00000000000
--- a/library/std/src/os/wasi/io/raw.rs
+++ /dev/null
@@ -1,20 +0,0 @@
-//! WASI-specific extensions to general I/O primitives.
-
-#![unstable(feature = "wasi_ext", issue = "71213")]
-
-// NOTE: despite the fact that this module is unstable,
-// stable Rust had the capability to access the stable
-// re-exported items from os::fd::raw through this
-// unstable module.
-// In PR #95956 the stability checker was changed to check
-// all path segments of an item rather than just the last,
-// which caused the aforementioned stable usage to regress
-// (see issue #99502).
-// As a result, the items in os::fd::raw were given the
-// rustc_allowed_through_unstable_modules attribute.
-// No regression tests were added to ensure this property,
-// as CI is not configured to test wasm32-wasi.
-// If this module is stabilized,
-// you may want to remove those attributes
-// (assuming no other unstable modules need them).
-pub use crate::os::fd::raw::*;
diff --git a/library/std/src/os/wasi/io/fd/tests.rs b/library/std/src/os/wasi/io/tests.rs
index 418274752b0..418274752b0 100644
--- a/library/std/src/os/wasi/io/fd/tests.rs
+++ b/library/std/src/os/wasi/io/tests.rs
diff --git a/library/std/src/os/windows/io/raw.rs b/library/std/src/os/windows/io/raw.rs
index 6658248d574..c0517fab950 100644
--- a/library/std/src/os/windows/io/raw.rs
+++ b/library/std/src/os/windows/io/raw.rs
@@ -6,7 +6,7 @@
 use crate::os::windows::io::{AsHandle, AsSocket};
 use crate::os::windows::io::{OwnedHandle, OwnedSocket};
 use crate::os::windows::raw;
-use crate::sys_common::{self, AsInner, FromInner, IntoInner};
+use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::{fs, io, net, ptr, sys};
 
 /// Raw HANDLEs.
@@ -262,7 +262,7 @@ impl FromRawSocket for net::TcpStream {
     unsafe fn from_raw_socket(sock: RawSocket) -> net::TcpStream {
         unsafe {
             let sock = sys::net::Socket::from_inner(OwnedSocket::from_raw_socket(sock));
-            net::TcpStream::from_inner(sys_common::net::TcpStream::from_inner(sock))
+            net::TcpStream::from_inner(sys::net::TcpStream::from_inner(sock))
         }
     }
 }
@@ -272,7 +272,7 @@ impl FromRawSocket for net::TcpListener {
     unsafe fn from_raw_socket(sock: RawSocket) -> net::TcpListener {
         unsafe {
             let sock = sys::net::Socket::from_inner(OwnedSocket::from_raw_socket(sock));
-            net::TcpListener::from_inner(sys_common::net::TcpListener::from_inner(sock))
+            net::TcpListener::from_inner(sys::net::TcpListener::from_inner(sock))
         }
     }
 }
@@ -282,7 +282,7 @@ impl FromRawSocket for net::UdpSocket {
     unsafe fn from_raw_socket(sock: RawSocket) -> net::UdpSocket {
         unsafe {
             let sock = sys::net::Socket::from_inner(OwnedSocket::from_raw_socket(sock));
-            net::UdpSocket::from_inner(sys_common::net::UdpSocket::from_inner(sock))
+            net::UdpSocket::from_inner(sys::net::UdpSocket::from_inner(sock))
         }
     }
 }
diff --git a/library/std/src/os/windows/process.rs b/library/std/src/os/windows/process.rs
index 0277b79b8b6..201274cf03a 100644
--- a/library/std/src/os/windows/process.rs
+++ b/library/std/src/os/windows/process.rs
@@ -590,10 +590,10 @@ impl<'a> ProcThreadAttributeListBuilder<'a> {
         value_ptr: *const T,
         value_size: usize,
     ) -> Self {
-        self.attributes.insert(attribute, ProcThreadAttributeValue {
-            ptr: value_ptr.cast::<c_void>(),
-            size: value_size,
-        });
+        self.attributes.insert(
+            attribute,
+            ProcThreadAttributeValue { ptr: value_ptr.cast::<c_void>(), size: value_size },
+        );
         self
     }
 
diff --git a/library/std/src/os/xous/ffi/definitions.rs b/library/std/src/os/xous/ffi/definitions.rs
index 1b16849af03..345005bcc78 100644
--- a/library/std/src/os/xous/ffi/definitions.rs
+++ b/library/std/src/os/xous/ffi/definitions.rs
@@ -126,36 +126,42 @@ impl From<i32> for Error {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl core::fmt::Display for Error {
     fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
-        write!(f, "{}", match self {
-            Error::NoError => "no error occurred",
-            Error::BadAlignment => "memory was not properly aligned",
-            Error::BadAddress => "an invalid address was supplied",
-            Error::OutOfMemory => "the process or service has run out of memory",
-            Error::MemoryInUse => "the requested address is in use",
-            Error::InterruptNotFound => "the requested interrupt does not exist on this platform",
-            Error::InterruptInUse => "the requested interrupt is currently in use",
-            Error::InvalidString => "the specified string was not formatted correctly",
-            Error::ServerExists => "a server with that address already exists",
-            Error::ServerNotFound => "the requetsed server could not be found",
-            Error::ProcessNotFound => "the target process does not exist",
-            Error::ProcessNotChild => "the requested operation can only be done on child processes",
-            Error::ProcessTerminated => "the target process has crashed",
-            Error::Timeout => "the requested operation timed out",
-            Error::InternalError => "an internal error occurred",
-            Error::ServerQueueFull => "the server has too many pending messages",
-            Error::ThreadNotAvailable => "the specified thread does not exist",
-            Error::UnhandledSyscall => "the kernel did not recognize that syscall",
-            Error::InvalidSyscall => "the syscall had incorrect parameters",
-            Error::ShareViolation => "an attempt was made to share memory twice",
-            Error::InvalidThread => "tried to resume a thread that was not ready",
-            Error::InvalidPid => "kernel attempted to use a pid that was not valid",
-            Error::AccessDenied => "no permission to perform the requested operation",
-            Error::UseBeforeInit => "attempt to use a service before initialization finished",
-            Error::DoubleFree => "the requested resource was freed twice",
-            Error::DebugInProgress => "kernel attempted to activate a thread being debugged",
-            Error::InvalidLimit => "process attempted to adjust an invalid limit",
-            Error::UnknownError => "an unknown error occurred",
-        })
+        write!(
+            f,
+            "{}",
+            match self {
+                Error::NoError => "no error occurred",
+                Error::BadAlignment => "memory was not properly aligned",
+                Error::BadAddress => "an invalid address was supplied",
+                Error::OutOfMemory => "the process or service has run out of memory",
+                Error::MemoryInUse => "the requested address is in use",
+                Error::InterruptNotFound =>
+                    "the requested interrupt does not exist on this platform",
+                Error::InterruptInUse => "the requested interrupt is currently in use",
+                Error::InvalidString => "the specified string was not formatted correctly",
+                Error::ServerExists => "a server with that address already exists",
+                Error::ServerNotFound => "the requetsed server could not be found",
+                Error::ProcessNotFound => "the target process does not exist",
+                Error::ProcessNotChild =>
+                    "the requested operation can only be done on child processes",
+                Error::ProcessTerminated => "the target process has crashed",
+                Error::Timeout => "the requested operation timed out",
+                Error::InternalError => "an internal error occurred",
+                Error::ServerQueueFull => "the server has too many pending messages",
+                Error::ThreadNotAvailable => "the specified thread does not exist",
+                Error::UnhandledSyscall => "the kernel did not recognize that syscall",
+                Error::InvalidSyscall => "the syscall had incorrect parameters",
+                Error::ShareViolation => "an attempt was made to share memory twice",
+                Error::InvalidThread => "tried to resume a thread that was not ready",
+                Error::InvalidPid => "kernel attempted to use a pid that was not valid",
+                Error::AccessDenied => "no permission to perform the requested operation",
+                Error::UseBeforeInit => "attempt to use a service before initialization finished",
+                Error::DoubleFree => "the requested resource was freed twice",
+                Error::DebugInProgress => "kernel attempted to activate a thread being debugged",
+                Error::InvalidLimit => "process attempted to adjust an invalid limit",
+                Error::UnknownError => "an unknown error occurred",
+            }
+        )
     }
 }
 
diff --git a/library/std/src/panic.rs b/library/std/src/panic.rs
index d649357a56d..153189b8b03 100644
--- a/library/std/src/panic.rs
+++ b/library/std/src/panic.rs
@@ -529,6 +529,3 @@ pub fn get_backtrace_style() -> Option<BacktraceStyle> {
         Err(new) => BacktraceStyle::from_u8(new),
     }
 }
-
-#[cfg(test)]
-mod tests;
diff --git a/library/std/src/path.rs b/library/std/src/path.rs
index 7fd08a97f1f..97e17acadea 100644
--- a/library/std/src/path.rs
+++ b/library/std/src/path.rs
@@ -67,9 +67,6 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 #![deny(unsafe_op_in_unsafe_fn)]
 
-#[cfg(test)]
-mod tests;
-
 use core::clone::CloneToUninit;
 
 use crate::borrow::{Borrow, Cow};
diff --git a/library/std/src/prelude/mod.rs b/library/std/src/prelude/mod.rs
index 4ec328208f0..14e6c2715df 100644
--- a/library/std/src/prelude/mod.rs
+++ b/library/std/src/prelude/mod.rs
@@ -120,16 +120,6 @@ mod common;
 pub mod v1 {
     #[stable(feature = "rust1", since = "1.0.0")]
     pub use super::common::*;
-
-    // Do not `doc(inline)` these `doc(hidden)` items.
-    #[unstable(
-        feature = "rustc_encodable_decodable",
-        issue = "none",
-        soft,
-        reason = "derive macro for `rustc-serialize`; should not be used in new code"
-    )]
-    #[allow(deprecated)]
-    pub use core::prelude::v1::{RustcDecodable, RustcEncodable};
 }
 
 /// The 2015 version of the prelude of The Rust Standard Library.
diff --git a/library/std/src/process.rs b/library/std/src/process.rs
index e0dd2e14817..fd0fd1cb755 100644
--- a/library/std/src/process.rs
+++ b/library/std/src/process.rs
@@ -2318,14 +2318,10 @@ pub fn exit(code: i32) -> ! {
 /// Terminates the process in an abnormal fashion.
 ///
 /// The function will never return and will immediately terminate the current
-/// process in a platform specific "abnormal" manner.
-///
-/// Note that because this function never returns, and that it terminates the
-/// process, no destructors on the current stack or any other thread's stack
-/// will be run.
-///
-/// Rust IO buffers (eg, from `BufWriter`) will not be flushed.
-/// Likewise, C stdio buffers will (on most platforms) not be flushed.
+/// process in a platform specific "abnormal" manner. As a consequence,
+/// no destructors on the current stack or any other thread's stack
+/// will be run, Rust IO buffers (eg, from `BufWriter`) will not be flushed,
+/// and C stdio buffers will (on most platforms) not be flushed.
 ///
 /// This is in contrast to the default behavior of [`panic!`] which unwinds
 /// the current thread's stack and calls all destructors.
diff --git a/library/std/src/process/tests.rs b/library/std/src/process/tests.rs
index e8cbfe337bc..69273d863eb 100644
--- a/library/std/src/process/tests.rs
+++ b/library/std/src/process/tests.rs
@@ -391,145 +391,6 @@ fn test_interior_nul_in_env_value_is_error() {
     }
 }
 
-/// Tests that process creation flags work by debugging a process.
-/// Other creation flags make it hard or impossible to detect
-/// behavioral changes in the process.
-#[test]
-#[cfg(windows)]
-fn test_creation_flags() {
-    use crate::os::windows::process::CommandExt;
-    use crate::sys::c::{BOOL, INFINITE};
-    #[repr(C)]
-    struct DEBUG_EVENT {
-        pub event_code: u32,
-        pub process_id: u32,
-        pub thread_id: u32,
-        // This is a union in the real struct, but we don't
-        // need this data for the purposes of this test.
-        pub _junk: [u8; 164],
-    }
-
-    extern "system" {
-        fn WaitForDebugEvent(lpDebugEvent: *mut DEBUG_EVENT, dwMilliseconds: u32) -> BOOL;
-        fn ContinueDebugEvent(dwProcessId: u32, dwThreadId: u32, dwContinueStatus: u32) -> BOOL;
-    }
-
-    const DEBUG_PROCESS: u32 = 1;
-    const EXIT_PROCESS_DEBUG_EVENT: u32 = 5;
-    const DBG_EXCEPTION_NOT_HANDLED: u32 = 0x80010001;
-
-    let mut child =
-        Command::new("cmd").creation_flags(DEBUG_PROCESS).stdin(Stdio::piped()).spawn().unwrap();
-    child.stdin.take().unwrap().write_all(b"exit\r\n").unwrap();
-    let mut events = 0;
-    let mut event = DEBUG_EVENT { event_code: 0, process_id: 0, thread_id: 0, _junk: [0; 164] };
-    loop {
-        if unsafe { WaitForDebugEvent(&mut event as *mut DEBUG_EVENT, INFINITE) } == 0 {
-            panic!("WaitForDebugEvent failed!");
-        }
-        events += 1;
-
-        if event.event_code == EXIT_PROCESS_DEBUG_EVENT {
-            break;
-        }
-
-        if unsafe {
-            ContinueDebugEvent(event.process_id, event.thread_id, DBG_EXCEPTION_NOT_HANDLED)
-        } == 0
-        {
-            panic!("ContinueDebugEvent failed!");
-        }
-    }
-    assert!(events > 0);
-}
-
-/// Tests proc thread attributes by spawning a process with a custom parent process,
-/// then comparing the parent process ID with the expected parent process ID.
-#[test]
-#[cfg(windows)]
-fn test_proc_thread_attributes() {
-    use crate::mem;
-    use crate::os::windows::io::AsRawHandle;
-    use crate::os::windows::process::{CommandExt, ProcThreadAttributeList};
-    use crate::sys::c::{BOOL, CloseHandle, HANDLE};
-    use crate::sys::cvt;
-
-    #[repr(C)]
-    #[allow(non_snake_case)]
-    struct PROCESSENTRY32W {
-        dwSize: u32,
-        cntUsage: u32,
-        th32ProcessID: u32,
-        th32DefaultHeapID: usize,
-        th32ModuleID: u32,
-        cntThreads: u32,
-        th32ParentProcessID: u32,
-        pcPriClassBase: i32,
-        dwFlags: u32,
-        szExeFile: [u16; 260],
-    }
-
-    extern "system" {
-        fn CreateToolhelp32Snapshot(dwflags: u32, th32processid: u32) -> HANDLE;
-        fn Process32First(hsnapshot: HANDLE, lppe: *mut PROCESSENTRY32W) -> BOOL;
-        fn Process32Next(hsnapshot: HANDLE, lppe: *mut PROCESSENTRY32W) -> BOOL;
-    }
-
-    const PROC_THREAD_ATTRIBUTE_PARENT_PROCESS: usize = 0x00020000;
-    const TH32CS_SNAPPROCESS: u32 = 0x00000002;
-
-    struct ProcessDropGuard(crate::process::Child);
-
-    impl Drop for ProcessDropGuard {
-        fn drop(&mut self) {
-            let _ = self.0.kill();
-        }
-    }
-
-    let parent = ProcessDropGuard(Command::new("cmd").spawn().unwrap());
-
-    let mut child_cmd = Command::new("cmd");
-
-    let parent_process_handle = parent.0.as_raw_handle();
-
-    let mut attribute_list = ProcThreadAttributeList::build()
-        .attribute(PROC_THREAD_ATTRIBUTE_PARENT_PROCESS, &parent_process_handle)
-        .finish()
-        .unwrap();
-
-    let child = ProcessDropGuard(child_cmd.spawn_with_attributes(&mut attribute_list).unwrap());
-
-    let h_snapshot = unsafe { CreateToolhelp32Snapshot(TH32CS_SNAPPROCESS, 0) };
-
-    let mut process_entry = PROCESSENTRY32W {
-        dwSize: mem::size_of::<PROCESSENTRY32W>() as u32,
-        cntUsage: 0,
-        th32ProcessID: 0,
-        th32DefaultHeapID: 0,
-        th32ModuleID: 0,
-        cntThreads: 0,
-        th32ParentProcessID: 0,
-        pcPriClassBase: 0,
-        dwFlags: 0,
-        szExeFile: [0; 260],
-    };
-
-    unsafe { cvt(Process32First(h_snapshot, &mut process_entry as *mut _)) }.unwrap();
-
-    loop {
-        if child.0.id() == process_entry.th32ProcessID {
-            break;
-        }
-        unsafe { cvt(Process32Next(h_snapshot, &mut process_entry as *mut _)) }.unwrap();
-    }
-
-    unsafe { cvt(CloseHandle(h_snapshot)) }.unwrap();
-
-    assert_eq!(parent.0.id(), process_entry.th32ParentProcessID);
-
-    drop(child)
-}
-
 #[test]
 fn test_command_implements_send_sync() {
     fn take_send_sync_type<T: Send + Sync>(_: T) {}
@@ -688,7 +549,7 @@ fn debug_print() {
 #[test]
 #[cfg(windows)]
 fn run_bat_script() {
-    let tempdir = crate::sys_common::io::test::tmpdir();
+    let tempdir = crate::test_helpers::tmpdir();
     let script_path = tempdir.join("hello.cmd");
 
     crate::fs::write(&script_path, "@echo Hello, %~1!").unwrap();
@@ -707,7 +568,7 @@ fn run_bat_script() {
 #[test]
 #[cfg(windows)]
 fn run_canonical_bat_script() {
-    let tempdir = crate::sys_common::io::test::tmpdir();
+    let tempdir = crate::test_helpers::tmpdir();
     let script_path = tempdir.join("hello.cmd");
 
     crate::fs::write(&script_path, "@echo Hello, %~1!").unwrap();
diff --git a/library/std/src/rt.rs b/library/std/src/rt.rs
index 384369b0012..3a22a16cb16 100644
--- a/library/std/src/rt.rs
+++ b/library/std/src/rt.rs
@@ -32,9 +32,14 @@ use crate::{mem, panic, sys};
 // - nothing (so this macro is a no-op)
 macro_rules! rtprintpanic {
     ($($t:tt)*) => {
+        #[cfg(not(feature = "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")]
+        {
+            let _ = format_args!($($t)*);
+        }
     }
 }
 
diff --git a/library/std/src/sync/barrier.rs b/library/std/src/sync/barrier.rs
index 862753e4765..067ff66d9af 100644
--- a/library/std/src/sync/barrier.rs
+++ b/library/std/src/sync/barrier.rs
@@ -1,6 +1,3 @@
-#[cfg(test)]
-mod tests;
-
 use crate::fmt;
 // FIXME(nonpoison_mutex,nonpoison_condvar): switch to nonpoison versions once they are available
 use crate::sync::{Condvar, Mutex};
diff --git a/library/std/src/sync/lazy_lock.rs b/library/std/src/sync/lazy_lock.rs
index 98c83d8d326..78cf8841efe 100644
--- a/library/std/src/sync/lazy_lock.rs
+++ b/library/std/src/sync/lazy_lock.rs
@@ -350,6 +350,3 @@ unsafe impl<T: Sync + Send, F: Send> Sync for LazyLock<T, F> {}
 impl<T: RefUnwindSafe + UnwindSafe, F: UnwindSafe> RefUnwindSafe for LazyLock<T, F> {}
 #[stable(feature = "lazy_cell", since = "1.80.0")]
 impl<T: UnwindSafe, F: UnwindSafe> UnwindSafe for LazyLock<T, F> {}
-
-#[cfg(test)]
-mod tests;
diff --git a/library/std/src/sync/mpmc/mod.rs b/library/std/src/sync/mpmc/mod.rs
index 0cf4902d6d5..00966ee3ecf 100644
--- a/library/std/src/sync/mpmc/mod.rs
+++ b/library/std/src/sync/mpmc/mod.rs
@@ -18,7 +18,7 @@
 //!    infinite buffer.
 //!
 //! 2. A synchronous, bounded channel. The [`sync_channel`] function will
-//!    return a `(SyncSender, Receiver)` tuple where the storage for pending
+//!    return a `(Sender, Receiver)` tuple where the storage for pending
 //!    messages is a pre-allocated buffer of a fixed size. All sends will be
 //!    **synchronous** by blocking until there is buffer space available. Note
 //!    that a bound of 0 is allowed, causing the channel to become a "rendezvous"
@@ -360,9 +360,17 @@ impl<T> Sender<T> {
     /// that a return value of [`Err`] means that the data will never be
     /// received, but a return value of [`Ok`] does *not* mean that the data
     /// will be received. It is possible for the corresponding receiver to
-    /// hang up immediately after this function returns [`Ok`].
+    /// hang up immediately after this function returns [`Ok`]. However, if
+    /// the channel is zero-capacity, it acts as a rendezvous channel and a
+    /// return value of [`Ok`] means that the data has been received.
     ///
-    /// This method will never block the current thread.
+    /// If the channel is full and not disconnected, this call will block until
+    /// the send operation can proceed. If the channel becomes disconnected,
+    /// this call will wake up and return an error. The returned error contains
+    /// the original message.
+    ///
+    /// If called on a zero-capacity channel, this method will wait for a receive
+    /// operation to appear on the other side of the channel.
     ///
     /// # Examples
     ///
@@ -650,7 +658,7 @@ impl<T> fmt::Debug for Sender<T> {
 }
 
 /// The receiving half of Rust's [`channel`] (or [`sync_channel`]) type.
-/// Different threads can share this [`Sender`] by cloning it.
+/// Different threads can share this [`Receiver`] by cloning it.
 ///
 /// Messages sent to the channel can be retrieved using [`recv`].
 ///
diff --git a/library/std/src/sync/mpsc/mod.rs b/library/std/src/sync/mpsc.rs
index c86b546e011..f942937c14d 100644
--- a/library/std/src/sync/mpsc/mod.rs
+++ b/library/std/src/sync/mpsc.rs
@@ -137,12 +137,6 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod tests;
-
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod sync_tests;
-
 // MPSC channels are built as a wrapper around MPMC channels, which
 // were ported from the `crossbeam-channel` crate. MPMC channels are
 // not exposed publicly, but if you are curious about the implementation,
@@ -737,9 +731,10 @@ impl<T> SyncSender<T> {
     // Attempts to send for a value on this receiver, returning an error if the
     // corresponding channel has hung up, or if it waits more than `timeout`.
     //
-    // This method is currently private and only used for tests.
-    #[allow(unused)]
-    fn send_timeout(&self, t: T, timeout: Duration) -> Result<(), mpmc::SendTimeoutError<T>> {
+    // This method is currently only used for tests.
+    #[unstable(issue = "none", feature = "std_internals")]
+    #[doc(hidden)]
+    pub fn send_timeout(&self, t: T, timeout: Duration) -> Result<(), mpmc::SendTimeoutError<T>> {
         self.inner.send_timeout(t, timeout)
     }
 }
diff --git a/library/std/src/sync/once_lock.rs b/library/std/src/sync/once_lock.rs
index 49f2dafd8fd..21e6b65a744 100644
--- a/library/std/src/sync/once_lock.rs
+++ b/library/std/src/sync/once_lock.rs
@@ -13,6 +13,9 @@ use crate::sync::Once;
 /// Where OnceLock shines is when LazyLock is too simple to support a given case, as LazyLock
 /// doesn't allow additional inputs to its function after you call [`LazyLock::new(|| ...)`].
 ///
+/// A `OnceLock` can be thought of as a safe abstraction over uninitialized data that becomes
+/// initialized once written.
+///
 /// [`OnceCell`]: crate::cell::OnceCell
 /// [`LazyLock<T, F>`]: crate::sync::LazyLock
 /// [`LazyLock::new(|| ...)`]: crate::sync::LazyLock::new
@@ -126,7 +129,7 @@ pub struct OnceLock<T> {
 }
 
 impl<T> OnceLock<T> {
-    /// Creates a new empty cell.
+    /// Creates a new uninitialized cell.
     #[inline]
     #[must_use]
     #[stable(feature = "once_cell", since = "1.70.0")]
@@ -141,8 +144,8 @@ impl<T> OnceLock<T> {
 
     /// Gets the reference to the underlying value.
     ///
-    /// Returns `None` if the cell is empty, or being initialized. This
-    /// method never blocks.
+    /// Returns `None` if the cell is uninitialized, or being initialized.
+    /// This method never blocks.
     #[inline]
     #[stable(feature = "once_cell", since = "1.70.0")]
     pub fn get(&self) -> Option<&T> {
@@ -156,7 +159,8 @@ impl<T> OnceLock<T> {
 
     /// Gets the mutable reference to the underlying value.
     ///
-    /// Returns `None` if the cell is empty. This method never blocks.
+    /// Returns `None` if the cell is uninitialized, or being initialized.
+    /// This method never blocks.
     #[inline]
     #[stable(feature = "once_cell", since = "1.70.0")]
     pub fn get_mut(&mut self) -> Option<&mut T> {
@@ -174,8 +178,6 @@ impl<T> OnceLock<T> {
     ///
     /// Waiting for a computation on another thread to finish:
     /// ```rust
-    /// #![feature(once_wait)]
-    ///
     /// use std::thread;
     /// use std::sync::OnceLock;
     ///
@@ -189,19 +191,20 @@ impl<T> OnceLock<T> {
     /// })
     /// ```
     #[inline]
-    #[unstable(feature = "once_wait", issue = "127527")]
+    #[stable(feature = "once_wait", since = "CURRENT_RUSTC_VERSION")]
     pub fn wait(&self) -> &T {
         self.once.wait_force();
 
         unsafe { self.get_unchecked() }
     }
 
-    /// Sets the contents of this cell to `value`.
+    /// Initializes the contents of the cell to `value`.
     ///
     /// May block if another thread is currently attempting to initialize the cell. The cell is
-    /// guaranteed to contain a value when set returns, though not necessarily the one provided.
+    /// guaranteed to contain a value when `set` returns, though not necessarily the one provided.
     ///
-    /// Returns `Ok(())` if the cell's value was set by this call.
+    /// Returns `Ok(())` if the cell was uninitialized and
+    /// `Err(value)` if the cell was already initialized.
     ///
     /// # Examples
     ///
@@ -230,13 +233,15 @@ impl<T> OnceLock<T> {
         }
     }
 
-    /// Sets the contents of this cell to `value` if the cell was empty, then
-    /// returns a reference to it.
+    /// Initializes the contents of the cell to `value` if the cell was uninitialized,
+    /// then returns a reference to it.
     ///
     /// May block if another thread is currently attempting to initialize the cell. The cell is
-    /// guaranteed to contain a value when set returns, though not necessarily the one provided.
+    /// guaranteed to contain a value when `try_insert` returns, though not necessarily the
+    /// one provided.
     ///
-    /// Returns `Ok(&value)` if the cell was empty and `Err(&current_value, value)` if it was full.
+    /// Returns `Ok(&value)` if the cell was uninitialized and
+    /// `Err((&current_value, value))` if it was already initialized.
     ///
     /// # Examples
     ///
@@ -269,8 +274,8 @@ impl<T> OnceLock<T> {
         }
     }
 
-    /// Gets the contents of the cell, initializing it with `f` if the cell
-    /// was empty.
+    /// Gets the contents of the cell, initializing it to `f()` if the cell
+    /// was uninitialized.
     ///
     /// Many threads may call `get_or_init` concurrently with different
     /// initializing functions, but it is guaranteed that only one function
@@ -278,7 +283,7 @@ impl<T> OnceLock<T> {
     ///
     /// # Panics
     ///
-    /// If `f` panics, the panic is propagated to the caller, and the cell
+    /// If `f()` panics, the panic is propagated to the caller, and the cell
     /// remains uninitialized.
     ///
     /// It is an error to reentrantly initialize the cell from `f`. The
@@ -308,13 +313,13 @@ impl<T> OnceLock<T> {
     }
 
     /// Gets the mutable reference of the contents of the cell, initializing
-    /// it with `f` if the cell was empty.
+    /// it to `f()` if the cell was uninitialized.
     ///
     /// This method never blocks.
     ///
     /// # Panics
     ///
-    /// If `f` panics, the panic is propagated to the caller, and the cell
+    /// If `f()` panics, the panic is propagated to the caller, and the cell
     /// remains uninitialized.
     ///
     /// # Examples
@@ -345,13 +350,13 @@ impl<T> OnceLock<T> {
         }
     }
 
-    /// Gets the contents of the cell, initializing it with `f` if
-    /// the cell was empty. If the cell was empty and `f` failed, an
-    /// error is returned.
+    /// Gets the contents of the cell, initializing it to `f()` if
+    /// the cell was uninitialized. If the cell was uninitialized
+    /// and `f()` failed, an error is returned.
     ///
     /// # Panics
     ///
-    /// If `f` panics, the panic is propagated to the caller, and
+    /// If `f()` panics, the panic is propagated to the caller, and
     /// the cell remains uninitialized.
     ///
     /// It is an error to reentrantly initialize the cell from `f`.
@@ -397,14 +402,14 @@ impl<T> OnceLock<T> {
     }
 
     /// Gets the mutable reference of the contents of the cell, initializing
-    /// it with `f` if the cell was empty. If the cell was empty and `f` failed,
-    /// an error is returned.
+    /// it to `f()` if the cell was uninitialized. If the cell was uninitialized
+    /// and `f()` failed, an error is returned.
     ///
     /// This method never blocks.
     ///
     /// # Panics
     ///
-    /// If `f` panics, the panic is propagated to the caller, and
+    /// If `f()` panics, the panic is propagated to the caller, and
     /// the cell remains uninitialized.
     ///
     /// # Examples
@@ -416,7 +421,7 @@ impl<T> OnceLock<T> {
     ///
     /// let mut cell: OnceLock<u32> = OnceLock::new();
     ///
-    /// // Failed initializers do not change the value
+    /// // Failed attempts to initialize the cell do not change its contents
     /// assert!(cell.get_mut_or_try_init(|| "not a number!".parse()).is_err());
     /// assert!(cell.get().is_none());
     ///
@@ -440,7 +445,7 @@ impl<T> OnceLock<T> {
     }
 
     /// Consumes the `OnceLock`, returning the wrapped value. Returns
-    /// `None` if the cell was empty.
+    /// `None` if the cell was uninitialized.
     ///
     /// # Examples
     ///
@@ -462,7 +467,7 @@ impl<T> OnceLock<T> {
 
     /// Takes the value out of this `OnceLock`, moving it back to an uninitialized state.
     ///
-    /// Has no effect and returns `None` if the `OnceLock` hasn't been initialized.
+    /// Has no effect and returns `None` if the `OnceLock` was uninitialized.
     ///
     /// Safety is guaranteed by requiring a mutable reference.
     ///
@@ -528,7 +533,7 @@ impl<T> OnceLock<T> {
 
     /// # Safety
     ///
-    /// The value must be initialized
+    /// The cell must be initialized
     #[inline]
     unsafe fn get_unchecked(&self) -> &T {
         debug_assert!(self.is_initialized());
@@ -537,7 +542,7 @@ impl<T> OnceLock<T> {
 
     /// # Safety
     ///
-    /// The value must be initialized
+    /// The cell must be initialized
     #[inline]
     unsafe fn get_unchecked_mut(&mut self) -> &mut T {
         debug_assert!(self.is_initialized());
@@ -562,7 +567,7 @@ impl<T: UnwindSafe> UnwindSafe for OnceLock<T> {}
 
 #[stable(feature = "once_cell", since = "1.70.0")]
 impl<T> Default for OnceLock<T> {
-    /// Creates a new empty cell.
+    /// Creates a new uninitialized cell.
     ///
     /// # Example
     ///
@@ -676,6 +681,3 @@ unsafe impl<#[may_dangle] T> Drop for OnceLock<T> {
         }
     }
 }
-
-#[cfg(test)]
-mod tests;
diff --git a/library/std/src/sync/poison/condvar.rs b/library/std/src/sync/poison/condvar.rs
index a6e2389c93b..7f0f3f652bc 100644
--- a/library/std/src/sync/poison/condvar.rs
+++ b/library/std/src/sync/poison/condvar.rs
@@ -1,6 +1,3 @@
-#[cfg(test)]
-mod tests;
-
 use crate::fmt;
 use crate::sync::poison::{self, LockResult, MutexGuard, PoisonError, mutex};
 use crate::sys::sync as sys;
diff --git a/library/std/src/sync/poison/mutex.rs b/library/std/src/sync/poison/mutex.rs
index 01ef71a187f..9362c764173 100644
--- a/library/std/src/sync/poison/mutex.rs
+++ b/library/std/src/sync/poison/mutex.rs
@@ -1,6 +1,3 @@
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod tests;
-
 use crate::cell::UnsafeCell;
 use crate::fmt;
 use crate::marker::PhantomData;
@@ -181,10 +178,29 @@ pub struct Mutex<T: ?Sized> {
     data: UnsafeCell<T>,
 }
 
-// these are the only places where `T: Send` matters; all other
-// functionality works fine on a single thread.
+/// `T` must be `Send` for a [`Mutex`] to be `Send` because it is possible to acquire
+/// the owned `T` from the `Mutex` via [`into_inner`].
+///
+/// [`into_inner`]: Mutex::into_inner
 #[stable(feature = "rust1", since = "1.0.0")]
 unsafe impl<T: ?Sized + Send> Send for Mutex<T> {}
+
+/// `T` must be `Send` for [`Mutex`] to be `Sync`.
+/// This ensures that the protected data can be accessed safely from multiple threads
+/// without causing data races or other unsafe behavior.
+///
+/// [`Mutex<T>`] provides mutable access to `T` to one thread at a time. However, it's essential
+/// for `T` to be `Send` because it's not safe for non-`Send` structures to be accessed in
+/// this manner. For instance, consider [`Rc`], a non-atomic reference counted smart pointer,
+/// which is not `Send`. With `Rc`, we can have multiple copies pointing to the same heap
+/// allocation with a non-atomic reference count. If we were to use `Mutex<Rc<_>>`, it would
+/// only protect one instance of `Rc` from shared access, leaving other copies vulnerable
+/// to potential data races.
+///
+/// Also note that it is not necessary for `T` to be `Sync` as `&T` is only made available
+/// to one thread at a time if `T` is not `Sync`.
+///
+/// [`Rc`]: crate::rc::Rc
 #[stable(feature = "rust1", since = "1.0.0")]
 unsafe impl<T: ?Sized + Send> Sync for Mutex<T> {}
 
@@ -211,8 +227,17 @@ pub struct MutexGuard<'a, T: ?Sized + 'a> {
     poison: poison::Guard,
 }
 
+/// A [`MutexGuard`] is not `Send` to maximize platform portablity.
+///
+/// On platforms that use POSIX threads (commonly referred to as pthreads) there is a requirement to
+/// release mutex locks on the same thread they were acquired.
+/// For this reason, [`MutexGuard`] must not implement `Send` to prevent it being dropped from
+/// another thread.
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: ?Sized> !Send for MutexGuard<'_, T> {}
+
+/// `T` must be `Sync` for a [`MutexGuard<T>`] to be `Sync`
+/// because it is possible to get a `&T` from `&MutexGuard` (via `Deref`).
 #[stable(feature = "mutexguard", since = "1.19.0")]
 unsafe impl<T: ?Sized + Sync> Sync for MutexGuard<'_, T> {}
 
diff --git a/library/std/src/sync/poison/once.rs b/library/std/src/sync/poison/once.rs
index 27db4b634fb..d2938b7a0c1 100644
--- a/library/std/src/sync/poison/once.rs
+++ b/library/std/src/sync/poison/once.rs
@@ -3,9 +3,6 @@
 //! This primitive is meant to be used to run one-time initialization. An
 //! example use case would be for initializing an FFI library.
 
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod tests;
-
 use crate::fmt;
 use crate::panic::{RefUnwindSafe, UnwindSafe};
 use crate::sys::sync as sys;
@@ -269,8 +266,6 @@ impl Once {
     /// # Example
     ///
     /// ```rust
-    /// #![feature(once_wait)]
-    ///
     /// use std::sync::Once;
     /// use std::thread;
     ///
@@ -289,7 +284,7 @@ impl Once {
     /// If this [`Once`] has been poisoned because an initialization closure has
     /// panicked, this method will also panic. Use [`wait_force`](Self::wait_force)
     /// if this behavior is not desired.
-    #[unstable(feature = "once_wait", issue = "127527")]
+    #[stable(feature = "once_wait", since = "CURRENT_RUSTC_VERSION")]
     pub fn wait(&self) {
         if !self.inner.is_completed() {
             self.inner.wait(false);
@@ -298,7 +293,7 @@ impl Once {
 
     /// Blocks the current thread until initialization has completed, ignoring
     /// poisoning.
-    #[unstable(feature = "once_wait", issue = "127527")]
+    #[stable(feature = "once_wait", since = "CURRENT_RUSTC_VERSION")]
     pub fn wait_force(&self) {
         if !self.inner.is_completed() {
             self.inner.wait(true);
diff --git a/library/std/src/sync/poison/rwlock.rs b/library/std/src/sync/poison/rwlock.rs
index 1519baf99a8..f9d9321f5f2 100644
--- a/library/std/src/sync/poison/rwlock.rs
+++ b/library/std/src/sync/poison/rwlock.rs
@@ -1,6 +1,3 @@
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod tests;
-
 use crate::cell::UnsafeCell;
 use crate::fmt;
 use crate::marker::PhantomData;
diff --git a/library/std/src/sync/reentrant_lock.rs b/library/std/src/sync/reentrant_lock.rs
index 0140e0d2129..e009eb410ef 100644
--- a/library/std/src/sync/reentrant_lock.rs
+++ b/library/std/src/sync/reentrant_lock.rs
@@ -1,6 +1,3 @@
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod tests;
-
 use cfg_if::cfg_if;
 
 use crate::cell::UnsafeCell;
@@ -324,7 +321,10 @@ impl<T: ?Sized> ReentrantLock<T> {
     /// Otherwise, an RAII guard is returned.
     ///
     /// This function does not block.
-    pub(crate) fn try_lock(&self) -> Option<ReentrantLockGuard<'_, T>> {
+    // FIXME maybe make it a public part of the API?
+    #[unstable(issue = "none", feature = "std_internals")]
+    #[doc(hidden)]
+    pub fn try_lock(&self) -> Option<ReentrantLockGuard<'_, T>> {
         let this_thread = current_id();
         // Safety: We only touch lock_count when we own the inner mutex.
         // Additionally, we only call `self.owner.set()` while holding
diff --git a/library/std/src/sys/alloc/wasm.rs b/library/std/src/sys/alloc/wasm.rs
index a308fafc68b..53fbc9529e5 100644
--- a/library/std/src/sys/alloc/wasm.rs
+++ b/library/std/src/sys/alloc/wasm.rs
@@ -1,6 +1,6 @@
 //! This is an implementation of a global allocator on wasm targets when
-//! emscripten is not in use. In that situation there's no actual runtime for us
-//! to lean on for allocation, so instead we provide our own!
+//! emscripten or wasi is not in use. In that situation there's no actual runtime
+//! for us to lean on for allocation, so instead we provide our own!
 //!
 //! The wasm instruction set has two instructions for getting the current
 //! amount of memory and growing the amount of memory. These instructions are the
diff --git a/library/std/src/sys/pal/hermit/io.rs b/library/std/src/sys/io/io_slice/iovec.rs
index 0424a1ac55a..072191315f7 100644
--- a/library/std/src/sys/pal/hermit/io.rs
+++ b/library/std/src/sys/io/io_slice/iovec.rs
@@ -1,8 +1,13 @@
-use hermit_abi::{c_void, iovec};
+#[cfg(target_os = "hermit")]
+use hermit_abi::iovec;
+#[cfg(target_family = "unix")]
+use libc::iovec;
 
+use crate::ffi::c_void;
 use crate::marker::PhantomData;
-use crate::os::hermit::io::{AsFd, AsRawFd};
 use crate::slice;
+#[cfg(target_os = "solid_asp3")]
+use crate::sys::pal::abi::sockets::iovec;
 
 #[derive(Copy, Clone)]
 #[repr(transparent)]
@@ -80,8 +85,3 @@ impl<'a> IoSliceMut<'a> {
         unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }
     }
 }
-
-pub fn is_terminal(fd: &impl AsFd) -> bool {
-    let fd = fd.as_fd();
-    hermit_abi::isatty(fd.as_raw_fd())
-}
diff --git a/library/std/src/sys/pal/unsupported/io.rs b/library/std/src/sys/io/io_slice/unsupported.rs
index 604735d32d5..1572cac6cd7 100644
--- a/library/std/src/sys/pal/unsupported/io.rs
+++ b/library/std/src/sys/io/io_slice/unsupported.rs
@@ -50,7 +50,3 @@ impl<'a> IoSliceMut<'a> {
         self.0
     }
 }
-
-pub fn is_terminal<T>(_: &T) -> bool {
-    false
-}
diff --git a/library/std/src/sys/pal/wasi/io.rs b/library/std/src/sys/io/io_slice/wasi.rs
index 57f81bc6257..87acbbd924e 100644
--- a/library/std/src/sys/pal/wasi/io.rs
+++ b/library/std/src/sys/io/io_slice/wasi.rs
@@ -1,7 +1,4 @@
-#![forbid(unsafe_op_in_unsafe_fn)]
-
 use crate::marker::PhantomData;
-use crate::os::fd::{AsFd, AsRawFd};
 use crate::slice;
 
 #[derive(Copy, Clone)]
@@ -77,8 +74,3 @@ impl<'a> IoSliceMut<'a> {
         unsafe { slice::from_raw_parts_mut(self.vec.buf as *mut u8, self.vec.buf_len) }
     }
 }
-
-pub fn is_terminal(fd: &impl AsFd) -> bool {
-    let fd = fd.as_fd();
-    unsafe { libc::isatty(fd.as_raw_fd()) != 0 }
-}
diff --git a/library/std/src/sys/pal/solid/io.rs b/library/std/src/sys/io/io_slice/windows.rs
index 9ef4b7049b6..c3d8ec87c19 100644
--- a/library/std/src/sys/pal/solid/io.rs
+++ b/library/std/src/sys/io/io_slice/windows.rs
@@ -1,86 +1,82 @@
-use libc::c_void;
-
-use super::abi::sockets::iovec;
 use crate::marker::PhantomData;
 use crate::slice;
+use crate::sys::c;
 
 #[derive(Copy, Clone)]
 #[repr(transparent)]
 pub struct IoSlice<'a> {
-    vec: iovec,
+    vec: c::WSABUF,
     _p: PhantomData<&'a [u8]>,
 }
 
 impl<'a> IoSlice<'a> {
     #[inline]
     pub fn new(buf: &'a [u8]) -> IoSlice<'a> {
+        assert!(buf.len() <= u32::MAX as usize);
         IoSlice {
-            vec: iovec { iov_base: buf.as_ptr() as *mut u8 as *mut c_void, iov_len: buf.len() },
+            vec: c::WSABUF { len: buf.len() as u32, buf: buf.as_ptr() as *mut u8 },
             _p: PhantomData,
         }
     }
 
     #[inline]
     pub fn advance(&mut self, n: usize) {
-        if self.vec.iov_len < n {
+        if (self.vec.len as usize) < n {
             panic!("advancing IoSlice beyond its length");
         }
 
         unsafe {
-            self.vec.iov_len -= n;
-            self.vec.iov_base = self.vec.iov_base.add(n);
+            self.vec.len -= n as u32;
+            self.vec.buf = self.vec.buf.add(n);
         }
     }
 
     #[inline]
     pub const fn as_slice(&self) -> &'a [u8] {
-        unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
+        unsafe { slice::from_raw_parts(self.vec.buf, self.vec.len as usize) }
     }
 }
 
 #[repr(transparent)]
 pub struct IoSliceMut<'a> {
-    vec: iovec,
+    vec: c::WSABUF,
     _p: PhantomData<&'a mut [u8]>,
 }
 
 impl<'a> IoSliceMut<'a> {
     #[inline]
     pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> {
+        assert!(buf.len() <= u32::MAX as usize);
         IoSliceMut {
-            vec: iovec { iov_base: buf.as_mut_ptr() as *mut c_void, iov_len: buf.len() },
+            vec: c::WSABUF { len: buf.len() as u32, buf: buf.as_mut_ptr() },
             _p: PhantomData,
         }
     }
 
     #[inline]
     pub fn advance(&mut self, n: usize) {
-        if self.vec.iov_len < n {
+        if (self.vec.len as usize) < n {
             panic!("advancing IoSliceMut beyond its length");
         }
 
         unsafe {
-            self.vec.iov_len -= n;
-            self.vec.iov_base = self.vec.iov_base.add(n);
+            self.vec.len -= n as u32;
+            self.vec.buf = self.vec.buf.add(n);
         }
     }
 
     #[inline]
     pub fn as_slice(&self) -> &[u8] {
-        unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
+        unsafe { slice::from_raw_parts(self.vec.buf, self.vec.len as usize) }
     }
 
     #[inline]
     pub const fn into_slice(self) -> &'a mut [u8] {
-        unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }
+        unsafe { slice::from_raw_parts_mut(self.vec.buf, self.vec.len as usize) }
     }
 
     #[inline]
     pub fn as_mut_slice(&mut self) -> &mut [u8] {
-        unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }
+        unsafe { slice::from_raw_parts_mut(self.vec.buf, self.vec.len as usize) }
     }
 }
-
-pub fn is_terminal<T>(_: &T) -> bool {
-    false
-}
diff --git a/library/std/src/sys/io/is_terminal/hermit.rs b/library/std/src/sys/io/is_terminal/hermit.rs
new file mode 100644
index 00000000000..61bdb6f0a54
--- /dev/null
+++ b/library/std/src/sys/io/is_terminal/hermit.rs
@@ -0,0 +1,6 @@
+use crate::os::fd::{AsFd, AsRawFd};
+
+pub fn is_terminal(fd: &impl AsFd) -> bool {
+    let fd = fd.as_fd();
+    hermit_abi::isatty(fd.as_raw_fd())
+}
diff --git a/library/std/src/sys/io/is_terminal/isatty.rs b/library/std/src/sys/io/is_terminal/isatty.rs
new file mode 100644
index 00000000000..6e0b46211b9
--- /dev/null
+++ b/library/std/src/sys/io/is_terminal/isatty.rs
@@ -0,0 +1,6 @@
+use crate::os::fd::{AsFd, AsRawFd};
+
+pub fn is_terminal(fd: &impl AsFd) -> bool {
+    let fd = fd.as_fd();
+    unsafe { libc::isatty(fd.as_raw_fd()) != 0 }
+}
diff --git a/library/std/src/sys/io/is_terminal/unsupported.rs b/library/std/src/sys/io/is_terminal/unsupported.rs
new file mode 100644
index 00000000000..cee4add32fb
--- /dev/null
+++ b/library/std/src/sys/io/is_terminal/unsupported.rs
@@ -0,0 +1,3 @@
+pub fn is_terminal<T>(_: &T) -> bool {
+    false
+}
diff --git a/library/std/src/sys/pal/windows/io.rs b/library/std/src/sys/io/is_terminal/windows.rs
index f2865d2ffc1..3ec18fb47b9 100644
--- a/library/std/src/sys/pal/windows/io.rs
+++ b/library/std/src/sys/io/is_terminal/windows.rs
@@ -1,90 +1,8 @@
-use core::ffi::c_void;
-
-use crate::marker::PhantomData;
+use crate::ffi::c_void;
 use crate::mem::size_of;
 use crate::os::windows::io::{AsHandle, AsRawHandle, BorrowedHandle};
-use crate::slice;
 use crate::sys::c;
 
-#[derive(Copy, Clone)]
-#[repr(transparent)]
-pub struct IoSlice<'a> {
-    vec: c::WSABUF,
-    _p: PhantomData<&'a [u8]>,
-}
-
-impl<'a> IoSlice<'a> {
-    #[inline]
-    pub fn new(buf: &'a [u8]) -> IoSlice<'a> {
-        assert!(buf.len() <= u32::MAX as usize);
-        IoSlice {
-            vec: c::WSABUF { len: buf.len() as u32, buf: buf.as_ptr() as *mut u8 },
-            _p: PhantomData,
-        }
-    }
-
-    #[inline]
-    pub fn advance(&mut self, n: usize) {
-        if (self.vec.len as usize) < n {
-            panic!("advancing IoSlice beyond its length");
-        }
-
-        unsafe {
-            self.vec.len -= n as u32;
-            self.vec.buf = self.vec.buf.add(n);
-        }
-    }
-
-    #[inline]
-    pub const fn as_slice(&self) -> &'a [u8] {
-        unsafe { slice::from_raw_parts(self.vec.buf, self.vec.len as usize) }
-    }
-}
-
-#[repr(transparent)]
-pub struct IoSliceMut<'a> {
-    vec: c::WSABUF,
-    _p: PhantomData<&'a mut [u8]>,
-}
-
-impl<'a> IoSliceMut<'a> {
-    #[inline]
-    pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> {
-        assert!(buf.len() <= u32::MAX as usize);
-        IoSliceMut {
-            vec: c::WSABUF { len: buf.len() as u32, buf: buf.as_mut_ptr() },
-            _p: PhantomData,
-        }
-    }
-
-    #[inline]
-    pub fn advance(&mut self, n: usize) {
-        if (self.vec.len as usize) < n {
-            panic!("advancing IoSliceMut beyond its length");
-        }
-
-        unsafe {
-            self.vec.len -= n as u32;
-            self.vec.buf = self.vec.buf.add(n);
-        }
-    }
-
-    #[inline]
-    pub fn as_slice(&self) -> &[u8] {
-        unsafe { slice::from_raw_parts(self.vec.buf, self.vec.len as usize) }
-    }
-
-    #[inline]
-    pub const fn into_slice(self) -> &'a mut [u8] {
-        unsafe { slice::from_raw_parts_mut(self.vec.buf, self.vec.len as usize) }
-    }
-
-    #[inline]
-    pub fn as_mut_slice(&mut self) -> &mut [u8] {
-        unsafe { slice::from_raw_parts_mut(self.vec.buf, self.vec.len as usize) }
-    }
-}
-
 pub fn is_terminal(h: &impl AsHandle) -> bool {
     handle_is_console(h.as_handle())
 }
diff --git a/library/std/src/sys/io/mod.rs b/library/std/src/sys/io/mod.rs
new file mode 100644
index 00000000000..e00b479109f
--- /dev/null
+++ b/library/std/src/sys/io/mod.rs
@@ -0,0 +1,44 @@
+#![forbid(unsafe_op_in_unsafe_fn)]
+
+mod io_slice {
+    cfg_if::cfg_if! {
+        if #[cfg(any(target_family = "unix", target_os = "hermit", target_os = "solid_asp3"))] {
+            mod iovec;
+            pub use iovec::*;
+        } else if #[cfg(target_os = "windows")] {
+            mod windows;
+            pub use windows::*;
+        } else if #[cfg(target_os = "wasi")] {
+            mod wasi;
+            pub use wasi::*;
+        } else {
+            mod unsupported;
+            pub use unsupported::*;
+        }
+    }
+}
+
+mod is_terminal {
+    cfg_if::cfg_if! {
+        if #[cfg(any(target_family = "unix", target_os = "wasi"))] {
+            mod isatty;
+            pub use isatty::*;
+        } else if #[cfg(target_os = "windows")] {
+            mod windows;
+            pub use windows::*;
+        } else if #[cfg(target_os = "hermit")] {
+            mod hermit;
+            pub use hermit::*;
+        } else {
+            mod unsupported;
+            pub use unsupported::*;
+        }
+    }
+}
+
+pub use io_slice::{IoSlice, IoSliceMut};
+pub use is_terminal::is_terminal;
+
+// Bare metal platforms usually have very small amounts of RAM
+// (in the order of hundreds of KB)
+pub const DEFAULT_BUF_SIZE: usize = if cfg!(target_os = "espidf") { 512 } else { 8 * 1024 };
diff --git a/library/std/src/sys/mod.rs b/library/std/src/sys/mod.rs
index f17dd47dece..1032fcba5e2 100644
--- a/library/std/src/sys/mod.rs
+++ b/library/std/src/sys/mod.rs
@@ -12,6 +12,8 @@ pub mod anonymous_pipe;
 pub mod backtrace;
 pub mod cmath;
 pub mod exit_guard;
+pub mod io;
+pub mod net;
 pub mod os_str;
 pub mod path;
 pub mod random;
diff --git a/library/std/src/sys/pal/sgx/net.rs b/library/std/src/sys/net/connection/sgx.rs
index c966886d163..b390a5eac5f 100644
--- a/library/std/src/sys/pal/sgx/net.rs
+++ b/library/std/src/sys/net/connection/sgx.rs
@@ -1,7 +1,7 @@
-use super::abi::usercalls;
 use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
 use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr, ToSocketAddrs};
 use crate::sync::Arc;
+use crate::sys::abi::usercalls;
 use crate::sys::fd::FileDesc;
 use crate::sys::{AsInner, FromInner, IntoInner, TryIntoInner, sgx_ineffective, unsupported};
 use crate::time::Duration;
diff --git a/library/std/src/sys_common/net.rs b/library/std/src/sys/net/connection/socket.rs
index 74306978d22..6fe3430b53f 100644
--- a/library/std/src/sys_common/net.rs
+++ b/library/std/src/sys/net/connection/socket.rs
@@ -5,12 +5,32 @@ use crate::ffi::{c_int, c_void};
 use crate::io::{self, BorrowedCursor, ErrorKind, IoSlice, IoSliceMut};
 use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr};
 use crate::sys::common::small_c_string::run_with_cstr;
-use crate::sys::net::{Socket, cvt, cvt_gai, cvt_r, init, netc as c, wrlen_t};
 use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::time::Duration;
 use crate::{cmp, fmt, mem, ptr};
 
 cfg_if::cfg_if! {
+    if #[cfg(target_os = "hermit")] {
+        mod hermit;
+        pub use hermit::*;
+    } else if #[cfg(target_os = "solid_asp3")] {
+        mod solid;
+        pub use solid::*;
+    } else if #[cfg(target_family = "unix")] {
+        mod unix;
+        pub use unix::*;
+    } else if #[cfg(all(target_os = "wasi", target_env = "p2"))] {
+        mod wasip2;
+        pub use wasip2::*;
+    } else if #[cfg(target_os = "windows")] {
+        mod windows;
+        pub use windows::*;
+    }
+}
+
+use netc as c;
+
+cfg_if::cfg_if! {
     if #[cfg(any(
         target_os = "dragonfly",
         target_os = "freebsd",
@@ -24,11 +44,11 @@ cfg_if::cfg_if! {
         target_os = "nuttx",
         target_vendor = "apple",
     ))] {
-        use crate::sys::net::netc::IPV6_JOIN_GROUP as IPV6_ADD_MEMBERSHIP;
-        use crate::sys::net::netc::IPV6_LEAVE_GROUP as IPV6_DROP_MEMBERSHIP;
+        use c::IPV6_JOIN_GROUP as IPV6_ADD_MEMBERSHIP;
+        use c::IPV6_LEAVE_GROUP as IPV6_DROP_MEMBERSHIP;
     } else {
-        use crate::sys::net::netc::IPV6_ADD_MEMBERSHIP;
-        use crate::sys::net::netc::IPV6_DROP_MEMBERSHIP;
+        use c::IPV6_ADD_MEMBERSHIP;
+        use c::IPV6_DROP_MEMBERSHIP;
     }
 }
 
diff --git a/library/std/src/sys/pal/hermit/net.rs b/library/std/src/sys/net/connection/socket/hermit.rs
index 4e12374203e..42179dcc915 100644
--- a/library/std/src/sys/pal/hermit/net.rs
+++ b/library/std/src/sys/net/connection/socket/hermit.rs
@@ -2,21 +2,20 @@
 
 use core::ffi::c_int;
 
-use super::fd::FileDesc;
+pub(crate) use hermit_abi as netc;
+
 use crate::io::{self, BorrowedBuf, BorrowedCursor, IoSlice, IoSliceMut};
 use crate::net::{Shutdown, SocketAddr};
 use crate::os::hermit::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, RawFd};
+use crate::sys::fd::FileDesc;
+use crate::sys::net::{getsockopt, setsockopt, sockaddr_to_addr};
 use crate::sys::time::Instant;
-use crate::sys_common::net::{getsockopt, setsockopt, sockaddr_to_addr};
+pub use crate::sys::{cvt, cvt_r};
 use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::time::Duration;
 use crate::{cmp, mem};
 
-#[allow(unused_extern_crates)]
-pub extern crate hermit_abi as netc;
-
-pub use crate::sys::{cvt, cvt_r};
-
+#[expect(non_camel_case_types)]
 pub type wrlen_t = usize;
 
 pub fn cvt_gai(err: i32) -> io::Result<()> {
diff --git a/library/std/src/sys/pal/solid/net.rs b/library/std/src/sys/net/connection/socket/solid.rs
index 5f6436807e2..f85ecbb883e 100644
--- a/library/std/src/sys/pal/solid/net.rs
+++ b/library/std/src/sys/net/connection/socket/solid.rs
@@ -1,24 +1,23 @@
 use libc::{c_int, c_void, size_t};
 
 use self::netc::{MSG_PEEK, sockaddr, socklen_t};
-use super::abi;
 use crate::ffi::CStr;
 use crate::io::{self, BorrowedBuf, BorrowedCursor, ErrorKind, IoSlice, IoSliceMut};
 use crate::net::{Shutdown, SocketAddr};
 use crate::os::solid::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, OwnedFd};
-use crate::sys_common::net::{getsockopt, setsockopt, sockaddr_to_addr};
+use crate::sys::abi;
+use crate::sys::net::{getsockopt, setsockopt, sockaddr_to_addr};
 use crate::sys_common::{FromInner, IntoInner};
 use crate::time::Duration;
 use crate::{cmp, mem, ptr, str};
 
 pub mod netc {
-    pub use super::super::abi::sockets::*;
+    pub use crate::sys::abi::sockets::*;
 }
 
+#[expect(non_camel_case_types)]
 pub type wrlen_t = size_t;
 
-const READ_LIMIT: usize = libc::ssize_t::MAX as usize;
-
 const fn max_iov() -> usize {
     // Judging by the source code, it's unlimited, but specify a lower
     // value just in case.
@@ -78,7 +77,7 @@ fn last_error() -> io::Error {
     io::Error::from_raw_os_error(unsafe { netc::SOLID_NET_GetLastError() })
 }
 
-pub(super) fn error_name(er: abi::ER) -> Option<&'static str> {
+pub fn error_name(er: abi::ER) -> Option<&'static str> {
     unsafe { CStr::from_ptr(netc::strerror(er)) }.to_str().ok()
 }
 
@@ -87,7 +86,7 @@ pub fn is_interrupted(er: abi::ER) -> bool {
     er == netc::SOLID_NET_ERR_BASE - libc::EINTR
 }
 
-pub(super) fn decode_error_kind(er: abi::ER) -> ErrorKind {
+pub fn decode_error_kind(er: abi::ER) -> ErrorKind {
     let errno = netc::SOLID_NET_ERR_BASE - er;
     match errno as libc::c_int {
         libc::ECONNREFUSED => ErrorKind::ConnectionRefused,
@@ -268,17 +267,6 @@ impl Socket {
         self.recv_from_with_flags(buf, MSG_PEEK)
     }
 
-    pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
-        let ret = cvt(unsafe {
-            netc::write(
-                self.as_raw_fd(),
-                buf.as_ptr() as *const c_void,
-                cmp::min(buf.len(), READ_LIMIT),
-            )
-        })?;
-        Ok(ret as usize)
-    }
-
     pub fn write_vectored(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
         let ret = cvt(unsafe {
             netc::writev(
diff --git a/library/std/src/sys_common/net/tests.rs b/library/std/src/sys/net/connection/socket/tests.rs
index fc236b8027b..fc236b8027b 100644
--- a/library/std/src/sys_common/net/tests.rs
+++ b/library/std/src/sys/net/connection/socket/tests.rs
diff --git a/library/std/src/sys/pal/unix/net.rs b/library/std/src/sys/net/connection/socket/unix.rs
index d73b9fd5eb8..da631605527 100644
--- a/library/std/src/sys/pal/unix/net.rs
+++ b/library/std/src/sys/net/connection/socket/unix.rs
@@ -5,8 +5,8 @@ use crate::io::{self, BorrowedBuf, BorrowedCursor, IoSlice, IoSliceMut};
 use crate::net::{Shutdown, SocketAddr};
 use crate::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, RawFd};
 use crate::sys::fd::FileDesc;
-use crate::sys::pal::unix::IsMinusOne;
-use crate::sys_common::net::{getsockopt, setsockopt, sockaddr_to_addr};
+use crate::sys::net::{getsockopt, setsockopt, sockaddr_to_addr};
+use crate::sys::pal::IsMinusOne;
 use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::time::{Duration, Instant};
 use crate::{cmp, mem};
@@ -19,11 +19,11 @@ cfg_if::cfg_if! {
     }
 }
 
-pub use crate::sys::{cvt, cvt_r};
+pub(crate) use libc as netc;
 
-#[allow(unused_extern_crates)]
-pub extern crate libc as netc;
+pub use crate::sys::{cvt, cvt_r};
 
+#[expect(non_camel_case_types)]
 pub type wrlen_t = size_t;
 
 pub struct Socket(FileDesc);
diff --git a/library/std/src/sys/pal/wasip2/net.rs b/library/std/src/sys/net/connection/socket/wasip2.rs
index f009a51821f..9d1c05a473e 100644
--- a/library/std/src/sys/pal/wasip2/net.rs
+++ b/library/std/src/sys/net/connection/socket/wasip2.rs
@@ -6,8 +6,8 @@ use crate::ffi::CStr;
 use crate::io::{self, BorrowedBuf, BorrowedCursor, IoSlice, IoSliceMut};
 use crate::net::{Shutdown, SocketAddr};
 use crate::os::wasi::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
+use crate::sys::net::{getsockopt, setsockopt, sockaddr_to_addr};
 use crate::sys::unsupported;
-use crate::sys_common::net::{getsockopt, setsockopt, sockaddr_to_addr};
 use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::time::{Duration, Instant};
 use crate::{cmp, mem, str};
diff --git a/library/std/src/sys/pal/windows/net.rs b/library/std/src/sys/net/connection/socket/windows.rs
index a92853c642c..80cf37eaf05 100644
--- a/library/std/src/sys/pal/windows/net.rs
+++ b/library/std/src/sys/net/connection/socket/windows.rs
@@ -9,7 +9,7 @@ use crate::os::windows::io::{
 };
 use crate::sync::OnceLock;
 use crate::sys::c;
-use crate::sys_common::{AsInner, FromInner, IntoInner, net};
+use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::time::Duration;
 use crate::{cmp, mem, ptr, sys};
 
@@ -110,6 +110,7 @@ pub mod netc {
     }
 }
 
+#[expect(missing_debug_implementations)]
 pub struct Socket(OwnedSocket);
 
 static WSA_CLEANUP: OnceLock<unsafe extern "system" fn() -> i32> = OnceLock::new();
@@ -400,12 +401,12 @@ impl Socket {
                 let error = unsafe { c::WSAGetLastError() };
 
                 if error == c::WSAESHUTDOWN {
-                    Ok((0, net::sockaddr_to_addr(&storage, addrlen as usize)?))
+                    Ok((0, super::sockaddr_to_addr(&storage, addrlen as usize)?))
                 } else {
                     Err(io::Error::from_raw_os_error(error))
                 }
             }
-            _ => Ok((result as usize, net::sockaddr_to_addr(&storage, addrlen as usize)?)),
+            _ => Ok((result as usize, super::sockaddr_to_addr(&storage, addrlen as usize)?)),
         }
     }
 
@@ -450,11 +451,11 @@ impl Socket {
             }
             None => 0,
         };
-        net::setsockopt(self, c::SOL_SOCKET, kind, timeout)
+        super::setsockopt(self, c::SOL_SOCKET, kind, timeout)
     }
 
     pub fn timeout(&self, kind: c_int) -> io::Result<Option<Duration>> {
-        let raw: u32 = net::getsockopt(self, c::SOL_SOCKET, kind)?;
+        let raw: u32 = super::getsockopt(self, c::SOL_SOCKET, kind)?;
         if raw == 0 {
             Ok(None)
         } else {
@@ -487,26 +488,26 @@ impl Socket {
             l_linger: linger.unwrap_or_default().as_secs() as c_ushort,
         };
 
-        net::setsockopt(self, c::SOL_SOCKET, c::SO_LINGER, linger)
+        super::setsockopt(self, c::SOL_SOCKET, c::SO_LINGER, linger)
     }
 
     pub fn linger(&self) -> io::Result<Option<Duration>> {
-        let val: c::LINGER = net::getsockopt(self, c::SOL_SOCKET, c::SO_LINGER)?;
+        let val: c::LINGER = super::getsockopt(self, c::SOL_SOCKET, c::SO_LINGER)?;
 
         Ok((val.l_onoff != 0).then(|| Duration::from_secs(val.l_linger as u64)))
     }
 
     pub fn set_nodelay(&self, nodelay: bool) -> io::Result<()> {
-        net::setsockopt(self, c::IPPROTO_TCP, c::TCP_NODELAY, nodelay as c::BOOL)
+        super::setsockopt(self, c::IPPROTO_TCP, c::TCP_NODELAY, nodelay as c::BOOL)
     }
 
     pub fn nodelay(&self) -> io::Result<bool> {
-        let raw: c::BOOL = net::getsockopt(self, c::IPPROTO_TCP, c::TCP_NODELAY)?;
+        let raw: c::BOOL = super::getsockopt(self, c::IPPROTO_TCP, c::TCP_NODELAY)?;
         Ok(raw != 0)
     }
 
     pub fn take_error(&self) -> io::Result<Option<io::Error>> {
-        let raw: c_int = net::getsockopt(self, c::SOL_SOCKET, c::SO_ERROR)?;
+        let raw: c_int = super::getsockopt(self, c::SOL_SOCKET, c::SO_ERROR)?;
         if raw == 0 { Ok(None) } else { Ok(Some(io::Error::from_raw_os_error(raw as i32))) }
     }
 
diff --git a/library/std/src/sys/pal/unsupported/net.rs b/library/std/src/sys/net/connection/uefi/mod.rs
index 87e6106468f..87e6106468f 100644
--- a/library/std/src/sys/pal/unsupported/net.rs
+++ b/library/std/src/sys/net/connection/uefi/mod.rs
diff --git a/library/std/src/sys/pal/teeos/net.rs b/library/std/src/sys/net/connection/unsupported.rs
index fed95205027..87e6106468f 100644
--- a/library/std/src/sys/pal/teeos/net.rs
+++ b/library/std/src/sys/net/connection/unsupported.rs
@@ -346,6 +346,7 @@ pub mod netc {
 
     #[derive(Copy, Clone)]
     pub struct sockaddr_in {
+        #[allow(dead_code)]
         pub sin_family: sa_family_t,
         pub sin_port: u16,
         pub sin_addr: in_addr,
@@ -358,6 +359,7 @@ pub mod netc {
 
     #[derive(Copy, Clone)]
     pub struct sockaddr_in6 {
+        #[allow(dead_code)]
         pub sin6_family: sa_family_t,
         pub sin6_port: u16,
         pub sin6_addr: in6_addr,
@@ -365,5 +367,3 @@ pub mod netc {
         pub sin6_scope_id: u32,
     }
 }
-
-pub type Socket = UdpSocket;
diff --git a/library/std/src/sys/pal/wasi/net.rs b/library/std/src/sys/net/connection/wasip1.rs
index a6486799828..27e3a528af4 100644
--- a/library/std/src/sys/pal/wasi/net.rs
+++ b/library/std/src/sys/net/connection/wasip1.rs
@@ -1,12 +1,11 @@
 #![forbid(unsafe_op_in_unsafe_fn)]
 
-use super::err2io;
-use super::fd::WasiFd;
 use crate::fmt;
 use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
 use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr};
 use crate::os::wasi::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, RawFd};
-use crate::sys::unsupported;
+use crate::sys::fd::WasiFd;
+use crate::sys::{err2io, unsupported};
 use crate::sys_common::{AsInner, FromInner, IntoInner};
 use crate::time::Duration;
 
diff --git a/library/std/src/sys/pal/xous/net/dns.rs b/library/std/src/sys/net/connection/xous/dns.rs
index ff6e49ed2d4..ff6e49ed2d4 100644
--- a/library/std/src/sys/pal/xous/net/dns.rs
+++ b/library/std/src/sys/net/connection/xous/dns.rs
diff --git a/library/std/src/sys/pal/xous/net/mod.rs b/library/std/src/sys/net/connection/xous/mod.rs
index 3e18ed24208..3e18ed24208 100644
--- a/library/std/src/sys/pal/xous/net/mod.rs
+++ b/library/std/src/sys/net/connection/xous/mod.rs
diff --git a/library/std/src/sys/pal/xous/net/tcplistener.rs b/library/std/src/sys/net/connection/xous/tcplistener.rs
index 640a02a64f5..640a02a64f5 100644
--- a/library/std/src/sys/pal/xous/net/tcplistener.rs
+++ b/library/std/src/sys/net/connection/xous/tcplistener.rs
diff --git a/library/std/src/sys/pal/xous/net/tcpstream.rs b/library/std/src/sys/net/connection/xous/tcpstream.rs
index 572dd6b3b63..572dd6b3b63 100644
--- a/library/std/src/sys/pal/xous/net/tcpstream.rs
+++ b/library/std/src/sys/net/connection/xous/tcpstream.rs
diff --git a/library/std/src/sys/pal/xous/net/udp.rs b/library/std/src/sys/net/connection/xous/udp.rs
index 1b7ecac6d3a..1b7ecac6d3a 100644
--- a/library/std/src/sys/pal/xous/net/udp.rs
+++ b/library/std/src/sys/net/connection/xous/udp.rs
diff --git a/library/std/src/sys/net/mod.rs b/library/std/src/sys/net/mod.rs
new file mode 100644
index 00000000000..646679a1cc8
--- /dev/null
+++ b/library/std/src/sys/net/mod.rs
@@ -0,0 +1,41 @@
+cfg_if::cfg_if! {
+    if #[cfg(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::*;
+        }
+    } else if #[cfg(all(target_vendor = "fortanix", target_env = "sgx"))] {
+        mod connection {
+            mod sgx;
+            pub use sgx::*;
+        }
+    } else if #[cfg(all(target_os = "wasi", target_env = "p1"))] {
+        mod connection {
+            mod wasip1;
+            pub use wasip1::*;
+        }
+    } else if #[cfg(target_os = "xous")] {
+        mod connection {
+            mod xous;
+            pub use xous::*;
+        }
+    } else if #[cfg(target_os = "uefi")] {
+        mod connection {
+            mod uefi;
+            pub use uefi::*;
+        }
+    } else {
+        mod connection {
+            mod unsupported;
+            pub use unsupported::*;
+        }
+    }
+}
+
+pub use connection::*;
diff --git a/library/std/src/sys/pal/hermit/mod.rs b/library/std/src/sys/pal/hermit/mod.rs
index d833c9d632c..3d555ad5050 100644
--- a/library/std/src/sys/pal/hermit/mod.rs
+++ b/library/std/src/sys/pal/hermit/mod.rs
@@ -23,8 +23,6 @@ pub mod env;
 pub mod fd;
 pub mod fs;
 pub mod futex;
-pub mod io;
-pub mod net;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
diff --git a/library/std/src/sys/pal/itron/time/tests.rs b/library/std/src/sys/pal/itron/time/tests.rs
index 28db4f8b679..d14035d9da4 100644
--- a/library/std/src/sys/pal/itron/time/tests.rs
+++ b/library/std/src/sys/pal/itron/time/tests.rs
@@ -8,24 +8,26 @@ fn reltim2dur(t: u64) -> Duration {
 fn test_dur2reltims() {
     assert_eq!(dur2reltims(reltim2dur(0)).collect::<Vec<_>>(), vec![]);
     assert_eq!(dur2reltims(reltim2dur(42)).collect::<Vec<_>>(), vec![42]);
-    assert_eq!(dur2reltims(reltim2dur(abi::TMAX_RELTIM as u64)).collect::<Vec<_>>(), vec![
-        abi::TMAX_RELTIM
-    ]);
-    assert_eq!(dur2reltims(reltim2dur(abi::TMAX_RELTIM as u64 + 10000)).collect::<Vec<_>>(), vec![
-        abi::TMAX_RELTIM,
-        10000
-    ]);
+    assert_eq!(
+        dur2reltims(reltim2dur(abi::TMAX_RELTIM as u64)).collect::<Vec<_>>(),
+        vec![abi::TMAX_RELTIM]
+    );
+    assert_eq!(
+        dur2reltims(reltim2dur(abi::TMAX_RELTIM as u64 + 10000)).collect::<Vec<_>>(),
+        vec![abi::TMAX_RELTIM, 10000]
+    );
 }
 
 #[test]
 fn test_dur2tmos() {
     assert_eq!(dur2tmos(reltim2dur(0)).collect::<Vec<_>>(), vec![0]);
     assert_eq!(dur2tmos(reltim2dur(42)).collect::<Vec<_>>(), vec![42]);
-    assert_eq!(dur2tmos(reltim2dur(abi::TMAX_RELTIM as u64)).collect::<Vec<_>>(), vec![
-        abi::TMAX_RELTIM
-    ]);
-    assert_eq!(dur2tmos(reltim2dur(abi::TMAX_RELTIM as u64 + 10000)).collect::<Vec<_>>(), vec![
-        abi::TMAX_RELTIM,
-        10000
-    ]);
+    assert_eq!(
+        dur2tmos(reltim2dur(abi::TMAX_RELTIM as u64)).collect::<Vec<_>>(),
+        vec![abi::TMAX_RELTIM]
+    );
+    assert_eq!(
+        dur2tmos(reltim2dur(abi::TMAX_RELTIM as u64 + 10000)).collect::<Vec<_>>(),
+        vec![abi::TMAX_RELTIM, 10000]
+    );
 }
diff --git a/library/std/src/sys/pal/sgx/mod.rs b/library/std/src/sys/pal/sgx/mod.rs
index ce8a2fed4bc..9a04fa4b97e 100644
--- a/library/std/src/sys/pal/sgx/mod.rs
+++ b/library/std/src/sys/pal/sgx/mod.rs
@@ -14,10 +14,7 @@ pub mod env;
 pub mod fd;
 #[path = "../unsupported/fs.rs"]
 pub mod fs;
-#[path = "../unsupported/io.rs"]
-pub mod io;
 mod libunwind_integration;
-pub mod net;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
diff --git a/library/std/src/sys/pal/sgx/stdio.rs b/library/std/src/sys/pal/sgx/stdio.rs
index 2e680e740fd..e79a3d971c6 100644
--- a/library/std/src/sys/pal/sgx/stdio.rs
+++ b/library/std/src/sys/pal/sgx/stdio.rs
@@ -62,7 +62,7 @@ impl io::Write for Stderr {
     }
 }
 
-pub const STDIN_BUF_SIZE: usize = crate::sys_common::io::DEFAULT_BUF_SIZE;
+pub const STDIN_BUF_SIZE: usize = crate::sys::io::DEFAULT_BUF_SIZE;
 
 pub fn is_ebadf(err: &io::Error) -> bool {
     // FIXME: Rust normally maps Unix EBADF to `Uncategorized`
diff --git a/library/std/src/sys/pal/solid/error.rs b/library/std/src/sys/pal/solid/error.rs
index e092497856d..b399463c0c2 100644
--- a/library/std/src/sys/pal/solid/error.rs
+++ b/library/std/src/sys/pal/solid/error.rs
@@ -1,6 +1,7 @@
 pub use self::itron::error::{ItronError as SolidError, expect_success};
-use super::{abi, itron, net};
+use super::{abi, itron};
 use crate::io::ErrorKind;
+use crate::sys::net;
 
 /// Describe the specified SOLID error code. Returns `None` if it's an
 /// undefined error code.
diff --git a/library/std/src/sys/pal/solid/mod.rs b/library/std/src/sys/pal/solid/mod.rs
index d41042be518..06af7bfade0 100644
--- a/library/std/src/sys/pal/solid/mod.rs
+++ b/library/std/src/sys/pal/solid/mod.rs
@@ -23,8 +23,6 @@ pub mod env;
 // `crate::sys::error`
 pub(crate) mod error;
 pub mod fs;
-pub mod io;
-pub mod net;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
@@ -51,7 +49,7 @@ pub fn unsupported_err() -> crate::io::Error {
 
 #[inline]
 pub fn is_interrupted(code: i32) -> bool {
-    net::is_interrupted(code)
+    crate::sys::net::is_interrupted(code)
 }
 
 pub fn decode_error_kind(code: i32) -> crate::io::ErrorKind {
diff --git a/library/std/src/sys/pal/teeos/mod.rs b/library/std/src/sys/pal/teeos/mod.rs
index a9900f55b19..f850fefc8f2 100644
--- a/library/std/src/sys/pal/teeos/mod.rs
+++ b/library/std/src/sys/pal/teeos/mod.rs
@@ -13,9 +13,6 @@ pub mod env;
 //pub mod fd;
 #[path = "../unsupported/fs.rs"]
 pub mod fs;
-#[path = "../unsupported/io.rs"]
-pub mod io;
-pub mod net;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
diff --git a/library/std/src/sys/pal/uefi/helpers.rs b/library/std/src/sys/pal/uefi/helpers.rs
index 7504a0f7ad7..dccc137d6f5 100644
--- a/library/std/src/sys/pal/uefi/helpers.rs
+++ b/library/std/src/sys/pal/uefi/helpers.rs
@@ -14,10 +14,12 @@ use r_efi::protocols::{device_path, device_path_to_text, shell};
 
 use crate::ffi::{OsStr, OsString};
 use crate::io::{self, const_error};
+use crate::marker::PhantomData;
 use crate::mem::{MaybeUninit, size_of};
 use crate::os::uefi::env::boot_services;
 use crate::os::uefi::ffi::{OsStrExt, OsStringExt};
 use crate::os::uefi::{self};
+use crate::path::Path;
 use crate::ptr::NonNull;
 use crate::slice;
 use crate::sync::atomic::{AtomicPtr, Ordering};
@@ -278,6 +280,10 @@ impl OwnedDevicePath {
     pub(crate) const fn as_ptr(&self) -> *mut r_efi::protocols::device_path::Protocol {
         self.0.as_ptr()
     }
+
+    pub(crate) const fn borrow<'a>(&'a self) -> BorrowedDevicePath<'a> {
+        BorrowedDevicePath::new(self.0)
+    }
 }
 
 impl Drop for OwnedDevicePath {
@@ -293,13 +299,37 @@ impl Drop for OwnedDevicePath {
 
 impl crate::fmt::Debug for OwnedDevicePath {
     fn fmt(&self, f: &mut crate::fmt::Formatter<'_>) -> crate::fmt::Result {
-        match device_path_to_text(self.0) {
+        match self.borrow().to_text() {
             Ok(p) => p.fmt(f),
             Err(_) => f.debug_struct("OwnedDevicePath").finish_non_exhaustive(),
         }
     }
 }
 
+pub(crate) struct BorrowedDevicePath<'a> {
+    protocol: NonNull<r_efi::protocols::device_path::Protocol>,
+    phantom: PhantomData<&'a r_efi::protocols::device_path::Protocol>,
+}
+
+impl<'a> BorrowedDevicePath<'a> {
+    pub(crate) const fn new(protocol: NonNull<r_efi::protocols::device_path::Protocol>) -> Self {
+        Self { protocol, phantom: PhantomData }
+    }
+
+    pub(crate) fn to_text(&self) -> io::Result<OsString> {
+        device_path_to_text(self.protocol)
+    }
+}
+
+impl<'a> crate::fmt::Debug for BorrowedDevicePath<'a> {
+    fn fmt(&self, f: &mut crate::fmt::Formatter<'_>) -> crate::fmt::Result {
+        match self.to_text() {
+            Ok(p) => p.fmt(f),
+            Err(_) => f.debug_struct("BorrowedDevicePath").finish_non_exhaustive(),
+        }
+    }
+}
+
 pub(crate) struct OwnedProtocol<T> {
     guid: r_efi::efi::Guid,
     handle: NonNull<crate::ffi::c_void>,
@@ -452,3 +482,21 @@ pub(crate) fn open_shell() -> Option<NonNull<shell::Protocol>> {
 
     None
 }
+
+/// Get device path protocol associated with shell mapping.
+///
+/// returns None in case no such mapping is exists
+pub(crate) fn get_device_path_from_map(map: &Path) -> io::Result<BorrowedDevicePath<'static>> {
+    let shell =
+        open_shell().ok_or(io::const_error!(io::ErrorKind::NotFound, "UEFI Shell not found"))?;
+    let mut path = os_string_to_raw(map.as_os_str())
+        .ok_or(io::const_error!(io::ErrorKind::InvalidFilename, "Invalid UEFI shell mapping"))?;
+
+    // The Device Path Protocol pointer returned by UEFI shell is owned by the shell and is not
+    // freed throughout it's lifetime. So it has a 'static lifetime.
+    let protocol = unsafe { ((*shell.as_ptr()).get_device_path_from_map)(path.as_mut_ptr()) };
+    let protocol = NonNull::new(protocol)
+        .ok_or(io::const_error!(io::ErrorKind::NotFound, "UEFI Shell mapping not found"))?;
+
+    Ok(BorrowedDevicePath::new(protocol))
+}
diff --git a/library/std/src/sys/pal/uefi/mod.rs b/library/std/src/sys/pal/uefi/mod.rs
index 111bed7a7eb..4766e2ef0a9 100644
--- a/library/std/src/sys/pal/uefi/mod.rs
+++ b/library/std/src/sys/pal/uefi/mod.rs
@@ -17,10 +17,6 @@ pub mod args;
 pub mod env;
 pub mod fs;
 pub mod helpers;
-#[path = "../unsupported/io.rs"]
-pub mod io;
-#[path = "../unsupported/net.rs"]
-pub mod net;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
diff --git a/library/std/src/sys/pal/uefi/process.rs b/library/std/src/sys/pal/uefi/process.rs
index 1a0754134df..0757f1cb490 100644
--- a/library/std/src/sys/pal/uefi/process.rs
+++ b/library/std/src/sys/pal/uefi/process.rs
@@ -1,6 +1,7 @@
 use r_efi::protocols::simple_text_output;
 
 use super::helpers;
+use crate::collections::BTreeMap;
 pub use crate::ffi::OsString as EnvKey;
 use crate::ffi::{OsStr, OsString};
 use crate::num::{NonZero, NonZeroI32};
@@ -21,6 +22,7 @@ pub struct Command {
     args: Vec<OsString>,
     stdout: Option<Stdio>,
     stderr: Option<Stdio>,
+    env: CommandEnv,
 }
 
 // passed back to std::process with the pipes connected to the child, if any
@@ -40,7 +42,13 @@ pub enum Stdio {
 
 impl Command {
     pub fn new(program: &OsStr) -> Command {
-        Command { prog: program.to_os_string(), args: Vec::new(), stdout: None, stderr: None }
+        Command {
+            prog: program.to_os_string(),
+            args: Vec::new(),
+            stdout: None,
+            stderr: None,
+            env: Default::default(),
+        }
     }
 
     pub fn arg(&mut self, arg: &OsStr) {
@@ -48,7 +56,7 @@ impl Command {
     }
 
     pub fn env_mut(&mut self) -> &mut CommandEnv {
-        panic!("unsupported")
+        &mut self.env
     }
 
     pub fn cwd(&mut self, _dir: &OsStr) {
@@ -76,7 +84,7 @@ impl Command {
     }
 
     pub fn get_envs(&self) -> CommandEnvs<'_> {
-        panic!("unsupported")
+        self.env.iter()
     }
 
     pub fn get_current_dir(&self) -> Option<&Path> {
@@ -140,8 +148,30 @@ impl Command {
             cmd.stderr_inherit()
         };
 
+        let env = env_changes(&self.env);
+
+        // Set any new vars
+        if let Some(e) = &env {
+            for (k, (_, v)) in e {
+                match v {
+                    Some(v) => crate::env::set_var(k, v),
+                    None => crate::env::remove_var(k),
+                }
+            }
+        }
+
         let stat = cmd.start_image()?;
 
+        // Rollback any env changes
+        if let Some(e) = env {
+            for (k, (v, _)) in e {
+                match v {
+                    Some(v) => crate::env::set_var(k, v),
+                    None => crate::env::remove_var(k),
+                }
+            }
+        }
+
         let stdout = cmd.stdout()?;
         let stderr = cmd.stderr()?;
 
@@ -460,7 +490,7 @@ mod uefi_command_internal {
                 helpers::open_protocol(self.handle, loaded_image::PROTOCOL_GUID).unwrap();
 
             let len = args.len();
-            let args_size: u32 = crate::mem::size_of_val(&args).try_into().unwrap();
+            let args_size: u32 = (len * crate::mem::size_of::<u16>()).try_into().unwrap();
             let ptr = Box::into_raw(args).as_mut_ptr();
 
             unsafe {
@@ -706,9 +736,10 @@ mod uefi_command_internal {
         res.push(QUOTE);
         res.extend(prog.encode_wide());
         res.push(QUOTE);
-        res.push(SPACE);
 
         for arg in args {
+            res.push(SPACE);
+
             // Wrap the argument in quotes to be treat as single arg
             res.push(QUOTE);
             for c in arg.encode_wide() {
@@ -719,10 +750,37 @@ mod uefi_command_internal {
                 res.push(c);
             }
             res.push(QUOTE);
-
-            res.push(SPACE);
         }
 
         res.into_boxed_slice()
     }
 }
+
+/// Create a map of environment variable changes. Allows efficient setting and rolling back of
+/// enviroment variable changes.
+///
+/// Entry: (Old Value, New Value)
+fn env_changes(env: &CommandEnv) -> Option<BTreeMap<EnvKey, (Option<OsString>, Option<OsString>)>> {
+    if env.is_unchanged() {
+        return None;
+    }
+
+    let mut result = BTreeMap::<EnvKey, (Option<OsString>, Option<OsString>)>::new();
+
+    // Check if we want to clear all prior variables
+    if env.does_clear() {
+        for (k, v) in crate::env::vars_os() {
+            result.insert(k.into(), (Some(v), None));
+        }
+    }
+
+    for (k, v) in env.iter() {
+        let v: Option<OsString> = v.map(Into::into);
+        result
+            .entry(k.into())
+            .and_modify(|cur| *cur = (cur.0.clone(), v.clone()))
+            .or_insert((crate::env::var_os(k), v));
+    }
+
+    Some(result)
+}
diff --git a/library/std/src/sys/pal/unix/fs.rs b/library/std/src/sys/pal/unix/fs.rs
index fdf011c1948..00cfa7a7fcf 100644
--- a/library/std/src/sys/pal/unix/fs.rs
+++ b/library/std/src/sys/pal/unix/fs.rs
@@ -9,9 +9,12 @@ use libc::c_char;
 #[cfg(any(
     all(target_os = "linux", not(target_env = "musl")),
     target_os = "android",
+    target_os = "fuchsia",
     target_os = "hurd"
 ))]
 use libc::dirfd;
+#[cfg(target_os = "fuchsia")]
+use libc::fstatat as fstatat64;
 #[cfg(any(all(target_os = "linux", not(target_env = "musl")), target_os = "hurd"))]
 use libc::fstatat64;
 #[cfg(any(
@@ -740,29 +743,27 @@ impl Iterator for ReadDir {
                 // to `byte_offset` and thus does not require the full extent of `*entry_ptr`
                 // to be in bounds of the same allocation, only the offset of the field
                 // being referenced.
-                macro_rules! entry_field_ptr {
-                    ($field:ident) => {
-                        &raw const (*entry_ptr).$field
-                    };
-                }
 
                 // d_name is guaranteed to be null-terminated.
-                let name = CStr::from_ptr(entry_field_ptr!(d_name).cast());
+                let name = CStr::from_ptr((&raw const (*entry_ptr).d_name).cast());
                 let name_bytes = name.to_bytes();
                 if name_bytes == b"." || name_bytes == b".." {
                     continue;
                 }
 
+                // When loading from a field, we can skip the `&raw const`; `(*entry_ptr).d_ino` as
+                // a value expression will do the right thing: `byte_offset` to the field and then
+                // only access those bytes.
                 #[cfg(not(target_os = "vita"))]
                 let entry = dirent64_min {
-                    d_ino: *entry_field_ptr!(d_ino) as u64,
+                    d_ino: (*entry_ptr).d_ino as u64,
                     #[cfg(not(any(
                         target_os = "solaris",
                         target_os = "illumos",
                         target_os = "aix",
                         target_os = "nto",
                     )))]
-                    d_type: *entry_field_ptr!(d_type) as u8,
+                    d_type: (*entry_ptr).d_type as u8,
                 };
 
                 #[cfg(target_os = "vita")]
@@ -850,7 +851,6 @@ impl Drop for Dir {
             target_os = "vita",
             target_os = "hurd",
             target_os = "espidf",
-            target_os = "fuchsia",
             target_os = "horizon",
             target_os = "vxworks",
             target_os = "rtems",
@@ -882,6 +882,7 @@ impl DirEntry {
         any(
             all(target_os = "linux", not(target_env = "musl")),
             target_os = "android",
+            target_os = "fuchsia",
             target_os = "hurd"
         ),
         not(miri) // no dirfd on Miri
@@ -910,6 +911,7 @@ impl DirEntry {
         not(any(
             all(target_os = "linux", not(target_env = "musl")),
             target_os = "android",
+            target_os = "fuchsia",
             target_os = "hurd",
         )),
         miri
@@ -1213,6 +1215,7 @@ impl File {
         }
         #[cfg(any(
             target_os = "freebsd",
+            target_os = "fuchsia",
             target_os = "linux",
             target_os = "android",
             target_os = "netbsd",
@@ -1225,6 +1228,7 @@ impl File {
         }
         #[cfg(not(any(
             target_os = "android",
+            target_os = "fuchsia",
             target_os = "freebsd",
             target_os = "linux",
             target_os = "netbsd",
@@ -1240,6 +1244,7 @@ impl File {
 
     #[cfg(any(
         target_os = "freebsd",
+        target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_vendor = "apple",
@@ -1251,6 +1256,7 @@ impl File {
 
     #[cfg(not(any(
         target_os = "freebsd",
+        target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_vendor = "apple",
@@ -1261,6 +1267,7 @@ impl File {
 
     #[cfg(any(
         target_os = "freebsd",
+        target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_vendor = "apple",
@@ -1272,6 +1279,7 @@ impl File {
 
     #[cfg(not(any(
         target_os = "freebsd",
+        target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_vendor = "apple",
@@ -1282,6 +1290,7 @@ impl File {
 
     #[cfg(any(
         target_os = "freebsd",
+        target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_vendor = "apple",
@@ -1299,6 +1308,7 @@ impl File {
 
     #[cfg(not(any(
         target_os = "freebsd",
+        target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_vendor = "apple",
@@ -1309,6 +1319,7 @@ impl File {
 
     #[cfg(any(
         target_os = "freebsd",
+        target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_vendor = "apple",
@@ -1326,6 +1337,7 @@ impl File {
 
     #[cfg(not(any(
         target_os = "freebsd",
+        target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_vendor = "apple",
@@ -1336,6 +1348,7 @@ impl File {
 
     #[cfg(any(
         target_os = "freebsd",
+        target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_vendor = "apple",
@@ -1347,6 +1360,7 @@ impl File {
 
     #[cfg(not(any(
         target_os = "freebsd",
+        target_os = "fuchsia",
         target_os = "linux",
         target_os = "netbsd",
         target_vendor = "apple",
diff --git a/library/std/src/sys/pal/unix/io.rs b/library/std/src/sys/pal/unix/io.rs
deleted file mode 100644
index 0d5a152dc0d..00000000000
--- a/library/std/src/sys/pal/unix/io.rs
+++ /dev/null
@@ -1,87 +0,0 @@
-use libc::{c_void, iovec};
-
-use crate::marker::PhantomData;
-use crate::os::fd::{AsFd, AsRawFd};
-use crate::slice;
-
-#[derive(Copy, Clone)]
-#[repr(transparent)]
-pub struct IoSlice<'a> {
-    vec: iovec,
-    _p: PhantomData<&'a [u8]>,
-}
-
-impl<'a> IoSlice<'a> {
-    #[inline]
-    pub fn new(buf: &'a [u8]) -> IoSlice<'a> {
-        IoSlice {
-            vec: iovec { iov_base: buf.as_ptr() as *mut u8 as *mut c_void, iov_len: buf.len() },
-            _p: PhantomData,
-        }
-    }
-
-    #[inline]
-    pub fn advance(&mut self, n: usize) {
-        if self.vec.iov_len < n {
-            panic!("advancing IoSlice beyond its length");
-        }
-
-        unsafe {
-            self.vec.iov_len -= n;
-            self.vec.iov_base = self.vec.iov_base.add(n);
-        }
-    }
-
-    #[inline]
-    pub const fn as_slice(&self) -> &'a [u8] {
-        unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
-    }
-}
-
-#[repr(transparent)]
-pub struct IoSliceMut<'a> {
-    vec: iovec,
-    _p: PhantomData<&'a mut [u8]>,
-}
-
-impl<'a> IoSliceMut<'a> {
-    #[inline]
-    pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> {
-        IoSliceMut {
-            vec: iovec { iov_base: buf.as_mut_ptr() as *mut c_void, iov_len: buf.len() },
-            _p: PhantomData,
-        }
-    }
-
-    #[inline]
-    pub fn advance(&mut self, n: usize) {
-        if self.vec.iov_len < n {
-            panic!("advancing IoSliceMut beyond its length");
-        }
-
-        unsafe {
-            self.vec.iov_len -= n;
-            self.vec.iov_base = self.vec.iov_base.add(n);
-        }
-    }
-
-    #[inline]
-    pub fn as_slice(&self) -> &[u8] {
-        unsafe { slice::from_raw_parts(self.vec.iov_base as *mut u8, self.vec.iov_len) }
-    }
-
-    #[inline]
-    pub const fn into_slice(self) -> &'a mut [u8] {
-        unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }
-    }
-
-    #[inline]
-    pub fn as_mut_slice(&mut self) -> &mut [u8] {
-        unsafe { slice::from_raw_parts_mut(self.vec.iov_base as *mut u8, self.vec.iov_len) }
-    }
-}
-
-pub fn is_terminal(fd: &impl AsFd) -> bool {
-    let fd = fd.as_fd();
-    unsafe { libc::isatty(fd.as_raw_fd()) != 0 }
-}
diff --git a/library/std/src/sys/pal/unix/kernel_copy/tests.rs b/library/std/src/sys/pal/unix/kernel_copy/tests.rs
index 1350d743ff6..54d8f8ed2ed 100644
--- a/library/std/src/sys/pal/unix/kernel_copy/tests.rs
+++ b/library/std/src/sys/pal/unix/kernel_copy/tests.rs
@@ -2,7 +2,7 @@ use crate::fs::OpenOptions;
 use crate::io;
 use crate::io::{BufRead, Read, Result, Seek, SeekFrom, Write};
 use crate::os::unix::io::AsRawFd;
-use crate::sys_common::io::test::tmpdir;
+use crate::test_helpers::tmpdir;
 
 #[test]
 fn copy_specialization() -> Result<()> {
diff --git a/library/std/src/sys/pal/unix/l4re.rs b/library/std/src/sys/pal/unix/l4re.rs
deleted file mode 100644
index 37dd370c514..00000000000
--- a/library/std/src/sys/pal/unix/l4re.rs
+++ /dev/null
@@ -1,564 +0,0 @@
-macro_rules! unimpl {
-    () => {
-        return Err(io::const_error!(
-            io::ErrorKind::Unsupported,
-            "No networking available on L4Re.",
-        ));
-    };
-}
-
-pub mod net {
-    #![allow(warnings)]
-    use crate::fmt;
-    use crate::io::{self, BorrowedCursor, IoSlice, IoSliceMut};
-    use crate::net::{Ipv4Addr, Ipv6Addr, Shutdown, SocketAddr};
-    use crate::os::unix::io::{AsFd, AsRawFd, BorrowedFd, FromRawFd, IntoRawFd, RawFd};
-    use crate::sys::fd::FileDesc;
-    use crate::sys_common::{AsInner, FromInner, IntoInner};
-    use crate::time::Duration;
-
-    #[allow(unused_extern_crates)]
-    pub extern crate libc as netc;
-
-    pub struct Socket(FileDesc);
-    impl Socket {
-        pub fn new(_: &SocketAddr, _: libc::c_int) -> io::Result<Socket> {
-            unimpl!();
-        }
-
-        pub fn new_raw(_: libc::c_int, _: libc::c_int) -> io::Result<Socket> {
-            unimpl!();
-        }
-
-        pub fn new_pair(_: libc::c_int, _: libc::c_int) -> io::Result<(Socket, Socket)> {
-            unimpl!();
-        }
-
-        pub fn connect_timeout(&self, _: &SocketAddr, _: Duration) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn accept(
-            &self,
-            _: *mut libc::sockaddr,
-            _: *mut libc::socklen_t,
-        ) -> io::Result<Socket> {
-            unimpl!();
-        }
-
-        pub fn duplicate(&self) -> io::Result<Socket> {
-            unimpl!();
-        }
-
-        pub fn read(&self, _: &mut [u8]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn read_buf(&self, _: BorrowedCursor<'_>) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn read_vectored(&self, _: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn is_read_vectored(&self) -> bool {
-            false
-        }
-
-        pub fn peek(&self, _: &mut [u8]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn recv_from(&self, _: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
-            unimpl!();
-        }
-
-        pub fn peek_from(&self, _: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
-            unimpl!();
-        }
-
-        pub fn write(&self, _: &[u8]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn write_vectored(&self, _: &[IoSlice<'_>]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn is_write_vectored(&self) -> bool {
-            false
-        }
-
-        pub fn set_timeout(&self, _: Option<Duration>, _: libc::c_int) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn timeout(&self, _: libc::c_int) -> io::Result<Option<Duration>> {
-            unimpl!();
-        }
-
-        pub fn shutdown(&self, _: Shutdown) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn set_linger(&self, _: Option<Duration>) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn linger(&self) -> io::Result<Option<Duration>> {
-            unimpl!();
-        }
-
-        pub fn set_nodelay(&self, _: bool) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn nodelay(&self) -> io::Result<bool> {
-            unimpl!();
-        }
-
-        pub fn set_nonblocking(&self, _: bool) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn take_error(&self) -> io::Result<Option<io::Error>> {
-            unimpl!();
-        }
-
-        // This is used by sys_common code to abstract over Windows and Unix.
-        pub fn as_raw(&self) -> RawFd {
-            self.as_raw_fd()
-        }
-    }
-
-    impl AsInner<FileDesc> for Socket {
-        #[inline]
-        fn as_inner(&self) -> &FileDesc {
-            &self.0
-        }
-    }
-
-    impl FromInner<FileDesc> for Socket {
-        fn from_inner(file_desc: FileDesc) -> Socket {
-            Socket(file_desc)
-        }
-    }
-
-    impl IntoInner<FileDesc> for Socket {
-        fn into_inner(self) -> FileDesc {
-            self.0
-        }
-    }
-
-    impl AsFd for Socket {
-        fn as_fd(&self) -> BorrowedFd<'_> {
-            self.0.as_fd()
-        }
-    }
-
-    impl AsRawFd for Socket {
-        #[inline]
-        fn as_raw_fd(&self) -> RawFd {
-            self.0.as_raw_fd()
-        }
-    }
-
-    impl IntoRawFd for Socket {
-        fn into_raw_fd(self) -> RawFd {
-            self.0.into_raw_fd()
-        }
-    }
-
-    impl FromRawFd for Socket {
-        unsafe fn from_raw_fd(raw_fd: RawFd) -> Self {
-            Self(FromRawFd::from_raw_fd(raw_fd))
-        }
-    }
-
-    pub struct TcpStream {
-        inner: Socket,
-    }
-
-    impl TcpStream {
-        pub fn connect(_: io::Result<&SocketAddr>) -> io::Result<TcpStream> {
-            unimpl!();
-        }
-
-        pub fn connect_timeout(_: &SocketAddr, _: Duration) -> io::Result<TcpStream> {
-            unimpl!();
-        }
-
-        #[inline]
-        pub fn socket(&self) -> &Socket {
-            &self.inner
-        }
-
-        pub fn into_socket(self) -> Socket {
-            self.inner
-        }
-
-        pub fn set_read_timeout(&self, _: Option<Duration>) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn set_write_timeout(&self, _: Option<Duration>) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn read_timeout(&self) -> io::Result<Option<Duration>> {
-            unimpl!();
-        }
-
-        pub fn write_timeout(&self) -> io::Result<Option<Duration>> {
-            unimpl!();
-        }
-
-        pub fn peek(&self, _: &mut [u8]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn read(&self, _: &mut [u8]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn read_buf(&self, _: BorrowedCursor<'_>) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn read_vectored(&self, _: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn is_read_vectored(&self) -> bool {
-            false
-        }
-
-        pub fn write(&self, _: &[u8]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn write_vectored(&self, _: &[IoSlice<'_>]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn is_write_vectored(&self) -> bool {
-            false
-        }
-
-        pub fn peer_addr(&self) -> io::Result<SocketAddr> {
-            unimpl!();
-        }
-
-        pub fn socket_addr(&self) -> io::Result<SocketAddr> {
-            unimpl!();
-        }
-
-        pub fn shutdown(&self, _: Shutdown) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn duplicate(&self) -> io::Result<TcpStream> {
-            unimpl!();
-        }
-
-        pub fn set_linger(&self, _: Option<Duration>) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn linger(&self) -> io::Result<Option<Duration>> {
-            unimpl!();
-        }
-
-        pub fn set_nodelay(&self, _: bool) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn nodelay(&self) -> io::Result<bool> {
-            unimpl!();
-        }
-
-        pub fn set_ttl(&self, _: u32) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn ttl(&self) -> io::Result<u32> {
-            unimpl!();
-        }
-
-        pub fn take_error(&self) -> io::Result<Option<io::Error>> {
-            unimpl!();
-        }
-
-        pub fn set_nonblocking(&self, _: bool) -> io::Result<()> {
-            unimpl!();
-        }
-    }
-
-    impl FromInner<Socket> for TcpStream {
-        fn from_inner(socket: Socket) -> TcpStream {
-            TcpStream { inner: socket }
-        }
-    }
-
-    impl fmt::Debug for TcpStream {
-        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-            write!(f, "No networking support available on L4Re")
-        }
-    }
-
-    pub struct TcpListener {
-        inner: Socket,
-    }
-
-    impl TcpListener {
-        pub fn bind(_: io::Result<&SocketAddr>) -> io::Result<TcpListener> {
-            unimpl!();
-        }
-
-        #[inline]
-        pub fn socket(&self) -> &Socket {
-            &self.inner
-        }
-
-        pub fn into_socket(self) -> Socket {
-            self.inner
-        }
-
-        pub fn socket_addr(&self) -> io::Result<SocketAddr> {
-            unimpl!();
-        }
-
-        pub fn accept(&self) -> io::Result<(TcpStream, SocketAddr)> {
-            unimpl!();
-        }
-
-        pub fn duplicate(&self) -> io::Result<TcpListener> {
-            unimpl!();
-        }
-
-        pub fn set_ttl(&self, _: u32) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn ttl(&self) -> io::Result<u32> {
-            unimpl!();
-        }
-
-        pub fn set_only_v6(&self, _: bool) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn only_v6(&self) -> io::Result<bool> {
-            unimpl!();
-        }
-
-        pub fn take_error(&self) -> io::Result<Option<io::Error>> {
-            unimpl!();
-        }
-
-        pub fn set_nonblocking(&self, _: bool) -> io::Result<()> {
-            unimpl!();
-        }
-    }
-
-    impl FromInner<Socket> for TcpListener {
-        fn from_inner(socket: Socket) -> TcpListener {
-            TcpListener { inner: socket }
-        }
-    }
-
-    impl fmt::Debug for TcpListener {
-        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-            write!(f, "No networking support available on L4Re.")
-        }
-    }
-
-    pub struct UdpSocket {
-        inner: Socket,
-    }
-
-    impl UdpSocket {
-        pub fn bind(_: io::Result<&SocketAddr>) -> io::Result<UdpSocket> {
-            unimpl!();
-        }
-
-        #[inline]
-        pub fn socket(&self) -> &Socket {
-            &self.inner
-        }
-
-        pub fn into_socket(self) -> Socket {
-            self.inner
-        }
-
-        pub fn peer_addr(&self) -> io::Result<SocketAddr> {
-            unimpl!();
-        }
-
-        pub fn socket_addr(&self) -> io::Result<SocketAddr> {
-            unimpl!();
-        }
-
-        pub fn recv_from(&self, _: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
-            unimpl!();
-        }
-
-        pub fn peek_from(&self, _: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
-            unimpl!();
-        }
-
-        pub fn send_to(&self, _: &[u8], _: &SocketAddr) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn duplicate(&self) -> io::Result<UdpSocket> {
-            unimpl!();
-        }
-
-        pub fn set_read_timeout(&self, _: Option<Duration>) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn set_write_timeout(&self, _: Option<Duration>) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn read_timeout(&self) -> io::Result<Option<Duration>> {
-            unimpl!();
-        }
-
-        pub fn write_timeout(&self) -> io::Result<Option<Duration>> {
-            unimpl!();
-        }
-
-        pub fn set_broadcast(&self, _: bool) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn broadcast(&self) -> io::Result<bool> {
-            unimpl!();
-        }
-
-        pub fn set_multicast_loop_v4(&self, _: bool) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn multicast_loop_v4(&self) -> io::Result<bool> {
-            unimpl!();
-        }
-
-        pub fn set_multicast_ttl_v4(&self, _: u32) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn multicast_ttl_v4(&self) -> io::Result<u32> {
-            unimpl!();
-        }
-
-        pub fn set_multicast_loop_v6(&self, _: bool) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn multicast_loop_v6(&self) -> io::Result<bool> {
-            unimpl!();
-        }
-
-        pub fn join_multicast_v4(&self, _: &Ipv4Addr, _: &Ipv4Addr) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn join_multicast_v6(&self, _: &Ipv6Addr, _: u32) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn leave_multicast_v4(&self, _: &Ipv4Addr, _: &Ipv4Addr) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn leave_multicast_v6(&self, _: &Ipv6Addr, _: u32) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn set_ttl(&self, _: u32) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn ttl(&self) -> io::Result<u32> {
-            unimpl!();
-        }
-
-        pub fn take_error(&self) -> io::Result<Option<io::Error>> {
-            unimpl!();
-        }
-
-        pub fn set_nonblocking(&self, _: bool) -> io::Result<()> {
-            unimpl!();
-        }
-
-        pub fn recv(&self, _: &mut [u8]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn peek(&self, _: &mut [u8]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn send(&self, _: &[u8]) -> io::Result<usize> {
-            unimpl!();
-        }
-
-        pub fn connect(&self, _: io::Result<&SocketAddr>) -> io::Result<()> {
-            unimpl!();
-        }
-    }
-
-    impl FromInner<Socket> for UdpSocket {
-        fn from_inner(socket: Socket) -> UdpSocket {
-            UdpSocket { inner: socket }
-        }
-    }
-
-    impl fmt::Debug for UdpSocket {
-        fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-            write!(f, "No networking support on L4Re available.")
-        }
-    }
-
-    pub struct LookupHost {
-        original: *mut libc::addrinfo,
-        cur: *mut libc::addrinfo,
-    }
-
-    impl Iterator for LookupHost {
-        type Item = SocketAddr;
-        fn next(&mut self) -> Option<SocketAddr> {
-            None
-        }
-    }
-
-    impl LookupHost {
-        pub fn port(&self) -> u16 {
-            0 // unimplemented
-        }
-    }
-
-    unsafe impl Sync for LookupHost {}
-    unsafe impl Send for LookupHost {}
-
-    impl TryFrom<&str> for LookupHost {
-        type Error = io::Error;
-
-        fn try_from(_v: &str) -> io::Result<LookupHost> {
-            unimpl!();
-        }
-    }
-
-    impl<'a> TryFrom<(&'a str, u16)> for LookupHost {
-        type Error = io::Error;
-
-        fn try_from(_v: (&'a str, u16)) -> io::Result<LookupHost> {
-            unimpl!();
-        }
-    }
-}
diff --git a/library/std/src/sys/pal/unix/mod.rs b/library/std/src/sys/pal/unix/mod.rs
index 3cc1cae8d00..027df6c5691 100644
--- a/library/std/src/sys/pal/unix/mod.rs
+++ b/library/std/src/sys/pal/unix/mod.rs
@@ -11,17 +11,10 @@ pub mod env;
 pub mod fd;
 pub mod fs;
 pub mod futex;
-pub mod io;
 #[cfg(any(target_os = "linux", target_os = "android"))]
 pub mod kernel_copy;
-#[cfg(target_os = "l4re")]
-mod l4re;
 #[cfg(target_os = "linux")]
 pub mod linux;
-#[cfg(not(target_os = "l4re"))]
-pub mod net;
-#[cfg(target_os = "l4re")]
-pub use self::l4re::net;
 pub mod os;
 pub mod pipe;
 pub mod process;
diff --git a/library/std/src/sys/pal/unix/process/process_unix.rs b/library/std/src/sys/pal/unix/process/process_unix.rs
index ec4965c1d71..2bff192a5bd 100644
--- a/library/std/src/sys/pal/unix/process/process_unix.rs
+++ b/library/std/src/sys/pal/unix/process/process_unix.rs
@@ -19,8 +19,7 @@ use crate::sys::process::process_common::*;
 use crate::{fmt, mem, sys};
 
 cfg_if::cfg_if! {
-    // This workaround is only needed for QNX 7.0 and 7.1. The bug should have been fixed in 8.0
-    if #[cfg(any(target_env = "nto70", target_env = "nto71"))] {
+    if #[cfg(target_os = "nto")] {
         use crate::thread;
         use libc::{c_char, posix_spawn_file_actions_t, posix_spawnattr_t};
         use crate::time::Duration;
@@ -187,12 +186,7 @@ impl Command {
 
     // Attempts to fork the process. If successful, returns Ok((0, -1))
     // in the child, and Ok((child_pid, -1)) in the parent.
-    #[cfg(not(any(
-        target_os = "watchos",
-        target_os = "tvos",
-        target_env = "nto70",
-        target_env = "nto71"
-    )))]
+    #[cfg(not(any(target_os = "watchos", target_os = "tvos", target_os = "nto")))]
     unsafe fn do_fork(&mut self) -> Result<pid_t, io::Error> {
         cvt(libc::fork())
     }
@@ -201,8 +195,7 @@ impl Command {
     // or closed a file descriptor while the fork() was occurring".
     // Documentation says "... or try calling fork() again". This is what we do here.
     // See also https://www.qnx.com/developers/docs/7.1/#com.qnx.doc.neutrino.lib_ref/topic/f/fork.html
-    // This workaround is only needed for QNX 7.0 and 7.1. The bug should have been fixed in 8.0
-    #[cfg(any(target_env = "nto70", target_env = "nto71"))]
+    #[cfg(target_os = "nto")]
     unsafe fn do_fork(&mut self) -> Result<pid_t, io::Error> {
         use crate::sys::os::errno;
 
diff --git a/library/std/src/sys/pal/unix/stdio.rs b/library/std/src/sys/pal/unix/stdio.rs
index 97e75f1b5b6..8c2f61a40de 100644
--- a/library/std/src/sys/pal/unix/stdio.rs
+++ b/library/std/src/sys/pal/unix/stdio.rs
@@ -92,7 +92,7 @@ pub fn is_ebadf(err: &io::Error) -> bool {
     err.raw_os_error() == Some(libc::EBADF as i32)
 }
 
-pub const STDIN_BUF_SIZE: usize = crate::sys_common::io::DEFAULT_BUF_SIZE;
+pub const STDIN_BUF_SIZE: usize = crate::sys::io::DEFAULT_BUF_SIZE;
 
 pub fn panic_output() -> Option<impl io::Write> {
     Some(Stderr::new())
diff --git a/library/std/src/sys/pal/unix/thread.rs b/library/std/src/sys/pal/unix/thread.rs
index f657f82e6e3..356669980c7 100644
--- a/library/std/src/sys/pal/unix/thread.rs
+++ b/library/std/src/sys/pal/unix/thread.rs
@@ -130,7 +130,12 @@ impl Thread {
         }
     }
 
-    #[cfg(any(target_os = "linux", target_os = "freebsd", target_os = "dragonfly"))]
+    #[cfg(any(
+        target_os = "linux",
+        target_os = "freebsd",
+        target_os = "dragonfly",
+        target_os = "nuttx"
+    ))]
     pub fn set_name(name: &CStr) {
         unsafe {
             cfg_if::cfg_if! {
@@ -139,7 +144,7 @@ impl Thread {
                     const TASK_COMM_LEN: usize = 16;
                     let name = truncate_cstr::<{ TASK_COMM_LEN }>(name);
                 } else {
-                    // FreeBSD and DragonFly BSD do not enforce length limits.
+                    // FreeBSD, DragonFly, FreeBSD and NuttX do not enforce length limits.
                 }
             };
             // Available since glibc 2.12, musl 1.1.16, and uClibc 1.0.20 for Linux,
@@ -150,7 +155,7 @@ impl Thread {
         }
     }
 
-    #[cfg(any(target_os = "openbsd", target_os = "nuttx"))]
+    #[cfg(target_os = "openbsd")]
     pub fn set_name(name: &CStr) {
         unsafe {
             libc::pthread_set_name_np(libc::pthread_self(), name.as_ptr());
diff --git a/library/std/src/sys/pal/unsupported/mod.rs b/library/std/src/sys/pal/unsupported/mod.rs
index 01d516f7568..b1aaeb1b4c8 100644
--- a/library/std/src/sys/pal/unsupported/mod.rs
+++ b/library/std/src/sys/pal/unsupported/mod.rs
@@ -3,8 +3,6 @@
 pub mod args;
 pub mod env;
 pub mod fs;
-pub mod io;
-pub mod net;
 pub mod os;
 pub mod pipe;
 pub mod process;
diff --git a/library/std/src/sys/pal/wasi/mod.rs b/library/std/src/sys/pal/wasi/mod.rs
index 5d54c790306..f4588a60ea9 100644
--- a/library/std/src/sys/pal/wasi/mod.rs
+++ b/library/std/src/sys/pal/wasi/mod.rs
@@ -1,8 +1,7 @@
 //! System bindings for the wasm/web platform
 //!
 //! This module contains the facade (aka platform-specific) implementations of
-//! OS level functionality for wasm. Note that this wasm is *not* the emscripten
-//! wasm, so we have no runtime here.
+//! OS level functionality for wasm.
 //!
 //! This is all super highly experimental and not actually intended for
 //! wide/production use yet, it's still all in the experimental category. This
@@ -21,9 +20,7 @@ pub mod fs;
 #[allow(unused)]
 #[path = "../wasm/atomics/futex.rs"]
 pub mod futex;
-pub mod io;
 
-pub mod net;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
@@ -46,5 +43,4 @@ mod helpers;
 // import conflict rules. If we glob export `helpers` and `common` together,
 // then the compiler complains about conflicts.
 
-use helpers::err2io;
-pub use helpers::{abort_internal, decode_error_kind, is_interrupted};
+pub(crate) use helpers::{abort_internal, decode_error_kind, err2io, is_interrupted};
diff --git a/library/std/src/sys/pal/wasi/stdio.rs b/library/std/src/sys/pal/wasi/stdio.rs
index ca49f871e19..d08b772e5fc 100644
--- a/library/std/src/sys/pal/wasi/stdio.rs
+++ b/library/std/src/sys/pal/wasi/stdio.rs
@@ -101,7 +101,7 @@ impl io::Write for Stderr {
     }
 }
 
-pub const STDIN_BUF_SIZE: usize = crate::sys_common::io::DEFAULT_BUF_SIZE;
+pub const STDIN_BUF_SIZE: usize = crate::sys::io::DEFAULT_BUF_SIZE;
 
 pub fn is_ebadf(err: &io::Error) -> bool {
     err.raw_os_error() == Some(wasi::ERRNO_BADF.raw().into())
diff --git a/library/std/src/sys/pal/wasip2/mod.rs b/library/std/src/sys/pal/wasip2/mod.rs
index 320712fdcc9..72c9742b2e5 100644
--- a/library/std/src/sys/pal/wasip2/mod.rs
+++ b/library/std/src/sys/pal/wasip2/mod.rs
@@ -17,10 +17,7 @@ pub mod fs;
 #[allow(unused)]
 #[path = "../wasm/atomics/futex.rs"]
 pub mod futex;
-#[path = "../wasi/io.rs"]
-pub mod io;
 
-pub mod net;
 #[path = "../wasi/os.rs"]
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
diff --git a/library/std/src/sys/pal/wasm/mod.rs b/library/std/src/sys/pal/wasm/mod.rs
index 8141bfac49a..32d59c4d0f7 100644
--- a/library/std/src/sys/pal/wasm/mod.rs
+++ b/library/std/src/sys/pal/wasm/mod.rs
@@ -2,7 +2,7 @@
 //!
 //! This module contains the facade (aka platform-specific) implementations of
 //! OS level functionality for wasm. Note that this wasm is *not* the emscripten
-//! wasm, so we have no runtime here.
+//! or wasi wasm, so we have no runtime here.
 //!
 //! This is all super highly experimental and not actually intended for
 //! wide/production use yet, it's still all in the experimental category. This
@@ -21,10 +21,6 @@ pub mod args;
 pub mod env;
 #[path = "../unsupported/fs.rs"]
 pub mod fs;
-#[path = "../unsupported/io.rs"]
-pub mod io;
-#[path = "../unsupported/net.rs"]
-pub mod net;
 #[path = "../unsupported/os.rs"]
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
diff --git a/library/std/src/sys/pal/windows/args/tests.rs b/library/std/src/sys/pal/windows/args/tests.rs
index 6d5c953cbd5..484a90ab056 100644
--- a/library/std/src/sys/pal/windows/args/tests.rs
+++ b/library/std/src/sys/pal/windows/args/tests.rs
@@ -47,10 +47,10 @@ fn whitespace_behavior() {
 fn genius_quotes() {
     chk(r#"EXE "" """#, &["EXE", "", ""]);
     chk(r#"EXE "" """"#, &["EXE", "", r#"""#]);
-    chk(r#"EXE "this is """all""" in the same argument""#, &[
-        "EXE",
-        r#"this is "all" in the same argument"#,
-    ]);
+    chk(
+        r#"EXE "this is """all""" in the same argument""#,
+        &["EXE", r#"this is "all" in the same argument"#],
+    );
     chk(r#"EXE "a"""#, &["EXE", r#"a""#]);
     chk(r#"EXE "a"" a"#, &["EXE", r#"a" a"#]);
     // quotes cannot be escaped in command names
diff --git a/library/std/src/sys/pal/windows/fs.rs b/library/std/src/sys/pal/windows/fs.rs
index b3659351b8c..bdb55643bb1 100644
--- a/library/std/src/sys/pal/windows/fs.rs
+++ b/library/std/src/sys/pal/windows/fs.rs
@@ -296,6 +296,10 @@ impl OpenOptions {
 impl File {
     pub fn open(path: &Path, opts: &OpenOptions) -> io::Result<File> {
         let path = maybe_verbatim(path)?;
+        Self::open_native(&path, opts)
+    }
+
+    fn open_native(path: &[u16], opts: &OpenOptions) -> io::Result<File> {
         let creation = opts.get_creation_mode()?;
         let handle = unsafe {
             c::CreateFileW(
@@ -328,9 +332,6 @@ impl File {
                         mem::size_of::<c::FILE_ALLOCATION_INFO>() as u32,
                     );
                     if result == 0 {
-                        if api::get_last_error().code != 0 {
-                            panic!("FILE_ALLOCATION_INFO failed!!!");
-                        }
                         let eof = c::FILE_END_OF_FILE_INFO { EndOfFile: 0 };
                         let result = c::SetFileInformationByHandle(
                             handle.as_raw_handle(),
@@ -1229,8 +1230,26 @@ pub fn readdir(p: &Path) -> io::Result<ReadDir> {
 
 pub fn unlink(p: &Path) -> io::Result<()> {
     let p_u16s = maybe_verbatim(p)?;
-    cvt(unsafe { c::DeleteFileW(p_u16s.as_ptr()) })?;
-    Ok(())
+    if unsafe { c::DeleteFileW(p_u16s.as_ptr()) } == 0 {
+        let err = api::get_last_error();
+        // if `DeleteFileW` fails with ERROR_ACCESS_DENIED then try to remove
+        // the file while ignoring the readonly attribute.
+        // This is accomplished by calling the `posix_delete` function on an open file handle.
+        if err == WinError::ACCESS_DENIED {
+            let mut opts = OpenOptions::new();
+            opts.access_mode(c::DELETE);
+            opts.custom_flags(c::FILE_FLAG_OPEN_REPARSE_POINT);
+            if let Ok(f) = File::open_native(&p_u16s, &opts) {
+                if f.posix_delete().is_ok() {
+                    return Ok(());
+                }
+            }
+        }
+        // return the original error if any of the above fails.
+        Err(io::Error::from_raw_os_error(err.code as i32))
+    } else {
+        Ok(())
+    }
 }
 
 pub fn rename(old: &Path, new: &Path) -> io::Result<()> {
diff --git a/library/std/src/sys/pal/windows/mod.rs b/library/std/src/sys/pal/windows/mod.rs
index 4282dbb5493..1eca346b76c 100644
--- a/library/std/src/sys/pal/windows/mod.rs
+++ b/library/std/src/sys/pal/windows/mod.rs
@@ -21,8 +21,6 @@ pub mod fs;
 #[cfg(not(target_vendor = "win7"))]
 pub mod futex;
 pub mod handle;
-pub mod io;
-pub mod net;
 pub mod os;
 pub mod pipe;
 pub mod process;
@@ -63,7 +61,7 @@ pub unsafe fn init(_argc: isize, _argv: *const *const u8, _sigpipe: u8) {
 // SAFETY: must be called only once during runtime cleanup.
 // NOTE: this is not guaranteed to run, for example when the program aborts.
 pub unsafe fn cleanup() {
-    net::cleanup();
+    crate::sys::net::cleanup();
 }
 
 #[inline]
diff --git a/library/std/src/sys/pal/windows/process/tests.rs b/library/std/src/sys/pal/windows/process/tests.rs
index 1bcc5fa6b20..9a1eaf42fd9 100644
--- a/library/std/src/sys/pal/windows/process/tests.rs
+++ b/library/std/src/sys/pal/windows/process/tests.rs
@@ -158,7 +158,7 @@ fn windows_exe_resolver() {
     use super::resolve_exe;
     use crate::io;
     use crate::sys::fs::symlink;
-    use crate::sys_common::io::test::tmpdir;
+    use crate::test_helpers::tmpdir;
 
     let env_paths = || env::var_os("PATH");
 
diff --git a/library/std/src/sys/pal/xous/mod.rs b/library/std/src/sys/pal/xous/mod.rs
index a64cd068560..1bd0e67f371 100644
--- a/library/std/src/sys/pal/xous/mod.rs
+++ b/library/std/src/sys/pal/xous/mod.rs
@@ -5,9 +5,6 @@ pub mod args;
 pub mod env;
 #[path = "../unsupported/fs.rs"]
 pub mod fs;
-#[path = "../unsupported/io.rs"]
-pub mod io;
-pub mod net;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
diff --git a/library/std/src/sys/pal/zkvm/mod.rs b/library/std/src/sys/pal/zkvm/mod.rs
index 6ea05772029..054c867f90d 100644
--- a/library/std/src/sys/pal/zkvm/mod.rs
+++ b/library/std/src/sys/pal/zkvm/mod.rs
@@ -16,10 +16,6 @@ pub mod args;
 pub mod env;
 #[path = "../unsupported/fs.rs"]
 pub mod fs;
-#[path = "../unsupported/io.rs"]
-pub mod io;
-#[path = "../unsupported/net.rs"]
-pub mod net;
 pub mod os;
 #[path = "../unsupported/pipe.rs"]
 pub mod pipe;
diff --git a/library/std/src/sys/pal/zkvm/stdio.rs b/library/std/src/sys/pal/zkvm/stdio.rs
index dd218c8894c..5f1d06dd1d7 100644
--- a/library/std/src/sys/pal/zkvm/stdio.rs
+++ b/library/std/src/sys/pal/zkvm/stdio.rs
@@ -54,7 +54,7 @@ impl io::Write for Stderr {
     }
 }
 
-pub const STDIN_BUF_SIZE: usize = crate::sys_common::io::DEFAULT_BUF_SIZE;
+pub const STDIN_BUF_SIZE: usize = crate::sys::io::DEFAULT_BUF_SIZE;
 
 pub fn is_ebadf(_err: &io::Error) -> bool {
     true
diff --git a/library/std/src/sys/path/mod.rs b/library/std/src/sys/path/mod.rs
index 24a94ec7828..1fa4e80d678 100644
--- a/library/std/src/sys/path/mod.rs
+++ b/library/std/src/sys/path/mod.rs
@@ -5,12 +5,12 @@ cfg_if::cfg_if! {
     } else if #[cfg(all(target_vendor = "fortanix", target_env = "sgx"))] {
         mod sgx;
         pub use sgx::*;
-    } else if #[cfg(any(
-        target_os = "uefi",
-        target_os = "solid_asp3",
-    ))] {
+    } else if #[cfg(target_os = "solid_asp3")] {
         mod unsupported_backslash;
         pub use unsupported_backslash::*;
+    } else if #[cfg(target_os = "uefi")] {
+        mod uefi;
+        pub use uefi::*;
     } else {
         mod unix;
         pub use unix::*;
diff --git a/library/std/src/sys/path/uefi.rs b/library/std/src/sys/path/uefi.rs
new file mode 100644
index 00000000000..a3f4a3bfe1b
--- /dev/null
+++ b/library/std/src/sys/path/uefi.rs
@@ -0,0 +1,105 @@
+#![forbid(unsafe_op_in_unsafe_fn)]
+use crate::ffi::OsStr;
+use crate::io;
+use crate::path::{Path, PathBuf, Prefix};
+use crate::sys::{helpers, unsupported_err};
+
+const FORWARD_SLASH: u8 = b'/';
+const COLON: u8 = b':';
+
+#[inline]
+pub fn is_sep_byte(b: u8) -> bool {
+    b == b'\\'
+}
+
+#[inline]
+pub fn is_verbatim_sep(b: u8) -> bool {
+    b == b'\\'
+}
+
+pub fn parse_prefix(_: &OsStr) -> Option<Prefix<'_>> {
+    None
+}
+
+pub const MAIN_SEP_STR: &str = "\\";
+pub const MAIN_SEP: char = '\\';
+
+/// UEFI paths can be of 4 types:
+///
+/// 1. Absolute Shell Path: Uses shell mappings (eg: `FS0:`). Does not exist if UEFI shell not present.
+///    It can be identified with `:`.
+///    Eg: FS0:\abc\run.efi
+///
+/// 2. Absolute Device Path: this is what we want
+///    It can be identified with `/`.
+///    Eg: PciRoot(0x0)/Pci(0x1,0x1)/Ata(Secondary,Slave,0x0)/\abc\run.efi
+///
+/// 3: Relative root: path relative to the current volume.
+///    It will start with `\`.
+///    Eg: \abc\run.efi
+///
+/// 4: Relative
+///    Eg: run.efi
+///
+/// The algorithm is mostly taken from edk2 UEFI shell implementation and is
+/// somewhat simple. Check for the path type in order.
+///
+/// The volume mapping in Absolute Shell Path (not the rest of the path) can be converted to Device
+/// Path Protocol using `EFI_SHELL->GetDevicePathFromMap`. The rest of the path (Relative root
+/// path), can just be appended to the remaining path.
+///
+/// For Relative root, we get the current volume (either in Shell Mapping, or Device Path Protocol
+/// form) and join it with the relative root path. We then recurse the function to resolve the Shell
+/// Mapping if present.
+///
+/// For Relative paths, we use the current working directory to construct
+/// the new path and recurse the function to resolve the Shell mapping if present.
+///
+/// Finally, at the end, we get the 2nd form, i.e. Absolute Device Path, which can be used in the
+/// normal UEFI APIs such as file, process, etc.
+/// Eg: PciRoot(0x0)/Pci(0x1,0x1)/Ata(Secondary,Slave,0x0)/\abc\run.efi
+pub(crate) fn absolute(path: &Path) -> io::Result<PathBuf> {
+    // Absolute Shell Path
+    if path.as_os_str().as_encoded_bytes().contains(&COLON) {
+        let mut path_components = path.components();
+        // Since path is not empty, it has at least one Component
+        let prefix = path_components.next().unwrap();
+
+        let dev_path = helpers::get_device_path_from_map(prefix.as_ref())?;
+        let mut dev_path_text = dev_path.to_text().map_err(|_| unsupported_err())?;
+
+        // UEFI Shell does not seem to end device path with `/`
+        if *dev_path_text.as_encoded_bytes().last().unwrap() != FORWARD_SLASH {
+            dev_path_text.push("/");
+        }
+
+        let mut ans = PathBuf::from(dev_path_text);
+        ans.push(path_components);
+
+        return Ok(ans);
+    }
+
+    // Absolute Device Path
+    if path.as_os_str().as_encoded_bytes().contains(&FORWARD_SLASH) {
+        return Ok(path.to_path_buf());
+    }
+
+    // cur_dir() always returns something
+    let cur_dir = crate::env::current_dir().unwrap();
+    let mut path_components = path.components();
+
+    // Relative Root
+    if path_components.next().unwrap() == crate::path::Component::RootDir {
+        let mut ans = PathBuf::new();
+        ans.push(cur_dir.components().next().unwrap());
+        ans.push(path_components);
+        return absolute(&ans);
+    }
+
+    absolute(&cur_dir.join(path))
+}
+
+pub(crate) fn is_absolute(path: &Path) -> bool {
+    let temp = path.as_os_str().as_encoded_bytes();
+    temp.contains(&COLON) || temp.contains(&FORWARD_SLASH)
+}
diff --git a/library/std/src/sys_common/io.rs b/library/std/src/sys_common/io.rs
deleted file mode 100644
index 6f6f282d432..00000000000
--- a/library/std/src/sys_common/io.rs
+++ /dev/null
@@ -1,49 +0,0 @@
-// Bare metal platforms usually have very small amounts of RAM
-// (in the order of hundreds of KB)
-pub const DEFAULT_BUF_SIZE: usize = if cfg!(target_os = "espidf") { 512 } else { 8 * 1024 };
-
-#[cfg(test)]
-#[allow(dead_code)] // not used on emscripten and wasi
-pub mod test {
-    use rand::RngCore;
-
-    use crate::path::{Path, PathBuf};
-    use crate::{env, fs, thread};
-
-    pub struct TempDir(PathBuf);
-
-    impl TempDir {
-        pub fn join(&self, path: &str) -> PathBuf {
-            let TempDir(ref p) = *self;
-            p.join(path)
-        }
-
-        pub fn path(&self) -> &Path {
-            let TempDir(ref p) = *self;
-            p
-        }
-    }
-
-    impl Drop for TempDir {
-        fn drop(&mut self) {
-            // Gee, seeing how we're testing the fs module I sure hope that we
-            // at least implement this correctly!
-            let TempDir(ref p) = *self;
-            let result = fs::remove_dir_all(p);
-            // Avoid panicking while panicking as this causes the process to
-            // immediately abort, without displaying test results.
-            if !thread::panicking() {
-                result.unwrap();
-            }
-        }
-    }
-
-    #[track_caller] // for `test_rng`
-    pub fn tmpdir() -> TempDir {
-        let p = env::temp_dir();
-        let mut r = crate::test_helpers::test_rng();
-        let ret = p.join(&format!("rust-{}", r.next_u32()));
-        fs::create_dir(&ret).unwrap();
-        TempDir(ret)
-    }
-}
diff --git a/library/std/src/sys_common/mod.rs b/library/std/src/sys_common/mod.rs
index 4f7a131f6bb..4dc67d26bd8 100644
--- a/library/std/src/sys_common/mod.rs
+++ b/library/std/src/sys_common/mod.rs
@@ -21,25 +21,10 @@
 mod tests;
 
 pub mod fs;
-pub mod io;
 pub mod process;
 pub mod wstr;
 pub mod wtf8;
 
-cfg_if::cfg_if! {
-    if #[cfg(any(
-        all(unix, not(target_os = "l4re")),
-        windows,
-        target_os = "hermit",
-        target_os = "solid_asp3",
-        all(target_os = "wasi", target_env = "p2")
-    ))] {
-        pub mod net;
-    } else {
-        pub use crate::sys::net;
-    }
-}
-
 // common error constructors
 
 /// A trait for viewing representations from std types
diff --git a/library/std/src/sys_common/wtf8/tests.rs b/library/std/src/sys_common/wtf8/tests.rs
index bc06eaa2b8f..b57c99a8452 100644
--- a/library/std/src/sys_common/wtf8/tests.rs
+++ b/library/std/src/sys_common/wtf8/tests.rs
@@ -356,32 +356,32 @@ fn wtf8buf_from_iterator() {
     fn f(values: &[u32]) -> Wtf8Buf {
         values.iter().map(|&c| CodePoint::from_u32(c).unwrap()).collect::<Wtf8Buf>()
     }
-    assert_eq!(f(&[0x61, 0xE9, 0x20, 0x1F4A9]), Wtf8Buf {
-        bytes: b"a\xC3\xA9 \xF0\x9F\x92\xA9".to_vec(),
-        is_known_utf8: true
-    });
+    assert_eq!(
+        f(&[0x61, 0xE9, 0x20, 0x1F4A9]),
+        Wtf8Buf { bytes: b"a\xC3\xA9 \xF0\x9F\x92\xA9".to_vec(), is_known_utf8: true }
+    );
 
     assert_eq!(f(&[0xD83D, 0xDCA9]).bytes, b"\xF0\x9F\x92\xA9"); // Magic!
-    assert_eq!(f(&[0xD83D, 0x20, 0xDCA9]), Wtf8Buf {
-        bytes: b"\xED\xA0\xBD \xED\xB2\xA9".to_vec(),
-        is_known_utf8: false
-    });
-    assert_eq!(f(&[0xD800, 0xDBFF]), Wtf8Buf {
-        bytes: b"\xED\xA0\x80\xED\xAF\xBF".to_vec(),
-        is_known_utf8: false
-    });
-    assert_eq!(f(&[0xD800, 0xE000]), Wtf8Buf {
-        bytes: b"\xED\xA0\x80\xEE\x80\x80".to_vec(),
-        is_known_utf8: false
-    });
-    assert_eq!(f(&[0xD7FF, 0xDC00]), Wtf8Buf {
-        bytes: b"\xED\x9F\xBF\xED\xB0\x80".to_vec(),
-        is_known_utf8: false
-    });
-    assert_eq!(f(&[0x61, 0xDC00]), Wtf8Buf {
-        bytes: b"\x61\xED\xB0\x80".to_vec(),
-        is_known_utf8: false
-    });
+    assert_eq!(
+        f(&[0xD83D, 0x20, 0xDCA9]),
+        Wtf8Buf { bytes: b"\xED\xA0\xBD \xED\xB2\xA9".to_vec(), is_known_utf8: false }
+    );
+    assert_eq!(
+        f(&[0xD800, 0xDBFF]),
+        Wtf8Buf { bytes: b"\xED\xA0\x80\xED\xAF\xBF".to_vec(), is_known_utf8: false }
+    );
+    assert_eq!(
+        f(&[0xD800, 0xE000]),
+        Wtf8Buf { bytes: b"\xED\xA0\x80\xEE\x80\x80".to_vec(), is_known_utf8: false }
+    );
+    assert_eq!(
+        f(&[0xD7FF, 0xDC00]),
+        Wtf8Buf { bytes: b"\xED\x9F\xBF\xED\xB0\x80".to_vec(), is_known_utf8: false }
+    );
+    assert_eq!(
+        f(&[0x61, 0xDC00]),
+        Wtf8Buf { bytes: b"\x61\xED\xB0\x80".to_vec(), is_known_utf8: false }
+    );
     assert_eq!(f(&[0xDC00]), Wtf8Buf { bytes: b"\xED\xB0\x80".to_vec(), is_known_utf8: false });
 }
 
@@ -396,36 +396,36 @@ fn wtf8buf_extend() {
         string
     }
 
-    assert_eq!(e(&[0x61, 0xE9], &[0x20, 0x1F4A9]), Wtf8Buf {
-        bytes: b"a\xC3\xA9 \xF0\x9F\x92\xA9".to_vec(),
-        is_known_utf8: true
-    });
+    assert_eq!(
+        e(&[0x61, 0xE9], &[0x20, 0x1F4A9]),
+        Wtf8Buf { bytes: b"a\xC3\xA9 \xF0\x9F\x92\xA9".to_vec(), is_known_utf8: true }
+    );
 
     assert_eq!(e(&[0xD83D], &[0xDCA9]).bytes, b"\xF0\x9F\x92\xA9"); // Magic!
-    assert_eq!(e(&[0xD83D, 0x20], &[0xDCA9]), Wtf8Buf {
-        bytes: b"\xED\xA0\xBD \xED\xB2\xA9".to_vec(),
-        is_known_utf8: false
-    });
-    assert_eq!(e(&[0xD800], &[0xDBFF]), Wtf8Buf {
-        bytes: b"\xED\xA0\x80\xED\xAF\xBF".to_vec(),
-        is_known_utf8: false
-    });
-    assert_eq!(e(&[0xD800], &[0xE000]), Wtf8Buf {
-        bytes: b"\xED\xA0\x80\xEE\x80\x80".to_vec(),
-        is_known_utf8: false
-    });
-    assert_eq!(e(&[0xD7FF], &[0xDC00]), Wtf8Buf {
-        bytes: b"\xED\x9F\xBF\xED\xB0\x80".to_vec(),
-        is_known_utf8: false
-    });
-    assert_eq!(e(&[0x61], &[0xDC00]), Wtf8Buf {
-        bytes: b"\x61\xED\xB0\x80".to_vec(),
-        is_known_utf8: false
-    });
-    assert_eq!(e(&[], &[0xDC00]), Wtf8Buf {
-        bytes: b"\xED\xB0\x80".to_vec(),
-        is_known_utf8: false
-    });
+    assert_eq!(
+        e(&[0xD83D, 0x20], &[0xDCA9]),
+        Wtf8Buf { bytes: b"\xED\xA0\xBD \xED\xB2\xA9".to_vec(), is_known_utf8: false }
+    );
+    assert_eq!(
+        e(&[0xD800], &[0xDBFF]),
+        Wtf8Buf { bytes: b"\xED\xA0\x80\xED\xAF\xBF".to_vec(), is_known_utf8: false }
+    );
+    assert_eq!(
+        e(&[0xD800], &[0xE000]),
+        Wtf8Buf { bytes: b"\xED\xA0\x80\xEE\x80\x80".to_vec(), is_known_utf8: false }
+    );
+    assert_eq!(
+        e(&[0xD7FF], &[0xDC00]),
+        Wtf8Buf { bytes: b"\xED\x9F\xBF\xED\xB0\x80".to_vec(), is_known_utf8: false }
+    );
+    assert_eq!(
+        e(&[0x61], &[0xDC00]),
+        Wtf8Buf { bytes: b"\x61\xED\xB0\x80".to_vec(), is_known_utf8: false }
+    );
+    assert_eq!(
+        e(&[], &[0xDC00]),
+        Wtf8Buf { bytes: b"\xED\xB0\x80".to_vec(), is_known_utf8: false }
+    );
 }
 
 #[test]
@@ -556,9 +556,10 @@ fn wtf8_encode_wide() {
     let mut string = Wtf8Buf::from_str("aé ");
     string.push(CodePoint::from_u32(0xD83D).unwrap());
     string.push_char('💩');
-    assert_eq!(string.encode_wide().collect::<Vec<_>>(), vec![
-        0x61, 0xE9, 0x20, 0xD83D, 0xD83D, 0xDCA9
-    ]);
+    assert_eq!(
+        string.encode_wide().collect::<Vec<_>>(),
+        vec![0x61, 0xE9, 0x20, 0xD83D, 0xD83D, 0xDCA9]
+    );
 }
 
 #[test]
diff --git a/library/std/src/test_helpers.rs b/library/std/src/test_helpers.rs
new file mode 100644
index 00000000000..7c20f38c863
--- /dev/null
+++ b/library/std/src/test_helpers.rs
@@ -0,0 +1,65 @@
+use rand::{RngCore, SeedableRng};
+
+use crate::hash::{BuildHasher, Hash, Hasher, RandomState};
+use crate::panic::Location;
+use crate::path::{Path, PathBuf};
+use crate::{env, fs, thread};
+
+/// Test-only replacement for `rand::thread_rng()`, which is unusable for
+/// us, as we want to allow running stdlib tests on tier-3 targets which may
+/// not have `getrandom` support.
+///
+/// Does a bit of a song and dance to ensure that the seed is different on
+/// each call (as some tests sadly rely on this), but doesn't try that hard.
+///
+/// This is duplicated in the `core`, `alloc` test suites (as well as
+/// `std`'s integration tests), but figuring out a mechanism to share these
+/// seems far more painful than copy-pasting a 7 line function a couple
+/// times, given that even under a perma-unstable feature, I don't think we
+/// want to expose types from `rand` from `std`.
+#[track_caller]
+pub(crate) fn test_rng() -> rand_xorshift::XorShiftRng {
+    let mut hasher = RandomState::new().build_hasher();
+    Location::caller().hash(&mut hasher);
+    let hc64 = hasher.finish();
+    let seed_vec = hc64.to_le_bytes().into_iter().chain(0u8..8).collect::<Vec<u8>>();
+    let seed: [u8; 16] = seed_vec.as_slice().try_into().unwrap();
+    SeedableRng::from_seed(seed)
+}
+
+pub struct TempDir(PathBuf);
+
+impl TempDir {
+    pub fn join(&self, path: &str) -> PathBuf {
+        let TempDir(ref p) = *self;
+        p.join(path)
+    }
+
+    pub fn path(&self) -> &Path {
+        let TempDir(ref p) = *self;
+        p
+    }
+}
+
+impl Drop for TempDir {
+    fn drop(&mut self) {
+        // Gee, seeing how we're testing the fs module I sure hope that we
+        // at least implement this correctly!
+        let TempDir(ref p) = *self;
+        let result = fs::remove_dir_all(p);
+        // Avoid panicking while panicking as this causes the process to
+        // immediately abort, without displaying test results.
+        if !thread::panicking() {
+            result.unwrap();
+        }
+    }
+}
+
+#[track_caller] // for `test_rng`
+pub fn tmpdir() -> TempDir {
+    let p = env::temp_dir();
+    let mut r = test_rng();
+    let ret = p.join(&format!("rust-{}", r.next_u32()));
+    fs::create_dir(&ret).unwrap();
+    TempDir(ret)
+}
diff --git a/library/std/src/thread/local.rs b/library/std/src/thread/local.rs
index 2313f4b5beb..ca04aa4ada4 100644
--- a/library/std/src/thread/local.rs
+++ b/library/std/src/thread/local.rs
@@ -2,12 +2,6 @@
 
 #![unstable(feature = "thread_local_internals", issue = "none")]
 
-#[cfg(all(test, not(any(target_os = "emscripten", target_os = "wasi"))))]
-mod tests;
-
-#[cfg(test)]
-mod dynamic_tests;
-
 use crate::cell::{Cell, RefCell};
 use crate::error::Error;
 use crate::fmt;
@@ -230,6 +224,14 @@ impl fmt::Display for AccessError {
 #[stable(feature = "thread_local_try_with", since = "1.26.0")]
 impl Error for AccessError {}
 
+// This ensures the panicking code is outlined from `with` for `LocalKey`.
+#[cfg_attr(not(feature = "panic_immediate_abort"), inline(never))]
+#[track_caller]
+#[cold]
+fn panic_access_error(err: AccessError) -> ! {
+    panic!("cannot access a Thread Local Storage value during or after destruction: {err:?}")
+}
+
 impl<T: 'static> LocalKey<T> {
     #[doc(hidden)]
     #[unstable(
@@ -269,10 +271,10 @@ impl<T: 'static> LocalKey<T> {
     where
         F: FnOnce(&T) -> R,
     {
-        self.try_with(f).expect(
-            "cannot access a Thread Local Storage value \
-             during or after destruction",
-        )
+        match self.try_with(f) {
+            Ok(r) => r,
+            Err(err) => panic_access_error(err),
+        }
     }
 
     /// Acquires a reference to the value in this TLS key.
@@ -327,10 +329,10 @@ impl<T: 'static> LocalKey<T> {
         let mut init = Some(init);
 
         let reference = unsafe {
-            (self.inner)(Some(&mut init)).as_ref().expect(
-                "cannot access a Thread Local Storage value \
-                 during or after destruction",
-            )
+            match (self.inner)(Some(&mut init)).as_ref() {
+                Some(r) => r,
+                None => panic_access_error(AccessError),
+            }
         };
 
         f(init, reference)
diff --git a/library/std/src/time.rs b/library/std/src/time.rs
index 9f4f8a0d088..88b3e9e0ceb 100644
--- a/library/std/src/time.rs
+++ b/library/std/src/time.rs
@@ -31,9 +31,6 @@
 
 #![stable(feature = "time", since = "1.3.0")]
 
-#[cfg(test)]
-mod tests;
-
 #[stable(feature = "time", since = "1.3.0")]
 pub use core::time::Duration;
 #[stable(feature = "duration_checked_float", since = "1.66.0")]
diff --git a/library/std/tests/common/mod.rs b/library/std/tests/common/mod.rs
index 7cf70c725e4..1e8e4cced6c 100644
--- a/library/std/tests/common/mod.rs
+++ b/library/std/tests/common/mod.rs
@@ -18,7 +18,7 @@ pub(crate) fn test_rng() -> rand_xorshift::XorShiftRng {
     rand::SeedableRng::from_seed(seed)
 }
 
-// Copied from std::sys_common::io
+// Copied from std::test_helpers
 pub(crate) struct TempDir(PathBuf);
 
 impl TempDir {
diff --git a/library/std/tests/env.rs b/library/std/tests/env.rs
index 44fe84c989f..e754cf8263b 100644
--- a/library/std/tests/env.rs
+++ b/library/std/tests/env.rs
@@ -1,163 +1,123 @@
 use std::env::*;
-use std::ffi::{OsStr, OsString};
-
-use rand::distributions::{Alphanumeric, DistString};
+use std::path::Path;
 
 mod common;
-use std::thread;
-
-use common::test_rng;
-
-#[track_caller]
-fn make_rand_name() -> OsString {
-    let n = format!("TEST{}", Alphanumeric.sample_string(&mut test_rng(), 10));
-    let n = OsString::from(n);
-    assert!(var_os(&n).is_none());
-    n
-}
-
-fn eq(a: Option<OsString>, b: Option<&str>) {
-    assert_eq!(a.as_ref().map(|s| &**s), b.map(OsStr::new).map(|s| &*s));
-}
 
 #[test]
-fn test_set_var() {
-    let n = make_rand_name();
-    set_var(&n, "VALUE");
-    eq(var_os(&n), Some("VALUE"));
+#[cfg_attr(any(target_os = "emscripten", target_os = "wasi", target_env = "sgx"), ignore)]
+fn test_self_exe_path() {
+    let path = current_exe();
+    assert!(path.is_ok());
+    let path = path.unwrap();
+
+    // Hard to test this function
+    assert!(path.is_absolute());
 }
 
 #[test]
-fn test_remove_var() {
-    let n = make_rand_name();
-    set_var(&n, "VALUE");
-    remove_var(&n);
-    eq(var_os(&n), None);
-}
+fn test() {
+    assert!((!Path::new("test-path").is_absolute()));
 
-#[test]
-fn test_set_var_overwrite() {
-    let n = make_rand_name();
-    set_var(&n, "1");
-    set_var(&n, "2");
-    eq(var_os(&n), Some("2"));
-    set_var(&n, "");
-    eq(var_os(&n), Some(""));
+    #[cfg(not(target_env = "sgx"))]
+    current_dir().unwrap();
 }
 
 #[test]
-#[cfg_attr(target_os = "emscripten", ignore)]
-fn test_var_big() {
-    let mut s = "".to_string();
-    let mut i = 0;
-    while i < 100 {
-        s.push_str("aaaaaaaaaa");
-        i += 1;
+#[cfg(windows)]
+fn split_paths_windows() {
+    use std::path::PathBuf;
+
+    fn check_parse(unparsed: &str, parsed: &[&str]) -> bool {
+        split_paths(unparsed).collect::<Vec<_>>()
+            == parsed.iter().map(|s| PathBuf::from(*s)).collect::<Vec<_>>()
     }
-    let n = make_rand_name();
-    set_var(&n, &s);
-    eq(var_os(&n), Some(&s));
-}
 
-#[test]
-#[cfg_attr(target_os = "emscripten", ignore)]
-fn test_env_set_get_huge() {
-    let n = make_rand_name();
-    let s = "x".repeat(10000);
-    set_var(&n, &s);
-    eq(var_os(&n), Some(&s));
-    remove_var(&n);
-    eq(var_os(&n), None);
+    assert!(check_parse("", &mut [""]));
+    assert!(check_parse(r#""""#, &mut [""]));
+    assert!(check_parse(";;", &mut ["", "", ""]));
+    assert!(check_parse(r"c:\", &mut [r"c:\"]));
+    assert!(check_parse(r"c:\;", &mut [r"c:\", ""]));
+    assert!(check_parse(r"c:\;c:\Program Files\", &mut [r"c:\", r"c:\Program Files\"]));
+    assert!(check_parse(r#"c:\;c:\"foo"\"#, &mut [r"c:\", r"c:\foo\"]));
+    assert!(check_parse(r#"c:\;c:\"foo;bar"\;c:\baz"#, &mut [r"c:\", r"c:\foo;bar\", r"c:\baz"]));
 }
 
 #[test]
-fn test_env_set_var() {
-    let n = make_rand_name();
+#[cfg(unix)]
+fn split_paths_unix() {
+    use std::path::PathBuf;
 
-    let mut e = vars_os();
-    set_var(&n, "VALUE");
-    assert!(!e.any(|(k, v)| { &*k == &*n && &*v == "VALUE" }));
+    fn check_parse(unparsed: &str, parsed: &[&str]) -> bool {
+        split_paths(unparsed).collect::<Vec<_>>()
+            == parsed.iter().map(|s| PathBuf::from(*s)).collect::<Vec<_>>()
+    }
 
-    assert!(vars_os().any(|(k, v)| { &*k == &*n && &*v == "VALUE" }));
+    assert!(check_parse("", &mut [""]));
+    assert!(check_parse("::", &mut ["", "", ""]));
+    assert!(check_parse("/", &mut ["/"]));
+    assert!(check_parse("/:", &mut ["/", ""]));
+    assert!(check_parse("/:/usr/local", &mut ["/", "/usr/local"]));
 }
 
 #[test]
-#[cfg_attr(not(any(unix, windows)), ignore, allow(unused))]
-#[allow(deprecated)]
-fn env_home_dir() {
-    use std::path::PathBuf;
+#[cfg(unix)]
+fn join_paths_unix() {
+    use std::ffi::OsStr;
 
-    fn var_to_os_string(var: Result<String, VarError>) -> Option<OsString> {
-        match var {
-            Ok(var) => Some(OsString::from(var)),
-            Err(VarError::NotUnicode(var)) => Some(var),
-            _ => None,
-        }
+    fn test_eq(input: &[&str], output: &str) -> bool {
+        &*join_paths(input.iter().cloned()).unwrap() == OsStr::new(output)
     }
 
-    cfg_if::cfg_if! {
-        if #[cfg(unix)] {
-            let oldhome = var_to_os_string(var("HOME"));
-
-            set_var("HOME", "/home/MountainView");
-            assert_eq!(home_dir(), Some(PathBuf::from("/home/MountainView")));
-
-            remove_var("HOME");
-            if cfg!(target_os = "android") {
-                assert!(home_dir().is_none());
-            } else {
-                // When HOME is not set, some platforms return `None`,
-                // but others return `Some` with a default.
-                // Just check that it is not "/home/MountainView".
-                assert_ne!(home_dir(), Some(PathBuf::from("/home/MountainView")));
-            }
-
-            if let Some(oldhome) = oldhome { set_var("HOME", oldhome); }
-        } else if #[cfg(windows)] {
-            let oldhome = var_to_os_string(var("HOME"));
-            let olduserprofile = var_to_os_string(var("USERPROFILE"));
-
-            remove_var("HOME");
-            remove_var("USERPROFILE");
-
-            assert!(home_dir().is_some());
-
-            set_var("HOME", "/home/PaloAlto");
-            assert_ne!(home_dir(), Some(PathBuf::from("/home/PaloAlto")), "HOME must not be used");
+    assert!(test_eq(&[], ""));
+    assert!(test_eq(&["/bin", "/usr/bin", "/usr/local/bin"], "/bin:/usr/bin:/usr/local/bin"));
+    assert!(test_eq(&["", "/bin", "", "", "/usr/bin", ""], ":/bin:::/usr/bin:"));
+    assert!(join_paths(["/te:st"].iter().cloned()).is_err());
+}
 
-            set_var("USERPROFILE", "/home/MountainView");
-            assert_eq!(home_dir(), Some(PathBuf::from("/home/MountainView")));
+#[test]
+#[cfg(windows)]
+fn join_paths_windows() {
+    use std::ffi::OsStr;
 
-            remove_var("HOME");
+    fn test_eq(input: &[&str], output: &str) -> bool {
+        &*join_paths(input.iter().cloned()).unwrap() == OsStr::new(output)
+    }
 
-            assert_eq!(home_dir(), Some(PathBuf::from("/home/MountainView")));
+    assert!(test_eq(&[], ""));
+    assert!(test_eq(&[r"c:\windows", r"c:\"], r"c:\windows;c:\"));
+    assert!(test_eq(&["", r"c:\windows", "", "", r"c:\", ""], r";c:\windows;;;c:\;"));
+    assert!(test_eq(&[r"c:\te;st", r"c:\"], r#""c:\te;st";c:\"#));
+    assert!(join_paths([r#"c:\te"st"#].iter().cloned()).is_err());
+}
 
-            set_var("USERPROFILE", "");
-            assert_ne!(home_dir(), Some(PathBuf::from("")), "Empty USERPROFILE must be ignored");
+#[test]
+fn args_debug() {
+    assert_eq!(
+        format!("Args {{ inner: {:?} }}", args().collect::<Vec<_>>()),
+        format!("{:?}", args())
+    );
+}
 
-            remove_var("USERPROFILE");
+#[test]
+fn args_os_debug() {
+    assert_eq!(
+        format!("ArgsOs {{ inner: {:?} }}", args_os().collect::<Vec<_>>()),
+        format!("{:?}", args_os())
+    );
+}
 
-            if let Some(oldhome) = oldhome { set_var("HOME", oldhome); }
-            if let Some(olduserprofile) = olduserprofile { set_var("USERPROFILE", olduserprofile); }
-        }
-    }
+#[test]
+fn vars_debug() {
+    assert_eq!(
+        format!("Vars {{ inner: {:?} }}", vars().collect::<Vec<_>>()),
+        format!("{:?}", vars())
+    );
 }
 
-#[test] // miri shouldn't detect any data race in this fn
-#[cfg_attr(any(not(miri), target_os = "emscripten"), ignore)]
-fn test_env_get_set_multithreaded() {
-    let getter = thread::spawn(|| {
-        for _ in 0..100 {
-            let _ = var_os("foo");
-        }
-    });
-
-    let setter = thread::spawn(|| {
-        for _ in 0..100 {
-            set_var("foo", "bar");
-        }
-    });
-
-    let _ = getter.join();
-    let _ = setter.join();
+#[test]
+fn vars_os_debug() {
+    assert_eq!(
+        format!("VarsOs {{ inner: {:?} }}", vars_os().collect::<Vec<_>>()),
+        format!("{:?}", vars_os())
+    );
 }
diff --git a/library/std/tests/env_modify.rs b/library/std/tests/env_modify.rs
new file mode 100644
index 00000000000..60747447350
--- /dev/null
+++ b/library/std/tests/env_modify.rs
@@ -0,0 +1,166 @@
+// These tests are in a separate integration test as they modify the environment,
+// and would otherwise cause some other tests to fail.
+
+use std::env::*;
+use std::ffi::{OsStr, OsString};
+
+use rand::distributions::{Alphanumeric, DistString};
+
+mod common;
+use std::thread;
+
+use common::test_rng;
+
+#[track_caller]
+fn make_rand_name() -> OsString {
+    let n = format!("TEST{}", Alphanumeric.sample_string(&mut test_rng(), 10));
+    let n = OsString::from(n);
+    assert!(var_os(&n).is_none());
+    n
+}
+
+fn eq(a: Option<OsString>, b: Option<&str>) {
+    assert_eq!(a.as_ref().map(|s| &**s), b.map(OsStr::new).map(|s| &*s));
+}
+
+#[test]
+fn test_set_var() {
+    let n = make_rand_name();
+    set_var(&n, "VALUE");
+    eq(var_os(&n), Some("VALUE"));
+}
+
+#[test]
+fn test_remove_var() {
+    let n = make_rand_name();
+    set_var(&n, "VALUE");
+    remove_var(&n);
+    eq(var_os(&n), None);
+}
+
+#[test]
+fn test_set_var_overwrite() {
+    let n = make_rand_name();
+    set_var(&n, "1");
+    set_var(&n, "2");
+    eq(var_os(&n), Some("2"));
+    set_var(&n, "");
+    eq(var_os(&n), Some(""));
+}
+
+#[test]
+#[cfg_attr(target_os = "emscripten", ignore)]
+fn test_var_big() {
+    let mut s = "".to_string();
+    let mut i = 0;
+    while i < 100 {
+        s.push_str("aaaaaaaaaa");
+        i += 1;
+    }
+    let n = make_rand_name();
+    set_var(&n, &s);
+    eq(var_os(&n), Some(&s));
+}
+
+#[test]
+#[cfg_attr(target_os = "emscripten", ignore)]
+fn test_env_set_get_huge() {
+    let n = make_rand_name();
+    let s = "x".repeat(10000);
+    set_var(&n, &s);
+    eq(var_os(&n), Some(&s));
+    remove_var(&n);
+    eq(var_os(&n), None);
+}
+
+#[test]
+fn test_env_set_var() {
+    let n = make_rand_name();
+
+    let mut e = vars_os();
+    set_var(&n, "VALUE");
+    assert!(!e.any(|(k, v)| { &*k == &*n && &*v == "VALUE" }));
+
+    assert!(vars_os().any(|(k, v)| { &*k == &*n && &*v == "VALUE" }));
+}
+
+#[test]
+#[cfg_attr(not(any(unix, windows)), ignore, allow(unused))]
+#[allow(deprecated)]
+fn env_home_dir() {
+    use std::path::PathBuf;
+
+    fn var_to_os_string(var: Result<String, VarError>) -> Option<OsString> {
+        match var {
+            Ok(var) => Some(OsString::from(var)),
+            Err(VarError::NotUnicode(var)) => Some(var),
+            _ => None,
+        }
+    }
+
+    cfg_if::cfg_if! {
+        if #[cfg(unix)] {
+            let oldhome = var_to_os_string(var("HOME"));
+
+            set_var("HOME", "/home/MountainView");
+            assert_eq!(home_dir(), Some(PathBuf::from("/home/MountainView")));
+
+            remove_var("HOME");
+            if cfg!(target_os = "android") {
+                assert!(home_dir().is_none());
+            } else {
+                // When HOME is not set, some platforms return `None`,
+                // but others return `Some` with a default.
+                // Just check that it is not "/home/MountainView".
+                assert_ne!(home_dir(), Some(PathBuf::from("/home/MountainView")));
+            }
+
+            if let Some(oldhome) = oldhome { set_var("HOME", oldhome); }
+        } else if #[cfg(windows)] {
+            let oldhome = var_to_os_string(var("HOME"));
+            let olduserprofile = var_to_os_string(var("USERPROFILE"));
+
+            remove_var("HOME");
+            remove_var("USERPROFILE");
+
+            assert!(home_dir().is_some());
+
+            set_var("HOME", "/home/PaloAlto");
+            assert_ne!(home_dir(), Some(PathBuf::from("/home/PaloAlto")), "HOME must not be used");
+
+            set_var("USERPROFILE", "/home/MountainView");
+            assert_eq!(home_dir(), Some(PathBuf::from("/home/MountainView")));
+
+            remove_var("HOME");
+
+            assert_eq!(home_dir(), Some(PathBuf::from("/home/MountainView")));
+
+            set_var("USERPROFILE", "");
+            assert_ne!(home_dir(), Some(PathBuf::from("")), "Empty USERPROFILE must be ignored");
+
+            remove_var("USERPROFILE");
+
+            if let Some(oldhome) = oldhome { set_var("HOME", oldhome); }
+            if let Some(olduserprofile) = olduserprofile { set_var("USERPROFILE", olduserprofile); }
+        }
+    }
+}
+
+#[test] // miri shouldn't detect any data race in this fn
+#[cfg_attr(any(not(miri), target_os = "emscripten"), ignore)]
+fn test_env_get_set_multithreaded() {
+    let getter = thread::spawn(|| {
+        for _ in 0..100 {
+            let _ = var_os("foo");
+        }
+    });
+
+    let setter = thread::spawn(|| {
+        for _ in 0..100 {
+            set_var("foo", "bar");
+        }
+    });
+
+    let _ = getter.join();
+    let _ = setter.join();
+}
diff --git a/library/std/src/error/tests.rs b/library/std/tests/error.rs
index 88a9f33c079..8fd6eb3c020 100644
--- a/library/std/src/error/tests.rs
+++ b/library/std/tests/error.rs
@@ -1,7 +1,8 @@
-use core::error::Request;
+#![feature(error_generic_member_access, error_reporter)]
 
-use super::Error;
-use crate::fmt;
+use std::backtrace::Backtrace;
+use std::error::{Error, Report, Request};
+use std::fmt;
 
 #[derive(Debug, PartialEq)]
 struct A;
@@ -38,9 +39,6 @@ fn downcasting() {
     }
 }
 
-use crate::backtrace::Backtrace;
-use crate::error::Report;
-
 #[derive(Debug)]
 struct SuperError {
     source: SuperErrorSideKick,
diff --git a/library/std/src/f128/tests.rs b/library/std/tests/floats/f128.rs
index cbcf9f96239..d0e8b157e6b 100644
--- a/library/std/src/f128/tests.rs
+++ b/library/std/tests/floats/f128.rs
@@ -1,11 +1,11 @@
 // FIXME(f16_f128): only tested on platforms that have symbols and aren't buggy
 #![cfg(reliable_f128)]
 
-use crate::f128::consts;
-use crate::num::FpCategory as Fp;
+use std::f128::consts;
+use std::num::FpCategory as Fp;
 #[cfg(reliable_f128_math)]
-use crate::ops::Rem;
-use crate::ops::{Add, Div, Mul, Sub};
+use std::ops::Rem;
+use std::ops::{Add, Div, Mul, Sub};
 
 // Note these tolerances make sense around zero, but not for more extreme exponents.
 
@@ -762,8 +762,6 @@ fn test_ln_gamma() {
 
 #[test]
 fn test_real_consts() {
-    use super::consts;
-
     let pi: f128 = consts::PI;
     let frac_pi_2: f128 = consts::FRAC_PI_2;
     let frac_pi_3: f128 = consts::FRAC_PI_3;
diff --git a/library/std/src/f16/tests.rs b/library/std/tests/floats/f16.rs
index 684ee3f3855..5180f3d40f3 100644
--- a/library/std/src/f16/tests.rs
+++ b/library/std/tests/floats/f16.rs
@@ -1,8 +1,8 @@
 // FIXME(f16_f128): only tested on platforms that have symbols and aren't buggy
 #![cfg(reliable_f16)]
 
-use crate::f16::consts;
-use crate::num::{FpCategory as Fp, *};
+use std::f16::consts;
+use std::num::FpCategory as Fp;
 
 /// Tolerance for results on the order of 10.0e-2
 #[allow(unused)]
@@ -54,7 +54,7 @@ macro_rules! assert_f16_biteq {
 
 #[test]
 fn test_num_f16() {
-    test_num(10f16, 2f16);
+    crate::test_num(10f16, 2f16);
 }
 
 #[test]
@@ -734,7 +734,6 @@ fn test_ln_gamma() {
 #[test]
 fn test_real_consts() {
     // FIXME(f16_f128): add math tests when available
-    use super::consts;
 
     let pi: f16 = consts::PI;
     let frac_pi_2: f16 = consts::FRAC_PI_2;
diff --git a/library/std/src/f32/tests.rs b/library/std/tests/floats/f32.rs
index 99cfcfb231d..bf7641986ad 100644
--- a/library/std/src/f32/tests.rs
+++ b/library/std/tests/floats/f32.rs
@@ -1,5 +1,5 @@
-use crate::f32::consts;
-use crate::num::{FpCategory as Fp, *};
+use std::f32::consts;
+use std::num::FpCategory as Fp;
 
 /// Smallest number
 const TINY_BITS: u32 = 0x1;
@@ -35,7 +35,7 @@ macro_rules! assert_f32_biteq {
 
 #[test]
 fn test_num_f32() {
-    test_num(10f32, 2f32);
+    crate::test_num(10f32, 2f32);
 }
 
 #[test]
@@ -700,8 +700,6 @@ fn test_ln_gamma() {
 
 #[test]
 fn test_real_consts() {
-    use super::consts;
-
     let pi: f32 = consts::PI;
     let frac_pi_2: f32 = consts::FRAC_PI_2;
     let frac_pi_3: f32 = consts::FRAC_PI_3;
diff --git a/library/std/src/f64/tests.rs b/library/std/tests/floats/f64.rs
index 3fac2efe0d7..cbbfcd15efd 100644
--- a/library/std/src/f64/tests.rs
+++ b/library/std/tests/floats/f64.rs
@@ -1,5 +1,5 @@
-use crate::f64::consts;
-use crate::num::{FpCategory as Fp, *};
+use std::f64::consts;
+use std::num::FpCategory as Fp;
 
 /// Smallest number
 const TINY_BITS: u64 = 0x1;
@@ -35,7 +35,7 @@ macro_rules! assert_f64_biteq {
 
 #[test]
 fn test_num_f64() {
-    test_num(10f64, 2f64);
+    crate::test_num(10f64, 2f64);
 }
 
 #[test]
@@ -112,7 +112,6 @@ fn test_neg_zero() {
     assert_eq!(Fp::Zero, neg_zero.classify());
 }
 
-#[cfg_attr(all(target_arch = "wasm32", target_os = "emscripten"), ignore)] // issue 42630
 #[test]
 fn test_one() {
     let one: f64 = 1.0f64;
@@ -165,7 +164,6 @@ fn test_is_finite() {
     assert!((-109.2f64).is_finite());
 }
 
-#[cfg_attr(all(target_arch = "wasm32", target_os = "emscripten"), ignore)] // issue 42630
 #[test]
 fn test_is_normal() {
     let nan: f64 = f64::NAN;
@@ -183,7 +181,6 @@ fn test_is_normal() {
     assert!(!1e-308f64.is_normal());
 }
 
-#[cfg_attr(all(target_arch = "wasm32", target_os = "emscripten"), ignore)] // issue 42630
 #[test]
 fn test_classify() {
     let nan: f64 = f64::NAN;
@@ -683,7 +680,6 @@ fn test_ln_gamma() {
 
 #[test]
 fn test_real_consts() {
-    use super::consts;
     let pi: f64 = consts::PI;
     let frac_pi_2: f64 = consts::FRAC_PI_2;
     let frac_pi_3: f64 = consts::FRAC_PI_3;
diff --git a/library/std/tests/floats/lib.rs b/library/std/tests/floats/lib.rs
new file mode 100644
index 00000000000..ad82f1a44e7
--- /dev/null
+++ b/library/std/tests/floats/lib.rs
@@ -0,0 +1,42 @@
+#![feature(f16, f128, float_gamma, float_minimum_maximum)]
+
+use std::fmt;
+use std::ops::{Add, Div, Mul, Rem, Sub};
+
+/// Verify that floats are within a tolerance of each other, 1.0e-6 by default.
+macro_rules! assert_approx_eq {
+    ($a:expr, $b:expr) => {{ assert_approx_eq!($a, $b, 1.0e-6) }};
+    ($a:expr, $b:expr, $lim:expr) => {{
+        let (a, b) = (&$a, &$b);
+        let diff = (*a - *b).abs();
+        assert!(
+            diff < $lim,
+            "{a:?} is not approximately equal to {b:?} (threshold {lim:?}, difference {diff:?})",
+            lim = $lim
+        );
+    }};
+}
+
+/// Helper function for testing numeric operations
+pub fn test_num<T>(ten: T, two: T)
+where
+    T: PartialEq
+        + Add<Output = T>
+        + Sub<Output = T>
+        + Mul<Output = T>
+        + Div<Output = T>
+        + Rem<Output = T>
+        + fmt::Debug
+        + Copy,
+{
+    assert_eq!(ten.add(two), ten + two);
+    assert_eq!(ten.sub(two), ten - two);
+    assert_eq!(ten.mul(two), ten * two);
+    assert_eq!(ten.div(two), ten / two);
+    assert_eq!(ten.rem(two), ten % two);
+}
+
+mod f128;
+mod f16;
+mod f32;
+mod f64;
diff --git a/library/std/tests/istr.rs b/library/std/tests/istr.rs
index 9a127ae803e..e481872977a 100644
--- a/library/std/tests/istr.rs
+++ b/library/std/tests/istr.rs
@@ -5,7 +5,7 @@ fn test_stack_assign() {
     let t: String = "a".to_string();
     assert_eq!(s, t);
     let u: String = "b".to_string();
-    assert!((s != u));
+    assert!(s != u);
 }
 
 #[test]
@@ -19,7 +19,7 @@ fn test_heap_assign() {
     let t: String = "a big ol' string".to_string();
     assert_eq!(s, t);
     let u: String = "a bad ol' string".to_string();
-    assert!((s != u));
+    assert!(s != u);
 }
 
 #[test]
diff --git a/library/std/src/num/tests.rs b/library/std/tests/num.rs
index df0df3f23f7..a7400f1c02d 100644
--- a/library/std/src/num/tests.rs
+++ b/library/std/tests/num.rs
@@ -1,4 +1,4 @@
-use crate::ops::Mul;
+use std::ops::Mul;
 
 #[test]
 fn test_saturating_add_uint() {
@@ -190,8 +190,8 @@ fn test_uint_to_str_overflow() {
     assert_eq!(u64_val.to_string(), "0");
 }
 
-fn from_str<T: crate::str::FromStr>(t: &str) -> Option<T> {
-    crate::str::FromStr::from_str(t).ok()
+fn from_str<T: std::str::FromStr>(t: &str) -> Option<T> {
+    std::str::FromStr::from_str(t).ok()
 }
 
 #[test]
diff --git a/library/std/src/panic/tests.rs b/library/std/tests/panic.rs
index b37d74011cc..f13b931dd22 100644
--- a/library/std/src/panic/tests.rs
+++ b/library/std/tests/panic.rs
@@ -1,9 +1,9 @@
 #![allow(dead_code)]
 
-use crate::cell::RefCell;
-use crate::panic::{AssertUnwindSafe, UnwindSafe};
-use crate::rc::Rc;
-use crate::sync::{Arc, Mutex, RwLock};
+use std::cell::RefCell;
+use std::panic::{AssertUnwindSafe, UnwindSafe};
+use std::rc::Rc;
+use std::sync::{Arc, Mutex, RwLock};
 
 struct Foo {
     a: i32,
diff --git a/library/std/src/path/tests.rs b/library/std/tests/path.rs
index 3f96ac4672a..978402b6fda 100644
--- a/library/std/src/path/tests.rs
+++ b/library/std/tests/path.rs
@@ -1,10 +1,19 @@
-use core::hint::black_box;
-
-use super::*;
-use crate::collections::{BTreeSet, HashSet};
-use crate::hash::DefaultHasher;
-use crate::mem::MaybeUninit;
-use crate::ptr;
+#![feature(
+    clone_to_uninit,
+    path_add_extension,
+    path_file_prefix,
+    maybe_uninit_slice,
+    os_string_pathbuf_leak
+)]
+
+use std::clone::CloneToUninit;
+use std::ffi::OsStr;
+use std::hash::{DefaultHasher, Hash, Hasher};
+use std::mem::MaybeUninit;
+use std::path::*;
+use std::ptr;
+use std::rc::Rc;
+use std::sync::Arc;
 
 #[allow(unknown_lints, unused_macro_rules)]
 macro_rules! t (
@@ -110,7 +119,7 @@ macro_rules! t (
 
 #[test]
 fn into() {
-    use crate::borrow::Cow;
+    use std::borrow::Cow;
 
     let static_path = Path::new("/home/foo");
     let static_cow_path: Cow<'static, Path> = static_path.into();
@@ -1525,7 +1534,7 @@ pub fn test_with_added_extension() {
 
 #[test]
 fn test_eq_receivers() {
-    use crate::borrow::Cow;
+    use std::borrow::Cow;
 
     let borrowed: &Path = Path::new("foo/bar");
     let mut owned: PathBuf = PathBuf::new();
@@ -1550,7 +1559,7 @@ fn test_eq_receivers() {
 
 #[test]
 pub fn test_compare() {
-    use crate::hash::{DefaultHasher, Hash, Hasher};
+    use std::hash::{DefaultHasher, Hash, Hasher};
 
     fn hash<T: Hash>(t: T) -> u64 {
         let mut s = DefaultHasher::new();
@@ -1867,12 +1876,12 @@ fn test_ord() {
 #[test]
 #[cfg(any(unix, target_os = "wasi"))]
 fn test_unix_absolute() {
-    use crate::path::absolute;
+    use std::path::absolute;
 
     assert!(absolute("").is_err());
 
     let relative = "a/b";
-    let mut expected = crate::env::current_dir().unwrap();
+    let mut expected = std::env::current_dir().unwrap();
     expected.push(relative);
     assert_eq!(absolute(relative).unwrap().as_os_str(), expected.as_os_str());
 
@@ -1888,7 +1897,7 @@ fn test_unix_absolute() {
     );
 
     // Test leading `.` and `..` components
-    let curdir = crate::env::current_dir().unwrap();
+    let curdir = std::env::current_dir().unwrap();
     assert_eq!(absolute("./a").unwrap().as_os_str(), curdir.join("a").as_os_str());
     assert_eq!(absolute("../a").unwrap().as_os_str(), curdir.join("../a").as_os_str()); // return /pwd/../a
 }
@@ -1896,12 +1905,12 @@ fn test_unix_absolute() {
 #[test]
 #[cfg(windows)]
 fn test_windows_absolute() {
-    use crate::path::absolute;
+    use std::path::absolute;
     // An empty path is an error.
     assert!(absolute("").is_err());
 
     let relative = r"a\b";
-    let mut expected = crate::env::current_dir().unwrap();
+    let mut expected = std::env::current_dir().unwrap();
     expected.push(relative);
     assert_eq!(absolute(relative).unwrap().as_os_str(), expected.as_os_str());
 
@@ -1953,116 +1962,6 @@ fn test_extension_path_sep_alternate() {
     assert_eq!(path, Path::new("path/to/file.d\\test"));
 }
 
-#[bench]
-#[cfg_attr(miri, ignore)] // Miri isn't fast...
-fn bench_path_cmp_fast_path_buf_sort(b: &mut test::Bencher) {
-    let prefix = "my/home";
-    let mut paths: Vec<_> =
-        (0..1000).map(|num| PathBuf::from(prefix).join(format!("file {num}.rs"))).collect();
-
-    paths.sort();
-
-    b.iter(|| {
-        black_box(paths.as_mut_slice()).sort_unstable();
-    });
-}
-
-#[bench]
-#[cfg_attr(miri, ignore)] // Miri isn't fast...
-fn bench_path_cmp_fast_path_long(b: &mut test::Bencher) {
-    let prefix = "/my/home/is/my/castle/and/my/castle/has/a/rusty/workbench/";
-    let paths: Vec<_> =
-        (0..1000).map(|num| PathBuf::from(prefix).join(format!("file {num}.rs"))).collect();
-
-    let mut set = BTreeSet::new();
-
-    paths.iter().for_each(|p| {
-        set.insert(p.as_path());
-    });
-
-    b.iter(|| {
-        set.remove(paths[500].as_path());
-        set.insert(paths[500].as_path());
-    });
-}
-
-#[bench]
-#[cfg_attr(miri, ignore)] // Miri isn't fast...
-fn bench_path_cmp_fast_path_short(b: &mut test::Bencher) {
-    let prefix = "my/home";
-    let paths: Vec<_> =
-        (0..1000).map(|num| PathBuf::from(prefix).join(format!("file {num}.rs"))).collect();
-
-    let mut set = BTreeSet::new();
-
-    paths.iter().for_each(|p| {
-        set.insert(p.as_path());
-    });
-
-    b.iter(|| {
-        set.remove(paths[500].as_path());
-        set.insert(paths[500].as_path());
-    });
-}
-
-#[bench]
-#[cfg_attr(miri, ignore)] // Miri isn't fast...
-fn bench_path_hashset(b: &mut test::Bencher) {
-    let prefix = "/my/home/is/my/castle/and/my/castle/has/a/rusty/workbench/";
-    let paths: Vec<_> =
-        (0..1000).map(|num| PathBuf::from(prefix).join(format!("file {num}.rs"))).collect();
-
-    let mut set = HashSet::new();
-
-    paths.iter().for_each(|p| {
-        set.insert(p.as_path());
-    });
-
-    b.iter(|| {
-        set.remove(paths[500].as_path());
-        set.insert(black_box(paths[500].as_path()))
-    });
-}
-
-#[bench]
-#[cfg_attr(miri, ignore)] // Miri isn't fast...
-fn bench_path_hashset_miss(b: &mut test::Bencher) {
-    let prefix = "/my/home/is/my/castle/and/my/castle/has/a/rusty/workbench/";
-    let paths: Vec<_> =
-        (0..1000).map(|num| PathBuf::from(prefix).join(format!("file {num}.rs"))).collect();
-
-    let mut set = HashSet::new();
-
-    paths.iter().for_each(|p| {
-        set.insert(p.as_path());
-    });
-
-    let probe = PathBuf::from(prefix).join("other");
-
-    b.iter(|| set.remove(black_box(probe.as_path())));
-}
-
-#[bench]
-fn bench_hash_path_short(b: &mut test::Bencher) {
-    let mut hasher = DefaultHasher::new();
-    let path = Path::new("explorer.exe");
-
-    b.iter(|| black_box(path).hash(&mut hasher));
-
-    black_box(hasher.finish());
-}
-
-#[bench]
-fn bench_hash_path_long(b: &mut test::Bencher) {
-    let mut hasher = DefaultHasher::new();
-    let path =
-        Path::new("/aaaaa/aaaaaa/./../aaaaaaaa/bbbbbbbbbbbbb/ccccccccccc/ddddddddd/eeeeeee.fff");
-
-    b.iter(|| black_box(path).hash(&mut hasher));
-
-    black_box(hasher.finish());
-}
-
 #[test]
 fn clone_to_uninit() {
     let a = Path::new("hello.txt");
diff --git a/library/std/tests/pipe_subprocess.rs b/library/std/tests/pipe_subprocess.rs
index df946cdcf2b..00d99a578d5 100644
--- a/library/std/tests/pipe_subprocess.rs
+++ b/library/std/tests/pipe_subprocess.rs
@@ -1,7 +1,7 @@
 #![feature(anonymous_pipe)]
 
 fn main() {
-    #[cfg(all(not(miri), any(unix, windows)))]
+    #[cfg(all(not(miri), any(unix, windows), not(target_os = "emscripten")))]
     {
         use std::io::{Read, pipe};
         use std::{env, process};
diff --git a/library/std/tests/process_spawning.rs b/library/std/tests/process_spawning.rs
index 3e72e371ade..43b45cb2d2b 100644
--- a/library/std/tests/process_spawning.rs
+++ b/library/std/tests/process_spawning.rs
@@ -5,7 +5,8 @@ use std::{env, fs, process, str};
 mod common;
 
 #[test]
-#[cfg_attr(any(miri, target_os = "wasi"), ignore)] // Process spawning not supported by Miri and wasi
+// Process spawning not supported by Miri, Emscripten and wasi
+#[cfg_attr(any(miri, target_os = "emscripten", target_os = "wasi"), ignore)]
 fn issue_15149() {
     // If we're the parent, copy our own binary to a new directory.
     let my_path = env::current_exe().unwrap();
diff --git a/library/std/tests/seq-compare.rs b/library/std/tests/seq-compare.rs
index 221f1c7cabd..ec39c5b603c 100644
--- a/library/std/tests/seq-compare.rs
+++ b/library/std/tests/seq-compare.rs
@@ -1,15 +1,15 @@
 #[test]
 fn seq_compare() {
-    assert!(("hello".to_string() < "hellr".to_string()));
-    assert!(("hello ".to_string() > "hello".to_string()));
-    assert!(("hello".to_string() != "there".to_string()));
-    assert!((vec![1, 2, 3, 4] > vec![1, 2, 3]));
-    assert!((vec![1, 2, 3] < vec![1, 2, 3, 4]));
-    assert!((vec![1, 2, 4, 4] > vec![1, 2, 3, 4]));
-    assert!((vec![1, 2, 3, 4] < vec![1, 2, 4, 4]));
-    assert!((vec![1, 2, 3] <= vec![1, 2, 3]));
-    assert!((vec![1, 2, 3] <= vec![1, 2, 3, 3]));
-    assert!((vec![1, 2, 3, 4] > vec![1, 2, 3]));
+    assert!("hello".to_string() < "hellr".to_string());
+    assert!("hello ".to_string() > "hello".to_string());
+    assert!("hello".to_string() != "there".to_string());
+    assert!(vec![1, 2, 3, 4] > vec![1, 2, 3]);
+    assert!(vec![1, 2, 3] < vec![1, 2, 3, 4]);
+    assert!(vec![1, 2, 4, 4] > vec![1, 2, 3, 4]);
+    assert!(vec![1, 2, 3, 4] < vec![1, 2, 4, 4]);
+    assert!(vec![1, 2, 3] <= vec![1, 2, 3]);
+    assert!(vec![1, 2, 3] <= vec![1, 2, 3, 3]);
+    assert!(vec![1, 2, 3, 4] > vec![1, 2, 3]);
     assert_eq!(vec![1, 2, 3], vec![1, 2, 3]);
-    assert!((vec![1, 2, 3] != vec![1, 1, 3]));
+    assert!(vec![1, 2, 3] != vec![1, 1, 3]);
 }
diff --git a/library/std/src/sync/barrier/tests.rs b/library/std/tests/sync/barrier.rs
index 0fbcd998812..8aefff9d507 100644
--- a/library/std/src/sync/barrier/tests.rs
+++ b/library/std/tests/sync/barrier.rs
@@ -1,6 +1,6 @@
-use crate::sync::mpsc::{TryRecvError, channel};
-use crate::sync::{Arc, Barrier};
-use crate::thread;
+use std::sync::mpsc::{TryRecvError, channel};
+use std::sync::{Arc, Barrier};
+use std::thread;
 
 #[test]
 #[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
diff --git a/library/std/src/sync/poison/condvar/tests.rs b/library/std/tests/sync/condvar.rs
index f9e9066bc92..834de6bb1c2 100644
--- a/library/std/src/sync/poison/condvar/tests.rs
+++ b/library/std/tests/sync/condvar.rs
@@ -1,8 +1,8 @@
-use crate::sync::atomic::{AtomicBool, Ordering};
-use crate::sync::mpsc::channel;
-use crate::sync::{Arc, Condvar, Mutex};
-use crate::thread;
-use crate::time::Duration;
+use std::sync::atomic::{AtomicBool, Ordering};
+use std::sync::mpsc::channel;
+use std::sync::{Arc, Condvar, Mutex};
+use std::thread;
+use std::time::Duration;
 
 #[test]
 fn smoke() {
diff --git a/library/std/src/sync/lazy_lock/tests.rs b/library/std/tests/sync/lazy_lock.rs
index 7d7dde54349..6c14b79f2ce 100644
--- a/library/std/src/sync/lazy_lock/tests.rs
+++ b/library/std/tests/sync/lazy_lock.rs
@@ -1,8 +1,8 @@
-use crate::cell::LazyCell;
-use crate::sync::atomic::AtomicUsize;
-use crate::sync::atomic::Ordering::SeqCst;
-use crate::sync::{LazyLock, Mutex, OnceLock};
-use crate::{panic, thread};
+use std::cell::LazyCell;
+use std::sync::atomic::AtomicUsize;
+use std::sync::atomic::Ordering::SeqCst;
+use std::sync::{LazyLock, Mutex, OnceLock};
+use std::{panic, thread};
 
 fn spawn_and_wait<R: Send + 'static>(f: impl FnOnce() -> R + Send + 'static) -> R {
     thread::spawn(f).join().unwrap()
@@ -149,7 +149,7 @@ fn is_sync_send() {
 #[should_panic = "has previously been poisoned"]
 fn lazy_force_mut_panic() {
     let mut lazy = LazyLock::<String>::new(|| panic!());
-    crate::panic::catch_unwind(crate::panic::AssertUnwindSafe(|| {
+    panic::catch_unwind(panic::AssertUnwindSafe(|| {
         let _ = LazyLock::force_mut(&mut lazy);
     }))
     .unwrap_err();
diff --git a/library/std/tests/sync/lib.rs b/library/std/tests/sync/lib.rs
new file mode 100644
index 00000000000..51190f0894f
--- /dev/null
+++ b/library/std/tests/sync/lib.rs
@@ -0,0 +1,31 @@
+#![feature(lazy_get)]
+#![feature(mapped_lock_guards)]
+#![feature(mpmc_channel)]
+#![feature(once_cell_try)]
+#![feature(lock_value_accessors)]
+#![feature(reentrant_lock)]
+#![feature(rwlock_downgrade)]
+#![feature(std_internals)]
+#![allow(internal_features)]
+
+mod barrier;
+mod condvar;
+mod lazy_lock;
+#[cfg(not(any(target_os = "emscripten", target_os = "wasi")))]
+mod mpmc;
+#[cfg(not(any(target_os = "emscripten", target_os = "wasi")))]
+mod mpsc;
+#[cfg(not(any(target_os = "emscripten", target_os = "wasi")))]
+mod mpsc_sync;
+#[cfg(not(any(target_os = "emscripten", target_os = "wasi")))]
+mod mutex;
+#[cfg(not(any(target_os = "emscripten", target_os = "wasi")))]
+mod once;
+mod once_lock;
+#[cfg(not(any(target_os = "emscripten", target_os = "wasi")))]
+mod reentrant_lock;
+#[cfg(not(any(target_os = "emscripten", target_os = "wasi")))]
+mod rwlock;
+
+#[path = "../common/mod.rs"]
+mod common;
diff --git a/library/std/src/sync/mpmc/tests.rs b/library/std/tests/sync/mpmc.rs
index ab14050df6c..81b92297f76 100644
--- a/library/std/src/sync/mpmc/tests.rs
+++ b/library/std/tests/sync/mpmc.rs
@@ -1,5 +1,6 @@
-use super::*;
-use crate::{env, thread};
+use std::sync::mpmc::*;
+use std::time::{Duration, Instant};
+use std::{env, thread};
 
 pub fn stress_factor() -> usize {
     match env::var("RUST_TEST_STRESS") {
diff --git a/library/std/src/sync/mpsc/tests.rs b/library/std/tests/sync/mpsc.rs
index 13892fa0d18..1d8edfde44b 100644
--- a/library/std/src/sync/mpsc/tests.rs
+++ b/library/std/tests/sync/mpsc.rs
@@ -1,5 +1,6 @@
-use super::*;
-use crate::{env, thread};
+use std::sync::mpsc::*;
+use std::time::{Duration, Instant};
+use std::{env, thread};
 
 pub fn stress_factor() -> usize {
     match env::var("RUST_TEST_STRESS") {
diff --git a/library/std/src/sync/mpsc/sync_tests.rs b/library/std/tests/sync/mpsc_sync.rs
index 49b65c8efe6..a7f326d201b 100644
--- a/library/std/src/sync/mpsc/sync_tests.rs
+++ b/library/std/tests/sync/mpsc_sync.rs
@@ -1,7 +1,8 @@
-use super::*;
-use crate::rc::Rc;
-use crate::sync::mpmc::SendTimeoutError;
-use crate::{env, thread};
+use std::rc::Rc;
+use std::sync::mpmc::SendTimeoutError;
+use std::sync::mpsc::*;
+use std::time::Duration;
+use std::{env, thread};
 
 pub fn stress_factor() -> usize {
     match env::var("RUST_TEST_STRESS") {
diff --git a/library/std/src/sync/poison/mutex/tests.rs b/library/std/tests/sync/mutex.rs
index 395c8aada08..74c62720107 100644
--- a/library/std/src/sync/poison/mutex/tests.rs
+++ b/library/std/tests/sync/mutex.rs
@@ -1,10 +1,10 @@
-use crate::fmt::Debug;
-use crate::ops::FnMut;
-use crate::panic::{self, AssertUnwindSafe};
-use crate::sync::atomic::{AtomicUsize, Ordering};
-use crate::sync::mpsc::channel;
-use crate::sync::{Arc, Condvar, MappedMutexGuard, Mutex, MutexGuard, TryLockError};
-use crate::{hint, mem, thread};
+use std::fmt::Debug;
+use std::ops::FnMut;
+use std::panic::{self, AssertUnwindSafe};
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::mpsc::channel;
+use std::sync::{Arc, Condvar, MappedMutexGuard, Mutex, MutexGuard, TryLockError};
+use std::{hint, mem, thread};
 
 struct Packet<T>(Arc<(Mutex<T>, Condvar)>);
 
diff --git a/library/std/src/sync/poison/once/tests.rs b/library/std/tests/sync/once.rs
index ce96468aeb6..a3ffc73fe06 100644
--- a/library/std/src/sync/poison/once/tests.rs
+++ b/library/std/tests/sync/once.rs
@@ -1,9 +1,9 @@
-use super::Once;
-use crate::sync::atomic::AtomicBool;
-use crate::sync::atomic::Ordering::Relaxed;
-use crate::sync::mpsc::channel;
-use crate::time::Duration;
-use crate::{panic, thread};
+use std::sync::Once;
+use std::sync::atomic::AtomicBool;
+use std::sync::atomic::Ordering::Relaxed;
+use std::sync::mpsc::channel;
+use std::time::Duration;
+use std::{panic, thread};
 
 #[test]
 fn smoke_once() {
diff --git a/library/std/src/sync/once_lock/tests.rs b/library/std/tests/sync/once_lock.rs
index 5113d436c3c..ac9aaa8892e 100644
--- a/library/std/src/sync/once_lock/tests.rs
+++ b/library/std/tests/sync/once_lock.rs
@@ -1,8 +1,8 @@
-use crate::sync::OnceLock;
-use crate::sync::atomic::AtomicUsize;
-use crate::sync::atomic::Ordering::SeqCst;
-use crate::sync::mpsc::channel;
-use crate::{panic, thread};
+use std::sync::OnceLock;
+use std::sync::atomic::AtomicUsize;
+use std::sync::atomic::Ordering::SeqCst;
+use std::sync::mpsc::channel;
+use std::{panic, thread};
 
 fn spawn_and_wait<R: Send + 'static>(f: impl FnOnce() -> R + Send + 'static) -> R {
     thread::spawn(f).join().unwrap()
@@ -34,15 +34,6 @@ fn sync_once_cell_get_mut() {
 }
 
 #[test]
-fn sync_once_cell_get_unchecked() {
-    let c = OnceLock::new();
-    c.set(92).unwrap();
-    unsafe {
-        assert_eq!(c.get_unchecked(), &92);
-    }
-}
-
-#[test]
 #[cfg_attr(any(target_os = "emscripten", target_os = "wasi"), ignore)] // no threads
 fn sync_once_cell_drop() {
     static DROP_CNT: AtomicUsize = AtomicUsize::new(0);
@@ -88,7 +79,6 @@ fn get_or_try_init() {
 
     let res = panic::catch_unwind(|| cell.get_or_try_init(|| -> Result<_, ()> { panic!() }));
     assert!(res.is_err());
-    assert!(!cell.is_initialized());
     assert!(cell.get().is_none());
 
     assert_eq!(cell.get_or_try_init(|| Err(())), Err(()));
@@ -174,7 +164,7 @@ fn sync_once_cell_does_not_leak_partially_constructed_boxes() {
                     break;
                 }
                 #[cfg(target_env = "sgx")]
-                crate::thread::yield_now();
+                std::thread::yield_now();
             }
         });
     }
diff --git a/library/std/src/sync/reentrant_lock/tests.rs b/library/std/tests/sync/reentrant_lock.rs
index aeef0289d28..2b7b87e3623 100644
--- a/library/std/src/sync/reentrant_lock/tests.rs
+++ b/library/std/tests/sync/reentrant_lock.rs
@@ -1,7 +1,6 @@
-use super::ReentrantLock;
-use crate::cell::RefCell;
-use crate::sync::Arc;
-use crate::thread;
+use std::cell::RefCell;
+use std::sync::{Arc, ReentrantLock};
+use std::thread;
 
 #[test]
 fn smoke() {
diff --git a/library/std/src/sync/poison/rwlock/tests.rs b/library/std/tests/sync/rwlock.rs
index 057c2f1a5d7..bd4bc7a14bc 100644
--- a/library/std/src/sync/poison/rwlock/tests.rs
+++ b/library/std/tests/sync/rwlock.rs
@@ -1,15 +1,15 @@
-use rand::Rng;
-
-use crate::fmt::Debug;
-use crate::ops::FnMut;
-use crate::panic::{self, AssertUnwindSafe};
-use crate::sync::atomic::{AtomicUsize, Ordering};
-use crate::sync::mpsc::channel;
-use crate::sync::{
+use std::fmt::Debug;
+use std::ops::FnMut;
+use std::panic::{self, AssertUnwindSafe};
+use std::sync::atomic::{AtomicUsize, Ordering};
+use std::sync::mpsc::channel;
+use std::sync::{
     Arc, MappedRwLockReadGuard, MappedRwLockWriteGuard, RwLock, RwLockReadGuard, RwLockWriteGuard,
     TryLockError,
 };
-use crate::{hint, mem, thread};
+use std::{hint, mem, thread};
+
+use rand::Rng;
 
 #[derive(Eq, PartialEq, Debug)]
 struct NonCopy(i32);
@@ -57,7 +57,7 @@ fn frob() {
         let tx = tx.clone();
         let r = r.clone();
         thread::spawn(move || {
-            let mut rng = crate::test_helpers::test_rng();
+            let mut rng = crate::common::test_rng();
             for _ in 0..M {
                 if rng.gen_bool(1.0 / (N as f64)) {
                     drop(r.write().unwrap());
@@ -704,7 +704,7 @@ fn test_downgrade_atomic() {
 
     // Wait for a good amount of time so that evil threads go to sleep.
     // Note: this is not strictly necessary...
-    let eternity = crate::time::Duration::from_millis(42);
+    let eternity = std::time::Duration::from_millis(42);
     thread::sleep(eternity);
 
     // Once everyone is asleep, set the value to `NEW_VALUE`.
diff --git a/library/std/src/thread/local/dynamic_tests.rs b/library/std/tests/thread_local/dynamic_tests.rs
index dd180041648..454462b3925 100644
--- a/library/std/src/thread/local/dynamic_tests.rs
+++ b/library/std/tests/thread_local/dynamic_tests.rs
@@ -1,6 +1,6 @@
-use crate::cell::RefCell;
-use crate::collections::HashMap;
-use crate::thread_local;
+use std::cell::RefCell;
+use std::collections::HashMap;
+use std::thread_local;
 
 #[test]
 fn smoke() {
diff --git a/library/std/tests/thread_local/lib.rs b/library/std/tests/thread_local/lib.rs
new file mode 100644
index 00000000000..c5291435425
--- /dev/null
+++ b/library/std/tests/thread_local/lib.rs
@@ -0,0 +1,4 @@
+#[cfg(not(any(target_os = "emscripten", target_os = "wasi")))]
+mod tests;
+
+mod dynamic_tests;
diff --git a/library/std/src/thread/local/tests.rs b/library/std/tests/thread_local/tests.rs
index 9d4f52a0921..aa020c2559c 100644
--- a/library/std/src/thread/local/tests.rs
+++ b/library/std/tests/thread_local/tests.rs
@@ -1,8 +1,8 @@
-use crate::cell::{Cell, UnsafeCell};
-use crate::sync::atomic::{AtomicU8, Ordering};
-use crate::sync::{Arc, Condvar, Mutex};
-use crate::thread::{self, Builder, LocalKey};
-use crate::thread_local;
+use std::cell::{Cell, UnsafeCell};
+use std::sync::atomic::{AtomicU8, Ordering};
+use std::sync::{Arc, Condvar, Mutex};
+use std::thread::{self, Builder, LocalKey};
+use std::thread_local;
 
 #[derive(Clone, Default)]
 struct Signal(Arc<(Mutex<bool>, Condvar)>);
diff --git a/library/std/src/time/tests.rs b/library/std/tests/time.rs
index e88f2d5e806..40709eae37c 100644
--- a/library/std/src/time/tests.rs
+++ b/library/std/tests/time.rs
@@ -1,9 +1,7 @@
-use core::fmt::Debug;
+#![feature(duration_constants)]
 
-#[cfg(not(target_arch = "wasm32"))]
-use test::{Bencher, black_box};
-
-use super::{Duration, Instant, SystemTime, UNIX_EPOCH};
+use std::fmt::Debug;
+use std::time::{Duration, Instant, SystemTime, UNIX_EPOCH};
 
 macro_rules! assert_almost_eq {
     ($a:expr, $b:expr) => {{
@@ -29,10 +27,10 @@ fn instant_monotonic() {
 
 #[test]
 #[cfg(not(target_arch = "wasm32"))]
-fn instant_monotonic_concurrent() -> crate::thread::Result<()> {
+fn instant_monotonic_concurrent() -> std::thread::Result<()> {
     let threads: Vec<_> = (0..8)
         .map(|_| {
-            crate::thread::spawn(|| {
+            std::thread::spawn(|| {
                 let mut old = Instant::now();
                 let count = if cfg!(miri) { 1_000 } else { 5_000_000 };
                 for _ in 0..count {
@@ -229,46 +227,3 @@ fn big_math() {
     check(instant.checked_add(Duration::from_secs(100)), Instant::checked_sub);
     check(instant.checked_add(Duration::from_secs(i64::MAX as _)), Instant::checked_sub);
 }
-
-macro_rules! bench_instant_threaded {
-    ($bench_name:ident, $thread_count:expr) => {
-        #[bench]
-        #[cfg(not(target_arch = "wasm32"))]
-        fn $bench_name(b: &mut Bencher) -> crate::thread::Result<()> {
-            use crate::sync::Arc;
-            use crate::sync::atomic::{AtomicBool, Ordering};
-
-            let running = Arc::new(AtomicBool::new(true));
-
-            let threads: Vec<_> = (0..$thread_count)
-                .map(|_| {
-                    let flag = Arc::clone(&running);
-                    crate::thread::spawn(move || {
-                        while flag.load(Ordering::Relaxed) {
-                            black_box(Instant::now());
-                        }
-                    })
-                })
-                .collect();
-
-            b.iter(|| {
-                let a = Instant::now();
-                let b = Instant::now();
-                assert!(b >= a);
-            });
-
-            running.store(false, Ordering::Relaxed);
-
-            for t in threads {
-                t.join()?;
-            }
-            Ok(())
-        }
-    };
-}
-
-bench_instant_threaded!(instant_contention_01_threads, 0);
-bench_instant_threaded!(instant_contention_02_threads, 1);
-bench_instant_threaded!(instant_contention_04_threads, 3);
-bench_instant_threaded!(instant_contention_08_threads, 7);
-bench_instant_threaded!(instant_contention_16_threads, 15);
diff --git a/library/std/tests/win_delete_self.rs b/library/std/tests/win_delete_self.rs
new file mode 100644
index 00000000000..1c3ce4d710c
--- /dev/null
+++ b/library/std/tests/win_delete_self.rs
@@ -0,0 +1,8 @@
+#![cfg(windows)]
+
+/// Attempting to delete a running binary should return an error on Windows.
+#[test]
+fn win_delete_self() {
+    let path = std::env::current_exe().unwrap();
+    assert!(std::fs::remove_file(path).is_err());
+}