diff --git a/library/std/src/collections/hash/map.rs b/library/std/src/collections/hash/map.rs
index fcd1c307b5af6..1f6a3e904795a 100644
--- a/library/std/src/collections/hash/map.rs
+++ b/library/std/src/collections/hash/map.rs
@@ -1018,7 +1018,7 @@ where
         K: Borrow<Q>,
         Q: Hash + Eq,
     {
-        self.base.get_many_unchecked_mut(ks)
+        unsafe { self.base.get_many_unchecked_mut(ks) }
     }
 
     /// Returns `true` if the map contains a value for the specified key.
diff --git a/library/std/src/env.rs b/library/std/src/env.rs
index 2f35e721610e0..36add02d68c5c 100644
--- a/library/std/src/env.rs
+++ b/library/std/src/env.rs
@@ -366,11 +366,8 @@ impl Error for VarError {
 #[rustc_deprecated_safe_2024]
 #[stable(feature = "env", since = "1.0.0")]
 pub unsafe fn set_var<K: AsRef<OsStr>, V: AsRef<OsStr>>(key: K, value: V) {
-    _set_var(key.as_ref(), value.as_ref())
-}
-
-unsafe fn _set_var(key: &OsStr, value: &OsStr) {
-    os_imp::setenv(key, value).unwrap_or_else(|e| {
+    let (key, value) = (key.as_ref(), value.as_ref());
+    unsafe { os_imp::setenv(key, value) }.unwrap_or_else(|e| {
         panic!("failed to set environment variable `{key:?}` to `{value:?}`: {e}")
     })
 }
@@ -433,11 +430,8 @@ unsafe fn _set_var(key: &OsStr, value: &OsStr) {
 #[rustc_deprecated_safe_2024]
 #[stable(feature = "env", since = "1.0.0")]
 pub unsafe fn remove_var<K: AsRef<OsStr>>(key: K) {
-    _remove_var(key.as_ref())
-}
-
-unsafe fn _remove_var(key: &OsStr) {
-    os_imp::unsetenv(key)
+    let key = key.as_ref();
+    unsafe { os_imp::unsetenv(key) }
         .unwrap_or_else(|e| panic!("failed to remove environment variable `{key:?}`: {e}"))
 }
 
diff --git a/library/std/src/ffi/os_str.rs b/library/std/src/ffi/os_str.rs
index 4a417c84a30a5..f9dba08da4c3c 100644
--- a/library/std/src/ffi/os_str.rs
+++ b/library/std/src/ffi/os_str.rs
@@ -184,7 +184,7 @@ impl OsString {
     #[inline]
     #[stable(feature = "os_str_bytes", since = "1.74.0")]
     pub unsafe fn from_encoded_bytes_unchecked(bytes: Vec<u8>) -> Self {
-        OsString { inner: Buf::from_encoded_bytes_unchecked(bytes) }
+        OsString { inner: unsafe { Buf::from_encoded_bytes_unchecked(bytes) } }
     }
 
     /// Converts to an [`OsStr`] slice.
@@ -813,7 +813,7 @@ impl OsStr {
     #[inline]
     #[stable(feature = "os_str_bytes", since = "1.74.0")]
     pub unsafe fn from_encoded_bytes_unchecked(bytes: &[u8]) -> &Self {
-        Self::from_inner(Slice::from_encoded_bytes_unchecked(bytes))
+        Self::from_inner(unsafe { Slice::from_encoded_bytes_unchecked(bytes) })
     }
 
     #[inline]
diff --git a/library/std/src/io/buffered/bufwriter.rs b/library/std/src/io/buffered/bufwriter.rs
index 1768bb05ddbcb..a8680e9b6ead1 100644
--- a/library/std/src/io/buffered/bufwriter.rs
+++ b/library/std/src/io/buffered/bufwriter.rs
@@ -433,9 +433,11 @@ impl<W: ?Sized + Write> BufWriter<W> {
         let old_len = self.buf.len();
         let buf_len = buf.len();
         let src = buf.as_ptr();
-        let dst = self.buf.as_mut_ptr().add(old_len);
-        ptr::copy_nonoverlapping(src, dst, buf_len);
-        self.buf.set_len(old_len + buf_len);
+        unsafe {
+            let dst = self.buf.as_mut_ptr().add(old_len);
+            ptr::copy_nonoverlapping(src, dst, buf_len);
+            self.buf.set_len(old_len + buf_len);
+        }
     }
 
     #[inline]
diff --git a/library/std/src/io/cursor.rs b/library/std/src/io/cursor.rs
index a1a8b2a3505c7..2ed64a40495ef 100644
--- a/library/std/src/io/cursor.rs
+++ b/library/std/src/io/cursor.rs
@@ -482,7 +482,7 @@ where
     A: Allocator,
 {
     debug_assert!(vec.capacity() >= pos + buf.len());
-    vec.as_mut_ptr().add(pos).copy_from(buf.as_ptr(), buf.len());
+    unsafe { vec.as_mut_ptr().add(pos).copy_from(buf.as_ptr(), buf.len()) };
     pos + buf.len()
 }
 
diff --git a/library/std/src/io/error/repr_bitpacked.rs b/library/std/src/io/error/repr_bitpacked.rs
index a5cefe2292be4..fbb74967df3f1 100644
--- a/library/std/src/io/error/repr_bitpacked.rs
+++ b/library/std/src/io/error/repr_bitpacked.rs
@@ -267,11 +267,14 @@ where
                 // Using this rather than unwrap meaningfully improves the code
                 // for callers which only care about one variant (usually
                 // `Custom`)
-                core::hint::unreachable_unchecked();
+                unsafe { core::hint::unreachable_unchecked() };
             });
             ErrorData::Simple(kind)
         }
-        TAG_SIMPLE_MESSAGE => ErrorData::SimpleMessage(&*ptr.cast::<SimpleMessage>().as_ptr()),
+        TAG_SIMPLE_MESSAGE => {
+            // SAFETY: per tag
+            unsafe { ErrorData::SimpleMessage(&*ptr.cast::<SimpleMessage>().as_ptr()) }
+        }
         TAG_CUSTOM => {
             // It would be correct for us to use `ptr::byte_sub` here (see the
             // comment above the `wrapping_add` call in `new_custom` for why),
diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index b464461277a0f..1345a30361e28 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -382,11 +382,11 @@ pub(crate) unsafe fn append_to_string<F>(buf: &mut String, f: F) -> Result<usize
 where
     F: FnOnce(&mut Vec<u8>) -> Result<usize>,
 {
-    let mut g = Guard { len: buf.len(), buf: buf.as_mut_vec() };
+    let mut g = Guard { len: buf.len(), buf: unsafe { buf.as_mut_vec() } };
     let ret = f(g.buf);
 
     // SAFETY: the caller promises to only append data to `buf`
-    let appended = g.buf.get_unchecked(g.len..);
+    let appended = unsafe { g.buf.get_unchecked(g.len..) };
     if str::from_utf8(appended).is_err() {
         ret.and_then(|_| Err(Error::INVALID_UTF8))
     } else {
diff --git a/library/std/src/lib.rs b/library/std/src/lib.rs
index 66aeb35aceec0..d4d68c2068d8a 100644
--- a/library/std/src/lib.rs
+++ b/library/std/src/lib.rs
@@ -252,6 +252,7 @@
 #![allow(internal_features)]
 #![deny(rustc::existing_doc_keyword)]
 #![deny(fuzzy_provenance_casts)]
+#![deny(unsafe_op_in_unsafe_fn)]
 #![allow(rustdoc::redundant_explicit_links)]
 // Ensure that std can be linked against panic_abort despite compiled with `-C panic=unwind`
 #![deny(ffi_unwind_calls)]
@@ -664,7 +665,7 @@ pub mod alloc;
 mod panicking;
 
 #[path = "../../backtrace/src/lib.rs"]
-#[allow(dead_code, unused_attributes, fuzzy_provenance_casts)]
+#[allow(dead_code, unused_attributes, fuzzy_provenance_casts, unsafe_op_in_unsafe_fn)]
 mod backtrace_rs;
 
 // Re-export macros defined in core.
diff --git a/library/std/src/os/mod.rs b/library/std/src/os/mod.rs
index 455fdd3c34d77..020a8b324f410 100644
--- a/library/std/src/os/mod.rs
+++ b/library/std/src/os/mod.rs
@@ -2,6 +2,7 @@
 
 #![stable(feature = "os", since = "1.0.0")]
 #![allow(missing_docs, nonstandard_style, missing_debug_implementations)]
+#![allow(unsafe_op_in_unsafe_fn)]
 
 pub mod raw;
 
diff --git a/library/std/src/os/windows/io/raw.rs b/library/std/src/os/windows/io/raw.rs
index 770583a9ce3e0..343cc6e4a8a5a 100644
--- a/library/std/src/os/windows/io/raw.rs
+++ b/library/std/src/os/windows/io/raw.rs
@@ -159,10 +159,12 @@ fn stdio_handle(raw: RawHandle) -> RawHandle {
 impl FromRawHandle for fs::File {
     #[inline]
     unsafe fn from_raw_handle(handle: RawHandle) -> fs::File {
-        let handle = handle as sys::c::HANDLE;
-        fs::File::from_inner(sys::fs::File::from_inner(FromInner::from_inner(
-            OwnedHandle::from_raw_handle(handle),
-        )))
+        unsafe {
+            let handle = handle as sys::c::HANDLE;
+            fs::File::from_inner(sys::fs::File::from_inner(FromInner::from_inner(
+                OwnedHandle::from_raw_handle(handle),
+            )))
+        }
     }
 }
 
@@ -260,24 +262,30 @@ impl AsRawSocket for net::UdpSocket {
 impl FromRawSocket for net::TcpStream {
     #[inline]
     unsafe fn from_raw_socket(sock: RawSocket) -> net::TcpStream {
-        let sock = sys::net::Socket::from_inner(OwnedSocket::from_raw_socket(sock));
-        net::TcpStream::from_inner(sys_common::net::TcpStream::from_inner(sock))
+        unsafe {
+            let sock = sys::net::Socket::from_inner(OwnedSocket::from_raw_socket(sock));
+            net::TcpStream::from_inner(sys_common::net::TcpStream::from_inner(sock))
+        }
     }
 }
 #[stable(feature = "from_raw_os", since = "1.1.0")]
 impl FromRawSocket for net::TcpListener {
     #[inline]
     unsafe fn from_raw_socket(sock: RawSocket) -> net::TcpListener {
-        let sock = sys::net::Socket::from_inner(OwnedSocket::from_raw_socket(sock));
-        net::TcpListener::from_inner(sys_common::net::TcpListener::from_inner(sock))
+        unsafe {
+            let sock = sys::net::Socket::from_inner(OwnedSocket::from_raw_socket(sock));
+            net::TcpListener::from_inner(sys_common::net::TcpListener::from_inner(sock))
+        }
     }
 }
 #[stable(feature = "from_raw_os", since = "1.1.0")]
 impl FromRawSocket for net::UdpSocket {
     #[inline]
     unsafe fn from_raw_socket(sock: RawSocket) -> net::UdpSocket {
-        let sock = sys::net::Socket::from_inner(OwnedSocket::from_raw_socket(sock));
-        net::UdpSocket::from_inner(sys_common::net::UdpSocket::from_inner(sock))
+        unsafe {
+            let sock = sys::net::Socket::from_inner(OwnedSocket::from_raw_socket(sock));
+            net::UdpSocket::from_inner(sys_common::net::UdpSocket::from_inner(sock))
+        }
     }
 }
 
diff --git a/library/std/src/os/windows/io/socket.rs b/library/std/src/os/windows/io/socket.rs
index 6ffdf907c8ed3..4334d041439d9 100644
--- a/library/std/src/os/windows/io/socket.rs
+++ b/library/std/src/os/windows/io/socket.rs
@@ -76,7 +76,7 @@ impl BorrowedSocket<'_> {
     #[stable(feature = "io_safety", since = "1.63.0")]
     pub const unsafe fn borrow_raw(socket: RawSocket) -> Self {
         assert!(socket != sys::c::INVALID_SOCKET as RawSocket);
-        Self { socket, _phantom: PhantomData }
+        unsafe { Self { socket, _phantom: PhantomData } }
     }
 }
 
@@ -201,8 +201,10 @@ impl IntoRawSocket for OwnedSocket {
 impl FromRawSocket for OwnedSocket {
     #[inline]
     unsafe fn from_raw_socket(socket: RawSocket) -> Self {
-        debug_assert_ne!(socket, sys::c::INVALID_SOCKET as RawSocket);
-        Self { socket }
+        unsafe {
+            debug_assert_ne!(socket, sys::c::INVALID_SOCKET as RawSocket);
+            Self { socket }
+        }
     }
 }
 
diff --git a/library/std/src/os/windows/mod.rs b/library/std/src/os/windows/mod.rs
index 52eb3b7c06769..f452403ee8426 100644
--- a/library/std/src/os/windows/mod.rs
+++ b/library/std/src/os/windows/mod.rs
@@ -24,6 +24,7 @@
 
 #![stable(feature = "rust1", since = "1.0.0")]
 #![doc(cfg(windows))]
+#![deny(unsafe_op_in_unsafe_fn)]
 
 pub mod ffi;
 pub mod fs;
diff --git a/library/std/src/os/windows/process.rs b/library/std/src/os/windows/process.rs
index 05ffb8925a1f0..3927b2ed9bb5c 100644
--- a/library/std/src/os/windows/process.rs
+++ b/library/std/src/os/windows/process.rs
@@ -16,7 +16,7 @@ use crate::sys_common::{AsInner, AsInnerMut, FromInner, IntoInner};
 #[stable(feature = "process_extensions", since = "1.2.0")]
 impl FromRawHandle for process::Stdio {
     unsafe fn from_raw_handle(handle: RawHandle) -> process::Stdio {
-        let handle = sys::handle::Handle::from_raw_handle(handle as *mut _);
+        let handle = unsafe { sys::handle::Handle::from_raw_handle(handle as *mut _) };
         let io = sys::process::Stdio::Handle(handle);
         process::Stdio::from_inner(io)
     }
@@ -407,7 +407,7 @@ impl CommandExt for process::Command {
         attribute: usize,
         value: T,
     ) -> &mut process::Command {
-        self.as_inner_mut().raw_attribute(attribute, value);
+        unsafe { self.as_inner_mut().raw_attribute(attribute, value) };
         self
     }
 }
diff --git a/library/std/src/process/tests.rs b/library/std/src/process/tests.rs
index b4f6bb71c79c4..055601d030799 100644
--- a/library/std/src/process/tests.rs
+++ b/library/std/src/process/tests.rs
@@ -385,29 +385,25 @@ fn test_interior_nul_in_env_value_is_error() {
 #[cfg(windows)]
 fn test_creation_flags() {
     use crate::os::windows::process::CommandExt;
-    use crate::sys::c::{BOOL, DWORD, INFINITE};
+    use crate::sys::c::{BOOL, INFINITE};
     #[repr(C)]
     struct DEBUG_EVENT {
-        pub event_code: DWORD,
-        pub process_id: DWORD,
-        pub thread_id: DWORD,
+        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: DWORD) -> BOOL;
-        fn ContinueDebugEvent(
-            dwProcessId: DWORD,
-            dwThreadId: DWORD,
-            dwContinueStatus: DWORD,
-        ) -> BOOL;
+        fn WaitForDebugEvent(lpDebugEvent: *mut DEBUG_EVENT, dwMilliseconds: u32) -> BOOL;
+        fn ContinueDebugEvent(dwProcessId: u32, dwThreadId: u32, dwContinueStatus: u32) -> BOOL;
     }
 
-    const DEBUG_PROCESS: DWORD = 1;
-    const EXIT_PROCESS_DEBUG_EVENT: DWORD = 5;
-    const DBG_EXCEPTION_NOT_HANDLED: DWORD = 0x80010001;
+    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();
diff --git a/library/std/src/sync/mpmc/array.rs b/library/std/src/sync/mpmc/array.rs
index 492e21d9bdb63..185319add745f 100644
--- a/library/std/src/sync/mpmc/array.rs
+++ b/library/std/src/sync/mpmc/array.rs
@@ -200,11 +200,12 @@ impl<T> Channel<T> {
             return Err(msg);
         }
 
-        let slot: &Slot<T> = &*(token.array.slot as *const Slot<T>);
-
         // Write the message into the slot and update the stamp.
-        slot.msg.get().write(MaybeUninit::new(msg));
-        slot.stamp.store(token.array.stamp, Ordering::Release);
+        unsafe {
+            let slot: &Slot<T> = &*(token.array.slot as *const Slot<T>);
+            slot.msg.get().write(MaybeUninit::new(msg));
+            slot.stamp.store(token.array.stamp, Ordering::Release);
+        }
 
         // Wake a sleeping receiver.
         self.receivers.notify();
@@ -291,11 +292,14 @@ impl<T> Channel<T> {
             return Err(());
         }
 
-        let slot: &Slot<T> = &*(token.array.slot as *const Slot<T>);
-
         // Read the message from the slot and update the stamp.
-        let msg = slot.msg.get().read().assume_init();
-        slot.stamp.store(token.array.stamp, Ordering::Release);
+        let msg = unsafe {
+            let slot: &Slot<T> = &*(token.array.slot as *const Slot<T>);
+
+            let msg = slot.msg.get().read().assume_init();
+            slot.stamp.store(token.array.stamp, Ordering::Release);
+            msg
+        };
 
         // Wake a sleeping sender.
         self.senders.notify();
@@ -471,7 +475,7 @@ impl<T> Channel<T> {
             false
         };
 
-        self.discard_all_messages(tail);
+        unsafe { self.discard_all_messages(tail) };
         disconnected
     }
 
diff --git a/library/std/src/sync/mpmc/counter.rs b/library/std/src/sync/mpmc/counter.rs
index a5a6bdc67f13f..3478cf41dc9d2 100644
--- a/library/std/src/sync/mpmc/counter.rs
+++ b/library/std/src/sync/mpmc/counter.rs
@@ -63,7 +63,7 @@ impl<C> Sender<C> {
             disconnect(&self.counter().chan);
 
             if self.counter().destroy.swap(true, Ordering::AcqRel) {
-                drop(Box::from_raw(self.counter));
+                drop(unsafe { Box::from_raw(self.counter) });
             }
         }
     }
@@ -116,7 +116,7 @@ impl<C> Receiver<C> {
             disconnect(&self.counter().chan);
 
             if self.counter().destroy.swap(true, Ordering::AcqRel) {
-                drop(Box::from_raw(self.counter));
+                drop(unsafe { Box::from_raw(self.counter) });
             }
         }
     }
diff --git a/library/std/src/sync/mpmc/list.rs b/library/std/src/sync/mpmc/list.rs
index 9e7148c716cda..edac7a0cb1835 100644
--- a/library/std/src/sync/mpmc/list.rs
+++ b/library/std/src/sync/mpmc/list.rs
@@ -91,7 +91,7 @@ impl<T> Block<T> {
         // It is not necessary to set the `DESTROY` bit in the last slot because that slot has
         // begun destruction of the block.
         for i in start..BLOCK_CAP - 1 {
-            let slot = (*this).slots.get_unchecked(i);
+            let slot = unsafe { (*this).slots.get_unchecked(i) };
 
             // Mark the `DESTROY` bit if a thread is still using the slot.
             if slot.state.load(Ordering::Acquire) & READ == 0
@@ -103,7 +103,7 @@ impl<T> Block<T> {
         }
 
         // No thread is using the block, now it is safe to destroy it.
-        drop(Box::from_raw(this));
+        drop(unsafe { Box::from_raw(this) });
     }
 }
 
@@ -265,9 +265,11 @@ impl<T> Channel<T> {
         // Write the message into the slot.
         let block = token.list.block as *mut Block<T>;
         let offset = token.list.offset;
-        let slot = (*block).slots.get_unchecked(offset);
-        slot.msg.get().write(MaybeUninit::new(msg));
-        slot.state.fetch_or(WRITE, Ordering::Release);
+        unsafe {
+            let slot = (*block).slots.get_unchecked(offset);
+            slot.msg.get().write(MaybeUninit::new(msg));
+            slot.state.fetch_or(WRITE, Ordering::Release);
+        }
 
         // Wake a sleeping receiver.
         self.receivers.notify();
@@ -369,19 +371,21 @@ impl<T> Channel<T> {
         // Read the message.
         let block = token.list.block as *mut Block<T>;
         let offset = token.list.offset;
-        let slot = (*block).slots.get_unchecked(offset);
-        slot.wait_write();
-        let msg = slot.msg.get().read().assume_init();
-
-        // Destroy the block if we've reached the end, or if another thread wanted to destroy but
-        // couldn't because we were busy reading from the slot.
-        if offset + 1 == BLOCK_CAP {
-            Block::destroy(block, 0);
-        } else if slot.state.fetch_or(READ, Ordering::AcqRel) & DESTROY != 0 {
-            Block::destroy(block, offset + 1);
-        }
+        unsafe {
+            let slot = (*block).slots.get_unchecked(offset);
+            slot.wait_write();
+            let msg = slot.msg.get().read().assume_init();
+
+            // Destroy the block if we've reached the end, or if another thread wanted to destroy but
+            // couldn't because we were busy reading from the slot.
+            if offset + 1 == BLOCK_CAP {
+                Block::destroy(block, 0);
+            } else if slot.state.fetch_or(READ, Ordering::AcqRel) & DESTROY != 0 {
+                Block::destroy(block, offset + 1);
+            }
 
-        Ok(msg)
+            Ok(msg)
+        }
     }
 
     /// Attempts to send a message into the channel.
diff --git a/library/std/src/sync/mpmc/zero.rs b/library/std/src/sync/mpmc/zero.rs
index 1b82713edc748..6d1c9d64e7a7a 100644
--- a/library/std/src/sync/mpmc/zero.rs
+++ b/library/std/src/sync/mpmc/zero.rs
@@ -103,9 +103,11 @@ impl<T> Channel<T> {
             return Err(msg);
         }
 
-        let packet = &*(token.zero.0 as *const Packet<T>);
-        packet.msg.get().write(Some(msg));
-        packet.ready.store(true, Ordering::Release);
+        unsafe {
+            let packet = &*(token.zero.0 as *const Packet<T>);
+            packet.msg.get().write(Some(msg));
+            packet.ready.store(true, Ordering::Release);
+        }
         Ok(())
     }
 
@@ -116,22 +118,24 @@ impl<T> Channel<T> {
             return Err(());
         }
 
-        let packet = &*(token.zero.0 as *const Packet<T>);
+        let packet = unsafe { &*(token.zero.0 as *const Packet<T>) };
 
         if packet.on_stack {
             // The message has been in the packet from the beginning, so there is no need to wait
             // for it. However, after reading the message, we need to set `ready` to `true` in
             // order to signal that the packet can be destroyed.
-            let msg = packet.msg.get().replace(None).unwrap();
+            let msg = unsafe { packet.msg.get().replace(None) }.unwrap();
             packet.ready.store(true, Ordering::Release);
             Ok(msg)
         } else {
             // Wait until the message becomes available, then read it and destroy the
             // heap-allocated packet.
             packet.wait_ready();
-            let msg = packet.msg.get().replace(None).unwrap();
-            drop(Box::from_raw(token.zero.0 as *mut Packet<T>));
-            Ok(msg)
+            unsafe {
+                let msg = packet.msg.get().replace(None).unwrap();
+                drop(Box::from_raw(token.zero.0 as *mut Packet<T>));
+                Ok(msg)
+            }
         }
     }
 
diff --git a/library/std/src/sync/once_lock.rs b/library/std/src/sync/once_lock.rs
index fe243550606f3..94955beaf37b7 100644
--- a/library/std/src/sync/once_lock.rs
+++ b/library/std/src/sync/once_lock.rs
@@ -502,7 +502,7 @@ impl<T> OnceLock<T> {
     #[inline]
     unsafe fn get_unchecked(&self) -> &T {
         debug_assert!(self.is_initialized());
-        (&*self.value.get()).assume_init_ref()
+        unsafe { (&*self.value.get()).assume_init_ref() }
     }
 
     /// # Safety
@@ -511,7 +511,7 @@ impl<T> OnceLock<T> {
     #[inline]
     unsafe fn get_unchecked_mut(&mut self) -> &mut T {
         debug_assert!(self.is_initialized());
-        (&mut *self.value.get()).assume_init_mut()
+        unsafe { (&mut *self.value.get()).assume_init_mut() }
     }
 }
 
diff --git a/library/std/src/sync/reentrant_lock.rs b/library/std/src/sync/reentrant_lock.rs
index f7fe8eb1c7fd5..042c439394e06 100644
--- a/library/std/src/sync/reentrant_lock.rs
+++ b/library/std/src/sync/reentrant_lock.rs
@@ -244,7 +244,9 @@ impl<T: ?Sized> ReentrantLock<T> {
     }
 
     unsafe fn increment_lock_count(&self) -> Option<()> {
-        *self.lock_count.get() = (*self.lock_count.get()).checked_add(1)?;
+        unsafe {
+            *self.lock_count.get() = (*self.lock_count.get()).checked_add(1)?;
+        }
         Some(())
     }
 }
diff --git a/library/std/src/sync/rwlock.rs b/library/std/src/sync/rwlock.rs
index e0a8a7603d71a..a4ec52a4abe63 100644
--- a/library/std/src/sync/rwlock.rs
+++ b/library/std/src/sync/rwlock.rs
@@ -578,7 +578,7 @@ impl<'rwlock, T: ?Sized> RwLockReadGuard<'rwlock, T> {
     // successfully called from the same thread before instantiating this object.
     unsafe fn new(lock: &'rwlock RwLock<T>) -> LockResult<RwLockReadGuard<'rwlock, T>> {
         poison::map_result(lock.poison.borrow(), |()| RwLockReadGuard {
-            data: NonNull::new_unchecked(lock.data.get()),
+            data: unsafe { NonNull::new_unchecked(lock.data.get()) },
             inner_lock: &lock.inner,
         })
     }
diff --git a/library/std/src/sys/mod.rs b/library/std/src/sys/mod.rs
index 4092e6080d548..e50758ce00d8b 100644
--- a/library/std/src/sys/mod.rs
+++ b/library/std/src/sys/mod.rs
@@ -1,3 +1,5 @@
+#![allow(unsafe_op_in_unsafe_fn)]
+
 /// The PAL (platform abstraction layer) contains platform-specific abstractions
 /// for implementing the features in the other submodules, e.g. UNIX file
 /// descriptors.
diff --git a/library/std/src/sys/pal/windows/alloc.rs b/library/std/src/sys/pal/windows/alloc.rs
index e6cbdb6ef7d64..9f0194492b0a3 100644
--- a/library/std/src/sys/pal/windows/alloc.rs
+++ b/library/std/src/sys/pal/windows/alloc.rs
@@ -15,7 +15,7 @@ mod tests;
 // See https://docs.microsoft.com/windows/win32/api/heapapi/
 
 // Flag to indicate that the memory returned by `HeapAlloc` should be zeroed.
-const HEAP_ZERO_MEMORY: c::DWORD = 0x00000008;
+const HEAP_ZERO_MEMORY: u32 = 0x00000008;
 
 // Get a handle to the default heap of the current process, or null if the operation fails.
 //
@@ -113,9 +113,9 @@ fn init_or_get_process_heap() -> c::HANDLE {
 #[cold]
 extern "C" fn process_heap_init_and_alloc(
     _heap: MaybeUninit<c::HANDLE>, // We pass this argument to match the ABI of `HeapAlloc`
-    flags: c::DWORD,
-    dwBytes: c::SIZE_T,
-) -> c::LPVOID {
+    flags: u32,
+    dwBytes: usize,
+) -> *mut c_void {
     let heap = init_or_get_process_heap();
     if core::intrinsics::unlikely(heap.is_null()) {
         return ptr::null_mut();
@@ -127,9 +127,9 @@ extern "C" fn process_heap_init_and_alloc(
 #[inline(never)]
 fn process_heap_alloc(
     _heap: MaybeUninit<c::HANDLE>, // We pass this argument to match the ABI of `HeapAlloc`,
-    flags: c::DWORD,
-    dwBytes: c::SIZE_T,
-) -> c::LPVOID {
+    flags: u32,
+    dwBytes: usize,
+) -> *mut c_void {
     let heap = HEAP.load(Ordering::Relaxed);
     if core::intrinsics::likely(!heap.is_null()) {
         // SAFETY: `heap` is a non-null handle returned by `GetProcessHeap`.
@@ -240,7 +240,7 @@ unsafe impl GlobalAlloc for System {
 
         // SAFETY: `heap` is a non-null handle returned by `GetProcessHeap`,
         // `block` is a pointer to the start of an allocated block.
-        unsafe { HeapFree(heap, 0, block as c::LPVOID) };
+        unsafe { HeapFree(heap, 0, block.cast::<c_void>()) };
     }
 
     #[inline]
@@ -253,7 +253,7 @@ unsafe impl GlobalAlloc for System {
             // SAFETY: `heap` is a non-null handle returned by `GetProcessHeap`,
             // `ptr` is a pointer to the start of an allocated block.
             // The returned pointer points to the start of an allocated block.
-            unsafe { HeapReAlloc(heap, 0, ptr as c::LPVOID, new_size) as *mut u8 }
+            unsafe { HeapReAlloc(heap, 0, ptr.cast::<c_void>(), new_size).cast::<u8>() }
         } else {
             // SAFETY: `realloc_fallback` is implemented using `dealloc` and `alloc`, which will
             // correctly handle `ptr` and return a pointer satisfying the guarantees of `System`
diff --git a/library/std/src/sys/pal/windows/api.rs b/library/std/src/sys/pal/windows/api.rs
index 17a0e47ad5950..00c816a6c09b8 100644
--- a/library/std/src/sys/pal/windows/api.rs
+++ b/library/std/src/sys/pal/windows/api.rs
@@ -227,8 +227,10 @@ pub fn set_file_information_by_handle<T: SetFileInformation>(
         info: *const c_void,
         size: u32,
     ) -> Result<(), WinError> {
-        let result = c::SetFileInformationByHandle(handle, class, info, size);
-        (result != 0).then_some(()).ok_or_else(get_last_error)
+        unsafe {
+            let result = c::SetFileInformationByHandle(handle, class, info, size);
+            (result != 0).then_some(()).ok_or_else(get_last_error)
+        }
     }
     // SAFETY: The `SetFileInformation` trait ensures that this is safe.
     unsafe { set_info(handle, T::CLASS, info.as_ptr(), info.size()) }
diff --git a/library/std/src/sys/pal/windows/c.rs b/library/std/src/sys/pal/windows/c.rs
index 7dfda4f714c77..296d19a926d96 100644
--- a/library/std/src/sys/pal/windows/c.rs
+++ b/library/std/src/sys/pal/windows/c.rs
@@ -4,12 +4,11 @@
 #![cfg_attr(test, allow(dead_code))]
 #![unstable(issue = "none", feature = "windows_c")]
 #![allow(clippy::style)]
+#![allow(unsafe_op_in_unsafe_fn)]
 
 use crate::ffi::CStr;
 use crate::mem;
-use crate::num::NonZero;
-pub use crate::os::raw::c_int;
-use crate::os::raw::{c_char, c_long, c_longlong, c_uint, c_ulong, c_ushort, c_void};
+use crate::os::raw::{c_char, c_int, c_uint, c_ulong, c_ushort, c_void};
 use crate::os::windows::io::{AsRawHandle, BorrowedHandle};
 use crate::ptr;
 
@@ -18,30 +17,10 @@ pub(super) mod windows_targets;
 mod windows_sys;
 pub use windows_sys::*;
 
-pub type DWORD = c_ulong;
-pub type NonZeroDWORD = NonZero<c_ulong>;
-pub type LARGE_INTEGER = c_longlong;
-#[cfg_attr(target_vendor = "uwp", allow(unused))]
-pub type LONG = c_long;
-pub type UINT = c_uint;
 pub type WCHAR = u16;
-pub type USHORT = c_ushort;
-pub type SIZE_T = usize;
-pub type CHAR = c_char;
-pub type ULONG = c_ulong;
-
-pub type LPCVOID = *const c_void;
-pub type LPOVERLAPPED = *mut OVERLAPPED;
-pub type LPSECURITY_ATTRIBUTES = *mut SECURITY_ATTRIBUTES;
-pub type LPVOID = *mut c_void;
-pub type LPWCH = *mut WCHAR;
-pub type LPWSTR = *mut WCHAR;
-
-#[cfg(target_vendor = "win7")]
-pub type PSRWLOCK = *mut SRWLOCK;
 
 pub type socklen_t = c_int;
-pub type ADDRESS_FAMILY = USHORT;
+pub type ADDRESS_FAMILY = c_ushort;
 pub use FD_SET as fd_set;
 pub use LINGER as linger;
 pub use TIMEVAL as timeval;
@@ -151,25 +130,25 @@ pub struct MOUNT_POINT_REPARSE_BUFFER {
 #[repr(C)]
 pub struct SOCKADDR_STORAGE_LH {
     pub ss_family: ADDRESS_FAMILY,
-    pub __ss_pad1: [CHAR; 6],
+    pub __ss_pad1: [c_char; 6],
     pub __ss_align: i64,
-    pub __ss_pad2: [CHAR; 112],
+    pub __ss_pad2: [c_char; 112],
 }
 
 #[repr(C)]
 #[derive(Copy, Clone)]
 pub struct sockaddr_in {
     pub sin_family: ADDRESS_FAMILY,
-    pub sin_port: USHORT,
+    pub sin_port: c_ushort,
     pub sin_addr: in_addr,
-    pub sin_zero: [CHAR; 8],
+    pub sin_zero: [c_char; 8],
 }
 
 #[repr(C)]
 #[derive(Copy, Clone)]
 pub struct sockaddr_in6 {
     pub sin6_family: ADDRESS_FAMILY,
-    pub sin6_port: USHORT,
+    pub sin6_port: c_ushort,
     pub sin6_flowinfo: c_ulong,
     pub sin6_addr: in6_addr,
     pub sin6_scope_id: c_ulong,
@@ -271,9 +250,9 @@ pub unsafe fn NtReadFile(
     apccontext: *mut c_void,
     iostatusblock: &mut IO_STATUS_BLOCK,
     buffer: *mut crate::mem::MaybeUninit<u8>,
-    length: ULONG,
-    byteoffset: Option<&LARGE_INTEGER>,
-    key: Option<&ULONG>,
+    length: u32,
+    byteoffset: Option<&i64>,
+    key: Option<&u32>,
 ) -> NTSTATUS {
     windows_sys::NtReadFile(
         filehandle.as_raw_handle(),
@@ -294,9 +273,9 @@ pub unsafe fn NtWriteFile(
     apccontext: *mut c_void,
     iostatusblock: &mut IO_STATUS_BLOCK,
     buffer: *const u8,
-    length: ULONG,
-    byteoffset: Option<&LARGE_INTEGER>,
-    key: Option<&ULONG>,
+    length: u32,
+    byteoffset: Option<&i64>,
+    key: Option<&u32>,
 ) -> NTSTATUS {
     windows_sys::NtWriteFile(
         filehandle.as_raw_handle(),
@@ -336,13 +315,13 @@ compat_fn_with_fallback! {
     // >= Win10 1607
     // https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-setthreaddescription
     pub fn SetThreadDescription(hthread: HANDLE, lpthreaddescription: PCWSTR) -> HRESULT {
-        SetLastError(ERROR_CALL_NOT_IMPLEMENTED as DWORD); E_NOTIMPL
+        SetLastError(ERROR_CALL_NOT_IMPLEMENTED as u32); E_NOTIMPL
     }
 
     // >= Win10 1607
     // https://docs.microsoft.com/en-us/windows/win32/api/processthreadsapi/nf-processthreadsapi-getthreaddescription
     pub fn GetThreadDescription(hthread: HANDLE, lpthreaddescription: *mut PWSTR) -> HRESULT {
-        SetLastError(ERROR_CALL_NOT_IMPLEMENTED as DWORD); E_NOTIMPL
+        SetLastError(ERROR_CALL_NOT_IMPLEMENTED as u32); E_NOTIMPL
     }
 
     // >= Win8 / Server 2012
@@ -403,27 +382,27 @@ compat_fn_with_fallback! {
     #[cfg(target_vendor = "win7")]
     pub fn NtCreateKeyedEvent(
         KeyedEventHandle: *mut HANDLE,
-        DesiredAccess: DWORD,
-        ObjectAttributes: LPVOID,
-        Flags: ULONG
+        DesiredAccess: u32,
+        ObjectAttributes: *mut c_void,
+        Flags: u32
     ) -> NTSTATUS {
         panic!("keyed events not available")
     }
     #[cfg(target_vendor = "win7")]
     pub fn NtReleaseKeyedEvent(
         EventHandle: HANDLE,
-        Key: LPVOID,
+        Key: *const c_void,
         Alertable: BOOLEAN,
-        Timeout: *mut c_longlong
+        Timeout: *mut i64
     ) -> NTSTATUS {
         panic!("keyed events not available")
     }
     #[cfg(target_vendor = "win7")]
     pub fn NtWaitForKeyedEvent(
         EventHandle: HANDLE,
-        Key: LPVOID,
+        Key: *const c_void,
         Alertable: BOOLEAN,
-        Timeout: *mut c_longlong
+        Timeout: *mut i64
     ) -> NTSTATUS {
         panic!("keyed events not available")
     }
@@ -453,9 +432,9 @@ compat_fn_with_fallback! {
         apccontext: *mut c_void,
         iostatusblock: &mut IO_STATUS_BLOCK,
         buffer: *mut crate::mem::MaybeUninit<u8>,
-        length: ULONG,
-        byteoffset: Option<&LARGE_INTEGER>,
-        key: Option<&ULONG>
+        length: u32,
+        byteoffset: Option<&i64>,
+        key: Option<&u32>
     ) -> NTSTATUS {
         STATUS_NOT_IMPLEMENTED
     }
@@ -467,9 +446,9 @@ compat_fn_with_fallback! {
         apccontext: *mut c_void,
         iostatusblock: &mut IO_STATUS_BLOCK,
         buffer: *const u8,
-        length: ULONG,
-        byteoffset: Option<&LARGE_INTEGER>,
-        key: Option<&ULONG>
+        length: u32,
+        byteoffset: Option<&i64>,
+        key: Option<&u32>
     ) -> NTSTATUS {
         STATUS_NOT_IMPLEMENTED
     }
diff --git a/library/std/src/sys/pal/windows/compat.rs b/library/std/src/sys/pal/windows/compat.rs
index f5d57a28db69a..49fa1603f3e1e 100644
--- a/library/std/src/sys/pal/windows/compat.rs
+++ b/library/std/src/sys/pal/windows/compat.rs
@@ -112,8 +112,10 @@ impl Module {
     /// (e.g. kernel32 and ntdll).
     pub unsafe fn new(name: &CStr) -> Option<Self> {
         // SAFETY: A CStr is always null terminated.
-        let module = c::GetModuleHandleA(name.as_ptr().cast::<u8>());
-        NonNull::new(module).map(Self)
+        unsafe {
+            let module = c::GetModuleHandleA(name.as_ptr().cast::<u8>());
+            NonNull::new(module).map(Self)
+        }
     }
 
     // Try to get the address of a function.
diff --git a/library/std/src/sys/pal/windows/fs.rs b/library/std/src/sys/pal/windows/fs.rs
index cc68f5ef5f08c..85fd9153d5370 100644
--- a/library/std/src/sys/pal/windows/fs.rs
+++ b/library/std/src/sys/pal/windows/fs.rs
@@ -1,3 +1,4 @@
+#![allow(unsafe_op_in_unsafe_fn)]
 use core::ptr::addr_of;
 
 use crate::os::windows::prelude::*;
@@ -28,12 +29,12 @@ pub struct File {
 
 #[derive(Clone)]
 pub struct FileAttr {
-    attributes: c::DWORD,
+    attributes: u32,
     creation_time: c::FILETIME,
     last_access_time: c::FILETIME,
     last_write_time: c::FILETIME,
     file_size: u64,
-    reparse_tag: c::DWORD,
+    reparse_tag: u32,
     volume_serial_number: Option<u32>,
     number_of_links: Option<u32>,
     file_index: Option<u64>,
@@ -41,8 +42,8 @@ pub struct FileAttr {
 
 #[derive(Copy, Clone, PartialEq, Eq, Hash, Debug)]
 pub struct FileType {
-    attributes: c::DWORD,
-    reparse_tag: c::DWORD,
+    attributes: u32,
+    reparse_tag: u32,
 }
 
 pub struct ReadDir {
@@ -75,16 +76,16 @@ pub struct OpenOptions {
     create_new: bool,
     // system-specific
     custom_flags: u32,
-    access_mode: Option<c::DWORD>,
-    attributes: c::DWORD,
-    share_mode: c::DWORD,
-    security_qos_flags: c::DWORD,
-    security_attributes: c::LPSECURITY_ATTRIBUTES,
+    access_mode: Option<u32>,
+    attributes: u32,
+    share_mode: u32,
+    security_qos_flags: u32,
+    security_attributes: *mut c::SECURITY_ATTRIBUTES,
 }
 
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct FilePermissions {
-    attrs: c::DWORD,
+    attrs: u32,
 }
 
 #[derive(Copy, Clone, Debug, Default)]
@@ -241,11 +242,11 @@ impl OpenOptions {
         // receive is `SECURITY_ANONYMOUS = 0x0`, which we can't check for later on.
         self.security_qos_flags = flags | c::SECURITY_SQOS_PRESENT;
     }
-    pub fn security_attributes(&mut self, attrs: c::LPSECURITY_ATTRIBUTES) {
+    pub fn security_attributes(&mut self, attrs: *mut c::SECURITY_ATTRIBUTES) {
         self.security_attributes = attrs;
     }
 
-    fn get_access_mode(&self) -> io::Result<c::DWORD> {
+    fn get_access_mode(&self) -> io::Result<u32> {
         match (self.read, self.write, self.append, self.access_mode) {
             (.., Some(mode)) => Ok(mode),
             (true, false, false, None) => Ok(c::GENERIC_READ),
@@ -261,7 +262,7 @@ impl OpenOptions {
         }
     }
 
-    fn get_creation_mode(&self) -> io::Result<c::DWORD> {
+    fn get_creation_mode(&self) -> io::Result<u32> {
         match (self.write, self.append) {
             (true, false) => {}
             (false, false) => {
@@ -287,7 +288,7 @@ impl OpenOptions {
         })
     }
 
-    fn get_flags_and_attributes(&self) -> c::DWORD {
+    fn get_flags_and_attributes(&self) -> u32 {
         self.custom_flags
             | self.attributes
             | self.security_qos_flags
@@ -397,21 +398,21 @@ impl File {
                 self.handle.as_raw_handle(),
                 c::FileBasicInfo,
                 core::ptr::addr_of_mut!(info) as *mut c_void,
-                size as c::DWORD,
+                size as u32,
             ))?;
             let mut attr = FileAttr {
                 attributes: info.FileAttributes,
                 creation_time: c::FILETIME {
-                    dwLowDateTime: info.CreationTime as c::DWORD,
-                    dwHighDateTime: (info.CreationTime >> 32) as c::DWORD,
+                    dwLowDateTime: info.CreationTime as u32,
+                    dwHighDateTime: (info.CreationTime >> 32) as u32,
                 },
                 last_access_time: c::FILETIME {
-                    dwLowDateTime: info.LastAccessTime as c::DWORD,
-                    dwHighDateTime: (info.LastAccessTime >> 32) as c::DWORD,
+                    dwLowDateTime: info.LastAccessTime as u32,
+                    dwHighDateTime: (info.LastAccessTime >> 32) as u32,
                 },
                 last_write_time: c::FILETIME {
-                    dwLowDateTime: info.LastWriteTime as c::DWORD,
-                    dwHighDateTime: (info.LastWriteTime >> 32) as c::DWORD,
+                    dwLowDateTime: info.LastWriteTime as u32,
+                    dwHighDateTime: (info.LastWriteTime >> 32) as u32,
                 },
                 file_size: 0,
                 reparse_tag: 0,
@@ -425,7 +426,7 @@ impl File {
                 self.handle.as_raw_handle(),
                 c::FileStandardInfo,
                 core::ptr::addr_of_mut!(info) as *mut c_void,
-                size as c::DWORD,
+                size as u32,
             ))?;
             attr.file_size = info.AllocationSize as u64;
             attr.number_of_links = Some(info.NumberOfLinks);
@@ -495,7 +496,7 @@ impl File {
             SeekFrom::End(n) => (c::FILE_END, n),
             SeekFrom::Current(n) => (c::FILE_CURRENT, n),
         };
-        let pos = pos as c::LARGE_INTEGER;
+        let pos = pos as i64;
         let mut newpos = 0;
         cvt(unsafe { c::SetFilePointerEx(self.handle.as_raw_handle(), pos, &mut newpos, whence) })?;
         Ok(newpos as u64)
@@ -511,7 +512,7 @@ impl File {
     fn reparse_point(
         &self,
         space: &mut Align8<[MaybeUninit<u8>]>,
-    ) -> io::Result<(c::DWORD, *mut c::REPARSE_DATA_BUFFER)> {
+    ) -> io::Result<(u32, *mut c::REPARSE_DATA_BUFFER)> {
         unsafe {
             let mut bytes = 0;
             cvt({
@@ -524,7 +525,7 @@ impl File {
                     ptr::null_mut(),
                     0,
                     space.0.as_mut_ptr().cast(),
-                    len as c::DWORD,
+                    len as u32,
                     &mut bytes,
                     ptr::null_mut(),
                 )
@@ -609,8 +610,7 @@ impl File {
                 "Cannot set file timestamp to 0",
             ));
         }
-        let is_max =
-            |t: c::FILETIME| t.dwLowDateTime == c::DWORD::MAX && t.dwHighDateTime == c::DWORD::MAX;
+        let is_max = |t: c::FILETIME| t.dwLowDateTime == u32::MAX && t.dwHighDateTime == u32::MAX;
         if times.accessed.map_or(false, is_max)
             || times.modified.map_or(false, is_max)
             || times.created.map_or(false, is_max)
@@ -641,7 +641,7 @@ impl File {
                 self.handle.as_raw_handle(),
                 c::FileBasicInfo,
                 core::ptr::addr_of_mut!(info) as *mut c_void,
-                size as c::DWORD,
+                size as u32,
             ))?;
             Ok(info)
         }
@@ -1020,7 +1020,7 @@ impl FileTimes {
 }
 
 impl FileType {
-    fn new(attrs: c::DWORD, reparse_tag: c::DWORD) -> FileType {
+    fn new(attrs: u32, reparse_tag: u32) -> FileType {
         FileType { attributes: attrs, reparse_tag }
     }
     pub fn is_dir(&self) -> bool {
@@ -1417,16 +1417,16 @@ pub fn canonicalize(p: &Path) -> io::Result<PathBuf> {
 
 pub fn copy(from: &Path, to: &Path) -> io::Result<u64> {
     unsafe extern "system" fn callback(
-        _TotalFileSize: c::LARGE_INTEGER,
-        _TotalBytesTransferred: c::LARGE_INTEGER,
-        _StreamSize: c::LARGE_INTEGER,
-        StreamBytesTransferred: c::LARGE_INTEGER,
-        dwStreamNumber: c::DWORD,
-        _dwCallbackReason: c::DWORD,
+        _TotalFileSize: i64,
+        _TotalBytesTransferred: i64,
+        _StreamSize: i64,
+        StreamBytesTransferred: i64,
+        dwStreamNumber: u32,
+        _dwCallbackReason: u32,
         _hSourceFile: c::HANDLE,
         _hDestinationFile: c::HANDLE,
-        lpData: c::LPCVOID,
-    ) -> c::DWORD {
+        lpData: *const c_void,
+    ) -> u32 {
         if dwStreamNumber == 1 {
             *(lpData as *mut i64) = StreamBytesTransferred;
         }
diff --git a/library/std/src/sys/pal/windows/handle.rs b/library/std/src/sys/pal/windows/handle.rs
index 3f85bb0a099a9..ae9ea8ff584ef 100644
--- a/library/std/src/sys/pal/windows/handle.rs
+++ b/library/std/src/sys/pal/windows/handle.rs
@@ -1,4 +1,5 @@
 #![unstable(issue = "none", feature = "windows_handle")]
+#![allow(unsafe_op_in_unsafe_fn)]
 
 #[cfg(test)]
 mod tests;
@@ -141,7 +142,7 @@ impl Handle {
         buf: &mut [u8],
         overlapped: *mut c::OVERLAPPED,
     ) -> io::Result<Option<usize>> {
-        let len = cmp::min(buf.len(), <c::DWORD>::MAX as usize) as c::DWORD;
+        let len = cmp::min(buf.len(), u32::MAX as usize) as u32;
         let mut amt = 0;
         let res =
             cvt(c::ReadFile(self.as_raw_handle(), buf.as_mut_ptr(), len, &mut amt, overlapped));
@@ -209,12 +210,7 @@ impl Handle {
         Ok(Self(self.0.try_clone()?))
     }
 
-    pub fn duplicate(
-        &self,
-        access: c::DWORD,
-        inherit: bool,
-        options: c::DWORD,
-    ) -> io::Result<Self> {
+    pub fn duplicate(&self, access: u32, inherit: bool, options: u32) -> io::Result<Self> {
         Ok(Self(self.0.as_handle().duplicate(access, inherit, options)?))
     }
 
@@ -233,7 +229,7 @@ impl Handle {
         let mut io_status = c::IO_STATUS_BLOCK::PENDING;
 
         // The length is clamped at u32::MAX.
-        let len = cmp::min(len, c::DWORD::MAX as usize) as c::DWORD;
+        let len = cmp::min(len, u32::MAX as usize) as u32;
         let status = c::NtReadFile(
             self.as_handle(),
             ptr::null_mut(),
@@ -281,7 +277,7 @@ impl Handle {
         let mut io_status = c::IO_STATUS_BLOCK::PENDING;
 
         // The length is clamped at u32::MAX.
-        let len = cmp::min(buf.len(), c::DWORD::MAX as usize) as c::DWORD;
+        let len = cmp::min(buf.len(), u32::MAX as usize) as u32;
         let status = unsafe {
             c::NtWriteFile(
                 self.as_handle(),
diff --git a/library/std/src/sys/pal/windows/io.rs b/library/std/src/sys/pal/windows/io.rs
index 77b8f3c410eb8..86d457db50a38 100644
--- a/library/std/src/sys/pal/windows/io.rs
+++ b/library/std/src/sys/pal/windows/io.rs
@@ -1,3 +1,4 @@
+#![allow(unsafe_op_in_unsafe_fn)]
 use crate::marker::PhantomData;
 use crate::mem::size_of;
 use crate::os::windows::io::{AsHandle, AsRawHandle, BorrowedHandle};
@@ -15,9 +16,9 @@ pub struct IoSlice<'a> {
 impl<'a> IoSlice<'a> {
     #[inline]
     pub fn new(buf: &'a [u8]) -> IoSlice<'a> {
-        assert!(buf.len() <= c::ULONG::MAX as usize);
+        assert!(buf.len() <= u32::MAX as usize);
         IoSlice {
-            vec: c::WSABUF { len: buf.len() as c::ULONG, buf: buf.as_ptr() as *mut u8 },
+            vec: c::WSABUF { len: buf.len() as u32, buf: buf.as_ptr() as *mut u8 },
             _p: PhantomData,
         }
     }
@@ -29,7 +30,7 @@ impl<'a> IoSlice<'a> {
         }
 
         unsafe {
-            self.vec.len -= n as c::ULONG;
+            self.vec.len -= n as u32;
             self.vec.buf = self.vec.buf.add(n);
         }
     }
@@ -49,9 +50,9 @@ pub struct IoSliceMut<'a> {
 impl<'a> IoSliceMut<'a> {
     #[inline]
     pub fn new(buf: &'a mut [u8]) -> IoSliceMut<'a> {
-        assert!(buf.len() <= c::ULONG::MAX as usize);
+        assert!(buf.len() <= u32::MAX as usize);
         IoSliceMut {
-            vec: c::WSABUF { len: buf.len() as c::ULONG, buf: buf.as_mut_ptr() },
+            vec: c::WSABUF { len: buf.len() as u32, buf: buf.as_mut_ptr() },
             _p: PhantomData,
         }
     }
@@ -63,7 +64,7 @@ impl<'a> IoSliceMut<'a> {
         }
 
         unsafe {
-            self.vec.len -= n as c::ULONG;
+            self.vec.len -= n as u32;
             self.vec.buf = self.vec.buf.add(n);
         }
     }
diff --git a/library/std/src/sys/pal/windows/mod.rs b/library/std/src/sys/pal/windows/mod.rs
index 6406cec9c27d2..b85a8318bcbbd 100644
--- a/library/std/src/sys/pal/windows/mod.rs
+++ b/library/std/src/sys/pal/windows/mod.rs
@@ -1,4 +1,5 @@
 #![allow(missing_docs, nonstandard_style)]
+#![deny(unsafe_op_in_unsafe_fn)]
 
 use crate::ffi::{OsStr, OsString};
 use crate::io::ErrorKind;
@@ -54,11 +55,13 @@ impl<T> IoResult<T> for Result<T, api::WinError> {
 // SAFETY: must be called only once during runtime initialization.
 // NOTE: this is not guaranteed to run, for example when Rust code is called externally.
 pub unsafe fn init(_argc: isize, _argv: *const *const u8, _sigpipe: u8) {
-    stack_overflow::init();
+    unsafe {
+        stack_overflow::init();
 
-    // Normally, `thread::spawn` will call `Thread::set_name` but since this thread already
-    // exists, we have to call it ourselves.
-    thread::Thread::set_name_wide(wide_str!("main"));
+        // Normally, `thread::spawn` will call `Thread::set_name` but since this thread already
+        // exists, we have to call it ourselves.
+        thread::Thread::set_name_wide(wide_str!("main"));
+    }
 }
 
 // SAFETY: must be called only once during runtime cleanup.
@@ -75,7 +78,7 @@ pub fn is_interrupted(_errno: i32) -> bool {
 pub fn decode_error_kind(errno: i32) -> ErrorKind {
     use ErrorKind::*;
 
-    match errno as c::DWORD {
+    match errno as u32 {
         c::ERROR_ACCESS_DENIED => return PermissionDenied,
         c::ERROR_ALREADY_EXISTS => return AlreadyExists,
         c::ERROR_FILE_EXISTS => return AlreadyExists,
@@ -216,7 +219,7 @@ pub fn to_u16s<S: AsRef<OsStr>>(s: S) -> crate::io::Result<Vec<u16>> {
 // from this closure is then the return value of the function.
 pub fn fill_utf16_buf<F1, F2, T>(mut f1: F1, f2: F2) -> crate::io::Result<T>
 where
-    F1: FnMut(*mut u16, c::DWORD) -> c::DWORD,
+    F1: FnMut(*mut u16, u32) -> u32,
     F2: FnOnce(&[u16]) -> T,
 {
     // Start off with a stack buf but then spill over to the heap if we end up
@@ -238,7 +241,7 @@ where
                 // We used `reserve` and not `reserve_exact`, so in theory we
                 // may have gotten more than requested. If so, we'd like to use
                 // it... so long as we won't cause overflow.
-                n = heap_buf.capacity().min(c::DWORD::MAX as usize);
+                n = heap_buf.capacity().min(u32::MAX as usize);
                 // Safety: MaybeUninit<u16> does not need initialization
                 heap_buf.set_len(n);
                 &mut heap_buf[..]
@@ -254,13 +257,13 @@ where
             // error" is still 0 then we interpret it as a 0 length buffer and
             // not an actual error.
             c::SetLastError(0);
-            let k = match f1(buf.as_mut_ptr().cast::<u16>(), n as c::DWORD) {
+            let k = match f1(buf.as_mut_ptr().cast::<u16>(), n as u32) {
                 0 if api::get_last_error().code == 0 => 0,
                 0 => return Err(crate::io::Error::last_os_error()),
                 n => n,
             } as usize;
             if k == n && api::get_last_error().code == c::ERROR_INSUFFICIENT_BUFFER {
-                n = n.saturating_mul(2).min(c::DWORD::MAX as usize);
+                n = n.saturating_mul(2).min(u32::MAX as usize);
             } else if k > n {
                 n = k;
             } else if k == n {
@@ -308,7 +311,7 @@ pub fn cvt<I: IsZero>(i: I) -> crate::io::Result<I> {
     if i.is_zero() { Err(crate::io::Error::last_os_error()) } else { Ok(i) }
 }
 
-pub fn dur2timeout(dur: Duration) -> c::DWORD {
+pub fn dur2timeout(dur: Duration) -> u32 {
     // Note that a duration is a (u64, u32) (seconds, nanoseconds) pair, and the
     // timeouts in windows APIs are typically u32 milliseconds. To translate, we
     // have two pieces to take care of:
@@ -320,7 +323,7 @@ pub fn dur2timeout(dur: Duration) -> c::DWORD {
         .checked_mul(1000)
         .and_then(|ms| ms.checked_add((dur.subsec_nanos() as u64) / 1_000_000))
         .and_then(|ms| ms.checked_add(if dur.subsec_nanos() % 1_000_000 > 0 { 1 } else { 0 }))
-        .map(|ms| if ms > <c::DWORD>::MAX as u64 { c::INFINITE } else { ms as c::DWORD })
+        .map(|ms| if ms > <u32>::MAX as u64 { c::INFINITE } else { ms as u32 })
         .unwrap_or(c::INFINITE)
 }
 
diff --git a/library/std/src/sys/pal/windows/net.rs b/library/std/src/sys/pal/windows/net.rs
index 9e15b15a3513a..d51fb56238f2c 100644
--- a/library/std/src/sys/pal/windows/net.rs
+++ b/library/std/src/sys/pal/windows/net.rs
@@ -250,7 +250,7 @@ impl Socket {
     pub fn read_vectored(&self, bufs: &mut [IoSliceMut<'_>]) -> io::Result<usize> {
         // On unix when a socket is shut down all further reads return 0, so we
         // do the same on windows to map a shut down socket to returning EOF.
-        let length = cmp::min(bufs.len(), c::DWORD::MAX as usize) as c::DWORD;
+        let length = cmp::min(bufs.len(), u32::MAX as usize) as u32;
         let mut nread = 0;
         let mut flags = 0;
         let result = unsafe {
@@ -335,7 +335,7 @@ impl Socket {
     }
 
     pub fn write_vectored(&self, bufs: &[IoSlice<'_>]) -> io::Result<usize> {
-        let length = cmp::min(bufs.len(), c::DWORD::MAX as usize) as c::DWORD;
+        let length = cmp::min(bufs.len(), u32::MAX as usize) as u32;
         let mut nwritten = 0;
         let result = unsafe {
             c::WSASend(
@@ -371,7 +371,7 @@ impl Socket {
     }
 
     pub fn timeout(&self, kind: c_int) -> io::Result<Option<Duration>> {
-        let raw: c::DWORD = net::getsockopt(self, c::SOL_SOCKET, kind)?;
+        let raw: u32 = net::getsockopt(self, c::SOL_SOCKET, kind)?;
         if raw == 0 {
             Ok(None)
         } else {
@@ -436,7 +436,7 @@ impl Socket {
     pub unsafe fn from_raw(raw: c::SOCKET) -> Self {
         debug_assert_eq!(mem::size_of::<c::SOCKET>(), mem::size_of::<RawSocket>());
         debug_assert_eq!(mem::align_of::<c::SOCKET>(), mem::align_of::<RawSocket>());
-        Self::from_raw_socket(raw as RawSocket)
+        unsafe { Self::from_raw_socket(raw as RawSocket) }
     }
 }
 
@@ -486,6 +486,6 @@ impl IntoRawSocket for Socket {
 
 impl FromRawSocket for Socket {
     unsafe fn from_raw_socket(raw_socket: RawSocket) -> Self {
-        Self(FromRawSocket::from_raw_socket(raw_socket))
+        unsafe { Self(FromRawSocket::from_raw_socket(raw_socket)) }
     }
 }
diff --git a/library/std/src/sys/pal/windows/os.rs b/library/std/src/sys/pal/windows/os.rs
index 62199c16bfed3..0a9279e50ba15 100644
--- a/library/std/src/sys/pal/windows/os.rs
+++ b/library/std/src/sys/pal/windows/os.rs
@@ -1,6 +1,7 @@
 //! Implementation of `std::os` functionality for Windows.
 
 #![allow(nonstandard_style)]
+#![allow(unsafe_op_in_unsafe_fn)]
 
 #[cfg(test)]
 mod tests;
@@ -52,10 +53,10 @@ pub fn error_string(mut errnum: i32) -> String {
         let res = c::FormatMessageW(
             flags | c::FORMAT_MESSAGE_FROM_SYSTEM | c::FORMAT_MESSAGE_IGNORE_INSERTS,
             module,
-            errnum as c::DWORD,
+            errnum as u32,
             0,
             buf.as_mut_ptr(),
-            buf.len() as c::DWORD,
+            buf.len() as u32,
             ptr::null(),
         ) as usize;
         if res == 0 {
@@ -81,7 +82,7 @@ pub fn error_string(mut errnum: i32) -> String {
 }
 
 pub struct Env {
-    base: c::LPWCH,
+    base: *mut c::WCHAR,
     iter: EnvIterator,
 }
 
@@ -126,7 +127,7 @@ impl Iterator for Env {
 }
 
 #[derive(Clone)]
-struct EnvIterator(c::LPWCH);
+struct EnvIterator(*mut c::WCHAR);
 
 impl Iterator for EnvIterator {
     type Item = (OsString, OsString);
@@ -383,7 +384,7 @@ pub fn home_dir() -> Option<PathBuf> {
 }
 
 pub fn exit(code: i32) -> ! {
-    unsafe { c::ExitProcess(code as c::UINT) }
+    unsafe { c::ExitProcess(code as u32) }
 }
 
 pub fn getpid() -> u32 {
diff --git a/library/std/src/sys/pal/windows/pipe.rs b/library/std/src/sys/pal/windows/pipe.rs
index 67ef3ca82da02..d8b785f027c76 100644
--- a/library/std/src/sys/pal/windows/pipe.rs
+++ b/library/std/src/sys/pal/windows/pipe.rs
@@ -1,3 +1,4 @@
+#![allow(unsafe_op_in_unsafe_fn)]
 use crate::os::windows::prelude::*;
 
 use crate::ffi::OsStr;
@@ -156,7 +157,7 @@ pub fn anon_pipe(ours_readable: bool, their_handle_inheritable: bool) -> io::Res
         opts.share_mode(0);
         let size = mem::size_of::<c::SECURITY_ATTRIBUTES>();
         let mut sa = c::SECURITY_ATTRIBUTES {
-            nLength: size as c::DWORD,
+            nLength: size as u32,
             lpSecurityDescriptor: ptr::null_mut(),
             bInheritHandle: their_handle_inheritable as i32,
         };
@@ -225,9 +226,9 @@ fn random_number() -> usize {
 // Abstracts over `ReadFileEx` and `WriteFileEx`
 type AlertableIoFn = unsafe extern "system" fn(
     BorrowedHandle<'_>,
-    c::LPVOID,
-    c::DWORD,
-    c::LPOVERLAPPED,
+    *mut core::ffi::c_void,
+    u32,
+    *mut c::OVERLAPPED,
     c::LPOVERLAPPED_COMPLETION_ROUTINE,
 ) -> c::BOOL;
 
@@ -244,7 +245,7 @@ impl AnonPipe {
 
     pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
         let result = unsafe {
-            let len = crate::cmp::min(buf.len(), c::DWORD::MAX as usize) as c::DWORD;
+            let len = crate::cmp::min(buf.len(), u32::MAX as usize) as u32;
             self.alertable_io_internal(c::ReadFileEx, buf.as_mut_ptr() as _, len)
         };
 
@@ -260,7 +261,7 @@ impl AnonPipe {
 
     pub fn read_buf(&self, mut buf: BorrowedCursor<'_>) -> io::Result<()> {
         let result = unsafe {
-            let len = crate::cmp::min(buf.capacity(), c::DWORD::MAX as usize) as c::DWORD;
+            let len = crate::cmp::min(buf.capacity(), u32::MAX as usize) as u32;
             self.alertable_io_internal(c::ReadFileEx, buf.as_mut().as_mut_ptr() as _, len)
         };
 
@@ -295,7 +296,7 @@ impl AnonPipe {
 
     pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
         unsafe {
-            let len = crate::cmp::min(buf.len(), c::DWORD::MAX as usize) as c::DWORD;
+            let len = crate::cmp::min(buf.len(), u32::MAX as usize) as u32;
             self.alertable_io_internal(c::WriteFileEx, buf.as_ptr() as _, len)
         }
     }
@@ -327,8 +328,8 @@ impl AnonPipe {
     unsafe fn alertable_io_internal(
         &self,
         io: AlertableIoFn,
-        buf: c::LPVOID,
-        len: c::DWORD,
+        buf: *mut core::ffi::c_void,
+        len: u32,
     ) -> io::Result<usize> {
         // Use "alertable I/O" to synchronize the pipe I/O.
         // This has four steps.
diff --git a/library/std/src/sys/pal/windows/process.rs b/library/std/src/sys/pal/windows/process.rs
index c62764696b86b..76d2cb77d474c 100644
--- a/library/std/src/sys/pal/windows/process.rs
+++ b/library/std/src/sys/pal/windows/process.rs
@@ -19,7 +19,7 @@ use crate::path::{Path, PathBuf};
 use crate::ptr;
 use crate::sync::Mutex;
 use crate::sys::args::{self, Arg};
-use crate::sys::c::{self, NonZeroDWORD, EXIT_FAILURE, EXIT_SUCCESS};
+use crate::sys::c::{self, EXIT_FAILURE, EXIT_SUCCESS};
 use crate::sys::cvt;
 use crate::sys::fs::{File, OpenOptions};
 use crate::sys::handle::Handle;
@@ -174,7 +174,7 @@ pub struct Command {
 
 pub enum Stdio {
     Inherit,
-    InheritSpecific { from_stdio_id: c::DWORD },
+    InheritSpecific { from_stdio_id: u32 },
     Null,
     MakePipe,
     Pipe(AnonPipe),
@@ -364,7 +364,7 @@ impl Command {
             };
             si_ptr = core::ptr::addr_of_mut!(si_ex) as _;
         } else {
-            si.cb = mem::size_of::<c::STARTUPINFOW>() as c::DWORD;
+            si.cb = mem::size_of::<c::STARTUPINFOW>() as u32;
             si_ptr = core::ptr::addr_of_mut!(si) as _;
         }
 
@@ -566,7 +566,7 @@ fn program_exists(path: &Path) -> Option<Vec<u16>> {
 }
 
 impl Stdio {
-    fn to_handle(&self, stdio_id: c::DWORD, pipe: &mut Option<AnonPipe>) -> io::Result<Handle> {
+    fn to_handle(&self, stdio_id: u32, pipe: &mut Option<AnonPipe>) -> io::Result<Handle> {
         let use_stdio_id = |stdio_id| match stdio::get_handle(stdio_id) {
             Ok(io) => unsafe {
                 let io = Handle::from_raw_handle(io);
@@ -601,7 +601,7 @@ impl Stdio {
             Stdio::Null => {
                 let size = mem::size_of::<c::SECURITY_ATTRIBUTES>();
                 let mut sa = c::SECURITY_ATTRIBUTES {
-                    nLength: size as c::DWORD,
+                    nLength: size as u32,
                     lpSecurityDescriptor: ptr::null_mut(),
                     bInheritHandle: 1,
                 };
@@ -713,11 +713,11 @@ impl Process {
 }
 
 #[derive(PartialEq, Eq, Clone, Copy, Debug, Default)]
-pub struct ExitStatus(c::DWORD);
+pub struct ExitStatus(u32);
 
 impl ExitStatus {
     pub fn exit_ok(&self) -> Result<(), ExitStatusError> {
-        match NonZeroDWORD::try_from(self.0) {
+        match NonZero::<u32>::try_from(self.0) {
             /* was nonzero */ Ok(failure) => Err(ExitStatusError(failure)),
             /* was zero, couldn't convert */ Err(_) => Ok(()),
         }
@@ -727,9 +727,9 @@ impl ExitStatus {
     }
 }
 
-/// Converts a raw `c::DWORD` to a type-safe `ExitStatus` by wrapping it without copying.
-impl From<c::DWORD> for ExitStatus {
-    fn from(u: c::DWORD) -> ExitStatus {
+/// Converts a raw `u32` to a type-safe `ExitStatus` by wrapping it without copying.
+impl From<u32> for ExitStatus {
+    fn from(u: u32) -> ExitStatus {
         ExitStatus(u)
     }
 }
@@ -750,7 +750,7 @@ impl fmt::Display for ExitStatus {
 }
 
 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
-pub struct ExitStatusError(c::NonZeroDWORD);
+pub struct ExitStatusError(NonZero<u32>);
 
 impl Into<ExitStatus> for ExitStatusError {
     fn into(self) -> ExitStatus {
@@ -765,7 +765,7 @@ impl ExitStatusError {
 }
 
 #[derive(PartialEq, Eq, Clone, Copy, Debug)]
-pub struct ExitCode(c::DWORD);
+pub struct ExitCode(u32);
 
 impl ExitCode {
     pub const SUCCESS: ExitCode = ExitCode(EXIT_SUCCESS as _);
@@ -779,13 +779,13 @@ impl ExitCode {
 
 impl From<u8> for ExitCode {
     fn from(code: u8) -> Self {
-        ExitCode(c::DWORD::from(code))
+        ExitCode(u32::from(code))
     }
 }
 
 impl From<u32> for ExitCode {
     fn from(code: u32) -> Self {
-        ExitCode(c::DWORD::from(code))
+        ExitCode(u32::from(code))
     }
 }
 
diff --git a/library/std/src/sys/pal/windows/rand.rs b/library/std/src/sys/pal/windows/rand.rs
index 09f527a09bf12..e366bb995626a 100644
--- a/library/std/src/sys/pal/windows/rand.rs
+++ b/library/std/src/sys/pal/windows/rand.rs
@@ -20,7 +20,7 @@ pub fn hashmap_random_keys() -> (u64, u64) {
 
     let mut v = (0, 0);
     let ret = unsafe {
-        c::RtlGenRandom(ptr::addr_of_mut!(v).cast::<c_void>(), mem::size_of_val(&v) as c::ULONG)
+        c::RtlGenRandom(ptr::addr_of_mut!(v).cast::<c_void>(), mem::size_of_val(&v) as u32)
     };
 
     if ret != 0 { v } else { panic!("RNG broken: {}", io::Error::last_os_error()) }
diff --git a/library/std/src/sys/pal/windows/stack_overflow.rs b/library/std/src/sys/pal/windows/stack_overflow.rs
index f93f31026f818..ea89429cb83cc 100644
--- a/library/std/src/sys/pal/windows/stack_overflow.rs
+++ b/library/std/src/sys/pal/windows/stack_overflow.rs
@@ -1,4 +1,5 @@
 #![cfg_attr(test, allow(dead_code))]
+#![allow(unsafe_op_in_unsafe_fn)]
 
 use crate::sys::c;
 use crate::thread;
@@ -11,7 +12,7 @@ pub unsafe fn reserve_stack() {
     debug_assert_ne!(result, 0, "failed to reserve stack space for exception handling");
 }
 
-unsafe extern "system" fn vectored_handler(ExceptionInfo: *mut c::EXCEPTION_POINTERS) -> c::LONG {
+unsafe extern "system" fn vectored_handler(ExceptionInfo: *mut c::EXCEPTION_POINTERS) -> i32 {
     unsafe {
         let rec = &(*(*ExceptionInfo).ExceptionRecord);
         let code = rec.ExceptionCode;
diff --git a/library/std/src/sys/pal/windows/stdio.rs b/library/std/src/sys/pal/windows/stdio.rs
index 10aeeac07ea2e..c6a21665157d7 100644
--- a/library/std/src/sys/pal/windows/stdio.rs
+++ b/library/std/src/sys/pal/windows/stdio.rs
@@ -68,7 +68,7 @@ const MAX_BUFFER_SIZE: usize = 8192;
 // UTF-16 to UTF-8.
 pub const STDIN_BUF_SIZE: usize = MAX_BUFFER_SIZE / 2 * 3;
 
-pub fn get_handle(handle_id: c::DWORD) -> io::Result<c::HANDLE> {
+pub fn get_handle(handle_id: u32) -> io::Result<c::HANDLE> {
     let handle = unsafe { c::GetStdHandle(handle_id) };
     if handle == c::INVALID_HANDLE_VALUE {
         Err(io::Error::last_os_error())
@@ -87,11 +87,7 @@ fn is_console(handle: c::HANDLE) -> bool {
     unsafe { c::GetConsoleMode(handle, &mut mode) != 0 }
 }
 
-fn write(
-    handle_id: c::DWORD,
-    data: &[u8],
-    incomplete_utf8: &mut IncompleteUtf8,
-) -> io::Result<usize> {
+fn write(handle_id: u32, data: &[u8], incomplete_utf8: &mut IncompleteUtf8) -> io::Result<usize> {
     if data.is_empty() {
         return Ok(0);
     }
@@ -182,12 +178,12 @@ fn write_valid_utf8_to_console(handle: c::HANDLE, utf8: &str) -> io::Result<usiz
         // Note that this theoretically checks validity twice in the (most common) case
         // where the underlying byte sequence is valid utf-8 (given the check in `write()`).
         let result = c::MultiByteToWideChar(
-            c::CP_UTF8,                      // CodePage
-            c::MB_ERR_INVALID_CHARS,         // dwFlags
-            utf8.as_ptr(),                   // lpMultiByteStr
-            utf8.len() as c::c_int,          // cbMultiByte
-            utf16.as_mut_ptr() as c::LPWSTR, // lpWideCharStr
-            utf16.len() as c::c_int,         // cchWideChar
+            c::CP_UTF8,                          // CodePage
+            c::MB_ERR_INVALID_CHARS,             // dwFlags
+            utf8.as_ptr(),                       // lpMultiByteStr
+            utf8.len() as i32,                   // cbMultiByte
+            utf16.as_mut_ptr() as *mut c::WCHAR, // lpWideCharStr
+            utf16.len() as i32,                  // cchWideChar
         );
         assert!(result != 0, "Unexpected error in MultiByteToWideChar");
 
@@ -341,9 +337,9 @@ fn read_u16s(handle: c::HANDLE, buf: &mut [MaybeUninit<u16>]) -> io::Result<usiz
     // traditional DOS method to indicate end of character stream / user input (SUB).
     // See #38274 and https://stackoverflow.com/questions/43836040/win-api-readconsole.
     const CTRL_Z: u16 = 0x1A;
-    const CTRL_Z_MASK: c::ULONG = 1 << CTRL_Z;
+    const CTRL_Z_MASK: u32 = 1 << CTRL_Z;
     let input_control = c::CONSOLE_READCONSOLE_CONTROL {
-        nLength: crate::mem::size_of::<c::CONSOLE_READCONSOLE_CONTROL>() as c::ULONG,
+        nLength: crate::mem::size_of::<c::CONSOLE_READCONSOLE_CONTROL>() as u32,
         nInitialChars: 0,
         dwCtrlWakeupMask: CTRL_Z_MASK,
         dwControlKeyState: 0,
@@ -355,7 +351,7 @@ fn read_u16s(handle: c::HANDLE, buf: &mut [MaybeUninit<u16>]) -> io::Result<usiz
             c::SetLastError(0);
             c::ReadConsoleW(
                 handle,
-                buf.as_mut_ptr() as c::LPVOID,
+                buf.as_mut_ptr() as *mut core::ffi::c_void,
                 buf.len() as u32,
                 &mut amount,
                 &input_control,
@@ -378,8 +374,8 @@ fn read_u16s(handle: c::HANDLE, buf: &mut [MaybeUninit<u16>]) -> io::Result<usiz
 }
 
 fn utf16_to_utf8(utf16: &[u16], utf8: &mut [u8]) -> io::Result<usize> {
-    debug_assert!(utf16.len() <= c::c_int::MAX as usize);
-    debug_assert!(utf8.len() <= c::c_int::MAX as usize);
+    debug_assert!(utf16.len() <= i32::MAX as usize);
+    debug_assert!(utf8.len() <= i32::MAX as usize);
 
     if utf16.is_empty() {
         return Ok(0);
@@ -390,9 +386,9 @@ fn utf16_to_utf8(utf16: &[u16], utf8: &mut [u8]) -> io::Result<usize> {
             c::CP_UTF8,              // CodePage
             c::WC_ERR_INVALID_CHARS, // dwFlags
             utf16.as_ptr(),          // lpWideCharStr
-            utf16.len() as c::c_int, // cchWideChar
+            utf16.len() as i32,      // cchWideChar
             utf8.as_mut_ptr(),       // lpMultiByteStr
-            utf8.len() as c::c_int,  // cbMultiByte
+            utf8.len() as i32,       // cbMultiByte
             ptr::null(),             // lpDefaultChar
             ptr::null_mut(),         // lpUsedDefaultChar
         )
diff --git a/library/std/src/sys/pal/windows/thread.rs b/library/std/src/sys/pal/windows/thread.rs
index 70099e0a3b560..3648272a343a5 100644
--- a/library/std/src/sys/pal/windows/thread.rs
+++ b/library/std/src/sys/pal/windows/thread.rs
@@ -1,3 +1,4 @@
+#![allow(unsafe_op_in_unsafe_fn)]
 use crate::ffi::CStr;
 use crate::io;
 use crate::num::NonZero;
@@ -45,7 +46,7 @@ impl Thread {
             Err(io::Error::last_os_error())
         };
 
-        unsafe extern "system" fn thread_start(main: *mut c_void) -> c::DWORD {
+        unsafe extern "system" fn thread_start(main: *mut c_void) -> u32 {
             // Next, reserve some stack space for if we otherwise run out of stack.
             stack_overflow::reserve_stack();
             // Finally, let's run some code.
diff --git a/library/std/src/sys/pal/windows/time.rs b/library/std/src/sys/pal/windows/time.rs
index 09e78a29304f9..b853daeffebd7 100644
--- a/library/std/src/sys/pal/windows/time.rs
+++ b/library/std/src/sys/pal/windows/time.rs
@@ -76,8 +76,8 @@ impl SystemTime {
     fn from_intervals(intervals: i64) -> SystemTime {
         SystemTime {
             t: c::FILETIME {
-                dwLowDateTime: intervals as c::DWORD,
-                dwHighDateTime: (intervals >> 32) as c::DWORD,
+                dwLowDateTime: intervals as u32,
+                dwHighDateTime: (intervals >> 32) as u32,
             },
         }
     }
@@ -172,7 +172,7 @@ mod perf_counter {
     use crate::time::Duration;
 
     pub struct PerformanceCounterInstant {
-        ts: c::LARGE_INTEGER,
+        ts: i64,
     }
     impl PerformanceCounterInstant {
         pub fn now() -> Self {
@@ -196,7 +196,7 @@ mod perf_counter {
         }
     }
 
-    fn frequency() -> c::LARGE_INTEGER {
+    fn frequency() -> i64 {
         // Either the cached result of `QueryPerformanceFrequency` or `0` for
         // uninitialized. Storing this as a single `AtomicU64` allows us to use
         // `Relaxed` operations, as we are only interested in the effects on a
@@ -206,7 +206,7 @@ mod perf_counter {
         let cached = FREQUENCY.load(Ordering::Relaxed);
         // If a previous thread has filled in this global state, use that.
         if cached != 0 {
-            return cached as c::LARGE_INTEGER;
+            return cached as i64;
         }
         // ... otherwise learn for ourselves ...
         let mut frequency = 0;
@@ -218,8 +218,8 @@ mod perf_counter {
         frequency
     }
 
-    fn query() -> c::LARGE_INTEGER {
-        let mut qpc_value: c::LARGE_INTEGER = 0;
+    fn query() -> i64 {
+        let mut qpc_value: i64 = 0;
         cvt(unsafe { c::QueryPerformanceCounter(&mut qpc_value) }).unwrap();
         qpc_value
     }
diff --git a/library/std/src/sys/sync/mutex/windows7.rs b/library/std/src/sys/sync/mutex/windows7.rs
index ef2f84082cd5c..689dba10f01ed 100644
--- a/library/std/src/sys/sync/mutex/windows7.rs
+++ b/library/std/src/sys/sync/mutex/windows7.rs
@@ -25,7 +25,7 @@ unsafe impl Send for Mutex {}
 unsafe impl Sync for Mutex {}
 
 #[inline]
-pub unsafe fn raw(m: &Mutex) -> c::PSRWLOCK {
+pub unsafe fn raw(m: &Mutex) -> *mut c::SRWLOCK {
     m.srwlock.get()
 }
 
diff --git a/library/std/src/sys/sync/thread_parking/windows.rs b/library/std/src/sys/sync/thread_parking/windows.rs
index 4b8102d505a1f..3a8d40dc5cfac 100644
--- a/library/std/src/sys/sync/thread_parking/windows.rs
+++ b/library/std/src/sys/sync/thread_parking/windows.rs
@@ -64,6 +64,7 @@ use crate::sync::atomic::{
 };
 use crate::sys::{c, dur2timeout};
 use crate::time::Duration;
+use core::ffi::c_void;
 
 pub struct Parker {
     state: AtomicI8,
@@ -117,7 +118,7 @@ impl Parker {
 
         loop {
             // Wait for something to happen, assuming it's still set to PARKED.
-            c::WaitOnAddress(self.ptr(), &PARKED as *const _ as c::LPVOID, 1, c::INFINITE);
+            c::WaitOnAddress(self.ptr(), &PARKED as *const _ as *const c_void, 1, c::INFINITE);
             // Change NOTIFIED=>EMPTY but leave PARKED alone.
             if self.state.compare_exchange(NOTIFIED, EMPTY, Acquire, Acquire).is_ok() {
                 // Actually woken up by unpark().
@@ -144,7 +145,7 @@ impl Parker {
         }
 
         // Wait for something to happen, assuming it's still set to PARKED.
-        c::WaitOnAddress(self.ptr(), &PARKED as *const _ as c::LPVOID, 1, dur2timeout(timeout));
+        c::WaitOnAddress(self.ptr(), &PARKED as *const _ as *const c_void, 1, dur2timeout(timeout));
         // Set the state back to EMPTY (from either PARKED or NOTIFIED).
         // Note that we don't just write EMPTY, but use swap() to also
         // include an acquire-ordered read to synchronize with unpark()'s
@@ -177,8 +178,8 @@ impl Parker {
         }
     }
 
-    fn ptr(&self) -> c::LPVOID {
-        core::ptr::addr_of!(self.state) as c::LPVOID
+    fn ptr(&self) -> *const c_void {
+        core::ptr::addr_of!(self.state).cast::<c_void>()
     }
 }
 
diff --git a/library/std/src/sys/thread_local/guard/windows.rs b/library/std/src/sys/thread_local/guard/windows.rs
index 81797f55170d7..f6cd457046ffc 100644
--- a/library/std/src/sys/thread_local/guard/windows.rs
+++ b/library/std/src/sys/thread_local/guard/windows.rs
@@ -65,6 +65,7 @@
 
 use crate::ptr;
 use crate::sys::c;
+use core::ffi::c_void;
 
 pub fn enable() {
     // When destructors are used, we don't want LLVM eliminating CALLBACK for any
@@ -74,9 +75,9 @@ pub fn enable() {
 
 #[link_section = ".CRT$XLB"]
 #[cfg_attr(miri, used)] // Miri only considers explicitly `#[used]` statics for `lookup_link_section`
-pub static CALLBACK: unsafe extern "system" fn(c::LPVOID, c::DWORD, c::LPVOID) = tls_callback;
+pub static CALLBACK: unsafe extern "system" fn(*mut c_void, u32, *mut c_void) = tls_callback;
 
-unsafe extern "system" fn tls_callback(_h: c::LPVOID, dw_reason: c::DWORD, _pv: c::LPVOID) {
+unsafe extern "system" fn tls_callback(_h: *mut c_void, dw_reason: u32, _pv: *mut c_void) {
     // See comments above for what this is doing. Note that we don't need this
     // trickery on GNU windows, just on MSVC.
     #[cfg(all(target_env = "msvc", not(target_thread_local)))]
diff --git a/library/std/src/sys/thread_local/key/windows.rs b/library/std/src/sys/thread_local/key/windows.rs
index baf23979c7c61..8b43e558d5d98 100644
--- a/library/std/src/sys/thread_local/key/windows.rs
+++ b/library/std/src/sys/thread_local/key/windows.rs
@@ -33,11 +33,11 @@ use crate::sync::atomic::{
 use crate::sys::c;
 use crate::sys::thread_local::guard;
 
-pub type Key = c::DWORD;
+pub type Key = u32;
 type Dtor = unsafe extern "C" fn(*mut u8);
 
 pub struct LazyKey {
-    /// The key value shifted up by one. Since TLS_OUT_OF_INDEXES == DWORD::MAX
+    /// The key value shifted up by one. Since TLS_OUT_OF_INDEXES == u32::MAX
     /// is not a valid key value, this allows us to use zero as sentinel value
     /// without risking overflow.
     key: AtomicU32,
diff --git a/library/std/src/sys_common/wtf8.rs b/library/std/src/sys_common/wtf8.rs
index 117a3e23044ea..6aeeb6259285d 100644
--- a/library/std/src/sys_common/wtf8.rs
+++ b/library/std/src/sys_common/wtf8.rs
@@ -602,7 +602,8 @@ impl Wtf8 {
     /// marked unsafe.
     #[inline]
     pub unsafe fn from_bytes_unchecked(value: &[u8]) -> &Wtf8 {
-        mem::transmute(value)
+        // SAFETY: start with &[u8], end with fancy &[u8]
+        unsafe { &*(value as *const [u8] as *const Wtf8) }
     }
 
     /// Creates a mutable WTF-8 slice from a mutable WTF-8 byte slice.
@@ -611,7 +612,8 @@ impl Wtf8 {
     /// marked unsafe.
     #[inline]
     unsafe fn from_mut_bytes_unchecked(value: &mut [u8]) -> &mut Wtf8 {
-        mem::transmute(value)
+        // SAFETY: start with &mut [u8], end with fancy &mut [u8]
+        unsafe { &mut *(value as *mut [u8] as *mut Wtf8) }
     }
 
     /// Returns the length, in WTF-8 bytes.
@@ -942,8 +944,12 @@ pub fn check_utf8_boundary(slice: &Wtf8, index: usize) {
 /// Copied from core::str::raw::slice_unchecked
 #[inline]
 pub unsafe fn slice_unchecked(s: &Wtf8, begin: usize, end: usize) -> &Wtf8 {
-    // memory layout of a &[u8] and &Wtf8 are the same
-    Wtf8::from_bytes_unchecked(slice::from_raw_parts(s.bytes.as_ptr().add(begin), end - begin))
+    // SAFETY: memory layout of a &[u8] and &Wtf8 are the same
+    unsafe {
+        let len = end - begin;
+        let start = s.as_bytes().as_ptr().add(begin);
+        Wtf8::from_bytes_unchecked(slice::from_raw_parts(start, len))
+    }
 }
 
 /// Copied from core::str::raw::slice_error_fail
diff --git a/src/tools/miri/tests/fail/alloc/global_system_mixup.rs b/src/tools/miri/tests/fail/alloc/global_system_mixup.rs
index 2e88e5644e441..19c62913b4c66 100644
--- a/src/tools/miri/tests/fail/alloc/global_system_mixup.rs
+++ b/src/tools/miri/tests/fail/alloc/global_system_mixup.rs
@@ -4,7 +4,7 @@
 
 //@normalize-stderr-test: "using [A-Za-z]+ heap deallocation operation" -> "using PLATFORM heap deallocation operation"
 //@normalize-stderr-test: "\| +\^+" -> "| ^"
-//@normalize-stderr-test: "libc::free\([^()]*\)|unsafe \{ HeapFree\([^()]*\) \};" -> "FREE();"
+//@normalize-stderr-test: "libc::free\([^()]*\)|unsafe \{ HeapFree\([^}]*\};" -> "FREE();"
 
 #![feature(allocator_api, slice_ptr_get)]