4 files changed, 18 insertions, 15 deletions
diff --git a/library/std/src/io/buffered/tests.rs b/library/std/src/io/buffered/tests.rs
index f4e688eb9..4c1b7d576 100644
--- a/library/std/src/io/buffered/tests.rs
+++ b/library/std/src/io/buffered/tests.rs
@@ -288,8 +288,8 @@ fn test_buffered_reader_seek_underflow_discard_buffer_between_seeks() {
     let mut reader = BufReader::with_capacity(5, ErrAfterFirstSeekReader { first_seek: true });
     assert_eq!(reader.fill_buf().ok(), Some(&[0, 0, 0, 0, 0][..]));
 
-    // The following seek will require two underlying seeks.  The first will
-    // succeed but the second will fail.  This should still invalidate the
+    // The following seek will require two underlying seeks. The first will
+    // succeed but the second will fail. This should still invalidate the
     // buffer.
     assert!(reader.seek(SeekFrom::Current(i64::MIN)).is_err());
     assert_eq!(reader.buffer().len(), 0);
diff --git a/library/std/src/io/error/repr_bitpacked.rs b/library/std/src/io/error/repr_bitpacked.rs
index 781ae03ad..358148405 100644
--- a/library/std/src/io/error/repr_bitpacked.rs
+++ b/library/std/src/io/error/repr_bitpacked.rs
@@ -166,7 +166,7 @@ impl Repr {
         // `new_unchecked` is safe.
         let res = Self(unsafe { NonNull::new_unchecked(tagged) }, PhantomData);
         // quickly smoke-check we encoded the right thing (This generally will
-        // only run in libstd's tests, unless the user uses -Zbuild-std)
+        // only run in std's tests, unless the user uses -Zbuild-std)
         debug_assert!(matches!(res.data(), ErrorData::Custom(_)), "repr(custom) encoding failed");
         res
     }
@@ -177,7 +177,7 @@ impl Repr {
         // Safety: `TAG_OS` is not zero, so the result of the `|` is not 0.
         let res = Self(unsafe { NonNull::new_unchecked(ptr::invalid_mut(utagged)) }, PhantomData);
         // quickly smoke-check we encoded the right thing (This generally will
-        // only run in libstd's tests, unless the user uses -Zbuild-std)
+        // only run in std's tests, unless the user uses -Zbuild-std)
         debug_assert!(
             matches!(res.data(), ErrorData::Os(c) if c == code),
             "repr(os) encoding failed for {code}"
@@ -191,7 +191,7 @@ impl Repr {
         // Safety: `TAG_SIMPLE` is not zero, so the result of the `|` is not 0.
         let res = Self(unsafe { NonNull::new_unchecked(ptr::invalid_mut(utagged)) }, PhantomData);
         // quickly smoke-check we encoded the right thing (This generally will
-        // only run in libstd's tests, unless the user uses -Zbuild-std)
+        // only run in std's tests, unless the user uses -Zbuild-std)
         debug_assert!(
             matches!(res.data(), ErrorData::Simple(k) if k == kind),
             "repr(simple) encoding failed {:?}",
@@ -348,7 +348,7 @@ fn kind_from_prim(ek: u32) -> Option<ErrorKind> {
 // that our encoding relies on for correctness and soundness. (Some of these are
 // a bit overly thorough/cautious, admittedly)
 //
-// If any of these are hit on a platform that libstd supports, we should likely
+// If any of these are hit on a platform that std supports, we should likely
 // just use `repr_unpacked.rs` there instead (unless the fix is easy).
 macro_rules! static_assert {
     ($condition:expr) => {
@@ -374,10 +374,10 @@ static_assert!((TAG_MASK + 1).is_power_of_two());
 static_assert!(align_of::<SimpleMessage>() >= TAG_MASK + 1);
 static_assert!(align_of::<Custom>() >= TAG_MASK + 1);
 
-static_assert!(@usize_eq: (TAG_MASK & TAG_SIMPLE_MESSAGE), TAG_SIMPLE_MESSAGE);
-static_assert!(@usize_eq: (TAG_MASK & TAG_CUSTOM), TAG_CUSTOM);
-static_assert!(@usize_eq: (TAG_MASK & TAG_OS), TAG_OS);
-static_assert!(@usize_eq: (TAG_MASK & TAG_SIMPLE), TAG_SIMPLE);
+static_assert!(@usize_eq: TAG_MASK & TAG_SIMPLE_MESSAGE, TAG_SIMPLE_MESSAGE);
+static_assert!(@usize_eq: TAG_MASK & TAG_CUSTOM, TAG_CUSTOM);
+static_assert!(@usize_eq: TAG_MASK & TAG_OS, TAG_OS);
+static_assert!(@usize_eq: TAG_MASK & TAG_SIMPLE, TAG_SIMPLE);
 
 // This is obviously true (`TAG_CUSTOM` is `0b01`), but in `Repr::new_custom` we
 // offset a pointer by this value, and expect it to both be within the same
diff --git a/library/std/src/io/mod.rs b/library/std/src/io/mod.rs
index 23a13523f..de528e853 100644
--- a/library/std/src/io/mod.rs
+++ b/library/std/src/io/mod.rs
@@ -2137,8 +2137,10 @@ pub trait BufRead: Read {
     }
 
     /// Read all bytes until a newline (the `0xA` byte) is reached, and append
-    /// them to the provided buffer. You do not need to clear the buffer before
-    /// appending.
+    /// them to the provided `String` buffer.
+    ///
+    /// Previous content of the buffer will be preserved. To avoid appending to
+    /// the buffer, you need to [`clear`] it first.
     ///
     /// This function will read bytes from the underlying stream until the
     /// newline delimiter (the `0xA` byte) or EOF is found. Once found, all bytes
@@ -2151,9 +2153,11 @@ pub trait BufRead: Read {
     ///
     /// This function is blocking and should be used carefully: it is possible for
     /// an attacker to continuously send bytes without ever sending a newline
-    /// or EOF.
+    /// or EOF. You can use [`take`] to limit the maximum number of bytes read.
     ///
     /// [`Ok(0)`]: Ok
+    /// [`clear`]: String::clear
+    /// [`take`]: crate::io::Read::take
     ///
     /// # Errors
     ///
diff --git a/library/std/src/io/stdio.rs b/library/std/src/io/stdio.rs
index 1141a957d..14bfef4c7 100644
--- a/library/std/src/io/stdio.rs
+++ b/library/std/src/io/stdio.rs
@@ -10,9 +10,8 @@ use crate::fmt;
 use crate::fs::File;
 use crate::io::{self, BufReader, IoSlice, IoSliceMut, LineWriter, Lines};
 use crate::sync::atomic::{AtomicBool, Ordering};
-use crate::sync::{Arc, Mutex, MutexGuard, OnceLock};
+use crate::sync::{Arc, Mutex, MutexGuard, OnceLock, ReentrantMutex, ReentrantMutexGuard};
 use crate::sys::stdio;
-use crate::sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
 
 type LocalStream = Arc<Mutex<Vec<u8>>>;