Merge from rustc

Author: The Miri Cronjob Bot

alloc/src/slice.rs

@@ -493,8 +493,6 @@ impl<T> [T] {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// assert_eq!([1, 2].repeat(3), vec![1, 2, 1, 2, 1, 2]);
     /// ```

alloc/src/str.rs

@@ -246,8 +246,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let s = "this is old";
     ///
@@ -303,8 +301,6 @@ impl str {
     ///
     /// # Examples
     ///
-    /// Basic usage:
-    ///
     /// ```
     /// let s = "foo foo 123 foo";
     /// assert_eq!("new new 123 foo", s.replacen("foo", "new", 2));

core/src/fmt/num.rs

@@ -678,8 +678,8 @@ impl fmt::Display for i128 {
 /// It also has to handle 1 last item, as 10^40 > 2^128 > 10^39, whereas
 /// 10^20 > 2^64 > 10^19.
 fn fmt_u128(n: u128, is_nonnegative: bool, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-    // 2^128 is about 3*10^38, so 39 gives an extra byte of space
-    let mut buf = [MaybeUninit::<u8>::uninit(); 39];
+    const MAX_DEC_N: usize = u128::MAX.ilog(10) as usize + 1;
+    let mut buf = [MaybeUninit::<u8>::uninit(); MAX_DEC_N];
     let mut curr = buf.len();
 
     let (n, rem) = udiv_1e19(n);

core/src/num/nonzero.rs

@@ -551,8 +551,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Examples
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// # use std::num::NonZero;
             /// #
@@ -583,8 +581,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Examples
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// # use std::num::NonZero;
             /// #
@@ -612,8 +608,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Example
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// #![feature(isolate_most_least_significant_one)]
             ///
@@ -644,8 +638,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Example
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// #![feature(isolate_most_least_significant_one)]
             ///
@@ -676,8 +668,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Examples
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// # use std::num::NonZero;
             /// #
@@ -713,8 +703,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Examples
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// #![feature(nonzero_bitwise)]
             /// # use std::num::NonZero;
@@ -746,8 +734,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Examples
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// #![feature(nonzero_bitwise)]
             /// # use std::num::NonZero;
@@ -775,8 +761,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Examples
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// #![feature(nonzero_bitwise)]
             /// # use std::num::NonZero;
@@ -805,8 +789,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Examples
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// #![feature(nonzero_bitwise)]
             /// # use std::num::NonZero;
@@ -837,8 +819,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Examples
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// #![feature(nonzero_bitwise)]
             /// # use std::num::NonZero;
@@ -872,8 +852,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Examples
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// #![feature(nonzero_bitwise)]
             /// # use std::num::NonZero;
@@ -907,8 +885,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Examples
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// #![feature(nonzero_bitwise)]
             /// # use std::num::NonZero;
@@ -942,8 +918,6 @@ macro_rules! nonzero_integer {
             ///
             /// # Examples
             ///
-            /// Basic usage:
-            ///
             /// ```
             /// #![feature(nonzero_bitwise)]
             /// # use std::num::NonZero;
@@ -1635,8 +1609,6 @@ macro_rules! nonzero_integer_signedness_dependent_methods {
         ///
         /// # Examples
         ///
-        /// Basic usage:
-        ///
         /// ```
         /// # use std::num::NonZero;
         /// #
@@ -1666,7 +1638,6 @@ macro_rules! nonzero_integer_signedness_dependent_methods {
         ///
         /// # Examples
         ///
-        /// Basic usage:
         /// ```
         /// # use std::num::NonZero;
         /// #
@@ -1699,8 +1670,6 @@ macro_rules! nonzero_integer_signedness_dependent_methods {
         ///
         /// # Examples
         ///
-        /// Basic usage:
-        ///
         /// ```
         /// # use std::num::NonZero;
         ///
@@ -2138,8 +2107,6 @@ macro_rules! nonzero_integer_signedness_dependent_methods {
         ///
         /// # Examples
         ///
-        /// Basic usage:
-        ///
         /// ```
         /// # use std::num::NonZero;
         ///

std/src/ffi/mod.rs

@@ -178,6 +178,8 @@ pub use core::ffi::{
     c_char, c_double, c_float, c_int, c_long, c_longlong, c_schar, c_short, c_uchar, c_uint,
     c_ulong, c_ulonglong, c_ushort,
 };
+#[unstable(feature = "c_size_t", issue = "88345")]
+pub use core::ffi::{c_ptrdiff_t, c_size_t, c_ssize_t};
 
 #[doc(inline)]
 #[stable(feature = "cstr_from_bytes_until_nul", since = "1.69.0")]

std/src/fs.rs

@@ -1311,9 +1311,39 @@ impl Write for &File {
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl Seek for &File {
+    /// Seek to an offset, in bytes in a file.
+    ///
+    /// See [`Seek::seek`] docs for more info.
+    ///
+    /// # Platform-specific behavior
+    ///
+    /// This function currently corresponds to the `lseek64` function on Unix
+    /// and the `SetFilePointerEx` function on Windows. Note that this [may
+    /// change in the future][changes].
+    ///
+    /// [changes]: io#platform-specific-behavior
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
         self.inner.seek(pos)
     }
+
+    /// Returns the length of this file (in bytes).
+    ///
+    /// See [`Seek::stream_len`] docs for more info.
+    ///
+    /// # Platform-specific behavior
+    ///
+    /// This function currently corresponds to the `statx` function on Linux
+    /// (with fallbacks) and the `GetFileSizeEx` function on Windows. Note that
+    /// this [may change in the future][changes].
+    ///
+    /// [changes]: io#platform-specific-behavior
+    fn stream_len(&mut self) -> io::Result<u64> {
+        if let Some(result) = self.inner.size() {
+            return result;
+        }
+        io::stream_len_default(self)
+    }
+
     fn stream_position(&mut self) -> io::Result<u64> {
         self.inner.tell()
     }
@@ -1363,6 +1393,9 @@ impl Seek for File {
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
         (&*self).seek(pos)
     }
+    fn stream_len(&mut self) -> io::Result<u64> {
+        (&*self).stream_len()
+    }
     fn stream_position(&mut self) -> io::Result<u64> {
         (&*self).stream_position()
     }
@@ -1412,6 +1445,9 @@ impl Seek for Arc<File> {
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
         (&**self).seek(pos)
     }
+    fn stream_len(&mut self) -> io::Result<u64> {
+        (&**self).stream_len()
+    }
     fn stream_position(&mut self) -> io::Result<u64> {
         (&**self).stream_position()
     }

std/src/io/mod.rs

@@ -2028,7 +2028,7 @@ pub trait Seek {
 
     /// Returns the length of this stream (in bytes).
     ///
-    /// This method is implemented using up to three seek operations. If this
+    /// The default implementation uses up to three seek operations. If this
     /// method returns successfully, the seek position is unchanged (i.e. the
     /// position before calling this method is the same as afterwards).
     /// However, if this method returns an error, the seek position is
@@ -2062,16 +2062,7 @@ pub trait Seek {
     /// ```
     #[unstable(feature = "seek_stream_len", issue = "59359")]
     fn stream_len(&mut self) -> Result<u64> {
-        let old_pos = self.stream_position()?;
-        let len = self.seek(SeekFrom::End(0))?;
-
-        // Avoid seeking a third time when we were already at the end of the
-        // stream. The branch is usually way cheaper than a seek operation.
-        if old_pos != len {
-            self.seek(SeekFrom::Start(old_pos))?;
-        }
-
-        Ok(len)
+        stream_len_default(self)
     }
 
     /// Returns the current seek position from the start of the stream.
@@ -2132,6 +2123,19 @@ pub trait Seek {
     }
 }
 
+pub(crate) fn stream_len_default<T: Seek + ?Sized>(self_: &mut T) -> Result<u64> {
+    let old_pos = self_.stream_position()?;
+    let len = self_.seek(SeekFrom::End(0))?;
+
+    // Avoid seeking a third time when we were already at the end of the
+    // stream. The branch is usually way cheaper than a seek operation.
+    if old_pos != len {
+        self_.seek(SeekFrom::Start(old_pos))?;
+    }
+
+    Ok(len)
+}
+
 /// Enumeration of possible methods to seek within an I/O object.
 ///
 /// It is used by the [`Seek`] trait.

std/src/keyword_docs.rs

@@ -1916,10 +1916,6 @@ mod type_keyword {}
 /// - and to declare that a programmer has checked that these contracts have been upheld (`unsafe
 /// {}` and `unsafe impl`, but also `unsafe fn` -- see below).
 ///
-/// They are not mutually exclusive, as can be seen in `unsafe fn`: the body of an `unsafe fn` is,
-/// by default, treated like an unsafe block. The `unsafe_op_in_unsafe_fn` lint can be enabled to
-/// change that.
-///
 /// # Unsafe abilities
 ///
 /// **No matter what, Safe Rust can't cause Undefined Behavior**. This is
@@ -1961,13 +1957,6 @@ mod type_keyword {}
 /// - `unsafe impl`: the contract necessary to implement the trait has been
 /// checked by the programmer and is guaranteed to be respected.
 ///
-/// By default, `unsafe fn` also acts like an `unsafe {}` block
-/// around the code inside the function. This means it is not just a signal to
-/// the caller, but also promises that the preconditions for the operations
-/// inside the function are upheld. Mixing these two meanings can be confusing, so the
-/// `unsafe_op_in_unsafe_fn` lint can be enabled to warn against that and require explicit unsafe
-/// blocks even inside `unsafe fn`.
-///
 /// See the [Rustonomicon] and the [Reference] for more information.
 ///
 /// # Examples
@@ -2109,6 +2098,7 @@ mod type_keyword {}
 /// impl Indexable for i32 {
 ///     const LEN: usize = 1;
 ///
+///     /// See `Indexable` for the safety contract.
 ///     unsafe fn idx_unchecked(&self, idx: usize) -> i32 {
 ///         debug_assert_eq!(idx, 0);
 ///         *self
@@ -2120,6 +2110,7 @@ mod type_keyword {}
 /// impl Indexable for [i32; 42] {
 ///     const LEN: usize = 42;
 ///
+///     /// See `Indexable` for the safety contract.
 ///     unsafe fn idx_unchecked(&self, idx: usize) -> i32 {
 ///         // SAFETY: As per this trait's documentation, the caller ensures
 ///         // that `idx < 42`.
@@ -2132,6 +2123,7 @@ mod type_keyword {}
 /// impl Indexable for ! {
 ///     const LEN: usize = 0;
 ///
+///     /// See `Indexable` for the safety contract.
 ///     unsafe fn idx_unchecked(&self, idx: usize) -> i32 {
 ///         // SAFETY: As per this trait's documentation, the caller ensures
 ///         // that `idx < 0`, which is impossible, so this is dead code.
@@ -2153,11 +2145,14 @@ mod type_keyword {}
 /// contract of `idx_unchecked`. Implementing `Indexable` is safe because when writing
 /// `idx_unchecked`, we don't have to worry: our *callers* need to discharge a proof obligation
 /// (like `use_indexable` does), but the *implementation* of `get_unchecked` has no proof obligation
-/// to contend with. Of course, the implementation of `Indexable` may choose to call other unsafe
-/// operations, and then it needs an `unsafe` *block* to indicate it discharged the proof
-/// obligations of its callees. (We enabled `unsafe_op_in_unsafe_fn`, so the body of `idx_unchecked`
-/// is not implicitly an unsafe block.) For that purpose it can make use of the contract that all
-/// its callers must uphold -- the fact that `idx < LEN`.
+/// to contend with. Of course, the implementation may choose to call other unsafe operations, and
+/// then it needs an `unsafe` *block* to indicate it discharged the proof obligations of its
+/// callees. For that purpose it can make use of the contract that all its callers must uphold --
+/// the fact that `idx < LEN`.
+///
+/// Note that unlike normal `unsafe fn`, an `unsafe fn` in a trait implementation does not get to
+/// just pick an arbitrary safety contract! It *has* to use the safety contract defined by the trait
+/// (or one with weaker preconditions).
 ///
 /// Formally speaking, an `unsafe fn` in a trait is a function with *preconditions* that go beyond
 /// those encoded by the argument types (such as `idx < LEN`), whereas an `unsafe trait` can declare

std/src/sys/fs/hermit.rs

@@ -422,6 +422,10 @@ impl File {
         self.0.seek(pos)
     }
 
+    pub fn size(&self) -> Option<io::Result<u64>> {
+        None
+    }
+
     pub fn tell(&self) -> io::Result<u64> {
         self.0.tell()
     }

std/src/sys/fs/solid.rs

@@ -459,6 +459,10 @@ impl File {
         self.tell()
     }
 
+    pub fn size(&self) -> Option<io::Result<u64>> {
+        None
+    }
+
     pub fn tell(&self) -> io::Result<u64> {
         unsafe {
             let mut out_offset = MaybeUninit::uninit();