Auto merge of #62704 - Mark-Simulacrum:rollup-oi94s2j, r=Mark-Simulacrum

Rollup of 14 pull requests

Successful merges:

 - #62103 (Add debug assertions to write_bytes and copy*)
 - #62405 (Remove never_type feature requirement for exhaustive patterns)
 - #62491 (Fix Pin urls in Option documentation)
 - #62533 (Add missing links for CannotReallocInPlace type)
 - #62634 (Less unsafe in the array example of MaybeUninit docs)
 - #62639 (Make VaListImpl<'f> invariant over the 'f lifetime)
 - #62646 (Tweak wording in feature gate errors)
 - #62662 (add spaces in front of trait requirements in libcore/cell.rs)
 - #62668 (Fix #62660)
 - #62673 (miri validation: better error messages for dangling references)
 - #62680 (Actually call `visit_block_entry` in `DataflowResultsConsumer`)
 - #62685 (Add info about undefined behavior to as_ref suggestions)
 - #62689 (Fix typo in RawWaker::new documentation)
 - #62698 (SGX target: don't pretend to be GNU/Linux to LLVM)

Failed merges:

r? @ghost

Author: bors

Cargo.lock

@@ -25,7 +25,7 @@ dependencies = [
 name = "alloc"
 version = "0.0.0"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
  "rand 0.6.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand_xorshift 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -131,7 +131,7 @@ dependencies = [
  "autocfg 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "backtrace-sys 0.1.27 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.54 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-demangle 0.1.15 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-core 1.0.0",
@@ -143,7 +143,7 @@ version = "0.1.27"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.54 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-core 1.0.0",
 ]
@@ -373,7 +373,7 @@ name = "cfg-if"
 version = "0.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-core 1.0.0",
 ]
 
@@ -502,7 +502,7 @@ dependencies = [
 
 [[package]]
 name = "compiler_builtins"
-version = "0.1.16"
+version = "0.1.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -834,7 +834,7 @@ name = "dlmalloc"
 version = "0.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.54 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-core 1.0.0",
 ]
@@ -1008,7 +1008,7 @@ name = "fortanix-sgx-abi"
 version = "0.3.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-core 1.0.0",
 ]
 
@@ -1199,7 +1199,7 @@ name = "hashbrown"
 version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-alloc 1.0.0",
  "rustc-std-workspace-core 1.0.0",
 ]
@@ -2066,7 +2066,7 @@ dependencies = [
 name = "panic_abort"
 version = "0.0.0"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
  "libc 0.2.54 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -2077,7 +2077,7 @@ version = "0.0.0"
 dependencies = [
  "alloc 0.0.0",
  "cfg-if 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
  "libc 0.2.54 (registry+https://github.com/rust-lang/crates.io-index)",
  "unwind 0.0.0",
@@ -2263,7 +2263,7 @@ name = "profiler_builtins"
 version = "0.0.0"
 dependencies = [
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
 ]
 
@@ -2835,7 +2835,7 @@ name = "rustc-demangle"
 version = "0.1.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-std-workspace-core 1.0.0",
 ]
 
@@ -2941,7 +2941,7 @@ dependencies = [
  "alloc 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.38 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
 ]
 
@@ -3160,7 +3160,7 @@ dependencies = [
  "alloc 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.38 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
 ]
 
@@ -3223,7 +3223,7 @@ dependencies = [
  "alloc 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.38 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
 ]
 
@@ -3341,7 +3341,7 @@ dependencies = [
  "alloc 0.0.0",
  "build_helper 0.1.0",
  "cmake 0.1.38 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
 ]
 
@@ -3648,7 +3648,7 @@ dependencies = [
  "backtrace 0.3.29 (registry+https://github.com/rust-lang/crates.io-index)",
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
  "dlmalloc 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "fortanix-sgx-abi 0.3.2 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -4309,7 +4309,7 @@ version = "0.0.0"
 dependencies = [
  "cc 1.0.35 (registry+https://github.com/rust-lang/crates.io-index)",
  "cfg-if 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)",
+ "compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)",
  "core 0.0.0",
  "libc 0.2.54 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -4527,7 +4527,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 "checksum colored 1.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b0aa3473e85a3161b59845d6096b289bb577874cafeaf75ea1b1beaa6572c7fc"
 "checksum commoncrypto 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d056a8586ba25a1e4d61cb090900e495952c7886786fc55f909ab2f819b69007"
 "checksum commoncrypto-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1fed34f46747aa73dfaa578069fd8279d2818ade2b55f38f22a9401c7f4083e2"
-"checksum compiler_builtins 0.1.16 (registry+https://github.com/rust-lang/crates.io-index)" = "e79ed19793c99771b386d76e08c3419409bb3d418b81a8b8afc73524247461cf"
+"checksum compiler_builtins 0.1.17 (registry+https://github.com/rust-lang/crates.io-index)" = "ad9b4731b9e701aefe9e6bd1e9173f30526661508f9aaadaa5caec25ddf95585"
 "checksum compiletest_rs 0.3.22 (registry+https://github.com/rust-lang/crates.io-index)" = "f40ecc9332b68270998995c00f8051ee856121764a0d3230e64c9efd059d27b6"
 "checksum constant_time_eq 0.1.3 (registry+https://github.com/rust-lang/crates.io-index)" = "8ff012e225ce166d4422e0e78419d901719760f62ae2b7969ca6b564d1b54a9e"
 "checksum core-foundation 0.6.3 (registry+https://github.com/rust-lang/crates.io-index)" = "4e2640d6d0bf22e82bed1b73c6aef8d5dd31e5abe6666c57e6d45e2649f4f887"

src/libcore/alloc.rs

@@ -359,9 +359,12 @@ impl fmt::Display for AllocErr {
     }
 }
 
-/// The `CannotReallocInPlace` error is used when `grow_in_place` or
-/// `shrink_in_place` were unable to reuse the given memory block for
+/// The `CannotReallocInPlace` error is used when [`grow_in_place`] or
+/// [`shrink_in_place`] were unable to reuse the given memory block for
 /// a requested layout.
+///
+/// [`grow_in_place`]: ./trait.Alloc.html#method.grow_in_place
+/// [`shrink_in_place`]: ./trait.Alloc.html#method.shrink_in_place
 #[unstable(feature = "allocator_api", issue = "32838")]
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct CannotReallocInPlace;

src/libcore/cell.rs

@@ -290,7 +290,7 @@ impl<T:Copy> Clone for Cell<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T:Default> Default for Cell<T> {
+impl<T: Default> Default for Cell<T> {
     /// Creates a `Cell<T>`, with the `Default` value for T.
     #[inline]
     fn default() -> Cell<T> {
@@ -299,18 +299,18 @@ impl<T:Default> Default for Cell<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T:PartialEq + Copy> PartialEq for Cell<T> {
+impl<T: PartialEq + Copy> PartialEq for Cell<T> {
     #[inline]
     fn eq(&self, other: &Cell<T>) -> bool {
         self.get() == other.get()
     }
 }
 
 #[stable(feature = "cell_eq", since = "1.2.0")]
-impl<T:Eq + Copy> Eq for Cell<T> {}
+impl<T: Eq + Copy> Eq for Cell<T> {}
 
 #[stable(feature = "cell_ord", since = "1.10.0")]
-impl<T:PartialOrd + Copy> PartialOrd for Cell<T> {
+impl<T: PartialOrd + Copy> PartialOrd for Cell<T> {
     #[inline]
     fn partial_cmp(&self, other: &Cell<T>) -> Option<Ordering> {
         self.get().partial_cmp(&other.get())
@@ -338,7 +338,7 @@ impl<T:PartialOrd + Copy> PartialOrd for Cell<T> {
 }
 
 #[stable(feature = "cell_ord", since = "1.10.0")]
-impl<T:Ord + Copy> Ord for Cell<T> {
+impl<T: Ord + Copy> Ord for Cell<T> {
     #[inline]
     fn cmp(&self, other: &Cell<T>) -> Ordering {
         self.get().cmp(&other.get())
@@ -1008,7 +1008,7 @@ impl<T: Clone> Clone for RefCell<T> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T:Default> Default for RefCell<T> {
+impl<T: Default> Default for RefCell<T> {
     /// Creates a `RefCell<T>`, with the `Default` value for T.
     #[inline]
     fn default() -> RefCell<T> {

src/libcore/ffi.rs

@@ -60,7 +60,10 @@ impl fmt::Debug for c_void {
 #[lang = "va_list"]
 pub struct VaListImpl<'f> {
     ptr: *mut c_void,
-    _marker: PhantomData<&'f c_void>,
+
+    // Invariant over `'f`, so each `VaListImpl<'f>` object is tied to
+    // the region of the function it's defined in
+    _marker: PhantomData<&'f mut &'f c_void>,
 }
 
 #[cfg(any(all(not(target_arch = "aarch64"), not(target_arch = "powerpc"),
@@ -96,7 +99,7 @@ pub struct VaListImpl<'f> {
     vr_top: *mut c_void,
     gr_offs: i32,
     vr_offs: i32,
-    _marker: PhantomData<&'f c_void>,
+    _marker: PhantomData<&'f mut &'f c_void>,
 }
 
 /// PowerPC ABI implementation of a `va_list`.
@@ -114,7 +117,7 @@ pub struct VaListImpl<'f> {
     reserved: u16,
     overflow_arg_area: *mut c_void,
     reg_save_area: *mut c_void,
-    _marker: PhantomData<&'f c_void>,
+    _marker: PhantomData<&'f mut &'f c_void>,
 }
 
 /// x86_64 ABI implementation of a `va_list`.
@@ -131,7 +134,7 @@ pub struct VaListImpl<'f> {
     fp_offset: i32,
     overflow_arg_area: *mut c_void,
     reg_save_area: *mut c_void,
-    _marker: PhantomData<&'f c_void>,
+    _marker: PhantomData<&'f mut &'f c_void>,
 }
 
 /// asm.js ABI implementation of a `va_list`.
@@ -148,7 +151,7 @@ pub struct VaListImpl<'f> {
 #[lang = "va_list"]
 pub struct VaListImpl<'f> {
     inner: [crate::mem::MaybeUninit<i32>; 4],
-    _marker: PhantomData<&'f c_void>,
+    _marker: PhantomData<&'f mut &'f c_void>,
 }
 
 #[cfg(all(target_arch = "asmjs", not(windows)))]

src/libcore/intrinsics.rs

@@ -36,6 +36,8 @@
             issue = "0")]
 #![allow(missing_docs)]
 
+use crate::mem;
+
 #[stable(feature = "drop_in_place", since = "1.8.0")]
 #[rustc_deprecated(reason = "no longer an intrinsic - use `ptr::drop_in_place` directly",
                    since = "1.18.0")]
@@ -1323,6 +1325,26 @@ extern "rust-intrinsic" {
 // (`transmute` also falls into this category, but it cannot be wrapped due to the
 // check that `T` and `U` have the same size.)
 
+/// Checks whether `ptr` is properly aligned with respect to
+/// `align_of::<T>()`.
+pub(crate) fn is_aligned_and_not_null<T>(ptr: *const T) -> bool {
+    !ptr.is_null() && ptr as usize % mem::align_of::<T>() == 0
+}
+
+/// Checks whether the regions of memory starting at `src` and `dst` of size
+/// `count * size_of::<T>()` overlap.
+fn overlaps<T>(src: *const T, dst: *const T, count: usize) -> bool {
+    let src_usize = src as usize;
+    let dst_usize = dst as usize;
+    let size = mem::size_of::<T>().checked_mul(count).unwrap();
+    let diff = if src_usize > dst_usize {
+        src_usize - dst_usize
+    } else {
+        dst_usize - src_usize
+    };
+    size > diff
+}
+
 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
 /// and destination must *not* overlap.
 ///
@@ -1412,7 +1434,11 @@ pub unsafe fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize) {
     extern "rust-intrinsic" {
         fn copy_nonoverlapping<T>(src: *const T, dst: *mut T, count: usize);
     }
-    copy_nonoverlapping(src, dst, count);
+
+    debug_assert!(is_aligned_and_not_null(src), "attempt to copy from unaligned or null pointer");
+    debug_assert!(is_aligned_and_not_null(dst), "attempt to copy to unaligned or null pointer");
+    debug_assert!(!overlaps(src, dst, count), "attempt to copy to overlapping memory");
+    copy_nonoverlapping(src, dst, count)
 }
 
 /// Copies `count * size_of::<T>()` bytes from `src` to `dst`. The source
@@ -1472,6 +1498,9 @@ pub unsafe fn copy<T>(src: *const T, dst: *mut T, count: usize) {
     extern "rust-intrinsic" {
         fn copy<T>(src: *const T, dst: *mut T, count: usize);
     }
+
+    debug_assert!(is_aligned_and_not_null(src), "attempt to copy from unaligned or null pointer");
+    debug_assert!(is_aligned_and_not_null(dst), "attempt to copy to unaligned or null pointer");
     copy(src, dst, count)
 }
 
@@ -1553,5 +1582,7 @@ pub unsafe fn write_bytes<T>(dst: *mut T, val: u8, count: usize) {
     extern "rust-intrinsic" {
         fn write_bytes<T>(dst: *mut T, val: u8, count: usize);
     }
+
+    debug_assert!(is_aligned_and_not_null(dst), "attempt to write to unaligned or null pointer");
     write_bytes(dst, val, count)
 }

src/libcore/mem/maybe_uninit.rs

@@ -112,7 +112,6 @@ use crate::mem::ManuallyDrop;
 ///
 /// ```
 /// use std::mem::{self, MaybeUninit};
-/// use std::ptr;
 ///
 /// let data = {
 ///     // Create an uninitialized array of `MaybeUninit`. The `assume_init` is
@@ -122,10 +121,13 @@ use crate::mem::ManuallyDrop;
 ///         MaybeUninit::uninit().assume_init()
 ///     };
 ///
-///     // Dropping a `MaybeUninit` does nothing, so if there is a panic during this loop,
-///     // we have a memory leak, but there is no memory safety issue.
+///     // Dropping a `MaybeUninit` does nothing. Thus using raw pointer
+///     // assignment instead of `ptr::write` does not cause the old
+///     // uninitialized value to be dropped. Also if there is a panic during
+///     // this loop, we have a memory leak, but there is no memory safety
+///     // issue.
 ///     for elem in &mut data[..] {
-///         unsafe { ptr::write(elem.as_mut_ptr(), vec![42]); }
+///         *elem = MaybeUninit::new(vec![42]);
 ///     }
 ///
 ///     // Everything is initialized. Transmute the array to the
@@ -151,7 +153,7 @@ use crate::mem::ManuallyDrop;
 /// let mut data_len: usize = 0;
 ///
 /// for elem in &mut data[0..500] {
-///     unsafe { ptr::write(elem.as_mut_ptr(), String::from("hello")); }
+///     *elem = MaybeUninit::new(String::from("hello"));
 ///     data_len += 1;
 /// }
 ///