split core::ptr module into multiple files

3 files changed, 3152 insertions, 0 deletions

diff --git a/src/libcore/ptr/mod.rs b/src/libcore/ptr/mod.rs
new file mode 100644
index 00000000000..80ac67d8eb5
--- /dev/null
+++ b/src/libcore/ptr/mod.rs
@@ -0,0 +1,2746 @@
+//! Manually manage memory through raw pointers.
+//!
+//! *[See also the pointer primitive types](../../std/primitive.pointer.html).*
+//!
+//! # Safety
+//!
+//! Many functions in this module take raw pointers as arguments and read from
+//! or write to them. For this to be safe, these pointers must be *valid*.
+//! Whether a pointer is valid depends on the operation it is used for
+//! (read or write), and the extent of the memory that is accessed (i.e.,
+//! how many bytes are read/written). Most functions use `*mut T` and `*const T`
+//! to access only a single value, in which case the documentation omits the size
+//! and implicitly assumes it to be `size_of::<T>()` bytes.
+//!
+//! The precise rules for validity are not determined yet. The guarantees that are
+//! provided at this point are very minimal:
+//!
+//! * A [null] pointer is *never* valid, not even for accesses of [size zero][zst].
+//! * All pointers (except for the null pointer) are valid for all operations of
+//!   [size zero][zst].
+//! * All accesses performed by functions in this module are *non-atomic* in the sense
+//!   of [atomic operations] used to synchronize between threads. This means it is
+//!   undefined behavior to perform two concurrent accesses to the same location from different
+//!   threads unless both accesses only read from memory. Notice that this explicitly
+//!   includes [`read_volatile`] and [`write_volatile`]: Volatile accesses cannot
+//!   be used for inter-thread synchronization.
+//! * The result of casting a reference to a pointer is valid for as long as the
+//!   underlying object is live and no reference (just raw pointers) is used to
+//!   access the same memory.
+//!
+//! These axioms, along with careful use of [`offset`] for pointer arithmetic,
+//! are enough to correctly implement many useful things in unsafe code. Stronger guarantees
+//! will be provided eventually, as the [aliasing] rules are being determined. For more
+//! information, see the [book] as well as the section in the reference devoted
+//! to [undefined behavior][ub].
+//!
+//! ## Alignment
+//!
+//! Valid raw pointers as defined above are not necessarily properly aligned (where
+//! "proper" alignment is defined by the pointee type, i.e., `*const T` must be
+//! aligned to `mem::align_of::<T>()`). However, most functions require their
+//! arguments to be properly aligned, and will explicitly state
+//! this requirement in their documentation. Notable exceptions to this are
+//! [`read_unaligned`] and [`write_unaligned`].
+//!
+//! When a function requires proper alignment, it does so even if the access
+//! has size 0, i.e., even if memory is not actually touched. Consider using
+//! [`NonNull::dangling`] in such cases.
+//!
+//! [aliasing]: ../../nomicon/aliasing.html
+//! [book]: ../../book/ch19-01-unsafe-rust.html#dereferencing-a-raw-pointer
+//! [ub]: ../../reference/behavior-considered-undefined.html
+//! [null]: ./fn.null.html
+//! [zst]: ../../nomicon/exotic-sizes.html#zero-sized-types-zsts
+//! [atomic operations]: ../../std/sync/atomic/index.html
+//! [`copy`]: ../../std/ptr/fn.copy.html
+//! [`offset`]: ../../std/primitive.pointer.html#method.offset
+//! [`read_unaligned`]: ./fn.read_unaligned.html
+//! [`write_unaligned`]: ./fn.write_unaligned.html
+//! [`read_volatile`]: ./fn.read_volatile.html
+//! [`write_volatile`]: ./fn.write_volatile.html
+//! [`NonNull::dangling`]: ./struct.NonNull.html#method.dangling
+
+#![stable(feature = "rust1", since = "1.0.0")]
+
+use crate::intrinsics;
+use crate::fmt;
+use crate::hash;
+use crate::mem::{self, MaybeUninit};
+use crate::cmp::Ordering::{self, Less, Equal, Greater};
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use crate::intrinsics::copy_nonoverlapping;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use crate::intrinsics::copy;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+pub use crate::intrinsics::write_bytes;
+
+mod non_null;
+#[stable(feature = "nonnull", since = "1.25.0")]
+pub use non_null::NonNull;
+
+mod unique;
+#[unstable(feature = "ptr_internals", issue = "0")]
+pub use unique::Unique;
+
+/// Executes the destructor (if any) of the pointed-to value.
+///
+/// This is semantically equivalent to calling [`ptr::read`] and discarding
+/// the result, but has the following advantages:
+///
+/// * It is *required* to use `drop_in_place` to drop unsized types like
+///   trait objects, because they can't be read out onto the stack and
+///   dropped normally.
+///
+/// * It is friendlier to the optimizer to do this over [`ptr::read`] when
+///   dropping manually allocated memory (e.g., when writing Box/Rc/Vec),
+///   as the compiler doesn't need to prove that it's sound to elide the
+///   copy.
+///
+/// [`ptr::read`]: ../ptr/fn.read.html
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `to_drop` must be [valid] for reads.
+///
+/// * `to_drop` must be properly aligned. See the example below for how to drop
+///   an unaligned pointer.
+///
+/// Additionally, if `T` is not [`Copy`], using the pointed-to value after
+/// calling `drop_in_place` can cause undefined behavior. Note that `*to_drop =
+/// foo` counts as a use because it will cause the value to be dropped
+/// again. [`write`] can be used to overwrite data without causing it to be
+/// dropped.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+/// [`Copy`]: ../marker/trait.Copy.html
+/// [`write`]: ../ptr/fn.write.html
+///
+/// # Examples
+///
+/// Manually remove the last item from a vector:
+///
+/// ```
+/// use std::ptr;
+/// use std::rc::Rc;
+///
+/// let last = Rc::new(1);
+/// let weak = Rc::downgrade(&last);
+///
+/// let mut v = vec![Rc::new(0), last];
+///
+/// unsafe {
+///     // Get a raw pointer to the last element in `v`.
+///     let ptr = &mut v[1] as *mut _;
+///     // Shorten `v` to prevent the last item from being dropped. We do that first,
+///     // to prevent issues if the `drop_in_place` below panics.
+///     v.set_len(1);
+///     // Without a call `drop_in_place`, the last item would never be dropped,
+///     // and the memory it manages would be leaked.
+///     ptr::drop_in_place(ptr);
+/// }
+///
+/// assert_eq!(v, &[0.into()]);
+///
+/// // Ensure that the last item was dropped.
+/// assert!(weak.upgrade().is_none());
+/// ```
+///
+/// Unaligned values cannot be dropped in place, they must be copied to an aligned
+/// location first:
+/// ```
+/// use std::ptr;
+/// use std::mem::{self, MaybeUninit};
+///
+/// unsafe fn drop_after_copy<T>(to_drop: *mut T) {
+///     let mut copy: MaybeUninit<T> = MaybeUninit::uninit();
+///     ptr::copy(to_drop, copy.as_mut_ptr(), 1);
+///     drop(copy.assume_init());
+/// }
+///
+/// #[repr(packed, C)]
+/// struct Packed {
+///     _padding: u8,
+///     unaligned: Vec<i32>,
+/// }
+///
+/// let mut p = Packed { _padding: 0, unaligned: vec![42] };
+/// unsafe {
+///     drop_after_copy(&mut p.unaligned as *mut _);
+///     mem::forget(p);
+/// }
+/// ```
+///
+/// Notice that the compiler performs this copy automatically when dropping packed structs,
+/// i.e., you do not usually have to worry about such issues unless you call `drop_in_place`
+/// manually.
+#[stable(feature = "drop_in_place", since = "1.8.0")]
+#[inline(always)]
+pub unsafe fn drop_in_place<T: ?Sized>(to_drop: *mut T) {
+    real_drop_in_place(&mut *to_drop)
+}
+
+// The real `drop_in_place` -- the one that gets called implicitly when variables go
+// out of scope -- should have a safe reference and not a raw pointer as argument
+// type.  When we drop a local variable, we access it with a pointer that behaves
+// like a safe reference; transmuting that to a raw pointer does not mean we can
+// actually access it with raw pointers.
+#[lang = "drop_in_place"]
+#[allow(unconditional_recursion)]
+unsafe fn real_drop_in_place<T: ?Sized>(to_drop: &mut T) {
+    // Code here does not matter - this is replaced by the
+    // real drop glue by the compiler.
+    real_drop_in_place(to_drop)
+}
+
+/// Creates a null raw pointer.
+///
+/// # Examples
+///
+/// ```
+/// use std::ptr;
+///
+/// let p: *const i32 = ptr::null();
+/// assert!(p.is_null());
+/// ```
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_promotable]
+pub const fn null<T>() -> *const T { 0 as *const T }
+
+/// Creates a null mutable raw pointer.
+///
+/// # Examples
+///
+/// ```
+/// use std::ptr;
+///
+/// let p: *mut i32 = ptr::null_mut();
+/// assert!(p.is_null());
+/// ```
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+#[rustc_promotable]
+pub const fn null_mut<T>() -> *mut T { 0 as *mut T }
+
+/// Swaps the values at two mutable locations of the same type, without
+/// deinitializing either.
+///
+/// But for the following two exceptions, this function is semantically
+/// equivalent to [`mem::swap`]:
+///
+/// * It operates on raw pointers instead of references. When references are
+///   available, [`mem::swap`] should be preferred.
+///
+/// * The two pointed-to values may overlap. If the values do overlap, then the
+///   overlapping region of memory from `x` will be used. This is demonstrated
+///   in the second example below.
+///
+/// [`mem::swap`]: ../mem/fn.swap.html
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * Both `x` and `y` must be [valid] for reads and writes.
+///
+/// * Both `x` and `y` must be properly aligned.
+///
+/// Note that even if `T` has size `0`, the pointers must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+///
+/// # Examples
+///
+/// Swapping two non-overlapping regions:
+///
+/// ```
+/// use std::ptr;
+///
+/// let mut array = [0, 1, 2, 3];
+///
+/// let x = array[0..].as_mut_ptr() as *mut [u32; 2]; // this is `array[0..2]`
+/// let y = array[2..].as_mut_ptr() as *mut [u32; 2]; // this is `array[2..4]`
+///
+/// unsafe {
+///     ptr::swap(x, y);
+///     assert_eq!([2, 3, 0, 1], array);
+/// }
+/// ```
+///
+/// Swapping two overlapping regions:
+///
+/// ```
+/// use std::ptr;
+///
+/// let mut array = [0, 1, 2, 3];
+///
+/// let x = array[0..].as_mut_ptr() as *mut [u32; 3]; // this is `array[0..3]`
+/// let y = array[1..].as_mut_ptr() as *mut [u32; 3]; // this is `array[1..4]`
+///
+/// unsafe {
+///     ptr::swap(x, y);
+///     // The indices `1..3` of the slice overlap between `x` and `y`.
+///     // Reasonable results would be for to them be `[2, 3]`, so that indices `0..3` are
+///     // `[1, 2, 3]` (matching `y` before the `swap`); or for them to be `[0, 1]`
+///     // so that indices `1..4` are `[0, 1, 2]` (matching `x` before the `swap`).
+///     // This implementation is defined to make the latter choice.
+///     assert_eq!([1, 0, 1, 2], array);
+/// }
+/// ```
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub unsafe fn swap<T>(x: *mut T, y: *mut T) {
+    // Give ourselves some scratch space to work with.
+    // We do not have to worry about drops: `MaybeUninit` does nothing when dropped.
+    let mut tmp = MaybeUninit::<T>::uninit();
+
+    // Perform the swap
+    copy_nonoverlapping(x, tmp.as_mut_ptr(), 1);
+    copy(y, x, 1); // `x` and `y` may overlap
+    copy_nonoverlapping(tmp.as_ptr(), y, 1);
+}
+
+/// Swaps `count * size_of::<T>()` bytes between the two regions of memory
+/// beginning at `x` and `y`. The two regions must *not* overlap.
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * Both `x` and `y` must be [valid] for reads and writes of `count *
+///   size_of::<T>()` bytes.
+///
+/// * Both `x` and `y` must be properly aligned.
+///
+/// * The region of memory beginning at `x` with a size of `count *
+///   size_of::<T>()` bytes must *not* overlap with the region of memory
+///   beginning at `y` with the same size.
+///
+/// Note that even if the effectively copied size (`count * size_of::<T>()`) is `0`,
+/// the pointers must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// use std::ptr;
+///
+/// let mut x = [1, 2, 3, 4];
+/// let mut y = [7, 8, 9];
+///
+/// unsafe {
+///     ptr::swap_nonoverlapping(x.as_mut_ptr(), y.as_mut_ptr(), 2);
+/// }
+///
+/// assert_eq!(x, [7, 8, 3, 4]);
+/// assert_eq!(y, [1, 2, 9]);
+/// ```
+#[inline]
+#[stable(feature = "swap_nonoverlapping", since = "1.27.0")]
+pub unsafe fn swap_nonoverlapping<T>(x: *mut T, y: *mut T, count: usize) {
+    let x = x as *mut u8;
+    let y = y as *mut u8;
+    let len = mem::size_of::<T>() * count;
+    swap_nonoverlapping_bytes(x, y, len)
+}
+
+#[inline]
+pub(crate) unsafe fn swap_nonoverlapping_one<T>(x: *mut T, y: *mut T) {
+    // For types smaller than the block optimization below,
+    // just swap directly to avoid pessimizing codegen.
+    if mem::size_of::<T>() < 32 {
+        let z = read(x);
+        copy_nonoverlapping(y, x, 1);
+        write(y, z);
+    } else {
+        swap_nonoverlapping(x, y, 1);
+    }
+}
+
+#[inline]
+unsafe fn swap_nonoverlapping_bytes(x: *mut u8, y: *mut u8, len: usize) {
+    // The approach here is to utilize simd to swap x & y efficiently. Testing reveals
+    // that swapping either 32 bytes or 64 bytes at a time is most efficient for Intel
+    // Haswell E processors. LLVM is more able to optimize if we give a struct a
+    // #[repr(simd)], even if we don't actually use this struct directly.
+    //
+    // FIXME repr(simd) broken on emscripten and redox
+    #[cfg_attr(not(any(target_os = "emscripten", target_os = "redox")), repr(simd))]
+    struct Block(u64, u64, u64, u64);
+    struct UnalignedBlock(u64, u64, u64, u64);
+
+    let block_size = mem::size_of::<Block>();
+
+    // Loop through x & y, copying them `Block` at a time
+    // The optimizer should unroll the loop fully for most types
+    // N.B. We can't use a for loop as the `range` impl calls `mem::swap` recursively
+    let mut i = 0;
+    while i + block_size <= len {
+        // Create some uninitialized memory as scratch space
+        // Declaring `t` here avoids aligning the stack when this loop is unused
+        let mut t = mem::MaybeUninit::<Block>::uninit();
+        let t = t.as_mut_ptr() as *mut u8;
+        let x = x.add(i);
+        let y = y.add(i);
+
+        // Swap a block of bytes of x & y, using t as a temporary buffer
+        // This should be optimized into efficient SIMD operations where available
+        copy_nonoverlapping(x, t, block_size);
+        copy_nonoverlapping(y, x, block_size);
+        copy_nonoverlapping(t, y, block_size);
+        i += block_size;
+    }
+
+    if i < len {
+        // Swap any remaining bytes
+        let mut t = mem::MaybeUninit::<UnalignedBlock>::uninit();
+        let rem = len - i;
+
+        let t = t.as_mut_ptr() as *mut u8;
+        let x = x.add(i);
+        let y = y.add(i);
+
+        copy_nonoverlapping(x, t, rem);
+        copy_nonoverlapping(y, x, rem);
+        copy_nonoverlapping(t, y, rem);
+    }
+}
+
+/// Moves `src` into the pointed `dst`, returning the previous `dst` value.
+///
+/// Neither value is dropped.
+///
+/// This function is semantically equivalent to [`mem::replace`] except that it
+/// operates on raw pointers instead of references. When references are
+/// available, [`mem::replace`] should be preferred.
+///
+/// [`mem::replace`]: ../mem/fn.replace.html
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `dst` must be [valid] for writes.
+///
+/// * `dst` must be properly aligned.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+///
+/// # Examples
+///
+/// ```
+/// use std::ptr;
+///
+/// let mut rust = vec!['b', 'u', 's', 't'];
+///
+/// // `mem::replace` would have the same effect without requiring the unsafe
+/// // block.
+/// let b = unsafe {
+///     ptr::replace(&mut rust[0], 'r')
+/// };
+///
+/// assert_eq!(b, 'b');
+/// assert_eq!(rust, &['r', 'u', 's', 't']);
+/// ```
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub unsafe fn replace<T>(dst: *mut T, mut src: T) -> T {
+    mem::swap(&mut *dst, &mut src); // cannot overlap
+    src
+}
+
+/// Reads the value from `src` without moving it. This leaves the
+/// memory in `src` unchanged.
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `src` must be [valid] for reads.
+///
+/// * `src` must be properly aligned. Use [`read_unaligned`] if this is not the
+///   case.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// let x = 12;
+/// let y = &x as *const i32;
+///
+/// unsafe {
+///     assert_eq!(std::ptr::read(y), 12);
+/// }
+/// ```
+///
+/// Manually implement [`mem::swap`]:
+///
+/// ```
+/// use std::ptr;
+///
+/// fn swap<T>(a: &mut T, b: &mut T) {
+///     unsafe {
+///         // Create a bitwise copy of the value at `a` in `tmp`.
+///         let tmp = ptr::read(a);
+///
+///         // Exiting at this point (either by explicitly returning or by
+///         // calling a function which panics) would cause the value in `tmp` to
+///         // be dropped while the same value is still referenced by `a`. This
+///         // could trigger undefined behavior if `T` is not `Copy`.
+///
+///         // Create a bitwise copy of the value at `b` in `a`.
+///         // This is safe because mutable references cannot alias.
+///         ptr::copy_nonoverlapping(b, a, 1);
+///
+///         // As above, exiting here could trigger undefined behavior because
+///         // the same value is referenced by `a` and `b`.
+///
+///         // Move `tmp` into `b`.
+///         ptr::write(b, tmp);
+///
+///         // `tmp` has been moved (`write` takes ownership of its second argument),
+///         // so nothing is dropped implicitly here.
+///     }
+/// }
+///
+/// let mut foo = "foo".to_owned();
+/// let mut bar = "bar".to_owned();
+///
+/// swap(&mut foo, &mut bar);
+///
+/// assert_eq!(foo, "bar");
+/// assert_eq!(bar, "foo");
+/// ```
+///
+/// ## Ownership of the Returned Value
+///
+/// `read` creates a bitwise copy of `T`, regardless of whether `T` is [`Copy`].
+/// If `T` is not [`Copy`], using both the returned value and the value at
+/// `*src` can violate memory safety. Note that assigning to `*src` counts as a
+/// use because it will attempt to drop the value at `*src`.
+///
+/// [`write`] can be used to overwrite data without causing it to be dropped.
+///
+/// ```
+/// use std::ptr;
+///
+/// let mut s = String::from("foo");
+/// unsafe {
+///     // `s2` now points to the same underlying memory as `s`.
+///     let mut s2: String = ptr::read(&s);
+///
+///     assert_eq!(s2, "foo");
+///
+///     // Assigning to `s2` causes its original value to be dropped. Beyond
+///     // this point, `s` must no longer be used, as the underlying memory has
+///     // been freed.
+///     s2 = String::default();
+///     assert_eq!(s2, "");
+///
+///     // Assigning to `s` would cause the old value to be dropped again,
+///     // resulting in undefined behavior.
+///     // s = String::from("bar"); // ERROR
+///
+///     // `ptr::write` can be used to overwrite a value without dropping it.
+///     ptr::write(&mut s, String::from("bar"));
+/// }
+///
+/// assert_eq!(s, "bar");
+/// ```
+///
+/// [`mem::swap`]: ../mem/fn.swap.html
+/// [valid]: ../ptr/index.html#safety
+/// [`Copy`]: ../marker/trait.Copy.html
+/// [`read_unaligned`]: ./fn.read_unaligned.html
+/// [`write`]: ./fn.write.html
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub unsafe fn read<T>(src: *const T) -> T {
+    let mut tmp = MaybeUninit::<T>::uninit();
+    copy_nonoverlapping(src, tmp.as_mut_ptr(), 1);
+    tmp.assume_init()
+}
+
+/// Reads the value from `src` without moving it. This leaves the
+/// memory in `src` unchanged.
+///
+/// Unlike [`read`], `read_unaligned` works with unaligned pointers.
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `src` must be [valid] for reads.
+///
+/// Like [`read`], `read_unaligned` creates a bitwise copy of `T`, regardless of
+/// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the returned
+/// value and the value at `*src` can [violate memory safety][read-ownership].
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL.
+///
+/// [`Copy`]: ../marker/trait.Copy.html
+/// [`read`]: ./fn.read.html
+/// [`write_unaligned`]: ./fn.write_unaligned.html
+/// [read-ownership]: ./fn.read.html#ownership-of-the-returned-value
+/// [valid]: ../ptr/index.html#safety
+///
+/// # Examples
+///
+/// Access members of a packed struct by reference:
+///
+/// ```
+/// use std::ptr;
+///
+/// #[repr(packed, C)]
+/// struct Packed {
+///     _padding: u8,
+///     unaligned: u32,
+/// }
+///
+/// let x = Packed {
+///     _padding: 0x00,
+///     unaligned: 0x01020304,
+/// };
+///
+/// let v = unsafe {
+///     // Take the address of a 32-bit integer which is not aligned.
+///     // This must be done as a raw pointer; unaligned references are invalid.
+///     let unaligned = &x.unaligned as *const u32;
+///
+///     // Dereferencing normally will emit an aligned load instruction,
+///     // causing undefined behavior.
+///     // let v = *unaligned; // ERROR
+///
+///     // Instead, use `read_unaligned` to read improperly aligned values.
+///     let v = ptr::read_unaligned(unaligned);
+///
+///     v
+/// };
+///
+/// // Accessing unaligned values directly is safe.
+/// assert!(x.unaligned == v);
+/// ```
+#[inline]
+#[stable(feature = "ptr_unaligned", since = "1.17.0")]
+pub unsafe fn read_unaligned<T>(src: *const T) -> T {
+    let mut tmp = MaybeUninit::<T>::uninit();
+    copy_nonoverlapping(src as *const u8,
+                        tmp.as_mut_ptr() as *mut u8,
+                        mem::size_of::<T>());
+    tmp.assume_init()
+}
+
+/// Overwrites a memory location with the given value without reading or
+/// dropping the old value.
+///
+/// `write` does not drop the contents of `dst`. This is safe, but it could leak
+/// allocations or resources, so care should be taken not to overwrite an object
+/// that should be dropped.
+///
+/// Additionally, it does not drop `src`. Semantically, `src` is moved into the
+/// location pointed to by `dst`.
+///
+/// This is appropriate for initializing uninitialized memory, or overwriting
+/// memory that has previously been [`read`] from.
+///
+/// [`read`]: ./fn.read.html
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `dst` must be [valid] for writes.
+///
+/// * `dst` must be properly aligned. Use [`write_unaligned`] if this is not the
+///   case.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+/// [`write_unaligned`]: ./fn.write_unaligned.html
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// let mut x = 0;
+/// let y = &mut x as *mut i32;
+/// let z = 12;
+///
+/// unsafe {
+///     std::ptr::write(y, z);
+///     assert_eq!(std::ptr::read(y), 12);
+/// }
+/// ```
+///
+/// Manually implement [`mem::swap`]:
+///
+/// ```
+/// use std::ptr;
+///
+/// fn swap<T>(a: &mut T, b: &mut T) {
+///     unsafe {
+///         // Create a bitwise copy of the value at `a` in `tmp`.
+///         let tmp = ptr::read(a);
+///
+///         // Exiting at this point (either by explicitly returning or by
+///         // calling a function which panics) would cause the value in `tmp` to
+///         // be dropped while the same value is still referenced by `a`. This
+///         // could trigger undefined behavior if `T` is not `Copy`.
+///
+///         // Create a bitwise copy of the value at `b` in `a`.
+///         // This is safe because mutable references cannot alias.
+///         ptr::copy_nonoverlapping(b, a, 1);
+///
+///         // As above, exiting here could trigger undefined behavior because
+///         // the same value is referenced by `a` and `b`.
+///
+///         // Move `tmp` into `b`.
+///         ptr::write(b, tmp);
+///
+///         // `tmp` has been moved (`write` takes ownership of its second argument),
+///         // so nothing is dropped implicitly here.
+///     }
+/// }
+///
+/// let mut foo = "foo".to_owned();
+/// let mut bar = "bar".to_owned();
+///
+/// swap(&mut foo, &mut bar);
+///
+/// assert_eq!(foo, "bar");
+/// assert_eq!(bar, "foo");
+/// ```
+///
+/// [`mem::swap`]: ../mem/fn.swap.html
+#[inline]
+#[stable(feature = "rust1", since = "1.0.0")]
+pub unsafe fn write<T>(dst: *mut T, src: T) {
+    intrinsics::move_val_init(&mut *dst, src)
+}
+
+/// Overwrites a memory location with the given value without reading or
+/// dropping the old value.
+///
+/// Unlike [`write`], the pointer may be unaligned.
+///
+/// `write_unaligned` does not drop the contents of `dst`. This is safe, but it
+/// could leak allocations or resources, so care should be taken not to overwrite
+/// an object that should be dropped.
+///
+/// Additionally, it does not drop `src`. Semantically, `src` is moved into the
+/// location pointed to by `dst`.
+///
+/// This is appropriate for initializing uninitialized memory, or overwriting
+/// memory that has previously been read with [`read_unaligned`].
+///
+/// [`write`]: ./fn.write.html
+/// [`read_unaligned`]: ./fn.read_unaligned.html
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `dst` must be [valid] for writes.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL.
+///
+/// [valid]: ../ptr/index.html#safety
+///
+/// # Examples
+///
+/// Access fields in a packed struct:
+///
+/// ```
+/// use std::{mem, ptr};
+///
+/// #[repr(packed, C)]
+/// #[derive(Default)]
+/// struct Packed {
+///     _padding: u8,
+///     unaligned: u32,
+/// }
+///
+/// let v = 0x01020304;
+/// let mut x: Packed = unsafe { mem::zeroed() };
+///
+/// unsafe {
+///     // Take a reference to a 32-bit integer which is not aligned.
+///     let unaligned = &mut x.unaligned as *mut u32;
+///
+///     // Dereferencing normally will emit an aligned store instruction,
+///     // causing undefined behavior because the pointer is not aligned.
+///     // *unaligned = v; // ERROR
+///
+///     // Instead, use `write_unaligned` to write improperly aligned values.
+///     ptr::write_unaligned(unaligned, v);
+/// }
+///
+/// // Accessing unaligned values directly is safe.
+/// assert!(x.unaligned == v);
+/// ```
+#[inline]
+#[stable(feature = "ptr_unaligned", since = "1.17.0")]
+pub unsafe fn write_unaligned<T>(dst: *mut T, src: T) {
+    copy_nonoverlapping(&src as *const T as *const u8,
+                        dst as *mut u8,
+                        mem::size_of::<T>());
+    mem::forget(src);
+}
+
+/// Performs a volatile read of the value from `src` without moving it. This
+/// leaves the memory in `src` unchanged.
+///
+/// Volatile operations are intended to act on I/O memory, and are guaranteed
+/// to not be elided or reordered by the compiler across other volatile
+/// operations.
+///
+/// [`write_volatile`]: ./fn.write_volatile.html
+///
+/// # Notes
+///
+/// Rust does not currently have a rigorously and formally defined memory model,
+/// so the precise semantics of what "volatile" means here is subject to change
+/// over time. That being said, the semantics will almost always end up pretty
+/// similar to [C11's definition of volatile][c11].
+///
+/// The compiler shouldn't change the relative order or number of volatile
+/// memory operations. However, volatile memory operations on zero-sized types
+/// (e.g., if a zero-sized type is passed to `read_volatile`) are noops
+/// and may be ignored.
+///
+/// [c11]: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `src` must be [valid] for reads.
+///
+/// * `src` must be properly aligned.
+///
+/// Like [`read`], `read_volatile` creates a bitwise copy of `T`, regardless of
+/// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the returned
+/// value and the value at `*src` can [violate memory safety][read-ownership].
+/// However, storing non-[`Copy`] types in volatile memory is almost certainly
+/// incorrect.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+/// [`Copy`]: ../marker/trait.Copy.html
+/// [`read`]: ./fn.read.html
+/// [read-ownership]: ./fn.read.html#ownership-of-the-returned-value
+///
+/// Just like in C, whether an operation is volatile has no bearing whatsoever
+/// on questions involving concurrent access from multiple threads. Volatile
+/// accesses behave exactly like non-atomic accesses in that regard. In particular,
+/// a race between a `read_volatile` and any write operation to the same location
+/// is undefined behavior.
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// let x = 12;
+/// let y = &x as *const i32;
+///
+/// unsafe {
+///     assert_eq!(std::ptr::read_volatile(y), 12);
+/// }
+/// ```
+#[inline]
+#[stable(feature = "volatile", since = "1.9.0")]
+pub unsafe fn read_volatile<T>(src: *const T) -> T {
+    intrinsics::volatile_load(src)
+}
+
+/// Performs a volatile write of a memory location with the given value without
+/// reading or dropping the old value.
+///
+/// Volatile operations are intended to act on I/O memory, and are guaranteed
+/// to not be elided or reordered by the compiler across other volatile
+/// operations.
+///
+/// `write_volatile` does not drop the contents of `dst`. This is safe, but it
+/// could leak allocations or resources, so care should be taken not to overwrite
+/// an object that should be dropped.
+///
+/// Additionally, it does not drop `src`. Semantically, `src` is moved into the
+/// location pointed to by `dst`.
+///
+/// [`read_volatile`]: ./fn.read_volatile.html
+///
+/// # Notes
+///
+/// Rust does not currently have a rigorously and formally defined memory model,
+/// so the precise semantics of what "volatile" means here is subject to change
+/// over time. That being said, the semantics will almost always end up pretty
+/// similar to [C11's definition of volatile][c11].
+///
+/// The compiler shouldn't change the relative order or number of volatile
+/// memory operations. However, volatile memory operations on zero-sized types
+/// (e.g., if a zero-sized type is passed to `write_volatile`) are noops
+/// and may be ignored.
+///
+/// [c11]: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
+///
+/// # Safety
+///
+/// Behavior is undefined if any of the following conditions are violated:
+///
+/// * `dst` must be [valid] for writes.
+///
+/// * `dst` must be properly aligned.
+///
+/// Note that even if `T` has size `0`, the pointer must be non-NULL and properly aligned.
+///
+/// [valid]: ../ptr/index.html#safety
+///
+/// Just like in C, whether an operation is volatile has no bearing whatsoever
+/// on questions involving concurrent access from multiple threads. Volatile
+/// accesses behave exactly like non-atomic accesses in that regard. In particular,
+/// a race between a `write_volatile` and any other operation (reading or writing)
+/// on the same location is undefined behavior.
+///
+/// # Examples
+///
+/// Basic usage:
+///
+/// ```
+/// let mut x = 0;
+/// let y = &mut x as *mut i32;
+/// let z = 12;
+///
+/// unsafe {
+///     std::ptr::write_volatile(y, z);
+///     assert_eq!(std::ptr::read_volatile(y), 12);
+/// }
+/// ```
+#[inline]
+#[stable(feature = "volatile", since = "1.9.0")]
+pub unsafe fn write_volatile<T>(dst: *mut T, src: T) {
+    intrinsics::volatile_store(dst, src);
+}
+
+#[lang = "const_ptr"]
+impl<T: ?Sized> *const T {
+    /// Returns `true` if the pointer is null.
+    ///
+    /// Note that unsized types have many possible null pointers, as only the
+    /// raw data pointer is considered, not their length, vtable, etc.
+    /// Therefore, two pointers that are null may still not compare equal to
+    /// each other.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s: &str = "Follow the rabbit";
+    /// let ptr: *const u8 = s.as_ptr();
+    /// assert!(!ptr.is_null());
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    #[inline]
+    pub fn is_null(self) -> bool {
+        // Compare via a cast to a thin pointer, so fat pointers are only
+        // considering their "data" part for null-ness.
+        (self as *const u8) == null()
+    }
+
+    /// Cast to a pointer to a different type
+    #[unstable(feature = "ptr_cast", issue = "60602")]
+    #[inline]
+    pub const fn cast<U>(self) -> *const U {
+        self as _
+    }
+
+    /// Returns `None` if the pointer is null, or else returns a reference to
+    /// the value wrapped in `Some`.
+    ///
+    /// # Safety
+    ///
+    /// While this method and its mutable counterpart are useful for
+    /// null-safety, it is important to note that this is still an unsafe
+    /// operation because the returned value could be pointing to invalid
+    /// memory.
+    ///
+    /// Additionally, the lifetime `'a` returned is arbitrarily chosen and does
+    /// not necessarily reflect the actual lifetime of the data.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let ptr: *const u8 = &10u8 as *const u8;
+    ///
+    /// unsafe {
+    ///     if let Some(val_back) = ptr.as_ref() {
+    ///         println!("We got back the value: {}!", val_back);
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// # Null-unchecked version
+    ///
+    /// If you are sure the pointer can never be null and are looking for some kind of
+    /// `as_ref_unchecked` that returns the `&T` instead of `Option<&T>`, know that you can
+    /// dereference the pointer directly.
+    ///
+    /// ```
+    /// let ptr: *const u8 = &10u8 as *const u8;
+    ///
+    /// unsafe {
+    ///     let val_back = &*ptr;
+    ///     println!("We got back the value: {}!", val_back);
+    /// }
+    /// ```
+    #[stable(feature = "ptr_as_ref", since = "1.9.0")]
+    #[inline]
+    pub unsafe fn as_ref<'a>(self) -> Option<&'a T> {
+        if self.is_null() {
+            None
+        } else {
+            Some(&*self)
+        }
+    }
+
+    /// Calculates the offset from a pointer.
+    ///
+    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is Undefined
+    /// Behavior:
+    ///
+    /// * Both the starting and resulting pointer must be either in bounds or one
+    ///   byte past the end of the same allocated object.
+    ///
+    /// * The computed offset, **in bytes**, cannot overflow an `isize`.
+    ///
+    /// * The offset being in bounds cannot rely on "wrapping around" the address
+    ///   space. That is, the infinite-precision sum, **in bytes** must fit in a usize.
+    ///
+    /// The compiler and standard library generally tries to ensure allocations
+    /// never reach a size where an offset is a concern. For instance, `Vec`
+    /// and `Box` ensure they never allocate more than `isize::MAX` bytes, so
+    /// `vec.as_ptr().add(vec.len())` is always safe.
+    ///
+    /// Most platforms fundamentally can't even construct such an allocation.
+    /// For instance, no known 64-bit platform can ever serve a request
+    /// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
+    /// However, some 32-bit and 16-bit platforms may successfully serve a request for
+    /// more than `isize::MAX` bytes with things like Physical Address
+    /// Extension. As such, memory acquired directly from allocators or memory
+    /// mapped files *may* be too large to handle with this function.
+    ///
+    /// Consider using `wrapping_offset` instead if these constraints are
+    /// difficult to satisfy. The only advantage of this method is that it
+    /// enables more aggressive compiler optimizations.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s: &str = "123";
+    /// let ptr: *const u8 = s.as_ptr();
+    ///
+    /// unsafe {
+    ///     println!("{}", *ptr.offset(1) as char);
+    ///     println!("{}", *ptr.offset(2) as char);
+    /// }
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    #[inline]
+    pub unsafe fn offset(self, count: isize) -> *const T where T: Sized {
+        intrinsics::offset(self, count)
+    }
+
+    /// Calculates the offset from a pointer using wrapping arithmetic.
+    ///
+    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// The resulting pointer does not need to be in bounds, but it is
+    /// potentially hazardous to dereference (which requires `unsafe`).
+    /// In particular, the resulting pointer may *not* be used to access a
+    /// different allocated object than the one `self` points to. In other
+    /// words, `x.wrapping_offset(y.wrapping_offset_from(x))` is
+    /// *not* the same as `y`, and dereferencing it is undefined behavior
+    /// unless `x` and `y` point into the same allocated object.
+    ///
+    /// Always use `.offset(count)` instead when possible, because `offset`
+    /// allows the compiler to optimize better. If you need to cross object
+    /// boundaries, cast the pointer to an integer and do the arithmetic there.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // Iterate using a raw pointer in increments of two elements
+    /// let data = [1u8, 2, 3, 4, 5];
+    /// let mut ptr: *const u8 = data.as_ptr();
+    /// let step = 2;
+    /// let end_rounded_up = ptr.wrapping_offset(6);
+    ///
+    /// // This loop prints "1, 3, 5, "
+    /// while ptr != end_rounded_up {
+    ///     unsafe {
+    ///         print!("{}, ", *ptr);
+    ///     }
+    ///     ptr = ptr.wrapping_offset(step);
+    /// }
+    /// ```
+    #[stable(feature = "ptr_wrapping_offset", since = "1.16.0")]
+    #[inline]
+    pub fn wrapping_offset(self, count: isize) -> *const T where T: Sized {
+        unsafe {
+            intrinsics::arith_offset(self, count)
+        }
+    }
+
+    /// Calculates the distance between two pointers. The returned value is in
+    /// units of T: the distance in bytes is divided by `mem::size_of::<T>()`.
+    ///
+    /// This function is the inverse of [`offset`].
+    ///
+    /// [`offset`]: #method.offset
+    /// [`wrapping_offset_from`]: #method.wrapping_offset_from
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is Undefined
+    /// Behavior:
+    ///
+    /// * Both the starting and other pointer must be either in bounds or one
+    ///   byte past the end of the same allocated object.
+    ///
+    /// * The distance between the pointers, **in bytes**, cannot overflow an `isize`.
+    ///
+    /// * The distance between the pointers, in bytes, must be an exact multiple
+    ///   of the size of `T`.
+    ///
+    /// * The distance being in bounds cannot rely on "wrapping around" the address space.
+    ///
+    /// The compiler and standard library generally try to ensure allocations
+    /// never reach a size where an offset is a concern. For instance, `Vec`
+    /// and `Box` ensure they never allocate more than `isize::MAX` bytes, so
+    /// `ptr_into_vec.offset_from(vec.as_ptr())` is always safe.
+    ///
+    /// Most platforms fundamentally can't even construct such an allocation.
+    /// For instance, no known 64-bit platform can ever serve a request
+    /// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
+    /// However, some 32-bit and 16-bit platforms may successfully serve a request for
+    /// more than `isize::MAX` bytes with things like Physical Address
+    /// Extension. As such, memory acquired directly from allocators or memory
+    /// mapped files *may* be too large to handle with this function.
+    ///
+    /// Consider using [`wrapping_offset_from`] instead if these constraints are
+    /// difficult to satisfy. The only advantage of this method is that it
+    /// enables more aggressive compiler optimizations.
+    ///
+    /// # Panics
+    ///
+    /// This function panics if `T` is a Zero-Sized Type ("ZST").
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(ptr_offset_from)]
+    ///
+    /// let a = [0; 5];
+    /// let ptr1: *const i32 = &a[1];
+    /// let ptr2: *const i32 = &a[3];
+    /// unsafe {
+    ///     assert_eq!(ptr2.offset_from(ptr1), 2);
+    ///     assert_eq!(ptr1.offset_from(ptr2), -2);
+    ///     assert_eq!(ptr1.offset(2), ptr2);
+    ///     assert_eq!(ptr2.offset(-2), ptr1);
+    /// }
+    /// ```
+    #[unstable(feature = "ptr_offset_from", issue = "41079")]
+    #[inline]
+    pub unsafe fn offset_from(self, origin: *const T) -> isize where T: Sized {
+        let pointee_size = mem::size_of::<T>();
+        assert!(0 < pointee_size && pointee_size <= isize::max_value() as usize);
+
+        // This is the same sequence that Clang emits for pointer subtraction.
+        // It can be neither `nsw` nor `nuw` because the input is treated as
+        // unsigned but then the output is treated as signed, so neither works.
+        let d = isize::wrapping_sub(self as _, origin as _);
+        intrinsics::exact_div(d, pointee_size as _)
+    }
+
+    /// Calculates the distance between two pointers. The returned value is in
+    /// units of T: the distance in bytes is divided by `mem::size_of::<T>()`.
+    ///
+    /// If the address different between the two pointers is not a multiple of
+    /// `mem::size_of::<T>()` then the result of the division is rounded towards
+    /// zero.
+    ///
+    /// Though this method is safe for any two pointers, note that its result
+    /// will be mostly useless if the two pointers aren't into the same allocated
+    /// object, for example if they point to two different local variables.
+    ///
+    /// # Panics
+    ///
+    /// This function panics if `T` is a zero-sized type.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(ptr_wrapping_offset_from)]
+    ///
+    /// let a = [0; 5];
+    /// let ptr1: *const i32 = &a[1];
+    /// let ptr2: *const i32 = &a[3];
+    /// assert_eq!(ptr2.wrapping_offset_from(ptr1), 2);
+    /// assert_eq!(ptr1.wrapping_offset_from(ptr2), -2);
+    /// assert_eq!(ptr1.wrapping_offset(2), ptr2);
+    /// assert_eq!(ptr2.wrapping_offset(-2), ptr1);
+    ///
+    /// let ptr1: *const i32 = 3 as _;
+    /// let ptr2: *const i32 = 13 as _;
+    /// assert_eq!(ptr2.wrapping_offset_from(ptr1), 2);
+    /// ```
+    #[unstable(feature = "ptr_wrapping_offset_from", issue = "41079")]
+    #[inline]
+    pub fn wrapping_offset_from(self, origin: *const T) -> isize where T: Sized {
+        let pointee_size = mem::size_of::<T>();
+        assert!(0 < pointee_size && pointee_size <= isize::max_value() as usize);
+
+        let d = isize::wrapping_sub(self as _, origin as _);
+        d.wrapping_div(pointee_size as _)
+    }
+
+    /// Calculates the offset from a pointer (convenience for `.offset(count as isize)`).
+    ///
+    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is Undefined
+    /// Behavior:
+    ///
+    /// * Both the starting and resulting pointer must be either in bounds or one
+    ///   byte past the end of the same allocated object.
+    ///
+    /// * The computed offset, **in bytes**, cannot overflow an `isize`.
+    ///
+    /// * The offset being in bounds cannot rely on "wrapping around" the address
+    ///   space. That is, the infinite-precision sum must fit in a `usize`.
+    ///
+    /// The compiler and standard library generally tries to ensure allocations
+    /// never reach a size where an offset is a concern. For instance, `Vec`
+    /// and `Box` ensure they never allocate more than `isize::MAX` bytes, so
+    /// `vec.as_ptr().add(vec.len())` is always safe.
+    ///
+    /// Most platforms fundamentally can't even construct such an allocation.
+    /// For instance, no known 64-bit platform can ever serve a request
+    /// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
+    /// However, some 32-bit and 16-bit platforms may successfully serve a request for
+    /// more than `isize::MAX` bytes with things like Physical Address
+    /// Extension. As such, memory acquired directly from allocators or memory
+    /// mapped files *may* be too large to handle with this function.
+    ///
+    /// Consider using `wrapping_offset` instead if these constraints are
+    /// difficult to satisfy. The only advantage of this method is that it
+    /// enables more aggressive compiler optimizations.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s: &str = "123";
+    /// let ptr: *const u8 = s.as_ptr();
+    ///
+    /// unsafe {
+    ///     println!("{}", *ptr.add(1) as char);
+    ///     println!("{}", *ptr.add(2) as char);
+    /// }
+    /// ```
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn add(self, count: usize) -> Self
+        where T: Sized,
+    {
+        self.offset(count as isize)
+    }
+
+    /// Calculates the offset from a pointer (convenience for
+    /// `.offset((count as isize).wrapping_neg())`).
+    ///
+    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is Undefined
+    /// Behavior:
+    ///
+    /// * Both the starting and resulting pointer must be either in bounds or one
+    ///   byte past the end of the same allocated object.
+    ///
+    /// * The computed offset cannot exceed `isize::MAX` **bytes**.
+    ///
+    /// * The offset being in bounds cannot rely on "wrapping around" the address
+    ///   space. That is, the infinite-precision sum must fit in a usize.
+    ///
+    /// The compiler and standard library generally tries to ensure allocations
+    /// never reach a size where an offset is a concern. For instance, `Vec`
+    /// and `Box` ensure they never allocate more than `isize::MAX` bytes, so
+    /// `vec.as_ptr().add(vec.len()).sub(vec.len())` is always safe.
+    ///
+    /// Most platforms fundamentally can't even construct such an allocation.
+    /// For instance, no known 64-bit platform can ever serve a request
+    /// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
+    /// However, some 32-bit and 16-bit platforms may successfully serve a request for
+    /// more than `isize::MAX` bytes with things like Physical Address
+    /// Extension. As such, memory acquired directly from allocators or memory
+    /// mapped files *may* be too large to handle with this function.
+    ///
+    /// Consider using `wrapping_offset` instead if these constraints are
+    /// difficult to satisfy. The only advantage of this method is that it
+    /// enables more aggressive compiler optimizations.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s: &str = "123";
+    ///
+    /// unsafe {
+    ///     let end: *const u8 = s.as_ptr().add(3);
+    ///     println!("{}", *end.sub(1) as char);
+    ///     println!("{}", *end.sub(2) as char);
+    /// }
+    /// ```
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn sub(self, count: usize) -> Self
+        where T: Sized,
+    {
+        self.offset((count as isize).wrapping_neg())
+    }
+
+    /// Calculates the offset from a pointer using wrapping arithmetic.
+    /// (convenience for `.wrapping_offset(count as isize)`)
+    ///
+    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// The resulting pointer does not need to be in bounds, but it is
+    /// potentially hazardous to dereference (which requires `unsafe`).
+    ///
+    /// Always use `.add(count)` instead when possible, because `add`
+    /// allows the compiler to optimize better.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // Iterate using a raw pointer in increments of two elements
+    /// let data = [1u8, 2, 3, 4, 5];
+    /// let mut ptr: *const u8 = data.as_ptr();
+    /// let step = 2;
+    /// let end_rounded_up = ptr.wrapping_add(6);
+    ///
+    /// // This loop prints "1, 3, 5, "
+    /// while ptr != end_rounded_up {
+    ///     unsafe {
+    ///         print!("{}, ", *ptr);
+    ///     }
+    ///     ptr = ptr.wrapping_add(step);
+    /// }
+    /// ```
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub fn wrapping_add(self, count: usize) -> Self
+        where T: Sized,
+    {
+        self.wrapping_offset(count as isize)
+    }
+
+    /// Calculates the offset from a pointer using wrapping arithmetic.
+    /// (convenience for `.wrapping_offset((count as isize).wrapping_sub())`)
+    ///
+    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// The resulting pointer does not need to be in bounds, but it is
+    /// potentially hazardous to dereference (which requires `unsafe`).
+    ///
+    /// Always use `.sub(count)` instead when possible, because `sub`
+    /// allows the compiler to optimize better.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // Iterate using a raw pointer in increments of two elements (backwards)
+    /// let data = [1u8, 2, 3, 4, 5];
+    /// let mut ptr: *const u8 = data.as_ptr();
+    /// let start_rounded_down = ptr.wrapping_sub(2);
+    /// ptr = ptr.wrapping_add(4);
+    /// let step = 2;
+    /// // This loop prints "5, 3, 1, "
+    /// while ptr != start_rounded_down {
+    ///     unsafe {
+    ///         print!("{}, ", *ptr);
+    ///     }
+    ///     ptr = ptr.wrapping_sub(step);
+    /// }
+    /// ```
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub fn wrapping_sub(self, count: usize) -> Self
+        where T: Sized,
+    {
+        self.wrapping_offset((count as isize).wrapping_neg())
+    }
+
+    /// Reads the value from `self` without moving it. This leaves the
+    /// memory in `self` unchanged.
+    ///
+    /// See [`ptr::read`] for safety concerns and examples.
+    ///
+    /// [`ptr::read`]: ./ptr/fn.read.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn read(self) -> T
+        where T: Sized,
+    {
+        read(self)
+    }
+
+    /// Performs a volatile read of the value from `self` without moving it. This
+    /// leaves the memory in `self` unchanged.
+    ///
+    /// Volatile operations are intended to act on I/O memory, and are guaranteed
+    /// to not be elided or reordered by the compiler across other volatile
+    /// operations.
+    ///
+    /// See [`ptr::read_volatile`] for safety concerns and examples.
+    ///
+    /// [`ptr::read_volatile`]: ./ptr/fn.read_volatile.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn read_volatile(self) -> T
+        where T: Sized,
+    {
+        read_volatile(self)
+    }
+
+    /// Reads the value from `self` without moving it. This leaves the
+    /// memory in `self` unchanged.
+    ///
+    /// Unlike `read`, the pointer may be unaligned.
+    ///
+    /// See [`ptr::read_unaligned`] for safety concerns and examples.
+    ///
+    /// [`ptr::read_unaligned`]: ./ptr/fn.read_unaligned.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn read_unaligned(self) -> T
+        where T: Sized,
+    {
+        read_unaligned(self)
+    }
+
+    /// Copies `count * size_of<T>` bytes from `self` to `dest`. The source
+    /// and destination may overlap.
+    ///
+    /// NOTE: this has the *same* argument order as [`ptr::copy`].
+    ///
+    /// See [`ptr::copy`] for safety concerns and examples.
+    ///
+    /// [`ptr::copy`]: ./ptr/fn.copy.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn copy_to(self, dest: *mut T, count: usize)
+        where T: Sized,
+    {
+        copy(self, dest, count)
+    }
+
+    /// Copies `count * size_of<T>` bytes from `self` to `dest`. The source
+    /// and destination may *not* overlap.
+    ///
+    /// NOTE: this has the *same* argument order as [`ptr::copy_nonoverlapping`].
+    ///
+    /// See [`ptr::copy_nonoverlapping`] for safety concerns and examples.
+    ///
+    /// [`ptr::copy_nonoverlapping`]: ./ptr/fn.copy_nonoverlapping.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn copy_to_nonoverlapping(self, dest: *mut T, count: usize)
+        where T: Sized,
+    {
+        copy_nonoverlapping(self, dest, count)
+    }
+
+    /// Computes the offset that needs to be applied to the pointer in order to make it aligned to
+    /// `align`.
+    ///
+    /// If it is not possible to align the pointer, the implementation returns
+    /// `usize::max_value()`.
+    ///
+    /// The offset is expressed in number of `T` elements, and not bytes. The value returned can be
+    /// used with the `offset` or `offset_to` methods.
+    ///
+    /// There are no guarantees whatsover that offsetting the pointer will not overflow or go
+    /// beyond the allocation that the pointer points into. It is up to the caller to ensure that
+    /// the returned offset is correct in all terms other than alignment.
+    ///
+    /// # Panics
+    ///
+    /// The function panics if `align` is not a power-of-two.
+    ///
+    /// # Examples
+    ///
+    /// Accessing adjacent `u8` as `u16`
+    ///
+    /// ```
+    /// # fn foo(n: usize) {
+    /// # use std::mem::align_of;
+    /// # unsafe {
+    /// let x = [5u8, 6u8, 7u8, 8u8, 9u8];
+    /// let ptr = &x[n] as *const u8;
+    /// let offset = ptr.align_offset(align_of::<u16>());
+    /// if offset < x.len() - n - 1 {
+    ///     let u16_ptr = ptr.add(offset) as *const u16;
+    ///     assert_ne!(*u16_ptr, 500);
+    /// } else {
+    ///     // while the pointer can be aligned via `offset`, it would point
+    ///     // outside the allocation
+    /// }
+    /// # } }
+    /// ```
+    #[stable(feature = "align_offset", since = "1.36.0")]
+    pub fn align_offset(self, align: usize) -> usize where T: Sized {
+        if !align.is_power_of_two() {
+            panic!("align_offset: align is not a power-of-two");
+        }
+        unsafe {
+            align_offset(self, align)
+        }
+    }
+}
+
+
+#[lang = "mut_ptr"]
+impl<T: ?Sized> *mut T {
+    /// Returns `true` if the pointer is null.
+    ///
+    /// Note that unsized types have many possible null pointers, as only the
+    /// raw data pointer is considered, not their length, vtable, etc.
+    /// Therefore, two pointers that are null may still not compare equal to
+    /// each other.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = [1, 2, 3];
+    /// let ptr: *mut u32 = s.as_mut_ptr();
+    /// assert!(!ptr.is_null());
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    #[inline]
+    pub fn is_null(self) -> bool {
+        // Compare via a cast to a thin pointer, so fat pointers are only
+        // considering their "data" part for null-ness.
+        (self as *mut u8) == null_mut()
+    }
+
+    /// Cast to a pointer to a different type
+    #[unstable(feature = "ptr_cast", issue = "60602")]
+    #[inline]
+    pub const fn cast<U>(self) -> *mut U {
+        self as _
+    }
+
+    /// Returns `None` if the pointer is null, or else returns a reference to
+    /// the value wrapped in `Some`.
+    ///
+    /// # Safety
+    ///
+    /// While this method and its mutable counterpart are useful for
+    /// null-safety, it is important to note that this is still an unsafe
+    /// operation because the returned value could be pointing to invalid
+    /// memory.
+    ///
+    /// Additionally, the lifetime `'a` returned is arbitrarily chosen and does
+    /// not necessarily reflect the actual lifetime of the data.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let ptr: *mut u8 = &mut 10u8 as *mut u8;
+    ///
+    /// unsafe {
+    ///     if let Some(val_back) = ptr.as_ref() {
+    ///         println!("We got back the value: {}!", val_back);
+    ///     }
+    /// }
+    /// ```
+    ///
+    /// # Null-unchecked version
+    ///
+    /// If you are sure the pointer can never be null and are looking for some kind of
+    /// `as_ref_unchecked` that returns the `&T` instead of `Option<&T>`, know that you can
+    /// dereference the pointer directly.
+    ///
+    /// ```
+    /// let ptr: *mut u8 = &mut 10u8 as *mut u8;
+    ///
+    /// unsafe {
+    ///     let val_back = &*ptr;
+    ///     println!("We got back the value: {}!", val_back);
+    /// }
+    /// ```
+    #[stable(feature = "ptr_as_ref", since = "1.9.0")]
+    #[inline]
+    pub unsafe fn as_ref<'a>(self) -> Option<&'a T> {
+        if self.is_null() {
+            None
+        } else {
+            Some(&*self)
+        }
+    }
+
+    /// Calculates the offset from a pointer.
+    ///
+    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is Undefined
+    /// Behavior:
+    ///
+    /// * Both the starting and resulting pointer must be either in bounds or one
+    ///   byte past the end of the same allocated object.
+    ///
+    /// * The computed offset, **in bytes**, cannot overflow an `isize`.
+    ///
+    /// * The offset being in bounds cannot rely on "wrapping around" the address
+    ///   space. That is, the infinite-precision sum, **in bytes** must fit in a usize.
+    ///
+    /// The compiler and standard library generally tries to ensure allocations
+    /// never reach a size where an offset is a concern. For instance, `Vec`
+    /// and `Box` ensure they never allocate more than `isize::MAX` bytes, so
+    /// `vec.as_ptr().add(vec.len())` is always safe.
+    ///
+    /// Most platforms fundamentally can't even construct such an allocation.
+    /// For instance, no known 64-bit platform can ever serve a request
+    /// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
+    /// However, some 32-bit and 16-bit platforms may successfully serve a request for
+    /// more than `isize::MAX` bytes with things like Physical Address
+    /// Extension. As such, memory acquired directly from allocators or memory
+    /// mapped files *may* be too large to handle with this function.
+    ///
+    /// Consider using `wrapping_offset` instead if these constraints are
+    /// difficult to satisfy. The only advantage of this method is that it
+    /// enables more aggressive compiler optimizations.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = [1, 2, 3];
+    /// let ptr: *mut u32 = s.as_mut_ptr();
+    ///
+    /// unsafe {
+    ///     println!("{}", *ptr.offset(1));
+    ///     println!("{}", *ptr.offset(2));
+    /// }
+    /// ```
+    #[stable(feature = "rust1", since = "1.0.0")]
+    #[inline]
+    pub unsafe fn offset(self, count: isize) -> *mut T where T: Sized {
+        intrinsics::offset(self, count) as *mut T
+    }
+
+    /// Calculates the offset from a pointer using wrapping arithmetic.
+    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// The resulting pointer does not need to be in bounds, but it is
+    /// potentially hazardous to dereference (which requires `unsafe`).
+    /// In particular, the resulting pointer may *not* be used to access a
+    /// different allocated object than the one `self` points to. In other
+    /// words, `x.wrapping_offset(y.wrapping_offset_from(x))` is
+    /// *not* the same as `y`, and dereferencing it is undefined behavior
+    /// unless `x` and `y` point into the same allocated object.
+    ///
+    /// Always use `.offset(count)` instead when possible, because `offset`
+    /// allows the compiler to optimize better. If you need to cross object
+    /// boundaries, cast the pointer to an integer and do the arithmetic there.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // Iterate using a raw pointer in increments of two elements
+    /// let mut data = [1u8, 2, 3, 4, 5];
+    /// let mut ptr: *mut u8 = data.as_mut_ptr();
+    /// let step = 2;
+    /// let end_rounded_up = ptr.wrapping_offset(6);
+    ///
+    /// while ptr != end_rounded_up {
+    ///     unsafe {
+    ///         *ptr = 0;
+    ///     }
+    ///     ptr = ptr.wrapping_offset(step);
+    /// }
+    /// assert_eq!(&data, &[0, 2, 0, 4, 0]);
+    /// ```
+    #[stable(feature = "ptr_wrapping_offset", since = "1.16.0")]
+    #[inline]
+    pub fn wrapping_offset(self, count: isize) -> *mut T where T: Sized {
+        unsafe {
+            intrinsics::arith_offset(self, count) as *mut T
+        }
+    }
+
+    /// Returns `None` if the pointer is null, or else returns a mutable
+    /// reference to the value wrapped in `Some`.
+    ///
+    /// # Safety
+    ///
+    /// As with `as_ref`, this is unsafe because it cannot verify the validity
+    /// of the returned pointer, nor can it ensure that the lifetime `'a`
+    /// returned is indeed a valid lifetime for the contained data.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let mut s = [1, 2, 3];
+    /// let ptr: *mut u32 = s.as_mut_ptr();
+    /// let first_value = unsafe { ptr.as_mut().unwrap() };
+    /// *first_value = 4;
+    /// println!("{:?}", s); // It'll print: "[4, 2, 3]".
+    /// ```
+    #[stable(feature = "ptr_as_ref", since = "1.9.0")]
+    #[inline]
+    pub unsafe fn as_mut<'a>(self) -> Option<&'a mut T> {
+        if self.is_null() {
+            None
+        } else {
+            Some(&mut *self)
+        }
+    }
+
+    /// Calculates the distance between two pointers. The returned value is in
+    /// units of T: the distance in bytes is divided by `mem::size_of::<T>()`.
+    ///
+    /// This function is the inverse of [`offset`].
+    ///
+    /// [`offset`]: #method.offset-1
+    /// [`wrapping_offset_from`]: #method.wrapping_offset_from-1
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is Undefined
+    /// Behavior:
+    ///
+    /// * Both the starting and other pointer must be either in bounds or one
+    ///   byte past the end of the same allocated object.
+    ///
+    /// * The distance between the pointers, **in bytes**, cannot overflow an `isize`.
+    ///
+    /// * The distance between the pointers, in bytes, must be an exact multiple
+    ///   of the size of `T`.
+    ///
+    /// * The distance being in bounds cannot rely on "wrapping around" the address space.
+    ///
+    /// The compiler and standard library generally try to ensure allocations
+    /// never reach a size where an offset is a concern. For instance, `Vec`
+    /// and `Box` ensure they never allocate more than `isize::MAX` bytes, so
+    /// `ptr_into_vec.offset_from(vec.as_ptr())` is always safe.
+    ///
+    /// Most platforms fundamentally can't even construct such an allocation.
+    /// For instance, no known 64-bit platform can ever serve a request
+    /// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
+    /// However, some 32-bit and 16-bit platforms may successfully serve a request for
+    /// more than `isize::MAX` bytes with things like Physical Address
+    /// Extension. As such, memory acquired directly from allocators or memory
+    /// mapped files *may* be too large to handle with this function.
+    ///
+    /// Consider using [`wrapping_offset_from`] instead if these constraints are
+    /// difficult to satisfy. The only advantage of this method is that it
+    /// enables more aggressive compiler optimizations.
+    ///
+    /// # Panics
+    ///
+    /// This function panics if `T` is a Zero-Sized Type ("ZST").
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(ptr_offset_from)]
+    ///
+    /// let mut a = [0; 5];
+    /// let ptr1: *mut i32 = &mut a[1];
+    /// let ptr2: *mut i32 = &mut a[3];
+    /// unsafe {
+    ///     assert_eq!(ptr2.offset_from(ptr1), 2);
+    ///     assert_eq!(ptr1.offset_from(ptr2), -2);
+    ///     assert_eq!(ptr1.offset(2), ptr2);
+    ///     assert_eq!(ptr2.offset(-2), ptr1);
+    /// }
+    /// ```
+    #[unstable(feature = "ptr_offset_from", issue = "41079")]
+    #[inline]
+    pub unsafe fn offset_from(self, origin: *const T) -> isize where T: Sized {
+        (self as *const T).offset_from(origin)
+    }
+
+    /// Calculates the distance between two pointers. The returned value is in
+    /// units of T: the distance in bytes is divided by `mem::size_of::<T>()`.
+    ///
+    /// If the address different between the two pointers is not a multiple of
+    /// `mem::size_of::<T>()` then the result of the division is rounded towards
+    /// zero.
+    ///
+    /// Though this method is safe for any two pointers, note that its result
+    /// will be mostly useless if the two pointers aren't into the same allocated
+    /// object, for example if they point to two different local variables.
+    ///
+    /// # Panics
+    ///
+    /// This function panics if `T` is a zero-sized type.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// #![feature(ptr_wrapping_offset_from)]
+    ///
+    /// let mut a = [0; 5];
+    /// let ptr1: *mut i32 = &mut a[1];
+    /// let ptr2: *mut i32 = &mut a[3];
+    /// assert_eq!(ptr2.wrapping_offset_from(ptr1), 2);
+    /// assert_eq!(ptr1.wrapping_offset_from(ptr2), -2);
+    /// assert_eq!(ptr1.wrapping_offset(2), ptr2);
+    /// assert_eq!(ptr2.wrapping_offset(-2), ptr1);
+    ///
+    /// let ptr1: *mut i32 = 3 as _;
+    /// let ptr2: *mut i32 = 13 as _;
+    /// assert_eq!(ptr2.wrapping_offset_from(ptr1), 2);
+    /// ```
+    #[unstable(feature = "ptr_wrapping_offset_from", issue = "41079")]
+    #[inline]
+    pub fn wrapping_offset_from(self, origin: *const T) -> isize where T: Sized {
+        (self as *const T).wrapping_offset_from(origin)
+    }
+
+    /// Calculates the offset from a pointer (convenience for `.offset(count as isize)`).
+    ///
+    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is Undefined
+    /// Behavior:
+    ///
+    /// * Both the starting and resulting pointer must be either in bounds or one
+    ///   byte past the end of the same allocated object.
+    ///
+    /// * The computed offset, **in bytes**, cannot overflow an `isize`.
+    ///
+    /// * The offset being in bounds cannot rely on "wrapping around" the address
+    ///   space. That is, the infinite-precision sum must fit in a `usize`.
+    ///
+    /// The compiler and standard library generally tries to ensure allocations
+    /// never reach a size where an offset is a concern. For instance, `Vec`
+    /// and `Box` ensure they never allocate more than `isize::MAX` bytes, so
+    /// `vec.as_ptr().add(vec.len())` is always safe.
+    ///
+    /// Most platforms fundamentally can't even construct such an allocation.
+    /// For instance, no known 64-bit platform can ever serve a request
+    /// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
+    /// However, some 32-bit and 16-bit platforms may successfully serve a request for
+    /// more than `isize::MAX` bytes with things like Physical Address
+    /// Extension. As such, memory acquired directly from allocators or memory
+    /// mapped files *may* be too large to handle with this function.
+    ///
+    /// Consider using `wrapping_offset` instead if these constraints are
+    /// difficult to satisfy. The only advantage of this method is that it
+    /// enables more aggressive compiler optimizations.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s: &str = "123";
+    /// let ptr: *const u8 = s.as_ptr();
+    ///
+    /// unsafe {
+    ///     println!("{}", *ptr.add(1) as char);
+    ///     println!("{}", *ptr.add(2) as char);
+    /// }
+    /// ```
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn add(self, count: usize) -> Self
+        where T: Sized,
+    {
+        self.offset(count as isize)
+    }
+
+    /// Calculates the offset from a pointer (convenience for
+    /// `.offset((count as isize).wrapping_neg())`).
+    ///
+    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// If any of the following conditions are violated, the result is Undefined
+    /// Behavior:
+    ///
+    /// * Both the starting and resulting pointer must be either in bounds or one
+    ///   byte past the end of the same allocated object.
+    ///
+    /// * The computed offset cannot exceed `isize::MAX` **bytes**.
+    ///
+    /// * The offset being in bounds cannot rely on "wrapping around" the address
+    ///   space. That is, the infinite-precision sum must fit in a usize.
+    ///
+    /// The compiler and standard library generally tries to ensure allocations
+    /// never reach a size where an offset is a concern. For instance, `Vec`
+    /// and `Box` ensure they never allocate more than `isize::MAX` bytes, so
+    /// `vec.as_ptr().add(vec.len()).sub(vec.len())` is always safe.
+    ///
+    /// Most platforms fundamentally can't even construct such an allocation.
+    /// For instance, no known 64-bit platform can ever serve a request
+    /// for 2<sup>63</sup> bytes due to page-table limitations or splitting the address space.
+    /// However, some 32-bit and 16-bit platforms may successfully serve a request for
+    /// more than `isize::MAX` bytes with things like Physical Address
+    /// Extension. As such, memory acquired directly from allocators or memory
+    /// mapped files *may* be too large to handle with this function.
+    ///
+    /// Consider using `wrapping_offset` instead if these constraints are
+    /// difficult to satisfy. The only advantage of this method is that it
+    /// enables more aggressive compiler optimizations.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// let s: &str = "123";
+    ///
+    /// unsafe {
+    ///     let end: *const u8 = s.as_ptr().add(3);
+    ///     println!("{}", *end.sub(1) as char);
+    ///     println!("{}", *end.sub(2) as char);
+    /// }
+    /// ```
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn sub(self, count: usize) -> Self
+        where T: Sized,
+    {
+        self.offset((count as isize).wrapping_neg())
+    }
+
+    /// Calculates the offset from a pointer using wrapping arithmetic.
+    /// (convenience for `.wrapping_offset(count as isize)`)
+    ///
+    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// The resulting pointer does not need to be in bounds, but it is
+    /// potentially hazardous to dereference (which requires `unsafe`).
+    ///
+    /// Always use `.add(count)` instead when possible, because `add`
+    /// allows the compiler to optimize better.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // Iterate using a raw pointer in increments of two elements
+    /// let data = [1u8, 2, 3, 4, 5];
+    /// let mut ptr: *const u8 = data.as_ptr();
+    /// let step = 2;
+    /// let end_rounded_up = ptr.wrapping_add(6);
+    ///
+    /// // This loop prints "1, 3, 5, "
+    /// while ptr != end_rounded_up {
+    ///     unsafe {
+    ///         print!("{}, ", *ptr);
+    ///     }
+    ///     ptr = ptr.wrapping_add(step);
+    /// }
+    /// ```
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub fn wrapping_add(self, count: usize) -> Self
+        where T: Sized,
+    {
+        self.wrapping_offset(count as isize)
+    }
+
+    /// Calculates the offset from a pointer using wrapping arithmetic.
+    /// (convenience for `.wrapping_offset((count as isize).wrapping_sub())`)
+    ///
+    /// `count` is in units of T; e.g., a `count` of 3 represents a pointer
+    /// offset of `3 * size_of::<T>()` bytes.
+    ///
+    /// # Safety
+    ///
+    /// The resulting pointer does not need to be in bounds, but it is
+    /// potentially hazardous to dereference (which requires `unsafe`).
+    ///
+    /// Always use `.sub(count)` instead when possible, because `sub`
+    /// allows the compiler to optimize better.
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```
+    /// // Iterate using a raw pointer in increments of two elements (backwards)
+    /// let data = [1u8, 2, 3, 4, 5];
+    /// let mut ptr: *const u8 = data.as_ptr();
+    /// let start_rounded_down = ptr.wrapping_sub(2);
+    /// ptr = ptr.wrapping_add(4);
+    /// let step = 2;
+    /// // This loop prints "5, 3, 1, "
+    /// while ptr != start_rounded_down {
+    ///     unsafe {
+    ///         print!("{}, ", *ptr);
+    ///     }
+    ///     ptr = ptr.wrapping_sub(step);
+    /// }
+    /// ```
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub fn wrapping_sub(self, count: usize) -> Self
+        where T: Sized,
+    {
+        self.wrapping_offset((count as isize).wrapping_neg())
+    }
+
+    /// Reads the value from `self` without moving it. This leaves the
+    /// memory in `self` unchanged.
+    ///
+    /// See [`ptr::read`] for safety concerns and examples.
+    ///
+    /// [`ptr::read`]: ./ptr/fn.read.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn read(self) -> T
+        where T: Sized,
+    {
+        read(self)
+    }
+
+    /// Performs a volatile read of the value from `self` without moving it. This
+    /// leaves the memory in `self` unchanged.
+    ///
+    /// Volatile operations are intended to act on I/O memory, and are guaranteed
+    /// to not be elided or reordered by the compiler across other volatile
+    /// operations.
+    ///
+    /// See [`ptr::read_volatile`] for safety concerns and examples.
+    ///
+    /// [`ptr::read_volatile`]: ./ptr/fn.read_volatile.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn read_volatile(self) -> T
+        where T: Sized,
+    {
+        read_volatile(self)
+    }
+
+    /// Reads the value from `self` without moving it. This leaves the
+    /// memory in `self` unchanged.
+    ///
+    /// Unlike `read`, the pointer may be unaligned.
+    ///
+    /// See [`ptr::read_unaligned`] for safety concerns and examples.
+    ///
+    /// [`ptr::read_unaligned`]: ./ptr/fn.read_unaligned.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn read_unaligned(self) -> T
+        where T: Sized,
+    {
+        read_unaligned(self)
+    }
+
+    /// Copies `count * size_of<T>` bytes from `self` to `dest`. The source
+    /// and destination may overlap.
+    ///
+    /// NOTE: this has the *same* argument order as [`ptr::copy`].
+    ///
+    /// See [`ptr::copy`] for safety concerns and examples.
+    ///
+    /// [`ptr::copy`]: ./ptr/fn.copy.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn copy_to(self, dest: *mut T, count: usize)
+        where T: Sized,
+    {
+        copy(self, dest, count)
+    }
+
+    /// Copies `count * size_of<T>` bytes from `self` to `dest`. The source
+    /// and destination may *not* overlap.
+    ///
+    /// NOTE: this has the *same* argument order as [`ptr::copy_nonoverlapping`].
+    ///
+    /// See [`ptr::copy_nonoverlapping`] for safety concerns and examples.
+    ///
+    /// [`ptr::copy_nonoverlapping`]: ./ptr/fn.copy_nonoverlapping.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn copy_to_nonoverlapping(self, dest: *mut T, count: usize)
+        where T: Sized,
+    {
+        copy_nonoverlapping(self, dest, count)
+    }
+
+    /// Copies `count * size_of<T>` bytes from `src` to `self`. The source
+    /// and destination may overlap.
+    ///
+    /// NOTE: this has the *opposite* argument order of [`ptr::copy`].
+    ///
+    /// See [`ptr::copy`] for safety concerns and examples.
+    ///
+    /// [`ptr::copy`]: ./ptr/fn.copy.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn copy_from(self, src: *const T, count: usize)
+        where T: Sized,
+    {
+        copy(src, self, count)
+    }
+
+    /// Copies `count * size_of<T>` bytes from `src` to `self`. The source
+    /// and destination may *not* overlap.
+    ///
+    /// NOTE: this has the *opposite* argument order of [`ptr::copy_nonoverlapping`].
+    ///
+    /// See [`ptr::copy_nonoverlapping`] for safety concerns and examples.
+    ///
+    /// [`ptr::copy_nonoverlapping`]: ./ptr/fn.copy_nonoverlapping.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn copy_from_nonoverlapping(self, src: *const T, count: usize)
+        where T: Sized,
+    {
+        copy_nonoverlapping(src, self, count)
+    }
+
+    /// Executes the destructor (if any) of the pointed-to value.
+    ///
+    /// See [`ptr::drop_in_place`] for safety concerns and examples.
+    ///
+    /// [`ptr::drop_in_place`]: ./ptr/fn.drop_in_place.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn drop_in_place(self) {
+        drop_in_place(self)
+    }
+
+    /// Overwrites a memory location with the given value without reading or
+    /// dropping the old value.
+    ///
+    /// See [`ptr::write`] for safety concerns and examples.
+    ///
+    /// [`ptr::write`]: ./ptr/fn.write.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn write(self, val: T)
+        where T: Sized,
+    {
+        write(self, val)
+    }
+
+    /// Invokes memset on the specified pointer, setting `count * size_of::<T>()`
+    /// bytes of memory starting at `self` to `val`.
+    ///
+    /// See [`ptr::write_bytes`] for safety concerns and examples.
+    ///
+    /// [`ptr::write_bytes`]: ./ptr/fn.write_bytes.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn write_bytes(self, val: u8, count: usize)
+        where T: Sized,
+    {
+        write_bytes(self, val, count)
+    }
+
+    /// Performs a volatile write of a memory location with the given value without
+    /// reading or dropping the old value.
+    ///
+    /// Volatile operations are intended to act on I/O memory, and are guaranteed
+    /// to not be elided or reordered by the compiler across other volatile
+    /// operations.
+    ///
+    /// See [`ptr::write_volatile`] for safety concerns and examples.
+    ///
+    /// [`ptr::write_volatile`]: ./ptr/fn.write_volatile.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn write_volatile(self, val: T)
+        where T: Sized,
+    {
+        write_volatile(self, val)
+    }
+
+    /// Overwrites a memory location with the given value without reading or
+    /// dropping the old value.
+    ///
+    /// Unlike `write`, the pointer may be unaligned.
+    ///
+    /// See [`ptr::write_unaligned`] for safety concerns and examples.
+    ///
+    /// [`ptr::write_unaligned`]: ./ptr/fn.write_unaligned.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn write_unaligned(self, val: T)
+        where T: Sized,
+    {
+        write_unaligned(self, val)
+    }
+
+    /// Replaces the value at `self` with `src`, returning the old
+    /// value, without dropping either.
+    ///
+    /// See [`ptr::replace`] for safety concerns and examples.
+    ///
+    /// [`ptr::replace`]: ./ptr/fn.replace.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn replace(self, src: T) -> T
+        where T: Sized,
+    {
+        replace(self, src)
+    }
+
+    /// Swaps the values at two mutable locations of the same type, without
+    /// deinitializing either. They may overlap, unlike `mem::swap` which is
+    /// otherwise equivalent.
+    ///
+    /// See [`ptr::swap`] for safety concerns and examples.
+    ///
+    /// [`ptr::swap`]: ./ptr/fn.swap.html
+    #[stable(feature = "pointer_methods", since = "1.26.0")]
+    #[inline]
+    pub unsafe fn swap(self, with: *mut T)
+        where T: Sized,
+    {
+        swap(self, with)
+    }
+
+    /// Computes the offset that needs to be applied to the pointer in order to make it aligned to
+    /// `align`.
+    ///
+    /// If it is not possible to align the pointer, the implementation returns
+    /// `usize::max_value()`.
+    ///
+    /// The offset is expressed in number of `T` elements, and not bytes. The value returned can be
+    /// used with the `offset` or `offset_to` methods.
+    ///
+    /// There are no guarantees whatsover that offsetting the pointer will not overflow or go
+    /// beyond the allocation that the pointer points into. It is up to the caller to ensure that
+    /// the returned offset is correct in all terms other than alignment.
+    ///
+    /// # Panics
+    ///
+    /// The function panics if `align` is not a power-of-two.
+    ///
+    /// # Examples
+    ///
+    /// Accessing adjacent `u8` as `u16`
+    ///
+    /// ```
+    /// # fn foo(n: usize) {
+    /// # use std::mem::align_of;
+    /// # unsafe {
+    /// let x = [5u8, 6u8, 7u8, 8u8, 9u8];
+    /// let ptr = &x[n] as *const u8;
+    /// let offset = ptr.align_offset(align_of::<u16>());
+    /// if offset < x.len() - n - 1 {
+    ///     let u16_ptr = ptr.add(offset) as *const u16;
+    ///     assert_ne!(*u16_ptr, 500);
+    /// } else {
+    ///     // while the pointer can be aligned via `offset`, it would point
+    ///     // outside the allocation
+    /// }
+    /// # } }
+    /// ```
+    #[stable(feature = "align_offset", since = "1.36.0")]
+    pub fn align_offset(self, align: usize) -> usize where T: Sized {
+        if !align.is_power_of_two() {
+            panic!("align_offset: align is not a power-of-two");
+        }
+        unsafe {
+            align_offset(self, align)
+        }
+    }
+}
+
+/// Align pointer `p`.
+///
+/// Calculate offset (in terms of elements of `stride` stride) that has to be applied
+/// to pointer `p` so that pointer `p` would get aligned to `a`.
+///
+/// Note: This implementation has been carefully tailored to not panic. It is UB for this to panic.
+/// The only real change that can be made here is change of `INV_TABLE_MOD_16` and associated
+/// constants.
+///
+/// If we ever decide to make it possible to call the intrinsic with `a` that is not a
+/// power-of-two, it will probably be more prudent to just change to a naive implementation rather
+/// than trying to adapt this to accommodate that change.
+///
+/// Any questions go to @nagisa.
+#[lang="align_offset"]
+pub(crate) unsafe fn align_offset<T: Sized>(p: *const T, a: usize) -> usize {
+    /// Calculate multiplicative modular inverse of `x` modulo `m`.
+    ///
+    /// This implementation is tailored for align_offset and has following preconditions:
+    ///
+    /// * `m` is a power-of-two;
+    /// * `x < m`; (if `x ≥ m`, pass in `x % m` instead)
+    ///
+    /// Implementation of this function shall not panic. Ever.
+    #[inline]
+    fn mod_inv(x: usize, m: usize) -> usize {
+        /// Multiplicative modular inverse table modulo 2⁴ = 16.
+        ///
+        /// Note, that this table does not contain values where inverse does not exist (i.e., for
+        /// `0⁻¹ mod 16`, `2⁻¹ mod 16`, etc.)
+        const INV_TABLE_MOD_16: [u8; 8] = [1, 11, 13, 7, 9, 3, 5, 15];
+        /// Modulo for which the `INV_TABLE_MOD_16` is intended.
+        const INV_TABLE_MOD: usize = 16;
+        /// INV_TABLE_MOD²
+        const INV_TABLE_MOD_SQUARED: usize = INV_TABLE_MOD * INV_TABLE_MOD;
+
+        let table_inverse = INV_TABLE_MOD_16[(x & (INV_TABLE_MOD - 1)) >> 1] as usize;
+        if m <= INV_TABLE_MOD {
+            table_inverse & (m - 1)
+        } else {
+            // We iterate "up" using the following formula:
+            //
+            // $$ xy ≡ 1 (mod 2ⁿ) → xy (2 - xy) ≡ 1 (mod 2²ⁿ) $$
+            //
+            // until 2²ⁿ ≥ m. Then we can reduce to our desired `m` by taking the result `mod m`.
+            let mut inverse = table_inverse;
+            let mut going_mod = INV_TABLE_MOD_SQUARED;
+            loop {
+                // y = y * (2 - xy) mod n
+                //
+                // Note, that we use wrapping operations here intentionally – the original formula
+                // uses e.g., subtraction `mod n`. It is entirely fine to do them `mod
+                // usize::max_value()` instead, because we take the result `mod n` at the end
+                // anyway.
+                inverse = inverse.wrapping_mul(
+                    2usize.wrapping_sub(x.wrapping_mul(inverse))
+                ) & (going_mod - 1);
+                if going_mod > m {
+                    return inverse & (m - 1);
+                }
+                going_mod = going_mod.wrapping_mul(going_mod);
+            }
+        }
+    }
+
+    let stride = mem::size_of::<T>();
+    let a_minus_one = a.wrapping_sub(1);
+    let pmoda = p as usize & a_minus_one;
+
+    if pmoda == 0 {
+        // Already aligned. Yay!
+        return 0;
+    }
+
+    if stride <= 1 {
+        return if stride == 0 {
+            // If the pointer is not aligned, and the element is zero-sized, then no amount of
+            // elements will ever align the pointer.
+            !0
+        } else {
+            a.wrapping_sub(pmoda)
+        };
+    }
+
+    let smoda = stride & a_minus_one;
+    // a is power-of-two so cannot be 0. stride = 0 is handled above.
+    let gcdpow = intrinsics::cttz_nonzero(stride).min(intrinsics::cttz_nonzero(a));
+    let gcd = 1usize << gcdpow;
+
+    if p as usize & (gcd - 1) == 0 {
+        // This branch solves for the following linear congruence equation:
+        //
+        // $$ p + so ≡ 0 mod a $$
+        //
+        // $p$ here is the pointer value, $s$ – stride of `T`, $o$ offset in `T`s, and $a$ – the
+        // requested alignment.
+        //
+        // g = gcd(a, s)
+        // o = (a - (p mod a))/g * ((s/g)⁻¹ mod a)
+        //
+        // The first term is “the relative alignment of p to a”, the second term is “how does
+        // incrementing p by s bytes change the relative alignment of p”. Division by `g` is
+        // necessary to make this equation well formed if $a$ and $s$ are not co-prime.
+        //
+        // Furthermore, the result produced by this solution is not “minimal”, so it is necessary
+        // to take the result $o mod lcm(s, a)$. We can replace $lcm(s, a)$ with just a $a / g$.
+        let j = a.wrapping_sub(pmoda) >> gcdpow;
+        let k = smoda >> gcdpow;
+        return intrinsics::unchecked_rem(j.wrapping_mul(mod_inv(k, a)), a >> gcdpow);
+    }
+
+    // Cannot be aligned at all.
+    usize::max_value()
+}
+
+
+
+// Equality for pointers
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> PartialEq for *const T {
+    #[inline]
+    fn eq(&self, other: &*const T) -> bool { *self == *other }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Eq for *const T {}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> PartialEq for *mut T {
+    #[inline]
+    fn eq(&self, other: &*mut T) -> bool { *self == *other }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Eq for *mut T {}
+
+/// Compares raw pointers for equality.
+///
+/// This is the same as using the `==` operator, but less generic:
+/// the arguments have to be `*const T` raw pointers,
+/// not anything that implements `PartialEq`.
+///
+/// This can be used to compare `&T` references (which coerce to `*const T` implicitly)
+/// by their address rather than comparing the values they point to
+/// (which is what the `PartialEq for &T` implementation does).
+///
+/// # Examples
+///
+/// ```
+/// use std::ptr;
+///
+/// let five = 5;
+/// let other_five = 5;
+/// let five_ref = &five;
+/// let same_five_ref = &five;
+/// let other_five_ref = &other_five;
+///
+/// assert!(five_ref == same_five_ref);
+/// assert!(ptr::eq(five_ref, same_five_ref));
+///
+/// assert!(five_ref == other_five_ref);
+/// assert!(!ptr::eq(five_ref, other_five_ref));
+/// ```
+///
+/// Slices are also compared by their length (fat pointers):
+///
+/// ```
+/// let a = [1, 2, 3];
+/// assert!(std::ptr::eq(&a[..3], &a[..3]));
+/// assert!(!std::ptr::eq(&a[..2], &a[..3]));
+/// assert!(!std::ptr::eq(&a[0..2], &a[1..3]));
+/// ```
+///
+/// Traits are also compared by their implementation:
+///
+/// ```
+/// #[repr(transparent)]
+/// struct Wrapper { member: i32 }
+///
+/// trait Trait {}
+/// impl Trait for Wrapper {}
+/// impl Trait for i32 {}
+///
+/// fn main() {
+///     let wrapper = Wrapper { member: 10 };
+///
+///     // Pointers have equal addresses.
+///     assert!(std::ptr::eq(
+///         &wrapper as *const Wrapper as *const u8,
+///         &wrapper.member as *const i32 as *const u8
+///     ));
+///
+///     // Objects have equal addresses, but `Trait` has different implementations.
+///     assert!(!std::ptr::eq(
+///         &wrapper as &dyn Trait,
+///         &wrapper.member as &dyn Trait,
+///     ));
+///     assert!(!std::ptr::eq(
+///         &wrapper as &dyn Trait as *const dyn Trait,
+///         &wrapper.member as &dyn Trait as *const dyn Trait,
+///     ));
+///
+///     // Converting the reference to a `*const u8` compares by address.
+///     assert!(std::ptr::eq(
+///         &wrapper as &dyn Trait as *const dyn Trait as *const u8,
+///         &wrapper.member as &dyn Trait as *const dyn Trait as *const u8,
+///     ));
+/// }
+/// ```
+#[stable(feature = "ptr_eq", since = "1.17.0")]
+#[inline]
+pub fn eq<T: ?Sized>(a: *const T, b: *const T) -> bool {
+    a == b
+}
+
+/// Hash a raw pointer.
+///
+/// This can be used to hash a `&T` reference (which coerces to `*const T` implicitly)
+/// by its address rather than the value it points to
+/// (which is what the `Hash for &T` implementation does).
+///
+/// # Examples
+///
+/// ```
+/// use std::collections::hash_map::DefaultHasher;
+/// use std::hash::{Hash, Hasher};
+/// use std::ptr;
+///
+/// let five = 5;
+/// let five_ref = &five;
+///
+/// let mut hasher = DefaultHasher::new();
+/// ptr::hash(five_ref, &mut hasher);
+/// let actual = hasher.finish();
+///
+/// let mut hasher = DefaultHasher::new();
+/// (five_ref as *const i32).hash(&mut hasher);
+/// let expected = hasher.finish();
+///
+/// assert_eq!(actual, expected);
+/// ```
+#[stable(feature = "ptr_hash", since = "1.35.0")]
+pub fn hash<T: ?Sized, S: hash::Hasher>(hashee: *const T, into: &mut S) {
+    use crate::hash::Hash;
+    hashee.hash(into);
+}
+
+// Impls for function pointers
+macro_rules! fnptr_impls_safety_abi {
+    ($FnTy: ty, $($Arg: ident),*) => {
+        #[stable(feature = "fnptr_impls", since = "1.4.0")]
+        impl<Ret, $($Arg),*> PartialEq for $FnTy {
+            #[inline]
+            fn eq(&self, other: &Self) -> bool {
+                *self as usize == *other as usize
+            }
+        }
+
+        #[stable(feature = "fnptr_impls", since = "1.4.0")]
+        impl<Ret, $($Arg),*> Eq for $FnTy {}
+
+        #[stable(feature = "fnptr_impls", since = "1.4.0")]
+        impl<Ret, $($Arg),*> PartialOrd for $FnTy {
+            #[inline]
+            fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+                (*self as usize).partial_cmp(&(*other as usize))
+            }
+        }
+
+        #[stable(feature = "fnptr_impls", since = "1.4.0")]
+        impl<Ret, $($Arg),*> Ord for $FnTy {
+            #[inline]
+            fn cmp(&self, other: &Self) -> Ordering {
+                (*self as usize).cmp(&(*other as usize))
+            }
+        }
+
+        #[stable(feature = "fnptr_impls", since = "1.4.0")]
+        impl<Ret, $($Arg),*> hash::Hash for $FnTy {
+            fn hash<HH: hash::Hasher>(&self, state: &mut HH) {
+                state.write_usize(*self as usize)
+            }
+        }
+
+        #[stable(feature = "fnptr_impls", since = "1.4.0")]
+        impl<Ret, $($Arg),*> fmt::Pointer for $FnTy {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                fmt::Pointer::fmt(&(*self as *const ()), f)
+            }
+        }
+
+        #[stable(feature = "fnptr_impls", since = "1.4.0")]
+        impl<Ret, $($Arg),*> fmt::Debug for $FnTy {
+            fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+                fmt::Pointer::fmt(&(*self as *const ()), f)
+            }
+        }
+    }
+}
+
+macro_rules! fnptr_impls_args {
+    ($($Arg: ident),+) => {
+        fnptr_impls_safety_abi! { extern "Rust" fn($($Arg),*) -> Ret, $($Arg),* }
+        fnptr_impls_safety_abi! { extern "C" fn($($Arg),*) -> Ret, $($Arg),* }
+        fnptr_impls_safety_abi! { extern "C" fn($($Arg),* , ...) -> Ret, $($Arg),* }
+        fnptr_impls_safety_abi! { unsafe extern "Rust" fn($($Arg),*) -> Ret, $($Arg),* }
+        fnptr_impls_safety_abi! { unsafe extern "C" fn($($Arg),*) -> Ret, $($Arg),* }
+        fnptr_impls_safety_abi! { unsafe extern "C" fn($($Arg),* , ...) -> Ret, $($Arg),* }
+    };
+    () => {
+        // No variadic functions with 0 parameters
+        fnptr_impls_safety_abi! { extern "Rust" fn() -> Ret, }
+        fnptr_impls_safety_abi! { extern "C" fn() -> Ret, }
+        fnptr_impls_safety_abi! { unsafe extern "Rust" fn() -> Ret, }
+        fnptr_impls_safety_abi! { unsafe extern "C" fn() -> Ret, }
+    };
+}
+
+fnptr_impls_args! { }
+fnptr_impls_args! { A }
+fnptr_impls_args! { A, B }
+fnptr_impls_args! { A, B, C }
+fnptr_impls_args! { A, B, C, D }
+fnptr_impls_args! { A, B, C, D, E }
+fnptr_impls_args! { A, B, C, D, E, F }
+fnptr_impls_args! { A, B, C, D, E, F, G }
+fnptr_impls_args! { A, B, C, D, E, F, G, H }
+fnptr_impls_args! { A, B, C, D, E, F, G, H, I }
+fnptr_impls_args! { A, B, C, D, E, F, G, H, I, J }
+fnptr_impls_args! { A, B, C, D, E, F, G, H, I, J, K }
+fnptr_impls_args! { A, B, C, D, E, F, G, H, I, J, K, L }
+
+// Comparison for pointers
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Ord for *const T {
+    #[inline]
+    fn cmp(&self, other: &*const T) -> Ordering {
+        if self < other {
+            Less
+        } else if self == other {
+            Equal
+        } else {
+            Greater
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> PartialOrd for *const T {
+    #[inline]
+    fn partial_cmp(&self, other: &*const T) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+
+    #[inline]
+    fn lt(&self, other: &*const T) -> bool { *self < *other }
+
+    #[inline]
+    fn le(&self, other: &*const T) -> bool { *self <= *other }
+
+    #[inline]
+    fn gt(&self, other: &*const T) -> bool { *self > *other }
+
+    #[inline]
+    fn ge(&self, other: &*const T) -> bool { *self >= *other }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> Ord for *mut T {
+    #[inline]
+    fn cmp(&self, other: &*mut T) -> Ordering {
+        if self < other {
+            Less
+        } else if self == other {
+            Equal
+        } else {
+            Greater
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T: ?Sized> PartialOrd for *mut T {
+    #[inline]
+    fn partial_cmp(&self, other: &*mut T) -> Option<Ordering> {
+        Some(self.cmp(other))
+    }
+
+    #[inline]
+    fn lt(&self, other: &*mut T) -> bool { *self < *other }
+
+    #[inline]
+    fn le(&self, other: &*mut T) -> bool { *self <= *other }
+
+    #[inline]
+    fn gt(&self, other: &*mut T) -> bool { *self > *other }
+
+    #[inline]
+    fn ge(&self, other: &*mut T) -> bool { *self >= *other }
+}
diff --git a/src/libcore/ptr/non_null.rs b/src/libcore/ptr/non_null.rs
new file mode 100644
index 00000000000..0a6985e334c
--- /dev/null
+++ b/src/libcore/ptr/non_null.rs
@@ -0,0 +1,226 @@
+use crate::convert::From;
+use crate::ops::{CoerceUnsized, DispatchFromDyn};
+use crate::fmt;
+use crate::hash;
+use crate::marker::Unsize;
+use crate::mem;
+use crate::ptr::Unique;
+use crate::cmp::Ordering;
+
+/// `*mut T` but non-zero and covariant.
+///
+/// This is often the correct thing to use when building data structures using
+/// raw pointers, but is ultimately more dangerous to use because of its additional
+/// properties. If you're not sure if you should use `NonNull<T>`, just use `*mut T`!
+///
+/// Unlike `*mut T`, the pointer must always be non-null, even if the pointer
+/// is never dereferenced. This is so that enums may use this forbidden value
+/// as a discriminant -- `Option<NonNull<T>>` has the same size as `*mut T`.
+/// However the pointer may still dangle if it isn't dereferenced.
+///
+/// Unlike `*mut T`, `NonNull<T>` is covariant over `T`. If this is incorrect
+/// for your use case, you should include some [`PhantomData`] in your type to
+/// provide invariance, such as `PhantomData<Cell<T>>` or `PhantomData<&'a mut T>`.
+/// Usually this won't be necessary; covariance is correct for most safe abstractions,
+/// such as `Box`, `Rc`, `Arc`, `Vec`, and `LinkedList`. This is the case because they
+/// provide a public API that follows the normal shared XOR mutable rules of Rust.
+///
+/// Notice that `NonNull<T>` has a `From` instance for `&T`. However, this does
+/// not change the fact that mutating through a (pointer derived from a) shared
+/// reference is undefined behavior unless the mutation happens inside an
+/// [`UnsafeCell<T>`]. The same goes for creating a mutable reference from a shared
+/// reference. When using this `From` instance without an `UnsafeCell<T>`,
+/// it is your responsibility to ensure that `as_mut` is never called, and `as_ptr`
+/// is never used for mutation.
+///
+/// [`PhantomData`]: ../marker/struct.PhantomData.html
+/// [`UnsafeCell<T>`]: ../cell/struct.UnsafeCell.html
+#[stable(feature = "nonnull", since = "1.25.0")]
+#[repr(transparent)]
+#[rustc_layout_scalar_valid_range_start(1)]
+#[cfg_attr(not(stage0), rustc_nonnull_optimization_guaranteed)]
+pub struct NonNull<T: ?Sized> {
+    pointer: *const T,
+}
+
+/// `NonNull` pointers are not `Send` because the data they reference may be aliased.
+// N.B., this impl is unnecessary, but should provide better error messages.
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> !Send for NonNull<T> { }
+
+/// `NonNull` pointers are not `Sync` because the data they reference may be aliased.
+// N.B., this impl is unnecessary, but should provide better error messages.
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> !Sync for NonNull<T> { }
+
+impl<T: Sized> NonNull<T> {
+    /// Creates a new `NonNull` that is dangling, but well-aligned.
+    ///
+    /// This is useful for initializing types which lazily allocate, like
+    /// `Vec::new` does.
+    ///
+    /// Note that the pointer value may potentially represent a valid pointer to
+    /// a `T`, which means this must not be used as a "not yet initialized"
+    /// sentinel value. Types that lazily allocate must track initialization by
+    /// some other means.
+    #[stable(feature = "nonnull", since = "1.25.0")]
+    #[inline]
+    pub const fn dangling() -> Self {
+        unsafe {
+            let ptr = mem::align_of::<T>() as *mut T;
+            NonNull::new_unchecked(ptr)
+        }
+    }
+}
+
+impl<T: ?Sized> NonNull<T> {
+    /// Creates a new `NonNull`.
+    ///
+    /// # Safety
+    ///
+    /// `ptr` must be non-null.
+    #[stable(feature = "nonnull", since = "1.25.0")]
+    #[inline]
+    pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
+        NonNull { pointer: ptr as _ }
+    }
+
+    /// Creates a new `NonNull` if `ptr` is non-null.
+    #[stable(feature = "nonnull", since = "1.25.0")]
+    #[inline]
+    pub fn new(ptr: *mut T) -> Option<Self> {
+        if !ptr.is_null() {
+            Some(unsafe { Self::new_unchecked(ptr) })
+        } else {
+            None
+        }
+    }
+
+    /// Acquires the underlying `*mut` pointer.
+    #[stable(feature = "nonnull", since = "1.25.0")]
+    #[inline]
+    pub const fn as_ptr(self) -> *mut T {
+        self.pointer as *mut T
+    }
+
+    /// Dereferences the content.
+    ///
+    /// The resulting lifetime is bound to self so this behaves "as if"
+    /// it were actually an instance of T that is getting borrowed. If a longer
+    /// (unbound) lifetime is needed, use `&*my_ptr.as_ptr()`.
+    #[stable(feature = "nonnull", since = "1.25.0")]
+    #[inline]
+    pub unsafe fn as_ref(&self) -> &T {
+        &*self.as_ptr()
+    }
+
+    /// Mutably dereferences the content.
+    ///
+    /// The resulting lifetime is bound to self so this behaves "as if"
+    /// it were actually an instance of T that is getting borrowed. If a longer
+    /// (unbound) lifetime is needed, use `&mut *my_ptr.as_ptr()`.
+    #[stable(feature = "nonnull", since = "1.25.0")]
+    #[inline]
+    pub unsafe fn as_mut(&mut self) -> &mut T {
+        &mut *self.as_ptr()
+    }
+
+    /// Cast to a pointer of another type
+    #[stable(feature = "nonnull_cast", since = "1.27.0")]
+    #[inline]
+    pub const fn cast<U>(self) -> NonNull<U> {
+        unsafe {
+            NonNull::new_unchecked(self.as_ptr() as *mut U)
+        }
+    }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> Clone for NonNull<T> {
+    #[inline]
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> Copy for NonNull<T> { }
+
+#[unstable(feature = "coerce_unsized", issue = "27732")]
+impl<T: ?Sized, U: ?Sized> CoerceUnsized<NonNull<U>> for NonNull<T> where T: Unsize<U> { }
+
+#[unstable(feature = "dispatch_from_dyn", issue = "0")]
+impl<T: ?Sized, U: ?Sized> DispatchFromDyn<NonNull<U>> for NonNull<T> where T: Unsize<U> { }
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> fmt::Debug for NonNull<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Pointer::fmt(&self.as_ptr(), f)
+    }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> fmt::Pointer for NonNull<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Pointer::fmt(&self.as_ptr(), f)
+    }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> Eq for NonNull<T> {}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> PartialEq for NonNull<T> {
+    #[inline]
+    fn eq(&self, other: &Self) -> bool {
+        self.as_ptr() == other.as_ptr()
+    }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> Ord for NonNull<T> {
+    #[inline]
+    fn cmp(&self, other: &Self) -> Ordering {
+        self.as_ptr().cmp(&other.as_ptr())
+    }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> PartialOrd for NonNull<T> {
+    #[inline]
+    fn partial_cmp(&self, other: &Self) -> Option<Ordering> {
+        self.as_ptr().partial_cmp(&other.as_ptr())
+    }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> hash::Hash for NonNull<T> {
+    #[inline]
+    fn hash<H: hash::Hasher>(&self, state: &mut H) {
+        self.as_ptr().hash(state)
+    }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> From<Unique<T>> for NonNull<T> {
+    #[inline]
+    fn from(unique: Unique<T>) -> Self {
+        unsafe { NonNull::new_unchecked(unique.as_ptr()) }
+    }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> From<&mut T> for NonNull<T> {
+    #[inline]
+    fn from(reference: &mut T) -> Self {
+        unsafe { NonNull { pointer: reference as *mut T } }
+    }
+}
+
+#[stable(feature = "nonnull", since = "1.25.0")]
+impl<T: ?Sized> From<&T> for NonNull<T> {
+    #[inline]
+    fn from(reference: &T) -> Self {
+        unsafe { NonNull { pointer: reference as *const T } }
+    }
+}
diff --git a/src/libcore/ptr/unique.rs b/src/libcore/ptr/unique.rs
new file mode 100644
index 00000000000..5911518919e
--- /dev/null
+++ b/src/libcore/ptr/unique.rs
@@ -0,0 +1,180 @@
+use crate::convert::From;
+use crate::ops::{CoerceUnsized, DispatchFromDyn};
+use crate::fmt;
+use crate::marker::{PhantomData, Unsize};
+use crate::mem;
+use crate::ptr::NonNull;
+
+/// A wrapper around a raw non-null `*mut T` that indicates that the possessor
+/// of this wrapper owns the referent. Useful for building abstractions like
+/// `Box<T>`, `Vec<T>`, `String`, and `HashMap<K, V>`.
+///
+/// Unlike `*mut T`, `Unique<T>` behaves "as if" it were an instance of `T`.
+/// It implements `Send`/`Sync` if `T` is `Send`/`Sync`. It also implies
+/// the kind of strong aliasing guarantees an instance of `T` can expect:
+/// the referent of the pointer should not be modified without a unique path to
+/// its owning Unique.
+///
+/// If you're uncertain of whether it's correct to use `Unique` for your purposes,
+/// consider using `NonNull`, which has weaker semantics.
+///
+/// Unlike `*mut T`, the pointer must always be non-null, even if the pointer
+/// is never dereferenced. This is so that enums may use this forbidden value
+/// as a discriminant -- `Option<Unique<T>>` has the same size as `Unique<T>`.
+/// However the pointer may still dangle if it isn't dereferenced.
+///
+/// Unlike `*mut T`, `Unique<T>` is covariant over `T`. This should always be correct
+/// for any type which upholds Unique's aliasing requirements.
+#[unstable(feature = "ptr_internals", issue = "0",
+           reason = "use NonNull instead and consider PhantomData<T> \
+                     (if you also use #[may_dangle]), Send, and/or Sync")]
+#[doc(hidden)]
+#[repr(transparent)]
+#[rustc_layout_scalar_valid_range_start(1)]
+pub struct Unique<T: ?Sized> {
+    pointer: *const T,
+    // NOTE: this marker has no consequences for variance, but is necessary
+    // for dropck to understand that we logically own a `T`.
+    //
+    // For details, see:
+    // https://github.com/rust-lang/rfcs/blob/master/text/0769-sound-generic-drop.md#phantom-data
+    _marker: PhantomData<T>,
+}
+
+/// `Unique` pointers are `Send` if `T` is `Send` because the data they
+/// reference is unaliased. Note that this aliasing invariant is
+/// unenforced by the type system; the abstraction using the
+/// `Unique` must enforce it.
+#[unstable(feature = "ptr_internals", issue = "0")]
+unsafe impl<T: Send + ?Sized> Send for Unique<T> { }
+
+/// `Unique` pointers are `Sync` if `T` is `Sync` because the data they
+/// reference is unaliased. Note that this aliasing invariant is
+/// unenforced by the type system; the abstraction using the
+/// `Unique` must enforce it.
+#[unstable(feature = "ptr_internals", issue = "0")]
+unsafe impl<T: Sync + ?Sized> Sync for Unique<T> { }
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: Sized> Unique<T> {
+    /// Creates a new `Unique` that is dangling, but well-aligned.
+    ///
+    /// This is useful for initializing types which lazily allocate, like
+    /// `Vec::new` does.
+    ///
+    /// Note that the pointer value may potentially represent a valid pointer to
+    /// a `T`, which means this must not be used as a "not yet initialized"
+    /// sentinel value. Types that lazily allocate must track initialization by
+    /// some other means.
+    // FIXME: rename to dangling() to match NonNull?
+    #[inline]
+    pub const fn empty() -> Self {
+        unsafe {
+            Unique::new_unchecked(mem::align_of::<T>() as *mut T)
+        }
+    }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> Unique<T> {
+    /// Creates a new `Unique`.
+    ///
+    /// # Safety
+    ///
+    /// `ptr` must be non-null.
+    #[inline]
+    pub const unsafe fn new_unchecked(ptr: *mut T) -> Self {
+        Unique { pointer: ptr as _, _marker: PhantomData }
+    }
+
+    /// Creates a new `Unique` if `ptr` is non-null.
+    #[inline]
+    pub fn new(ptr: *mut T) -> Option<Self> {
+        if !ptr.is_null() {
+            Some(unsafe { Unique { pointer: ptr as _, _marker: PhantomData } })
+        } else {
+            None
+        }
+    }
+
+    /// Acquires the underlying `*mut` pointer.
+    #[inline]
+    pub const fn as_ptr(self) -> *mut T {
+        self.pointer as *mut T
+    }
+
+    /// Dereferences the content.
+    ///
+    /// The resulting lifetime is bound to self so this behaves "as if"
+    /// it were actually an instance of T that is getting borrowed. If a longer
+    /// (unbound) lifetime is needed, use `&*my_ptr.as_ptr()`.
+    #[inline]
+    pub unsafe fn as_ref(&self) -> &T {
+        &*self.as_ptr()
+    }
+
+    /// Mutably dereferences the content.
+    ///
+    /// The resulting lifetime is bound to self so this behaves "as if"
+    /// it were actually an instance of T that is getting borrowed. If a longer
+    /// (unbound) lifetime is needed, use `&mut *my_ptr.as_ptr()`.
+    #[inline]
+    pub unsafe fn as_mut(&mut self) -> &mut T {
+        &mut *self.as_ptr()
+    }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> Clone for Unique<T> {
+    #[inline]
+    fn clone(&self) -> Self {
+        *self
+    }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> Copy for Unique<T> { }
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized, U: ?Sized> CoerceUnsized<Unique<U>> for Unique<T> where T: Unsize<U> { }
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized, U: ?Sized> DispatchFromDyn<Unique<U>> for Unique<T> where T: Unsize<U> { }
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> fmt::Debug for Unique<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Pointer::fmt(&self.as_ptr(), f)
+    }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> fmt::Pointer for Unique<T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        fmt::Pointer::fmt(&self.as_ptr(), f)
+    }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> From<&mut T> for Unique<T> {
+    #[inline]
+    fn from(reference: &mut T) -> Self {
+        unsafe { Unique { pointer: reference as *mut T, _marker: PhantomData } }
+    }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<T: ?Sized> From<&T> for Unique<T> {
+    #[inline]
+    fn from(reference: &T) -> Self {
+        unsafe { Unique { pointer: reference as *const T, _marker: PhantomData } }
+    }
+}
+
+#[unstable(feature = "ptr_internals", issue = "0")]
+impl<'a, T: ?Sized> From<NonNull<T>> for Unique<T> {
+    #[inline]
+    fn from(p: NonNull<T>) -> Self {
+        unsafe { Unique::new_unchecked(p.as_ptr()) }
+    }
+}