Move the alloc::allocator module to core::heap

This is the `Alloc` trait and its dependencies.

3 files changed, 5 insertions, 1086 deletions

diff --git a/src/liballoc/allocator.rs b/src/liballoc/allocator.rs
deleted file mode 100644
index fdc4efc66b9..00000000000
--- a/src/liballoc/allocator.rs
+++ /dev/null
@@ -1,1082 +0,0 @@
-// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
-// file at the top-level directory of this distribution and at
-// http://rust-lang.org/COPYRIGHT.
-//
-// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
-// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
-// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
-// option. This file may not be copied, modified, or distributed
-// except according to those terms.
-
-#![unstable(feature = "allocator_api",
-            reason = "the precise API and guarantees it provides may be tweaked \
-                      slightly, especially to possibly take into account the \
-                      types being stored to make room for a future \
-                      tracing garbage collector",
-            issue = "32838")]
-
-use core::cmp;
-use core::fmt;
-use core::mem;
-use core::usize;
-use core::ptr::{self, NonNull};
-
-/// Represents the combination of a starting address and
-/// a total capacity of the returned block.
-#[derive(Debug)]
-pub struct Excess(pub *mut u8, pub usize);
-
-fn size_align<T>() -> (usize, usize) {
-    (mem::size_of::<T>(), mem::align_of::<T>())
-}
-
-/// Layout of a block of memory.
-///
-/// An instance of `Layout` describes a particular layout of memory.
-/// You build a `Layout` up as an input to give to an allocator.
-///
-/// All layouts have an associated non-negative size and a
-/// power-of-two alignment.
-///
-/// (Note however that layouts are *not* required to have positive
-/// size, even though many allocators require that all memory
-/// requests have positive size. A caller to the `Alloc::alloc`
-/// method must either ensure that conditions like this are met, or
-/// use specific allocators with looser requirements.)
-#[derive(Clone, Debug, PartialEq, Eq)]
-pub struct Layout {
-    // size of the requested block of memory, measured in bytes.
-    size: usize,
-
-    // alignment of the requested block of memory, measured in bytes.
-    // we ensure that this is always a power-of-two, because API's
-    // like `posix_memalign` require it and it is a reasonable
-    // constraint to impose on Layout constructors.
-    //
-    // (However, we do not analogously require `align >= sizeof(void*)`,
-    //  even though that is *also* a requirement of `posix_memalign`.)
-    align: usize,
-}
-
-
-// FIXME: audit default implementations for overflow errors,
-// (potentially switching to overflowing_add and
-//  overflowing_mul as necessary).
-
-impl Layout {
-    /// Constructs a `Layout` from a given `size` and `align`,
-    /// or returns `None` if any of the following conditions
-    /// are not met:
-    ///
-    /// * `align` must be a power of two,
-    ///
-    /// * `align` must not exceed 2<sup>31</sup> (i.e. `1 << 31`),
-    ///
-    /// * `size`, when rounded up to the nearest multiple of `align`,
-    ///    must not overflow (i.e. the rounded value must be less than
-    ///    `usize::MAX`).
-    #[inline]
-    pub fn from_size_align(size: usize, align: usize) -> Option<Layout> {
-        if !align.is_power_of_two() {
-            return None;
-        }
-
-        if align > (1 << 31) {
-            return None;
-        }
-
-        // (power-of-two implies align != 0.)
-
-        // Rounded up size is:
-        //   size_rounded_up = (size + align - 1) & !(align - 1);
-        //
-        // We know from above that align != 0. If adding (align - 1)
-        // does not overflow, then rounding up will be fine.
-        //
-        // Conversely, &-masking with !(align - 1) will subtract off
-        // only low-order-bits. Thus if overflow occurs with the sum,
-        // the &-mask cannot subtract enough to undo that overflow.
-        //
-        // Above implies that checking for summation overflow is both
-        // necessary and sufficient.
-        if size > usize::MAX - (align - 1) {
-            return None;
-        }
-
-        unsafe {
-            Some(Layout::from_size_align_unchecked(size, align))
-        }
-    }
-
-    /// Creates a layout, bypassing all checks.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe as it does not verify that `align` is
-    /// a power-of-two that is also less than or equal to 2<sup>31</sup>, nor
-    /// that `size` aligned to `align` fits within the address space
-    /// (i.e. the `Layout::from_size_align` preconditions).
-    #[inline]
-    pub unsafe fn from_size_align_unchecked(size: usize, align: usize) -> Layout {
-        Layout { size: size, align: align }
-    }
-
-    /// The minimum size in bytes for a memory block of this layout.
-    #[inline]
-    pub fn size(&self) -> usize { self.size }
-
-    /// The minimum byte alignment for a memory block of this layout.
-    #[inline]
-    pub fn align(&self) -> usize { self.align }
-
-    /// Constructs a `Layout` suitable for holding a value of type `T`.
-    pub fn new<T>() -> Self {
-        let (size, align) = size_align::<T>();
-        Layout::from_size_align(size, align).unwrap()
-    }
-
-    /// Produces layout describing a record that could be used to
-    /// allocate backing structure for `T` (which could be a trait
-    /// or other unsized type like a slice).
-    pub fn for_value<T: ?Sized>(t: &T) -> Self {
-        let (size, align) = (mem::size_of_val(t), mem::align_of_val(t));
-        Layout::from_size_align(size, align).unwrap()
-    }
-
-    /// Creates a layout describing the record that can hold a value
-    /// of the same layout as `self`, but that also is aligned to
-    /// alignment `align` (measured in bytes).
-    ///
-    /// If `self` already meets the prescribed alignment, then returns
-    /// `self`.
-    ///
-    /// Note that this method does not add any padding to the overall
-    /// size, regardless of whether the returned layout has a different
-    /// alignment. In other words, if `K` has size 16, `K.align_to(32)`
-    /// will *still* have size 16.
-    ///
-    /// # Panics
-    ///
-    /// Panics if the combination of `self.size` and the given `align`
-    /// violates the conditions listed in `from_size_align`.
-    #[inline]
-    pub fn align_to(&self, align: usize) -> Self {
-        Layout::from_size_align(self.size, cmp::max(self.align, align)).unwrap()
-    }
-
-    /// Returns the amount of padding we must insert after `self`
-    /// to ensure that the following address will satisfy `align`
-    /// (measured in bytes).
-    ///
-    /// E.g. if `self.size` is 9, then `self.padding_needed_for(4)`
-    /// returns 3, because that is the minimum number of bytes of
-    /// padding required to get a 4-aligned address (assuming that the
-    /// corresponding memory block starts at a 4-aligned address).
-    ///
-    /// The return value of this function has no meaning if `align` is
-    /// not a power-of-two.
-    ///
-    /// Note that the utility of the returned value requires `align`
-    /// to be less than or equal to the alignment of the starting
-    /// address for the whole allocated block of memory. One way to
-    /// satisfy this constraint is to ensure `align <= self.align`.
-    #[inline]
-    pub fn padding_needed_for(&self, align: usize) -> usize {
-        let len = self.size();
-
-        // Rounded up value is:
-        //   len_rounded_up = (len + align - 1) & !(align - 1);
-        // and then we return the padding difference: `len_rounded_up - len`.
-        //
-        // We use modular arithmetic throughout:
-        //
-        // 1. align is guaranteed to be > 0, so align - 1 is always
-        //    valid.
-        //
-        // 2. `len + align - 1` can overflow by at most `align - 1`,
-        //    so the &-mask wth `!(align - 1)` will ensure that in the
-        //    case of overflow, `len_rounded_up` will itself be 0.
-        //    Thus the returned padding, when added to `len`, yields 0,
-        //    which trivially satisfies the alignment `align`.
-        //
-        // (Of course, attempts to allocate blocks of memory whose
-        // size and padding overflow in the above manner should cause
-        // the allocator to yield an error anyway.)
-
-        let len_rounded_up = len.wrapping_add(align).wrapping_sub(1) & !align.wrapping_sub(1);
-        return len_rounded_up.wrapping_sub(len);
-    }
-
-    /// Creates a layout describing the record for `n` instances of
-    /// `self`, with a suitable amount of padding between each to
-    /// ensure that each instance is given its requested size and
-    /// alignment. On success, returns `(k, offs)` where `k` is the
-    /// layout of the array and `offs` is the distance between the start
-    /// of each element in the array.
-    ///
-    /// On arithmetic overflow, returns `None`.
-    #[inline]
-    pub fn repeat(&self, n: usize) -> Option<(Self, usize)> {
-        let padded_size = self.size.checked_add(self.padding_needed_for(self.align))?;
-        let alloc_size = padded_size.checked_mul(n)?;
-
-        // We can assume that `self.align` is a power-of-two that does
-        // not exceed 2<sup>31</sup>. Furthermore, `alloc_size` has already been
-        // rounded up to a multiple of `self.align`; therefore, the
-        // call to `Layout::from_size_align` below should never panic.
-        Some((Layout::from_size_align(alloc_size, self.align).unwrap(), padded_size))
-    }
-
-    /// Creates a layout describing the record for `self` followed by
-    /// `next`, including any necessary padding to ensure that `next`
-    /// will be properly aligned. Note that the result layout will
-    /// satisfy the alignment properties of both `self` and `next`.
-    ///
-    /// Returns `Some((k, offset))`, where `k` is layout of the concatenated
-    /// record and `offset` is the relative location, in bytes, of the
-    /// start of the `next` embedded within the concatenated record
-    /// (assuming that the record itself starts at offset 0).
-    ///
-    /// On arithmetic overflow, returns `None`.
-    pub fn extend(&self, next: Self) -> Option<(Self, usize)> {
-        let new_align = cmp::max(self.align, next.align);
-        let realigned = Layout::from_size_align(self.size, new_align)?;
-
-        let pad = realigned.padding_needed_for(next.align);
-
-        let offset = self.size.checked_add(pad)?;
-        let new_size = offset.checked_add(next.size)?;
-
-        let layout = Layout::from_size_align(new_size, new_align)?;
-        Some((layout, offset))
-    }
-
-    /// Creates a layout describing the record for `n` instances of
-    /// `self`, with no padding between each instance.
-    ///
-    /// Note that, unlike `repeat`, `repeat_packed` does not guarantee
-    /// that the repeated instances of `self` will be properly
-    /// aligned, even if a given instance of `self` is properly
-    /// aligned. In other words, if the layout returned by
-    /// `repeat_packed` is used to allocate an array, it is not
-    /// guaranteed that all elements in the array will be properly
-    /// aligned.
-    ///
-    /// On arithmetic overflow, returns `None`.
-    pub fn repeat_packed(&self, n: usize) -> Option<Self> {
-        let size = self.size().checked_mul(n)?;
-        Layout::from_size_align(size, self.align)
-    }
-
-    /// Creates a layout describing the record for `self` followed by
-    /// `next` with no additional padding between the two. Since no
-    /// padding is inserted, the alignment of `next` is irrelevant,
-    /// and is not incorporated *at all* into the resulting layout.
-    ///
-    /// Returns `(k, offset)`, where `k` is layout of the concatenated
-    /// record and `offset` is the relative location, in bytes, of the
-    /// start of the `next` embedded within the concatenated record
-    /// (assuming that the record itself starts at offset 0).
-    ///
-    /// (The `offset` is always the same as `self.size()`; we use this
-    ///  signature out of convenience in matching the signature of
-    ///  `extend`.)
-    ///
-    /// On arithmetic overflow, returns `None`.
-    pub fn extend_packed(&self, next: Self) -> Option<(Self, usize)> {
-        let new_size = self.size().checked_add(next.size())?;
-        let layout = Layout::from_size_align(new_size, self.align)?;
-        Some((layout, self.size()))
-    }
-
-    /// Creates a layout describing the record for a `[T; n]`.
-    ///
-    /// On arithmetic overflow, returns `None`.
-    pub fn array<T>(n: usize) -> Option<Self> {
-        Layout::new::<T>()
-            .repeat(n)
-            .map(|(k, offs)| {
-                debug_assert!(offs == mem::size_of::<T>());
-                k
-            })
-    }
-}
-
-/// The `AllocErr` error specifies whether an allocation failure is
-/// specifically due to resource exhaustion or if it is due to
-/// something wrong when combining the given input arguments with this
-/// allocator.
-#[derive(Clone, PartialEq, Eq, Debug)]
-pub enum AllocErr {
-    /// Error due to hitting some resource limit or otherwise running
-    /// out of memory. This condition strongly implies that *some*
-    /// series of deallocations would allow a subsequent reissuing of
-    /// the original allocation request to succeed.
-    Exhausted { request: Layout },
-
-    /// Error due to allocator being fundamentally incapable of
-    /// satisfying the original request. This condition implies that
-    /// such an allocation request will never succeed on the given
-    /// allocator, regardless of environment, memory pressure, or
-    /// other contextual conditions.
-    ///
-    /// For example, an allocator that does not support requests for
-    /// large memory blocks might return this error variant.
-    Unsupported { details: &'static str },
-}
-
-impl AllocErr {
-    #[inline]
-    pub fn invalid_input(details: &'static str) -> Self {
-        AllocErr::Unsupported { details: details }
-    }
-    #[inline]
-    pub fn is_memory_exhausted(&self) -> bool {
-        if let AllocErr::Exhausted { .. } = *self { true } else { false }
-    }
-    #[inline]
-    pub fn is_request_unsupported(&self) -> bool {
-        if let AllocErr::Unsupported { .. } = *self { true } else { false }
-    }
-    #[inline]
-    pub fn description(&self) -> &str {
-        match *self {
-            AllocErr::Exhausted { .. } => "allocator memory exhausted",
-            AllocErr::Unsupported { .. } => "unsupported allocator request",
-        }
-    }
-}
-
-// (we need this for downstream impl of trait Error)
-impl fmt::Display for AllocErr {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}", self.description())
-    }
-}
-
-/// The `CannotReallocInPlace` error is used when `grow_in_place` or
-/// `shrink_in_place` were unable to reuse the given memory block for
-/// a requested layout.
-#[derive(Clone, PartialEq, Eq, Debug)]
-pub struct CannotReallocInPlace;
-
-impl CannotReallocInPlace {
-    pub fn description(&self) -> &str {
-        "cannot reallocate allocator's memory in place"
-    }
-}
-
-// (we need this for downstream impl of trait Error)
-impl fmt::Display for CannotReallocInPlace {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "{}", self.description())
-    }
-}
-
-/// Augments `AllocErr` with a CapacityOverflow variant.
-#[derive(Clone, PartialEq, Eq, Debug)]
-#[unstable(feature = "try_reserve", reason = "new API", issue="48043")]
-pub enum CollectionAllocErr {
-    /// Error due to the computed capacity exceeding the collection's maximum
-    /// (usually `isize::MAX` bytes).
-    CapacityOverflow,
-    /// Error due to the allocator (see the `AllocErr` type's docs).
-    AllocErr(AllocErr),
-}
-
-#[unstable(feature = "try_reserve", reason = "new API", issue="48043")]
-impl From<AllocErr> for CollectionAllocErr {
-    fn from(err: AllocErr) -> Self {
-        CollectionAllocErr::AllocErr(err)
-    }
-}
-
-/// An implementation of `Alloc` can allocate, reallocate, and
-/// deallocate arbitrary blocks of data described via `Layout`.
-///
-/// Some of the methods require that a memory block be *currently
-/// allocated* via an allocator. This means that:
-///
-/// * the starting address for that memory block was previously
-///   returned by a previous call to an allocation method (`alloc`,
-///   `alloc_zeroed`, `alloc_excess`, `alloc_one`, `alloc_array`) or
-///   reallocation method (`realloc`, `realloc_excess`, or
-///   `realloc_array`), and
-///
-/// * the memory block has not been subsequently deallocated, where
-///   blocks are deallocated either by being passed to a deallocation
-///   method (`dealloc`, `dealloc_one`, `dealloc_array`) or by being
-///   passed to a reallocation method (see above) that returns `Ok`.
-///
-/// A note regarding zero-sized types and zero-sized layouts: many
-/// methods in the `Alloc` trait state that allocation requests
-/// must be non-zero size, or else undefined behavior can result.
-///
-/// * However, some higher-level allocation methods (`alloc_one`,
-///   `alloc_array`) are well-defined on zero-sized types and can
-///   optionally support them: it is left up to the implementor
-///   whether to return `Err`, or to return `Ok` with some pointer.
-///
-/// * If an `Alloc` implementation chooses to return `Ok` in this
-///   case (i.e. the pointer denotes a zero-sized inaccessible block)
-///   then that returned pointer must be considered "currently
-///   allocated". On such an allocator, *all* methods that take
-///   currently-allocated pointers as inputs must accept these
-///   zero-sized pointers, *without* causing undefined behavior.
-///
-/// * In other words, if a zero-sized pointer can flow out of an
-///   allocator, then that allocator must likewise accept that pointer
-///   flowing back into its deallocation and reallocation methods.
-///
-/// Some of the methods require that a layout *fit* a memory block.
-/// What it means for a layout to "fit" a memory block means (or
-/// equivalently, for a memory block to "fit" a layout) is that the
-/// following two conditions must hold:
-///
-/// 1. The block's starting address must be aligned to `layout.align()`.
-///
-/// 2. The block's size must fall in the range `[use_min, use_max]`, where:
-///
-///    * `use_min` is `self.usable_size(layout).0`, and
-///
-///    * `use_max` is the capacity that was (or would have been)
-///      returned when (if) the block was allocated via a call to
-///      `alloc_excess` or `realloc_excess`.
-///
-/// Note that:
-///
-///  * the size of the layout most recently used to allocate the block
-///    is guaranteed to be in the range `[use_min, use_max]`, and
-///
-///  * a lower-bound on `use_max` can be safely approximated by a call to
-///    `usable_size`.
-///
-///  * if a layout `k` fits a memory block (denoted by `ptr`)
-///    currently allocated via an allocator `a`, then it is legal to
-///    use that layout to deallocate it, i.e. `a.dealloc(ptr, k);`.
-///
-/// # Unsafety
-///
-/// The `Alloc` trait is an `unsafe` trait for a number of reasons, and
-/// implementors must ensure that they adhere to these contracts:
-///
-/// * Pointers returned from allocation functions must point to valid memory and
-///   retain their validity until at least the instance of `Alloc` is dropped
-///   itself.
-///
-/// * It's undefined behavior if global allocators unwind.  This restriction may
-///   be lifted in the future, but currently a panic from any of these
-///   functions may lead to memory unsafety. Note that as of the time of this
-///   writing allocators *not* intending to be global allocators can still panic
-///   in their implementation without violating memory safety.
-///
-/// * `Layout` queries and calculations in general must be correct. Callers of
-///   this trait are allowed to rely on the contracts defined on each method,
-///   and implementors must ensure such contracts remain true.
-///
-/// Note that this list may get tweaked over time as clarifications are made in
-/// the future. Additionally global allocators may gain unique requirements for
-/// how to safely implement one in the future as well.
-pub unsafe trait Alloc {
-
-    // (Note: existing allocators have unspecified but well-defined
-    // behavior in response to a zero size allocation request ;
-    // e.g. in C, `malloc` of 0 will either return a null pointer or a
-    // unique pointer, but will not have arbitrary undefined
-    // behavior. Rust should consider revising the alloc::heap crate
-    // to reflect this reality.)
-
-    /// Returns a pointer meeting the size and alignment guarantees of
-    /// `layout`.
-    ///
-    /// If this method returns an `Ok(addr)`, then the `addr` returned
-    /// will be non-null address pointing to a block of storage
-    /// suitable for holding an instance of `layout`.
-    ///
-    /// The returned block of storage may or may not have its contents
-    /// initialized. (Extension subtraits might restrict this
-    /// behavior, e.g. to ensure initialization to particular sets of
-    /// bit patterns.)
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe because undefined behavior can result
-    /// if the caller does not ensure that `layout` has non-zero size.
-    ///
-    /// (Extension subtraits might provide more specific bounds on
-    /// behavior, e.g. guarantee a sentinel address or a null pointer
-    /// in response to a zero-size allocation request.)
-    ///
-    /// # Errors
-    ///
-    /// Returning `Err` indicates that either memory is exhausted or
-    /// `layout` does not meet allocator's size or alignment
-    /// constraints.
-    ///
-    /// Implementations are encouraged to return `Err` on memory
-    /// exhaustion rather than panicking or aborting, but this is not
-    /// a strict requirement. (Specifically: it is *legal* to
-    /// implement this trait atop an underlying native allocation
-    /// library that aborts on memory exhaustion.)
-    ///
-    /// Clients wishing to abort computation in response to an
-    /// allocation error are encouraged to call the allocator's `oom`
-    /// method, rather than directly invoking `panic!` or similar.
-    unsafe fn alloc(&mut self, layout: Layout) -> Result<*mut u8, AllocErr>;
-
-    /// Deallocate the memory referenced by `ptr`.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe because undefined behavior can result
-    /// if the caller does not ensure all of the following:
-    ///
-    /// * `ptr` must denote a block of memory currently allocated via
-    ///   this allocator,
-    ///
-    /// * `layout` must *fit* that block of memory,
-    ///
-    /// * In addition to fitting the block of memory `layout`, the
-    ///   alignment of the `layout` must match the alignment used
-    ///   to allocate that block of memory.
-    unsafe fn dealloc(&mut self, ptr: *mut u8, layout: Layout);
-
-    /// Allocator-specific method for signaling an out-of-memory
-    /// condition.
-    ///
-    /// `oom` aborts the thread or process, optionally performing
-    /// cleanup or logging diagnostic information before panicking or
-    /// aborting.
-    ///
-    /// `oom` is meant to be used by clients unable to cope with an
-    /// unsatisfied allocation request (signaled by an error such as
-    /// `AllocErr::Exhausted`), and wish to abandon computation rather
-    /// than attempt to recover locally. Such clients should pass the
-    /// signaling error value back into `oom`, where the allocator
-    /// may incorporate that error value into its diagnostic report
-    /// before aborting.
-    ///
-    /// Implementations of the `oom` method are discouraged from
-    /// infinitely regressing in nested calls to `oom`. In
-    /// practice this means implementors should eschew allocating,
-    /// especially from `self` (directly or indirectly).
-    ///
-    /// Implementations of the allocation and reallocation methods
-    /// (e.g. `alloc`, `alloc_one`, `realloc`) are discouraged from
-    /// panicking (or aborting) in the event of memory exhaustion;
-    /// instead they should return an appropriate error from the
-    /// invoked method, and let the client decide whether to invoke
-    /// this `oom` method in response.
-    fn oom(&mut self, _: AllocErr) -> ! {
-        unsafe { ::core::intrinsics::abort() }
-    }
-
-    // == ALLOCATOR-SPECIFIC QUANTITIES AND LIMITS ==
-    // usable_size
-
-    /// Returns bounds on the guaranteed usable size of a successful
-    /// allocation created with the specified `layout`.
-    ///
-    /// In particular, if one has a memory block allocated via a given
-    /// allocator `a` and layout `k` where `a.usable_size(k)` returns
-    /// `(l, u)`, then one can pass that block to `a.dealloc()` with a
-    /// layout in the size range [l, u].
-    ///
-    /// (All implementors of `usable_size` must ensure that
-    /// `l <= k.size() <= u`)
-    ///
-    /// Both the lower- and upper-bounds (`l` and `u` respectively)
-    /// are provided, because an allocator based on size classes could
-    /// misbehave if one attempts to deallocate a block without
-    /// providing a correct value for its size (i.e., one within the
-    /// range `[l, u]`).
-    ///
-    /// Clients who wish to make use of excess capacity are encouraged
-    /// to use the `alloc_excess` and `realloc_excess` instead, as
-    /// this method is constrained to report conservative values that
-    /// serve as valid bounds for *all possible* allocation method
-    /// calls.
-    ///
-    /// However, for clients that do not wish to track the capacity
-    /// returned by `alloc_excess` locally, this method is likely to
-    /// produce useful results.
-    #[inline]
-    fn usable_size(&self, layout: &Layout) -> (usize, usize) {
-        (layout.size(), layout.size())
-    }
-
-    // == METHODS FOR MEMORY REUSE ==
-    // realloc. alloc_excess, realloc_excess
-
-    /// Returns a pointer suitable for holding data described by
-    /// `new_layout`, meeting its size and alignment guarantees. To
-    /// accomplish this, this may extend or shrink the allocation
-    /// referenced by `ptr` to fit `new_layout`.
-    ///
-    /// If this returns `Ok`, then ownership of the memory block
-    /// referenced by `ptr` has been transferred to this
-    /// allocator. The memory may or may not have been freed, and
-    /// should be considered unusable (unless of course it was
-    /// transferred back to the caller again via the return value of
-    /// this method).
-    ///
-    /// If this method returns `Err`, then ownership of the memory
-    /// block has not been transferred to this allocator, and the
-    /// contents of the memory block are unaltered.
-    ///
-    /// For best results, `new_layout` should not impose a different
-    /// alignment constraint than `layout`. (In other words,
-    /// `new_layout.align()` should equal `layout.align()`.) However,
-    /// behavior is well-defined (though underspecified) when this
-    /// constraint is violated; further discussion below.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe because undefined behavior can result
-    /// if the caller does not ensure all of the following:
-    ///
-    /// * `ptr` must be currently allocated via this allocator,
-    ///
-    /// * `layout` must *fit* the `ptr` (see above). (The `new_layout`
-    ///   argument need not fit it.)
-    ///
-    /// * `new_layout` must have size greater than zero.
-    ///
-    /// * the alignment of `new_layout` is non-zero.
-    ///
-    /// (Extension subtraits might provide more specific bounds on
-    /// behavior, e.g. guarantee a sentinel address or a null pointer
-    /// in response to a zero-size allocation request.)
-    ///
-    /// # Errors
-    ///
-    /// Returns `Err` only if `new_layout` does not match the
-    /// alignment of `layout`, or does not meet the allocator's size
-    /// and alignment constraints of the allocator, or if reallocation
-    /// otherwise fails.
-    ///
-    /// (Note the previous sentence did not say "if and only if" -- in
-    /// particular, an implementation of this method *can* return `Ok`
-    /// if `new_layout.align() != old_layout.align()`; or it can
-    /// return `Err` in that scenario, depending on whether this
-    /// allocator can dynamically adjust the alignment constraint for
-    /// the block.)
-    ///
-    /// Implementations are encouraged to return `Err` on memory
-    /// exhaustion rather than panicking or aborting, but this is not
-    /// a strict requirement. (Specifically: it is *legal* to
-    /// implement this trait atop an underlying native allocation
-    /// library that aborts on memory exhaustion.)
-    ///
-    /// Clients wishing to abort computation in response to an
-    /// reallocation error are encouraged to call the allocator's `oom`
-    /// method, rather than directly invoking `panic!` or similar.
-    unsafe fn realloc(&mut self,
-                      ptr: *mut u8,
-                      layout: Layout,
-                      new_layout: Layout) -> Result<*mut u8, AllocErr> {
-        let new_size = new_layout.size();
-        let old_size = layout.size();
-        let aligns_match = layout.align == new_layout.align;
-
-        if new_size >= old_size && aligns_match {
-            if let Ok(()) = self.grow_in_place(ptr, layout.clone(), new_layout.clone()) {
-                return Ok(ptr);
-            }
-        } else if new_size < old_size && aligns_match {
-            if let Ok(()) = self.shrink_in_place(ptr, layout.clone(), new_layout.clone()) {
-                return Ok(ptr);
-            }
-        }
-
-        // otherwise, fall back on alloc + copy + dealloc.
-        let result = self.alloc(new_layout);
-        if let Ok(new_ptr) = result {
-            ptr::copy_nonoverlapping(ptr as *const u8, new_ptr, cmp::min(old_size, new_size));
-            self.dealloc(ptr, layout);
-        }
-        result
-    }
-
-    /// Behaves like `alloc`, but also ensures that the contents
-    /// are set to zero before being returned.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe for the same reasons that `alloc` is.
-    ///
-    /// # Errors
-    ///
-    /// Returning `Err` indicates that either memory is exhausted or
-    /// `layout` does not meet allocator's size or alignment
-    /// constraints, just as in `alloc`.
-    ///
-    /// Clients wishing to abort computation in response to an
-    /// allocation error are encouraged to call the allocator's `oom`
-    /// method, rather than directly invoking `panic!` or similar.
-    unsafe fn alloc_zeroed(&mut self, layout: Layout) -> Result<*mut u8, AllocErr> {
-        let size = layout.size();
-        let p = self.alloc(layout);
-        if let Ok(p) = p {
-            ptr::write_bytes(p, 0, size);
-        }
-        p
-    }
-
-    /// Behaves like `alloc`, but also returns the whole size of
-    /// the returned block. For some `layout` inputs, like arrays, this
-    /// may include extra storage usable for additional data.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe for the same reasons that `alloc` is.
-    ///
-    /// # Errors
-    ///
-    /// Returning `Err` indicates that either memory is exhausted or
-    /// `layout` does not meet allocator's size or alignment
-    /// constraints, just as in `alloc`.
-    ///
-    /// Clients wishing to abort computation in response to an
-    /// allocation error are encouraged to call the allocator's `oom`
-    /// method, rather than directly invoking `panic!` or similar.
-    unsafe fn alloc_excess(&mut self, layout: Layout) -> Result<Excess, AllocErr> {
-        let usable_size = self.usable_size(&layout);
-        self.alloc(layout).map(|p| Excess(p, usable_size.1))
-    }
-
-    /// Behaves like `realloc`, but also returns the whole size of
-    /// the returned block. For some `layout` inputs, like arrays, this
-    /// may include extra storage usable for additional data.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe for the same reasons that `realloc` is.
-    ///
-    /// # Errors
-    ///
-    /// Returning `Err` indicates that either memory is exhausted or
-    /// `layout` does not meet allocator's size or alignment
-    /// constraints, just as in `realloc`.
-    ///
-    /// Clients wishing to abort computation in response to an
-    /// reallocation error are encouraged to call the allocator's `oom`
-    /// method, rather than directly invoking `panic!` or similar.
-    unsafe fn realloc_excess(&mut self,
-                             ptr: *mut u8,
-                             layout: Layout,
-                             new_layout: Layout) -> Result<Excess, AllocErr> {
-        let usable_size = self.usable_size(&new_layout);
-        self.realloc(ptr, layout, new_layout)
-            .map(|p| Excess(p, usable_size.1))
-    }
-
-    /// Attempts to extend the allocation referenced by `ptr` to fit `new_layout`.
-    ///
-    /// If this returns `Ok`, then the allocator has asserted that the
-    /// memory block referenced by `ptr` now fits `new_layout`, and thus can
-    /// be used to carry data of that layout. (The allocator is allowed to
-    /// expend effort to accomplish this, such as extending the memory block to
-    /// include successor blocks, or virtual memory tricks.)
-    ///
-    /// Regardless of what this method returns, ownership of the
-    /// memory block referenced by `ptr` has not been transferred, and
-    /// the contents of the memory block are unaltered.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe because undefined behavior can result
-    /// if the caller does not ensure all of the following:
-    ///
-    /// * `ptr` must be currently allocated via this allocator,
-    ///
-    /// * `layout` must *fit* the `ptr` (see above); note the
-    ///   `new_layout` argument need not fit it,
-    ///
-    /// * `new_layout.size()` must not be less than `layout.size()`,
-    ///
-    /// * `new_layout.align()` must equal `layout.align()`.
-    ///
-    /// # Errors
-    ///
-    /// Returns `Err(CannotReallocInPlace)` when the allocator is
-    /// unable to assert that the memory block referenced by `ptr`
-    /// could fit `layout`.
-    ///
-    /// Note that one cannot pass `CannotReallocInPlace` to the `oom`
-    /// method; clients are expected either to be able to recover from
-    /// `grow_in_place` failures without aborting, or to fall back on
-    /// another reallocation method before resorting to an abort.
-    unsafe fn grow_in_place(&mut self,
-                            ptr: *mut u8,
-                            layout: Layout,
-                            new_layout: Layout) -> Result<(), CannotReallocInPlace> {
-        let _ = ptr; // this default implementation doesn't care about the actual address.
-        debug_assert!(new_layout.size >= layout.size);
-        debug_assert!(new_layout.align == layout.align);
-        let (_l, u) = self.usable_size(&layout);
-        // _l <= layout.size()                       [guaranteed by usable_size()]
-        //       layout.size() <= new_layout.size()  [required by this method]
-        if new_layout.size <= u {
-            return Ok(());
-        } else {
-            return Err(CannotReallocInPlace);
-        }
-    }
-
-    /// Attempts to shrink the allocation referenced by `ptr` to fit `new_layout`.
-    ///
-    /// If this returns `Ok`, then the allocator has asserted that the
-    /// memory block referenced by `ptr` now fits `new_layout`, and
-    /// thus can only be used to carry data of that smaller
-    /// layout. (The allocator is allowed to take advantage of this,
-    /// carving off portions of the block for reuse elsewhere.) The
-    /// truncated contents of the block within the smaller layout are
-    /// unaltered, and ownership of block has not been transferred.
-    ///
-    /// If this returns `Err`, then the memory block is considered to
-    /// still represent the original (larger) `layout`. None of the
-    /// block has been carved off for reuse elsewhere, ownership of
-    /// the memory block has not been transferred, and the contents of
-    /// the memory block are unaltered.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe because undefined behavior can result
-    /// if the caller does not ensure all of the following:
-    ///
-    /// * `ptr` must be currently allocated via this allocator,
-    ///
-    /// * `layout` must *fit* the `ptr` (see above); note the
-    ///   `new_layout` argument need not fit it,
-    ///
-    /// * `new_layout.size()` must not be greater than `layout.size()`
-    ///   (and must be greater than zero),
-    ///
-    /// * `new_layout.align()` must equal `layout.align()`.
-    ///
-    /// # Errors
-    ///
-    /// Returns `Err(CannotReallocInPlace)` when the allocator is
-    /// unable to assert that the memory block referenced by `ptr`
-    /// could fit `layout`.
-    ///
-    /// Note that one cannot pass `CannotReallocInPlace` to the `oom`
-    /// method; clients are expected either to be able to recover from
-    /// `shrink_in_place` failures without aborting, or to fall back
-    /// on another reallocation method before resorting to an abort.
-    unsafe fn shrink_in_place(&mut self,
-                              ptr: *mut u8,
-                              layout: Layout,
-                              new_layout: Layout) -> Result<(), CannotReallocInPlace> {
-        let _ = ptr; // this default implementation doesn't care about the actual address.
-        debug_assert!(new_layout.size <= layout.size);
-        debug_assert!(new_layout.align == layout.align);
-        let (l, _u) = self.usable_size(&layout);
-        //                      layout.size() <= _u  [guaranteed by usable_size()]
-        // new_layout.size() <= layout.size()        [required by this method]
-        if l <= new_layout.size {
-            return Ok(());
-        } else {
-            return Err(CannotReallocInPlace);
-        }
-    }
-
-
-    // == COMMON USAGE PATTERNS ==
-    // alloc_one, dealloc_one, alloc_array, realloc_array. dealloc_array
-
-    /// Allocates a block suitable for holding an instance of `T`.
-    ///
-    /// Captures a common usage pattern for allocators.
-    ///
-    /// The returned block is suitable for passing to the
-    /// `alloc`/`realloc` methods of this allocator.
-    ///
-    /// Note to implementors: If this returns `Ok(ptr)`, then `ptr`
-    /// must be considered "currently allocated" and must be
-    /// acceptable input to methods such as `realloc` or `dealloc`,
-    /// *even if* `T` is a zero-sized type. In other words, if your
-    /// `Alloc` implementation overrides this method in a manner
-    /// that can return a zero-sized `ptr`, then all reallocation and
-    /// deallocation methods need to be similarly overridden to accept
-    /// such values as input.
-    ///
-    /// # Errors
-    ///
-    /// Returning `Err` indicates that either memory is exhausted or
-    /// `T` does not meet allocator's size or alignment constraints.
-    ///
-    /// For zero-sized `T`, may return either of `Ok` or `Err`, but
-    /// will *not* yield undefined behavior.
-    ///
-    /// Clients wishing to abort computation in response to an
-    /// allocation error are encouraged to call the allocator's `oom`
-    /// method, rather than directly invoking `panic!` or similar.
-    fn alloc_one<T>(&mut self) -> Result<NonNull<T>, AllocErr>
-        where Self: Sized
-    {
-        let k = Layout::new::<T>();
-        if k.size() > 0 {
-            unsafe { self.alloc(k).map(|p| NonNull::new_unchecked(p as *mut T)) }
-        } else {
-            Err(AllocErr::invalid_input("zero-sized type invalid for alloc_one"))
-        }
-    }
-
-    /// Deallocates a block suitable for holding an instance of `T`.
-    ///
-    /// The given block must have been produced by this allocator,
-    /// and must be suitable for storing a `T` (in terms of alignment
-    /// as well as minimum and maximum size); otherwise yields
-    /// undefined behavior.
-    ///
-    /// Captures a common usage pattern for allocators.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe because undefined behavior can result
-    /// if the caller does not ensure both:
-    ///
-    /// * `ptr` must denote a block of memory currently allocated via this allocator
-    ///
-    /// * the layout of `T` must *fit* that block of memory.
-    unsafe fn dealloc_one<T>(&mut self, ptr: NonNull<T>)
-        where Self: Sized
-    {
-        let raw_ptr = ptr.as_ptr() as *mut u8;
-        let k = Layout::new::<T>();
-        if k.size() > 0 {
-            self.dealloc(raw_ptr, k);
-        }
-    }
-
-    /// Allocates a block suitable for holding `n` instances of `T`.
-    ///
-    /// Captures a common usage pattern for allocators.
-    ///
-    /// The returned block is suitable for passing to the
-    /// `alloc`/`realloc` methods of this allocator.
-    ///
-    /// Note to implementors: If this returns `Ok(ptr)`, then `ptr`
-    /// must be considered "currently allocated" and must be
-    /// acceptable input to methods such as `realloc` or `dealloc`,
-    /// *even if* `T` is a zero-sized type. In other words, if your
-    /// `Alloc` implementation overrides this method in a manner
-    /// that can return a zero-sized `ptr`, then all reallocation and
-    /// deallocation methods need to be similarly overridden to accept
-    /// such values as input.
-    ///
-    /// # Errors
-    ///
-    /// Returning `Err` indicates that either memory is exhausted or
-    /// `[T; n]` does not meet allocator's size or alignment
-    /// constraints.
-    ///
-    /// For zero-sized `T` or `n == 0`, may return either of `Ok` or
-    /// `Err`, but will *not* yield undefined behavior.
-    ///
-    /// Always returns `Err` on arithmetic overflow.
-    ///
-    /// Clients wishing to abort computation in response to an
-    /// allocation error are encouraged to call the allocator's `oom`
-    /// method, rather than directly invoking `panic!` or similar.
-    fn alloc_array<T>(&mut self, n: usize) -> Result<NonNull<T>, AllocErr>
-        where Self: Sized
-    {
-        match Layout::array::<T>(n) {
-            Some(ref layout) if layout.size() > 0 => {
-                unsafe {
-                    self.alloc(layout.clone())
-                        .map(|p| {
-                            NonNull::new_unchecked(p as *mut T)
-                        })
-                }
-            }
-            _ => Err(AllocErr::invalid_input("invalid layout for alloc_array")),
-        }
-    }
-
-    /// Reallocates a block previously suitable for holding `n_old`
-    /// instances of `T`, returning a block suitable for holding
-    /// `n_new` instances of `T`.
-    ///
-    /// Captures a common usage pattern for allocators.
-    ///
-    /// The returned block is suitable for passing to the
-    /// `alloc`/`realloc` methods of this allocator.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe because undefined behavior can result
-    /// if the caller does not ensure all of the following:
-    ///
-    /// * `ptr` must be currently allocated via this allocator,
-    ///
-    /// * the layout of `[T; n_old]` must *fit* that block of memory.
-    ///
-    /// # Errors
-    ///
-    /// Returning `Err` indicates that either memory is exhausted or
-    /// `[T; n_new]` does not meet allocator's size or alignment
-    /// constraints.
-    ///
-    /// For zero-sized `T` or `n_new == 0`, may return either of `Ok` or
-    /// `Err`, but will *not* yield undefined behavior.
-    ///
-    /// Always returns `Err` on arithmetic overflow.
-    ///
-    /// Clients wishing to abort computation in response to an
-    /// reallocation error are encouraged to call the allocator's `oom`
-    /// method, rather than directly invoking `panic!` or similar.
-    unsafe fn realloc_array<T>(&mut self,
-                               ptr: NonNull<T>,
-                               n_old: usize,
-                               n_new: usize) -> Result<NonNull<T>, AllocErr>
-        where Self: Sized
-    {
-        match (Layout::array::<T>(n_old), Layout::array::<T>(n_new), ptr.as_ptr()) {
-            (Some(ref k_old), Some(ref k_new), ptr) if k_old.size() > 0 && k_new.size() > 0 => {
-                self.realloc(ptr as *mut u8, k_old.clone(), k_new.clone())
-                    .map(|p| NonNull::new_unchecked(p as *mut T))
-            }
-            _ => {
-                Err(AllocErr::invalid_input("invalid layout for realloc_array"))
-            }
-        }
-    }
-
-    /// Deallocates a block suitable for holding `n` instances of `T`.
-    ///
-    /// Captures a common usage pattern for allocators.
-    ///
-    /// # Safety
-    ///
-    /// This function is unsafe because undefined behavior can result
-    /// if the caller does not ensure both:
-    ///
-    /// * `ptr` must denote a block of memory currently allocated via this allocator
-    ///
-    /// * the layout of `[T; n]` must *fit* that block of memory.
-    ///
-    /// # Errors
-    ///
-    /// Returning `Err` indicates that either `[T; n]` or the given
-    /// memory block does not meet allocator's size or alignment
-    /// constraints.
-    ///
-    /// Always returns `Err` on arithmetic overflow.
-    unsafe fn dealloc_array<T>(&mut self, ptr: NonNull<T>, n: usize) -> Result<(), AllocErr>
-        where Self: Sized
-    {
-        let raw_ptr = ptr.as_ptr() as *mut u8;
-        match Layout::array::<T>(n) {
-            Some(ref k) if k.size() > 0 => {
-                Ok(self.dealloc(raw_ptr, k.clone()))
-            }
-            _ => {
-                Err(AllocErr::invalid_input("invalid layout for dealloc_array"))
-            }
-        }
-    }
-}
diff --git a/src/liballoc/heap.rs b/src/liballoc/heap.rs
index c13ad39e5e1..9296a113071 100644
--- a/src/liballoc/heap.rs
+++ b/src/liballoc/heap.rs
@@ -19,7 +19,7 @@ use core::intrinsics::{min_align_of_val, size_of_val};
 use core::mem::{self, ManuallyDrop};
 use core::usize;
 
-pub use allocator::*;
+pub use core::heap::*;
 #[doc(hidden)]
 pub mod __core {
     pub use core::*;
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index 19d64d8fea9..5594caa65b9 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -81,6 +81,7 @@
 #![cfg_attr(not(test), feature(exact_size_is_empty))]
 #![cfg_attr(not(test), feature(generator_trait))]
 #![cfg_attr(test, feature(rand, test))]
+#![feature(allocator_api)]
 #![feature(allow_internal_unstable)]
 #![feature(ascii_ctype)]
 #![feature(box_into_raw_non_null)]
@@ -145,9 +146,9 @@ extern crate std_unicode;
 #[macro_use]
 mod macros;
 
-// Allocator trait and helper struct definitions
-
-pub mod allocator;
+#[rustc_deprecated(since = "1.27.0", reason = "use the heap module in core, alloc, or std instead")]
+#[unstable(feature = "allocator_api", issue = "32838")]
+pub use core::heap as allocator;
 
 // Heaps provided for low-level allocation strategies