Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1331 insertions, 0 deletions

diff --git a/third_party/rust/bumpalo/src/lib.rs b/third_party/rust/bumpalo/src/lib.rs
new file mode 100644
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+++ b/third_party/rust/bumpalo/src/lib.rs
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+/*!
+
+**A fast bump allocation arena for Rust.**
+
+[![](https://docs.rs/bumpalo/badge.svg)](https://docs.rs/bumpalo/)
+[![](https://img.shields.io/crates/v/bumpalo.svg)](https://crates.io/crates/bumpalo)
+[![](https://img.shields.io/crates/d/bumpalo.svg)](https://crates.io/crates/bumpalo)
+[![Build Status](https://dev.azure.com/fitzgen/bumpalo/_apis/build/status/fitzgen.bumpalo?branchName=master)](https://dev.azure.com/fitzgen/bumpalo/_build/latest?definitionId=2&branchName=master)
+
+![](https://github.com/fitzgen/bumpalo/raw/master/bumpalo.png)
+
+## Bump Allocation
+
+Bump allocation is a fast, but limited approach to allocation. We have a chunk
+of memory, and we maintain a pointer within that memory. Whenever we allocate an
+object, we do a quick test that we have enough capacity left in our chunk to
+allocate the object and then update the pointer by the object's size. *That's
+it!*
+
+The disadvantage of bump allocation is that there is no general way to
+deallocate individual objects or reclaim the memory region for a
+no-longer-in-use object.
+
+These trade offs make bump allocation well-suited for *phase-oriented*
+allocations. That is, a group of objects that will all be allocated during the
+same program phase, used, and then can all be deallocated together as a group.
+
+## Deallocation en Masse, but No `Drop`
+
+To deallocate all the objects in the arena at once, we can simply reset the bump
+pointer back to the start of the arena's memory chunk. This makes mass
+deallocation *extremely* fast, but allocated objects' `Drop` implementations are
+not invoked.
+
+> **However:** [`bumpalo::boxed::Box<T>`][crate::boxed::Box] can be used to wrap
+> `T` values allocated in the `Bump` arena, and calls `T`'s `Drop`
+> implementation when the `Box<T>` wrapper goes out of scope. This is similar to
+> how [`std::boxed::Box`] works, except without deallocating its backing memory.
+
+[`std::boxed::Box`]: https://doc.rust-lang.org/std/boxed/struct.Box.html
+
+## What happens when the memory chunk is full?
+
+This implementation will allocate a new memory chunk from the global allocator
+and then start bump allocating into this new memory chunk.
+
+## Example
+
+```
+use bumpalo::Bump;
+use std::u64;
+
+struct Doggo {
+    cuteness: u64,
+    age: u8,
+    scritches_required: bool,
+}
+
+// Create a new arena to bump allocate into.
+let bump = Bump::new();
+
+// Allocate values into the arena.
+let scooter = bump.alloc(Doggo {
+    cuteness: u64::max_value(),
+    age: 8,
+    scritches_required: true,
+});
+
+assert!(scooter.scritches_required);
+```
+
+## Collections
+
+When the `"collections"` cargo feature is enabled, a fork of some of the `std`
+library's collections are available in the `collections` module. These
+collection types are modified to allocate their space inside `bumpalo::Bump`
+arenas.
+
+```rust
+# #[cfg(feature = "collections")]
+# {
+use bumpalo::{Bump, collections::Vec};
+
+// Create a new bump arena.
+let bump = Bump::new();
+
+// Create a vector of integers whose storage is backed by the bump arena. The
+// vector cannot outlive its backing arena, and this property is enforced with
+// Rust's lifetime rules.
+let mut v = Vec::new_in(&bump);
+
+// Push a bunch of integers onto `v`!
+for i in 0..100 {
+    v.push(i);
+}
+# }
+```
+
+Eventually [all `std` collection types will be parameterized by an
+allocator](https://github.com/rust-lang/rust/issues/42774) and we can remove
+this `collections` module and use the `std` versions.
+
+## `bumpalo::boxed::Box`
+
+When the `"boxed"` cargo feature is enabled, a fork of `std::boxed::Box` library
+is available in the `boxed` module. This `Box` type is modified to allocate its
+space inside `bumpalo::Bump` arenas.
+
+**A `Box<T>` runs `T`'s drop implementation when the `Box<T>` is dropped.** You
+can use this to work around the fact that `Bump` does not drop values allocated
+in its space itself.
+
+```rust
+# #[cfg(feature = "boxed")]
+# {
+use bumpalo::{Bump, boxed::Box};
+use std::sync::atomic::{AtomicUsize, Ordering};
+
+static NUM_DROPPED: AtomicUsize = AtomicUsize::new(0);
+
+struct CountDrops;
+
+impl Drop for CountDrops {
+    fn drop(&mut self) {
+        NUM_DROPPED.fetch_add(1, Ordering::SeqCst);
+    }
+}
+
+// Create a new bump arena.
+let bump = Bump::new();
+
+// Create a `CountDrops` inside the bump arena.
+let mut c = Box::new_in(CountDrops, &bump);
+
+// No `CountDrops` have been dropped yet.
+assert_eq!(NUM_DROPPED.load(Ordering::SeqCst), 0);
+
+// Drop our `Box<CountDrops>`.
+drop(c);
+
+// Its `Drop` implementation was run, and so `NUM_DROPS` has been incremented.
+assert_eq!(NUM_DROPPED.load(Ordering::SeqCst), 1);
+# }
+```
+
+## `#![no_std]` Support
+
+Bumpalo is a `no_std` crate. It depends only on the `alloc` and `core` crates.
+
+ */
+
+#![deny(missing_debug_implementations)]
+#![deny(missing_docs)]
+#![no_std]
+
+#[doc(hidden)]
+pub extern crate alloc as core_alloc;
+
+#[cfg(feature = "boxed")]
+pub mod boxed;
+#[cfg(feature = "collections")]
+pub mod collections;
+
+mod alloc;
+
+use core::cell::Cell;
+use core::iter;
+use core::marker::PhantomData;
+use core::mem;
+use core::ptr::{self, NonNull};
+use core::slice;
+use core::str;
+use core_alloc::alloc::{alloc, dealloc, Layout};
+
+/// An arena to bump allocate into.
+///
+/// ## No `Drop`s
+///
+/// Objects that are bump-allocated will never have their `Drop` implementation
+/// called &mdash; unless you do it manually yourself. This makes it relatively
+/// easy to leak memory or other resources.
+///
+/// If you have a type which internally manages
+///
+/// * an allocation from the global heap (e.g. `Vec<T>`),
+/// * open file descriptors (e.g. `std::fs::File`), or
+/// * any other resource that must be cleaned up (e.g. an `mmap`)
+///
+/// and relies on its `Drop` implementation to clean up the internal resource,
+/// then if you allocate that type with a `Bump`, you need to find a new way to
+/// clean up after it yourself.
+///
+/// Potential solutions are
+///
+/// * calling [`drop_in_place`][drop_in_place] or using
+///   [`std::mem::ManuallyDrop`][manuallydrop] to manually drop these types,
+/// * using [`bumpalo::collections::Vec`] instead of [`std::vec::Vec`]
+/// * using [`bumpalo::boxed::Box::new_in`] instead of [`Bump::alloc`],
+///   that will drop wrapped values similarly to [`std::boxed::Box`].
+/// * simply avoiding allocating these problematic types within a `Bump`.
+///
+/// Note that not calling `Drop` is memory safe! Destructors are never
+/// guaranteed to run in Rust, you can't rely on them for enforcing memory
+/// safety.
+///
+/// [drop_in_place]: https://doc.rust-lang.org/std/ptr/fn.drop_in_place.html
+/// [manuallydrop]: https://doc.rust-lang.org/std/mem/struct.ManuallyDrop.html
+/// [`bumpalo::collections::Vec`]: ./collections/struct.Vec.html
+/// [`std::vec::Vec`]: https://doc.rust-lang.org/std/vec/struct.Vec.html
+/// [`bumpalo::boxed::Box::new_in`]: ./boxed/struct.Box.html#method.new_in
+/// [`Bump::alloc`]: ./struct.Bump.html#method.alloc
+/// [`std::boxed::Box`]: https://doc.rust-lang.org/std/boxed/struct.Box.html
+///
+/// ## Example
+///
+/// ```
+/// use bumpalo::Bump;
+///
+/// // Create a new bump arena.
+/// let bump = Bump::new();
+///
+/// // Allocate values into the arena.
+/// let forty_two = bump.alloc(42);
+/// assert_eq!(*forty_two, 42);
+///
+/// // Mutable references are returned from allocation.
+/// let mut s = bump.alloc("bumpalo");
+/// *s = "the bump allocator; and also is a buffalo";
+/// ```
+#[derive(Debug)]
+pub struct Bump {
+    // The current chunk we are bump allocating within.
+    current_chunk_footer: Cell<NonNull<ChunkFooter>>,
+}
+
+#[repr(C)]
+#[derive(Debug)]
+struct ChunkFooter {
+    // Pointer to the start of this chunk allocation. This footer is always at
+    // the end of the chunk.
+    data: NonNull<u8>,
+
+    // The layout of this chunk's allocation.
+    layout: Layout,
+
+    // Link to the previous chunk, if any.
+    prev: Cell<Option<NonNull<ChunkFooter>>>,
+
+    // Bump allocation finger that is always in the range `self.data..=self`.
+    ptr: Cell<NonNull<u8>>,
+}
+
+impl Default for Bump {
+    fn default() -> Bump {
+        Bump::new()
+    }
+}
+
+impl Drop for Bump {
+    fn drop(&mut self) {
+        unsafe {
+            dealloc_chunk_list(Some(self.current_chunk_footer.get()));
+        }
+    }
+}
+
+#[inline]
+unsafe fn dealloc_chunk_list(mut footer: Option<NonNull<ChunkFooter>>) {
+    while let Some(f) = footer {
+        footer = f.as_ref().prev.get();
+        dealloc(f.as_ref().data.as_ptr(), f.as_ref().layout);
+    }
+}
+
+// `Bump`s are safe to send between threads because nothing aliases its owned
+// chunks until you start allocating from it. But by the time you allocate from
+// it, the returned references to allocations borrow the `Bump` and therefore
+// prevent sending the `Bump` across threads until the borrows end.
+unsafe impl Send for Bump {}
+
+#[inline]
+pub(crate) fn round_up_to(n: usize, divisor: usize) -> Option<usize> {
+    debug_assert!(divisor > 0);
+    debug_assert!(divisor.is_power_of_two());
+    Some(n.checked_add(divisor - 1)? & !(divisor - 1))
+}
+
+// After this point, we try to hit page boundaries instead of powers of 2
+const PAGE_STRATEGY_CUTOFF: usize = 0x1000;
+
+// We only support alignments of up to 16 bytes for iter_allocated_chunks.
+const SUPPORTED_ITER_ALIGNMENT: usize = 16;
+const CHUNK_ALIGN: usize = SUPPORTED_ITER_ALIGNMENT;
+const FOOTER_SIZE: usize = mem::size_of::<ChunkFooter>();
+
+// Assert that ChunkFooter is at most the supported alignment. This will give a compile time error if it is not the case
+const _FOOTER_ALIGN_ASSERTION: bool = mem::align_of::<ChunkFooter>() <= CHUNK_ALIGN;
+const _: [(); _FOOTER_ALIGN_ASSERTION as usize] = [()];
+
+// Maximum typical overhead per allocation imposed by allocators.
+const MALLOC_OVERHEAD: usize = 16;
+
+// This is the overhead from malloc, footer and alignment. For instance, if
+// we want to request a chunk of memory that has at least X bytes usable for
+// allocations (where X is aligned to CHUNK_ALIGN), then we expect that the
+// after adding a footer, malloc overhead and alignment, the chunk of memory
+// the allocator actually sets asside for us is X+OVERHEAD rounded up to the
+// nearest suitable size boundary.
+const OVERHEAD: usize = (MALLOC_OVERHEAD + FOOTER_SIZE + (CHUNK_ALIGN - 1)) & !(CHUNK_ALIGN - 1);
+
+// Choose a relatively small default initial chunk size, since we double chunk
+// sizes as we grow bump arenas to amortize costs of hitting the global
+// allocator.
+const FIRST_ALLOCATION_GOAL: usize = 1 << 9;
+
+// The actual size of the first allocation is going to be a bit smaller
+// than the goal. We need to make room for the footer, and we also need
+// take the alignment into account.
+const DEFAULT_CHUNK_SIZE_WITHOUT_FOOTER: usize = FIRST_ALLOCATION_GOAL - OVERHEAD;
+
+#[inline]
+fn layout_for_array<T>(len: usize) -> Option<Layout> {
+    // TODO: use Layout::array once the rust feature `alloc_layout_extra`
+    // gets stabilized
+    //
+    // According to https://doc.rust-lang.org/reference/type-layout.html#size-and-alignment
+    // the size of a value is always a multiple of it's alignment. But that does not seem to match
+    // with https://doc.rust-lang.org/std/alloc/struct.Layout.html#method.from_size_align
+    //
+    // Let's be on the safe size and round up to the padding in any case.
+    //
+    // An interesting question is whether there needs to be padding at the end of
+    // the last object in the array. Again, we take the safe approach and include it.
+
+    let layout = Layout::new::<T>();
+    let size_rounded_up = round_up_to(layout.size(), layout.align())?;
+    let total_size = len.checked_mul(size_rounded_up)?;
+
+    Layout::from_size_align(total_size, layout.align()).ok()
+}
+
+/// Wrapper around `Layout::from_size_align` that adds debug assertions.
+#[inline]
+unsafe fn layout_from_size_align(size: usize, align: usize) -> Layout {
+    if cfg!(debug_assertions) {
+        Layout::from_size_align(size, align).unwrap()
+    } else {
+        Layout::from_size_align_unchecked(size, align)
+    }
+}
+
+#[inline(never)]
+fn allocation_size_overflow<T>() -> T {
+    panic!("requested allocation size overflowed")
+}
+
+impl Bump {
+    /// Construct a new arena to bump allocate into.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::new();
+    /// # let _ = bump;
+    /// ```
+    pub fn new() -> Bump {
+        Self::with_capacity(0)
+    }
+
+    /// Attempt to construct a new arena to bump allocate into.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::try_new();
+    /// # let _ = bump.unwrap();
+    /// ```
+    pub fn try_new() -> Result<Bump, alloc::AllocErr> {
+        Bump::try_with_capacity(0)
+    }
+
+    /// Construct a new arena with the specified byte capacity to bump allocate into.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::with_capacity(100);
+    /// # let _ = bump;
+    /// ```
+    pub fn with_capacity(capacity: usize) -> Bump {
+        Bump::try_with_capacity(capacity).unwrap_or_else(|_| oom())
+    }
+
+    /// Attempt to construct a new arena with the specified byte capacity to bump allocate into.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::try_with_capacity(100);
+    /// # let _ = bump.unwrap();
+    /// ```
+    pub fn try_with_capacity(capacity: usize) -> Result<Self, alloc::AllocErr> {
+        let chunk_footer = Self::new_chunk(
+            None,
+            Some(unsafe { layout_from_size_align(capacity, 1) }),
+            None,
+        )
+        .ok_or(alloc::AllocErr {})?;
+
+        Ok(Bump {
+            current_chunk_footer: Cell::new(chunk_footer),
+        })
+    }
+
+    /// Allocate a new chunk and return its initialized footer.
+    ///
+    /// If given, `layouts` is a tuple of the current chunk size and the
+    /// layout of the allocation request that triggered us to fall back to
+    /// allocating a new chunk of memory.
+    fn new_chunk(
+        old_size_with_footer: Option<usize>,
+        requested_layout: Option<Layout>,
+        prev: Option<NonNull<ChunkFooter>>,
+    ) -> Option<NonNull<ChunkFooter>> {
+        unsafe {
+            // As a sane default, we want our new allocation to be about twice as
+            // big as the previous allocation
+            let mut new_size_without_footer =
+                if let Some(old_size_with_footer) = old_size_with_footer {
+                    let old_size_without_footer = old_size_with_footer - FOOTER_SIZE;
+                    old_size_without_footer.checked_mul(2)?
+                } else {
+                    DEFAULT_CHUNK_SIZE_WITHOUT_FOOTER
+                };
+
+            // We want to have CHUNK_ALIGN or better alignment
+            let mut align = CHUNK_ALIGN;
+
+            // If we already know we need to fulfill some request,
+            // make sure we allocate at least enough to satisfy it
+            if let Some(requested_layout) = requested_layout {
+                align = align.max(requested_layout.align());
+                let requested_size = round_up_to(requested_layout.size(), align)
+                    .unwrap_or_else(allocation_size_overflow);
+                new_size_without_footer = new_size_without_footer.max(requested_size);
+            }
+
+            // We want our allocations to play nice with the memory allocator,
+            // and waste as little memory as possible.
+            // For small allocations, this means that the entire allocation
+            // including the chunk footer and mallocs internal overhead is
+            // as close to a power of two as we can go without going over.
+            // For larger allocations, we only need to get close to a page
+            // boundary without going over.
+            if new_size_without_footer < PAGE_STRATEGY_CUTOFF {
+                new_size_without_footer =
+                    (new_size_without_footer + OVERHEAD).next_power_of_two() - OVERHEAD;
+            } else {
+                new_size_without_footer =
+                    round_up_to(new_size_without_footer + OVERHEAD, 0x1000)? - OVERHEAD;
+            }
+
+            debug_assert_eq!(align % CHUNK_ALIGN, 0);
+            debug_assert_eq!(new_size_without_footer % CHUNK_ALIGN, 0);
+            let size = new_size_without_footer
+                .checked_add(FOOTER_SIZE)
+                .unwrap_or_else(allocation_size_overflow);
+            let layout = layout_from_size_align(size, align);
+
+            debug_assert!(size >= old_size_with_footer.unwrap_or(0) * 2);
+
+            let data = alloc(layout);
+            let data = NonNull::new(data)?;
+
+            // The `ChunkFooter` is at the end of the chunk.
+            let footer_ptr = data.as_ptr() as usize + new_size_without_footer;
+            debug_assert_eq!((data.as_ptr() as usize) % align, 0);
+            debug_assert_eq!(footer_ptr % CHUNK_ALIGN, 0);
+            let footer_ptr = footer_ptr as *mut ChunkFooter;
+
+            // The bump pointer is initialized to the end of the range we will
+            // bump out of.
+            let ptr = Cell::new(NonNull::new_unchecked(footer_ptr as *mut u8));
+
+            ptr::write(
+                footer_ptr,
+                ChunkFooter {
+                    data,
+                    layout,
+                    prev: Cell::new(prev),
+                    ptr,
+                },
+            );
+
+            Some(NonNull::new_unchecked(footer_ptr))
+        }
+    }
+
+    /// Reset this bump allocator.
+    ///
+    /// Performs mass deallocation on everything allocated in this arena by
+    /// resetting the pointer into the underlying chunk of memory to the start
+    /// of the chunk. Does not run any `Drop` implementations on deallocated
+    /// objects; see [the `Bump` type's top-level
+    /// documentation](./struct.Bump.html) for details.
+    ///
+    /// If this arena has allocated multiple chunks to bump allocate into, then
+    /// the excess chunks are returned to the global allocator.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let mut bump = bumpalo::Bump::new();
+    ///
+    /// // Allocate a bunch of things.
+    /// {
+    ///     for i in 0..100 {
+    ///         bump.alloc(i);
+    ///     }
+    /// }
+    ///
+    /// // Reset the arena.
+    /// bump.reset();
+    ///
+    /// // Allocate some new things in the space previously occupied by the
+    /// // original things.
+    /// for j in 200..400 {
+    ///     bump.alloc(j);
+    /// }
+    ///```
+    pub fn reset(&mut self) {
+        // Takes `&mut self` so `self` must be unique and there can't be any
+        // borrows active that would get invalidated by resetting.
+        unsafe {
+            let cur_chunk = self.current_chunk_footer.get();
+
+            // Deallocate all chunks except the current one
+            let prev_chunk = cur_chunk.as_ref().prev.replace(None);
+            dealloc_chunk_list(prev_chunk);
+
+            // Reset the bump finger to the end of the chunk.
+            cur_chunk.as_ref().ptr.set(cur_chunk.cast());
+
+            debug_assert!(
+                self.current_chunk_footer
+                    .get()
+                    .as_ref()
+                    .prev
+                    .get()
+                    .is_none(),
+                "We should only have a single chunk"
+            );
+            debug_assert_eq!(
+                self.current_chunk_footer.get().as_ref().ptr.get(),
+                self.current_chunk_footer.get().cast(),
+                "Our chunk's bump finger should be reset to the start of its allocation"
+            );
+        }
+    }
+
+    /// Allocate an object in this `Bump` and return an exclusive reference to
+    /// it.
+    ///
+    /// ## Panics
+    ///
+    /// Panics if reserving space for `T` would cause an overflow.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::new();
+    /// let x = bump.alloc("hello");
+    /// assert_eq!(*x, "hello");
+    /// ```
+    #[inline(always)]
+    #[allow(clippy::mut_from_ref)]
+    pub fn alloc<T>(&self, val: T) -> &mut T {
+        self.alloc_with(|| val)
+    }
+
+    /// Pre-allocate space for an object in this `Bump`, initializes it using
+    /// the closure, then returns an exclusive reference to it.
+    ///
+    /// Calling `bump.alloc(x)` is essentially equivalent to calling
+    /// `bump.alloc_with(|| x)`. However if you use `alloc_with`, then the
+    /// closure will not be invoked until after allocating space for storing
+    /// `x` on the heap.
+    ///
+    /// This can be useful in certain edge-cases related to compiler
+    /// optimizations. When evaluating `bump.alloc(x)`, semantically `x` is
+    /// first put on the stack and then moved onto the heap. In some cases,
+    /// the compiler is able to optimize this into constructing `x` directly
+    /// on the heap, however in many cases it does not.
+    ///
+    /// The function `alloc_with` tries to help the compiler be smarter. In
+    /// most cases doing `bump.alloc_with(|| x)` on release mode will be
+    /// enough to help the compiler to realize this optimization is valid
+    /// and construct `x` directly onto the heap.
+    ///
+    /// ## Warning
+    ///
+    /// This function critically depends on compiler optimizations to achieve
+    /// its desired effect. This means that it is not an effective tool when
+    /// compiling without optimizations on.
+    ///
+    /// Even when optimizations are on, this function does not **guarantee**
+    /// that the value is constructed on the heap. To the best of our
+    /// knowledge no such guarantee can be made in stable Rust as of 1.33.
+    ///
+    /// ## Panics
+    ///
+    /// Panics if reserving space for `T` would cause an overflow.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::new();
+    /// let x = bump.alloc_with(|| "hello");
+    /// assert_eq!(*x, "hello");
+    /// ```
+    #[inline(always)]
+    #[allow(clippy::mut_from_ref)]
+    pub fn alloc_with<F, T>(&self, f: F) -> &mut T
+    where
+        F: FnOnce() -> T,
+    {
+        #[inline(always)]
+        unsafe fn inner_writer<T, F>(ptr: *mut T, f: F)
+        where
+            F: FnOnce() -> T,
+        {
+            // This function is translated as:
+            // - allocate space for a T on the stack
+            // - call f() with the return value being put onto this stack space
+            // - memcpy from the stack to the heap
+            //
+            // Ideally we want LLVM to always realize that doing a stack
+            // allocation is unnecessary and optimize the code so it writes
+            // directly into the heap instead. It seems we get it to realize
+            // this most consistently if we put this critical line into it's
+            // own function instead of inlining it into the surrounding code.
+            ptr::write(ptr, f())
+        }
+
+        let layout = Layout::new::<T>();
+
+        unsafe {
+            let p = self.alloc_layout(layout);
+            let p = p.as_ptr() as *mut T;
+            inner_writer(p, f);
+            &mut *p
+        }
+    }
+
+    /// `Copy` a slice into this `Bump` and return an exclusive reference to
+    /// the copy.
+    ///
+    /// ## Panics
+    ///
+    /// Panics if reserving space for the slice would cause an overflow.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::new();
+    /// let x = bump.alloc_slice_copy(&[1, 2, 3]);
+    /// assert_eq!(x, &[1, 2, 3]);
+    /// ```
+    #[inline(always)]
+    #[allow(clippy::mut_from_ref)]
+    pub fn alloc_slice_copy<T>(&self, src: &[T]) -> &mut [T]
+    where
+        T: Copy,
+    {
+        let layout = Layout::for_value(src);
+        let dst = self.alloc_layout(layout).cast::<T>();
+
+        unsafe {
+            ptr::copy_nonoverlapping(src.as_ptr(), dst.as_ptr(), src.len());
+            slice::from_raw_parts_mut(dst.as_ptr(), src.len())
+        }
+    }
+
+    /// `Clone` a slice into this `Bump` and return an exclusive reference to
+    /// the clone. Prefer `alloc_slice_copy` if `T` is `Copy`.
+    ///
+    /// ## Panics
+    ///
+    /// Panics if reserving space for the slice would cause an overflow.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// #[derive(Clone, Debug, Eq, PartialEq)]
+    /// struct Sheep {
+    ///     name: String,
+    /// }
+    ///
+    /// let originals = vec![
+    ///     Sheep { name: "Alice".into() },
+    ///     Sheep { name: "Bob".into() },
+    ///     Sheep { name: "Cathy".into() },
+    /// ];
+    ///
+    /// let bump = bumpalo::Bump::new();
+    /// let clones = bump.alloc_slice_clone(&originals);
+    /// assert_eq!(originals, clones);
+    /// ```
+    #[inline(always)]
+    #[allow(clippy::mut_from_ref)]
+    pub fn alloc_slice_clone<T>(&self, src: &[T]) -> &mut [T]
+    where
+        T: Clone,
+    {
+        let layout = Layout::for_value(src);
+        let dst = self.alloc_layout(layout).cast::<T>();
+
+        unsafe {
+            for (i, val) in src.iter().cloned().enumerate() {
+                ptr::write(dst.as_ptr().add(i), val);
+            }
+
+            slice::from_raw_parts_mut(dst.as_ptr(), src.len())
+        }
+    }
+
+    /// `Copy` a string slice into this `Bump` and return an exclusive reference to it.
+    ///
+    /// ## Panics
+    ///
+    /// Panics if reserving space for the string would cause an overflow.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::new();
+    /// let hello = bump.alloc_str("hello world");
+    /// assert_eq!("hello world", hello);
+    /// ```
+    #[inline(always)]
+    #[allow(clippy::mut_from_ref)]
+    pub fn alloc_str(&self, src: &str) -> &mut str {
+        let buffer = self.alloc_slice_copy(src.as_bytes());
+        unsafe {
+            // This is OK, because it already came in as str, so it is guaranteed to be utf8
+            str::from_utf8_unchecked_mut(buffer)
+        }
+    }
+
+    /// Allocates a new slice of size `len` into this `Bump` and returns an
+    /// exclusive reference to the copy.
+    ///
+    /// The elements of the slice are initialized using the supplied closure.
+    /// The closure argument is the position in the slice.
+    ///
+    /// ## Panics
+    ///
+    /// Panics if reserving space for the slice would cause an overflow.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::new();
+    /// let x = bump.alloc_slice_fill_with(5, |i| 5*(i+1));
+    /// assert_eq!(x, &[5, 10, 15, 20, 25]);
+    /// ```
+    #[inline(always)]
+    #[allow(clippy::mut_from_ref)]
+    pub fn alloc_slice_fill_with<T, F>(&self, len: usize, mut f: F) -> &mut [T]
+    where
+        F: FnMut(usize) -> T,
+    {
+        let layout = layout_for_array::<T>(len).unwrap_or_else(|| oom());
+        let dst = self.alloc_layout(layout).cast::<T>();
+
+        unsafe {
+            for i in 0..len {
+                ptr::write(dst.as_ptr().add(i), f(i));
+            }
+
+            let result = slice::from_raw_parts_mut(dst.as_ptr(), len);
+            debug_assert_eq!(Layout::for_value(result), layout);
+            result
+        }
+    }
+
+    /// Allocates a new slice of size `len` into this `Bump` and returns an
+    /// exclusive reference to the copy.
+    ///
+    /// All elements of the slice are initialized to `value`.
+    ///
+    /// ## Panics
+    ///
+    /// Panics if reserving space for the slice would cause an overflow.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::new();
+    /// let x = bump.alloc_slice_fill_copy(5, 42);
+    /// assert_eq!(x, &[42, 42, 42, 42, 42]);
+    /// ```
+    #[inline(always)]
+    #[allow(clippy::mut_from_ref)]
+    pub fn alloc_slice_fill_copy<T: Copy>(&self, len: usize, value: T) -> &mut [T] {
+        self.alloc_slice_fill_with(len, |_| value)
+    }
+
+    /// Allocates a new slice of size `len` slice into this `Bump` and return an
+    /// exclusive reference to the copy.
+    ///
+    /// All elements of the slice are initialized to `value.clone()`.
+    ///
+    /// ## Panics
+    ///
+    /// Panics if reserving space for the slice would cause an overflow.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::new();
+    /// let s: String = "Hello Bump!".to_string();
+    /// let x: &[String] = bump.alloc_slice_fill_clone(2, &s);
+    /// assert_eq!(x.len(), 2);
+    /// assert_eq!(&x[0], &s);
+    /// assert_eq!(&x[1], &s);
+    /// ```
+    #[inline(always)]
+    #[allow(clippy::mut_from_ref)]
+    pub fn alloc_slice_fill_clone<T: Clone>(&self, len: usize, value: &T) -> &mut [T] {
+        self.alloc_slice_fill_with(len, |_| value.clone())
+    }
+
+    /// Allocates a new slice of size `len` slice into this `Bump` and return an
+    /// exclusive reference to the copy.
+    ///
+    /// The elements are initialized using the supplied iterator.
+    ///
+    /// ## Panics
+    ///
+    /// Panics if reserving space for the slice would cause an overflow, or if the supplied
+    /// iterator returns fewer elements than it promised.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::new();
+    /// let x: &[i32] = bump.alloc_slice_fill_iter([2, 3, 5].iter().cloned().map(|i| i * i));
+    /// assert_eq!(x, [4, 9, 25]);
+    /// ```
+    #[inline(always)]
+    #[allow(clippy::mut_from_ref)]
+    pub fn alloc_slice_fill_iter<T, I>(&self, iter: I) -> &mut [T]
+    where
+        I: IntoIterator<Item = T>,
+        I::IntoIter: ExactSizeIterator,
+    {
+        let mut iter = iter.into_iter();
+        self.alloc_slice_fill_with(iter.len(), |_| {
+            iter.next().expect("Iterator supplied too few elements")
+        })
+    }
+
+    /// Allocates a new slice of size `len` slice into this `Bump` and return an
+    /// exclusive reference to the copy.
+    ///
+    /// All elements of the slice are initialized to `T::default()`.
+    ///
+    /// ## Panics
+    ///
+    /// Panics if reserving space for the slice would cause an overflow.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::new();
+    /// let x = bump.alloc_slice_fill_default::<u32>(5);
+    /// assert_eq!(x, &[0, 0, 0, 0, 0]);
+    /// ```
+    #[inline(always)]
+    #[allow(clippy::mut_from_ref)]
+    pub fn alloc_slice_fill_default<T: Default>(&self, len: usize) -> &mut [T] {
+        self.alloc_slice_fill_with(len, |_| T::default())
+    }
+
+    /// Allocate space for an object with the given `Layout`.
+    ///
+    /// The returned pointer points at uninitialized memory, and should be
+    /// initialized with
+    /// [`std::ptr::write`](https://doc.rust-lang.org/std/ptr/fn.write.html).
+    #[inline(always)]
+    pub fn alloc_layout(&self, layout: Layout) -> NonNull<u8> {
+        self.try_alloc_layout(layout).unwrap_or_else(|_| oom())
+    }
+
+    /// Attempts to allocate space for an object with the given `Layout` or else returns
+    /// an `Err`.
+    ///
+    /// The returned pointer points at uninitialized memory, and should be
+    /// initialized with
+    /// [`std::ptr::write`](https://doc.rust-lang.org/std/ptr/fn.write.html).
+    #[inline(always)]
+    pub fn try_alloc_layout(&self, layout: Layout) -> Result<NonNull<u8>, alloc::AllocErr> {
+        if let Some(p) = self.try_alloc_layout_fast(layout) {
+            Ok(p)
+        } else {
+            self.alloc_layout_slow(layout).ok_or(alloc::AllocErr {})
+        }
+    }
+
+    #[inline(always)]
+    fn try_alloc_layout_fast(&self, layout: Layout) -> Option<NonNull<u8>> {
+        // We don't need to check for ZSTs here since they will automatically
+        // be handled properly: the pointer will be bumped by zero bytes,
+        // modulo alignment. This keeps the fast path optimized for non-ZSTs,
+        // which are much more common.
+        unsafe {
+            let footer = self.current_chunk_footer.get();
+            let footer = footer.as_ref();
+            let ptr = footer.ptr.get().as_ptr() as usize;
+            let start = footer.data.as_ptr() as usize;
+            debug_assert!(start <= ptr);
+            debug_assert!(ptr <= footer as *const _ as usize);
+
+            let ptr = ptr.checked_sub(layout.size())?;
+            let aligned_ptr = ptr & !(layout.align() - 1);
+
+            if aligned_ptr >= start {
+                let aligned_ptr = NonNull::new_unchecked(aligned_ptr as *mut u8);
+                footer.ptr.set(aligned_ptr);
+                Some(aligned_ptr)
+            } else {
+                None
+            }
+        }
+    }
+
+    /// Gets the remaining capacity in the current chunk (in bytes).
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// use bumpalo::Bump;
+    ///
+    /// let bump = Bump::with_capacity(100);
+    ///
+    /// let capacity = bump.chunk_capacity();
+    /// assert!(capacity >= 100);
+    /// ```
+    pub fn chunk_capacity(&self) -> usize {
+        let current_footer = self.current_chunk_footer.get();
+        let current_footer = unsafe { current_footer.as_ref() };
+
+        current_footer as *const _ as usize - current_footer.data.as_ptr() as usize
+    }
+
+    /// Slow path allocation for when we need to allocate a new chunk from the
+    /// parent bump set because there isn't enough room in our current chunk.
+    #[inline(never)]
+    fn alloc_layout_slow(&self, layout: Layout) -> Option<NonNull<u8>> {
+        unsafe {
+            let size = layout.size();
+
+            // Get a new chunk from the global allocator.
+            let current_footer = self.current_chunk_footer.get();
+            let current_layout = current_footer.as_ref().layout;
+            let new_footer = Bump::new_chunk(
+                Some(current_layout.size()),
+                Some(layout),
+                Some(current_footer),
+            )?;
+            debug_assert_eq!(
+                new_footer.as_ref().data.as_ptr() as usize % layout.align(),
+                0
+            );
+
+            // Set the new chunk as our new current chunk.
+            self.current_chunk_footer.set(new_footer);
+
+            let new_footer = new_footer.as_ref();
+
+            // Move the bump ptr finger down to allocate room for `val`. We know
+            // this can't overflow because we successfully allocated a chunk of
+            // at least the requested size.
+            let ptr = new_footer.ptr.get().as_ptr() as usize - size;
+            // Round the pointer down to the requested alignment.
+            let ptr = ptr & !(layout.align() - 1);
+            debug_assert!(
+                ptr <= new_footer as *const _ as usize,
+                "{:#x} <= {:#x}",
+                ptr,
+                new_footer as *const _ as usize
+            );
+            let ptr = NonNull::new_unchecked(ptr as *mut u8);
+            new_footer.ptr.set(ptr);
+
+            // Return a pointer to the freshly allocated region in this chunk.
+            Some(ptr)
+        }
+    }
+
+    /// Returns an iterator over each chunk of allocated memory that
+    /// this arena has bump allocated into.
+    ///
+    /// The chunks are returned ordered by allocation time, with the most
+    /// recently allocated chunk being returned first, and the least recently
+    /// allocated chunk being returned last.
+    ///
+    /// The values inside each chunk are also ordered by allocation time, with
+    /// the most recent allocation being earlier in the slice, and the least
+    /// recent allocation being towards the end of the slice.
+    ///
+    /// ## Safety
+    ///
+    /// Because this method takes `&mut self`, we know that the bump arena
+    /// reference is unique and therefore there aren't any active references to
+    /// any of the objects we've allocated in it either. This potential aliasing
+    /// of exclusive references is one common footgun for unsafe code that we
+    /// don't need to worry about here.
+    ///
+    /// However, there could be regions of uninitialized memory used as padding
+    /// between allocations, which is why this iterator has items of type
+    /// `[MaybeUninit<u8>]`, instead of simply `[u8]`.
+    ///
+    /// The only way to guarantee that there is no padding between allocations
+    /// or within allocated objects is if all of these properties hold:
+    ///
+    /// 1. Every object allocated in this arena has the same alignment,
+    ///    and that alignment is at most 16.
+    /// 2. Every object's size is a multiple of its alignment.
+    /// 3. None of the objects allocated in this arena contain any internal
+    ///    padding.
+    ///
+    /// If you want to use this `iter_allocated_chunks` method, it is *your*
+    /// responsibility to ensure that these properties hold before calling
+    /// `MaybeUninit::assume_init` or otherwise reading the returned values.
+    ///
+    /// Finally, you must also ensure that any values allocated into the bump
+    /// arena have not had their `Drop` implementations called on them,
+    /// e.g. after dropping a [`bumpalo::boxed::Box<T>`][crate::boxed::Box].
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let mut bump = bumpalo::Bump::new();
+    ///
+    /// // Allocate a bunch of `i32`s in this bump arena, potentially causing
+    /// // additional memory chunks to be reserved.
+    /// for i in 0..10000 {
+    ///     bump.alloc(i);
+    /// }
+    ///
+    /// // Iterate over each chunk we've bump allocated into. This is safe
+    /// // because we have only allocated `i32`s in this arena, which fulfills
+    /// // the above requirements.
+    /// for ch in bump.iter_allocated_chunks() {
+    ///     println!("Used a chunk that is {} bytes long", ch.len());
+    ///     println!("The first byte is {:?}", unsafe {
+    ///         ch.get(0).unwrap().assume_init()
+    ///     });
+    /// }
+    ///
+    /// // Within a chunk, allocations are ordered from most recent to least
+    /// // recent. If we allocated 'a', then 'b', then 'c', when we iterate
+    /// // through the chunk's data, we get them in the order 'c', then 'b',
+    /// // then 'a'.
+    ///
+    /// bump.reset();
+    /// bump.alloc(b'a');
+    /// bump.alloc(b'b');
+    /// bump.alloc(b'c');
+    ///
+    /// assert_eq!(bump.iter_allocated_chunks().count(), 1);
+    /// let chunk = bump.iter_allocated_chunks().nth(0).unwrap();
+    /// assert_eq!(chunk.len(), 3);
+    ///
+    /// // Safe because we've only allocated `u8`s in this arena, which
+    /// // fulfills the above requirements.
+    /// unsafe {
+    ///     assert_eq!(chunk[0].assume_init(), b'c');
+    ///     assert_eq!(chunk[1].assume_init(), b'b');
+    ///     assert_eq!(chunk[2].assume_init(), b'a');
+    /// }
+    /// ```
+    pub fn iter_allocated_chunks(&mut self) -> ChunkIter<'_> {
+        ChunkIter {
+            footer: Some(self.current_chunk_footer.get()),
+            bump: PhantomData,
+        }
+    }
+
+    /// Calculates the number of bytes currently allocated across all chunks.
+    ///
+    /// If you allocate types of different alignments or types with
+    /// larger-than-typical alignment in the same arena, some padding
+    /// bytes might get allocated in the bump arena. Note that those padding
+    /// bytes will add to this method's resulting sum, so you cannot rely
+    /// on it only counting the sum of the sizes of the things
+    /// you've allocated in the arena.
+    ///
+    /// ## Example
+    ///
+    /// ```
+    /// let bump = bumpalo::Bump::new();
+    /// let _x = bump.alloc_slice_fill_default::<u32>(5);
+    /// let bytes = bump.allocated_bytes();
+    /// assert!(bytes >= core::mem::size_of::<u32>() * 5);
+    /// ```
+    pub fn allocated_bytes(&self) -> usize {
+        let mut footer = Some(self.current_chunk_footer.get());
+
+        let mut bytes = 0;
+
+        while let Some(f) = footer {
+            let foot = unsafe { f.as_ref() };
+
+            let ptr = foot.ptr.get().as_ptr() as usize;
+            debug_assert!(ptr <= foot as *const _ as usize);
+
+            bytes += foot as *const _ as usize - ptr;
+
+            footer = foot.prev.get();
+        }
+
+        bytes
+    }
+
+    #[inline]
+    unsafe fn is_last_allocation(&self, ptr: NonNull<u8>) -> bool {
+        let footer = self.current_chunk_footer.get();
+        let footer = footer.as_ref();
+        footer.ptr.get() == ptr
+    }
+}
+
+/// An iterator over each chunk of allocated memory that
+/// an arena has bump allocated into.
+///
+/// The chunks are returned ordered by allocation time, with the most recently
+/// allocated chunk being returned first.
+///
+/// The values inside each chunk is also ordered by allocation time, with the most
+/// recent allocation being earlier in the slice.
+///
+/// This struct is created by the [`iter_allocated_chunks`] method on
+/// [`Bump`]. See that function for a safety description regarding reading from the returned items.
+///
+/// [`Bump`]: ./struct.Bump.html
+/// [`iter_allocated_chunks`]: ./struct.Bump.html#method.iter_allocated_chunks
+#[derive(Debug)]
+pub struct ChunkIter<'a> {
+    footer: Option<NonNull<ChunkFooter>>,
+    bump: PhantomData<&'a mut Bump>,
+}
+
+impl<'a> Iterator for ChunkIter<'a> {
+    type Item = &'a [mem::MaybeUninit<u8>];
+    fn next(&mut self) -> Option<&'a [mem::MaybeUninit<u8>]> {
+        unsafe {
+            let foot = self.footer?;
+            let foot = foot.as_ref();
+            let data = foot.data.as_ptr() as usize;
+            let ptr = foot.ptr.get().as_ptr() as usize;
+            debug_assert!(data <= ptr);
+            debug_assert!(ptr <= foot as *const _ as usize);
+
+            let len = foot as *const _ as usize - ptr;
+            let slice = slice::from_raw_parts(ptr as *const mem::MaybeUninit<u8>, len);
+            self.footer = foot.prev.get();
+            Some(slice)
+        }
+    }
+}
+
+impl<'a> iter::FusedIterator for ChunkIter<'a> {}
+
+#[inline(never)]
+#[cold]
+fn oom() -> ! {
+    panic!("out of memory")
+}
+
+unsafe impl<'a> alloc::Alloc for &'a Bump {
+    #[inline(always)]
+    unsafe fn alloc(&mut self, layout: Layout) -> Result<NonNull<u8>, alloc::AllocErr> {
+        self.try_alloc_layout(layout)
+    }
+
+    #[inline]
+    unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout) {
+        // If the pointer is the last allocation we made, we can reuse the bytes,
+        // otherwise they are simply leaked -- at least until somebody calls reset().
+        if self.is_last_allocation(ptr) {
+            let ptr = NonNull::new_unchecked(ptr.as_ptr().add(layout.size()));
+            self.current_chunk_footer.get().as_ref().ptr.set(ptr);
+        }
+    }
+
+    #[inline]
+    unsafe fn realloc(
+        &mut self,
+        ptr: NonNull<u8>,
+        layout: Layout,
+        new_size: usize,
+    ) -> Result<NonNull<u8>, alloc::AllocErr> {
+        let old_size = layout.size();
+
+        if old_size == 0 {
+            return self.alloc(layout);
+        }
+
+        if new_size <= old_size {
+            if self.is_last_allocation(ptr)
+                // Only reclaim the excess space (which requires a copy) if it
+                // is worth it: we are actually going to recover "enough" space
+                // and we can do a non-overlapping copy.
+                && new_size <= old_size / 2
+            {
+                let delta = old_size - new_size;
+                let footer = self.current_chunk_footer.get();
+                let footer = footer.as_ref();
+                footer
+                    .ptr
+                    .set(NonNull::new_unchecked(footer.ptr.get().as_ptr().add(delta)));
+                let new_ptr = footer.ptr.get();
+                // NB: we know it is non-overlapping because of the size check
+                // in the `if` condition.
+                ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_ptr(), new_size);
+                return Ok(new_ptr);
+            } else {
+                return Ok(ptr);
+            }
+        }
+
+        if self.is_last_allocation(ptr) {
+            // Try to allocate the delta size within this same block so we can
+            // reuse the currently allocated space.
+            let delta = new_size - old_size;
+            if let Some(p) =
+                self.try_alloc_layout_fast(layout_from_size_align(delta, layout.align()))
+            {
+                ptr::copy(ptr.as_ptr(), p.as_ptr(), old_size);
+                return Ok(p);
+            }
+        }
+
+        // Fallback: do a fresh allocation and copy the existing data into it.
+        let new_layout = layout_from_size_align(new_size, layout.align());
+        let new_ptr = self.try_alloc_layout(new_layout)?;
+        ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_ptr(), old_size);
+        Ok(new_ptr)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn chunk_footer_is_five_words() {
+        assert_eq!(mem::size_of::<ChunkFooter>(), mem::size_of::<usize>() * 5);
+    }
+
+    #[test]
+    #[allow(clippy::cognitive_complexity)]
+    fn test_realloc() {
+        use crate::alloc::Alloc;
+
+        unsafe {
+            const CAPACITY: usize = 1024 - OVERHEAD;
+            let mut b = Bump::with_capacity(CAPACITY);
+
+            // `realloc` doesn't shrink allocations that aren't "worth it".
+            let layout = Layout::from_size_align(100, 1).unwrap();
+            let p = b.alloc_layout(layout);
+            let q = (&b).realloc(p, layout, 51).unwrap();
+            assert_eq!(p, q);
+            b.reset();
+
+            // `realloc` will shrink allocations that are "worth it".
+            let layout = Layout::from_size_align(100, 1).unwrap();
+            let p = b.alloc_layout(layout);
+            let q = (&b).realloc(p, layout, 50).unwrap();
+            assert!(p != q);
+            b.reset();
+
+            // `realloc` will reuse the last allocation when growing.
+            let layout = Layout::from_size_align(10, 1).unwrap();
+            let p = b.alloc_layout(layout);
+            let q = (&b).realloc(p, layout, 11).unwrap();
+            assert_eq!(q.as_ptr() as usize, p.as_ptr() as usize - 1);
+            b.reset();
+
+            // `realloc` will allocate a new chunk when growing the last
+            // allocation, if need be.
+            let layout = Layout::from_size_align(1, 1).unwrap();
+            let p = b.alloc_layout(layout);
+            let q = (&b).realloc(p, layout, CAPACITY + 1).unwrap();
+            assert!(q.as_ptr() as usize != p.as_ptr() as usize - CAPACITY);
+            b = Bump::with_capacity(CAPACITY);
+
+            // `realloc` will allocate and copy when reallocating anything that
+            // wasn't the last allocation.
+            let layout = Layout::from_size_align(1, 1).unwrap();
+            let p = b.alloc_layout(layout);
+            let _ = b.alloc_layout(layout);
+            let q = (&b).realloc(p, layout, 2).unwrap();
+            assert!(q.as_ptr() as usize != p.as_ptr() as usize - 1);
+            b.reset();
+        }
+    }
+
+    #[test]
+    fn invalid_read() {
+        use alloc::Alloc;
+
+        let mut b = &Bump::new();
+
+        unsafe {
+            let l1 = Layout::from_size_align(12000, 4).unwrap();
+            let p1 = Alloc::alloc(&mut b, l1).unwrap();
+
+            let l2 = Layout::from_size_align(1000, 4).unwrap();
+            Alloc::alloc(&mut b, l2).unwrap();
+
+            let p1 = b.realloc(p1, l1, 24000).unwrap();
+            let l3 = Layout::from_size_align(24000, 4).unwrap();
+            b.realloc(p1, l3, 48000).unwrap();
+        }
+    }
+}