242 lines
7.7 KiB
Rust
242 lines
7.7 KiB
Rust
//! Memory allocation APIs
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#![stable(feature = "alloc_module", since = "1.28.0")]
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use core::intrinsics::{min_align_of_val, size_of_val};
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use core::ptr::{NonNull, Unique};
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use core::usize;
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#[stable(feature = "alloc_module", since = "1.28.0")]
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#[doc(inline)]
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pub use core::alloc::*;
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#[cfg(test)]
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mod tests;
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extern "Rust" {
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// These are the magic symbols to call the global allocator. rustc generates
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// them from the `#[global_allocator]` attribute if there is one, or uses the
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// default implementations in libstd (`__rdl_alloc` etc in `src/libstd/alloc.rs`)
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// otherwise.
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#[rustc_allocator]
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#[rustc_allocator_nounwind]
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fn __rust_alloc(size: usize, align: usize) -> *mut u8;
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#[rustc_allocator_nounwind]
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fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);
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#[rustc_allocator_nounwind]
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fn __rust_realloc(ptr: *mut u8, old_size: usize, align: usize, new_size: usize) -> *mut u8;
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#[rustc_allocator_nounwind]
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fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;
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}
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/// The global memory allocator.
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///
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/// This type implements the [`Alloc`] trait by forwarding calls
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/// to the allocator registered with the `#[global_allocator]` attribute
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/// if there is one, or the `std` crate’s default.
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///
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/// Note: while this type is unstable, the functionality it provides can be
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/// accessed through the [free functions in `alloc`](index.html#functions).
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///
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/// [`Alloc`]: trait.Alloc.html
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#[unstable(feature = "allocator_api", issue = "32838")]
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#[derive(Copy, Clone, Default, Debug)]
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pub struct Global;
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/// Allocate memory with the global allocator.
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///
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/// This function forwards calls to the [`GlobalAlloc::alloc`] method
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/// of the allocator registered with the `#[global_allocator]` attribute
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/// if there is one, or the `std` crate’s default.
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///
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/// This function is expected to be deprecated in favor of the `alloc` method
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/// of the [`Global`] type when it and the [`Alloc`] trait become stable.
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///
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/// # Safety
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///
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/// See [`GlobalAlloc::alloc`].
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///
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/// [`Global`]: struct.Global.html
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/// [`Alloc`]: trait.Alloc.html
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/// [`GlobalAlloc::alloc`]: trait.GlobalAlloc.html#tymethod.alloc
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///
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/// # Examples
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///
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/// ```
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/// use std::alloc::{alloc, dealloc, Layout};
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///
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/// unsafe {
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/// let layout = Layout::new::<u16>();
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/// let ptr = alloc(layout);
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///
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/// *(ptr as *mut u16) = 42;
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/// assert_eq!(*(ptr as *mut u16), 42);
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///
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/// dealloc(ptr, layout);
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/// }
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/// ```
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#[stable(feature = "global_alloc", since = "1.28.0")]
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#[inline]
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pub unsafe fn alloc(layout: Layout) -> *mut u8 {
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__rust_alloc(layout.size(), layout.align())
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}
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/// Deallocate memory with the global allocator.
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///
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/// This function forwards calls to the [`GlobalAlloc::dealloc`] method
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/// of the allocator registered with the `#[global_allocator]` attribute
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/// if there is one, or the `std` crate’s default.
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///
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/// This function is expected to be deprecated in favor of the `dealloc` method
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/// of the [`Global`] type when it and the [`Alloc`] trait become stable.
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///
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/// # Safety
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///
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/// See [`GlobalAlloc::dealloc`].
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///
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/// [`Global`]: struct.Global.html
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/// [`Alloc`]: trait.Alloc.html
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/// [`GlobalAlloc::dealloc`]: trait.GlobalAlloc.html#tymethod.dealloc
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#[stable(feature = "global_alloc", since = "1.28.0")]
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#[inline]
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pub unsafe fn dealloc(ptr: *mut u8, layout: Layout) {
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__rust_dealloc(ptr, layout.size(), layout.align())
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}
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/// Reallocate memory with the global allocator.
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///
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/// This function forwards calls to the [`GlobalAlloc::realloc`] method
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/// of the allocator registered with the `#[global_allocator]` attribute
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/// if there is one, or the `std` crate’s default.
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///
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/// This function is expected to be deprecated in favor of the `realloc` method
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/// of the [`Global`] type when it and the [`Alloc`] trait become stable.
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///
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/// # Safety
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///
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/// See [`GlobalAlloc::realloc`].
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///
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/// [`Global`]: struct.Global.html
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/// [`Alloc`]: trait.Alloc.html
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/// [`GlobalAlloc::realloc`]: trait.GlobalAlloc.html#method.realloc
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#[stable(feature = "global_alloc", since = "1.28.0")]
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#[inline]
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pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
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__rust_realloc(ptr, layout.size(), layout.align(), new_size)
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}
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/// Allocate zero-initialized memory with the global allocator.
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///
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/// This function forwards calls to the [`GlobalAlloc::alloc_zeroed`] method
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/// of the allocator registered with the `#[global_allocator]` attribute
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/// if there is one, or the `std` crate’s default.
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///
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/// This function is expected to be deprecated in favor of the `alloc_zeroed` method
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/// of the [`Global`] type when it and the [`Alloc`] trait become stable.
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///
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/// # Safety
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///
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/// See [`GlobalAlloc::alloc_zeroed`].
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///
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/// [`Global`]: struct.Global.html
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/// [`Alloc`]: trait.Alloc.html
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/// [`GlobalAlloc::alloc_zeroed`]: trait.GlobalAlloc.html#method.alloc_zeroed
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///
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/// # Examples
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///
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/// ```
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/// use std::alloc::{alloc_zeroed, dealloc, Layout};
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///
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/// unsafe {
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/// let layout = Layout::new::<u16>();
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/// let ptr = alloc_zeroed(layout);
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///
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/// assert_eq!(*(ptr as *mut u16), 0);
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///
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/// dealloc(ptr, layout);
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/// }
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/// ```
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#[stable(feature = "global_alloc", since = "1.28.0")]
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#[inline]
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pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
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__rust_alloc_zeroed(layout.size(), layout.align())
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}
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#[unstable(feature = "allocator_api", issue = "32838")]
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unsafe impl Alloc for Global {
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#[inline]
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unsafe fn alloc(&mut self, layout: Layout) -> Result<NonNull<u8>, AllocErr> {
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NonNull::new(alloc(layout)).ok_or(AllocErr)
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}
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#[inline]
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unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout) {
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dealloc(ptr.as_ptr(), layout)
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}
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#[inline]
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unsafe fn realloc(
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&mut self,
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ptr: NonNull<u8>,
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layout: Layout,
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new_size: usize,
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) -> Result<NonNull<u8>, AllocErr> {
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NonNull::new(realloc(ptr.as_ptr(), layout, new_size)).ok_or(AllocErr)
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}
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#[inline]
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unsafe fn alloc_zeroed(&mut self, layout: Layout) -> Result<NonNull<u8>, AllocErr> {
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NonNull::new(alloc_zeroed(layout)).ok_or(AllocErr)
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}
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}
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/// The allocator for unique pointers.
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// This function must not unwind. If it does, MIR codegen will fail.
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#[cfg(not(test))]
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#[lang = "exchange_malloc"]
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#[inline]
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unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
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if size == 0 {
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align as *mut u8
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} else {
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let layout = Layout::from_size_align_unchecked(size, align);
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let ptr = alloc(layout);
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if !ptr.is_null() { ptr } else { handle_alloc_error(layout) }
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}
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}
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#[cfg_attr(not(test), lang = "box_free")]
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#[inline]
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pub(crate) unsafe fn box_free<T: ?Sized>(ptr: Unique<T>) {
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let ptr = ptr.as_ptr();
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let size = size_of_val(&*ptr);
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let align = min_align_of_val(&*ptr);
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// We do not allocate for Box<T> when T is ZST, so deallocation is also not necessary.
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if size != 0 {
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let layout = Layout::from_size_align_unchecked(size, align);
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dealloc(ptr as *mut u8, layout);
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}
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}
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/// Abort on memory allocation error or failure.
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///
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/// Callers of memory allocation APIs wishing to abort computation
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/// in response to an allocation error are encouraged to call this function,
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/// rather than directly invoking `panic!` or similar.
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///
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/// The default behavior of this function is to print a message to standard error
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/// and abort the process.
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/// It can be replaced with [`set_alloc_error_hook`] and [`take_alloc_error_hook`].
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///
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/// [`set_alloc_error_hook`]: ../../std/alloc/fn.set_alloc_error_hook.html
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/// [`take_alloc_error_hook`]: ../../std/alloc/fn.take_alloc_error_hook.html
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#[stable(feature = "global_alloc", since = "1.28.0")]
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#[rustc_allocator_nounwind]
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pub fn handle_alloc_error(layout: Layout) -> ! {
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extern "Rust" {
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#[lang = "oom"]
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fn oom_impl(layout: Layout) -> !;
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}
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unsafe { oom_impl(layout) }
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}
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