441 lines
16 KiB
Rust
441 lines
16 KiB
Rust
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// SPDX-License-Identifier: Apache-2.0 OR MIT
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//! Memory allocation APIs
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#![stable(feature = "alloc_module", since = "1.28.0")]
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#[cfg(not(test))]
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use core::intrinsics;
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use core::intrinsics::{min_align_of_val, size_of_val};
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use core::ptr::Unique;
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#[cfg(not(test))]
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use core::ptr::{self, NonNull};
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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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use core::marker::Destruct;
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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 to call `__rg_alloc` etc. if there is a `#[global_allocator]` attribute
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// (the code expanding that attribute macro generates those functions), or to call
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// the default implementations in libstd (`__rdl_alloc` etc. in `library/std/src/alloc.rs`)
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// otherwise.
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// The rustc fork of LLVM also special-cases these function names to be able to optimize them
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// like `malloc`, `realloc`, and `free`, respectively.
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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 [`Allocator`] 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`](self#functions).
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#[unstable(feature = "allocator_api", issue = "32838")]
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#[derive(Copy, Clone, Default, Debug)]
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#[cfg(not(test))]
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pub struct Global;
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#[cfg(test)]
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pub use std::alloc::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 [`Allocator`] 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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/// # 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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#[must_use = "losing the pointer will leak memory"]
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#[inline]
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pub unsafe fn alloc(layout: Layout) -> *mut u8 {
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unsafe { __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 [`Allocator`] 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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#[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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unsafe { __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 [`Allocator`] 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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#[stable(feature = "global_alloc", since = "1.28.0")]
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#[must_use = "losing the pointer will leak memory"]
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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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unsafe { __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 [`Allocator`] 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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/// # 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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#[must_use = "losing the pointer will leak memory"]
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#[inline]
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pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
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unsafe { __rust_alloc_zeroed(layout.size(), layout.align()) }
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}
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#[cfg(not(test))]
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impl Global {
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#[inline]
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fn alloc_impl(&self, layout: Layout, zeroed: bool) -> Result<NonNull<[u8]>, AllocError> {
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match layout.size() {
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0 => Ok(NonNull::slice_from_raw_parts(layout.dangling(), 0)),
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// SAFETY: `layout` is non-zero in size,
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size => unsafe {
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let raw_ptr = if zeroed { alloc_zeroed(layout) } else { alloc(layout) };
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let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
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Ok(NonNull::slice_from_raw_parts(ptr, size))
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},
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}
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}
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// SAFETY: Same as `Allocator::grow`
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#[inline]
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unsafe fn grow_impl(
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&self,
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ptr: NonNull<u8>,
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old_layout: Layout,
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new_layout: Layout,
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zeroed: bool,
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) -> Result<NonNull<[u8]>, AllocError> {
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debug_assert!(
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new_layout.size() >= old_layout.size(),
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"`new_layout.size()` must be greater than or equal to `old_layout.size()`"
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);
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match old_layout.size() {
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0 => self.alloc_impl(new_layout, zeroed),
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// SAFETY: `new_size` is non-zero as `old_size` is greater than or equal to `new_size`
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// as required by safety conditions. Other conditions must be upheld by the caller
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old_size if old_layout.align() == new_layout.align() => unsafe {
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let new_size = new_layout.size();
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// `realloc` probably checks for `new_size >= old_layout.size()` or something similar.
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intrinsics::assume(new_size >= old_layout.size());
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let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);
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let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
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if zeroed {
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raw_ptr.add(old_size).write_bytes(0, new_size - old_size);
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}
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Ok(NonNull::slice_from_raw_parts(ptr, new_size))
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},
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// SAFETY: because `new_layout.size()` must be greater than or equal to `old_size`,
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// both the old and new memory allocation are valid for reads and writes for `old_size`
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// bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
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// `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
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// for `dealloc` must be upheld by the caller.
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old_size => unsafe {
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let new_ptr = self.alloc_impl(new_layout, zeroed)?;
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ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), old_size);
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self.deallocate(ptr, old_layout);
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Ok(new_ptr)
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},
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}
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}
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}
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#[unstable(feature = "allocator_api", issue = "32838")]
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#[cfg(not(test))]
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unsafe impl Allocator for Global {
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#[inline]
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fn allocate(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
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self.alloc_impl(layout, false)
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}
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#[inline]
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fn allocate_zeroed(&self, layout: Layout) -> Result<NonNull<[u8]>, AllocError> {
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self.alloc_impl(layout, true)
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}
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#[inline]
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unsafe fn deallocate(&self, ptr: NonNull<u8>, layout: Layout) {
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if layout.size() != 0 {
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// SAFETY: `layout` is non-zero in size,
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// other conditions must be upheld by the caller
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unsafe { dealloc(ptr.as_ptr(), layout) }
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}
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}
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#[inline]
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unsafe fn grow(
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&self,
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ptr: NonNull<u8>,
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old_layout: Layout,
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new_layout: Layout,
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) -> Result<NonNull<[u8]>, AllocError> {
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// SAFETY: all conditions must be upheld by the caller
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unsafe { self.grow_impl(ptr, old_layout, new_layout, false) }
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}
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#[inline]
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unsafe fn grow_zeroed(
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&self,
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ptr: NonNull<u8>,
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old_layout: Layout,
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new_layout: Layout,
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) -> Result<NonNull<[u8]>, AllocError> {
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// SAFETY: all conditions must be upheld by the caller
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unsafe { self.grow_impl(ptr, old_layout, new_layout, true) }
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}
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#[inline]
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unsafe fn shrink(
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&self,
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ptr: NonNull<u8>,
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old_layout: Layout,
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new_layout: Layout,
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) -> Result<NonNull<[u8]>, AllocError> {
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debug_assert!(
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new_layout.size() <= old_layout.size(),
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"`new_layout.size()` must be smaller than or equal to `old_layout.size()`"
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);
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match new_layout.size() {
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// SAFETY: conditions must be upheld by the caller
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0 => unsafe {
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self.deallocate(ptr, old_layout);
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Ok(NonNull::slice_from_raw_parts(new_layout.dangling(), 0))
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},
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// SAFETY: `new_size` is non-zero. Other conditions must be upheld by the caller
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new_size if old_layout.align() == new_layout.align() => unsafe {
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// `realloc` probably checks for `new_size <= old_layout.size()` or something similar.
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intrinsics::assume(new_size <= old_layout.size());
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let raw_ptr = realloc(ptr.as_ptr(), old_layout, new_size);
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let ptr = NonNull::new(raw_ptr).ok_or(AllocError)?;
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Ok(NonNull::slice_from_raw_parts(ptr, new_size))
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},
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// SAFETY: because `new_size` must be smaller than or equal to `old_layout.size()`,
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// both the old and new memory allocation are valid for reads and writes for `new_size`
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// bytes. Also, because the old allocation wasn't yet deallocated, it cannot overlap
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// `new_ptr`. Thus, the call to `copy_nonoverlapping` is safe. The safety contract
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// for `dealloc` must be upheld by the caller.
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new_size => unsafe {
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let new_ptr = self.allocate(new_layout)?;
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ptr::copy_nonoverlapping(ptr.as_ptr(), new_ptr.as_mut_ptr(), new_size);
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self.deallocate(ptr, old_layout);
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Ok(new_ptr)
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},
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}
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}
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}
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/// The allocator for unique pointers.
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#[cfg(all(not(no_global_oom_handling), 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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let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
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match Global.allocate(layout) {
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Ok(ptr) => ptr.as_mut_ptr(),
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Err(_) => 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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#[rustc_const_unstable(feature = "const_box", issue = "92521")]
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// This signature has to be the same as `Box`, otherwise an ICE will happen.
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// When an additional parameter to `Box` is added (like `A: Allocator`), this has to be added here as
|
|||
|
|
// well.
|
|||
|
|
// For example if `Box` is changed to `struct Box<T: ?Sized, A: Allocator>(Unique<T>, A)`,
|
|||
|
|
// this function has to be changed to `fn box_free<T: ?Sized, A: Allocator>(Unique<T>, A)` as well.
|
|||
|
|
pub(crate) const unsafe fn box_free<T: ?Sized, A: ~const Allocator + ~const Destruct>(
|
|||
|
|
ptr: Unique<T>,
|
|||
|
|
alloc: A,
|
|||
|
|
) {
|
|||
|
|
unsafe {
|
|||
|
|
let size = size_of_val(ptr.as_ref());
|
|||
|
|
let align = min_align_of_val(ptr.as_ref());
|
|||
|
|
let layout = Layout::from_size_align_unchecked(size, align);
|
|||
|
|
alloc.deallocate(From::from(ptr.cast()), layout)
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// # Allocation error handler
|
|||
|
|
|
|||
|
|
#[cfg(not(no_global_oom_handling))]
|
|||
|
|
extern "Rust" {
|
|||
|
|
// This is the magic symbol to call the global alloc error handler. rustc generates
|
|||
|
|
// it to call `__rg_oom` if there is a `#[alloc_error_handler]`, or to call the
|
|||
|
|
// default implementations below (`__rdl_oom`) otherwise.
|
|||
|
|
fn __rust_alloc_error_handler(size: usize, align: usize) -> !;
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// Abort on memory allocation error or failure.
|
|||
|
|
///
|
|||
|
|
/// Callers of memory allocation APIs wishing to abort computation
|
|||
|
|
/// in response to an allocation error are encouraged to call this function,
|
|||
|
|
/// rather than directly invoking `panic!` or similar.
|
|||
|
|
///
|
|||
|
|
/// The default behavior of this function is to print a message to standard error
|
|||
|
|
/// and abort the process.
|
|||
|
|
/// It can be replaced with [`set_alloc_error_hook`] and [`take_alloc_error_hook`].
|
|||
|
|
///
|
|||
|
|
/// [`set_alloc_error_hook`]: ../../std/alloc/fn.set_alloc_error_hook.html
|
|||
|
|
/// [`take_alloc_error_hook`]: ../../std/alloc/fn.take_alloc_error_hook.html
|
|||
|
|
#[stable(feature = "global_alloc", since = "1.28.0")]
|
|||
|
|
#[rustc_const_unstable(feature = "const_alloc_error", issue = "92523")]
|
|||
|
|
#[cfg(all(not(no_global_oom_handling), not(test)))]
|
|||
|
|
#[cold]
|
|||
|
|
pub const fn handle_alloc_error(layout: Layout) -> ! {
|
|||
|
|
const fn ct_error(_: Layout) -> ! {
|
|||
|
|
panic!("allocation failed");
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
fn rt_error(layout: Layout) -> ! {
|
|||
|
|
unsafe {
|
|||
|
|
__rust_alloc_error_handler(layout.size(), layout.align());
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
unsafe { core::intrinsics::const_eval_select((layout,), ct_error, rt_error) }
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// For alloc test `std::alloc::handle_alloc_error` can be used directly.
|
|||
|
|
#[cfg(all(not(no_global_oom_handling), test))]
|
|||
|
|
pub use std::alloc::handle_alloc_error;
|
|||
|
|
|
|||
|
|
#[cfg(all(not(no_global_oom_handling), not(test)))]
|
|||
|
|
#[doc(hidden)]
|
|||
|
|
#[allow(unused_attributes)]
|
|||
|
|
#[unstable(feature = "alloc_internals", issue = "none")]
|
|||
|
|
pub mod __alloc_error_handler {
|
|||
|
|
use crate::alloc::Layout;
|
|||
|
|
|
|||
|
|
// called via generated `__rust_alloc_error_handler`
|
|||
|
|
|
|||
|
|
// if there is no `#[alloc_error_handler]`
|
|||
|
|
#[rustc_std_internal_symbol]
|
|||
|
|
pub unsafe extern "C-unwind" fn __rdl_oom(size: usize, _align: usize) -> ! {
|
|||
|
|
panic!("memory allocation of {size} bytes failed")
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
// if there is an `#[alloc_error_handler]`
|
|||
|
|
#[rustc_std_internal_symbol]
|
|||
|
|
pub unsafe extern "C-unwind" fn __rg_oom(size: usize, align: usize) -> ! {
|
|||
|
|
let layout = unsafe { Layout::from_size_align_unchecked(size, align) };
|
|||
|
|
extern "Rust" {
|
|||
|
|
#[lang = "oom"]
|
|||
|
|
fn oom_impl(layout: Layout) -> !;
|
|||
|
|
}
|
|||
|
|
unsafe { oom_impl(layout) }
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
/// Specialize clones into pre-allocated, uninitialized memory.
|
|||
|
|
/// Used by `Box::clone` and `Rc`/`Arc::make_mut`.
|
|||
|
|
pub(crate) trait WriteCloneIntoRaw: Sized {
|
|||
|
|
unsafe fn write_clone_into_raw(&self, target: *mut Self);
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
impl<T: Clone> WriteCloneIntoRaw for T {
|
|||
|
|
#[inline]
|
|||
|
|
default unsafe fn write_clone_into_raw(&self, target: *mut Self) {
|
|||
|
|
// Having allocated *first* may allow the optimizer to create
|
|||
|
|
// the cloned value in-place, skipping the local and move.
|
|||
|
|
unsafe { target.write(self.clone()) };
|
|||
|
|
}
|
|||
|
|
}
|
|||
|
|
|
|||
|
|
impl<T: Copy> WriteCloneIntoRaw for T {
|
|||
|
|
#[inline]
|
|||
|
|
unsafe fn write_clone_into_raw(&self, target: *mut Self) {
|
|||
|
|
// We can always copy in-place, without ever involving a local value.
|
|||
|
|
unsafe { target.copy_from_nonoverlapping(self, 1) };
|
|||
|
|
}
|
|||
|
|
}
|