309 lines
10 KiB
Rust
309 lines
10 KiB
Rust
//! Memory allocation APIs
|
||
|
||
#![stable(feature = "alloc_module", since = "1.28.0")]
|
||
|
||
use core::intrinsics::{self, min_align_of_val, size_of_val};
|
||
use core::ptr::{NonNull, Unique};
|
||
|
||
#[stable(feature = "alloc_module", since = "1.28.0")]
|
||
#[doc(inline)]
|
||
pub use core::alloc::*;
|
||
|
||
#[cfg(test)]
|
||
mod tests;
|
||
|
||
extern "Rust" {
|
||
// These are the magic symbols to call the global allocator. rustc generates
|
||
// them from the `#[global_allocator]` attribute if there is one, or uses the
|
||
// default implementations in libstd (`__rdl_alloc` etc in `src/libstd/alloc.rs`)
|
||
// otherwise.
|
||
#[rustc_allocator]
|
||
#[rustc_allocator_nounwind]
|
||
fn __rust_alloc(size: usize, align: usize) -> *mut u8;
|
||
#[rustc_allocator_nounwind]
|
||
fn __rust_dealloc(ptr: *mut u8, size: usize, align: usize);
|
||
#[rustc_allocator_nounwind]
|
||
fn __rust_realloc(ptr: *mut u8, old_size: usize, align: usize, new_size: usize) -> *mut u8;
|
||
#[rustc_allocator_nounwind]
|
||
fn __rust_alloc_zeroed(size: usize, align: usize) -> *mut u8;
|
||
}
|
||
|
||
/// The global memory allocator.
|
||
///
|
||
/// This type implements the [`AllocRef`] trait by forwarding calls
|
||
/// to the allocator registered with the `#[global_allocator]` attribute
|
||
/// if there is one, or the `std` crate’s default.
|
||
///
|
||
/// Note: while this type is unstable, the functionality it provides can be
|
||
/// accessed through the [free functions in `alloc`](index.html#functions).
|
||
///
|
||
/// [`AllocRef`]: trait.AllocRef.html
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
#[derive(Copy, Clone, Default, Debug)]
|
||
pub struct Global;
|
||
|
||
/// Allocate memory with the global allocator.
|
||
///
|
||
/// This function forwards calls to the [`GlobalAlloc::alloc`] method
|
||
/// of the allocator registered with the `#[global_allocator]` attribute
|
||
/// if there is one, or the `std` crate’s default.
|
||
///
|
||
/// This function is expected to be deprecated in favor of the `alloc` method
|
||
/// of the [`Global`] type when it and the [`AllocRef`] trait become stable.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// See [`GlobalAlloc::alloc`].
|
||
///
|
||
/// [`Global`]: struct.Global.html
|
||
/// [`AllocRef`]: trait.AllocRef.html
|
||
/// [`GlobalAlloc::alloc`]: trait.GlobalAlloc.html#tymethod.alloc
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::alloc::{alloc, dealloc, Layout};
|
||
///
|
||
/// unsafe {
|
||
/// let layout = Layout::new::<u16>();
|
||
/// let ptr = alloc(layout);
|
||
///
|
||
/// *(ptr as *mut u16) = 42;
|
||
/// assert_eq!(*(ptr as *mut u16), 42);
|
||
///
|
||
/// dealloc(ptr, layout);
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "global_alloc", since = "1.28.0")]
|
||
#[inline]
|
||
pub unsafe fn alloc(layout: Layout) -> *mut u8 {
|
||
__rust_alloc(layout.size(), layout.align())
|
||
}
|
||
|
||
/// Deallocate memory with the global allocator.
|
||
///
|
||
/// This function forwards calls to the [`GlobalAlloc::dealloc`] method
|
||
/// of the allocator registered with the `#[global_allocator]` attribute
|
||
/// if there is one, or the `std` crate’s default.
|
||
///
|
||
/// This function is expected to be deprecated in favor of the `dealloc` method
|
||
/// of the [`Global`] type when it and the [`AllocRef`] trait become stable.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// See [`GlobalAlloc::dealloc`].
|
||
///
|
||
/// [`Global`]: struct.Global.html
|
||
/// [`AllocRef`]: trait.AllocRef.html
|
||
/// [`GlobalAlloc::dealloc`]: trait.GlobalAlloc.html#tymethod.dealloc
|
||
#[stable(feature = "global_alloc", since = "1.28.0")]
|
||
#[inline]
|
||
pub unsafe fn dealloc(ptr: *mut u8, layout: Layout) {
|
||
__rust_dealloc(ptr, layout.size(), layout.align())
|
||
}
|
||
|
||
/// Reallocate memory with the global allocator.
|
||
///
|
||
/// This function forwards calls to the [`GlobalAlloc::realloc`] method
|
||
/// of the allocator registered with the `#[global_allocator]` attribute
|
||
/// if there is one, or the `std` crate’s default.
|
||
///
|
||
/// This function is expected to be deprecated in favor of the `realloc` method
|
||
/// of the [`Global`] type when it and the [`AllocRef`] trait become stable.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// See [`GlobalAlloc::realloc`].
|
||
///
|
||
/// [`Global`]: struct.Global.html
|
||
/// [`AllocRef`]: trait.AllocRef.html
|
||
/// [`GlobalAlloc::realloc`]: trait.GlobalAlloc.html#method.realloc
|
||
#[stable(feature = "global_alloc", since = "1.28.0")]
|
||
#[inline]
|
||
pub unsafe fn realloc(ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
|
||
__rust_realloc(ptr, layout.size(), layout.align(), new_size)
|
||
}
|
||
|
||
/// Allocate zero-initialized memory with the global allocator.
|
||
///
|
||
/// This function forwards calls to the [`GlobalAlloc::alloc_zeroed`] method
|
||
/// of the allocator registered with the `#[global_allocator]` attribute
|
||
/// if there is one, or the `std` crate’s default.
|
||
///
|
||
/// This function is expected to be deprecated in favor of the `alloc_zeroed` method
|
||
/// of the [`Global`] type when it and the [`AllocRef`] trait become stable.
|
||
///
|
||
/// # Safety
|
||
///
|
||
/// See [`GlobalAlloc::alloc_zeroed`].
|
||
///
|
||
/// [`Global`]: struct.Global.html
|
||
/// [`AllocRef`]: trait.AllocRef.html
|
||
/// [`GlobalAlloc::alloc_zeroed`]: trait.GlobalAlloc.html#method.alloc_zeroed
|
||
///
|
||
/// # Examples
|
||
///
|
||
/// ```
|
||
/// use std::alloc::{alloc_zeroed, dealloc, Layout};
|
||
///
|
||
/// unsafe {
|
||
/// let layout = Layout::new::<u16>();
|
||
/// let ptr = alloc_zeroed(layout);
|
||
///
|
||
/// assert_eq!(*(ptr as *mut u16), 0);
|
||
///
|
||
/// dealloc(ptr, layout);
|
||
/// }
|
||
/// ```
|
||
#[stable(feature = "global_alloc", since = "1.28.0")]
|
||
#[inline]
|
||
pub unsafe fn alloc_zeroed(layout: Layout) -> *mut u8 {
|
||
__rust_alloc_zeroed(layout.size(), layout.align())
|
||
}
|
||
|
||
#[unstable(feature = "allocator_api", issue = "32838")]
|
||
unsafe impl AllocRef for Global {
|
||
#[inline]
|
||
fn alloc(&mut self, layout: Layout, init: AllocInit) -> Result<MemoryBlock, AllocErr> {
|
||
unsafe {
|
||
let size = layout.size();
|
||
if size == 0 {
|
||
Ok(MemoryBlock { ptr: layout.dangling(), size: 0 })
|
||
} else {
|
||
let raw_ptr = match init {
|
||
AllocInit::Uninitialized => alloc(layout),
|
||
AllocInit::Zeroed => alloc_zeroed(layout),
|
||
};
|
||
let ptr = NonNull::new(raw_ptr).ok_or(AllocErr)?;
|
||
Ok(MemoryBlock { ptr, size })
|
||
}
|
||
}
|
||
}
|
||
|
||
#[inline]
|
||
unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout) {
|
||
if layout.size() != 0 {
|
||
dealloc(ptr.as_ptr(), layout)
|
||
}
|
||
}
|
||
|
||
#[inline]
|
||
unsafe fn grow(
|
||
&mut self,
|
||
ptr: NonNull<u8>,
|
||
layout: Layout,
|
||
new_size: usize,
|
||
placement: ReallocPlacement,
|
||
init: AllocInit,
|
||
) -> Result<MemoryBlock, AllocErr> {
|
||
let size = layout.size();
|
||
debug_assert!(
|
||
new_size >= size,
|
||
"`new_size` must be greater than or equal to `memory.size()`"
|
||
);
|
||
|
||
if size == new_size {
|
||
return Ok(MemoryBlock { ptr, size });
|
||
}
|
||
|
||
match placement {
|
||
ReallocPlacement::InPlace => Err(AllocErr),
|
||
ReallocPlacement::MayMove if layout.size() == 0 => {
|
||
let new_layout = Layout::from_size_align_unchecked(new_size, layout.align());
|
||
self.alloc(new_layout, init)
|
||
}
|
||
ReallocPlacement::MayMove => {
|
||
// `realloc` probably checks for `new_size > size` or something similar.
|
||
intrinsics::assume(new_size > size);
|
||
let ptr = realloc(ptr.as_ptr(), layout, new_size);
|
||
let memory =
|
||
MemoryBlock { ptr: NonNull::new(ptr).ok_or(AllocErr)?, size: new_size };
|
||
init.init_offset(memory, size);
|
||
Ok(memory)
|
||
}
|
||
}
|
||
}
|
||
|
||
#[inline]
|
||
unsafe fn shrink(
|
||
&mut self,
|
||
ptr: NonNull<u8>,
|
||
layout: Layout,
|
||
new_size: usize,
|
||
placement: ReallocPlacement,
|
||
) -> Result<MemoryBlock, AllocErr> {
|
||
let size = layout.size();
|
||
debug_assert!(
|
||
new_size <= size,
|
||
"`new_size` must be smaller than or equal to `memory.size()`"
|
||
);
|
||
|
||
if size == new_size {
|
||
return Ok(MemoryBlock { ptr, size });
|
||
}
|
||
|
||
match placement {
|
||
ReallocPlacement::InPlace => Err(AllocErr),
|
||
ReallocPlacement::MayMove if new_size == 0 => {
|
||
self.dealloc(ptr, layout);
|
||
Ok(MemoryBlock { ptr: layout.dangling(), size: 0 })
|
||
}
|
||
ReallocPlacement::MayMove => {
|
||
// `realloc` probably checks for `new_size < size` or something similar.
|
||
intrinsics::assume(new_size < size);
|
||
let ptr = realloc(ptr.as_ptr(), layout, new_size);
|
||
Ok(MemoryBlock { ptr: NonNull::new(ptr).ok_or(AllocErr)?, size: new_size })
|
||
}
|
||
}
|
||
}
|
||
}
|
||
|
||
/// The allocator for unique pointers.
|
||
// This function must not unwind. If it does, MIR codegen will fail.
|
||
#[cfg(not(test))]
|
||
#[lang = "exchange_malloc"]
|
||
#[inline]
|
||
unsafe fn exchange_malloc(size: usize, align: usize) -> *mut u8 {
|
||
let layout = Layout::from_size_align_unchecked(size, align);
|
||
match Global.alloc(layout, AllocInit::Uninitialized) {
|
||
Ok(memory) => memory.ptr.as_ptr(),
|
||
Err(_) => handle_alloc_error(layout),
|
||
}
|
||
}
|
||
|
||
#[cfg_attr(not(test), lang = "box_free")]
|
||
#[inline]
|
||
// This signature has to be the same as `Box`, otherwise an ICE will happen.
|
||
// When an additional parameter to `Box` is added (like `A: AllocRef`), this has to be added here as
|
||
// well.
|
||
// For example if `Box` is changed to `struct Box<T: ?Sized, A: AllocRef>(Unique<T>, A)`,
|
||
// this function has to be changed to `fn box_free<T: ?Sized, A: AllocRef>(Unique<T>, A)` as well.
|
||
pub(crate) unsafe fn box_free<T: ?Sized>(ptr: Unique<T>) {
|
||
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);
|
||
Global.dealloc(ptr.cast().into(), layout)
|
||
}
|
||
|
||
/// 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_allocator_nounwind]
|
||
pub fn handle_alloc_error(layout: Layout) -> ! {
|
||
extern "Rust" {
|
||
#[lang = "oom"]
|
||
fn oom_impl(layout: Layout) -> !;
|
||
}
|
||
unsafe { oom_impl(layout) }
|
||
}
|