1.28.0[−][src]Struct std::alloc::System
The default memory allocator provided by the operating system.
This is based on malloc
on Unix platforms and HeapAlloc
on Windows,
plus related functions.
This type implements the GlobalAlloc
trait and Rust programs by default
work as if they had this definition:
use std::alloc::System; #[global_allocator] static A: System = System; fn main() { let a = Box::new(4); // Allocates from the system allocator. println!("{}", a); }Run
You can also define your own wrapper around System
if you'd like, such as
keeping track of the number of all bytes allocated:
use std::alloc::{System, GlobalAlloc, Layout}; use std::sync::atomic::{AtomicUsize, Ordering::SeqCst}; struct Counter; static ALLOCATED: AtomicUsize = AtomicUsize::new(0); unsafe impl GlobalAlloc for Counter { unsafe fn alloc(&self, layout: Layout) -> *mut u8 { let ret = System.alloc(layout); if !ret.is_null() { ALLOCATED.fetch_add(layout.size(), SeqCst); } return ret } unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) { System.dealloc(ptr, layout); ALLOCATED.fetch_sub(layout.size(), SeqCst); } } #[global_allocator] static A: Counter = Counter; fn main() { println!("allocated bytes before main: {}", ALLOCATED.load(SeqCst)); }Run
It can also be used directly to allocate memory independently of whatever
global allocator has been selected for a Rust program. For example if a Rust
program opts in to using jemalloc as the global allocator, System
will
still allocate memory using malloc
and HeapAlloc
.
Trait Implementations
impl Debug for System
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impl Copy for System
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impl Clone for System
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impl Default for System
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impl GlobalAlloc for System
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unsafe fn alloc(&self, layout: Layout) -> *mut u8
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unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8
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unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout)
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unsafe fn realloc(
&self,
ptr: *mut u8,
layout: Layout,
new_size: usize
) -> *mut u8
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&self,
ptr: *mut u8,
layout: Layout,
new_size: usize
) -> *mut u8
impl Alloc for System
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unsafe fn alloc(&mut self, layout: Layout) -> Result<NonNull<u8>, AllocErr>
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unsafe fn alloc_zeroed(
&mut self,
layout: Layout
) -> Result<NonNull<u8>, AllocErr>
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&mut self,
layout: Layout
) -> Result<NonNull<u8>, AllocErr>
unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout)
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unsafe fn realloc(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize
) -> Result<NonNull<u8>, AllocErr>
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&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize
) -> Result<NonNull<u8>, AllocErr>
fn usable_size(&self, layout: &Layout) -> (usize, usize)
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unsafe fn alloc_excess(&mut self, layout: Layout) -> Result<Excess, AllocErr>
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unsafe fn realloc_excess(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize
) -> Result<Excess, AllocErr>
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&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize
) -> Result<Excess, AllocErr>
unsafe fn grow_in_place(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize
) -> Result<(), CannotReallocInPlace>
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&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize
) -> Result<(), CannotReallocInPlace>
unsafe fn shrink_in_place(
&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize
) -> Result<(), CannotReallocInPlace>
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&mut self,
ptr: NonNull<u8>,
layout: Layout,
new_size: usize
) -> Result<(), CannotReallocInPlace>
fn alloc_one<T>(&mut self) -> Result<NonNull<T>, AllocErr>
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unsafe fn dealloc_one<T>(&mut self, ptr: NonNull<T>)
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fn alloc_array<T>(&mut self, n: usize) -> Result<NonNull<T>, AllocErr>
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unsafe fn realloc_array<T>(
&mut self,
ptr: NonNull<T>,
n_old: usize,
n_new: usize
) -> Result<NonNull<T>, AllocErr>
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&mut self,
ptr: NonNull<T>,
n_old: usize,
n_new: usize
) -> Result<NonNull<T>, AllocErr>
unsafe fn dealloc_array<T>(
&mut self,
ptr: NonNull<T>,
n: usize
) -> Result<(), AllocErr>
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&mut self,
ptr: NonNull<T>,
n: usize
) -> Result<(), AllocErr>
Auto Trait Implementations
impl UnwindSafe for System
impl RefUnwindSafe for System
impl Unpin for System
impl Send for System
impl Sync for System
Blanket Implementations
impl<T> From<T> for T
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impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
type Error = Infallible
The type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,
type Error = <U as TryFrom<T>>::Error
The type returned in the event of a conversion error.
fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>
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impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
ⓘImportant traits for &'_ mut Ffn borrow_mut(&mut self) -> &mut T
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impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> ToOwned for T where
T: Clone,
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T: Clone,