pub struct 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);
}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));
}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.
impl AllocRef for System[src]
fn alloc(&mut self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr>[src]
fn alloc_zeroed(&mut self, layout: Layout) -> Result<NonNull<[u8]>, AllocErr>[src]
unsafe fn dealloc(&mut self, ptr: NonNull<u8>, layout: Layout)[src]
unsafe fn grow(
    &mut self,
    ptr: NonNull<u8>,
    layout: Layout,
    new_size: usize
) -> Result<NonNull<[u8]>, AllocErr>[src]
unsafe fn grow_zeroed(
    &mut self,
    ptr: NonNull<u8>,
    layout: Layout,
    new_size: usize
) -> Result<NonNull<[u8]>, AllocErr>[src]
unsafe fn shrink(
    &mut self,
    ptr: NonNull<u8>,
    layout: Layout,
    new_size: usize
) -> Result<NonNull<[u8]>, AllocErr>[src]
fn by_ref(&mut self) -> &mut SelfⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,Â
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,Â
type Item = <I as Iterator>::Item;
impl<R:Â Read + ?Sized, '_> Read for &'_ mut R
impl<W:Â Write + ?Sized, '_> Write for &'_ mut W
[src]
impl Clone for System[src]
impl Copy for System[src]
impl Debug for System[src]
impl Default for System[src]
impl GlobalAlloc for System[src]
impl RefUnwindSafe for Systemimpl Send for Systemimpl Sync for Systemimpl Unpin for Systemimpl UnwindSafe for Systemimpl<T> Any for T where
    T: 'static + ?Sized, [src]
impl<T> Borrow<T> for T where
    T: ?Sized, [src]
fn borrow(&self) -> &TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,Â
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,Â
type Item = <I as Iterator>::Item;
impl<R:Â Read + ?Sized, '_> Read for &'_ mut R
impl<W:Â Write + ?Sized, '_> Write for &'_ mut W
[src]
impl<T> BorrowMut<T> for T where
    T: ?Sized, [src]
fn borrow_mut(&mut self) -> &mut TⓘNotable traits for &'_ mut F
impl<'_, F> Future for &'_ mut F where
    F: Unpin + Future + ?Sized,Â
type Output = <F as Future>::Output;
impl<'_, I> Iterator for &'_ mut I where
    I: Iterator + ?Sized,Â
type Item = <I as Iterator>::Item;
impl<R:Â Read + ?Sized, '_> Read for &'_ mut R
impl<W:Â Write + ?Sized, '_> Write for &'_ mut W
[src]
impl<T> From<T> for T[src]
impl<T, U> Into<U> for T where
    U: From<T>, [src]
impl<T> ToOwned for T where
    T: Clone, [src]
type Owned = TThe resulting type after obtaining ownership.
fn to_owned(&self) -> T[src]
fn clone_into(&self, target: &mut T)[src]
impl<T, U> TryFrom<U> for T where
    U: Into<T>, [src]
type Error = InfallibleThe type returned in the event of a conversion error.
fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>[src]
impl<T, U> TryInto<U> for T where
    U: TryFrom<T>, [src]
© 2010 The Rust Project Developers
Licensed under the Apache License, Version 2.0 or the MIT license, at your option.
https://doc.rust-lang.org/std/alloc/struct.System.html