Expand description
Memory allocation APIs.
In a given program, the standard library has one “global” memory allocator
that is used for example by Box<T>
and Vec<T>
.
Currently the default global allocator is unspecified. Libraries, however,
like cdylib
s and staticlib
s are guaranteed to use the System
by
default.
§The #[global_allocator]
attribute
This attribute allows configuring the choice of global allocator. You can use this to implement a completely custom global allocator to route all default allocation requests to a custom object.
use std::alloc::{GlobalAlloc, System, Layout};
struct MyAllocator;
unsafe impl GlobalAlloc for MyAllocator {
unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
System.alloc(layout)
}
unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
System.dealloc(ptr, layout)
}
}
#[global_allocator]
static GLOBAL: MyAllocator = MyAllocator;
fn main() {
// This `Vec` will allocate memory through `GLOBAL` above
let mut v = Vec::new();
v.push(1);
}
The attribute is used on a static
item whose type implements the
GlobalAlloc
trait. This type can be provided by an external library:
The #[global_allocator]
can only be used once in a crate
or its recursive dependencies.
Structs§
- Layout of a block of memory.
- The parameters given to
Layout::from_size_align
or some otherLayout
constructor do not satisfy its documented constraints. - The default memory allocator provided by the operating system.
- Alloc
Error Experimental TheAllocError
error indicates an allocation failure that may be due to resource exhaustion or to something wrong when combining the given input arguments with this allocator. - Global
Experimental The global memory allocator.
Traits§
- A memory allocator that can be registered as the standard library’s default through the
#[global_allocator]
attribute. - Allocator
Experimental An implementation ofAllocator
can allocate, grow, shrink, and deallocate arbitrary blocks of data described viaLayout
.
Functions§
- Allocates memory with the global allocator.
- Allocates zero-initialized memory with the global allocator.
- Deallocates memory with the global allocator.
- Signals a memory allocation error.
- Reallocates memory with the global allocator.
- set_
alloc_ error_ hook Experimental Registers a custom allocation error hook, replacing any that was previously registered. - take_
alloc_ error_ hook Experimental Unregisters the current allocation error hook, returning it.
Type Aliases§
- Layout
Err Deprecated