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// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements. See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership. The ASF licenses this file
// to you under the Apache License, Version 2.0 (the
// "License"); you may not use this file except in compliance
// with the License. You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing,
// software distributed under the License is distributed on an
// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
// KIND, either express or implied. See the License for the
// specific language governing permissions and limitations
// under the License..
//! 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.
//!
//! ```rust
//! 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:
//!
//! ```rust,ignore (demonstrates crates.io usage)
//! use jemallocator::Jemalloc;
//!
//! #[global_allocator]
//! static GLOBAL: Jemalloc = Jemalloc;
//!
//! fn main() {}
//! ```
//!
//! The `#[global_allocator]` can only be used once in a crate
//! or its recursive dependencies.
use core::sync::atomic::{AtomicPtr, Ordering};
use core::{mem, ptr};
#[doc(inline)]
pub use alloc_crate::alloc::*;
pub use sgx_alloc::System;
static HOOK: AtomicPtr<()> = AtomicPtr::new(ptr::null_mut());
/// Registers a custom allocation error hook, replacing any that was previously registered.
///
/// The allocation error hook is invoked when an infallible memory allocation fails, before
/// the runtime aborts. The default hook prints a message to standard error,
/// but this behavior can be customized with the [`set_alloc_error_hook`] and
/// [`take_alloc_error_hook`] functions.
///
/// The hook is provided with a `Layout` struct which contains information
/// about the allocation that failed.
///
/// The allocation error hook is a global resource.
///
/// # Examples
///
/// ```
/// #![feature(alloc_error_hook)]
///
/// use std::alloc::{Layout, set_alloc_error_hook};
///
/// fn custom_alloc_error_hook(layout: Layout) {
/// panic!("memory allocation of {} bytes failed", layout.size());
/// }
///
/// set_alloc_error_hook(custom_alloc_error_hook);
/// ```
pub fn set_alloc_error_hook(hook: fn(Layout)) {
HOOK.store(hook as *mut (), Ordering::SeqCst);
}
/// Unregisters the current allocation error hook, returning it.
///
/// *See also the function [`set_alloc_error_hook`].*
///
/// If no custom hook is registered, the default hook will be returned.
pub fn take_alloc_error_hook() -> fn(Layout) {
let hook = HOOK.swap(ptr::null_mut(), Ordering::SeqCst);
if hook.is_null() { default_alloc_error_hook } else { unsafe { mem::transmute(hook) } }
}
fn default_alloc_error_hook(layout: Layout) {
extern "Rust" {
// This symbol is emitted by rustc next to __rust_alloc_error_handler.
// Its value depends on the -Zoom={panic,abort} compiler option.
static __rust_alloc_error_handler_should_panic: u8;
}
#[allow(unused_unsafe)]
if unsafe { __rust_alloc_error_handler_should_panic != 0 } {
panic!("memory allocation of {} bytes failed\n", layout.size());
} else {
rtprintpanic!("memory allocation of {} bytes failed\n", layout.size());
}
}
#[doc(hidden)]
#[alloc_error_handler]
pub fn rust_oom(layout: Layout) -> ! {
let hook = HOOK.load(Ordering::SeqCst);
let hook: fn(Layout) =
if hook.is_null() { default_alloc_error_hook } else { unsafe { mem::transmute(hook) } };
hook(layout);
crate::sys::abort_internal()
}
#[doc(hidden)]
#[allow(unused_attributes)]
pub mod __default_lib_allocator {
use super::{GlobalAlloc, Layout, System};
// These magic symbol names are used as a fallback for implementing the
// `__rust_alloc` etc symbols (see `src/liballoc/alloc.rs`) when there is
// no `#[global_allocator]` attribute.
// for symbol names src/librustc_ast/expand/allocator.rs
// for signatures src/librustc_allocator/lib.rs
// linkage directives are provided as part of the current compiler allocator
// ABI
#[rustc_std_internal_symbol]
pub unsafe extern "C" fn __rdl_alloc(size: usize, align: usize) -> *mut u8 {
// SAFETY: see the guarantees expected by `Layout::from_size_align` and
// `GlobalAlloc::alloc`.
let layout = Layout::from_size_align_unchecked(size, align);
System.alloc(layout)
}
#[rustc_std_internal_symbol]
pub unsafe extern "C" fn __rdl_dealloc(ptr: *mut u8, size: usize, align: usize) {
// SAFETY: see the guarantees expected by `Layout::from_size_align` and
// `GlobalAlloc::dealloc`.
System.dealloc(ptr, Layout::from_size_align_unchecked(size, align))
}
#[rustc_std_internal_symbol]
pub unsafe extern "C" fn __rdl_realloc(
ptr: *mut u8,
old_size: usize,
align: usize,
new_size: usize,
) -> *mut u8 {
// SAFETY: see the guarantees expected by `Layout::from_size_align` and
// `GlobalAlloc::realloc`.
let old_layout = Layout::from_size_align_unchecked(old_size, align);
System.realloc(ptr, old_layout, new_size)
}
#[rustc_std_internal_symbol]
pub unsafe extern "C" fn __rdl_alloc_zeroed(size: usize, align: usize) -> *mut u8 {
// SAFETY: see the guarantees expected by `Layout::from_size_align` and
// `GlobalAlloc::alloc_zeroed`.
let layout = Layout::from_size_align_unchecked(size, align);
System.alloc_zeroed(layout)
}
}