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Remove unnecessary parts from alloc_system

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This commit is contained in:
bjorn3 2021-02-21 10:49:55 +01:00
parent a8f3877c36
commit b36fd9d82b
2 changed files with 4 additions and 132 deletions
build_sysroot/alloc_system
Cargo.tomllib.rs

2
build_sysroot/alloc_system/Cargo.toml

@ -2,11 +2,13 @@
authors = ["The Rust Project Developers", "bjorn3 (edited to be usable outside the rust source)"]
name = "alloc_system"
version = "0.0.0"
[lib]
name = "alloc_system"
path = "lib.rs"
test = false
doc = false
[dependencies]
core = { path = "../sysroot_src/library/core" }
libc = { version = "0.2.43", features = ['rustc-dep-of-std'], default-features = false }

134
build_sysroot/alloc_system/lib.rs

@ -8,66 +8,24 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
#![no_std]
#![allow(unused_attributes)]
#![unstable(feature = "alloc_system",
reason = "this library is unlikely to be stabilized in its current \
form or name",
issue = "32838")]
#![feature(allocator_api)]
#![feature(core_intrinsics)]
#![feature(nll)]
#![feature(staged_api)]
#![feature(rustc_attrs)]
#![feature(alloc_layout_extra)]
#![cfg_attr(
all(target_arch = "wasm32", not(target_os = "emscripten")),
feature(integer_atomics, stdsimd)
)]
#![cfg_attr(any(unix, target_os = "redox"), feature(libc))]
// The minimum alignment guaranteed by the architecture. This value is used to
// add fast paths for low alignment values.
#[cfg(all(any(target_arch = "x86",
target_arch = "arm",
target_arch = "mips",
target_arch = "powerpc",
target_arch = "powerpc64",
target_arch = "asmjs",
target_arch = "wasm32")))]
#[allow(dead_code)]
target_arch = "powerpc64")))]
const MIN_ALIGN: usize = 8;
#[cfg(all(any(target_arch = "x86_64",
target_arch = "aarch64",
target_arch = "mips64",
target_arch = "s390x",
target_arch = "sparc64")))]
#[allow(dead_code)]
const MIN_ALIGN: usize = 16;
/// 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 can be used in a `static` item
/// with the `#[global_allocator]` attribute
/// to force the global allocator to be the system’s one.
/// (The default is jemalloc for executables, on some platforms.)
///
/// ```rust
/// use std::alloc::System;
///
/// #[global_allocator]
/// static A: System = System;
///
/// fn main() {
/// let a = Box::new(4); // Allocates from the system allocator.
/// println!("{}", a);
/// }
/// ```
///
/// It can also be used directly to allocate memory
/// independently of the standard library’s global allocator.
#[stable(feature = "alloc_system_type", since = "1.28.0")]
pub struct System;
#[cfg(any(windows, unix, target_os = "redox"))]
mod realloc_fallback {
@ -96,7 +54,6 @@ mod platform {
use MIN_ALIGN;
use System;
use core::alloc::{GlobalAlloc, Layout};
#[stable(feature = "alloc_system_type", since = "1.28.0")]
unsafe impl GlobalAlloc for System {
#[inline]
unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
@ -221,7 +178,6 @@ mod platform {
};
ptr as *mut u8
}
#[stable(feature = "alloc_system_type", since = "1.28.0")]
unsafe impl GlobalAlloc for System {
#[inline]
unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
@ -254,89 +210,3 @@ mod platform {
}
}
}
// This is an implementation of a global allocator on the wasm32 platform when
// emscripten is not in use. In that situation there's no actual runtime for us
// to lean on for allocation, so instead we provide our own!
//
// The wasm32 instruction set has two instructions for getting the current
// amount of memory and growing the amount of memory. These instructions are the
// foundation on which we're able to build an allocator, so we do so! Note that
// the instructions are also pretty "global" and this is the "global" allocator
// after all!
//
// The current allocator here is the `dlmalloc` crate which we've got included
// in the rust-lang/rust repository as a submodule. The crate is a port of
// dlmalloc.c from C to Rust and is basically just so we can have "pure Rust"
// for now which is currently technically required (can't link with C yet).
//
// The crate itself provides a global allocator which on wasm has no
// synchronization as there are no threads!
#[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))]
mod platform {
extern crate dlmalloc;
use core::alloc::{GlobalAlloc, Layout};
use System;
static mut DLMALLOC: dlmalloc::Dlmalloc = dlmalloc::DLMALLOC_INIT;
#[stable(feature = "alloc_system_type", since = "1.28.0")]
unsafe impl GlobalAlloc for System {
#[inline]
unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
let _lock = lock::lock();
DLMALLOC.malloc(layout.size(), layout.align())
}
#[inline]
unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
let _lock = lock::lock();
DLMALLOC.calloc(layout.size(), layout.align())
}
#[inline]
unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
let _lock = lock::lock();
DLMALLOC.free(ptr, layout.size(), layout.align())
}
#[inline]
unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
let _lock = lock::lock();
DLMALLOC.realloc(ptr, layout.size(), layout.align(), new_size)
}
}
#[cfg(target_feature = "atomics")]
mod lock {
use core::arch::wasm32;
use core::sync::atomic::{AtomicI32, Ordering::SeqCst};
static LOCKED: AtomicI32 = AtomicI32::new(0);
pub struct DropLock;
pub fn lock() -> DropLock {
loop {
if LOCKED.swap(1, SeqCst) == 0 {
return DropLock
}
unsafe {
let r = wasm32::atomic::wait_i32(
&LOCKED as *const AtomicI32 as *mut i32,
1, // expected value
-1, // timeout
);
debug_assert!(r == 0 || r == 1);
}
}
}
impl Drop for DropLock {
fn drop(&mut self) {
let r = LOCKED.swap(0, SeqCst);
debug_assert_eq!(r, 1);
unsafe {
wasm32::atomic::wake(
&LOCKED as *const AtomicI32 as *mut i32,
1, // only one thread
);
}
}
}
}
#[cfg(not(target_feature = "atomics"))]
mod lock {
#[inline]
pub fn lock() {} // no atomics, no threads, that's easy!
}
}