mirror of
https://github.com/rust-lang/rust.git
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343 lines
13 KiB
Rust
343 lines
13 KiB
Rust
// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
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// file at the top-level directory of this distribution and at
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// http://rust-lang.org/COPYRIGHT.
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//
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// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
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// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
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// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
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// option. This file may not be copied, modified, or distributed
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// except according to those terms.
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#![no_std]
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#![allow(unused_attributes)]
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#![unstable(feature = "alloc_system",
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reason = "this library is unlikely to be stabilized in its current \
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form or name",
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issue = "32838")]
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#![feature(allocator_api)]
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#![feature(core_intrinsics)]
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#![feature(nll)]
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#![feature(staged_api)]
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#![feature(rustc_attrs)]
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#![feature(alloc_layout_extra)]
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#![cfg_attr(
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all(target_arch = "wasm32", not(target_os = "emscripten")),
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feature(integer_atomics, stdsimd)
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)]
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#![cfg_attr(any(unix, target_os = "redox"), feature(libc))]
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// The minimum alignment guaranteed by the architecture. This value is used to
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// add fast paths for low alignment values.
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#[cfg(all(any(target_arch = "x86",
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target_arch = "arm",
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target_arch = "mips",
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target_arch = "powerpc",
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target_arch = "powerpc64",
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target_arch = "asmjs",
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target_arch = "wasm32")))]
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#[allow(dead_code)]
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const MIN_ALIGN: usize = 8;
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#[cfg(all(any(target_arch = "x86_64",
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target_arch = "aarch64",
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target_arch = "mips64",
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target_arch = "s390x",
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target_arch = "sparc64")))]
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#[allow(dead_code)]
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const MIN_ALIGN: usize = 16;
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/// The default memory allocator provided by the operating system.
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///
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/// This is based on `malloc` on Unix platforms and `HeapAlloc` on Windows,
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/// plus related functions.
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///
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/// This type can be used in a `static` item
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/// with the `#[global_allocator]` attribute
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/// to force the global allocator to be the system’s one.
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/// (The default is jemalloc for executables, on some platforms.)
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///
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/// ```rust
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/// use std::alloc::System;
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///
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/// #[global_allocator]
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/// static A: System = System;
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///
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/// fn main() {
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/// let a = Box::new(4); // Allocates from the system allocator.
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/// println!("{}", a);
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/// }
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/// ```
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///
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/// It can also be used directly to allocate memory
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/// independently of the standard library’s global allocator.
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#[stable(feature = "alloc_system_type", since = "1.28.0")]
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pub struct System;
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#[cfg(any(windows, unix, target_os = "redox"))]
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mod realloc_fallback {
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use core::alloc::{GlobalAlloc, Layout};
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use core::cmp;
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use core::ptr;
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impl super::System {
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pub(crate) unsafe fn realloc_fallback(&self, ptr: *mut u8, old_layout: Layout,
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new_size: usize) -> *mut u8 {
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// Docs for GlobalAlloc::realloc require this to be valid:
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let new_layout = Layout::from_size_align_unchecked(new_size, old_layout.align());
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let new_ptr = GlobalAlloc::alloc(self, new_layout);
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if !new_ptr.is_null() {
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let size = cmp::min(old_layout.size(), new_size);
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ptr::copy_nonoverlapping(ptr, new_ptr, size);
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GlobalAlloc::dealloc(self, ptr, old_layout);
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}
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new_ptr
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}
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}
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}
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#[cfg(any(unix, target_os = "redox"))]
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mod platform {
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extern crate libc;
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use core::ptr;
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use MIN_ALIGN;
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use System;
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use core::alloc::{GlobalAlloc, Layout};
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#[stable(feature = "alloc_system_type", since = "1.28.0")]
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unsafe impl GlobalAlloc for System {
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#[inline]
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unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
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if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
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libc::malloc(layout.size()) as *mut u8
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} else {
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#[cfg(target_os = "macos")]
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{
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if layout.align() > (1 << 31) {
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return ptr::null_mut()
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}
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}
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aligned_malloc(&layout)
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}
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}
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#[inline]
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unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
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if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
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libc::calloc(layout.size(), 1) as *mut u8
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} else {
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let ptr = self.alloc(layout.clone());
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if !ptr.is_null() {
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ptr::write_bytes(ptr, 0, layout.size());
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}
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ptr
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}
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}
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#[inline]
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unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
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libc::free(ptr as *mut libc::c_void)
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}
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#[inline]
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unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
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if layout.align() <= MIN_ALIGN && layout.align() <= new_size {
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libc::realloc(ptr as *mut libc::c_void, new_size) as *mut u8
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} else {
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self.realloc_fallback(ptr, layout, new_size)
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}
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}
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}
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#[cfg(any(target_os = "android",
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target_os = "hermit",
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target_os = "redox",
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target_os = "solaris"))]
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#[inline]
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unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 {
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// On android we currently target API level 9 which unfortunately
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// doesn't have the `posix_memalign` API used below. Instead we use
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// `memalign`, but this unfortunately has the property on some systems
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// where the memory returned cannot be deallocated by `free`!
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//
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// Upon closer inspection, however, this appears to work just fine with
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// Android, so for this platform we should be fine to call `memalign`
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// (which is present in API level 9). Some helpful references could
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// possibly be chromium using memalign [1], attempts at documenting that
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// memalign + free is ok [2] [3], or the current source of chromium
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// which still uses memalign on android [4].
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//
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// [1]: https://codereview.chromium.org/10796020/
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// [2]: https://code.google.com/p/android/issues/detail?id=35391
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// [3]: https://bugs.chromium.org/p/chromium/issues/detail?id=138579
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// [4]: https://chromium.googlesource.com/chromium/src/base/+/master/
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// /memory/aligned_memory.cc
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libc::memalign(layout.align(), layout.size()) as *mut u8
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}
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#[cfg(not(any(target_os = "android",
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target_os = "hermit",
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target_os = "redox",
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target_os = "solaris")))]
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#[inline]
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unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 {
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let mut out = ptr::null_mut();
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let ret = libc::posix_memalign(&mut out, layout.align(), layout.size());
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if ret != 0 {
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ptr::null_mut()
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} else {
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out as *mut u8
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}
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}
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}
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#[cfg(windows)]
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#[allow(nonstandard_style)]
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mod platform {
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use MIN_ALIGN;
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use System;
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use core::alloc::{GlobalAlloc, Layout};
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type LPVOID = *mut u8;
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type HANDLE = LPVOID;
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type SIZE_T = usize;
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type DWORD = u32;
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type BOOL = i32;
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extern "system" {
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fn GetProcessHeap() -> HANDLE;
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fn HeapAlloc(hHeap: HANDLE, dwFlags: DWORD, dwBytes: SIZE_T) -> LPVOID;
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fn HeapReAlloc(hHeap: HANDLE, dwFlags: DWORD, lpMem: LPVOID, dwBytes: SIZE_T) -> LPVOID;
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fn HeapFree(hHeap: HANDLE, dwFlags: DWORD, lpMem: LPVOID) -> BOOL;
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fn GetLastError() -> DWORD;
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}
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#[repr(C)]
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struct Header(*mut u8);
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const HEAP_ZERO_MEMORY: DWORD = 0x00000008;
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unsafe fn get_header<'a>(ptr: *mut u8) -> &'a mut Header {
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&mut *(ptr as *mut Header).offset(-1)
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}
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unsafe fn align_ptr(ptr: *mut u8, align: usize) -> *mut u8 {
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let aligned = ptr.add(align - (ptr as usize & (align - 1)));
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*get_header(aligned) = Header(ptr);
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aligned
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}
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#[inline]
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unsafe fn allocate_with_flags(layout: Layout, flags: DWORD) -> *mut u8 {
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let ptr = if layout.align() <= MIN_ALIGN {
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HeapAlloc(GetProcessHeap(), flags, layout.size())
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} else {
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let size = layout.size() + layout.align();
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let ptr = HeapAlloc(GetProcessHeap(), flags, size);
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if ptr.is_null() {
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ptr
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} else {
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align_ptr(ptr, layout.align())
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}
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};
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ptr as *mut u8
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}
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#[stable(feature = "alloc_system_type", since = "1.28.0")]
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unsafe impl GlobalAlloc for System {
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#[inline]
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unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
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allocate_with_flags(layout, 0)
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}
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#[inline]
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unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
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allocate_with_flags(layout, HEAP_ZERO_MEMORY)
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}
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#[inline]
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unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
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if layout.align() <= MIN_ALIGN {
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let err = HeapFree(GetProcessHeap(), 0, ptr as LPVOID);
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debug_assert!(err != 0, "Failed to free heap memory: {}",
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GetLastError());
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} else {
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let header = get_header(ptr);
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let err = HeapFree(GetProcessHeap(), 0, header.0 as LPVOID);
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debug_assert!(err != 0, "Failed to free heap memory: {}",
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GetLastError());
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}
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}
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#[inline]
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unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
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if layout.align() <= MIN_ALIGN {
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HeapReAlloc(GetProcessHeap(), 0, ptr as LPVOID, new_size) as *mut u8
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} else {
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self.realloc_fallback(ptr, layout, new_size)
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}
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}
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}
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}
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// This is an implementation of a global allocator on the wasm32 platform when
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// emscripten is not in use. In that situation there's no actual runtime for us
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// to lean on for allocation, so instead we provide our own!
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//
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// The wasm32 instruction set has two instructions for getting the current
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// amount of memory and growing the amount of memory. These instructions are the
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// foundation on which we're able to build an allocator, so we do so! Note that
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// the instructions are also pretty "global" and this is the "global" allocator
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// after all!
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//
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// The current allocator here is the `dlmalloc` crate which we've got included
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// in the rust-lang/rust repository as a submodule. The crate is a port of
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// dlmalloc.c from C to Rust and is basically just so we can have "pure Rust"
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// for now which is currently technically required (can't link with C yet).
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//
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// The crate itself provides a global allocator which on wasm has no
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// synchronization as there are no threads!
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#[cfg(all(target_arch = "wasm32", not(target_os = "emscripten")))]
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mod platform {
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extern crate dlmalloc;
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use core::alloc::{GlobalAlloc, Layout};
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use System;
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static mut DLMALLOC: dlmalloc::Dlmalloc = dlmalloc::DLMALLOC_INIT;
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#[stable(feature = "alloc_system_type", since = "1.28.0")]
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unsafe impl GlobalAlloc for System {
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#[inline]
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unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
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let _lock = lock::lock();
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DLMALLOC.malloc(layout.size(), layout.align())
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}
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#[inline]
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unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
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let _lock = lock::lock();
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DLMALLOC.calloc(layout.size(), layout.align())
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}
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#[inline]
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unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
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let _lock = lock::lock();
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DLMALLOC.free(ptr, layout.size(), layout.align())
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}
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#[inline]
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unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
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let _lock = lock::lock();
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DLMALLOC.realloc(ptr, layout.size(), layout.align(), new_size)
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}
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}
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#[cfg(target_feature = "atomics")]
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mod lock {
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use core::arch::wasm32;
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use core::sync::atomic::{AtomicI32, Ordering::SeqCst};
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static LOCKED: AtomicI32 = AtomicI32::new(0);
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pub struct DropLock;
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pub fn lock() -> DropLock {
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loop {
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if LOCKED.swap(1, SeqCst) == 0 {
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return DropLock
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}
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unsafe {
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let r = wasm32::atomic::wait_i32(
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&LOCKED as *const AtomicI32 as *mut i32,
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1, // expected value
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-1, // timeout
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);
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debug_assert!(r == 0 || r == 1);
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}
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}
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}
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impl Drop for DropLock {
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fn drop(&mut self) {
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let r = LOCKED.swap(0, SeqCst);
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debug_assert_eq!(r, 1);
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unsafe {
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wasm32::atomic::wake(
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&LOCKED as *const AtomicI32 as *mut i32,
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1, // only one thread
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);
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}
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}
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}
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}
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#[cfg(not(target_feature = "atomics"))]
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mod lock {
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#[inline]
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pub fn lock() {} // no atomics, no threads, that's easy!
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}
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}
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