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alloc_system.rs
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// SPDX-License-Identifier: MIT OR Apache-2.0
// SPDX-FileCopyrightText: The Rust Project Developers (see https://thanks.rust-lang.org)
#![no_std]
#![feature(allocator_api, rustc_private)]
#![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(any(target_arch = "x86",
target_arch = "arm",
target_arch = "mips",
target_arch = "mips32r6",
target_arch = "powerpc",
target_arch = "powerpc64"))]
const MIN_ALIGN: usize = 8;
#[cfg(any(target_arch = "x86_64",
target_arch = "aarch64",
target_arch = "loongarch64",
target_arch = "mips64",
target_arch = "mips64r6",
target_arch = "s390x",
target_arch = "sparc64"))]
const MIN_ALIGN: usize = 16;
pub struct System;
#[cfg(any(windows, unix, target_os = "redox"))]
mod realloc_fallback {
use core::alloc::{GlobalAlloc, Layout};
use core::cmp;
use core::ptr;
impl super::System {
pub(crate) unsafe fn realloc_fallback(&self, ptr: *mut u8, old_layout: Layout,
new_size: usize) -> *mut u8 {
// Docs for GlobalAlloc::realloc require this to be valid:
let new_layout = Layout::from_size_align_unchecked(new_size, old_layout.align());
let new_ptr = GlobalAlloc::alloc(self, new_layout);
if !new_ptr.is_null() {
let size = cmp::min(old_layout.size(), new_size);
ptr::copy_nonoverlapping(ptr, new_ptr, size);
GlobalAlloc::dealloc(self, ptr, old_layout);
}
new_ptr
}
}
}
#[cfg(any(unix, target_os = "redox"))]
mod platform {
extern crate libc;
use core::ptr;
use MIN_ALIGN;
use System;
use core::alloc::{GlobalAlloc, Layout};
unsafe impl GlobalAlloc for System {
#[inline]
unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
libc::malloc(layout.size()) as *mut u8
} else {
#[cfg(target_os = "macos")]
{
if layout.align() > (1 << 31) {
return ptr::null_mut()
}
}
aligned_malloc(&layout)
}
}
#[inline]
unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
if layout.align() <= MIN_ALIGN && layout.align() <= layout.size() {
libc::calloc(layout.size(), 1) as *mut u8
} else {
let ptr = self.alloc(layout.clone());
if !ptr.is_null() {
ptr::write_bytes(ptr, 0, layout.size());
}
ptr
}
}
#[inline]
unsafe fn dealloc(&self, ptr: *mut u8, _layout: Layout) {
libc::free(ptr as *mut libc::c_void)
}
#[inline]
unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
if layout.align() <= MIN_ALIGN && layout.align() <= new_size {
libc::realloc(ptr as *mut libc::c_void, new_size) as *mut u8
} else {
self.realloc_fallback(ptr, layout, new_size)
}
}
}
#[cfg(any(target_os = "android",
target_os = "hermit",
target_os = "redox",
target_os = "solaris"))]
#[inline]
unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 {
// On android we currently target API level 9 which unfortunately
// doesn't have the `posix_memalign` API used below. Instead we use
// `memalign`, but this unfortunately has the property on some systems
// where the memory returned cannot be deallocated by `free`!
//
// Upon closer inspection, however, this appears to work just fine with
// Android, so for this platform we should be fine to call `memalign`
// (which is present in API level 9). Some helpful references could
// possibly be chromium using memalign [1], attempts at documenting that
// memalign + free is ok [2] [3], or the current source of chromium
// which still uses memalign on android [4].
//
// [1]: https://codereview.chromium.org/10796020/
// [2]: https://code.google.com/p/android/issues/detail?id=35391
// [3]: https://bugs.chromium.org/p/chromium/issues/detail?id=138579
// [4]: https://chromium.googlesource.com/chromium/src/base/+/master/
// /memory/aligned_memory.cc
libc::memalign(layout.align(), layout.size()) as *mut u8
}
#[cfg(not(any(target_os = "android",
target_os = "hermit",
target_os = "redox",
target_os = "solaris")))]
#[inline]
unsafe fn aligned_malloc(layout: &Layout) -> *mut u8 {
let mut out = ptr::null_mut();
let ret = libc::posix_memalign(&mut out, layout.align(), layout.size());
if ret != 0 {
ptr::null_mut()
} else {
out as *mut u8
}
}
}
#[cfg(windows)]
#[allow(nonstandard_style)]
mod platform {
use MIN_ALIGN;
use System;
use core::alloc::{GlobalAlloc, Layout};
type LPVOID = *mut u8;
type HANDLE = LPVOID;
type SIZE_T = usize;
type DWORD = u32;
type BOOL = i32;
extern "system" {
fn GetProcessHeap() -> HANDLE;
fn HeapAlloc(hHeap: HANDLE, dwFlags: DWORD, dwBytes: SIZE_T) -> LPVOID;
fn HeapReAlloc(hHeap: HANDLE, dwFlags: DWORD, lpMem: LPVOID, dwBytes: SIZE_T) -> LPVOID;
fn HeapFree(hHeap: HANDLE, dwFlags: DWORD, lpMem: LPVOID) -> BOOL;
fn GetLastError() -> DWORD;
}
#[repr(C)]
struct Header(*mut u8);
const HEAP_ZERO_MEMORY: DWORD = 0x00000008;
unsafe fn get_header<'a>(ptr: *mut u8) -> &'a mut Header {
&mut *(ptr as *mut Header).sub(1)
}
unsafe fn align_ptr(ptr: *mut u8, align: usize) -> *mut u8 {
let aligned = ptr.add(align - (ptr as usize & (align - 1)));
*get_header(aligned) = Header(ptr);
aligned
}
#[inline]
unsafe fn allocate_with_flags(layout: Layout, flags: DWORD) -> *mut u8 {
let ptr = if layout.align() <= MIN_ALIGN {
HeapAlloc(GetProcessHeap(), flags, layout.size())
} else {
let size = layout.size() + layout.align();
let ptr = HeapAlloc(GetProcessHeap(), flags, size);
if ptr.is_null() {
ptr
} else {
align_ptr(ptr, layout.align())
}
};
ptr as *mut u8
}
unsafe impl GlobalAlloc for System {
#[inline]
unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
allocate_with_flags(layout, 0)
}
#[inline]
unsafe fn alloc_zeroed(&self, layout: Layout) -> *mut u8 {
allocate_with_flags(layout, HEAP_ZERO_MEMORY)
}
#[inline]
unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
if layout.align() <= MIN_ALIGN {
let err = HeapFree(GetProcessHeap(), 0, ptr as LPVOID);
debug_assert!(err != 0, "Failed to free heap memory: {}",
GetLastError());
} else {
let header = get_header(ptr);
let err = HeapFree(GetProcessHeap(), 0, header.0 as LPVOID);
debug_assert!(err != 0, "Failed to free heap memory: {}",
GetLastError());
}
}
#[inline]
unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
if layout.align() <= MIN_ALIGN {
HeapReAlloc(GetProcessHeap(), 0, ptr as LPVOID, new_size) as *mut u8
} else {
self.realloc_fallback(ptr, layout, new_size)
}
}
}
}