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Introduce get_process_heap and fix atomic ordering.

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This commit is contained in:
Christiaan Dirkx 2021-04-02 17:37:52 +02:00
parent 4cce9e3db2
commit c86e0985f9
1 changed files with 22 additions and 13 deletions
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35
library/std/src/sys/windows/alloc.rs
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@ -89,10 +89,10 @@ extern "system" {
static HEAP: AtomicPtr<c_void> = AtomicPtr::new(ptr::null_mut());
// Get a handle to the default heap of the current process, or null if the operation fails.
// SAFETY: If this operation is successful, `HEAP` will be successfully initialized and contain
// If this operation is successful, `HEAP` will be successfully initialized and contain
// a non-null handle returned by `GetProcessHeap`.
#[inline]
unsafe fn init_or_get_process_heap() -> c::HANDLE {
fn init_or_get_process_heap() -> c::HANDLE {
let heap = HEAP.load(Ordering::Relaxed);
if heap.is_null() {
// `HEAP` has not yet been successfully initialized
@ -100,7 +100,7 @@ unsafe fn init_or_get_process_heap() -> c::HANDLE {
if !heap.is_null() {
// SAFETY: No locking is needed because within the same process,
// successful calls to `GetProcessHeap` will always return the same value, even on different threads.
HEAP.store(heap, Ordering::Relaxed);
HEAP.store(heap, Ordering::Release);
// SAFETY: `HEAP` contains a non-null handle returned by `GetProcessHeap`
heap
@ -114,16 +114,25 @@ unsafe fn init_or_get_process_heap() -> c::HANDLE {
}
}
// Get a non-null handle to the default heap of the current process.
// SAFETY: `HEAP` must have been successfully initialized.
#[inline]
unsafe fn get_process_heap() -> c::HANDLE {
HEAP.load(Ordering::Acquire)
}
// Header containing a pointer to the start of an allocated block.
// SAFETY: Size and alignment must be <= `MIN_ALIGN`.
#[repr(C)]
struct Header(*mut u8);
// Allocate a block of optionally zeroed memory for a given `layout`.
// SAFETY: Returns a pointer satisfying the guarantees of `System` about allocated pointers.
// SAFETY: Returns a pointer satisfying the guarantees of `System` about allocated pointers,
// or null if the operation fails. If this returns non-null `HEAP` will have been successfully
// initialized.
#[inline]
unsafe fn allocate(layout: Layout, zeroed: bool) -> *mut u8 {
let heap = unsafe { init_or_get_process_heap() };
let heap = init_or_get_process_heap();
if heap.is_null() {
// Allocation has failed, could not get the current process heap.
return ptr::null_mut();
@ -209,11 +218,11 @@ unsafe impl GlobalAlloc for System {
};
// SAFETY: because `ptr` has been successfully allocated with this allocator,
// `HEAP` must have been successfully initialized and contain a non-null handle
// returned by `GetProcessHeap`.
let heap = HEAP.load(Ordering::Relaxed);
// `HEAP` must have been successfully initialized.
let heap = unsafe { get_process_heap() };
// SAFETY: `block` is a pointer to the start of an allocated block.
// SAFETY: `heap` is a non-null handle returned by `GetProcessHeap`,
// `block` is a pointer to the start of an allocated block.
unsafe {
let err = HeapFree(heap, 0, block as c::LPVOID);
debug_assert!(err != 0, "Failed to free heap memory: {}", c::GetLastError());
@ -224,11 +233,11 @@ unsafe impl GlobalAlloc for System {
unsafe fn realloc(&self, ptr: *mut u8, layout: Layout, new_size: usize) -> *mut u8 {
if layout.align() <= MIN_ALIGN {
// SAFETY: because `ptr` has been successfully allocated with this allocator,
// `HEAP` must have been successfully initialized and contain a non-null handle
// returned by `GetProcessHeap`.
let heap = HEAP.load(Ordering::Relaxed);
// `HEAP` must have been successfully initialized.
let heap = unsafe { get_process_heap() };
// SAFETY: `ptr` is a pointer to the start of an allocated block.
// SAFETY: `heap` is a non-null handle returned by `GetProcessHeap`,
// `ptr` is a pointer to the start of an allocated block.
// The returned pointer points to the start of an allocated block.
unsafe { HeapReAlloc(heap, 0, ptr as c::LPVOID, new_size) as *mut u8 }
} else {