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Auto merge of #119433 - taiki-e:rc-uninit-ref, r=Nilstrieb
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rc,sync: Do not create references to uninitialized values

Closes #119241

r? `@RalfJung`
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@bors
bors committed Jan 23, 2024
2 parents 6265a95 + 4e973b0 commit dfe53af
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Showing 2 changed files with 25 additions and 20 deletions.
27 changes: 16 additions & 11 deletions library/alloc/src/rc.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1886,10 +1886,10 @@ impl<T: ?Sized> Rc<T> {
// Initialize the RcBox
let inner = mem_to_rcbox(ptr.as_non_null_ptr().as_ptr());
unsafe {
debug_assert_eq!(Layout::for_value(&*inner), layout);
debug_assert_eq!(Layout::for_value_raw(inner), layout);

ptr::write(&mut (*inner).strong, Cell::new(1));
ptr::write(&mut (*inner).weak, Cell::new(1));
ptr::addr_of_mut!((*inner).strong).write(Cell::new(1));
ptr::addr_of_mut!((*inner).weak).write(Cell::new(1));
}

Ok(inner)
Expand All @@ -1903,7 +1903,7 @@ impl<T: ?Sized, A: Allocator> Rc<T, A> {
// Allocate for the `RcBox<T>` using the given value.
unsafe {
Rc::<T>::allocate_for_layout(
Layout::for_value(&*ptr),
Layout::for_value_raw(ptr),
|layout| alloc.allocate(layout),
|mem| mem.with_metadata_of(ptr as *const RcBox<T>),
)
Expand All @@ -1919,7 +1919,7 @@ impl<T: ?Sized, A: Allocator> Rc<T, A> {
// Copy value as bytes
ptr::copy_nonoverlapping(
&*src as *const T as *const u8,
&mut (*ptr).value as *mut _ as *mut u8,
ptr::addr_of_mut!((*ptr).value) as *mut u8,
value_size,
);

Expand Down Expand Up @@ -1953,7 +1953,11 @@ impl<T> Rc<[T]> {
unsafe fn copy_from_slice(v: &[T]) -> Rc<[T]> {
unsafe {
let ptr = Self::allocate_for_slice(v.len());
ptr::copy_nonoverlapping(v.as_ptr(), &mut (*ptr).value as *mut [T] as *mut T, v.len());
ptr::copy_nonoverlapping(
v.as_ptr(),
ptr::addr_of_mut!((*ptr).value) as *mut T,
v.len(),
);
Self::from_ptr(ptr)
}
}
Expand Down Expand Up @@ -1988,10 +1992,10 @@ impl<T> Rc<[T]> {
let ptr = Self::allocate_for_slice(len);

let mem = ptr as *mut _ as *mut u8;
let layout = Layout::for_value(&*ptr);
let layout = Layout::for_value_raw(ptr);

// Pointer to first element
let elems = &mut (*ptr).value as *mut [T] as *mut T;
let elems = ptr::addr_of_mut!((*ptr).value) as *mut T;

let mut guard = Guard { mem: NonNull::new_unchecked(mem), elems, layout, n_elems: 0 };

Expand Down Expand Up @@ -2097,7 +2101,8 @@ unsafe impl<#[may_dangle] T: ?Sized, A: Allocator> Drop for Rc<T, A> {
self.inner().dec_weak();

if self.inner().weak() == 0 {
self.alloc.deallocate(self.ptr.cast(), Layout::for_value(self.ptr.as_ref()));
self.alloc
.deallocate(self.ptr.cast(), Layout::for_value_raw(self.ptr.as_ptr()));
}
}
}
Expand Down Expand Up @@ -2525,7 +2530,7 @@ impl<T, A: Allocator> From<Vec<T, A>> for Rc<[T], A> {
let (vec_ptr, len, cap, alloc) = v.into_raw_parts_with_alloc();

let rc_ptr = Self::allocate_for_slice_in(len, &alloc);
ptr::copy_nonoverlapping(vec_ptr, &mut (*rc_ptr).value as *mut [T] as *mut T, len);
ptr::copy_nonoverlapping(vec_ptr, ptr::addr_of_mut!((*rc_ptr).value) as *mut T, len);

// Create a `Vec<T, &A>` with length 0, to deallocate the buffer
// without dropping its contents or the allocator
Expand Down Expand Up @@ -3515,7 +3520,7 @@ unsafe impl<#[may_dangle] T> Drop for UniqueRc<T> {
self.ptr.as_ref().dec_weak();

if self.ptr.as_ref().weak() == 0 {
Global.deallocate(self.ptr.cast(), Layout::for_value(self.ptr.as_ref()));
Global.deallocate(self.ptr.cast(), Layout::for_value_raw(self.ptr.as_ptr()));
}
}
}
Expand Down
18 changes: 9 additions & 9 deletions library/alloc/src/sync.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1828,11 +1828,11 @@ impl<T: ?Sized> Arc<T> {
mem_to_arcinner: impl FnOnce(*mut u8) -> *mut ArcInner<T>,
) -> *mut ArcInner<T> {
let inner = mem_to_arcinner(ptr.as_non_null_ptr().as_ptr());
debug_assert_eq!(unsafe { Layout::for_value(&*inner) }, layout);
debug_assert_eq!(unsafe { Layout::for_value_raw(inner) }, layout);

unsafe {
ptr::write(&mut (*inner).strong, atomic::AtomicUsize::new(1));
ptr::write(&mut (*inner).weak, atomic::AtomicUsize::new(1));
ptr::addr_of_mut!((*inner).strong).write(atomic::AtomicUsize::new(1));
ptr::addr_of_mut!((*inner).weak).write(atomic::AtomicUsize::new(1));
}

inner
Expand All @@ -1847,7 +1847,7 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
// Allocate for the `ArcInner<T>` using the given value.
unsafe {
Arc::allocate_for_layout(
Layout::for_value(&*ptr),
Layout::for_value_raw(ptr),
|layout| alloc.allocate(layout),
|mem| mem.with_metadata_of(ptr as *const ArcInner<T>),
)
Expand All @@ -1863,7 +1863,7 @@ impl<T: ?Sized, A: Allocator> Arc<T, A> {
// Copy value as bytes
ptr::copy_nonoverlapping(
&*src as *const T as *const u8,
&mut (*ptr).data as *mut _ as *mut u8,
ptr::addr_of_mut!((*ptr).data) as *mut u8,
value_size,
);

Expand Down Expand Up @@ -1898,7 +1898,7 @@ impl<T> Arc<[T]> {
unsafe {
let ptr = Self::allocate_for_slice(v.len());

ptr::copy_nonoverlapping(v.as_ptr(), &mut (*ptr).data as *mut [T] as *mut T, v.len());
ptr::copy_nonoverlapping(v.as_ptr(), ptr::addr_of_mut!((*ptr).data) as *mut T, v.len());

Self::from_ptr(ptr)
}
Expand Down Expand Up @@ -1934,10 +1934,10 @@ impl<T> Arc<[T]> {
let ptr = Self::allocate_for_slice(len);

let mem = ptr as *mut _ as *mut u8;
let layout = Layout::for_value(&*ptr);
let layout = Layout::for_value_raw(ptr);

// Pointer to first element
let elems = &mut (*ptr).data as *mut [T] as *mut T;
let elems = ptr::addr_of_mut!((*ptr).data) as *mut T;

let mut guard = Guard { mem: NonNull::new_unchecked(mem), elems, layout, n_elems: 0 };

Expand Down Expand Up @@ -3380,7 +3380,7 @@ impl<T, A: Allocator + Clone> From<Vec<T, A>> for Arc<[T], A> {
let (vec_ptr, len, cap, alloc) = v.into_raw_parts_with_alloc();

let rc_ptr = Self::allocate_for_slice_in(len, &alloc);
ptr::copy_nonoverlapping(vec_ptr, &mut (*rc_ptr).data as *mut [T] as *mut T, len);
ptr::copy_nonoverlapping(vec_ptr, ptr::addr_of_mut!((*rc_ptr).data) as *mut T, len);

// Create a `Vec<T, &A>` with length 0, to deallocate the buffer
// without dropping its contents or the allocator
Expand Down

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