use core::fmt;
use core::cmp::Ordering;
use core::intrinsics::abort;
-use core::mem::{self, size_of_val, uninitialized};
+use core::mem::{self, align_of_val, size_of_val, uninitialized};
use core::ops::Deref;
use core::ops::CoerceUnsized;
use core::ptr::{self, Shared};
Ok(elem)
}
}
+}
+impl<T: ?Sized> Arc<T> {
/// Consumes the `Arc`, returning the wrapped pointer.
///
/// To avoid a memory leak the pointer must be converted back to an `Arc` using
/// ```
#[stable(feature = "rc_raw", since = "1.17.0")]
pub unsafe fn from_raw(ptr: *const T) -> Self {
- // To find the corresponding pointer to the `ArcInner` we need to subtract the offset of the
- // `data` field from the pointer.
- let ptr = (ptr as *const u8).offset(-offset_of!(ArcInner<T>, data));
+ // Align the unsized value to the end of the ArcInner.
+ // Because it is ?Sized, it will always be the last field in memory.
+ let align = align_of_val(&*ptr);
+ let layout = Layout::new::<ArcInner<()>>();
+ let offset = (layout.size() + layout.padding_needed_for(align)) as isize;
+
+ // Reverse the offset to find the original ArcInner.
+ let fake_ptr = ptr as *mut ArcInner<T>;
+ let arc_ptr = set_data_ptr(fake_ptr, (ptr as *mut u8).offset(-offset));
+
Arc {
- ptr: Shared::new_unchecked(ptr as *mut u8 as *mut _),
+ ptr: Shared::new_unchecked(arc_ptr),
}
}
-}
-impl<T: ?Sized> Arc<T> {
/// Creates a new [`Weak`][weak] pointer to this value.
///
/// [weak]: struct.Weak.html
}
}
+ #[test]
+ fn test_into_from_raw_unsized() {
+ use std::fmt::Display;
+ use std::string::ToString;
+
+ let arc: Arc<str> = Arc::from("foo");
+
+ let ptr = Arc::into_raw(arc.clone());
+ let arc2 = unsafe { Arc::from_raw(ptr) };
+
+ assert_eq!(unsafe { &*ptr }, "foo");
+ assert_eq!(arc, arc2);
+
+ let arc: Arc<Display> = Arc::new(123);
+
+ let ptr = Arc::into_raw(arc.clone());
+ let arc2 = unsafe { Arc::from_raw(ptr) };
+
+ assert_eq!(unsafe { &*ptr }.to_string(), "123");
+ assert_eq!(arc2.to_string(), "123");
+ }
+
#[test]
fn test_cowarc_clone_make_mut() {
let mut cow0 = Arc::new(75);
macro_rules! format {
($($arg:tt)*) => ($crate::fmt::format(format_args!($($arg)*)))
}
-
-// Private macro to get the offset of a struct field in bytes from the address of the struct.
-macro_rules! offset_of {
- ($container:path, $field:ident) => {{
- // Make sure the field actually exists. This line ensures that a compile-time error is
- // generated if $field is accessed through a Deref impl.
- let $container { $field : _, .. };
-
- // Create an (invalid) instance of the container and calculate the offset to its
- // field. Using a null pointer might be UB if `&(*(0 as *const T)).field` is interpreted to
- // be nullptr deref.
- let invalid: $container = ::core::mem::uninitialized();
- let offset = &invalid.$field as *const _ as usize - &invalid as *const _ as usize;
-
- // Do not run destructors on the made up invalid instance.
- ::core::mem::forget(invalid);
- offset as isize
- }};
-}
use core::intrinsics::abort;
use core::marker;
use core::marker::Unsize;
-use core::mem::{self, forget, size_of_val, uninitialized};
+use core::mem::{self, align_of_val, forget, size_of_val, uninitialized};
use core::ops::Deref;
use core::ops::CoerceUnsized;
use core::ptr::{self, Shared};
Err(this)
}
}
+}
+impl<T: ?Sized> Rc<T> {
/// Consumes the `Rc`, returning the wrapped pointer.
///
/// To avoid a memory leak the pointer must be converted back to an `Rc` using
/// ```
#[stable(feature = "rc_raw", since = "1.17.0")]
pub unsafe fn from_raw(ptr: *const T) -> Self {
- // To find the corresponding pointer to the `RcBox` we need to subtract the offset of the
- // `value` field from the pointer.
+ // Align the unsized value to the end of the RcBox.
+ // Because it is ?Sized, it will always be the last field in memory.
+ let align = align_of_val(&*ptr);
+ let layout = Layout::new::<RcBox<()>>();
+ let offset = (layout.size() + layout.padding_needed_for(align)) as isize;
+
+ // Reverse the offset to find the original RcBox.
+ let fake_ptr = ptr as *mut RcBox<T>;
+ let rc_ptr = set_data_ptr(fake_ptr, (ptr as *mut u8).offset(-offset));
- let ptr = (ptr as *const u8).offset(-offset_of!(RcBox<T>, value));
Rc {
- ptr: Shared::new_unchecked(ptr as *mut u8 as *mut _)
+ ptr: Shared::new_unchecked(rc_ptr),
}
}
-}
-impl<T: ?Sized> Rc<T> {
/// Creates a new [`Weak`][weak] pointer to this value.
///
/// [weak]: struct.Weak.html
}
}
+ #[test]
+ fn test_into_from_raw_unsized() {
+ use std::fmt::Display;
+ use std::string::ToString;
+
+ let rc: Rc<str> = Rc::from("foo");
+
+ let ptr = Rc::into_raw(rc.clone());
+ let rc2 = unsafe { Rc::from_raw(ptr) };
+
+ assert_eq!(unsafe { &*ptr }, "foo");
+ assert_eq!(rc, rc2);
+
+ let rc: Rc<Display> = Rc::new(123);
+
+ let ptr = Rc::into_raw(rc.clone());
+ let rc2 = unsafe { Rc::from_raw(ptr) };
+
+ assert_eq!(unsafe { &*ptr }.to_string(), "123");
+ assert_eq!(rc2.to_string(), "123");
+ }
+
#[test]
fn get_mut() {
let mut x = Rc::new(3);