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change the box_free lang item to accept pointers to unsized types #37708

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merged 1 commit into from
Nov 12, 2016
Merged

change the box_free lang item to accept pointers to unsized types #37708

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4 changes: 2 additions & 2 deletions src/doc/book/lang-items.md
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Original file line number Diff line number Diff line change
Expand Up @@ -46,8 +46,8 @@ unsafe fn deallocate(ptr: *mut u8, _size: usize, _align: usize) {
}

#[lang = "box_free"]
unsafe fn box_free<T>(ptr: *mut T) {
deallocate(ptr as *mut u8, ::core::mem::size_of::<T>(), ::core::mem::align_of::<T>());
unsafe fn box_free<T: ?Sized>(ptr: *mut T) {
deallocate(ptr as *mut u8, ::core::mem::size_of_val(&*ptr), ::core::mem::align_of_val(&*ptr));
}

#[start]
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9 changes: 5 additions & 4 deletions src/liballoc/heap.rs
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Expand Up @@ -17,7 +17,7 @@

use core::{isize, usize};
#[cfg(not(test))]
use core::intrinsics::{min_align_of, size_of};
use core::intrinsics::{min_align_of_val, size_of_val};

#[allow(improper_ctypes)]
extern "C" {
Expand Down Expand Up @@ -152,11 +152,12 @@ unsafe fn exchange_free(ptr: *mut u8, old_size: usize, align: usize) {
#[cfg(not(test))]
#[lang = "box_free"]
#[inline]
unsafe fn box_free<T>(ptr: *mut T) {
let size = size_of::<T>();
unsafe fn box_free<T: ?Sized>(ptr: *mut T) {
let size = size_of_val(&*ptr);
let align = min_align_of_val(&*ptr);
// We do not allocate for Box<T> when T is ZST, so deallocation is also not necessary.
if size != 0 {
deallocate(ptr as *mut u8, size, min_align_of::<T>());
deallocate(ptr as *mut u8, size, align);
}
}

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