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use MaybeUninit in core::ptr::swap

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Code by @japaric, I just split it into individual commits
This commit is contained in:
Ralf Jung 2018-10-12 08:59:38 +02:00
parent 0bb2e2d6d4
commit 3fb03d0650
1 changed files with 5 additions and 8 deletions
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13
src/libcore/ptr.rs
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@ -295,17 +295,14 @@ pub const fn null_mut<T>() -> *mut T { 0 as *mut T }
#[inline]
#[stable(feature = "rust1", since = "1.0.0")]
pub unsafe fn swap<T>(x: *mut T, y: *mut T) {
// Give ourselves some scratch space to work with
let mut tmp: T = mem::uninitialized();
// Give ourselves some scratch space to work with.
// We do not have to worry about drops: `MaybeUninit` does nothing when dropped.
let mut tmp = MaybeUninit::<T>::uninitialized();
// Perform the swap
copy_nonoverlapping(x, &mut tmp, 1);
copy_nonoverlapping(x, tmp.as_mut_ptr(), 1);
copy(y, x, 1); // `x` and `y` may overlap
copy_nonoverlapping(&tmp, y, 1);
// y and t now point to the same thing, but we need to completely forget `tmp`
// because it's no longer relevant.
mem::forget(tmp);
copy_nonoverlapping(tmp.get_ref(), y, 1);
}
/// Swaps `count * size_of::<T>()` bytes between the two regions of memory