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Fix example in transmute; add safety requirement to Vec::from_raw_parts

This commit is contained in:
Havvy 2017-09-13 01:27:41 -07:00
parent 7eefed392f
commit 9dd2ee1942
2 changed files with 4 additions and 3 deletions

View file

@ -370,6 +370,7 @@ impl<T> Vec<T> {
///
/// * `ptr` needs to have been previously allocated via [`String`]/`Vec<T>`
/// (at least, it's highly likely to be incorrect if it wasn't).
/// * `ptr`'s `T` needs to have the same size and alignment as it was allocated with.
/// * `length` needs to be less than or equal to `capacity`.
/// * `capacity` needs to be the capacity that the pointer was allocated with.
///

View file

@ -848,12 +848,12 @@ extern "rust-intrinsic" {
/// // The no-copy, unsafe way, still using transmute, but not UB.
/// // This is equivalent to the original, but safer, and reuses the
/// // same Vec internals. Therefore the new inner type must have the
/// // exact same size, and the same or lesser alignment, as the old
/// // type. The same caveats exist for this method as transmute, for
/// // exact same size, and the same alignment, as the old type.
/// // The same caveats exist for this method as transmute, for
/// // the original inner type (`&i32`) to the converted inner type
/// // (`Option<&i32>`), so read the nomicon pages linked above.
/// let v_from_raw = unsafe {
/// Vec::from_raw_parts(v_orig.as_mut_ptr(),
/// Vec::from_raw_parts(v_orig.as_mut_ptr() as *mut Option<&i32>,
/// v_orig.len(),
/// v_orig.capacity())
/// };