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doc: explain why it is unsafe to construct Vec<u8> from Vec<u16>

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Co-authored-by: Steve Klabnik <steve@steveklabnik.com>
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Lzu Tao 2019-10-27 17:31:01 +00:00
parent 0f677c65e8
commit 3f980785fb
1 changed files with 5 additions and 1 deletions
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6
src/liballoc/vec.rs
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@ -411,7 +411,11 @@ impl<T> Vec<T> {
///
/// Violating these may cause problems like corrupting the allocator's
/// internal data structures. For example it is **not** safe
/// to build a `Vec<u8>` from a pointer to a C `char` array and a `size_t`.
/// to build a `Vec<u8>` from a pointer to a C `char` array with length `size_t`.
/// It's also not safe to build one from a `Vec<u16>` and its length, because
/// the allocator cares about the alignment, and these two types have different
/// alignments. The buffer was allocated with alignment 2 (for `u16`), but after
/// turning it into a `Vec<u8>` it'll be deallocated with alignment 1.
///
/// The ownership of `ptr` is effectively transferred to the
/// `Vec<T>` which may then deallocate, reallocate or change the