vendor/maybe-uninit/README.md

   1 # maybe-uninit
   2
   3 Quite often, uses of `std::mem::uninitialized()` end up in unsound code.
   4 Therefore, the `MaybeUninit` union has been added to `std::mem` and `std::mem::uninitialized()` is being deprecated.
   5 However, `MaybeUninit` has been added quite recently.
   6 Sometimes you might want to support older versions of Rust as well.
   7 Here is where `maybe-uninit` comes in: it supports stable Rust versions starting with 1.20.0.
   8
   9 Sadly, a feature-complete implementation of `MaybeUninit` is not possible on stable Rust.
  10 Therefore, the library offers the guarantees of `MaybeUninit` in a staged fashion:
  11
  12 * Rust 1.36.0 onward: `MaybeUninit` implementation of Rust stable is being re-exported
  13
  14 * Rust 1.22.x - 1.35.0: No panicing on uninhabited types,
  15   unsoundness when used with types like `bool` or enums.
  16   However, there is protection from accidentially `Drop`ing e.g. during unwind!
  17
  18 * Rust 1.20.x - 1.21.x: No support for Copy/Clone of `MaybeUninit<T>`,
  19   even if `T` impls `Copy` or even `Clone`.