Undefined behavior in `fmt::Debug` impl for `os::windows::Library`

[Jarek Samic]

I happened to notice this while glancing around the code for #82. Link to src.

            let mut buf =
                mem::MaybeUninit::<[mem::MaybeUninit::<WCHAR>; 1024]>::uninit().assume_init();

Based on the docs for assume_init, it sounds like this is UB:

Calling this when the content is not yet fully initialized causes immediate undefined behavior.

[Jarek Samic]

Oh, duh. That's not UB because the contents of the array are actually initialized there, as uninitialized data.

Also realized it's copied from the impl in the stdlib.

Closing, my bad! 😄

[Simonas Kazlauskas]

The assume_init is fine becaue the array values are themselves MaybeUninit, yeah.