We're violating the safety assumption of Vec::set_len by calling it before the elements are initialized. This is Undefined Behavior. As far as I know, it's not causing any observable problem today, but that's dependent on the compiler version.
The obvious fix is to use Vec<MaybeUninit<u8>> instead and transmute it later. I'd like to use MaybeUninit::write_slice to extend it, but that's unstable. I might just punt until that changes, but filing this issue so I don't forget entirely.
We could instead use std::ptr::copy_nonoverlapping on a *mut u8, but it'd be nice to keep using bounds checking.
https://github.com/scottlamb/moonfire-nvr/blob/0406e09ca470d85d71145a9b6d5b88ea95f4b785/server/src/mp4.rs#L447-L448
We're violating the safety assumption of
Vec::set_lenby calling it before the elements are initialized. This is Undefined Behavior. As far as I know, it's not causing any observable problem today, but that's dependent on the compiler version.The obvious fix is to use
Vec<MaybeUninit<u8>>instead and transmute it later. I'd like to useMaybeUninit::write_sliceto extend it, but that's unstable. I might just punt until that changes, but filing this issue so I don't forget entirely.We could instead use
std::ptr::copy_nonoverlappingon a*mut u8, but it'd be nice to keep using bounds checking.