nix not compatible with freebsd 13

[densone]

ext field needs to be added to kevent data structure and functions.

error[E0063]: missing field `ext` in initializer of `kevent`
   --> /root/.cargo/registry/src/github.com-1ecc6299db9ec823/nix-0.22.2/src/sys/event.rs:221:26
    |
221 |         KEvent { kevent: libc::kevent {
    |                          ^^^^^^^^^^^^ missing `ext`

For more information about this error, try `rustc --explain E0063`.
error: could not compile `nix` due to previous error

I was able to fix it for my usecase but unsure how you'd implement it in nix for varying bsd versions.

Our hack to make I compile:

impl KEvent {
    pub fn new(ident: uintptr_t, filter: EventFilter, flags: EventFlag,
               fflags:FilterFlag, data: intptr_t, udata: intptr_t) -> KEvent {
        KEvent { kevent: libc::kevent {
            ident,
            filter: filter as type_of_event_filter,
            flags: flags.bits(),
            fflags: fflags.bits(),
            data: data as type_of_data,
            udata: udata as type_of_udata,
            ext: [0,0,0,0],       //this is likely bad but we are not using this part of nix 
        } }
    }

[asomers]

It's a libc bug. I'm trying to get it fixed here rust-lang/libc#2585 .