Can't use sys::statfs::statfs without unsafe

[alesharik]

Current implementation of statfs requires mutable reference of result variable, but I can't pass it to statfs without initialization. For example this code

let mut statf: libc::statfs;
sys::statfs::statfs(Path::new(&String::from("/")), &mut statf).unwrap();

gives me this error:

error[E0381]: use of possibly uninitialized variable: `statf`
sys::statfs::statfs(Path::new(&String::from("/")), &mut statf).unwrap();
                                                        ^^^^^ use of possibly uninitialized `statf`

So I need to somehow initialize the variable:

let mut statf: libc::statfs = unsafe { mem::uninitialized() };
sys::statfs::statfs(Path::new(&String::from("/")), &mut statf).unwrap();

Maybe it will be better to return result with libc::statfs struct instead of empty result?

[Susurrus]

Yes, that seems like the correct change. Additionally we should use a newtype wrapper around libc::statfs so we don't export libc types directly (this prevents libc breaking changes to become major-release breaking changes in nix).

The only open question here is whether reusing a statfs struct is ever necessary in practice. If so, we'd probably want two versions of each function, one returning the struct the other filling it in-place. I'd bet this functionality isn't necessary, but a look at production code would be useful here.

@alesharik Would you be willing to file a PR to fix this? It's unlikely to get fixed anytime soon if you aren't.