Impossible to construct an in6_addr

[mrmonday]

The new definition of in6_addr:

pub struct in6_addr {
    pub s6_addr: [u8; 16],
    __align: [u32; 0],
}

Link: https://github.com/rust-lang-nursery/libc/blob/e7ff66ba3df6eb0d10953245a2a6fd2ecf082ccd/src/unix/mod.rs#L62

Means that it is now impossible to construct a value of type in6_addr from Rust, outside of the libc crate, since the __align field is private. I've had to fix libpnet to an old version of libc to work around this.

[alexcrichton]

Thanks for the report! This has also been reported here and here, and unfortunately this is just a place where Rust doesn't handle FFI unions very well right now. The underlying type is a union which gains it higher alignment but the exposed fields right now don't give us that alignment. When we have custom alignment we may be able to get around this via other means, but for now you can construct this like you would in C:

let mut foo: libc::in6_addr = mem::uninitialized();
// initialize foo.s6_addr
return foo

Which is to say it's not necessarily "impossible", just not very idiomatic!

[mrmonday]

Thanks you. Sorry for the noise, I didn't find those issues when I searched for some reason.

It should be possible to replace __align with #[repr(C, align(4))] now. Or am I wrong here?

Edit turns out I am:
<sfackler> sebk: that will bump the minimum supported rust version