std::repr does not work properly for packed fields

[stepancheg]

Problem with std::repr (and with std::reflect) is that TyVisitor does not tell whether struct is packed or not.

I think, proper solution would be adding offset parameter to fn visit_class_field(...) callback, to remove all complex offsets/alignment computation code from libstd (because it is already done in librustc).

[emberian]

eugh what a pain. I thought reflect was already doing this.

[KokaKiwi]

Just a comment to give a code example of the issue (which doesn't appears to have been fixed):

#[packed]
struct Packed {
    a: u8,
    b: u32,
    c: [u8, ..3],
}

struct NonPacked {
    a: u8,
    b: u32,
    c: [u8, ..3],
}

fn main() {
    let p = Packed {
        a: 1,
        b: 3,
        c: [3, 4, 5],
    };

    println!("{:?}", p);

    let p = NonPacked {
        a: 1,
        b: 3,
        c: [3, 4, 5],
    };

    println!("{:?}", p);
}

Output:

$ rustc -o packed main.rs
$ ./packed
Packed{a: 1u8, b: 84148992u32, c: [243u8, 144u8, 68u8]}
NonPacked{a: 1u8, b: 3u32, c: [3u8, 4u8, 5u8]}

My rustc version:

$ rustc --version
rustc 0.11-pre-nightly (2dcbad5 2014-05-06 22:01:43 -0700)
host: x86_64-unknown-linux-gnu

[thestinger]

Reflection has been removed.