Incorrect alignment of structs.

[BarabasGitHub]

I would think that these both need to produce a struct with an alignment of 8, instead TestStruct1 ends up with an alignment of 1.

const std = @import("std");

const TestStruct1 = struct {
    small: u8,
    big: u64,
};
const TestStruct2 = struct {
    big: u64,
    small: u8,
};

test "alignment" {
    std.debug.warn("\n");
    std.debug.warn("Align TestStruct1 = {}\n", u64(@alignOf(TestStruct1)));
    std.debug.warn("Align TestStruct2 = {}\n", u64(@alignOf(TestStruct2)));
    std.debug.assert(@alignOf(TestStruct1) == 8);
    std.debug.assert(@alignOf(TestStruct2) == 8);
}

In addition to this I think it would be helpful if you can specify the default alignment of structs. And maybe especially for packed structs. Currently all packed structs get an alignment of 1, while that might not be appropriate if you want to pass them to some C function.

[andrewrk]

See #1052

For ABI compatibility with C, use extern struct.

[BarabasGitHub]

Oops. I somehow missed the existing issue.
extern struct has the same issue by the way. TestStruct1 also gets an alignment of 1.