Bindgen generates unnecessary padding inside nsIDocument on Windows

[upsuper]

On my machine, the generated nsIDocument is like this:

    #[repr(C)]
    #[derive(Debug)]
    pub struct nsIDocument {
        pub _base: root::nsINode,
        pub _base_1: root::mozilla::dom::DispatcherTrait,
        pub mDeprecationWarnedAbout: u64,
        pub mDocWarningWarnedAbout: u32,
        pub mSelectorCache: root::nsIDocument_SelectorCache,
        pub __bindgen_padding_0: [u64; 10usize],
        pub mReferrer: root::nsCString,
        pub mLastModified: ::nsstring::nsStringRepr,
        // ...
    }

I see no reason why there needs to be a 80byte padding.

This causes a mismatch between offset from C++ and from Rust (mReferrer's offset is 248 in C++ but 328 in Rust), which leads to servo/servo#15483 on Windows.

It seems that this doesn't happen on Mac or Linux, so --target=x86_64-pc-win32 is probably a necessary condition.

[emilio]

That is fixed in #512, and in servo/servo#15216. That was why the bindgenup has been blocked for so long. Sorry about that.

[emilio]

This was not windows specific, it was a regression from #468, that isn't yet in the rest of platforms (I believe you updated your bindgen checkout in msvc, right?).

[upsuper]

Oh, the same issue? Great... so probably I'm seeing this because I'm using a more recent version of bindgen for the crash.

[upsuper]

Let me try the latest master with your patch in #512.

[emilio]

This should be fixed on master now, feel free to reopen if the problem persists (though I hope not! :P).