[v0.18] Use #[repr(C)] for vertex & constant structs.

[alexheretic]

Fixes issues exposed by rust 1.67 field ordering changes (rust-lang/rust#102750)

This PR adds #[repr(C)] to vertex & constant structs preventing field ordering issues.

Note: This actually still works fine even if users have manually specified #[repr(C)] themselves since declaring it multiple times works fine, e.g. this works:

#[repr(C)]
#[repr(C)]
#[repr(C)]
pub struct Vertex { ...

Resolves #3790

Could we get a new gfx crate release with this in it please? I think this will help out any old-school users of this crate.

[alexheretic]

Hey @kvark i know v0.18 is ancient these days, but this fix is quite valuable for anyone still using it with rust 1.67 (like me). I think it's worth making a 0.18.3 release with this. Wdyt?

[kvark]

@alexheretic sure, sounds good!

[kvark]

Would you mind bumping the version to 0.18.3 in the PR?

[alexheretic]

Would you mind bumping the version to 0.18.3 in the PR?

✔️

[kvark]

Published now. Thank you for support!