Tracking rustc bugs/features/RFCs that affect bindgen

This is a meta issue tracking rustc bugs and features that impact bindgen.

Appropriate things to list here would be either

• RFCs proposing some feature that bindgen can leverage to emit better bindings, or
• issues detailing rustc bugs we need fixed as a prerequisite to fixing bugs in our emitted bindings, or
• pull requests adding new features that enable us to emit new kinds of bindings we haven't been able to before.

• Extern types: https://github.com/rust-lang/rust/issues/43467

• u128 / i128 https://github.com/rust-lang/rust/issues/35118

• #[repr(align="N")] https://github.com/rust-lang/rust/issues/33626

  • https://github.com/rust-lang-nursery/rust-bindgen/issues/1034

• #[repr(packed="N")] https://github.com/rust-lang/rust/issues/33158

  • https://github.com/rust-lang-nursery/rust-bindgen/issues/537

• Support for thiscall calling convention https://github.com/rust-lang/rust/issues/42202

• Support for the System V AMD64 C++ ABI https://github.com/rust-lang/rust/issues/36167

• Support for placement new https://github.com/rust-lang/rust/issues/27779

• #[repr(transparent)] https://github.com/rust-lang/rust/issues/43036

• const generics https://github.com/rust-lang/rust/issues/44580

  • https://github.com/rust-lang-nursery/rust-bindgen/issues/886 Drop logic of the "manual" implementation of traits for arrays which size is more than 32.
  • https://github.com/rust-lang-nursery/rust-bindgen/issues/362 Handle non-type template parameters

• const_fn https://github.com/rust-lang/rust/issues/24111

Review the linked rustc issues and the related bindgen issues 1034, 537, 886, and 362 to determine which tracked items are still relevant. Start by checking their current status and update this checklist only when the corresponding rustc capability or bindgen prerequisite has changed.