stdbind

stdbind is a pair of C++ and Rust libraries intended to make bindgen usage around the C++ standard library more ergonomic: on the C++ side, there are basic ‘adapter’ types of known ABI for things like std::optional; and on the Rust side, there are ABI-compatible Rust equivalents adapters for the corresponding standard Rust type (e.g., for Option in the case of std::optional). The idea is that one would use the adapters on the C++ side and then constrain bindgen to use the Rust equivalents.

Example usage

import("//build/rust/rustc_bindgen.gni)

rustc_bindgen_crate("my-bindings") {
    # ...

    # Uses <lib/stdbind/optional.h>
    headers = ["my-header.h"]

    type_blocklist = [ "stdbind::optional" ]
    raw_lines = [ "use stdbind::Optional as stdbind_optional;" ]
    deps = [ "//src/lib/stdbind:stdbind-rs" ]
}

ABI Specification

optional

The fixed-ABI adapters in C++ and Rust are stdbind::optional<T> and stdbind::Optional<T>, respectively.

• Discriminant Tag: An 8-byte uint64_t / u64 located at offset 0.
  • 0: indicates absence
  • 1: indicates presence
• Padding: Sufficient padding bytes after the tag to satisfy alignof(T) when alignof(T) > 8.
• Payload: The value of type T placed immediately following the tag (at offset 8 for types with alignment <= 8).