dtolnay/cxx

Shared structs with type parameters

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#54 opened on Mar 2, 2020

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help wanted

Description

We should support structs that have type parameters and translate them to an ABI-compatible class template in C++.

#[cxx::bridge]
mod ffi {
    struct Generic<T> {
        wow: T,
    }

    extern "C" {
        fn f(g: Generic<String>);
    }
}

Contributor guide

Tech stack
rustcpp
Domain
backend
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
RustC++FFI concepts
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
50
Research direction
Investigate how existing non generic structs are translated to C++ in cxx. Look at the codegen module for struct handling (likely in `gen/` directory). Consider how C++ templates differ from Rust generics and ensure ABI compatibility. Check existing tests for templated structs and any related issues or PRs.