Support passing function pointers across the FFI

描述

#[cxx::bridge]
mod ffi {
    extern "Rust" {
        fn f(arg: u8, callback: fn(u8));
    }
}

fn f(arg: u8, callback: fn(u8)) {
    callback(256 - arg);
}

贡献者指南

技术栈

rustcpp

领域

backendapi

议题类型

feature

难度面向新贡献者的预计实现难度，1 表示很小改动，5 表示专家级工作。

5

预计时间有经验贡献者完成调查、实现、测试并准备 pull request 的粗略时间范围。

over 1 week

活动状态议题当前的可参与程度：新鲜、活跃、陈旧、阻塞或等待维护者输入。

stale

清晰度议题是否清楚说明期望改动、验收标准和下一步。

clear

前置要求

Rust FFI knowledgeC++ interopcxx crate internals

新手友好度1-100 的估计分数，表示该议题对首次贡献者的友好程度。

10

研究方向

The issue requests adding support for function pointer types in cxx bridge. The current implementation likely does not handle `fn(...)` parameters. To start, examine how cxx currently handles other types like references and boxes in the code generation. Look for existing handling of function pointer types in the source code (e.g., in `src/`). Consider how closures or extern functions are currently supported. The PRs and comments may provide guidance. Focus on the parser and code generation for the `extern "Rust"` block. Also check for any previous attempts or discussions in the comments.