Handle &CStr <-> const char*

Description

void example(const char *s);

use std::ffi::CStr;

#[cxx::bridge]
mod ffi {
    unsafe extern "C++" {
        fn example(s: &CStr);
    }
}

fn main() {
    let cstr = CStr::from_bytes_with_nul(b"test\0").unwrap();
    ffi::example(cstr);
}

Contributor guide

Tech stack

rustcpp

Domain

apideveloper experience

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.

half day

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

Rust FFIC++cxx interopCStr

Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.

40

Research direction

The issue requests support for passing &CStr to C++ functions expecting const char*. The implementation likely requires adding a new type mapping in the cxx codegen. Start by examining how cxx handles existing string types (e.g., CxxString) in the 'types' module of the cxx crate. Look at the code generation for extern functions to see how argument types are translated. The conversion from &CStr to const char* should involve getting the raw pointer from the CStr. Check if there are any existing discussions or PRs related to CStr support. The solution should ensure safety and proper lifetime handling.