dtolnay/cxx

Preserve cause-chain of errors propagated from rust -> c++ -> rust

Open

#290 opened on Sep 9, 2020

View on GitHub
 (1 comment) (0 reactions) (0 assignees)Rust (253 forks)batch import
help wantedneeds design

Repository metrics

Stars
 (4,472 stars)
PR merge metrics
 (Avg merge 8m) (3 merged PRs in 30d)

Description

use anyhow::{anyhow, Result};

#[cxx::bridge]
mod ffi {
    extern "C" {
        include!("repro.h");
        fn cthing() -> Result<()>;
    }

    extern "Rust" {
        fn rustthing() -> Result<()>;
    }
}

fn rustthing() -> Result<()> {
    Err(anyhow!("no such file or directory").context("failed to open: /nonexist"))
}

fn main() -> Result<()> {
    ffi::cthing()?;
    Ok(())
}

// repro.cc

void cthing() {
  rustthing();
}

This currently loses the cause chain and only prints:

Error: failed to open: /nonexist

Contributor guide

Research direction
Investigate the error conversion mechanism in cxx crate between Rust and C++ and ensure the cause chain is preserved through the boundary.
Tech stack
rustcpp
Domain
api
Issue type
Bug
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.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
RustC++
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30