panics when log is called after pty closes with EIO

[Allen-Webb]

I am running into the following error:
failed to set color: Os { code: 5, kind: Uncategorized, message: "Input/output error" }', <registry path>/stderrlog-0.5.3/src/lib.rs:333:18

When I look at lib.rs, it looks inconsistent in that we ignore errors for write!() but panic on error for .set_color(). I don't believe panicking in this scenario makes sense. I am working on getting a repro example.

[Allen-Webb]

This is really ugly, but I have a minimalistic repro case:

Cargo.toml

[package]
name = "crash-demo"
version = "0.1.0"
edition = "2021"

[dependencies]
libc = "0.2"
log = "0.4"
stderrlog = "0.5"

src/main.rs

fn check_ret(ret: std::os::raw::c_int, msg: &str) {
    if ret < 0 {
        panic!("{}: {}", msg, std::io::Error::last_os_error());
    }
}

fn main() {
    println!("Setting up PTY");
    // Set up a pseudo terminal.
    let pt = unsafe { libc::getpt() };
    check_ret(pt, "getpt");
    check_ret(unsafe { libc::grantpt(pt) }, "grantpt");
    check_ret(unsafe { libc::unlockpt(pt) }, "unlockpt");

    let name = unsafe { libc::ptsname(pt) };
    if name.is_null() {
        panic!("ptsname: {}", std::io::Error::last_os_error());
    }

    let client = unsafe { libc::open(name, libc::O_RDWR) };
    check_ret(client, "open client pty");

    // Back up stderr
    let dup_stderr = unsafe { libc::dup(2) };
    check_ret(dup_stderr, "dup stderr");

    // Set up the panic handler to restore stderr.
    let default_panic = std::panic::take_hook();
    std::panic::set_hook(Box::new(move |info| {
        check_ret(unsafe { libc::dup2(dup_stderr, 2) }, "dup2 restore stderr");
        default_panic(info);
        std::process::abort();
    }));

    // Replace stderr with pty
    check_ret(unsafe { libc::dup2(client, 2) }, "dup2 restore stderr");

    println!("Setting up stderrlog");
    stderrlog::new().verbosity(50).init().unwrap();
    log::info!("This should work.");

    println!("Closing PTY");
    check_ret(unsafe { libc::close(pt) }, "close pt");

    println!("Sending log after PTY closed");
    log::info!("This should trigger an EIO.");

    // Restore stderr
    check_ret(unsafe { libc::dup2(dup_stderr, 2) }, "dup2 restore stderr");

    println!("Done!");

    check_ret(unsafe { libc::close(client) }, "close client");
    check_ret(unsafe { libc::close(dup_stderr) }, "close dup_stderr");
}