read_line_async crashing because of assertion

[abenz1267]

Hi,

i have this inside a app.connect_command_line:

                        let stdin = cmd.stdin();
                        let data_stream = gio::DataInputStream::new(&stdin.unwrap());
                        let data_stream_rc = Rc::new(data_stream);

                        fn read_line_callback(
                            stream: Rc<gio::DataInputStream>,
                            i: i32,
                            items: gio::ListStore,
                        ) {
                            let stream_clone = Rc::clone(&stream);

                            stream.read_line_async(
                                Priority::DEFAULT,
                                Cancellable::NONE,
                                move |line_slice| match line_slice {
                                    Ok(line_slice) => {
                                        if line_slice.is_empty() {
                                            return;
                                        }

                                        if let Ok(line_str) = std::str::from_utf8(&line_slice) {
                                            // irrelevant
                                        }

                                        read_line_callback(
                                            Rc::clone(&stream_clone),
                                            i + 1,
                                            items.clone(),
                                        );
                                    }
                                    Err(e) => {
                                        eprintln!("Error reading: {}", e);
                                        return;
                                    }
                                },
                            );
                        }

                        read_line_callback(Rc::clone(&data_stream_rc), 0, items.clone());

The problem is that when there's data on stdin, it always runs into this error:

thread 'main' panicked at /home/andrej/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/glib-0.20.12/src/collections/slice.rs:511:9:
assertion failed: !ptr.is_null() || len == 0

I have no idea why...

gtk4 = { version = "^0.9.7", features = ["v4_6", "v4_12", "gio_v2_80"] }

Anyone has a clue what i'm missing? Or is this a bug?

[abenz1267]

jesus. i'm dumb. if the last line in stdin isnt \n terminated => crash. sorry.

[abenz1267]

Actually: this does seem like a bug. Because f.e. something like fd might not print a newline at the last line, so the output of fd will cause a crash in the GTK program.

[abenz1267]

the crash does not happen when using read_line_utf8_async

[abenz1267]

read_line also crashes, if it contains an escape char like f.e. echo "test\x0bla"

edit: ofc this crashes cuz no \n ...

[sdroege]

Yes, this shouldn't crash. Can you provide a full, runnable testcase (and instructions for how to get it crash) that shows this behaviour?

[sdroege]

This is probably fixed by #1803 but it's not clear to me why it was NULL in your case but the length reported was > 0, so a testcase would be very helpful.

[abenz1267]

https://github.com/abenz1267/gtkrustbug

Simply run echo "hello\nworld" | cargo run and it will crash, while echo "hello\nworld\n" | cargo run won't.

[sdroege]

Thanks! Ok, so if NULL is returned then it also does not initialize the length and it contains a random value.

Just as a side-note, clone() on the stream directly basically behaves like an Rc. You don't need to wrap it into an Rc.