Using IpcSender<T> as a field and implementing Deserialize/Serialize causes panic.

[gatoWololo]

@asajeffrey

With the latest ipc-channel commit, the following code panics when ran:

// main.rs
use serde::{Serialize, Deserialize};
use ipc_channel::ipc;

#[derive(Serialize, Deserialize, Debug)]
struct IpcWrapper<T> {
    s: ipc::IpcSender<T>
}

fn main() {
    let (sender, receiver) = ipc::channel::<i32>().unwrap();
    let wrapper = IpcWrapper { s: sender };

    let ser = serde_json::to_string(&wrapper).unwrap();
    let deser: IpcWrapper<i32> = serde_json::from_str(&ser).unwrap();
}

Error: thread 'main' panicked at 'index out of bounds: the len is 0 but the index is 0'

Cargo.toml:

[dependencies]
ipc-channel = {git = "https://github.com/servo/ipc-channel"}
serde = { version = "1.0", features = ["derive"] }
serde_json = "1.0"

All you need is to "wrap" IpcSender<T> in your own type and derive Serialize/Deserialize. The error happens during deserialization.

From the backtrace. The error is happening here:

fn deserialize_os_ipc_sender<'de, D>(deserializer: D)
                                -> Result<OsIpcSender, D::Error> where D: Deserializer<'de> {
    let index: usize = Deserialize::deserialize(deserializer)?;
    OS_IPC_CHANNELS_FOR_DESERIALIZATION.with(|os_ipc_channels_for_deserialization| {
        // FIXME(pcwalton): This could panic if the data was corrupt and the index was out of
        // bounds. We should return an `Err` result instead.
        Ok(os_ipc_channels_for_deserialization.borrow_mut()[index].to_sender())
    })
}

I'm not sure why though.

[jdm]

I see the problem. The ipc channels expect that they will only be serialized as part of being sent over an IPC channel, so the code that prepares os_ipc_channels_for_deserialization to contain the expected values is never called because the deserialization does not occur as part of receiving on an IPC channel.