serial::windows::com::COMPort does not implement Send trait

[apoloval]

I'm writing an application using serial-rs, and I've found an obstacle trying to use it in a multithreading context.

The point is that I'm make a sort of serial port scanner. A listener thread will scan serial ports until a new device is connected. Then it creates a new thread and passes the SerialPort instance to it using move semantics.

In order to do that, SerialPort implementations must implement Send trait. The native implementation for Windows, serial::windows::com::COMPort if I'm not wrong, does not according to the following compilation error:

src\port\serial.rs:43:9: 43:18 error: the trait `core::marker::Send` is not implemented for the type `*mut *mut libc::c_void` [E0277]
src\port\serial.rs:43         Self::new(domain, proto::oacsp())
                              ^~~~~~~~~
src\port\serial.rs:43:9: 43:18 help: run `rustc --explain E0277` to see a detailed explanation
src\port\serial.rs:43:9: 43:18 note: `*mut *mut libc::c_void` cannot be sent between threads safely
src\port\serial.rs:43:9: 43:18 note: required because it appears within the type `serial::windows::com::COMPort`
src\port\serial.rs:43:9: 43:18 note: required because it appears within the type `proto::oacsp::output::MessageConsumer<serial::windows::com::COMPort>`
src\port\serial.rs:43:9: 43:18 note: required because it appears within the type `proto::oacsp::writer::EventWriter<proto::oacsp::output::MessageConsumer<serial::windows::com::COMPort>>`
src\port\serial.rs:43:9: 43:18 note: required by `port::serial::SerialPort::new` 

Moving the SerialPort instance from one thread to another should not be forbidden. Sharing it perhaps should not. Thus, Send + 'static should be implemented but Sync should not.

[dcuddeback]

@apoloval Thanks for catching this. I merged your PR that fixes this for Windows. Did you happen to try your serial port scanner on Unix as well?

[apoloval]

No, I didn't. But I guess there should be no problem. In Unix, file descriptors are integer values, which are Send by default in Rust. In Windows, resource handles are pointers, which are not Send.

[dcuddeback]

@apoloval No worries. I came to the same conclusion. Just thought I'd check.

[dcuddeback]

I wrote something quick to verify that it works on Unix. Looks okay.