[upstream] RtMidi: opening midi device causes device count inflation

[atsushieno]

This is an upstream issue (could be up to ALSA) but the proof of concept issue shows up in RtMidi:

#include "RtMidi.h"
#include <stdio.h>
#include <iostream>
#include <vector>

using namespace std;

int main ()
{
    vector<RtMidi::Api> apis;
    RtMidi::getCompiledApi (apis);
    cout << "apis: " << apis.size() << endl;
    RtMidiIn *input = new RtMidiIn (apis[0], "input");
    RtMidiOut *output = new RtMidiOut (apis[0], "output");
    cout << "before opening port: inputs: " << input->getPortCount ()
         << " outputs: " << output->getPortCount () << endl;
    output->openPort (0, "port0");
    cout << "after opening port: inputs: " << input->getPortCount ()
         << " outputs: " << output->getPortCount () << endl;
    output->closePort ();
    cout << "after closing port: inputs: " << input->getPortCount ()
         << " outputs: " << output->getPortCount () << endl;
    cout << "after opening port: inputs: " << input->getPortCount ()
         << " outputs: " << output->getPortCount () << endl;

    delete input;
    delete output;
    return 0;
}

$ g++ -I/devel/include/rtmidi -L/devel/lib testrtmidi.c -lasound -lpthread -lrtmidi

$ ./a.out
apis: 1
before opening port: inputs: 1 outputs: 2
after opening port: inputs: 2 outputs: 2
after closing port: inputs: 2 outputs: 2
after opening port: inputs: 2 outputs: 2

(Note that it should NOT increase the input port count.)

This affects our managed bindings too. Basically it messes RtMidiAccess and descendants.

The problem however does not seem to be in RtMidi. I get similar results from PortMidiAccess either. So it's more likely in the underlying layer like ALSA I'm on (Ubuntu 14.04). No idea where the problem lies.

So far, without fixes, things don't get work appropriately (it doesn't for me).