Fix inaccessible audio device crash

Throw an exception form pa_sink::pa_sink
Better exceptions handling in receiver::set_output_device
Set conf_ok to false in MainWindow::loadConfig if
rx->set_output_device fails.

Author: vladisslav2011

src/applications/gqrx/mainwindow.cpp

@@ -549,6 +549,7 @@ bool MainWindow::loadConfig(const QString& cfgfile, bool check_crash,
                                      "Please select another device.")
                                  .arg(x.what()),
                          QMessageBox::Ok);
+        conf_ok = false;
     }
 
     int_val = m_settings->value("input/sample_rate", 0).toInt(&conv_ok);

src/applications/gqrx/receiver.cpp

@@ -273,17 +273,16 @@ void receiver::set_output_device(const std::string device)
         tb->disconnect(audio_gain0, 0, audio_snk, 0);
         tb->disconnect(audio_gain1, 0, audio_snk, 1);
     }
-    audio_snk.reset();
 
     try {
 #ifdef WITH_PULSEAUDIO
-        audio_snk = make_pa_sink(device, d_audio_rate, "GQRX", "Audio output");
+        auto new_audio_snk = make_pa_sink(device, d_audio_rate, "GQRX", "Audio output");
 #elif WITH_PORTAUDIO
-        audio_snk = make_portaudio_sink(device, d_audio_rate, "GQRX", "Audio output");
+        auto new_audio_snk = make_portaudio_sink(device, d_audio_rate, "GQRX", "Audio output");
 #else
-        audio_snk = gr::audio::sink::make(d_audio_rate, device, true);
+        auto new_audio_snk = gr::audio::sink::make(d_audio_rate, device, true);
 #endif
-
+        audio_snk = new_audio_snk;
         if (d_demod != RX_DEMOD_OFF)
         {
             tb->connect(audio_gain0, 0, audio_snk, 0);
@@ -293,6 +292,12 @@ void receiver::set_output_device(const std::string device)
         tb->unlock();
 
     } catch (std::exception &x) {
+        if (d_demod != RX_DEMOD_OFF)
+        {
+            tb->connect(audio_gain0, 0, audio_snk, 0);
+            tb->connect(audio_gain1, 0, audio_snk, 1);
+        }
+
         tb->unlock();
         // handle problems on non-freeing devices
         throw x;

src/pulseaudio/pa_sink.cc

@@ -69,8 +69,8 @@ pa_sink::pa_sink(const string device_name, int audio_rate,
                              &error);
 
     if (!d_pasink) {
-        /** FIXME: Throw an exception **/
         fprintf(stderr, __FILE__": pa_simple_new() failed: %s\n", pa_strerror(error));
+        throw std::runtime_error("Failed to open pulseaudio device '" + device_name + "'");
     }
 
 }
@@ -114,8 +114,8 @@ void pa_sink::select_device(string device_name)
                              &error);
 
     if (!d_pasink) {
-        /** FIXME: Throw an exception **/
         fprintf(stderr, __FILE__": pa_simple_new() failed: %s\n", pa_strerror(error));
+        throw std::runtime_error("Failed to select pulseaudio device '" + device_name + "'");
     }
 }