Avoided a possible null pointer when opening non-functional linux midi devices

modules/juce_audio_devices/native/juce_linux_Midi.cpp

@@ -113,9 +113,9 @@ public:
             snd_seq_ev_clear (&event);
 
             auto numBytes = (long) message.getRawDataSize();
-            const uint8* data = message.getRawData();
+            auto* data = message.getRawData();
 
-            auto* seqHandle = client.get();
+            auto seqHandle = client.get();
             bool success = true;
 
             while (numBytes > 0)
@@ -154,12 +154,12 @@ public:
 
         void createPort (const String& name, bool enableSubscription)
         {
-            if (auto* seqHandle = client.get())
+            if (auto seqHandle = client.get())
             {
                 const unsigned int caps =
-                    isInput
-                    ? (SND_SEQ_PORT_CAP_WRITE | (enableSubscription ? SND_SEQ_PORT_CAP_SUBS_WRITE : 0))
-                    : (SND_SEQ_PORT_CAP_WRITE | (enableSubscription ? SND_SEQ_PORT_CAP_SUBS_READ : 0));
+                    isInput ? (SND_SEQ_PORT_CAP_WRITE | (enableSubscription ? SND_SEQ_PORT_CAP_SUBS_WRITE : 0))
+                            : (SND_SEQ_PORT_CAP_WRITE | (enableSubscription ? SND_SEQ_PORT_CAP_SUBS_READ : 0));
+
                 portId = snd_seq_create_simple_port (seqHandle, name.toUTF8(), caps,
                                                      SND_SEQ_PORT_TYPE_MIDI_GENERIC |
                                                      SND_SEQ_PORT_TYPE_APPLICATION);
@@ -260,12 +260,16 @@ private:
         jassert (instance == nullptr);
 
         snd_seq_open (&handle, "default", SND_SEQ_OPEN_DUPLEX, 0);
-        snd_seq_nonblock (handle, SND_SEQ_NONBLOCK);
-        snd_seq_set_client_name (handle, JUCE_ALSA_MIDI_NAME);
-        clientId = snd_seq_client_id(handle);
 
-        // It's good idea to pre-allocate a good number of elements
-        ports.ensureStorageAllocated (32);
+        if (handle != nullptr)
+        {
+            snd_seq_nonblock (handle, SND_SEQ_NONBLOCK);
+            snd_seq_set_client_name (handle, JUCE_ALSA_MIDI_NAME);
+            clientId = snd_seq_client_id (handle);
+
+            // It's good idea to pre-allocate a good number of elements
+            ports.ensureStorageAllocated (32);
+        }
     }
 
     ~AlsaClient()
@@ -295,9 +299,10 @@ private:
 
         void run() override
         {
+            auto seqHandle = client.get();
+
             const int maxEventSize = 16 * 1024;
             snd_midi_event_t* midiParser;
-            snd_seq_t* seqHandle = client.get();
 
             if (snd_midi_event_new (maxEventSize, &midiParser) >= 0)
             {
@@ -321,8 +326,8 @@ private:
                             if (snd_seq_event_input (seqHandle, &inputEvent) >= 0)
                             {
                                 // xxx what about SYSEXes that are too big for the buffer?
-                                const long numBytes = snd_midi_event_decode (midiParser, buffer,
-                                                                            maxEventSize, inputEvent);
+                                auto numBytes = snd_midi_event_decode (midiParser, buffer,
+                                                                       maxEventSize, inputEvent);
 
                                 snd_midi_event_reset_decode (midiParser);
 
@@ -360,7 +365,7 @@ static AlsaClient::Port* iterateMidiClient (const AlsaClient::Ptr& client,
 {
     AlsaClient::Port* port = nullptr;
 
-    snd_seq_t* seqHandle = client->get();
+    auto seqHandle = client->get();
     snd_seq_port_info_t* portInfo = nullptr;
 
     snd_seq_port_info_alloca (&portInfo);
@@ -406,7 +411,7 @@ static AlsaClient::Port* iterateMidiDevices (bool forInput,
     AlsaClient::Port* port = nullptr;
     auto client = AlsaClient::getInstance();
 
-    if (auto* seqHandle = client->get())
+    if (auto seqHandle = client->get())
     {
         snd_seq_system_info_t* systemInfo = nullptr;
         snd_seq_client_info_t* clientInfo = nullptr;
@@ -503,8 +508,7 @@ void MidiOutput::sendMessageNow (const MidiMessage& message)
 }
 
 //==============================================================================
-MidiInput::MidiInput (const String& nm)
-    : name (nm), internal (nullptr)
+MidiInput::MidiInput (const String& nm)  : name (nm)
 {
 }
 
@@ -538,8 +542,6 @@ StringArray MidiInput::getDevices()
 
 MidiInput* MidiInput::openDevice (int deviceIndex, MidiInputCallback* callback)
 {
-    MidiInput* newDevice = nullptr;
-
     StringArray devices;
     auto* port = iterateMidiDevices (true, devices, deviceIndex);
 
@@ -548,26 +550,22 @@ MidiInput* MidiInput::openDevice (int deviceIndex, MidiInputCallback* callback)
 
     jassert (port->isValid());
 
-    newDevice = new MidiInput (devices [deviceIndex]);
+    auto newDevice = new MidiInput (devices [deviceIndex]);
     port->setupInput (newDevice, callback);
     newDevice->internal = port;
-
     return newDevice;
 }
 
 MidiInput* MidiInput::createNewDevice (const String& deviceName, MidiInputCallback* callback)
 {
-    MidiInput* newDevice = nullptr;
-
     auto client = AlsaClient::getInstance();
     auto* port = client->createPort (deviceName, true, true);
 
     jassert (port->isValid());
 
-    newDevice = new MidiInput (deviceName);
+    auto newDevice = new MidiInput (deviceName);
     port->setupInput (newDevice, callback);
     newDevice->internal = port;
-
     return newDevice;
 }
 
@@ -584,7 +582,7 @@ MidiOutput* MidiOutput::createNewDevice (const String&)             { return nul
 MidiOutput::~MidiOutput()   {}
 void MidiOutput::sendMessageNow (const MidiMessage&)    {}
 
-MidiInput::MidiInput (const String& nm) : name (nm), internal (nullptr)  {}
+MidiInput::MidiInput (const String& nm) : name (nm)  {}
 MidiInput::~MidiInput() {}
 void MidiInput::start() {}
 void MidiInput::stop()  {}