Fix compilation warnings

src/Envelope.cpp

@@ -336,7 +336,7 @@ float Envelope::ValueOfPixel( int y, int height, bool upper, bool dB,
       // TODO: Cache the gPrefs value.  Reading it every time is inefficient.
       dBRange = gPrefs->Read(wxT("/GUI/EnvdBRange"), ENV_DB_RANGE);
 
-   float v = ::ValueOfPixel(y, height, mContourOffset, dB, dBRange, zoomMin, zoomMax);
+   float v = ::ValueOfPixel(y, height, 0 != mContourOffset, dB, dBRange, zoomMin, zoomMax);
 
    // MB: this is mostly equivalent to what the old code did, I'm not sure
    // if anything special is needed for asymmetric ranges
@@ -1413,7 +1413,7 @@ double Envelope::SolveIntegralOfInverse( double t0, double area )
    if(area == 0.0)
       return t0;
 
-   unsigned int count = mEnv.Count();
+   int count = mEnv.Count();
    if(count == 0) // 'empty' envelope
       return t0 + area * mDefaultValue;
 

src/commands/CommandHandler.cpp

@@ -32,7 +32,7 @@ CommandHandler::~CommandHandler()
    delete mCurrentContext;
 }
 
-void CommandHandler::SetProject(AudacityProject *proj)
+void CommandHandler::SetProject(AudacityProject *)
 {
    // TODO:  Review if the extend command handling is ever utilized
    // mCurrentContext->proj = proj;

src/effects/nyquist/Nyquist.cpp

@@ -1391,7 +1391,7 @@ void NyquistEffect::Parse(wxString line)
       long v;
       // Splits are restored by default. Set to 0 to prevent.
       tokens[1].ToLong(&v);
-      mRestoreSplits = v;
+      mRestoreSplits = !!v;
       return;
    }
 #endif

src/import/ImportMIDI.cpp

@@ -69,7 +69,7 @@ bool ImportMIDI(wxString fName, NoteTrack * dest)
    Alg_event_ptr evt;
    int note_count = 0;
    int pitch_sum = 0;
-   while ((evt = iterator.next())) {
+   while (NULL != (evt = iterator.next())) {
       // if the event is a note
        if (evt->get_type() == 'n') {
            Alg_note_ptr note = (Alg_note_ptr) evt;

src/prefs/LibraryPrefs.cpp

@@ -140,6 +140,9 @@ void LibraryPrefs::PopulateOrExchange(ShuttleGui & S)
 #if !defined(USE_FFMPEG) || defined(DISABLE_DYNAMIC_LOADING_FFMPEG)
          bdwn->Enable(FALSE);
          bfnd->Enable(FALSE);
+#else
+         // fix compilation warnings about unused variables
+         bfnd, bdwn;
 #endif
       }
       S.EndTwoColumn();